End-point detector for plasma etcher

• US 6,088,096 A
• Filed: 06/12/1998
• Issued: 07/11/2000
• Est. Priority Date: 06/20/1997
• Status: Expired due to Fees

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Aoki, Masahiro, Saito, Susumu
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US09/096,524
• Time in Patent Office: 760 Days
• Field of Search: 356/300, 356/316, 356/310, 356/302, 356/303
• US Class Current: 356/316
• CPC Class Codes: G01N 21/68 using high frequency electric fields
• 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 end-point detector for a plasma etcher, includes a converging lens for receiving strip-like plasma light produced between a pair of opposed electrodes and a spectroscope, having a slit located at a substantial rear-side focal plane of the converging lens, for detecting an etching end time point from a time-based variation of spectrum light intensity of the plasma light which has been converged at the slit and has passed through the slit. The converging lens has a pupil diameter of not greater than ##EQU1## where W is a width of a short side of the strip-like plasma light produced between the electrodes, 1 is a distance between an end of each electrode and a pupil face of the converging lens, NAm is a numerical aperture required by the spectroscope, and h is a width of a short side of the slit of the spectroscope. The converging lens has a numerical aperture of not less than NAm.

Claims

1. An end-point detector for a plasma etcher, the detector comprising:

at least one converging lens for receiving strip-like plasma light produced between electrodes of the plasma etcher; and

spectroscopic means, having a slit located at a rear-side focal plane of the converging lens, for detecting an etching end time point from a time-based variation of spectrum light intensity of the plasma light which has been converged at the slit and has passed through the slit,

wherein said converging lens has a pupil diameter of not greater than ##EQU4## where W is a width of a short side of the strip-like plasma light produced between the electrodes, 1 is a distance between an end of each electrode and a pupil face of the converging lens, NAm is a numerical aperture required by the spectroscopic means, and h is a width of a short side of the slit of the spectro-scopic means, and

wherein the converging lens has a numerical aperture of not less than NAm.

2. The-end point detector according to claim 1, wherein even if there is no real number solution for the pupil diameter φ

in the equation in claim 1, the converging lens has a pupil diameter of not greater than

space="preserve" listing-type="equation">φ

=8W1NAm/{π

(W+h)}

and has a numerical aperture of not less than NAm.

3. The end-point detector according to claim 1, further comprising an optical fiber having a light incidence face located at the rear-side focal plane of the converging lens and having a light emission face located at the slit.

4. The end-point detector according to claim 1, further comprising:

a plurality of converging lenses arranged to receive the plasma light produced between the electrodes of the plasma etcher; and

an optical fiber bundle comprising a plurality of optical fibers each having a light incidence face located at a rear-side focal plane of an associated one of the converging lenses, the optical fiber bundle having a light emission face located at the slit.

6. The-end point detector according to claim 5, wherein even if there is no real number solution for the pupil diameter φ

in the equation in claim 1, the converging lens has a pupil diameter defined by

space="preserve" listing-type="equation">φ

=8W1NAm/{π

(W+h)}.

5. An end-point detector for a plasma etcher, the detector comprising:

at least one converging lens for receiving strip- like plasma light produced between electrodes of the plasma etcher; and

spectroscopic means, having a slit located at a substantial rear-side focal plane of the converging lens, for detecting an etching end time point from a time-based variation of spectrum light intensity of the plasma light which has been converged at the slit and has passed through the slit,

wherein said converging lens has a pupil diameter φ

defined by ##EQU5## where W is a width of a short side of the strip-like plasma light produced between the electrodes, 1 is a distance between an end of each electrode and a pupil face of the converging lens, NAm is a numerical aperture required by the spectroscopic means, and h is a width of a short side of the slit of the spectroscopic means.

7. The-end point detector according to claim 5, wherein the converging lens has a numerical aperture of not less than NAm.