Bottom alignment grating preparation method and bottom alignment grating

Abstract

The invention relates to a bottom alignment grating preparation method and a bottom alignment grating, and the bottom alignment grating preparation method comprises the steps: depositing a grating material on a light-transmitting substrate, so as to form a grating material layer on the light-transmitting substrate; etching the grating material layer to form a plurality of grating areas with different heights on the grating material layer; and respectively etching each grating area to the light-transmitting substrate to form a plurality of groups of gratings with different heights so as to obtain a bottom-aligned grating. The partition structure of each grating area of the bottom-aligned grating is bottom-aligned, so that the optical efficiency of an optical device can be improved, and an optical film interference effect caused by a residual film is reduced. The bottom alignment grating can be prepared through the preparation method of the bottom alignment grating provided by the invention.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical device preparation, in particular to a bottom-alignment grating preparation method and a bottom-alignment grating. BACKGROUND

[0002] With the development of optical technology, diffractive optical waveguides gradually become an important part of the AR (Augmented Reality) industry. At present, the mainstream development direction of diffractive optical waveguides can be divided into two, one is the diffractive optical waveguide mainly based on nanoimprinting, and the other is the etching optical waveguide mainly based on semiconductor equipment yellow light and etching.

[0003] At present, the etching optical waveguide is mainly a top-alignment structure. In the design and preparation, the three sub-zone gratings of the coupling-in region, the turning region and the coupling-out region are top-aligned, or the two sub-zone gratings of the coupling-in region and the coupling-out region are top-aligned, while the height of the bottom residual layer is inconsistent. From the perspective of optical design, the bottom residual layer will bring optical film interference and reduce the display efficiency of the optical device. SUMMARY

[0004] Therefore, it is necessary to provide a bottom-alignment grating preparation method and a bottom-alignment grating in view of the problem of inconsistent height of the bottom residual layer existing in the existing etching optical waveguide.

[0005] A bottom-alignment grating preparation method, comprising the steps of:

[0006] depositing a grating material on a light-transmitting substrate to form a grating material layer on the light-transmitting substrate;

[0007] etching the grating material layer to form a plurality of grating regions with different heights on the grating material layer; and

[0008] respectively etching each of the grating regions to the light-transmitting substrate to form a plurality of grating groups with different heights, thereby obtaining a bottom-alignment grating.

[0009] In one embodiment, the step of etching the grating material layer to form a plurality of grating regions with different heights on the grating material layer comprises:

[0010] depositing a mask material on the grating material layer to form a sub-zone mask layer on the grating material layer;

[0011] etching the sub-zone mask layer to form a first region contour pattern on the grating material layer;

[0012] etching the region of the grating material layer corresponding to the first region contour pattern to a first predetermined height through the first region contour pattern to form a first grating region with the first predetermined height on the grating material layer; and

[0013] removing the partition mask layer.

[0014] In one embodiment, between the step of etching the region of the grating material layer corresponding to the first region profile pattern to a first predetermined height by the first region profile pattern to form a first grating region with the first predetermined height on the grating material layer and the step of removing the partition mask layer, comprises steps of:

[0015] etching the partition mask layer in a second region different from the first grating region to form a second region profile pattern on the grating material layer; and

[0016] etching the region of the grating material layer corresponding to the second region profile pattern to a second predetermined height by the second region profile pattern to form a second grating region with the second predetermined height on the grating material layer.

[0017] In one embodiment, between the step of depositing a mask material on the grating material layer to form a partition mask layer on the grating material layer and the step of etching the partition mask layer to form a first region profile pattern on the grating material layer, comprises steps of:

[0018] etching the partition mask layer to form a plurality of positioning mask patterns on the grating material layer; and

[0019] etching the grating material layer by the positioning mask patterns to form a plurality of positioning marks.

[0020] In one embodiment, the step of etching the partition mask layer to form a first region profile pattern on the grating material layer comprises:

[0021] coating a photoresist on the partition mask layer to form a partition pattern layer;

[0022] performing a pattern definition on the partition pattern layer to obtain a first region pattern;

[0023] etching the region of the partition mask layer corresponding to the first region pattern to the grating material layer by the first region pattern to form a first region profile pattern on the grating material layer; and

[0024] removing the partition pattern layer.

