Blazed grating preparation method and blazed grating

Abstract

Disclosed in the present invention are a blazed grating preparation method and a blazed grating prepared by the method. The preparation method comprises: providing a monocrystalline silicon substrate, the monocrystalline silicon substrate having a first surface; preparing a mask layer on the first surface of the monocrystalline silicon substrate; using the mask layer to perform wet etching of silicon on the first surface of the monocrystalline silicon substrate to obtain a grating structure having a flat inclined surface; and using an etching process to etch the monocrystalline silicon substrate from the inclined surface of the grating structure to obtain a blazed grating. The blazed grating preparation method and the blazed grating in the present invention have the advantages of simple operation, large-area preparation, high tolerance for defects in the mask layer, and low surface roughness.

Description

Preparation method of blazed grating and blazed grating

[0001] The present invention claims priority to Chinese patent application No. 2023115931537, filed with the Patent Office of China on November 27, 2023, entitled “Method for preparing blazed grating and blazed grating”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the technical field of diffraction optical element manufacturing, and in particular to a preparation method of a blazed grating and a blazed grating. Background Art

[0003] A diffraction grating is an optical element that periodically modulates the amplitude or phase of a light beam. Its most significant function in optical applications is dispersion, making it a core component in grating-type spectrometers. When the grating's grooves are sawtooth-shaped (asymmetric triangles), the light energy is concentrated at a fixed angle, or at a specific spectral level, where the spectral intensity is greatest. This phenomenon is called blaze, and the corresponding grating is called a blazed grating.

[0004] Currently, methods for fabricating blazed gratings primarily include mechanical scribing and holographic ion beam etching. Mechanical scribing is the earliest method for processing blazed gratings and can produce large-area grating structures. However, its disadvantages include long processing time, high surface roughness, high levels of stray light, and low diffraction efficiency. Holographic ion beam etching places high demands on the mask; defects in the mask can increase the roughness of the blazed surface, and variations in the ion velocity can also cause changes in the grating groove profile.

[0005] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0006] Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing a blazed grating and a blazed grating, which have the advantages of simple operation, large-area preparation, large tolerance to mask layer defects, and low surface roughness.

[0008] To achieve the above-mentioned objectives, an embodiment of the present invention provides a method for preparing a blazed grating, comprising: providing a single-crystal silicon substrate, wherein the single-crystal silicon substrate has a first surface; preparing a mask layer on the first surface of the single-crystal silicon substrate; using the mask layer to perform silicon wet etching on the first surface of the single-crystal silicon substrate to obtain a grating structure having a flat inclined surface; and using an etching process to etch the single-crystal silicon substrate from the inclined surface of the grating structure to obtain a blazed grating.

[0009] In one or more embodiments of the present invention, before the step of etching the single crystal silicon substrate using an etching process, it also includes: depositing a protective layer on the first surface of the single crystal silicon substrate; partially etching the protective layer to form the protective layer into a specific shape; while etching the single crystal silicon substrate using an etching process, also etching the remaining protective layer.

[0010] In one or more embodiments of the present invention, by controlling the etching ratio of the single crystal silicon substrate and the protective layer, an etching process with an etching ratio of the single crystal silicon substrate and the protective layer in the range of 0.8-1.2 is selected to obtain blazed gratings with different angles.

[0011] In one or more embodiments of the present invention, an etching process with an etching ratio of 1:1 between the single crystal silicon substrate and the protective layer is selected to obtain the blazed grating.

[0012] In one or more embodiments of the present invention, the protective layer is deposited until the protective layer covers the grating structure.

[0013] In one or more embodiments of the present invention, the protection layer is deposited until the surface of the protection layer is flush with the tip of the grating structure.

[0014] In one or more embodiments of the present invention, the partial etching of the protective layer to form the protective layer into a specific shape includes: etching the protective layer using an alignment mask photolithography process so that the protective layer between adjacent gratings in the grating structure forms an etched surface perpendicular to the first surface of the single crystal silicon substrate, and the remaining protective layer still covers one of the inclined surfaces of the grating in the grating structure.

