i Digital PECVD Machine Construction ECE4007 Senior Design
Contents
1. aysis SJouo UEJEIZ UNC Sunsi JO jpaoway uoneBayu wiayss Joysyed mau sped WOJBULEH uoser queuuzoe des pue 13p10 uaysas Suns Yo JO ONE NUE uoneiado ways s Suns Y YIM UOIETUE uE saue 20100524 aue yee a dl 27 Plasma Project ECE4007L012. Figure 3 5 Panduit DIN rail example Panduit DIN rail makes wiring clean efficient and easily expandable Please note the large amount of wires in relation to the small amount of space utilized Plasma Project ECE4007L01 13 4 Design Approach and Details 4 1 Design Approach Physical Components The PECVD will be built as a single entity inside a chassis that will be the machine s stand The chassis is a Gator Jaw Anodized Aluminum 6063 alloy tubing stand shown in Figure 4 1 it will contain all of the hardware The stand has been fabricated to meet the needs of housing each individual component As the components are purchased and installed the size of the compartments can be adjusted The HMI will be mounted onto the external of the stand where it will be visible at all times The display will stay on and monitor the process as each step is activated within the PLC The plasma chamber was purchased pre owned and requires corrosion removal and minor refurbishing Figure 4 1 Frame used to build the PECVD machine Plasma Project ECE4007L01 14 Control System The Allen Bradley CompactLogix 1769 L35E was chosen as the PLC and it will process all signals through input and output cards These cards will handle analog and digital inputs and outputs A back plate will house the PLC terminal blocks and all interface connections In Figure 4 2 the completed back plate with the approximate location of the components
3. 00 163 97 System Frame Parts 1 600 00 2 150 40 120V power supply 428 00 575 23 Pressure sensors 37 10 49 86 Vacuum Tubing Parts 506 70 681 00 Mass Flow Controller 1 500 00 8 064 00 Throttle Valve me A m m m m m m m Rl 3 600 00 4 838 40 Plasma Project ECE4007L01 34 275 98 23 8 Summary The Design Team has meets weekly with project manager Jason Herrington He provided the specifications that are expected from the PEVCD The program that is required to produce the code for the PLC has been installed Example software code has been received and is being used as an aid Jason has ordered most of the parts that will be needed to complete the fabrication From the list of parts and their technical data all of the inputs and outputs that the PLC will monitor and control have been determined This also includes producing AutoCad drawings that will act as a wiring diagram With the parts that have arrived the stand has been assembled the back plate is installed The top hat rails which will house the PLC and the terminal boards and the wire duct is installed on the back plate Also all of the corrosion has been scrubbed from the chamber and the components that will not be utilized were removed Plasma Project ECE4007L01 24 1 2 3 4 5 6 References Allen Bradley 1769 L35E CompactL
4. 000 funding from the Georgia Institute of Technology Microelectronics Research Center MiRC to construct and automate a Plasma Enhanced Chemical Vapor Deposition PECVD machine Jason Harrington engineer for the MiRC will be providing specifications and will be overseeing the project The new machine will allow for digital control of the variables such as RF power vacuum level and gas flow rate using a programmable logic controller PLC and touch screen interface 1 1 Objective The team was supplied with an old Plasma Therm 700 series Reactive Ion Etching machine to recover the components necessary to assemble and automate a digital PECVD machine The final product will be a stand alone machine directed toward university micro and nanotechnology research facilities as well as semiconductor manufacture industries The design will utilize four different types of gases and an external mounted touch screen monitor for the user interface The PLC will be used to control the three fundamental parameters of a PECVD machine including vacuum pressure gas flow rate and RF power The program to run the PLC will be coded in ladder programming language using the RSLogix5000 software from Rockwell Automation Ladder logic language is a means of writing program in circuit blocks that can then be converted into machine code by the PLC microprocessor A human machine interface HMI consists of hardware and software will allow for user interaction with the
