Method and apparatus for monitoring plasma processing operations

• US 6,134,005 A
• Filed: 04/23/1998
• Issued: 10/17/2000
• 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 O'Don
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US09/064,793
• Time in Patent Office: 908 Days
• Field of Search: 356/346, 356/437, 356/445, 356/369, 356/382
• US Class Current: 356/369
• 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 plasma processing system, comprising:

a processing chamber comprising a window, 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;

a plasma generator in said processing chamber, wherein said plasma process may be run in said processing chamber when said plasma generator is activated;

a first spectrometer assembly disposed outside of said processing chamber;

a first fiber optic cable assembly operatively interconnecting said first spectrometer assembly and said window;

a calibration light source disposed outside of said processing chamber and comprising a calibration light;

a second fiber optic cable assembly operatively interconnecting said calibration light source and said window; and

a comparator operatively interconnected with said first spectrometer assembly, wherein a first input to said comparator is data relating said calibration light sent to said window by said calibration light source through said second fiber optic cable assembly and wherein a second input to said comparator is data relating to a first portion of said calibration light reflected by said inner surface of said window and provided to said first spectrometer assembly through said first fiber optic cable assembly.

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

said first spectrometer assembly is selected from the group consisting of at least one scanning-type spectrometer and at least one solid state spectrometer.

3. A system, as claimed in claim 1, wherein:

said first spectrometer assembly comprises a plurality of spectrometers, wherein each said spectrometer covers a different wavelength region.

4. A system, as claimed in claim 1, wherein:

said window comprises a first location and a second location which is spaced from said first location, wherein a thickness of said window varies progressing from said first location to said second location to limit that portion of said calibration light, which is reflected by said window and collected by said first fiber optic cable assembly for use by said first spectrometer assembly and said comparator, to said first portion of said calibration light.

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

a first end of each of said first and second fiber optic cable assemblies are coaxially disposed, wherein said inner surface of said window is disposed at least substantially perpendicular to an axis of light leaving and entering said first end of said second and first fiber optic cable assemblies, respectively, and wherein said outer surface of said window is disposed at an angle other than perpendicular relative to said axis of light leaving and entering said first end of said second and first fiber optic cable assemblies, respectively, both of which limits that portion of said calibration light, which is reflected by said window and collected by said first fiber optic cable assembly for use by said first spectrometer assembly and said comparator, to said first portion of said calibration light.

6. A system, as claimed in claim 1, wherein:

said inner and outer surfaces of said window are disposed other than in parallel relation to limit that portion of said calibration light, which is reflected by said window and collected by said first fiber optic cable assembly for use by said first spectrometer assembly and said comparator, to said first portion of said calibration light.

7. A system, as claimed in claim 1, wherein:

said window is at least generally wedge-shaped.

8. A system, as claimed in claim 1, wherein:

a first end of said second fiber optic cable assembly directed toward said window is coaxially disposed with a first end of said first fiber optic cable assembly directed toward said window to receive said first portion of said calibration light reflected by said inner surface of said window.

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

said inner and outer surfaces of said window are disposed other than in parallel relation, and wherein said system further comprises;

means for maintaining said first end of each of said first and second fiber optic cable assemblies in a fixed positional relationship relative to said window whereby;

said calibration light from said calibration light source directed through said second fiber optic cable assembly impacts said outer surface of said window at an angle other than perpendicular relative to said outer surface to direct at least substantially all portions of said calibration light reflected by said outer surface of said window away from said first fiber optic cable assembly, and further whereby a portion of said calibration light from said calibration light source which impacts said inner surface of said window does so at least substantially perpendicular to said inner surface of said window to direct said first portion of said calibration light reflected by said inner surface of said window into said first fiber optic cable assembly for provision to said first spectrometer assembly for use by said comparator.

