Chessboard grating photomask manufacturing precision optimization method

Abstract

The present application relates to a kind of chessboard grating photomask manufacturing precision optimization method, comprising: according to the height of product precision requirement, select different photoetching process;According to the different photoetching process selected above, substrate is handled, the thickness of chromium layer on substrate is set, while chromium layer has high reflectivity, different photoresist layer is coated on chromium layer according to different photoetching process;Different photoetching process is adjusted and designed to photomask plate pattern respectively;According to different application scenarios, REG precision compensation in different positions is realized, and the position precision change caused by different photoetching process is matched.The present application relates to a kind of chessboard grating photomask manufacturing precision optimization method, eliminates the influence of chessboard grating Dark position break link and optimizes connection position precision, improves CD and position precision, improves round angle radius, local customer process compensation etc., greatly improves terminal optical diffraction efficiency and uniformity, improves optical performance, improves the quality and reliability of photomask.

Description

Technical Field

[0001] This invention relates to the field of photomask technology, and in particular to a method for optimizing the manufacturing precision of a checkerboard grating photomask. Background Technology

[0002] A checkerboard grating is a special type of grating with a two-dimensional, periodically arranged square or rectangular pattern resembling a chessboard. Compared to traditional linear gratings, checkerboard gratings possess two-dimensional diffraction characteristics, giving them unique advantages in certain applications. As an optical element with unique two-dimensional diffraction properties, checkerboard gratings have broad application prospects in photolithography, imaging, sensing, display, and materials processing. With the continuous development of micro-nano manufacturing technology, the design and manufacturing precision of checkerboard gratings will continue to improve, thereby driving the emergence of more innovative applications. Some major application areas of checkerboard gratings include: photolithography, optical imaging, optical sensing, display technology, and quantum information.

[0003] Currently, many clients across various industries urgently need to improve diffraction efficiency and uniformity, and enhance optical performance due to product iteration and upgrades. This has led to demands for high REG (Registration) stitching accuracy, improved control of high corner radius deformation (corner radius), and matching of positional accuracy variations caused by process technology. The aforementioned REG stitching accuracy refers to the accuracy of alignment of multi-layer mask patterns on the wafer during photolithography. It is typically measured by overlay error and is one of the key parameters affecting yield in chip manufacturing.

[0004] Existing chessboard grating photomask manufacturing technology has the following problems:

[0005] 1. Insufficient precision in corner radius. The corner radius can only reach 400-500nm under laser lithography and only about 100nm under electron beam lithography, which cannot meet the requirement of high-end products for a corner radius ≤80nm.

[0006] 2. Poor line edge roughness (LER) affects the quality of the graphics.

[0007] 3. The overall splicing accuracy is insufficient and cannot meet the requirement of ±10nm.

[0008] 4. It cannot achieve local positional accuracy compensation in different areas on the same photomask, making it difficult to meet the needs of customers in different application scenarios.

[0009] 5. Special high reflectivity materials can exacerbate electron scattering in electron beam lithography, leading to enhanced proximity effect, decreased 3D structure accuracy, and problems such as charge accumulation interference causing beam trajectory deviation and reduced imaging stability. Summary of the Invention

[0010] Therefore, the technical problem to be solved by the present invention is to overcome the fact that the existence of the above-mentioned problems makes it impossible to meet the increasingly higher requirements of customers for diffraction efficiency, uniformity and optical performance of high-order checkerboard grating photomask products, thus restricting the iterative upgrading of products.

[0011] To address the aforementioned technical problems, this invention provides a method for optimizing the manufacturing precision of a checkerboard grating photomask, comprising:

[0012] Different photolithography processes are selected based on the product's required precision.

[0013] The substrate is processed according to the different photolithography processes selected above, and the thickness of the chromium layer on the substrate is set. At the same time, the chromium layer has high reflectivity, and different photoresist layers are coated on the chromium layer according to different photolithography processes.

[0014] The photomask layout is adjusted and designed for different photolithography processes;

[0015] To achieve REG precision compensation at different positions based on different application scenarios, and to match the positional precision changes caused by different photolithography processes.

[0016] In one embodiment of the present invention, the above-mentioned selection of different photolithography processes according to the product precision requirements includes laser photolithography and electron beam photolithography. The process parameters are optimized according to different photolithography processes. Laser photolithography is used for low-end products, and electron beam photolithography is used for high-end products. When electron beam photolithography is used, the rounded corners of the checkerboard grating mask are corrected, and the REG precision is controlled.

