End point detection in time division multiplexed etch processes

• US 6,982,175 B2
• Filed: 02/02/2004
• Issued: 01/03/2006
• Est. Priority Date: 02/14/2003
• Status: Active Grant

• Current Assignee: Plasma-Therm Corporation
• Original Assignee: Unaxis USA Incorporated (Unaxis)
• Inventors: Johnson, David, Westerman, Russell
• Primary Examiner(s): Goudreau, George A.
• Application Number:
  US10/770,839
• Publication Number:
  US 20040175913A1
• Time in Patent Office: 701 Days
• Field of Search: 216/60, 216/67, 438/7, 438/8, 438/9, 438/16, 438/695, 438/714
• US Class Current: 438/9
• 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

Abstract

An improved method for determining endpoint of a time division multiplexed process by monitoring an identified region of a spectral emission of the process at a characteristic process frequency. The region is identified based upon the expected emission spectra of materials used during the time division multiplexed process. The characteristic process frequency is determined based upon the duration of the steps in the time division multiplexed process. Changes in the magnitude of the monitored spectra indicate the endpoint of processes in the time division multiplexed process and transitions between layers of materials.

Claims

1. A method for establishing endpoint in a plasma etching process, the method comprising the steps of:

placing a substrate in a vacuum chamber;

etching a material from the substrate by means of a plasma;

depositing a passivation layer on the substrate by means of a plasma;

performing a process loop of repeating the etching step and the deposition step;

monitoring a variation in a plasma emission intensity at a characteristic frequency corresponding to the repetitive rate of the etching step or the deposition step of the process loop step;

discontinuing the process loop step based on said monitoring step; and

removing the substrate from the vacuum chamber.

2. The method of claim 1 wherein the characteristic frequency is determined based on a sum of the duration of the etching step and the deposition step of the process loop step.

3. The method of claim 1 wherein said process imposed frequency is less than about 5 Hz.

4. The method of claim 1 wherein said process loop further comprises multiple etch steps per process loop.

5. The method of claim 1 wherein said process loop further comprises multiple deposition steps per process loop.

6. The method of claim 1 wherein the step of monitoring further comprises monitoring plasma emission intensity at a plurality of wavelength regions.

7. The method of claim 6 wherein the step of monitoring said plurality of wavelength regions further comprises performing mathematical operations to extract a plurality of frequency components to acquire at least one characteristic frequency.

8. The method of claim 7 wherein the mathematical operations is a Fast Fourier Transform.

9. The method of claim 7 wherein the step of monitoring said plurality of wavelength regions further comprises performing mathematical operations to correct for a background plasma emission.

10. The method of claim 6 wherein said wavelength regions are chosen through mathematical analysis of the plasma emission spectrum.

11. The method of claim 10 wherein said mathematical analysis is principal component analysis.

12. A method for detecting the transition between different materials in a time division multiplexed process, the method comprising the steps of:

placing a substrate in a vacuum chamber;

performing the time division multiplexed process;

monitoring a variation in a plasma emission intensity at a characteristic frequency corresponding to the frequency of the time division multiplexed process;

discontinuing the time division multiplexed process based on said monitoring step; and

removing the substrate from the vacuum chamber.

13. The method of claim 12 wherein the characteristic frequency is determined based on a sum of the duration of the steps of the time division multiplexed process.

14. The method of claim 12 wherein said characteristic frequency is less than about 5 Hz.

15. The method of claim 12 wherein the step of monitoring further comprises monitoring plasma emission intensity at a plurality of wavelength regions.

16. The method of claim 15 wherein the step of monitoring said plurality of wavelength regions further comprises performing mathematical operations to extract a plurality of frequency components to acquire at least one characteristic frequency.

17. The method of claim 16 wherein the mathematical operations is a Fast Fourier Transform.

18. The method of claim 16 wherein the step of monitoring said plurality of wavelength regions further comprises performing mathematical operations to correct for a background plasma emission.

19. The method of claim 15 wherein said wavelength regions are chosen through mathematical analysis of the plasma emission spectrum.

20. The method of claim 19 wherein said mathematical analysis is principal component analysis.