Method and apparatus for monitoring plasma processing operations

• US 6,165,312 A
• Filed: 04/23/1998
• Issued: 12/26/2000
• 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): Stinson, Frankie L.
• Assistant Examiner(s): WILKINS, YOLANDA E
• Application Number:
  US09/064,966
• Time in Patent Office: 978 Days
• Field of Search: 204/298.3, 204/298.32, 204/192.13, 204/192.33, 156/345, 216/59, 216/60, 438/7, 438/9, 438/8, 438/14
• US Class Current: 156/345.24
• 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 a first plasma step and a second plasma step, said method comprising the steps of:

loading a quantity of product into a processing chamber;

exposing said product in said processing chamber to a plasma;

obtaining data on optical emissions of said plasma in said processing chamber at least within a first wavelength range extending from about 250 nanometers to about 1,000 nanometers, at least at every 1 nanometer throughout said first wavelength range, and at least at every 1 second during at least a substantial portion of said exposing step;

selecting any first optical emissions endpoint indicator within said first wavelength range;

selecting any second optical emissions endpoint indicator within said first wavelength range;

performing said first plasma step on said product, wherein there is a first endpoint of said first plasma step which is when said first plasma step has produced a first predetermined result on said product, wherein said first optical emissions endpoint indicator comprises optical emissions at a first wavelength which is within said first wavelength range and which undergoes a change over time during said performing said first plasma step which is indicative of said first endpoint;

monitoring said first optical emissions endpoint indicator during at least a portion of said performing said first plasma step to identify an occurrence of said first endpoint;

performing said second plasma step on said product, wherein there is a second endpoint of said second plasma step which is when said second plasma step has produced a second predetermined result on said product, wherein said second predetermined result is different from said first predetermined result, wherein said second optical emissions endpoint indicator comprises optical emissions at a second wavelength which is within said second wavelength range and which undergoes a change over time during said performing said second plasma step which is indicative of said second endpoint; and

monitoring said second optical emissions endpoint indicator during at least a portion of said performing said second plasma step to identify an occurrence of said second endpoint, wherein said monitoring said first and second optical emissions endpoint indicator steps are each executed without requiring identification of any species within said plasma.

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

said quantity of product comprises at least one wafer.

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

said monitoring said first optical emissions endpoint indicator step is initiated in an intermediate portion of said performing said first plasma step and said monitoring said second optical emissions endpoint indicator step is initiated in an intermediate portion of said performing said second plasma step.

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

said evaluating step is executed after expiration of every first time period and each of said monitoring said first optical emissions endpoint indicator step and said monitoring said second optical emissions endpoint indicator step are executed after expiration of every second time period, said first time period being longer than said second time period.

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

said monitoring said first optical emissions endpoint indicator step comprises;

comparing a pattern of said first optical emissions endpoint indicator at a current time in said performing said first plasma step to a pattern of said first optical emissions indicator from an earlier time in said performing said first plasma step; and

determining when said pattern of said first optical emissions endpoint indicator from said current time of said performing said first plasma step is a match with said pattern of said first optical emissions indicator from said earlier time in said performing said first plasma step and equating this with said first endpoint; and

said monitoring said second optical emissions endpoint indicator step comprises;

comparing a pattern of said second optical emissions endpoint indicator at a current time in said performing said second plasma step to a pattern of said second optical emissions endpoint indicator from an earlier time in said performing said second plasma step; and

determining when said pattern of said second optical emissions endpoint indicator from said current time of said performing said second plasma step is a match with said pattern of said second optical emissions endpoint indicator from said earlier time in said performing said second plasma step and equating this with said second endpoint.

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

said comparing a pattern of said first optical emissions endpoint indicator step comprises comparing said pattern of said first optical emissions endpoint indicator at a first time in said performing said first plasma step with said pattern of said first optical emissions endpoint indicator from an immediately preceding time in said performing said first plasma step; and

said comparing a pattern of said second optical emissions endpoint indicator step comprises comparing said pattern of said second optical emissions endpoint indicator at a first time in said performing said second plasma step with said pattern of said second optical emissions endpoint indicator from an immediately preceding time in said performing said second plasma step.

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

said monitoring said first optical emissions endpoint indicator step and said monitoring said second optical emissions endpoint indicator step each comprise using a pattern recognition technique.

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

said monitoring said first optical emissions endpoint indicator step comprises;

comparing a pattern of said first optical emissions endpoint indicator at a current time in said performing said first plasma step to a pattern of said first optical emissions endpoint indicator from a previous execution of said performing said first plasma step which has been equated with said first endpoint; and

determining when said pattern of said first optical emissions endpoint indicator from said current time of said performing said first plasma step is a match with said pattern of said first optical emissions endpoint indicator from said previous execution of said performing said first plasma step and equating this with said first endpoint; and

said monitoring said second optical emissions endpoint indicator step comprises;

comparing a pattern of said second optical emissions endpoint indicator at a current time in said performing said second plasma step to a pattern of said second optical emissions endpoint indicator from a previous execution of said performing said second plasma step which has been equated with said second endpoint; and

determining when said pattern of said second optical emissions endpoint indicator from said current time of said performing said second plasma step is a match with said pattern of said second optical emissions endpoint indicator from said previous execution of said performing said second plasma step and equating this with said second endpoint.

