1. 11/8/99 SFR Workshop - Sensors 1 Small Feature Reproducibility A Focus on Sensor Integration UC-SMART Major Program Award Poolla, Solgaard, Dunn, Smith Second Annual Workshop 11/8/99

2. SFR Workshop - Sensors 2 Agenda 8:30 – 9:00 Introductions, Overview / Spanos 9:00 – 10:15 Lithography / Spanos, Neureuther, Bokor 10:15 – 10:45 Break 10:45 – 12:00 Sensor Integration / Poolla, Smith, Solgaard, Dunn 12:00 – 1:00 lunch, poster session begins 1:00 – 2:15 Plasma, TED / Graves, Lieberman, Cheung, Aydil, Haller 2:15 – 2:45 CMP / Dornfeld 2:45 – 3:30 Education / Graves, King, Spanos 3:30 – 3:45 Break 3:45 – 5:30 Steering Committee Meeting in room 775A / Lozes 5:30 – 7:30 Reception, Dinner / Heynes rm, Men’s Faculty Club

3. 11/8/99 SFR Workshop - Sensors 3 Our Vision: Smart Sensor Wafers In-situ sensor array, with integrated power and telemetry Applications: process control, calibration, diagnostics & monitoring, process design

4. 11/8/99 SFR Workshop - Sensors 4 Issues Sensor arrays –inexpensive, modular –environmentally isolated –transparent to wafer handling robotics –on-board power & communications Operating mode –no equipment modifications !! –Smart “dummy” wafer for in-situ metrology

5. 11/8/99 SFR Workshop - Sensors 5 Outline Prototypes of sensor wafers –Mason Freed Optical communication –Olav Solgaard Lithium batteries for powering sensor arrays –Bruce Dunn Microsensors for Monitoring Wafer Uniformity –Rosemary Smith

6. 11/8/99 SFR Workshop - Sensors 6 Prototypes of Sensor Wafers Mason Freed, Darin Fisher, Michiel Kruger Andy Gleckman, Scott Eitapence, Tim Duncan, Kevin Cho, Costas Spanos, Kameshwar Poolla

7. 11/8/99 SFR Workshop - Sensors 7 Division of Research Power, communications, and isolation –Use readily available sensors and electronics –Try different power, communication, and isolation options Integrated transducers –Use wired power and communications –Research novel sensor structures

8. 11/8/99 SFR Workshop - Sensors 8 Component-Based Approach Technology set –Surface mount components only –Minimal processing of host wafer (metal lines only) –On-board microprocessor –Off-the-shelf battery technology Features –Distributed array of sensors –Real-time data acquisition –Wireless power & data transfer

9. 11/8/99 SFR Workshop - Sensors 9 Temperature Sensor Useful for DUV resist bake monitoring Objectives –Monitor wafer temperature at 4 locations (within 0.5ºC) –PalmPilot inter-operability Design –Off-the-shelf temperature sensor modules –PIC microprocessor (with integrated 4 channel A/D) –Infrared data transfer (IrDA compliant) –Error detection (CRC-16)

10. 11/8/99 SFR Workshop - Sensors 10 The Wafers Ir-LED PP Batteries Sensor Ir-LED PP Batteries Sensor Silver paste mount on Al Direct SMD, on Al+nickel

11. 11/8/99 SFR Workshop - Sensors 11 PalmPilot Interface

12. 11/8/99 SFR Workshop - Sensors 12 Long Term Reliability Testing Computer-controlled bake plate used Sensor output compared to actual temperature Temperature cycling behavior evaluated Wafer Ir-receiver Probes Bake-plate

13. 11/8/99 SFR Workshop - Sensors 13 Results

14. 11/8/99 SFR Workshop - Sensors 14 Results

15. 11/8/99 SFR Workshop - Sensors 15 Rapid Transient Temperature Readings

16. 11/8/99 SFR Workshop - Sensors 16 Future Plans (Component-Based) Short Term –Work on passivation techniques –Test in plasma-etch chamber –Raise upper temp limit to 150°C Long Term –Move to flip-chip components (for reduced profile) –Incorporate UCLA thin-battery technology –Use other sensor types –Implement closed loop control using data –Measure thermal transient during DUV bake

