Mask plate structure, optical structure forming method and diffraction optical waveguide

Abstract

The invention discloses a mask plate structure, an optical structure and a forming method thereof, and the method comprises the steps: providing a substrate which comprises one or more optical structure regions; providing a mask plate structure, wherein the mask plate structure comprises a first mask plate and a second mask plate which are arranged in the direction perpendicular to the surface of the substrate; providing a target material, and arranging the target material above the substrate; the mask plate structure is arranged between the target material and the substrate, the second mask plate is in contact with the substrate, the second through hole corresponds to the optical structure area, and the first through hole corresponds to the target material; and bombarding a target material to form a material layer with the thickness continuously and gradually changing on the optical structure area, so that the continuous change of the thickness of the optical structure is accurately controlled.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a mask plate structure, an optical structure and a forming method thereof. Background Art

[0002] As one of the important optical devices of augmented reality display technology, diffractive waveguides are favored by the industry for their advantages such as large eye movement range, small size, and good mass production. In order to achieve uniformity of field of view, color uniformity, and efficient optical transmission, continuous exploration is often carried out in the design and preparation process of diffractive waveguides. Especially in the preparation process, how to achieve high-efficiency diffractive waveguide production has become the focus of research in the industry.

[0003] In semiconductor processing, how to optimize optical structures with continuously varying thickness is an ongoing problem that needs to be solved. Summary of the invention

[0004] The present invention provides a mask plate structure, an optical structure and a method for forming the same, which solves the technical problem of precise control of continuous thickness change of the optical structure.

[0005] To solve the above technical problems, an embodiment of the present invention provides a mask plate structure, including: a first mask plate, wherein the first mask plate has a first through hole passing through the first mask plate; a second mask plate, wherein the second mask plate has a second through hole passing through the second mask plate; there is a spacing between the first mask plate and the second mask plate, and the first mask plate and the second mask plate are used to form a material layer with a continuously gradient thickness in the second through hole area.

[0006] Optionally, the first mask plate and the second mask plate are connected via a connecting portion to form an integrated structure, and the second mask plate is attached to the substrate.

[0007] Alternatively, in some other embodiments, the first mask plate and the second mask plate are independently formed on a substrate, and the second mask plate is in contact with the substrate.

[0008] Optionally, a projection range of the first through hole projected onto the second mask plate is located within the second through hole; and the first mask plate and the second mask plate are arranged in parallel.

[0009] Optionally, a center line of the first through hole coincides with a center line of the second through hole.

[0010] Optionally, the thickness of the material layer changes continuously and gradually, and the thickness T(r) is calculated by the formula:

[0011] Wherein, a is the radial coordinate of any sputtering point of the target relative to the center line of the target, M is the mass of the target material, ρ is the density of the target material, h is the distance from the center of the target to the surface of the substrate, r is the coordinate of any point on the top surface of the material layer relative to the origin of the coordinate system, T(r) is the thickness at any point r on the top surface of the material layer, H is the distance between the first mask plate and the substrate, R1 is the first aperture of the first through hole, and S is the radial length of the target.

[0012] Correspondingly, the technical solution of the present invention also provides a method for forming an optical structure, comprising: providing a substrate, the substrate comprising one or more optical structure regions; providing a mask plate structure, the mask plate structure comprising: a first mask plate and a second mask plate arranged in a direction perpendicular to the surface of the substrate; providing a target material, arranged above the substrate; arranging the mask plate structure between the target material and the substrate, the second mask plate contacts the substrate, the second through hole corresponds to the optical structure region, and the first through hole corresponds to the target material; forming a material layer with a continuously gradient thickness on the optical structure region by bombarding the target material.

[0013] Optionally, the continuous gradient thickness T(r) of the material layer is calculated by the following formula: , where a is the radial coordinate of any sputtering point of the target relative to the center line of the target, M is the mass of the target material, ρ is the density of the target material, h is the distance from the center of the target to the surface of the substrate, r is the coordinate of any point on the top surface of the material layer relative to the origin of the coordinate system, T(r) is the thickness at any point r on the top surface of the material layer, H is the distance between the first mask and the substrate, R1 is the first aperture of the first through hole, and S is the radial length of the target.

