A laser interference exposure optical path system for making a grating

Abstract

The application discloses a kind of laser interference exposure optical path systems for making grating, it is characterized in that, including laser, light guide optical path, exposure optical path and stripe locking optical path;A mirror M1 is provided between the laser and light guide optical path, so that laser can be reflected into light guide optical path;PID module is connected on the light guide optical path, and three-axis piezoelectric displacement stage cooperating with the PID module is arranged in the exposure pipeline.This application provides a kind of laser interference exposure optical path systems for making grating, can effectively avoid monitoring light beam to carry out secondary excessive exposure damage to latent image grating, greatly reduce the difficulty of adjustment, effectively adjust and lock the phase and attitude of latent image grating, very good to promote the development and progress of industry.

Description

Technical Field

[0001] This application relates to the field of laser interferometric exposure equipment, and more specifically to a laser interferometric exposure optical path system for fabricating gratings. Background Technology

[0002] Laser interferometry systems are widely used in mechanical engineering, lithography, industry, agriculture, and other fields. These systems typically consist of a laser source, interferometers, mirrors, and measurement software, and are characterized by a large measurement range, high speed, high precision, and high resolution. In the field of micro / nano grating manufacturing, laser interferometry is a key method for achieving high-precision, large-area periodic structure fabrication. With the increasing integration of semiconductor devices and optical components, extremely stringent requirements are placed on the uniformity, continuity, and positional accuracy of grating lines. Therefore, achieving high-precision phase and attitude locking of interference fringes during the exposure process to ensure continuous alignment of the exposure pattern has become an important research direction in the field of laser interferometry.

[0003] Currently, to address the stability issue of interference fringes, the main measures adopted include using a single-lock detection method, indirect monitoring based on a reference beam, and conventional light intensity feedback control. For example, the phase drift of the interference fringes can be calculated by monitoring changes in the light intensity of the reference optical path; or a fixed photodetector can be used to directly receive a portion of the interference beam, and the frequency of the acousto-optic modulator can be adjusted through a feedback circuit to maintain phase stability; another approach uses a simple beam-splitting structure to directly illuminate the substrate surface with monitoring light for real-time observation. However, traditional laser interferometry exposure systems rely on a relatively simple locking detection method, which is susceptible to inhomogeneous efficiency due to latent image grating diffraction and affected by light intensity fluctuations. This results in large phase-locking errors, insufficient stability and sensitivity, and an inability to guarantee continuous fringe alignment. Furthermore, conventional optical paths lack dedicated attenuation monitoring structures, making it easy for the monitoring beam to cause secondary overexposure damage to the formed latent image grating, and it is difficult to control the fringe spacing and contrast, leading to poor monitoring signal quality. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a laser interference exposure optical path system for fabricating gratings. This system effectively avoids secondary overexposure damage to the latent image grating caused by the monitoring beam, greatly reduces the difficulty of adjustment, and effectively adjusts and locks the phase and orientation of the latent image grating, thus significantly promoting the development and progress of the industry.

[0005] A laser interferometric exposure optical path system for fabricating gratings includes: Laser, used to generate laser light; The light guide path is used to receive and split the laser into two paths: a transmission path and a reflection path. The exposure optical path is used to expose the two laser paths, the transmission path and the reflection path, to form a latent image grating; The fringe locking optical path, in conjunction with the light guide optical path and the exposure optical path, is used to adjust the phase and orientation of the latent image grating; A reflector M1 is provided between the laser and the light guide path to allow the laser to be reflected into the light guide path; a PID module is connected to the light guide path, and a triaxial piezoelectric displacement stage that cooperates with the PID module is provided in the exposure pipeline.

[0006] Furthermore, the light guide path consists of a beam splitter, a transmission path formed by transmission through the beam splitter, and a reflection path formed by reflection through the beam splitter.

[0007] Preferably, the beam splitting route consists of a shutter K that allows the laser to pass through / block, a reflector M2 and a reflector M3 arranged sequentially along the optical path for reflecting the laser, and a polarizing beam splitter prism PBS for receiving the laser reflected from the reflector M3 and splitting the laser into reflected and transmitted lasers; a through-hole lens A1 is provided between the shutter K and the reflector M2, and a half-wave plate P1 is provided between the reflector M3 and the polarizing beam splitter PBS.

