Method and apparatus for detecting endpoint

• US 7,297,560 B2
• Filed: 10/31/2003
• Issued: 11/20/2007
• Est. Priority Date: 10/31/2002
• Status: Expired due to Fees

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Yue, Hongyu
• Primary Examiner(s): CHEN, KIN CHAN
• Application Number:
  US10/531,468
• Publication Number:
  US 20060037938A1
• Time in Patent Office: 1,481 Days
• Field of Search: 438/8, 438/9, 438/706, 438/710, 438/712, 438/714, 216/60, 216/61
• US Class Current: 438/9
• CPC Class Codes: G01N 21/73 using plasma burners or torches
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring

Abstract

The present invention presents a method for detecting an endpoint of an etch process for etching a substrate in plasma processing system (1) comprising: etching the substrate; measuring at least one endpoint signal; generating at least one filtered endpoint signal by filtering the at least one endpoint signal, wherein the filtering comprises applying a Savitsky Golay filter (12) to the at least one endpoint signal; and determining (14) an endpoint of the etch process from the at least one filtered endpoint signal.

Claims

1. A method for detecting an endpoint of a process in a plasma processing system comprising:

starting said process in a process chamber;

measuring at least two endpoint signals;

generating at least two filtered endpoint signals by applying a Savitsky Golay filter to said at least two endpoint signals; and

determining an endpoint of said process from said at least two filtered endpoint signals,

wherein said at least two filtered endpoint signals comprise a first filtered endpoint signal corresponding to a first chemical constituent found in the process chamber and a second filtered endpoint signal corresponding to a second chemical constituent found in the process chamber,

wherein said endpoint is determined from a ratio signal, said ratio signal generated by a ratio of said first filtered endpoint signal and said second filtered endpoint signal,

wherein the first filtered signal corresponds to a first chemical constituent whose concentration decays during endpoint, and

wherein the second filtered signal corresponds to a second chemical constituent whose concentration rises during endpoint.

2. The method as recited in claim 1, wherein said at least two filtered endpoint signals each comprise a smoothed endpoint signal.

3. The method as recited in claim 1, wherein said at least two filtered endpoint signals comprise at least one of a smoothed first derivative of each of said at least two endpoint signals, and a smoothed second derivative of each of said at least two endpoint signals.

4. The method as recited in claim 1, wherein said ratio comprises an endpoint transition.

5. The method as recited in claim 4, wherein said determining said endpoint from said at least two filtered endpoint signals comprises using at least one of a start time of said endpoint transition, an end time of said endpoint transition, and an inflection time of said endpoint transition.

6. The method as recited in claim 1, wherein said at least two endpoint signals comprise optical signals from said plasma processing system.

7. The method as recited in claim 6, wherein said optical signals are related to a spectral irradiance of emitted light from said plasma processing system.

8. The method as recited in claim 6, wherein said optical signals are measured using an optical diagnostic subsystem, said optical diagnostic subsystem comprising at least one of a detector, an optical filter, a grating, a prism, a monochromator, a spectrometer, a CCD array, and a CID array.

9. The method as recited in claim 1, wherein said endpoint is determined from a differential signal, said differential signal comprising at least one of a first derivative, and a second derivative of said ratio signal.

10. The method as recited in claim 1, wherein said applying said Savitsky Golay filter comprises setting a filter window width and a polynomial order.

11. The method as recited in claim 1, wherein the first filtered endpoint signal corresponds to an emission intensity of light at a first wavelength corresponding to the first chemical constituent found in the process chamber, and

the second filtered endpoint signal corresponds to an emission intensity of light at a second wavelength corresponding to the second chemical constituent found in the process chamber.

12. The method as recited in claim 11, wherein each wavelength is measured using optical emission spectroscopy.

13. A method for detecting an endpoint of a process comprising:

starting said process in a process chamber;

measuring a first endpoint signal corresponding to a first chemical constituent found in the process chamber;

measuring a second endpoint signal corresponding to a second chemical constituent found in the process chamber;

determining a ratio signal from a ratio of said first endpoint signal and said second endpoint signal, said ratio signal comprises an endpoint transition;

determining a differential signal from said ratio signal by applying a differential filter to said ratio signal, wherein said differential filter comprises a Savitsky Golay filter; and

determining an endpoint of said process from said differential signal,

wherein the first filtered signal corresponds to a first chemical constituent whose concentration decays during endpoint, and

wherein the second filtered signal corresponds to a second chemical constituent whose concentration rises during endpoint.