[0017] In one embodiment of the present invention, the thickness of the chromium layer is selected according to the final application scenario, and the photoresist layer coated is either IP photoresist or FEP photoresist, depending on the process used.

[0018] In one embodiment of the present invention, when using laser lithography, dry etching is combined with an ultra-low temperature baking process to make the sidewalls of the photoresist in the substrate smooth and improve the roughness of the pattern sidewalls.

[0019] In one embodiment of the present invention, when electron beam lithography is used, the electron scattering effect and charge accumulation are reduced by fogging effect correction and proximity effect correction, thereby optimizing the overall CD accuracy.

[0020] In one embodiment of the present invention, when electron beam lithography is used in the photolithography process, the electron beam lithography machine has built-in fogging effect correction and proximity effect correction. The optimal correction conditions are found through split testing to complete the compensation for the influence of electronic effects, eliminate the influence of electronic effects on CD accuracy during electron beam lithography exposure, optimize the overall CD accuracy and local CD accuracy, and simultaneously compensate for position accuracy before electron beam lithography. That is, the position accuracy deviation is analyzed through data processing model, the position accuracy correction file is updated, and the REG accuracy of the machine is corrected. The REG accuracy of the electron beam lithography machine is controlled within ±10nm through correction. After the compensation is completed, the lithography is carried out continuously to ensure the overall CD accuracy and REG accuracy.

[0021] In one embodiment of the present invention, when multiple photomasks need to be fabricated according to different application scenarios, it is necessary to achieve REG precision compensation at different positions to match the positional precision changes caused by different photolithography processes.

[0022] In one embodiment of the present invention, the local position difference compensation of multiple photomasks under different application scenarios is imported through a data processing model to generate a lithography machine compensation file, and the accuracy correction of the corresponding placement position of multiple photomasks is completed to achieve local compensation of single or multiple regions, and to achieve accuracy correction of irregular positions, so that different regions on multiple photomasks can meet their respective accuracy requirements.

[0023] In one embodiment of the present invention, the thickness of the chromium layer is selected according to the actual final application scenario, and the etching rate for different chromium layer thicknesses is matched. The morphological quality of the etched pattern is confirmed by key-size scanning electron microscopy and atomic force microscopy, and a corresponding dry etching formula is formulated.

[0024] The method for optimizing the manufacturing precision of the checkerboard grating photomask of the present invention has the following advantages compared with the prior art:

[0025] By optimizing product quality through methods such as matching exposure equipment to actual product needs, correcting electronic effects on exposure equipment, applying special MAP compensation, and changing process methods, we can adapt to all stages of customer mass production requirements. We utilize SEM (Scanning Electron Microscopy) and IPR measurements to confirm the finished product manufacturing effect, resolving process challenges such as high splicing accuracy, high deformation control, and matching positional accuracy variations caused by process variations. Ultimately, this enables successful plate making for customer-integrated products, client verification, and mass production. Product preparation requires no changes to any manufacturing equipment. By optimizing processes at each site, we achieve smooth pattern transfer on the photomask, enabling mass production of special checkerboard grating photomasks at each node based on existing process equipment. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the Binary photomask manufacturing process;

[0028] Figure 2 This is a structural diagram of a normal Binary material;

[0029] Figure 3 This is a structural schematic diagram of the improved Binary material;

[0030] Figure 4 This is a SEM image created using laser lithography before the iteration.

[0031] Figure 5 yes Figure 4 A magnified view of a portion of the image;

[0032] Figure 6 This is a SEM image created using electron beam lithography before the iteration.

[0033] Figure 7 This is a rendering of the SEM image produced by electron beam lithography after iteration;

[0034] Figure 8 This is a diagram showing the SEM measurement results of the fillet radius after laser lithography optimization according to the present invention;

[0035] Figure 9 This is a schematic diagram of the lithography machine before compensation.

[0036] Figure 10 This is a schematic diagram of the photolithography machine after compensation according to the present invention;

[0037] Figure 11 This is a SEM measurement result of the IP series photoresist before the improvement of the rounded corners of the low-temperature baking process and dry etching process.

[0038] Figure 12 This is a SEM measurement result image of the IP series photoresist combined with the low-temperature baking process and the improved rounded corners of the dry etching process after the invention.

