Methods of filling a feature on a substrate with copper nanocrystals

• US 6,897,151 B2
• Filed: 11/08/2002
• Issued: 05/24/2005
• Est. Priority Date: 11/08/2002
• Status: Expired due to Fees

• Current Assignee: Wayne State University
• Original Assignee: Wayne State University
• Inventors: Dezelah, Charles L. IV, Goldstein, Avery N., Yu, Zhengkun, Winter, Charles H.
• Primary Examiner(s): Elms, Richard
• Assistant Examiner(s): SMITH, BRADLEY
• Application Number:
  US10/290,498
• Publication Number:
  US 20040091625A1
• Time in Patent Office: 928 Days
• Field of Search: 438/584, 438/597, 438/660, 438/687
• US Class Current: 438/687
• CPC Class Codes: C23C 18/06 Coating on selected surface areas, e.g. using masks
• CPC Class Codes: C23C 18/08 characterised by the deposition of metallic material
• CPC Class Codes: C25D 7/123 Semiconductors first coated with a seed layer or a conductive layer
• CPC Class Codes: H01L 21/288 from a liquid, e.g. electrolytic deposition
• CPC Class Codes: H01L 21/76877 Filling of holes, grooves or trenches, e.g. vias, with conductive material
• CPC Class Codes: H01L 23/53238 Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 2201/0257 Nanoparticles inks comprising nanoparticles H05K1/097
• CPC Class Codes: H05K 3/102 by bonding of conductive powder, i.e. metallic powder H05K3/12 takes precedence
• CPC Class Codes: H05K 3/107 by filling grooves in the support with conductive material H05K3/045, H05K3/101, H05K3/1258 and H05K3/465 take precedence

Abstract

The invention relates to methods of making monodisperse nanocrystals comprising the steps of reducing a copper salt with a reducing agent, providing a passivating agent comprising a nitrogen and/or an oxygen donating moitey and isolating the copper nanocrystals. Moreover, the invention relates to methods for making a copper film comprising the steps of applying a solvent comprising copper nanocrystals onto a substrate and heating the substrate to form a film of continuous bulk copper from said nanocrystals. Finally, the invention also relates to methods for filling a feature on a substrate with copper comprising the steps of applying a solvent comprising copper nanocrystals onto the featured substrate and heating the substrate to fill the feature by forming continuous bulk copper in the feature.

Claims

1. A method for producing a copper film comprising the steps of:

(a) applying a solvent comprising copper nanocrystals dissolved therein onto a substrate, wherein said copper nanocrystals are made by;

(i) reducing a copper salt with a reducing agent to obtain reduced copper;

(ii) providing a passivating agent to contact said reduced copper, wherein said passivating agent comprises at least one moiety selected from the group consisting of a nitrogen donor and an oxygen donor; and

(iii) isolating said nanocrystals comprising said reduced copper; and

(b) heating said substrate to form a film of continuous bulk copper from said nanocrystals on said substrate.

2. The method of claim 1, wherein said substrate comprises silicon.

3. A method of claim 1, wherein said substrate comprises SiO₂.

4. A method of claim 1, wherein said substrate is covered with a barrier layer.

5. A method of claim 1, wherein said substrate is washed with a surfactant.

6. A method of claim 1, wherein said nanocrystals are re-dissolved prior to said heating.

7. A method of claim 1, wherein the solvent further comprises a binder.

8. The method of claim 1, wherein the passivating agent comprises an imidazole moiety.

9. The method of claim 1, wherein the nitrogen donor is selected from the group consisting of imidazole, pyridine, bipyridine, phenanthroline, ammine, amine, nitrile, and nitride.

10. The method of claim 1, wherein the passivating agent is 1-decyl-2-methylimidazole.

11. The method of claim 1, wherein the passivating agent comprises an ammonium or alkylammonium alkylcarboxylate moiety.

12. The method of claim 1, wherein the oxygen donor is selected from the group consisting of tetraoctylammonium, alkoxides, oxides, ethers, carboxylates, acetoacenoates, sulphoxide, hydroxide, acetate, lactate, propionate, oxalate, and maltolate.

13. The method of claim 1, wherein the oxygen donor is selected from the group consisting of sodium decanoate, tetraoctylammonium octylxanthate, potassium octylxanthate and tetraoctylammonium octylxanthate.

