Electrochemical drive circuitry and method

• US 7,427,346 B2
• Filed: 05/04/2004
• Issued: 09/23/2008
• Est. Priority Date: 05/04/2004
• Status: Active Grant

• Current Assignee: Ancosys GmbH (Nova Ltd.)
• Original Assignee: Advanced Technology Materials, Inc. (Entegris Incorporated)
• Inventors: Lurcott, Steven, Tom, Glenn M.
• Primary Examiner(s): Olsen, Kaj K
• Application Number:
  US10/838,390
• Publication Number:
  US 20050247576A1
• Time in Patent Office: 1,603 Days
• Field of Search: 204/406, 204/434
• US Class Current: 205/775
• CPC Class Codes: G01N 27/42 Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte

Abstract

An electrochemical drive circuitry and method, such as may be employed in electroplating bath chemical monitoring. A microcontroller can be utilized to selectively apply galvanostatic or potentiostatic conditions on the electrochemical cell, for measurement of response of the electrochemical cell to such conditions, with the microcontroller arranged to generate an offset potential to control potential across the electrochemical cell within a range of potential accommodated by a unipolar power supply, and/or a CMOS analog switch can be employed in combination with individual digital-to-analog converters for each of the current-controlled and potential-controlled conditions, to provide high-speed, dual mode operating capability.

Claims

1. A circuitry for monitoring an electrochemical process in an electrochemical cell including working, reference and counter electrodes, arranged to carry out galvanostatic and potentiostatic modes of operation of said electrochemical cell, involving electrochemical plating in a galvanostatic mode of operation, and stripping, cyclic voltammetry, equilibration and nucleation in a potentiostatic mode of operation, said circuitry comprising a microcontroller programmably arranged in a feedback loop with said electrochemical cell, and circuit elements between said microcontroller and electrochemical cell for switching between galvanostatic and potentiostatic modes of operation of said electrochemical cell, wherein said circuitry comprises a CMOS analog switch including a first set of switch positions connectable to one another for said galvanostatic mode of operation, and a second set of switch positions connectable to one another for said potentiostatic mode of operation, a current control digital-to-analog converter arranged for linking to said working electrode and to said CMOS analog switch, and adapted to bring the circuitry to a predetermined current condition for said galvanostatic mode of operation, and a potential control digital-to-analog converter arranged for linking to said CMOS analog switch and to said reference electrode, and adapted to bring the circuitry to a predetermined potential condition for said potentiostatic mode of operation, and wherein said current control digital-to-analog converter and said potential control digital-to-analog converter are respectively adapted to provide rise time, to said predetermined current condition in said galvanostatic mode of operation, and to said predetermined potential condition in said potentiostatic mode of operation, of less than one millisecond, and with said CMOS analog switch arranged for linking with said counter electrode.

2. The circuitry of claim 1, which is devoid of analog switches other than said CMOS analog switch.

3. The circuitry of claim 1, wherein the microcontroller is programmably arranged to inject an offset voltage in said feedback loop corresponding to an operating potential range of said circuitry.

4. The circuitry of claim 3, operatively coupled with a unipolar power supply, wherein said operating potential range of said circuitry is within a potential range of said unipolar power supply.

5. The circuitry of claim 3, wherein the microcontroller is programmably arranged to modulate the offset voltage to control electrical potential across the electrochemical cell within a potential range accommodated by a unipolar power supply in both of said potentiostatic and galvanostatic modes of operation.

6. The circuitry of claim 3, which is devoid of analog switches other than said CMOS analog switch.

7. The circuitry of claim 1, which is devoid of mechanical switches.

8. The circuitry of claim 1, operatively coupled to said electrochemical cell, wherein said microcontroller is arranged for monitoring of a copper electrodeposition process.

9. The circuitry of claim 1, wherein said microcontroller is programmably arranged for carrying out a pulsed cyclic galvanostatic analysis procedure in said galvanostatic mode of operation.

10. The circuitry of claim 1, operatively coupled to a computational unit arranged to produce a monitoring output indicative of concentration of a species of interest in an electrochemical process conducted in said electrochemical cell, when the electrochemical process is monitored by said circuitry.

11. The circuitry of claim 1, wherein a portion of said circuitry for linking said CMOS analog switch to said counter electrode contains a first relay, and a second portion of said circuitry for linking the current control digital-to-analog converter with the working electrode contains a second relay, to provide open circuit capability so that the electrochemical cell can be rendered electrically inactive when fluids in the electrochemical cell are changed.

