Oxide/nitride stacked gate dielectric and associated methods

• US 6,207,586 B1
• Filed: 06/17/1999
• Issued: 03/27/2001
• Est. Priority Date: 10/28/1998
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Ma, Yi, Roy, Pradip Kumar
• Primary Examiner(s): Bowers, Charles
• Assistant Examiner(s): Smoot, Stephen W.
• Application Number:
  US09/334,911
• Time in Patent Office: 649 Days
• Field of Search: 438/763, 438/761, 438/762, 438/287, 438/792, 438/791
• US Class Current: 438/763
• CPC Class Codes: C23C 16/345 Silicon nitride
• CPC Class Codes: C23C 16/56 After-treatment
• CPC Class Codes: H01L 21/02164 the material being a silicon oxide, e.g. SiO2
• 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 21/022 the layer being a laminate, i.e. composed of sublayers, e.g. stacks of alternating high-k metal oxides adhesion layers or buffer layers H01L21/02304, H01L21/02362
• CPC Class Codes: H01L 21/02211 the compound being a silane, e.g. disilane, methylsilane or chlorosilane
• CPC Class Codes: H01L 21/02238 silicon in uncombined form, i.e. pure silicon
• CPC Class Codes: H01L 21/02255 formation by thermal treatment H01L21/02252 takes precedence; after treatment of an insulating film H01L21/3105 and subgroups
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/02337 treatment by exposure to a gas or vapour
• CPC Class Codes: H01L 21/3145 formed by deposition from a gas or vapour
• CPC Class Codes: H01L 21/3185 of siliconnitrides

Abstract

A method for making an oxide/nitride stacked layer makes the nitride layer defective so that it is semi-transparent or permeable to oxygen. The method includes first forming an oxide layer on a semiconductor substrate. The defective nitride layer is formed on the oxide layer using direct plasma enhanced chemical vapor deposition. The defective nitride layer is formed while exposing the plasma with a low energy magnetic field for providing a uniform energy distribution across a surface of the oxide layer. A resulting distribution of thicknesses of the defective nitride layer has a standard deviation less than about 1.5% across a wafer. The defective nitride layer is permeable to oxygen so that when the semiconductor substrate is annealed, the interface trap sites are significantly reduced or eliminated.

Claims

1. A method of making a dielectric layer for a semiconductor device, the method comprising the steps of:

forming an oxide layer on a semiconductor substrate; and

forming a defective nitride layer on the oxide layer using direct plasma enhanced chemical vapor deposition so that the defective nitride layer is permeable to oxygen, the defective nitride layer being formed while exposing the plasma with a magnetic field for providing a uniform energy distribution across a surface of the oxide layer.

2. A method according to claim 1, wherein the semiconductor substrate comprises a wafer;

and wherein the step of providing a uniform energy distribution provides a distribution of nitride thicknesses having a standard deviation of less than about 1.5% across the wafer.

3. A method according to claim 2, wherein the wafer has a diameter of less than about 8 inches.

4. A method according to claim 1, wherein the step of exposing the plasma with a magnetic field is performed using a radio frequency signal having an operating frequency in a range of about 50 kHz to 400 kHz.

5. A method according to claim 1, wherein the step of exposing the plasma with a magnetic field is performed using a radio frequency signal having a power level in a range of about 1 watt to 10 watts.

6. A method according to claim 1, further comprising the step of annealing the dielectric layer.

7. A method according to claim 1, wherein an interface trap site density of the oxide layer is in a range of about 0.5E10/cm² to 5E10/cm².

8. A method according to claim 1, wherein the direct plasma enhanced chemical vapor deposition is performed with a radio frequency signal having a frequency in a range of about 11 MHz to 16 MHz.

9. A method according to claim 1, wherein the direct plasma enhanced chemical vapor deposition is performed with a plasma power in a range of about 10 watts to 500 watts.

10. A method according to claim 1, wherein the step of forming the defective nitride layer comprises reacting silane and ammonia in an inert gas.

11. A method according to claim 1, further comprising the steps of providing a flow of silane at a rate in a range of about 1 sccm to 500 sccm, and providing a flow of ammonia at a rate in a range of about 1 sccm to 500 sccm.

12. A method according to claim 1, wherein the step of forming the defective nitride layer comprises reacting silane in a nitrogen plasma.

13. A method according to claim 1, wherein the plasma comprises nitrogen and argon;

and further comprising the step of providing a flow of nitrogen at a rate in a range of about 100 sccm to 2,000 sccm, and providing a flow of argon at a rate in a range of about 100 sccm to 2,000 sccm.

14. A method according to claim 1, wherein the direct plasma enhanced chemical vapor deposition is performed in a temperature range of about 250°

C. to 550°

C.

15. A method according to claim 1, wherein the direct plasma enhanced chemical vapor deposition is performed with a pressure in a range of about 1 mTorr to 500 Torr.