[0039] Figure 13 This is a diagram showing the optimized electron beam lithography fillet SEM measurement results of the present invention;

[0040] Figure 14 These are REG measurement results before and after the local position accuracy correction of this invention. Detailed Implementation

[0041] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0042] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] It should be noted that the following description covers various aspects of embodiments within the scope of the appended claims. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0044] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0045] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0046] A chessboard grating is a periodically arranged phase grating whose structure consists of alternating transparent and opaque regions (or phase delay regions) that resemble a chessboard grid.

[0047] The manufacturing process of a binary photomask is as follows (e.g.) Figure 1As shown): After the photoresist on the surface of the quartz substrate is exposed to light, the chemical properties of the photoresist change. After the development process, the designed photomask pattern is transferred to the quartz substrate through an etching process. Then, the remaining photoresist is cleaned off to obtain the target photomask pattern. After that, it is necessary to measure the key dimensions and overlay accuracy of the pattern, and inspect and repair the completed photomask pattern.

[0048] In the process of improving the performance of photomasks, special customized high reflectivity materials are used. In the initial stage, laser lithography is used for the products. High reflectivity materials can improve energy utilization and accurately match wavelength in laser lithography, but cannot meet the requirements of the above-mentioned high-level iterative products. Electron beam lithography needs to be switched. However, high reflectivity materials have the following problems in electron beam lithography: (1) The electron scattering effect is aggravated, which leads to the enhancement of proximity effect and the decrease of 3D structure accuracy; (2) Charge accumulation interference leads to beam trajectory deviation and reduced imaging stability. Among them, the key requirements are: rounded corner radius (R≤50-200nm), uniform position connection using smooth connection technology for the whole plate, splicing accuracy of the whole plate ±10nm, and special correction of the mask due to local position deviation caused by the process.

[0049] For example, the previous product was manufactured using laser lithography, and the radius of the circular hole could only reach R = 400-500nm, and the line quality LER (line edge roughness) was poor. Figure 4 , 5 As shown.

[0050] Before the iteration, the product used electron beam lithography to fabricate the LER (line edge roughness) to meet the requirements. However, the radius of the circular hole could only be R≥100nm, while high-end products need to ensure R≤80nm. Furthermore, the accuracy and uniformity of the R radius in smooth connections were poor, directly affecting the performance of the end product. Figure 6 As shown.

[0051] In a checkerboard grating photomask, it is necessary to ensure that the radius of the entire opaque square is R≤80nm. If R≤80nm is not achieved, it will directly affect: ① diffraction efficiency and uniformity, including abrupt changes that will cause additional diffraction and scattering, affect the uniformity of the grating, and affect the beam quality; ② optical performance, including increased optical loss, introduction of phase error, and changes in polarization characteristics.

[0052] Based on the above analysis, the process of existing checkerboard grating photomasks is optimized and improved.

[0053] The method for optimizing the manufacturing precision of a checkerboard grating photomask according to the present invention includes:

[0054] Different lithography processes are selected based on the product's precision requirements. Depending on the customer's end-use scenario, and considering varying requirements for splicing effects and uniformity, corner radius, and LER (line edge roughness), multiple types of lithography machines and exposure methods can be chosen. These processes include laser lithography and electron beam lithography. Process parameters are optimized for each process; laser lithography is used for lower-end products, while electron beam lithography is used for higher-end products. When electron beam lithography is used, the corner radius of the checkerboard grating mask is corrected, and REG (Real Edge Grating) accuracy is controlled.

[0055] The substrate is processed according to the different photolithography processes selected above, and the thickness of the chromium layer on the substrate is set. At the same time, the chromium layer has high reflectivity, and different photoresist layers are coated on the chromium layer according to different photolithography processes.

[0056] The photomask layout is adjusted and designed for different photolithography processes;

[0057] To achieve REG precision compensation at different positions based on different application scenarios, and to match the positional precision changes caused by different photolithography processes.

[0058] Laser lithography and electron beam lithography employ different mask patterns to achieve smooth dark connection processes. For laser lithography, the sizes of the transparent and opaque areas are adjusted so that the rectangular cross-sectional area of ​​the opaque area is larger than that of the transparent area. The opaque areas are connected at the corners, while the transparent areas are separated by the opaque areas. This process adjustment meets the smooth connection requirements of the opaque areas. For electron beam lithography, the corner positions of the transparent areas are adjusted to beveled. Through the above design improvements, the uniformity requirements of the rounded corner connection positions in end applications are improved. With the achievement of smooth connection and precision optimization, the R-value and uniformity of the connection positions are improved, making it easier to meet the high quality control requirements of end applications.