[0025] In one embodiment, in the step of etching the grating material layer to form a plurality of grating regions with different heights on the grating material layer, the height of the grating region is controlled by controlling the etching time.

[0026] In one of the embodiments, in the step of depositing grating material on the light-transmitting substrate to form a grating material layer on the light-transmitting substrate, the height of the grating material layer is the highest grating height of the grating to be made.

[0027] In one of the embodiments, the step of etching each of the grating regions to the light-transmitting substrate respectively to form a plurality of groups of gratings with different heights to obtain the bottom-aligned gratings comprises:

[0028] depositing a mask material on all the grating regions to form a full-grating mask layer;

[0029] etching the full-grating mask layer to obtain a full-grating mask pattern corresponding to all the grating regions;

[0030] etching the area of each of the grating regions corresponding to the full-grating mask pattern to the light-transmitting substrate respectively through the full-grating mask pattern to form a plurality of groups of gratings respectively; and

[0031] removing the full-grating mask layer to obtain the bottom-aligned gratings.

[0032] In one of the embodiments, the step of etching the full-grating mask layer to obtain a full-grating mask pattern comprises the steps of:

[0033] coating a photoresist on the full-grating mask layer to form a full-grating pattern layer;

[0034] performing a pattern definition on the full-grating pattern layer to obtain a full-grating pattern; and

[0035] etching the full-grating mask layer through the full-grating pattern to form a full-grating mask pattern.

[0036] In one of the embodiments, the step of etching the area of each of the grating regions corresponding to the full-grating mask pattern to the light-transmitting substrate respectively through the full-grating mask pattern to form a plurality of groups of gratings respectively comprises the steps of:

[0037] coating a photoresist on the full-grating mask layer to form a single-group grating pattern layer;

[0038] performing a pattern definition on the single-group grating pattern layer to expose a single-group grating pattern of the full-grating mask pattern;

[0039] etching the area of the grating region corresponding to the single-group grating pattern to the light-transmitting substrate through the single-group grating pattern to form a group of gratings;

[0040] removing the single-group grating pattern layer; and

[0041] repeating the above steps to form a plurality of groups of gratings.

[0042] A bottom-aligned grating, wherein the bottom-aligned grating is prepared according to any one of the bottom-aligned grating preparation methods described above.

[0043] The above-mentioned bottom-aligned grating fabrication method processes the partitioned structure of each grating region of the grating into bottom alignment, which can improve the optical efficiency of optical devices and reduce the optical thin film interference effect caused by the inconsistent thickness of the residual layer at the bottom of the grating. Attached Figure Description

[0044] Figure 1 A schematic flowchart illustrating a method for fabricating a bottom-aligned grating according to an embodiment of this application;

[0045] Figure 2 A flowchart illustrating step S200 of the bottom-aligned grating fabrication method according to the above embodiments of this application is shown;

[0046] Figure 3 As shown Figure 2 A schematic flowchart illustrating a modified example of step S200 of the bottom-aligned grating fabrication method shown;

[0047] Figure 4 As shown Figure 2 A schematic flowchart illustrating another variation of step S200 of the bottom-aligned grating fabrication method shown;

[0048] Figure 5 As shown Figure 2 A schematic flowchart of step S210 of the bottom-aligned grating fabrication method is shown;

[0049] Figure 6 A schematic flowchart of step S300 of the bottom-aligned grating fabrication method according to the above embodiments of this application is shown;

[0050] Figure 7 A schematic flowchart of step S300 of the bottom-aligned grating fabrication method according to the above embodiments of this application is shown;

[0051] Figure 8 As shown Figure 7 A schematic flowchart of step S320 of the bottom-aligned grating fabrication method is shown.

[0052] Figure 9 As shown Figure 7 The flowchart of step S330 of the bottom-aligned grating fabrication method is shown.

