Reflection-type double-beam interference exposure system and adjustment method of reflection-type double-beam interference exposure system considering scribed line density and aberration

Abstract

The invention relates to a reflective double-beam interference exposure system reticle density and aberration considered adjustment method, which comprises the following steps: constructing a reticle density standard module, and generating a standard reference beam for adjusting the reticle density of an exposure system; a reflection type double-beam interference exposure system is built, points formed after + / -1-level standard reference beams are focused through an off-axis parabolic mirror serve as nominal focuses of all off-axis mirrors in a double-beam light path, the spatial position of the off-axis parabolic mirror is continuously adjusted, wavefront measurement is combined with a spherical interferometer, and the reflection type double-beam interference exposure system is obtained. And enabling the nominal focus of the off-axis mirror to coincide with the spatial position of the real focus, thereby completing the construction of the double-beam interference exposure system. According to the invention, the problem that the aberration and the scribed line density are difficult to accurately control at the same time in the adjustment process of the reflective double-beam interference exposure system is solved, and a new idea is provided for the high-precision adjustment of the meter-scale large-aperture reflective interference exposure system.

Description

Technical Field

[0001] The present invention relates to the field of large-aperture diffraction grating preparation, and in particular to a reflective double-beam interference exposure system and an assembly and adjustment method thereof that takes both scribed line density and aberration into consideration. Background Art

[0002] Meter-scale large-aperture diffraction grating elements are core components of systems such as ultra-strong ultra-short laser devices, high-energy spectral beam combining laser weapons, and high-precision displacement measurement grating scales. Their preparation process is very complex, mainly including photoresist coating on the grating substrate surface, exposure lithography, development, ion beam etching, and coating reconstruction. Among them, exposure lithography is a key process link in the preparation of high-quality diffraction gratings. The line density and wavefront aberration of the grating mainly depend on this link. At present, meter-scale large-aperture dual-beam interference exposure systems are mainly used for exposure lithography. In this technical solution, the ultraviolet laser beam emitted by the laser is divided into two beams of equal intensity by a beam splitter. After being expanded and collimated by the exposure system, interference occurs inside the photoresist on the surface of the grating substrate to form a photoresist grating latent image. Subsequently, the diffraction grating element is prepared through processes such as wet development and etching. Compared to traditional large-aperture transmissive dual-beam interference exposure systems, reflective dual-beam interference exposure systems based on off-axis parabolic reflectors are less restricted by the diameter of the collimating mirror material, making it easier to fabricate large-aperture diffraction gratings exceeding meters in diameter. However, the characteristics of reflective dual-beam interference exposure systems are a small field of view and a non-coaxial collimating optical path. This results in greater aberrations under the same optical processing and assembly conditions. The non-coaxial nature of the collimating system makes precise control of the grating line density more difficult. This is mainly because the line density of the dual-beam interference exposure system (the inverse of the grating period Λ, i.e., 1 / Λ) depends on the interference angle between the two beams. From the interference fringe period formula Λ = λ / 2 / sin(θ), it can be seen that when the wavelength λ of the exposure system light source is constant, controlling the exposure system line density is actually adjusting the interference angle θ between the two beams. However, when adjusting the angle between the two beams of light, it means that the focus of the off-axis parabolic collimator in the exposure system will also change. This results in the mutual coupling of the wavefront aberration and the line density of the system during the adjustment of the reflective dual-beam interference exposure system, making it extremely difficult to adjust the interference system aberration and the line density at the same time, and the system needs to be repeatedly adjusted iteratively. In order to solve the aberration control problem of the reflective dual-beam interference exposure system, the invention patent with patent number CN202311186275, the invention name of which is "A method for adjusting the aberration of a reflective dual-beam interference exposure system", proposes a method for adjusting the wavefronts of two interfering light beams using a deformable mirror. This method can well control the wavefront aberration of the interference light field, but cannot simultaneously take into account the adjustment of the line density of the interference system during the adjustment process.

[0003] Therefore, studying and solving the problem of precise adjustment of large-aperture reflective dual-beam interference exposure systems that take into account both line density and aberration is of great significance for promoting the application of reflective interference exposure technology in the field of large-aperture diffraction grating manufacturing above the meter level. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that it is difficult to accurately control the line density and aberration of the existing reflective dual-beam interference exposure system during the assembly and adjustment process, and to provide a reflective dual-beam interference exposure system assembly and adjustment method that takes both line density and aberration into consideration. By constructing a line density standard module and combining interferometer wavefront detection and spatial filtering adjustment, high-precision assembly of the reflective dual-beam interference system can be achieved.