5. interface with the PLC to keep track of the amount of gas which has been injected An RF Power supply and a matching network are required to generate a high enough current to ignite and maintain the plasma The Advanced Turner ADX Generator was chosen because it contains the Power Supply as well as the Matching Network with the controller Generation of plasma is only possible when the gas has been excited to a level similar to 600 watts of power passing through a 50 ohm load Plasma Project ECE4007L01 16 A mechanical roughing pump will bring the pressure in the chamber close to 0 Torr Once the pressure is achieved gases will be ejected into the chamber The PLC will stabilize the gas ratio Next the RF Power will be applied to generate a cloud of plasma depositing a layer onto the silicon wafer Based on the desired film a defined amount of time will be required The gases are then removed from the chamber and atmospheric pressure is restored The process is shown in Figure 4 3 Mechanical Pump Chamber Activated Pressure Achieved MFCs Inject Gas Film Deposited on RF Power Desired Gas Ratio Present in Wafer Chamber oy Figure 4 3 Process Flow for PECVD Plasma Project ECE4007L01 17 4 2 Codes and Standards e The Allen Bradley 1769 L35E CompactLogix has two communication ports o RS 232 and a RJ 45 e The RJ 45 will be utilized and uses the 10BaseT standard with CatSe as the ca
6. it is anticipated that a sizable margin can be obtained Table 7 1 shows that nearly 50 of the total cost is associated with the plasma chamber power supply mass flow controller and throttle valve Plasma Project ECE4007L01 22 Table 7 1 Itemized Cost Item Cost unit Inflation Total Salvaged Plasma Chamber 2 500 00 1 00 2 500 00 10 Amp 3 pole circuit breaker 122 00 1 12 163 97 contactor for pump chiller 170 00 1 12 456 96 overload for pump chiller 54 20 1 12 145 69 enclosure for contactors 388 30 1 12 521 88 pushbuttons for contactor box 3 position 37 10 1 12 49 86 pushbuttons for contactor box 2 position 37 10 49 86 Eee PC Touch screen 500 00 672 00 Touch screen Swing Arm 100 00 134 40 AutoCAD 2010 Software 3 995 00 5 369 28 RF Power Supply Warranty 4 950 00 6 652 80 Rockwell Student Software Package 100 00 134 40 end cap right for compactlogix system 31 41 66 relay spst 24vdc coil ha 93 16 40 286 54 terminal block 0 98 158 05 terminal block jumpers uy 3 78 15 24 terminal block anchor 1 77 11 89 15VDC Supply 136 86 183 94 24vdc power supply 119 09 160 06 single pole circuit breaker 33 20 44 62 3 pole circuit breaker 122
7. on hard drives or any storage Plasma Project ECE4007L01 2 devices and upload to the PLC via an Ethernet connection The CompactLogix L35E microprocessor converts ladder logic code to machine code which can operate at faster speeds 2 The mounted touch screen monitor provides a larger color display and simpler user interface when compared to the old onboard control and screen of the Plasma Therm 700 1 3 Background Plasma Enhanced Chemical Vapor Deposition machines are required as semiconductor and electronic component feature sizes push into and past nanometer scale dimensions The need for close tolerances in substrate manufacturing is most evident in the processing of semiconductor lasers that require very thin layers when forming a p n junction 3 Additional methods of chemical vapor deposition include atmospheric pressure chemical vapor deposition APCVD and low pressure chemical vapor deposition LPCVD however they are limited by temperature and film thickness PECVD uses RF power to transfer energy into the reacting gas allowing the substrate to remain at a lower temperature than LPCVD and APCVD also plasma enhanced film can achieve thickness up to 5 um without cracking 4 Plasma Therm LLC currently manufactures the 790 series of reactive ion etchers RIE which is similar to a PECVD machine except RIE used plasma to etch away the substrate instead of deposit the plasma film onto the substrate This machine can be retoole
8. that will be added is shown The plate will be secured to the stand and all signals from each individual component of the PECVD will be wired to the appropriate terminal blocks A PLC programming language called ladder logic will be used to control the PLC and process the information 1 This will allow autonomous control of the throttle valves as well as the mechanical pump to maintain a list of user defined set points The top down structure of ladder logic programming will insure the next process does not start until the set point of the previous task is achieved The PLC will make it possible for the PECVD to reach the set points and maintain all of the values within a given variance This ensures that the correct pressures gas ratio and power are maintained throughout the duration of the cycle A touch screen HMI will allow users to select and start the process as well as select the combination of gases to use There will be one preset recipe and an option to input others on demand Plasma Project ECE4007L01 15 Figure 4 2 Back plate used to mount PLC and terminal boards Plasma Generation amp Film Deposition There will be four gases available to generate the plasma O2 Ar CHF3 and CaFs A predefined recipe given by the MiRC staff will determine how much of each gas is required for the process MFCs will inject the gas into the chamber through throttling valves that will manage gas ratios in the chamber These controllers