17. 11/8/99 SFR Workshop - Sensors 17 Integrated Transducer: Etch Rate + Temp Sensor to measure polysilicon etch rate Based on van der Pauw probe electrical film- thickness measurement: I I Poly-Si V

18. 11/8/99 SFR Workshop - Sensors 18 Experimental Method Use wired connections for power and communications –Edge-board connector used to make connections to wafer Initial testing in XeF 2 etch chamber –Isotropic, non-plasma gaseous etchant –No problem making connections to wafer –No electrical or physical isolation necessary

19. 11/8/99 SFR Workshop - Sensors 19 Previous Design No onboard electronics, only sensors Simple, two-mask process Features –Three film-thickness sensors –Polysilicon “guard ring” around sensors –Clip-on wire connections –Parallel connection of sensors

20. 11/8/99 SFR Workshop - Sensors 20 Previous Design

21. 11/8/99 SFR Workshop - Sensors 21 Results from old Design Eleven etch cycles performed, reflectometric thickness measurements made between each cycle

22. 11/8/99 SFR Workshop - Sensors 22 Temperature Sensitivity  Use isolated “reference” sensor to compensate

23. 11/8/99 SFR Workshop - Sensors 23 Spatial Non-Uniformity Close-up  Make sensors smaller

24. 11/8/99 SFR Workshop - Sensors 24 Rough Polysilicon Surface For more heavily-etched samples, reflectometry fails  Use profilometer instead

25. 11/8/99 SFR Workshop - Sensors 25 Results from previous Integrated Etch-rate Sensor Repeatability: ~ 13Å Accuracy: ~ 45.9 Å Stability: < 5Å

26. 11/8/99 SFR Workshop - Sensors 26 Latest Etch Rate Sensor Design Surface mount analog multiplexers used –Number of sensors increased to 16 Sensors are smaller (200  m on a side vs. 3000  m) Each sensor has a buried temperature reference I Buried I Exposed V th V temp

27. 11/8/99 SFR Workshop - Sensors 27 Latest Design

28. 11/8/99 SFR Workshop - Sensors 28 Temperature compensated etch sensor reading Preliminary test of a single sensor only, during etch

29. 11/8/99 SFR Workshop - Sensors 29 Future Plans (Transducers) Test latest design Research isolation schemes to allow operation in plasma conditions Work on integrating power and communications modules onto sensor wafer, for wireless operation Develop sensors for other measurements in plasma –Ion flux measurement in plasma etch Develop sensors other processes –Wafer stress sensor for deposition processes

30. 11/8/99 SFR Workshop - Sensors 30 Free-Space Communication for Autonomous Sensors using Grating Light Modulators David R. Pedersen, Michael H. Guddal University of California, Davis Olav Solgaard Stanford University

31. 11/8/99 SFR Workshop - Sensors 31 Outline Summary of Year 1 Milestones –Developed, modeled and characterized GLM –Demonstrated free-space optical link using GCC modulator Improvements in GLM design –Reduce angle dependence and dispersion –Increase damping –No interference with plasma => “buried” GLM Year 2 Milestones –Integrate micromachined GLM with on-board power –Buried GLM, through-the-wafer interconnects, wafer bonding

32. 11/8/99 SFR Workshop - Sensors 32 GCC Communication Link 90100110120 -12 -10 -8 -6 -4 -2 0 2 4 6 actuation voltage (V) time (us) 4.4 4.8 5.2 5.6 6.0 6.4 6.8 7.2 detector signal actuation force actuation voltage +/-5% steady-state detector voltage (V) -20 0 20 40 60

33. 11/8/99 SFR Workshop - Sensors 33 High Contrast GLM Reflective State Diffractive State Reduced Angle dependence Increased damping

34. 11/8/99 SFR Workshop - Sensors 34 Full-wafer Grating Light Modulators Period: 10 Gap: 10  m Beam Width: 10  m Substrate/Beam Spacing: 2um Beam Length: 200  m to 600  m Beams: Doped low stress polysilicon Insulating Material: PSG

35. 11/8/99 SFR Workshop - Sensors 35 Layout Back Each line: 2mm open- circuit region etched to the substrate and aligned with the front Backside contact to the substrate Front