[0014] Optionally, the material layer includes an effective area and an ineffective area; the formation method also includes: forming a protective layer on the surface of the material layer, the surface of the protective layer is a flat surface, and the protective layer exposes the surface of the ineffective area; using the protective layer as a mask to remove the ineffective area; forming a patterned mask layer on the surface of the protective layer; etching the protective layer and the effective area using the patterned mask layer as a mask, so that the effective area is formed into an optical structure on the optical structure area of ​​the substrate, the protective layer is located on the optical structure, and the thickness of the optical structures gradually increases along the edge of the optical structure area toward the center; after the optical structure is formed, the protective layer is removed.

[0015] Optionally, the formation method also includes: forming a patterned mask layer on the surface of the material layer; etching the material layer using the patterned mask layer as a mask to form a grating structure on the optical structure area, and the thickness of the plurality of optical structures gradually increases along the edge of the optical structure area toward the center.

[0016] Correspondingly, the technical solution of the present invention also provides a diffraction optical waveguide, which at least includes a coupling-out grating region and / or a turning grating region, and the grating structure in the coupling-out grating region or the turning grating region is prepared based on the above-mentioned method for forming the optical structure.

[0017] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects: The mask plate structure of the technical solution of the present invention, the first mask plate and the second mask plate are used to form a material layer with a continuously gradient thickness in the second through-hole area. The mask plate structure can form a material layer with a continuously gradient thickness on the substrate. The thickness variation of the material layer at different positions can be accurately controlled by designing the mask plate structure, so as to form an optical structure with a continuously gradient thickness. On the one hand, based on this structural design, the diffraction efficiency modulation of the optical structure at different positions can be realized to improve the display uniformity of the optical structure at different positions and improve the display effect; on the other hand, the design of the structure can also improve the display appearance of the optical structure. The design of the continuously gradient thickness can prevent sudden thickness changes at different positions. Such a design improves the dimensional accuracy and visual effect of the optical structure.

[0018] Furthermore, the center line of the first through hole of the first mask plate coincides with the center line of the second through hole of the second mask plate, and the projection range of the first through hole on the second mask plate is within the range of the second through hole. The use of the mask plate structure can form a material layer with a continuously varying thickness on the substrate, can accurately control the display appearance of the optical structure, and improve the dimensional accuracy and visual effect of the optical structure.

[0019] The method for forming an optical structure of the technical solution of the present invention, by arranging the above-mentioned mask plate structure between the target material and the substrate, the second through hole corresponds to the optical structure area, the first through hole corresponds to the target material, and the position of the mask structure and the sputtering process are controlled, so that a material layer with a continuously changing thickness can be formed on the substrate, and the display appearance of the optical structure can be accurately controlled, especially it is not easy to have sudden stripes between different optical structure areas, so that the thickness of different optical structure areas is continuously and gradually changed, thereby improving the display appearance of the formed optical structure; and further, based on this method, a grating structure in a diffraction optical waveguide is formed. The method can form a grating structure with a continuously gradient depth, and different grating structures have different depths. On the one hand, the method modulates the diffraction efficiency of the prepared grating structure at different positions, so that the grating structure has a continuously gradient diffraction efficiency at different positions, thereby improving the display uniformity of the diffraction optical waveguide and improving the display effect of the waveguide. On the other hand, based on the diffraction optical waveguide obtained in this way, different grating structures have a continuously gradient depth at different positions, which is different from the existing partition structure in terms of display appearance, thereby preventing the visual difference caused by the sudden change of thickness at different positions, and visually obtaining a better appearance effect.

[0020] Furthermore, by adjusting the first spacing between the first mask plate and the second mask plate, and adjusting the size of the first area of ​​the first through hole, the thickness of the material layer at each position on the optical structure area is accurately adjusted, and the design of the thickness continuous gradient structure is controlled to improve the display efficiency of the optical structure at different positions and improve the display uniformity, thereby improving the display effect of the optical structure. At the same time, the display appearance of the optical structure is improved, and the dimensional accuracy and visual effect of the optical structure are enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 and Figure 2 is a structural schematic diagram of a mask plate structure in an embodiment of the present invention; Figures 3 to 13 It is a structural schematic diagram of the process of forming an optical structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] As described in the background art, how to optimize an optical structure with continuously varying thickness is a problem that needs to be solved continuously.

