Apparatus for controlling and/or measuring additive concentration in an electroplating bath

• US 6,551,479 B1
• Filed: 05/17/2000
• Issued: 04/22/2003
• Est. Priority Date: 05/01/1998
• Status: Active Grant

• Current Assignee: Semitool Incorporated (Applied Materials Incorporated)
• Original Assignee: Semitool Incorporated (Applied Materials Incorporated)
• Inventors: Taylor, Thomas C., Lindberg, Fredrick A., Carpenter, Bradley C., Ritzdorf, Thomas L., Graham, Lyndon W.
• Primary Examiner(s): Tung, T.
• Application Number:
  US09/572,603
• Time in Patent Office: 1,070 Days
• Field of Search: 204/434, 204/400, 205/775, 205/790.5, 205/791, 205/791.5
• US Class Current: 204/434
• CPC Class Codes: G01N 27/4161 measuring the voltage and using a constant current supply, e.g. chronopotentiometry
• CPC Class Codes: G01N 27/48 using polarography, i.e. measuring changes in current under a slowly-varying voltage

Abstract

A method for measuring a target constituent of an electroplating solution using an electroanalytical technique is set forth in which the electroplating solution includes one or more constituents whose by-products skew an initial electrical response to an energy input of the electroanalytical technique. The method comprises a first step in which an electroanalytical measurement cycle of the target constituent is initiated by providing an energy input to a pair of electrodes disposed in the electroplating solution. The energy input to the pair of electrodes is provided for at least a predetermined time period corresponding to a time period in which the electroanalytical measurement cycle reaches a steady-state condition. In a subsequent step, an electroanalytical measurement of the energy output of the electroanalytical technique is taken after the electroanalytical measurement cycle has reached the steady-state condition. The electroanalytical measurement is then used to determine an amount of the target constituent in the electroplating solution. An automatic dosing system that includes the foregoing method and/or one or more known electroanalytical techniques in a close-loop system is also set forth.

Claims

1. An apparatus for maintaining a concentration level of a target constituent of an electroplating bath, said electroplating bath also including one or more by-products that during a first time period skew a response to the initial plating and/or stripping energy applied in an electroanalytical technique, said apparatus comprising:

(a) a bath sample extraction unit connected to automatically remove a sample amount of said electroplating bath, said bath sample including said one or more by-products;

(b) an electroanalysis unit connected to receive said bath sample obtained by said bath sample extraction unit;

(c) a constituent dosing supply unit connected to provide an amount of said target constituent to said electroplating bath;

(d) a programmable control unit connected to communicate with;

a) said bath sample extraction unit for control of the extraction of said bath sample from said electroplating bath and supply of the bath sample to the electroanalysis unit,

b) said electroanalysis unit to execute an electroanalytical technique to determine the amount of said target constituent in said bath sample, and

c) said constituent dosing supply unit to provide an amount of said target constituent to said electroplating bath based on the amount of said target constituent measured in said bath sample through the use of said electroanalytical technique;

(e) said programmable control unit initiating a plating and/or stripping electroanalytical measurement cycle for measurement of said target constituent by providing electrical energy to at least a pair of electrodes disposed in said bath sample, the electrical energy input to the pair of electrodes being provided to either plate or strip a metal to or from at least one of the electrodes during a predetermined time period after the first time period has elapsed; and

(f) said programmable control unit further directing the taking of an electroanalytical measurement of the energy output of the electroanalytical technique after the first time period has elapsed and before the predetermined time period has elapsed during which the effects of said by-products are negligible.

2. An apparatus as claimed in claim 1 wherein the electroanalysis unit performs one or more analysis techniques including at least one of potentiometry, amperometry, conductometry, voltammetry, polarography, and coulometry on said bath sample.

3. An apparatus as claimed in claim 1 wherein the target constituent provided by the constituent dosing supply unit comprises a suppressor.

4. An apparatus as claimed in claim 1 wherein the electrodes include a working electrode, an auxiliary electrode and a reference electrode.

5. An apparatus as claimed in claim 1 wherein the electroanalysis unit is controlled by the programmable control unit to perform a cyclic voltammetric stripping.

6. An apparatus as claimed in claim 1 wherein the electroanalysis unit is controlled by the programmable control unit to perform a cyclic pulsed voltammetric stripping.

7. An apparatus as claimed in claim 1 wherein the electroanalysis unit is controlled by the programmable control unit to perform a chronoamperometry.

8. An apparatus as claimed in claim 1 wherein the electroanalysis unit is controlled by the programmable control unit to perform a chronopotentiometry.

9. An apparatus for electroplating a metal on a microelectronic workpiece comprising:

(a) an electroplating solution, said electroplating solution including a target constituent and one or more by-products that skew an initial plating and/or stripping response for a first period of time;

(b) one or more electroplating reactors containing said electroplating solution, each of the reactors allowing electroplating of one or more workpieces therein;

(c) an electroanalysis unit connected to automatically receive samples of said electroplating solution for analysis, the electroanalysis unit executing a plating and/or stripping electroanalytical technique on the received samples;

(d) a constituent dosing supply unit connected to provide an amount of the target constituent to said electroplating solution;

(e) a programmable control unit connected to communicate with;

a) said electroanalysis unit to execute an electroanalytical technique to determine the amount of said target constituent in said samples of said electroplating solution, and

b) said constituent dosing supply unit to provide an amount of said target constituent to said electroplating solution based on the amount of said target constituent measured in said samples through the use of said electroanalytical technique;

(f) said programmable control unit initiating a plating and/or stripping electroanalytical measurement cycle for measurement of said target constituent by providing electrical energy to at least a pair of electrodes disposed in said bath sample, the electrical energy input to the pair of electrodes being provided to either plate or strip a metal to or from at least one of the electrodes during a predetermined time period after the first time period has elapsed; and

(g) said programmable control unit further directing the taking of an electroanalytical measurement of the energy output of the electroanalytical technique after the first time period has elapsed and before the predetermined time period has elapsed during which the effects of said by-products are negligible.

10. The apparatus of claim 9 wherein the electroanalysis unit is programmed to execute an electroanalytical technique comprising potentiometry.

11. The apparatus of claim 9 wherein the electroanalysis unit is programmed to execute an electroanalytical technique comprising amperometry.

12. The apparatus of claim 9 wherein the electroanalysis unit is programmed to execute an electroanalytical technique comprising conductometry.

13. The apparatus claim 9 wherein the electroanalysis unit is programmed to execute an electroanalytical technique comprising voltammetry.

14. The apparatus of claim 9 wherein the electroanalysis unit is programmed to execute an electroanalytical technique comprising coulometry.

15. The apparatus of claim 9 wherein the electroanalysis unit is programmed to execute an electroanalytical technique comprising cyclic voltammetric stripping.

16. The apparatus of claim 9 wherein the electroanalysis unit is programmed to measure an amount of suppressor in the electroplating solution.