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Ossila SuperFACT User Manual

1. 2009 2015 85 enabling innovative electronics Measurement and Accuracy The two PXI Source Measurement Units SMUs are capable of very accurate voltage and current measurements see SMU Specifications section in the NI PXI 4132 Specifications documents The sensitivity and accuracy of the SMU is strongly affected by electromagnetic noise such as the one generated by mobile phones computers too close to the SMU etc temperature and most importantly the PXI measurement settings In particular when low currents of the order of magnitude of few tens of nano Ampere or less are measured external interferences and inappropriate settings may sensibly reduce the accuracy or if the order of magnitude of the noise is comparable or larger than the current being measured even hamper the measurement Temperature and self calibration As specified by the Keithley 2612B Specifications the SMU should be operated at a temperature of 23 C 5 C lt amp 0 of humidity Outside this temperature range the nominal resolution of both output and measurement cannot be guaranteed Operating under high humidity gt 90 or dusty conditions may cause increased leakage between circuit components and can result in additional sourcing and measurement errors To limit the detrimental effect of temperature humidity and ageing it is advisable to execute a Self Calibration regularly through Measurement and Automation MAX Self Calibrati
2. Guide to the Reader Symbols Acronyms and Common Definitions The Organic Field Effect Transistor OFET or Thin Film Transistor TFT that is being characterised is called Device Under Test DUT The equipment that is driving controlling and measuring the output of the DUT is the Source Measurement Unit SMU The SMU drives the DUT by providing an increasing voltage or current to the DUT source function and reading the output measurement function The reading usually takes place after a delay time At called settling time or dwell time has elapsed The delay is introduced to allow the system SMU DUT to settle before a measurement is taken When the driving voltage is increased from an initial value Vstrat to a final value Vena the SMU is said to sweep the DUT A transistor is characterised by applying a constant voltage to the gate and sweeping the drain and then by applying a constant voltage to the drain and sweeping the gate Consequently transistor characterisation requires two SMUs or a double channel SMU working in parallel Throughout this User s guide the SMU driving the gate and the drain will be denoted as GATE SMU and DRAIN SMU so to distinguish them from the Gate and Drain of the transistor Finally both this manual and the SuperFACT numerical controls conform the SI International System system of measurement including the adoption of the SI prefixes for multiples and submultiples of the original unit For
3. Manual Mode forces the application to operate in manual mode Note When operating in manual mode multiplexing capabilities are disabled see Operation Mode for more details on SuperFACT operation modes System settings E mail settings Outgoing Mail Server SMTP Sender s Email Address smtp gmail com E mail Account User ID Recipient s Email Address This enables automatic e mailing functionally whereby errors and ee eee nee eng See ee failure messages are e mailed to the e mail address specified in Enable SSL Recipient s Name Sender s Email Address Available in Lifetime mode only pa Ossila Ltd Copyright 2009 2015 51 enabling innovative electronics Application settings SMU settings PLC Power Line Cycle specifies frequency of the electric power grid 50 or 60 Hz Keithley 26XX series automatically detects the PLC Power Line Cycle Samples To Avg Aperture Time PLC of the power supply grid Power Line Cycle is the oscillation frequency of the AC current supplied to the end users through the electrical power grid In the EU Australia part of Japan and several other countries the PLC is 50 Hz with a voltage range of 220 240 V In USA Canada and Taiwan part of Japan etc the PLC is 60 Hz with a voltage range of 100 120 V Note Providing the correct PLC is detected set SMUs are usually equipped with built in filter capable of rejecting the noise originated from the oscillatory behaviour of the po
4. EN 61010 1 2010 Safety requirements for electrical equipment for measurement control and laboratory use Part 1 General requirements IEC 61010 1 2010 EN 61010 2 030 2010 Safety requirements for electrical equipment for measurement control and laboratory use Part 2 030 Particular requirements for testing and measuring circuits IEC 61010 2 030 2010 EN 61140 2002 Protection against electric shock Common aspects for installation and equipment IEC 61140 2001 EN 61187 1994 Electrical and electronic measuring equipment Documentation IEC 61187 1993 Modified EN 61010 2 081 2002 Safety requirements for electrical equipment for measurement control and laboratory use Part 2 081 Particular requirements for automatic and semi automatic laboratory equipment for analysis and other purposes IEC 61010 2 081 2001 Ossila Ltd Copyright 2009 2015 8 enabling innovative electronics Declaration hereby declare that the equipment named above has been designed to comply with the relevant sections of the above referenced specifications The unit complies with all applicable Essential Requirements of the Directives Signed Name Dr James Kingsley Date System Setup The Multiplexer Measurement Unit is easy and straightforward to set up Only a few cable connections are required to make the system fully operational Nonetheless the User must read carefully the following instructions in order to safely and efficiently exp
5. A and B are not properly connected Action Required Switch OFF both PXIs or SMUs and check the connections Make sure that the Front Panel I O PXI connectors Backshell are both tightly plugged to the PXI receptacles and that the WARNING label is on right side of the I O PXI Check the substrate has been inserted correctly The Gates on the substrate should be placed nearest to the Front Panel Check the USB cable us connected from the socket of the National Instruments NI PXI 413 to the computer If the problem persists unplug the Backshell use a screwdriver to remove the lids and check if the Central Core D in Figure 19 and the metallic shield B in Figure 19 of the coaxial cable are connected to the first and fourth pins inside the Backshell The pins are numbered from top to bottom with the WARNING label of the Backshell on the right side Make sure that the Central Core and the metallic shield are connected through the Backshell to the High and Low output for both SMU channel The output type of the SMU can be read directly on their front panels Copyright 2009 2015 91 enabling innovative electronics If the Backshell are opened for maintenance before use make sure they are roperly sealed with both the Central Core and metallic shield tightly wired and completely enclosed inside the Backshell Ask the assistance of qualified technical support if not familiar with the maintena
6. Copyright 2009 2015 76 enabling innovative electronics Mobility algorithms interval of validity issues and caveats The field effect transistor figures of merit are calculated under the assumption that the transistor model detailed in the Transfer Characteristics section applies to the DUT For the sake of this manual we call a device that complies with such a model well behaved Figures of merit calculated from devices that categorically fails to satisfy the standard field effect model should not be considered valid SuperFACT automatically runs a basic check for the validity of the transistor models when it executes the mobility computation algorithm however a visual inspection of the l V and TC curves by the user is still required to avoid taking into account data extrapolated from DUT non complying with the field effect transistor model Interval of validity Eqs 4 and 8 or their generalisations Eqs 9 and 10 are based on the assumption that the drain current depends on the gate voltage according to Eqs 1 and 2 For the sake of easy reading we rewrite here these last two equations WwW I5 UCox Ves Vrn Vps with Vps K Ves Vral and Ve5 gt IVral Eq 3 W Ips Uox 5 Was Vr with Vos gt Vgs Vrnl and Ves gt Vrn Eq 6 These two equations are valid under the assumption that the drain current satisfies the gradual channel approximation and that the gate and drain voltage satisfy
7. Source probes Column of Source 5 Probes Device 16 Column of Signal Drain Probes Device 16 a o o CU sh 4 SD See Row of Gate Probes S 44 aww o Figure 4 Location of Signal and Source Drain probes for Dev 16 The first column on the left therefore acts as the Source ground while the second is used to apply the desired voltage Drain to the transistors This pattern alternate Source and Drain columns repeats itself for the successive six columns Ossila Ltd Copyright 2009 2015 17 enabling innovative electronics On the front panel of the Multiplexer Measurement Unit the LEDs indicate when a particular Device Blue LED or Gate Red LED is connected to the DRAIN or GATE SMU The Device and Gate LEDs arrangement matches exactly with the Device and Gate layout on the substrate see figure 4 Conversely as the substrate is placed face down on the POGOS the position of the probes is a flipped version of the device location on the substrate see figure 5 5 0mm imm neiaa Imm Figure 5 Front panel of the Multiplexer Measurement Unit corresponds to location of the transistor on the substrate Ossila Ltd Copyright 2009 2015 18 enabling innovative electronics Back panel The back panel houses the coaxial connections for the Drain channel B and Gate channel A the USB B socket for the USB cable and the earthing pin see figure 6 There is also an earthing
8. as IHR a Ves Vrp with Vps constant such that Vps Ves Vral Eq 5 Vin o 8 16 24 32 40 48 56 64 72 80 Ves V Figure 16 The linear mobility is proportional to the slope a of the IDS VGS curves while the threshold voltage is the intercept of these curves with the x axis red dot on the picture The field effect mobility can then be calculated by fitting the Ipsi Vps i points satisfying Eq 3 toa straight line the slope of which is inserted into Eq 4 in order to obtain u while the intercept with the x axis gives the threshold voltage j Here the extra index is added to underline that Ips i Vpsi are experimental quantities with Vps the nth drive voltage and lps the corresponding nth measured current Ossila Ltd Copyright 2009 2015 37 enabling innovative electronics If Eis the applied electrical field the carrier speed v is given by the equation v HE The unit of measure of the mobility u is therefore cm V s Saturation mobility If the transistor is operated in saturation regime the drain current is W x oy Ves Vrn with Vpsl Ves Vrpl and Vesl gt Vral Ips UC Eq 6 Eq 6 means that when the transistor is ON Vgs gt Vra 152 is a quadratic function of the gate sat voltage To calculate the mobility it is convenient to take the square root of Ips and rewrite Eq 6 aS WwW VIRS MCox vy Ves Vr Eq 7 Ex
9. as Von It is common practice however to use the larger in absolute value Vss swept as Von To automatically use Vss eng as Von select the At Max V_DS option from the drop down menu of the ON current ring selector To select a different value for lon select the User option instead and the enter Von using the Von input Ossila Ltd Copyright 2009 2015 69 enabling innovative electronics Fitting Algorithm For the partition and linear fit method Fitting Algorithm specifies which fitting algorithm to employ to calculate the linear fit The three available options are e Least Square e Least Absolute Residual e Bisquare also known as Tukey s biweight If the noise on the measured values p is described by a Gaussian distribution the Least Square method should suffice The Bisquare method is a robust fitting method to be applied if outliers are present Outliers are point that lies far away from the majority of the measured data a phenomenon that may be caused by short and strong external interferences during the measurement acquisition Whereas the Bisquare method is robust against outliers the resulting Linear Fit does not strongly depends on few points located far away from the rest of the data set the Least Square is severely affected by the these points These three options are accessible through the drop down menu of the Fitting Algorithm ring control Tolerance The Tolerance applicable to Least Square and Bisqu
10. be Low 0 if the voltage is between 0 and 2 V and high 1 if the voltage is between 2 2 and 5V SuperFACT multiplexer is complying with TTL logic 13 Without loss of generality we have assumed that the slope a is gate voltage independent For an ideal FET with constant slope over the ON region the second derivative of the transfer characteristic with respect to the gate voltage is a Delta of Dirac Ossila Ltd Copyright 2009 2015 40 enabling innovative electronics For real world FETs the current discontinuity at Vy the step should be replaced by a steeply increasing yet continuous function However as far as Eq 13 is an adequate approximation of the FET behaviour and AV is reasonably small Eq 14 indicates that the second derivative of Ips can still be expected to show a peak i e a maximum as the transistor cross the threshold Based on these considerations the field effect threshold voltage can be defined as d V2 max 2s aVGs Eq 15 Eq 15 is provides us with an alternative to the linear fit method to calculate the threshold voltage Since the maximum of Eq 15 detects at which Vg the drain current changes its functional dependence on the driving voltage see Eq 13 from an operational perspective Eq 15 is in principle a mathematically more rigorous definition of the threshold voltage than the standard definition given at the beginning of this chapter see figure 16 The calculation of the thresh
11. be able to recognise the hardware and will return an error Channel is the SMU channel used for output input operation Input a for Keithley 26XX dual channel and 0 for NI PXI 4132 Auto Zero controls the Auto Zero functionality If Auto Zero is enabled ON the SMU disconnects the external load shorts the internal measurement circuitry and measures the internal short This value is then subtracted to the load current so that the output current is given by loutput ILoad lnternal Eq 20 For an ideal SMU the internal short current linterna should be zero For a real SMU however this value is always different from zero and represents the internal current bias This bias is responsible for a temperature and range dependent measurement error which affects any measurement Auto Zero ring selector allows the user to choose among three options Off no the correction is applied i e output lLoad Once the internal current linterna Is Measured at the beginning of each measurement session and its value is subtracted to lioag according to Eq1 On the internal current is measured for any acquisition point and its value subtracted to the corresponding lroad Ossila Ltd Copyright 2009 2015 60 enabling innovative electronics Note Auto Zero option On improves accuracy dramatically but almost doubles the total acquisition time Refer to the Measurement and Accuracy section for more detailed information on the Auto Zero
12. below Output IV selects deselects output characteristic IV sweep acquisition Transfer selects deselects transfer TC sweeps To calculate the mobility and the other transistor figures of merit this control must be selected Stress Bias enables the SuperFACT bias capability In Stress Bias mode SuperFACT can be programmed to execute up to four l acquisition cycles at specified time interval During the time i intervals between two consecutive cycles the DUTs can be kept at a constant bias voltage Vbias With Vbias lt 10V Important The Voltage is applied to the selected DUTs on a column by column basis i e that if at least one device belonging to a column is selected the entire column will be kept under biased Lifetime enables SuperFACT continuous measurement mode ER whereby the user can set infinitely repeating acquisition cycles Tip Select Lifetime in conjunction with Sweep Bias to combine continuous and stress biased measurements r x Ossila Ltd Copyright 2009 2015 55 enabling innovative electronics Target f The target section of this UI allows the user to control the DUTs to measure and to select the gate channels gate pogos Press DUT to automatically select all twenty DUTs on the substrate The single devices can be selected deselect through the device keypad located on the left of DUT Gate Ring Selector controls the behaviour of the gate channels
13. cable to earth the chassis Cheanel B Drain Source Figure 6 Back panel of the Multiplexer Measurement Unit Ossila Ltd Copyright 2009 2015 19 enabling g innovative electronics Safety operational considerations e The Ossila Multiplexer Measurement Unit was designed to be used with Drain Channel B and Gate Channel A currents and voltages below 100 mA and 100 V respectively The Ossila SuperFACT Control Software automatically limits both output currents and driving voltages to comply with these limits Due to this reason and in order to avoid any signal degradation there is no safety fuse in the signal paths If not using the Ossila SuperFACT Control Software ensure the Drain Channel B and Gate Channel A currents and voltages signals are always limited to 100 mA and 100 V respectively These limits should be hard coded in the control software so that no user can unintentionally supply read voltages currents whose values are outside the operational range of the multiplexer e If using alternative software is the software engineer programmer is responsible for testing whether the application is working correctly and the SMU is operating within the limit described above e Itis also strongly recommended to include error handling routine to make sure the application will attempt to disarm the channel whenever an error occurs The multiplexer is equipped with an interlock on the top panel figure 7 This is a sa
14. for Ves gt Vr Condition 1 guarantees that the DUT is really a field effect transistor Discard any device that does not comply with condition 1 A poor carrier injection from the drain electrode to the semiconductor will results in underperforming current Ips at low drain voltage i e Ips Vps will increase less than linearly as a function Vps Condition 2 is required in order for the mobility equations 4 and 8 or 9 and 10 to be valid Important Failure to satisfy this condition can prevent SuperFACT from calculating the mobility Refer to Mobility Errors for a detailed description of the mobility errors code Monotonically increasing function means that for any Ves 1 lt Ves2 the drain current is such that Ips Ves 1 lt Ips Ves 2 large voltage always means larger drain current For p type transistor where both voltage and current are negative these relations hold true if the inequality symbol is reversed These derivatives apart from a multiplicative factor are the mobility of the transistor see Eqs 4 and 8 Ossila Ltd Copyright 2009 2015 42 enabling innovative electronics Vas los Vos 70 10 8 5 3 0 80 Vos V Figure 17 OFET Curve details of the linear region in figure 14 Condition 3 is equivalent to state that the transfer current increases in absolute value as a larger driving voltage is applied to the gate Despite being an intrinsic property
15. inequality in Eq 6 the condition for Vena can be found to be Venal lt Vos Vral Eq 31 In case of current degradation the same considerations as for the linear case apply The interval of validity for the saturation mode figure of merits calculates is therefore defined as see figure 29 Ossila Ltd Copyright 2009 2015 78 enabling innovative electronics the set of measured los Vesi complying with the FET standard model with Vps chosen in a manner such that the DUT operates in saturation regime and with the gate voltage values satisfying the inequality Vstart Vesi lt Vena With Vstart gt Vn and Venal lt Vos Vral or Vena lt V s 1 4E 05 pr 1 2E 05 1 0E 05 8 0E 06 6 0E 06 4 0E 06 2 0E 06 0 0 00 gt O 8 16 24 32 40 48 56 64 72 80 Ves V Figure 29 Linear and saturation TC curves and their interval of validity Mobility algorithm optimisation flags The optimisation flags of the mobility algorithms implemented in SuperFACT attempt to locate the validity interval Vstart Vena for each DUT automatically using the measured data Ipsi Vesi as input Important SuperFACT automatically excludes any Ips in compliance Flag 0 None No optimisation routine is enabled Note The mobility will be calculated for each Ves i gt Vos linear regime or for Ves i gt Vix where Vi is the voltage at which drain current Ips is 1 of its maxim