[0023] For a type of optical structure, the thickness needs to change gradually to modulate the performance parameters of the optical structure to achieve the expected function. Usually, the thickness gradient difference of this type of optical structure varies in the range of tens of nanometers. How to accurately control the structure with continuous thickness modulation to achieve continuous thickness gradient is a difficult problem to solve, especially for the thickness gradient at the nanometer level, which is a technical problem that needs to be solved urgently. For example, the grating structure in the diffraction optical waveguide needs to achieve continuous gradient modulation of the grating depth to modulate the diffraction efficiency distribution of the grating structure.

[0024] In addition, when forming an optical structure with a continuously changing thickness, it is easy to form abrupt stripes when the thickness changes gradually between different gradient areas. The abrupt stripes are the locations where the thickness of the optical structure suddenly changes. The abrupt stripes will affect the appearance of the product formed by the optical structure and are not easily accepted by consumers visually. Therefore, it is necessary to improve the generation of abrupt stripes and accurately control the continuous change of the thickness of the optical structure. For example, the grating structure in the diffraction waveguide needs to realize the continuous gradual modulation of the grating depth to modulate the visibility of the grating structure in the diffraction waveguide.

[0025] In order to solve the above problems, the embodiments of the present invention provide a mask plate structure, a method for forming an optical structure, and a diffraction optical waveguide. By arranging the mask plate structure between the target material and the substrate, the second through hole corresponds to the optical structure area, and the first through hole corresponds to the target material, a material layer with continuously varying thickness can be formed on the substrate, and the thickness variation in different areas can be accurately controlled to form an optical structure with continuously varying thickness. While modulating the diffraction efficiency of the optical structure, the appearance of the optical structure is improved based on this technical means, so that sudden stripes are less likely to appear between different optical structure areas. The optical structure can visually obtain a better appearance effect, and has a higher diffraction efficiency, thereby improving the display effect.

[0026] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0027] Figure 1 and Figure 2 Schematic diagram of the structure of the mask plate in an embodiment of the present invention.

[0028] Please refer to Figure 1 and Figure 2 , Figure 2 for Figure 1 A top view of Figure 1 for Figure 2A schematic diagram of the structure along the section line BB1, wherein the mask plate structure comprises: a first mask plate 101, wherein the first mask plate 101 has a first through hole 104 penetrating the first mask plate 101; a second mask plate 102, wherein the second mask plate 102 has a second through hole 105 penetrating the second mask plate 102; a gap is provided between the first mask plate 101 and the second mask plate 102, and the first mask plate 101 and the second mask plate 102 are used to form a material layer with a continuous and gradual thickness in the region of the second through hole 105. Figure 6 The material layer 203 is shown with a continuously gradient thickness.

[0029] In this embodiment, the mask plate structure further includes: a connecting portion 103, wherein the connecting portion 103 connects the first mask plate 101 and the second mask plate 102, the first mask plate 101 and the second mask plate 102 are connected via the connecting portion 103 to form an integrated structure, and the second mask plate 102 is bonded to the substrate.

[0030] In other embodiments, the mask plate structure may not include the connecting portion, the first mask plate and the second mask plate are independently formed on a substrate, and the second mask plate is in contact with the substrate.

[0031] The above two embodiments of the mask plate structure are both within the protection scope of the present invention. As long as they do not deviate from the purpose of the present invention, that is, to achieve a material layer with a continuously gradient thickness, no limitation is imposed on the connection method of the mask structure.

[0032] In this embodiment, the center line L1 of the first through hole 104 coincides with the center line L2 of the second through hole 105, and the projection range of the first through hole 104 on the second mask plate 102 is within the range of the second through hole 105, so as to accurately control the process of realizing the thickness of the continuous gradient material layer.

[0033] In this embodiment, the first mask plate 101 and the second mask plate 102 are arranged in parallel to form a material layer with a preset thickness variation.

[0034] The first mask plate 101 and the second mask plate 102 are arranged in parallel, which can reduce the risk of interference between the mask plate structure and the material source or the machine chamber, and facilitates the adjustment of the thickness variation trend of the material formed in the second through hole 105 .

[0035] In this embodiment, the area of ​​the first through hole 104 is smaller than the area of ​​the second through hole 105 .

[0036] The shape of the first through hole 104 includes a circle, an ellipse, a rectangle, a trapezoid or a polygon, and the number of sides of the polygon is greater than or equal to 5.

[0037] In this embodiment, the shape of the first through hole 104 includes a circle.

