Method of determining etch endpoint using principal components analysis of optical emission spectra

• US 6,582,618 B1
• Filed: 01/26/2000
• Issued: 06/24/2003
• 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
• Primary Examiner(s): GOUDREAU, GEORGE A
• Application Number:
  US09/491,845
• Time in Patent Office: 1,245 Days
• Field of Search: 216/59, 216/60, 216/61, 438/9, 438/7, 438/8, 438/16, 438/17, 438/18, 438/10, 438/11
• US Class Current: 216/59
• 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 21/73 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 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: 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 calculating Scores from at least a portion of the collected intensity data using at most first, second, third and fourth Principal Components derived from a model. The method also includes determining the etch endpoint using Scores corresponding to at least one of the first, second, third and fourth Principal Components as an indicator for the etch endpoint.

Claims

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

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

determining a plurality of Loadings using at least a portion of previous intensity data representative of optical emission at the plurality of spectral wavelengths, the previous intensity data being collected during a plurality of previous plasma etch processes;

calculating a plurality of approximate Scores from at least a portion of the collected intensity data using the plurality of Loadings; and

determining the etch endpoint using the approximate Scores.

2. The method of claim 1, wherein determining the etch endpoint using the approximate Scores as an indicator includes using a trace of the approximate Scores.

3. The method of claim 2, wherein using the trace of the approximate Scores includes using the trace of the approximate Scores corresponding to at least one of a first, second, third, and fourth Principal Components.

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

selecting multiple wavelengths as indicator variables based on the Loadings, 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 using the approximate Scores further comprises:

selecting multiple wavelengths as indicator variables based on the Loadings, 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 using the approximate Scores corresponding to the at least one of the first, second, third and fourth Principal Components as the indicator further comprises:

selecting multiple wavelengths as indicator variables based on the Loadings for 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:

scaling the at least the portion of the collected intensity data to generate mean values and mean-scaled values for the collected intensity data.

8. The method of claim 1, wherein determining the plurality of Loadings comprises determining the plurality of Loadings using an eigenanalysis method.

9. The method of claim 1, wherein determining the plurality of Loadings comprises determining the plurality of Loadings using a singular value decomposition method.

10. The method of claim 1, wherein determining the plurality of Loadings comprises determining the plurality of Loadings 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 at a plurality of spectral wavelengths during a plasma etch process;

determining a plurality of Loadings using at least a portion of previous intensity data representative of optical emission at the plurality of spectral wavelengths, the previous intensity data being collected during a plurality of previous plasma etch processes;

calculating a plurality of approximate Scores from at least a portion of the collected intensity data using the plurality of Loadings; and

determining the etch endpoint using the approximate Scores.

12. The method of claim 11, wherein determining the etch endpoint using the approximate Scores includes using a trace of the approximate Scores.

13. The method of claim 12, wherein using the trace of the approximate Scores includes using the trace of the approximate Scores corresponding to at least one of a first, second, third, and fourth Principal Components.

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

selecting multiple wavelengths as indicator variables based on the Loadings, 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 using the approximate Scores further comprises:

selecting multiple wavelengths as indicator variables based on the Loadings, 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 using the approximate Scores corresponding to the at least one of the first, second, third and fourth Principal Components further comprises:

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

17. The method of claim 11, further comprising:

scaling the at least the portion of the collected intensity data to generate mean values and mean-scaled values for the collected intensity data.

18. The method of claim 11, wherein determining the plurality of Loadings comprises determining the plurality of Loadings using an eigenanalysis method.

19. The method of claim 11, wherein determining the plurality of Loadings comprises determining the plurality of Loadings using a singular value decomposition method.

20. The method of claim 11, wherein determining the plurality of Loadings comprises determining the plurality of Loadings using a power method.