1. The Effects of Process Parameters during the Deposition of SiNx using PECVD Presented by John Nice and Joyce Palmer Georgia Institute of Technology NNIN RETs Summer 2006

2. Objective Evaluate the effect of process parameter changes for the deposition of Silicon Nitride (SiNx) using Plasma Enhanced Chemical Vapor Deposition (PECVD) – Utilized the Plasma Therm, Unaxis and STS PECVD systems – Changed the standard settings for gas flow rate, pressure, temperature and power – Determined the effect of process changes on deposition rate, uniformity, and index of refraction.

3. Methodology Ten minute cleaning process performed before process runs. One minute seasoning run performed for each recipe prior to deposition. Typical process run time of ten minutes unless otherwise noted. Ten minute cleaning process run between consecutive depositions. Two hour standard cleaning process run at conclusion of testing session.

4. Analysis of Films Woollam Ellipsometer: Thin nitride 5-point scan recipe used. Film thickness, index of refraction (n) @ λ=633nm, and uniformity compared. Plas-Mos Ellipsometer: Film thickness and index (n) @ λ=633nm compared Nanospec Refractometer: Thin nitride recipe used. Film thickness compared. Tencor P-15 Profilometer-FC: Thin nitride recipe used. Stress measurements compared.

5. Plasma Therm PECVD

6. Changed gas flow rates for SiH4 and NH3. Changed pressure up and down 100 mTorr. Changed temperature from 200-325°C in 25°C increments. Deposited films for 10 minutes except for deposition rate analysis experiment.

7. Standard Recipe Used for the Plasma Therm PECVD (Stdnit.prc) 2% SiH 4 /N 2 200 sccm NH 3 5 sccm N 2 900 sccm Temperature 250 °C Pressure900 mTorr Power 30 Watt

8. SiH 4 Changes for Plasma Therm Varied Silane gas flow rate from 180 sccm to 220 sccm. – NH 3 5 sccm – N 2 900 sccm – Temperature250°C – Pressure 900 mTorr – Power 30 Watt

9. Woollam Ellipsometer Analysis for Deposition

10. Woollam Ellipsometer Analysis for Index of Refraction

11. Woollam Ellipsometer for Uniformity for Silane Changes on Plasma Therm PECVD

12. Film Deposition Comparison for NH 3 as Measured on both Woollam and Plas-Mos Ellipsometers and Nanospec

13. NH 3 Changes for Plasma Therm Changed gas flow rate from 3-7 sccm in 0.5 sccm increments – 2% SiH 4 /N 2 200 sccm – N 2 900 sccm – Temperature 250°C – Pressure 900 mTorr – Power 30 Watt

14. Film Deposition Analysis Measured on Woollam Ellipsometer for NH 3 Changes

15. Film Deposition Analysis Measured on Plas-Mos for NH 3 Changes

16. Film Deposition Analysis Measured on Nanospec Refractometer for NH 3 Changes

17. The Plas-Mos Ellipsometer and the Woollam Ellipsometer each can measure the film thickness and the index of refraction. The data from the Woollam is generally preferred, since the Woollam determines its values from a large range of wavelengths and measures at multiple points on the wafer. The Plas-Mos and the Nanospec only measure at one point. The Plas-Mos uses only one frequency of light. Choices of Metrology Tools

18. Index of Refraction Analysis for NH 3 Changes Measured on Woollam

19. Uniformity for NH 3 Changes on Woollam

20. Pressure Changes on Plasma Therm PECVD The following pressures were tested: 900 mTorr, 1000 mTorr, and 800 mTorr – 2% SiH 4 /N 2 200 sccm – NH 3 5 sccm – N 2 900 sccm – Temperature250°C – Power 30 Watt

21. Woollam Analysis for Film Deposition for Pressure Change

22. Woollam Analysis for Index of Refraction for Pressure Changes

23. Uniformity for Pressure Changes on Woollam

24. Temperature Changes on Plasma Therm PECVD Temperature was changed between 200°C and around 325°C in 25°C increments. – 2% SiH 4 /N 2 200 sccm – NH 3 5 sccm – N 2 900 sccm – Pressure 900 mTorr – Power 30 Watt