10. A system, as claimed in claim 1, wherein:

an axis of light leaving said second fiber optic cable assembly impacts said inner surface of said window at a first acute angle relative to said inner surface, and wherein an end of said first fiber optic cable assembly is disposed so as to collect said first portion of said calibration light reflected by said inner surface, whereby an end of said second fiber optic cable assembly which directs said calibration light toward said window is disposed on an opposite side of a reference plane which intersects said window than said end of said first fiber optic cable assembly which receives said first portion of said calibration light reflected by said window.

11. A system, as claimed in claim 1, wherein:

said comparator comprises means for comparing a pattern of said calibration light sent to said window with a pattern of said first portion of said calibration light reflected by said inner surface of said window.

12. A system, as claimed in claim 1, further comprising:

a plasma monitoring assembly operatively interconnected with said window and comprising said first spectrometer assembly; and

means for making at least one adjustment in relation to said plasma monitoring assembly based upon an output from said comparator.

13. A system, as claimed in claim 1, wherein:

at least a portion of said outer surface of said window comprises an anti-reflective coating aligned with said second fiber optic cable assembly.

14. A system, as claimed in claim 1, wherein:

said calibration light source comprises a first calibration light source and a second calibration light source, said first calibration light source being of a different type of light than said second calibration light source.

15. A system, as claimed in claim 14, wherein:

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

16. A system, as claimed in claim 14, wherein:

said first calibration light source is used to identify a wavelength shift and said second calibration light source is used to identify an intensity shift.

17. A system, as claimed in claim 1, further comprising:

a fiber optic cable fixture assembly, wherein said fixture assembly comprises a recessed region which interfaces with at least a portion of said outer surface of said window and a first port which extends through said fixture assembly to intersect with said recessed region, wherein at least a portion of said fixture assembly which defines said recessed region comprises a light absorbing material, wherein first ends of said first and second fiber optic cable assemblies are attached to said fixture assembly in axial alignment with said first port, and wherein a reference axis projecting from said first ends of said first and second fiber optic cable assemblies toward said window each intersect said outer surface of said window at an angle other than perpendicular and each intersect said inner surface of said window at least at a substantially perpendicular angle.

18. A system, as claimed in claim 17, wherein:

said first ends of said first and second fiber optic cable assemblies are coaxially disposed and threadably interconnected with said fixture assembly.

19. A plasma processing system, comprising:

a processing chamber comprising a window, 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;

a plasma generator in said processing chamber, wherein said plasma process may be run in said processing chamber when said plasma generator is activated;

a first spectrometer assembly disposed outside of said processing chamber;

a first fiber optic cable assembly operatively interconnecting said first spectrometer assembly and said window;

a calibration light source disposed outside of said processing chamber and comprising a calibration light; and

a second fiber optic cable operatively interconnecting said calibration light source and said window, wherein said inner and outer surfaces of said window on said processing chamber are disposed other than in parallel relation to reduce interference between portions of said calibration light reflected by said inner and outer surfaces, respectively.

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

said first spectrometer assembly is selected from the group consisting of at least one scanning-type spectrometer and at least one solid state spectrometer.

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

said first spectrometer assembly comprises a plurality of spectrometers, wherein each said spectrometer covers a different wavelength region.

22. A system, as claimed in claim 19, wherein:

said window comprises a first location and a second location which is spaced from said first location, wherein a thickness of said window varies progressing from said first location to said second location to limit that portion of said calibration light, which is reflected by said window and collected by said first fiber optic cable assembly for use by said first spectrometer assembly, to a portion of said calibration light which is reflected by said inner surface of said window.

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

a first end of each of said first and second fiber optic cable assemblies are coaxially disposed, wherein said inner surface of said window is disposed at least substantially perpendicular to an axis of light leaving and entering said first end of said second and first fiber optic cable assemblies, respectively, and wherein said outer surface of said window is disposed at an angle other than perpendicular relative to said axis of light leaving and entering said first end of said second and first fiber optic cable assemblies, respectively, both of which limits that portion of said calibration light, which is reflected by said window and collected by said first fiber optic cable assembly for use by said first spectrometer assembly, to a portion of said calibration light reflected by said inner surface of said window.

24. A system, as claimed in claim 19, wherein:

said window is at least generally wedge-shaped.

