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1. ea ka 60 Deposition System o eei eo ev loe hte 62 Plasma Depositioner Assembly pp 63 Electrical Cabinet es 64 ix 4 6 4 7 4 8 4 9 5 1 52 5 3 5 4 A 1 A 2 Gas Control System ai dE A AE o o Eso o ots 70 Gas 30 6 1101 M 71 Pressure Initialization uico nde tu e De SA 72 Frame no 1 of Initialize System vi esee 73 The front Panel when the parameters are stabilized 76 Pressure Stabilization ooo tete t bete ere la 77 Flow a A 78 Spectrometer Readings oni 79 Mass Flow Controller Wiring Diagram pp 84 Gas Control CCU MER MER DERIT 85 CHAPTER I INTRODUCTION Growing technological requirements and the widespread acceptance of sophisticated electronic devices have created an unprecedented demand for large scale complex integrated circuits Meeting these demands has required technological advances in materials and processing equipment and an increased emphasis on effectively utilizing the computer to aid the process of manufacturing integrated circuits The IC manufacturing process involves many physical and chemical processing steps such as oxidation photolithography epitaxy ion implantation chemical vapor deposition etching and diffusion To create an IC these processes have to be repeated many times 1 IC fabrication requires the
2. war t N S He J l o bos SOLENOID CONN r z f i gt v 1 Lac 72 v 65 Figure A 2 Gas Control Circuitry 85 re 1 7 4 D H PERMISSION TO COPY In presenting this thesis in partial fulfillment of the requirements for a master s degree at Texas Tech University or Texas Tech University Health Sciences Center I agree that the Library and my major department shall make it freely available for research purposes Permission to copy this thesis for scholarly purposes may be granted by the Director of the Library or my major professor It is understood that any copying or publication of this thesis for financial gain shall not be allowed without my further written permission and that any user may be liable for copyright infringement Agree Permission is granted Student s Signature Date Disagree Permission is not granted Student s Signature Date
3. ED 30 Optical se 32 Diagram of operation of DDA 06 pp 35 viii 3 8 3 9 3 10 3 18 3 19 3 20 3 21 3 22 3 23 3 24 3 25 3 26 3 27 4 1 4 2 4 3 Diagram of operation of PC LPM 16 35 External Interface Boards sss 38 mne INGEWOEK TRE 40 Control Program Flow Chart 42 Front Panel of Plasma Etcher Program sss 44 Different Frames of the Setup stage 060 45 Fraime for the Dimer oes oO es e ee Eo e 46 Gas Selection VI a Front Panel b Block Diagram 47 Pressure and Time selection screen 48 Frame No 0 of the Initialize System vi ccc ccc 48 Frame Number 1 of the Initialize System vi 49 Setting of Gas Flow Rates and Activation of Solenoids 1111 50 Binary Values for Gas Solenoids pp 52 Erame 9 3 tee eite a est LASTS OES hes 53 Montor Stage scion ee as rtu ctae eda stad t PU Oa uM 53 Acquire Runtime Data Vla God hok Ria 56 Diagram Of Validate Data Vi e e pt eda rbd 57 Stellt Viere A er ao EZ 58 Purine WILL NILTOBOIL TO ded elei ROA 59 Control PLO Sa so ce EAR
4. Lab PC jg i HUE Hi Analog Input Signals Figure 4 5 Operation of Lab PC 67 gt bi gt Ee Table 4 1 Pin Configuration for Lab PC Pin Number Pin Function Pin Assignment ACHI CF Flow Rate ACH2 Hydrogen Flow Rate ACH3 Oxygen Flow rate ACHO Ar flow Rate i ACH4 RF Power ACHS Pressure ACH6 RF Impedance Setpoint for Ar Flow rate Analog Ground Digital ground Argon Relay PA3 10 12 11 3 1 Hydrogen Relay DACO device 2 Setpoint for CF4 flow rate 12 DACI device 2 Setpoint for H flow rate 1 1 1 1 4 5 6 7 0 1 The digital I O consists of three ports ports A B C They are eight bit bi directional ports The analog output channel DACO on devicel is used to control the pressure 68 setpoint for the chamber pressure The output channel DAC is used for controlling Ar gas flow rate setpoint Similarly the DACO and DACI channels on 06 1662 are used for controlling CF4 and Hydrogen gas flow rate setpoints The port A is used to trigger the relays to switch on the gas solenoids 4 3 Gas Control System and Sequencer Box The sequencer box originally had RAM chips and EPROMs 3 which had to be programmed for each run to perform operations in sequence etch ash deposit It was tedious and has been replaced with solid state relays actuated from the computer The sequencer box is a control dev
5. PY 0 4 O ORKA v Wie d POWER CHASSIS mta Zu 0 Cabinet Figure 4 3 Electrica 64 4 1 1 Gas and Compressed Air System The function of the gas system is to furnish various gases at selected rates to the reactor chamber The system consists of necessary piping valves mass flow controllers and gauges to control and monitor the process of etching and deposition At the depositioner assembly each process gas is controlled by a solenoid valve and monitored by a flow meter and pressure gauge The solenoid valves are actuated by toggle switches manual mode or by signals from the sequencer box activated by the computer which inturn operate the air valves to permit gas to flow into the manifold There is also provision for Nitrogen gas to purge the chamber Compressed air is supplied to the unit at 70 psi The compressed air performs three functions It raises and lowers the reactor cover operates the air valves that control the pump out rate of the reactor operates the air valves that control the application of input gases to the chamber Compressed air enters and evacuates the reactor cover control air cylinder through a piping arrangement containing two solenoid valves and an adjustment needle valve An air cylinder controls the reactor cover It can also be controlled through a signal from the computer Also a toggle switch LID UP DOWN manual mode controls the lid When the switch is in t
6. Ar flow rate channel Value 0 4095 i 1 AMLA AA 7 DIE s ORY VT awa QU OO LAC LL j elis Ne 17 152116 Moya he RE nomm 61 vi Lr 5 5252 15 Figure3 25 Shutdown System vi Shut down Svstem vi Frame 0 initializes the DDA 06 card as before In frame 1 b00000000 is written at Port B to power off all the gas solenoids There are 5 frames in this Frame itself in which the D A channels are reset Once the system is shut down the user gets an option to purge the system A snapshot of the program when purging was being done is shown in Figure 3 26 Shut Down System vi Purge System with Nitrogen 255306695 UNA WAN RGN ARN AAA ARR ARA AAA P 22442 OLZA 0 i AOR 050 I NA ISE 77 6202 IE 7 2 7 2 7 VM NS SEMEN YE ISSS AAA Y NN 157222 222 4 2220090 D 3 2 ooo A YY L E 0 22232200 355055352555 22 252 OOOO OOOO OO O O O OOOO SEK SMSEESSMNNNNSNNANS OOO TE EA 7 12 EE ee 253 45494040900 CE 7 55 10
7. The coefficients for this equation were experimentally determined Here F is the set point value of the flow rate in SCCM Standard Cubic Centimeters per Minute The mV equivalent of FS is made available between DA Gas Number and GND ground by Analog Number Out vi For setting the flow rate of Argon DA 0 Pin 18 is selected since the gas number for Argon is 0 The binary value for activating the Ar Gas solenoid is 100000b From Table 3 2 the bit 5 of 8 bit digital Port B has to be set to binary 1 to activate the Ar Solenoid while all the other bits should remain 0 Figure 3 20 lists all binary values for activation of different gas solenoids 51 A 1 RA ijt SDI LL ee eens ez ee Argon Gas PB7 PB6 PBS PB4 PB3 PB2 PBI PBO CF4 Gas UNE ME LUN l 0 PB7 PB6 PBS PB4 PB3 PB2 PBI PBO Hydrogen Gas Gu EUR UM UNE SE PB7 PB6 PBS PB4 PB3 PB2 PBI PBO Oxygen Gas A OE ZE R AE A PB7 PB6 PBS PB4 PB3 PB2 PBI PBO Figure 3 20 Binary Values for Gas Solenoids The sub VI Digital Out vi is used to write to a digital port The other sequence structures for other gases in Frame 2 are similar except for the governing equation for the flow rates Each sequence has an equation and its binary value for activating its solenoid The equations for other gases are given belo
8. AUTOMATION OF SEMICONDUCTOR PROCESSING EQUIPMENT by VIJAY VUPPALADADIUM B E A THESIS IN ELECTRICAL ENGINEERING Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING Approved August 1999 no 05 Z ACKNOWLEDGEMENTS 444 Alb 13 gt Co d AM 3726 I am deeply indebted to my advisor Dr Micheal Parten for his most valuable guidance and colossal support during my education at the Texas Tech University Thank you for being patient and understanding I thank Dr David Mehrl and Dr Sunanda Mitra thesis committee members for their excellent cooperation and interest in this project special thanks to the Department of Electrical Engineering for giving me this valuable opportunity to study at Texas Tech University I wish to extend my deepest gratitude to my grandparents Mr Nageshwara Sharma and Mrs Padmavati my parents Mr Venkat Rathnam and Mrs Meena Kumari for their love encouragement and blessings throughout my entire life I thank my little sister Sirisha for her affection and well wishes I would like to thank my uncle Dr Naga S Bushan and my aunt Mrs Jyothi Bushan for their guidance and encouragement during my stay at Lubbock I am extremely thankful to Mr Amit Deshpande and Mr Vishal Agrawal for their timely help A special thanks to Mr Tasnim Murad Hossain for his he
9. EAT k noS Ut OHEPEHHUMBEMHLUMILUTLHEUIDUUMOSO Hess UH THBBEREBHSHESEHBEEAITS L REFERENCES 1 Sze S M VLSI Technology New York McGraw Hill Publication 1996 2 Texas Instruments Autoload Single Slice Plasma Reactor Manual Dallas Texas Texas Instruments Inc 1981 3 Plasma Deposition System Texas Instruments Inc 1985 4 Robert H Bishop Learning With Labview Reading MA Addison Weslev Pub Co 5 National Instruments PC LPM 16 User Manual Austin Texas National Instruments Corporation 1990 6 National Instruments Lab PC User Manual Austin Texas National Instruments Corporation 1990 7 Manos D M Flann D L Plasma Etching An Introduction San Diego Academic Press Inc 1991 tye E 4 LE p bon Lo d m m dame 2 E 2 cdm Lo E Bb sie I lt ail PRI ta n Te SE APPENDIX 83 AV RIN 13V 35V RIN RTN 24 SW SW Power Supply Board TB4 Signal Distribution sy 15V 24V 24V ATM Boar 117 To D stributian Board ey To Distabutien Heard MFC Connector gud 8 10 7 on Setpoint Com Mr MEC Mies 14 MECH 4 Figure 1 Mass Flow Controller Wiring 84 MAII ness ce mame ANIM ne arwein t 1