[0008] Preferably, the reflection path consists of an acousto-optic modulator AOM1 for receiving reflected laser light and a reflector M5 for reflecting the Bragg diffraction-1st order reflected laser light emitted from the acousto-optic modulator AOM1 into the exposure optical path; a reflector M6 for reflecting reflected laser light is also provided before the acousto-optic modulator AOM1, and a through-hole lens A3 is also provided between the acousto-optic modulator AOM1 and the reflector M5.

[0009] Preferably, the transmission route includes an acousto-optic modulator AOM2 for receiving the transmitted laser light, and a reflector M4 for reflecting the -1st order Bragg diffraction transmitted laser light emitted from the acousto-optic modulator AOM2 into the exposure optical path; a half-wave plate P2 is also provided before the acousto-optic modulator AOM2, and a through-hole lens A2 is also provided between the acousto-optic modulator AOM2 and the reflector M4.

[0010] Furthermore, the exposure light route comprises a spatial filter SF1 for receiving and expanding the reflected laser emitted from the acousto-optic modulator AOM1 and filtering it, a lens L1 for forming a first parallel collimated beam from the laser emitted from the spatial filter SF1, a spatial filter SF2 for receiving and expanding the transmitted laser emitted from the acousto-optic modulator AOM2 and filtering it, a lens L2 for forming a second parallel collimated beam from the laser emitted from the spatial filter SF2, and a substrate G for carrying the first and second parallel collimated beams to form a latent image grating; an attenuator A4 is disposed between the lens L1 and the substrate G, and an attenuator A5 is disposed between the lens L2 and the substrate G; the spatial filters SF1 and SF2 are respectively disposed on a triaxial piezoelectric displacement stage.

[0011] Preferably, attenuator A4 is a lens with a parallel plate structure and a metal attenuation film coated on its surface, and attenuator A5 is a half-wave plate with a wedge structure and a metal attenuation film coated on its surface; attenuator A4 blocks half of the first parallel collimated beam, and attenuator A5 blocks half of the second parallel collimated beam; the unblocked half of the first parallel collimated beam and the unblocked half of the second parallel collimated beam coincide on the substrate G, and the blocked half of the first parallel collimated beam and the second parallel collimated beam coincide on the substrate G.

[0012] Furthermore, the stripe-locked optical route consists of a reflector M7 for reflecting the laser refracted by the attenuator A5, a beam splitter BS for splitting the laser reflected by the reflector M7 into two groups, and a CCD camera and a photomultiplier tube PMT for receiving one group of lasers respectively.

[0013] Preferably, the CCD camera and the photomultiplier tube (PMT) are electrically connected to the PID module, and the PID module is also electrically connected to the two triaxial piezoelectric displacement stages, the acousto-optic modulator (AOM1), and the acousto-optic modulator (AOM2).

[0014] The implementation process of the above optical path system is as follows: (1) Start the laser; After the laser is turned on, it emits a laser beam. The laser beam passes through the reflector M1 and enters the light guide path, illuminating the shutter K.

[0015] (2) The laser beam is split into a transmission path and a reflection path through the light guide path; When shutter speed K is opened, the laser is split into two paths at the polarization beam splitter PBS: a transmission path and a reflection path. These paths are then processed into Bragg diffraction-1 order lasers by acousto-optic modulators AOM2 and AOM1, respectively.

[0016] Among them, the function of reflectors M2, M3, M4, M5, and M6 is to change the laser path; the function of through-hole lenses A1, A2, and A is to shape the laser and remove any scattered light that may be present in the laser; half-wave plate P1 is used to adjust the intensity of the laser before splitting, and half-wave plate P2 is used to adjust the intensity of the laser in the transmission path to ensure that the laser intensity in the transmission path is consistent with the laser intensity in the reflection path.

[0017] (3) The lasers from the transmission path and the reflection path enter the exposure optical path, and the exposure forms a latent image grating, and a laser is refracted into the stripe locking optical path; The laser beams from the transmission path and the reflection path are expanded and filtered by spatial filters SF2 and SF1, respectively, and then pass through lenses L2 and L1 to become the second parallel collimated beam and the first parallel collimated beam, respectively, and are simultaneously directed toward the substrate G to form a latent image grating. Attenuators A5 and A4 are respectively installed along the paths of the second and first parallel collimated beams. The attenuators can attenuate the portion of the parallel collimated beam that is blocked, so as to make it better contrasted with the unattenuated portion. The portion of the second parallel collimated beam attenuated by attenuator A5 coincides with the portion of the first parallel collimated beam attenuated by attenuator A4 on the substrate G.

