Multi-step helical-tooth grating structure and preparation method thereof
By forming a stepped structure with multiple refractive layers on a transparent substrate and combining spectral signal detection to control etching and polishing, the problem of high fabrication difficulty of oblique tooth gratings was solved, and the simplified fabrication and performance improvement of oblique tooth gratings with large aspect ratio were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI UNIV
- Filing Date
- 2026-02-04
- Publication Date
- 2026-04-24
AI Technical Summary
The existing technology for processing helical tooth gratings is difficult, especially the processing equipment for large aspect ratio helical tooth etching is complex, which makes the processing even more difficult.
A method for fabricating a multi-step oblique tooth grating structure is adopted, which involves forming N+1 stacked refractive layers on a transparent substrate. Each refractive layer includes a low refractive index layer and a through-step layer. The step layer contains a high refractive index layer. By combining high refractive index layers and low refractive index layers of different materials, a step structure is formed. The etching and polishing depth is controlled by combining spectral signal detection.
It simplifies the fabrication process of high aspect ratio helical tooth gratings, improves processing accuracy and efficiency, enhances light energy utilization, and enriches the performance design of helical tooth gratings.
Smart Images
Figure CN121918239A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical devices, and in particular to a multi-step oblique tooth grating structure and its fabrication method. Background Technology
[0002] A zigzag grating is a nanoscale periodic structure fabricated on a substrate surface. Its teeth are tilted at a specific angle to guide light in a specific direction, thereby improving the utilization rate of light energy, i.e., diffraction efficiency.
[0003] However, the fabrication of oblique toothed gratings for enhanced display diffractive waveguides is a micro-nano process, involving techniques such as nanoimprinting or oblique etching to form flat oblique toothed gratings. Therefore, the fabrication of oblique toothed gratings is extremely difficult, and the equipment required is also quite complex. This is especially true for oblique tooth etching with a large aspect ratio, which presents even greater challenges. Summary of the Invention
[0004] This invention provides a multi-step oblique tooth grating structure and its fabrication method, which simplifies the fabrication method of oblique tooth gratings with large aspect ratio and enriches the performance design direction of oblique tooth gratings.
[0005] According to a first aspect of the present invention, a method for fabricating a multi-step oblique tooth grating structure is provided, comprising: Provide a transparent substrate; N+1 stacked refractive layers are formed on the transparent substrate. Each refractive layer includes a low-refractive-index layer and a step layer penetrating the low-refractive-index layer. The top surface of the low-refractive-index layer is flush with the top surface of the corresponding step layer. Each step layer within a refractive layer includes a plurality of high-refractive-index layers spaced apart in a first direction. The refractive index of the high-refractive-index layers is greater than that of the low-refractive-index layers. The materials of the high-refractive-index layers in any two adjacent refractive layers are different. Each (n+1)th high-refractive-index layer corresponds to an nth high-refractive-index layer. Each (n+1)th high refractive index layer is located on a portion of the surface of the corresponding nth high refractive index layer, and each (n+1)th high refractive index layer protrudes laterally relative to the corresponding nth high refractive index layer. The (n+1)th high refractive index layer is a high refractive index layer in the (n+1)th refractive layer. In the N+1th refractive layer, the lateral protrusion directions from the corresponding 1st high refractive index layer to the N+1th high refractive index layer are consistent, forming a stepped structure. N is a positive integer, and n is a positive integer less than or equal to N. The first direction is parallel to the surface of the transparent substrate.
[0006] Optionally, based on a cyclic processing method, N+1 stacked refractive layers are formed on the transparent substrate, the cyclic processing method comprising: An nth step layer is formed on the surface of the (n-1)th preceding layer. When n equals 1, the (n-1)th preceding layer is the transparent substrate; when n is greater than 1, the (n-1)th preceding layer is the (n-1)th refractive layer. After forming the nth step layer on the surface of the (n-1)th front layer, the nth low refractive index layer is formed on the (n-1)th front layer.
[0007] Optionally, methods for forming the nth step layer on the surface of the (n-1)th preceding layer include: A high-refractive-index material layer is formed on the surface of the (n-1)th front layer, and the thickness of the nth high-refractive-index material layer is the same as that of the nth high-refractive-index layer. A patterned first mask layer is formed on the nth high-refractive-index material layer; When n equals 1, the nth high-refractive-index material layer is etched using the patterned first mask layer as a mask to form the nth high-refractive-index layer; When n is greater than 1, the patterned first mask layer is used as a mask, and when the spectral signal corresponding to the (n-1)th high refractive index layer is detected during the etching process, the etching of the nth high refractive index material layer is stopped to form the nth high refractive index layer.