36. 11/8/99 SFR Workshop - Sensors 36 Buried Grating Light Modulators - Technology Development AR-coating DRIE trenches for interconnects and corner-cube reflectors Oxidation-smoothed TIR surface GLM aperture

37. 11/8/99 SFR Workshop - Sensors 37 Autonomous Sensor Wafer with Buried GLMs

38. 11/8/99 SFR Workshop - Sensors 38 Conclusion Met Year 1 Milestones: –Fabricated and tested micro-machined GLMs –Demonstrated free-space communication Full-wafer fabrication process Year 2 Milestones –Integrate micromachined GLMs with on-board power, sensors, and electronics sources Technology development –Buried GLMs –Through-the-wafer interconnects –Wafer bonding

39. 11/8/99 SFR Workshop - Sensors 39 Lithium Batteries for Powering Sensor Arrays SFR Workshop November 8, 1999 Bruce Dunn UCLA Student contributors: Nelson Chong, Brianna Fehlberg, Jimmy Lim, Jeff Sakamoto

40. 11/8/99 SFR Workshop - Sensors 40 Progress Since May Battery encapsulation using two-layer system Battery operation under aggressive conditions –Vacuum –Temperatures up to 85°C Battery encapsulated in wafer

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43. 11/8/99 SFR Workshop - Sensors 43 TMSA Protection of Lithium Si CH 3 H3CH3C C CH Trimethylsilylacetylene (TMSA) TMSA coating prevents adverse lithium reactions

44. 11/8/99 SFR Workshop - Sensors 44

45. 11/8/99 SFR Workshop - Sensors 45 Side by Side Battery Fabrication V 2 O 5 Sprayed Electrodes on Stainless Steel Foil Vacuum Heated 1 Hour Transferred into Argon Glove Box Electrolyte Application over Cellguard® sheets Electrode leads placed over electrolyte Battery placed on Oxidized Silicon Wafer and coated with TMSA Battery encapsulated by Epoxy Celgard® 3401 placed on both sides over electrolyte Electrolyte Application by Spatula on both V 2 O 5 and Lithium on base plate electrode PAN based electrolyte heated in Silicon Oil bath at 125 o C Lithium Foil pressed on electrodes

46. 11/8/99 SFR Workshop - Sensors 46 Battery Test Parameters 3.5 Volt single cells; 1 cm x 1 cm 2 mA discharge current (0.2mA/cm 2 ) Operation from 3.5 V to 1.8 V Exposure to vacuum and temperature followed by cycling Operation under vacuum and elevated temperature

47. 11/8/99 SFR Workshop - Sensors 47 Comparison of Encapsulated and Packaged Battery Encapsulated battery comparable to packaged; 3 cm x 3 cm cell to provide > 2 mAh capacity Discharge at 1 mA/cm 2 5 cycles

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49. 11/8/99 SFR Workshop - Sensors 49

50. 11/8/99 SFR Workshop - Sensors 50 Present Direction: Wafer With Encapsulated Battery Connection to sensor grid Ni Wire Epoxy Al Wire SiO 2 Ni Current Collector Lithium Anode Polymer Electrolyte Vanadia Cathode Al Current Collector trimethylsilylacetylene Multi-layer encapsulation scheme

51. 11/8/99 SFR Workshop - Sensors 51 Progress vs. Milestones Year 1: Milestones accomplished Packaged 7 Volt lithium battery mounted on wafer Encapsulation scheme identified and under test Year 2: Program in progress Encapsulated lithium battery integrated in wafer well Battery robustness evaluated - Vacuum - Elevated temperature - r.f. fields

52. 11/8/99 SFR Workshop - Sensors 52 Plans for 2000 - 2002 Develop higher temperature capability (150°C) –Utilize higher temperature component materials Construct battery directly on wafer –Integrate materials processing into battery fabrication

53. 11/8/99 SFR Workshop - Sensors 53 Microsensors for Monitoring Wafer Uniformity of Plasma Processes Ribi Leung, Dwight Howard, Scott D. Collins, and Rosemary L. Smith MicroInstruments and Systems Laboratory UCDavis

54. 11/8/99 SFR Workshop - Sensors 54 Abstract The goal of this project is to realize specific microsensors for in situ plasma process monitoring. Thin, multilayer, metal film resistors are being evaluated as surface peak temperature recording devices. –Au/Cr resistors, which are effective for 150 <T < 250 C, have been fabricated and tested in an ECR plasma tool. –Au/Al and Au/Cr/Al resistors are being evaluated for detection of T≤150C. –An RIE undercut sensor has been designed and is in the testing phase. Temperature and undercut sensors will be integrated for combined measurements later this year.