[0015] In one or more embodiments of the present invention, the etching surface of the protective layer is used as a reference plane, and an ICP etching process is adopted to etch the remaining protective layer and the single crystal silicon substrate to form a blazed grating groove shape consisting of a groove surface and a blazed surface arranged perpendicular to the first surface.

[0016] In one or more embodiments of the present invention, the protective layer is a silicon dioxide layer.

[0017] In one or more embodiments of the present invention, the method of preparing a mask layer on the first surface of the single crystal silicon substrate includes: growing an oxide layer on the first surface of the single crystal silicon substrate using a thermal oxidation process; spin-coating a photoresist layer on the surface of the oxide layer; exposing and developing the photoresist layer to obtain a photoresist mask; etching the oxide layer using the photoresist mask until a portion of the single crystal silicon substrate is exposed; and removing the photoresist mask to obtain a mask layer.

[0018] In one or more embodiments of the present invention, the first surface of the single crystal silicon substrate is a {110} crystal plane, and the flat inclined surface of the grating structure is a {111} crystal plane.

[0019] In one or more embodiments of the present invention, the step of performing silicon wet etching on the first surface of the single-crystal silicon substrate using the mask layer to obtain a grating structure having a flat inclined surface includes: performing silicon wet etching on the first surface of the single-crystal silicon substrate using a silicon anisotropic etching solution, and adjusting the ratio of the etching solution, the etching time, and the size of the mask window formed by the mask layer so that the etching ends at the {111} crystal plane of the single-crystal silicon substrate; and a plurality of the {111} crystal planes intersect each other to form a pointed grating structure on the single-crystal silicon substrate.

[0020] In one or more embodiments of the present invention, the etching solution of the silicon wet etching process includes: a TMAH etching solution containing additives, and a KOH solution containing additives, wherein the additives include ammonium persulfate and IPA.

[0021] An embodiment of the present invention provides a blazed grating, which is prepared by the above-mentioned method for preparing a blazed grating.

[0022] Compared with the prior art, the method for preparing the blazed grating according to the embodiment of the present invention has the advantages of simple operation, large-area preparation, large tolerance to mask layer defects, and low surface roughness.

[0023] According to the method for preparing a blazed grating in an embodiment of the present invention, there is no need to bevel the single-crystal silicon substrate. It can be directly subjected to silicon wet etching to obtain the required inclined surface with a smooth surface, and then the blazed grating is obtained by ICP etching from the inclined surface.

[0024] According to the method for preparing a blazed grating according to an embodiment of the present invention, the surface roughness of the inclined surface - the {111} crystal plane - obtained by wet etching of silicon is low, and the same surface roughness can be maintained after further ICP etching and extended to the blazed surface, so that the diffraction efficiency of the obtained blazed grating will be relatively higher.

[0025] According to the method for preparing a blazed grating according to an embodiment of the present invention, a protective layer - a silicon dioxide layer - is deposited, and then the protective layer is etched to form a vertical etched surface, which is used as a reference plane to obtain a vertical groove surface of the blazed grating groove shape, thereby reducing the formation of stray light and improving the diffraction efficiency of the blazed grating. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0027] FIG1 is a process flow chart of a method for preparing a blazed grating according to one embodiment of the present invention;

[0028] 2 and 3 are process flow charts of a method for preparing a blazed grating according to an embodiment of the present invention;

[0029] 4a-4j are process step diagrams of a method for preparing a blazed grating according to an embodiment of the present invention;

[0030] FIG5 is an angular schematic diagram of a grating structure having desired crystal planes prepared by a method for preparing a blazed grating according to an embodiment of the present invention;

[0031] FIG6 is a schematic diagram of the blaze angle of a blazed grating prepared by the method for preparing a blazed grating according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0034] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0035] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0036] In the description of this application, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0037] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, or electrical connections; direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0038] As mentioned in the background, current methods for fabricating blazed gratings primarily include mechanical scribing and holographic ion beam etching. Mechanical scribing is the oldest method for processing blazed gratings, capable of producing large-area grating structures. However, its disadvantages include long processing time, high surface roughness, high levels of stray light, and low diffraction efficiency. Holographic ion beam etching places high demands on the mask; defects in the mask can increase the roughness of the blazed surface, and variations in the ion velocity can also cause changes in the grating groove profile.