[0005] The technical solutions of the present invention are as follows:

[0006] A reflective dual-beam interference exposure system assembly and adjustment method taking both line density and aberration into consideration is characterized by comprising:

[0007] Construct a line density standard module to generate a standard reference beam for adjusting the line density of the exposure system and the system adjustment; the line density standard module includes: a laser autocollimator, a standard reference grating, a large-aperture standard plane mirror, a semi-transparent and semi-reflective mirror, a CCD camera and a computer; the laser autocollimator is used to emit a parallel laser beam; the standard reference grating has a period of Among them, λ r is the output wavelength of the laser autocollimator, λ e is the output wavelength of the UV exposure light source, and d is the target grating period; a large-aperture standard plane mirror is used to reflect the diffracted light and achieve self-collimation of the optical path; a semi-transparent and semi-reflective mirror and a CCD camera are used to monitor the interference fringes and calibrate the verticality of the optical path;

[0008] The line density standard module is used to generate ±1-order reflected / transmitted diffraction light as a reference beam. By adjusting the pitch and yaw angles of the large-aperture standard plane reflector, the transmitted diffraction light and the reflected diffraction light are superimposed and interfered on the CCD camera until the interference fringes disappear, thereby completing the vertical calibration of the large-aperture standard plane reflector;

[0009] A reflective dual-beam interference exposure system is constructed. By adjusting the spatial position of the off-axis parabolic reflector and combining it with the wavefront measurement of the spherical interferometer, the wavefront aberration of the large-aperture light beam reflected by the large-aperture standard plane is minimized, the true focal position of each off-axis mirror in the dual-beam optical path is determined, and the construction of a dual-beam interference exposure system with precise line density is completed.

[0010] A standard reference beam is generated using the line density standard module to control the angle of the interference beam and thus the interference line density. Using the nominal focus of the standard reference beam generated by the line density standard module after being focused by the off-axis mirror as a reference, a spherical interferometer is installed and the wavefront of the beam emitted by the large-aperture off-axis mirror is measured to determine the true focal position of the off-axis parabolic reflector. The above operations complete the assembly and adjustment of a reflective dual-beam interference exposure system with controllable line density and aberration. Specifically,

[0011] Step 1) Construction of the line density standard module

[0012] Step 1.1) According to the laser autocollimator output wavelength λ r 、UV exposure light source output wavelength λ e And the grating period d to be prepared, the design preparation period Standard reference grating;

[0013] Step 1.2) Install the laser autocollimator and standard reference grating. Adjust their spatial orientation so that the parallel laser beam emitted by the laser autocollimator is perpendicular to the surface of the standard grating. After beam splitting, two beams of ±1st order reflected diffracted light and two beams of ±1st order transmitted diffracted light are formed. The angle θ between the reflected diffracted light and the normal line of the grating surface satisfies the following formula:

[0014]

[0015] Step 2) Adjust the optical path of the reflective dual-beam interference exposure system

[0016] Step 2.1) Install a large-aperture standard plane mirror and a semi-transparent and semi-reflective mirror in sequence, and connect the CCD camera to the control computer. Adjust the yaw and pitch angles of the large-aperture standard plane mirror so that the reflected +1-order transmitted diffraction light returns along the original path, passes through the standard reference grating in the ruled density standard module, and then interferes with the +1-order reflected diffraction light on the CCD camera.

[0017] Step 2.2) Continue fine-tuning the pitch and yaw of the large-aperture standard plane mirror until the interference fringes on the CCD camera disappear, indicating that the +1-order transmitted diffraction light is strictly perpendicular to the large-aperture standard plane mirror. At this point, fix the position of the standard plane mirror. This completes the construction of the line density standard module for lower optical path adjustment and the generation of the standard reference beam.

[0018] Step 2.3) Preliminary installation of the large-aperture off-axis parabolic reflector in the lower optical path;

[0019] Step 2.4) Install and adjust the position of the spatial filter so that the focus of the converging beam formed by the +1-order reflected diffraction reference light emitted by the line density standard module after passing through the large-aperture off-axis parabolic reflector passes through the pinhole on the spatial filter;

[0020] Step 2.5) Install and adjust the position of the spherical interferometer so that the focus of its outgoing beam also passes through the pinhole on the spatial filter. Use the spherical interferometer to measure and record the wavefront aberration of the large-aperture beam reflected by the large-aperture standard plane mirror;

[0021] Repeat step 2.6) to adjust the spatial position of the large-aperture off-axis parabolic reflector in the lower optical path, and repeat the operations of steps 2.4) to 2.5) until the wavefront aberration of the large-aperture beam measured by the spherical interferometer is minimized. Then, fix the positions of the large-aperture off-axis parabolic reflector and the spatial filter in the lower optical path.

