3. Operation manual
Contents
1. P x za p Document nr EriHeu 20111220 1V01 Page nr 0 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 Author Eric van den Heuvel Veeco RF350S Ion Beam Etch tool Table of contents 0 Changes Compared to previous Versions sssssssseeeessssssseeeeresssssseceteressssssseereesssssseeeeeeo l 1 S ILS ia PAE E E taps estos AA E E E A E EE E A 2 2 TE PICA TOE ON Ll AU OI oct E E sats eins unl E E cos oet E E 3 2e FECA N ose tcc arpa eeteses E A E tease eqessancesecetocustuasdamenseces stevasnmeneceee 3 2 EeP TOC CSS CS aetrcrecrc a a 3 2o PEATE AIC SON CUNY NSS scarry cee cece ge ett E soteeptce chen A 4 2 4 Redeposition and measures fOr suppression ccccccccccccecesseseeeecceeeeeeaeeeeseeeeeeeeeeeas 5 2 Secundary Ion Mass Spectrometry SIMS ccceccccccccccccessseeseceeeeeeeeaeesseseeeeeeeeeaas 5 3 PETAL IAA once ds bo ete cet ae E no satusiianehenste dn seedtliaaciencie odsheiiuneloacieioaseune 6 3 1 Process selection and preparation wets inn icotsdesavsacandasobsanasicbacdmndoonaesaebacandebodwenasebac nebvonies 7 2 LO EN e a eee 8 ee PUO Shc ene cr E ee eee ee eee eee 9 3 4 Secundary Ion Mass Spectrometer SIMS cceecccccccccccccsssesseeceeeeeeaeaeeseeeeeeeeeeeeas 12 4 FING SAG He UAE ONG ace ctee e whe ctoe ry scce or E E ts ion ceete tosses E A N 16 4 1 Instruction test and authorization ce2. prevents build up of charge For etch monitoring or endpoint detection a secondary ion mass spectrometer SIMS is available that analyses the secondary ions that get off from the substrate Intensity changes indicate the passage of interfaces An option prepared but not available 1s to introduce chemically active gases to assist in the etch process Depending on the method of introduction the process is then called reactive ion beam etching RIBE introduction of active gases via the plasma source or chemically as sisted ion beam etching CAIBE straight introduction of active gas into the process chamber Both techniques are attractive for dedicated processing only and don t match well with multi purpose use of the tool The price to be paid for chemical assistance is fast contamination of source and chamber frequent preventive maintenance considerable tool down time and short life time of the sensitive SIMS detector if compatible at all with chemical assistance 2 2 Etch recipes processes The set up of etch recipes called processes in the Veeco software is relatively simple Any combination of three acceleration voltages 200 400 800V and two beam currents 100 300mA is available in ready to use processes Almost all of them have argon as the only process gas only in rare cases oxygen is added for etching with a metal hard mask like Mo oxydizing the hard mask during the etch Additional process parameters are the
3. 3 4 1b Do you like to monitor exactly the same elements as you did in previous MASsOFt runs If YES go to step 3 4 1c If NO go to step 3 4 4 Changing a process file 3 4 1 c By File Open open an existing process exp file you used before all files can be found within the file folder C SIMS_Stand alone or one of its subfolders 3 4 1 d Activate the multiplier by pressing the _ sC buttton shown H here on the right The detector is ready for operation now go to step 3 4 2 3 4 2 Run the selected program Prepare data acquisition by pressing the green light on the SIMS toolbar The DataAcquisi tion pop up menu will ask for file options as automated data storage is active and file numbers are up numbered automatically The user can ooe choose between either overwrite the existing file in case the last run is a iee not of interest to the user or open and store data in a new file After making your choice the SIMS detector is stand by for action As soon as the mechanical shutter in the ion beam tool has opened Sect 3 3 1 f and the ion beam strikes the wafer SIMS detection can be started by pressing OK in the Data Acquisition pop up menu Press OK when the etch tool monitor displays a rain of ions coming down on the wafer at the same moment switching the wafer colour from blue to yellow Opening earli er is not recommended as most likely overshoots will occur in the transient state of
4. When desired this is the right moment to manually start the SIMS detector Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Page nr 11 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 3 3 2 Elapsed and remaining process time can be found in the Process Module I part of the Control window Fig l Without any user action wafer processing will proceed until the re maining process time has expired Then the wafer will be returned automatically to the load lock and brought back to atmospheric pressure However there are two alternative options 3 3 2a User defined endpoint and overetch time based on SIMS detector signal Press End Current Step to stop wafer processing for a single step process or stop the current step in a multi step process This is the only command in this situation that doesn t interrupt automated control The shutter will close and the ion beam will be po wered down remaining process time automatically set to zero If Abort is pressed processing will certainly stop but so will the automated control PMI will go Off line should be switched back to OM iine Wafer can be removed by the command Auto Unload then 3 3 2b Process interruption For whatever reason the user may press Stop to interrupt wafer processing The shutter will close and the ion beam will be power
