WETTING PRETREATMENT FOR ENHANCED DAMASCENE METAL FILLING

• US 20100320609A1
• Filed: 01/08/2010
• Published: 12/23/2010
• Est. Priority Date: 06/17/2009
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Willey, Mark J., Porter, David W., Mayer, Steven T.
• Granted Patent: US 8,962,085 B2
• Time in Patent Office: Days
• US Class Current: 257/773
• CPC Class Codes: C25D 17/001 Apparatus specially adapted for electrolytic coating of wafers, e.g. semiconductors or solar cells
• CPC Class Codes: C25D 21/04 Removal of gases or vapours ; Gas or pressure control
• CPC Class Codes: C25D 3/38 of copper
• CPC Class Codes: C25D 5/003 Electroplating using gases, e.g. pressure influence
• CPC Class Codes: C25D 5/02 Electroplating of selected surface areas
• CPC Class Codes: C25D 5/34 Pretreatment of metallic surfaces to be electroplated
• CPC Class Codes: C25D 7/123 Semiconductors first coated with a seed layer or a conductive layer
• CPC Class Codes: H01L 21/2885 using an external electrical current, i.e. electro-deposition
• CPC Class Codes: H01L 21/76861 Post-treatment or after-treatment not introducing additional chemical elements into the layer
• CPC Class Codes: H01L 21/76898 formed through a semiconductor substrate

Abstract

Disclosed are pre-wetting apparatus designs and methods. These apparatus designs and methods are used to pre-wet a wafer prior to plating a metal on the surface of the wafer. Disclosed compositions of the pre-wetting fluid prevent corrosion of a seed layer on the wafer and also improve the filling rates of features on the wafer.

Claims

1. A method of pre-wetting a wafer substrate prior to electrolytically processing the wafer substrate, the method comprising:

(a) providing a wafer substrate having an exposed metal layer on at least a portion of its surface to a pre-wetting process chamber;

(b) reducing pressure in the pre-wetting process chamber to a subatmospheric pressure;

and

(c) contacting the wafer substrate with a pre-wetting fluid at a subatmospheric pressure to form a wetting layer on the wafer substrate.

2. The method of claim 1, wherein the wafer substrate is positioned in a substantially horizontal orientation during the contacting.

3. The method of claim 1, wherein the wafer substrate is positioned in a substantially vertical orientation during the contacting.

4. The method of claim 1, wherein the wafer substrate has at least one recessed feature.

5. The method of claim 4, wherein the recessed feature is a damascence feature.

6. The method of claim 4, wherein the recessed feature is a through-mask feature.

7. The method of claim 1, wherein the pre-wetting fluid is substantially free of dissolved gases.

8. The method of claim 1, wherein (c) comprises delivering a liquid pre-wetting fluid onto the wafer substrate.

9. The method of claim 8, wherein (c) comprises immersing the wafer substrate in the pre-wetting fluid.

10. The method of claim 8, wherein (c) comprises spraying or covering the wafer substrate with the pre-wetting fluid.

11. The method of claim 1, wherein (c) comprises delivering a gaseous pre-wetting fluid onto the wafer substrate, and allowing the gaseous fluid to condense and form the wetting layer on the wafer substrate.

12. The method of claim 11 further comprising:

prior to (c), reducing the temperature of the wafer substrate below the condensation temperature of the pre-wetting fluid.

13. The method of claim 1, further comprising:

rotating the wafer substrate while a liquid pre-wetting fluid is delivered onto the wafer substrate.

14. The method of claim 13, wherein the wafer substrate is rotated at a rate of between about 10 rpm to 300 rpm.

15. The method of claim 14, wherein the wafer substrate is rotated at a rate of between about 10 rpm to 100 rpm.

16. The method of claim 2, wherein (c) comprises contacting the wafer substrate with the pre-wetting fluid from about 10 seconds to 120 seconds.

17. The method of claim 1, further comprising:

removing excess pre-wetting fluid from the wafer substrate.

18. The method of claim 17, wherein the excess pre-wetting fluid is removed from the wafer substrate by rotating the wafer substrate.

19. The method of claim 18, wherein the wafer substrate is rotated from about 300 rpm to 1000 rpm during removal of the excess pre-wetting fluid.

20. The method of claim 18, wherein the wafer substrate is rotated less than about 20 seconds during removal of the excess pre-wetting fluid.

21. The method of claim 1 further comprising:

after contacting the wafer substrate with a pre-wetting fluid, raising the pressure in the pre-wetting process chamber to an atmospheric pressure.

