A method of manufacturing a grating structure

Abstract

This application provides a method for manufacturing a grating structure. A film layer to be etched is provided, and the film layer is etched to obtain a wire grid array. The wire grid array includes multiple trenches arranged sequentially, with the trenches having the same depth. A filling material is formed in the trenches through a deposition process in a deposition direction that is not parallel to the surface normal of the film layer to be etched. The thickness of the filling material gradually changes in the arrangement direction of the trenches, causing the trench depth to gradually change in the arrangement direction. In other words, by adding one deposition process, trenches with gradually varying depths can be obtained. These trenches with varying depths can form a gradient grating structure, simplifying the manufacturing process and reducing manufacturing costs.

Description

Technical Field

[0001] This invention relates to the field of optics, and in particular to a method for manufacturing a grating structure. Background Technology

[0002] A grating consists of a large number of parallel slits of equal width and spacing. Also known as a diffraction grating, it is an optical element that uses the principle of multi-slit diffraction to disperse light (decompose it into a spectrum). Gratings can be used to create various special effects on specially made films, displaying lifelike three-dimensional worlds on a flat surface, smooth animated sequences like those in movies, and incredible illusionary effects.

[0003] Augmented reality (AR) and virtual reality (VR) are technologies that have garnered significant attention in recent years. Both technologies use near-eye display systems to project a distant virtual image onto the viewer's eye, formed from pixels on a display screen through a series of optical imaging elements. The difference lies in the fact that AR glasses require see-through; they need to see both the real external world and the virtual information, so the imaging system cannot obstruct the view. This necessitates the addition of one or more optical combiners to layer the virtual information and the real-world scene, allowing them to complement and enhance each other.

[0004] Optical waveguide technology is a unique optical component developed to meet the needs of AR glasses. Due to its thinness and high light transmittance, it is considered an essential optical solution for consumer AR glasses. The demand for gratings in surface relief grating waveguides has increased significantly because of their ability to provide high diffraction efficiency for a predefined order.

[0005] Typically, the operating conditions of gratings in optical waveguide instruments are fixed. To achieve ideal diffraction efficiency, it is necessary to optimize the design of the grating structure parameters. For gratings, the most important parameters include the grating height and whether there is a difference in the angles of the two sidewalls, i.e., the parallelism of the two sides. A higher height can increase the diffraction area, while high parallelism can maximize the diffraction efficiency and ensure that the optical path input and output ends are matched.

[0006] With the development of technology, in order to obtain higher optical performance, the design of gratings has become increasingly complex, and the need for gradient depth and tilt angle has gradually emerged. These complex designs have brought challenges to the processing and fabrication process. At present, the feasible process route is basically formed by a combination of multiple processes such as etching, coating, grayscale gradient exposure, and re-etching. It requires multiple processing systems, has many steps, is time-consuming, and costly. Summary of the Invention

[0007] In view of this, the purpose of this application is to provide a method for manufacturing a grating structure, which forms a gradient grating structure through a simple manufacturing process.

[0008] This application provides a method for manufacturing a grating structure, the method comprising:

[0009] Provide the film layer to be etched;

[0010] The film layer to be etched is etched to obtain a grid array, the grid array including a plurality of trenches arranged in sequence, the plurality of trenches having the same depth;

[0011] In a deposition direction that is not parallel to the surface normal of the film to be etched, a filling material is formed in the trench by a deposition process. The thickness of the filling material gradually changes in the direction in which the trenches are arranged, so that the depth of the trenches gradually changes in the direction in which the trenches are arranged.

[0012] Optionally, the film layer to be etched includes a target layer and a mask layer on the target layer, an etch stop layer is provided under the target layer, the wire grid array penetrates the mask layer and the target layer, and the wire grid array serves as a gradient depth grating.