5. attacked by ion bombardment This report pays attention to these two misunderstandings and gives practical suggestions for the selection and treatment of mask materials A2 Etch rate and selectivity In the Veeco IBE system the ion energy in eV and beam current in mA can be set independently Etch rates are proportional to beam current but the relationship be tween etch rate ER and ion energy is non linear ER increases with energy in the low energy range but more energy has less effect in the high energy range Further more ER s depend on the ion angle of incidence not just because beam intensity drops by the well known cosine law as the angle goes from zero straight on normal incidence to 90 degrees glancing inci dence but also because of the physics involved The relationship between ER and angle of incidence depends on the specific material being etched The ER s of pure metals and some com pounds are shown in Table 1 shown in Section 2 3 of the operational manual These values were taken from literature some values were at random tested and verified on the Veeco system A typical ER for gold is 45nm min 400eV 300mA normal incidence The large variation in ER s shows that a general remark about IBE lacking selectivity is not applicable but admittedly it depends on specific tasks Silicon etching with a resist mask has a selectivity of just 1 8 3 8 2 1 good Philips Resea
6. Auto Vent in the Auto Vacuum Sequences part Fig 6 of the Process Control window to vent and open the load lock gt 3 2 2 Take notice of the section Rules amp Regulations Sect 4 about wafers Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Pagenr 9 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 Auto Vacuum Sequences Auto Vent Auto Pump Arm Onon ET Fig 6 Load lock and robot control window 3 2 3 Open the load lock door and place your wafer into the load lock wafer flat at 12 o clock By gentle rotation feel whether the wafer is fixed in the cutout it is designed to be compatible with both Semistandard and Jeida wafer flats Close the door Wafer detection the only wafer sensor is present in the load lock After placement into the load lock a blue wafer should appear on screen If so go to the next step The sensor is sensitive to wafer backside coatings and in some cases the user has simply bad luck the coating makes the wafer invisible to the sensor or it leads to an ambiguous perception wafer displayed blinking present not present Such a situation impeeds any further normal action however there is a way around In case wafer sensing problems press by exception the button Load in the robot con trol window Fig 6 the robot will place t
7. it is a step editor By conven tion the name of a single step process 1s identical to the step name 3 1 1 Press the Load button in the Process list part Fig 4 top right corner and select your process from the displayed process list The name of your process will appear at the left in the line above Step1 in the list The distinct blue line right above the process line displays the name of a step involved in the process gt Users are not allowed to change any parameter settings except for the process time setting Hours Minutes Seconds in the orange rectangle in Fig 4 For parameter changes or a new process set up please always consult the machine owner or back up 3 1 2 Adjust the process time and save it by pressing the Save button in the Step list part Fig 4 at the right If you don t know the exact process time take plenty of time and stop the process manually on endpoint while it is running 3 1 3 Using the Main Menu button return to the Process Control window 3 1 4 Press the Select button in the Process Control part Fig 5 of the Control window to select your process its name will appear in the black line below the button Operator Process Control Process ass RAITT eC RGA lt T PM Process Unprocessed Wafer i A ba pt Door Closed ai Run No 4 Fig 5 Process Control window 3 2 Loading a wafer 3 2 1 By convention the load lock is left under vacuum after using the tool Press
8. shutter opening Data acquisition can be stopped with the red light on the SIMS toolbar 3 4 3 Closing off SIMS detection When the last run has ended with the red light on the toolbar the detector has to Ter be de activated multiplier back to OV by pressing the 2 Dg button in the SIMS toolbar shown here on the right A Philips Research MiPlaza TL Company Restricted Operation manual E17 Plaza Plaza Px za p Document nr EriHeu 20111220 1V01 Page nr 13 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 Notice that the high voltage down button has effect only when an open process file is present in standby phase After this action close the process file stop the MASsoft program and switch off the monitor 3 4 4 Changing a process file 3 4 4 1 The easiest way to make a new process file is to open an existing file with an element selection that come close to the one you are interested in first make a copy of the file with a new name ending with the number 00 change or extend the new file the only item that may be changed or extended is the selection of element preferable ask the tool owner to carry out this procedure Global ion SIMS Scan 1 Pt 195 000 Scan 2 Cr 52 000 lt 8 8 8 8 wwe ununnnnnnnnwn nnn ewe ee T Fig 6 Listing of monitored element