[0059] The thickness of the chromium layer is selected based on the final application scenario, and depending on the process used, the coated photoresist layer is either IP photoresist or FEP photoresist. The chromium layer thickness is chosen according to the actual final application scenario, matching the etching rate with different chromium layer thicknesses. The morphology quality of the etched pattern is confirmed using critical dimension scanning electron microscopy and atomic force microscopy, and a corresponding dry etching formula is formulated. For example... Figure 2 , 3 A comparison chart showing the thickness of the chromium layer before and after the improvement.

[0060] When using laser lithography in conjunction with dry etching, an ultra-low temperature baking process is required. This process eliminates the standing wave effect and reduces development inhomogeneity, while simultaneously improving adhesion. During exposure, the high reflectivity of the incident and reflected light causes interference, resulting in standing wave patterns on the photoresist sidewalls. Ultra-low temperature baking promotes uniform distribution of photoreaction products through thermal diffusion, significantly reducing the standing wave effect. The diffusion of reaction products after the process makes the sidewalls of the developed photoresist structure steeper and smoother, reducing development fluctuations. It also strengthens the adhesion between the photoresist and the substrate, reducing the risk of resist peeling in subsequent processes, improving the roughness of the pattern sidewalls, enhancing edge sharpness, and improving the corner radius. The corner radius is improved from R=400-500nm to approximately R=150. See details... Figure 5 The results of SEM measurement (scanning electron microscope) of the fillet radius after laser lithography optimization show that the sidewalls of the photoresist in the substrate are smooth and the roughness of the pattern sidewalls is improved.

[0061] For example, laser lithography using IP series photoresists, combined with low-temperature baking and dry etching processes, can control CD accuracy within ±30nm, far superior to the 80-120nm CD deviation before optimization. The aforementioned REG accuracy control and customized position accuracy correction techniques are also applicable to matching position accuracy optimization in laser lithography.

[0062] Laser direct writing technology is limited by the diffraction and scattering of the laser used, especially when processing features close to their resolution limits (such as small square corners), where more significant diffraction occurs. The corner distortion effect introduces a deviation of approximately 30-35 nm in actual measurements.

[0063] In the IP photoresist and dry etching process, a low-temperature baking process is introduced to eliminate the standing wave effect, reduce development non-uniformity, and improve adhesion. Specifically, due to the material's unique characteristics, the interference between incident and reflected light during exposure is more pronounced than the blank standing wave effect in normal IP series photoresist, confirming the formation of standing wave patterns on the photoresist sidewalls. Low-temperature baking ensures uniform distribution of photoreaction products through thermal diffusion, significantly reducing the standing wave effect. The diffusion of photoreaction products after PEB (post-exposure baking) makes the sidewalls of the photoresist structure steeper and smoother after development, reducing development fluctuations. It also strengthens the adhesion between the photoresist and the substrate, reducing the risk of resist layer detachment in subsequent processes, improving the roughness of the pattern sidewalls, enhancing edge clarity, and improving the fillet radius. The radius of the circular aperture can be increased from the original Wet process R = 400-500nm to 150-200nm. Figure 10 , 11 As shown.

[0064] When using electron beam lithography, fogging effect correction and proximity effect correction are used to reduce electron scattering and charge accumulation, optimizing the overall CD (cathode scattering) accuracy of the entire image. Specifically, when electron beam lithography is used, the lithography machine itself has built-in fogging effect correction and proximity effect correction. Optimal correction conditions are found through split testing to compensate for the influence of electron effects, eliminating the impact of electron effects during electron beam lithography exposure on CD accuracy, optimizing the overall and local CD accuracy. Position accuracy is compensated synchronously before electron beam lithography; that is, position accuracy deviations are analyzed through data processing models, the position accuracy correction file is updated, and the machine's REG (Real-Genre scattering) accuracy is corrected. By correcting the REG accuracy of the electron beam lithography machine, it is controlled within ±10nm. After compensation, continuous lithography is performed to ensure the overall CD and REG accuracy of the image. Figure 8 , 9 As shown.

[0065] Regarding material differences, testing revealed that using low-temperature baking combined with dry etching significantly improves LER (Left Edge Reduction) and also enhances the corner fillet effect. Thanks to this combination, the corner fillet radius R can be achieved up to 150nm. Figure 7 SEM measurement results of fillet radius after laser lithography optimization; details of LER improvement are below. Figure 7 SEM images showing the improvement in LER and fillet quality of IP photoresist using dry etching combined with low-temperature baking technology.