25. Woollam Analysis for Film Deposition for Temperature Changes

26. Woollam Analysis for Index of Refraction for Temperature Changes

27. Woollam Analysis of Uniformity for Temperature Changes

28. Unaxis PECVD

29. Standard Recipe For Unaxis PECVD (stdnit.prc) 5% SiH 4 /He 200 sccm NH 3 8 sccm He 560 sccm N 2 150 sccm Temperature 250°C Pressure 1100 mTorr Power 50 watt

30. SiH 4 Gas Flow Rate Changes The following gas flow rates in sccm for Silane were tested: 220, 215, 210,205, 200, 195, 190, 185, 180 – NH 3 8 sccm – He 560 sccm – N 2 150 sccm – Temperature 250°C – Pressure 1100 mTorr – Power 50 watt

31. Woollam Analysis for Film Deposition for Silane Changes

32. Woollam Analysis for Index of Refraction for Silane Changes

33. Woollam Uniformity Analysis for Silane Changes

34. Tencor P-15 Profilometer Stress Analysis for Silane Changes

35. NH 3 Changes for Unaxis PECVD The following NH 3 gas flow rates in sccm were tested: 10, 9.5, 9, 8, 7, 6 – 5% SiH 4 /He 200 sccm – He 560 sccm – N 2 150 sccm – Temperature 250°C – Pressure 1100 mTorr – Power 50 watt

36. Woollam Analysis for Film Deposition for NH 3 Change

37. Woollam Analysis for Index n @633nm for Ammonia Change

38. Woollam Uniformity Analysis for Ammonia Change

39. Tencor P-15 Profilometer Analysis for Ammonia Change

40. Pressure Changes on Unaxis PECVD The following pressures were tested in mTorr: 1200, 1100, 900, 800 – 5% SiH 4 /He 200 sccm – NH 3 8 sccm – He 560 sccm – N 2 150 sccm – Temperature250°C – Power 50 watt

41. Woollam Analysis for Film Deposition for Pressure Change

42. Woollam Analysis for Index n@633nm for Pressure Change

43. Uniformity Analysis for Pressure Change

44. STS PECVD

45. Low Frequency Standard Thin Nitride Recipe Used (lfsin.set) 2% SiH 4 /N 2 2000 sccm NH 3 20 sccm Temperature 300°C Pressure 550 mTorr Power 60 watts

46. SiH 4 Gas Flow Changes for STS PECVD The following SiH 4 gas flow changes in sccm were tested: 2200, 2150, 2100, 2050, 1950, 1900, 1850, 1800, – NH 3 20 sccm – Temperature 300°C – Pressure 550 mTorr – Power 60 watts

47. Woollam Analysis for Film Deposition for Silane Changes

48. Woollam Analysis for Index n@633nm for Silane Changes

49. Uniformity Analysis for Silane Changes

50. Tencor P-15 Profilometer Stress Analysis for Silane Changes

51. Conclusions As the silane flow rate increased, we saw an increase in the deposition rate and the index of refraction. Uniformity was generally constant. As the ammonia flow rate increased, the deposition rate decreased on the Plasma-Therm, but was unchanged on the Unaxis. The index of refraction decreased as ammonia flow rate increased on both PECVDs. Uniformity was generally constant

52. Conclusions As the pressure of the chamber increases, the deposition rate increases. The film becomes more porous. The index of refraction decreased as pressure increased on the Plasma-Therm. The uniformity was better as the pressure decreased on the Plasma-Therm. The results for the Unaxis were inconclusive for all cases.

53. Conclusions As temperature increased, the deposition rate decreased, the index of refraction increased, and the uniformity improved. The cleaning process is very important for getting consistent results. If process parameters are changed by a large amount, rather than in small steps, the results can be skewed. Longer cleaning is indicated for more consistent results.

54. Mentors Dr. Nancy Healy Dr. Kevin Martin Janet Cobb-Sullivan Steven Parente