16. is the capacitance of the semiconductor depletion layer Well behaved transistor and validation of the figures of merit For non optimised R amp D devices it is not always straightforward to determine if the DUT is actually an acceptable transistor and to what extend the equations introduced above constitute a valid description of the behaviour of the DUT itself It can therefore be useful to benchmark the behaviour of areal R amp D DUT with an ideal well behaved transistor The aim of this section is to give to graduate students or researchers with no previous experience of TFT OFET characterisation a very brief guide on data validation Despite not being strictly rigorous this section should help the beginner to easily tell apart a good from a bad transistor In this user manual we define a transistor as well behaved if 1 The IV output curves comply with the following conditions see page Output Characteristic I V e Ips is a linear function of the driving voltage for small Vps e Ips approximately saturates for larger Vps e Ips increase with Ves field effect 2 Linear and transfer characteristic curves are approximately described by Eqs 1 and 6 3 The current TC current Ips is a monotonically increasing function of Ves can 4 The derivatives a av for linear TC or for saturation TC are constant or if functions of the gate voltage e must always oy lies with possibly no more than one peak
17. linear fit SuperFACT calculates also the Upper and Lower Bounds of the fit at a 0 95 confidence level see figure 26 whose meaning is the following There is a 95 probability that the actual best linear fit lies in the region demarcated by the upper and lower bounds where the blue dashed line represent the linear fit bounds 60 50 40 Gate Voltages Figure 26 Linear Fit Red solid line and Upper and Lower Bound defining the confidence interval dashed blue line for two subsets of input Gate Voltages and measured point Drain Current for TC in Saturation Mode Ossila Ltd Copyright 2009 2015 75 enabling innovative electronics Example Let us suppose that a TC curve is acquired for Gate voltages ranging from 0 to 80 V ata constant Drain voltage of 60 V where the transistor is operating in Saturation mode Let also suppose that the drain current is measured for any voltage change i e AVgs 1V and that N the size of the data subset is set equal to 10 When the measurement is completed the TC data set is then represented by 81 couples V s5 losi with index labelling the input output couples The first couple Ves o 0 Ipso is discarded while the rest of the data is organized in ten point subset The first subset is formed by the gate voltages 1 2 3 9 10 V and the respective measured currents The second one is composed by the gate voltages 11 12 13 19 20 V with the current measu
18. may result in board damage or device damage and potentially hazardous situations The Ossila Multiplexer Measurement Unit was designed to be used with Drain Channel B and Gate Channel A input currents below 100 mA The Ossila SuperFact Control Software automatically limits the input currents Due to this reason there is no fuse in the signal paths to conserve the accuracy of the measurement If not using the Ossila SuperFact controlled Software ensure the Drain and Gate input signals are limited to 100 mA Caution To avoid damaging devices or equipment obey the following Avoid electrostatic discharge ESD as this may damage the device To avoid damage use Static discharge and prevention equipment where necessary Only use the System for the purposes intended described in this document Do not expose the System to any cleaning fluids or solvents Ensure that the SMU s are not exposed to heat source and are well ventilated to avoid overheating Follow good practice when setting up the test system Avoid placing mobile phones electrical devices close to the system as this can cause interference Ossila Ltd Copyright 2009 2015 enabling innovative electronics System Components Keithley 2612B system SMU Ossila Multiplexer Measurement Unit containing NI USB 6501 OEM electronic controls LED display and the signal board supporting POGO pin contacts probes for 20 devices and 8 gates Desktop PC Window 8 1 operat
19. the ON Current ring control select At Max V_DS 30 On the Fitting Method and Fit Optimisation ring menu select Least Square and None respectively 31 Press Measure to start the acquisition Save experiment settings To save an experiment for later use you can on the Measurement Settings and Device Parameters UI press Save As enter the file name on the Saved Experiments List then press Save to confirm Important A newly saved experiment is not automatically loaded into memory For the new settings to take effect the experiment needs to be committed first see Commit an Experiment below Alternatively if an experiment is already loaded into memory but not saved you can press the Save As button on the main UI and you will then be given the option to save the experiment straightaway or double check the settings first Delete an existing experiment On the main UI press Delete Experiment choose the experiment settings to remove press Delete and then confirm this action when prompted to Alternatively a file loaded into memory can be deleted using the Delete option on Measurement Settings and Device Parameters Ul Commit an experiment To commit an experiment press Load Settings on the main UI choose the experiment name from the list of saved experiment and press open On the Advanced SMU and Acquisition Settings Ul press Load Exp to open the Select Devices to Measure and Measurement Type UI On this UI press Apply and on
20. the inequality as detailed on the left side of Eqs 3 and 6 In particular the measured gate voltage Ves must be greater than the threshold voltage i e Eqs 3 and 8 are valid only in the ON operation region of the transistor In addition for the linear regime Vesi must satisfies the condition v K Vesi Vrn l Vee a Vra K Ves zi lVosil gt gt Vee Vrn Eq 30 According to Eq 30 the gate voltage must be larger than the drain source voltage deducted of the threshold voltage To complicate matters for non optimised R amp D devices it is not unusual to observe high voltage stress Severe voltage stress can result in drain current degradation In case voltage stress is present the transistor model and therefore Eq 3 and 6 should not be considered a valid description of the system see Fig 16 for an example of drain current degradation However if a Voltage stress can be due to intrinsic semiconductor deficiency traps impurity architectural of fabrication issue etc or simply be an indication that the gate voltage applied exceeds the maximum operation voltage of the device Clearly at the R amp D stage it may not be known yet the operational range of the new material or device architecture Ossila Ltd Copyright 2009 2015 77 enabling innovative electronics the voltage stress causes a drain current with negative slope at large gate voltage only i e for Vesi gt Ves with Ves large when compared with Vma SuperFA
21. C Toe ko l This section serves as GATE SMU for TC sweeps SMU Name is the alias name of the SMU unit as specified in MAX Measurement amp Automation Explorer For Keithley series 26XX dual channel series the SMU alias name must be KeithleyO while for NI PXI 4132 the name is SMUA Channel is the SMU channel used for output input operation Input a for Keithley 26XX dual channel series and O for NI PXI 4132 Ossila Ltd Copyright 2009 2015 64 enabling innovative electronics Auto Zero sets the Auto Zero for the GATE SMU refer to the IV GATE section above for more information For both Vp Linear and Saturation regime the Gate sub panel is used to determine the start end and measurement points of the Transfer Characteristic curves Ips Ves by means of the controls Ves Start Ves End and AVg s respectively ps Ves is measured at Vgs with Vesi Ves start X AVes Eq 24 with i 0 1 2 N and N number of data points number of steps N is given by V V N GS Start GS Start 1 AVGs Eq 25 Note Since the TC data is used to estimate the mobility and due to the nature of the mobility computation algorithm see Mobility Computation below it is advisable to measure the drain current for at least each Volts change in the gate potential i e AV s lt 1V and in any case acquire no less than 50 60 data points Current Limit specifies the maximum gate current Ics that the GATE sour
22. CT will still return the FET figures of merit for the Ips i Ves satisfying Eq 30 and the additional condition V s lt Ves For the purpose of FET characterisation the SuperFACT Interval of validity Vstart Vena J i e the portion of the transfer curves used to calculate the FET figures of merits is therefore defined as the set of measured los Vesi complying with the FET standard model with Vps chosen in a manner such that the DUT operates in linera regime and with the gate voltage values satisfying the inequality Vstart Vesi Vena Drain Current A 50 45 40 35 136 25 0 Gate Voltage V EA 2 Figure 28 TC Linear Current for a p type OFET The red dots are the measured data while the continuous black line is the linear fit and the thin green and yellow lines barely visible are the upper and lower bound of the linear fit The arrow indicates an incipient voltage stress for VGS lt 50 V For severe drain current degradation the current IDS will decrease as the gate voltage increases in absolute value For the linear regime Vstat must be larger than the threshold voltage Vn with the extra condition Vstart gt gt V5 Vrn see Eq 31 Conversely Vena lt Ves If no current degradation is present Veng Vos end WIth Ves eng the largest voltage swept Similarly to the linear regime for the saturation regime the gate voltage must satisfy the condition V gt gt Vr By reordering the first
23. Contro 20 must be connected to the host PC via a USB cable otherwise error code 5040 will be generated an no acquisition can start Manual Mode the multiplexor unit is disregarded Consequently SuperFACT can operate with any manual test fixture by simply connecting the test fixture BNC gate and source drain inputs to any supported SMU Note If at application start or during hardware reset the SwitchControl20 is not detected or it is not working properly the application will switch to Manual Mode automatically Important Do not use the multiplexer in manual mode When in manual mode the multiplexer unit remains inactive throughout the acquisition cycle However providing the host computer is connected to the multiplexer it is possible to take measurement using a manual text fixture in manual mode In this case you need to connect the SMU to the manual test fixture manually select the device to measure and programme SuperFACT to measure only one device at the time See Quick Start section for details on how programme an OFET TFT acquisition Acquisition Mode SuperFACT supports two main acquisition modes Finite Measurement and Continuous Measurement Finite Measurement One single measurement per substrate device Standard FET characterisation or alternatively a finite number of repeated Standard Characterisations carried out at regular time intervals and with the option of keeping the substrate at a constant bias voltage betwe
24. Control Windows Reboot Time Auto Run Make Settings Default a isso fic Does AutoRun OFF Last Reboot Time Self Calibration LT AN a ao a ee i A Default dl L 00 00 ol Measurement Advanced Settings m a Reboot TC Initial Delay Time TC Discard Measurements Manual Mod ic m PrE Erom T Elam E _ratoct or eal IV Discard Measurements oe i E mail Settings Data Analysis Advanced Settings Outgoing Mail Server SMTP Sender s Email Address Partition Method Set Size Partition Method R squared Bess z z z i CE mail Account User ID Recipient s Email Address DDE N Linear Fit Method Min Sample Linear Fit Method R Squared E mail Account Password Sender s Name fo Q 0 95 _ Recipient s Name Lifetime Data Storage Volume es oe Figure 18 Advanced SMU and Acquisition Settings UI Ossila Ltd Copyright 2009 2015 44 enabling innovative electronics 2 Upon pressing Create Exp the current UI is closed and replaced by Se ect Devices to Measure and Measurement Type UI 3 Under Measurement Type select Output IV and Transfer to measure both output and transfer characteristics curves of the DUT 4 Toselect the entirety of the devices on the substrates press the DUT button under Target Single devices can be selected deselected by pressing the corresponding buttons on the device keypad inside the Target subpanel Note The position and numbering of the
25. DIO channels are reserved to control the Security Bits See section Digital DIO Lines below for more details instruction son how to programme the Multiplexer Ossila Ltd Copyright 2009 2015 24 enabling innovative electronics Digital DIO lines The DIO channels are split between three ports PO P1 and P2 PortO contains channels to address the choice of device columns the Safety Bits and Devices 1 2 16 and 17 Port1 addresses the selection of rest of the Devices while Port2 controls the selection of the Gates To turn on a Device or Gate the security Bit PO 6 and PO 7 must be set to LOW and HIGH respectively A Device is selected setting two channels HIGH a column selector channel and a Device selector channel For example to turn Dev 1 on P0 0 and P0 4 must be set HIGH The Gates can be turned on by setting the corresponding P2 lines HIGH Any number and combination of Gates can be turned on at any one time It is intended that only one Device is to be turned on at a time as the current or voltage to be measured is accesed via Channel B However the Multiplexer Measuring Unit can also be used for stress biased measurement whereby all the Devices are switched on see section Operation Table 2 Digital DIO channels controlling the Multiplexer Measurement Unit Signal Name DIREEEON Description 6 software selectable P Column 1 Selector Column 2 Selector Column 3 Selector Output Column 4 Selector Selects Dev 1 and 16 Sel
26. Example 0 01V is written as 1 mV see table below 10 nano 10 micro milli Ossila Ltd Copyright 2009 2015 94 enabling innovative electronics Warranty Information and Contact Details Ossila warrants that a Ossila has or will have at the relevant time the right to sell the Products b the Customer shall enjoy quiet possession of the Products c the Products correspond to any description of the Products supplied by Ossila to the Customer d the Products are of satisfactory quality e the Products are fit for any purpose expressly but not merely impliedly made known by the Customer to Ossila before the relevant Contract is made f the Products correspond to any sample of the Products supplied by Ossila to the Customer and will be free from any defect making their quality unsatisfactory which would not be apparent on reasonable examination of the sample g the Products will comply with all laws rules regulations applicable to the marketing and sale of the Products in United Kingdom h if within one year of purchase the customer experiences system failure or damage within reasonable constraints the system may be returned to Ossila for maintenance Please note that if any system compartment is opened within this period warranty will be voided To the best of our knowledge the technical information provided here is accurate However Ossila assume no liability for the accuracy of this inf
27. For real world DUT conditions 1 and 2 may not be strictly satisfied For example in presence of non Ohmic injection barrier at the drain semiconductor interface and for small drain voltage Ips i Sweeping is a common jargon used to describe a measurement where an initial voltage Vstart or current is applied to the DUT and then gradually increased till a final value Vengis reached Ossila Ltd Copyright 2009 2015 35 enabling innovative electronics shows a sub linear dependence on Vps A DUT satisfying conditions 1 and 2 in an approximate manner can still be described approximately by the FET standard model However DUTs failing to satisfy condition 3 must be discarded Important The calculation of the transistor figures of merit are based on equations derived from the FET standard model For non optimised R amp D devices it is often the case that the hallmark features of figure 13 are only approximately reproduced The user must therefore always validate any TFT OFET figures of merit data against the hypothesis under which the standard model is derived by a simple visual inspection of the l V curves of the DUT Transfer characteristic TC If a constant drain source voltage Vps is applied to the drain while the gate voltage is swept the measured drain current Ips Ves is called Transfer Characteristic TC of the transistor transfer for short A transfer curve swept with a Vps value belonging to the I V linear region i
28. Ossila enabling innovative electronics Ossila SuperFACT User Manual Ossila Ltd Copyright 2009 2015 enabling innovative electronics CONTENTS OVERVIEW ass cece oo ov ccc eae tone EEEE AEE EE AA S 4 SAFET se oecc sa ccen cate ciceeeseccce ic toca EEEE dete sececeis voce ania se sscees sen eveoeauonssbevacesd onceasecoese NA 5 SYSTEM COMPONENTS sis ociasen oc ene de Sass evn bie cnc bee ci outed ov de Dew ena eae sewn ena ease wena eeawnke eens cecaeesanceetessenes 6 EC DECLARATION OF CONFORMITY ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccecces 7 SISTEM a orcs cia ss esas ss oes ein ees wip we bce was ec eis ewe cn vac sues wad ees ce vedi we cw wecsuscuwscesuedeceveccatesseeeuaneseseenceveecenostevesieeteee 9 EUPIA Se IP ea EA A daresctoay aoc aransen EE anata arenas ornament nated 10 SUPERFACT SOFTWARE INSTALLATION ccceccesccccceccecccecceccceccecacecccencecccencecacesceseeenceseeensesacensescesceescesseeasesseessesaes 13 MULTIPLEXER MEASUREMENT UNIT cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccscceccees 16 FRONT PANEL SUBSTRATE PLACEMENT ccensaventeucercaueenawieceuatewedaiaceonianacesncecensinswuenensaneeuaearaceuaseadonsonneanteonaeue ones 16 PACKE NE aa A AAE A E A A a a a ea 19 SAFETY OPERATIONAL CONSIDERATIONS ssccscccssccscccsccesscescesscesccesccesscesseesseesseceesseecseeceeeceesseesseesseusseec
29. TC smoothed curves are the measured transfer curves raw data filtered smoothed by the recursive application of the Savitzky Golay filter Ossila Ltd Copyright 2009 2015 82 enabling innovative electronics Best Fit Linear 150n See Go i GZ 500n 60 55 50 45 40 35 30 25 20 Gate Voltage V Figure 30 Example of a too large fit interval Linear Fit Method User Falg Enabled with VStart VEnd 20 60 V The red line represent the linear fit over the interval 20 60 V with the green a blue line upper and lower fit bonds Clearly the red line represent the linear fit over the interval 20 60 V with the green a blue line upper and lower fit bonds Clearly the red line is not a good fit of the experimental data red dots A better choice could have been the interval 45 60 V To reduce the risk of erroneous validation the user must carefully choose the TC sweep parameters that are appropriate for the DUTs or carefully select the lower and upper bonds Vstart Vena if the flag User is selected After the acquisition is completed a visual inspection of the TC and mobility plots will usually suffice to validate the data User validation is always strictly required when the mobility is calculated without enabling any optimisation flag The table below gives a set of recommendations on the use of the Mobility flags In this table well defined behaviour DUTs are the TFTs OFETs whose l
30. Zero Delay Sec coon oe ea eee oe x Cancel amp Close Transfer Characteristic Gate SMU Name T Limit E a 2 G J Data Analysis Advanced Measurement Transistor Parameters Data Analysis Options Lifetime End Measurement Cycle eee 60 50 40 30 h Acquisition Rate on come oe S Bias F cm Width cm e ac 1 09E 3 ms ii Select i S J S J S J v J o j J A 4 Figure 23 Measurement Settings and Device Parameters UI Acquisition settings Output characteristics IV Drain SMU Name Vos Start Vos End AVos om om Ie Flom com Sweep Use this UI subpanel to control the DRAIN SMU for IV acquisition SMU Name is the alias name of the drain SMU unit as specified in MAX Measurement amp Automation Explorer For Keithley series 26XX dual channel the SMU alias name must be KeithleyO while for NI PXI 4132 the name is SMUB Channel is the SMU channel used for output input operation Input b for Keithley 26XX dual channel series and O for NI PXI 4132 Auto Zero controls the DRAIN GATE Auto Zero see IV Gate for details Vps Start Vps End and AVps specify the sweep parameters of a single IV curves For any constant gate voltage Ves defined in the Gate control panel the l V output characteristics curve Ips Vps is acquired in correspondence of the following Drain voltages V psi Ossila Ltd Copyright 2009 2015 63 enabling innovative electronic
31. a Ltd Copyright 2009 2015 52 enabling innovative electronics point PXI SMU or for any discarded measurement see below Keithley SMU Important For Keithley 26XX series TC Initial Delay Time takes effect only if TC Discarded Measurement is different from zero Tip A longer initial settling time is usually required to counteract the spurious current generated by stray capacitive components in the measurement equipment SMU cable and multiplexer Figure 21 Schematic of TC acquisition with initial settling time TC Discarded Measurement specifies the number of initial measurements lps oto take and discard before the actual acquisition is commenced This functionality improves measurement accuracy by allowing the discharge of the stray capacitors of the measurement equipment For NI PXI It can be used in combination with or in substitution of TC Initial Delay Time TC Discarded Measurement Min allowed value 0 Max allowed value 10 IV Initial Delay Time The same as TC Initial Delay Time but with the extra settling time applied to the DRAIN SMU during the IV sweeps IV Discarded Measurement The same as TC Discarded Measurement but it applies to the output characteristic current Ip and to the leakage gate current les Min allowed value 0 Max allowed value 10 Application settings Data analysis SSS ES __ Partition Method Set Size specifies the minimum size els foss of the data po