[0008] Optionally, the method for forming the nth low-refractive-index layer on the (n-1)th front layer includes: A low-refractive-index material layer is formed on the surface of the (n-1)th front layer and the nth high-refractive-index layer; Polishing is performed on the nth low-refractive-index material layer. When the spectral signal corresponding to the nth high-refractive-index layer is detected during the polishing process, the polishing of the nth low-refractive-index material layer is stopped to form the nth low-refractive-index layer.
[0009] Optionally, the transparent substrate may be made of any one of glass, quartz, and silicon carbide.
[0010] Optionally, the material of the low refractive index layer is silicon oxide.
[0011] Optionally, the high refractive index layer is made of titanium oxide or niobium oxide.
[0012] According to a second aspect of the present invention, a multi-step oblique tooth grating structure is provided, obtained by applying the above-described method for fabricating the multi-step oblique tooth grating structure, comprising: Transparent substrate; An N+1 stacked refractive layer is located on the transparent substrate. Each refractive layer includes a low-refractive-index layer and a step layer penetrating the low-refractive-index layer. The top surface of the low-refractive-index layer and the step layer are flush. Each step layer within the refractive layer includes several high-refractive-index layers spaced apart in a first direction. The refractive index of the high-refractive-index layers is greater than that of the low-refractive-index layers. The high-refractive-index layers in any two adjacent refractive layers are made of different materials. Each (n+1)th high-refractive-index layer corresponds to an nth high-refractive-index layer. Each (n+1)th high refractive index layer is located on a portion of the surface of the corresponding nth high refractive index layer, and each (n+1)th high refractive index layer protrudes laterally relative to the corresponding nth high refractive index layer. The (n+1)th high refractive index layer is a high refractive index layer in the (n+1)th refractive layer. In the N+1th refractive layer, the lateral protrusion directions from the corresponding 1st high refractive index layer to the N+1th high refractive index layer are consistent, forming a stepped structure. N is a positive integer, and n is a positive integer less than or equal to N. The first direction is parallel to the surface of the transparent substrate.
[0013] Optionally, the stepped structure includes an alternating first high refractive index layer and a second high refractive index layer, wherein the refractive index of the first high refractive index layer and the material of the second high refractive index layer are different.
[0014] Optionally, the refractive index n1 of the first high refractive index layer, the layer thickness d1 of the first high refractive index layer, the refractive index n2 of the second high refractive index layer, the layer thickness d2 of the second high refractive index layer, the step width w1 of the first high refractive index layer, and the step width w2 of the second high refractive index layer satisfy the following: The step width w1 of the first high refractive index layer is the length of the area of the first high refractive index layer that is not covered by the corresponding second high refractive index layer in the upper refractive layer in the first direction, and the step width w2 of the second high refractive index layer is the length of the area of the second high refractive index layer that is not covered by the corresponding first high refractive index layer in the upper refractive layer in the first direction.
[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: In the fabrication method of a multi-step oblique tooth grating structure provided by the present invention, N+1 stacked refractive layers are formed on a transparent substrate. Each refractive layer includes a low refractive index layer and a step layer penetrating the low refractive index layer. The top surface of the low refractive index layer and the step layer are flush. The multi-step oblique tooth grating structure is formed by stacking refractive layers layer by layer, thus the fabrication method is simple and precise. Furthermore, since each step layer within the refractive layer includes several high refractive index layers spaced apart along a first direction, each (n+1)th high refractive index layer corresponds to an nth high refractive index layer. Each (n+1)th high refractive index layer is located on a portion of the surface of the corresponding nth high refractive index layer, and each (n+1)th high refractive index layer protrudes laterally relative to the corresponding nth high refractive index layer. In the N+1 refractive layers, the lateral protrusion directions from the corresponding 1st to the N+1th high refractive index layer are consistent, forming a step structure. N is a positive integer, n is a positive integer less than or equal to N, and the first direction is parallel to the surface of the transparent substrate. Each step structure can be approximated as a helical tooth structure; therefore, this fabrication method can be used to prepare stepped helical tooth grating structures with large aspect ratios. Furthermore, since the materials of the high-refractive-index layers in any two adjacent refractive layers are different, the design and corresponding performance of the formed multi-step helical tooth grating structures are diverse.
