Topography reduction and control by selective accelerator removal

• US 20090277867A1
• Filed: 11/20/2006
• Published: 11/12/2009
• Est. Priority Date: 10/20/2003
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Webb, Eric G., Mayer, Steven T., Hill, Richard S., Stowell, R. Marshall, Kepten, Avishai, Rea, Mark L.
• Granted Patent: US 8,158,532 B2
• Time in Patent Office: Days
• US Class Current: 216/13
• CPC Class Codes: B23H 5/08 Electrolytic grinding
• CPC Class Codes: C25D 17/001 Apparatus specially adapted for electrolytic coating of wafers, e.g. semiconductors or solar cells
• CPC Class Codes: C25D 17/06 Suspending or supporting devices for articles to be coated
• CPC Class Codes: C25D 17/14 for pad-plating
• CPC Class Codes: C25D 5/02 Electroplating of selected surface areas
• CPC Class Codes: C25D 5/06 Brush or pad plating
• CPC Class Codes: C25D 5/08 Electroplating with moving electrolyte e.g. jet electroplating using locally applied jets of electrolyte C25D5/026
• 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: C25F 3/16 Polishing
• CPC Class Codes: C25F 3/30 of semiconducting materials
• CPC Class Codes: H01L 21/02068 during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
• CPC Class Codes: H01L 21/2885 using an external electrical current, i.e. electro-deposition
• CPC Class Codes: H01L 21/32115 Planarisation
• CPC Class Codes: H01L 21/3212 by chemical mechanical polishing [CMP]
• CPC Class Codes: H01L 21/32134 by liquid etching only
• CPC Class Codes: H01L 21/7684 Smoothing; Planarisation
• CPC Class Codes: H01L 21/76849 the layer being positioned on top of the main fill metal
• CPC Class Codes: H01L 21/76877 Filling of holes, grooves or trenches, e.g. vias, with conductive material

Abstract

Plating accelerator is applied selectively to a substantially-unfilled wide (e.g., low-aspect-ratio feature cavity. Then, plating of metal is conducted to fill the wide feature cavity and to form an embossed structure in which the height of a wide-feature metal protrusion over the metal-filled wide-feature cavity is higher than the height of metal over field regions. Most of the overburden metal is removed using non-contact techniques, such as chemical wet etching. Metal above the wide feature cavity protects the metal-filled wide-feature interconnect against dishing, and improved planarization techniques avoid erosion of the metal interconnect and dielectric insulating layer. In some embodiments, plating of metal onto a substrate is conducted to fill narrow (e.g., high-aspect-ratio feature cavities) in the dielectric layer before selective application of plating accelerator and filling of the wide feature cavity.

Claims

1. A method of forming a metal structure, comprising steps of:

(a) providing a substrate having a base layer and a substrate surface, said base layer including a wide feature cavity and a field, said wide feature cavity defining a wide-feature region, said field being adjacent to said wide feature cavity and defining a field region;

(b) exposing at least said wide-feature region of said substrate to a deposition accelerator, without simultaneously depositing metal;

(c) ceasing exposing said substrate to a deposition accelerator;

(d) causing said accelerator to become attached selectively to said substrate in said wide-feature region relative to said field region, without simultaneously depositing metal in said wide-feature region;

(e) then after all of steps (b), (c) and (d), exposing said substrate to a deposition solution;

(f) then conducting a wide-feature metal deposition, wherein said accelerator increases a rate of metal deposition in said wide-feature region relative to a rate of metal deposition in said field region.

2. A method as in claim 1, wherein:

said feature cavity has a width at least three times greater than its depth, so that said feature cavity has an aspect ratio not exceeding about 0.33.

3. A method as in claim 2, further comprising:

continuing depositing metal on said substrate until deposited metal in said wide-feature region comprises a wide-feature protrusion having a wide-feature protrusion height above said base layer that is greater than a thickness of deposited field metal in said field region, thereby forming an embossed structure.

4. A method as in claim 3, wherein:

said deposited field metal in said field region has a thickness less than one-half of the width of said feature cavity.

5. A method as in claim 3, wherein:

said deposited field metal in said field region has a thickness less than ⅕

of the width of said wide feature cavity.

6. A method as in claim 3, further comprising:

after said forming an embossed structure, removing deposited metal from said field region.

7. A method as in claim 6 wherein said removing deposited metal from said substrate comprises removing deposited metal from said substrate at a uniform removal rate.