9. tool The beam angle of incidence can be chosen freely between 90 extraordinary beam parallel to the wafer surface and 0 degrees beam perpendicular to wafer surface Wafers can be fixed passively or rotated around their axis of symmetry Wafer cooling is accomplished by mechanical clamping and a flow of helium gas at the wafer backside helium being the medium to transfer heat from the wafer towards a cooled metal chuck called Fixture The Control window Fig l shows a planview of the system together with four subfields to control the system The planview informs the user about the wafer location vacuum status of load lock and process module PM1 and status of robot arm and the beam shutter the hori zontal green line in PM1 View Data Log Loader Vacuum oO Unprotected Ve CCC Q Operator Veeco Process Control Select Process 200V_Odeg_ thr Run a PM Process Stopped D E 5 ae Z Auto Vacuum Sequences Auto Vent Epsmccm Auto Pump o Ready BEETH EE O PM1 Clear Line BRR Rey Events 13 26 44 89910 Welcome to Veeco s MicroEtch System o Process Module 1 CEREA Tiit Angle a A Status Etch Flowcool eea neay Toto Gas Etch Source Usage In Minutes 2 669 2 665 PN Source Readback Gas Channels Gas Beam V Supp V PBN Body Forward RF a A A oo A oo Flowcool Beam mA SuppmA Filament Ref RF Forefie 5 0 0 Rough V
10. afer transfer to PM1 robot arm wafer processing in PM1 wafer transfer back to the load lock and load lock venting Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Pagenr 10 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 Three buttons are available in automated operation Fig 5 Run to start automated control This button can be pressed after putting a wafer into the load lock normal operation or after solving the wafer sensing problem and procedures explained at the end of part 3 2 3 Stop to cancel automated control When pressed during transfer that action is completed before the tool actually stops When pressed during processing the stop command is inter preted as an abort process command In all cases PM1 will go Off line impeding any fur ther action it needs to be switched back to OmWime see last part of 3 2 4 Auto Unload to get a wafer back from PM1 when automated control has stopped because of a user command gt Don tuse this button after a system alarm 3 3 1 Press the Run button in the Process Control window a In normal situation the load lock will be pumped down in two steps with a 1 switch point at 1 0E 1 Torr and a 2 switch point at 1 0E 4 Torr b The wafer will be transported from the load lock station into the process module PM1 c After re
11. any Restricted Operation Manual Veeco IonBeamEtch tool Administrator Documents Administrator TFF MiPlaza y lt i a _ am D lt a x Page nr 20 Epcode E17 Date 20 12 2011 undesirable effect of IBE facetting at mask edges Fig A3 10um wide gaps are opened into a 2 5um platinum film using an argon oxygen ion beam and a 0 6um Mo mask A6 Conclusion Without proper measures IBE is accompanied by sloped etch profiles and fences Proper choice of the etch mask material or its pre treatment helps in effective suppression of fences In special cases depending on the mask lay out proper choice of the ion beam directionality reduces redeposition of material on sidewalls References 1 E van den Heuvel DTS Report 05 016 2005 2 H Kaufman and R Robinson Opera tion of broad beam sources 1987 data selected from Table XIII 2 3 Intlvac website Ontario Canada Operation manual E17
12. be exposed to the beam for a certain fraction of the rotational period the fraction depending on the local mask lay out The ion beam angle of incidence will then oscillate between and the tilt angle The tilt angle needs tuning for best result the optimum being dependent on the specific materials involved Just occasionally this strategy works out well the degree of success largely depends on the mask lay out Usually it is very hard to suppress redeposition at every location on the wafer the shading effect being responsible for troubles for example at corners and at densely packed structures A5 Resist mask reflow From an etch selectivity point of view resist is an excellent mask material Usu ally resist film thickness is in the lum range and beyond in the 50 250nm range in e beam lithography Lithography pro files are often steep and close to 80 90 which makes these profiles very likely to collect etched material Fences like de scribed in Sect A3 can be suppressed by a Operation manual E17 Document nr EriHeu 20111220 1V0O1 Document resist treatment preceeding the IBE step After development many resists can be forced to reflow on a hotplate such that surface tension forces steep walls to change into smoothly sloped profiles without loss of pattern definition For some resists AZ HPR the slope angle can be as low as 20 provided that the specific mask lay out allows for reflow ev
13. ce eee eeccecceccecceccecescesccscescescescescescescescescens 16 BD BUOCCSS COU E E E E E E E E T 16 ko MOO LOC INNS ee E E 16 AA Water handling and penalties icc scacssncoueswrncsnasrcroueswnavsdactransteswaarsnacarcveuesenarsdaceeoveveues 16 5 Appendix A Redeposition and Etch mask strategy nessessseoeeenssssssssseerrsssssseseeeees 18 Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Page nr 1 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 0 Changes compared to previous versions Date Page New ver Description number sion num ber 20 12 2012 O1 New and combined version of the documents 1 User Manual Veeco IBE 2006 2 User Manual Hiden SIMS 2006 and 3 Bedieningsvoorschrift Veeco IBE RWV 011 023 2006 4 TL Report 09 001 E v d Heuvel 2009 Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Page nr 2 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 1 Safety EMergency Off EMO buttons The tool is equiped with a number of emergency off buttons BCE yellow that can be pressed in case of potentially dangerous situations These switches will shut off the electrical power supply to the tool except for the power suppli