32. act timings will depend upon the power and temperature of the sonic bath To achieve hot solutions we generally fill the sonic bath with boiling water from a kettle which results in a bath temperature of around 70 to 80 degrees e 5 mins sonication in hot 1 Hellmanex III solution e 2x boiling water dump rinse e 5 mins sonication in warm IPA e 2x cold water dump rinse e Optional 5 mins sonication in hot 10 NaOH and 2x cold water dump rinse e Storage in cold DI water Once placed in DI water the substrates are stable for at least 24 hours and probably much more Ossila Ltd Copyright 2009 2015 96 enabling innovative electronics Appendix Il PMMA gate dielectric For top gate devices the choice of dielectric material is a critical consideration as it must have low leakage and also have an orthogonal solvent to the semiconductor layers below Solution processed gate dielectrics are therefore an area of active research with many new polymers being developed with the desired properties However of the commercially available polymers we have found that PMMA gives the best combination of performance simplicity and compatibility However the molecular weight and solvent used has a large impact on performance We have found that PMMA with M 120K gives good performance when dissolved in butanone Molecular weights significantly higher than this can cause solubility issues and uneven films while significantly lower can cause pin h
33. ames select the Permissions for Pier Allow Deny relevant PC user Full control e Click on edit and make sure that Full Read amp execute control is ticked List folder contents Read e Press apply and then OK White For special permissions or advanced settings click Advanced Leam about access control and pennissions Reinstalling the application To avoid losing experiment acquisition settings the User is strongly advised to e Make a copy of the data folder e After the re installation is completed delete the content of the new data folder with the exception of the file with extension ddl e Copy all the files in the old data folder to the new data folder again with the exception of the file with extension ddl Ossila Ltd Copyright 2009 2015 14 enabling innovative electronics Note Make sure to delete every single file in the new data folder and replace them with the entirety of the file in the data folder with the exception of the ddl file otherwise the application may stop working properly Alternatively before re installing the application delete the data folder to delete any previous reference to old experiment settings Ossila Ltd Copyright 2009 2015 15 enabling innovative electronics Multiplexer Measurement Unit Front panel amp substrate placement The Multiplexer measurement Unit contains the control and signal circuitry It uses the NI 6501 OEM Board to communicate with the com
34. arameters in the Output Characteristics IV section enter the Gate SMU Name and Channel SMU Name is the SMU alias name specified in MAX KeithleyO or SMUA while channel is a for Keithley SMU or 0 for PXI 10 Define the family of IV curves to sweep by choosing Ves Start Ves End and Gate Sweeps Gate Sweeps is the number of IV curves to sweep at constant gate voltage with the first curve swept at Vegte Ves starr and the last at Vegte Ves eng The other curves are then swept at a constant gate voltage given by Voate Ves stat tNAV Eq 18 with AV VGS End VGs Start Gate Sweeps 1 Eq 19 and n 1 2 3 Gate Sweeps 1 Note Remember that p type transistors are switched ON with negative voltage while n type require positive voltage to operate 11 Enter the Delay the gate source settling time For Organic OFETs typical settling time can vary from a few tens of milliseconds to hundreds of milliseconds See Application Settings Measurement Advanced Settings for further information on the choice of the settling time Note The unit of measure of Delay is seconds Enter 0 1 or 100 m to set a 100 milliseconds gate source settling time Do not enter a very large delay time such as 10 seconds otherwise Keithley will return a timeout error 12 Enter Current Limit Current Limit in Ampere specifies the maximum current that the SMU is expecting to measure during the current session Therefore the SMU determines the me
35. are method only determines when to stop the iterative adjustment of the slope and intercept of the Linear Fit The Linear Fit is extrapolated from the data set using iterative methods At each interaction the slope and the intercept of the Linear Fit approaches the Best Linear Fit If the residual between two iterations is less than Tolerance the iteration is terminated and the slope and intercept of the resulting Linear Fit are returned The minimum value of Tolerance is 0 0001 Please refer to a statistical data analysis manual textbook for detailed explanation of the linear fit theory and common algorithms If Derivative Method is selected the Derivative Algorithm ring selector replaces Fitting Algorithm The two available options are now e None no smoothing filter is applied to the first derivative dIps dVgs e Smooth First Derivative Savitzky Golay filter is used to smooth dIps dVgs Fit Optimisation enables disabled specific optimisation routines flags associated with the mobility computation algorithm These routines are designed to estimate the range of validity of the mobility equation and to discard figures of merit that are not in conformity with the mobility computation hypothesis Refer to Mobility Algorithms Refer to Mobility Computations for further details Do not confuse the algorithm used to calculate the linear fit with the algorithm method used to calculate the mobility The former refer to the algorithm that th
36. asurement current range from this value For more information on Current Limit measurement range and the implication of the latter on resolution and accuracy refer to Acquisition Settings Output Characteristics IV Gate and Calculation of the Measurement Accuracy as well as the SMU Data Sheet 13 Enter the maximum leakage current in Ampere using Max Gate Current Note If the measured gate leakage current is greater than Max Gate Current SuperFACT will stop the DUT acquisition and start the acquisition of the successive device if any Ossila Ltd Copyright 2009 2015 46 enabling innovative electronics Output Characteristics Drain 14 Enter SMU Name Channel and set Auto Zero Once The Drain SMU name and channel are KeithleyO and b respectively for Keithley and SWUB and 0 respectively for PXI 15 Enter the Ips Vps sweep parameter Vps start Vos ena and AVps in Volts 16 Enter Delay for the Drain SMU settling time after the DRAIN source applies the driving voltage Vps Drain delay can be substantially lower than GATE Delay 17 Enter DRAIN SMU Current Limit in Ampere Transfer Characteristics Gate 18 Enter SMU Name Channel these commands are the same as for the Output Characteristic case Set Auto Zero Once 19 Set the saturation and transfer curves sweep by entering the start end and step voltage using Vas start Ves end and AV s in Volts 20 Enter GATE Delay in seconds Depending on the valu
37. b Vie 1 edi gt 444 Scales Serial Number 4071675 po for my j 6 Software Firmware Revision 3 0 4 SED ED IVI Drivers BA Remote Systems What do you want to do Vendor Keithley Instruments Inc Model Model 26128 gt Communicate with my Status Present VISA Resource Name GP1B0 26 INSTR GPIB Instrument Settings This section provides basic information about your instrument such as Primary Address PAD Secondary Address SAD and response to the IDN query gt _ Settings Attributes R VISA Properties Figure 12 MAX Measurement amp Automation Explorer user interface Operation Mode SuperFACT can automatically acquire OFET TFT output and transfer characteristics of a multi device substrate by switching between the different channels of a multiplexor with each channel pogo being connected to a different device Alternatively if a manual test fixture is used instead such as probe station manual test board etc SuperFACT can be set to acquire a single device at the time These two modes of operation are referred to as Automatic Mode and Manual Mode respectively Ossila Ltd Copyright 2009 2015 31 enabling innovative electronics Automatic Mode the User can choose to characterise up to 20 devices and independently control up to eight gate lines See Quick Start for more details on how to set up an automatic acquisition In automatic mode the Ossila multiplexor Switch
38. ccccceccecccecceeccceacecceencesccenceeacencesceseeenceseeesseseensesseeneeeas 40 FOORE O IER rA NA T A AAE E EAA 41 WELL BEHAVED TRANSISTOR AND VALIDATION OF THE FIGURES OF MERIT ccccccecccccecccenceccceacecccencecacencecncesceeusesceencecaes 42 E START e E EEE E E EE E E E ere 43 DATAA NA SS EE EAE EEEE AEE E AEEA 48 SAVE EXPERIMENT SETTINGS nssssooosssseseesessessessssssosseererrererserssesesooeeeorsrrrrrrrrrrrereresessesooererrrrrrrrrreeeseseosoerereeerereeerene 49 DELETE AN EXISTING EXPERIMENT nssssssssssssessssssssssssssssesesernnsrsrrerrrrrerrrrrrresssesseresrrrererrrrrrereoessesssesseeseserereerrrererrrrrre 49 COMMIT AN EXPERIMENT sisisscuasiesswewsmesonnranaswainesinnsauewsiieaiewewsmesasewusewwaiunisaenaatbadhdaahitcad end bwntades aaiieban thn sidantadcatandbenaiensbanad 49 STAR WAN ACO MON casetnacensuranccacntecanstiasetanetaianacadmaanccammaosaintscemaabanecnenodesutancesiuabecenawenaanienendteawaantesiuaecenaasanees 50 CHECK CURRENT EXPERIMENT AND MODIFY DEFAULT ADVANCED SETTINGS ccccccccccecceccccceacecccecceccceccecacesceenceseeeaceneers 50 SUPERFACT UI FRONT PANELS ccccccccccccccccccccccccccccccccccccccccccccccccccccccccecccccecccccccccccccccccccccccccccccccccccscceccs 51 ADVANCED SMU AND ACQUISITION SETTINGS ccccccccccccccccccecccenccscceccecacecceencesceeacesccenceeneesacesseeaceseeeaseseeusesseensenas 51 SELECT DEVICES TO MEASURE AND MEASUREMENT TYPE UL ccecceccecccccceccccccccacecceeccecccencecace
39. ce Imn is the largest current that a transistor output before entering the ON region for characterisation purpose it is useful to consider the threshold current to be the OFF current of the FET We therefore define the OFF current as lorr Ith los Vth Eq 11 Similarly the ON current lon is defined as lon los Von Eq 12 where Von is the typical operational gate voltage applied to the transistor to switch it ON Von is therefore a not well defined quantity and its actual numerical value can depend on the application purpose of the transistor itself For example for inorganic FETs complying with TTL 11 Refer to references 6 7 and 8 for more detailed analysis of the mathematical relationship between lps applied voltages and FET intrinsic material properties Ossila Ltd Copyright 2009 2015 39 enabling innovative electronics Logic Von can be any value between 2 2 and 5 V For OFET TFT unless the operation voltage at which the DUT is expected to operate as component of some OFET TFT based device Von is usually assumed to be the maximum gate voltage at which the FET is swept in linear or saturation regime The ratio between the lon and lopp currents is referred to as the ON OFF ratio It is important transistor figure of merit especially if the transistor is to be used as digital component Threshold voltage second derivative method From the definition of FET operation regions above we saw that the transisto
40. ce generated across the target as the User s selected drain voltages are applied to the target itself i e Current Limit refers to Igs Ves for any Vps applied Delay is the PXIGATE settling time For each data point the current ps is acquired after a time t Delay has elapsed from the application of gate voltage Vgs i Acquisition settings Transfer characteristics IV Gate SMU Name Ds Li DS Vos Linear Vos Sat Meas type Channel Auto Zero Delay Sec Current Limit FET Type This panel control the GATE SMU for TC sweeps SMU Name is the alias name of the SMU unit as specified in MAX Measurement amp Automation Explorer For Keithley series 26XX dual channel series the SMU alias name must be KeithleyO while for NI PXI 4132 the name is SMUB Channel is the SMU channel used for output input operation Input b for Keithley 26XX dual channel series and O for NI PXI 4132 Ossila Ltd Copyright 2009 2015 65 enabling innovative electronics Auto Zero sets the Auto Zero for the DRAIN SMU refer to the IV GATE section above for more information Drain Voltage Linear Region selects the value Vp that the DRAIN source applies to the target with Vps drain voltage for which the target transistor is operating in Linear Mode as it appears in the l V curves when lps AVps with a proportionality constant Usually Drain Voltage Linear Region for organic transistors is approximately 5 to 10 of the drain v
41. d b 1 0 uA Accuracy 2 x 0 028 100 mA 1 0 uA 0 56 uA 1 0 uA 1 56 uA Therefore the current and its uncertainty are 2mA 1 56 uA Ossila SuperFACT automatically selects the appropriate measurement range depending on the PXI Current Limit chosen by the User For each current acquisition chose the appropriate Current Limit i e a value that is greater than the maximum expected current under measurement but not greater than the lowest SMU current range required for the measurement For example if PXIDRAIN Current Limit for the OFET Characteristic Curves is set to 10 UA or less the PXIDRAIN carries out the measurement in the 10 WA range On the other hand if the maximum current is expected to be 50 60 uA choose as Current Limit any value greater than 60 and not larger than 100 uA 100 uA is acceptable For the sake of easy reference the PXI voltage output and voltage measurement accuracy and resolution are also reported in the two tables below Voltage Output Accuracy and Resolution Accuracy of reading offset 50 uV 0 025 3 0 mV 100 V 500 uV 0 025 10 mV Refer to NI PXI 4132 Specification for more detailed information on output and measurement accuracy and resolution Ossila Ltd Copyright 2009 2015 87 enabling innovative electronics Voltage Measurement Accuracy and Resolution Accuracy of reading offset 10 uV 0 02 3 0 mV 100 V 100 uV 0 02 5 0 mV Temperature eff
42. dered to be a sufficiently good approximation of Eqs 10 and 11 These considerations are particularly important in the field of organic electronic because with few notable exceptions OFET TFT mobilities are gate voltage dependent However for weakly dependence Eqs 4 and 8 and Eqs 9 and 10 yield approximately the same numerical value for the field effect mobility Transfer characteristic curves ideal and real behaviour For an ideal TC curves the drain current is zero for Vgs lt Vz and increases rapidly for Ves gt Vrz In actual fact the relation between drain current and both gate and drain voltage is more involved For the sake of simplicity we neglect the details of the functional dependence of Ips on the driving voltages and simply assume that for a well behaved FET the current for Ves lt Vin is very small when compared with lps for Ves gt gt Vr Notwithstanding these simplifications depending on the value of Ves a transistor can be found in two different operation regions Subthreshold or Cutoff for Ves lt Vrn and ON for Ves gt Vrn It follows that a FET can be considered as two state device bit with the state OFF logical state 0 and ON logical state 1 corresponding to the two operation regions Cutoff and ON respectively A good transistor must therefore output a tiny ideally zero current while OFF and switch on very steeply as Ves approaches V7 see Eq 16 so to allow for fast steep ON OFF transition Sin
43. device buttons mirror the layout of the transistor on the substrates 5 Select the active gate channels by choosing the option Edge on the Gate ring control to activate both the rightmost and leftmost gate pads This control is located at the bottom of the Target panel Tip To minimise gate leakage current it is recommended activating only the gate pads strictly required to charge the FET dielectric 6 Fillin the entry fields on the Log Data panel User Name Experiment Name Substrate Type and File Name and use the browse button of Folder Name to choose the directory in which the data files are to be stored 7 Instruct SuperFACT to save all the data files in an appositely created folder and append a time stamp to the data files and folder by enabling these options through the Create Folder and Time Stamp buttons located next to the File Name input 8 Press Apply to proceed to the Measurement Settings and Device Parameters UI I Ossila SuperFACT Select Devices to Measure and Measurement Type New Experiment Setting Measurement Type Target Log Data User Name fosia Experiment Name PCBTTT Substrate Type Notes rcarrinocetce Folder 4 C Users Pier Desktop File Name Multiplexer Figure 19 Select Devices to Measure and Measurement Type UI Ossila Ltd Copyright 2009 2015 45 enabling innovative electronics Output Characteristics Gate 9 On Measurement Settings and Device P
44. ductor t tte t t e Insulator Conductor gate Vas Vi Figure 13 Schematic of bottom gate bottom contact OFET device Since for a given device the drain current depends on both drain and source voltage Ips is a two variable function i e Ips lps Ves Vps requiring a 3D plot for its representation For practical purposes a field effect transistor is more conveniently described by two correlated family of curves e Output Characteristics l V obtained by keeping the gate voltage constant and varying the drain voltage only Ips v Ips Ves cosnt Vps Ips Vos e Transfer Characteristics TC obtained by keeping the drain voltage constant and varying the gate voltage only los tc Ips Ves Vos cosnt lps WVes Physics of Semiconductor Devices 7 i Edition Sze S M Wiley Interscience 1981 Organic Field Effect Transistors Zhenan Bao Jason Locklin CRC Press 2007 i Organic Electronics Materials Manufacturing and Applications Hagen Klauk John Wiley amp Sons 2006 Ossila Ltd Copyright 2009 2015 34 enabling innovative electronics Output characteristic l V If a constant voltage Ves gt Vy is applied to the gate while a varying voltage sweeps the drain an output characteristic curve Ips Vps is measured If this operation is repeated for several Ves s the resulting family of output curves constitutes the well know hallmark of transistor behaviour see figure 14 Figur
45. e This option allows to individually enter the DUTs channel length one at the time Ossila Ltd Copyright 2009 2015 66 enabling innovative electronics Constant By selecting this option the user sets the channel of every single device on the substrates to be equal to a unique value inputted through the constant channel length control located next to the ring selector Ossila E323 or Ossila E325 or Ossila E327 loads the channel length configuration corresponding to the equivalent Ossila variable channel length mask design Note The Channel Length input entries are locked when Constant or any of the Ossila mask configurations is loaded Width specifies the channel width in cm of the OFET TFT see figure 24 Channel Width Figure 24 Sketch of channel width of an OFET device Capacitance is the capacitance per unit area Co in Farad cm of the substrates dielectric The typical value of Cy for a 300 nm thick SiO diel ectric is 1 09 10 F cm Note C depends on dielectric constant of the material and on the thickness of the dielectric as such it can be written as C A Co a C Eok P Eq 26 Where 8 854 1071 F m is the vacuum permittivity k is the material dependent dielectric constant while A and d are the overlap area and separation distance between two parallel conductive plates respectively see figure 25 Experimentally Co can be indirectly measured by measuring C the capacitance of the te
46. e 14 Output Characteristics or IV curves The output curves are sometimes referred to as I V IV characteristic curves In this user manual the two terms will be used interchangeably Note It is common practice to acquire at least one l V curves for Ves lt Vin On figure 14 two main transistor operation regions are clearly visible For small Vps the drain current is linearly dependent on the drain voltage this constitutes the linear or Ohmic region For large Vps the current tends to saturates i e Ip becomes independent of Vps and the transistor is said to operate in the saturation region A third important feature of the IV curve in figure 14 is the so called field effect response of Ips whereby the drain current increase as a larger Ves is applied A simple visual inspection of figure 13 can help in evaluating the quality of the transistor contact resistance and device architecture issues identify problems with the semiconductor etc Refer to the books mentioned previously refs 6 7 and 8 for further information on this For the intent and purpose of this manual the three l V features detailed above will suffice to determine the validity of the transistor model More specifically the DUT will be considered to comply with the standard FET model if 1 For small Vps Ips is a linear function of the driving voltage 2 for larger Vps the current lps saturates 3 The current Ips increase with Ves gt Vrn field effect
