1. Modulator Design for Plasma Ion Implantation Professor Michael Bradley Dale Heggie, Joel Leslie, Curtis Olson March 24 th, 2004

2. Objective Convert an existing vacuum chamber into a plasma ion source for Ion Implantation

3. Applications in Materials Processing 1. Electronics Industry Semiconductor dopingSemiconductor doping IC FabricationIC Fabrication 2. Mechanical Treatment Surface hardnessSurface hardness Frictional PropertiesFrictional Properties 3.Biomedical Implants Biocompatible materialsBiocompatible materials

4. Applications in Materials Processing 1. Electronics Industry Semiconductor dopingSemiconductor doping IC FabricationIC Fabrication 2. Mechanical Treatment Surface hardnessSurface hardness Frictional PropertiesFrictional Properties 3.Biomedical Implants Biocompatible materialsBiocompatible materials

5. What’s a plasma?? Four States of Matter 1. Solid 2. Liquid 3. Gas 4. Plasma

6. Plasma Examples Neon lights Neon lights Lightning Lightning Sun Sun Aurora Borealis Aurora Borealis

7. Plasma Examples Neon lights Neon lights Lightning Lightning Aurora Borealis Aurora Borealis

8. PII Material Processing 1.Insert sample into chamber 2.Strike a plasma 3.Apply high negative voltage 4.Ions hit the sample and are implanted + + + + + + + Silicon -5 kV

9. PII Material Processing -5 kV ++++ Characterize the effects of implant depth and dose Characterize the effects of implant depth and dose -10 kV-20 kV Sample Material Sample Holder

10. Implant Implications  Kinetic energy is transferred into heat  Sample overheating from continuous implant  Requires pulsed voltage + + + + + + +

11. Voltage Pulsing  Energy contamination from rising and falling edges Time Voltage Implanting Cooling +++++++++

12. Final System + - High Voltage Source Modulator Vacuum Chamber

13. Modulator Design  Solid state transistor modules  One master timer  Expandable Time Start Master Timer Optical Fiber + - High Voltage Source To Vacuum

14. Final System

15. Circuit Performance  5 switching modules  Excellent rise and fall times  Expandable without affecting performance TimerHigh Voltage

16. Successful Implant 5 switching modules 5 switching modules 1600 V negative bias 1600 V negative bias 2” Silicon Wafer 2” Silicon Wafer Short Nitrogen implant Short Nitrogen implant

17. Special Thanks  Dr. Michael Bradley  Dave McColl, P. Eng.  Dr. Ajay Singh  Dr. Akira Hirose  Perry Balon  Vic Meyer, Electrical Shops

18. Questions???

19. Master Controller Circuit Description Circuit Description Monostable 555 for implant duration Monostable 555 for implant duration Astable 555 for pulse frequency Astable 555 for pulse frequency Features Features Duty cycle variation Duty cycle variation Implant Time (5, 10, 30 seconds) Implant Time (5, 10, 30 seconds) Start Control Start Control

20. Circuit Development High Voltage Switching Units High Voltage Switching Units PC Board layout in Traxmaker PC Board layout in Traxmaker Fabricated by Electrical Engineering Shops Fabricated by Electrical Engineering Shops

21. Vacuum Chamber Results 2 x 10 -7 Torr base pressure2 x 10 -7 Torr base pressure 0.01% impurities from background gas0.01% impurities from background gas

22. Sample Holder Secure silicon wafer inside chamber Secure silicon wafer inside chamber Thermal conductivity Thermal conductivity Aluminum Aluminum

23. Plasma Generation Raise to 2 mTorr pressure with Nitrogen Raise to 2 mTorr pressure with Nitrogen Filament generation Filament generation

24. Testing

25. By the Numbers… Vacuum Chamber Goal - Base pressure < 1 µTorrGoal - Base pressure < 1 µTorr Result – 2 x 10 -7 Torr Result – 2 x 10 -7 Torr High Voltage Switching Goal - < 10 microsecond rise and fallGoal - < 10 microsecond rise and fall Result – 300 ns rise, 700 ns fall Result – 300 ns rise, 700 ns fall

26. Switching Problems Less than 1% energy contaminationLess than 1% energy contamination

27. Overall Circuit Performance 5 modules at 1600 Volts5 modules at 1600 Volts Expandable without affecting performanceExpandable without affecting performance

28. Vacuum Chamber Base pressure Base pressure 1 in 10 000 contamination 1 in 10 000 contamination

29. Langmuir Probe Characterize our plasma for accurate implant doses Characterize our plasma for accurate implant doses Ion saturation current of 12 mA Ion saturation current of 12 mA Ion Density of Plasma (~2 x 10 9 ions/cm 3 ) Ion Density of Plasma (~2 x 10 9 ions/cm 3 ) 0.57% ionization 0.57% ionization

30. Modulator Design ModulesModules Insulated gate bipolar junction transistor (IGBT)Insulated gate bipolar junction transistor (IGBT) Internal battery powerInternal battery power Optical IsolationOptical Isolation SynchronizationSynchronization

31. Future Design Projects 1.High Voltage Isolation 1.Metal boxes 2.Fast Zener clamping for each module 2.Increase Plasma density 1.Shorter implant times 2.Increase saturation current via RF source 3.Better Power Supply