14. eam setting 400eV 300mA 0 degrees tilt sorted alphabetically left and by etch rate right Etch rates are linearly proportional to the beam current The relation between etch rate and beam energy or voltage is non linear and depending on the specific material As a rule of Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Pagenr 5 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 thumb doubling the energy from 400 to 800eV tends to have less effect than doubling the energy from 200 to 400eV The relation between etch rate and tilt angle is complex and dif ferent for different materials and crystal orientations Some materials have maximum etch rates at non zero tilt angles some have at 0 tilt angle For all materials etch rates gradually drop off to zero at 90 tilt angle 2 4 Redeposition and measures for suppression Inherent to Ion Beam Etching is the side effect of materials redeposition Because of low process chamber pressures and consequently low collision rates overall redeposition of ex pelled material is unlikely to take place in a random way from the space above the wafer More likely is local redeposition on sidewalls of steps and mask edges those parts that are in direct line of sight when seen from the film being etched Steep and high steps tend to be covered up by expell
15. ed down but the remaining process time will not be set to zero Automated operation will stop as well and the stop command will be interpreted as a process abort PM1 will go Off line should be switched back to OW ine Either confirm a process abort by pressing the Abort button or more consistent with the very reason to press Stop in the first place resume processing by pressing the Con tinue button Then the ion beam will again be powered up the shutter opened and processing continued at the point where it was stopped When finished press Auto Unload to get the wafer in PM1 back to the load lock 3 3 3 Remove the wafer from the load lock when atmospheric pressure 7 5E 2Torr has been reached Philips Research MiPlaza TL Company Restricted Operation manual E17 a ane za pP Document nr EriHeu 20111220 1V01 Page nr 12 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 3 4 Secundary Ion Mass Spectrometer SIMS In stand alone mode the detector and the ion beam etch tool have no mutual interaction The detector is controlled manually and serves as a process monitor rather than as a fully auto mated endpoint detector For most applications this mode of operation works very well 3 4 1 Preparation of the SIMS detector 3 4 1a On the desktop activate the Hiden MASsoft program with the icon shown on the right and maximize the window
16. ed material having a finite probability of sticking to those surfaces For many applications the effects of redeposition is not acceptable and measures need to be taken to suppress it as much as possible This is the subject of Appendix A Redeposition in Ion Beam Etching a reproduction of MiPlaza Technology Laboratory Report no 09 001 2 5 Secundary Ion Mass Spectrometry SIMS Part of the etched material is in the ionized state A fraction of these ions can be collected and analysed by mass spectrometry In this way progress of an etch can be monitored as count rates at different masses will change upon passage of an interface between different materials The IBE tool is equipped with such a SIMS detector Usually it is applied in stand alone mode so without any communication between the tool and the detector Monitoring at differ ent masses allows users to identify interface s during etch runs and to determine the right moment to stop etching or to start countdown of a predefined overetch time Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Pagenr 6 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 3 Operation manual The tool is of single wafer design Wafer are loaded and transfered to the process chamber in horizontal position the ion beam is directed from back to frontside of the
17. ed to the vacuum pump on the first floor Ad ditionally local switches are available to shut off the electrical power supplied to the tool AND the local power sockets Electricity Radiation Pinch points The equipment satisfies all usual safety regulations and there is no danger when the tool is used properly Danger comes into play when used with removed panels or opened doors leathal voltages 1 83MHz RF radiation pinch points Chemical hazardous gases The only gases in use are argon and sometimes oxygen there are no hazardous gases in volved in processing Maintenance by qualified people only Once in a while the process chamber has to be opened in order to remove and clean the liners and the interior of the chamber Surfaces can be covered with a variety of etched materials that may come off as flakes and or small particles Proper care must be taken because materi als especially fine metal particles may react violently with organic solvents and air and may start a fire by self ignition Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Pagenr 3 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 2 General information 2 1 Equipment The Veeco RF350S system is a single wafer etch tool equiped with a remote plasma source separated from the process chamber by a set of grids
