CN-122015658-A - Device for realizing large-stroke direct traceability type grating interferometer

CN122015658ACN 122015658 ACN122015658 ACN 122015658ACN-122015658-A

Abstract

The invention discloses a device for realizing a large-stroke direct tracing type grating interferometer, which belongs to the technical field of precise displacement measurement and comprises a grating base plate, a coherent light source and an optical fiber beam splitter, wherein a plurality of gratings are arranged on the grating base plate, each grating comprises a first grating, a second grating, a third grating, a fourth grating and a fifth grating, the gratings are staggered and distributed on the grating base plate, the gratings are self-tracing gratings, the coherent light source is connected with the optical fiber beam splitter, the output end of the optical fiber beam splitter is respectively connected with two reading heads, the two reading heads are respectively a first reading head and a second reading head, the other ends of the first reading head and the second reading head are respectively connected with a signal processing unit, the grating base plate is driven by a displacement table to perform one-dimensional translation, and the first reading head and the second reading head are fixed. The device solves the problem that the existing large-stroke grating interferometer is difficult to directly trace the source, and has the advantages of range self-calibration splicing, large expansion space and embedded use.

Inventors

CHENG XINBIN
WEI ZHENBO
LI TONGBAO
DENG XIAO
HE CHUNLING
WANG JUN
Yang Yaao
Chang Jikun
LIN ZICHAO
Xue Dongbai
XIE YUYING

Assignees

同济大学

Dates

Publication Date: 20260512
Application Date: 20260212

Claims (10)