[0013] Optionally, the thickness of the mask layer is denoted as a, the thickness of the target layer is denoted as b, the total width of the grid array is L, the grid period is c, the linewidth of the protrusion between two adjacent trenches is d, the angle between the surface normal direction and the deposition direction is α, and the angle between the upper and lower surfaces of the filling material is β.

[0014] The range of α is And / or, the range of β is

[0015] Optionally, the filler material is the same as the material of the target layer.

[0016] Optionally, the film layer to be etched includes a mask layer on the target layer, an etch stop layer is provided below the target layer, the wire grid array penetrates the mask layer, and the method further includes:

[0017] The filler material and the target layer beneath it are etched to obtain a gradient depth grating.

[0018] Optionally, the thickness of the mask layer is denoted as a, the total width of the grid array is L, the grid period is c, the linewidth of the protrusion between two adjacent trenches is d, the angle between the surface normal direction and the deposition direction is α, and the angle between the upper and lower surfaces of the filling material is γ.

[0019] The range of α is And / or, the range of γ is

[0020] Optionally, the filler material is at least one of Cr, Mo, Al, Ti, photoresist, SOC, and SOH.

[0021] Optionally, the etching selectivity ratio of the target layer material to the filling material is denoted as k, and the angle between the plane where the bottom of the trench obtained after etching is located and the plane where the bottom of the target layer is located is denoted as δ;

[0022] The value of k is in the range of 0.1 to 50, and the value of γ is kδ.

[0023] Optionally, the method further includes:

[0024] After forming the gradient depth grating, the mask layer is removed.

[0025] Optionally, the range of α is 0 to 45°, and the range of the angle between the upper and lower surfaces of the filling material is 0 to 4°.

[0026] Optionally, during the deposition process, the ratio of the deposition rate of the filling material on the side of the film to be etched near the target to the side far from the target is m. If m > L*cosα, then the angle between the upper and lower surfaces of the filling material is greater than the angle between the surface normal and the deposition direction. If m ≤ L*cosα, then the angle between the upper and lower surfaces of the filling material is less than or equal to the angle between the surface normal and the deposition direction.

[0027] Optionally, the material of the mask layer is at least one of Cr, Mo, Al, and Ti, the material of the target layer is at least one of Al2O3, Ga2O3, Ta2O3, Si, SiO2, Si3N4, quartz, and TiO2, and the etching stop layer is at least one of Si, quartz glass, and LiNbO3.

[0028] Optionally, the angle between the sidewall and bottom of the trench in the wire grid array is 90°, or less than 90° and greater than 60°.

[0029] Optionally, the L ranges from 1 micrometer to 10 centimeters, the c ranges from 50 nanometers to 5 micrometers, and the duty cycle d / c is 0-0.7.

[0030] This application provides a method for manufacturing a grating structure. A film layer to be etched is provided, and the film layer is etched to obtain a wire grid array. The wire grid array includes multiple trenches arranged sequentially, with the trenches having the same depth. A filling material is formed in the trenches through a deposition process in a deposition direction that is not parallel to the surface normal of the film layer to be etched. The thickness of the filling material gradually changes in the arrangement direction of the trenches, causing the trench depth to gradually change in the arrangement direction. In other words, by adding one deposition process, trenches with gradually varying depths can be obtained. These trenches with varying depths can form a gradient grating structure, simplifying the manufacturing process and reducing manufacturing costs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic flowchart illustrating a method for manufacturing a grating structure according to an embodiment of this application;

[0033] Figures 2-16 This is a schematic diagram of the grating structure provided in the embodiments of this application during the manufacturing process. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0036] This application is described in detail with reference to the schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0037] To better understand the technical solution and effects of this application, the specific embodiments will be described in detail below with reference to the accompanying drawings.

[0038] See Figure 1 The diagram shown is a flowchart illustrating a method for manufacturing a grating structure according to an embodiment of this application. (Refer to...) Figures 2-16 This is a schematic diagram of the grating structure during the manufacturing process in an embodiment of this application. The method may include:

[0039] S101, provides the film to be etched, reference. Figure 2 As shown.

