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

• US 6,365,033 B1
• Filed: 08/31/1999
• Issued: 04/02/2002
• Est. Priority Date: 05/03/1999
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Semitool Incorporated (Applied Materials Incorporated)
• Inventors: Taylor, Thomas C., Ritzdorf, Thomas L., Lindberg, Fredrick A., Carpenter, Bradley C., Graham, Lyndon W.
• Primary Examiner(s): Tung, T.
• Application Number:
  US09/387,084
• Time in Patent Office: 945 Days
• Field of Search: 204/434, 205/775, 205/790.5, 205/791, 205/791.5
• US Class Current: 205/775
• 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. A method for measuring a target constituent of an electroplating solution using a plating and/or stripping electroanalytical technique, the electroplating solution including one or more constituents that form a byproduct that skews an initial plating and/or stripping response to an energy input of the electroanalytical technique for a first time period beyond which such skewing is negligible, the method comprising the steps of:

initiating a plating and/or stripping electroanalytical measurement cycle for measurement of the target constituent by providing electrical energy to at least a pair of electrodes disposed in the electroplating solution, 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 for at least a predetermined time period that extends beyond the first time period;

taking 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;

using the electroanalytical measurement to determine an amount of the target constituent in the electroplating solution so as to reduce the effect of the skewing of the initial plating and/or stripping response caused by the one or more by-products in calculating the amount of the target constituent.

2. A method as claimed in claim 1 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

3. A method as claimed in claim 1 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

4. A method as claimed in claim 1 wherein the electroanalytical technique comprises chronoamperometry.

5. A method as claimed in claim 1 wherein the electroanalytical technique comprises chronopotentiometry.

6. A method as claimed in claim 1 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

7. A method as claimed in claim 1 wherein the target constituent comprises a suppressor.

8. A method as claimed in claim 1 wherein the electroanalytical technique comprises titration.

9. A method as claimed in claim 8 wherein the electroplating solution is used as the diluent and the target constituent is used as the titrant.

10. A method as claimed in claim 8 wherein a virgin make-up of the electroplating solution is used as the diluent and the electroplating solution is used as the titrant.

11. A method for measuring a suppressor of an electroplating solution using a metal plating and/or stripping electroanalytical technique, the electroplating solution including one or more constituents that form a by-product that operates as a pseudo-suppressor during an initial electrical energy input of the electroanalytical technique for a first-time period beyond which such skewing is negligible, the method comprising the steps of:

initiating a plating and/or stripping electroanalytical measurement cycle to measure the suppressor by providing an electrical energy input to at least one pair of electrodes disposed in the electroplating solution, 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 for at least a predetermined time period that extends beyond the first time period;

taking 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;

using the electroanalytical measurement taken after the first time period has elapsed and before the predetermined time period has elapsed to determine an amount of the suppressor in the electroplating solution so as to reduce the effect of the skewing of the initial plating and/or stripping response caused by the pseudo-suppressor in calculating the amount of the suppressor.

12. A method as claimed in claim 11 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

13. A method as claimed in claim 11 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

14. A method as claimed in claim 11 wherein the electroanalytical technique comprises chronoamperometry.

15. A method as claimed in claim 11 wherein the electroanalytical technique comprises chronopotentiometry.

16. A method as claimed in claim 11 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

17. A method for measuring a target constituent of an electroplating solution using an electroanalytical technique, the electroplating solution including one or more constituents that form a by-product that skews an initial electrical response to an energy input of the electroanalytical technique for a first time period beyond which such skewing is negligible, the method comprising the steps of:

a) removing an amount of electroplating solution from an electroplating reactor;

b) executing a metal plating and/or stripping electroanalytical technique using the electroplating solution removed in Step a, ensuring that a measurement is taken during the electroanalytical technique process after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

c) comparing the measurement taken in Step b with a calibration curve to determine an amount of the target constituent in the electroplating solution.

