Method and apparatus for monitoring plasma processing operations

• US 6,221,679 B1
• Filed: 04/23/1998
• Issued: 04/24/2001
• Est. Priority Date: 04/23/1998
• Status: Expired due to Fees

• Current Assignee: Sandia Corporation (Martin Marietta Corporation)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Ward, Pamela Peardon Denise, Smith, Michael Lane Jr., Stevenson, Joel OʼDon
• Primary Examiner(s): Gulakowski, Randy
• Assistant Examiner(s): ALANKO, ANITA KAREN
• Application Number:
  US09/064,957
• Time in Patent Office: 1,097 Days
• Field of Search: 156/345, 702/155, 356/346, 356/72, 356/311, 356/316, 438/7, 438/9, 438/16, 216/60, 427/10
• US Class Current: 438/7
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/443 Emission spectrometry

Abstract

The invention generally relates to various aspects of a plasma process, and more specifically the monitoring of such plasma processes. One aspect relates in at least some manner to calibrating or initializing a plasma monitoring assembly. This type of calibration may be used to address wavelength shifts, intensity shifts, or both associated with optical emissions data obtained on a plasma process. A calibration light may be directed at a window through which optical emissions data is being obtained to determine the effect, if any, that the inner surface of the window is having on the optical emissions data being obtained therethrough, the operation of the optical emissions data gathering device, or both. Another aspect relates in at least some manner to various types of evaluations which may be undertaken of a plasma process which was run, and more typically one which is currently being run, within the processing chamber. Plasma health evaluations and process identification through optical emissions analysis are included in this aspect. Yet another aspect associated with the present invention relates in at least some manner to the endpoint of a plasma process (e.g., plasma recipe, plasma clean, conditioning wafer operation) or discrete/discernible portion thereof (e.g., a plasma step of a multiple step plasma recipe). A final aspect associated with the present invention relates to how one or more of the above-noted aspects may be implemented into a semiconductor fabrication facility, such as the distribution of wafers to a wafer production system.

Claims

1. A method for monitoring a plasma process comprising the steps of:

initializing a plasma monitoring assembly which obtains optical emissions of plasma in a processing chamber during said plasma process, said optical emissions including at least wavelengths from about 250 nanometers to about 1,000 nanometers, which defines a first wavelength range, at least at every 1 nanometer throughout said first wavelength range, said processing chamber comprising a window and said plasma monitoring assembly being operatively interfaced with said window, said initializing step comprising the steps of;

directing a calibration light toward said window, said calibration light comprising a second wavelength range;

reflecting a first portion of said calibration light from said window;

comparing said calibration light from said directing step with said first portion of said calibration light from said reflecting step across said second wavelength range; and

making at least one adjustment in relation to said plasma monitoring assembly when said comparing step yields at least a first result.

2. A method, as claimed in claim 1, wherein:

said second wavelength range is at least substantially equal to said first wavelength range.

3. A method, as claimed in claim 1, wherein said window comprises inner and outer surfaces, wherein said inner surface is exposed to said plasma in said processing chamber, wherein said outer surface is isolated from said plasma in said processing chamber, and wherein:

said reflecting step comprises reflecting said first portion of said calibration light from said inner surface of said window.

4. A method, as claimed in claim 1, wherein said calibration light from said directing step has a first pattern and wherein said first portion of said calibration light from said reflecting step has a second pattern, and wherein said comparing step comprises:

noting any differences in said second pattern in relation to said first pattern.

5. A method, as claimed in claim 1, wherein:

said comparing step comprises determining if there is one of a first and second type of intensity shift between said calibration light from said directing step and said first portion of said calibration light from said reflecting step anywhere within said second wavelength range, said first and second types of intensity shifts being different and comprising said first result.

6. A method, as claimed in claim 5, wherein:

said making at least one adjustment step comprises accounting for any said first type of intensity shift identified by said comparing step by said plasma monitoring assembly implementing a single calibration factor.

7. A method, as claimed in claim 6, wherein:

said accounting step comprises applying said single calibration factor to data representative of said optical emissions.

8. A method, as claimed in claim 5, wherein:

said making at least one adjustment step comprises accounting for any said second type of intensity shift identified by said comparing step by said plasma monitoring assembly implementing a plurality of calibration factors.

9. A method, as claimed in claim 8, wherein:

said accounting step comprises applying each of said plurality of calibration factors to data representative of different portions of said optical emissions.

10. A method, as claimed in claim 9, wherein:

a first of said plurality of calibration factors is applied to data representative of said optical emissions within a first wavelength region which is within said first wavelength range, and wherein a second of said plurality of calibration factors is applied to data representative of said optical emissions within a second wavelength region which is both within said first wavelength range and outside of said first wavelength region.

11. A method, as claimed in claim 5, wherein:

said making at least one adjustment step comprises accounting for any said second type of intensity shift identified by said comparing step through normalizing data representative of said optical emissions.