10. ZADANO ZERA OOO 277 AAAA BB EEE 2 DZA LL E ELSE LLL CCA DM 2 17227 os 122127 2 POZNAC ae 22 27 222552 LLL LEE RIEL E 22 A RAZ se Figure 3 26 Purging with Nitrogen Now that all the modules in the diagram are explained the entire etcher source code is shown in Figure 3 27 So once the user sets the parameters in the setup stage the program initializes all the cards starts the system sends the appropriate voltages to different peripherals and sends the control to the next stage monitor stage which receives signals from the machine processes them and makes it compatible for the display and once the process time is finished the system shuts down PPP RDUM arr M eE er r OR STAGE PELE 3 RRA NAAN Figure 3 27 Control Program Thus the Control program was designed using the generic approach discussed in Chapter II This modular approach of designing the program is easy and changes to the code can be made easily This methodology of automation was successfully implemented on the Plasma Etcher The next chapter Chapter IV discusses the implementation of the automation approach on an other system called Plasma deposition system TRUSTe eA can MT TE cee tire 1 CHAPTER IV IMPLEMENTATION OF AUTO
11. 0 4 2 Set De LIMOS rp Convert the Pressure Set Point to a s Number to be written to the D port TASTE TEES SEE AO BARS 0024 REDOM RAB AAC O PANNO BRANO EB jouguopgudgugugugupgguggggugugo 3 Figure 4 8 Pressure Initialization Figure 4 9 Frame no 1 of Initialize system vi So once the parameters are set in the first stage the control goes to the second stage to get the feed back signals from the machine into the Acquire runtime data vi which is explained in the monitor stage for the Plasma Etcher The shutdown stage is explained in Chapter III In the shut down stage binary O s are written to all the digital channels and the setpoints are made zero to the Analog output channels using the analog output vi and the write to digitalport vi Finally the system is purged The next chapter Chapter V discusses the results obtained and the measurements taken 3 H t K 73 SENS Z Ar CHAPTER V MEASUREMENTS The automation approach was implemented on two systems namely a Plasma Etcher and a Plasma Deposition system The LabVIEW control program takes the setpoint values from the user converts them to equivalent volts or millivolts sends the signals to the controllers on the machine through the D A Board reads the parameter values from the machine throu
12. solenoids and their voltage ratings etc The signals sent out by the computer are digital but the machine may accept analog and or signals At the same time the machine sends analog and or signals as inputs to the computer Therefore DAQ data acquisition boards that have the capability to do D A Digital to Analog conversion and A D Analog to Digital conversion are needed 2 2 1 DAQ Data Acquisition Boards The D A DAQ board must accommodate the right number of D A channels with a good bit resolution sampling rate and extra lines of digital input output The D A channels are used to control the analog inputs to the system The extra lines of digital outputs are used to control the energizing of components like solenoids and relays Figure 2 2 a shows the diagram of operation of a D A board The A D DAQ board is used to read in the analog input signals into the computer It should have the right number of A D channels to accommodate all the parameters that affect the process Figure 2 2 b shows the diagram of operation of an A D board Analog 5 Channels Digital Ports Set Point Values From LabVIEW Software D A Board Set Point Voltages a Values Displayed On the Comnuter Analog Input Signals b Figure 2 2 DAQ Boards a D A DAQ Board b A D DAQ board The DAQ boards should have an option for the user to select the voltage ranges of incoming and outgoing signals to s
13. Software Analog Digital Port B Set Point Voltages Digital Port C Figure 3 7 Diagram of operation of DD 4 06 3 2 2 National Instruments PC LPM 16 Analog Input Board The PC LPM 16 6 Analog input board has 16 single ended input channels with 12 bit plus sign bit resolution Each input channel is jumper selectable to accept inputs of 2 5 5 OV to 5V OV to 10V All input channels have been set to OV to 5V for this application A maximum sampling rate of SOKHz can be achieved The board also has one 8 bit digital input port one 8 bit digital output port and 16 bit counter timers Figure 3 8 summarize the operation of this card Table 3 3 shows the pin assignments and the pin functions for the PC LPM 16 card PC LPM 16 Signals from the Plasma Etcher Values Displayed On the Computer Figure 3 8 Diagram of operation of PC LPM 16 D tes Table 3 2 Pin configuration of the DDA 06 Analog Output Board Pin Number Pin Function Pin Assignment 1 D A 5 RF Power Set Point 2 D A 4 Pressure Set Point Gas Solenoid H PB6 Gas Solenoid O2 pts 5 PB5 Gas Solenoid Ar RF m Gesell 9 PBI Gas Solenoid N 11 Digital com Digital Ground 12 D A 3 O Flow Rate Set Point 14 D A 2 H Flow Rate Set Point CF Flow Rate Set Point 17 GND Analog Ground 18 D A 0 Ar Flow rate set Point 24 PCS RF Power OfF 25 PC4 RF
14. This idea of automation has many advantages over conventional systems designed using microcontrollers and EPROMS First the user intervention is less compared to those systems The cost of building the system and its automation is reduced Installation and fault location are easier The industry has a number of DAQ Boards available and the 80 ZPCH i yE et 4 EOS d HI RE Hha user will have ample choice to make a proper selection Measurements and results can be obtained with a high accuracy and precision The methodology developed has been implemented on a project called Web Interface Design For A Plasma Etcher by Mr Tasnim Murad Hossain where the setpoint values for the parameters are set from a web page and the controlling of the system is done from the Internet This approach should be implemented not only on Semiconductor Processing Equipment but also on systems like Hybrid Electric Vehicle Fuel Cell where results and measurements can be obtained with high accuracy and efficiency The advantages of such a generic approach are that system monitoring and control are easier to understand and modify because of LabVIEW s flexibility and ease of programming Excellent control can be maintained over process parameters because of the real time feedback control system This approach can be implemented without losing the integrity and the safety parameters of the equipment 81 OBN
15. board was used to read in the analog signals from the machine The boards were selected depending on the number of parameters that had to be controlled and monitored as mentioned in the generic approach in the previous chapter The DAQ boards used met the specifications mentioned in the automation approach 3 2 1 Metrabyte DDA 06 Analog Output Board The metrabyte DDA 06 board is an analog output board which provides six channels of analog output with 12 bit resolution and 24 lines of digital input output Each output channel occupies its own I O address location The output channels are switch selectable to OV to 10V OV to 5V 2 5V to 2 5V 5V to 5V 10V to 10V and 4 20mA current All output channels are set to OV to SV range in this application The digital I O consists of three ports ports A B and C They are 8 bit ports Each of the ports can be configured as an input or output port Analog output channels 0 through 3 are used to control the set points for the flow rates of four process gases Analog output channel 4 is used to control the set point for the chamber pressure and the channel 5 is used for RF power set point Bits 1 2 5 6 7 of port B are used to control the process and purge gas solenoids Bits 4 and 5 are used to turn the RF generator on and off 34 respectively Figure 3 7 summarizes the operation of this board Table 3 2 shows the pin connections and the functions for the DDA 06 Set Point Values From
16. many changes in the system setup Hence for a successful high yield process automation and control of semiconductor fabrication equipment is necessary With the evolution of single wafer processing systems and using microprocessor based hardware and software real time monitoring and control systems have been developed to ensure that wafers are processed properly at every step An automated wafer fab increases productivity and cycle time through manufacturing by as much as 50 and reduces the cost of manufacturing and labor The current processing industry makes use of automated equipment for each process The processes use stand alone equipment with built in microprocessors or application specific microcontrollers which are hardcoded or programmed to accomplish that particular process If equipment for an other process has to be automated then again a process of designing an entire stand alone system takes place The disadvantages of using such systems are they are expensive to manufacture it consumes a lot of time to program the devices for such systems and the user has little control of the internal system In todays rapidly changing environment manufacturers want to be able to 2 improve the processes continually This can require being able to alter the monitoring and control of the individual process To accomplish these changes a generic approach for monitoring and control of processes and equipment is desired The main emphasi
17. phase detector controls the servo motor of the series tunign capacitor and the signal from the magnitude detector controls the servo motor driving the shunt capacitor Both the detectors operate simulataneously to transform the impedance of the load to 50 ohms DD Se gt PHASE AND MAGNITUDE POWER DETECTOR SERVO MOTORS CHAMBER Figure 3 10 Tuning Network 3 5 LabVIEW Control Program for the Plasma Etcher The software should be in such a way that it is flexible and modifiable The input parameters that the user has to select are the following e Selection of a gas Ar CF4 Hp O2 e Set the gas flow rate e Set the pressure e Set the RF power e Set the total time for the process The user has to monitor the following parameters in a plasma chamber e Pressure e Power e Flow rate e Impedance e Process time left Figure 3 11 shows the flow chart for the automation Program for the etcher The program is designed according to the algorithm mentioned in the generic approach The user sets all the parameters and the D A DAQ board sets the set point voltages to the machine and the A D DAQ board feeds the run time data from the machine into the computer 41 Select Gas Gas Flow rate Select Pressure Power On the Selected Gas Solenoid Set the Process Time Set Temperature Set RF Power Read and Display Flow Rate RF Power Pressure RF Impedance Temperature Proce