[0066] Electron beam lithography, employing smooth interconnect technology, allows for modifications to the layout design to fully meet the high-end product manufacturing needs of customers, including Dark position percentage interconnection, CD precision, and LER (Light Response Level). REG precision control and electronic correction optimization for LCD / GCD implementation have increased the corner radius from 100nm to between 45nm and 65nm, while achieving corner interconnection uniformity control within ±10nm. See details... Figure 13 Optimized EBM lithography fillet SEM measurement results.

[0067] When multiple photomasks need to be fabricated for different application scenarios, REG accuracy compensation is required for different positions to match the positional accuracy variations caused by different lithography processes. Specifically, by importing local positional difference compensation data from multiple photomasks under different application scenarios through a data processing model, a lithography machine compensation file is generated. This completes the accuracy correction of the corresponding placement positions of multiple photomasks, enabling local compensation for single or multiple regions and correcting irregular positional accuracy, ensuring that different areas on multiple photomasks meet their respective accuracy requirements. For example, before product fabrication, photomasks #1, #2, #3, #4, and #XXX for different application scenarios are returned to the mask factory for corresponding REG measurements to confirm positional accuracy differences under the corresponding application scenarios, i.e., confirming the X and Y direction scale and orthogonal differences of #1, #2, #3, #4, and #XXX. Then, by importing local positional difference compensation data from different application scenarios through a data processing model, a lithography machine compensation file is generated to complete the accuracy correction of the corresponding placement positions. After exposure, the positional accuracy of the corresponding areas of the photomasks can be matched to different customer application scenarios. This method can also be used to correct irregular positional accuracy.

[0068] For clients with diverse application scenarios, customized positional accuracy correction technology can be implemented to achieve local compensation in single or multiple areas. This means that clients may have different application scenario patterns arranged on the same photomask, such as... Figure 13 The customer's layout shows four chips arranged on a single board. One area is used in different applications. REG accuracy compensation is implemented to match the positional accuracy variations caused by different processes, based on the customer's different application scenarios. Local correction is not limited to the localized, regular accuracy compensation shown in the figure; the correction technology can cover partial point correction in small areas, thus achieving compensation in any shape. The positional accuracy measurement results before and after local positional accuracy correction compensation are shown in [link to image]. Figure 14 Examples of REG measurement results before and after local position accuracy correction.

[0069] Based on the above solutions, this invention optimizes the manufacturing precision of special high-order checkerboard grating photomasks through design modifications, diversified exposure options and process optimization, the introduction of IP photoresist combined with low-temperature baking processes, and customized local positional accuracy compensation. The customized process matches various application scenarios and is adapted to panel manufacturing, fully adapting to customer product upgrades and iterations. The process technology can cover the needs of similar grating products, achieving the industry-leading manufacturing precision of special ultra-high-precision checkerboard grating photomasks.

[0070] Among these, the derived IP series photoresist plus dry etching plus low temperature baking process can be extended to other types of special mask products; experience has been accumulated in the development of new processes for different types of special Blank substrates; the successful application of local position accuracy compensation provides effective technical reference for more customized panel manufacturing in the future, expanding the application scope of customers while increasing our own revenue; and the photolithography and other manufacturing processes of photomasks are realized based on existing process equipment, improving the manufacturing efficiency and yield of photomask manufacturing and reducing production costs.

[0071] The terms involved in this invention are explained as follows:

[0072] Baking processes are primarily used for DUV / EBM photoresists, especially Chemically Amplified (CA) photoresists. The photosensitizer in CA photoresists is a photoacid generator (PAG). PAG (photoacid generator, a core component of chemically amplified (CA) photoresists, produces acid-catalyzed changes in resin solubility through photochemical reactions, enabling micro / nanoscale pattern transfer) generates photoacid after DUV / EBM exposure. The baking step, through heating, uses the generated acid as a catalyst to further initiate chemical reactions in the resin (e.g., deprotection reactions), thereby significantly altering the solubility difference between exposed and unexposed areas, ultimately achieving pattern transfer. The IP3600 series is an I-line photoresist. Its working principle mainly involves the photoactive compound (PAC) undergoing a photochemical reaction upon exposure to I-line light (365nm), decomposing the photosensitizer and altering its solubility. In positive photoresists, the solubility in the exposed area increases, while in negative photoresists, the opposite occurs. The development process of I-line photoresist mainly relies on this difference in solubility, and a baking process is usually not required to further amplify this difference.

[0073] IPRO refers to KLA-Tencor's IPRO series of devices, used for measurement registration.