18. ery where Reflow can be expected to work out well for large structures only large mean ing lateral dimensions of 5 to 10 times lar ger than the resist thickness A6 Hard mask selectivity A hard mask can be designed in such a way that it almost vanishes within the Same amount of time as it takes to fully etch down the material of interest Advantage of this set up is optimum suppression of fences disadvantage is the introduction of extra steps in this double layer approach First it takes resist lithography to define the structures then it takes a wet or dry etch technique to pattern the hard mask and finally a resist strip preceeding the actual IBE step In the end the remaining part of the hard mask has to be stripped selectively with respect to all other materials present on the wafer Practical hardmask material are molybdenum titanium tungsten and silicon oxide they have low etch rates and can easily be patterned by reactive ion etching RIE An example of IBE with a hardmask is shown in Fig A3 a platinum film structured using a Mo hardmask and an argon oxygen beam Oxygen was added to oxidize Mo and reduce its etch rate IBE selectivity dictates the minimum mask thickness needed for the ion beam etch There are two reasons to take the actual thickness a bit more than that One is to allow for the possibility of some overetch time the second is to compensate for the Philips Research MiPlaza TL Comp
19. es everything in its way inside the process chamber including stainless steel and titanium parts elements like Fe Ni Cr Ti and Mo will always be present in the stream of ions collected by the detector they will cause a constant background at relatively high count rates and may make it difficult for you to see what it going on in those cases you try to etch down into these very materials when being part of the stack present on the wafer discrimination between elements of nearly the same mass takes special measures as mass resolution is limited e g to discriminate between Al 27 and Si 28 29 30 take 26 for Al Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Pagenr 15 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 no abundance but still resolution limited Al counts and 29 or 30 for Si for clarity it is a good habbit to add the monitored mass to the element name it will appear in the legend discription additionally use a special mark like in Si 30 to point out that the chosen mass doesn t correspond to the most abundant species of the element 3 4 4 4 Data screen settings with the IBE tool in idle mode make a first dummy run by activating the SIMS detector with the green light in the toolbar at the top in the DataAcquisition window select Overwrite current file and press OK le
20. essure Fixture 0 Fixture Angle 30 FlowCool Flowrate Fault Tolerance Monitor Faults M Abort On Error Fixture Rotation Rotate Continuous C Static Angle Process Time Hours Minutes Seconds 1800 000 Time In Seconds l Use Etch Rate Correction Yalve Control Fixture Rotation Spe C Sweep From lo To lo lo ed 10 0 RPM Source Magnet ms p MV Rotate Magnet 40 0 RPM Target Don t Move Target 1 Blank SSG sp M Open Turbo Gate O2 Cr 6 3 CCP C7 4 Blank Eg fao Target Angle Ta Blank Not Installe Not Installe PmM1 Clear Line Events 13 26 44 Philips Research MiPlaza TL Company Restricted Fig 4 Process Create window F Use R Theta Shaper 18 Quick Copy STEP LIST amp _ SAVE W Filter files by Module Type E Don t change R and Theta PM2 F Calibration Mode PM3 r o oo0 Theta o 000 Pma R Theta Shaper 89910 Welcome to Veeco s MicroEtch System View General Log Abort Operation manual E17 Plaza ex 34 25 Document nr EriHeu 20111220 1V0O1 Pagenr 8 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 A Process is composed of one or more Steps that are stored separately The process editor is used step by step one step at a time so in a way you might say
21. he substrate has to be inspected by the IBE tool owner upon compliance with the above mentioned rules After this whenever the user is to blame for another accident that user permanently loses his authorization to use the IBE tool If it turns out that a user uses the tool just once in a while it may become questionable whether this user will keep experienced enough to operate the tool in the proper way In case of doubt the machine owner may decide to cancel the authorisation Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Document Operation Manual Veeco IonBeamEtch tool Administrator Documents Administrator TFF Pagenr 18 Epcode E17 Date 20 12 2011 5 Appendix A Redeposition and Etch mask strategy taken from TL Report 09 001 E van den Heuvel 2009 Redeposition in lon Beam Etching Al Introduction In the Veeco RF350S Ion Beam Etching IBE system a wide collimated beam of argon ions is applied for etching It is a physical process there are no chemically reactive process gasses involved A very common misunderstanding about IBE is to think that pattern transfer from the mask material to the etched material is absolutely perfect the etch process is thought to proceed exactly along the line of flight of the incoming ions A second misunderstanding about IBE is selectivity which is supposed to be more or less absent afterall all materials are
22. he wafer in PM1 however without tool confir mation about wafer presence Additionally inform the tool about the presence of a wafer in PM1 after return of the robot arm move the cursor to the empty position in PM1 where the wafer is supposed to be double click at this position and in the pop up window press Add A blue disc unprocessed wafer should appear in PM1 on the display 3 2 4 Check whether the set of 6 lines present in the Process control window Fig 5 have all changed from black to green If so the tool is ready for processing continue with the steps in the next section If not all 6 lines in Fig 5 are coloured green further action is impeeded If lines other than the 2 or 6 one remain black something is wrong please inform the tool owner For different reasons the 6 line PM online can be coloured black It can be changed into green by pressing the only button present in the Process Module 1 part of the Control window Fig 1 The button in the top left corner switches between Off line and On Line the latter being the right one Although important the button has no additional functionality 3 3 Runa process Check whether the SIMS detector when needed is ready for operation If not take preparations Sect 3 4 before starting automated processing of the wafer The etch tool has been designed for automated operation such that in principle the tool takes care of load lock pump down w