18. A method as claimed in claim 17 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

19. A method as claimed in claim 17 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

20. A method as claimed in claim 17 wherein the electroanalytical technique comprises chronoamperometry.

21. A method as claimed in claim 17 wherein the electroanalytical technique comprises chronopotentiometry.

22. A method as claimed in claim 17 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

23. A method as claimed in claim 17 wherein the target constituent comprises a suppressor.

24. A method for measuring a target constituent of an electroplating solution using an electroanalytical technique, the electroplating solution including one or more constituents that form a by-product that skews an initial plating and/or stripping response to an energy input of the electroanalytical technique for a first time period beyond which such skewing is negligible, the method comprising the steps of:

a) removing an amount of electroplating solution from an electroplating reactor;

b) executing a metal plating and/or stripping electroanalytical technique using the electroplating solution removed in Step a, ensuring that a measurement is taken during the electroanalytical technique after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

c) adding an amount of the target constituent to the amount of electroplating solution;

d) executing a metal plating and/or stripping electroanalytical technique using the electroplating bath of Step c, ensuring that a measurement is taken during the electroanalytical technique after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

e) repeating Steps c and d as necessary to generate a slope, or to otherwise gather enough data to answer a logic criteria;

f) comparing the measurement results obtained during one or more cycles of Steps c and d to a calibration curve; and

g) calculating the amount of the target constituent based on the comparison made in Step f whereby the effect of the skewing of the initial plating and/or stripping response caused by the by-product on the calculation is reduced.

25. A method as claimed in claim 24 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

26. A method as claimed in claim 24 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

27. A method as claimed in claim 24 wherein the electroanalytical technique comprises chronoamperometry.

28. A method as claimed in claim 24 wherein the electroanalytical technique comprises chronopotentiometry.

29. A method as claimed in claim 24 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

30. A method as claimed in claim 24 wherein the target constituent comprises a suppressor.

31. A method for measuring a target constituent of an electroplating solution using a plating and/or stripping electroanalytical technique, the electroplating solution including one or more constituents that form a by-product that skews an initial plating and/or stripping response to an energy input of the electroanalytical technique for a first time period beyond which such skewing is negligible, the method comprising the steps of:

a) removing an amount of electroplating solution from an electroplating reactor;

b) adding an amount of virgin make-up solution of the electroplating solution to the amount of electroplating solution removed in Step a;

c) executing a metal plating and/or stripping electroanalytical technique using the electroplating solution formed in Step b, ensuring that a measurement is taken during the electroanalytical technique after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

d) adding an amount of the target constituent to the amount of electroplating solution;

e) executing a metal plating and/or stripping electroanalytical technique using the electroplating solution of Step d, ensuring that a measurement is taken during the electroanalytical technique measurement process after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

f) repeating Steps d and e as necessary to generate a slope, or to otherwise gather enough data to answer a logic criteria;

g) comparing the measurement results obtained during one or more cycles of Steps d and e to a calibration curve; and

h) calculating the amount of the target constituent based on the comparison made in Step g whereby the effect of the skewing of the initial plating and/or stripping response caused by the by-product on the calculation is reduced.

32. A method as claimed in claim 31 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

33. A method as claimed in claim 31 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

34. A method as claimed in claim 31 wherein the electroanalytical technique comprises chronoamperometry.

35. A method as claimed in claim 31 wherein the electroanalytical technique comprises chronopotentiometry.

36. A method as claimed in claim 31 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

37. A method as claimed in claim 31 wherein the target constituent comprises a suppressor.

38. A method for measuring a target constituent of an electroplating solution using an electroanalytical technique, the electroplating solution including one or more constituents that form a by-product that skews an initial plating and/or stripping response to an energy input of the electroanalytical technique for a first time period beyond which such skewing is negligible, the method comprising the steps of:

a) removing an amount of electroplating solution from an electroplating reactor;

b) providing an amount of virgin make-up solution;

c) executing a metal plating and/or stripping electroanalytical technique using the virgin make-up solution formed in Step b, ensuring that a measurement is taken during the electroanalytical technique after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

d) adding an amount of the electroplating solution removed in Step b to the virgin make-up solution formed in Step b;

e) executing a metal plating and/or stripping electroanalytical technique measurement process using the electroplating solution of Step d, ensuring that a measurement is taken during the electroanalytical technique measurement process after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

f) repeating Steps d and e as necessary to generate a slope, or to otherwise gather enough data to answer a logic criteria;

g) comparing the measurement results obtained during one or more cycles of Steps d and e to a calibration curve; and

h) calculating the amount of the target constituent based on the comparison made in Step g whereby the effect of the skewing of the initial plating and/or stripping response caused by the by-product on the calculation is reduced.

