Electroplating apparatus and process for wafer level packaging

Patent metadata

Field	Value
Publication number	US-2018237933-A1
Application number	US-201815958525-A
Country	US
Kind code	A1
Filing date	Apr 20, 2018
Priority date	Dec 1, 2010
Publication date	Aug 23, 2018
Grant date	—

Abstract

An apparatus for continuous simultaneous electroplating of two metals having substantially different standard electrodeposition potentials (e.g., for deposition of Sn—Ag alloys) comprises an anode chamber for containing an anolyte comprising ions of a first, less noble metal, (e.g., tin), but not of a second, more noble, metal (e.g., silver) and an active anode; a cathode chamber for containing catholyte including ions of a first metal (e.g., tin), ions of a second, more noble, metal (e.g., silver), and the substrate; a separation structure positioned between the anode chamber and the cathode chamber, where the separation structure substantially prevents transfer of more noble metal from catholyte to the anolyte; and fluidic features and an associated controller coupled to the apparatus and configured to perform continuous electroplating, while maintaining substantially constant concentrations of plating bath components for extended periods of use.

First claim

1 . An apparatus for simultaneous electroplating of a first metal and of a second, more noble metal onto a substrate, comprising:
(a) an anode chamber for containing anolyte and an active anode, said active anode comprising the first metal; (b) a cathode chamber for containing catholyte and the substrate; (c) a separation structure positioned between the anode chamber and the cathode chamber; and (d) fluidic features and an associated controller coupled to the apparatus and configured to perform at least the following operations:
deliver an acid solution to the anode chamber from a source outside the anode chamber;
deliver a solution comprising ions of the first metal to the anode chamber from a source outside the anode chamber;
remove a portion of the catholyte from the cathode chamber;
deliver ions of a second metal to the cathode chamber; and
deliver anolyte from the anode chamber to the cathode chamber via a conduit other than the separation structure,
wherein the apparatus is configured to conduct plating in a manner allowing ions of a first metal present in the anolyte to flow from the anode chamber to the cathode chamber, but substantially preventing ions of a second metal to flow from the cathode chamber to the anode chamber during electroplating, and wherein the apparatus is configured to maintain the concentration of protons in the catholyte such that it does not fluctuate by more than about 10% over the period of at least about 0.2 plating bath turnovers.

2 . The apparatus of claim 1 , wherein the first metal is tin and the second metal is silver.

3 . The apparatus of claim 1 , wherein the separation structure comprises a cationic membrane, configured for allowing transport of protons, water, and ions of the first metal from anolyte to catholyte during plating.

4 . The apparatus of claim 1 , wherein the active anode comprises low alpha tin.

5 . The apparatus of claim 1 , further comprising a pressure regulator in fluid communication with the anode chamber.

6 . The apparatus of claim 5 , wherein the pressure regulator comprises a vertical column arranged to serve as a conduit through which the electrolyte flows upward before spilling over a top of the vertical column, and wherein, in operation, the vertical column provides a pressure head which maintains a substantially constant pressure in the anode chamber.

7 . The apparatus of claim 5 , wherein the pressure regulator is incorporated into an anolyte circulation loop which circulates anolyte out of the anode chamber, through the pressure regulator, and back into the anode chamber.

8 . The apparatus of claim 7 , wherein the anolyte circulation loop further comprises an inlet for introducing additional fluid comprising a component selected from the group consisting of water, acid, and ions of the first metal, into the anolyte circulation loop.

9 . The apparatus of claim 1 , further comprising a source comprising a component selected from the group consisting of water, acid, and ions of the first metal fluidically coupled with the anode chamber.

10 . The apparatus of claim 2 , further comprising a source of silver ions fluidically coupled to the cathode chamber.

11 . The apparatus of claim 2 , further comprising a silver anode fluidically coupled to the cathode chamber, wherein the silver anode is configured to be electrochemically dissolved into the catholyte and thereby provide silver ions to the catholyte, but not to the anolyte.

12 . The apparatus of claim 1 , wherein the apparatus is configured to conduct electroplating in a manner allowing ions of the first metal present in the anolyte to flow from the anode chamber to the cathode chamber via a fluidic conduit other than the separation structure residing between the anode and the cathode chambers, wherein the apparatus comprises a pump associated with said fluidic conduit which enables transfer of anolyte to the catholyte either directly or via a reservoir.

13 . The apparatus of claim 12 , wherein the apparatus is configured to conduct plating in a manner allowing ions of the first metal present in the anolyte to flow from the anode chamber to the cathode chamber via a fluidic conduit other than the separation structure residing between the anode and the cathode chambers, and also through the separation structure.

14 . The apparatus of claim 2 , further comprising a structure configured for:
(i) receiving the removed portion of catholyte; (ii) separating tin from silver in the removed portion of catholyte; and (iii) forming a first solution comprising tin ions and/or a second solution comprising silver ions, wherein at least one of said solutions is suitable for reuse.

15 . The apparatus of claim 14 , wherein the apparatus comprises an electrowinning station configured for electrowinning silver from the removed portion of catholyte under controlled potential, wherein the apparatus is further configured for delivering a tin-containing silver-free solution obtained after electrowinning to the anode chamber.

16 . A system comprising the apparatus of claim 1 and a stepper.

17 . An apparatus for simultaneous electroplating of a first metal and of a second, more noble metal on a cathodic substrate, comprising:
(a) a cathode and anode chambers having a separation structure therebetween; and (b) a controller comprising program instructions for conducting a process comprising the steps of:
(i) providing an anolyte containing ions of the first metal but not the second metal in the anode chamber comprising an active anode comprising the first metal;
(ii) providing a catholyte containing ions of both the first metal and the second metal in the cathode chamber; and
(iii) simultaneously plating the first and the second metal onto the substrate,
while substantially preventing ions of the second metal from entering the anode chamber, while delivering an acid solution to the anode chamber from a source outside the anode chamber, while delivering a solution comprising ions of the first metal to the anode chamber from a source outside the anode chamber, while removing a portion of the catholyte, while delivering ions of the second metal to the cathode chamber, while delivering anolyte from the anode chamber to the cathode chamber via a conduit other than the separation structure, wherein the apparatus is configured to maintain the concentration of protons in the catholyte such that it does not fluctuate by more than about 10% over the period of at least about 0.2 plating bath turnovers.

Assignees

• Novellus Systems Inc

Inventors

• Mayer Steven T
• Porter David W

Classifications

• C25D17/002

  Cell separation, e.g. membranes, diaphragms · CPC title

• C25C7/00

  Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells (for the production of aluminium C25C3/06 - C25C3/22) · CPC title

• C25D17/001

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

• C25D3/56

  of alloys · CPC title

• C25D5/022

  using masking means · CPC title