Method and system for analyzing plasma data

• US 5,546,322 A
• Filed: 04/12/1994
• Issued: 08/13/1996
• Est. Priority Date: 04/12/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Osborn, Brock E., Gifford, George G.
• Primary Examiner(s): Trammell, James P.
• Application Number:
  US08/226,781
• Time in Patent Office: 854 Days
• Field of Search: 364/468, 364/498, 364/550, 364/497, 364/571.01-571.08, 156/626.1, 156/643, 156/345, 204/192.33, 204/192.32, 356/319, 356/301, 356/325, 356/326, 250/281
• US Class Current: 702/32
• CPC Class Codes: G01N 21/71 thermally excited
• CPC Class Codes: H05H 1/0037 by spectrometry

Abstract

Analysis of plasma data indicative of gaseous species therein, such as Optical Emission Spectroscopy (OES) data, is aided through the interactive use of a computer. OES data may be calibrated by the computer with minimal input from the user regarding a gas the user knows or suspects is present. The computer then assumes the presence of that gas and assigns relative intensity peaks to known wavelengths for that gas, allowing calibration to take place. Selective identification of particular gases from the data is also possible. Used in conjunction with selective identification, a learning function allows the system to improve the accuracy of future gaseous species identification. Certain characteristics of a particular gas over time, such as intensity at a particular wavelength or at all wavelengths, may also be automatically plotted.

Claims

1. A method for analyzing data derived from a plasma including a plurality of gaseous species, said method comprising:

inputting said data into a computer;

indicating to said computer a gaseous specie to be assumed present in said plasma;

automatically calibrating via said computer said data based on said indicated gaseous specie; and

identifying at least one of said plurality of gaseous species.

2. The method of claim 1 wherein said step of identifying is automatically performed by said computer in response to appropriate input.

3. The method of claim 1, wherein said computer includes a display, said method further comprising:

automatically displaying said data; and

automatically displaying said automatically calibrated data.

4. The method of claim 3, wherein each of said data and said automatically calibrated data include relative intensity data and corresponding electromagnetic wavelength data and wherein each said step of automatically displaying comprises plotting said relative intensity data against said corresponding electromagnetic wavelength data.

5. The method of claim 4 wherein said step of automatically calibrating comprises creating a scale for said corresponding electromagnetic wavelength data.

6. The method of claim 5 wherein said step of creating comprises incorporating linear regression.

7. The method of claim 4, wherein said step of plotting comprises creating a plot and wherein said method further comprises creating an exploded view of a portion of said plot.

8. The method of claim 1 wherein said step of indicating comprises indicating to said computer said gaseous specie to be assumed present in response to a prompt therefor from said computer.

9. The method of claim 1, wherein said data includes relative intensity data and wherein said step of indicating comprises indicating to said computer a gaseous specie expected to have high relative intensity data in comparison to the other of said relative intensity data corresponding to the other of said plurality of gaseous species.

10. The method of claim 1, wherein said computer includes a memory storing known plasma data for a predetermined plurality of gaseous species and wherein said step of automatically calibrating comprises correlating said data to said known plasma data for said indicated gaseous specie.

11. The method of claim 10, wherein said data includes a plurality of sets of data and wherein said step of correlating comprises correlating a predetermined number of said plurality of sets of data to said known plasma data for said indicated gaseous specie.

12. The method of claim 2 wherein said step of identifying comprises automatically identifying via said computer said plurality of gaseous species.

13. The method of claim 12 further comprising automatically determining via said computer a configuration for said identified plurality of gaseous species.

14. The method of claim 13 further comprising automatically determining via said computer a probability that a given gaseous species in said configuration is actually present.

15. The method of claim 14 further comprising automatically determining via said computer a confidence interval for said probability.

16. The method of claim 1, wherein said data includes a plurality of sets of data and wherein said step of identifying comprises associating a predetermined number of peak sets of data with said at least one of said plurality of gaseous species.

17. The method of claim 1, wherein said data includes optical emission spectroscopy data, said optical emission spectroscopy data including relative intensity data and corresponding visible light wavelength data, and wherein said step of inputting said data comprises inputting said relative intensity data and said corresponding visible light wavelength data.

18. The method of claim 1 further comprising indicating to said computer at least one gaseous specie to be identified, wherein said step of identifying comprises automatically identifying via said computer said at least one gaseous specie.

19. The method of claim 18, wherein said step of automatically identifying comprises automatically identifying via said computer said at least one gaseous specie based on assumed parameters, said method further comprising modifying said assumed parameters based on results of said step of identifying such that a subsequent result of said step of automatically identifying is improved.