[0039] Based on the fact that existing methods for preparing blazed gratings all have certain defects, the present application provides a method for preparing a blazed grating and a blazed grating prepared by the preparation method. The preparation method is to directly perform silicon wet etching on it to obtain the required flat inclined surface - {111} crystal plane, and then obtain the blazed grating by etching from the flat inclined surface - {111} crystal plane. It has the advantages of simple operation, large-area preparation, large tolerance to mask layer defects, and low surface roughness.

[0040] As shown in FIG1 , a method for fabricating a blazed grating according to an embodiment of the present invention includes the following steps: s1, providing a single-crystal silicon substrate having a first surface; s2, preparing a mask layer on the first surface of the single-crystal silicon substrate; s3, using the mask layer to perform a silicon wet etching on the first surface of the single-crystal silicon substrate to obtain a grating structure having a flat inclined surface; and s4, etching the single-crystal silicon substrate from the inclined surface of the grating structure using an etching process to obtain a blazed grating. The first surface of the single-crystal silicon substrate is a {110} crystal plane.

[0041] As shown in Figure 2, the step of preparing a mask layer on the first surface of the single crystal silicon substrate in step s2 specifically includes: s201 using a thermal oxidation process to grow an oxide layer on the first surface of the single crystal silicon substrate; s202 spin-coating a photoresist layer on the surface of the oxide layer; s203 exposing and developing the photoresist layer to obtain a photoresist mask; s204 using the photoresist mask to etch the oxide layer until a portion of the single crystal silicon substrate is exposed; s205 removing the photoresist mask to obtain a mask layer.

[0042] The step s3 of performing silicon wet etching on the first surface of the single crystal silicon substrate using the mask layer to obtain a grating structure having a flat inclined surface specifically includes: performing silicon wet etching on the first surface of the single crystal silicon substrate using a silicon anisotropic etching solution, and adjusting the ratio of the etching solution, the etching time, and the size of the mask window formed by the mask layer so that the etching ends at the {111} crystal plane of the single crystal silicon substrate; and intersecting multiple {111} crystal planes in pairs to form a pointed grating structure on the single crystal silicon substrate.

[0043] As shown in FIG3 , between step s3 and step s4, the following steps may also be included: sA01, depositing a protective layer on the first surface of the single crystal silicon substrate; depositing the protective layer until the protective layer covers the grating structure or until the surface of the protective layer is flush with the tip of the grating structure. sA02, partially etching the protective layer to form the protective layer into a specific shape; specifically, etching the protective layer using an aligned mask photolithography process such that the protective layer between adjacent gratings in the grating structure forms an etched surface perpendicular to the first surface of the single crystal silicon substrate, while the remaining protective layer still covers one of the inclined surfaces of the grating within the grating structure.

[0044] In step s4, the single-crystal silicon substrate is etched using an etching process while simultaneously etching the remaining protective layer. Specifically, using the etched surface of the protective layer as a reference plane, an ICP etching process is selected with an etching ratio between the single-crystal silicon substrate and the protective layer within a range of 0.8-1.2. The remaining protective layer and the single-crystal silicon substrate are etched to form a blazed grating groove pattern consisting of groove planes perpendicular to the first surface and {111} crystal planes (i.e., blazed planes). Blazed gratings with different angles can be obtained depending on the etching ratio. The provision of the protective layer ensures that the surface of the subsequently produced blazed grating opposite the blazed plane is perpendicular, reducing stray light and improving diffraction efficiency.

[0045] Figures 4a to 4j illustrate the process of a method for preparing a blazed grating according to an embodiment of the present application. The following detailed description of the method for preparing a blazed grating according to this embodiment is provided in conjunction with Figures 4a to 4j to facilitate understanding of the present application.