23. iew General Log Abort Fig 1 Control window with status bar bottom gt Although the plan view contains several graphical control buttons for example for switching pumps on off or for opening closing gate valves users are urgently asked not to use those unless stated otherwise in this manual Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Document Administrator Documents Administrator TFF Operation Manual Veeco IonBeamEtch tool 7 EI7 20 12 2011 Page nr Epcode Date Next all subfields will be described just the way as they appear when handling and processing wafers 3 1 Process selection and preparation Additional to the Control window a recipe editor window is needed for tool operation It can be accessed via the Main Menu button in the top left corner Fig 2 View Data Loader Log Vacuum Fig 2 Main Menu button This button enables switching between the Process Control window and the Process Create window recipe editor as indicated in the pop up menu Fig 3 Process Control Process Module 1 Configuration Sign ON OFF Fig 3 Main Menu pop up menu After pressing the Process Create button the Process Create windows appears Fig 4 a z z le es Nexus Cluster Tool Controller Version CTCflex_V2 01 00 Process Create 400V 30dea 10mi Process 400V_30deg_10min Step_1 400V_30deg 10min Ste
24. ing clamped thin wafers with thickness lt 0 45mm are not allowed in the tool bonded wafers and glued sandwiches of wafers are not allowed in the tool follow the instructions for a 5mm edge exclusion also along the wafer flat this area should be clean free of resist tape or any soft or sticky material the backside of the wafer should be clean as well no resist tape or any soft or sticky ma terial small substrates should be glued on a carrier wafer with brown kapton tape only take notice of the 5mm edge area of the carrier wafer always consult the machine owner or the back up in case of doubt gt Never try to return a wafer from the process chamber to the load lock after a tool alarm or when the wafer didn t return in the normal way usually it worsens the situation These rules cannot guarantee zero wafer breakage but at least minimize the risk Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Page nr 17 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 Penalties If a wafer gets crunched in the tool it s up to the tool owner backed up by technicians to decide whether that specific wafer or the preparations made by the user are responsible for the accident If yes the user gets a warning first Prior to the next time this user needs to process in the IBE t
25. l remark redeposition in IBE sys tems is largely dominated by the direct line of sight mechanism Fig A1 Rede position of species back scattered within the volume of the process chamber or at the process chamber walls is very unlikely because of the combination of large mean free paths at the low operation pressures at least ten times lower than in sputter etch tools and high wall sticking prob abilities A4 Beam directionality One might think that the ion beam itself can be used to keep clean sidewalls just by adjusting its angle of incidence with respect to the substrate surface Indeed at a particular angle setting the rates of mutual redeposition bottom to wall amp wall to bottom may balance However this tilt angle is close to 45 which means that this measure works well only for walls facing the beam Opposite walls and part of the area to be etched are simply shaded and out of sight for the ion beam For special applications like the etching of Philips Research MiPlaza TL Company Restricted Operation Manual Veeco IonBeamEtch tool Administrator Documents Administrator TFF Pagenr 19 Epcode E17 Date 20 12 2011 unidirectional structures the in plane wafer orientation can be alternated between two set values Alternatively the wafer can be set to rotate continuously along its axis of symmetry allowing all unmasked area to be etched by the ion beam That is each location will
26. p_2 Step_3 Step_4 Step_5 Step_6 Step_7 Step_8 Step_9 Step_10 Step_11 Step_12 Step_13 Step_14 Step_15 Step_16 Step_17 Step_18 Step_19 Step_20 Step_21 Step_22 Step_23 Step_24 Step_25 Step_26 Step_27 Step_28 Step_29 Step_30 Step_31 Step_32 Step_33 Step Edit Insert Delete L 800 620 500 Suppressor Voltage 8 PBN Flow 0 K Factor Gas Values Etch Beam Parameters M Beam On MV PBN On Continuous Beam F UseStepRF Beam Voltage Beam Current mA Incident RF Power ho 1 Ar 0 50 sccm 0 2 N2 0 50 sccm 0 3 02 0 50 sccm 0 4 Ar 0 50 sccm lo 5 Ar 0 50 sccm RIBE CAIBE Depo Beam Parameters l Beam On F PBN On F Continuous Beam F UseStepRF Beam Voltage Etch Shutter Shutter Control Close v Jat Start Open v Jat Beam Close v Jat End Beam Current mA Incident RF Power Suppressor Voltage PBN Flow Target Shutter Close Y Jat Start Close v Jat Beam Open vat End K Factor 0 1 Xe 0 10 sccm 2 Ar 0 50 sccm Fixture Shutter Open vat Start Open vat Beam Open vat End PROCESS CREATE 0 3 Ar 0 50 sccm 0 4 Ar 0 50 sccm rc Use RGA 0 5 Ar 0 50 sccm Data Tracing Misc Interval 5 r Process Process Ends By Time z Endpoint Script Process Control Parameters 1 0E 1 Process Pressure High 1 0E6 Process Pressure Low M Ignore Process Pr