[0022] Step 2.7) Remove the spherical interferometer, turn on the UV laser light source, and place a half-wave plate and a polarization beam splitter prism along the transmission direction of the UV laser beam. The UV laser beam is split into two beams, namely a reflected beam and a transmitted beam, by the polarization beam splitter prism. A reflector and a focusing lens are sequentially placed along the transmission direction of the reflected beam. The positions of the reflector and focusing lens are repeatedly adjusted until the focus of the UV laser beam, after being focused by the focusing lens, passes through the pinhole on the spatial filter. This completes the alignment of the lower optical path.

[0023] Step 3) Adjust the optical path of the reflective dual-beam interference exposure system

[0024] Step 3.1) Rotate the large-aperture standard plane mirror counterclockwise and adjust it to be perpendicular to the -1st order transmitted diffraction light according to the procedures from Steps 2.1) to 2.2) to complete the construction of the line density standard module for upper optical path adjustment and the generation of the standard reference beam.

[0025] Step 3.2) Preliminary installation of the large-aperture off-axis parabolic reflector in the upper optical path;

[0026] Step 3.3) Install and adjust the position of the spatial filter so that the focus of the converging beam formed by the -1 order reflected diffraction reference light emitted by the line density standard module after passing through the large-aperture off-axis parabolic reflector passes through the pinhole on the spatial filter;

[0027] Step 3.4) Install and adjust the position of the spherical interferometer so that the focus of its outgoing beam also passes through the pinhole on the spatial filter, and use the spherical interferometer to test and record the wavefront aberration of the large-aperture beam reflected by the large-aperture standard plane reflector 8;

[0028] Step 3.5) Repeat the adjustment of the spatial position of the large-aperture off-axis parabolic reflector in the upper optical path, and repeat the operation process of steps 2.3) to 2.4) until the wavefront aberration of the large-aperture beam measured by the spherical interferometer is minimized. Then, fix the position of the large-aperture off-axis parabolic reflector and the spatial filter in the upper optical path;

[0029] (Step 3.6) Remove the spherical interferometer, turn on the UV laser light source, and place the half-wave plate, reflector, and focusing lens in the direction of the transmitted beam. Repeatedly adjust the positions of the reflector and focusing lens until the focus of the UV laser beam, after being focused by the focusing lens, passes through the pinhole on the spatial filter. This completes the alignment of the upper optical path.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] 1. A line density standard module constructed using a standard reference grating, a laser autocollimator, a semi-transparent and semi-reflective mirror, and a CCD camera provides a benchmark for the alignment of a reflective dual-beam interferometer exposure system. The alignment process simultaneously takes into account the alignment accuracy of both the line density and wavefront aberration of the exposure system, solving the problem of crosstalk between the line density adjustment and the wavefront aberration adjustment of the exposure system in traditional alignment methods.

[0032] 2. The reference beam in the line density standard module greatly facilitates the search for the focal position of large-aperture off-axis parabolic reflectors, significantly improving the adjustment efficiency of the dual-beam interference exposure system. Furthermore, the line density standard module utilizes a standard reference grating, ensuring the repeatability of the line density adjustment of the dual-beam interference exposure system and laying the foundation for the preparation of diffraction gratings with high line density consistency requirements.

[0033] 3. This assembly and adjustment method is applicable to any technical solution for preparing diffraction gratings using double-beam interference exposure technology and has strong versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the lower optical path of an adjustment method that takes both scribed line density and aberration into consideration in an embodiment of a reflective dual-beam interference exposure system of the present invention;

[0035] Figure 2 Schematic diagram of the upper optical path of an adjustment method that takes both scribed line density and aberration into consideration in an embodiment of a reflective dual-beam interference exposure system of the present invention;

[0036] In the figure: 1-laser autocollimator, 2-parallel laser beam, 3-standard reference grating, 4-+1 order reflected diffraction light, 5--1 order reflected diffraction light, 6-+1 order transmitted diffraction light, 7--1 order transmitted diffraction light, 8-large aperture standard plane mirror, 9-semi-transparent and semi-reflective mirror, 10-CCD camera, 11-computer, 12-lower optical path off-axis parabolic mirror, 13-upper optical path off-axis parabolic mirror, 14-first focused beam, 15-second focused beam, 16-first pinhole, 17-second pinhole, 18-first focusing objective lens, 19-second focusing objective lens, 20-spherical interferometer, 21-first reflector, 22-second reflector, 23-third reflector, 24-first half-wave plate, 25-polarization beam splitter, 26-second half-wave plate, 27-ultraviolet laser light source, 28-first large aperture beam, 29-second large aperture beam DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the embodiments and drawings, but the scope of protection of the present invention should not be limited thereto.