8. A method as in claim 7 wherein said removing deposited metal from said substrate at a uniform removal rate comprises:

removing deposited metal from said wide-feature protrusion at a metal removal rate and removing deposited metal from said field region substantially at said metal removal rate.

9. A method as in claim 8 wherein said removing deposited metal from said wide-feature region and from said field region selectively removes deposited metal at a removal rate greater than removing other substrate material from said substrate.

10. A method as in claim 8 wherein said removing deposited metal from said substrate comprises:

isotropically removing deposited metal from said substrate until deposited metal in said field region is substantially completely removed and a wide-feature protrusion of deposited metal remains in said wide-feature region.

11. A method as in claim 10 wherein said isotropically removing deposited metal from said substrate comprises:

isotropically removing deposited metal from said substrate until a thin conductive metal seed layer in said field region is substantially completely removed and a wide-feature protrusion of deposited metal is located in said wide-feature region.

12. A method as in claim 6 wherein:

said removing deposited metal comprises isotropic wet etching said substrate.

13. A method as in claim 1, characterized by:

not removing metal from said substrate during said wide-feature metal deposition of step (f).

14. A method as in claim 1, wherein:

said accelerator comprises accelerator species selected from the group consisting of 2-mercaptoethane sulfonic acid (MESA), 3-mercapto-1-propane sulfonic acid (MPSA), 3-mercaptopropionic acid, mercaptopyruvate, 3-mercapto-2-butanol, 2,3 dimercaptopropane sulphonic acid, 1-thioglycerol, salts thereof, and derivatives thereof.

15. A method as in claim 1 wherein said step (b) of exposing at least said wide-feature region to a deposition accelerator comprises:

contacting said substrate with an accelerator solution containing accelerator species.

16. A method as in claim 15, wherein:

said precursor solution comprises an accelerator concentration substantially greater than an accelerator concentration in said deposition solution.

17. A method as in claim 1 wherein said step (b) of exposing at least said wide-feature region to a deposition accelerator comprises:

contacting said substrate with a phase containing an accelerator species, said phase selected from the group consisting of a liquid, a solution, and a vapor.

18. A method as in claim 1 wherein:

substantially no metal deposition occurs during said steps (b) and (d).

19. A method as in claim 1 further characterized in that:

substantially no accelerator becomes attached to said substrate during said wide-feature metal deposition of step (f).

20. A method as in claim 1 wherein:

said step (d) of causing an accelerator to become attached selectively to said substrate is conducted in a processing chamber in which metal deposition is not conducted.

21. A method as in claim 1, wherein:

said step (b) of exposing at least said wide-feature region to a deposition accelerator comprises;

applying an accelerator film on said substrate; and

said step (d) of causing said accelerator to become attached selectively to said substrate in said wide-feature region relative to said field region comprises;

then selectively removing at least a portion of said accelerator film from at least said field region.

22. A method as in claim 21, wherein:

said step (f) of conducting said wide-feature metal deposition includes cathodizing said substrate surface; and

said selectively removing at least a portion of said accelerator film is not conducted during cathodizing said substrate surface.

23. A method as in claim 21 wherein said applying an accelerator film on said substrate comprises:

contacting said substrate with a precursor solution containing accelerator precursor molecules;

transforming said accelerator precursor molecules to accelerator species.

24. A method as in claim 23, wherein:

said precursor solution comprises accelerator precursor species selected from the group consisting of dimercaptopropane sulfonic acid (DMPSA), dimercaptoethane sulfonic acid (DMESA), salts thereof, and derivatives thereof.

25. A method as in claim 23, wherein said transforming said accelerator precursor molecules to accelerator species comprises:

applying sufficient electric current to said substrate to transform said accelerator precursor molecules to accelerator species.

26. A method as in claim 21, wherein said selectively removing at least a portion of said accelerator film comprises:

contacting said substrate with a pad that selectively removes said accelerator film from at least said field region.

27. A method as in claim 26, wherein contacting said substrate with said pad is performed for a period of time and then stopped prior to conducting said wide-feature metal deposition.

28. A method as in claim 26, characterized in that said contacting said substrate with a pad further comprises contacting said substrate and said pad with a lubricant that is different from said deposition solution.

29. A method as in claim 21, wherein said selectively removing at least a portion of said accelerator film comprises:

using a contact-less technique.