22. The method of claim 21, wherein raising the pressure in the pre-wetting process chamber to an atmospheric pressure comprises filling the pre-wetting process chamber with an oxygen-free gas.

23. The method of claim 1 further comprising:

removing the pre-wetted wafer substrate from the pre-wetting process chamber; and

transferring the pre-wetted wafer substrate to a chamber configured to perform an anodic process selected from the group consisting of electroetching and electropolishing.

24. The method of claim 1 further comprising:

removing the pre-wetted wafer substrate from the pre-wetting process chamber; and

transferring the pre-wetted wafer substrate to an electroplating chamber.

25. The method of claim 24, wherein the pre-wetted wafer substrate is exposed to an environment outside of the pre-wetting process chamber and the electroplating chamber for less than about one minute.

26. The method of claim 24, further comprising electroplating a layer of metal on the wafer substrate.

27. The method of claim 26, wherein the metal is copper.

28. The method of claim 24, further comprising cathodically polarizing the pre-wetted wafer substrate with respect to a plating solution in the electroplating chamber before contacting the pre-wetted wafer substrate with the plating solution.

29. The method of claim 24, further comprising electroplating the wafer substrate in the electroplating chamber using a degassed plating solution.

30. The method of claim 1, further comprising electroplating a layer of metal on the wafer substrate in the pre-wetting process chamber.

31. The method of claim 30, wherein the electroplating is performed using a degassed plating solution.

32. The method of claim 24, wherein the pre-wetting process chamber and the electroplating chamber are distinct stations of one apparatus module.

33. The method of claim 1 further comprising:

removing one or more dissolved gases from the pre-wetting fluid prior to contacting the wafer substrate with the pre-wetting fluid.

34. The method of claim 33 further comprising:

cooling the pre-wetting fluid to less than about 20°

C. during removing the one or more dissolved gases from the pre-wetting fluid.

35. The method of claim 1 further comprising:

transferring the pre-wetted wafer substrate to an electroplating chamber, wherein the wafer substrate has a wetting layer having a thickness of between about 50 to 500 μ

m immediately prior to electroplating.

36. The method of claim 1, wherein the pre-wetting fluid is water.

37. The method of claim 1, further comprising electroplating a layer of metal on the wafer substrate in the pre-wetting process chamber, wherein the pre-wetting fluid and a plating solution have the same composition.

38. The method of claim 1, wherein the pre-wetting fluid comprises a water-miscible solvent selected from the group consisting of an alcohol, a dialkylcarbonate, dimethylformamide, and dimethyl sulfoxide.

39. The method of claim 1, wherein the pre-wetting fluid comprises water and a copper salt.

40. The method of claim 39, wherein the pre-wetting fluid comprises a copper salt at a concentration of at least about 50% of a saturation limit.

41. The method of claim 39, wherein the copper salt is selected from the group consisting of copper sulfate, a copper alkylsulphonate, and mixtures thereof.

42. The method of claim 39, further comprising electroplating a layer of copper on the pre-wetted wafer substrate with a copper-containing plating solution, wherein the pre-wetting fluid contains a copper salt at a copper concentration that is the same or higher than the copper concentration in the plating solution.

43. The method of claim 42, wherein the copper concentration in the pre-wetting fluid is at least about 25% greater than the copper concentration in the plating solution.

44. The method of claim 39, wherein the copper salt is at a concentration of greater than about 20 g/L of copper.

45. The method of claim 1, wherein the pre-wetting fluid comprises deionized water, an acid, and a copper salt, wherein the pre-wetting fluid has a pH of not lower than about 2.

46. The method of claim 45, wherein the pre-wetting fluid has a pH of between about 2 and 4.

47. The method of claim 45, wherein the acid comprises an acid selected from the group consisting of sulfuric acid, an alkylsulphonic acid, and mixtures thereof

48. The method of claim 45, wherein the pre-wetting fluid comprises less than about 2 g/L of sulfuric acid or methane sulfonic acid.

49. The method of claim 1, wherein the pre-wetting fluid comprises water and an acid, and wherein the pre-wetting fluid has a pH of greater than about 2.

50. The method of claim 1, wherein the pre-wetting fluid consists essentially of water, an acid, and a copper salt, and wherein the pre-wetting fluid has a pH of greater than about 2.

51. The method of claim 1, wherein the pre-wetting fluid consists essentially of water and a copper salt.

52. The method of claim 1, wherein the pre-wetting fluid is substantially free from one or more additives selected from the group consisting of halides, plating accelerators, and plating levelers.