9. 1769 L35E Communication Ports RS 232 19200Kbytes sec EtherNet IP 10 100 Mbytes sec User Memory 1 5 Mbytes Nonvolatile Memory 1784 CF64 CompactFlash Max I O Modules 30 I O Modules Max I O Banks 3 I O banks Power Supply Distance Rating 4 logic must be 4 slots from power supply Operating Temperature 0 60 C Storage Temperature 40 85 C Vibration Operating 5G 10 500 Hz This project will utilize both communication ports RS 232 and EtherNet and five of the I O modules Having additional unused I O modules allows future expansion if needed The HMI for this project is the RSLogix 5000 from Rockwell Automation It features easy to use IEC61131 3 compliant interface symbolic programming with structures and arrays and a comprehensive instruction set that serves many types of applications 12 The HMI software will be installed on an ASUS Eee touch screen PC The graphical user interface GUI will resemble the screen shot in Figure 3 3 Plasma Project ECE4007L01 10 System Status Recipe idle ia Nanotechnology Cogen Research Center Vacuum Status Vocuurn Process idle Chamber Pressure Setpoint mT 100 0 Chamber Pressure mT 6E 2 Chamber Pressure THSES Chamber Low Pressure Th 75 6 Argon MFC mi MFC Actual 0 2 j MEC Setpoint 0 0 EAC interlock Oxygen MFC m MFC Actual 2 6 Water Flow GPM 0 000 i MFC Setpoint 0 0 Flow psii 0 550 i M
10. Digital PECVD Machine Construction ECE4007 Senior Design Project Section L01 Plasma Project Team Project Advisor Dr Keezer William Edwards Zlatan Ceric David Ogden Quan Tran Timothy Gurtler Submitted September 22 2010 Table of Contents EXECUTIVE S MMAFy la A tence saved A A asec iii l troduction nea eee A 1 Td ODISEA AAA AA 1 1 2 a A E 2 AR A O a a ees 3 2 Project Description and Goals ooooooonnnocccnnccccconcccnonccononccononcnononcnonnno cnn nc nonnnccnnnncnnnnos 5 3 Technical Specification oa 6 4 Design Approach and DetallS ooonooncnnnnccnnnncccnoncccnoncnononcnononccnnnnc cnn noconnnocnnnncnn 14 Al E AS A A a a ne a 14 A a A A ON 18 4 3 Constraints Alternatives and Tradeoffs ccccccnnoncnonananiconnnanananananicnononannnnnness 18 5 Schedule Tasks and MilestoNes oooo occcccncncccccicncccocociconacacana nana ra rara ra rara ra rana 19 6 Project DEMOS AMOO ii A ia 20 7 Marketing and Cost ANalysiS ooooooocnnncccnnncccnoocccoonccononcnonnnccononcccnnnc non nc nono nccnnnncnnnnos 20 LA Marketing Analysis A dada 20 Pl SC A A O ON 22 Se SIMA A A A AT A ies a eee 24 9 References ti A viata ea 25 APPENA A a al Fal Sel hE A AR TNE 27 Plasma Project ECE4007L01 Executive Summary The Microelectronics Research Center MiRC has commissioned the construction of a digital plasma enhanced chemical vapor deposition PECVD machine that will be used for semicond
11. EC MO Flow psi z o Trifluoromethane MFC t t Comp Ale pal 9 875 Throttle Valve Setpoint 100 MFC Setpoint 0 0 m eo MEC Actual 0 2 Setpoint 0 Actual 100 l Sulfur Hexefluoride MPC Forwerd 24 a SE MEC Actual 0 0 Keflected 5 2 MFC Setpoint 0 0 DCV 24 Purge J rough cate vate Nitrogen Gas Settle i BeF Deisy sec MC Pressure T 566 Settle Time Left sec Foreline Pressure 1 0 3 l Vent Running For MM MAM S5 0 0 0 Purmpdown Running For HHAMMESS 1 0 0 Eoraline Gate Vah Recipe Running For MM MM S5 0 0 0 i Start Recipe Start Vent Start Pumpdown 08 2009 4 11 21 RECIPE TRENDING Admin Login Figure 3 3 RSLogix 5000 HMI software controlling a PECVD machine 10 The user will be able to select pre made recipes or programmed states that the PECVD machine performs Please note the Recipe button at the lower left of the screen All of these components will be installed on a custom designed Gator Jaw Anodized Aluminum 6063 alloy tubing frame see Figure 3 4 Plasma Project ECE4007L01 11 4 Figure 3 4 Schematic of the frame to house all of the PECVD equipments 11 This AutoCAD drawling lists all of the dimensions for the various rails needed for construction All of the wiring and PLC modules will be mounted on Panduit DIN rail inside the Gator frame see Figure 3 5 for an example of this type of mount Plasma Project ECE4007L01 12