[0016] Furthermore, when n is greater than 1, the nth high-refractive-index material layer is etched using the patterned first mask layer as a mask. When the spectral signal corresponding to the (n-1)th high-refractive-index layer is detected during the etching process, the etching of the nth high-refractive-index material layer is stopped to form the nth high-refractive-index layer. Since the material of the (n-1)th high-refractive-index layer is different from that of the nth high-refractive-index layer, the etching depth can be better controlled based on the detected spectral signal changes.
[0017] Furthermore, when the nth low-refractive-index material layer is polished and the spectral signal corresponding to the nth high-refractive-index layer is detected during the polishing process, the polishing of the nth low-refractive-index material layer is stopped to form the nth low-refractive-index layer. In other words, the polishing depth of the nth low-refractive-index material layer is controlled by detecting the spectral signal of the nth high-refractive-index layer, resulting in a better flush effect between the top surface of the formed low-refractive-index layer and the top surface of the nth high-refractive-index layer, and also better ensuring the accuracy of the thickness of the nth high-refractive-index layer. Attached Figure Description
[0018] Figures 1-6 This is a schematic diagram of the cross-sectional structure corresponding to each step in the fabrication method of a high aspect ratio helical tooth grating plate structure; Figures 7-16This is a schematic cross-sectional view of each step in the fabrication method of a multi-step oblique tooth grating structure including four refractive layers provided in this embodiment of the invention.
[0019] Figure label: 1. Transparent substrate; 20. High refractive index material layer; 30. Low refractive index material layer; 21. High refractive index layer; 31. Low-refractive-index layer; 21-1, First high refractive index layer; 20-1, First high refractive index material layer; 21-2, Second High Refractive Index Layer; 20-2, Second high refractive index material layer; 4. Stepped structure; X, the first direction. Detailed Implementation
[0020] As described in the background section, the machining of helical teeth with a large aspect ratio is very difficult.
[0021] Figures 1-6 This is a schematic diagram of the cross-sectional structure corresponding to each step in the fabrication method of a high aspect ratio oblique tooth grating plate structure.
[0022] Please refer to Figures 1-6 The specific methods for fabricating high aspect ratio helical tooth grating structures include: Please refer to Figure 1 A plurality of asymmetric oblique tooth grating plates 100 are obtained, wherein the asymmetric oblique tooth grating plates 100 have a plurality of grooves 200 arranged at intervals, and the cross section of the grooves 200 along the arrangement direction is a parallelogram; Please refer to Figure 2 A first dielectric film 300 is disposed on the asymmetric oblique tooth grating plate 100 for full coverage; Please refer to Figure 3 The upper surface of the asymmetric oblique tooth grating plate 100 is ground to remove the first dielectric film 300; Please refer to Figure 4 After grinding, the two asymmetric oblique tooth grating plates 100 are bonded together, and the upper and lower asymmetric oblique tooth grating plates 100 have corresponding positions of the first dielectric film 300. Please refer to Figure 5 The bonded upper asymmetric oblique tooth grating plate 100 is ground to remove the substrate on the upper surface of the first dielectric film 300. Please refer to Figure 6The first dielectric film 300 of the asymmetric oblique tooth grating plate 100 is removed by etching, and the process of setting the first dielectric film 300, grinding, bonding, re-grinding and etching is repeated multiple times to form a high aspect ratio oblique tooth grating plate structure.
[0023] Since the formation of a large aspect ratio helical tooth grating plate mainly relies on the sequential bonding of asymmetric helical tooth gratings, this method depends on the bonding accuracy. The alignment deviation in the bonding process will affect the morphology and performance of the formed helical tooth grating. Furthermore, the repeated execution of the process of setting the first dielectric film 300, grinding, bonding, re-grinding, and etching also makes the preparation method relatively complex.
[0024] In view of this, the present invention creatively proposes a method for fabricating a multi-step oblique tooth grating structure, comprising: providing a transparent substrate; forming N+1 stacked refractive layers on the transparent substrate, each of the refractive layers comprising a low refractive index layer and a step layer penetrating the low refractive index layer, the low refractive index layer being flush with the top surface of the corresponding step layer, the step layer within each of the refractive layers comprising a plurality of high refractive index layers spaced apart in a first direction, the refractive index of the high refractive index layers being greater than the refractive index of the low refractive index layers, and the materials of the high refractive index layers in any two adjacent refractive layers being different. The (n+1)th high refractive index layer corresponds to an nth high refractive index layer. Each (n+1)th high refractive index layer is located on a portion of the surface of the corresponding nth high refractive index layer, and each (n+1)th high refractive index layer protrudes laterally relative to the corresponding nth high refractive index layer. The (n+1)th high refractive index layer is a high refractive index layer in the (n+1)th refractive layer. In the N+1th refractive layer, the lateral protrusion directions from the corresponding 1st high refractive index layer to the N+1th high refractive index layer are consistent, forming a stepped structure. N is a positive integer, and n is a positive integer less than or equal to N. The first direction is parallel to the surface of the transparent substrate.
