Selection of wavelengths for end point in a time division multiplexed process

• US 20060006139A1
• Filed: 08/23/2005
• Published: 01/12/2006
• Est. Priority Date: 05/09/2003
• Status: Abandoned Application

• Current Assignee: Plasma-Therm Corporation
• Original Assignee: Plasma-Therm Corporation
• Inventors: Johnson, David, Westerman, Russell
• Application Number:
  US11/210,248
• Publication Number:
  US 20060006139A1
• Time in Patent Office: Days
• US Class Current: 216/60
• CPC Class Codes: B81C 1/00579 Avoid charge built-up
• 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: H01J 37/32963 End-point detection
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

The present invention provides a method for establishing endpoint during an alternating cyclical etch process or time division multiplexed process. A substrate is placed within a plasma chamber and subjected to an alternating cyclical process having an etching step and a deposition step. A variation in plasma emission intensity is monitored using known optical emission spectrometry techniques. A first wavelength region is selected based on a plasma emission from an etch by product and a second wavelength region is selected based on a plasma emission from a plasma background. A ratio of the first wavelength region to the second wavelength region is computed and used to adjust the monitoring of an attribute of a signal generated from the time division multiplex process. The alternating cyclical process is discontinued when endpoint is reached at a time that is based on the monitoring step.

Claims

1. A method of establishing endpoint during a time division multiplex process comprising the steps of:

subjecting a substrate to the time division multiplex process;

selecting a first wavelength region based on a plasma emission from an etch by product;

selecting a second wavelength region based on a plasma emission from a plasma background;

computing a ratio of said first wavelength region to said second wavelength region;

monitoring an attribute of a signal generated from the time division multiplex process;

adjusting said monitoring step based on said ratio of said computation step;

processing said adjusted attribute of the periodic signal generated from the time division multiplex process using an envelope follower; and

discontinuing the time division multiplex process at a time based on the processing step.

2. The method of claim 1 wherein said attribute is plasma emission intensity.

3. The method of claim 2 wherein said monitoring step further comprising monitoring a plurality of regions of plasma emission intensity.

4. The method of claim 3 wherein said plurality of regions of plasma emission intensity are chosen using a statistical method.

5. The method of claim 4 wherein said statistical method further comprising factor analysis.

6. The method of claim 5 wherein said plurality of regions of plasma emission intensity are chosen using an off-line analysis.

7. The method of claim 6 wherein said off-line analysis further comprising spectra differencing.

8. The method of claim 3 wherein said monitoring step further comprising performing mathematical operations on said multiple regions of plasma emission intensity.

9. The method of claim 1 wherein said attribute is plasma impedance.

10. The method of claim 1 wherein said processing step further comprising using a plurality of peak detect algorithms.

11. The method of claim 10 wherein said plurality of peak detect algorithms are processed in parallel.

12. The method of claim 10 wherein said plurality of peak detect algorithms are reset sequentially in a round robin fashion.

13. The method of claim 12 wherein said reset further comprising a clock period that is at least half the process period of the time division multiplex process.

14. The method of claim 1 wherein said processing step further comprising post processing of an extracted amplitude detection signal.

15. The method of claim 14 wherein said post processing is digital signal processing.

16. The method of claim 15 wherein said digital signal processing comprises a filter.

17. The method of claim 16 wherein said filter is an infinite impulse response filter.

18. The method of claim 16 wherein said filter is a finite impulse response filter.

19. A method for establishing endpoint during a time division multiplexed process, the method comprising the steps of:

a. etching a surface of a substrate in an etching step by contact with a reactive etching gas to removed material from the surface of the substrate and provide exposed surfaces;

b. passivating the surface of the substrate in a passivating step during which the surfaces that were exposed in the preceding etching step are covered by a passivation layer thereby forming a temporary etching stop;

c. alternatingly repeating the etching step and the passivating step;

d. selecting a first wavelength region based on a plasma emission from an etch by product;

e. selecting a second wavelength region based on a plasma emission from a plasma background;

f. computing a ratio of said first wavelength region to said second wavelength region;

g. analyzing an intensity of at least one wavelength region of a plasma emission through the use of an envelope follower algorithm;

h. adjusting said analysis step based on said ratio of said computation step; and

i. discontinuing the time division multiplexed process at a time which is dependent on said analysis step.

20. A method of establishing endpoint during a time division multiplex process comprising the steps of:

subjecting a substrate to the time division multiplex process;

selecting a first wavelength region based on a plasma emission from an etch by product;

selecting a second wavelength region based on a plasma emission from a plasma background;

computing a ratio of said first wavelength region to said second wavelength region;

monitoring an attribute of a signal generated from the time division multiplex process;

adjusting said monitoring step based on said ratio of said computation step;

processing said adjusted attribute of the periodic signal generated from the time division multiplex process using a peak-hold and decay algorithm; and

discontinuing the time division multiplex process at a time based on the processing step.

21. The method of claim 20 wherein said attribute is plasma emission intensity.

22. The method of claim 20 wherein said processing step further comprising using a linear decay algorithm.

23. The method of claim 20 wherein said processing step further comprising using a non-linear decay algorithm.

24. The method of claim 20 wherein said processing step further comprising post processing of an extracted amplitude detection signal.

25. The method of claim 24 wherein said post processing is digital signal processing.

26. The method of claim 25 wherein said digital signal processing comprises a filter.

27. The method of claim 26 wherein said filter is an infinite impulse response filter.

28. The method of claim 26 wherein said filter is a finite impulse response filter.