1. A device for realizing a large-stroke direct tracing type grating interferometer is characterized by comprising a grating base plate, a coherent light source and an optical fiber beam splitter, wherein a plurality of gratings are arranged on the grating base plate, each grating comprises a first grating, a second grating, a third grating, a fourth grating and a fifth grating, the gratings are distributed on the grating base plate in an staggered mode, four overlapping areas which are R1, R2, R3 and R4 are respectively arranged between adjacent gratings in the grating period direction, the gratings are self-tracing gratings, the coherent light source is connected with the optical fiber beam splitter, the output end of the optical fiber beam splitter is respectively connected with two reading heads, the two reading heads are respectively a first reading head and a second reading head, the other ends of the first reading head and the second reading head are respectively connected with a signal processing unit, the grating base plate is driven by a displacement table to conduct one-dimensional translation, and the first reading head and the second reading head are fixed.
2. The device for realizing the large-stroke direct traceable grating interferometer according to claim 1, wherein the coherent light source guides laser light into the first reading head and the second reading head through the optical fiber beam splitter, the first reading head and the second reading head enable the laser light to be incident on the grating surface and to be subjected to diffraction action with the grating, the laser light returns to the reading head to form an interference signal, the interference signal is transmitted to the signal processing unit, and the grating displacement and the movement direction are obtained through calculation.
3. The device for realizing the large-stroke direct traceable grating interferometer according to claim 1, wherein the periodic direction of the first grating is consistent with the motion axis of the displacement table, the ideal installation of the reading head and the traceable grating is ensured, the distance between the adjacent traceable gratings is adjusted to enable the reading head to have an interference signal overlapping area when passing, and the space attitude error of the adjacent traceable gratings is calibrated by utilizing the theoretical distance between the traceable gratings.
4. The device for realizing the large-stroke direct traceable grating interferometer according to claim 3, wherein the process of calibrating the spatial attitude error of the adjacent traceable grating by utilizing the theoretical spacing of the traceable grating is that the cosine error is calculated by the ratio of the number of the original signal periods acquired by the two reading heads in the overlapping area of the interference signals, and the length reference on all the measuring strokes is the theoretical spacing of the traceable grating; the ideal installation method of the self-tracing grating and the reading head is that laser is incident to the self-tracing grating at a Littrow angle to realize original return.
5. The device for realizing the large-stroke direct traceable grating interferometer according to claim 1, wherein the reading head adopts any one displacement measurement mode selected from homodyne interference, heterodyne interference and self-mixing interference, and the reading head and the corresponding self-traceable grating are arranged in the same motion plane.
6. The device for realizing the large-stroke direct traceable type grating interferometer according to claim 1, wherein a coherent light source adopts a 405nm narrow linewidth laser, an optical fiber beam splitter adopts a single-mode polarization maintaining optical fiber, a signal processing unit has four paths of sampling rates of 100MHz and 16 sampling bits, and is used for converting collected voltage signals into digital signals and performing displacement calculation and error calibration on the four paths of signals through an FPGA.
7. The device for realizing the large-stroke direct tracing type grating interferometer according to claim 1, wherein the first reading head and the second reading head adopt the same optical path, when the first reading head and the second reading head adopt homodyne interferometry, the optical path structures of the first reading head and the second reading head comprise an optical fiber collimator, a diffraction light generating unit and a signal receiving unit, wherein the diffraction light generating unit comprises a fourth wave plate, a polarization splitting prism, a first wave plate, a second wave plate, a first reflecting mirror, a second reflecting mirror and a third reflecting mirror, the signal receiving unit comprises a third wave plate, a non-polarization splitting prism, a first polarizing plate, a second polarizing plate, a first detector and a second detector, the optical fiber collimator is connected with the polarization splitting prism through the first reflecting mirror, the fourth wave plate is connected with the second wave plate, the first wave plate is connected with the third reflecting mirror, the first wave plate is connected with the second reflecting mirror, the third wave plate is connected with the polarization splitting prism is connected with the first linear polarization splitter and the first linear detector, the second linear detector is connected with the first linear detector and the first linear detector is connected with the first linear detector.
8. The apparatus for implementing a large travel direct traceable grating interferometer of claim 7, wherein the fourth wave plate is a half wave plate, the first wave plate, the second wave plate, and the third wave plate are quarter wave plates, the fast axes of the first wave plate, the second wave plate, and the third wave plate are each 45 ° from the plane of light incidence, the first linear polarizer has a polarization direction that is 45 ° from the plane of light incidence, and the second linear polarizer has a polarization direction that is 22.5 ° from the plane of light incidence.
9. The device for realizing the large-stroke direct tracing type grating interferometer according to claim 7, wherein laser light enters from the optical fiber collimator, enters the diffraction light generating unit through the first reflecting mirror, adjusts the rotatable fourth wave plate to enable the polarization direction of the incident laser light to be 45 degrees with the incident plane, and decomposes the laser light into two components of vertical polarization and horizontal polarization through the polarization splitting prism, wherein the vertical polarization light is transmitted and then is changed into right-handed circularly polarized light through the second wave plate, the right-handed circularly polarized light enters the tracing type grating through the third reflecting mirror at a Littrow angle, the incident light is diffracted at the tracing type grating, returns from the 1-order diffraction light source, passes through the second wave plate again and becomes horizontal polarization light, and the horizontal polarization light is reflected after passing through the polarization splitting prism and enters the signal receiving unit; The other path of horizontal polarized light reflected by the polarization beam splitter prism is changed into left-handed circularly polarized light after passing through the first wave plate, the left-handed circularly polarized light is incident to the self-tracing grating through the second reflecting mirror at a Littrow angle, the incident light is diffracted on the self-tracing grating, the-1 st-order diffracted light returns to the original path, the horizontal polarized light is changed into vertical polarized light after passing through the first wave plate again, the vertical polarized light is transmitted after passing through the polarization beam splitter prism, and the vertical polarized light is combined with the previous path of diffracted light and is injected into the signal receiving unit together; The two beams of vertically polarized diffracted light are changed into circularly polarized light through a third wave plate, the circularly polarized light is divided into two paths through a non-polarized beam splitter prism in the same proportion, one path of the circularly polarized light is transmitted through a first linear polarizer to enter a first photoelectric detector, the other path of the circularly polarized light is transmitted through a second linear polarizer to enter a second photoelectric detector, two paths of orthogonal interference signals acquired by the photoelectric detectors are connected into a signal processing unit, and the interference signals are subjected to arctangent calculation and phase unwrapping to obtain the motion distance and motion reversal of a self-tracing grating.
10. The device for realizing a large-stroke direct tracing type grating interferometer according to claim 1, wherein when the displacement table moves unidirectionally and uniformly, and the laser diffraction measurement area moves to any overlapping area, the first reading head and the second reading head collect interference signals of two gratings simultaneously, each reading head takes one signal, the interference signal of the second reading head is calibrated by an interference signal period T1 of the first reading head, and the calibration coefficients are as follows: ; Wherein, the Indicating the period of interference of the first read head, Representing an interference period of the first read head; the displacement data collected by the second digital head is multiplied by a coefficient And obtaining a measured displacement result.