47. e application calls to fit the experimental data toa straight line linear fit while the latter is the method that is employed by the application to pre process and handle the data to fit 2 The drain current is already smoothed during the pre processing stage of the data analysis routine and Derivative Algorithm control has no effect on this stage Ossila Ltd Copyright 2009 2015 70 enabling innovative electronics Important It is not guaranteed that these optimisation flags will correctly work in any conceivable situation The flags may still fail to discard figures of merit not fulfilling the mobility equation or do not include legitimate Figures of Merit complying the ones defined previously The options selectable through the drop down menu of Fit Optimisation are 1 None The mobility algorithm executes with no optimisation flags enabled 2 Cut off As for the None case no optimisation flags are enabled but the figures of merit are calculated using the experimental data defined by interval Vstart Venal Vstart and Veng are entered through the two dedicated numeric input entries located next to the ring selector 3 AutoFWHM enables the FWHM optimisation routine see Mobility Computation 4 AutoRange enables the AutoRange optimisation routine see Mobility Computation Options 3 and 4 automatically determine the range of validity of the mobility equation In this sense these optimisation flags are similar to opt
48. e independent variable Vps Ins Vos Ips iS a function of depends on the independent variable Vps Iesi Ves i Current measured at Ves ixAVes with i 0 1 2 Weasurements Points the same for the drain current l V curves Output Characteristic curves Ips Vps SMU Source Measurement Units TC Transfer Characteristic Ips Ves DUT Device Under Test Ossila Ltd Copyright 2009 2015 89 enabling innovative electronics SuperFACT Troubleshooting SuperFACT does not start Action Required Reinstall SuperFACT Read carefully the Installation Guide section of this user manual before installing reinstalling the application SuperFACT opens but it returns message 5018 or 5019 or 5020 or 5021 or 5022 These error codes are associated with an issue with the current Measurement and Application Setting files Action Required None These two file are rewritten every time that an error on a new setting is applied and measurement is started If the error persists contact the technical support at Ossila at info ossila com SuperFACT opens but it returns the error message 5040 Action Required Check the USB connection PC Multiplexer You can use MAX Measurement amp Automation explorer to check whether the multiplexer is correctly connected to the PC by running a self test and or reset If the hardware is properly connected check whether the alias names SwitchControl20 are properly assigned to the equipment SuperFACT op
49. e of AVgs and on the dielectrics charging time delay can vary from a few ms or less to hundreds of milliseconds 21 Set DRAIN Current Limit in Ampere Transfer Characteristics Drain 22 Enter SMU Name Channel these commands are the same as for the Output Characteristic case Set Auto Zero Once 23 Enter the constant drain voltage at which the field effect transistor is operating in linear regime using the input field Vps tinear Vos sat respectively 24 Enter Delay and Current Limit for the DRAIN SMU 25 Select the FET type n type for n type FET or p type for p type FET Ossila Ltd Copyright 2009 2015 47 enabling innovative electronics Eh Ossila SuperFACT Measurement Settings and Device Parameters New Experiment Setting Acquisition Settings Output Characteristic IV Gate SMU Name Ves Start Ves End Gate Sweeps SMU Name Vos Start Vos End AVobs reine fo gt kemo J fo Channel Auto Zero Delay Sec Current Limit Max Gate Current Channel Auto Zero Delay Sec Current Limit Sweep back i J x cancel amp Close t Transfer Characteristic Gate SMU Name Ves Start Ves End AVes SMU Name Vos Linear Vos Sat Meas type _ e CE E Channel Auto Zero Channel Auto Zero Delay Sec Current Limit Hysteresis Delay Sec Current Limit FET Type f U k e ICD Data Analysis Advanced Measurement Transistor Parameters Data Analysis Options Comp tatio Method oltage Lifetime End Measurem
50. eanessues 88 LIST OF SYMBOLS AND ACRONYMS cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccscccccccceccees 89 SUPERFACT TROUBLESHOOTING cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccecceccccccccccccccccccccccccccscceccccceccs 90 GUIDE TO THE READER SYMBOLS ACRONYMS AND COMMON DEFINITIONG cccsccccscsccccccsccccccscccsccsces 94 WARRANTY INFORMATION AND CONTACT DETAILG cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccceecs 95 OPPENDICES a nee net ae eS nt es a A eee eee eee ee eee ene ee ne ete 96 APPENDIX CEA III Ge ROUTINE correran NEE E AEA E 96 APPENDIX Il PMMA GATE DIELECTRIC cccccccccecccecccecccecccecnceecccecuceecceecccecaceesseeeseeeeceeseeesaceesseeseeesaseecseeseseeaces 97 APPENDIX l PEDOT PSS GATE ROUTINE sissciaissowdcnicoidaaiciaud smnrsnudusaitiaewdanioaiadcaiediowddumulastearedanuie auaidauntestinidwresiew ulecewnanedannc 98 APPENDIX IV QIS PREPARATION casintsccdasencndseeeacdacnnss N nenatwasovenseuntenesascovandecsne 99 APPENDIX V NOTE ON TRANSIENT TIME ccccccccccecccecccccccceccceccceccceeccceeseenceeseceeaseeenseeceeesaceesseeseceeaceeseeesesesueenees 100 APPENDIX VI MEASUREMENT FLOWCHART cccccceccceccccccceccceccceecceecccecceecceescceeaseessesenceesuceeseeeseceeaseeseeeseseeasenses 101 Ossila Ltd Copyright 2009 2015 3 enabling innovative electronics Overview The Ossila Fast Auto
51. ects Dev 2 and 17 Security Bit to be set LOW Security Bit to be set HIGH Selects Dev 3 and 18 Selects Dev 4 and 19 Selects Dev 5 and 20 autour Selects Dev 6 and 11 Selects Dev 10 and 15 Selects Dev 7 and 12 Selects Dev 8 and 13 Selects Dev 9 and 14 Selects G5 Selects G8 Selects G7 Output Selects G4 Selects G3 Selects G6 Selects G1 Selects G2 Ossila Ltd Copyright 2009 2015 25 enabling innovative electronics 3 MAX Measurement and Automation Explorer Legal Notice This section is neither a comprehensive nor a partial User s guide to Measurement and Automation Explorer or any other National Instruments hereafter NI products The scope of this section is to provide the Users with the information necessary to install test and maintain the accuracy level of the measurement system Accordingly this section is exclusively intended for Ossila Multiplexer Measurement Unit users and any other use is explicitly forbidden Please refer to National Instruments Measurement and Automation Explorer Help for comprehensive documentation and User guide MAX is an NI product covered by one or more of the following Patents U S Patent No s 6 690 390 7 130 760 7 134 109 7 152 116 Introduction MAX Measurement and Automation Explorer is the National Instruments application that provides direct access to NI hardware According to NI specifications MAX can be used to e Configure your National Instruments hardware and
52. ects on SMU accuracy Devices operating outside the five degree range of the last calibration temperature with the calibration carried out no later than one year from the time the acquisition is carried out have an accuracy that is given by the sum of the factory standard accuracy see above with an extra term depending on the Tempco temperature coefficient where Tempco is express as of the factory accuracy specification per degree C For both NI PXI 4132 and Keithley 2612B Tempco is 0 15 As an example let us suppose that a PXI calibrated at T 25 C is operated at 35 C The PXI is use as SMU with output voltage Vou 20 V From the Voltage Output accuracy table and Eq 32 the uncertainty on the output is given by Accuracy 20 x 0 025 100 10 mV 15 mV The correction factor due to the temperature is Temp_ Accuracy Accuracy x Tempo 100 Calibration temp Meas_ Temperature 15x0 15x 10 22 5 mV The PXI output is then given by Vou 20 V 37 5 mV Ossila Ltd Copyright 2009 2015 88 enabling innovative electronics List of Symbols and Acronyms Vcs Gate Source potential difference Vps Drain Source potential difference los Gate Source current lbs Darin Source current AVgs5 Gate Voltage step width AVps Gate Voltage step width AVgs Drain Voltage step width f x fis a function of the independent variable x Therefore Ins Ves Ips is a function of depends on th
53. en two consecutive acquisitions Biased Finite Measurement Ossila Ltd Copyright 2009 2015 32 enabling innovative electronics The transfer characteristic and transistor figures of merits mobility threshold voltage etc are stored ina single overview excel file one per substrate Conversely the output and ancillary transfer data such as linear fit upper lower fit bounds etc are saved on separate csv files one per device Continuous Measurement multiple measurement cycles of the selected devices executed consecutively or intermittently for a protracted period of time Continuous measurement is designed for gathering lifetime data on the device performance over a user defined period of time whose duration can be at the most infinite The transistor figures of merit are stored as time series ona single csv file per device Combine Measurement Modes The user can combine bias acquisition with continuous measurement in order to carry out lifetime experiments with the devices kept at a constant voltage bias between two consecutive acquisitions A Brief Introduction to Field Effect Transistors A Field Effect Transistor FET is a three terminal device where the source drain current Ips is controlled by the electrical field applied to the semiconductor through the gate dielectric The gate field Ves induces a charge separation within the semiconductor layers closest to the dielectric with these field effect induced char
54. ens but it returns the error message 5042 Action Check the GBIP connection with the SMU Make sure that the Keithley is switched on You can use MAX Measurement amp Automation explorer to check whether the GBIP can see the SMU by right clicking on GBIP under Devices and Interfaces in MAX and then choosing Locate Device on the right side panel of MAX NI SMUs appear under Devices and Interfaces nested under Chassis Note If the SMU is an NI PXI you may need to reboot the computer after turning on the chassis If the hardware is properly connected check whether the alias names KeithleyO or SMU and SMUB for NI PXI are properly assigned to the equipment SuperFACT returns an error when loading a previously saved experiment settings For each saved experiment SuperFACT stores the corresponding settings in two separate files ExperimentName_A ExperimentName_M An error can occurs if one or both settings file is corrupt or not present Action If an error occurs when loading ExperimentName navigate to the data folder located at C Programme Files 86X SuperFACT data the actual path depends on where the Application is saved and locate the files ExperimentName_A ExperimentName_M_ and delete them if present Open the file ConfFileList with MS Notepad this file contains a list of the saved user s experiments and delete the ExperimentName entry ExperimentName AppSettings C Users Pier Desktop UI Super Fact Test Settings Exp
55. ent Cycle f FJ Partition Method F Linear Fit Extrapol hese v a rd E second Derivative Ad Infinitum pepe ane ie d J Fitting Algorithm PM z Bias 30 ossia e322 Least square t acitance F cm Width cm imisati Ves Start Vas End Bias Voltage _ i wie eede q q meas L J L J t J 4 t J t J U Figure 20 Measurement Settings and Device Parameters Ul Data analysis Use this UI section to enter the transistor parameters and set the mobility computation algorithm 26 Select the transistor channel length layout by choosing the appropriate substrate models on the ring menu selector located below the Channel Length table Tip Use the option User and the Channel Length table to assign the channel length on a device by device basis Use the option Constant and the numeric input located below the ring menu to enter a unique constant channel for all the DUT on the substrates 27 Enter the Capacitance in F cm and the Channel Width in cm 28 On the Data Analysis Options section select the mobility estimation algorithm by checking off the Partition Method options of the Extrapolation Method control The Linear Fit Extrapolation option of the Threshold Voltage control will be automatically selected and locked See Mobility Computation for a detailed explanation of the mobility computation algorithm Ossila Ltd Copyright 2009 2015 48 enabling innovative electronics 29 On
56. eptacle e Weight 4 Kg e USB A B cable is included Ossila Ltd Copyright 2009 2015 23 enabling innovative electronics NI 6501 OEM outputs The Multiplexer Measurement Unit is controlled by the NI 6501 board At the NI 6501 board startup and reset the hardware sets all DIO digital I O lines to high impedance inputs As each line has a weak pull up resistor of 4 7kOhm connected to it all pins are set to HIGH The default output configuration of the port pins is open drain This configuration allows the digital output signal to swing to 5V Each port pin can be programmed as a digital input or output To operate the system the DIO lines should be programmed as digital outputs The USB 6501 input ouput signal is constituted of 24 independent DIO lines or channels arranged in three groups of eight Four DIO lines P0 0 PO 1 PO 2 and PO 3 are assigned to select toa particular Device column see figure 8 while the DIO lines used to address each single Device are shared between two columns For example Dev 1 is controlled by the column line P0 0 and row line P0 4 while Dev 16 is turned on off by the lines P0 3 and P 04 The Gates G1 G2 G3 G4 G5 G6 G7 Dev 11 Dev 12 Dev 13 Dev 14 ODev 15 a a a OQOa ea a 6 a Channel A Gates 100 V Max Figure 8 The Multiplexer Measurement Unit addresses Devices by assigning Device columns and G8 are addressed using an exclusive single DIO channel Additionally two
57. erimentName _A MeasSettings C Users Pier Desktop UI Super Fact Test Settings ExperimentName _M TagNumber 0 Date 24 12 201412 23 Note with this action ExperimentName settings are permanently deleted Ossila Ltd Copyright 2009 2015 90 enabling innovative electronics Close the file restart SuperFACT and try to load a different experiment If the problem persists contact technical support at info ossila com e SuperFACT opens it performs the measurement cycle the output is constituted by noise current Possible causes for this are Ossila Ltd O Multiplexer toggle switch is OFF Action Required switch ON Multiplexer Measurement Unit The Lid of Multiplexer Measurement Unit is open Device and Gate LED may be on but no signal will be present on the probes in the substrate holder Action Required Close the Lid make sure that the Lid presses against the interlock on the casing so that the relay is ON when the Lid is shut Check the safety bits have been set no Device or Gate LEDs will light up if the Safety Bits have not been set Action Required Set the Safety Bits See Operation Mode The push fit connector of the test board inside Multiplexer Unit is not present or not properly fitted Action Required Make sure that the push fit connector is tightly arranged on the top of the test board The coaxial cables connecting the PXI 4321s SMUs with the Gate and Drain input of the Multiplexer Unit Channel
58. ess between consecutive measurement cycles During bias stress operations all or some of the Devices can be switched In addition to the devices up to two gate Channel B Drain Source 100 V Max Dev 9 Dev 14 Dev10 Devis eana Aoa Aua Sas A AG Channel A Gates 100 V Max Figure 10 The Multiplexer Measurement Unit used for stress biased acquisition lines can be energised however this is deprecated because the application of both drain and gate voltage to more than one devices can result in a total FET current exceeding the specification of the multiplexer 100 mA The current specifications of the NI USB 6501 limits the number of Drains and Gates that can be switched ON to 22 see figure 10 Due to the topology of the multiplexer network only the following operations are possible 1 Switch on off a single device 2 Switch on off all the devices of a column 3 Switch on off all the devices of a row 4 Switch on off devices pairs The pairs in point 4 are the ones that share the same column row selectors see Table 3 and figure 11 Table 3 Table showing pairs of Devices shown with the same colour which can be switched off together when the Multiplexer Measurement Unit is used as a Lifetime Tester Ossila Ltd Copyright 2009 2015 28 enabling innovative electronics 7 oe gt one oman omi ons omn ome w omn om w osn ony Dev 2 gt oms 2 oen deus oms e o
59. ew file next to the device number See table below for the complete list of fatal errors 5200 Data In Empty no experimental data is received by the Mobility subroutine 5201 Data Out Empty the mobility algorithm does not output any data For example this error can occur if the subroutine processing the data fails to calculate the linear fit 5202 Not enough data points A minimum number of data points are required to calculate the mobility For example at least 11 data point Vesi gt Vos are required for the linear regime mobility subroutine to reliably compute the mobility If such a condition is not fulfilled SuperFACT will not return any figures of merit for the DUT in linear regime Similar condition applies for the saturation regime subroutine 5204 Data not match For Example this error can occur if a p type device is measured but FET type controls is set to n type instead of p type 5205 Device behaviour unknown This error occurs when the TC curves and or its first and second derivative present a behaviour that is not compatible with the standard FET model In case of non fatal error the mobility legend on the UI will show an exclamation mark and the mobility plot background will turn into a red light if a warning message is associated to either linear or saturation mobility warning The mobility plot will turn dark red if both linear and saturation mobility are accompanied with a warning Ossila Ltd Copyright
60. fety feature that gt Dev 1 Channeli B 7 eed 100 V Max gt Dev 3 Dev 4 Figure 7 Interlock on the top panel disconnects the probes when the lid is open Note No measurement can be taken unless the lid is properly closed and the interlock is disengaged Ossila Ltd Copyright 2009 2015 20 enabling innovative electronics The earth cable does not supply power to the unit however it earths the chassis and it is advisable to use it especially if the electrical installation is not already fitted with high voltage current protection such as Residual Current Devices RCD Grounding the chassis unit is a safety precaution and should not affect the quality of the measurement The Multiplexer Measurement Unit is powered via the USB connection to the computer For the Unit to operate properly you must ensure the Unit is connected to a computer USB socket version 2 0 or above capable of delivering at least 500 mA The Unit is intended to be used to measure one Device transistor at a time with any number of Gates switched on It can also be used to carry out stress biased measurements where all the twenty Devices are on but all the Gates are switched off see chapter Lifetime and Stress Biased Acquisition in this User s Manual Note It is also possible to programme the multiplexer to carry out stress biased measurement with two Gates switched on this configuration is however deprecated Important The maximum c
61. functionality and duration of the acquisition Ves Start Ves End and Gate Sweeps specifies the family of output characteristics IV curves to acquire according to the following equation Vasi Ves Start nAV Eq 22 with AV Vos End VGS Start Gate Sweeps 1 Eq 23 Example If Ves start O V Ves eng 60 p type transistor and Gate Sweeps 4 then according to Eqs 22 and 23 four IV curves will be swept at constant Ves gate voltage given by Vssi 0 V 20 V 40 V 60 V Important Due to hardware limitations the maximum voltage that is possible to safely handle with SuperFACT multiplexer is 100 V therefore the controls were programmed not to accept values exceeding this threshold Delay is the total settling time and determines for how long an output is applied before the next action is taken Specifically GATE delay is the lapse time between the application of the gate voltage and the first drain voltage of the sweep Delay must be larger than the time required to the system to deliver a stable output and the duration of the transient of the transistor under measurement see Appendix V According to the National Instruments specification the typical settling time of the PXI 4132 is 300 uS on a 1 V step and a load of 50 percent of the current range setting When the capacitance of Ossila SuperFACT is taken into account and for short BNC cables i e lt 1 m the Delay for fast inorganic transistor can be set at 1 m
