Method and apparatus for detecting endpoint

• US 20060037938A1
• Filed: 10/31/2003
• Published: 02/23/2006
• Est. Priority Date: 10/31/2002
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Yue, Hongyu
• Granted Patent: US 7,297,560 B2
• Time in Patent Office: Days
• US Class Current: 216/59
• 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;

measuring at least one endpoint signal;

generating at least one filtered endpoint signal by applying a Savitsky Golay filter to said at least one endpoint signal; and

determining an endpoint of said process from said at least one filtered endpoint signal.

2. The method as recited in claim 1, wherein said at least one filtered endpoint signal comprises a smoothed endpoint signal.

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

4. The method as recited in claim 1, wherein said at least one filtered endpoint signal comprises an endpoint transition.

5. The method as recited in claim 4, wherein said determining said endpoint from said at least one filtered endpoint signal 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 one endpoint signal comprises an optical signal from said plasma processing system.

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

8. The method as recited in claim 6, wherein said optical signal is 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 at least one filtered endpoint signal comprises a first filtered endpoint signal and a second filtered endpoint signal.

10. The method as recited in claim 9, 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.

11. The method as recited in claim 10, 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.

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

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

starting said process;

measuring a first endpoint signal;

measuring a second endpoint signal;

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.

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 an optical signal from a plasma process.

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

18. The method as recited in claim 16, wherein said optical signal is 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. A plasma processing system comprising:

a process chamber;

a diagnostic system coupled to said process chamber and configured to measure at least one endpoint signal; and

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

23. The plasma processing system as recited in claim 22, wherein said diagnostic system comprises an optical diagnostic subsystem.

24. The plasma processing system as recited in claim 23, 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.

25. The plasma processing system as recited in claim 22, wherein said at least one endpoint signal comprises an endpoint transition.

26. The plasma processing system as recited in claim 25, wherein said controller is further configured to determine said endpoint from said at least one filtered endpoint signal 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.

27. The plasma processing system as recited in claim 22, wherein said at least one filtered endpoint signal comprises a first filtered endpoint signal and a second filtered endpoint signal.

28. The plasma processing system as recited in claim 27, wherein said controller is configure 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.

29. The plasma processing system as recited in claim 28, 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 22, wherein said said Savitsky Golay filter comprises a filter window width and a polynomial order.