18. use of electromechanical optical and electronic equipment and materials capable of precisely maintaining close tolerances and small geometries VLSI processing requires that the process parameters like gas flow rates pressure and RF power be tightly monitored and controlled In any typical fabrication equipment with minimal automation the process parameter settings have to be controlled manually Any changes in process parameters leads to variation in the results that are unacceptable for sub micron device geometries Manual control of process parameters and equipment may induce errors that are cost prohibitive in todays wafer labs As wafer size increases and the critical dimensions decrease stringent requirements are imposed on processing It is desirable to process every wafer under identical conditions Process yield has increased with the evolution of single wafer 1 processing systems that are fast replacing batch reactors where several wafers are processed together Due to the nature of single slice processing machine dynamics may change from second to second and from wafer to wafer It becomes necessary to monitor all the run time data such as pressure changes flow rate changes RF power and other parameters With changing technology newer recipes for processing are developed at increasing frequency for smaller device sizes and to increase the yield The fabrication systems must be able to implement the new recipes without
19. 1 3 2 DAQ Boards Used For Plasma Etcher 34 3 2 1 Metrabyte DDA 06 Analog Output Board 34 3 2 2 National Instruments PC LPM 16 Analog Input Board 35 3 3 External Interface Board ae 38 3 4 RE T ntnip ttt baa E ttu dtd 39 3 5 LabVIEW Control Program for the Plasma Etcher 41 3 5 Setup SACO 1 ae ne etica edis b eR UU e Re Duplex 43 349 2 MONITOR SII E oc eoe 54 3 5 3 SNU A WN SYSTEM sso oe GAGA 58 IMPLEMENTATION OF AUTOMATION APPROACH ON A PLASMA DEPOSITION SYSTEM aaa aaa 61 4 1 Introduction to the Plasma Deposition System 61 4 1 1 Gas and Compressed Air system RN 65 iv 4 1 2 Vacuum System and Reactor 65 4 2 Lab PC DAQ Board for the Deposition System 67 4 3 Gas Control System and Sequencer 88076 sass 69 4 4 Control Program for Deposition System 2 71 V MEASUREMENTS wro eee Ek 74 Nb CONCLUSION wa e ZA nz 80 REFERENCES WS odes Oc O id EZ 82 APPENDIX fem Mx s 83 V ABSTRACT This thesis describes a methodology to Automate Semiconductor Fabrication Equipment The current processing Industry makes use of stand alone equipment with built in M
20. 22 Monitor Stage A shift register is used to count down the time The time from the previous stage is subtracted from the current time and it is compared with the process time specified by the user and if they are equal the program stops Since the tick count function counts time in milli seconds it is necessary to convert the time to seconds by dividing with 1000 The Acquire run time data vi is the data acquisition VI for the etcher software The PC LPM 16 card is used to read in the data This VI uses the sub VI AI Sample Channel vi to acquire data from the plasma etcher 1 nMIEEMHHHHNUOERDBRESRREDBERBERELLUPHERDEMHENR Figure 3 23 shows the diagram of acquire runtime data vi The device number assigned to the PC LPM 16 card is 1 The channel numbers for different input Dee Mantes Dey Du M DAG fr Convert to Channel Kacey CY Oe votes oy Poe 1 ARWYN 2 Ee Figure 3 23 Acquire Runtime Data vi parameters are shown in Table 3 3 The high limit is set to 5 0 volts and the Low limit is set to Ovolts A formula node is used for each input parameter Formula nodes for the gas flow rates are grouped together inside a CASE structure The gas number selects the sequence with the formula node for that particular gas The convert to channel vi is used to convert the gas numbers to a string The coefficients for the equations in the formula nodes are experi
21. ASES ooi Le Ee ene eeu PEU 57 Pin Configuration of L b PC e essor ve OR I ERE Ed 68 Setpoint and Runtime Values for 2 2 2 16 21 74 Setpoint and Runtime Values for the Mass Flow Controllers 75 vii 2 4 2 2 23 2 4 23 2 6 24 2 8 2 9 2 10 2 11 2 12 2 13 2 4 3 1 3 2 3 3 3 4 3 5 3 6 3 7 LIST OF FIGURES Block diagram of an automated system n 5 DAQ Boards a D A DAQ Board b A D DAQ board 7 External Interface Board a CHO AC Ehe Rada 8 Different stages of setup stage Hee 12 Example to show bundling and CASE selection pp 13 Writing a value to an output 00 2 eene 14 Analog Number Out vi sese se aeree renes 15 Analog Output Update Chanel vi cse 15 Writing a value to a Digital Port sese 16 TIGI 16 Write to digital DOE Vi 1 1 1 1 1 1 1 hay S 16 VI used to read in an Analog Input sese 17 MI used to read Digital Input tonto etra itte hdi bac pt 18 Flow Chart of Process Control aeo t e E EE E eae 20 The automated Plasma Etcher System 22 Cross Section of Process Chamber 24 ROSE 28 Plitmbing WSI 29 Mass Flow ASSembly ots detras date Yep edi
22. M 16 board to connect them to the interface board one 50 pin stick header connector and one 40 pin edge connector The 50 pin connector goes to the signal termination board from where the connections are given to the MFCs RF generator pressure transducer and other parts of the etcher The 40 pin connector goes to the solenoid board Figure 3 9 shows the logical connection of the two chips along with the schematic layout of the interface board and termination board 24 VDC SOLENOID INTERFACE BOARD BOARD PC LPM 16 SETPOINTS READ PARAMFTFR Figure 3 9 External Interface Boards 38 util 1 ME U ORDEN oOx TP TS 3 4 RF Tuning Network To minimize the reflections in the RF power due to the impedance mismatch between the ASPR s capacitive impedance and the RF generator s output impedance a tuning network is necessary The tuning network is designed to transform wide range of resistive and reactive impedances to the 50 ohms desired by the RF generator The tuning network employd here is an L configuration which includes two capacitors and an inductor as shown in Figure 3 10 The tuning network has a shunt capacitor Cp to handle the loading a fixed inductor and a series capacitor Cs for tuning The capacitors are servo motor driven simultaneously to allow the instant tuning To accomplish the automatic tuning of the system a phase detector and a magnitude detector are used The signal from the
23. MATION APPROACH ON PLASMA DEPOSITION SYSTEM 4 Introduction to the Plasma Deposition System The generic approach explained in Chapter II was also used to automate an other equipment a Plasma Deposition system 3 This plasma reactor system is designed to deposit a variety of types of films at high speeds onto large numbers of semiconductor slices The block diagram of the system is shown in Figure 4 1 The signals to select the gases certain controls like selecting the vacuum valves raising the chamber cover these signals come from a sequencer box which will be explained further Even though it is called a deposition system it can also etch and ash wafers Ashing is a process of removing photoresist on wafers There are two modes of operation on the system One is manual mode and the other is automatic mode In manual mode all the controls toggle switches are on the electrical cabinet In the automatic mode the system is controlled by signals from the computer Before discussing the DAQ Boards External Interface boards a brief explanation of the system setup is given The reactor system 1s comprised of three major assemblies the plasma depositioner assembly the electronic cabinet and the vacuum pump The reactor system is comprised of subsystems that function to perform deposition etching or ashing processes The subsystems are Gas and compressed air system vacuum system RF power generator system the reactor sequencer and pr
24. NI 488 2 driver software The DDA 06 and the PC LPM 16 are configured using the NI DAQ 53 412 configuration utility software which checks for the cards and allows the user to specify the Interrupts DMA channels and the base address Finally the user makes use of the device numbers specified by the driver software in the LabVIEW source code for it to communicate with the peripherals The output of the spectrometer is connected directly to the port of the GPIB The GPIB consists of a bi directional bus that has the capability of sending and receiving signals from a device The wavelengths of light emitted by different species in the plasma chamber are displayed on the display which enables the end point detection The next frame frame number 4 Figure 3 14 starts the timer which is compared in the next stage to the process time and if they are equal the program halts 3 5 2 Monitor Stage This stage takes the run time data from the machine and processes it for displaying Figure 3 22 shows the Monitor Stage The sub VIs for this stage are 1 Acquire Run Time Data vi 2 Validate Data vi MONITOR STAG NME MELLEL EEC NM 7 GY Optical Spectroscopy my I Gratin 5 Uy i EC got C i A Flow Rate Tol 10000000 00 Qpes rana 7 A DIALOG HERE 1 i ZO SIGNIFY AN ERROR 8 LOLLUR D T Figure 3