20. The method of claim 19, wherein said computer includes a memory storing for each of a predetermined plurality of gaseous species a plurality of sets of known plasma data, each of said plurality of sets of known plasma data including a known relative intensity value and a corresponding known electromagnetic wavelength, wherein said data includes a plurality of sets of data, each of said plurality of sets of data including a raw relative intensity value and a corresponding raw electromagnetic wavelength, and wherein said step of automatically identifying comprises:

(a) determining whether a given known electromagnetic wavelength is within a range of electromagnetic wavelengths present in said plurality of sets of data;

(b) modifying a relative probability that said given known electromagnetic wavelength will be present in said plurality of sets of data if said given known electromagnetic wavelength is determined in step (a) to be within said range, wherein said relative probability includes a numerator and a denominator;

(c) determining whether said given known electromagnetic wavelength has previously been associated with a given raw relative intensity value in said plurality of sets of data corresponding to said at least one gaseous specie to be identified if said relative probability has been modified in step (b);

(d) modifying said numerator if said given known electromagnetic wavelength is determined in step (c) to have previously been associated with said given raw relative intensity value;

(e) determining whether said denominator is greater than a predetermined number indicating insufficient information to modify a raw relative intensity value associated with said at least one gaseous specie to be identified; and

(f) modifying said raw relative intensity value of step (e) if said denominator is determined in step (e) to be greater than said predetermined number.

21. The method of claim 20 wherein step (f) comprises modifying said raw relative intensity value F according to the following equation:

space="preserve" listing-type="equation">F=(p2-0.5244)/0. 018847,

wherein

p2=log_c ((p1×

1.10825)/(1-p1)),

p1=n/d,

n=said numerator, and

d=said denominator.

22. The method of claim 20 wherein said at least one gaseous specie to be identified includes at least two gaseous species, said method further comprising:

(g) repeating steps (a) through (f) for each of said at least two gaseous species.

23. The method of claim 1 further comprising determining a change in a characteristic of said at least one of said plurality of gaseous species over time.

24. A method for identifying gaseous species in a plasma, comprising:

performing a plasma process, wherein a plasma comprising a plurality of gaseous species is created;

obtaining data from said plasma process;

inputting said data into a computer;

indicating to said computer a gaseous specie to be assumed present in said plurality of gaseous species;

automatically calibrating via said computer said data based on said indicated gaseous specie; and

identifying at least one of said plurality of gaseous species.

25. The method of claim 24, wherein said plasma process is performed based on a plurality of plasma process parameters, said method further comprising:

altering at least one of said plasma process parameters based on said step of identifying; and

performing said plasma process based on said altered at least one plasma process parameter.

26. The method of claim 24 further comprising indicating to said computer at least one gaseous species to be identified, wherein said step of identifying comprises identifying said at least one gaseous species.

27. The method of claim 26, wherein said step of identifying comprises identifying said at least one gaseous species based on assumed parameters, said method further comprising modifying said assumed parameters based on results of said step of identifying such that a subsequent result of said step of identifying is improved.

28. The method of claim 24 further comprising determining a change in a characteristic of said at least one of said plurality of gaseous species over time.

29. A system for assisting an analyst with analyzing data derived from a plasma including a plurality of gaseous species, said system comprising:

a computer;

means for inputting said data into said computer;

means for indicating to said computer a gaseous specie to be assumed present in said plurality of gaseous species;

means for automatically calibrating said data based on said indicated gaseous specie; and

means for automatically identifying at least one of said plurality of gaseous species.

30. The system of claim 29 further comprising means for displaying said data and said calibrated data.

31. The system of claim 30 wherein said displaying means comprises means for graphically displaying said data and said calibrated data.

32. The system of claim 29 further comprising means for prompting said analyst for said gaseous specie to be assumed present.

33. The system of claim 29 further comprising a memory for storing known plasma data for a predetermined plurality of gaseous species.

34. The system of claim 33 wherein said automatic calibration means comprises means for correlating said data to said known plasma data.

35. The system of claim 34 further comprising means for determining a probability that a given identified gaseous specie is actually present.

36. The system of claim 29 wherein said automatic identification means comprises means for selectively identifying at least one gaseous specie.

37. The system of claim 36 further comprising means for improving automatic identification of said at least one gaseous specie based on past automatic identifications.

38. The system of claim 29 further comprising means for determining a change in a characteristic of said at least one of said plurality of gaseous species over time.

39. A method for analyzing data derived from a plasma including a plurality of gaseous species, said data including wavelength data and at least one data peak, said method comprising:

inputting said data into a computer;

indicating to said computer one of a gaseous specie and a wavelength to be associated with said at least one data peak;

automatically calibrating via said computer said data based on said indicated one of a gaseous specie and a wavelength; and

identifying at least one of said plurality of gaseous species.