Preparation method of trapezoidal grating and trapezoidal grating

Abstract

The invention discloses a preparation method of a trapezoidal grating and the trapezoidal grating prepared by the method. The method comprises the following steps: providing a substrate; forming a plurality of material layers on the surface of the substrate; the multiple material layers at least comprise a first material layer and a second material layer in sequence along the direction far away from the substrate; the first material layer and the second material layer are made of different materials; forming a patterned mask on the surface of the multi-layer material layer; etching the multi-layer material layer to the first material layer at a first preset angle, and removing the residual patterned mask layer to form a plurality of grooves; forming a filling type mask in the groove; the groove is filled with the filling type mask, and the material of the filling type mask is different from the material of the multiple material layers; and etching the multi-layer material layer to the first material layer at a second preset angle, and removing the residual filling type mask and the second material layer to form the trapezoidal grating.

Description

Technical Field

[0001] The present application relates to the field of augmented reality, and in particular to a method for preparing a trapezoidal grating and the trapezoidal grating. Background Art

[0002] Waveguide display technology is one of the most challenging and complex problems in the field of augmented reality. Diffraction waveguides are a common type of waveguide used in this technology. Their optical display relies primarily on surface-relief gratings. Research has shown that trapezoidal gratings offer superior optical performance compared to conventional rectangular or skewed gratings. However, there is currently no effective method for fabricating trapezoidal gratings. Therefore, developing a method for fabricating these gratings has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0003] To solve the above problems, the present application provides a method for preparing a trapezoidal grating, comprising:

[0004] providing a substrate;

[0005] forming a plurality of material layers on the surface of the substrate; the plurality of material layers sequentially including at least a first material layer and a second material layer in a direction away from the substrate; the first material layer and the second material layer are made of different materials;

[0006] forming a patterned mask on the surface of the multi-layer material layer;

[0007] Etching the multi-layer material layer to the first material layer at a first preset angle, removing the remaining patterned mask layer, and forming a plurality of grooves;

[0008] forming a filling mask in the groove; the filling mask fills the groove, and the material of the filling mask is different from the material of the multi-layer material layer;

[0009] The multi-layer material layer is etched to the first material layer at a second preset angle, and the remaining filling mask and the second material layer are removed to form a trapezoidal grating.

[0010] Optionally, a first etching direction when etching the multilayer material layer at the first preset angle is defined as a first reference direction, and an angle between the grating surface and the substrate surface along the first reference direction is defined as a first bottom angle; and the size of the first bottom angle is modulated by modulating the first preset angle.

[0011] Optionally, a second etching direction when etching the multilayer material layer at the second preset angle is defined as a second reference direction, and an angle between the grating surface and the substrate surface along the second reference direction is defined as a second bottom angle; and the size of the second bottom angle is modulated by modulating the second preset angle.

[0012] Optionally, the etching directions of the multilayer material layer when etching at the first preset angle and the etching directions of the multilayer material layer when etching at the second preset angle are different, and / or the first preset angle and the second preset angle are different in size.

[0013] Optionally, forming a filling mask in the groove specifically includes:

[0014] Depositing a mask material on the multi-layer material layer, wherein the thickness of the mask material is not less than the depth of the groove;

[0015] The mask material on the multi-layer material layer is removed until the multi-layer material layer is exposed, so as to retain the mask material filled in the groove to form a filling mask.

[0016] Optionally, removing the remaining filling mask and the second material layer to form a trapezoidal grating specifically includes:

[0017] removing the remaining filling mask;

[0018] placing the substrate in a target solution;

[0019] The target solution is heated to a target temperature and maintained for a target time to dissolve the second material layer and keep the first material layer undissolved, thereby forming a trapezoidal grating.

[0020] Optionally, etching the multilayer material layer to the first material layer at a first preset angle specifically includes: etching the multilayer material layer to the bottom of the first material layer at a first preset angle; and etching the multilayer material layer to the first material layer at a second preset angle specifically includes: etching the multilayer material layer to the bottom of the first material layer at a second preset angle.

[0021] Optionally, the thickness of the second material layer is in the range of 20 nm to 40 nm.

[0022] Optionally, the multi-layer material layer further includes a third material layer formed on the second material layer.

[0023] Optionally, the etching rates of the first material layer and the third material layer are substantially the same under the same conditions.

[0024] The present application also provides a trapezoidal grating, and the augmented reality display device includes an optical-mechanical component and a diffraction optical waveguide as described in any one of the above items.

