CN-115720624-B - Determination of measurement errors in etalons

Abstract

Information related to an etalon is accessed, the etalon being associated with a calibration parameter having a preset default value, the etalon being configured to produce an interference pattern comprising a plurality of fringes from a received light beam, and the information related to the etalon comprising first spatial information related to a first fringe of the plurality of fringes and second spatial information related to a second fringe of the plurality of fringes. A first wavelength value of the received light beam is determined based on the spatial information associated with the first fringes and an initial value of a calibration parameter. A second wavelength value of the received light beam is determined based on the spatial information associated with the second fringes and an initial value of the calibration parameter. The first wavelength value and the second wavelength value are compared to determine a measurement error value.

Inventors

• R A bode te
• J. T. Melchior
• ZHENG GUOTAI

Assignees

• 西默有限公司

Dates

Publication Date

20260508

Application Date

20210525

Priority Date

20200624

Claims (20)

1. 1. An optical measurement device for a light source, the optical measurement device comprising: An etalon comprising a focusing lens configured to focus light at an image plane, wherein the etalon is associated with a calibration parameter related to the focusing lens, the calibration parameter comprising a focal length of the focusing lens, and the calibration parameter having a preset default value; an optical detector configured to detect an interference pattern produced by the etalon and to produce information related to the etalon, the information comprising first spatial information for a first fringe and second spatial information for a second fringe, the first spatial information comprising a diameter of the first fringe and the second spatial information comprising a diameter of the second fringe, and A control system coupled to the optical detector, the control system configured to: Determining a measurement error value of the etalon based on the first spatial information from the detector, the second spatial information, and an initial value of the calibration parameter, and The measurement error value is analyzed to determine whether to adjust the preset default value.
2. 2. The optical measurement device of claim 1, wherein the light source comprises a deep ultraviolet light source.
3. 3. A light source, comprising: Light generating device, and An optical measurement device comprising: An etalon comprising a focusing lens configured to focus light at an image plane, the etalon being associated with a calibration parameter related to the focusing lens, the calibration parameter comprising a focal length of the focusing lens, and the calibration parameter having a preset default value; an optical detector configured to detect an interference pattern produced by the etalon and to produce information related to the etalon, the information comprising first spatial information for a first fringe and second spatial information for a second fringe, the first spatial information comprising a diameter of the first fringe and the second spatial information comprising a diameter of the second fringe, and A control system coupled to the optical detector, the control system configured to: Determining a measurement error value of the etalon based on the first spatial information, the second spatial information, and initial values of the calibration parameters, and The measurement error value is analyzed to determine whether to adjust the preset default value.
4. 4. A light source according to claim 3, wherein the light generating means comprises a deep ultraviolet light source.
5. 5. The light source of claim 4, wherein the light generating means comprises a master oscillator.
6. 6. The light source of claim 4, wherein the light generating means further comprises a power amplifier.
7. 7. The light source of claim 4, wherein the light generating means comprises a plurality of master oscillators.
8. 8. The light source of claim 3, further comprising an optical element configured to receive light from the light generating device and direct the light to the etalon.
9. 9. The light source of claim 8, wherein the optical element is a dispersive optical element.
10. 10. A method for determining a measurement error value, comprising: Accessing information related to an etalon, wherein the etalon is associated with a calibration parameter having a preset default value, the etalon is configured to generate an interference pattern comprising a plurality of fringes from a received light beam, and the information related to the etalon comprises first spatial information related to a first fringe of the plurality of fringes and second spatial information related to a second fringe of the plurality of fringes, the calibration parameter comprises a focal length of a lens at an output of the etalon, the first spatial information comprises a diameter of the first fringe, and the second spatial information comprises a diameter of the second fringe; determining a first wavelength value of the received light beam based on the spatial information related to the first fringes and an initial value of the calibration parameter; Determining a second wavelength value of the received light beam based on the spatial information related to the second fringes and an initial value of the calibration parameter, and The first wavelength value and the second wavelength value are compared to determine a measurement error value.
11. 11. The method of claim 10, further comprising determining whether to adjust the preset default value of the calibration parameter based on the measurement error value.
12. 12. The method of claim 11, wherein the measurement error value comprises a difference between the first wavelength value and the second wavelength value, and a preset default value is adjusted to a value that causes the magnitude of the measurement error value to be less than a threshold value.
13. 13. The method of claim 12, wherein the preset default value is adjusted to a value that causes the measurement error value to be zero.
14. 14. The method of claim 10, wherein the measurement error comprises a difference between the first wavelength value and the second wavelength value.
15. 15. The method of claim 10, further comprising directing a beam of light to the etalon, and wherein the first fringe is produced by a first portion of the beam of light and the second fringe is produced by a second portion of the beam of light.
16. 16. The method of claim 15, wherein the light beam comprises a plurality of pulses and the first portion of the light beam comprises a first pulse of the plurality of pulses and the second portion of the light beam comprises a second pulse of the plurality of pulses.
17. 17. The method of claim 15, wherein the light beam comprises a continuous wave light beam and the first portion of the light beam comprises a first sample of the continuous wave light beam and the second portion of the light beam comprises a second sample of the continuous wave light beam.
18. 18. The method of claim 15, further comprising: changing the initial value of the calibration parameter to an updated value of the calibration parameter; actuating an optical element to thereby change the wavelength of the received light beam; determining a first wavelength value of the received light beam based on the spatial information related to the first fringes and the updated value of the calibration parameter; determining a second wavelength value of the received light beam based on the spatial information related to the second stripe and the updated value of the calibration parameter, and The first wavelength value and the second wavelength value are compared to determine a measurement error value based on the updated value of the calibration parameter.
19. 19. The method of claim 18, wherein the optical element is actuated to increase the wavelength or decrease the wavelength prior to determining the second wavelength value.
20. 20. The method of claim 18, wherein the first wavelength value and the second wavelength value are determined more than once each time the optical element is actuated.

