Copper electroplating solutions and processes

• US 5,252,196 A
• Filed: 12/05/1991
• Issued: 10/12/1993
• Est. Priority Date: 12/05/1991
• Status: Expired due to Term

• Current Assignee: Shipley Company, Inc.
• Original Assignee: Shipley Company, Inc.
• Inventors: Bernards, Roger F., Sonnenberg, Wade, Fisher, Gordon, Houle, Patrick
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): BOLAM, BRIAN
• Application Number:
  US07/803,281
• Time in Patent Office: 677 Days
• Field of Search: 205/125, 205/296, 205/297, 205/298, 205/920, 205/126, 106/1.26
• US Class Current: 205/296
• CPC Class Codes: C25D 3/38 of copper

Abstract

Compositions and processes for electrolytic plating. The compositions are characterized by critical amounts of one or more brightening and leveling agents. The compositions are particularly useful for plating through hole walls of printed circuit boards, including through holes having an aspect ratio equal or greater than about ten to one.

Claims

1. An aqueous electroplating solution, comprising:

at least one soluble copper salt, an electrolyte, and one or more brightening agents of the formula HS--R--SO₃ wherein R is substituted or unsubstituted aryl or substituted or unsubstituted alkyl, and wherein the concentration of said brightening agents of formula HS--R--SO₃ is from about 1 ppb to 250 ppb based on total weight of the electroplating solution.

2. The electroplating solution of claim 1 where the concentration of the brightening agent of the formula HS--R--SO₃ in the electroplating solution is from about 1 ppb to 100 ppb based on total weight of the electroplating solution.

3. The electroplating solution of claim 1 wherein R is selected from the group consisting of substituted or unsubstituted phenyl and substituted or unsubstituted alkyl having from 1 to 6 carbon atoms.

4. The electroplating solution of claim 1 where the one or more brightening agents comprise a brightening agent of the formula O₃ S--R--S--S--R¹ --SO₃ wherein R and R¹ are each independently selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl.

5. The electroplating solution of claim 4 where the concentration of the brightening agent of the formula O₃ S--R--S--S--R¹ --SO₃ in the electroplating solution is from about 10 ppb to 200 ppb based on total weight of the electroplating solution.

6. The electroplating solution of claim 4 wherein R and R¹ are each independently selected from the group consisting of substituted or unsubstituted phenyl and substituted or unsubstituted alkyl having from 1 to 6 carbon atoms.

7. The electroplating solution of claim 1 where the one or more brightening agents are selected from the group consisting of mercapto-propylsulfonic acid, mercapto-ethanesulfonic acid and bissulfopropyl disulfide.

8. The electroplating solution of claim 1 where the one or more brightening agents is a mixture of brightening agents,

said mixture consisting essentially of one or more brightening agents of the formula HS--R--SO₃ wherein R is selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl,

and one or more brightening agents of the formula O₃ S--R--S--S--R¹ --SO₃ wherein R and R¹ are each independently selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl,

the concentration of said mixture in the electroplating solution being from about 1 ppb to 500 ppb based on total weight of the electroplating solution.

9. The electroplating solution of claim 1 further comprising one or more wetting agents.

10. The electroplating solution of claim 1 where the electrolyte is an acid used in combination with halide ions.

11. The electroplating solution of claim 1 where the electrolyte comprises a base.

12. The electroplating solution of claim 1 further comprising a leveling agent.

13. The electroplating solution of claim 12 where the leveling agent contains a group of the formula N--R--S, where R is selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl.

14. The electroplating solution of claim 12 where the leveling agent is present in the electroplating solution in a concentration, based on total weight of the electroplating solution, in a range equal to 1 ppm or less divided by the Leveler Potency Constant of the leveling agent.

16. The electroplating solution of claim 12 where the leveling agent-brightener w/w ratio is less than about 20:

1 divided by the Leveler Potency Constant of the leveling agent.

17. The electroplating solution of claim 12 where the leveling agent-brightener w/w ratio is less than about 5:

1 divided by the Leveler Potency Constant of the leveling agent.

18. The electroplating solution of claim 12 where the leveling agent is 1-(2-hydroxyethyl)-2-imidazolidinethione.

19. The electroplating solution of claim 18 where the leveling agent is present in the electroplating solution in a concentration of less than about 1 ppm based on total weight of the electroplating solution.

20. The electroplating solution of claim 18 where the leveling agent is present in the electroplating solution in a concentration of less than about 500 ppb based on total weight of the electroplating solution.