[0038] The second through hole 105 has a shape of a rectangle, a trapezoid or a polygon, and the number of sides of the polygon is greater than or equal to 5.

[0039] In one embodiment, the shape of the first through hole 104 is the same as the shape of the second through hole 105. The shape of the first through hole 104 and the shape of the second through hole 105 include a rectangle, a trapezoid or a polygon.

[0040] In another embodiment, the shape of the first through hole 104 is different from the shape of the second through hole 105 .

[0041] The material of the mask plate structure includes metal or metal alloy, the metal alloy includes stainless steel and iron-nickel alloy, and the metal includes iron, aluminum or titanium.

[0042] Figures 3 to 13 It is a structural schematic diagram of the process of forming an optical structure in an embodiment of the present invention.

[0043] Please refer to Figure 3 and Figure 4 , Figure 3 for Figure 4 A top view of Figure 4 for Figure 3 A cross-sectional structural schematic diagram is provided, providing a substrate 200, wherein the substrate 200 includes one or more optical structure areas 201.

[0044] The optical structure region 201 is a region where a material layer is subsequently formed.

[0045] like Figure 3 As shown, Figure 3 A single optical structure region 201 is schematically shown, and a continuous region 20 is schematically shown, wherein the continuous region 20 includes two or more optical structure regions 201, Figure 3 The continuous area 20 in the figure shows three different optical structure areas 201. The different optical structure areas 201 shown in the figure are only examples and do not constitute a limitation on the structure and position of the optical structure area 201. If multiple optical structure areas 201 are independently separated, or divided into regions, or have other structural shapes, etc., they all belong to the optical structure areas indicated in the present invention. Figure 3 The various structural regions shown are for simple illustration only.

[0046] The material of the substrate 200 includes an inorganic material or a semiconductor material. The inorganic material includes quartz. The semiconductor material includes silicon, silicon carbide, titanium oxide, lithium niobate, germanium, gallium arsenide, etc.

[0047] Please refer to Figure 5 , a mask plate structure is provided, wherein the mask plate structure includes: a first mask plate 101 and a second mask plate 102 arranged in a direction perpendicular to the surface of the substrate 200.

[0048] For the specific setting of the mask plate structure, please refer to Figure 1 and Figure 2 The text description of the Chinese characters will not be repeated here.

[0049] Please continue to refer to Figure 5 There is a first distance H′ between the first mask plate 101 and the second mask plate 102 , the first through hole 104 has a first aperture R1 , the second through hole 105 has a second aperture R2 , and the first aperture R1 is smaller than the second aperture R2 .

[0050] The first aperture R1 is the maximum size of the first through hole 104 , and the second aperture R2 is the maximum size of the second through hole 105 .

[0051] In this embodiment, the first aperture R1 ranges from 6 mm to 10 mm.

[0052] In this embodiment, the second aperture R2 ranges from 10 mm to 50 mm.

[0053] In this embodiment, the first spacing H' is in the range of 25 mm to 35 mm.

[0054] In this embodiment, the first mask plate 101 has a first thickness d1, and the first thickness d1 ranges from 2 micrometers to 500 micrometers.

[0055] In this embodiment, the second mask plate 102 has a second thickness d2, and the second thickness d2 is in a range of 2 micrometers to 500 micrometers.

[0056] The first through hole 104 has a first area S1 , and the second through hole 105 has a second area S2 .

[0057] Please refer to Figure 6, provide a target material 202, which is arranged above the substrate 200; arrange the mask plate structure between the target material 202 and the substrate 200, the second mask plate 102 is adjacent to the substrate 200, the second through hole 105 corresponds to the optical structure area 201, and the first through hole 104 corresponds to the target material 202; and form a material layer 203 with a continuously gradient thickness on the optical structure area 201 by bombarding the target material 202.

[0058] In this embodiment, the thickness of the material layer 203 changes continuously and gradually, including: the thickness of the material layer 203 gradually increases along the direction from the edge to the center of the optical structure area 201.

[0059] The continuous thickness gradient defined in the present invention does not require absolute continuity in a mathematical sense, and the thickness change difference between adjacent positions of the material layer may be less than 1%, 3% or 5%, etc. The actual thickness change difference may be determined based on the performance requirements of the actual product.

[0060] In this embodiment, the second mask plate 102 is adjacent to the substrate 200 , which includes: the second mask plate 102 is disposed on the substrate 200 and in contact with the substrate 200 .