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

said pattern of said first optical emissions endpoint indicator from said previous execution is different from said pattern of said second optical emissions endpoint indicator from said previous execution, wherein said pattern of said first optical emissions endpoint indicator from said previous execution further was obtained from said previous execution of the same said performing said first plasma step on the same type of said product in the same said processing chamber, and wherein said pattern of said second optical emissions endpoint indicator from said previous execution further was obtained from said previous execution of the same said performing said second plasma step on the same type of said product in the same said processing chamber.

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

said pattern of said first optical emissions endpoint indicator from said previous execution of said performing said first plasma step which has been equated with said first endpoint and said pattern of said second optical emissions endpoint indicator from said previous execution of said performing said second plasma step which has been equated with said second endpoint are each stored on a computer-readable medium.

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

said monitoring said first optical emissions endpoint indicator step comprises using at least two different techniques, wherein said first endpoint is identifiable by at least one of said at least two different techniques; and

said monitoring said second optical emissions indicator step comprises using at least two different techniques, wherein said second endpoint is also identifiable by at least one of said at least two different techniques associated with said second endpoint.

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

one of said at least two different techniques associated with said first endpoint is determining when there is at least a first change in an impedance of said processing chamber through identifying a modal change in at least a portion of said optical emissions from said obtaining step; and

one of said at least two different techniques associated with said second endpoint is determining when there is at least a first change in an impedance of said processing chamber through identifying a modal change in at least a portion of said optical emissions from said obtaining step.

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

said monitoring said first optical emissions endpoint indicator step comprises determining if there is at least a first change in an impedance of said processing chamber and equating this with said first endpoint; and

said monitoring said second optical emissions endpoint indicator step comprises determining if there is at least a second change in an impedance of said processing chamber and equating this with said second endpoint.

14. A method, as claimed in claim 13, wherein:

said first and second changes in said impedance are both identified through identifying a modal change in at least a portion of said optical emissions from said obtaining step.

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

said monitoring said first optical emissions endpoint indicator step comprises evaluating at least one individual first wavelength of said plasma in said processing chamber; and

said monitoring said second optical emissions endpoint indicator comprises evaluating at least one individual second wavelength of said plasma in said processing chamber.

16. A method, as claimed in claim 15, wherein:

said monitoring said first optical emissions endpoint indicator step comprises using a technique selected from the group consisting of determining when a plot of intensity versus time of said at least one individual first wavelength deviates by more than a predetermined amount from a predetermined equation, determining when a time rate of change of a slope of said plot of intensity versus time of said at least one individual first wavelength deviates by more than a predetermined amount, and combinations thereof; and

said monitoring said second optical emissions endpoint indicator step comprises using a technique selected from the group consisting of determining when a plot of intensity versus time of said at least one individual second wavelength deviates by more than a predetermined amount from a predetermined equation, determining when a time rate of change of a slope of said plot of intensity versus time of said at least one individual second wavelength deviates by more than a predetermined amount, and combinations thereof.

17. A method, as claimed in claim 15, wherein:

said monitoring said first optical emissions endpoint indicator step comprises using a technique selected from the group consisting of determining when a plot of intensity versus time of said at least one individual first wavelength deviates by more than a predetermined amount from a first predetermined function, determining when an output of a first derivative of said first predetermined function deviates by more than a predetermined amount, determining when an output of a second derivative of said first predetermined function deviates by more than a predetermined amount, and combinations thereof; and

said monitoring said second optical emissions indicator step comprises using a technique selected from the group consisting of determining when a plot of intensity versus time of said at least one individual second wavelength deviates by more than a predetermined amount from a second predetermined function, determining when an output of a first derivative of said second predetermined function deviates by more than a predetermined amount, determining when an output of a second derivative of said second predetermined function deviates by more than a predetermined amount, and combinations thereof.

18. A method, as claimed in claim 15 wherein:

said at least one individual first and second wavelengths are different.

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

evaluating a condition of said plasma in said processing chamber during said performing said first and second plasma steps and using at least a portion of said optical emissions from said obtaining step, wherein said condition is a cumulative result of all parameters having an effect on said plasma in said processing chamber, and wherein said evaluating a condition step provides a different function from each of said monitoring said first and second optical emissions endpoint indicator steps.

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

said evaluating step comprises comparing a pattern of said optical emissions from said obtaining step with a pattern of optical emissions within said first wavelength range from a previous execution of said performing said first and second plasma steps.

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

said monitoring said first and second optical emissions endpoint indicator steps are each executed without identifying any species within said plasma.

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

said monitoring said first optical emissions endpoint indicator step comprises analyzing said first optical emissions endpoint indicator a plurality of times, wherein each execution of said analyzing said first optical emissions endpoint indicator step is completed in no more than about 1 second; and

said monitoring said second optical emissions endpoint indicator step comprises analyzing said second optical emissions endpoint indicator a plurality of times, wherein each execution of said analyzing said second optical emissions endpoint indicator step is completed in no more than about 1 second.

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

said obtaining step comprises obtaining first data on said optical emissions at a first time in said exposing step, wherein a total amount of time which lapses from a start of said obtaining first data step and said monitoring said first optical emissions endpoint indicator step for said first data is no more than about 1 second.