[0025] The fabrication method of this multi-step oblique tooth grating structure is simple and can be used to fabricate stepped oblique tooth structures with large aspect ratios. Since the high refractive index layers in any two adjacent refractive layers have different materials, the design and corresponding performance of the formed multi-step oblique tooth grating structure are diverse.
[0026] To make the above-mentioned objectives, features, and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The terms "second," "first," "second," etc., in the specification, claims, and accompanying drawings of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the present invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0027] Figures 7-16 This is a cross-sectional structural diagram of each step in the fabrication method of a multi-step oblique tooth grating structure including four refractive layers provided in this embodiment of the invention, i.e., N+1=4. The high refractive index layer 21 uses two materials, namely, the high refractive index layer 21 includes a first high refractive index layer 21-1 and a second high refractive index layer 22-1. For ease of distinction, the first high refractive index material layer 20-1 and the second high refractive index material layer 20-2 corresponding to the first high refractive index layer 21-1 and the second high refractive index layer 22-1 are also distinguished by their designations. Specifically, Figures 8-11 This is a schematic cross-sectional view of the step of forming the first refractive layer on a transparent substrate. Figures 12-15 This is a schematic cross-sectional view of the step of forming the second refractive layer on a transparent substrate. Figure 16 The method for forming the third refractive layer in [the text] can be referred to Figures 8-11 , Figure 16 The method for forming the fourth refractive layer in [the text] can be referred to Figures 12-15 .
[0028] Please refer to Figures 7-16 This invention provides a method for fabricating a multi-step oblique tooth grating structure, including: Please refer to... Figure 7 Provide transparent substrate 1; please refer to Figures 8-16 An N+1 stacked refractive layer is formed on the transparent substrate 1.
[0029] In this embodiment, the transparent substrate 1 is made of any one of glass, quartz, and silicon carbide. In this embodiment, each of the refractive layers includes a low refractive index layer 31 and a step layer penetrating the low refractive index layer 31. The low refractive index layer 31 is flush with the top surface of the corresponding step layer. The step layer in each of the refractive layers includes a plurality of high refractive index layers 21 spaced apart along a first direction X.
[0030] In this embodiment, each (n+1)th high refractive index layer 21 corresponds to an nth high refractive index layer 21. Each (n+1)th high refractive index layer 21 is located on a portion of the surface of the corresponding nth high refractive index layer 21, and each (n+1)th high refractive index layer 21 protrudes laterally relative to the corresponding nth high refractive index layer 21. The (n+1)th high refractive index layer 21 is a high refractive index layer in the (n+1)th refractive layer. In the N+1 refractive layers, the lateral protrusion directions of the corresponding 1st to N+1th high refractive index layers 21 are consistent, forming a stepped structure 4. N is a positive integer, and n is a positive integer less than or equal to N. The first direction X is parallel to the surface of the transparent substrate 1. The lateral protrusion direction is either the first direction X or the opposite direction of the first direction X.
[0031] In this embodiment, the refractive index of the high refractive index layer 21 is greater than that of the low refractive index layer 31, and the materials of the high refractive index layers 21 in any two adjacent refractive layers are different.
[0032] In this embodiment, based on a cyclic processing method, N+1 stacked refractive layers are formed on the transparent substrate 1. Please refer to... Figures 8-15 The cyclic processing method includes: forming the nth step layer on the surface of the (n-1)th preceding layer; when n equals 1, please refer to... Figures 8-9 The (n-1)th front layer is a transparent substrate 1. When n is greater than 1, please refer to... Figures 12-13 The (n-1)th front layer is the (n-1)th refractive layer; after the nth step layer is formed on the surface of the (n-1)th front layer, the nth low refractive index layer 31 is formed on the (n-1)th front layer.
[0033] In this embodiment, the method for forming the nth step layer on the surface of the (n-1)th preceding layer includes: A high-refractive-index material layer 20 is formed on the surface of the (n-1)th front layer, and the high-refractive-index material layer 20 has the same thickness as the high-refractive-index layer 21. Specifically, when n equals 1, please refer to... Figure 8 A first high-refractive-index material layer 20 (i.e., the first high-refractive-index material layer 20-1) is formed on the surface of the transparent substrate 1. When n is greater than 1, an nth high-refractive-index material layer 20 is formed on the surface of the (n-1)th refractive layer. For example, please refer to... Figure 12 When n equals 2, a second high refractive index material layer 20 (i.e., the second high refractive index material layer 20-2) is formed on the surface of the first refractive layer.