[0038] The aberration control device of the reflective double-beam interference exposure system includes:

[0039] Spherical interferometer, used to measure and record the wavefront aberration of the output beam of the reflective interferometric exposure system, and to achieve dynamic testing and feedback of the aberration through a self-collimating optical path (combined with a standard plane mirror);

[0040] A spatial filter is used to locate the position of the ideal point light source generated by the spherical interferometer and perform spatial filtering on it to ensure that the standard reference beam and the ultraviolet beam share the same path;

[0041] Deformable mirrors are used to dynamically control the wavefront of one beam in a dual-beam interference exposure system, compensating for aberrations and matching the wavefront aberration of the other beam, thereby reducing the grating diffraction wavefront aberration formed after interference and improving the grating quality.

[0042] The standard plane mirror is used to reflect the laser beam emitted by the interference exposure system and return it to its original path. It forms a wavefront aberration self-collimation measurement optical path with the spherical interferometer to ensure the verticality of the optical path and provide a benchmark for aberration testing.

[0043] A method for assembling and adjusting a reflective dual-beam interference exposure system taking both line density and aberration into consideration, specifically comprising:

[0044] S1. Construction of standard module for line density:

[0045] The line density standard module generates a standard reference beam for adjusting the line density of the exposure system and the system adjustment. It mainly includes the following components:

[0046] The laser autocollimator 1 emits a parallel beam perpendicular to the standard reference grating to generate ±1st order diffracted light. In this embodiment, a NORMAT-3210 (Shanghai Nuoxu Electromechanical Technology Co., Ltd.) with an output wavelength of 630 nm is used.

[0047] Standard reference grating 3, size 50mm×50mm, grating period d 标 It is 2307.67nm.

[0048] The large-aperture standard plane reflector 8 reflects the transmitted light beam and forms interference with the reflected light. The fringe state is monitored by the CCD. The size of this embodiment is 1650mm×1120mm, and the reflected wavefront is better than λ / 8@632.8nm.

[0049] The semi-transparent and semi-reflective mirror 9 splits the beam to the CCD and the spherical interferometer, realizing simultaneous interference calibration and wavefront measurement.

[0050] The CCD camera 10, model MV-CA013-20GM of Hikvision Robotics, is used to capture the moiré fringe offset.

[0051] Step 1) Adjust the optical path of the reflective dual-beam interference exposure system

[0052] Step 1.1) Prepare a standard reference grating 3. The dual-beam interference exposure system used in this embodiment has a line density of 1400 lines / mm (grating period 714.28 nm), and the output wavelength λe of the UV exposure light source 27 is 390 nm. Therefore, the period of the standard reference grating 3 is 2307.67 nm.

[0053] Step 1.2) Install the laser autocollimator 1 and the standard reference grating 3. Adjust their spatial orientation so that the parallel laser beam emitted by the laser autocollimator 1 is perpendicularly incident on the surface of the standard grating 3. After beam splitting, two beams of ±1st-order reflected diffracted light 4 and 5 and two beams of ±1st-order transmitted diffracted light 6 and 7 are formed. The angle θ between the reflected diffracted light 4 and 5 and the grating surface normal is 15.84°:

[0054] Step 1.3) Install the large-aperture standard plane mirror 8 and the semi-transparent and semi-reflective mirror 9 in sequence, and connect the CCD camera 10 to the computer 11. Adjust the yaw and pitch angles of the large-aperture standard plane mirror 8 so that the -1st order transmitted diffraction light 7 reflected by it returns along the original path, passes through the standard reference grating 3, and then interferes with the +1st order reflected diffraction light 4 on the CCD camera 10.

[0055] Step 1.4) Continuously fine-tune the pitch and yaw of the large-aperture standard plane mirror 8 until the interference fringes on the CCD camera 10 disappear, indicating that the -1-order transmitted diffraction light 7 is strictly perpendicular to the large-aperture standard plane mirror. At this point, fix the position of the standard plane mirror 8. This completes the construction of the line density standard module that can be used for lower optical path adjustment and the generation of the standard reference beam 4.

