Selective refractory metal and nitride capping

• US 6,844,258 B1
• Filed: 05/09/2003
• Issued: 01/18/2005
• Est. Priority Date: 05/09/2003
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Taylor, Nerissa, Fair, James A., Lee, Sang-Hyeob, Havemann, Robert H., Sung, Jungwan, Plano, Mary Anne
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Ho, Tu-Tu
• Application Number:
  US10/435,010
• Time in Patent Office: 620 Days
• Field of Search: 438/648, 438/650
• US Class Current: 438/648
• CPC Class Codes: H01L 21/28556 by chemical means, e.g. CVD, LPCVD, PECVD, laser CVD H01L21/28518 - H01L21/28537 and H01L21/28568 take precedence
• CPC Class Codes: H01L 21/28562 Selective deposition
• CPC Class Codes: H01L 21/76849 the layer being positioned on top of the main fill metal
• CPC Class Codes: H01L 21/76856 by treatment in plasmas or gaseous environments, e.g. nitriding a refractory metal liner
• CPC Class Codes: H01L 21/76867 characterized by methods of formation other than PVD, CVD or deposition from a liquids PVD H01L21/2855; CVD H01L21/28556; deposition from liquids H01L21/288
• CPC Class Codes: H01L 21/76883 Post-treatment or after-treatment of the conductive material
• CPC Class Codes: H01L 21/76889 by forming silicides of refractory metals

Abstract

A method for creating a refractory metal and refractory metal nitride cap effective for reducing copper electromigration and copper diffusion is described. The method includes depositing a refractory metal nucleation layer and nitriding at least the upper portion of the refractory metal layer to form a refractory metal nitride. Methods to reduce and clean the copper lines before refractory metal deposition are also described. Methods to form a thicker refractory metal layer using bulk deposition are also described.

Claims

1. A method of forming a capping layer on copper lines of a semiconductor device, the method comprising:

(a) providing a partially fabricated semiconductor device having a surface comprising exposed surfaces of the copper lines and dielectric around the copper lines,

(b) creating a nucleation refractory metal layer over at least the exposed surfaces of the copper lines;

(c) depositing a bulk refractory metal layer over at least the nucleation refractory metal layer created in (b); and

(d) nitriding at least an upper portion of the bulk refractory metal layer deposited in (c) to form a refractory metal nitride layer effective for reducing electromigration of the copper line and for blocking diffusion of copper from the copper conductive lines.

2. The method of claim 1, wherein the exposed surfaces of the copper lines comprise copper oxide and wherein the method further comprises reducing the copper oxide before creating the nucleation refractory metal layer.

3. The method of claim 2, wherein reducing the copper oxide comprises contacting the copper oxide with hydrogen gas.

4. The method of claim 2, wherein reducing the copper oxide comprises contacting the copper oxide with hydrogen gas and one or both of argon or nitrogen gas.

5. The method of claim 2, wherein reducing the copper oxide comprises contacting the copper oxide with at least one of SiH₄, SiH₄, Si₂H₆ and B₂H₆.

6. The method of claim 2, wherein reducing the copper oxide and creating the nucleation refractory metal layer are performed using different chamber temperatures and pressures.

7. The method of claim 2, wherein the copper surface is cleaned by hydrogen plasma or by wet cleaning before reducing the copper oxide.

8. The method of claim 1, wherein the bulk refractory metal layer is a tungsten layer.

9. The method of claim 8, wherein creating the bulk refractory metal layer comprises reacting a tungsten containing precursor including at least one of WF₆, WCl₆ or W(CO)₆.

10. The method of claim 1, wherein the bulk refractory metal layer comprises at least one of tantalum, titanium, molybdenum, ruthenium or cobalt.

11. The method of claim 1, wherein creating the nucleation refractory metal layer comprises depositing refractory metal by atomic layer deposition (ALD).

12. The method of claim 11, wherein the ALD comprises sequentially injecting WF₆ and at least one of SiH₄ and H₂ gases.

13. The method of claim 1, wherein creating the nucleation refractory metal layer comprises depositing refractory metal by chemical vapor deposition (CVD).

14. The method of claim 1, wherein creating the nucleation refractory metal layer comprises (i) converting the exposed surfaces of the copper lines into a copper silicide and (ii) converting the copper silicide layer to the nucleation refractory metal layer.

15. The method of claim 14, wherein converting the exposed surfaces of the copper lines into the copper silicide comprises exposing the surfaces to SiH₄ to form the copper silicide, and wherein converting the copper silicide layer to the nucleation refractory metal layer comprises exposing the copper silicide to a refractory metal-containing gas to form the nucleation refractory metal layer.

16. The method of claim 14, wherein (i) and (ii) are performed at different chamber temperatures and pressures.

17. The method of claim 1, wherein creating the nucleation refractory metal layer is performed in a manner that selectively deposits the nucleation refractory metal layer on the copper lines, without depositing significantly on surrounding dielectric.

18. The method of claim 1, further comprising repeating (b) one or more times prior to (c).

19. The method of claim 18, wherein depositing bulk refractory metal layer is performed in a manner that selectively deposits the bulk refractory metal layer on the refractory metal layer created in (b), without depositing significantly on surrounding dielectric.

20. The method of claim 18, wherein creating the nucleation refractory metal layer (b) and depositing the bulk refractory metal layer are performed using different chamber temperatures and pressures.

21. The method of claim 18, wherein the bulk refractory metal layer is between about 3 and 100 angstroms thick.

22. The method of claim 1, wherein nitriding at least an upper portion of the bulk the refractory metal layer in (d) comprises exposing the bulk refractory metal layer to a plasma that contains a nitrogen-containing compound.