[0034] A patterned first mask layer (not shown) is formed on the nth high-refractive-index material layer 20; When n equals 1, the nth high-refractive-index material layer is etched using the patterned first mask layer as a mask to form the nth high-refractive-index layer 21; For details, please refer to Figure 9 Using the patterned first mask layer as a mask, the first high refractive index material layer 20 (i.e., the first high refractive index material layer 20-1) is etched to form the first high refractive index layer 21 (i.e., the first high refractive index layer 21-1).
[0035] When n is greater than 1, the patterned first mask layer is used as a mask, and when the spectral signal corresponding to the (n-1)th high refractive index layer 21 is detected during the etching process, the etching of the nth high refractive index material layer 20 is stopped to form the nth high refractive index layer 21. For example, when n equals 2, please refer to... Figure 13 Using the patterned first mask layer as a mask, and when the spectral signal corresponding to the first high refractive index layer 21 (i.e., the first high refractive index layer 21-1) is detected during the etching process, the etching of the second high refractive index material layer 20 (i.e., the second high refractive index material layer 20-2) is stopped to form the second high refractive index layer 21 (i.e., the second high refractive index layer 21-2).
[0036] The material of the first mask layer can be, for example, photoresist.
[0037] In this embodiment, the method for forming the nth low-refractive-index layer 31 on the (n-1)th front layer includes: A low-refractive-index material layer 30 is formed on the surfaces of the (n-1)th front layer and the nth high-refractive-index layer 21; Specifically, when n equals 1, please refer to... Figure 10 A first low-refractive-index material layer 30 is formed on the surface of the transparent substrate 1 and the surface of the first high-refractive-index layer (i.e., the first high-refractive-index layer 21-1). When n is greater than 1, for example, when n equals 2, please refer to... Figure 14 A second low-refractive-index material layer 30 is formed on the surface of the first refractive layer (including several first high-refractive-index layers 21 and first low-refractive-index layers 31) and the second high-refractive-index layer 21 (i.e., the second high-refractive-index layer 21-2).
[0038] Polishing is performed on the nth low-refractive-index material layer 30. When the spectral signal corresponding to the nth high-refractive-index layer 21 is detected during the polishing process, the polishing of the nth low-refractive-index material layer 30 is stopped to form the nth low-refractive-index layer 31.
[0039] Specifically, when n equals 1, please refer to... Figure 11 The first low-refractive-index material layer 30 is polished. When a spectral signal corresponding to the first high-refractive-index layer 21 is detected during polishing, polishing of the first low-refractive-index material layer 30 is stopped to form the first low-refractive-index layer 31. When n is greater than 1, for example, when n equals 2, please refer to... Figure 15 Polishing is performed on the first low-refractive-index material layer 30. When the spectral signal corresponding to the first high-refractive-index layer 21 is detected during the polishing process, the polishing of the first low-refractive-index material layer 30 is stopped to form the first low-refractive-index layer 31.
[0040] In this embodiment, please refer to Figure 16 The stepped structure 4 includes an alternately arranged first high refractive index layer 21-1 and second high refractive index layer 21-2, the materials of the first high refractive index layer 21-1 and the second high refractive index layer 21-2 are different.
[0041] In this embodiment, the low refractive index layer 31 is made of silicon oxide, and the high refractive index layer 21 is made of titanium oxide or niobium oxide.
[0042] Please refer to Figure 16 Because the refractive indices of the first high refractive index layer 21-1 and the second high refractive index layer 21-2 are different, and in order to maintain the consistency of the application of the first high refractive index layer 21-1 and the second high refractive index layer 21-2 in electromagnetic waves or optical waveguides, the step tilt angle corresponding to the first high refractive index layer 21-1 is... Step tilt angle corresponding to the second high refractive index layer 21-2 They are different. Specifically, the step angle of the first high-refractive-index layer 21-1... In a triangular prism formed by the sidewall of the first high refractive index layer 21-1, the step surface of the adjacent second high refractive index layer 21-2 below it, and the connecting inclined plane of the corresponding step edge of the first high refractive index layer 21-1 and the second high refractive index layer 21-2, the angle formed by the connecting inclined plane and the corresponding step surface of the second high refractive index layer 21-2, and the step inclination angle of the second high refractive index layer 21-2. In a triangular prism formed by the side wall surface of the second high refractive index layer 21-2 and the step surface of the adjacent first high refractive index layer 21-1 below, and the connecting inclined surface of the corresponding step edge of the second high refractive index layer 21-2 and the first high refractive index layer 21-1, the included angle formed by the connecting inclined surface and the step surface of the corresponding first high refractive index layer 21-1.
