Method for analyzing additive concentration

• US 4,917,774 A
• Filed: 04/24/1986
• Issued: 04/17/1990
• Est. Priority Date: 04/24/1986
• Status: Expired due to Term

• Current Assignee: Shipley Company, Inc.
• Original Assignee: Shipley Company, Inc.
• Inventors: Fisher, Gordon
• Primary Examiner(s): TUNG, TA HSUNG
• Application Number:
  US06/855,360
• Time in Patent Office: 1,454 Days
• Field of Search: 204/1 T, 204/434, 204/402
• US Class Current: 205/787
• CPC Class Codes: G01N 27/423 Coulometry
• CPC Class Codes: H05K 3/241 characterised by the electroplating method; means therefor, e.g. baths or apparatus
• CPC Class Codes: H05K 3/423 characterised by electroplating method

Abstract

A method for determining the effective quantity of an organic additive in an electroplating bath involving passing an inert electrode through a predetermined sequence of voltammetric steps including a step of plating the electrode at a given applied potential, stripping the plated metal at a given applied potential, and conditioning the inert electrode without applied potential; correlating the quantity of additive with the coulombs utilized during the metal stripping step; and using the same predetermined sequence of voltammetric steps for a bath having an unknown quantity of additive.

Claims

1. A method for determining the effective quantity of organic additive in an electroplating bath comprising the steps of:

a. obtaining a plurality of plating baths, each having a known and different quantity of organic additive;

b. for each bath, repeatedly cycling an inert electrode through a predetermined sequence of voltammetric steps where for each cycle, a first step is within a metal plating range, a next step is within a metal stripping range, a next step of cleaning the inert electrode and a final step is without applied potential whereby the electrode is prepared for the next subsequent cycle initiated upon completion of the prior cycle;

c. correlating the effective quantity of additive with the coulombs utilized during the metal stripping step;

d. obtaining a plating bath having an unknown quantity of organic additive, repeatedly cycling a working electrode through said bath using the aforesaid predetermined sequence of voltammetric steps until a steady state condition is obtained for said bath;

e. measuring the coulombs utilized during the metal stripping step of said cycle for said bath having an unknown quantity of organic additive; and

f. choosing from said correlation a quantity of organic additive which corresponds to said coulombs utilized for said bath with said unknown quantity of organic additive.

2. The method of claim 1 where the voltammetric step without an applied potential is for a period of at least five seconds.

3. The method of claim 2 where the working electrode is continuously swept through said sequence of voltammetric steps.

4. The method of claim 2 where the working electrode is cycled through said series of voltammetric steps at a constant potential for each of said steps.

5. The method of claim 2 where the sequence of voltammetric steps includes the step of equilibrating the inert electrode.

6. The method of claim 2 where the voltammetric step without an applied potential for a period of from 20 to 30 seconds.

7. The method of claim 2 where the electroplating bath comprises a bath for electroplating copper.

8. The method of claim 1 where the predetermined sequence of voltammetric steps includes the step of equilibrating the inert electrode, each step being at a constant applied potential.

9. A method for determining the effective quantity of organic leveling agent in a copper electroplating bath comprising the steps of:

a. obtaining a plurality of plating baths, each having a known and different quantity of organic leveling agent;

b. for each bath, repeatedly cycling an inert electrode through a predetermined sequence of voltammetric steps at constant potential for each step where for each cycle a first voltammetric step is within a metal plating range, a next step is within a metal stripping range, a next step is cleaning the inert electrode, and a final step is without applied potential whereby the electrode is prepared for the next subsequent cycle initiated upon completion of the prior cycle;

c. correlating the effective quantity of organic leveling agent with the coulombs utilized during the metal stripping step;

d. obtaining a bath having an unknown quantity of organic leveling agent, repeatedly cycling a working electrode through said bath using the aforesaid predetermined sequence of voltammetric steps until a steady-state condition is obtained for said bath;

e. measuring the coulombs utilized during said metal stripping step of said cycle for said bath having a unknown quantity of leveling agent; and

f. choosing from said correlation a quantity of organic leveling agent which corresponds to said coulombs utilized for said bath having an unknown quantity of organic leveling agent.

10. The method of claim 9 where the voltammetric step without an applied potential is for a period of at least five seconds.

11. The method of claim 10 where the sequence of voltammetric steps includes the step of equilibrating the inert electrode.

12. The method of claim 10 where the voltammetric step without an applied potential is for a period of from 20 to 30 seconds.