25. A system, as claimed in claim 19, wherein:

a first end of said second fiber optic cable assembly directed toward said window is coaxially disposed with a first end of said first fiber optic cable assembly directed toward said window to receive a portion of said calibration light reflected by said inner surface of said window.

26. A system, as claimed in claim 25, further comprising:

means for maintaining said first end of each of said first and second fiber optic cable assemblies in a fixed positional relationship relative to said window whereby;

said calibration light from said calibration light source directed through said second fiber optic cable assembly impacts said outer surface of said window at an angle other than perpendicular relative to said outer surface to direct at least substantially all portions of said calibration light reflected by said outer surface of said window away from said first fiber optic cable assembly, and further whereby a portion of said calibration light from said calibration light source which impacts said inner surface of said window does so at least substantially perpendicular to said inner surface of said window to direct at least a portion of said calibration light reflected by said inner surface of said window into said first fiber optic cable assembly for provision to said first spectrometer assembly.

27. A system, as claimed in claim 19, wherein:

an axis of light leaving said second fiber optic cable assembly impacts said inner surface of said window at a first acute angle relative to said inner surface, and wherein an end of said first fiber optic cable assembly is disposed so as to collect at least a portion of said calibration light reflected by said inner surface, whereby an end of said second fiber optic cable assembly which directs said calibration light toward said window is disposed on an opposite side of a reference plane which intersects said window than said end of said first fiber optic cable assembly which receives said at least a portion of said calibration light reflected by said inner surface of said window.

28. A system, as claimed in claim 19, further comprising:

a comparator operatively interconnected with said first spectrometer assembly, wherein a first input to said comparator is data relating said calibration light sent to said window by said calibration light source through said second fiber optic cable assembly and wherein a second input to said comparator is data relating to a first portion of said calibration light reflected by said inner surface of said window and provided to said first spectrometer assembly through said first fiber optic cable assembly.

29. A system, as claimed in claim 28, wherein:

said comparator comprises means for comparing a pattern of said calibration light sent to said window with a pattern of said first portion of said calibration light reflected by said inner surface of said window.

30. A system, as claimed in claim 28, further comprising:

a plasma monitoring assembly operatively interconnected with said window and comprising said first spectrometer assembly; and

means for making at least one adjustment in relation to said plasma monitoring assembly based upon an output from said comparator.

31. A system, as claimed in claim 19, wherein:

at least a portion of said outer surface of said window comprises an anti-reflective coating aligned with said second fiber optic cable assembly through which said calibration light exits said second fiber optic cable assembly.

32. A system, as claimed in claim 19, wherein:

said calibration light source comprises a first calibration light source and a second calibration light source, said first calibration light source being of a different type of light than said second calibration light source.

33. A system, as claimed in claim 32, wherein:

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

34. A system, as claimed in claim 32, wherein:

said first calibration light source is used to identify a wavelength shift and said second calibration light source is used to identify an intensity shift.

35. A system, as claimed in claim 19, further comprising:

a fiber optic cable fixture assembly, wherein said fixture assembly comprises a recessed region which interfaces with at least a portion of said outer surface of said window and a first port which extends through said fixture assembly to intersect with said recessed region, wherein at least a portion of said fixture assembly which defines said recessed region comprises a light absorbing material, wherein first ends of said first and second fiber optic cable assemblies are attached to said fixture assembly in axial alignment with said first port, and wherein a reference axis projecting from said first ends of said first and second fiber optic cable assemblies toward said window each intersect said outer surface of said window at an angle other than perpendicular and each intersect said inner surface of said window at least at a substantially perpendicular angle.

36. A system, as claimed in claim 35, wherein:

said first ends of said first and second fiber optic cable assemblies are coaxially disposed and threadably interconnected with said fixture assembly.