12. PLC The MiRC staff will supply recipes for semiconductor fabrication that will be loaded into the HMI Recipes are parameters of flow rate RF power and vacuum Plasma Project ECE4007L01 1 pressure having the correct composition to ignite plasma from a gas A GUI will be created using the FactoryTalk View software which will display pre determined recipes and users recipes For the given time constraint the completed product will be able to ignite a single gas No for a pre determined recipe 1 2 Motivation The Georgia Institute of Technology MiRC has requested the group to assemble and automate the machine There are PECVD machines currently available on the market however new PEVCD machine cost in the 250 000 range With a cost of 35 000 the recovered chamber and the four flow controllers together with the Allen Bradley CompactLogix L35E PLC the group will construct a functional machine The CompactLogix L35E shown in Figure 1 2 utilizes modular cards for it input and output connections thus allowing for future expansion 1 Figure 1 2 Allen Bradley CompactLogix L35E PLC Using modular components allows for simpler repair as the user can replace any defective components unlike the whole board in the old system The programs for the PLC are typically stored in battery backed memory allowing the system to function immediately after replacement of defective parts Users can also keep a backup of the programs
13. al companies which market these controllers including Bronkhorst Litre Meter and Aalborg The prices for these controllers range from 650 to 1 500 Roughing pump Roughing pumps are used to evacuate a vacuum system Roughing pump such as the HYVAC 150 can bring the system down to as low as 5x10 torr and cost 500 Turbo pump can further invokes to bring the system to as low as 10 torr TMG is one of many companies that specialize in turbo pump The appropriate vacuum pressure depends on the recipes the user selects in a PECVD machine Plasma Project ECE4007L01 4 2 Project Description and Goals The purpose of this project is to convert an outdated plasma therm RIE machine to a digital PECVD machine This will be accomplished by replacing the outdated knobs and switches with a PLC based controls system and HMI The device will have the following properties PLC e Small enough to be enclosed within chassis e Control power vacuum and gas flow sub systems e Intuitive modification with Ladder logic programming Functionality e Provide standard recipes for users created by MiRC staff e Allow users to create modify and execute deposition processes e Display current deposition recipe status e Allow Touch screen interface e Incorporate pressure sensor for safety precaution e Ignite plasma with RF power supply e Ability to control mixing of gases with mass flow controllers e Worth 250 000 upon completion e Cost of
14. ble type 1 e The international standard for PLC programming language is IEC 1131 13 e The code for electrical wiring in the industrial environment is defined in Article 670 of the National Electrical Code 14 e All other components are hardware and do not have associated standards 4 3 Constraints Alternatives and Tradeoffs Customer Jason Harrington of the Georgia Tech MiRC has defined most of the parameters of the project in explicit detail This leaves minimal room for design variation However rather than simply using a single mechanical pump a turbo could be implemented This would ensure that the pressure inside the pump is as low as possible The turbo pump would raise the cost of production and require the mechanical pump to have two stages a hard rough followed by a soft rough It is believed that the plasma can be generated and maintained at the pressure level the single mechanical roughing pump will obtain Also a new chamber would ensure all seals are vacuum tight The salvaged chamber has corrosion and minor abrasions Rather than spending the additional money to purchase a new chamber the old chamber will be cleaned and polished Plasma Project ECE4007L01 18 5 Schedule Tasks and Milestones The team is composed of two sub sections software and hardware The software team is responsible for the programming of the PLC and HMI while the hardware team edits the wiring schematics and installs electrical c
15. d to be either RIE or PECVD and generally can process multiple wafers simultaneously 5 There are three basic components of a PECVD machine including RF power supply flow regulators and a roughing pump RF power supply The RF power supply system consists of the RF power generator and an RF power matching network System matching is important due to the reduction of power lost by reflection Plasma Project ECE4007L01 3 in the transmission lines The matching network monitors the reflections and adjusting the matching impedance to insure the power to the load is maximized and consistent There are manual matching network and auto matching network manufacture by several companies such as Advanced Energy Comdel and Drytek price range from 3 000 to as much as 15 000 6 An RF power of 13 5 MHz is often used in industry to create high density plasma however varying the RF power allow for different plasma composition and duration of ignition Flow regulator Flow regulator system controls the rate of gas being input into the chamber Flow regulators have a set point value specify by the user which govern the output rate Mass flow regulator measures the flow directly without diversion and can switch between different gases specify by the user The control circuit compares the flow rate with the set point rate Deviations from the set point are corrected by compensating valve adjustments maintaining the desired flow rate 7 There are sever