25. Power On The mass flow rates of the gases are inputs to channels 0 through 3 the RF power is input to channel 4 the pressure is input to channel 5 and the RF impedance is input to channels 8 and 9 Neither the digital I O ports nor the counters are currently used for this project Table 3 3 Pin Configuration of PC LPM 16 Analog Input Board 1 AIGND Analog Ground 2 ACHO Ar Flow rate 5 ACHI CF Flow Rate 7 ACH2 H5 Flow rate 9 ACH3 O Flow Rate 11 ACHA RF power ACHS Chamber Pressure 13 By using these A D and D A interface boards 6 analog parameters are set and 8 analog parameters are monitored The boards have to be configured before using them The LabVIEW code generates the set point voltages and they are assigned to corresponding channels 3 3 External Interface Board The external interface board was designed as mentioned in the generic approach Digital signals from the DDA 06 are used to control the solenoid switches These solenoids operate at 24 VDC and 250mA which is far greater than the TTL voltages and currents provided by the DDA 06 The interface board has three ECG 2013 Darlington 37 transistor array drivers and two 74LS245 line drivers The ECG 2013 drivers can handle more than 24 VDC and 600 mA on the output All the digital and analog signals for the plasma etcher go through the board There are two 37 pin D subconnectors one for the DDA 06 and the other for the PC LP
26. R tir TI 4 4 Control Program for Deposition System The software for the deposition system is also divided into three The algorithm explained for the generic approach is used to design the program But instead of using two DAQ boards only one board i e a Lab PC is used The pin configuration of PC is shown in Table 4 1 In the program for the Deposition System provision for three more gases was given The gas selection vi is shown in Figure 4 7 ges select 17 UJ A PEAR 7 27 Figure 4 7 Gas selection vi As in the previous program the Gas number flow rate value power and pressure are bundled together and passed to the Initialize system vi For communicating with PC and to send the Analog signal out it is not necessary to specify the address of the DAQ board but we need to specify the device number To send out the Analog signal a sub VI called Analog Output Update Channel vi explained in Chapter II is used Figure 4 8 shows frame 0 i e initialization of Pressure It shows the equation and the device number in this case it is 1 Frame 1 shows the setpoint of Argon Flow rate Another sub VI called write to digital Port vi is used to switch on the relays in the E sequencer box Figure 4 9 shows the Flow rate screen for Argon Gas ooo 0 2
27. REW Ig NITROGEN HEAT SINK LIGHT DETECTOR Figure 3 6 Optical Setup Micrometer screw the spectrometer can be tuned to different ranges so that wavelengths from 200nm to 1100nm can be measured This type of setup makes it very easy for the user to decide on the endpoint detection by looking at the optical emission lines and their 32 ow MHBRIBEHHDUEUMMMIETELAMBLLDUTUELUOHMMSM 4505104101008 S wavelengths Table 3 1shows the optical emission lines used for endpoint detection It shows the Etchant gas to be used for a particular type of material the emitted species and its corresponding wavelength Table 3 1 Optical Emission Lines Used for endpoint Detection CF4 02 F Etchant 704 Si3 N4 CF4 02 SiF4 Product CO Product N2 Product CN Product N Product F Etchant CO Product 484 OH Product 309 H Product 656 O Etchant 711 843 The next topics discuss about the hardware and software required to automate the plasma etcher 3 2 DAQ Boards Used For Plasma Etcher The ASPR was originally controlled by an ASD 99 on board computer and a manual data terminal and the software was stored in EPROMs Any modification in the software was a difficult and time consuming process Two DAQ boards were used to automate the plasma etcher A DDA 06 D A board was used to send analog signals to the etcher and a PC LPM 16 A D
28. VI can have a number of sub VIs which are like Functions in a C Program The graphic tools have all the control loops like for and while loops all the arithmetic and logical tools and some in built VIs for data acquisition and statistical analysis The user sets all the parameters using a LabVIEW control program and the DAQ boards send the set point voltages to the machine and feed the run time data from the machine into the computer and the control program displays the data on the screen Once the process time finishes the system shut downs automatically The program has to be written in such a way that the entire system can have a sequential control or closed loop control depending on the application 2 3 An Approach to Control Program The software is divided into three stages They are 1 Setup Stage 2 Monitor Stage 3 Shut Down Stage The DAQ boards are used to output the setpoints to the Machine and to get the fedback signals into the computer The next section discusses how each stage should be designed 10 and also explains the LabVIEW tools to be used for reading analog and digital Signals into the computer and sending out the same to the machine Before designing the control program the user has to configure all the boards using driver software so that the system can recognize the boards and their addresses 2 3 1 Setup stage This stage takes different input values from the user LabVIEW allows the us
29. ameters using an IBM PC and a LabVIEW control program A block diagram of a general processing system is shown in Figure 2 1 Digital Analog Inputs Outputs Figure 2 1 Block diagram of an automated system A processing machine may require digital input signals or analog input signals from the computer and it can send out digital signals or analog signals or both back to the computer Digital signals are used to control the energizing of components like solenoids and relays on the machine Analog inputs to the machine may be setpoint voltages to throttle valve controllers or mass flow controllers MFCs Analog outputs from the machine can be feed back signals like gas flow rates from MFCs or signals from other transducers An example of digital input signal to the computer is a set point from a temperature sensor 2 2 Approach and Requirements To properly control the process an interface is needed to allow the computer and machine to communicate with each other efficiently without making many modifications to the machine LabVIEW is an excellent GUI software tool that can be used as a control program The first step in developing a controller is to determine the parameters that need to be controlled The corresponding components on the machine must be identified along with their voltage and current specifications like MFCs for gas flow rate throttle valve controllers to control pressure in the chamber of a processing equipment
30. amount of gas flow 21 1444 HT a eae tags ic RF TUNING pA A A SARUM SINN AMAN ANANAS UM A 5 1 PII SOLENOID GAS SUPPLIES CONTROL Figure 3 1 The automated Plasma Etcher System is controlled using mass flow controllers The by products during etching are removed by the exhaust system The pressure is controlled by software actuation of a throttle valve The ASPR was originally designed to be controlled by an ASD 99A on board computer and a manual data terminal The control software was stored in EPROMs Thus the modifications to the control program were time consuming and inconvenient Hence it is interfaced with a PC and DAQ boards which proved to be efficient Before discussing the DAQ Boards and interface boards a brief explanation of the system is given 3 1 1 Process Chamber The process chamber assembly consists of the upper electrode assembly the chamber housing and the substrate plate The process chamber electrode assembly consists of a parallel plate electrode design with the radial gas flow from the top to bottom of the chamber The ion and electron production between the electrodes in the chamber housing and the gas flow determine the etch characteristics The upper electrode is powered by the RF generator it provides the electrical field between the electrodes that ionizes the gases to produce the ions and
31. an be used alone or in a mixture for the etching process The gases pass through electrically operated solenoid valves a mass flow controller MFC a normally closed pneumatic bellow valve a process gas manifold and a normally open pneumatic bellow valve on the top of the chamber The flow rates of gases are controlled by the MFCs On entering the MFC the gas stream is divided into two parallel paths one path is directed through the thermal sensor tube and the other passes through a bypass The two are rejoined to pass through the control valve The bypass forces a proportional flow through the thermal sensor tube The thermal sensor converts the gas flow into a voltage As shown in the Figure 3 5 the valve the thermal sensor and the valve controller form a closed loop control system The input signal from the computer varies from 0 to 5 volts which controls the valve from a fully open to fully closed position The difference between the voltage from the thermal sensor and the input signal is used to adjust the valve position and thus the flow rate of the gas 14 raka a PO Pi TMCIDENT RF POWER METER D RF RF OFF 2 TET ELSE RAE RF ON POWER ON RESET PA TUNING AUTO MANUAL SWITCH LOCAL REMOTE SWITCH INCIDENT POWER CONTROL OSCILLATOR TUNING PROCESSOR OPERATOR SWITCH LINE CIRCUIT BREAKER Zi NE SY oor
32. and and modify because of LabVIEW s flexibility and ease of programming Excellent control can still be maintained over process parameters because 3 of the real time feedback control system This system can be implemented without losing the integrity and the safety parameters of the equipment This generic approach i e using LabVIEW controlled DAQ system for automation has been realized and implemented on two semiconductor processing pieces of equipment namely a Plasma Etcher and a Plasma Deposition system The methodology results and applications are discussed in the ongoing Chapters Chapter II explains the approach for Automation It discusses the requirements of DAQ Boards and External Interface Boards along with the tools that have to be used in automation Chapter III explains the implementation of the Generic approach on a Plasma Etcher and Chapter IV explains the implementation of the approach on a Plasma Deposition System Both the chapters explain the DAQ Boards Used their specifications and the design of external interface boards The LabVIEW code used for automation is also explained in both the chapters Chapter V discusses the Measurements taken Chapter VI discusses the merits of such an automation approach and its applications CHAPTER II APPROACH FOR AUTOMATION 2 1 Introduction This chapter discusses an approach to automate i e to enhance the monitoring and control of a process and its par