62. ges acting as a conductive channel connecting the source with drain The minimum gate voltage required to form the drain source channel is the threshold voltage Vin see figure 13 Ossila Ltd Copyright 2009 2015 33 enabling innovative electronics For an ideal FET an electrical current starts to flow from the source to the drain as the gate voltage Ves exceeds a threshold voltage Vn and a second voltage Vp is applied to the drain In a real device however the current Ip is small but different from zero for Vz lt Ves Important Both gate and drain voltage share the same ground more specifically Vss and Vps potentials are measured with respect to the source terminal In this section the mathematical model describing an ideal field effect transistor is briefly introduced please refer Physics of Semiconductor Devices Organic Filed Effect Transistors and Organic Electronics Materials Manufacutring and Applications for detailed descriptions of the field effect working principles The standard field effect transistor model FET model for short is valid under the condition that the density of the charge Q in the drain source channel depends only on the distance from the source see figure 13 In other words the charge can be approximately described by one variable function i e Q Q y This approximation is referred in the literature as gradual channel approximation Channel length gt 5 um Organic semicon
63. ias Voltage accepts voltage in the range 10 to 10 Volts Important If the total current measured during stress biased exceeds 10 mA SuperFACT will return error code 5600 and the acquisition will be terminated Lifetime acquisition On the Select Devices to Measure and Measurement Type UI select Lifetime to set a lifetime experiment or Lifetime and Stress Bias to programme a lifetime combined with stress biased Proceed to select the measurement type TC and or IV and the device to measure etc as for a standard acquisition Select Apply to open the Measurement Settings and Device Parameters Ul Ossila Ltd Copyright 2009 2015 72 enabling innovative electronics Under Advanced Settings select one of the three Measurement Cycle options which are Finite the acquisition will execute a number of cycles specified in Cycles The maximum number of cycles is 9999 Time Limit the acquisition will stop at a time and date set with the Acquisition End timestamp control Ad Infinitum the acquisition will continue forever Use the STOP button on the main user interface to terminate the Lifetime experiment Use the drop down menu of the Acquisition Rate ring control to set the rate of the measurement cycle The two available options are 1 Maximum SuperFACT will start a new acquisition as soon as the previous one is completed 2 User The User can force an idle time between two consecutive acquisitions The interval is set in Meas Inte
64. ime Vps r 1 2 Initialisation Multiplexer i 0 07 CC Apply Ves j 0 TC Apply Vps r r 0 j j 1 Wait t Gate Delay Wait t Drain Delay N II O Hi Apply Vos Apply Ves i i 1 k k 1 Wait t Drain Delay j 0 Wait t Gate Delay Acquire Ips Vps Acquire lesi Vps i Acquire Ips x Ves NO Mi LL Yes i Yes lt n Log CC data Log TC data Yes Yes NO Yes Yes AKH i STOP Ossila Ltd Copyright 2009 2015 101
65. inear and saturation transfer characteristic can be described using Eqs 3 and 6 respectively see figure 14 Ossila Ltd Copyright 2009 2015 83 enabling innovative electronics Measurement Type Mobility computation Mobility Optimisation Flag TFT OFET Behaviour Method None Cut off AutoFHWM AutoRange Finite Measurement DUTs with similar well defined behaviour medium large current Linear Fit Method Deprecated Recommended Recommended Recommended gt 80 100 uA Mobility present a peak Finite Measurement Partition Method s DUTS with similar well defined Derivative Method h K K behaviour medium large current Linear Fit Method Deprecated Recommended OK gt 80 100 uA Mobility does not peak K Recommended K Finite Measurement Partition Method OK Recommended Recommended DUTs with different well defined Derivative Method OK Recommended OK OK OK behaviour medium large current Linear Fit Method Deprecated Deprecated Recommended Recommended gt 80 100 uA Mobility present a peak oe behaviour medium large current Linear Fit Method Deprecated Recommended OK issue OK issue gt 80 100 uA Mobility present not present a peak Finite Measurement Partition Method OK issue OK issue DUTs with different ill defined Derivative Method OK issue OK issue oe behaviour medium large current Linear Fit Method Deprecated OK issue OK issue OK issue gt 80 100 uA Mobility presen
66. int subsets the partition method Be algorithm uses to calculate the mobility see Partition fpo Flfoo5 Method Min allowed value 5 Max allowed value 10 Partition Method R squared sets the minimum R squared goodness of fit the experimental data fit is required to satisfy for the mobility to be returned without a warning flag Min allowed value 0 90 Max allowed value 1 Linear Fit Min Sample sets the minimum number of data points required by the Linear Fit Method algorithm to calculate the mobility Min allowed value 10 Max allowed value 50 Linear Fit R squared specifies the minimum R squared goodness of fit the linear fit must satisfied in order for the mobility to be returned without a warning flag Min allowed value 0 90 Max allowed value 1 Ossila Ltd Copyright 2009 2015 53 enabling innovative electronics Lifetime Data storage volume Data Storage Volume specifies the disk volume partition used as repository for the life data L D C Volume free space GB fo id ake I acquisition To be used as repository volume a disk partition must have at least 1 GB of free space Important You can use external disk partition as well such as USB memory card server s volumes etc If you use an external memory storage facility make sure that the connection with the host computer is stable and reliable so to avoid data acquisition failure due to the peripheral becoming disconnected and or irresponsive Sa
67. ion 2 with the difference that while the validity range Vstart Vena for the figure of merit is fixed for all the DUTs by the user at the beginning of the acquisition Cut Off flags 3 and 4 enables SuperFACT to automatically calculate the appropriate Vstarty Vena for each DUT For a detailed explanation of the panel control Advanced Measurement Lifetime Bias refer to the chapter Lifetime and Stress Biased Acquisition below Ossila Ltd Copyright 2009 2015 71 enabling innovative electronics Lifetime and Stress Biased Acquisition Stress biased acquisition On the Select Devices to Measure and Measurement Type UI select Stress Bias and proceed to select the measurement type TC and or IV and the device to measure etc as for a standard acquisition Select Apply to open the Measurement Settings and Device Parameters UI Under Advanced Settings enter the number of measurement cycle in Cycles The minimum number of cycles is 1 the maximum is 4 On the Acquisition Rate drop down menu select User to force SuperFACT to wait a user defined amount of time before starting the successive cycle Meas Interval is used to enter the interval between two successive acquisition cycles This control accepts value in the format hours minutes seconds The Bias On option of the Bias ring control drop down menu is used to enable the voltage bias capability The desired voltage bias is entered through the Bias Voltage input field B
68. ive system endowed with Core i7 Intel microprocessors Eo E Ossila Ltd Copyright 2009 2015 enabling innovative electronics Two flexible coaxial cables endowed with BNC and I O connectors One USB cables with Standard A and Standard B plugs on the opposite ends One GPIB cable with USB connectors Also included Three Power Supply Leads Cords for the monitor computer and the SMU EC Declaration of Conformity In line with directive 2004 108 EC of the European Parliament and of the Council and directive 2006 95 EC of the European Parliament and of the Council Ossila Ltd Copyright 2009 2015 enabling innovative electronics Manufacturer Name Ossila Limited Manufacturer Address Kroto Innovation Centre North Campus Broad Lane Sheffield S3 7HQ Item OFET testing rig for use with PXI system Model number SuperFACT1 Software release Super FACT v1 0 Specifications of product under harmonised standards 2004 108 EC EN 61326 1 2006 Electrical equipment for measurement control and laboratory use EMC requirements Part 1 General requirements IEC 61326 1 2005 EN 61326 2 1 2006 Electrical equipment for measurement control and laboratory use EMC requirements Part 2 1 Particular requirements Test configurations operational conditions and performance criteria for sensitive test and measurement equipment for EMC unprotected applications IEC 61326 2 1 2005 2006 95 EC
69. l configuration control through MAX For this drivers install the full development support to allow full configuration control through MAX and the soft panel NI native User Interface functionalities Ossila Ltd Copyright 2009 2015 13 enabling innovative electronics e When prompted with the query Windows cannot create a shortcut here Do you want to place the shortcut on the desktop instead select Yes Windows will automatically place the shortcut on the User s desktop Important The icon itself i e the executable must not be moved to any other location on disk otherwise the application will stop working properly Enabling data settings storage folder The application allows the user to save the Experiment Acquisition settings in an appositely created data folder contained in C Programme Files 86X SuperFACT If you are using Windows 7 8 8 1 or later distributions you must enable the application to write the data folder supportfiles Properties To change the data folder access permission Navigate to C Programme Files Object name C Users Pier Desktop builds Ossila IV Probe Tim 86X SuperFACT and right click the data Group or user names 82 SYSTEM aie F Fie SHEFFELDUK ey e Onthe drop down menu click on 2 Administrators SHEFFIELDUK Administrators Properties and on tab menu of select Secu rity l To change permissions click Edit e Under Group or user n
70. les with time stamp are generated These files are the same as files 1 and 2 for the finite acquisition mode case The times series of the OFET TFT figures of merit for saturation and linear regime are saved in two separate files one per each DUT The experiment settings are also recorded on a header file 18 it is possible that an Excel instance remains open in the background i e not visible to the user even after any open Excel files have been closed Every time that a finite mode measurement is initiated SuperFACT opens an Excel instance in background mode This instance may remain open if SuperFACT fails to close it because for example an execution error has occurred If Excel is still open in the background SuperFACT will try to close this instance and ask the user to restart the acquisition Ossila Ltd Copyright 2009 2015 58 enabling innovative electronics Supposing that the user has selected disk partition D as data storage volume the complete logging tree for a life time file will then be D SuperFACT_Data UserName ExperimentName SubstrateName Devn files Where SuperFACT_Data is data logging directory that SuperFACT automatically create in the storage volume D while UserName ExperimentName and SubstrateName are the string entered in User Name Experiment Name and Substrate Type input field on the Select Devices to Measure and Measurement Type UI Devn is the folder associated with the n th DUT and file
71. lity peak peak if does not exist it locates the maximum of the derivative which should be located at Ves eng and then dips dVGs analyses the behaviour of to located Vstart Ossila Ltd Copyright 2009 2015 80 enabling innovative electronics This page is intentionally left blank Ossila Ltd Copyright 2009 2015 81 enabling innovative electronics Issue and caveats with SuperFACT OFET mobility algorithm Eqs 3 and 6 are only approximation of the actual OFET behaviour Due to the complex nature of charge transport dielectric effects surface traps environmental degradation and environmental electromagnetic noise affecting the measurement of low currents the mobility extrapolated from the equations above is not always reliable In the following non exhaustive list typical common issues with interpretation of mobility data is presented 1 Mobility values extrapolated outside the range of validity of Eqs 2 and 3 can still be erroneously flagged as valid maximum mobility by SuperFACT The User should always check that the maximum mobility is computed in correspondence of data set belonging to the range of validity of Eqs 2 and 3 In case the Linear Fit method is used the R squared value can be used to evaluate the goodness of the linear fit Due to impurity degradation etc a linear relation could not exist between the voltage and the current in both saturation and liner a regime Consequentl
72. loit the performance and accuracy of the Ossila Multiplexer Measurement Unit For explanation purposes it is assumed the Ossila Ltd Copyright 2009 2015 enabling innovative electronics source meter being used as a SMU is the Keithley source meter model 2612B The system is compatible with Keithley 26XX double channel SMU and NI PXI 4132 The system is composed of the following parts e Ossila Multiplexer Measurement Unit containing signal board with twenty probes and eight gates NI USB 6501 OEM and control and LED display electronics e Keithley 2612B e GBIP USB HS e Two flexible coaxial cables endowed with SMU I O Connector e One USB cables with Standard A and Standard B plugs on the opposite ends Before starting to assemble the components make sure that the cables and connections do not present any damage or alteration that can compromise the safety of the personnel in charge of the measurement unit and or affect the performance of the device In addition you must read the Keithley 2612B System SMU manuals first which are provided with the SMU with particular reference to the Safety information Do not operate any third party devices outside the operational range specified by their respective manufacturers Ossila must not be held responsible for any injury or damage due to the non strict observance of the guideline outlined in the User Manuals of any third party equipment provided as part of SuperFACT Equipment
73. lug the Standard A USB end of this cable to any USB 2 0 or higher socket on the computer casing The USB socket must be capable of delivering enough current to switch the multiplexor channels ON OFF 500 mA Note The USB ports on the back of the desktop computer can usually supply more electrical power that the ones located on the front 5 The Ossila Multiplexer Measurement Unit comes supplied with an earth plug this does not supply power to the unit Its use is advised in case your electrical installation is not equipped with Residual Current Devices RCD The earth plug is a safety precaution and should not affect the quality of the measurement Ossila Ltd Copyright 2009 2015 11 enabling innovative electronics Figure 1 USB cable and coaxial cables BNCs connection Channel A is the Gate Channel B is the Drain Ossila Ltd Copyright 2009 2015 12 enabling innovative electronics SuperFACT software installation To install the application e Insert the installation CD in the target computer e Copy the rar folder containing the application to the target computer e Uncompress the folder and browse to the executable file called setup contained in the Volume folder Note Do not move modify or delete any file or folder contained in the Volume folder prior completion of the installation e Run the executable and follow the instructions to install the application in C Programme Files 86X SuperFACT e The dri
74. ly store OTS under inert atmosphere N2 glovebox However in order to get a good coating on a substrate a small amount of water is beneficial for the cross linking process For this reason and also the amount of solvents used we generally prepare OTS substrates under ambient conditions The choice of solvent is also critical and we have found cyclohexane to work well using the following procedure OTS preparation procedure e OTS stored under inert atmosphere N2 glovebox e Small amount of OTS mixed 1 9 with anhydrous cyclohexane in inert conditions glovebox e Clean substrates placed in a beaker with lid and immersed in HPLC grade cyclohexane under ambient conditions e OTS cyclohexane mixture removed from glovebox and small amount added to beaker to produce overall concentration of 1 mMol e Left under ambient conditions for 20 mins e 2x dump rinses in cyclohexane e Baked on hotplate under ambient conditions at 150 C The above recipe should result in a water contact angle of around 110 C or greater Ossila Ltd Copyright 2009 2015 99 enabling innovative electronics Appendix V Note on transient time If the capacitance and resistivity component of the measurement apparatus and of the DUM Cpuy and Rm are different from zero a constant voltage Vo applied at time t 0 will not instantaneously transfer to the DUM but it will instead be governed by the following equation Voum t 1 enc Eq Al where Vpy
75. mated Characterisation and Test SuperFACT system is designed to make testing and characterisation of organic field effect transistors as simple as possible when combined with Ossila s FET substrate systems Fabrication of devices can be as simple as spin coating a material on a test chip and loading it into the system The automated test routines will then perform output and or transfer sweeps and automatically calculate the key OFET TFT parameters for each of the twenty devices on the substrate SuperFACT multiplexor makes use of a 2D array of gold coated spring loaded probes POGOS to connects the devices to the source meter s while the transistor to measure are selected through a high performance switching network At the core of the measurement system is a computer controlled Keithley dual source measure unit with maximum output of 100 V and accuracy up to 10 pA The Multiplexer Measurement Unit is highly specified to introduce the minimum amount of distorsion in the measurement as possible The resistance introduced in each Drain path is lt 1 Q leakage noise current is lt 500 pA and Capacitance is lt 300 pF This combined high level of output voltage and accuracy makes for maximum experimental versatility and speed Ossila Ltd Copyright 2009 2015 4 enabling innovative electronics Safety Warning To avoid safety hazards obey the following Do not leave devices with applied bias or current unattended as a power failure
76. n on the control bar of the Settings panel For NI PXI e On the left side panel click on the arrow next to NI PXle 1071 Chassis 1 to expand the associated tree menu e Right click on NI PXle 83060 and change the default alias name to Remote Control e Navigate to the two SMU units NI PXI 4132 and rename them as SMUA unit in slot 2 and SMUB unit in slot 3 These alias names are case sensitive e Save the new settings Ossila Ltd Copyright 2009 2015 30 enabling innovative electronics Note MAX allows the user to reset self test and self calibrate if applicable any NI hardware For VISA instruments such as Keithley MAX is shipped with an equivalent VISA Test Panels In addition it gives direct access to these instruments via text based command strings These functionalities usually require that the corresponding full hardware drivers are installed on the host computer see SuperFACT Software Installation tf Model 2612B KeithleyO Measurement amp Automation Explorer D File Edit View Tools Help Ea My System bel Seve K Refresh 5 Open VISA Test Panel 3 Communicate with Instrument 2 Interactive Control Data Neighborhood 4 g Devices and Interfaces Back fy T ASRL10 INSTR LPT1 Settings 4 amp GPIB USB HS GPIBO Model 2612B KeithleyO Name KeithleyO p z Rename my resource NI USB 6501 SwitchControl20 a e NI USB 6501 USB1 Pillans a Network Devices
77. nce of high voltage electrical equipment Figure 19 Coaxial cable internal details Figure 16 Coaxial cable Connection to backshell e SuperFACT opens runs and acquires measurement properly but suddenly it stops Check the content of the error message if any and take action accordingly Ossila Ltd Copyright 2009 2015 92 enabling innovative electronics Possible reasons for a sudden interruption of the acquisition and or stop of the programme are the following o The lid of the multiplexer is open As the lid open the security system interrupts the connection with the SMU The aperture of the lid and the consequential sudden abrupt variation of the PXI load can force one of the PXI to generate an error which in turn stops Ossila SuperFACT o One or more cables are inadvertently unplugged Depending on which connection is unplugged Ossila SuperFACT may stop with an error message or acquire the background noise only Action Required Refer to the Required Actions for the same issues detailed above Warning If SuperFACT stops but the Output Enabled LED of one or both PXI is still ON you must programmatically shut down the PXI Run a dummy acquisition few points for a single device so that the PXI s with Output Enabled active are gracefully and safely switched off When the Output Enabled LED is ON Shock Hazard exists Ossila Ltd Copyright 2009 2015 93 enabling innovative electronics