[0053] Figure 10A A schematic diagram of the structure of a bottom-aligned grating fabricated by the bottom-aligned grating fabrication method provided in the above embodiments of this application when it is in fabrication process (A);

[0054] Figure 10B FIG. 6 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (B);

[0055] Figure 10C FIG. 7 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (C);

[0056] Figure 10D FIG. 8 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (D);

[0057] Figure 10E FIG. 9 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (E);

[0058] Figure 10F FIG. 10 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (F);

[0059] Figure 10G FIG. 11 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (G);

[0060] Figure 10H FIG. 12 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (H);

[0061] Figure 10I FIG. 13 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (I);

[0062] Figure 10J FIG. 14 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (J);

[0063] Figure 10K FIG. 15 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (K);

[0064] Figure 10L FIG. 16 shows a structural schematic diagram of a bottom-alignment grating prepared by the bottom-alignment grating preparation method according to the above embodiment of the present application, when in preparation procedure (L).

[0065] 10, light-transmitting substrate; 20, grating material layer; 21, positioning mark; 22, out-coupling grating region; 221, out-coupling grating; 23, turning grating region; 231, turning grating; 24, in-coupling grating region; 241, in-coupling grating; 30, partition mask layer; 31, positioning mask pattern; 32, out-coupling grating region contour pattern; 33, turning grating region contour pattern; 40, positioning pattern layer; 41, positioning pattern; 50, partition pattern layer; 51, out-coupling grating region pattern; 52, turning grating region pattern; 60, full-grating mask layer; 61, full-grating mask pattern; 70, full-grating pattern layer; 71, full-grating pattern; 80, single set of grating pattern layer. DETAILED DESCRIPTION

[0066] In order to make the above objectives, features and advantages of the present application more clear and easily understood, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the present application can be practiced without using some or all of these specific details, and that the present application is not limited to the specific embodiments disclosed below.

[0067] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0068] In addition, the terms "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one set of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0069] In the present application, unless specifically defined and limited otherwise, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the internal communication of two elements or the interaction relationship of two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0070] In the present application, unless specifically defined and limited otherwise, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "on", "above" and "above" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "under", "below" and "below" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0071] It should be noted that when an element is referred to as "fixed to" or "provided on" another group of elements, it can be directly on another group of elements or there can be a middle element. When a group of elements is considered to be "connected" to another group of elements, it can be directly connected to another group of elements or there can be a middle element. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are for illustrative purposes only and are not the only embodiment.

[0072] The present application provides a bottom alignment grating preparation method and a bottom alignment grating, which processes the partition structure of each grating region to be bottom alignment, can improve the optical efficiency of the optical device, and reduce the optical film interference effect caused by the inconsistent thickness of the grating bottom residual layer. The bottom alignment grating can be prepared by the bottom alignment grating preparation method provided by the present application.

[0073] Specifically, please refer to Figure 1 The bottom alignment grating preparation method comprises the steps of:

[0074] S100, depositing a grating material on a light-transmitting substrate to form a grating material layer on the light-transmitting substrate;

[0075] S200, etching the grating material layer to form a plurality of grating regions with different heights on the grating material layer; and

[0076] S300, etching each of the grating regions to the light-transmitting substrate respectively to form multiple groups of gratings with different heights, to obtain the bottom-aligned gratings.

[0077] In the above method for preparing the bottom-aligned gratings, the step S100 is used to deposit a grating material layer on the light-transmitting substrate, the grating material includes but is not limited to silicon nitride (SiN), silicon dioxide (SiO2) or titanium dioxide (TiO2) and other optical materials; the step S200 is used to etch the grating material layer to form multiple grating regions with different heights on the grating material layer, the height of each grating region can be determined according to the height of the designed grating region, and the height of the etched grating material layer can be determined by subtracting the height of the grating region from the height of the grating material layer; the step S300 is used to etch each of the grating regions to obtain multiple groups of gratings, the bottom of each group of gratings is the plane between the light-transmitting substrate and the grating material layer, i.e., the bottom of each group of gratings is aligned.

[0078] More specifically, as shown in one of the embodiments, Figure 2 the step S200 of etching the grating material layer to form multiple grating regions with different heights on the grating material layer includes:

[0079] S210, depositing a mask material on the grating material layer to form a partition mask layer on the grating material layer;

[0080] S220, etching the partition mask layer to form a first area contour pattern on the grating material layer;

[0081] S230, etching the region of the grating material layer corresponding to the first area contour pattern to a first predetermined height through the first area contour pattern to form a first grating region with a first predetermined height on the grating material layer; and

[0082] S240, removing the partition mask layer.