33. compensation for the RF chamber impedance in an attempt to match the chamber load to the 50 2 impedance of the transmission line A directional coupler is provided at the end of the PA stage to sense both the incident and reflected power The front panel of the RF generator is shown in Figure 3 3 3 1 6 Plumbing System The plumbing system provides for the gas system which supplies the process gases to the chamber a vacuum system and the chamber pressure monitoring assembly Figure 3 4 shows the plumbing system The flow rate for the process gases are monitored by the MFCs The setpoint is an analog signal 0 to 5 VDC from the D A board The MFC produces an analog signal 0 to 5 VDC proportional to gas flow which is read into the computer through the A D board The DAQ boards are explained in later sections The process gas is piped in through the floor of the etcher directly to the mass flow panel If the solenoid valve is open the gas flows into the MFC to an air operated bellow valve If the bellow valve is enabled the gas flows through the process gas manifold to another air operated valve located on the top of the process chamber This allows the gas to enter the chamber Chamber gases are exhausted through a vacuum pump The actual flow in SCCM standard cubic centimeters per minute can be read on the computer using LabVIEW control program 26 3 1 7 Gas System The gas system provides for four gases Ar CF4 Hz O2 which c
34. d their controllers using DAQ Boards and external Interface boards Figure 5 4 Spectrometer Reading 79 4 i h up ji 5 PUn mm 3 4 22 2 SE EO e CHAPTER VI CONCLUSION This methodology of automation to control a process using DAQ Boards and External Interface Boards controlled by LabVIEW was implemented and verified on two semiconductor processing systems namely a Plasma Etcher System and a Plasma Deposition System The control program for both the systems is designed in a modular approach Changes can be made to the system and the program very easily Provision has been given to monitor Power and RF Impedance Provision has to be made on both the systems to apply temperature to the substrate and cooling water too This generic approach for automation can be extended to any semiconductor processing system The user has to determine the parameters that affect the process their corresponding controllers on the machine along with their specifications Then DAQ Boards have to be selected based on the number of A D and D A channels sampling rates and the External Interface board has to be designed according to the specifications of the controllers on the machine Finally the control program has to be designed making use of the tools and the approach discussed Improved processing performance can be achieved by using such a setup and the user will have efficient control over the process
35. electrons The cross section view of process chamber is shown in Figure 3 2 3 1 2 Chamber Housing The chamber housing consists of the bottom plate which is the lower enclosing surface of the process chamber an optical window and a window for end point detection 23 The bottom plate has ports for various accesses to the chamber Th exhaust gases are removed through the exhaust port The pressure is monitored by the sensor assembly mounted below the bottom plate Chamber housing has an inlet to let the air inside the Spaces Gas Inlet port Top Plate Clamp Electrode Plate Top Cover Insulator I 7 Ring DYR EZ fure Capacitance 7 Sensor Bottom ad Chamber Plate P 4 X Housing Heater 2 Capacitive sensor Heater Connector Plate Insulator Figure 3 2 Cross Section of Process Chamber pressure housing which prevents the RF generator from being turned on until the chamber is evacuated to a low pressure An additional aluminum spacer is added between the bottom plate and the chamber housing to facilitate the addition of an external heater in the chamber 24 2 22 111 1 3 1 3 Upper Electrode The feature that separates the ASPR from the conventional parallel plate plasma reactors is the use of porous non flat upper electrode The multiple process gas enters through the upper electrode The upper electrode assembly consists of a number of spacers fastened together It is i
36. er to create a VI and to call it in an other VI It is called a subVI It has inbuilt control loops like WHILE loop FOR loop CASE structure and SEQUENCE structure LabVIEW allows the user to use one loop inside an other loop This feature is an advantage in designing the control program The setup stage is divided into three more substages In the first substage the user selects the parameters and sets the values along with the process time These values are bundled and passed onto the next stage where the DAQ boards are initialized and the values are written to the output Ports substage 2 In the third substage the timer is started The Timer stage is optional This is shown in Figure 2 4 As mentioned earlier Lab VIEW allows use of one loop in another loop This is shown in Figure 2 5 Here a CASE structure is used in a SEQUENCE structure This is an example which shows how multiple CASE structures can be used to send out values to the next stage A parameter selection sub VI is shown in Figure 2 5 where the user selects a parameter out of four along with its value The wires which go to the CASE structure are parameter values and the wires which go to the function Build Array are 11 Boolean values which indicate the parameter selected by a binary 1 and the one not selected by a binary 0 Parameter Selection Screen vi Bundle Values Initialize system vi c Figure 2 4 Different Stages o
37. essure control system Heating and cooling systems are optional The optical spectroscopy is not used in the automation The 61 other systems of the depositioner assembly are explained in the ongoing topics The Plasma depositioner assembly and the electrical cabinet are shown in Figure 4 2 and Figure 4 3 respectively GAS MANIFOLD WAFER PRESSURE SENSOR SOLENOIDS W SEQUENCER RELAYS MANUAL CONTROLS PRESSURE amp TEMPERATURE TNDICATORS RF GENERATOR GAS SUPPLIES ELECTRICAL CABINET Figure 4 1 Deposition System 62 0 pt xe TO COMPUTER D I NE CZNA Hs 5 0 e 5 S D O E ghk 8 B o fg z 5 CE z 7 z 1 3 E 5 xu 5 l Pi KA E 0 C 00 8 defe Uv A Pur 2 i i i o V E gt ge Seb 5 E EP gt BRE OR EE pg O TAT rene GI vos S LA t DS MOK A MEO cq cT S A 0 A U A TT 2 gt MATIC 2 55 ROL DRAWER TEMPERATURE DRAWER SEQUENCER DRAWER CONTROL DRAWER AUTO CONT AUTOMATIC POWER CONTROLLER DRAWER m via 92 1 ae GENERATOR RF EAE SS d RF GENERATOR POWER SUPPLY ECT AS P 4 4 m o
38. etween Pin 2 and Pin 17 of DDA 06 49 POP re 4 LL4 M48 IMAAT The 16 bit value is written at the 16 bit address by calling a shared library function DIPortWritePortUlong This function resides in DLPORTIO DLL a Dvnamic Link Library file written in other language LabVIEW allows the programmer to call this DLL file to communicate with the DDA 06 Figure 3 19 shows the frame number 2 of the Initialize system vi The gas number and flow rates are unbundled here This frame has four sequence structures which get selected according to the gas number Table 3 4 shows the number allotted to each gas When a particular gas is chosen it activates the corresponding sequence That sequence has a governing equation for the flow rate of that particular gas and also a binary value to activate the solenoid for that gas In Figure 3 19 the sequence structure for Argon is shown Base Address 6 Flow Rate Data Pressure amp Power Data taga WR Lguguoggogusgugoaguguguuluuogmuguogudtultocoutscu Figure 3 19 Setting of Gas Flow Rates and Activation of Solenoids If Argon is chosen sequence number 0 of frame 2 is selected The flow rate equation for Argon is FS floor 8 19 10 848 F 14 0267 50 1 3 LIED peters DH 11 1 Table 3 4 Gas Number Assignment Name of the Gas Number Assigned Argon 0 CF4 1 Hydrogen l 2
39. f Setup Stage a Substagel b Substage2 c Substage3 12 Build Array CASE Boolean duni Values z Ed Parameter selection sub VI MN Y RAS At AA P Ly 3 E m Figure 2 5 Example to show bundling and CASE selection Then these Boolean values which are either lor O are given to a function in LabVIEW called Build Array The build array function appends any number of array or element inputs in top to bottom to create an array with appended elements This array is then given to function called Boolean Array to number which converts this Boolean array to long integer by interpreting it as 2 s complement representation of an integer with 0 element as least significant bit This number is then given to a Logarithm Base 2 function tool which computes the log of the number to the base 2 This final number is given to the CASE structure Depending on the value of the number that particular CASE will be evaluated The number of CASE structures will depend on number of parameters used Then the parameter number CASE number and value are bundled together and advanced into 13 next Sequence frame There are other ways of selecting a CASE but this way of selection is efficient and useful when an operation in a CASE has to be evaluated depending on the input selection in another VI In SubStage 2 of Figure 2 4 the DAQ Boards are initialized The values set by the user in the previ
40. for Tolerance If either the tolerance is exceeded or if the process time finishes the control goes to the next stage the shutdown stage To read in the data an inbuilt VI called Analog Input Sample Channel vi is used This VI is explained in Figure 2 12 If it is a digital input a VI called Read from Digital Port vi is used This is shown in Figure 2 13 Device No Channel Sample Wich Limit AI Sample Channel vi Tow Limit Figure 2 12 VI used to read in an Analog Input The terminals for this VI are 1 Device No the number assigned to the DAQ device during configuration 2 Channel The analog channel which will be used for data acquisition This is a string type variable 3 High Limit The expected level of the signals 17 GT 4 Low Limit The lowest expected signal level 5 Sample The measured signal Device Number Read From Digital totem Port vi Channel Figure 2 13 VI used to read Digital Input 2 3 3 Shutdown Stage This stage de energizes all the controls on the machine and writes 0 s to all the output ports and the system will be ready for the user to repeat the process 2 4 Flow of Data A flow chart is shown in Figure 2 14 to depict the flow of data and to explain the entire process control using the hardware described and the LabVIEW control program First the user selects the parameters needed for the process and their setpoint values u
