Method and system for modifying a gate dielectric stack containing a high-k layer using plasma processing

• US 7,163,877 B2
• Filed: 08/18/2004
• Issued: 01/16/2007
• Est. Priority Date: 08/18/2004
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc., Tokyo Electron Limited
• Original Assignee: Texas Instruments, Inc., Tokyo Electron Limited
• Inventors: Niimi, Hiroaki, Colombo, Luigi, Sugawara, Takuya, Matsudo, Tatsuo, Shimomura, Koji
• Primary Examiner(s): Nhu; David
• Application Number:
  US10/920,990
• Publication Number:
  US 20060040483A1
• Time in Patent Office: 881 Days
• Field of Search: 438/513, 438/514, 438/515, 438/423, 438/197, 438/602, 438/603, 438/604, 438/536, 438/905, 438/935, 438/474, 438/475, 438/770, 438/775
• US Class Current: 438/513
• CPC Class Codes: H01L 21/02142 the material containing silicon and at least one metal element, e.g. metal silicate based insulators or metal silicon oxynitrides
• CPC Class Codes: H01L 21/02175 characterised by the metal H01L21/02197 takes 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 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/28185 with a treatment, e.g. annealing, after the formation of the gate insulator and before the formation of the definitive gate conductor
• CPC Class Codes: H01L 21/28202 in a nitrogen-containing ambient, e.g. nitride deposition, growth, oxynitridation, NH3 nitridation, N2O oxidation, thermal nitridation, RTN, plasma nitridation, RPN
• CPC Class Codes: H01L 21/3115 Doping the insulating layers
• CPC Class Codes: H01L 21/3144 on silicon
• CPC Class Codes: H01L 21/3165 formed by oxidation H01L21/31691, H01L21/31695 take precedence
• CPC Class Codes: H01L 29/513 the variation being perpendicular to the channel plane
• CPC Class Codes: H01L 29/517 the insulating material comprising a metallic compound, e.g. metal oxide, metal silicate H01L29/518 takes precedence

Abstract

A method and system for modifying a gate dielectric stack by exposure to a plasma. The method includes providing the gate dielectric stack having a high-k layer formed on a substrate, generating a plasma from a process gas containing an inert gas and one of an oxygen-containing gas or a nitrogen-containing gas, where the process gas pressure is selected to control the amount of neutral radicals relative to the amount of ionic radicals in the plasma, and modifying the gate dielectric stack by exposing the stack to the plasma.

Claims

1. A method for modifying a gate dielectric stack, the method comprising:

providing a gate dielectric stack having a high-k metal oxide or metal silicate layer formed on a substrate, wherein the high-k metal oxide or metal silicate layer has an effective dielectric constant;

generating a first plasma comprising an amount of neutral oxygen radicals and an amount of ionic oxygen radicals from a first process gas containing a first inert gas and an oxygen-containing gas, and selecting a pressure for the first process gas effective to increase the amount of neutral oxygen radicals relative to the amount of ionic oxygen radicals in the first plasma; and

modifying the gate dielectric stack by exposing the gate dielectric stack to the first plasma.

2. The method according to claim 1, wherein the substrate comprises a Si substrate, a Ge-containing Si substrate, a Ge substrate, or a compound semiconductor substrate.

3. The method according to claim 1, wherein the high-k layer comprises Ta₂O₅, TiO₂, ZrO₂, Al₂O₃, Y₂O₃, HfSiO_x, HfO₂, ZrSiO_x, TaSiO_x, SrO_x, SrSiO_x, LaO_x, LaSiO_x, YO_x, or YSiO_x, or a combination of two or more thereof.

4. The method according to claim 1, wherein the oxygen-containing gas comprises O₂, O₃, H₂O, or H₂O₂, or a combination of two or more thereof.

5. The method according to claim 1, wherein the first inert gas comprises He, Ar, He, Kr, or Xe, or a combination of two or more thereof.