[0061] In other embodiments, the second mask plate is adjacent to the substrate, including: there is a gap between the second mask plate and the substrate, and the second mask plate is not in direct contact with the substrate.

[0062] In this embodiment, the surface of the target 202 is arranged opposite to the surface of the substrate 200 , that is, the sputtering surface of the target 202 is opposite to the surface of the substrate 200 .

[0063] Please combine Figure 3 Continue to refer Figure 6 , the second through hole 105 corresponds to the optical structure area 201, including: the second through hole 105 corresponds to a single optical structure area 201.

[0064] In this embodiment, the second through hole 105 corresponds to the optical structure area 201 , including: the second through hole 105 and the optical structure area 201 have the same shape and area; the center line of the second through hole 105 coincides with the center line of the optical structure area 201 .

[0065] The second through hole 105 corresponds to the optical structure area 201 , and the shape and area of ​​the second through hole 105 determine the shape and area of ​​the material layer 203 formed on the surface of the substrate 200 .

[0066] In this embodiment, the first through hole 104 corresponds to the target 202 , including: a center line of the first through hole 104 coincides with a center line of the target 202 .

[0067] The center line of the first through hole 104 coincides with the center line of the target material 202 , that is, the target material 202 is located at the center of the first through hole 104 and the second through hole 105 , so that the thickness of the subsequently formed material layer 203 can show a continuous change trend with the thickest at the center and the thinnest at the edge.

[0068] The material of the material layer 203 includes an inorganic dielectric material, and the inorganic dielectric material includes titanium oxide, niobium oxide, silicon carbide, silicon oxide, lithium niobate, silicon nitride, tantalum oxide, hafnium oxide, and aluminum oxide.

[0069] The target material 202 may be made of titanium oxide, niobium oxide, silicon carbide, silicon oxide, lithium niobate, silicon nitride, tantalum oxide, hafnium oxide, aluminum oxide or titanium.

[0070] There is a first distance H' between the first mask plate 101 and the second mask plate 102, and the first through hole 104 has a first area S1. A material layer 203 with a continuously gradient thickness is formed on the optical structure area 201 by bombarding a target material, and further includes: adjusting the thickness and thickness variation of the material layer 203 at each position on the optical structure area 201 by adjusting the size of the first distance H' and adjusting the size of the first area S1.

[0071] The specific process of adjusting the thickness of the material layer 203 at each position on the optical structure region 201 by adjusting the size of the first spacing H' and adjusting the size of the first area S1 is shown in FIG. Figure 7 and Figure 8 , Figure 7 Schematic diagram of establishing a coordinate system based on the material layer 203. Figure 8 A schematic diagram of establishing a coordinate system for each structure according to the material layer 203 .

[0072] Please refer to Figure 7 , an axially symmetric coordinate system (r, h) is established with the intersection of the central axis L3 of the material layer 203 and the substrate 200 as the coordinate origin O, the horizontal coordinate r of the coordinate system (r, h) is the distance of any point on the top surface of the material layer 203 relative to the coordinate origin O, and the vertical coordinate h of the coordinate system (r, h) is the distance from the center of the target material 202 to the surface of the substrate 200.

[0073] The central axis L3 of the material layer 203 coincides with the center line of the optical structure region 201 .

[0074] Please refer to Figure 8, the target 202 has a radial length S, the center line of the target 202 passes through the coordinate origin O, that is, the target 202 is symmetrically arranged with respect to the ordinate of the coordinate system in the length direction, the target 202 has a sputtering point A at any position relative to the surface of the substrate 200, and the active coordinate range of the sputtering point A relative to the center of the target 202 is (-S / 2, S / 2); a is the radial coordinate of any sputtering point A of the target 202 relative to the center line of the target 202; M is the target 202 material mass; ρ is the density of the target material 202; h is the distance from the center of the target material 202 to the surface of the substrate 200; r is the coordinate of any point on the top surface of the material layer 203 relative to the coordinate origin O; T(r) is the thickness at any point r on the top surface of the material layer 203; H is the distance between the first mask plate 101 and the substrate 200; R1 is the first aperture of the first through hole 104, and da is the integral factor of the sputtering point A of the target material 202 in the radial direction of the target material 202.