[0040] In this embodiment, the film layer to be etched may include a target layer 120 forming a grating, and may also include a mask layer 130 on the target layer 120. An etch stop layer 110 may be present below the target layer 120. The etch stop layer 110 has a high etch selectivity for the target layer 120, allowing etching of the target layer 120 to stop at the etch stop layer 110. The etch stop layer 110 may also serve as a support structure for the film layer to be etched. In this embodiment, the thicknesses of the mask layer 130 and the target layer 120 can be determined according to actual conditions. The thickness of the mask layer 130 is denoted as 'a', and the thickness of the target layer 120 is denoted as 'b'.

[0041] The mask layer 130 can be made of a metallic material and serves as a hard mask. The material of the mask layer 130 is at least one of Cr, Mo, Al, Ti, etc. The target layer 120 can be made of at least one of a dielectric material or a high refractive index material. The dielectric material is at least one of Al2O3, Ga2O3, Ta2O3, Si, SiO2, Si3N4, etc., and the high refractive index material is at least one of quartz, TiO2, etc. The etching stop layer 110 is at least one of Si, quartz glass, LiNbO3, etc.

[0042] As an example, the mask layer 130 can be made of Cr or Al, and its thickness can be 80 nanometers; the target layer is made of SiN. x The material of the etching stop layer 110 is SiO2 or TiO2 with a thickness of 300 nanometers; the material of the etching stop layer 110 is Si or LiNbO3.

[0043] S102, etch the film layer to be etched to obtain a wire grid array, the wire grid array including multiple trenches arranged in sequence, reference. Figures 3-5 As shown.

[0044] In this embodiment, the film layer to be etched can be etched to obtain a wire grid array. The wire grid array includes a plurality of trenches 131 arranged in sequence, and the plurality of trenches 131 have the same depth. The etching of the film layer to be etched can be achieved by ion beam etching (IBE) or reactive ion beam etching (RIBE), and the etching equipment can be ICP, CCP, or RIBE equipment.

[0045] When the film layer to be etched includes the target layer 120 and the mask layer 130, the wire grid array can be obtained by etching the mask layer 130. The etching depth can be equal to the thickness of the mask layer 130 (when the wire grid array is a slanted grating, the etching depth can be greater than the thickness of the mask layer 130) or less than the thickness of the mask layer 130. The wire grid array can also be obtained by etching the mask layer 130 and the target layer 120. The etching depth of the target layer 120 can be equal to the thickness of the target layer 120 (when the wire grid array is a slanted grating, the etching depth of the target layer 120 can be greater than the thickness of the target layer 120) or less than the thickness of the target layer 120.

[0046] Typically, the wire grid array can penetrate the mask layer 130, reference Figure 3 As shown; the wire grid array can also penetrate through the mask layer 130 and the target layer 120, see reference. Figure 4 and Figure 5 As shown, the etching can stop on the upper surface of the target layer 120 or on the upper surface of the etching stop layer 110, which is beneficial for etching control.

[0047] In cases where a linear grid array can also be obtained by etching the mask layer 130 and the target layer 120, the upper structure of the linear grid array can be obtained by first etching the mask layer 130, as shown in the reference. Figure 3 As shown, the mask layer 130 can be etched using ICP or CCP equipment; then, using the mask layer 130 as a mask, the target layer 120 is etched to obtain the lower structure of the wire grid array, as shown in the reference. Figure 4 and Figure 5 As shown, the target layer 120 can be etched using the RIBE method.