12. A circuitry for monitoring an electrochemical process in an electrochemical cell, said circuitry comprising a microcontroller programmably arranged in a feedback loop with said electrochemical cell, and circuit elements between said microcontroller and electrochemical cell for switching between galvanostatic and potentiostatic modes of operation of said electrochemical cell, said circuitry comprising:

a first analog-to-digital converter operatively linked to said electrochemical cell and arranged to input to said microcontroller a first digital signal correlative of a voltage in said electrochemical cell, in said galvanostatic mode of operation of said electrochemical cell;

a second analog-to-digital converter coupled with the electrochemical cell and arranged to input to said microcontroller a second digital signal correlative of current passing through said electrochemical cell, in said galvanostatic mode of operation of said electrochemical cell;

a first digital-to-analog convener linked to (i) said microcontroller for receiving a potential control digital signal from said microcontroller, and (ii) said electrochemical cell, for transmitting thereto a fixed voltage for measurement of electrochemical cell current in said potentiostatic mode of operation of said electrochemical cell;

a second digital-to-analog converter linked to said microcontroller for receiving an offset voltage digital signal from said microcontroller and responsively producing an analog signal for modulating the current for voltage measurement of the response of said electrochemical cell;

an operational amplifier having a first input thereof linked to said electrochemical cell, a second input thereof linked to said second digital-to-analog converter for receiving said analog signal for modulating potentiostatic measurement of response of said electrochemical cell, and an output linked to said second analog-to-digital converter for transmission of an output signal to said second analog-to-digital converter, wherein the operational amplifier is arranged to amplify current required to maintain said offset voltage in said potentiostatic mode of operation of said electrochemical cell; and

a current measurement scaling unit coupled between said output and said first input of said operational amplifier, and arranged to set scaling of said output signal from the operational amplifier.

13. The circuitry of claim 12, wherein said current measuring scaling unit is arranged to set scaling of said output signal from the operational amplifier at a level enabling the circuitry to be powered by a unipolar power supply in both of said potentiostatic and galvanostatic modes of operation.

14. The circuitry of claim 12, further comprising a buffer linked between said electrochemical cell and said first analog-to-digital converter.

15. A method of monitoring an electrochemical process in an electrochemical cell, said method comprising subjecting the contents of the electrochemical cell to a potentiostatic mode and a galvanostatic mode of analysis by a microprocessor programmably arranged in a feedback loop with said electrochemical cell utilizing a monitoring circuitry comprising a microcontroller programmably arranged in a feedback loop with said electrochemical cell, and circuit elements between said microcontroller and electrochemical cell for switching between galvanostatic and potentiostatic modes of operation of said electrochemical cell, wherein said circuitry comprises a CMOS analog switch including a first set of switch positions connectable to one another for said galvanostatic mode of operation, and a second set of switch positions connectable to one another for said potentiostatic mode of operation, a current control digital-to-analog converter arranged for linking to said working electrode and to said CMOS analog switch, and adapted to bring the circuitry to a predetermined current condition for said galvanostatic mode of operation, and a potential control digital-to-analog converter arranged for linking to said CMOS analog switch and to said reference electrode, and adapted to bring the circuitry to a predetermined potential condition for said potentiostatic mode of operation, and wherein said current control digital-to-analog converter and said potential control digital-to-analog converter are respectively adapted to provide rise time, to said predetermined current condition in said galvanostatic mode of operation, and to said predetermined potential condition in said potentiostatic mode of operation, of less than one millisecond, and with said CMOS analog switch arranged for linking with said counter electrode.

16. A method of monitoring an electrochemical process in an electrochemical cell in accordance with claim 15, wherein said microcontroller-selectively applies galvanostatic or potentiostatic, or both, conditions on the electrochemical cell for measurement of response of the electrochemical cell to such conditions, and generates an offset potential to control potential across the electrochemical cell within a range of potential accommodated by a unipolar power supply.

17. The method of claim 16, wherein the said galvanostatic and potentiostatic conditions are applied by the microcontroller without analog switching steps.

18. The method of claim 16, wherein the said galvanostatic and potentiostatic conditions are applied by the microcontroller without mechanical switching steps.

19. The method of claim 16, further comprising use of a unipolar power supply as a power source for said microcontroller and electrochemical cell.