[0056] Step 1.5) Install the large-aperture off-axis parabolic reflector 12 in the lower optical path;

[0057] Step 1.6) Install and adjust the position of the first pinhole 16 so that the focus of the first focused beam 14 formed by the standard reference beam 4 emitted by the scribed density standard module after passing through the large-aperture off-axis parabolic reflector passes through the first pinhole 16;

[0058] Step 1.7) Install and adjust the position of the spherical interferometer 20 so that the focus of its outgoing light beam also passes through the first pinhole 16. Use the spherical interferometer 20 to measure and record the wavefront aberration of the first large-aperture light beam 28 reflected by the large-aperture standard plane mirror;

[0059] Step 1.8) Repeat the adjustment of the spatial position of the large-aperture off-axis parabolic reflector 12 in the lower optical path, and repeat the operations of steps 1.6) to 1.7) until the wavefront aberration of the first large-aperture light beam 28 measured by the spherical interferometer 20 is minimized. Then, the positions of the large-aperture off-axis parabolic reflector 12 and the first pinhole 16 in the lower optical path are fixed;

[0060] Step 1.9) Remove the spherical interferometer 20, turn on the ultraviolet laser light source 27, and place the second half-wave plate 26 and the polarization beam splitter prism 25 along the transmission direction of the ultraviolet laser beam. The ultraviolet laser beam is split into two beams, namely a reflected beam and a transmitted beam, by the polarization beam splitter prism 25. Place the first reflector 21 and the first focusing lens 18 in sequence along the transmission direction of the reflected beam. Repeatedly adjust the positions of the first reflector 21 and the first focusing lens 18 until the focus of the ultraviolet laser beam after being focused by the first focusing lens 18 passes through the first pinhole 16. This completes the alignment of the lower optical path.

[0061] Step 2) Adjust the optical path of the reflective dual-beam interference exposure system

[0062] Step 2.1) Rotate the large-aperture standard plane mirror 8 counterclockwise and adjust it to be perpendicular to the +1-order transmitted diffraction light 6 according to the operation method of steps 1.2) to 1.4), completing the construction of the line density standard module for upper optical path adjustment and the generation of the standard reference beam 5;

[0063] Step 2.2) Preliminary installation of the large-aperture off-axis parabolic reflector 13 on the upper optical path;

[0064] Step 2.3) Install and adjust the position of the second pinhole 17 so that the focus of the second focused beam 15 formed by the standard reference beam 5 passing through the large-aperture off-axis parabolic reflector 13 passes through the second pinhole 17;

[0065] Step 2.4) Install and adjust the position of the spherical interferometer 20 so that the focus of its outgoing light beam also passes through the second pinhole 17. Use the spherical interferometer 20 to measure and record the wavefront aberration of the second large-aperture light beam 29 reflected by the large-aperture standard plane mirror 8;

[0066] Step 2.5) Repeat the adjustment of the spatial position of the upper optical path large-aperture off-axis parabolic reflector 13, and repeat the operation process of steps 1.3) to 1.4) until the wavefront aberration of the second largest aperture light beam 29 measured by the spherical interferometer 20 is minimized. Then, fix the positions of the upper optical path large-aperture off-axis parabolic reflector 13 and the second pinhole 17;

[0067] Step 2.6) Remove the spherical interferometer 20, turn on the ultraviolet laser light source 27, and place the third reflector 23, first half-wave plate 24, second reflector 22, and second focusing lens 19 in sequence along the direction of the transmitted light beam. Repeatedly adjust the positions of the second reflector 22 and second focusing lens 19 so that the focus of the ultraviolet laser beam after being focused by the second focusing lens 19 passes through the second pinhole 17. This completes the adjustment of the upper optical path.

[0068] This technology ensures that the system grating period error is less than 0.1% through the coordination of the aberration control device and the adjustment method, achieving micron-level accuracy and reducing the adjustment time to 1 / 3 of the traditional method.