[0048] The etching angle at which the film to be etched is etched determines the angle between the etching direction of the trench and the surface normal of the film to be etched. The angle between the bottom and sidewall of the trench is greater than or equal to 60° and less than or equal to 90°. In practice, the wire grating array can be a straight grating or a slanted grating. In a straight grating, the angle between the etching direction of the trench 131 and the surface normal of the film to be etched is small, close to 0 or equal to 0. That is, the etching direction of the trench in the straight grating is nearly perpendicular to the surface of the film to be etched. At this time, the angle between the sidewall and the bottom of the trench is 90°. Straight gratings can be formed by ICP, CCP, or RIBE equipment. In a slanted grating, the angle between the etching direction of the trench 131 and the surface normal of the film to be etched is slightly larger, for example, less than or equal to 30°. That is, the angle between the slanted grating and the surface of the film to be etched can be greater than or equal to 60°. At this time, the angle between the sidewall and the bottom of the trench 131 is less than 90° and greater than or equal to 60°. Slanted gratings can be formed by RIBE equipment.

[0049] Specifically, the total width of the wire grid array can be denoted as L, the wire grid period as c, the linewidth (the width of the protrusion between two adjacent trenches) as d, and the wire grid period is the sum of the linewidth and the trench width. L ranges from 1 micrometer to 10 centimeters, c ranges from 50 nanometers to 5 micrometers, and the duty cycle d / c is 0-0.7. As an example, the period can be 400 nanometers, the linewidth 200 nanometers, and the total width 5 micrometers.

[0050] S103, In a deposition direction not parallel to the surface normal of the film to be etched, a filling material is formed in the trenches through a deposition process. The thickness of the filling material gradually changes in the trench arrangement direction, so that the trench depth gradually changes in the trench arrangement direction. (Refer to...) Figures 6-16 As shown.

[0051] In this embodiment, a filling material is formed in the trenches through a deposition process in a deposition direction that is not parallel to the surface normal of the film to be etched. During the deposition process, the angle between the surface normal of the film to be etched and the deposition direction can be controlled to α. The deposition direction is the normal direction of the target material 200°, where α is greater than 0 and less than or equal to 45°. The deposition time can be determined according to the actual situation, for example, it can be 50-200s. The thickness of the filling material gradually changes in the trench arrangement direction, so that the depth of the trench gradually changes in the trench arrangement direction. That is to say, by adding one deposition process, trenches with varying depths can be obtained. The trenches with varying depths can form variable depth gratings, replacing the existing coating and grayscale gradient exposure processes with variable depth film deposition, which simplifies the manufacturing process to a certain extent and reduces the processing difficulty and cost.

[0052] The deposition process can be ion beam assisted deposition (IBAD) or ion beam deposition, and the deposition equipment can be IBD or PECVD equipment.

[0053] When an online gate array is obtained by etching the mask layer 130 and the target layer 120, the filling material and the target layer 120 can be the same, i.e., the material can be SiN. x The deposition method can be SiO2 or TiO2, with a deposition time of 200s. Ion beam assisted deposition can be used, allowing the trench depth to be altered by the filling material. A wire grating array can be used as a gradient depth grating. For cases where the wire grating array is a straight grating, refer to [reference needed]. Figure 6 As shown, the reference case is a slanted grating for the wire grating array. Figure 8 As shown; after forming the gradient depth grating, the mask layer 130 can be removed. After removing the mask layer 130, the material of the gradient depth grating is a single material (which includes the retained target layer and the filling material). For the case where the wire grating array is a straight grating, refer to... Figure 7 As shown, the reference case is a slanted grating for the wire grating array. Figure 9 As shown.

[0054] The angle between the upper and lower surfaces of the resulting filling material is denoted as β (called the first gradient angle of the filling material). β ranges from 0 to 4°. The smaller α is, the smaller β is; the larger α is, the larger β is. As an example, α can be 30°, corresponding to β of 2.5°; α can be 45°, corresponding to β of 4°.

