Method of controlling the film properties of PECVD-deposited thin films

• US 20050255257A1
• Filed: 12/22/2004
• Published: 11/17/2005
• Est. Priority Date: 04/20/2004
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Park, Beom Soo, Choi, Soo Young, White, John M., Wang, Qunhua
• Granted Patent: US 7,785,672 B2
• Time in Patent Office: Days
• US Class Current: 427/585
• CPC Class Codes: C23C 16/345 Silicon nitride
• CPC Class Codes: C23C 16/45565 Shower nozzles
• CPC Class Codes: C23C 16/5096 Flat-bed apparatus
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01L 21/0217 the material being a silicon nitride not containing oxygen, e.g. SixNy or SixByNz H01L21/02126 and H01L21/0214 take precedence
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/31612 on a silicon body

Abstract

We have discovered methods of controlling a combination of PECVD deposition process parameters during deposition of thin films which provides improved control over surface standing wave effects which affect deposited film thickness uniformity and physical property uniformity. By minimizing surface standing wave effects, the uniformity of film properties across a substrate surface onto which the films have been deposited is improved. In addition, we have developed a gas diffusion plate design which assists in the control of plasma density to be symmetrical or asymmetrical over a substrate surface during film deposition, which also provides improved control over uniformity of deposited film thickness.

Claims

1. A method of improving film deposition uniformity of a PECVD deposited film over a substrate surface having an equivalent radius of about 0.5 meter or greater, the method comprising controlling a plasma density across said substrate surface during film deposition.

2. A method in accordance with claim 1, wherein said PECVD deposited film is a silicon-containing film.

3. A method in accordance with claim 2, wherein said silicon-containing film is selected from the group consisting of silicon nitride, silicon oxide, silicon oxynitride, a-Si, doped a-Si, and combinations thereof.

4. A method in accordance with claim 1, wherein said PECVD deposited film is a carbon-containing film.

5. A method of improving film deposition uniformity of a PECVD deposited film over a substrate surface having an equivalent radius of about 0.5 meter or greater, the method comprising controlling a plasma density across said substrate surface during film deposition, wherein said plasma density is controlled across said substrate surface by employing apparatus which includes a gas distribution plate which provides a varying hollow cathode cavity effect at various points across said gas distribution plate.

6. A method in accordance with claim 5, wherein said hollow cathode cavity effect is varied by varying the surface area or volume or both surface area and volume of hollow cathode cavities across said gas distribution plate.

7. A method in accordance with claim 6, wherein the surface area or volume of said hollow cathode cavities is varied by changing a design variable of a hollow cathode cavity selected from the group consisting of cavity depth, cavity diameter, cavity shape, and combinations thereof.

8. A method in accordance with claim 7, wherein said cavity shape is changed by varying the depth of hollow cathode cavities across said gas distribution plate.

9. A method in accordance with claim 8, wherein a depth distribution profile of said hollow cathode cavities across said gas distribution plate is symmetrical.

10. A method in accordance with claim 8, wherein a depth distribution profile of said hollow cathode cavities across said gas distribution plate is asymmetrical.

11. A method in accordance with claim 7, wherein said cavity shape is changed by adjusting an angle between the center of a hollow cathode cavity and a sidewall of said hollow cathode cavity.

12. A method in accordance with claim 5, wherein said hollow cathode effect is varied by varying the numerical density of hollow cathode cavities across said gas distribution plate.

13. A method in accordance with claim 5, wherein said hollow cathode effect is varied by varying both the surface area and numerical density of hollow cathode cavities across said gas distribution plate.

14. A method in accordance with claim 5, wherein said hollow cathode cavity effect increases from the center of said gas distribution plate toward the edge of said gas distribution plate.

15. A method in accordance with claim 14, wherein said hollow cathode cavity effect is increased from the center of said gas distribution plate toward the edge of said gas distribution plate by increasing the surface area or volume or both surface area and volume of hollow cathode cavities from the center toward the edge of said gas distribution plate.

16. A method of improving film deposition uniformity of a PECVD deposited, silicon-containing film over a substrate surface having an equivalent radius of about 0.5 meter or greater, the method comprising controlling a plasma density across said substrate surface during film deposition.

17. A method in accordance with claim 16, wherein a plasma sheath thickness, s, between a parallel plate electrode and a plasma region is more than about 20 mils.

18. A method in accordance with claim 16, wherein spacing between electrodes within said chamber ranges between about 400 mils and 1200 mils.

19. A method in accordance with claim 16, wherein power applied to produce said plasma is RF power which is applied at a frequency ranging between about 27.12 MHz and about 7 MHz.

20. A method in accordance with claim 16, wherein the total gas flow to said process chamber is such that the volumetric gas turnover is at least 0.015 process chamber volumes per minute.

21. A method in accordance with claim 20, wherein said volumetric gas turnover ranges from about 0.015 to about 0.08 chamber volumes per minute.

22. A method in accordance with claim 21, wherein said volumetric gas turnover ranges from about 0.02 to about 0.07 chamber volumes per minute.

23. A method in accordance with claim 16, wherein the temperature of said substrate ranges from about 100°

C. to about 400°

C. during deposition of said silicon-containing film.

24. A method in accordance with claim 23, wherein the temperature of said substrate ranges from about 240°

C. to about 340°

C. during deposition of said silicon-containing film.

25. A method in accordance with claim 16, wherein said silicon-containing film is a silicon nitride film, and wherein said silicon nitride film is deposited from a precursor gas composition comprising SiH₄, NH₃, and N₂.

