WO2008016541B1

WO2008016541B1 - Constituent maintenance of a copper sulfate bath through chemical dissolution of copper metal

Info

Publication number: WO2008016541B1
Application number: PCT/US2007/016844
Authority: WO
Inventors: Wayne Charles Walker
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-07-31
Filing date: 2007-07-27
Publication date: 2008-05-15
Anticipated expiration: 2009-01-31
Also published as: WO2008016541A1

Abstract

A copper electroplating bath is provided with a constant source of copper ions by monitoring the copper concentration in the bath. Copper metal is dissolved with sulfuric acid in the separate system which comprises one or more reactors that are electrically isolated from the bath. The reactors are pressurized with oxygen gas. Plating bath that is depleted of copper is transferred to a mixing tank where it is mixed with copper solution from the reactor(s). The replenished plating solution is filtered and is returned to the plating bath. The dissolution rate of the copper is determined by the rate of oxygen addition to the reactors which in turn is controlled by the pressure of the oxygen in the reactors and the use of a controller such as an ampere-time indicator which monitors the amount of electrical current applied to the plating tank during operation.

Claims

AMENDED CLAIMS received by the International Bureau on 12 February 2008 (12.02.2008)

1. An apparatus for electroplating copper on a receptive substrate from an acid copper plating bath, the apparatus comprising a plating tank containing

a. a cathode electrical connection that connects to the substrate and applies a potential allowing the substrate to become a cathode; and

b. an insoluble anode;

the apparatus further characterized by

c. at least one vertical pressurized vessel for the chemical dissolution of high purity metallic copper, said vessel being electrically isolated from the plating bath, and having a top inlet opening for depleted plating solution;

d. a monitoring device for controlling the amount of oxidizing agent added to the at least one pressurized vessel, based upon the concentration of copper ions in said plating bath, and

e. an open mixing/vent tank in which copper depleted solution from the plating tank is replenished with copper solution containing a higher concentration of dissolved copper generated by the chemical oxidation of metallic copper in said at least one pressurized vessel.

3. The apparatus according to claim 1 including a filter to remove particulates from the replenished solution before being returned from the mixing tank to the plating tank.

4. The apparatus according to claim 1 wherein the at least one pressurized vessel comprises a reactor system consisting of between 1 and 4 vertical dissolution

25 reactors connected in series and maintained at a pressure of between about 40 psi (2.7 kg/cm² ) and about 80 psi (5.4 kg/cm² ).

5. The apparatus according to claim 4 wherein each dissolution reactor comprises a tower having a diameter between about 2 D (5.1 cm.) and 12 inches (30.48 cm) and a length of between about 2 feet (61 cm.) and about 12 feet (365 ,8 cm).

6. The apparatus according to claim 1 wherein the monitoring device is an ampere-time indicator which controls the addition of oxidizing agent to an inlet of said at least one pressurized vessel based on the monitored usage of copper ions in the plating bath.

7. The apparatus according to claim 6 wherein the oxidizing agent is oxygen, and the ampere-time indicator directs oxygen at a pressure that is 5 psi to 10 psi higher than the pressure of the pressurized vessel to be added to the depleted copper solution before contact with the copper in the first of the dissolution reactors.

8. The apparatus according to claim 7, wherein oxygen containing acid solution is maintained at a temperature of between about 25° and about 80° Celsius before addition to the pressurized reactor system.

9. The apparatus according to claim 8, wherein the reactor system serves to replenish the copper solution by the dissolving action of sulfuric acid and a controlling amount of oxygen on copper metal before this solution is returned to the mixing/venting tank.

10. A process for electroplating copper metal on to a receptive substrate from an acid copper plating bath, comprising the steps of:

a) maintaining the plating bath comprising an electrolyte and a source of copper ions in solution or suspension; and

b) passing a rectified DC current through the plating bath; the process further characterized by c) generating copper sulfate from high purity metallic copper as the source of the copper ions for the bath in a pressurized system that is electrically isolated from the plating bath, said pressurized system consisting of at least one vertical dissolution reactor that is maintained at least about 50% full of copper metal and

d) controlling the demand for the addition of the generated copper sulfate based upon the concentration of copper ions in the plating bam.

12. The process according to claim 10 wherein copper metal is oxidized to copper sulfate in the pressurized system utilizing an oxidizer in the presence of sulfuric acid.

13. The process according to claim 12 wherein the copper metal is oxidized to copper sulfate utilizing oxygen gas as the oxidizer at a temperature above ambient temperature, wherein the oxygen gas is introduced into the pressurized system at a pressure up to about 20 psi greater than the pressure in the system.

15. The process according to claim 13 wherein the concentration of copper is enriched to between about 5 and about 80 grams/liter of dissolved copper.

16. The process according to claim 13 wherein the generated copper sulfate is sent to a mixing/venting tank where entrained oxygen gas is vented to the atmosphere, and copper depleted solution flows from a plating tank into said mixing tank where it is replenished with the generated copper sulfate sent from the dissolution reactor into the mixing tank.

18. The process according to claim 16 wherein the replenished solution from the mixing/venting tank is pumped through a filter and is then transferred to the plating tank.

19. The process according to claim 18 wherein between about 1 and about 6 volumes of solution in the plating tank are circulated between the plating tank and the mixing tank each hour.

20. The process according to claim 15 wherein depleted plating solution in the mixing tank is pumped to the pressurized system that is maintained at a pressure of between about 40 psi ((2.7 kg/cm² ) and about 80 psi (5.4 kg/cm² ).

21. The process according to claim 15 wherein the amount of electrical current applied to the plating tank is monitored by an ampere-time indicator, and the consumption of copper that is plated is used to control the addition of oxidizer to the pressurized system.

22. The process according to claim 11 including maintaining the concentrations of copper and sulfuric acid in the plating solution to within about 5% of predeterm ined optimum limits.

23. The process according to claim 13 wherein the oxygen gas is introduced into the pressurized system at a pressure of between about 5 psi. and about 10 psi greater than the pressure in the system.

24. The process according to claim 16 wherein the depleted plating solution flows from the top of the plating tank into the mixing/venting tank.