[0055] The range of α is And / or, the range of β is

[0056] When the wire grid array is obtained by etching the mask layer 130, the wire grid array penetrates the mask layer 130. The filling material can be the same as or different from the target layer 120. The deposition method can be ion beam deposition. (Refer to...) Figure 10 As shown. When the filling material differs from the target layer 120, the filling material can be at least one of the following: metals such as Cr, Mo, Al, and Ti; photoresist (PR); spin-on carbon (SOC); spin-on hard mask (SOH); etc. As an example, the material can be SiN. x The material can be SiO2 or TiO2, and the deposition time can be 100s; or the material can be Mo, and the deposition time can be 50s.

[0057] After the filling material is formed, the filling material and the target layer 120 beneath it can be etched to obtain a gradient depth grating. The etching method for the filling material and the target layer 120 beneath it can be perpendicular to the surface of the target layer. Figure 11 As shown, the resulting gradient depth grating is a straight grating, with reference to... Figure 12 As shown; the etching method for the filler material and the target layer 120 beneath it can also be at a certain angle to the surface normal of the target layer, denoted as σ, where σ ranges from 0 to 30°, see reference. Figure 14 As shown, the resulting gradient depth grating is a slanted grating, with reference to... Figure 15 As shown, the angle between the bottom and sidewall of the trench in the slanted grating is 90°-60°. After forming the gradient depth grating, the mask layer 130 can be removed, as shown in the reference. Figure 13 and Figure 16 As shown, the gradient depth grating is formed using ion beam assisted deposition and ion beam etching techniques.

[0058] When an online grating array is obtained by etching the mask layer 130 and the target layer 120, the angle between the upper and lower surfaces of the resulting filling material is denoted as γ (called the second gradient angle of the filling material). γ can range from 0 to 1°; the smaller α is, the smaller γ is; the larger α is, the larger γ is. In the gradient depth grating obtained after etching the filling material and the target layer 120, the angle between the plane containing the bottom of the trench and the plane containing the bottom of the target layer 120 is denoted as δ (called the gradient angle of the gradient depth grating).

[0059] The range of α is And / or, the range of γ is

[0060] When the filler material is the same as the target layer 120, it is equivalent to increasing the thickness of the target layer 120 to be etched to varying degrees. The gradient angle of the resulting gradient depth grating is approximately equal to the second gradient angle. For example, if the second gradient angle ranges from 0 to 1°, the gradient angle of the gradient depth grating also ranges from 0 to 1°. When the filler material is different from the target layer 120, it is equivalent to adding a mask layer 130 to the target layer 120. The gradient gradient can be adjusted using the etching selectivity ratio (denoted as k) between the target layer 120 material and the filler material. The range of k is 0.1-50. Furthermore, γ = kδ, meaning that the gradient angle of the resulting gradient depth grating is greater than the second gradient angle. For example, if the second gradient angle ranges from 0 to 1°, the gradient angle of the gradient depth grating also ranges from 0 to 4°.

[0061] During deposition, the ratio of the deposition rate of the filler material on the side of the film to be etched near the target to the deposition rate on the side farther from the target is m. If m > L*cosα, then the angle between the upper and lower surfaces of the filler material is greater than the angle between the surface normal and the deposition direction, i.e., β > α or γ > α. If m ≤ L*cosα, then the angle between the upper and lower surfaces of the filler material is less than or equal to the angle between the surface normal and the deposition direction, i.e., β ≤ α or γ ≤ α. This allows control of the first gradient angle and the second gradient angle, and consequently, the gradient angle of the gradient depth grating.

[0062] This application provides a method for manufacturing a grating structure. A film layer to be etched is provided, and the film layer is etched to obtain a wire grid array. The wire grid array includes multiple trenches arranged sequentially, with the trenches having the same depth. A filling material is formed in the trenches through a deposition process in a deposition direction that is not parallel to the surface normal of the film layer to be etched. The thickness of the filling material gradually changes in the arrangement direction of the trenches, causing the trench depth to gradually change in the arrangement direction. In other words, by adding one deposition process, trenches with gradually varying depths can be obtained. These trenches with varying depths can form a gradient grating structure, simplifying the manufacturing process and reducing manufacturing costs.