27. rch MiPlaza TL Company Restricted reason to reject IBE as an appropriate way for standard silicon etching On the other hand resist and SiO are excellent candi dates to etch down into noble metals like Au and Pt with selectivities of 8 and 4 respectively A3 Redeposition and etch profile At the impact of energetic ions Fig Al top their energy is dumped into a small volume close to the substrate surface Ma terial gets scattered in all directions ac cording to a material specific distribution Fig Al middle Inevitably a fraction of material will hit the sidewalls including the etch mask with a certain chance to adhere to those walls IBE is always ac companied by this process of redeposition a process that prevents clean vertical etch ing at the edges of structures defined in the mask Generally the sidewalls are sloped and after resist strip fence like structures appear at the structure edges Fig A1 bot tom Fig A2 Very often these fences are extremely thin and do not always ex actly follow the edges they may partly fall down or disappear for example during a wet resist strip process Precautions can be taken to suppress the IBE side effect of redeposition Sect A4 A6 Operation manual E17 Document nr EriHeu 20111220 1V0O1 Document Fig Al Impact of ions top scattering of material and redeposition middle final result after resist strip fences bottom As a fina
28. s e g platinum and chromium 3 4 4 2 Each element you like to monitor is represented by a SEM Scan x line Fig 6 The list should preferentially include all metallic or semiconductor elements present in the materials to be etched including those present in the material on which the etch should stop to add lines use the mouse to select a line and insert a new line by Edit Insert new sequence or the toolbar icon right lines may be deleted by mouse selection and the delete key One exception the top line cannot be deleted 3 4 4 3 Mass selection dubbel click on a selected line a Scan editor window will show up Fig 7 enter the name of the element you like to monitor e g Si in the Scan Legend line from the table on paper in the log book select the mass that corresponds to the selected element considering the points below Fig 7 enter the mass number in both the Start value and Stop value lines Philips Research MiPlaza TL Company Restricted Operation manual E17 Plaza Document nr EriHeu 20111220 1V01 Page nr 14 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 select the mass channels Scan lines you like to monitor probably all selection 1s made with the left hand mouse button while keeping down the CTRL key on the keybord press the binocular icon right on the toolbar to open a data view window be sure yo
29. t data acquisition run for a few seconds virtually no counts will be detected maybe some low level noise will show up by default the y axis will have linear scale stop the run with the red light in the toolbar adjust the settings of the X axis by clicking the right handside mouse button somewhere at the periphery of the data plot select X axis and continue in the subwindow by default the X axis has limited history but you may select otherwise likewise adjust the settings of the Y axis logarithmic scale selection in the full range be tween 1E 2 and 1E 7 c s works fine if too wide this range can be changed later in the same way while an etch run and the SIMS detector are in operation overwriting the first dummy run do a second dummy run and check the result save the file and ignore warnings about possible loss of data Sometimes software chooses identical colours for different mass channels both in the data plot and the legend in that case choose Views TrendViewSetup and select the element the Available Scan number list change the data point colour settings save the file and ignore warnings about possible loss of data The detector is ready now for operation Philips Research MiPlaza TL Company Restricted Operation manual E17 Document nr EriHeu 20111220 1V0O1 Pagenr 16 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 4 Rules and regula
30. tions 4 1 Instruction test and authorization Instructions are given to new users by the machine owner and users are authorized after a suc cessful test Usually this procedure will do especially when the authorized persons use the tool regularly 4 2 Process editor As a rule users are supposed not to make changes in existing processes except for the proc ess time The machine owner has to be consulted when a user likes to make changes or likes to create a new process 4 3 Tool problems In case of unusual behaviour of the etch tool or problems the machine owner back up should be informed immediately Essential for the tool and for all other users never try to solve problems yourself limit your contribution to notification of one of the afore mentioned persons especially when a wafer doesn t return from the process chamber 4 4 Wafer handling and penalties The mechanical wafer clamping mechanism imposes restraints on the use and handling of silicon and glass wafers All users are expected to strictly follow the rules for wafer handling in order to avoid wafer breakage and unnecessary tool down times preferably use wafers of standard size 150mm and thickness 0 67mm wafers should have a major flat both Semistandard and Jeida flat are accepted confirm good wafer fixture in load lock flat cut away at 12 o clock position thin wafers impose an extra risk because of the torques to which they are exposed while be