[0046] 4 a , a common single crystal silicon substrate 10 —{110} silicon — is provided. The single crystal silicon substrate 10 has a first surface 10 a , and the first surface 10 a is a {110} crystal plane.

[0047] Referring to FIG4b , a thermal oxidation process is used to grow an oxide layer 20 on the first surface 10a of the single crystal silicon substrate 10. For example, the cleaned single crystal silicon substrate 10 is placed in a quartz boat or an alumina tray, placed in a high-temperature oxidation furnace, and heated to 1100°C for approximately three hours while flowing with O2. This forms a dense SiO2 film on the first surface 10a of the single crystal silicon substrate 10. The thermal oxidation process barely affects the substrate's surface shape.

[0048] Referring to Figure 4c, a photoresist layer 30 is spin-coated on the surface of the oxide layer 20. For example, a single-crystal silicon substrate 10 with a SiO2 film oxide layer 20 is vacuum-adsorbed onto the spin stage of a spin coater. Photoresist is dripped onto the center of the substrate using a dropper until the entire surface is covered. The substrate is then centrifuged at high speed to form a uniform layer of photoresist 30. Before coating, the surface is cleaned with an O2 plasma cleaner and then heated on a 90°C hot plate to change the hydrophobicity of the substrate surface to a hydrophilicity, facilitating subsequent photoresist adhesion. The spin coat speed is 3000-4000 rpm, and the spin coat time is 40 seconds. This ensures uniformity of the photoresist and removes moisture from the photoresist, facilitating curing. The final thickness is approximately 300 nm. After spin coat, the substrate is heated on a hot plate at 90°C for 10 minutes to remove excess moisture, stabilize the photoresist, and ensure close adhesion to the substrate for subsequent processing.

[0049] Referring to FIG4 d , the photoresist layer 30 is exposed and developed to obtain a photoresist mask 31. The oxide layer 20 is etched using the photoresist mask 31, and the pattern of the photoresist mask 31 is transferred to the oxide layer 20 until a portion of the single crystal silicon substrate 10 is exposed. Exemplarily, an ICP plasma etcher is used to vertically etch the SiO2 layer using reactive ion etching. The etching conditions are as follows: the pressure of the plasma etcher is controlled to be 10.0 mTorr, the etching temperature is 20° C., the Ar gas flow rate is controlled to be 20 sccm, the CHF3 gas flow rate is controlled to be 30 sccm, the RF power is 150 W, and the ICP power is 0 W. The reacted portion of the substrate is exposed to air.

[0050] As shown in FIG4e , the photoresist mask 31 is removed to obtain a mask layer 21. A plurality of mask windows 22 are formed on the mask layer 21 to facilitate subsequent wet etching of the single crystal silicon substrate 20. For example, the substrate is immersed in acetone, isopropyl alcohol, and deionized water for 10 minutes each and ultrasonically cleaned to remove the photoresist mask 31 and obtain the mask layer 21.

[0051] As shown in FIG4f , a mask layer 21 is used to wet-etch the first surface 10a of the single-crystalline silicon substrate 10 to obtain a grating structure 11 having a flat, inclined surface. Specifically, an anisotropic silicon etchant is used to wet-etch the first surface 10a of the single-crystalline silicon substrate 10. By adjusting the ratio of the etchant, the etching time, and the size of the mask window 22 formed by the mask layer 21, the etching is terminated at the {111} crystal planes A of the single-crystalline silicon substrate 10. Multiple {111} crystal planes A intersect with each other to form a pointed grating structure 11 on the single-crystalline silicon substrate 10. Each grating of the pointed grating structure 11 is symmetrically arranged, i.e., the two {111} crystal planes A corresponding to the grating each form an angle of 35.26° with the first surface 10a, as shown in FIG5 . Theoretical results show that the corrosion trend of the {110} single crystal silicon substrate beneath the mask window 22 is that the {110} bottom surface of the etching cavity will gradually shrink and eventually disappear completely, and two {111} crystal planes A, which are inclined at a 35.26° angle with the first surface 10a, will intersect in a straight line. Exemplarily, the etching solution for the silicon wet etching process includes a TMAH etching solution containing additives or a KOH solution containing additives. The additives include ammonium persulfate and IPA. The etching solution has a ratio of 25 wt% TMAH:4 wt% ammonium persulfate, and the etching time is 3-4 hours.