6. The method according to claim 1, wherein the first process gas pressure is between about 0.5 Torr and about 5 Torr.

7. The method according to claim 1, wherein the first process gas pressure is between about 1 Torr and about 3 Torr.

8. The method according to claim 1, wherein the ratio of the first inert gas to the oxygen-containing gas is between about 20 and about 5.

9. The method according to claim 1, wherein the first process gas comprises Ar and O₂.

10. The method according to claim 9, wherein the Ar/O₂ ratio is between about 20 and 5.

11. The method according to claim 1, further comprising maintaining the substrate at a temperature between about 150°

C. and about 450°

C. during the modifying.

12. The method according to claim 1, wherein the modifying comprises exposing the gate dielectric stack to the first plasma for a time period between about 5 sec and about 60 sec.

13. The, method according to claim 1, wherein the gate dielectric stack further comprises an interfacial layer between the high-k layer and the substrate.

14. The method according to claim 13, wherein the modifying is performed for a time sufficient to increase the effective dielectric constant of the high-k layer through at least one of minimizing the interfacial layer, reducing defects in the high-k layer, incorporating oxygen in the high-k layer, or removing carbon impurities from the high-k layer.

15. The method according to claim 13, wherein the interfacial layer comprises an oxide layer, a nitride layer, or an oxynitride layer.

16. The method according to claim 1, further comprising:

generating a second plasma comprising an amount of ionic nitrogen radicals and an amount of neutral nitrogen radicals from a second process gas containing a second inert gas and a nitrogen-containing gas, and selecting a pressure for the second process gas effective to increase the amount of ionic nitrogen radicals relative to the amount of neutral nitrogen radicals in the second plasma; and

exposing the modified gate dielectric stack to the second plasma without the first plasma.

17. The method according to claim 16, wherein the nitrogen-containing gas comprises N₂ or NH₃, or a combination thereof.

18. The method according to claim 16, wherein the second inert gas comprises He, Ar, He, Kr, or Xe, or a combination of two or more thereof.

19. The method according to claim 16, wherein the second process gas pressure is between about 10 mTorr and about 400 mTorr.

20. A method for modifying a gate dielectric stack, the method comprising:

providing a gate dielectric stack having a high-k layer formed on a substrate;

generating a first plasma comprising an amount of ionic nitrogen radicals and an amount of neutral nitrogen radicals from a first process gas containing a first inert gas and a nitrogen-containing gas, and selecting a pressure for the first process gas effective to increase the amount of ionic nitrogen radicals relative to the amount of neutral nitrogen radicals in the first plasma;

modifying the gate dielectric stack by exposing the gate dielectric stack to the first plasma;

generating a second plasma comprising an amount of neutral oxygen radicals and an amount of ionic oxygen radicals from a second process gas containing a second inert gas and an oxygen-containing gas, and selecting a pressure for the second process gas effective to increase the amount of neutral oxygen radicals relative to the amount of ionic oxygen radicals in the second plasma; and

exposing the modified gate dielectric stack to the second plasma without the first plasma.

21. The method according to claim 20, wherein the substrate comprises a Si substrate, a Ge-contained Si substrate, a Ge substrate, or a compound semiconductor substrate.

22. The method according to claim 20, wherein the high-k layer comprises a metal oxide layer or a metal silicate layer.

23. The method according to claim 20, wherein the high-k layer comprises Ta₂O₅, TiO₂, ZrO₂, Al₂O₃, Y₂O₃, HfSiO_x, HfO₂, ZrSiO_x, TaSiO_x, SrO_x, SrSiO_x, LaO_x, LaSiO_x, YO_x, or YSiO_x, or a combination of two or more thereof.

24. The method according to claim 20, wherein the nitrogen-containing gas comprises N₂ or NH₃, or a combination thereof.

25. The method according to claim 20, wherein the first inert gas comprises He, Ar, He, Kr, or Xe, or a combination of two or more thereof.

26. The method according to claim 20, wherein the first process gas pressure is between about 10 mTorr and about 400 mTorr.

