Electrochemical method and system for monitoring hydrogen peroxide concentration in slurries

• US 20040069625A1
• Filed: 09/27/2002
• Published: 04/15/2004
• Est. Priority Date: 09/27/2002
• Status: Active Grant

• Current Assignee: Bell Semiconductor, LLC (Hilco Inc. (d/b/a Hilco Global))
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Tamboli, Dnyanesh Chandrakant, Desai, Vimalkur Haribhai
• Granted Patent: US 6,972,083 B2
• Time in Patent Office: Days
• US Class Current: 204/400
• CPC Class Codes: G01N 27/4045 for gases other than oxygen

Abstract

Electrochemical monitoring system and method are provided for online determination of hydrogen peroxide concentration in slurries, e.g., a chemical mechanical polishing slurry. The monitoring system includes an electrochemical cell fluidly coupled to receive a slurry including hydrogen peroxide. The cell includes at least a working electrode made up of tungsten, a reference electrode and a counter electrode. The system further includes a potentiostat electrically coupled to the working electrode to supply a desired potentials in increments to the working electrode and measure current flow between the working electrode and the counter electrode. The amount of passive current established between the working electrode and the counter electrode over a selected time window is indicative of the concentration of hydrogen peroxide in the slurry.

Claims

1. An electrochemical monitoring system comprising:

an electrochemical cell fluidly coupled to receive a slurry including hydrogen peroxide, the cell including at least a working electrode comprising tungsten, and a counter electrode; and

a potentiostat electrically coupled to the working electrode to supply a desired potential to that electrode and measure current flow between the working electrode and the counter electrode, with the amount of passive current therebetween over a selected time window being indicative of the concentration of H₂O₂ in said slurry.

2. The monitoring system of claim 1 further comprising a processor coupled to the potentiostat to process the passive current measurements, the processor including a memory configured to store a predefined relationship between current and hydrogen peroxide concentration.

3. The monitoring system of claim 1 wherein the processor further comprises a comparator for relating the passive current measurements supplied to the processor relative to the predefined relationship stored in memory and determine the concentration of hydrogen peroxide in the slurry.

4. The monitoring system of claim 3 wherein the predefined relationship stored in memory comprises a set of values arranged as a look-up table.

5. The monitoring system of claim 3 wherein the predefined relationship stored in memory comprises a functional relationship between current and the hydrogen peroxide concentration.

6. The monitoring system of claim 1 wherein the working electrode is configured as a relatively thin roll of tungsten.

7. The monitoring system of claim 1 further comprising a holder configured to rotate the working electrode to expose fresh surface for subsequent measurements.

8. The monitoring system of claim 1 fluidly coupled to receive slurry from a chemical mechanical polishing tool.

9. The monitoring system of claim 1 and including a reference electrode immersed in the slurry for providing a measurement of potential applied to the working electrode.

10. An electrochemically-based monitoring method comprising:

fluidly coupling an electrochemical cell to receive a chemical mechanical polishing slurry including hydrogen peroxide, the cell including at least a working electrode comprising tungsten, and a counter electrode;

applying a desired potential to the working electrode;

measuring current flow between the working electrode and the counter electrode, with the amount of passive current therebetween over a selected time window being indicative of the concentration of hydrogen peroxide in said slurry.

11. The monitoring method of claim 10 further comprising storing in memory a predefined relationship between passive current measurements and hydrogen peroxide concentration.

12. The monitoring method of claim 11 further comprising relating the passive current measurements between the working electrode and the counter electrode relative to the predefined relationship stored in memory to determine the concentration of hydrogen peroxide in the slurry.

13. The monitoring method of claim 10 further comprising configuring the working electrode as a relatively thin roll of tungsten.

14. The monitoring method of claim 13 further comprising rotating the working electrode to ensure generally uniform exposure of the working electrode relative to the slurry.

15. The monitoring system of claim 10 and including a reference electrode immersed in the slurry for providing a measurement of potential applied to the working electrode.