[0052] It is understood that the silicon wet etching process itself can produce a flat inclined surface, namely a {111} crystal plane, and the surface flatness of the {111} crystal plane also meets the flatness requirements of the blazed grating fabricated in this application. Of course, in other embodiments, other methods can be used to form the inclined surface on the first surface of the single crystal silicon substrate, as long as the flatness of the inclined surface meets certain requirements. However, currently, other etching or corrosion processes other than silicon wet etching have not yet been developed that can meet the required requirements.

[0053] 4g, the mask layer 21 is removed, and a protective layer 40 is deposited on the first surface 10a of the single crystal silicon substrate 10. The protective layer 40 covers the grating structure 11 or the surface of the protective layer 40 is flush with the tip of the grating structure 11. For example, the protective layer 40 is a silicon dioxide layer.

[0054] As shown in FIG4h , the protective layer 40 is partially etched to form a specific shape. The specific shape is a right triangle. Specifically, the protective layer 40 is etched using an aligned mask photolithography process so that the protective layer 40 between adjacent gratings in the grating structure 11 forms an etched surface B (a right-angled surface of the right triangle) perpendicular to the first surface 10a of the single crystal silicon substrate 10. The remaining protective layer 40 (a sloped surface of the right triangle) still covers one of the crystal planes A of the gratings in the grating structure 11.

[0055] Referring to Figures 4i and 4j, using the etched surface B of the protective layer 40 as a reference plane, an etching process that is non-selective to silicon dioxide and silicon, such as an ICP etching process, is used to etch the remaining protective layer 40 and the single-crystal silicon substrate 10 to form a blazed grating groove pattern consisting of groove planes C and {111} crystal planes (i.e., blaze planes D) perpendicular to the first surface 10a. By controlling the etching ratio of silicon to silicon dioxide and selecting an etching process with a silicon to silicon dioxide etching ratio within the range of 0.8-1.2, different blaze angles (the angle between the blaze plane D and the first surface 10a) can be obtained. Referring to Figure 6, which shows the blaze angles obtained using an etching process with a silicon to silicon dioxide etching ratio of approximately 1:1, the angle between the {111} crystal planes (i.e., blaze planes D) that constitute the blazed grating groove pattern and the first surface 10a is 35.26°.

[0056] In the above embodiment, after the step shown in FIG4f , a protective layer of silicon dioxide is deposited, and then the silicon dioxide and single-crystal silicon substrate are etched within a certain range of ratios to obtain the desired blazed gratings with different angles. In other embodiments, after the step shown in FIG4f , the single-crystal silicon substrate can be directly etched at a certain angle by an etching process, such as an ICP etching process, to obtain the desired blazed gratings. However, in this method, both surfaces of the grating are inclined (one of which serves as the blazed surface). When a portion of light strikes the other surface, this portion of light will reflect and generate stray light, affecting the diffraction efficiency of the blazed grating.

[0057] Compared with the prior art, the method for preparing the blazed grating according to the embodiment of the present invention has the advantages of simple operation, large-area preparation, large tolerance to mask layer defects, and low surface roughness.

[0058] According to the method for preparing a blazed grating in an embodiment of the present invention, there is no need to bevel the single-crystal silicon substrate. It can be directly subjected to silicon wet etching to obtain the required inclined surface with a smooth surface, and then the blazed grating is obtained by ICP etching from the inclined surface.

[0059] According to the method for preparing a blazed grating according to an embodiment of the present invention, the surface roughness of the inclined surface - the {111} crystal plane - obtained by wet etching of silicon is low, and the same surface roughness can be maintained after further ICP etching, and extended to the blazed surface, so that the diffraction efficiency of the obtained blazed grating will be relatively higher.