[0025] The present application provides a novel method for preparing a trapezoidal grating. The method comprises forming multiple material layers on a substrate, performing a first etching to determine one base angle of the trapezoidal grating and forming a groove for forming a second etching mask. A filling mask is then formed in the groove, and a second etching is performed to determine the other base angle of the trapezoidal grating. The remaining material layers above the first material layer of the multilayer material layer are then removed. Thus, a trapezoidal grating can be formed in the first material layer of the multilayer material layer. The resulting trapezoidal grating has high morphological accuracy and good repeatability, and can simultaneously control both base angles of the trapezoidal grating, thereby increasing design freedom and having significant significance for optimizing the diffraction performance of the grating. The present invention creatively prepares the trapezoidal grating by removing the remaining material layers above the first material layer of the multilayer material layer, particularly by removing the second material layer. This method, unlike conventional preparation methods, results in a more conformal trapezoidal grating structure, with the grating structure's morphology more closely aligned with the design parameters. This method also results in higher diffraction efficiency for the trapezoidal grating, resulting in unexpected technical benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A schematic flow chart of a method for preparing a trapezoidal grating provided in an embodiment of the present application;

[0028] Figure 2A A schematic diagram of forming multiple material layers on a substrate according to an embodiment of the present application;

[0029] Figure 2B A schematic diagram of forming multiple material layers on a substrate according to another embodiment of the present application;

[0030] Figure 3 A schematic diagram of forming a patterned mask on the surface of a multi-layer material layer provided in an embodiment of the present application;

[0031] Figure 4 A schematic diagram of forming several grooves after the first etching according to an embodiment of the present application;

[0032] Figure 5 A schematic diagram of forming a filling mask in a groove according to an embodiment of the present application;

[0033] Figure 6 A schematic diagram after the second etching provided in an embodiment of the present application;

[0034] Figure 7 A schematic structural diagram of a trapezoidal grating provided in an embodiment of the present application;

[0035] Figure 8A A schematic structural diagram of another trapezoidal grating provided in an embodiment of the present application;

[0036] Figure 8B A schematic structural diagram of another trapezoidal grating provided in an embodiment of the present application;

[0037] Figure 9 A schematic diagram of the tooth shape of a trapezoidal grating when etching the same side twice according to an embodiment of the present application;

[0038] Figure 10 A schematic diagram of the tooth shape of a trapezoidal grating when etching two different sides according to an embodiment of the present application;

[0039] Figure 11 A schematic structural diagram of another trapezoidal grating provided in an embodiment of the present application;

[0040] Figure ID:

[0041] 110: base;

[0042] 120: multi-layer material layer; 121: first material layer; 122: second material layer; 123: third material layer;

[0043] 130: Patterned mask;

[0044] 140: Filled mask. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0046] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0047] refer to Figure 1-10 , the direction of the arrow in the figure is the etching direction, and the present application provides a method for preparing a trapezoidal grating, comprising:

[0048] S10, providing a substrate.

[0049] It is understood that the trapezoidal grating prepared in this application can be a microstructure on a diffraction waveguide or a microstructure on an imprint master. When the trapezoidal grating is a microstructure on a diffraction waveguide, the substrate is the waveguide substrate and should have a certain degree of light transmittance. Translucent materials such as glass or resin substrates can be used. When the trapezoidal grating is a microstructure on an imprint master, light transmittance is not required for the substrate, and conventional semiconductor silicon wafers can be used.

[0050] refer to Figure 2A and Figure 2B , the embodiment of the present application provides a substrate 110 when preparing a trapezoidal grating.

[0051] S20, forming a plurality of material layers on the surface of the substrate; the plurality of material layers sequentially include at least a first material layer and a second material layer in a direction away from the substrate; the first material layer and the second material layer are made of different materials.

[0052] Specifically, refer to Figure 2A A first material layer 121 and a second material layer 122 are sequentially formed on the surface of the substrate 110. The first material layer is the material layer where the trapezoidal grating resides. When the trapezoidal grating is a microstructure on a diffractive waveguide, the first material layer should be made of a relatively high or relatively high refractive index material suitable for the grating structure, such as titanium oxide or niobium oxide. When the trapezoidal grating is a microstructure on an imprint master, the first material layer can be made of a hard material suitable for imprinting, such as silicon dioxide.