[0083] The partition mask layer formed by the step S210 can be used to shield the grating material layer, the mask material includes but is not limited to chromium (Cr) material or other hard mask materials; the first area contour pattern formed by the step S220 can be the shape of the first grating region, so that the first grating region can be etched on the grating material layer in the subsequent step S230; the partition mask layer is removed by the step S240 to obtain the grating material layer with multiple grating regions with different heights.

[0084] Preferably, as shown in one of the embodiments, Figure 3As shown, in one embodiment, step S230, etching the region corresponding to the first region contour pattern on the grating material layer to a first predetermined height to form a first grating region with a first predetermined height on the grating material layer, and step S240, removing the partition mask layer, include the following steps:

[0085] S250. In a second region different from the first grating region, the partition mask layer is etched to form a second region contour pattern on the grating material layer; and

[0086] S260. Using the second region outline pattern, etch the region on the grating material layer corresponding to the second region outline pattern to a second predetermined height, so as to form a second grating region with a second predetermined height on the grating material layer.

[0087] Steps S250 and S260 can form a second grating region with a different height from the first grating region on the grating material layer. By repeating the above steps multiple times, multiple grating regions with different heights can be formed.

[0088] Furthermore, such as Figure 4 As shown, in one embodiment, the step between step S210, depositing mask material on the grating material layer to form a partitioned mask layer on the grating material layer, and step S220, etching the partitioned mask layer to form a first region contour pattern on the grating material layer, includes the following step:

[0089] S270, Etch the partitioned mask layer to form multiple positioning mask patterns on the grating material layer; and

[0090] S280. Using the positioning mask pattern, etch the grating material layer to form multiple positioning marks.

[0091] Steps S270 and S280 can be used to etch positioning marks on the partitioned mask layer for positioning during subsequent processing, resulting in a more accurate grating. These positioning marks can be distributed on both sides of the grating material layer, dividing the area between two positioning marks into a working area, within which the subsequent grating area can be formed.

[0092] Preferably, such as Figure 5 As shown, in one embodiment, step S220, etching the partition mask layer to form a first region contour pattern on the grating material layer, includes:

[0093] S211. Apply photoresist to the partitioned mask layer to form a partitioned patterned layer;

[0094] S212, performing a pattern definition on the partitioned pattern layer to obtain a first area pattern;

[0095] S213, etching the partitioned mask layer corresponding to the first area pattern to the grating material layer to form a first area contour pattern on the grating material layer; and

[0096] S214, removing the partitioned pattern layer.

[0097] In step S212, the pattern definition can be implemented by developing photoresist according to the shape of the designed grating area, thereby obtaining the first area pattern; in step S213, the partitioned pattern layer can shield other parts of the partitioned mask layer except the first area pattern exposed part, thereby etching the first area contour pattern on the partitioned mask layer according to the first area pattern.

[0098] Similarly, as shown in Figure 6 S250, etching the partitioned mask layer in a second area different from the first grating area to form a second area contour pattern on the grating material layer.

[0099] S251: coating photoresist on the partitioned mask layer to form a partitioned pattern layer;

[0100] S252, performing a pattern definition on the partitioned pattern layer to obtain a second area pattern;

[0101] S253, etching the partitioned mask layer corresponding to the second area pattern to the grating material layer to form a second area contour pattern on the grating material layer; and

[0102] S254, removing the partitioned pattern layer.

[0103] It can be understood that in one embodiment, in the step S100, the height of the grating area is controlled by controlling the etching time. By controlling the etching time of each grating area, the thickness of the grating material of each grating area removed can be controlled respectively, thereby forming multiple grating areas with different heights.

[0104] In particular, in one of the embodiments, the step of S100, depositing grating material on the light-transmissive substrate to form a grating material layer on the light-transmissive substrate, the height of the grating material layer is the highest grating height of the grating to be fabricated. Preferably, the grating material layer is formed by depositing grating material according to the highest grating height. In this way, the step of etching the grating with the highest grating height can be omitted, and the processing procedure is reduced.