[0043] Please refer to Figure 16 , although the step inclination angle and the step inclination angle are different in terms of geometric structure, but under the formula constraints of refractive index, layer thickness, and step width described below, the optical effects of the first high refractive index layer 21-1 and the second high refractive index layer 21-2 are made equivalent. Among them, since the refractive index of the first high refractive index layer 21-1 is different from that of the second high refractive index layer 21-2, therefore, in order to make the propagation degree of incident light in the first high refractive index layer 21-1 and the second high refractive index layer 21-2 equivalent, it is necessary to set the optical thickness (the product of refractive index and layer thickness) of the first high refractive index layer 21-1 and the second high refractive index layer 21-2 to be the same, that is .
[0044] Furthermore, please refer to Figure 16 , the refractive index n1 of the first high refractive index layer 21-1, the layer thickness d1 of the first high refractive index layer 21-1, the refractive index n2 of the second high refractive index layer 21-2, the layer thickness d2 of the second high refractive index layer 21-2, the step width w1 of the first high refractive index layer 21-1, and the step width w2 of the second high refractive index layer 21-2 satisfy: , that is , the step width w1 of the first high refractive index layer 21-1 is the length of the region of the first high refractive index layer 21-1 in the first direction X that is not covered by the corresponding second high refractive index in the upper refractive layer, and the step width w2 of the second high refractive index layer 21-2 is the length of the region of the second high refractive index layer 21-2 in the first direction X that is not covered by the corresponding first high refractive index in the upper refractive layer. Specifically, when the refractive index of the first high refractive index layer 21-1 is different from that of the second high refractive index layer 21-2, the layer thickness d1 of the first high refractive index layer 21-1, the layer thickness d2 of the second high refractive index layer 21-2, the step width w1 of the first high refractive index layer 21-1, and the step width w2 of the second high refractive index layer 21-2 satisfy: , that is, when n1 > n2, , when n1 < n2, Based on this, in the first case, the thickness d1 of the first high-refractive-index layer 21-1 and the thickness d2 of the second high-refractive-index layer are different, and the step width w1 of the first high-refractive-index layer and the step width w2 of the second high-refractive-index layer 21-2 are different; in the second case, the thickness d1 of the first high-refractive-index layer 21-1 and the thickness d2 of the second high-refractive-index layer are the same, then... In the third case, if the step width w1 of the first high-refractive-index layer and the step width w2 of the second high-refractive-index layer 21-2 are the same, then... Since n1≠n2, that is, d1≠d2. Therefore, the design of multi-step helical tooth grating structures can be more diverse, thus enabling diverse performance of multi-step helical tooth grating structures.
[0045] As an example, the material of the first high refractive index layer is niobium oxide, with a refractive index of n1=2.2, a layer thickness of d1=54.5nm, and a step width of w1=50nm. The material of the second high refractive index layer is titanium oxide, with a refractive index of n2=2.4, a layer thickness of d2=50nm, and a step width of w2=49.96nm.
[0046] In summary, in the fabrication method of the multi-step oblique tooth grating structure provided by the present invention, N+1 stacked refractive layers are formed on a transparent substrate 1. Each refractive layer includes a low refractive index layer 31 and a step layer penetrating the low refractive index layer 31, with the top surface of the low refractive index layer 31 flush with the top surface of the step layer. Since this multi-step oblique tooth grating structure is formed by stacking refractive layers layer by layer, the fabrication method of this multi-step oblique tooth grating structure is simple. Based on this, since each step layer within a refractive layer includes several high-refractive-index layers 21 spaced apart in the first direction X, each (n+1)th high-refractive-index layer 21 corresponds to an nth high-refractive-index layer 21, each (n+1)th high-refractive-index layer 21 is located on a portion of the surface of the corresponding nth high-refractive-index layer 21, and each (n+1)th high-refractive-index layer 21 protrudes laterally relative to the corresponding nth high-refractive-index layer 21, in the N+1 refractive layer, the lateral protrusion directions of the corresponding 1st to N+1th high-refractive-index layers 21 are consistent, forming a step structure 4. Each step structure 4 can be approximated as a helical tooth structure. Therefore, this multi-step helical tooth grating structure can be used to fabricate a step structure 4 with a large aspect ratio, approximating a helical tooth structure with a large aspect ratio. Furthermore, since the materials of the high-refractive-index layers 21 in any two adjacent refractive layers are different, the design and corresponding performance of the formed multi-step helical tooth grating structure are diverse.
