Determining endpoint in etching processes using principal components analysis of optical emission spectra with thresholding

• US 6,238,937 B1
• Filed: 01/26/2000
• Issued: 05/29/2001
• Est. Priority Date: 09/08/1999
• Status: Expired due to Term

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Yue, Hongyu, Toprac, Anthony John, Wiseman, Joseph William
• Primary Examiner(s): POWELL, WILLIAM A
• Application Number:
  US09/491,248
• Time in Patent Office: 489 Days
• Field of Search: 438/9, 438/14, 438/16, 438/710, 438/719, 438/723, 438/724, 438/743, 438/744, 216/59, 216/60, 216/79, 216/67, 156/345 MT, 156/345 P
• US Class Current: 438/9
• CPC Class Codes: A61K 39/00 Medicinal preparations containing antigens or antibodies materials for immunoassay G01N33/53
• CPC Class Codes: C07K 14/195 from bacteria
• CPC Class Codes: G01N 21/71 thermally excited
• CPC Class Codes: G01N 21/73 using plasma burners or torches
• CPC Class Codes: G05B 2219/32187 Correlation between controlling parameters for influence on quality parameters
• CPC Class Codes: G05B 2219/45031 Manufacturing semiconductor wafers
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 2237/3341 Reactive etching
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32963 End-point detection
• CPC Class Codes: H01J 37/32972 Spectral analysis
• CPC Class Codes: H01J 37/3299 Feedback systems
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

A method is provided for determining an etch endpoint. The method includes collecting intensity data representative of optical emission spectral wavelengths during a plasma etch process. The method further includes analyzing at least a portion of the collected intensity data into at most first and second Principal Components with respective Loadings and corresponding Scores. The method also includes determining the etch endpoint using the respective Loadings and corresponding Scores of the second Principal Component as an indicator for the etch endpoint using thresholding applied to the respective Loadings of the second Principal Component.

Claims

1. A method for determining an etch endpoint, the method comprising:

collecting intensity data representative of optical emission spectral wavelengths during a plasma etch process;

analyzing at least a portion of the collected intensity data into at most first and second Principal Components with respective Loadings and corresponding Scores; and

determining the etch endpoint using the respective Loadings and corresponding Scores of the second Principal Component as an indicator for the etch endpoint using thresholding applied to the respective Loadings of the second Principal Component.

2. The method of claim 1, wherein determining the etch endpoint includes using a trace of Scores corresponding to at least one of the first and the second Principal Components along time to signal the etch endpoint.

3. The method of claim 2, wherein using the trace of the Scores corresponding to the at least one of the first and the second Principal Components along time to signal the etch endpoint includes using the trace of the Scores corresponding to the second Principal Component along time to signal the etch endpoint.

4. The method of claim 1 wherein determining the etch endpoint further comprises:

selecting multiple wavelengths as indicator variables based on the respective Loadings of at least one of the first and the second Principal Components, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

5. The method of claim 2 wherein determining the etch endpoint further comprises:

selecting multiple wavelengths as indicator variables based on the respective Loadings of the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

6. The method of claim 3 wherein determining the etch endpoint further comprises:

selecting multiple wavelengths as indicator variables based on the respective Loadings of the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

7. The method of claim 1 further comprising mean-scaling the at least the portion of the collected intensity data prior to analyzing the at least the portion of the collected intensity data.

8. The method of claim 1, wherein analyzing the at least the portion of the collected intensity data into the at most first and second Principal Components includes using an eigenanalysis method.

9. The method of claim 1, wherein analyzing the at least the portion of the collected intensity data into the at most first and second Principal Components includes using a singular value decomposition method.

10. The method of claim 1, wherein analyzing the at least the portion of the collected intensity data into the at most first and second Principal Components includes using a power method.

11. A method for etching a wafer, the method comprising:

etching a wafer using a plasma process so that a light-emitting discharge is produced;

terminating the etching of the wafer when an etch endpoint is determined, wherein the determination of the etch endpoint further comprises;

collecting intensity data representative of optical emission spectral wavelengths during a plasma etch process;

analyzing at least a portion of the collected intensity data into at most first and second Principal Components with respective Loadings and corresponding Scores; and

determining the etch endpoint using the respective Loadings and corresponding Scores of the second Principal Component as an indicator for the etch endpoint using thresholding applied to the respective Loadings of the second Principal Component.

12. The method of claim 11, wherein determining the etch endpoint includes using a trace of Scores corresponding to at least one of the first and the second Principal Components along time to signal the etch endpoint.

13. The method of claim 12, wherein using the trace of the Scores corresponding to the at least one of the first and the second Principal Components along time to signal the etch endpoint includes using the trace of the Scores corresponding to the second Principal Component along time to signal the etch endpoint.

14. The method of claim 11 wherein determining the etch endpoint further comprises:

selecting multiple wavelengths as indicator variables based on the respective Loadings of at least one of the first and the second Principal Components, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

15. The method of claim 12 wherein determining the etch endpoint further comprises:

selecting multiple wavelengths as indicator variables based on the respective Loadings of the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

16. The method of claim 13 wherein determining the etch endpoint further comprises:

selecting multiple wavelengths as indicator variables based on the respective Loadings of the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

17. The method of claim 11 further comprising mean-scaling the at least the portion of the collected intensity data prior to analyzing the at least the portion of the collected intensity data.