16. lled throughout the machine In addition to this the user will be able to program recipes in the HMI that will be stored in the PLC These recipes will allow the user to preselect modes so that every variable does not need to be adjusted each time the PECVD is used The automated PECVD machine will be demonstrated on the Georgia Tech campus at the new Marcus Nanotechnology Building s clean room The PECVD machine will have the ability to use up to four different gases however at the request of MiRC only nitrogen will be used to generate a plasma during demonstration due to its non explosive properties Viewers should see a bright purple emission when the device reaches the correct operating settings During operation the viewers will be able to see the operation of the HMI and its various inputs and feedback Finally a recipe will be programmed into the device and then recalled to demonstrate its functionality 7 Marketing and Cost Analysis 7 1 Marketing Analysis PECVD units are custom tailored to each client s needs and hence reflect the requirements of the particular user The types of gases used to generate the transport plasma the copious organic gases employed in the chamber and RF power levels are all bespoke to the customers need The primary target clientele are research institutions along with semiconductor and microelectronic manufacturing companies More generally the client spectrum consists of those organizations wishi
17. ng elements makes this system highly amicable to the production of photonic crystal waveguides 15 At the higher temperatures encountered in CVD many process driven defects can form in the deposited layers thus lowering yield and consequently process efficiency When properly equipped with a magnetic field module further stimulation of the plasma chamber at an electron cyclotron resonance enables several prospects in ion implantation and varied doping structures This feature is of interest to companies working with GaAs GaN and Plasma Project ECE4007L01 21 other III V optoelectronic or high frequency microwave materials The ability to locally modulate temperature driven defects further opens the possibility of depositing novel material thin films for energy research applications 7 2 Cost Analysis A comprehensive cost analysis of the PECVD system includes not only parts and labor but also associated design and testing cost After carefully itemized review of required materials the total part cost was determined to be 34 275 98 Considering an annual salary for an ECE graduate to be 77 700 00 a total of 400 man hours 5 design and implementation team members the total labor cost comes to 104 711 54 This cost consists of labor design reports meetings lectures and final product testing and standards assessment Unadjusted for inflation or rise in manufacturer costs the total PECVD cost reaches 138 987 52 At this level
18. ng to deposit substrate layers with a large degree of uniformity and high Plasma Project ECE4007L01 20 rate of speed The ability to deposit controlled layers of poly silicon makes PECVD an outstanding tool for companies working with solar cells and silicon based renewable energy This PECVD model features a touch screen HMI ideal for environments requiring ease of use and a small operational learning curve The HMI interface allows users to select key recipes with great ease thus cutting the need for costly and time consuming training of personnel Company technicians can readily select a recipe from our pre programmed menus effectively controlling the deposited substrate composition and thickness with turnkey alacrity The user centric approach of our HMI display endows this product with a multitude of advantages over its analog controlled counterparts often found in today s research and manufacturing institutions Apart from uniformity user interaction and substrate choice versatility this PECVD employs RF generated plasma to facilitate reaction between user specified gases within the chamber RF generated plasma dictates relatively low operational temperatures particularly on the order of 300 C or more less that regular Chemical Vapor Deposition instruments This operating temperature range is particularly attractive to companies working with Silicon substrate formation technology The ability to abstract away the function of heati