21. The electroplating solution of claim 18 where the leveling agent is present in the electroplating solution in a concentration of less than about 200 ppb based on total weight of the electroplating solution.

22. The electroplating solution of claim 18 where the leveling agent-brightener w/w ratio is less than about 20:

1.

23. The electroplating solution of claim 18 where the leveling agent-brightener w/w ratio is less than about 5:

1.

15. The electroplating solution of 12 further comprising one or more wetting agents.

24. A process for electrodepositing copper on a substrate, comprising:

electrolytically depositing copper on the substrate from an aqueous electroplating solution, the solution comprising at least one soluble copper salt, an electrolyte, and one or more brightening agents of the formula HS--R--SO₃ wherein R is substituted or unsubstituted aryl or substituted or unsubstituted alkyl, and wherein the concentration of said brightening agents of formula HS--R--SO₃ is from about 1 ppb to 250 ppb based on total weight of the electroplating solution.

25. The process of claim 24 where the substrate has irregular topography.

26. The process of claim 24 where the concentration of the brightening agent of the formula HS--R--SO₃ in the electroplating solution is from about 1 ppb to 100 ppb based on total weight of the electroplating solution.

27. The process of claim 24 where the substrate is a printed circuit board having through holes.

28. The process of claim 27 where the through holes have an aspect ratio equal to or greater than about ten to one.

29. The process of claim 27 where the one or more brightening agents is a mixture of brightening agents,

said mixture consisting essentially of (1) one or more brightening agents of the formula HS--R--SO₃ wherein R is selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl, and

(2) one or more brightening agents of the formula O₃ S--R--S--S--R¹ --SO₃ wherein R and R¹ are each independently selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl,

the concentration of said mixture in the electroplating solution being from about 1 ppb to 500 ppb.

30. The process of claim 27 where the one or more brightening agents comprise a brightening agent of the formula O₃ S--R--S--S--R¹ --SO₃ wherein R and R¹ are each independently selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl.

31. The process of claim 30 where the concentration of the brightening agent of the formula O₃ S--R--S--S--R¹ --SO₃ in the electroplating solution is from about 1 ppb to 500 ppb based on total weight of the electroplating solution.

32. The process of claim 30 where the concentration of the brightening agent of the formula O₃ S--R--S--S--R¹ --SO₃ in the electroplating solution is from about 10 ppb to 200 ppb based on total weight of the electroplating solution.

33. The process of claim 27 further comprising a leveling agent.

34. The process of claim 33 where the leveling agent-brightener w/w ratio is less than about 20:

1 divided by the Leveler Potency Constant of the leveling agent.

35. The process of claim 33 where the leveling agent-brightener w/w ratio is less than about 5:

1 divided by the Leveler Potency Constant of the leveling agent.

36. The process of claim 33 where copper is deposited at a current density of about 30 ASF or greater and the leveling agent-brightener w/w ratio is less than about 0.5:

1.

37. The process of claim 33 where the leveling agent is present in the electroplating solution in a concentration, based on total weight of the electroplating solution, in a range equal to 1 ppm or less divided by the Leveler Potency Constant of the leveling agent.

38. The process of claim 36 where the leveling agent is present in the electroplating solution in a concentration of less than about 1 ppm, and the leveling agent-brightener w/w ratio is equal to a value of less than about 20 divided by the Leveler Potency Constant of the leveling agent.

39. The process of claim 33 where the electroplating solution further comprises one or more wetting agents.

40. The process of claim 33 where the leveling agent is 1-(2-hydroxyethyl)-2-imidazolidinethione and is present in the electroplating solution in a concentration of less than about 1 ppm based on total weight of the solution.

41. The process of claim 40 where the leveling agent is present in the electroplating solution in a concentration of less than about 500 ppb based on total weight of the solution.

42. The process of claim 40 where the leveling agent is present in the electroplating solution in a concentration of less than about 200 ppb based on total weight of the solution.

43. The process of claim 40 where the leveling agent-brightener w/w ratio is less than about 20:

1.

44. The process of claim 40 where the leveling agent-brightener w/w ratio is less than about 5:

1.

45. The process of claim 40 where copper is deposited at a current density of about 30 ASF or greater and the leveling agent-brightener w/w ratio is less than about 0.5:

1.

46. An aqueous electroplating solution, comprising:

at least one soluble copper salt, an electrolyte, and one or more brightening agents, at least of one of said one or more brightening agents having the structural formula HS--R--SO₃ wherein R is selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted alkyl, and

wherein the concentration of said brightening agent of the structural formula HS--R--SO₃ in the electroplating solution is from about 1 ppb to 250 ppb.