[0018] The attenuator A5 uses a wedge-shaped structure, which allows it to attenuate while also refracting a laser beam to enter the stripe-locking optical path.

[0019] (4) Acquire the refracted laser light by locking the fringe optical path and send the corresponding parameters to the PID module; The laser beam is directed through the beam splitter SB into the CCD camera and the photomultiplier tube PMT, respectively. The CCD camera and the photomultiplier tube PMT then send the collected parameters to the PID module.

[0020] (5) The PID module adjusts the two triaxial piezoelectric displacement stages, the acousto-optic modulator AOM1 and the acousto-optic modulator AOM2 according to the parameters; The PID module uses the light intensity signal V collected by the photomultiplier tube (PMT) to... T Synchronously adjust acousto-optic modulators AOM1 and AOM2 to make the light intensity signal V T =V0, then lock the operating parameters of the acousto-optic modulators AOM1 and AOM2 to complete phase locking and avoid the generation of phase error.

[0021] The CCD camera calculates the average grayscale difference ΔI between two rows of symmetrical sampling points on the latent image grating. If ΔI > 0, it outputs a feedback voltage to the PID module. The PID module adjusts the position coordinates of spatial filters SF1 and SF2 by controlling two triaxial piezoelectric displacement stages until ΔI = 0.

[0022] (6) Form the final latent image grating.

[0023] In light intensity signal V T When the average gray level difference ΔI = 0, the final latent image grating is formed on the substrate G.

[0024] When using the above optical path system for the first time, the position of the photomultiplier tube (PMT) needs to be manually adjusted to complete the initialization settings, specifically as follows: 1) Obtain the maximum value V of the light intensity signal V of the initial latent image grating by moving the photomultiplier tube (PMT). max and minimum value V min Let V0 be the median value of the light intensity signal V, i.e., V0 = (V max +V min ) / 2; 2) Manually adjust the position of the photomultiplier tube (PMT) to ensure that the light intensity signal V it detects is within acceptable limits. C =V0; 3) Fix the position of the photomultiplier tube (PMT); simultaneously record the CCD camera. 4) Select two rows of symmetrical sampling points on the initial latent image grating captured by the CCD camera, so that the average gray level difference ΔI=0, and complete the initialization setting. The optical path system enters the automatic locking mode.

[0025] Compared with the prior art, the embodiments of this application have the following beneficial effects: (1) The present invention adopts a dual detector scheme combining a photomultiplier tube (PMT) and a CCD camera; the PMT provides a high-speed, high-sensitivity phase error signal for high-frequency feedback control; the CCD camera is used to monitor the overall shape of the stripes; the combination of the two effectively eliminates the locking error caused by the non-uniform diffraction efficiency of the latent image grating or the fluctuation of light intensity, and realizes high-precision phase locking.

[0026] (2) By installing a three-axis piezoelectric displacement stage under the spatial filter SF1 and the spatial filter SF2 respectively, and independently controlling it by the PID module according to the image feedback of the CCD camera, the present invention achieves precise adjustment of the attitude of the interference fringes, ensuring the uniformity and consistency of the large-area exposure grating.

[0027] (3) The present invention can effectively avoid secondary overexposure damage to the latent image grating by the monitoring beam, greatly reduce the difficulty of adjustment, effectively adjust and lock the phase and attitude of the latent image grating, and greatly promote the development and progress of the industry.

[0028] Some of the additional features of this application can be further described in the following description. By examining the following description and corresponding drawings, or by understanding the operation and training process of the embodiments, those skilled in the art can clearly recognize some of the additional technical effects proposed in this application. The features disclosed in this application can be implemented and obtained through the practice of various construction methods, training processes, and combinations of different modules, strategies, and structures in specific embodiments. Attached Figure Description

[0029] The accompanying drawings, which are provided to further illustrate this application and constitute a part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute a limitation thereof. In the drawings, the same reference numerals denote the same components. Figure 1 This is a schematic diagram of the structure of the present invention.

