System and method for correcting optical path length measurement errors

Patent metadata

Field	Value
Publication number	US-11920928-B2
Application number	US-202217733846-A
Country	US
Kind code	B2
Filing date	Apr 29, 2022
Priority date	May 7, 2021
Publication date	Mar 5, 2024
Grant date	Mar 5, 2024

Abstract

A system includes a first optical unit that emits light to a measurement target object and receives first interference light incident from the measurement target object, a second optical unit that emits the light to a reference object configured to have a constant optical path length with respect to a temperature fluctuation and receives second interference light incident from the reference object, a spectroscope connected to the first optical unit and the second optical unit and receives the first interference light and the second interference light to be incident, and a control unit connected to the spectroscope, and the control unit calculates a fluctuation rate of a measurement optical path length with respect to a reference optical path length under a predetermined temperature environment on the basis of the optical path length of the reference object calculated on the basis of the second interference light incident on the spectroscope under the predetermined temperature environment, and the reference optical path length of the reference object acquired in advance, and corrects, on the basis of the fluctuation rate, the optical path length of the measurement target object calculated on the basis of the first interference light incident on the spectroscope under the predetermined temperature environment.

First claim

What is claimed is:

1. A system for correcting an optical path length measurement error, the system comprising:
a light source configured to generate light;
a first optical unit configured to emit the light to a measurement target object and receive first interference light incident from the measurement target object;
a second optical unit configured to emit the light to a reference object configured to have a constant optical path length with respect to a temperature fluctuation and receive second interference light incident from the reference object;
a spectroscope connected to the first optical unit and the second optical unit and configured to receive the first interference light and the second interference light to be incident; and
a control unit connected to the spectroscope,
wherein the control unit
calculates a fluctuation rate of a measurement optical path length with respect to a reference optical path length under a predetermined temperature environment on the basis of the optical path length of the reference object calculated on the basis of the second interference light incident on the spectroscope under the predetermined temperature environment, and the reference optical path length of the reference object acquired in advance, and
corrects, on the basis of the fluctuation rate, the optical path length of the measurement target object calculated on the basis of the first interference light incident on the spectroscope under the predetermined temperature environment.

2. The system for correcting an optical path length measurement error according to claim 1 , further comprising:
a circulator connected to the light source; and
an optical switch connected to the circulator,
wherein the first optical unit includes
a first optical fiber configured to propagate light from the optical switch; and
a first optical element configured to emit the light to the measurement target object and receive the first interference light incident from the measurement target object.

3. The system for correcting an optical path length measurement error according to claim 2 , wherein the first optical element is a focuser or a collimator.

4. The system for correcting an optical path length measurement error according to claim 2 ,
wherein the second optical unit includes
a second optical fiber configured to propagate the light from the optical switch; and
a second optical element configured to emit the light to the reference object and receive the second interference light incident from the reference object.

5. The system for correcting an optical path length measurement error according to claim 4 , wherein the second optical element is a focuser or a collimator.

6. The system for correcting an optical path length measurement error according to claim 1 ,
wherein the reference object is an etalon element, and
the second optical unit includes a third optical element configured to emit the light to the etalon element, and a fourth optical element configured to receive transmitted light incident from the etalon element.

7. The system for correcting an optical path length measurement error according to claim 6 , wherein the third optical element and the fourth optical element are focusers or collimators.

8. The system for correcting an optical path length measurement error according to claim 1 , wherein the reference object includes a pair of opposing parallel flat plates.

9. The system for correcting an optical path length measurement error according to claim 8 , wherein the inside of a space between the parallel flat plates is a vacuum.

10. The system for correcting an optical path length measurement error according to claim 8 , wherein the reference object includes a reflective film on at least one of facing inner surfaces of the parallel flat plates.

11. The system for correcting an optical path length measurement error according to claim 8 , wherein the pair of opposing parallel flat plates are formed of single crystal silicon.

12. The system for correcting an optical path length measurement error according to claim 1 , further comprising a holder configured to hold a relative position between the second optical unit and the reference object.

13. A method of correcting an optical path length measurement error, the method comprising:
a step of emitting light to a measurement target object and causing first interference light from the measurement target object to be incident on a spectroscope under a predetermined temperature environment;
a step of calculating an optical path length of the measurement target object on the basis of the first interference light;
a step of emitting the light to a reference object configured to have a constant optical path length with respect to a temperature fluctuation, and causing second interference light from the reference object to be incident on the spectroscope under the predetermined temperature environment;
a step of calculating a measurement optical path length of the reference object on the basis of the second interference light;
a step of acquiring a reference optical path length of the reference object;
a step of calculating a fluctuation rate of the measurement optical path length with respect to the reference optical path length under the predetermined temperature environment on the basis of the measurement optical path length of the reference object calculated on the basis of the second interference light and the reference optical path length of the reference object; and
a step of correcting the optical path length of the measurement target object on the basis of the fluctuation rate.

Assignees

• Tokyo Electron Ltd

Inventors

• Nagai Kenji
• Nagasaki Hideaki

Classifications

• G01B9/02071 Primary

  by measuring path difference independently from interferometer · CPC title

• G01B9/02028

  Two or more reference or object arms in one interferometer · CPC title

• G01B2290/60

  Reference interferometer, i.e. additional interferometer not interacting with object · CPC title

• G01K11/00 Primary

  Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 · CPC title

• G01B9/02044 Primary

  Imaging in the frequency domain, e.g. by using a spectrometer · CPC title