16. A method of making a dielectric layer for a semiconductor device, the method comprising the steps of:

forming an oxide layer on a semiconductor substrate; and

forming a defective nitride layer on the oxide layer using direct plasma enhanced chemical vapor deposition so that the defective nitride layer is permeable to oxygen, the defective nitride layer being formed while exposing the plasma with a magnetic field for providing a uniform energy distribution across a surface of the oxide layer; and

annealing the dielectric layer so that the oxide layer has an interface trap site density in a range of about 0.5E10/cm² to 5E10/cm².

17. A method according to claim 16, wherein the semiconductor substrate comprises a wafer;

and wherein the step of providing a uniform energy distribution provides a distribution of nitride thicknesses having a standard deviation of less than about 1.5% across the wafer.

18. A method according to claim 16, wherein the wafer has a diameter of less than about 8 inches.

19. A method according to claim 16, wherein the step of exposing the plasma with a magnetic field is performed using a radio frequency signal having an operating frequency in a range of about 50 kHz to 400 kHz.

20. A method according to claim 16, wherein the step of exposing the plasma with a magnetic field is performed using a radio frequency signal having a power level in a range of about 1 watt to 10 watts.

21. A method according to claim 16, wherein the direct plasma enhanced chemical vapor deposition is performed with a radio frequency signal having a frequency in a range of about 11 MHZ to 16 MHZ.

22. A method according to claim 16 wherein the direct plasma enhanced chemical vapor deposition is performed with a plasma power in a range of about 10 watts to 500 watts.

23. A method according to claim 16, wherein the step of forming the defective nitride layer comprises reacting silane and ammonia in an inert gas.

24. A method according to claim 16, further comprising the steps of providing a flow of silane at a rate in a range of about 1 sccm to 500 sccm, and providing a flow of ammonia at a rate in a range of about 1 sccm to 500 sccm.

25. A method according to claim 16, wherein the step of forming the defective nitride layer comprises reacting silane in a nitrogen plasma.

26. A method according to claim 16, wherein the plasma comprises nitrogen and argon;

and further comprising the step of providing a flow of nitrogen at a rate in a range of about 100 sccm to 2,000 sccm, and providing a flow of argon at a rate in a range of about 100 sccm to 2,000 sccm.

27. A method according to claim 16, wherein the direct plasma enhanced chemical vapor deposition is performed in a temperature range of about 250°

C. to 550°

C.

28. A method according to claim 16, wherein the direct plasma enhanced chemical vapor deposition is performed with a pressure in a range of about 1 mTorr to 500 Torr.

29. A method of making a dielectric layer for a semiconductor device, the method comprising the steps of:

forming an oxide layer on a wafer comprising a plurality of semiconductor substrates; and

forming a defective nitride layer on the oxide layer using direct plasma enhanced chemical vapor deposition so that the defective nitride layer is permeable to oxygen, the defective nitride layer being formed while exposing the plasma with a magnetic field for providing a uniform energy distribution of nitride thicknesses having a standard deviation of less than about 1.5% across the wafer.

30. A method according to claim 29, wherein the wafer has a diameter of less than about 8 inches.

31. A method according to claim 29, wherein the step of exposing the plasma with a magnetic field is performed using a radio frequency signal having an operating frequency in a range of about 50 kHz to 400 kHz.

32. A method according to claim 29, wherein the step of exposing the plasma with a magnetic field is performed using a radio frequency signal having a power level in a range of about 1 watt to 10 watts.

33. A method according to claim 29, further comprising the step of annealing the dielectric layer.

34. A method according to claim 29, wherein an interface trap site density of the oxide layer is in a range of about 0.5E10/cm² to 5E10/cm².

35. A method according to claim 29, wherein the direct plasma enhanced chemical vapor deposition is performed with a radio frequency signal having a frequency in a range of about 11 MHz to 16 MHz.

36. A method according to claim 29, wherein the direct plasma enhanced chemical vapor deposition is performed with a plasma power in a range of about 10 watts to 500 watts.

37. A method according to claim 29, wherein the step of forming the defective nitride layer comprises reacting silane and ammonia in an inert gas.

38. A method according to claim 29, further comprising the steps of providing a flow of silane at a rate in a range of about 1 sccm to 500 sccm, and providing a flow of ammonia at a rate in a range of about 1 sccm to 500 sccm.

39. A method according to claim 29, wherein the step of forming the defective nitride layer comprises reacting silane in a nitrogen plasma.

40. A method according to claim 29, wherein the plasma comprises nitrogen and argon;

and further comprising the step of providing a flow of nitrogen at a rate in a range of about 100 sccm to 2,000 sccm, and providing a flow of argon at a rate in a range of about 100 sccm to 2,000 sccm.

41. A method according to claim 29, wherein the direct plasma enhanced chemical vapor deposition is performed in a temperature range of about 250°

C. to 550°

C.