[0053] It should be noted that the first material layer and the second material layer are made of different materials so that they can be separated under specific conditions and / or specific environments, thereby removing the second material layer on the first material layer to form a trapezoidal grating. For example, the second material layer and the first material layer have different solubility. In a specific solution, the second material layer can dissolve while the first material layer does not dissolve. In this way, the second material layer on the first material layer can be removed, forming a trapezoidal grating in the first material layer. For another example, the second material layer and the first material layer have different solubility conditions. In a specific solution, the second material layer dissolves while the first material layer does not dissolve. In this way, the second material layer on the first material layer can be removed, forming a trapezoidal grating in the first material layer. For another example, the interlayer bonding between the first material layer and the second material layer is affected by conditions. Under specific conditions, the first material layer and the second material layer separate. In this way, the second material layer on the first material layer can be removed, forming a trapezoidal grating in the first material layer. By way of example, the material of the second material layer is, for example, aluminum oxide.

[0054] In some embodiments, the multi-layer material layer further includes a third material layer formed on the second material layer. That is, the multi-layer material layer includes at least the first material layer, the second material layer and the third material layer in sequence in a direction away from the substrate. Figure 2B, a first material layer 121, a second material layer 122, and a third material layer 123 are sequentially formed on the surface of the substrate 110. Of course, the multi-layer material layer also includes more material layers above the third material layer and / or below the first material layer. This application does not limit the number of material layers, nor does it limit the number of material layers in the first material layer.

[0055] Furthermore, the materials of the first material layer and the third material layer may be the same or different. When the first material layer and the third material layer are the same, or when the first material layer and the third material layer are different but have the same etching rate under the same conditions, the flatness of the etched side surface can be achieved. When the first material layer and the third material layer are different and have different etching rates under the same conditions, it is necessary to adjust the etching parameters for the first and third material layers separately to ensure the flatness of the etched side surface.

[0056] Practically, the thickness of the first material layer is greater than or equal to the thickness of the trapezoidal grating, ranging from tens to hundreds of nanometers. The thickness of the second material layer should be neither too large nor too small. If it is too large, it will be difficult to separate from the first material layer, while if it is too small, the preparation process will be difficult and unnecessary, and it can range from 20nm to 40nm. The thickness of the third material layer depends on the period and depth of the trapezoidal grating, as well as the size of the two base angles.

[0057] S30, forming a patterned mask on the surface of the multi-layer material layer.

[0058] The patterned mask is a hard mask. The material of the patterned mask can be a metal material such as Cr, Al, W, etc. Preferably, the thickness of the patterned mask is greater than 60nm. Figure 3 A patterned mask 130 is formed on the surface of the multilayer material layer. This figure only takes the multilayer material layer including 3 layers as an example, and does not limit the number of layers of the multilayer material layer. The multilayer material layer can have more or fewer layers.

[0059] In one embodiment, S20 specifically includes the following steps: forming a photoresist layer on the surface of the multilayer material layer, exposing and developing the photoresist layer to form a patterned photoresist layer; depositing a hard mask material on the patterned photoresist layer to form a hard mask material layer; removing the patterned photoresist layer to strip off the hard mask material deposited on the patterned photoresist layer, thereby forming a patterned mask.

[0060] For example, a spin coating process is used to spin-coat a 700nm thick photoresist on a substrate that has undergone surface purification; then, any of all possible exposure methods such as holographic interference exposure, mask exposure, laser direct writing or electron beam direct writing is used to expose the photoresist and form a patterned photoresist layer after stripping and development; then, an evaporation process is used to deposit a layer of hard mask material, such as metal Cr with a thickness of 100nm, on the surface of the patterned substrate; finally, a stripping liquid or dry stripping equipment (Strip equipment) is used to strip off the remaining photoresist and the hard mask material on the photoresist to produce a patterned mask.

[0061] S40 , etching the multi-layer material layer to the first material layer at a first preset angle, removing the remaining patterned mask layer, and forming a plurality of grooves.

[0062] Specifically, in the embodiments of the present application, etching of the multilayer material layer at a first preset angle is performed as vertical etching or oblique etching. The first preset angle is the angle between the etching direction and the normal direction of the substrate surface. Practically, the first etching direction when etching the multilayer material layer at the first preset angle is defined as a first reference direction, and the angle between the grating surface and the substrate surface along the first reference direction is defined as a first base angle; the magnitude of the first base angle is modulated by modulating the first preset angle.