30. A method as in claim 29, wherein said selectively removing at least a portion of said accelerator film comprises:

not physically rubbing said substrate.

31. A method as in claim 29, wherein said selectively removing at least a portion of said accelerator film comprises:

conducting selective membrane-mediated accelerator removal.

32. A method as in claim 29, wherein said selectively removing at least a portion of said accelerator film comprises:

performing a technique selected from the group consisting of electropolishing, electrochemical mechanical polishing (eCMP), and electrochemical anodization with selective abrasion.

33. A method of claim 1 wherein said wide-feature metal deposition step (f) comprises:

not simultaneously contacting said substrate with a rubbing pad.

34. A method of claim 1 wherein said wide-feature metal deposition step (f) comprises:

simultaneously contacting said substrate with a rubbing pad.

35. A method as in claim 1 wherein:

said base layer has a base field height; and

further comprising;

continuing said wide-feature metal deposition so that deposited metal in said wide-feature region comprises a wide-feature protrusion;

removing metal substantially completely from said field region; and

removing deposited metal from said wide-feature region until a metal level in said wide-feature region is lower than said base field height.

36. A method as in claim 1, further comprising:

continuing said wide-feature metal deposition so that deposited metal in said wide-feature region comprises a wide-feature protrusion;

then isotropically removing deposited metal from said substrate until metal is substantially completely removed from said field region, and a wide-feature protrusion of metal remains in said wide-feature region.

37. A method as in claim 36, further comprising:

performing chemical mechanical polishing (CMP) of said substrate surface to planarize said substrate surface.

38. A method as in claim 36, wherein:

said base layer has a base field height; and

further comprising;

after said CMP, isotropically removing deposited metal from said substrate until deposited metal in said wide-feature region is lower than said base field height, thereby forming a recess in said wide feature cavity.

39. A method as in claim 38, further comprising:

forming a metal capping layer in said wide-feature region to cover deposited metal in said wide feature cavity.

40. A method as in claim 39, further comprising:

after forming said metal capping layer, performing chemical mechanical polishing (CMP) of said substrate surface to remove a small amount of capping layer metal from said capping layer.

41. A method as in claim 1 wherein said substrate comprises a barrier layer on said base layer and a metal seed layer on said barrier layer, and further comprising:

continuing said wide-feature metal deposition so that said wide-feature region contains a wide-feature metal protrusion;

then isotropically removing deposited metal and said metal seed layer from said field region;

then removing said barrier film from said field region of said base layer.

42. A method as in claim 1 wherein:

said base layer further includes a narrow feature cavity defining a narrow-feature region, said narrow feature cavity having a higher aspect ratio than said wide feature cavity; and

further comprising;

before said step (b), exposing said substrate to a narrow-feature deposition solution;

then before said step (b), conducting a narrow-feature metal deposition using said narrow-feature deposition solution to deposit metal on said substrate in at least said narrow feature cavity; and

then before said step (b), ceasing exposure of said substrate to said narrow-feature deposition solution.

43. A method as in claim 42, further comprising:

continuing said narrow-feature metal deposition until deposited metal in said narrow feature cavity has an adjusted aspect ratio less than 1.

44. A method as in claim 43, further comprising:

continuing said narrow-feature metal deposition until deposited metal in said narrow-feature region comprises a narrow-feature protrusion.

45. A method as in claim 44, further comprising:

continuing said wide-feature metal deposition of step (f) until deposited metal in said wide-feature region comprises a wide-feature protrusion.

46. A method as in claim 45, further comprising:

continuing said wide-feature metal deposition until a narrow-feature protrusion height of said narrow-feature protrusion and a wide-feature protrusion height of said wide-feature protrusion are substantially equal.

47. A method as in claim 43, further comprising:

continuing said wide-feature metal deposition so that deposited metal in said narrow-feature region comprises a narrow-feature protrusion.

48. A method as in claim 47, further comprising:

continuing said wide-feature metal deposition until deposited metal in said wide-feature region comprises a wide-feature protrusion.

49. A method as in claim 48, further comprising:

continuing said wide-feature metal deposition until a narrow-feature protrusion height of said narrow-feature protrusion and a wide-feature protrusion height of said wide-feature protrusion are substantially equal.

50. A method as in claim 42, further comprising:

removing deposited metal from said substrate after said step (f).

