Cleaning electroplating substrate holders using reverse current deplating

Patent metadata

Field	Value
Publication number	US-9476139-B2
Application number	US-201313853935-A
Country	US
Kind code	B2
Filing date	Mar 29, 2013
Priority date	Mar 30, 2012
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

Provided are cleaning methods and systems to remove unintended metallic deposits from electroplating apparatuses using reverse current deplating techniques. Such cleaning involves positioning a cleaning (deplating) disk in an electroplating cup similar to a regular processed substrate. The front surface of the cleaning disk includes a corrosion resistant conductive material to form electrical connections to deposits on the cup's surfaces. The disk is sealed in the cup and submerged into a plating solution. A reverse current is then applied to the front conductive surface of the disk to initiate deplating of the deposits. Sealing compression in the cup may change during cleaning to cause different deformation of the lip seal and to form new electrical connections to the deposits. The proposed cleaning may be applied to remove deposits formed during electroplating of alloys, in particular, tin-silver alloys widely used for semiconductor and wafer level packaging.

First claim

What is claimed is:

1. A method of mitigating an electroplating deposit on a substrate holder that is configured to hold a wafer substrate in an electroplating cell while applying a cathodic current to electroplate metal on the substrate, the method comprising:
when the electroplating cell is not being used for electroplating metal on a substrate, providing a deplating disk in the substrate holder such that the deplating disk makes electrical contact with a plurality of electrical contacts in the substrate holder;
immersing the deplating disk and substrate holder into an electroplating solution within the electroplating cell; and
applying an anodic potential to the deplating disk under conditions sufficient to remove, at least partially, the electroplating deposit from the substrate holder,
wherein the deplating disk has a size and a shape matching those of a standard semiconductor wafer.

2. The method of claim 1 , wherein the deplating disk comprises a metal around its perimeter in a region for making said electrical contact with said plurality of electrical contacts in the substrate holder.

3. The method of claim 2 , wherein the metal is a noble metal.

4. The method of claim 2 , wherein the deplating disk comprises an insulator in a central region of the deplating disk.

5. The method of claim 1 , wherein the electroplating deposit on a substrate holder comprises silver and tin.

6. The method of claim 1 , wherein the substrate holder comprises a lip seal.

7. The method of claim 6 , further comprising compressing the deplating disk on the lip seal to cause the deplating disk to come into electrical contact with the electroplating deposit.

8. The method of claim 7 , further comprising:
after applying the anodic potential to the deplating disk, varying compression on the deplating disk to cause the lip seal to flex to a new position and thereby cause the deplating disk to come into electrical contact with the electroplating deposit.

9. The method of claim 1 , further comprising moving the deplating disk to a storage area for the deplating disk.

10. A method of cleaning a semiconductor plating apparatus, comprising:
providing a deplating disk in a wafer holder assembly, wherein the deplating disk comprises corrosion-resistant conductive material around at least the periphery of the deplating disk,
said wafer holder assembly comprising a peripheral lip seal and a plurality of electrical contacts, wherein the wafer holder assembly is positioned in an electroplating cell, and wherein the wafer holder assembly has metal deposited thereon, and
sealing the deplating disk in the wafer holder assembly by applying a force to the deplating disk to thereby deform the lip seal and provide a liquid-tight seal, and thereby establish electrical communication between the plurality of electrical contacts and the metal deposited on the wafer holder assembly,
submerging the deplating disk in cleaning solution in the electroplating cell, and
applying anodic current to the deplating disk to thereby remove metal deposited on the wafer holder assembly.

11. The method of claim 10 , further comprising changing the force applied to the deplating disk as current is applied to further deform the lip seal and thereby provide new electrical connections between the deplating disk and metal deposited on the wafer holder assembly.

12. The method of claim 10 , wherein the force applied to the deplating disk is the same as a force applied to a plating wafer when a plating wafer is sealed in the wafer holder assembly.

13. The method of claim 10 , wherein the force applied to the deplating disk is different from a force applied to a plating wafer when a plating wafer is sealed in the wafer holder assembly.

14. The method of claim 10 , wherein the deplating disk comprises an insulated center portion.

15. The method of claim 10 , wherein the metal deposited on the wafer holder assembly comprises an alloy.

16. The method of claim 15 , wherein the alloy comprises tin and silver.

17. The method of claim 15 , wherein applying anodic current to the deplating disk comprises:
applying current at a first voltage potential, and
applying current at a second voltage potential, wherein the first potential corresponds to a potential that is slightly beyond the voltage potential of a metal in the alloy.

18. The method of claim 10 , wherein the cleaning solution is the same as a solution used for electroplating a plating wafer.

19. The method of claim 18 , wherein anodic current is applied to the deplating disk in a potentiostatic mode.

20. The method of claim 19 , wherein anodic current is applied to the deplating disk until a target current density is reached.

21. The method of claim 10 , wherein when applying anodic current to the deplating disk, the current density is controlled to avoid oxygen generation.

22. The method of claim 10 , wherein anodic current is applied to the deplating disk in a galvanostatic mode.

23. The method of claim 22 , wherein a current density is between about 0.05-2 Amps per square decimeter.

24. The method of claim 10 , wherein anodic current is applied to the deplating disk in pulses.

25. The method of claim 10 , further comprising rotating the deplating disk at about 30 RPM or greater during at least the applying current operation.

26. The method of claim 10 , wherein the deplating disk is rotated in a first direction and then in a second direction.

27. The method of claim 10 , further comprising:
removing the deplating disk from the cleaning solution;
spinning the deplating disk between about 100-600 RPM to reclaim the cleaning solution from the deplating disk;
rinsing the deplating disk with deionized water; and
spinning the deplating disk to remove the deionized water.

28. The method of claim 10 , further comprising repeating the method periodically.

29. The method of claim 28 , wherein the method is repeated after a time interval.

Assignees

• Novellus Systems Inc

Inventors

• Chua Lee Peng
• Mayer Steven T
• Ponnuswamy Thomas A
• Kumar Santosh

Classifications

• H10P72/7602

  the wafers being placed on a robot blade or gripped by a gripper for conveyance · CPC title

• H10P72/3404

  Storage means · CPC title

• H10P72/3402

  Mechanical parts of transfer devices · CPC title

• C25D21/12

  Process control or regulation (controlling or regulating in general G05) · CPC title

• C25D17/001 Primary

  Apparatus specially adapted for electrolytic coating of wafers, e.g. semiconductors or solar cells · CPC title