[0030] Figure 2 This is a flowchart illustrating the implementation process of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0032] It should be noted that if the terms "first," "second," etc., are used in the specification, claims, and accompanying drawings of this application, they are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] In this application, when terms such as "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" are used, they indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly for better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0034] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0035] Furthermore, in this application, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] Example 1 like Figure 1 As shown, a laser interference exposure optical path system for fabricating a grating includes a laser for generating laser light, a light guide path for receiving and splitting the laser light into two paths, a transmission path and a reflection path, an exposure optical path for exposing the two laser paths to form a latent image grating, and a fringe locking optical path that cooperates with the light guide path for adjusting the latent image grating; a reflector M1 is provided between the laser and the light guide path to allow the laser light to be reflected into the light guide path; a PID module is connected to the light guide path, and a triaxial piezoelectric displacement stage that cooperates with the PID module is provided in the exposure pipeline.

[0038] The light guide path consists of a beam splitter, a transmission path formed by transmission through the beam splitter, and a reflection path formed by reflection through the beam splitter.

[0039] The beam splitter consists of a shutter K that allows the laser to pass through / block, a reflector M2 and a reflector M3 arranged sequentially along the optical path for reflecting the laser, and a polarizing beam splitter prism PBS for receiving the laser reflected from the reflector M3 and splitting the laser into reflected and transmitted lasers; a through-hole lens A1 is provided between the shutter K and the reflector M2, and a half-wave plate P1 is provided between the reflector M3 and the polarizing beam splitter PBS.

[0040] The reflection path consists of an acousto-optic modulator AOM1 for receiving reflected laser light and a reflector M5 for reflecting the Bragg diffraction-1st order reflected laser light emitted from the acousto-optic modulator AOM1 into the exposure optical path; a reflector M6 for reflecting reflected laser light is also provided before the acousto-optic modulator AOM1, and a through-hole lens A3 is also provided between the acousto-optic modulator AOM1 and the reflector M5.

[0041] The transmission path includes an acousto-optic modulator AOM2 for receiving transmitted laser light and a reflector M4 for reflecting the -1st order Bragg diffraction transmitted laser light emitted from the acousto-optic modulator AOM2 into the exposure optical path. A half-wave plate P2 is also provided before the acousto-optic modulator AOM2, and a through-hole lens A2 is also provided between the acousto-optic modulator AOM2 and the reflector M4.

[0042] The exposure optical path comprises a spatial filter SF1 for receiving and expanding the reflected laser emitted from the acousto-optic modulator AOM1 and filtering it, a lens L1 for forming a first parallel collimated beam from the laser emitted from the spatial filter SF1, a spatial filter SF2 for receiving and expanding the transmitted laser emitted from the acousto-optic modulator AOM2 and filtering it, a lens L2 for forming a second parallel collimated beam from the laser emitted from the spatial filter SF2, and a substrate G for carrying the first and second parallel collimated beams to form a latent image grating; an attenuator A4 is disposed between the lens L1 and the substrate G, and an attenuator A5 is disposed between the lens L2 and the substrate G; the spatial filters SF1 and SF2 are respectively disposed on a triaxial piezoelectric displacement stage.

[0043] The attenuator A4 is a parallel plate lens with a metal attenuation film coated on its surface, and the attenuator A5 is a half-wave plate with a wedge-shaped plate structure and a metal attenuation film coated on its surface. The attenuator A4 blocks half of the first parallel collimated beam, and the attenuator A5 blocks half of the second parallel collimated beam. The unblocked half of the first parallel collimated beam and the unblocked half of the second parallel collimated beam coincide on the substrate G, and the blocked half of the first parallel collimated beam and the second parallel collimated beam coincide on the substrate G.

[0044] The stripe-locked optical route consists of a reflector M7 for reflecting the laser refracted by attenuator A5, a beam splitter BS for splitting the laser reflected by reflector M7 into two groups, and a CCD camera and a photomultiplier tube PMT for receiving one group of lasers respectively.

[0045] The CCD camera and photomultiplier tube PMT are electrically connected to the PID module, and the PID module is also electrically connected to the two triaxial piezoelectric displacement stages, the acousto-optic modulator AOM1 and the acousto-optic modulator AOM2.

[0046] The emissivity of the aforementioned reflectors is ≥95%, and the adjustment range is ≥±4°. The polarization beam splitting ratio of the polarization beam splitter (PBS) is adjustable. The period of the latent image grating is 500nm-1000nm, with an adjustment accuracy of ≤10%. The duty cycle of the latent image grating is 0.4-0.6, with an adjustable accuracy of ≤0.1. The through-aperture lens uses a pinhole filter, and its maximum adjustment range is ≥300μm×300μm×300μm.