53. The method of claim 1, wherein the pre-wetting fluid is substantially free from halides, plating accelerators, and plating levelers, and comprises a plating suppressor at a small concentration.

54. A method of electroplating a layer of copper on a wafer substrate, the method comprising:

(a) providing the wafer substrate having an exposed metal layer on at least a portion of its surface to a pre-wetting process chamber;

(b) contacting the wafer substrate with a pre-wetting fluid, the pre-wetting fluid comprising water and copper ions and being substantially free of plating additives, to form a layer of pre-wetting fluid on the wafer substrate;

(c) contacting the pre-wetted wafer substrate with a plating solution, the plating solution comprising copper ions and plating additives, to electroplate a layer of copper on the wafer substrate, wherein the concentration of copper ions in the pre-wetting fluid is greater than the concentration of copper ions in the plating solution.

55. The method of claim 54, wherein the pre-wetting fluid is substantially free of additives selected from the group consisting of halides, accelerators, and levelers.

56. The method of claim 54, wherein the pre-wetting fluid contains polyethylene oxide at a concentration of less than about 15 ppm.

57. The method of claim 54, wherein the plating solution contains an additive selected from the group consisting of halides, accelerators, levelers, and suppressors.

58. A method of electroplating a layer of metal on a wafer substrate, the method comprising:

(a) providing the wafer substrate having an exposed metal layer on at least a portion of its surface to a pre-wetting process chamber;

(b) contacting the wafer substrate with a pre-wetting fluid comprising a water-miscible solvent to form a layer of pre-wetting fluid on the wafer substrate;

(c) contacting the pre-wetted wafer substrate with a plating solution comprising metal ions to electroplate a layer of metal on the wafer substrate.

59. The method of claim 58, wherein the water-miscible solvent is selected from the group consisting of an alcohol, dimethylcarbonate, diethylcarbonate, dimethyl sulfoxide, and dimethyl formamide.

60. The method of claim 58, wherein the plating solution comprises copper ions to electroplate a layer of copper on the wafer substrate.

61. A method of electroplating a layer of metal on a wafer substrate, the method comprising:

(a) providing the wafer substrate having an exposed metal layer on at least a portion of its surface to a pre-wetting process chamber;

(b) reducing pressure in the pre-wetting process chamber to a subatmospheric pressure;

(c) contacting the wafer substrate, at a subatmospheric pressure, with a pre-wetting fluid comprising an acid to at least partially remove surface oxide from the exposed metal layer and to form a layer of pre-wetting fluid on the wafer substrate, wherein the pre-wetting fluid has a pH of between about 2 to 6;

(d) contacting the pre-wetted wafer substrate with a plating solution comprising metal ions to electroplate a layer of metal on the wafer substrate, wherein the plating solution has a pH of between about 2 to 6, wherein the plating solution and the pre-wetting fluid have different compositions.

62. The method of claim 61, wherein the plating solution comprises copper ions to electroplate a layer of copper on the wafer substrate.

63. A method of electroplating a layer of metal on a wafer substrate, the method comprising:

(a) providing the wafer substrate having an exposed metal layer on at least a portion of its surface to a pre-wetting process chamber;

(b) contacting the wafer substrate with a pre-wetting fluid comprising a reducing agent to at least partially reduce surface oxide on the exposed metal layer and to form a layer of pre-wetting fluid on the wafer substrate;

(c) contacting the pre-wetted wafer substrate with a plating solution comprising metal ions to electroplate a layer of metal on the wafer substrate.

64. The method of claim 63, wherein the plating solution comprises copper ions to electroplate a layer of copper on the wafer substrate.

65. A method of electroplating a layer of metal on a wafer substrate, the method comprising:

(a) providing the wafer substrate having an exposed metal layer on at least a portion of its surface to a pre-wetting process chamber;

(b) contacting the wafer substrate with a pre-wetting fluid comprising a metal complexing agent to at least partially remove surface oxide from the exposed metal layer and to form a layer of pre-wetting fluid on the wafer substrate, wherein the pre-wetting fluid has a pH of between about 4 to 12;

(c) contacting the pre-wetted wafer substrate with a plating solution comprising metal ions to electroplate a layer of metal on the wafer substrate.

66. The method of claim 65, wherein the plating solution comprises copper ions to electroplate a layer of copper on the wafer substrate.

67. A partially fabricated semiconductor device structure comprising:

at least one recessed feature, said recessed feature having a layer of metal substantially lining the feature, wherein the recessed feature comprises a substantially gas-free pre-wetting fluid filling the feature, said pre-wetting fluid comprising an aqueous metal salt solution substantially free from plating accelerators and levelers.