19. ogix System User Manual Rockwell Automation Milwaukee WI 2003 D Du X Xu and K Yamazaki A Study on the Generation of Silicon based Hardware Plc by Means of the Direct Conversion of the Ladder Diagram to Circuit Design Language International Journal of Advanced Manufacturing Technology vol 49 pp 615 626 Jul 2010 M Zverev D Peregudov I Sedova S Sorokin S Ivanov and P Kop ev Low threshold electron beam pumped green quantum well heterostructure semiconductor lasers Quantum Electronics vol 34 pp 909 Nov 2004 S Han M Ceiler S Bidstrup P Kohl and G May 2004 Jun Modeling the Properties of PECVD Silicon Dioxide Films Using Optimized Back Propagation Neutral Networks IEEE Transaction on Components Packaging and Manufacturing Technology Online 17 2 Available http www chbe gatech edu kohl Publication 20Articles 39 Modeling 20the 20Properties 200f 20PECVD 20Silicon 20Dioxide 20Films 2 0U pdf Accessed Sept 20 2010 Plasma Therm Inc 700 Series User Manual Books I amp 2 Plasma Therm Inc St Petersburg FL 1990 RF Gen Equipment Bid Service LLC Online Available http www bidservice com Browses SearchEngine Browse asp keywords 20RF 20 Plasma Project ECE4007L01 25 7 8 9 10 11 12 13 14 15 Gen amp source GooglePPC_Semi_General amp gclid CIPa25HG9aMCFQgQswodBAMI3A Accessed Sept 21 2010 GFC Ma
20. omponents Table 5 1 shows the task resource names and timeline of each major task The start date of the project is August 15 and the end date is November 28 These tasks may also be seen in the Gantt chart located in appendix A The removal of existing controls systems was done promptly so that construction of the new system will not be hindered Much of the programming and testing will occur once the system has been entirely assembled Table 5 1 Scheduled Tasks Task Name Resource Names End Date Familiarization w existing system All 29 Aug Identification of existing component and wiring All 19 Sep Order replacement new parts for system integration Jason Harrington 19 Sep Removal of existing controls system Quan Zlatan 22 Aug Installation of new control system Tim Zlatan 3 Oct System Documentation Will David 28 Nov System Testing All 28 Nov Programming of PLC and HMI Quan Tim 28 Nov Corrosion Removal Will Tim Zlatan 12 Sep Plasma Project ECE4007L01 19 6 Project Demonstration The goal of this project is to create a functional PECVD machine that is fully controlled by a user at a touch screen HMI The HMI in conjunction with the PLC will have the ability to set gas flow rates roughing pump levels and RF power levels The HMI will also transmit data back to the user through sensors insta
21. ow rate is regulated and consistent The RF power supply is controlled by an ATX tuner which is a RF matching network designed to convert the complex impedance of a plasma at 13 56 MHz to 50 ohms resistive 9 The physical specifications for this device are in Table 3 2 Table 3 2 Specifications for ATX 600 Tuner Power Capacity 600 W 1250 W 2500 W Frequency 13 56 MHz nominal Impedance Range 5 ohms to 2000 ohms RF Input Connector 600 W Type N 1250 2500 W Type HN RF Output Connect Universal output kit provided Input Power 115 V ac 10 or 220 V ac 10 This matching network helps maximize power transfer while restricting reflected powered The ATX tuner specified in Table 3 3 has an automatic mode that allows the device to automatically Plasma Project ECE4007L01 tune the RF power supply ensuring that stabilization occurs and a plasmid is achieved A Plasma Present indicator light gives the user a visual display that the device is operating correctly The Plasma Present indictor light is located midway on the panel and to the right of the Tuned indicator as shown in Figure 3 1 Table 3 3 Physical Specifications for RFX 600 Power Supply 10 Power Output 600 W max into a 50 ohm load Frequency 13 56 MHz 0 005 Output Impedance 50 ohms Input Power 115 V ac 10 or 230 V ac 10 single pha
22. parts 35 000 00 Plasma Project ECE4007L01 3 Technical Specifications The proposed digitally automated PECVD machine is composed of the following main components e Plasma chamber made for two inch wafers e Four mass flow controllers for different gases e ATX tuner for RF matching network e RF power supply e PLC e HMI e Custom built frame to hold all of these components Along with these main components there are two sensors on the PECVD machine that communicate with the PLC a chamber sensor for reading chamber pressure and a pressure sensor for measuring the roughing pump base pressure The PECVD machine can utilize four different gases Ar O2 CHF3 and C4Fs The flow rate of each gas is controlled by a Brooks Model 5850E Mass Flow Controller as seen in Table 3 1 The mass flow controller MFC is regulated by the PLC which is able to send and receive data from the MFC This ensures that the gas flow rate is regulated and consistent Plasma Project ECE4007L01 Table 3 1 Physical Specifications for Brooks Model 5850E Mass Flow Controller 8 Flow Ranges 0 to 3 sccm Performance Accuracy 1 of set mark Repeatability 0 25 of predetermined rate Command Input Voltage 0 to 5 Vde Output Signals 0 to 5 Vde Max Operating Pressure 103 bar The mass flow controller MFC is regulated by the PLC which is able to send and receive data from the MFC This ensures that the gas fl