[0075] In this embodiment, the distance H between the first mask plate 101 and the substrate 200 is H′+d2, where H′ is a first distance between the first mask plate 101 and the second mask plate 102 , and d2 is a second thickness of the second mask plate 102 .

[0076] In this embodiment, the distance h from the center of the target 202 to the surface of the substrate 200 is H+d1+the distance between the target and the first mask 101 , where d1 is the first thickness of the first mask 101 .

[0077] In other embodiments, the second mask plate is not in direct contact with the substrate, and the distance H between the first mask plate and the substrate is H′+d2+the distance between the second mask plate and the substrate.

[0078] according to Figure 8 The thickness of the material layer 203 is obtained by using the coordinate system in By adjusting the size of the first spacing H' and the size of the first area S1, the thickness T(r) of the material layer 203 at each position on the optical structure area 201 is adjusted.

[0079] The size of the first area S1 is adjusted, that is, the size of the first area S1 is adjusted by adjusting the first aperture R1 of the first through hole 104 .

[0080] The size of the first interval H' is adjusted, that is, the size of the vertical coordinate h is adjusted by adjusting the size of the first interval H'.

[0081] The thickness T(r) of the material layer 203 at different positions r is calculated by the above formula to determine the thickness variation of the material layer 203 at different positions. The thickness T(r) of the material layer 203 at different positions is calculated based on different technical requirements or gradient requirements of the grating depth.

[0082] Along the direction from the edge to the center of the optical structure area 201, the thickness of the material layer 203 gradually increases.

[0083] Specifically, within a preset size range along the surface of the substrate 200 , the thickness of the material layer 203 varies continuously from 15 nanometers to 400 nanometers.

[0084] In this embodiment, the preset size range is 3 cm to 4 cm, or 2 cm to 3 cm, 4 cm to 5 cm, or even less than 2 cm or greater than 5 cm, etc., which are all within the scope of protection requested by the present invention. The present invention does not limit the preset size range. The specific size range can be limited according to the requirements of the optical structure during design, or the regional requirements for forming the grating structure. In this regard, what is shown in the figure is only an example, which is feasible.

[0085] Please refer to Fig. 9 The material layer 203 includes an effective area A and an ineffective area. The effective area A is an area where an optical structure is subsequently formed, and the ineffective area is an area that needs to be removed. A protective layer 210 is formed on the surface of the material layer 203. The surface of the protective layer 210 is a flat surface, and the protective layer 210 exposes the surface of the ineffective area.

[0086] The protective layer 210 is used to fill the top surface of the material layer 203. The surface of the protective layer 210 is a flat surface, which provides a flat surface for the subsequent formation of a patterned mask layer to form a patterned mask layer with precise dimensions.

[0087] The material of the protection layer 210 includes photoresist.

[0088] The method for forming the protection layer 210 includes: forming an initial protection layer (not shown) on the top surface of the material layer 203 ; removing the initial protection layer on the ineffective area, and forming the protection layer 210 on the effective area A.

[0089] Please refer to Fig.10 , using the protection layer 210 as a mask, the ineffective area is removed, and the effective area A is retained on the substrate 200 .

[0090] Please refer to Fig.11 , a patterned mask layer 212 is formed on the protection layer 210 .

[0091] In this embodiment, the material of the patterned mask layer 212 includes photoresist.

[0092] Please refer to Fig.12 The protective layer 210 and the effective area A are etched using the patterned mask layer 212 as a mask, so that the effective area A is formed into an optical structure 211 on the optical structure area 201 of the substrate 200. The protective layer 210 is located on the optical structure 211, and the thickness of the optical structures 211 gradually increases from the edge of the optical structure area 201 to the center.

[0093] In one embodiment, the protective layer 210 and the effective area A are etched by mask until the surface of the substrate 200 is exposed, so that the effective area A is formed into an optical structure 211 on the optical structure region 201 of the substrate 200 .

[0094] In this embodiment, the process of etching the protection layer 210 and the active area A using the patterned mask layer 212 as a mask includes a dry etching process.

[0095] Please refer to Fig.13 After forming the optical structure 211, the method further includes: removing the patterned mask layer 212 and the protective layer 210 to form the optical structure.

[0096] The optical structure comprises: a substrate 200, wherein the substrate 200 comprises one or more optical structure regions 201; optical structures 211 located on the optical structure regions 201, wherein the thickness of the optical structures 211 gradually increases along the direction from the edge of the optical structure region 201 to the center.