14. The method as recited in claim 13, wherein said measuring said first endpoint signal further comprises filtering said first endpoint signal, said filtering comprising at least one of a moving average, a finite impulse response filter, and a Savitsky Golay filter.

15. The method as recited in claim 14, wherein said measuring said second endpoint signal further comprises filtering said second endpoint signal, said filtering comprising at least one of a moving average, a finite impulse response filter, and a Savitsky Golay filter.

16. The method as recited in claim 13, wherein each of said first endpoint signal and said second endpoint signal comprise optical signals from a plasma process.

17. The method as recited in claim 16, wherein each of said optical signals is related to a spectral irradiance of emitted light from said plasma process.

18. The method as recited in claim 16, wherein said optical signals are measured using an optical diagnostic subsystem, said optical diagnostic subsystem comprising at least one of a detector, an optical filter, a grating, a prism, a monochromator, a spectrometer, a CCD array, and a CID array.

19. The method as recited in claim 13, wherein said applying said differential filter comprises setting a filter window width and a polynomial order.

20. The method as recited in claim 13, wherein said differential signal comprises at least one of a first derivative of said ratio signal and a second derivative of said ratio signal.

21. The method as recited in claim 13, wherein said determining said endpoint comprises using at least one of a start time of said endpoint transition, an end time of said endpoint transition, and an inflection time of said endpoint transition.

22. The method as recited in claim 13, wherein the first filtered endpoint signal corresponds to an emission intensity of light at a first wavelength corresponding to the first chemical constituent found in the process chamber, and

the second filtered endpoint signal corresponds to an emission intensity of light at a second wavelength corresponding to the second chemical constituent found in the process chamber.

23. The method as recited in claim 22, wherein each wavelength is measured using optical emission spectroscopy.

24. A plasma processing system comprising:

a process chamber;

a diagnostic system coupled to said process chamber and configured to measure at least two filtered endpoint signals; and

a controller coupled to said diagnostic system, configured to filter said at least two filtered endpoint signals using a Savitsky Golay filter, and configured to determine an endpoint from the filtered endpoint signals,

wherein said at least two filtered endpoint signals comprise a first filtered endpoint signal corresponding to a first chemical constituent found in the process chamber and a second filtered endpoint signal corresponding to a second chemical constituent found in the process chamber,

wherein said controller is configured to determine said endpoint from a ratio signal, said ratio signal generated by a ratio of said first filtered endpoint signal and said second filtered endpoint signal, wherein the first filtered signal corresponds to a first chemical constituent whose concentration decays during endpoint, and

wherein the second filtered signal corresponds to a second chemical constituent whose concentration rises during endpoint.

25. The plasma processing system as recited in claim 24, wherein said diagnostic system comprises an optical diagnostic subsystem.

26. The plasma processing system as recited in claim 25, wherein said optical diagnostic subsystem comprises at least one of a detector, an optical filter, a grating, a prism, a monochromator, a spectrometer, a CCD array, and a CID array.

27. The plasma processing system as recited in claim 24, wherein said ratio comprises an endpoint transition.

28. The plasma processing system as recited in claim 27, wherein said controller is further configured to determine said endpoint from said at least two filtered endpoint signals using at least one of a start time of said endpoint transition, an end time of said endpoint transition, and an inflection time of said endpoint transition.

29. The plasma processing system as recited in claim 24, wherein said controller is configure to determine said endpoint from a differential signal, said differential signal comprising at least one of a first derivative, and a second derivative of said ratio signal.

30. The plasma processing system as recited in claim 24, wherein said Savitsky Golay filter comprises a filter window width and a polynomial order.

31. The system as recited in claim 24, wherein the first filtered endpoint signal corresponds to an emission intensity of light at a first wavelength corresponding to the first chemical constituent found in the process chamber, and

the second filtered endpoint signal corresponds to an emission intensity of light at a second wavelength corresponding to the second chemical constituent found in the process chamber.

32. The system as recited in claim 31, wherein each wavelength is measured using optical emission spectroscopy.