Spatially resolved optical emission spectroscopy (OES) in plasma processing

• US 10,473,525 B2
• Filed: 07/12/2017
• Issued: 11/12/2019
• Est. Priority Date: 11/01/2013
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Meng, Ching-Ling, Tuitje, Holger, Chen, Yan, Mihaylov, Mihail
• Primary Examiner(s): Ton, Tri T
• Assistant Examiner(s): Phillips, Rufus L
• Application Number:
  US15/648,035
• Publication Number:
  US 20170314991A1
• Time in Patent Office: 853 Days
• CPC Class Codes: G01J 3/443 Emission spectrometry
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 21/68 using high frequency electric fields
• CPC Class Codes: G01N 2201/10 Scanning

Abstract

Disclosed is a method, system, and apparatus for optical emission measurement. The apparatus includes a collection system for collecting a plasma optical emission spectra through an optical window disposed at a wall of a plasma processing chamber. The optical system includes a mirror configured to scan a plurality of non-coincident rays across the plasma processing chamber; and a telecentric coupler for collecting an optical signal from a plasma and directing the optical signal to a spectrometer for measuring the plasma optical emission spectra.

Claims

1. An apparatus for optical emission measurement, the apparatus comprising:

a plasma processing chamber;

an optical window disposed on a wall of the plasma processing chamber; and

a collection system for collecting a plasma optical emission spectra through the optical window, the collection system including;

a mirror system configured to scan a plurality of non-coincident rays across the plasma processing chamber; and

a telecentric coupler for collecting an optical signal from a plasma and directing the optical signal to a spectrometer for measuring the plasma optical emission spectra, wherein a center of rotation of the plurality of non-coincident rays is substantially at the optical window.

2. The apparatus of claim 1, wherein the telecentric coupler includes:

at least one collection lens; and

at least one coupling lens.

3. The apparatus of claim 2, wherein the at least one collection lens or the at least one coupling lens are achromatic lenses.

4. The apparatus of claim 2, wherein the telecentric coupler further includes:

an aperture disposed between the at least one collection lens and the at least coupling lens for defining a diameter of the plurality of non-coincident rays.

5. The apparatus of claim 1, wherein the mirror system includes a scanning mirror.

6. The apparatus of claim 5, wherein the scanning mirror is mounted on and scanned by a galvanometer scanning stage.

7. The apparatus of claim 5, wherein the scanning mirror is mounted on and scanned by a stepper motor.

8. The apparatus of claim 5, wherein the mirror system includes:

a transfer mirror;

a fold mirror; and

wherein the transfer mirror is configured to transfer the collected signal to the fold mirror and the fold mirror is configured to transfer the collected signal to a scanning mirror.

9. The apparatus of claim 1, wherein the telecentric coupler includes:

a collection triplet lens configured to collect the optical signal from the mirror system; and

two coupling triplet lenses configured to focus the collected signal into an end of an optical fiber coupled to the spectrometer.

10. The apparatus of claim 1, further comprising:

a second optical window; and

a second collection system for collecting the plasma optical emission spectra through the second optical window disposed at the wall of the plasma processing chamber, the second optical window having a center axis perpendicular to the center axis of the optical window.

11. The apparatus of claim 1, wherein the collection system further includes:

a linear arc stage holding the mirror system, and the telecentric coupler, the linear arc stage being configured to move radially with respect to a center axis of the optical window causing the plurality of non-coincident rays to scan across the plasma processing chamber.

12. The apparatus of claim 11, wherein the mirror system includes a fold mirror.

13. The apparatus of claim 1, wherein the plurality of non-coincident rays are scanned 25°

of a center axis of the optical window across the plasma processing chamber.

14. The apparatus of claim 1, wherein the collection system has a low numerical aperture.

15. The apparatus of claim 1, wherein the optical signal is collected from 21 non-coincident rays.

16. A system for plasma processing, comprising:

a plasma processing chamber;

an optical window disposed on a wall of the plasma processing chamber;

a collection system for collecting plasma optical emission spectra through the optical window;

a spectrometer coupled to the collection system for measuring the plasma optical emission spectra; and

wherein the collection system includes

a mirror system configured to scan a plurality of non-coincident rays across the plasma processing chamber, and

a telecentric coupler for collecting an optical signal from a plasma and directing the optical signal to the spectrometer, wherein a center of rotation of the plurality of non-coincident rays is substantially at the optical window.

19. The system of claim 16, wherein the spectrometer is an ultra broadband high resolution spectrometer.

20. The system of claim 16, wherein the plurality of non-coincident rays are scanned 30°

of a center axis of the optical window across the plasma processing chamber.

17. A method for optical emission measurement, comprising:

depositing an optical window at a wall of a plasma processing chamber;

providing a collection system for collecting plasma optical emission spectra through the optical window, the collection system including a mirror system and a telecentric coupler;

scanning a plurality of non-coincident rays across the plasma processing chamber using the mirror system;

collecting an optical signal from a plasma via the telecentric coupler; and

directing the optical signal to a spectrometer for measuring the plasma optical emission spectra, wherein a center of rotation of the plurality of non-coincident rays is substantially at the optical window.

18. The method of claim 17, wherein the mirror system includes at least a transfer mirror and a fold mirror.