Description

Device for realizing large-stroke direct traceability type grating interferometer Technical Field The invention relates to the technical field of precise displacement measurement, in particular to a device for realizing a large-stroke direct traceability type grating interferometer. Background In integrated circuit fabrication, the performance of the lithographic apparatus directly determines the process and integration level of the chip. As a core subsystem of the photoetching machine, a workpiece table bears the key task of accurately positioning a wafer, and the movement and control precision of the workpiece table is the fundamental guarantee of the alignment precision and the line width uniformity of a chip pattern. Currently, advanced lithography machines commonly use 12-inch wafers, which requires a large motion range of 300mm or more for the workpiece stage. However, to such a large extent, how to achieve and maintain ultra-high positioning accuracy on the nanometer scale and even sub-nanometer scale is a serious challenge. In many displacement measurement technologies, the grating-based interferometry technology has advantages of high accuracy, high stability, strong anti-interference capability and the like compared with the measurement technology based on laser wavelength, so that the grating-based interferometry technology is widely applied to the fields of precision manufacturing, detection and integrated circuits. The displacement measurement technology based on the grating is used for measuring the grating pitch, so that the accuracy of the grating pitch becomes a key factor of displacement measurement. The common grating needs to be calibrated to determine the grating pitch, and the uniformity of the grating pitch is difficult to ensure. The self-tracing grating is a high-precision grating manufactured based on an atomic lithography technology, and the grating pitch of the self-tracing grating directly traces to an atomic transition frequency, so that the self-tracing grating has the advantages of direct tracing and uniform grating pitch. The displacement measurement mode based on the self-tracing grating has three types of heterodyne measurement, homodyne measurement and self-mixing measurement, and the grating interferometer taking the self-tracing grating pitch as a measurement reference has the advantages of strong stability and direct traceability, and the existing self-tracing grating interferometer can be used as a standard of a calibration instrument. However, the size of the monolithic self-tracing grating is limited, which severely limits the measurement range of the grating interferometer, and the requirement of the integrated circuit manufacturing field on large-stroke displacement measurement is difficult to meet. Based on the above, the invention provides a device for realizing a large-stroke direct traceability type grating interferometer. Disclosure of Invention The invention aims to provide a device for realizing a large-stroke direct tracing type grating interferometer, which solves the problem that the existing large-stroke grating interferometer is difficult to trace directly, and has the advantages of self-calibration splicing of measuring range, large expansion space and embedded use. The invention provides a device for realizing a large-stroke direct tracing type grating interferometer, which comprises a grating base plate, a coherent light source and an optical fiber beam splitter, wherein a plurality of gratings are arranged on the grating base plate, each grating comprises a first grating, a second grating, a third grating, a fourth grating and a fifth grating, the gratings are distributed in an staggered manner on the grating base plate, four overlapping areas are formed between adjacent gratings in the grating period direction, R1, R2, R3 and R4 are respectively arranged between the adjacent gratings, the gratings are self tracing gratings, the coherent light source is connected with the optical fiber beam splitter, the output end of the optical fiber beam splitter is respectively connected with two reading heads, the two reading heads are respectively connected with a first reading head and a second reading head, the other ends of the first reading head and the second reading head are respectively connected with a signal processing unit, and the grating base plate is driven by a displacement table to perform one-dimensional translation, and the first reading head and the second reading head are fixed. Preferably, the coherent light source guides laser into the first reading head and the second reading head through the optical fiber beam splitter, the first reading head and the second reading head make the laser incident on the surface of the grating to generate diffraction action with the grating, the laser returns to the reading head to form interference signals, the interference signals are transmitted to the signal processing unit, and the displacement and the