[0047] Example 2 First use of optical path system: In the above optical path system, the position of the photomultiplier tube (PMT) needs to be manually adjusted to complete the initialization settings, specifically as follows: 1) Obtain the maximum value V of the light intensity signal V of the initial latent image grating by moving the photomultiplier tube (PMT). max and minimum value V min Let V0 be the median value of the light intensity signal V, i.e., V0 = (V max +V min ) / 2; 2) Manually adjust the position of the photomultiplier tube (PMT) to ensure that the light intensity signal V it detects is within acceptable limits. C =V0; 3) Fix the position of the photomultiplier tube (PMT); simultaneously record the CCD camera. 4) Select two rows of symmetrical sampling points on the initial latent image grating captured by the CCD camera, so that the average gray level difference ΔI=0, and complete the initialization setting. The optical path system enters the automatic locking mode.

[0048] like Figure 2 As shown, the implementation process of the initialized optical path system is as follows: (1) Start the laser; After the laser is turned on, it emits a laser beam. The laser beam passes through the reflector M1 and enters the light guide path, illuminating the shutter K.

[0049] (2) The laser beam is split into a transmission path and a reflection path through the light guide path; When shutter speed K is opened, the laser is split into two paths at the polarization beam splitter PBS: a transmission path and a reflection path. These paths are then processed into Bragg diffraction-1 order lasers by acousto-optic modulators AOM2 and AOM1, respectively.

[0050] Among them, the function of reflectors M2, M3, M4, M5, and M6 is to change the laser path; the function of through-hole lenses A1, A2, and A is to shape the laser and remove any scattered light that may be present in the laser; half-wave plate P1 is used to adjust the intensity of the laser before splitting, and half-wave plate P2 is used to adjust the intensity of the laser in the transmission path to ensure that the laser intensity in the transmission path is consistent with the laser intensity in the reflection path.

[0051] (3) The lasers from the transmission path and the reflection path enter the exposure optical path, and the exposure forms a latent image grating, and a laser is refracted into the stripe locking optical path; The laser beams from the transmission path and the reflection path are expanded and filtered by spatial filters SF2 and SF1, respectively, and then pass through lenses L2 and L1 to become the second parallel collimated beam and the first parallel collimated beam, respectively, and are simultaneously directed toward the substrate G to form a latent image grating. Attenuators A5 and A4 are respectively installed along the paths of the second and first parallel collimated beams. The attenuators can attenuate the portion of the parallel collimated beam that is blocked, so as to make it better contrasted with the unattenuated portion. The portion of the second parallel collimated beam attenuated by attenuator A5 coincides with the portion of the first parallel collimated beam attenuated by attenuator A4 on the substrate G.

[0052] The attenuator A5 uses a wedge-shaped structure, which allows it to attenuate while also refracting a laser beam to enter the stripe-locking optical path.

[0053] (4) Acquire the refracted laser light by locking the fringe optical path and send the corresponding parameters to the PID module; The laser beam is directed through the beam splitter SB into the CCD camera and the photomultiplier tube PMT, respectively. The CCD camera and the photomultiplier tube PMT then send the collected parameters to the PID module.

[0054] (5) The PID module adjusts the two triaxial piezoelectric displacement stages, the acousto-optic modulator AOM1 and the acousto-optic modulator AOM2 according to the parameters; The PID module uses the light intensity signal V collected by the photomultiplier tube (PMT) to... T Synchronously adjust acousto-optic modulators AOM1 and AOM2 to make the light intensity signal V T =V0, then lock the operating parameters of the acousto-optic modulators AOM1 and AOM2 to complete phase locking and avoid the generation of phase error.

[0055] The CCD camera calculates the average grayscale difference ΔI between two rows of symmetrical sampling points on the latent image grating. If ΔI > 0, it outputs a feedback voltage to the PID module. The PID module adjusts the position coordinates of spatial filters SF1 and SF2 by controlling two triaxial piezoelectric displacement stages until ΔI = 0.

[0056] (6) Form the final latent image grating.

[0057] In light intensity signal V T When the average gray level difference ΔI = 0, the final latent image grating is formed on the substrate G.

[0058] It should be noted that all features disclosed in this specification, or all steps in all methods or processes disclosed, may be combined in any way, except for mutually exclusive features and / or steps.