41. gh the A D board and displays it for the user on the computer For the Plasma Etcher different setpoint values for the pressure were set and their corresponding voltages to the throttle valve controller were measured These values are tabulated in Table 5 1 The corresponding runtime values are also shown in the table Table 5 1 Setpoints and Runtime Values for the Pressure Pressure setpoint Setpoint Runtime values millitorrs milliVolts millitorrs E 5 CO 7 e rv on e os we a po Il on e Different setpoint values in sccm Standard Cubic centimeters were set for the Mass Flow Controllers and their corresponding voltages were measured The runtime values are shown in the Table 5 2 The data is taken by using CF4 Freon gas KE TRU KAI Table 5 2 Setpoints and runtime Values for the Mass Flow Controllers Flow Rate setpoint Setpoint Runtime values SCCM Volts SCCM The deviation between input values and runtime data is less than 5 percent and within the tolerance level Provision is given in the control program of both the systems to monitor the RF power and Impedance The objective 15 to implement and validate the automation approach and be able to operate the systems using DAQ Boards external interface boards controlled by LabVIEW The con
42. he up position air goes into the cylinder causing the piston inside it raise the lid In down position the cylinder is gradually vented from the cylinder causing the lid to lower over the reactor chamber 4 1 2 Vacuum System and Reactor The function of the vacuum system 3 is to establish the flow rate of the reactant gases over the substrates control the pressure in the chamber and remove the gaseous 65 reaction products after deposition or etching process The amount of vacuum furnished in the chamber determines the velocity of gas across the substrates and the pressure in the gas mixture Three solenoid operated valves are actuated by associated Vacuum Valves toggle switches or the computer through the sequencer to apply a selected amount of vacuum to the reactor The amount is determined by the throttle valves associated to each uus HILBET SH UIN CUP HHMEIRU QS Nr vacuum valve The reactor provides a controlled environment in which RF plasma processes take place The cylindrical design of the reactor chamber permits high volume processing of substrates as result of radially inward flow of the gases within the reactor The interior of the reactor contains a RF power plate and a heater plate The RF power plate is the means by which RF power is coupled into the reactant gases Three circular windows enable the operator to observe the RF glow discharge inside the reactor The radial flow of gas inside the react
43. i 00 4120 500 6000 6228 E Gas Flew Rate Ar scom 400 0 0 Figure 3 12 Front Panel of Plasma Etcher Program The setup stage has 5 sub frames Figure 3 13 shows different frames 0 through 3 of the Setup Stage Figure 3 14 shows the frame 4 The substagel which is frame 0 uses a Gas Setup Screen VI to read the selected gas number and the flow rate setpoint The user will get a screen as shown in Figure 3 15 a to select the gas and the flow rate The block diagram source code of the gas selection screen vi is shown in Figure 3 15 b 44 0 0 uA d le e See ENZO 2020202 75 S FUP STAGE JuUguiz uiQ4i1 oa4jp mpmuumnocgugJgrog Fria Pusey FLAY Tarr VY Bundle Pressure i amp Power Data P lab SETUP STAGE OOO dq 30 4 DOE Ata da Sago VI fo ef Set Dag Mak hy YA pa aee PRAIA SPEC IRN 3 vas 9 0 s gt 0 E JG c d Figure 3 13 Different Frames of the Setup stage a Frame No 0 b Frame No 1 c Frame No 2 d Frame No 3 ABEL RA TORA Dp FCU KI COTON BONY SIRRI Figure 3 14 Frame for the Timer The gas number and the flow rate are bundled together in frame 1 and advanced i
44. ice designed to drive the solenoids in the depositioner assembly and actuate other signals It has a 5 VDC power supply and solid state relays The DAQ boards residing in the computer send the signals to turn the relays on or off Each relay controls the application of 115VAC to a depositioner function solenoid valve The sequencer box is used if automatic operation is needed Figure 4 6 shows the operation In plasma etcher the driver circuit was used to switch the solenoids on or off The deposition system uses 120 VAC to operate the solenoids The sequencer box helps in this operation The digital outputs from the PC are used to trigger all valves and solenoids via the relays in the sequencer box The sixteen control relays have input rating of 5 VDC and output rating of 5 VDC This output is used to trigger the next stage the solid state relays The solid state rely is DC controlled and uses SCR switching When these relays are switched on they send 120 V AC to the solenoids causing them to turn on TO E rw wk ku e FLOW RATES FROM MFCs TO Lab PC CONTROL SIGNALS FROM Lab PC SETPOINTS 0 5 VDC RELAYS SEQUENCER BOX MASS FLOW CONTROLLERS BELLOW VALVE SOLENOID VALVE GAS INLET Figure 4 6 Gas Control System 70 ee 5 It E ire 0 ETT m rare wer a ea 358 P
45. icrocontrollers which are hardcoded or programmed using EPROMs to accomplish that particular process The cost of building such systems is expensive Automation of these systems is time consuming and difficult These systems require a lot of user intervention during processing This thesis presents a comprehensive insight into a generic approach of Automation of a process A methodology has been discussed to automate a machine using DAQ Data Acquisition Boards and External Interface Boards controlled by LabVIEW a graphical programming language tool This approach of automation is implemented and verified on two processing systems namely a Plasma Etcher and a Plasma Deposition System The project explains the specifications of the hardware needed and describes a modular approach to design the Lab VIEW control program It explains how this approach can achieve improved process performance by efficient monitoring and controlling of the process parameters for increased yield and productivity The advantages of this methodology of automation are discussed along with applications 3 1 32 3 3 3 4 3 5 4 1 5 1 52 LIST OF TABLES Optical Emission Lines For Endpoint Detection sss 33 Pin Configuration of DDA 06 Analog output Board 36 Pin Configuration of PC LPM 16 Analog Input Board 37 Gas Number Assignment 0000 00 cscs cece cee cece e 51 Equations for G
46. lor aw CEE SESS AS Fill Color Disebled AUCEPT rrr 1 FF EF rH nr Fn ey ru Figure 3 16 Pressure and Time selection screen Flow Rate Data ub fIokse b Port A Outpt ta Figure 3 17 Frame No 0 of the Initialize System vi Figure 3 18 shows the frame number 1 for the same VI This frame sets the chamber pressure The governing equation is PS floor P 1 22466663 g 1 THEN 01 0 Base Address of DDA 06 LR DA 4 4 T 2 n Convert the Pressure Set Poin to a E Pressure amp Power Data 1 ROEE othe DA por PS floo 4095 49 P 153755 B L J Analog Number Outi 0 0 0 0 aooi 3 0 83 Figure 3 18 Frame Number 1 of the Initialize system vi Here P is the setpoint value of the pressure in milli torrs The pressure and power are unbundled to get the pressure alone The floor function truncates any value after the decimal point and makes PS a whole integer The pin assignment for DDA 06 is shown in Table 3 2 The analog number out vi commands DD 06 card to convert the value of PS into milli volts and make it available between D A Pin2 and analog ground GND Pin 17 For a setpoint of 100 milli torrs the value of PS will be 94 and 94mV will be available b
47. lp and cooperation Finally I thank all my friends for their support encouragement and well wishes Thanks for the memorable moments and friendship ii TABLE OF CONTENTS RO LT ML C ES ii RAT vi LISTOPTABLED e totes A qot LA Z ten vii LISE OE FIGURES wad O AS A A WO Kd viii CHAPTER I INTRODUCTION EAN anette 1 II APPROACH FOR 1 2 02 5 2 0 DS m 5 2 2 Approach and Requlrements pp 6 2 2 1 DAQ Data Acquisition Boards pp 7 222 External Interface Boards coerente te ota 8 2 2 3 LabVIEW Control Program RR 9 2 3 An Approach to Control Program RN 10 2 3 1 Setup Sape OOO AS Es Pa d gem etel 11 23 2 Monitor Stage 17 23 3 Shutdown Stage 1 opi elati e DI elu 18 2 4 Blow Ol DAEs eoe 1 1 1 1 pa a eiue LEO NN CN UM RUE 18 III IMPLEMENTATION OF AUTOMATION APPROACH ON A PLASMA IC ER 21 3 1 Introduction to the Plasma Etcher 21 3 1 1 Process EC 23 iii IV 3 1 2 Chamber Housing ined e t e Od 23 3 1 3 Upper ECHOES ASSESS aE 25 3 14 Substrate Plate ase W SN 25 3 1 5 RE generator tees 25 3 1 6 Plumbing System ron CA 26 Sl GAS SYSIEM a ii od E Pus 27 3 1 8 Vacuum Systemic 30 3 1 9 Pressure Monitoring System 0000000600006 aaa 31 3 1 10 Power Supplies ond iecit a a 31 JI TT Optical Setup 40 1 1 pde eese etes 3
48. mentally determined The flow rate equations for different gases are listed in Table 3 5 56 Table 3 5 Equations for the gases Gas Flow Rate Equation Ar X O 9 21 X 1 19 CF T I 10 4096 5 100 O T 0 5 27 75 H2 T I 10 4096 5 100 O T 0 11 12 O2 T I 10 4096 5 100 O T 00171292 2 7328 Pressure O 0 961001 1000000 I 0 000539 These parameters are then passed into Validate Data vi where they are checked to determine if they have exceeded the specified tolerance level or not The diagram for this VI is shown in Figure 3 24 The Boolean variables True or False from the validate data vi are given to the compound Arithmetic function The remaining time Paramter Graph 3 Mu oe DO tush sees ae n 0 j 1 a Dic WN peus 220007 T Tolerance Exceeded Lene e p P gt Figure 3 24 Diagram of Validate Data vi 57 Z of the timer is also given to this function This compound Arithmetic function performs logical OR on these Boolean variables If any of the parameters exceed the tolerance or if the etcher system times out then the WHILE loop terminates causing the shutdown of the System 3 5 3 Shutdown System The shutdown System de energizes the solenoids and switches off the Mass Flow Controllers and the sends 0 Volts to the pressure controller Figure 3 25 shows the Bate Andress