78. ncecaeesceencesceeaceseensesaes 55 MEASUREMENT SETTINGS AND DEVICE PARAMETERS ccccceccecccccececccenceecceeacecccencecccencesaceneeeacesseenceseeensesseensesscessenas 60 Ossila Ltd Copyright 2009 2015 2 enabling innovative electronics LIFETIME AND STRESS BIASED ACQUISITION ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccees 72 STRESS BIASED ACOUISITION specs sieadicen ces acsicie sass EEE wadiicwn aesnasien aun ubninbuss cay saveuteohnsarewe EE 72 NV TWN PAN SUMO EEEE 72 MOBILITY COMPUTATION aaneneesssssesossssssssossssssssossssssssossssssssossssosssossssssossssesssssssosssssssssssssssssosssssssssssssosssosssso 74 VINE Be TIEMEN AA nen A E 74 DERRAT E A THAO aE AREARE TAEAE AAE AARE EEEE E AE EEEREN 74 PARTON MET 1 aAA 75 MOBILITY ALGORITHMS INTERVAL OF VALIDITY ISSUES AND CAVEATS cccececcsccececcccuceccccueeacuceeseccceeeeeaceeeesaeeseeeeusenses 77 MEASUREMENT AND ACCURACY ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccceccccccccccccccccccccscccccees 86 TEMPERATURE AND SELF CALIBRATION cccceccecccccceccecacecceeccecccencecacencesacesceenseceeesacescesasesseccesceesceseeeasecseessesseeneenas 86 CALCULATION OF THE MEASUREMENT ACCURACY csicicieovieceedvcodsitinuiecxesiedeantneasnandeaneandiandinea sua EAEE AE i 86 TEMPERATURE EFFECTS ON SMU ACCURACY cceciscsvscdcserescddeceecdenustestanesvasseoerascdseceweelbasseuwsensnaedcnsseevecerseunmecav
79. nded enabling this option to neatly save the data files in a single folder per substrate If you wish to add files to an existing substrate folder disable this option and use the Folder command to select the existing substrate directory Time Stamp forces a time stamp to be added in front of the file and folder name command not available in continuous measurement mode Tip Enabling time stamp helps better keep track of past experiments while avoiding name conflict when using the Start button to run repeated acquisition of the same substrate Data logging tree Important SuperFACT requires MS Excel 2007 or later version to be installed on the host computer in order for the application to execute properly Ossila Ltd Copyright 2009 2015 57 enabling innovative electronics In finite measurement mode the output and transfer data are saved in two separate files one per device In addition the main figures of merit and the transfer curves are also collectively saved in an overview file so as to facilitate statistical analysis and data representation The complete data logging structure for finite measurement mode is the following IV file It contains the output characteristics and the gate leakage current TC file Depending on the measurement settings chosen it contains the linear and transfer characteristics the entire set of transistor figures of merit as function of the gate voltage if applicable the linear fit with u
80. of FET R amp D devices can show a different behaviour for Ips Vgs Lack of monotonic of the TC curves can be ascribed to poor electromechanical contacts between the DUT and the test fixture materials and or interface issue and environmental degradation caused by oxygen and or light For example an untested new material can show a decrease in drain current for high voltage due to current voltage degradation carrier traps etc In addition for extremely low current the non monotonic Ips can be due to the noise degradation of the signal Condition 4 is equivalent to condition 3 in the part requiring the first derivative to be positive a negative derivative means a decreasing current In addition it demands the mobility to have a simple dependence on the gate voltage Here simple means that for a gate dependent mobility the mobility can either be a monotonically increasing function of the gate voltage or peak at some point Vice The last case is relatively common for OFET FET and it is known as mobility degradation Example Let us suppose that Ves max is the largest in absolute value gate voltage swept For a well behaved FET the maximum current is then Ima Ips Ves max For an ill behaved FET the current Ips can present a maximum at some Ves lt Ves max If only one of such a maximum exits SuperFACT will discard any experimental data Vses gt V s However if lp shows a more complicated behaviour with more than one local maximum fo
81. old voltage through Eq 15 is referred in the literature as Second Derivative Method For OFET TFT devices especially for non optimised R amp D and or low mobility DUTs a larger switch transition region AV manifest itself in broad peak or even complete absence of this feature at V To complicate matter a gate voltage dependent mobility i e a a V s will also result in a broader less defined peak at V with the second derivative method becoming non applicable in the worst case scenario Figures of merit The figures of merit or transistor performance parameters are those measureable features that define the performance of a transistor The figures of merit that are automatically calculate by SuperFACT are mobility u Threshold Voltage Vn and Vin OFF current lorr minimum current Inn ON current lon ON OFF ratio lon lorr and Min Max ratio lon Imn Two additional figures of merit that are not calculated by SuperFACT are the ON OFF frequency f and the subthreshold swing S render f LVps Q7eL2 Eq 16 kpyT OV kpT CoxtC S In 10 tb 2 DS In 10 wb zox D q Olps q Cox Eq 17 1 gt A Ortiz Conde et al A review of recent MOSFET threshold voltage extraction methods Microelectronics Reliability 2002 42 583 596 Ossila Ltd Copyright 2009 2015 41 enabling innovative electronics Here Lis the channel length k the Boltzmann constant T the temperature q the electrical charge and Cp
82. oles and solvent incompatibility with solution process gates While there are many non polar solvents that will dissolve PMMA very well these often also dissolve polymeric semiconductor layers We have therefore found that butanone gives the right combination of solubility for the PMMA with a moderate boiling point ideal for film forming properties and with little effect on most polymeric semiconductors such as P3HT PBTTT and PCDTBT it will however still dissolve small molecule materials such as TIPS pentacene and PCBM Process routine for PMMA gate dielectric e PMMA with Mw 120 000 bought from Sigma Aldrich e Dissolved in butanone at 100 mg ml using stirbar and hotplate set to 80 C e Cooled for 10 mins before filtering with 0 45 um PVDF syringe filter e Spin coat using a static dispense of 100 ul and fully coat the substrate before spinning e Spin speed of 1000 RPM for 30 seconds fastest acceleration e Bake at 105 C for 5 mins to fully evaporate solvent and take the PMMA to the glass transition temperature to reduce leakage e Solutions stable for at least several weeks The thickness of the resulting layer should be around 1200 nm and we generally obtain a film uniformity of better than 10 Ossila Ltd Copyright 2009 2015 97 enabling innovative electronics Appendix Ill PEDOT PSS Gate Routine The use of a solution processed gate enables rapid fabrication without the use of costly and slow vacuum deposition equipment H
83. oltage at which the transistor is operating in saturation mode Drain Voltage Saturation Mode is the drain voltage at which the transistor operates in saturation mode i e Ios Vps Isat With lsat Constant drain saturation current reads from the l V Output Characteristic curves Delay is the PXI DRAIN settling time For Transfer Characteristic OFF gt ON measurement indicative DRAIN and GATE Delay time are 10 to 200 ms and 10 to 100 ms respectively The actual delay time depends on dielectric capacitance organic semiconductor device architecture and measurement settings Current Limit specifies the maximum drain current ps that the DRAIN source is allowed to generate across the target OFET for example as the User s selected gate voltages are applied to the target itself i e Current Limit refers to ps Ves for any Vps applied Data analysis Transistor parameters T poo Channel length table is used to enter the OFET TFT channel length in um for the DUTs that have been previously selected on the Measurement Settings and Device Parameters UI The input table field needs to be enabled by selecting one of the options on the ring selector below the table itself Channel length ring selector allows the user to select the appropriate substrate channel length layout The available options are User Selection The User directly input the channel length using the Channel Length tabl
84. omatically estimate the mobility with the partition method SuperFACT executes the following algorithm 1 The input and output points defining the Transfer Characteristics curves Vesi Ipsi are divided into subsets of N point each with 5 lt Ns10 User s defined quantity specified on Advanced SMU and Acquisition Settings with Partition Method Set Size control 2 For each subset the Best Linear Fit and its respective slope are estimated The mobility is then computed using Eq 4 for the Transfer Characteristic in Linear Regime and Eq 8 for the Transfer Characteristic in Saturation Regime see figure 26 3 The resulting mobility u u VE is then plotted as function of the gate voltage with VE median pints of the data point subsets used to calculate the liner fits 4 For both linear and saturation regime the maximum mobility is highlighted on the mobility plot and reported on the data file providing that the linear fit R squared parameter is larger than a User s defined threshold specified on Advanced SMU and Acquisition Settings through the Partition Method R squared control The recommended value of R squared for this algorithm is 0 99 If no data point set satisfies this condition the mobility plot turns red with an exclamation mark in the plot legend flagging which mobility does not fulfil this requirement A warning message flag is also logged in the data file by printing an acclamation mark next to device number For each
85. on through MAX is available for supported hardware only Note Execute the self calibration 10 15 minutes after the SMU are switched on to allow enough time for both SMUs to reach a stable internal temperature Set the chassis fan toggle on the back panel of the chassis on the high position to allow better control of the internal temperature and reduce output input noise Calculation of the measurement accuracy Note The example below applies to any SMU For information about range accuracy temperature correction factors refer to the SMU manuals For a SMU the transfer function is given by y gxtb Eq 32 where g is the gain b the offset x the input and y the output The transfer equation describes how a nominal output x is sourced by the SMU For an ideal SMU b 0 and m 1 and therefore y x 26 NI DC power Supply SMU Help Ossila Ltd Copyright 2009 2015 86 enabling innovative electronics For an actual SMU however m 1 and b 0 For example for the NI PXI 4132 current measurement accuracy at 23 C 5 C is reported in the table below from NI PXI 4132 Specification 0 028 0 1 pA 0 028 1 0 pA 100 mA 100 nA 0 028 10 pA Here resolution means the smallest difference in current that the SMU is capable of discriminating while accuracy is the measurement uncertainty From this table and Eq 32 the accuracy of a current 2mA measured in the 10 mA range is then given by m 0 028 x 2mA an
86. ormation The values provided here are typical at the time of manufacture and may vary over time and from batch to batch Ossila Contact Details Kroto Innovation Centre Technical Contact North Campus Dr James Kingsley Broad Lane j kingsley ossila com Sheffield S3 7HQ UK Customer Services Contact Lucy Pickford Phone no 44 0 114 213 2770 pickford ossila com Fax no 44 0 800 098 8142 Ossila Ltd Copyright 2009 2015 95 enabling innovative electronics Appendices Appendix Cleaning Routine The starting point for any good organic devices is a pristinely clean substrate However physical cleanliness i e the absence of dust and particulate matter is often different to a chemically clean surface free from residues and contaminants To ensure that substrates are pristinely clean we generally start by using a hot Hellmanex III solution which acts as an electronic grade detergent Keeping the substrates vertical during cleaning also helps to ensure that any particulate matter falls off the substrate When using Hellmanex III it is also important to use a hot dump rinse and an IPA sonication to ensure that no residues are left behind In addition we also find that for ITO based substrates it is useful to use a hot sodium hydroxide NaOH sonication to provide a more hydrophillic surface and avoid the need for a plasma ash The below cleaning routine is generally found to provide good surface preparation although ex
87. owever any solution processed gate also needs to be solvent compatible with the gate insulator and preferably organic semiconductor as well It should also have the right wetting and film forming properties to enable good even substrate coverage We have found that high conductivity formulations of PEDOT PSS with additives to control the wetting and drying process give good performance with the below recipe working well Solution components Orderto add _ by weight PH1000 PEDOT PSS a R5 O N Methyl 2 pyrrolidone 2 25 Triton X 100 E isopropyl Alcohol aooo fa Fabrication Routine e Mix the above components in the given order using a magnetic stir bar but not heated PEDOT PSS will phase separate if heated above 40 C e Spin coat using a 50 ul dynamic dispense at 4000 RPM e Spin for 2 mins until fully dry e Solutions stable for several days but resistivity increased over time Using the Ossila ITO OFET substrates this should result in a resistance between the two cathode connection terminals of around 250 Q Ossila Ltd Copyright 2009 2015 98 enabling innovative electronics Appendix IV OTS Preparation Getting a good OTS preparation on a substrate surface can increase mobilities by orders of magnitude however getting a good monolayer can be hard to achieve In general OTS will polymerise over time when exposed to ambient conditions resulting and stringy white aggregates in the bottle As such we general
88. pogos during the measurement The gate channels can be set to operate in standard or match mode In standard mode any selected gate pogos will remain engaged for each sweeps no matter which device is under measurement Conversely in match mode the gate pogos are alternatively switched ON OFF in a manner such that only the gates belonging to the same column as the DUT are activated see figure 22 For example when device 1 to 5 is measured gates 1 and 2 are energised while gates 3 to 8 are disengaged and so on Ea pa 6 fiom Figure 22 Gate 1 and 8 are always ON left side only the two Gates belonging to the same column as the DUT are energized right side The gate options accessible from the gate ring selector are All for each DUT the eight gate channels pogos are all engaged Edge Only the leftmost 1 and rightmost 8 gate channels are energised during the IV SWEEPS User the user can select the gate channels to activate The corresponding pogos will be energised no matter which DUT is measured Match only the two gates belonging to the same column as the DUT are engaged while the other gate pogos are kept idle UserM the same as Match but with the gate pogo s to engaged during measurement manually selected by the user Ossila Ltd Copyright 2009 2015 56 enabling innovative electronics Tip Use the option Edge to measure TFT OFET fabricated with Ossila masks or with equivalent masks i e wi
89. pper and lower bounds or alternatively the first and second derivative of the transfer curves JPEG file It stores the IV TC mobility etc plots as screenshot on the output UI Overview file contains the OFET TFT figures of merit and both linear and transfer curves for all the DUTs measured during the session If both Create Folder and Time Stamp options are enabled the data logging tree is Volume Folder d_m_Y h_m_s_ File Name_ V_Devn d_m_Y h_m_s_ File Name_TC_Devn d_m_Y h_m_s_ File Name_Devn d_m_Y h_m_s_ File Name_ V_Overview Where Folder and File Name are the path and the string specified in the Folder and File Name inputs of the Select Devices to Measure and Measurement Type UI respectively d_m_Y h_m_s is the time stamp with day d of the month m and year Y The current time is specified by h hour m minute and s second Finally n in Devn is the DUT number Important When operating in finite measurement mode SuperFACT requires exclusive use of MS Excel Consequently you must close any open Excel files before starting a measurement and avoid using this application while a measurement is underway otherwise SuperFACT may fail to store the data and return an error If an instance of MS Excel is open when a measurement session is started SuperFACT will prompt the user to close any open Excel files and then restart the acquisition In lifetime mode for each acquisition cycle and for each DUT a IV and TC fi
90. pressed in this manner the square root of the TC current 52 becomes a linearly function of the gate voltage and g can therefore be calculated exactly the same way as HUn by inverting Eq 7 _ y 2L Hsat Z Asat wc Eq 8 with sat slope of Isqt Ves Gate dependent mobility Eqs 5 and 7 are simply the equations of straight lines This holds true as far as the mobility is an independent function of the gate voltage in the range of validity of these two equations Conversely if the mobility is gate voltage dependent so must be the slope a and Eqs 5 and 7 are no more representing straight lines In turn equations 4 and 8 now read Alin L 1 Eq 9 2 GRIP 2L Usat Ves vt WC Eq 10 In Eqs 9 and 10 the slope of Ips Ves has been replaced with the derivative of the drain current with respect to the driving voltage Ves Ossila Ltd Copyright 2009 2015 38 enabling innovative electronics Note Since the derivative of a function y f x at a point yo is the slope of the tangent curve of f x at Yo the derivative of straight line y ax gives the same numerical value a for any point y belonging to y In other words the slope of the linear fit of a straight line y f x and the derivative at any of its points yo are the same Therefore for a straight line Eqs 9 and 10 reduce to Eqs 4 and 8 Most importantly to the extent the drain current is weakly dependent on Ves Eqs 4 and 8 can be consi
91. puter The NI 6501 OEM Board also supplies the power to the Multiplexer Unit via the USB connection to the computer To access the substrate holder open the multiplexor lid see figure 2 The holder consists of a push fit bracket and a 2D array of twenty eight POGO probes When a substrate is placed in the holder with the lid secured with its four screws the probes provide low resistance contact with all the device and gate pads on the substrate wa oe 5 rows of Drain Probes f papa f 3 4 lt Row of Gate Figure 2 Substrate holder containing twenty Drain Source probes and eight Gate probes The Gate connections are provided by the bottom row i e by the row nearest to the front panel of the Multiplexer Unit see figure 2 It follows that the substrate must be placed face down with the gate side nearest to the front panel see figure 3 Ossila Ltd Copyright 2009 2015 16 enabling innovative electronics Figure 3 Orientation of the substrate When the substrate is placed in the holder each device is probed by a pair of Drain and Source probes If the device is switched on the Drain probe connects the Drain of the device to the High output of the DRAIN SMU while the Source is connected to the DRAIN SMU ground If a particular Gate is switched on the corresponding Gate probe connects it to the signal generated by the GATE SMU Figure 4 shows which column of POGOS are Drain or
92. r Vss greater than the threshold voltage SuperFACT will not return any figures of merit for the DUT since the device cannot be considered a proper transistor Quick Start To start an acquisition the user needs first to configure the SMU set the multiplexer to sweep the required DUTs and finally enter the sweep parameters These instructions are inputted through three configuration and setting User Interface UI front panels See SuperFACT UI Front Panels for a detailed description of each Ossila Ltd Copyright 2009 2015 43 enabling innovative electronics Follow the set of instructions below to programme a simple finite measurement acquisition of a standard high density Ossila substrate 1 Onthe main front panel click on Add Settings to open the Advanced SMU and Acquisition Settings Ul On this Ul in the bottom left corner locate Lifetime Data Storage Volume and select which disk volume disk partition to use as data storage repository for Continuous Lifetime experiments Click on the ring control to see the available disk partitions and select one of them D for example as lifetime repository Note If you are using NI PXI 4132 you must also select the appropriate PLC Power Line Cycle located on the SMU Settings setting control cluster of this UI see Application Settings SMU Settings Ossila SuperFACT Advanced S Load Default Settings Application Settings Acquisition settings OS Control Application