[0059] Furthermore, the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents.

Claims

1. A laser interference exposure optical path system for fabricating gratings, characterized in that, The system includes a laser for generating laser light, a light guide path for receiving and splitting the laser light into two paths, a transmission path and a reflection path, an exposure path for exposing the two laser paths to form a latent image grating, and a fringe locking path that works in conjunction with the light guide path and the exposure path to adjust the latent image grating; a reflector M1 is provided between the laser and the light guide path to allow the laser light to be reflected into the light guide path; a PID module is connected to the light guide path, and a triaxial piezoelectric displacement stage that works in conjunction with the PID module is provided in the exposure path.

2. The laser interference exposure optical path system for fabricating gratings according to claim 1, characterized in that, The light guide path consists of a beam splitter, a transmission path formed by transmission through the beam splitter, and a reflection path formed by reflection through the beam splitter. The beam splitter consists of a shutter K that allows the laser to pass through / block, a reflector M2 and a reflector M3 arranged sequentially along the optical path for reflecting the laser, and a polarizing beam splitter prism PBS for receiving the laser reflected from the reflector M3 and splitting the laser into reflected and transmitted laser light; a through-hole lens A1 is provided between the shutter K and the reflector M2, and a half-wave plate P1 is provided between the reflector M3 and the polarizing beam splitter PBS. The reflection path consists of an acousto-optic modulator AOM1 for receiving reflected laser light and a reflector M5 for reflecting the Bragg diffraction-1st order reflected laser light emitted from the acousto-optic modulator AOM1 into the exposure optical path; a reflector M6 for reflecting reflected laser light is also provided before the acousto-optic modulator AOM1, and a through-hole lens A3 is also provided between the acousto-optic modulator AOM1 and the reflector M5. The transmission path includes an acousto-optic modulator AOM2 for receiving transmitted laser light and a reflector M4 for reflecting the -1st order Bragg diffraction transmitted laser light emitted from the acousto-optic modulator AOM2 into the exposure optical path. A half-wave plate P2 is also provided before the acousto-optic modulator AOM2, and a through-hole lens A2 is also provided between the acousto-optic modulator AOM2 and the reflector M4.

3. The laser interference exposure optical path system for fabricating gratings according to claim 2, characterized in that, The exposure optical path comprises a spatial filter SF1 for receiving and expanding the reflected laser emitted from the acousto-optic modulator AOM1, and a lens L1 for forming a first parallel collimated beam from the laser emitted from the spatial filter SF1; a spatial filter SF2 for receiving and expanding the transmitted laser emitted from the acousto-optic modulator AOM2, and a lens L2 for forming a second parallel collimated beam from the laser emitted from the spatial filter SF2; and a substrate G for carrying the first and second parallel collimated beams to form a latent image grating. An attenuator A4 is disposed between the lens L1 and the substrate G, and an attenuator A5 is disposed between the lens L2 and the substrate G. The spatial filters SF1 and SF2 are respectively disposed on a triaxial piezoelectric displacement stage. The attenuator A4 is a parallel plate lens with a metal attenuation film coated on its surface, and the attenuator A5 is a half-wave plate with a wedge-shaped plate structure and a metal attenuation film coated on its surface. The attenuator A4 blocks half of the first parallel collimated beam, and the attenuator A5 blocks half of the second parallel collimated beam. The unblocked half of the first parallel collimated beam and the unblocked half of the second parallel collimated beam coincide on the substrate G, and the blocked half of the first parallel collimated beam and the second parallel collimated beam coincide on the substrate G.

4. The laser interference exposure optical path system for fabricating gratings according to claim 3, characterized in that, The stripe-locked optical route consists of a reflector M7 for reflecting the laser refracted by attenuator A5, a beam splitter BS for splitting the laser reflected by reflector M7 into two groups, and a CCD camera and a photomultiplier tube PMT for receiving one group of lasers respectively.

5. The laser interference exposure optical path system for fabricating gratings according to claim 4, characterized in that, The CCD camera and photomultiplier tube PMT are electrically connected to the PID module, and the PID module is also electrically connected to the two triaxial piezoelectric displacement stages, the acousto-optic modulator AOM1 and the acousto-optic modulator AOM2.