Description

Determination of measurement errors in etalons Cross Reference to Related Applications The present application claims priority from U.S. application Ser. No.63/043,312, filed on even 24/6/2020, and entitled "DETERMINATION OF MEASUREMENT ERROR IN AN ETALON," which is incorporated herein by reference in its entirety. Technical Field The present disclosure relates to determination of measurement errors in etalons. Etalons may be used in Deep Ultraviolet (DUV) optical systems. Background An etalon is an optical cavity made of two partially reflective optical surfaces. The etalon produces an interference pattern and can be used to measure or estimate the wavelength of light incident on the etalon. Disclosure of Invention In one aspect, a method includes accessing information related to an etalon associated with a calibration parameter having a preset default value, the etalon configured to generate an interference pattern comprising a plurality of fringes from a received light beam, and the information related to the etalon comprises first spatial information related to a first fringe of the plurality of fringes and second spatial information related to a second fringe of the plurality of fringes, determining a first wavelength value of the received light beam based on the spatial information related to the first fringe and an initial value of the calibration parameter, determining a second wavelength value of the received light beam based on the spatial information related to the second fringe and an initial value of the calibration parameter, and comparing the first wavelength value and the second wavelength value to determine a measurement error value. Implementations can include one or more of the following features. The method may further include determining whether to adjust a preset default value of the calibration parameter based on the measured error value. The measurement error value may include a difference between the first wavelength value and the second wavelength value, and the preset default value may be adjusted to a value such that the magnitude of the measurement error value is less than the threshold value. The preset default value may be adjusted to a value that causes the measurement error value to be zero. The calibration parameter may comprise a focal length of the lens at an output of the etalon and the measurement error may comprise a difference between the first wavelength value and the second wavelength value. The first spatial information may include a diameter of the first stripe, and the second spatial information may include a diameter of the second stripe. The method may further comprise directing the beam of light towards an etalon. The first fringes may be produced by a first portion of the light beam and the second fringes may be produced by a second portion of the light beam. The light beam may comprise a plurality of pulses, the first portion of the light beam may comprise a first one of the plurality of pulses, and the second portion of the light beam may comprise a second one of the plurality of pulses. The light beam may comprise a continuous wave light beam, the first portion of the light beam may comprise a first sample of the light beam, and the second portion of the light beam may comprise a second sample of the light beam. The method may further include changing an initial value of the calibration parameter to an updated value of the calibration parameter, actuating the optical element to thereby change the wavelength of the received light beam, determining a first wavelength value of the received light beam based on the spatial information associated with the first stripe and the updated value of the calibration parameter, determining a second wavelength value of the received light beam based on the spatial information associated with the second stripe and the updated value of the calibration parameter, and comparing the first wavelength value and the second wavelength value to determine a measurement error value based on the updated value of the calibration parameter. The optical element may be actuated to increase the wavelength or decrease the wavelength before the second wavelength value is determined. The first wavelength value and the second wavelength value may be determined more than once each time the optical element is actuated. The method may further include determining whether to adjust the preset default value of the calibration parameter by comparing the error measurement value determined based on the initial value of the calibration parameter with the error measurement value determined based on the updated value of the calibration parameter. The initial value of the calibration parameter may be a preset default value. The first and second fringes may be in the interference pattern at the same time. In another aspect, a method for calibrating an etalon includes accessing information related to the etalon, the etalon being associated with a calibration