[0097] The thickness of the optical structure 211 gradually increases along the edge to the center of the optical structure region 201. Specifically, within a preset size range along the surface of the substrate 200, the thickness of the optical structure 211 continuously changes from 15 nanometers to 400 nanometers.

[0098] In this embodiment, the preset size range is 3 cm to 4 cm.

[0099] In this embodiment, the process of removing the patterned mask layer 212 and the protection layer 210 includes a wet etching process.

[0100] In another embodiment, after removing the patterned mask layer 212 and the protective layer 210, the method further includes: thinning the substrate 200 to form the optical structure. Specifically, the substrate 200 is etched by an etching process to form an optical structure with a continuously gradient thickness on the substrate.

[0101] In other embodiments, the substrate 200 may not be thinned.

[0102] In summary, the optical structure 211 formed has a thickness that gradually increases along the edge of the optical structure region 201 toward the center. Therefore, the thickness variation trend of the optical structure 211 can be accurately controlled, and the thickness variation trend of some optical structures 211 is a continuous variation. The thickness variation of the material layer at different positions can be accurately controlled by designing the mask plate structure, so as to form an optical structure with a continuous and gradual thickness variation. On the one hand, based on this structural design, the diffraction efficiency modulation of the optical structure at different positions can be realized to improve the display uniformity of the optical structure at different positions and improve the display effect; on the other hand, the design of this structure can also improve the display appearance of the optical structure. The design of the continuous and gradual thickness variation can prevent the thickness mutation at different positions. Such a design improves the dimensional accuracy and visual effect of the optical structure.

[0103] In another embodiment, the method for forming the optical structure includes: forming a patterned photoresist layer on the surface of the effective area of ​​the material layer 203, the patterned photoresist layer exposing the surface of the invalid area and exposing a portion of the surface of the effective area; etching the effective area and the invalid area using the patterned photoresist layer as a mask until the surface of the substrate is exposed, removing the invalid area, and forming the material layer into an optical structure.

[0104] In another embodiment, the effective area is the entire material layer, and the method for forming the optical structure includes: forming a patterned mask layer on the top surface of the entire material layer, and then etching the material layer with the patterned mask layer to form an optical structure on the substrate.

[0105] In another embodiment, in the process of etching a material layer to form an optical structure, the material layer is etched to a preset depth to form an optical structure and a plurality of grooves within the optical structure, wherein the bottom of the grooves is located within the material layer, the depths of the plurality of grooves are the same, and the depths of the plurality of grooves are less than any thickness of the material layer.

[0106] In the above embodiment, by adjusting the first spacing between the first mask plate and the second mask plate, and adjusting the size of the first area of ​​the first through hole, the thickness of the material layer at each position on the optical structure area is accurately adjusted, and the design of the thickness continuous gradient structure is controlled to improve the display efficiency of the optical structure at different positions and improve the display uniformity, thereby improving the display effect of the optical structure. At the same time, the display appearance of the optical structure is improved, and the dimensional accuracy and visual effect of the optical structure are enhanced.

[0107] Accordingly, further, an embodiment of the present invention further provides a diffraction optical waveguide, wherein the diffraction optical waveguide at least includes an outcoupling grating region and / or a turning grating region, wherein the grating structure in the outcoupling grating region or the turning grating region is based on Figures 3 to 13 The optical structure is prepared by the forming method.

[0108] In the above embodiments, the grating structure in the grating region is obtained by any of the above embodiments. The optical structure in the above embodiments is the grating structure, and the grating structure with a continuous and gradual thickness change is formed in this way.

[0109] The diffraction optical waveguide is used for diffraction imaging; and the optical structure includes a grating structure.

[0110] Of course, in some other embodiments, the diffraction optical waveguide may also include a recycling grating region, a pupil expansion grating region, etc. In this regard, the present invention does not limit the specific grating function.

[0111] The diffraction optical waveguide obtained by the above method is based on a material layer with a continuously changing thickness formed on a substrate to form a grating structure with a continuously changing depth, and different grating structures have different depths; on the one hand, the method modulates the diffraction efficiency of the prepared grating structure at different positions, so that the grating structure has a continuously changing diffraction efficiency at different positions, thereby improving the display uniformity and display efficiency of the diffraction optical waveguide and improving the display effect of the waveguide; on the other hand, based on the diffraction optical waveguide obtained in this way, different grating structures have a continuously changing depth at different positions, which is different from the existing partition structure in terms of display appearance, thereby preventing the visual difference caused by the sudden change of thickness at different positions, and visually obtaining a better appearance effect. Compared with the prior art, the present invention has unexpected technical effects and significant progress.