23. The method of claim 22, wherein the nitrogen-containing compound is one of N₂, NH₃ or N₂H₄.

24. The method of claim 22, wherein exposing the bulk refractory metal layer to the plasma comprises biasing the substrate with an RF powered electrode.

25. The method of claim 22, wherein exposing the bulk refractory metal layer to a plasma comprises grounding the substrate with a grounded electrode while applying RF energy via a second electrode.

26. The method of claim 22, wherein the plasma of the nitrogen-containing compound is generated through the use of an external electrode.

27. The method of claim 22, wherein plasma of the nitrogen-containing compound is a downstream plasma.

28. The method of claim 1, wherein the nucleation refractory metal nitride layer formed in (b) is between about 3 and 30 angstroms thick.

29. The method of claim 1, further comprising depositing a layer of silicon nitride onto the refractory metal nitride layer.

30. A method of forming a capping layer on copper lines of a semiconductor device, the method comprising:

(a) providing a partially fabricated semiconductor device having a surface comprising exposed surfaces of the copper lines and dielectric around the copper lines;

(b) creating a nucleation refractory metal layer over at least the exposed surfaces of the copper lines;

(c) depositing a bulk refractory metal layer over at least the nucleation refractory metal layer created in (b).

31. The method of claim 30, wherein depositing bulk refractory metal layer is performed in a manner that selectively deposits the bulk refractory metal layer on the nucleation refractory metal layer created in (b), without depositing significantly on surrounding dielectric.

32. The method of claim 30, wherein the exposed surfaces of the copper lines comprise copper oxide and wherein the method further comprises reducing the copper oxide before creating the nucleation refractory metal layer.

33. The method of claim 32, wherein reducing the copper oxide comprises contacting the copper oxide with hydrogen gas.

34. The method of claim 32, wherein reducing the copper oxide comprises contacting the copper oxide with hydrogen gas and one or both of argon or nitrogen gas.

35. The method of claim 32, wherein reducing the copper oxide comprises contacting the copper oxide with at least one of SiH₄, Si₂H₆ and B₂H₆.

36. The method of claim 32, wherein the copper surface is cleaned by hydrogen plasma or by wet cleaning before reducing the copper oxide.

37. The method of claim 30, wherein the nucleation refractory metal layer and bulk refractory metal layer are both tungsten layers.

38. The method of claim 37, wherein creating the nucleation refractory metal layer comprises reacting a tungsten containing precursor including at least one of WF₆, WCl₆ and W(CO)₆.

39. The method of claim 30, wherein the nucleation refractory metal layer and bulk refractory metal layer both comprise at least one of tantalum, titanium and molybdenum.

40. The method of claim 30, wherein creating the nucleation refractory metal layer comprises depositing refractory metal by atomic layer deposition (ALD).

41. The method of claim 40, wherein the ALD comprises sequentially injecting WF₆ and at least one of SiH₄ and H₂ gases.

42. The method of claim 30, wherein creating the nucleation refractory metal layer comprises depositing refractory metal by chemical vapor deposition (CVD).

43. The method of claim 30, wherein creating the nucleation refractory metal layer comprises (i) converting the exposed surfaces of the copper lines into a copper silicide and (ii) converting the copper silicide layer to the nucleation refractory metal layer.

44. The method of claim 32, wherein converting the exposed surfaces of the copper lines into the copper silicide comprises exposing the surfaces to SiH₄ to form the copper silicide, and wherein converting the copper silicide layer to the nucleation refractory metal layer comprises exposing the copper silicide to a refractory metal-containing gas to form the nucleation refractory metal layer.

45. The method of claim 30, wherein creating the nucleation refractory metal layer is performed in a manner that selectively deposits the refractory metal layer on the copper lines, without depositing significantly on surrounding dielectric.

46. The method of claim 30, wherein the nucleation refractory metal layer is between about 3 and 30 angstroms thick.

47. The method of claim 30, wherein the bulk refractory metal layer is between about 8 and 100 angstroms thick.

48. A method of forming a capping layer on copper lines of a semiconductor device, the method comprising:

(a) providing a partially fabricated semiconductor device having a surface comprising exposed surfaces of the copper lines and dielectric around the copper lines;

(b) creating a refractory metal layer over at least the exposed surfaces of the copper lines; and

(c) nitriding at least an upper portion of the refractory metal layer deposited in (c) to form a refractory metal nitride layer effective for reducing electromigration of the copper line and for blocking diffusion of copper from the copper conductive lines,

wherein the exposed surfaces of the copper lines comprise copper oxide and wherein the method further comprises reducing the copper oxide before creating the refractory metal layer.

49. The method of claim 48, wherein reducing the copper oxide comprises contacting the copper oxide with hydrogen gas.

50. The method of claim 48, wherein reducing the copper oxide comprises contacting the copper oxide with hydrogen gas and one or both of argon or nitrogen gas.

51. The method of claim 48, wherein reducing the copper oxide comprises contacting the copper oxide with at least one of SiH₄, Si₂H₆ and B₂H₆.

52. The method of claim 48, wherein reducing the copper oxide and creating the refractory metal layer are performed using different chamber temperatures and pressures.

53. The method of claim 48, wherein the copper surface is cleaned by hydrogen plasma or by wet cleaning before reducing the copper oxide.

54. A method of forming a capping layer on copper lines of a semiconductor device, the method comprising:

(a) providing a partially fabricated semiconductor device having a surface comprising exposed surfaces of the copper lines and dielectric around the copper lines;

(b) creating a nucleation refractory metal layer over at least the exposed surfaces of the copper lines; and

(c) nitriding at least an upper portion of the nucleation refractory metal layer deposited in (b) to form a refractory metal nitride layer effective for reducing electromigration of the copper line and for blocking diffusion of copper from the copper conductive lines.

55. The method of claim 54, further comprising repeating (b) one or more times prior to (c).