37. A plasma processing system, comprising:

a processing chamber comprising a window, 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;

means for generating a plasma within said processing chamber to conduct said plasma process within said processing chamber;

means for obtaining optical emissions of said plasma within said chamber which are emitted through said window during said plasma process;

means for evaluating said plasma process through output from said means for obtaining; and

a calibration assembly operatively interconnected with said means for evaluating, wherein said calibration assembly comprises;

means for directing a calibration light to said window;

means for comparing a portion of said calibration light reflected by said window with said calibration light from said means for directing; and

means for limiting said portion of said calibration light used by said means for comparing to a portion of said calibration light from said means for directing which is reflected by said inner surface of said window.

38. A system, as claimed in claim 37, wherein:

said means for obtaining comprises at least one spectrometer.

39. A system, as claimed in claim 37, wherein:

said means for evaluating comprises means for comparing a pattern of said optical emissions from a current said plasma process with a pattern of previous-in-time optical emissions from at least one said plasma process.

40. A system, as claimed in claim 37, wherein:

said means for limiting comprises means for directing said calibration light to said window to impact said outer surface of said window at an angle other than perpendicular relative to said outer surface to direct at least substantially all portions of said calibration light reflected by said outer surface of said window so as to be unavailable for use by said means for comparing, and such that a portion of said calibration light impacts said inner surface of said window to direct at least a portion of said calibration light reflected by said inner surface of said window so as to be available for use by said means for comparing.

41. A system, as claimed in claim 37, wherein:

said means for comparing comprises means for comparing a pattern of said calibration light from said means for directing with a pattern of said portion of said calibration light reflected by said window.

42. A system, as claimed in claim 37, wherein:

said calibration assembly further comprises means for calibrating said means for evaluating for each of first and second conditions, said first condition being a wavelength shift associated with said optical emissions which are used by said means for evaluating, said second condition being an intensity shift associated with said optical emissions which are used by said means for evaluating.

43. A system, as claimed in claim 37, wherein:

said optical emissions associated with said means for obtaining are within a first wavelength range, and wherein said calibration assembly further comprises means for determining if said window is filtering out any said optical emissions which are within a first wavelength region which is contained within said first wavelength range.

44. A system, as claimed in claim 37, wherein:

said optical emissions associated with said means for obtaining are within a first wavelength range, and wherein said calibration assembly further comprises means for determining if said window is having a first dampening effect on a first wavelength region which is within said first wavelength range, as well as a second dampening effect on a second wavelength region which is both within said first wavelength range and outside of said first wavelength region, wherein said first and second dampening effects are different.

45. A system, as claimed in claim 37, wherein:

said means for limiting comprises an anti-reflective coating on at least a portion of said outer surface of said window.

46. A system, as claimed in claim 37, wherein:

said means for directing comprises means for directing first and second calibration lights to said window, said first calibration light being of a different type of light than said second calibration light.

47. A system, as claimed in claim 46, wherein:

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

48. A system, as claimed in claim 47, wherein:

said first calibration light source is used by said calibration assembly to identify a wavelength shift associated with said means for evaluating and said second calibration light source is used by said calibration assembly to identify an intensity shift associated with said means for evaluating.

49. A system, as claimed in claim 37, wherein:

said means for obtaining comprises a first fiber optic cable assembly and said means for calibration assembly comprises a second fiber optic cable assembly, said system further comprising a fiber optic cable fixture assembly, wherein said fixture assembly comprises a recessed region which interfaces with at least a portion of said outer surface of said window and a first port which extends through said fixture assembly to intersect with said recessed region, wherein at least a portion of said fixture assembly which defines said recessed region comprises a light absorbing material, wherein first ends of said first and second fiber optic cable assemblies are attached to said fixture assembly in axial alignment with said first port, and wherein said window is configured and said fixture assembly is disposed relative to said window such that a reference axis projecting from said first ends of said first and second fiber optic cable assemblies toward said window each intersect said outer surface of said window at an angle other than perpendicular and each intersect said inner surface of said window at least at a substantially perpendicular angle.

50. A system, as claimed in claim 49, wherein:

said first ends of said first and second fiber optic cable assemblies are coaxially disposed and threadably interconnected with said fixture assembly.