6. The laser interference exposure optical path system for fabricating gratings according to claim 5, characterized in that, The implementation process of the optical path system is as follows: (1) Start the laser; After the laser is turned on, it emits a laser beam. The laser beam passes through the reflector M1 and enters the light guide path, illuminating the shutter K. (2) The laser beam is split into a transmission path and a reflection path through the light guide path; (3) The lasers from the transmission path and the reflection path enter the exposure optical path, and the exposure forms a latent image grating, and a laser is refracted into the stripe locking optical path; (4) Acquire the refracted laser light by locking the fringe optical path and send the corresponding parameters to the PID module; The laser beam is directed through the beam splitter SB into the CCD camera and the photomultiplier tube PMT respectively. The CCD camera and the photomultiplier tube PMT respectively send the collected parameters to the PID module. (5) The PID module adjusts the two triaxial piezoelectric displacement stages, the acousto-optic modulator AOM1 and the acousto-optic modulator AOM2 according to the parameters; (6) Form the final latent image grating.

7. The laser interference exposure optical path system for fabricating gratings according to claim 6, characterized in that, When using the above optical path system for the first time, the position of the photomultiplier tube (PMT) needs to be manually adjusted to complete the initialization settings, specifically as follows: 1) Obtain the maximum value V of the light intensity signal V of the initial latent image grating by moving the photomultiplier tube (PMT). max and minimum value V min Let V0 be the median value of the light intensity signal V, i.e., V0 = (V max +V min ) / 2; 2) Manually adjust the position of the photomultiplier tube (PMT) to ensure that the light intensity signal V it detects is within acceptable limits. C =V0; 3) Fix the position of the photomultiplier tube (PMT); simultaneously record the CCD camera. 4) Select two rows of symmetrical sampling points on the initial latent image grating captured by the CCD camera, so that the average gray level difference ΔI=0, and complete the initialization setting. The optical path system enters the automatic locking mode.

8. The laser interference exposure optical path system for fabricating gratings according to claim 7, characterized in that, In process (2): When shutter speed K is opened, the laser is split into two paths at the polarization beam splitter PBS: a transmission path and a reflection path. These paths are then processed into Bragg diffraction-1 order lasers by acousto-optic modulators AOM2 and AOM1, respectively. Among them, the function of reflectors M2, M3, M4, M5, and M6 is to change the laser path; the function of through-hole lenses A1, A2, and A is to shape the laser and remove any scattered light that may be present in the laser; half-wave plate P1 is used to adjust the intensity of the laser before splitting, and half-wave plate P2 is used to adjust the intensity of the laser in the transmission path to ensure that the laser intensity in the transmission path is consistent with the laser intensity in the reflection path.

9. The laser interference exposure optical path system for fabricating gratings according to claim 8, characterized in that, In process (3): The laser beams from the transmission path and the reflection path are expanded and filtered by spatial filters SF2 and SF1, respectively, and then pass through lenses L2 and L1 to become the second parallel collimated beam and the first parallel collimated beam, respectively, and are simultaneously directed toward the substrate G to form a latent image grating. Attenuators A5 and A4 are respectively installed along the paths of the second and first parallel collimated beams. The attenuators can attenuate the portion of the parallel collimated beam that is blocked, so as to make it better contrasted with the unattenuated portion. The portion of the second parallel collimated beam attenuated by attenuator A5 coincides with the portion of the first parallel collimated beam attenuated by attenuator A4 on the substrate G. The attenuator A5 uses a wedge-shaped structure, which allows it to attenuate while also refracting a laser beam to enter the stripe-locking optical path.

10. A laser interference exposure optical path system for fabricating gratings according to claim 8, characterized in that, In step (5): The PID module uses the light intensity signal V collected by the photomultiplier tube (PMT) to... T Synchronously adjust acousto-optic modulators AOM1 and AOM2 to make the light intensity signal V T =V0, then lock the operating parameters of the acousto-optic modulators AOM1 and AOM2 to complete phase locking and avoid the generation of phase error. The CCD camera calculates the average gray level difference ΔI between two rows of symmetrical sampling points on the latent image grating. If ΔI > 0, it outputs a feedback voltage to the PID module. The PID module adjusts the position coordinates of the spatial filter SF1 and spatial filter SF2 by controlling two triaxial piezoelectric displacement stages until ΔI = 0. In step (6): In light intensity signal V T When the average gray level difference ΔI = 0, the final latent image grating is formed on the substrate G.

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