93. r is entering the ON region for Ves gt Vz The transition however is not step like and an extra AV voltage is required on top of V to drive the transition to its operative ON state For inorganic FETs as the gate voltage crosses the threshold the current increase is so steep that we can safely assume the FET to be fully ON for Ves gt Vin tAV with AV Von lt lt 1 with AV extra voltage required to move the DUT from the OFF to the fully ON region Inorganic standard FETs are therefore characterised by a very narrow ON OFF transition region For OFET TFT the current increase for Ves gt V7 can far more gradually low mobility with a wider ON OFF transition region Nevertheless it is still reasonable to approximate Ips as in _ bal with PEF K 1 for Ves lt Vr lon for Vgs gt Vr AV Eq 13 where Ion is given by Eq 1 or Eq 6 while orp is the current for Vgs lt Vr For an ideal FET with lorr O and AV 0 steep ON OFF transition the derivative of Ips with respect to the gate voltage would then be a step function i e dlorr eS Vre lt V dips _ aVcgs GS T dV s dl cs q 0 for Ves Vr aVcGs Eq 14 with a slope of the TC curve If Eq 3 is differentiated again and if a is constant the resulting function will be zero everywhere with the exception of the threshold voltage Vm where the derivative is infinite 12 TTL Transistor Transistor Logic is a protocol whereby a signal state is assumed to
94. rebooted after the PXI chassis is turned on in order to link the PXI to the target PC If the reboot is not executed neither MAX nor SuperFACT will be able to communicate with the PXI hardware To configure multiplexor and SMU take the following actions see figure 12 e With the system fully set up i e with every hardware units properly connected see Equipment Setup open NI MAX and click on My System and the on Devices and Interfaces Multiplexor through NI USB Card e Search for Dev1 the identification number may be different see explanation above and right click on this entry to show the drop down menu options e Select Rename and rename Dev1 as SwitchControl20 this name is case sensitive For Keithley SMU e In Devices and Interfaces search for the GBIP device and with the mouse left click to expand the list of devices connected to the target PC through the GBIP interface e If the list is empty on the control bar located on the top side of MAX right panel click on Scan for instrument e Providing Keithley 26XX SMU is properly connected and switched on MAX will identify this SMU with its VISA resource name GPIBO NUMBER INSTR e Under Devices and Interfaces click on the VISA NAME to show the Settings panel for this VISA instrument on the right side panel of MAX e On the Settings panel go to Name and replace the default alias name with KeithleyO case sensitive e Save the new settings using the Save butto
95. red at these gate voltages and so on For each subset the linear fit is calculated and its slope is used to calculate the mobility through Eqs 4 and 9 The motilities so obtained are then plotted as function of the average gate voltage for each subset which in these example are 5 5 V 15 5 V 25 5 V and so on up to 75 5 V Figure 27 shows the mobility calculated with the partition method using Eq 9 for each data set and the derivative method Eq 11 In both case the data are not processed through any filter so that the effect of the noise on the derivative can be fully appreciated On figure 27 the derivative is calculated using the both backward numerical differentiation BW and the more error robust two point method TW see Eq 30 Since the numerical differentiation amplifies the measurement uncertainty noise the resulting mobility curve can be non smooth and noisy On the other hand the modified linear fit method extrapolates the mobility over ten data point set and is therefore intrinsically more robust against measurement noise while still providing the correct gate voltage dependence of the mobility Saturation Mobility Linear Fit Figure 27 Comparison between the field effect saturation mobility calculated from the modified Eq 9 Linear Fit BW TP using two different numerical derivative methods For each data set the saturation mobility is plotted as function of the mid point interval Vs Ossila Ltd
96. ressing the Adv Settings button On the Advanced SMU and Acquisition Settings UI use the Default button to save the current settings as default The Default setting will be loaded by pressing the Load Default button Note Each experiment is associated with its own set of Advanced and SMU Settings and these are automatically loaded into memory with the experiment Ossila Ltd Copyright 2009 2015 50 enabling innovative electronics SuperFACT UI Front Panels A detailed overview of SuperFACT s three front panel user interfaces Advanced SMU and acquisition settings This UI controls the application and SMU settings System settings OS control Windows Reboot Time Windows Reboot Time sets the PC reboot time available in Continuous Measurement mode only Reboot enables disables the reboot functionality AutoRun enables automatic acquisition functionality whereby a lifetime experiment is initiated whenever the application is started Use this functionally together with reboot to automatically restart a lifetime acquisition or to initiate at a set date Note SuperFACT is not currently shipped with auto start functionality use Windows Time Scheduler with AutoRun set to ON to automatically start the application and initiate a life time acquisition at a predetermined time Self Calibration enables disables SMU self calibration routine at lifetime acquisition start This feature is available for PXI SMU only
97. rval by entering it with the format hours minutes seconds For lifetime run in conjunction with stress biased experiments the voltage bias to apply between two consecutive acquisition cycles is set by selecting the Bias On option on the Bias drop down menu with the bias voltage specified in the Bias Voltage input field Bias Voltage accepts voltage in the range 10 to 10 Volts Note make sure that Meas Interval is different from zero to allow the stress bias to be applied Important If a total current measured during stress biased exceeds 10 mA SuperFACT will return error code 5600 and the acquisition will be terminated Tip Introduce an idle time between two consecutive acquisition cycles to reduce the amount of data produced during a lifetime experiment Ossila Ltd Copyright 2009 2015 73 enabling innovative electronics Mobility Computation Refer to the Transfer Characteristic TC for a brief overview of the mobility the relevant equations used to describe FET linear and saturation regime The measured current Ips is pre processed through the recursive application of the Savitzky Golay digital filter This filter increases the signal to noise ratio by smoothing away the random EM noise The figures of merit lore Imin are calculated from this smoothed Ips Conversely lon being a value order of magnitude larger than the typical EM noise is calculated from the as measured Ipsi Linear fit method This algorithm compu
98. s Vosi Vos start X AVps Eq 22 where i 0 1 2 N and N is the number of data points number of steps with V V N DS Start DS End ait 1 AVps Eq 23 Example Let us suppose that the User wants to acquire a data point for each steps AVp 1 over the interval Vps Start O V to Vps Start 10 V the equation above gives then N 11 which fulfils the User s request since the acquisition is carried out from 0 to 10 V over 11 voltages separated by 1 V step Current Limit specifies the maximum drain current ps that the DRAIN source is allowed to induce in the DUT as the User s selected gate voltages are applied to the DUT itself i e Current Limit refers to maximum allowed p lt Vps for any applied Vss Delay DRAIN Delay is the dwell time between the application of a specific drain voltage and the acquisition of the respective drain and gate current data points Delay must be greater than the total settling time which is given by the sum of the system settling time and the DUM transient for drain voltage sweeps see GATE Delay above Sweep Back is selected to sweep back each l V curves for any Ves SuperFACT sweeps the drain current from Drain Voltage Start to Drain Voltage End and hence backward from Drain Voltage End back to Drain Voltage Start Acquisition settings Transfer characteristics IV Gate SMU Name Vos Start raoean A a gt 2 Channel Auto Zero Delay Sec Current Limit
99. s Absolute maximum ratings e Maximum input Drain Channel B Voltage 100 V e Maximum input Gate Channel A Voltage 100 V e Maximum input Drain Channel B Current 100 mA e Maximum input Gate Channel A Current 100 mA Software driver The Ossila Multiplexer Measurement Unit is controlled by a NI USB 6501 OEM card The card is compatible with Linux Mac OS Pocket PC and Windows operative system and it can be programmed by using a variety of languages such as e LabVIEW e MATLAB Data Acquisition toolbox required e ANSIC e LabWindows CVI e Measurement Studio e Visual Basic e Visual Studio e Visual Studio NET In order for the Ossila Multiplexer Measurement Unit to be recognised by your computer please ensure that the National Instruments DAQm x driver version 14 or above is installed on your system Many computers running LabVIEW with other national instruments hardware will already have DAQm x drivers installed and should recognise the board instantly To check if DAQm x is installed on a PC navigate to Start Menu gt All Programs gt National Instruments and look for NI DAQ If DAQm x is not installed on your system please download and install it from the National Instruments Website www ni com where it is available free of charge registration required Physical characteristics e Dimensions 23 cm L x 20 cm W x 15 cm H e Oconnectors 1 x USB series B receptacle cable included 2 x BNC rec
100. s called Linear Transfer Characteristic Conversely if the Vp is chosen such that the transistor according to the l V plot is operating in its saturation region the corresponding TC is called Saturation Transfer Characteristic Figure 15 depicts an example of linear and saturation TC 0 0E 00 0 8 16 24 32 40 48 56 64 72 80 Ves V Figure 15 Linear VDS 5 V and saturation VDS 80 V field effect transistor TC curves In linear regime the drain current can be written as W V Ine a 7 lox Ves E Vrah Vps 23 2 Eq 1 where u is the mobility Cox is the capacitance per unit area and Vn is the threshold voltage Eq 1 is valid under the conditions Ossila Ltd Copyright 2009 2015 36 enabling innovative electronics Vos lt lt Wes Vrn and Ves gt Vral Eq 2 Eq 2 defines the range or region of validity of Eq 1 In the range of validity of Eq 1 Vps is small compared to Ves and therefore it follows that this equation can be simplified as w Do ia z Ves Vrn Vps Eq 3 By inverting Eq 3 the mobility u can be written as a L 1 Ulin lin WCox Vps Eq 4 where Qin is the slope of the curve lps Ves see Fig 5 Eq 6 is the equation SuperFACT uses to calculate the field effect linear mobility Since the mobility is proportional to the slope of the linear transfer characteristic curves it follows that these curves can be written
101. s for 1 V step or lower For Keithley 2612B the typical settling time are given in the following table from Keithley 2612B datasheet Settling Time 200 mV lt 50 us typical 50 us typical 110 us typical 200 V 700 us typical Ossila Ltd Copyright 2009 2015 61 enabling innovative electronics The table details the time required to within reach 0 1 of final value after source level command is processed on a fixed range Keithley 2612B datasheet Organic transistors have much longer transient time Accordingly IEEE standard for OFET characterisation recommends a minimum settling time dwell time of 10 ms up to 100 ms for each data point The appropriate settling time depends on the dielectric organic semiconductor OFET architecture and measurement settings For accurate measurements indicative Delay values are 100 200 ms for each gate sweeps GATE Delay with AVgs lt 20 V and 10 to 20 ms for each drain current acquired DRAIN Delay with AV ns 2V These values refer to OFF gt ON sweep For ON OFF sweep the required delay times are higher Refer to the Measurement and Accuracy section for more detailed information on Settling Time Important For IV Sweeps SuperFACT will always force the SMU GATE to wait at least 5 ms after Vss is applied Current Limit specifies the maximum gate current range Ics that the GATE source is allowed to induce across the target OFET for example If the curren
102. s is a placeholder for the data files which are h m s_d_m_Y_IV_Devn contains the IV output curves and gate leakage one file per each acquisition cycle with time stamp h m s_d_m_Y h m s_d_m_Y_TC_Devn contains the TC output data one file per each acquisition cycle with time stamp h m s_d_m_Y FileName_Lin_1 contains the time series of the FET TFT figures of merit calculated with the device in linear regime one file per device FileName_Sat_1 Same as above but with the figures of merit calculated with the transistor operating in saturation regime FileName_Overhead_1 records the experiment settings Ossila Ltd Copyright 2009 2015 59 enabling innovative electronics Measurement settings and device parameters This Ul is used to specify the sweeps the transistor features required to compute the mobility and to programme and Bias Lifetime acquisitions Acquisition settings Output characteristics IV Gate oom Name T ro Zero E TE Limit T Gate Current Use this UI subpanel to control the GATE SMU for IV acquisition SMU Name is the alias name of the SMU unit as specified in MAX Measurement amp Automation Explorer For Keithley series 26XX dual channel series the SMU alias name must be KeithleyO while for NI PXI 4132 the name is SMUA Important These names are case sensitive spell them correctly and pay attention to the correct position of the lower and upper case letters otherwise SuperFACT will not
103. seceueceusces 20 PEETA TT E E EE E A E 22 NIGSOLOEM OUTPUTS asorin AEE EEEE 22 D AUDO EN eere EA AE E E EEEE 25 STRESS BIASED MEASUREMENT noossssssnssssssssssssssssssseserserseseessesesoooseorererereeererereresessososeeeeerrrreerreeesessosoerereeeeereeereee 27 HARDWARE CONFIGURATION ssssoscossessoocossossoocossoseoocossessoccossessoosossessssoosoossssossoossssossosssssossossessossosssssosssosss 29 OPERATION MO ODeE sssssssosssssssssssssssssosssssssssssssssssossssssssossssssssossssssssossssssssossssssossssssssssssossssssssssssssssssssssosso 31 ACQUISITION MODE cccccccceccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccceccecceecs 32 A BRIEF INTRODUCTION TO FIELD EFFECT TRANSISTORS ccccccccecccccccccccccccccccccccccccccccccccccccccccccccccceecs 33 OUTPUT CHARACTERISTIC l V trace scie mesa masse oivincnate arundinacea ceca atadentiea madanteatintenteanarataadeacessaaseiesandeaiatecdnacsaatenaceaaueneen aes 35 TRAN SE BERR CPA Ce eth I ces stecesceccteasen ce teatutstet E E ct oamnede RA AA R 36 GATE DEPENDENT MOBILITY scuscauiseaacstictoacawGctnadiaeacsaedioamadieterdGavanteiunaeawtainadioowsdaaanatonmalatietgamsioan diamiealenauteaasemaseamaustsrenmmeareuumealannne 38 TRANSFER CHARACTERISTIC CURVES IDEAL AND REAL BEHAVIOUR ccccceccccceccccccecccecccencecacencesacesceenceseeenseseeessesseencenas 39 THRESHOLD VOLTAGE SECOND DERIVATIVE METHOD cceccee
104. setup 1 With all the devices switched off place the components used with the Multiplexer Measurement Unit In order to achieve high precision measurement it is important to reduce any source of electromagnetic interference avoid operating the system with a mobile phone or any other electronic devices in the proximity of the SMU and Ossila Multiplexer Measurement Unit maximise the distance between the measurement units SMU and Ossila Multiplexer and the computer case Ossila Ltd Copyright 2009 2015 10 enabling innovative electronics 2 When the measurement is being carried out the Unit should not be moved or touched as this can impact on the accuracy of the measurement 3 Connect the two coaxial cables connectors to their respective female BNC sockets on the Multiplexer Measurement Unit back panel see figure 1 Channel A is the Gate channel while Channel B is the Drain Plug the I O Connector located at the other ends of the coaxial cable to the SMU channel A and B connectors located on the back panel The SMU channel A is the GATE source while Channel B is the DRAIN source Be careful to plug the connectors correctly take advantage of the labels at both ends of the cables to double check the connections 4 Use the USB cable provided to connect the Multiplexer Measurement Unit with the computer case To do this plug the Standard B USB plug to the Standard B USB receptacle located on the back panel of the Unit see figure 1 P
105. sn m 18 i omn oms Q om 9 omi own s 9 ows O omr os ome O omr 7 oms os 2 sa i Sa Sa oa oa sa a a ta Sa Sa Ai a Quemmat A Gates 100 V Mes o ow we e Dev 1t omi Cw Ga Dev e Oev 12 a owl o ow oon mi o ows o oo oon e Ome oms omw O ou e omw Sa sa sea 9a 9a Sa 42 8 Trannai A Gates 100 V Mas Figure 11 Any number of Device column or rows can be switched off when the Multiplexer Measurement Unit is operated as a Lifetime Tester Hardware Configuration In order for the application to communicate and control the acquisition hardware and PC SMU interface GBIP for Keithley and NI PXI 8360 for PXI alias names must be assigned to the SMU and peripheral units through NI MAX Measurement amp Automation Explorer gt If MAX is not yet installed please download and install it MAX is freely available at www ni com registration to NI website may be required to download NI applications and drivers Ossila Ltd Copyright 2009 2015 29 enabling innovative electronics NI National Instruments hardware will appear on MAX with their factory alias name For example the multiplexer unit hosts a NI USB card interface and will appear on MAX as Dev1 If more than one NI USB card has been connected to the target computer MAX will automatically assign a different sequential number to the multiplexor Important If the SMU of choice is the 4132 NI PXI the computer needs to be
106. so the less robust against noise 3 Linear Fit Method computes the linear fit for the whole experimental data set Ips i Vesi and returns the mobility with the associated threshold voltage as a single gate voltage independent value u The threshold voltage is calculated as the x intercept of the linear fit Tip Use the Fit Optimisation options see below to exclude Ips i Vesi data that do not comply with the linear fit requirements Refer to Mobility Computation for a review of the validity conditions for the linear fit algorithm Threshold Voltage specifies the threshold voltage extrapolation method The available options are 1 Linear Fit Extrapolation It calculates Vz according to the selected mobility computation method see the description of Computation Method controls above 2 Second Derivative Vm is calculated as the Ves at which the second derivative of the drain current with respect to the gate voltage is maximum i e d I l l Vrn Ves such that P is a global maximum GS Eq 28 3 IV Integration Method is not currently available for OFET TFT On Current ring selector is used to specify at which gate voltage the ON current lon must be read The ON current is the lps current output at which the DUT can be considered fully ON As such this value is intrinsically not well defined and the ON gate voltage is arbitrarily selected As a rule of thumb any voltage Ves such that Ves gt gt Vm is acceptable
107. software e Back up or replicate configuration data e Create and edit channels tasks interfaces scales and virtual instruments e Execute system diagnostics e View devices and instruments connected to your system e Update your National Instruments software In the following we refer to the Source Measurement Units SMU dedicated to source and measure the gate and drain voltage current of transistor as GATE and DRAIN respectively Gate and drain lower case letter refers to the transistor gate and drain respectively Configure and Test National Instrument NI 6501B OEM Board Make sure that all the connections are well connected all the power cords are plugged in an Open NI MAX 1 On the left side MAX subpanel click on My System NI USB 6501 Settings 2 Click on Device and Interface a list of devices installed or simulated on the computer will appear see figure 14 If the USB cable is properly connected to both PC and the Multiplexer Measurement Unit the NI USB 6501 icon is green The icon of a device installed but not currently present or properly connected is grey with a superimposed red cross When first installed MAX assigns a standard alias name to MAX compatible hardware For NI USB 6501 this is Devn where n is an integer indicating the number of device currently installed on the computer MAX Measurement and Automation Explorer 1999 2013 National Instruments All rights reserved Measurement and Automation E
108. st capacitor and then dividing by A Conductive plates A d Dielectric Figure 25 Capacitor diagram Ossila Ltd Copyright 2009 2015 67 enabling innovative electronics Data analysis Data analysis options ON Current Fitting Algorithm Linear Fit Method Option Ves Start Vv Gs End Computation Method specifies the algorithm used to calculate the mobility Important Before computing the mobility the drain current is smoothed through recursive application of the Savitzky Golay filter on the raw measured current data Any current based figures of merit minimum and OFF current ON current etc are then calculated using the filtered data Consequently the value of the reported drain current figures of merit may not correspond to the values read directly from the raw data Important The user is strongly recommended to familiarise with the caveats associated with each mobility computation algorithm see Mobility Computation The three mobility algorithms currently available with SuperFACT are 1 Partition Method The experimental data p Ves are grouped partitioned in subsets made of M data points M can be any number ranging from 5 to 10 as specified by the user on the Data Analysis Advanced Settings panel of the Advanced SMU and Acquisition Settings Advanced Ul For each data subset the linear fit is calculated and the slope of this fit inserted in Eqs 4 and 9 to compute the mobili