[0112] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A mask plate structure, characterized in that: include: A first mask plate, wherein the first mask plate has a first through hole penetrating the first mask plate; A second mask plate, wherein the second mask plate has a second through hole penetrating the second mask plate; There is a distance between the first mask plate and the second mask plate, and the first mask plate and the second mask plate are used to form a material layer with a continuously gradient thickness in the second through hole region.

2. The mask structure according to claim 1, characterized in that: The first mask plate and the second mask plate are connected by a connecting portion to form an integrated structure, and the second mask plate is attached to the substrate; or, the first mask plate and the second mask plate are independently formed on the substrate, and the second mask plate is in contact with the substrate.

3. The mask plate structure according to claim 1 or 2, characterized in that: A projection range of the first through hole projected onto the second mask plate is located within the second through hole; and the first mask plate and the second mask plate are arranged in parallel.

4. The mask structure according to claim 3, characterized in that: A center line of the first through hole coincides with a center line of the second through hole.

5. The mask structure according to claim 1, characterized in that: The thickness of the material layer changes continuously and gradually, and the thickness T(r) is calculated as follows: Wherein, a is the radial coordinate of any sputtering point of the target relative to the center line of the target, M is the mass of the target material, ρ is the density of the target material, h is the distance from the center of the target to the surface of the substrate, r is the coordinate of any point on the top surface of the material layer relative to the coordinate origin, T(r) is the thickness at any point r on the surface of the material layer, H is the distance between the first mask plate and the substrate, R1 is the first aperture of the first through hole, and S is the radial length of the target; the mask plate structure is arranged on the surface of the substrate.

6. A method for forming an optical structure, characterized in that: include: Providing a substrate, the substrate comprising one or more optical structure regions; A mask plate structure according to any one of claims 1 to 5 is provided, wherein the mask plate structure comprises: a first mask plate and a second mask plate arranged in a direction perpendicular to a surface of a substrate; Providing a target material, disposed above the substrate; The mask plate structure is arranged between the target material and the substrate, the second mask plate is in contact with the substrate, the second through hole corresponds to the optical structure area, and the first through hole corresponds to the target material; A material layer with a continuously gradient thickness is formed on the optical structure region by bombarding the target material.

7. The method for forming an optical structure according to claim 6, wherein: The continuous gradient thickness T(r) of the material layer is calculated by the following formula: Wherein, a is the radial coordinate of any sputtering point of the target relative to the center line of the target, M is the mass of the target material, ρ is the density of the target material, h is the distance from the center of the target to the surface of the substrate, r is the coordinate of any point on the top surface of the material layer relative to the origin of the coordinate system, T(r) is the thickness at any point r on the top surface of the material layer, H is the distance between the first mask plate and the substrate, R1 is the first aperture of the first through hole, and S is the radial length of the target.

8. The method for forming an optical structure according to claim 6 or 7, characterized in that: The material layer includes an effective area and an ineffective area; the formation method also includes: forming a protective layer on the surface of the material layer, the surface of the protective layer is a flat surface, and the protective layer exposes the surface of the ineffective area; using the protective layer as a mask to remove the ineffective area; forming a patterned mask layer on the surface of the protective layer; etching the protective layer and the effective area using the patterned mask layer as a mask, so that the effective area is formed into an optical structure on the optical structure area of ​​the substrate, the protective layer is located on the optical structure, and the thickness of several optical structures gradually increases along the edge of the optical structure area toward the center; after the optical structure is formed, the protective layer is removed.

9. The method for forming an optical structure according to claim 6 or 7, characterized in that: The formation method also includes: forming a patterned mask layer on the surface of the material layer; etching the material layer using the patterned mask layer as a mask to form an optical structure on the optical structure area, and the thickness of the optical structures gradually increases along the edge of the optical structure area toward the center.

10. A diffractive optical waveguide, characterized in that: At least it includes a coupling-out grating region and / or a turning grating region, and the grating structure in the coupling-out grating region or the turning grating region is prepared based on the method for forming an optical structure according to any one of claims 6 to 9.

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