12. A method, as claimed in claim 1, wherein:

said comparing step comprises performing a first determining step comprising determining if said window is filtering out said optical emissions within a first wavelength region which is within said first wavelength range.

13. A method, as claimed in claim 12, wherein said making at least one adjustment step comprises:

having said plasma monitoring assembly ignore data representative of said optical emissions within said first wavelength region if said filtering is identified by said performing a first determining step.

14. A method, as claimed in claim 12, wherein said comparing step further comprises the step of:

identifying a plurality of intensity peaks in said calibration light from said directing step; and

performing a second determining step comprising determining when any of said peaks from said identifying step are at least substantially absent in said first portion of said calibration light from said reflecting step and which defines said first wavelength region.

15. A method, as claimed in claim 12, further comprising the step of:

recommending that said window be replaced if said filtering is identified by said performing a first determining step.

16. A method, as claimed in claim 1, wherein:

said comparing step comprises determining if there is at least one of an intensity shift and a wavelength shift between said calibration light from said directing step and said first portion of said calibration light from said reflecting step.

17. A method, as claimed in claim 16, wherein said plasma monitoring assembly comprises a first spectrometer and wherein said determining step comprises:

identifying an intensity shift in said optical emissions which is caused by said window, said identifying step using said comparing step, wherein said making at least one adjustment step comprises adjusting an output of said first spectrometer based upon said intensity shift being identified by said identifying step.

18. A method, as claimed in claim 16, wherein said plasma monitoring assembly comprises a first spectrometer and wherein said determining step comprises:

identifying a wavelength shift of at least about 0.25 nanometers in said optical emissions which is caused by said first spectrometer, said identifying step using said comparing step, wherein said making at least one adjustment step comprises adjusting at least one of an output of said first spectrometer and at least one component of said first spectrometer based said wavelength shift being identified by said identifying step.

19. A method, as claimed in claim 1, further comprising the steps of:

introducing said plasma into said processing chamber;

conducting said plasma process in said processing chamber;

monitoring said optical emissions of said plasma in said processing chamber at least within said first wavelength range throughout at least substantially an entirety of said conducting step and at least at every 1 nanometer throughout said first wavelength range;

obtaining output from said monitoring step from a plurality of different times during said conducting step;

comparing said output at each of said plurality of different times with a first output, wherein said comparing said output step is executed after said comparing said calibration light step and any corresponding said making at least one adjustment step.

20. A method, as claimed in claim 19, wherein:

each said output has an associated output pattern and said first output comprises a plurality of first output patterns, wherein said comparing said output step comprises comparing each said output pattern with at least one of said first output patterns.

21. A method, as claimed in claim 19, wherein:

said first output of said comparing said output step comprises at least one of said outputs from an earlier of said plurality of different times from said obtaining step.

22. A method, as claimed in claim 21, wherein:

said first output of said comparing said output step is said output at an immediately preceding time from said obtaining step.

23. A method, as claimed in claim 19, wherein:

said first output of said comparing said output step was obtained from a previous execution of said conducting step in said processing chamber.

24. A method, as claimed in claim 1, wherein said window comprises an inner surface which is exposed to a plasma process conducted within said chamber and an outer surface which is isolated from said plasma process, and wherein:

said directing step comprises directing a first calibration light toward said window from a location which is exterior of said processing chamber and directing a second calibration light toward said window from a location which is exterior of said processing chamber, said second calibration light being different from said first calibration light, wherein at least one of said first and second calibration lights comprises said second wavelength range;

said reflecting step comprises reflecting a first portion of said first calibration light from said inner surface said window and reflecting a first portion of said second calibration light from said inner surface said window; and

said comparing step comprises comparing said first calibration light from said directing a first calibration light step with said first portion of said first calibration light from said reflecting a first portion of said first calibration light step, and comparing said second calibration light from said directing a second calibration light step with said first portion of said second calibration light from said reflecting a first portion of said second calibration light step.

25. A method, as claimed in claim 24, wherein:

said directing a first calibration light step, said reflecting a first portion of said first calibration light step, and said comparing said first calibration light step collectively comprise a performing a first calibrating step, said performing a first calibrating step accounting for a wavelength shift associated with said plasma monitoring assembly; and

said directing a second calibration light step, said reflecting a first portion of said second calibration light step, and said comparing said second calibration light step collectively comprise a performing a second calibrating step, said performing a second calibrating step accounting for an intensity shift associated with said plasma monitoring assembly.

26. A method, as claimed in claim 25, wherein:

said first calibration light comprises a plurality of discrete intensity peaks and wherein said second calibration light comprises a continuum of intensity.

27. A method, as claimed in claim 25, wherein:

said performing a first calibrating step and said performing a second calibrating step are executed at different and non-overlapping times.

28. A method, as claimed in claim 24, wherein:

said first calibration light comprises a plurality of discrete intensity peaks and wherein said second calibration light comprises a continuum of intensity; and

said performing a first calibrating step and said performing a second calibrating step are executed at different and non-overlapping times.