109. t Unit is designed to minimize the amount of distortion in the measurement The resistance of each Drain path is lt 1 Q leakage noise current is lt 500 pA and Capacitance is lt 300 pF Typical values for the Multiplexer Measurement Unit obtained using a DMM are shown below in table 1 These values apply to the Multiplexer Measurement Unit only and exclude the coaxial cables Table 1 Typical Resistance Capacitance values for the Multiplexer Measurement Unit DMM measured C 142 pF C 141 pF C 137 pF C 137 pF C 137 pF C 135 pF e Maximum Device Drain Channel B current 100 mA e Maximum Device Gate Channel A current 100 mA e Maximum Drain Channel B Voltage 100V to 100V e Maximum Gate Channel A Voltage 100V to 100V e Resistance introduced in Device path lt 10 e Capacitance introduced in Device path lt 300 pF e Drain Channel B Leakage Current One device on Gates G1 and G2 on typ 350 pA max lt 500 pA e Gate Channel A Leakage Current One device on Gates G1 and G2 on typ 100 pA max lt 200 pA e Drain Channel B Gate Channel A Transfer Leakage Current One device on Gates G1 and G2 on typ 200 pA max lt 300 pA Ossila Ltd Copyright 2009 2015 22 enabling innovative electronics Relay specifications e Initial Contact Resistance 100 mQ e Maximum Switching Voltage 110 V e Maximum Switching Current 1 A DC e Maximum Switching Power 30 W e Relay Operate Time 8 m
110. t a peak Finite Measurement Partition Method OK issue DUTs with different ill defined Derivative Method Deprecated Deprecated Deprecated behaviour low current lt 80 pA Linear Fit Method Deprecated Recommended OK issue OK issue Mobility present not present a peak Table legend Parameters corresponding to voltages outside the actual interval of validity Vstart Vena can be wrongly considered as belonging to this interval A The interval of validity is determined before starting the acquisition and remains the same for each DUT Unless the DUTs have similar behaviour interval of validity and this is already roughly known to the user the chosen Vstart Vena Could not match the actual interval of validity Ossila Ltd Copyright 2009 2015 84 enabling innovative electronics Mobility error The mobility algorithm checks whether the experimental data meet a set of requirements with the outcome used to validate or discard the DUT figures of merits These requirements are essentially conditions on the data set number of data available noise feature of the transfer curves and its first and second derivative and a classified as mandatory or desirable Failure to fulfil a mandatory requirement will result in a fatal error and no figures of merit will be returned for the DUT Conversely a desirable requirement failure will generate a warning non fatal error Both fatal and no fatal errors are printed on the Overvi
111. t exceed Current Limit the SMU will complete the acquisition without increasing the voltage further to avoid damaging the internal circuitry Refer to the Measurement and Accuracy section for the appropriate setting of Current Limit and its relation with measurement accuracy Max Gate Current is a User s selected threshold on les as leakage current More specifically Max Gate Current is the maximum lIg s5 Vps that the User deems acceptable for the DUT If leak les SuperFACT stops acquiring the l V curves for the particular Vss for which the limit has been exceeded and moves to acquire the next if any DUT Tip Use Max Gate Current to speed up data acquisition by avoiding measuring transistors which present very high gate current leakage Note Set Max Gate Current to be lower than Current Limit IEEE recommends gate current leakage to be less than 1 of the drain current Ips Vps Max Gate Current is disabled if its value matches Current Limit 1 IEEE Standard for Test Methods for the Characterization of Organic Transistors and Materials IEEE Std 1620 2008 Ossila Ltd Copyright 2009 2015 62 enabling innovative electronics Ossila SuperFACT Measurement Settings and Device Parameters New Experiment Setting Acquisition Settings Output Characteristic IV Gate SMU Name Ves Start Vos End Gate Sweeps SMU Name Vos Start Vos End AVpbs Kethey0 f eo am m e Current Limit Max Gate Current Channel Auto Zero Channel Auto
112. tes the mobility by fitting the data Ipsi Vpsi to a straight line and then calculates u and threshold voltage V from the slope and the x axis intercept of the fitting line respectively by making use of Eqs 4 and 8 If the linear fit R squared is less than a User s defined threshold the mobility plot turns red and an exclamation mark will serve as warning flag to inform the user of the failure in meeting the R squared condition Derivative method The mobility is obtained according to Eqs 10 and 11 by employing the two point central difference formula to compute the numerical differentiation carried i e dIps _ Ipsjiti Ipsi 1 _ ps it 1 pDs i 1 aVgs V si e1 VGsi 1 2A4VGs Eq 29 with the last equality being satisfied if and only if the sweeps AV gs are constant The threshold voltage Vn is expressed as the x intercept of the tangent line of the maximum of Zos GS As already explained in Sec Transfer Characteristic TC the derivative method and the Linear Fit method give the same constant mobility if Ips Vps is straight line over the interval of validity of Eqs 4 and 8 23 R squared R is a statistic ranging from 0 to 1 which assume the value R 1 incase the linear fit exactly describes the relation between the data points and R Oifno linear relation between current and voltage exists Ossila Ltd Copyright 2009 2015 74 enabling innovative electronics Partition method In order to aut
113. th single layer dielectric substrates whose gate pads are located on the bottom left and right corners Use Match or UserM to characterise transistor architecture defined by separate gate dielectric layers one for each device column In order to minimise the gate leakage current it is of paramount importance to keep the number of active gates to a minimum possibly no more than two at any given time during the measurement Log data User Name is used to enter the name of the person in charge of the experiment Experiment Name is the experiment identification name In continuous measurement mode the appositely created Experiment Name directory will contain all the experiments sharing the same identification name Substrate Type is the substrates identification name In continuous measurement mode the appositely created Substrate Type directory will contain all the experiments sharing the same experiment and substrate identification name Folder is the existing directory in which the data files of a finite mode acquisition are saved Tip To avoid imputing the wrong directory path use the browse button to navigate to the selected folder In continuous mode this entry is locked and showing the data storage volume File Name is the base name for the data logging file 5 Folder Button if enabled forces the data files to be saved in an appositely created directory command not available in continuous measurement mode Tip It is recomme
114. the last Ul Measurement Settings and Device Parameters press Commit or Measure to commit the settings and start the acquisition straightaway A new not yet saved experiment can be committed by selecting the option Commit on the Measurement Settings and Device Parameters UI Note A committed but not saved experiment will be lost when the application is closed Ossila Ltd Copyright 2009 2015 49 enabling innovative electronics Start an acquisition Once an experiment is committed press Start on the main UI enter the data file name and then press OK to initiate the acquisition Note The current experiment settings are saved in a temporary file which is overwritten every time the settings are modified When SuperFACT is restarted the last executed experiment is automatically loaded into memory and it can be executed by pressing the Start command on the main Ul Important If you modify and experiment and without saving it and then press Measure or Commit followed by Start the changes will take immediate effect but the original experiment setting will not be modified It follows that the changes will be lost when the original experiment is reloaded into memory Check current experiment and modify default Advanced Settings The current experiment can be inspected by pressing the See Experiment button This control is available even if an acquisition is underway The advanced settings can be accessed modified saved by p
115. ty Therefore for each subset the partition method will provide a gate voltage dependent mobility u V csi where Ves is the median gate voltage of the subset The x axis intercept of the linear fits gives the gate dependent threshold voltage Vrni The partition method will return any u complying with the R squared condition specified by the user on the Data Analysis Advanced Settings section of the Advanced SMU and Acquisition Settings Advanced UI The maximum mobility u V cs satisfying this condition is flagged as the reference mobility of the DUT Tip Partition Method can be especially useful to calculate gate voltage dependent mobility in presence of noise poor quality experimental data 2 Derivative Method The mobility is computed by differentiating the drain current Ips with respect to the gate voltage Ves i e the Cartesian x axis is the voltage axis Ossila Ltd Copyright 2009 2015 68 enabling innovative electronics dl uUVes are Eq 27 Unless algorithm optimisation is enabled see below the resulting gate voltage dependent mobility are plotted and saved with no further data validation As for the partition method the maximum of u Vgs is flagged as the DUT reference mobility The threshold voltage is calculated as the x intercept of the tangent curve to the maximum of the derivative dIps dVgs Tip Derivative method allows the most detailed gate voltage dependent mobility however itis al
116. um lmax These two conditions prevent calculating the figures of merit over data acquired when the transistor is operating in the subthreshold region OFF Flag 1 User The User manually enter the validity interval Vstart Vena and the mobility is calculated only over this interval This option is useful when all working DUTs on the substrates show similar transfer curves whose features are broadly known a priori Ossila Ltd Copyright 2009 2015 79 enabling innovative electronics Note With this flag enabled the mobility will be calculated in correspondence of the gate voltage interval Vstart Vena which remains the same for each DUTs Use this flag to force SuperFACT to calculate the mobility over a pre determined and constant gate voltage interval Flag 2 AutoFWHM The interval of validity is estimated on the assumption that the mobility can peak ata value Vgs Vv see figure 26 The AUtoOFWHM locates the peak of Tos if any and estimates GS the Full Width at Half Maximum FWHM The interval of validity is the calculated from this FWHM If no peak is detected the Vstart is taken as the maximum voltage between if exists and Vsq i e Vstart Max V Vso with Vso gate voltage at which the drain current is equal to 5 of Imax Flag 2 AutoRange As for AutoFWHM the AutoRange subroutine attempts to locate the es GS any and use it to calculate the upper and lower bound of the validity intervals If the mobi
117. urrent that the USB can supply to the multiplexor relay network limits the number of lines Drains and Gates that can be switched and maintained on to twenty two For lifetime and stress biased measurements it is recommended to connect the USB cable using a USB power adapter version 3 0 or later to ensure continuous operation Please note that the coaxial cables used to connect the Multiplexer Measurement Unit to the SMU can add leakage current to the measurement This current is proportional to the length of the cable and it is therefore desirable to keep the coaxial cable as short as possible To further minimize leakage noise low noise it is recommended to use low resistance and capacitance RG RGL cables The grounds of Drain Channel B and Gate Channel A inputs are connected together inside the multiplexer It follows that Gate and Drain voltages are measured with respect to the same zero voltage reference The common ground condition is an essential requirement for OFET TFT measurement and must be maintained throughout the entire acquisition cycle Note If the experimental set up is such that the signal passes through a BNC to BNC connectors for example GloveBox BNC feedthrough it is recommended that the ground of the connectors should be connected together with a wire to minimise measurement distortion Ossila Ltd Copyright 2009 2015 21 enabling innovative electronics Specifications The Multiplexer Measuremen
118. ve advanced settings as default settings Press Default to save the current settings as default settings and then press Apply amp Close to commit the changes and return the control to the main UI or alternatively press Create Exp to enter a new experiment settings Default settings are loaded by pressing Load Default button on the Advanced SMU and Acquisition Settings Ul Tip Once you have determined a reasonably general set of advanced SMU settings that are appropriate for the majority of your measurements such as aperture time initial settling time etc it is good practice to save them as default However you should avoid changing the default settings just because a specific experiment requires so In this manner especially when multiple users have access to the measurement equipment it will be easier to guarantee consistency between similar experiments by loading the same advanced SMU settings Ossila Ltd Copyright 2009 2015 54 enabling innovative electronics Select devices to measure and measurement type UI This UI allow the User to specify the type of measurement to execute select the devices to measure and enter experiment identification tags and data logging controls Measurement type Measure All forces SuperFACT to acquire both IV and TC curves for all 20 devices You can deselect IV or TC sweeps and specific devices by using the corresponding controls on this UI see
119. vers shipped with the application will be automatically installed in the folder C Programme Files 86X National e Reboot the target computer to complete the installation e You can now remove the both rar and Volume folder Important Do not install this application on a target computer running Labview If the target PC is already running Labview you should run the executable instead Contact Ossila at info ossila om for further information on installing and using the executable on a target computer already running Labview Required drivers 1 LabVIEW Run Time Engine 2014 or later version 2 NI 488 2 Application Development Support 14 0 or later version 3 NlI DCPower Development Support only for NI PXI 4132 SMU 4 NI DAQmx Runtime with configuration support 5 NI System Configuration Runtime 6 Nl Measurement amp Automation Explorer 14 7 NI VISA Runtime Engine 14 0 or later version 8 NI VISA Configuration Support 14 0 or later version The drivers are shipped with the application and are automatically installed by the NI Installer on the target PC Post installation e After installation a shortcut should appear on the User Desktop If the shortcut fails to show e Navigate to the application executable in C Programme Files 86X Application e Place the cursor on the application s icon right click the mouse button and select Create a Shortcut For this drivers install the full development support to allow ful
120. wer supply This SMU capability is often referred to as PLC noise rejection Sample to Avg specifies the number of current readings that the SMU requires to output a single measurement point For example if Sample to Avg is set to N the SMU takes N independent measurements which are then averaged so that a single averaged output is returned Increasing N will increase accuracy at the cost of measurement speed N 1 is usually adequate unless stringent accuracy requirements or specific measurement needs require larger data sample Refer to the SMU user manual for the maximum number of sample to average supported by the SMU Aperture Time sets the duration of a single current or voltage reading Aperture Time is expressed in unit of PLC The actual value of Aperture Time therefore depends on the PLC frequency as detailed in the following table where Aperture Time is expressed in term of PLC units and seconds 83 8 133ms_ 160ms_ a a 66 6ms 80 0 ms_ As for sample to average longer aperture time increases accuracy by slowing down the acquisition rate Application settings Measurement Advanced settings TC Initial Delay Time is the extra settling time the GATE TC Initial Delay Time TC Discard Measurements Sfm e SMU waits after applying the target voltage when acquiring IV Initial Delay Time TEE E TC curves see diagram in figure 21 2m TC Initial Delay Time is applied only for the first sweep data Ossil
121. xplorer Help Version 370694R 01 June 2013 Ossila Ltd Copyright 2009 2015 26 enabling innovative electronics If required to change the alias right click on the alias name select Rename on the drop down menu and input the new alias 3 Familiarise with the tool bar commands on the central subpanel of MAX see figure 14 Use Reset to reset the hardware and Self Test to test the hardware P lt NIUSB 6501 SwitchControl Measurement amp Automation Explorer o f File Edit View Tools Help ors be cave K Refresh a Reset Zb Self Test BH Test Panels gt 57 Hide Help b E Data Neighborhood i 4 g Devices and Interfaces Ea Back aE gt p NI PXIe 1071 Chassis 1 Settings 7 m ASRL1O INSTR LPT1 NI P NIUSB 6501 SwitchControl Name SwitchControl ea Device a Network Devices Wer asics TRE endor National Instruments aeaea b 444 Scales Model NI USB 6501 gt D Run the NI gt Bosso Serial Number 016C2061 DAQmx Test gt i M Drivers Panels b Remote Systems tatus Present ii vet gt Remove the device gt View or change device configuration 7 le Figure 9 SwitchControl NI USB 6501 MAX front panel Stress Biased Measurement Ossila Ltd Copyright 2009 2015 27 enabling innovative electronics The Multiplexer measurement Unit can be used for stress biased measurement whereby the devices are kept under a bias str
122. y the mobility cannot be reliably calculated using the Eqs presented in the Transfer Characteristic section False high mobility Gate dependent mobility Derivative Method and Partition Method Some OFET TFT devices can show a steep increase of the current in the subthreshold region This feature is well known for traditional inorganic FET as Ves approaches Vz the tiny lps increases exponentially with the applied gate voltage If the subthreshold region is not excluded from the mobility calculation Ves can show a steep peak for Ves lt Vrp This peak so pronounced to be the global maximum of the function u Ves and it can be wrongly interpreted as a valid mobility by SuperFACT Valid DUT discarded With the optimisation flags enabled SuperFACT can wrongly discard otherwise valid DUTs For example devices whose TC curves are severely degraded by noise can be discarded during the data a pre processing because the discrepancy measured as R squared between the raw and the smoothed TC curves is too large A second common pitfall is the selection of a too large validity interval see figure 30 As figure 30 clearly shows the fit is calculated for value of the gate voltage for which the DUT still in its OFF region Since in this case the mobility was calculated with the linear fit method over the constant interval 20 60 V SuperFACT discarded this device since the R squared condition is not fulfilled R squared lt lt 0 90
123. y t is the voltage at the DUM at a time t with R Rm Royy and C Cm Cpum total resistance and capacitance of the measurement apparatus and DUM RC has the unit of measure of time and is usually indicated as the time constant t of the system t RC If a voltage Vo is applied at t 0 Vpum T 0 63 Vo Therefore for each acquired data point Delay must be 9 10 time larger than the time constant RC For Ossila FACT1 with two meter long BNC cable typical value of resistance and capacitance are R 1 4 Q and C 250 pF which gives negligible time constant T The time constant T is sometimes more conveniently expresses in term of the cutting off frequency In addition to the device time constant the dielectric capacitance charging time and more importantly the transistor ON OFF frequency While the former time constant is described by EqA1 with f ranging 1250 KHz for SiO to 9 KHz for Al O3 the latter is given by _ WVps fe 2nL Eq A2 In Eq A2 wis the mobility Vp the drain voltage and L is the channel length Here we assume that the resistance and Capacitance elements of both DUM and measurement apparatus are in series and parallel respectively Ossila Ltd Copyright 2009 2015 100 enabling innovative electronics Appendix VI Measurement Flowchart CC Ips Vps i and gate leakage les Vps with 1 2 N for j 1 2 M gate voltage sweep TC Ips k Ves x with k 1 2 L for linear and saturation reg

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