Claims

1. A reflective dual-beam interference exposure system adjustment method that takes into account both line density and aberration, characterized in that: include: Construct a line density standard module, the line density standard module comprising: Laser autocollimator, used to emit parallel laser beam; Standard reference grating, its period Among them, λ r is the output wavelength of the laser autocollimator, λ e is the output wavelength of the UV exposure light source, and d is the target grating period; Large-aperture standard plane mirror, used to reflect diffracted light and achieve self-collimation of the optical path; A semi-transparent mirror and a CCD camera are used to monitor interference fringes and calibrate the perpendicularity of the optical path; The line density standard module is used to generate ±1-order reflected / transmitted diffraction light as a reference beam. By adjusting the pitch and yaw angles of the large-aperture standard plane reflector, the transmitted diffraction light and the reflected diffraction light are superimposed and interfered on the CCD camera until the interference fringes disappear, thereby completing the vertical calibration of the large-aperture standard plane reflector; A reflective dual-beam interference exposure system is constructed. By adjusting the spatial position of the off-axis parabolic reflector and combining it with the wavefront measurement of the spherical interferometer, the wavefront aberration of the large-aperture light beam reflected by the large-aperture standard plane is minimized, the true focal position of each off-axis mirror in the dual-beam optical path is determined, and the construction of a dual-beam interference exposure system with precise line density is completed.

2. The method for controlling line density of a reflective dual-beam interference exposure system according to claim 1, wherein: The construction of the scribed line density standard module specifically includes: S1.1 According to the output wavelength λ of the laser autocollimator r 、UV exposure light source output wavelength λ e As well as the period d of the grating to be prepared, a standard reference grating is designed and prepared, and its period S1.1 Install the laser autocollimator and the standard reference grating, and adjust their relative positions so that the parallel laser beam emitted by the laser autocollimator is perpendicularly incident on the surface of the standard grating. After beam splitting, two beams of ±1st order reflected diffraction light and two beams of ±1st order transmitted diffraction light are formed. Among them, the diffraction angle θ of the standard reference beam is ， That is, the angle θ between the reflected diffracted light and the normal line of the standard grating surface satisfies the following formula:

3. The method for controlling line density of a reflective dual-beam interference exposure system according to claim 1, wherein: The steps for adjusting the lower optical path of the reflective dual-beam interference exposure system are as follows: S2.1 Install and adjust a large-aperture standard plane mirror so that the -1st order transmitted diffraction light returns along its original path. Install a semi-transparent mirror so that the -1st order transmitted diffraction light that returns along its original path passes through the standard reference grating and is reflected by the semi-transparent mirror together with the +1st order reflected diffraction light, forming interference on the CCD camera. S2.2 Finely adjust the large-aperture standard plane mirror until the interference fringes disappear, fix its position, and complete the generation of the standard reference beam in the lower optical path; S2.3 Install the lower optical path off-axis parabolic reflector and adjust its position so that the focus of the lower optical path focused beam formed after the reflection of the lower optical path standard reference beam passes through the first pinhole; S2.4 Install the spherical interferometer so that the focus of the outgoing beam passes through the first pinhole and measure the wavefront aberration of the first large-aperture beam; S2.5 Iteratively adjust the position of the off-axis parabolic reflector until the wavefront aberration is minimized and fix its position.

4. The method for controlling line density of a reflective dual-beam interference exposure system according to claim 1, wherein: The steps for adjusting the upper optical path of the reflective dual-beam interference exposure system are as follows: S3.1 Adjust the large-aperture standard plane mirror so that it is perpendicular to the +1-order transmitted diffraction light to complete the generation of the standard reference beam in the upper optical path; S3.2 Install the upper optical path off-axis parabolic reflector and adjust its position so that the focus of the upper optical path focused beam formed after the upper optical path standard reference beam is reflected passes through the second pinhole; S3.3 Install the spherical interferometer so that the focus of the outgoing beam passes through the second pinhole and measure the wavefront aberration of the second largest aperture beam; S3.4 Iteratively adjust the position of the off-axis parabolic reflector until the wavefront aberration is minimized and fix its position.

5. The method for controlling line density of a reflective dual-beam interference exposure system according to claim 1, wherein: The UV light path adjustment steps of the reflective dual-beam interference exposure system are as follows: S4.1 Turn on the ultraviolet laser light source and split it into a reflected beam and a transmitted beam through a polarization beam splitter prism; S4.2 Adjust the first reflector and the first focusing lens of the lower optical path so that the focus of the reflected light beam passes through the first pinhole; S4.3 Adjust the second reflector and the second focusing objective lens in the upper optical path so that the focus of the transmitted light beam passes through the second pinhole.

6. A method for controlling line density in a reflective dual-beam interference exposure system according to any one of claims 1 to 5, characterized in that: The installation position of the semi-transparent and semi-reflective mirror satisfies the following requirements: splitting the interference light beam captured by the CCD camera to the computer, while allowing part of the light beam to be reflected back to the large-aperture plane reflective mirror to form a self-collimating loop.

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