[0074] REG (overlay error) accuracy in a mask is a key indicator in semiconductor manufacturing, directly affecting the pattern alignment quality of the photolithography process.

[0075] CD is the critical size.

[0076] Split testing is an experimental method that compares two or more versions (A / B variants) to determine the optimal solution. It is widely used in product design, marketing, and user experience optimization. Its core principle is to randomly assign users to different groups and collect behavioral data (such as click-through rate and conversion rate) for comparative analysis.

[0077] In photolithography, Corner distortion (corner rounding effect) is one of the key issues in optical proximity (OPC). It manifests as right angles or acute angles in the design becoming rounded or shortened at the edges after photolithography, affecting the accuracy of the pattern.

[0078] The blank standing wave effect is a phenomenon in photolithography where the interference between incident light and reflected light from the substrate causes uneven light intensity distribution within the photoresist. This manifests as periodic stripes or sawtooth structures on the sidewalls of the pattern after development, affecting linewidth uniformity and resolution.

[0079] GCD refers to the precision of a full CD with a mask.

[0080] LCD refers to the local CD precision of a photomask.

[0081] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for optimizing the manufacturing precision of a checkerboard grating photomask, characterized in that, include: Different photolithography processes are selected based on the product's required precision. The substrate is processed according to the different photolithography processes selected above, and the thickness of the chromium layer on the substrate is set. At the same time, the chromium layer has high reflectivity, and different photoresist layers are coated on the chromium layer according to different photolithography processes. The photomask layout is adjusted and designed for different photolithography processes; To achieve REG precision compensation at different positions according to different application scenarios, and to match the positional precision changes caused by different photolithography processes; The above-mentioned selection of different photolithography processes based on the product's precision requirements includes laser photolithography and electron beam photolithography. Process parameters are optimized according to different photolithography processes. Laser photolithography is used for low-end products, while electron beam photolithography is used for high-end products. When electron beam photolithography is used, the rounded corners of the checkerboard grating mask are corrected, and the REG precision is controlled. When using laser lithography, dry etching is combined with an ultra-low temperature baking process to make the sidewalls of the photoresist in the substrate smooth and improve the roughness of the pattern sidewalls. When using electron beam lithography, the electron scattering effect and charge accumulation are reduced by correcting the fogging effect and the proximity effect, thereby optimizing the overall CD accuracy. When electron beam lithography is used in the photolithography process, the electron beam lithography machine has built-in fogging effect correction and proximity effect correction. The optimal correction conditions are found through split testing to complete the compensation for the influence of electronic effects, eliminate the impact of electronic effects on CD accuracy during electron beam lithography exposure, and optimize the CD accuracy of the whole plate and local CD. The position accuracy is compensated synchronously before electron beam lithography, that is, the position accuracy deviation is analyzed by data processing model, the position accuracy correction file is updated, and the REG accuracy of the machine is completed. By correcting the REG accuracy of the electron beam lithography machine, it is controlled within ±10nm. After the compensation is completed, the lithography is carried out continuously to ensure the CD accuracy and REG accuracy of the whole plate.

2. The method for optimizing the manufacturing accuracy of a checkerboard grating photomask according to claim 1, characterized in that: The thickness of the chromium layer is selected according to the final application scenario, and depending on the process used, the coated photoresist layer is either IP photoresist or FEP photoresist.

3. The method for optimizing the manufacturing accuracy of a checkerboard grating photomask according to claim 1, characterized in that: When multiple photomasks need to be fabricated for different application scenarios, it is necessary to achieve REG precision compensation at different positions to match the positional precision changes caused by different photolithography processes.

4. The method for optimizing the manufacturing accuracy of a checkerboard grating photomask according to claim 3, characterized in that: By importing local positional difference compensation data from multiple photomasks under different application scenarios through a data processing model, a lithography machine compensation file is generated. This completes the accuracy correction of the corresponding placement positions of multiple photomasks, enabling local compensation for single or multiple regions and accuracy correction of irregular positions. This ensures that different regions on multiple photomasks can meet their respective accuracy requirements.

5. The method for optimizing the manufacturing accuracy of a checkerboard grating photomask according to claim 1, characterized in that: The thickness of the chromium layer is selected according to the actual final application scenario. The etching rate is matched with different chromium layer thicknesses. The morphology quality of the etched pattern is confirmed by key dimension scanning electron microscopy and atomic force microscopy, and the corresponding dry etching formula is formulated.

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