23. se 50 60 Hz The Plasma Present indictor light is located midway on the panel and to the right of the Tuned indicator As stated above the ATX tuner controls the RF power supply Its physical specifications are listed below in Table 3 3 FORWARD POWER O TUNE POSITION O DODDOOODUDDDONUOUOIS POWER POSITION REFLECTED POWER O SHUNT POSITION Figure 3 1 Front panel display of ATX 600 tuner 9 Plasma Project ECE4007L01 Please note that the power output of the RF power supply matches with the power input of the ATX tuner the RF power supply output impedance matches with the input impedance of the ATX tuner and the frequency of both devices are identical A circuit level representation of the RF power supply can be seen below in Figure 3 2 The plasma chamber is represented in Figure 3 2 by the dome shaped device on the far right The RF power supply working in conjunction with the ATX tuner transforms a gas into the plasma To user pin 2 DC bias To user pin 1 dc bias Figure 3 2 Circuit representation of the RF power supply connected to a plasma chamber 10 The PLC will interface with the various sensors MFCs RF power network and the HMI The PLC being used for this project is a CompactLogix 1769 L35E and its specifications are listed in Table 3 4 11 Plasma Project ECE4007L01 9 Table 3 4 System Specifications for CompactLogix
24. ss Flow Controller Manual Aalborg Orangeburg NY 2006 Brooks Instrument Brooks Model 5850E Mass Flow Controller DS TMF 5850 MFC eng datasheet Oct 2008 Advanced Energy ATX 600 Tuner User Manual Advanced Energy Industries INC Fort Collins CO 1994 Advanced Energy RFX 600 Generator User Manual Advanced Energy Industries INC Fort Collins CO 1991 E Ellis N Lourenco R Mainampati Z Costello and A Kardomates RIE Control Upgrade for the Georgia Tech Nanotechnology Research Center Georgia Institute of Technology Atlanta GA 16 Sept 2009 Rockwell Automation RSLogix 5000 CD ROM Milwaukee WI 2003 Rockwell Automation What is IEC 1131 Rockwell Automation 2008 Online Available http www software rockwell com corporate reference lec1131 Accessed Sept 21 2010 National Fire Protection Agency NFPA 70 National Electrical Code 2011 S Saini C Hong N Pfaff L Kimerling and J Michel Partial confinement photonic crystal waveguides Applied Physics Letters vol 93 no 26 Dec 2009 Plasma Project ECE4007L01 26 Appendix A Project Gantt Chart 22 vee Wl n MI ITT TEOT YEOT LUOT OTOT EOT Eg 61 6 daguana GE RINO te Ts RWS vejejz ueno MUI nin uee Z Wl IM paoway uorsouoy swegod yyH pue wung yd Josue Bog Y Sunsa waski pegun uonepuaumog wasis ways Jouo uee MaU JO ONE JENS
25. uctor fabrication The plasma chamber for the new PECVD machine was removed from an old reactive ion etching RIE machine in the Marcus building A PLC will be used to control the components while a touch screen interface will be used as the human machine interface HMI The HMI interface allows users to select key recipes with great ease thus cutting the need for costly and time consuming training of personnel The gas recipes control the thin film deposition of each layer during the process The Programmable Logic Controller PLC will control and automate the three fundamentals sub systems of the PECVD including RF power supply mechanical pump and mass flow regulators There are three necessary set points for the PECVD to function the chamber vacuum pressure RF power and gas flow rate A mechanical pump reduces the plasma chamber pressure to a specific point depending on the type of gas used The gas is then ionized by a RF voltage which can then be deposited on a substrate The digital PECVD machine will be more efficient easier to use and more reliable than its analog predecessor The cost of materials for construction of the PECVD machine will be 34 275 98 The finished machine will automate the fabrication process and allow for code modifications in the future This machine will have a market value of approximately 250 000 Plasma Project ECE4007L01 111 PECVD Machine Upgrade 1 Introduction The Plasma group is requesting 35
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