Silicon electrode assembly surface decontamination by acidic solution

• US 20060141802A1
• Filed: 12/23/2004
• Published: 06/29/2006
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Shih, Hong, Zhou, Chunhong, Huang, Tuochuan
• Granted Patent: US 7,507,670 B2
• Time in Patent Office: Days
• US Class Current: 438/753
• CPC Class Codes: C11D 2111/22 Electronic devices, e.g. PCBs or semiconductors
• CPC Class Codes: C11D 7/08 Acids
• CPC Class Codes: Y10T 137/0329 Mixing of plural fluids of diverse characteristics or conditions

Abstract

Methods for cleaning silicon surfaces of electrode assemblies by efficiently removing contaminants from the silicon surfaces without discoloring the silicon surfaces using an acidic solution comprising hydrofluoric acid, nitric acid, acetic acid, and balance deionized water.

Claims

1. A method of cleaning a used electrode assembly comprising a plasma-exposed silicon surface, the method comprising contacting the silicon surface with an acidic cleaning solution comprising:

hydrofluoric acid;

nitric acid;

acetic acid; and

balance deionized water; and

wherein contaminants are removed from the silicon surface; and

further wherein the silicon surface is not discolored.

2. The method of claim 1, wherein the acidic solution etches the silicon surface.

3. The method of claim 2, wherein the hydrofluoric acid is present in an amount such that the silicon surface is etched in a diffusion-controlled process.

4. The method of claim 1, wherein the hydrofluoric acid and nitric acid are present in an amount effective to remove contaminants from the silicon surface.

5. The method of claim 1, wherein the nitric acid removes contaminants selected from the group consisting of Al, Ca, Cr, Cu, Fe, K, Li, Mg, Mo, Na, Ni, Ti, Zn, and combinations thereof from the silicon surface.

6. The method of claim 1, wherein the nitric acid is present in an amount effective to oxidize contaminants selected from the group consisting of Al, Ca, Cr, Cu, Fe, K, Li, Mg, Mo, Na, Ni, Ti, Zn, and combinations thereof.

7. The method of claim 1, wherein the nitric acid is present in an amount effective to form ions with contaminants selected from the group consisting of Al, Ca, Cr, Cu, Fe, K, Li, Mg, Mo, Na, Ni, Ti, Zn, and combinations thereof.

8. The method of claim 1, wherein the nitric acid is present in an amount that does not cause silicon surface discoloration.

9. The method of claim 1, wherein the nitric acid oxidizes silicon to form oxidized silicon.

10. The method of claim 9, wherein the hydrofluoric acid dissolves the oxidized silicon.

11. The method of claim 1, wherein the acetic acid is present in an amount effective to control oxidation by the nitric acid.

12. The method of claim 1, wherein the acetic acid is present in an amount effective to avoid silicon surface discoloration.

13. The method of claim 1, wherein the acetic acid forms complex ions with contaminants.

14. The method of claim 1, wherein the contacting comprises wiping the silicon surface with the acidic solution.

15. The method of claim 1, wherein the electrode assembly is a showerhead electrode having gas outlets.

16. The method of claim 1, wherein the silicon surface is elastomer bonded to a graphite backing member.

17. The method of claim 16, wherein the graphite backing member contains mounting holes.

18. The method of claim 1, wherein electrode assembly comprises an inner electrode surrounded by an outer electrode member.

19. The method of claim 18, wherein the outer electrode member is comprised of silicon segments arranged in an annular configuration.

20. The method of claim 1, wherein the silicon surface is single crystalline silicon.

21. The cleaning solution according to claim 1.

22. The cleaning solution of claim 21, wherein the hydrofluoric acid is present in an amount of 0.25 to 1% by volume.

23. The cleaning solution of claim 21, wherein the nitric acid is present in an amount of 10 to 40% by volume.

24. The cleaning solution of claim 21, wherein the acetic acid is present in an amount of 10 to 20% by volume.

25. An electrode assembly cleaned according to the method of claim 1.

26. A method of etching a dielectric material in a plasma etching chamber using the cleaned electrode assembly of claim 1.