31. to extract ions from the plasma and cre ate a uniform and collimated ion beam 35cm diameter In contrast to the local technique of focussed ion beam FIB etching full wafers are exposed to ion bombardment The etch mechanism is of physical nature and is called ion milling or ion beam etching IBE Virtu ally every material can be etched with this tool including the noble metals Ion energy in eVolts and beam intensity current in milliAmps can be set independently and the ion energy spectrum is extremely narrow all in contrast to the situation in traditional sput ter etching The absense of a direct contact between plasma and substrates is another differ ence with sputter etching Because of low pressure in the process chamber typically ten times lower than in the plasma source and consequently long particle mean free path etched material ends up at the cham ber walls or liners redeposition back from the gas phase is very unlikely to take place Without measures charge would build up on the wafer especially when coated with an insu lating layer This would then lead to beam deflection and potential damage to the wafer due to arcing to grounded surfaces or arcing within the device layers on the wafer However charg ing and arcing are suppressed by an electron gun being part of a feedback loop that includes a charge sensor located near the wafer Software controlled the gun called plasma bridge neu tralizer PBN
32. turn of the transport arm and closure of the gate valve the selected process file will be loaded and the wafer will be clamped mechanically onto the chuck called fixture d Then helium cooling gas will be supplied to the wafer backside and shortly afterwards the pressure in PM1 is checked In normal situation there is a temporal pressure rise within tolerance limits and proce dures will continue Too high a pressure indicates excessive escape of helium gas into PM In that case an error message is generated and further processing is stopped automatically gt Please consult the tool owner or back up about how to proceed The wafer may have been broken or crunched by the clamping mechanism in any case don t try to get it back e If the leakage check has ended successfully two things will start simultaneously fixture tilt to position the wafer at the tilt angle stored in the selected process and ion source ramp up with the shutter in closed position source ramping is a software controlled procedure resulting in a beam with the desired acceleration voltage Beam V and current Beam mA both shown in the Source Readback part of the Control window Fig l f Shortly after finishing the previous actions the shutter green bar in PM1 will open up it takes a few seconds before this command takes effect shutter bar yellow The shutter is fully open when a shower of ions is visualised on screen in PM1 gt
33. u really created a new file name see 3 4 4 1 save the file and ignore warnings about possible loss of data Scan Editor i x Scan Mode Global ion SIMS Ta 181 181 000 amu 181 000 amu amp Advanced Relative Sensitivity 1 000 AvailabletoScan mass ts Minimum Value Dau Maximum Value 300 amu Minimum Increment 0 01 amu Description scanable quad control DAC Fig 7 Scan Editor window Points of consideration in mass selection most elements have more than one mass in the list natural abundance of isotopes in prin ciple select the mass that is most abundant e g 208 for Pb for highest detector count rate counts second but also consider the recommendations given below count rates are limited to le Q7 c s beyond that value the multiplier will eventually get damaged the SIMS detector is safeguarded and will ignore the concerning mass channel when exceeding this limit nevertheless try to avoid these situations obviously NEVER try to monitor the ion beam element argon itself light elements tend to produce higher counts rates than heavy elements even when etch rates suggest otherwise e g Al versus Au this also means that light elements are more likely result in count rates of 1E 7 c s and beyond especially when large areas are exposed to the ion beam in that case take a less abundant mass e g 29 or 30 instead of 28 for Si etching is not limited to the wafer as the ion beam strik
34. wafer Philips Research MiPlaza TL Company Restricted Operation manual E17 Plaza zs e A p Document nr EriHeu 20111220 1V01 Page nr 4 Document Operation Manual Veeco IonBeamEtch tool Epcode E17 Administrator Documents Administrator TFF Date 20 12 2011 tilt angle and the wafer motion Any tilt angle can be chosen between 0 wafer fully faces the beam and 90 beam parallel to wafer surface wafer facing UP or 90 beam parallel to wafer surface wafer facing DOWN In most processes the wafer is rotating at a speed of 10 rpm for better uniformity and or better film exposure in case of non zero tilt angles In static mode it is only at 0 tilt angle that the film to be etched is fully exposed to the beam At non zero tilt angles unmasked areas can partially be shielded off from the beam being in the shade of the etch mask profile near structure edges and wafer rotation is recommended Nevertheless for special applications static position can be chosen freely 2 3 Etch rates and selectivities Rough indications of etch rates for an arbitrarily selected number of materials is given in Ta ble 1 Selectivities can be calculated using these numbers for example the selectivity for the combination Au and AZ resist is 45 5 4 8 SiC 0001 9 y LiNbO Y SiO 001 3 Si GaAs 100 G i ai Ti GaAs 110 V SiC 0001 Table 1 Typical etch rates in nm min of metals and non metals at a typical b
Download Pdf Manuals
Related Search