49. nnel AO Update Channel vi Value Figure 2 8 Analog Output Update channel vi To send out a digital signal a VI called Digital Out vi is used This VI is shown in Figure 2 9 This sub VI is used to write to a digital port It is basically the same as an Analog Out Vi with a difference that instead of D A channel number integer 0 is Base Address of the DAQ Board 2 Digital Out vi Value to be sent out in Binarv Figure 2 9 Writing a value to a Digital Port assigned to each PORT A binary value is written to a port An example where base address is H330 is shown in Figure 2 10 In cases where it is not necessary to specify the base address another VI called write to digital port vi is used The function diagram is shown in Figure 2 11 Digital Port Base Address H330 Byte HO HFF Figure2 10 Digital Out vi Device No Write to Digital Channel Port vi Pattern Figure 2 11 write to digital port vi 16 Once the Boards are initialized and values are written to output ports the Timer turns on in the substage 3 If time is necessary in the process and the control goes to the next stage of the program Monitor Stage 2 3 2 Monitor Stage This stage takes the run time data from the machine and processes it for displaying on the computer In this stage the values of different parameters are obtained using DAQ boards A D and checked
50. nsulated from the rest of the chamber using dielectric rings The spacers help in changing the plate to electrode distance The process gases enter the chamber through the gas filter block The gases flow through the central passage between the spacers and the upper electrode The upper side of the electrode has a gas plenum chamber to equalize the flow from multiple orifices The gas orifices are radially distributed with greater density towards the center The upper electrode is connected to a RF generator through the ASPR tuning network for the maximum power transfer of power 3 1 4 Substrate Plate The substrate plate holds the wafer during the process A heater can be placed below the substrate plate to increase the temperature of the wafer 3 1 5 RF generator The HFS 1500D RF generator is manufactured by RF Power Products it has a maximum output of 1500 Watts at a frequency of 13 56 MHz 2 The RF generator is composed of power supplies an oscillator a buffer amplifier a power amplifier and a tuning network The oscillator of this generator is a crystal controlled oscillator that 25 drives a buffer amplifier The buffer stage reduces the effect of loading and also provides some intermediate amplification The buffer amplifier drives the power amplifier for more amplification in the output stage The RF power is coupled to the reaction chamber through an automatic RF matching network The purpose of this network is to provide
51. nto frame 2 In frame no 1 the power pressure and the etch time are specified by the user The Power and Pressure data are also bundled and advanced into frame no 2 The screen for selection is shown in Figure 3 16 Frame No 2 receives Gas Number gas flow rate power and pressure and these are passed to an another VI called Initialize system vi As the name implies this VI initializes the system and plugs in the setpoint values Figure 3 17 shows frame number 0 of the diagram for the initialize system vi The total number of frames in this VI are four Frame 0 sets digital Port A Port B Port C as output ports Different pins of these ports are used to activate the gas solenoids The base address for the DDA 06 card is 330H 46 mi 9 DM f Gas Setup Screen f4 vi NA 77 gt ITI 7 4 AA 77 UA 7 7777 A Le E p se gt p 7 7 ty 77 MELEE L 7 ty 77 7 R 7 17 EM 1111111112 Yj 7 Turn Ar On EE FAJ 4 LAT O Figure 3 15 Gas Selection VI a Front Panel b Block Diagram i VASA AN WA VM b ETE 6227 7 Z 7 p e 5 Za M UN 7 Gs 72 7 77 oda 111 IL E 1 CF4 Activated ome nu Fill Co
52. ome degree 2 2 2 External Interface Boards In most cases the signals sent out by the computer are 5 volts or maximum of 10 volts But a machine may use components like solenoids and relays which operate at a DC or AC voltage that is far greater than TTL voltages and currents provided by DAQ boards Hence to energize these switches and high voltage rated components on the machine and to buffer the DAQ card signals an external interface board is needed The driver circuits for the interface should be designed taking the specifications of the components on the machine into consideration Figure 2 3 shows the data flow Computer with mom mmi m m men mme m t m 1 LabVIEW Program SOLENOIDS RELAYS TRANSDUCERS 1 i i wee em em ee ee ee i I 1 DAQ Boards i i i I i i eee ew wm Z z ew eww l www m SETPOINTS SIGNAL TERMINATION BOARD Figure 2 3 External Interface Board All the signals should be routed through a signal termination board to avoid the complexity of wiring For example the computer can send a setpoint voltage to a Mass Flow controller through a signal termination board and also read the flow rate value from that MFC through the same board With this kind of hardware setup the communication between the computer and the machine can be established very efficiently and the use
53. or is shown in Figure 4 4 ge RF Generator gt ue dr ate 2 a B A 1 i 2 up Source Gas Figure 4 4 Radial Flow of Gas M 4 2 Lab PC DAQ Board for the Deposition System In automating this equipment two Lab PC DAQ boards 6 are used The Lab PC is a low cost multifunction analog digital and timing I O board for the PC The Lab PC contains a 12 bit successive approximation ADC with eight analog inputs which can be configured as eight single ended or four differential channels The Lab PC also has two 12 bit DACs with voltage outputs 24 lines of TTL compatible digital UO and six 16 bit counter timer channels for timing I O The Lab PC contains six jumpers and one DIP switch to configure the PC bus interface and analog I O settings The DIP switch is used to set the base I O address Two jumpers are used as interrupt channel and DMA selectors The remaining four jumpers are used to change the analog input and output circuitry The first PC board is configured as devicel and the second one as device2 For device the Base I O address is Hex240 and Hex280 for the other The DMA channel is 3 for both the devices and the interrupt line is 5 for both the devices Channels ACHO through ACH7 are for analog inputs The Figure 4 5 shows the operational diagram of Lab PC Table 4 1 shows the pin configuration of PC board EP DACO DACI Ports B amp C
54. ous stage are used to write to the ports But before writing to the port the value must be converted to an equivalent value in volts This is done using a function called Formula Node This is shown in Figure 2 6 The left side of the node has the incoming value P and the right side of the node has outgoing value in volts or millivolts PS The floor function truncates the value to a decimal value D A Channel Value of a parameter Base Address of the D A Figure 2 6 Writing a value to an output port A sub VI called Analog Number Out vi is used to write the value to a port Figure 2 7 describes the operation of this VI with a Base address of H330 The absolute address of the D A channel is calculated by multiplying the D A channel number by 2 and adding it to the base address which in this case is 330H All addresses are sixteen bit So for a D A 44 the absolute address is 0330H 4 2 008H 0338H or 0000 0011 0011 1000 b This VI makes use of a call library function that calls standard libraries and DLL function libraries The 16 bit value is written at the sixteen bit address by calling a shared library function For some boards for which specifying base address is not necessary an inbuilt VI in LabVIEW called Analog Output Update channel vi is used Figure 2 8 shows the necessary inputs to this VI Base Address H330 Figure 2 7 Analog Number Out vi Device No Cha
55. r will have tight control over the process With the interface found and DAQ boards selected the next step is to develop the software to control the process 2 2 3 LabVIEW Control Program The control program is written in LabVIEW It controls the parameters that effect the process LabVIEW is short for Laboratory Virtual Engineering Workbench LabVIEW is a program development application much like commercially available C or BASIC development systems The only difference between LabVIEW and other programming languages is that LabVIEW is graphical in nature while the other languages are text based LabVIEW uses a graphical programming language G to create programs in a flow chart like form eliminating a lot of syntactical details 4 LabVIEW is a powerful and very flexible instrumentation and analysis software system that runs on PCs Apple Macintoshes Sun SPARC stations and HP 9000 700 series workstations running HP UX LabVIEW programs are called Virtual Instruments VIs because their appearance and operation imitate actual instruments It has two main parts a The front panel is an interactive user interface of a VI because it simulates the panel of a physical system The front panel can contain Switches knobs graphs and all kinds of numeric Boolean or string controls user input and indicators result of program b The block diagram is the VI s source code which is designed using LabVIEW s graphical tools A