[0063] refer to Figure 4 , angle φ is the first base angle. This figure illustrates a multilayer material layer comprising three layers and does not limit the number of layers. A multilayer material layer may have more or fewer layers. It will be understood that angle φ is substantially unaffected by the number of layers.

[0064] Practically, the first preset angle can be selected in a range of 0°-70°, and the first base angle can be modulated in a range of 15°-160°. For example, an ion beam with an incident angle of 55° is used to etch a multilayer material layer carrying a patterned mask, forming a plurality of grooves in the multilayer material layer. The angle between the groove sides and the substrate surface is 35° or 145°, i.e., the first base angle of the trapezoidal grating is 35° or 145°.

[0065] In one embodiment, when etching a multilayer material layer at a first preset angle, the etching stops when it reaches the bottom of the first material layer, that is, the substrate surface. The bottom surface of the several grooves formed at this time is the substrate surface, and the angle between the side surface of the groove and the substrate surface is one of the bottom angles of the trapezoidal grating.

[0066] In one embodiment, when etching a multilayer material layer at a first preset angle, the etching stops when it reaches a certain depth in the first material layer. At this time, the bottom surfaces of the several grooves formed are still some distance away from the substrate surface, and the angle between the side surfaces of the grooves and the substrate surface is one of the bottom angles of the trapezoidal grating.

[0067] It should be noted that the etching depth when etching the multi-layer material layer at the first preset angle will affect the structure of the trapezoidal grating formed in the end. If the multi-layer material layer is etched through, that is, etched to the substrate surface, the structure of the trapezoidal grating obtained in the end will be similar to that of the first preset angle. Figure 7 In this embodiment, the height of the trapezoidal grating is the thickness of the first material layer. If the multi-layer material layer is not etched through, that is, the etching stop position is still a distance away from the substrate surface, the structure of the trapezoidal grating obtained is referenced. Figure 8A As shown, it can be seen that there is a first material layer of a certain thickness between the trapezoidal grating teeth and the substrate. In this embodiment, the height of the trapezoidal grating is the depth of etching the first material layer. Figure 7 、 8A The structures shown have certain differences in performance. In the actual preparation process, the preparation method can be selected according to the actual effect to be achieved or the design performance requirements. Figure 7 or Figure 8A The structure shown.

[0068] In another embodiment, a material layer may be included between the substrate and the first material layer. The material of the material layer is different from that of the first material layer, and the number of material layers is not limited. Preferably, the material layer is used as an etching stop layer for the first material layer. The structure of the trapezoidal grating obtained is referenced to Figure 8B In this case, there is an intermediate dielectric layer between the grating structure and the substrate. The material of the grating structure is different from that of the intermediate dielectric layer, which can also bring other performance improvements.

[0069] S50 , forming a filling mask in the groove; the filling mask fills the groove, and the material of the filling mask is different from the material of the multi-layer material layer.

[0070] It should be noted that since the material of the filling mask is different from that of the multilayer material layer, the etching rate of the filling mask is different from that of the multilayer material layer, so that the filling mask can be used as a heterogeneous mask relative to the multilayer material layer.

[0071] For example, the material of the filling mask may be an organic material or a metal.

[0072] Practically, a filling mask is formed in the groove, specifically including: depositing a mask material on a multilayer material layer, wherein the thickness of the mask material is not less than the depth of the groove; removing the mask material on the multilayer material layer until the multilayer material layer is exposed, so as to retain the mask material filled in the groove to form a filling mask.

[0073] It should be noted that when removing the mask material from the multi-layer material layer, surface flatness should be maintained. For example, chemical polishing (CMP) can be used. In actual process, atomic force microscopy testing can show that the mask material on the surface of the multi-layer material layer is completely removed.

[0074] refer to Figure 5 , a filling mask 140 is formed in the groove of the multilayer material layer. The figure only takes the multilayer material layer including 3 layers as an example, and does not limit the number of layers of the multilayer material layer. The multilayer material layer can have more or fewer layers.

[0075] S60 , etching the multi-layer material layer to the first material layer at a second preset angle, removing the remaining filling mask and the second material layer, and forming a trapezoidal grating.

[0076] Specifically, in the embodiments of the present application, etching the multilayer material layer at a second preset angle is an oblique etching. The second preset angle is the angle between the etching direction and the normal direction of the substrate surface. Practically, the second etching direction when etching the multilayer material layer at the second preset angle is defined as a second reference direction, and the angle between the grating surface and the substrate surface along the second reference direction is defined as a second base angle. The magnitude of the second base angle is modulated by modulating the second preset angle.