39. A method as claimed in claim 38 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

40. A method as claimed in claim 38 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

41. A method as claimed in claim 38 wherein the electroanalytical technique comprises chronoamperometry.

42. A method as claimed in claim 38 wherein the electroanalytical technique comprises chronopotentiometry.

43. A method as claimed in claim 38 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

44. A method as claimed in claim 38 wherein the target constituent comprises a suppressor.

45. A method for measuring a target constituent of an electroplating solution using an electroanalytical technique, the electroplating solution including one or more constituents that form a by-product that skews an initial plating and/or stripping response to an energy input of the electroanalytical technique for a first time period beyond which such skewing is negligible, the method comprising the steps of:

a) removing an amount of electroplating solution from an electroplating reactor;

b) providing an amount of virgin make-up solution;

c) executing a metal plating and/or stripping electroanalytical technique using the virgin make-up solution formed in Step b;

d) adding an amount of the electroplating solution removed in Step a to the virgin make-up solution formed in Step b;

e) executing a metal plating and/or stripping electroanalytical technique using the electroplating solution of Step d, ensuring that a measurement is taken during the electroanalytical technique measurement process after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

f) adding an amount of the target constituent to the solution formed in Step d;

g) executing a metal plating and/or stripping electroanalytical technique using the solution formed in of Step f, ensuring that a measurement is taken during the electroanalytical technique measurement process after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

h) repeating Steps f and g to generate a measurement curve;

i) calculating the amount of the target constituent based on the measurement curve obtained in Step h whereby the effect of the skewing of the initial plating and/or stripping response caused by the by-product on the calculation is reduced.

46. A method as claimed in claim 45 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

47. A method as claimed in claim 45 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

48. A method as claimed in claim 45 wherein the electroanalytical technique comprises chronoamperometry.

49. A method as claimed in claim 45 wherein the electroanalytical technique comprises chronopotentiometry.

50. A method as claimed in claim 45 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

51. A method as claimed in claim 45 wherein the target constituent comprises a suppressor.

52. A method for measuring a target constituent of an electroplating solution using an electroanalytical technique, the electroplating solution including one or more constituents that form a by-product that skews an initial plating and/or stripping response to an energy input of the electroanalytical technique for a first time period beyond which such skewing is negligible, the method comprising the steps of:

a) removing an amount of electroplating solution from an electroplating reactor;

b) providing an amount of virgin make-up solution;

c) executing an electroanalytical technique measurement process using the virgin make-up solution formed in Step b;

d) adding an amount of virgin make-up solution to the amount of electroplating solution removed in Step a;

e) executing a plating and/or stripping electroanalytical technique measurement process using the electroplating solution of Step d, ensuring that a measurement is taken during the electroanalytical technique measurement process after plating or stripping power has been provided for a predetermined period of time that extends beyond the first time period;

f) calculating the slope of the measurements taken in Steps c and d whereby the effect of the skewing of the initial plating and/or stripping response caused by the byproduct on the calculation is reduced;

g) comparing the measurement results obtained during Step f to a calibration curve to calculate the amount of the target constituent.

53. A method as claimed in claim 52 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

54. A method as claimed in claim 52 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

55. A method as claimed in claim 52 wherein the electroanalytical technique comprises chronoamperometry.

56. A method as claimed in claim 52 wherein the electroanalytical technique comprises chronopotentiometry.

57. A method as claimed in claim 52 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

58. A method as claimed in claim 52 wherein the target constituent comprises a suppressor.

59. A method for measuring a target constituent of an electroplating solution using an electroanalytical technique, the electroplating solution comprising one or more by-products that skew an initial electrical response to an energy input of the electroanalytical technique, the method comprising:

applying the electroanalytical technique using metal plating or stripping parameters that facilitate measurement taking during a time at which the skewing of the initial electrical response is negligible;

taking electroanalytical measurements during the time at which the skewing of the initial electrical response is negligible;

using the electroanalytical measurements that are taken during the time at which the skewing of the initial electrical response is negligible to determine an amount of the target constituent in the electroplating solution.

60. A method as claimed in claim 59 wherein the electroanalytical technique comprises cyclic pulsed voltammetric stripping.

61. A method as claimed in claim 59 wherein the electroanalytical technique comprises cyclic voltammetric stripping.

62. A method as claimed in claim 59 wherein the electroanalytical technique comprises chronoamperometry.

63. A method as claimed in claim 59 wherein the electroanalytical technique comprises chronopotentiometry.

64. A method as claimed in claim 59 wherein the electroanalytical technique comprises linear sweeps of the energy input that are performed at a slow rate and then calibrated versus concentration of the target constituent.

65. A method as claimed in claim 59 wherein the target constituent comprises a suppressor.

66. A method as claimed in claim 59 wherein the electroanalytical technique comprises titration.

67. A method as claimed in claim 66 wherein the electroplating solution is used as the diluent and the target constituent is used as the titrant.

68. A method as claimed in claim 66 wherein a virgin make-up of the electroplating solution is used as the diluent and the electroplating solution is used as the titrant.