56. ric pressure because the diaphragm may get spoiled thus making the vacuum switch necessary 3 1 10 Power Supplies The electric circuits in the plasma etcher are powered by three power supplies A 24 VDC supply is used for the solenoid and the relays 5 VDC power supply is used to power the MFCs and a regulated 15VDc and 15VDC is used for the tuning network controlling card in the matching network 2 3 1 11 Optical Setup The optical setup is used for analyzing the light emissions from the plasma reactor system The major components of the optical setup are a spectrometer EG amp G PARC model 1229 detector interface model 1452A fiber optic bundle and a host computer see Figure 3 6 The light is collected and sent to the spectrometer that separates the different wavelengths of light The detector determines the intensity of different wavelengths of 31 light which are sent to the computer via a GPIB board The resolution of the spectrometer depends on the spectral response and calibration of the system There is a grating inside the spectrometer that defracts the light into its component wavelengths and directs them to a focusing mirror The mirror reflects the light out of the assembly The light detector which is mounted on the exit of the assembly has an array of 512 photo diodes that sense the light coming from the spectrometer With the help of an external FIBER OPTIC BUNDLE MICROMETER SPECTROMETER SC
57. s Set Timer amp Start the process Read the parameters Tolerance Exceeded No No Yes Current time Process time Yes i Shut down system Repeat No Yes FINISH Figure 2 14 Flow Chart of Process Control 20 CHAPTER III IMPLEMENTATION OF AUTOMATION APPROACH ON A PLASMA ETCHER 3 1 Introduction to the Plasma Etcher An Autoload Single Slice plasma reactor ASPR 2 Plasma Etcher was originally manufactured by Texas Instruments Inc It has the capability of processing a single slice at one time It has a non symmetric parallel plate capacitively coupled planar reactor where the power is applied to the top electrode and the bottom electrode is grounded The discharge is created between these two plates The ASPR consists of a RF generator cabinet Process Chamber remote vacuum pump and a computer controlled automation system as illustrated in Figure 3 1 The original monitoring and control system has been replaced with a PC based system The process chamber provides a controlled process environment for plasma etching The chamber consists of an enclosure powered electrode plate and substrate plate The process gases flow from top to bottom through the chamber The electrical system of the power supplies RF tuning assembly remote RF console the DAQ system The plumbing system provides for the various gases an exhaust system and chamber vacuum control The gases are controlled by Solenoid valves and the
58. s of this Work is to develop a methodology for automatic monitoring and control of fabrication equipment using readily available hardware and software while still providing tight control over the process parameters for increased yield and productivity The challenge is to achieve improved processing performance by monitoring and controlling parameters using readily available and modifiable systems This can be done by using a data acquisition DAQ and control system with LabVIEW a graphical programming language GUT tool Data acquisition is the process of bringing a real world signal such as voltage into the computer for processing analysis storage or other manipulation Each process is characterized by certain parameters like gas flow rate pressure inside the chamber temperature and RF power Using a PC based DAQ and control system run by LabVIEW it is possible to control the equipment with a hardware and software system that can be easily understood and modified LabVIEW can command DAQ boards in the computer to read analog input signals A D conversion generate analog output signals D A conversion read and write digital signals So using a data acquisition system and generic LabVIEW code that can be easy modified automation of equipment for any process can be implemented instead of using embedded devices and stand alone automation The advantages of such a generic approach are that system monitoring and control are easier to underst
59. sing the control program These setpoint values are converted to equivalent volts or millivolts and are given to their corresponding controllers on the machine through the DAQ boards D A The user sets the timer and the process is started The controllers on the machine adjust the parameters of the process by comparing their current value to the value set by the user The values of the process parameters are read into the computer using the DAQ boards A D and the control program displays them on the monitor The program also checks values for their tolerance If either the parameters exceed their tolerance value or if the process time finishes the system is shut down by making the 18 setpoint values going to the machine zero The system will be readv for the user to make an other run A LabVIEW program designed using this modular approach will be efficient in monitoring and controlling a process With these kind of tools and VIs to send out signals from the computer and to read in signals into the computer using DAQ boards and interface boards automation of an equipment can be done efficiently This generic approach to automation was implemented and verified on two semiconductor processing systems namely a Plasma etcher and a Plasma Deposition System The next chapters discuss how the two systems were automated using this methodology of automation 19 AU OS HELD P OCK 4 Set the parameters gt Ye
60. ss Time False Current Time Process Time Shut Down System Close MFC RF Power Off Power Off Solenoids Figure 3 11 Control Program Flow Chart and the software displays the data on the screen The program controls the machine until the process time completes and then the system shut downs automatically The Etcher software is divided into three stages as mentioned previously They are l Setup Stage 2 Monitor Stage 3 Shut Down Stage The DDA 06 D A DAQ board is used to output the setpoints to the Machine and the PC LPM 16 A D DAQ board is used to get the feedback signals into the computer The pin configuration and the functioning of these boards are already The front panel of the Plasma Etcher program is shown in Figure 3 12 The source code is shown at the end of this chapter The individual blocks in the code are explained first and finally the integration is showed 3 5 1 Setup Stage This stage takes the different input values from the user The main sub VIs for this stage are the following 1 Gas Setup Screen Vi 2 Power Pressure and Time Setup Screen Vi 3 Initialize system Vi The tools method to select CASE structures and bundling of data that were discussed in the generic approach were used et eranan te 9 EL SATE ANE MCA natns trit Le B System Stop ANS K 3000 5 20004000 Y 1 10 i
61. trol program is written in a modular approach so the user can make necessary changes to it and accommodate the control of extra parameters on the system Figure 5 1 shows the front panel of the plasma deposition system The snap shot is taken when the system stabilized the Pressure and gas flow rate Normally the runtime data stabilizes within a very short period of time It is possible to view the dynamic changes in the parameters too Figure 5 2 is taken when the throttle valve controller was 75 ZA 1 7 2 M eZ P 111 77 Figure 5 1 The front Panel when the parameters are stabilized stabilizing the pressure in the chamber Figure 5 3 shows the fluctuations when the MFC was controlling the gas flow rate according to the setpoint value 76 pn mma z ROET DER A mue 4 7 Y 7 Figure 5 2 Pressure Stabilization O LAN 1800 0 SUL C na 11238 Measured RF Power RE Power Set Point Figure 5 3 Flow Rate Stabilization Figure 5 4 shows the spectrum of a He Neon Laser The spectrum has a maximum intensity at 632 8nm This proved that the GPIB is able to read the information from the spectrometer It can be concluded from the data and figures that the LabVIEW control program is fully functional and efficiently controls the parameters an
62. w For CF4 FS floor 8 19 2 15 55 2 For Hydrogen FS floor 8 19 8 55 F 100 8 52 RRS Me eme tr tmm a wii dion OTS HU LURE 14 1415302070703 ZP 89 02 1111808 0 For Oxygen FS floor 8 19 5 8387 F 15 954 These FS values are converted to mV by the DDA 06 card and applied to the Mass Flow Controllers Figure 3 21 shows the frame number 3 of the diagram of Initialize system vi This frame sets and turns the RF power on This value of PS is written by Analog Number Out vi ddress of DDA 06 Convert the Power Set Point to a number to be written to the DA output port gp pe Eae Nuber Flow Rate peo e Figure 3 21 Frame Number 3 The next frame frame no 3 in the setup stage See Figure 3 13 sets the DAQ mode for the spectrometer for the end point detection and initializes the AT GPIB TNT board The GPIB initialization is shown in Figure 3 13 The base address for the GPIB board is 1200 the DMA channel is 5 and the Interrupt line is 11 Once the program runs the user gets a prompt if there is any error like error connecting to driver GPIB bus errors and error if board is not present or 1f address specified is not correct This is done by the General Error handler vi The GPIB is configured using the
63. wae a CZE EI 2 re 0 Vii bor sas Figure 3 3 RF Generator 28 AIR MANIFOLD EN E PURGE EM a PROCESS SOLENOID CHAMBER e VALVES GAS MANIFOLD BEAMER THROTTLE BELLOW VACUUM VALVES TO VACUUM MFC PUMP PROCESS GASES Figure 3 4 Plumbing System 29 INPUT Valve Driver SOLENOID VALVE Sensor Assembly GAS OUTLET INLET Figure 3 5 Mass Flow Assembly 3 1 8 Vacuum System The vacuum system consists of a remote vacuum pump and a throttle valve controller The vacuum system first pumps down the chamber to remove any contaminants then it is used to remove the process gases during the etching process Variation in the pumping speed is achieved with the help of the exhaust valve controller that controls the throttle valve 30 AE BP THU HMI KS NI mm 3 1 9 Pressure Monitoring System Constant monitoring of the chamber pressure is necessary for the etching process This is done by a MKS manometer which is a pressure transducer and an exhaust valve controller The MKS manometer converts the pressure inside the chamber into voltage This is then compared with setpoint in the exhaust valve controller depending on the difference the exhaust valve opens or closes A vacuum switch allows the MKS manometer to be exposed to the chamber when the chamber is under vacuum The sensitive manometer cannot be exposed to atmosphe

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