51. A method as in claim 50 wherein:

said removing deposited metal initially is substantially uniform.

52. A method as in claim 50 wherein:

said removing deposited metal comprises isotropic wet etching said substrate.

53. A method as in claim 42 wherein said removing deposited metal from said substrate comprises:

removing deposited metal from said substrate until deposited metal in said field region is substantially completely removed and a protrusion of deposited metal remains in each of said narrow-feature region and said wide-feature region.

54. A method as in claim 42 further characterized in that:

substantially no accelerator becomes attached to said substrate during said narrow-feature metal deposition.

55. A method as in claim 42, wherein:

said step of conducting said narrow-feature metal deposition and said step (e) of conducting said wide-feature metal deposition include cathodizing said substrate surface; and

said selectively removing at least a portion of said accelerator film is not conducted during cathodizing said substrate surface.

56. A method as in claim 42, wherein:

said base layer has a base field height; and

further comprising;

continuing said wide-feature metal deposition so that deposited metal in said narrow-feature region comprises a narrow-feature protrusion and deposited metal in said wide-feature region comprises a wide-feature protrusion;

removing metal substantially completely from said field region; and

removing deposited metal from said narrow-feature region and from said wide-feature region until a metal level in said narrow-feature region and a metal level in said wide-feature region are lower than said base field height.

57. A method as in claim 42, further comprising:

continuing said wide-feature metal deposition so that deposited metal in said narrow-feature region comprises a narrow-feature protrusion and deposited metal in said wide-feature region comprises a wide-feature protrusion;

then isotropically removing deposited metal from said substrate until metal is substantially completely removed from said field region, and a narrow-feature protrusion of metal remains in said narrow-feature region and a wide-feature protrusion of metal remains in said wide-feature region.

58. A method as in claim 57, further comprising:

performing chemical mechanical polishing (CMP) of said substrate surface to planarize said substrate surface.

59. A method as in claim 58, wherein:

said base layer has a base field height; and

further comprising;

after said CMP, isotropically removing deposited metal from said substrate until deposited metal in said narrow-feature region and in said wide-feature region is lower than said base field height, thereby forming a recess in said narrow feature cavity and a recess in said wide feature cavity.

60. A method as in claim 59, further comprising:

forming a metal capping layer in said recess in said narrow-feature cavity to cover deposited metal in said narrow feature cavity and a metal capping layer in said recess in said wide-feature cavity to cover deposited metal in said wide feature cavity.

61. A method as in claim 60, further comprising:

after forming metal capping layers, performing chemical mechanical polishing (CMP) of said substrate surface to remove a small amount of capping layer metal from said capping layers.

62. A method as in claim 1 wherein said substrate comprises a barrier layer on said base layer and a metal seed layer on said barrier layer, and further comprising:

continuing said wide-feature metal deposition so that said narrow-feature region contains a narrow-feature metal protrusion and said wide-feature region contains a wide-feature metal protrusion;

then isotropically removing deposited metal and said metal seed layer from said field region;

then removing said barrier film from said field region of said base layer.

63. A method as in claim 42, further comprising:

applying an initial accelerator to said substrate at least in said narrow-feature region before said step of exposing said substrate to a narrow-feature deposition solution.

64. A method as in claim 63, further comprising:

deactivating said initial accelerator before said step (d) of causing an accelerator to become attached selectively in said wide feature cavity.

65. A method as in claim 42, further comprising:

conducting a surface and edge treatment (SET) operation after ceasing exposure to narrow-feature deposition solution and before said exposing at least said wide-feature region of said substrate to a deposition accelerator in step (b).

66. A method as in claim 65 wherein said SET operation comprises:

cleaning said substrate surface.

67. A method as in claim 66 wherein said wherein said cleaning comprises:

removing a thin layer of metal from metal deposited during said narrow-feature metal deposition; and

wherein removing a thin layer of metal comprises;

removing a thin layer having a thickness in a range of about from 1 nm to 10 nm; and

wherein said removing a thin layer of metal comprises;

conducting a chemical wet etch.

68. A method as in claim 65 wherein said SET operation comprises:

deactivating initial accelerator that is present in said narrow-feature region to avoid excessive overplating in said narrow-feature region during said wide-feature deposition in step (f).

69. A method as in claim 42, further comprising:

conducting edge accelerator removal (EAR) processes after said exposing at least said wide-feature region of said substrate to a deposition accelerator in step (b).