26. A method in accordance with claim 25, wherein a ratio of NH₃ to SiH₄ within said precursor gas composition is within a range of about 2:

1 to about 30;

1.

27. A method in accordance with claim 26, wherein a ratio of NH₃ to SiH₄ within said precursor gas composition is within a range of about 2:

1 to about 15;

1.

28. A method in accordance with claim 25, wherein a ratio of N₂ to SiH₄ within said precursor gas composition is within a range of about 5:

1 to about 80;

1.

29. A method in accordance with claim 28, wherein a ratio of N₂ to SiH₄ within said precursor gas composition is within a range of about 5:

1 to about 60;

1.

30. A method in accordance with claim 25, wherein a ratio of NH₃ to N₂ within said precursor gas composition is within a range of about 1:

10 to about 3;

1.

31. A method in accordance with claim 30, wherein a ratio of NH₃ to N₂ within said precursor gas composition is within a range of about 1:

7 to about 2;

1.

32. A method in accordance with claim 25, wherein said precursor gas composition further includes H₂, and wherein said H₂ does not exceed 30 volume % of said precursor gas composition.

33. A method in accordance with claim 32, wherein said H₂ comprises about 15 volume % to about 25 volume % of said precursor gas composition.

34. A method in accordance with claim 25, wherein a process chamber pressure during film deposition is within the range of about 0.7 Torr to about 2.5 Torr.

35. A method in accordance with claim 34, wherein said process chamber pressure is within the range of about 0.9 Torr to about 1.8 Torr.

36. A method in accordance with claim 25, wherein RF power is provided to said process chamber at a power density within the range of about 0.125 W/cm² to about 0.75 W/cm².

37. A method in accordance with claim 26, wherein RF power is provided to said process chamber at a power density within the range of about 0.175 W/cm² to about 0.55 W/cm².

38. A method in accordance with claim 16, wherein said silicon-containing film is an a-Si film, and wherein said a-Si film is deposited from a precursor gas composition comprising SiH₄ and H₂.

39. A method in accordance with claim 38, wherein a ratio of H₂ to SiH₄ within said precursor gas composition is within a range of about 2:

1 to about 10;

1.

40. A method in accordance with claim 39, wherein a ratio of H₂ to SiH₄ within said precursor gas composition is within a range of about 3:

1 to about 6;

1.

41. A method in accordance with claim 38, wherein a process chamber pressure during film deposition is within the range of about 1 Torr to about 4 Torr.

42. A method in accordance with claim 41, wherein said process chamber pressure is within the range of about 1.5 Torr to about 3 Torr.

43. A method in accordance with claim 38, wherein RF power is provided to said process chamber at a power density within the range of about 0.0375 W/cm² to about 0.5 W/cm².

44. A method in accordance with claim 43, wherein RF power is provided to said process chamber at a power density within the range of about 0.0375 W/cm² to about 0.35 W/cm².

45. A method of improving film deposition uniformity of a PECVD deposited film over a substrate surface having an equivalent radius of about 0.5 meter or greater, the method comprising controlling surface standing wave effects across said substrate surface during film deposition.

46. A method in accordance with claim 45, wherein said surface standing wave effects are controlled by adjusting the following combination of variables:

adjusting the electrode spacing between parallel plate electrodes in a process chamber in which the PECVD film is deposited to be about 1200 mils or less;

adjusting the electron density of the plasma used during deposition to be about 10¹⁰/cm³ or less;

selecting a plasma source gas in which reactive species are dissociated at an electron density used during deposition of the film; and

, employing a plasma source gas diffusion system which improves plasma density uniformity over said substrate surface.

47. A gas diffusion plate for use in a PECVD film deposition apparatus, said gas diffusion plate comprising a series of openings wherein a hollow cathode effect is created, and wherein said hollow cathode effect is varied at points within said diffusion plate by varying the surface area or volume or both surface area and volume of particular hollow cathode cavities within said gas diffusion plate.

48. A gas diffusion plate in accordance with claim 47, wherein said variation in surface area or volume or both surface area and volume of said hollow cathode cavities is symmetrical with respect to said gas diffusion plate surface area.

49. A gas diffusion plate in accordance with claim 47, wherein said variation in surface area of said hollow cathode cavities is asymmetrical with respect to said gas diffusion plate surface area.

50. A gas diffusion plate in accordance with claim 47, wherein a major surface of said gas diffusion plate which is in close proximity to said hollow cathode cavities is essentially flat.

51. A gas diffusion plate in accordance with claim 47, wherein a major surface of said gas diffusion plate which is in close proximity to said hollow cathode cavities is concave.

52. A gas diffusion plate in accordance with claim 51, wherein said concave shape is achieved by a method selected from the group consisting of thermal processing and vacuuming processing.

53. A gas diffusion plate in accordance with claim 47, wherein a major surface of said gas diffusion plate which is in close proximity to said hollow cathode cavities is convex.

54. A gas diffusion plate in accordance with claim 53, wherein said convex shape is achieved by a method selected from the group consisting of thermal processing and vacuum processing.