[0047] Furthermore, when n is greater than 1, the nth high-refractive-index material layer 20 is etched using the patterned first mask layer as a mask. When the spectral signal corresponding to the (n-1)th high-refractive-index layer 21 is detected during the etching process, the etching of the nth high-refractive-index material layer 20 is stopped to form the nth high-refractive-index layer 21. Since the material of the (n-1)th high-refractive-index layer 21 is different from that of the nth high-refractive-index layer 21, the etching depth can be better controlled based on the change in the spectral signal of the (n-1)th high-refractive-index layer 21.
[0048] Furthermore, when the nth low-refractive-index material layer 30 is polished and the spectral signal corresponding to the nth high-refractive-index layer 21 is detected during the polishing process, the polishing of the nth low-refractive-index material layer 30 is stopped to form the nth low-refractive-index layer 31. That is, the polishing depth of the nth low-refractive-index material layer 30 is controlled by the change in the spectral signal of the nth high-refractive-index layer 21, resulting in a better flush effect between the top surface of the formed low-refractive-index layer 31 and the top surface of the nth high-refractive-index layer 21, and thus better ensuring the accuracy of the thickness of the nth high-refractive-index layer 21.
[0049] Please refer to Figure 16 The present invention also provides a multi-step oblique tooth grating structure, which is obtained by applying the above-described method for preparing the multi-step oblique tooth grating structure.
[0050] The multi-step oblique tooth grating structure includes a transparent substrate 1 and N+1 refractive layers stacked on the transparent substrate 1.
[0051] Each of the aforementioned refractive layers includes a low-refractive-index layer 31 and a step layer penetrating the low-refractive-index layer 31. The low-refractive-index layer 31 is flush with the top surface of the step layer. The step layer within each refractive layer includes a plurality of high-refractive-index layers 21 spaced apart in a first direction X. The refractive index of the high-refractive-index layers 21 is greater than that of the low-refractive-index layers 31. The materials of the high-refractive-index layers 21 in any two adjacent refractive layers are different. Each (n+1)th high-refractive-index layer 21 corresponds to an nth high-refractive-index layer 21. The refractive index layer 21 is located on a portion of the surface of the corresponding nth high refractive index layer 21, and each (n+1)th high refractive index layer 21 protrudes laterally relative to the corresponding nth high refractive index layer 21. The (n+1)th high refractive index layer 21 is a high refractive index layer in the (n+1)th refractive layer. In the (N+1)th refractive layer, the lateral protrusion directions of the corresponding 1st high refractive index layer 21 to the (N+1)th high refractive index layer 21 are consistent, forming a stepped structure 4. N is a positive integer, n is a positive integer and less than or equal to N, and the first direction X is parallel to the surface of the transparent substrate 1.
[0052] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A method for fabricating a multi-step oblique tooth grating structure, characterized in that... ,include: Provide a transparent substrate; N+1 stacked refractive layers are formed on the transparent substrate. Each refractive layer includes a low-refractive-index layer and a step layer penetrating the low-refractive-index layer. The top surface of the low-refractive-index layer is flush with the top surface of the corresponding step layer. Each step layer within a refractive layer includes several high-refractive-index layers spaced apart along a first direction. The refractive index of the high-refractive-index layers is greater than that of the low-refractive-index layers. The high-refractive-index layers in any two adjacent refractive layers are made of different materials. Each (n+1)th high-refractive-index layer corresponds to an nth high-refractive-index layer. Each (n+1)th high refractive index layer is located on a portion of the surface of the corresponding nth high refractive index layer, and each (n+1)th high refractive index layer protrudes laterally relative to the corresponding nth high refractive index layer. The (n+1)th high refractive index layer is a high refractive index layer in the (n+1)th refractive layer. In the N+1th refractive layer, the lateral protrusion directions from the corresponding 1st high refractive index layer to the N+1th high refractive index layer are consistent, forming a stepped structure. N is a positive integer, and n is a positive integer less than or equal to N. The first direction is parallel to the surface of the transparent substrate.