18. The method of claim 11, wherein analyzing the at least the portion of the collected intensity data into the at most first and second Principal Components includes using an eigenanalysis method.

19. The method of claim 11, wherein analyzing the at least the portion of the collected intensity data into the at most first and second Principal Components includes using a singular value decomposition method.

20. The method of claim 11, wherein analyzing the at least the portion of the collected intensity data into the at most first and second Principal Components includes using a power method.

21. A method for determining an etch endpoint, the method comprising:

collecting intensity data representative of optical emission spectral wavelengths during a plasma etch process;

analyzing the collected intensity data into at most first and second Principal Components; and

determining the etch endpoint using Loadings and Scores corresponding to the second Principal Component as an indicator for the etch endpoint using thresholding applied to the Loadings corresponding to the second Principal Component.

22. The method of claim 21, wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as an indicator includes using a trace of Scores of at least one of the first and the second Principal Components along time to signal the etch endpoint.

23. The method of claim 22, wherein using the trace of the Scores of the at least one of the first and the second Principal Components along time to signal the etch endpoint includes using the trace of the Scores of the second Principal Component along time to signal the etch endpoint.

24. The method of claim 21 wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as an indicator further comprises:

selecting multiple wavelengths as indicator variables based on Loadings of at least one of the first and the second Principal Components, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

25. The method of claim 22 wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as an indicator further comprises:

selecting multiple wavelengths as indicator variables based on the Loadings corresponding to the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

26. The method of claim 23 wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as the indicator further comprises:

selecting multiple wavelengths as indicator variables based on the Loadings corresponding to the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

27. The method of claim 21 further comprising mean-scaling the collected intensity data prior to analyzing the collected intensity data.

28. The method of claim 21, wherein analyzing the collected intensity data into the at most first and second Principal Components includes using an eigenanalysis method.

29. The method of claim 21, wherein analyzing the collected intensity data into the at most first and second Principal Components includes using a singular value decomposition method.

30. The method of claim 21, wherein analyzing the collected intensity data into the at most first and second Principal Components includes using a power method.

31. A method for etching a wafer, the method comprising:

etching a wafer using a plasma process so that a light-emitting discharge is produced;

terminating the etching of the wafer when an etch endpoint is determined, wherein the determination of the etch endpoint further comprises;

collecting intensity data representative of optical emission spectral wavelengths during a plasma etch process;

analyzing the collected intensity data into at most first and second Principal Components; and

determining the etch endpoint using Loadings and Scores corresponding to the second Principal Component as an indicator for the etch endpoint using thresholding applied to the Loadings corresponding to the second Principal Component.

32. The method of claim 31, wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as an indicator includes using a trace of Scores of at least one of the first and the second Principal Components along time to signal the etch endpoint.

33. The method of claim 32, wherein using the trace of the Scores of the at least one of the first and the second Principal Components along time to signal the etch endpoint includes using the trace of the Scores of the second Principal Component along time to signal the etch endpoint.

34. The method of claim 31 wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as an indicator further comprises:

selecting multiple wavelengths as indicator variables based on Loadings of at least one of the first and the second Principal Components, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

35. The method of claim 32 wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as an indicator further comprises:

selecting multiple wavelengths as indicator variables based on the Loadings corresponding to the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

36. The method of claim 33 wherein determining the etch endpoint using the Scores corresponding to the second Principal Component as the indicator further comprises:

selecting multiple wavelengths as indicator variables based on the Loadings corresponding to the second Principal Component, the multiple wavelengths varying during the plasma process so that the etch endpoint can be determined by monitoring the multiple wavelengths.

37. The method of claim 31 further comprising mean-scaling the collected intensity data prior to analyzing the collected intensity data.

38. The method of claim 31, wherein analyzing the collected intensity data into the at most first and second Principal Components includes using an eigenanalysis method.

39. The method of claim 31, wherein analyzing the collected intensity data into the at most first and second Principal Components includes using a singular value decomposition method.

40. The method of claim 31, wherein analyzing the collected intensity data into the at most first and second Principal Components includes using a power method.

41. A computer-readable, program storage device encoded with instructions that, when executed by a computer, perform a method, the method comprising:

collecting intensity data representative of optical emission spectral wavelengths during a plasma etch process;

analyzing at least a portion of the collected intensity data into at most first and second Principal Components with respective Loadings and corresponding Scores; and

determining the etch endpoint using the respective Loadings and corresponding Scores of the second Principal Component as an indicator for the etch endpoint using thresholding applied to the respective Loadings of the second Principal Component.

42. A computer programmed to perform a method, the method comprising:

collecting intensity data representative of optical emission spectral wavelengths during a plasma etch process;

analyzing at least a portion of the collected intensity data into at most first and second Principal Components with respective Loadings and corresponding Scores; and

determining the etch endpoint using the respective Loadings and corresponding Scores of the second Principal Component as an indicator for the etch endpoint using thresholding applied to the respective Loadings of the second Principal Component.