55. 11/8/99 SFR Workshop - Sensors 55 Relevant Milestones June 1999 –Evaluate wafer surface temperature variation during RIE processing using Au/Cr resistor array. June 2000 –Optimize materials for temperature sensitivity and range. –Test undercut sensors in RIE. –Test integrated Temperature and undercut sensors in RIE. –Determine wafer variation in specific RIE tools.

56. 11/8/99 SFR Workshop - Sensors 56 Interdiffusion of Cr / Au

57. 11/8/99 SFR Workshop - Sensors 57 Thin Film Resistor Pattern

58. 11/8/99 SFR Workshop - Sensors 58 RIE Experiments Plasmaquest, Electron Cyclotron Resonance (ECR) RIE Sample: 4” Wafer, Cr/Au on SiO 2, coated with photoresist Power= 1200 W, 2.45 GHz, Ar@ 2mTorr, time = 5 minutes -- No substrate cooling -- v 150 Watt Bias --> Surface Temperature > 200C v 0 Watt Bias --> Surface Temp ≤ 100 C (∆R≈0) v 150 Watt Bias, only 3 minutes --> ∆R≈0

59. 11/8/99 SFR Workshop - Sensors 59 Wafer Resistance Map Peak T ranged from 220-240C, across the wafer

60. 11/8/99 SFR Workshop - Sensors 60 Interdiffusion of Au / Al color change

61. 11/8/99 SFR Workshop - Sensors 61 RIE Undercut Variation Sensor I Resistance determined by lateral diffusion (≈1µm) Resistance increases with undercut Submicron undercut yields 10-15% ∆R i V oxide doped poly-Si undoped poly-Si

62. 11/8/99 SFR Workshop - Sensors 62 Resistor Fabrication Sequence Oxide Mask Polysilicon Ion Implantation Boron doped undoped RIE undercut Drive in for 10min at 1000C

63. 11/8/99 SFR Workshop - Sensors 63 Lateral Diffusion after Drive-in

64. 11/8/99 SFR Workshop - Sensors 64 Continuing Work RIE undercut variation determination/ demonstration of sensor Evaluate Au/Al structures for room T stability. Stabilize, if necessary, with interposed layer of Cr. Integration of temperature mapping with RIE etch - rate and degree of undercut

65. 11/8/99 SFR Workshop - Sensors 65 Future Directions? A MEMS Device for T Mapping versus Time Thermal microactuator positions shadow mask over etch/deposition window, creating steps in film height. Location of step edge corresponds to Temperature, height indicates time.

66. 11/8/99 SFR Workshop - Sensors 66 Relevant Milestones June 1999 –Demonstrate untethered temperature measurements in plasma. (have focused on bakeplate instead) –Demonstrate tethered, real-time etch-rate measurements in chemical, non-plasma etch. (done) –Mount thick-film Lithium battery onto test wafer, and develop isolation schemes. (done) –Fabricate and test micro-machined GLV for communication. (done)

67. 11/8/99 SFR Workshop - Sensors 67 Relevant Milestones June 2000 –Demonstrate untethered real-time measurements with integrated power and data processing. (etch/temp) –Develop integrated processing schemes for incorporating thick film batteries, and complete detailed study of robustness to processing conditions. –Integrate micromachined GLV communication scheme with on-board power sources.

68. 11/8/99 SFR Workshop - Sensors 68 Future Plans New sensors –Ion flux –Stress profile –DUV latent image Modular platform development –Host wafer, generic sensor module –Manufacturing issues

69. 11/8/99 SFR Workshop - Sensors 69 Future Plans (Continued) Applications: these sensors can be very useful –Close a control loop to demonstrate non-uniformity reduction –Demonstrate reduced need for test wafers in process design / qualification –Use sensor data to calibrate DUV resist models –Investigate extensions to large-area wafer processing Successful completion of these goals will require extensive participation with industrial sponsors