27. The method according to claim 20, wherein the first process gas pressure is between about 50 mTorr and about 300 mTorr.

28. The method according to claim 20, wherein the ratio of the first inert gas to the nitrogen-containing gas is between about 20 and about 500.

29. The method according to claim 20, wherein the first process gas comprises Ar and N₂.

30. The method according to claim 20, wherein the Ar/N₂ ratio is between about 20 and about 500.

31. The method according to claim 20, further comprising maintaining the substrate at a temperature between about 150°

C. and about 450°

C. during the modifying.

32. The method according to claim 20, wherein the gate dielectric stack is exposed to the first plasma for a time period between about 60 sec and about 300 sec.

33. The method according to claim 20, wherein the modifying is performed for a time sufficient to increase the nitrogen content of the high-k layer.

34. The method according to claim 20, wherein the gate dielectric stack further comprises an interfacial layer between the high-k layer and the substrate.

35. The method according to claim 34, wherein the interfacial layer comprises an oxide layer, a nitride layer, or an oxynitride layer.

36. The method according to claim 20, wherein the oxygen-containing gas comprises O₂, O₃, H₂O, or H₂O₂, or a combination of two or more thereof.

37. The method according to claim 20, wherein the second inert gas comprises He, Ar, He, Kr, or Xe, or a combination of two or more thereof.

38. The method according to claim 20, wherein the second process gas pressure is between about 0.5 Torr and about 5 Torr.

39. The method according to claim 20, wherein the second process gas pressure is between about 1 Torr and about 3 Torr.

40. A method for modifying a gate dielectric stack, the method comprising:

providing a gate dielectric stack having a high-k layer formed on a substrate;

generating a first plasma comprising an amount of neutral oxygen radicals and an amount of ionic oxygen radicals from a first process gas containing a first inert gas and an oxygen-containing gas, and selecting a pressure for the first process gas effective to increase the amount of neutral oxygen radicals relative to the amount of ionic oxygen radicals in the first plasma;

modifying the gate dielectric stack by exposing the gate dielectric stack to the first plasma;

generating a second plasma comprising an amount of ionic nitrogen radicals and an amount of neutral nitrogen radicals from a second process gas containing a second inert gas and a nitrogen-containing gas, and selecting a pressure for the second process gas effective to increase the amount of ionic nitrogen radicals relative to the amount of neutral nitrogen radicals in the second plasma; and

exposing the modified gate dielectric stack to the second plasma without the first plasma.

41. The method according to claim 40, wherein the substrate comprises a Si substrate, a Ge-containing Si substrate, a Ge substrate, or a compound semiconductor substrate.

42. The method according to claim 40, wherein the oxygen-containing gas comprises O₂, O₃, H₂O, or H₂O₂, or a combination of two or more thereof.

43. The method according to claim 40, wherein each of the first inert gas and the second inert gas comprises He, Ar, He, Kr, or Xe, or a combination of two or more thereof.

44. The method according to claim 40, wherein the first process gas pressure is between about 0.5 Torr and about 5 Torr.

45. The method according to claim 40, wherein the ratio of the first inert gas to the oxygen-containing gas is between about 20 and about 5.

46. The method according to claim 40, further comprising maintaining the substrate at a temperature between about 150°

C. and about 450°

C. during the modifying.

47. The method according to claim 40, wherein the modifying comprises exposing the gate dielectric stack to the first plasma for a time period between about 5 sec and about 60 sec.

48. The method according to claim 40, wherein the gate dielectric stack further comprises an interfacial layer between the high-k layer and the substrate.

49. The method according to claim 48, wherein the interfacial layer comprises an oxide layer, a nitride layer, or an oxynitride layer.

50. The method according to claim 40, wherein the nitrogen-containing gas comprises N₂ or NH₃, or a combination thereof.

51. The method according to claim 40, wherein the second process gas pressure is between about 10 mTorr and about 400 mTorr.