2. The method for fabricating the multi-step oblique tooth grating structure according to claim 1, characterized in that... Based on a cyclic processing method, N+1 stacked refractive layers are formed on the transparent substrate, the cyclic processing method comprising: An nth step layer is formed on the surface of the (n-1)th preceding layer. When n equals 1, the (n-1)th preceding layer is the transparent substrate; when n is greater than 1, the (n-1)th preceding layer is the (n-1)th refractive layer. After forming the nth step layer on the surface of the (n-1)th front layer, the nth low refractive index layer is formed on the (n-1)th front layer.
3. The method for fabricating the multi-step oblique tooth grating structure according to claim 2, characterized in that... The methods for forming the nth step layer on the surface of the (n-1)th preceding layer include: A high-refractive-index material layer is formed on the surface of the (n-1)th front layer, and the thickness of the nth high-refractive-index material layer is the same as that of the nth high-refractive-index layer. A patterned first mask layer is formed on the nth high-refractive-index material layer; When n equals 1, the nth high-refractive-index material layer is etched using the patterned first mask layer as a mask to form the nth high-refractive-index layer; When n is greater than 1, the nth high refractive index material layer is etched using the patterned first mask layer as a mask. When the spectral signal corresponding to the (n-1)th high refractive index layer is detected during the etching process, the etching of the nth high refractive index material layer is stopped to form the nth high refractive index layer.
4. The method for fabricating the multi-step oblique tooth grating structure according to claim 2, characterized in that... The method for forming the nth low-refractive-index layer on the (n-1)th front layer includes: A low-refractive-index material layer is formed on the surface of the (n-1)th front layer and the nth high-refractive-index layer; Polishing is performed on the nth low-refractive-index material layer. When the spectral signal corresponding to the nth high-refractive-index layer is detected during the polishing process, the polishing of the nth low-refractive-index material layer is stopped to form the nth low-refractive-index layer.
5. The method for fabricating the multi-step oblique tooth grating structure according to claim 1, characterized in that... The transparent substrate is made of any one of glass, quartz, and silicon carbide.
6. The method for fabricating the multi-step oblique tooth grating structure according to claim 1, characterized in that... The material of the low refractive index layer is silicon oxide.
7. The method for fabricating the multi-step oblique tooth grating structure according to claim 1, characterized in that... The high refractive index layer is made of titanium oxide or niobium oxide.
8. A multi-step oblique tooth grating structure, obtained by the fabrication method of the multi-step oblique tooth grating structure as described in any one of claims 1 to 7, characterized in that... ,include: Transparent substrate; An N+1 stacked refractive layer is located on the transparent substrate. Each refractive layer includes a low-refractive-index layer and a step layer penetrating the low-refractive-index layer. The top surface of the low-refractive-index layer and the step layer are flush. Each step layer within the refractive layer includes several high-refractive-index layers spaced apart in a first direction. The refractive index of each high-refractive-index layer is greater than that of the low-refractive-index layer. The materials of the high-refractive-index layers in any two adjacent refractive layers are different. Each (n+1)th high-refractive-index layer corresponds to an nth high-refractive-index layer. Each (n+1)th high refractive index layer is located on a portion of the surface of the corresponding nth high refractive index layer, and each (n+1)th high refractive index layer protrudes laterally relative to the corresponding nth high refractive index layer. The (n+1)th high refractive index layer is a high refractive index layer in the (n+1)th refractive layer. In the N+1th refractive layer, the lateral protrusion directions from the corresponding 1st high refractive index layer to the N+1th high refractive index layer are consistent, forming a stepped structure. N is a positive integer greater than 1, and n is a positive integer less than or equal to N. The first direction is parallel to the surface of the transparent substrate.
9. The multi-step oblique tooth grating structure according to claim 8, characterized in that... The stepped structure includes an alternating first high refractive index layer and a second high refractive index layer, the materials of which are different.
10. The method for fabricating the multi-step oblique tooth grating structure according to claim 9, characterized in that... The refractive index n1 of the first high refractive index layer, the layer thickness d1 of the first high refractive index layer, the refractive index n2 of the second high refractive index layer, the layer thickness d2 of the second high refractive index layer, the step width w1 of the first high refractive index layer, and the step width w2 of the second high refractive index layer satisfy the following: The step width w1 of the first high refractive index layer is the length of the area of the first high refractive index layer that is not covered by the corresponding second high refractive index layer in the upper refractive layer in the first direction, and the step width w2 of the second high refractive index layer is the length of the area of the second high refractive index layer that is not covered by the corresponding first high refractive index layer in the upper refractive layer in the first direction.