[0077] refer to Figure 6 , angle θ is the second base angle. This figure illustrates a multilayer material layer comprising three layers and does not limit the number of layers. A multilayer material layer may have more or fewer layers. It will be appreciated that angle θ is substantially unaffected by the number of layers.

[0078] The second preset angle can be selected in the range of 0°-70°, and the second base angle can be modulated in the range of 15°-160°. For example, when an ion beam with a 60° incident angle is used to etch a multi-layer material layer carrying a patterned mask, the second base angle of the trapezoidal grating is 30° or 150°.

[0079] Practically, in the embodiments of the present application, when etching the multilayer material layer at the second predetermined angle, the etching stops when it reaches the substrate surface, thereby forming another bottom angle of the trapezoidal grating. The thickness of the multilayer material layer can be reduced during etching. The width of the multilayer material layer between two adjacent grooves can be reduced during etching.

[0080] In one embodiment, the remaining filling mask and the second material layer are removed to form a trapezoidal grating, specifically including: removing the remaining filling mask; placing the substrate in a target solution; heating the target solution to a target temperature and maintaining it for a target time, dissolving the second material layer and keeping the first material layer undissolved to form a trapezoidal grating.

[0081] The first material layer and the second material layer have different solubilities or dissolution conditions in the target solution, such that the first material layer is insoluble in the target solution but the second material layer is soluble; or, when the second material layer reaches the dissolution condition and dissolves, the first material layer has not yet dissolved, so that the second material layer on the first material layer can be removed. It is understood that when a third material layer exists above the second material layer, as the second material layer separates from the first material layer, the third material layer will also separate from the first material layer.

[0082] For example, the target solution can be an acidic solution, and the dissolution conditions of the second material layer and the first material layer in the acidic solution are different. The target solution is heated to a target temperature and maintained for a target time. When the second material layer reaches the dissolution condition and dissolves and separates from the first material layer, the first material layer has not yet dissolved. In this way, the second material layer and the third material layer on the first material layer can be removed. For example, the first material layer is SiO2 and the material of the second material layer is Al2O3. After removing the remaining fill mask on the substrate, the substrate is immersed in an H3PO4 solution and heated to 40°C-70°C. It is maintained at a temperature of 40°C-60°C for 30 minutes. The second material layer Al2O3 reaches the dissolution condition and dissolves, while the first material layer SiO2 has not yet dissolved.

[0083] The present application provides a novel method for preparing a trapezoidal grating. The method comprises forming multiple material layers on a substrate, performing a first etching to determine one of the bottom angles of the trapezoidal grating and forming a groove for forming a second etching mask. A filling mask is then formed in the groove, and a second etching is performed to determine the other bottom angle of the trapezoidal grating. The remaining material layers above the first material layer in the multiple material layers are then removed. Thus, a trapezoidal grating can be formed in the first material layer of the multiple material layers. The resulting trapezoidal grating has high morphology accuracy and good repeatability. Furthermore, the first etching forms one of the bottom angles of the trapezoidal grating, and the angle of the first etching can be modulated to adjust the size of the bottom angle. The second etching forms the other bottom angle of the trapezoidal grating, and the angle of the second etching can be modulated to adjust the size of the bottom angle. Controlling the two bottom angles of the trapezoidal grating improves the degree of freedom in design and is of great significance for optimizing the diffraction performance of the grating.

[0084] At the same time, the present invention creatively prepares a trapezoidal grating by removing other material layers above the first material layer in the multi-layer material layer, especially by removing the second material layer to form a trapezoidal grating. Different from the preparation method in the prior art, the method of removing material layers makes the formed trapezoidal grating structure more conformal, and the morphology of the grating structure is closer to the design parameters, so that the diffraction efficiency is higher, and it has unexpected technical effects.

[0085] Furthermore, the method for preparing a trapezoidal grating provided in the present application involves two etching steps, the directions of which affect the tooth profile of the trapezoidal grating. Practically, in the first case, the etching direction for etching the multilayer material layer at a first preset angle and the etching direction for etching the multilayer material layer at a second preset angle are on the same side of the substrate surface normal direction, resulting in a trapezoidal grating with a tooth profile that is narrow at the top and narrow at the bottom. In the second case, the etching direction for etching the multilayer material layer at the first preset angle and the etching direction for etching the multilayer material layer at the second preset angle are on opposite sides of the substrate surface normal direction, resulting in a trapezoidal grating with a tooth profile that is narrow at the top and narrow at the bottom.