[0060] According to the method for preparing a blazed grating according to an embodiment of the present invention, a protective layer - a silicon dioxide layer - is deposited, and then the protective layer is etched to form a vertical etched surface, which is used as a reference plane to obtain a vertical groove surface of the blazed grating groove shape, thereby reducing the formation of stray light and improving the diffraction efficiency of the blazed grating.

[0061] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

[0062] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present application is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing a blazed grating, characterized in that, it includes: providing a single-crystal silicon substrate having a first surface; preparing a mask layer on the first surface of the single-crystal silicon substrate; using the mask layer to perform wet etching of silicon on the first surface of the single-crystal silicon substrate to obtain a grating structure with a flat inclined surface; adopting an etching process to etch the single-crystal silicon substrate from the inclined surface of the grating structure to obtain a blazed grating.

2. The method for preparing a blazed grating according to claim 1, characterized in that, before the step of etching the single-crystal silicon substrate by using an etching process, it further includes: depositing a protective layer on the first surface of the single-crystal silicon substrate; partially etching the protective layer to make the protective layer form a specific shape; while etching the single-crystal silicon substrate by using an etching process, also etching the remaining protective layer.

3. The method for preparing a blazed grating according to claim 2, characterized in that, by controlling the etching ratio of the single-crystal silicon substrate and the protective layer, selecting an etching process with an etching ratio of the single-crystal silicon substrate and the protective layer within the range of 0.8 - 1.2, different-angle blazed gratings are obtained.

4. The method for preparing a blazed grating according to claim 2, characterized in that, depositing the protective layer until the protective layer covers the grating structure.

5. The method for preparing a blazed grating according to claim 2, characterized in that, depositing the protective layer until the surface of the protective layer is flush with the tip of the grating structure.

6. The method for preparing a blazed grating according to claim 2, characterized in that, the partial etching of the protective layer to make the protective layer form a specific shape includes: using an alignment mask lithography process to etch the protective layer so that the protective layer between adjacent gratings in the grating structure forms an etching surface perpendicular to the first surface of the single-crystal silicon substrate, and the remaining protective layer still covers one of the inclined surfaces of the gratings in the grating structure.

7. The method for preparing a blazed grating according to claim 6, characterized in that, taking the etching surface of the protective layer as a reference surface, using an ICP etching process to etch the remaining protective layer and the single-crystal silicon substrate to form a blazed grating groove shape composed of a groove surface and a blazed surface perpendicular to the first surface.

8. The method for preparing a blazed grating according to claim 1, characterized in that, the preparation of the mask layer on the first surface of the single-crystal silicon substrate includes: using a thermal oxidation process to grow an oxide layer on the first surface of the single-crystal silicon substrate; spin-coating a photoresist layer on the surface of the oxide layer; performing exposure and development on the photoresist layer to obtain a photoresist mask; using the photoresist mask to etch the oxide layer until part of the single-crystal silicon substrate is exposed; removing the photoresist mask to obtain a mask layer.

9. The method for preparing a blazed grating according to claim 1, characterized in that, the first surface of the single-crystal silicon substrate is a {110} crystal plane, and the flat inclined surface of the grating structure is a {111} crystal plane.

10. The method for preparing a blazed grating according to claim 9, characterized in that, Performing wet etching of silicon on the first surface of the single-crystalline silicon substrate by using the mask layer to obtain a grating structure with a flat inclined surface, comprising: Performing wet etching of silicon on the first surface of the single-crystalline silicon substrate by using a silicon anisotropic etching solution, and by adjusting the ratio of the etching solution, the etching time, and the size of the mask window formed by the mask layer, making the etching end at the {111} crystal plane of the single-crystalline silicon substrate; Two by two intersections of multiple said {111} crystal planes to form a sharp-cornered grating structure on the single-crystalline silicon substrate.

11. A blazed grating, characterized in that, it is prepared by the preparation method of the blazed grating according to any one of claims 1-10.

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