[0063] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. A method of manufacturing a grating structure, characterized by, The method includes: Provide the film layer to be etched; The film layer to be etched is etched to obtain a grid array, the grid array including a plurality of trenches arranged in sequence, the plurality of trenches having the same depth; In a deposition direction that is not parallel to the surface normal of the film to be etched, a filling material is formed in the trench by a deposition process. The thickness of the filling material gradually changes in the direction in which the trenches are arranged, so that the depth of the trenches gradually changes in the direction in which the trenches are arranged.

2. The method of claim 1, wherein, The film layer to be etched includes a target layer and a mask layer on the target layer. An etch stop layer is provided under the target layer. The wire grid array penetrates the mask layer and the target layer. The wire grid array serves as a gradient depth grating.

3. The method of claim 2, wherein, The thickness of the mask layer is denoted as a, the thickness of the target layer is denoted as b, the total width of the grid array is L, the grid period is c, and the linewidth of the protrusion between two adjacent trenches is d; the angle between the surface normal direction and the deposition direction is α, and the angle between the upper and lower surfaces of the filling material is β. said a is in the range of and / or, said b is in the range of 4. The method of claim 2, wherein, The filling material is the same as the material of the target layer.

5. The method of claim 1, wherein, The film layer to be etched includes a mask layer on the target layer, an etch stop layer is provided below the target layer, and the wire grid array penetrates the mask layer. The method further includes: The filler material and the target layer beneath it are etched to obtain a gradient depth grating.

6. The method of claim 5, wherein, The thickness of the mask layer is denoted as a, the total width of the wire grid array is L, the wire grid period is c, and the linewidth of the protrusion between two adjacent trenches is d. The angle between the surface normal direction and the deposition direction is α, and the angle between the upper and lower surfaces of the filling material is γ. said a is in the range of and / or, said g is in the range of 7. The method of claim 6, wherein, The etching selectivity ratio of the target layer material to the filling material is denoted as k, and the angle between the plane where the bottom of the trench obtained after etching is located and the plane where the bottom of the target layer is located is denoted as δ. The value of k is in the range of 0.1 to 50, and the value of γ is kδ.

8. The method of claim 5, wherein, The filler material is at least one of Cr, Mo, Al, Ti, photoresist, SOC, and SOH.

9. The method according to any one of claims 2-8, characterized in that, The method further includes: After forming the gradient depth grating, the mask layer is removed.

10. The method of any one of claims 3, 4, 6, 7, wherein, The range of α is 0 to 45°, and the range of the angle between the upper and lower surfaces of the filling material is 0 to 4°.

11. The method according to any one of claims 1 to 8, characterized in that, During the deposition process, the ratio of the deposition rate of the filler material on the side of the film to be etched that is closer to the target and the side that is farther from the target is m. If m > L*cosα, then the angle between the upper and lower surfaces of the filler material is greater than the angle between the surface normal and the deposition direction. If m ≤ L*cosα, then the angle between the upper and lower surfaces of the filler material is less than or equal to the angle between the surface normal and the deposition direction.

12. The method according to any one of claims 1 to 8, characterized in that, The mask layer is made of at least one of Cr, Mo, Al, and Ti; the target layer is made of at least one of Al2O3, Ga2O3, Ta2O3, Si, SiO2, Si3N4, quartz, and TiO2; and the etching stop layer is made of at least one of Si, quartz glass, and LiNbO3.

13. The method according to any one of claims 1 to 8, characterized in that, In a wire grid array, the angle between the sidewall and the bottom of the trench is 90°, or less than 90° and greater than 60°.

14. The method according to any one of claims 1 to 8, characterized in that, The L range is 1 micrometer to 10 centimeters, the c range is 50 nanometers to 5 micrometers, and the duty cycle d / c is 0 to 0.7.

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