Plane grating calibration system

Patent metadata

Field	Value
Publication number	US-11940349-B2
Application number	US-202017610730-A
Country	US
Kind code	B2
Filing date	May 13, 2020
Priority date	May 16, 2019
Publication date	Mar 26, 2024
Grant date	Mar 26, 2024

Abstract

Disclosed is a plane grating calibration system, comprising an optical subsystem, a frame, first vibration isolator, a vacuum chuck, a workpiece stage, second vibration isolator, a base platform and a controller; the optical subsystem is mounted on the frame, and the frame is isolated from vibration by the first vibration isolator; the vacuum chuck is rotatably mounted on the workpiece stage, the workpiece stage is positioned on the base platform, and the base platform is isolated from vibration by the second vibration isolator. A displacement interferometer is integrated into the optical subsystem, and the entire optical subsystem adopts a method of sharing a light source, thereby avoiding the problems of low wavelength precision and poor coherence of separate light sources.

First claim

What is claimed is:

1. A plane grating calibration system, comprising an optical subsystem, a frame, a first vibration isolator, a vacuum chuck, a workpiece stage, a second vibration isolator, a base platform and a controller,
wherein the optical subsystem is mounted on the frame, the frame is isolated from vibration by the first vibration isolator, the vacuum chuck is rotatably mounted on the workpiece stage, the workpiece stage is positioned on the base platform, and the base platform is isolated from vibration by the second vibration isolator,
wherein the controller comprises a phase plate,
wherein the optical subsystem comprises a dual-frequency laser, a first beam splitter, a first mirror, a first corner cube mirror, a second corner cube mirror, a first polarizing beam splitter, a phase modulator, a first phase meter, a second polarizing beam splitter, a second mirror, a third mirror, a first collimating lens, a second collimating lens, a first beam sampler, a second beam sampler, a second phase meter, and a displacement interferometer;
wherein the controller is respectively connected with the phase modulator, the first phase meter, the second phase meter and the displacement interferometer; a plane grating to be calibrated is mounted on the vacuum chuck, a dual-frequency orthogonal polarizing laser light emitted by the dual-frequency laser is divided into two beams of dual-frequency orthogonal polarizing laser light transmitted and reflected respectively after passing through the first beam splitter, the transmitted dual-frequency orthogonal polarization laser is split into transmitted light P and reflected light S by the first polarizing beam splitter after being reflected by the first mirror, the transmitted light P sequentially passes through the second mirror, the first collimating lens and the first beam sampler, the light P reflected by the first beam sampler transmits through the second polarizing beam splitter, the light P transmitted through the first beam sampler generates a 0-order diffracted light after passing through the plane grating, and the 0-order diffracted light is reflected by the second beam sampler; the light S reflected by the first polarizing beam splitter sequentially passes through the phase modulator, the third mirror, the second collimating lens and the second beam sampler, the light S reflected by the second beam sampler is reflected by the second polarizing beam splitter and the light P transmitted through the second polarizing beam splitter compose a first measuring light, and the first measuring light is input into the first phase meter; the light S transmitted through the second beam sampler is diffracted by the plane grating to generate a −1-order diffracted light, the −1-order diffracted light is reflected by the second beam sampler and the light P which is the 0-order diffracted light reflected by the second beam sampler compose a second measuring light, and the second measuring light is input into the second phase meter; the orthogonal polarization laser reflected by the first beam splitter is sequentially reflected by the first corner cube mirror and the second corner cube mirror and input into the displacement interferometer to be used for scanning a displacement of the workpiece stage; and
wherein information about the first measuring light obtained by the first phase meter, the second measuring light obtained by the second phase meter and the displacement of the workpiece stage obtained by the displacement interferometer are input into the controller, the dual-frequency laser emits a reference light to the phase plate of the controller, the controller generates a control command through calculating and processing and transmits the control command to the phase modulator, and the phase modulator modulates the laser beam according to the control command to correct an error in the calibration of the plane grating.

2. The plane grating calibration system of claim 1 , wherein the phase modulator is an electro-optic modulator.

3. The plane grating calibration system of claim 1 , wherein the phase modulator comprises a first acousto-optic modulator and a second acousto-optic modulator,
wherein the first acousto-optic modulator is disposed on an optical path of the light P transmitted through the first polarizing beam splitter, the transmitted light P generated by the first polarizing beam splitter is modulated by the first acousto-optic modulator and then travels to the second mirror; and
wherein the second acousto-optic modulator is disposed on an optical path of the light S reflected by the first polarizing beam splitter, the light S reflected by the first polarizing beam splitter is modulated by the second acousto-optic modulator and then travels to the third mirror.

4. The plane grating calibration system of claim 1 , wherein the displacement interferometer comprises an X-direction interferometer, a Y-direction interferometer, a third corner cube mirror and a second beam splitter, and
wherein the laser input to the displacement interferometer is reflected to the second beam splitter by the third corner cube mirror, the transmitted light generated by the second beam splitter is used for scanning a displacement of the workpiece stage through the X-direction interferometer, and the reflected light generated by the second beam splitter is used for scanning a displacement of the workpiece stage through the Y-direction interferometer.

5. The plane grating calibration system of claim 4 , wherein the plane grating is a one-dimensional plane grating, and the workpiece stage performs step motion along an X direction and scanning motion along an Y direction.

6. The plane grating calibration system of claim 4 , wherein the plane grating is a two-dimensional plane grating, and
wherein the workpiece stage first performs step motion along the X direction and scanning motion along the Y direction to realize a first dimension calibration of the plane grating, then, the vacuum chuck drives the plane grating to rotate 90 degrees around a Z axis, and the workpiece stage subsequently performs step motion along the X direction and scanning motion along the Y direction to realize a second dimension calibration of the plane grating.

7. The plane grating calibration system of claim 4 , wherein the controller performs process on the information about the first measuring light input from the first phase meter and the information about the reference light according to the following formula:

ϕ
1

=

2
⁢
π
*
P
⁢

M
1

F

,

wherein ϕ 1 represents a radian value of a phase change of the first measuring light, PM 1 represents a value obtained by comparing the first measuring light with the reference light by using the phase plate; and F represents the resolution of the phase plate in the controller,
wherein the controller performs process on the information about the second measuring light input from the second phase meter and the information about the reference light according to the following formula:

ϕ
2

=

2

Assignees

• Univ Tsinghua
• Beijing U Prec Tech Co Ltd

Inventors

• Wang Leijie
• Zhang Ming
• Zhu Yu
• Hao Jiankun
• Li Xin
• Cheng Rong
• Yang Kaiming
• Hu Jinchun

Classifications

• G01M11/0214 Primary

  Details of devices holding the object to be tested · CPC title

• G01M11/04 Primary

  Optical benches therefor · CPC title

• G02B5/1857

  using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams · CPC title

• G02B7/003

  Alignment of optical elements (G02B7/001, G02B7/002 take precedence; for mirrors G02B7/1822) · CPC title

• G02B27/1006

  for splitting or combining different wavelengths (G02B27/1086, G02B27/141 take precedence) · CPC title