[0086] For example, Figure 9 A schematic diagram of the tooth shape of a trapezoidal grating obtained when the etching directions of two oblique etchings are on the same side provided in another embodiment of the present application; Figure 10 This is a schematic diagram of the tooth shape of the trapezoidal grating obtained when the etching directions of the two oblique etchings are on different sides provided in another embodiment of the present application.

[0087] It should be noted that the first material layer in the present application is not limited to comprising only one layer of material, but may also be a composite layer structure of multiple layers of material. In this way, the trapezoidal grating formed in the first material layer may be a multi-layer grating structure, which has better optical performance. Preferably, the etching rates of the various layers of material in the first material layer are substantially the same under the same conditions. Figure 11 The first material layer 121 includes a material layer 121a and a material layer 121b. This figure only uses the example that the first material layer includes two layers of material, and does not limit the number of layers of material in the first material layer. There can be more or fewer layers.

[0088] According to one aspect of the present application, a trapezoidal grating is further provided. The trapezoidal grating is prepared by the method for preparing the trapezoidal grating described in any of the aforementioned embodiments.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a trapezoidal grating, characterized in that: include: providing a substrate; forming a plurality of material layers on the surface of the substrate; The multiple material layers include at least a first material layer and a second material layer in sequence along a direction away from the substrate; The first material layer and the second material layer are made of different materials; forming a patterned mask on the surface of the multi-layer material layer; Etching the multi-layer material layer to the first material layer at a first preset angle, removing the remaining patterned mask layer, and forming a plurality of grooves; forming a filling mask in the groove; The filling mask fills the groove, and the material of the filling mask is different from the material of the multi-layer material layer; The multi-layer material layer is etched to the first material layer at a second preset angle, and the remaining filling mask and the second material layer are removed to form a trapezoidal grating.

2. The method for preparing a trapezoidal grating according to claim 1, wherein: A first etching direction when etching the multilayer material layer at the first preset angle is defined as a first reference direction, and an angle between the grating surface and the substrate surface along the first reference direction is defined as a first base angle; and the size of the first base angle is modulated by modulating the first preset angle.

3. The method for preparing a trapezoidal grating according to claim 1, wherein: A second etching direction when etching the multilayer material layer at the second preset angle is defined as a second reference direction, and an angle between the grating surface and the substrate surface along the second reference direction is defined as a second base angle; and the size of the second base angle is modulated by modulating the second preset angle.

4. The method according to claim 1, wherein The etching directions of the multi-layer material layer when being etched at the first preset angle and the etching directions of the multi-layer material layer when being etched at the second preset angle are different, and / or the first preset angle and the second preset angle are different in size.

5. The method according to claim 1, wherein The forming of a filling mask in the groove specifically includes: Depositing a mask material on the multi-layer material layer, wherein the thickness of the mask material is not less than the depth of the groove; The mask material on the multi-layer material layer is removed until the multi-layer material layer is exposed, so as to retain the mask material filled in the groove to form a filling mask.

6. The method for preparing a trapezoidal grating according to claim 1, wherein: The step of removing the remaining filling mask and the second material layer to form a trapezoidal grating specifically includes: removing the remaining filling mask; placing the substrate in a target solution; The target solution is heated to a target temperature and maintained for a target time to dissolve the second material layer and keep the first material layer undissolved, thereby forming a trapezoidal grating.

7. The method for preparing a trapezoidal grating according to claim 1, wherein: The etching of the multilayer material layer to the first material layer at a first preset angle specifically includes: etching the multilayer material layer to the bottom of the first material layer at a first preset angle; and the etching of the multilayer material layer to the first material layer at a second preset angle specifically includes: etching the multilayer material layer to the bottom of the first material layer at a second preset angle.

8. The method for preparing a trapezoidal grating according to claim 1, wherein: The thickness of the second material layer is in the range of 20 nm to 40 nm.

9. The method for preparing a trapezoidal grating according to claim 1, wherein: The multi-layer material layer further includes a third material layer formed on the second material layer.

10. The method for preparing a trapezoidal grating according to claim 9, wherein: The etching rates of the first material layer and the third material layer are substantially the same under the same conditions.

11. A trapezoidal grating, characterized in that: The trapezoidal grating is manufactured by the method for manufacturing a trapezoidal grating according to any one of claims 1 to 10.

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