14. The method of claim 1, wherein the passivating agent is tetra-n-octylammonium decanoate.

15. The method of claim 1, wherein said nanocrystals are about 1 to about 20 nanometers in size.

16. The method of claim 1, where the nanocrystals melt at less than about 350°

C.

17. The method of claim 1, wherein the nanocrystals are soluble in a solvent.

18. The method of claim 16, wherein the solvent is selected from the group consisting of water, acetonitrile, methanol, isopropanol, hexanes, dodecane, toluene, cyclohexanone, diethyl ether, tetrahydrofuran, ethyl lactate, dichloromethane, acetone and ethanol.

19. The method of claim 1, wherein the passivating agent volatilizes between about 125°

C. to about 250°

C.

20. The method of claim 1, wherein weight loss upon heating said nanocrystals is in the range of about 15 to about 40%.

21. A method for filling a feature on a substrate with copper comprising the steps of:

(a) applying a solvent comprising copper nanocrystals dissolved therein onto said featured substrate, wherein said copper nanocrystals are made by;

(i) reducing a copper salt with a reducing agent to obtain reduced copper;

(ii) providing a passivating agent to contact said reduced copper, wherein said passivating agent comprises at least one moiety selected from the group consisting of a nitrogen donor and an oxygen donor; and

(iii) isolating said nanocrystals comprising said reduced copper; and

(b) heating said substrate to fill said feature by forming continuous bulk copper from said nanocrystals in said feature.

22. The method of claim 21, wherein said substrate comprises silicon.

23. A method of claim 21, wherein said substrate comprises SiO₂.

24. A method of claim 21, wherein said substrate is covered with a barrier layer.

25. A method of claim 21, wherein said substrate is washed with a surfactant.

26. A method of claim 21, wherein said nanocrystals are re-dissolved prior to said heating.

27. A method of claim 21, wherein the solvent further comprises a binder.

28. A method of claim 21, wherein said feature is a via.

29. A method of claim 21, wherein said feature is a trench with an aspect ratio in the range of about 1.6 to about 10000.

30. A method of claim 21, wherein said feature is in the form of an interconnect (IC).

31. A method of claim 21, wherein said nanocrystals selectively collect within recesses of said features as opposed to plateaus of said substrate.

32. The method of claim 31, wherein the solution evaporates prior to said heating.

33. The method of claim 21, wherein said feature is filled such that the nanocrystals are at or above their percolation threshold.

34. The method of claim 21, wherein the passivating agent comprises an imidazole moiety.

35. The method of claim 21, wherein the nitrogen donor is selected from the group consisting of imidazole, pyridine, bipyridine, phenanthroline, ammine, amine, nitrile, and nitride.

36. The method of claim 21, wherein the passivating agent is 1-decyl-2-methylimidazole.

37. The method of claim 21, wherein the passivating agent comprises an ammonium or alkylammonium alkylcarboxylate moiety.

38. The method of claim 21, wherein the moiety is selected from the group consisting of tetraoctylammonium, alkoxides, oxides, ethers, carboxylates, acetoacenoates, sulphoxide, hydroxide, acetate, lactate, propionate, oxalate, and maltolate.

39. The method of claim 21, wherein the oxygen donor is selected from the group consisting of sodium decanoate, tetraoctylammonium octylxanthate, potassium octylxanthate and tetraoctylammonium octylxanthate.

40. The method of claim 21, wherein the passivating agent is tetra-n-octylammonium decanoate.

41. The method of claim 21, wherein said nanocrystals are about 1 to about 20 nanometers in size.

42. The method of claim 21, where the nanocrystals melt at less than about 350°

C.

43. The method of claim 21, wherein the nanocrystals are soluble in a solvent.

44. The method of claim 43, wherein the solvent is selected from the group consisting of water, acetonitrile, methanol, isopropanol, hexanes, dodecane, toluene, cyclohexanone, diethyl ether, tetrahydrofuran, ethyl lactate, dichloromethane, acetone and ethanol.

45. The method of claim 21, wherein the passivating agent volatilizes between about 125°

C. to about 250°

C.

46. The method of claim 21, wherein weight loss upon heating said nanocrystals is in the range of about 15 to about 40%.