[0105] Further, as shown in Figure 7 one of the embodiments, the step of S300, etching each of the grating regions to the light-transmissive substrate respectively to form a plurality of groups of gratings with different heights, to obtain the bottom-aligned gratings, includes:

[0106] S310, depositing a mask material on all the grating regions to form a full-grating mask layer;

[0107] S320, etching the full-grating mask layer to obtain a full-grating mask pattern corresponding to all the grating regions;

[0108] S330, etching each of the grating regions corresponding to the area of the full-grating mask pattern to the light-transmissive substrate respectively through the full-grating mask pattern to form a plurality of groups of gratings respectively; and

[0109] S340, removing the full-grating mask layer to obtain the bottom-aligned gratings.

[0110] In step S310, the mask material is deposited on the grating material layer, so that the mask material covers all the grating regions to form a full-grating mask layer. In step S320, the full-grating mask layer is etched according to the designed gratings, so that the full-grating mask layer can cover the grating material layer to be reserved for subsequent etching of each grating region. In step S330, each grating region is etched according to the division of each grating region, so that a plurality of groups of gratings are obtained. In step S340, the full-grating mask layer is removed, so that the bottom-aligned gratings can be obtained.

[0111] Optionally, as shown in Figure 8 one of the embodiments, the step of S320, etching the full-grating mask layer to obtain a full-grating mask pattern, includes the steps of:

[0112] S321, coating photoresist on the full-grating mask layer to form a full-grating pattern layer;

[0113] S322, performing pattern definition on the full-grating pattern layer to obtain a full-grating pattern;

[0114] S323, etching the full-grating mask layer through the full-grating pattern to form a full-grating mask pattern; and

[0115] S324, removing the full-grating pattern layer.

[0116] In step S321, photoresist is coated on the full-grating mask layer to form a full-grating pattern layer capable of covering the full-grating mask layer; in step S322, the full-grating pattern layer can be pattern-defined by means of imprinting or exposure, etc., according to the designed grating shape, to obtain a full-grating pattern corresponding to the designed grating; in step S323, the full-grating mask layer is covered by the full-grating pattern layer, and the area of the full-grating mask layer where the full-grating pattern layer is located is etched to form a full-grating mask pattern, which includes a plurality of single-group grating patterns corresponding to grating areas; in step S324, the full-grating pattern layer is removed so as to remove the full-grating mask layer in subsequent steps.

[0117] Optionally, as shown in one of the embodiments, Figure 9 the step of S330 etching each grating area corresponding to the area of the full-grating mask pattern to the light-transmitting substrate to form a plurality of groups of gratings includes steps of:

[0118] S331, coating photoresist on the full-grating mask layer to form a single-group grating pattern layer;

[0119] S332, pattern-defining the single-group grating pattern layer to expose one single-group grating pattern of the full-grating mask pattern;

[0120] S333, etching the grating area corresponding to the single-group grating pattern to the light-transmitting substrate to form a group of gratings;

[0121] S334, removing the single-group grating pattern layer; and

[0122] S335, repeating the above steps to form a plurality of groups of gratings.

[0123] In step S331, photoresist is coated on the full-grating mask layer to form a single-group grating pattern layer capable of covering the full-grating mask layer; in step S332, the single-group grating pattern layer can be pattern-defined by means of exposure to remove photoresist on one grating area; in step S333, since other single-group grating patterns of the full-grating mask pattern are covered by the single-group grating pattern layer, one grating area can be etched alone; in step S334, the single-group grating pattern layer is removed so as to repeat the above steps subsequently; in step S335, after repeating steps S331 to S334 for multiple times, all grating areas are etched to form a plurality of groups of gratings.

[0124] For example, this application provides a specific embodiment of a three-section bottom-aligned grating, which may include an outgoing grating, a transition grating, and an incoming grating. The specific fabrication process of the bottom-aligned grating according to the above-described fabrication method is as follows:

[0125] (A) such as Figure 10A As shown, titanium dioxide (TiO2) material is deposited on the light-transmitting substrate 10 to form a grating material layer 20 with the same height as the coupled grating 241;

[0126] (B) such as Figure 10B As shown, chromium (Cr) material is deposited on the grating material layer 20 to form a partitioned mask layer 30;

[0127] (C) such as Figure 10C As shown, photoresist is coated on the partition mask layer 30 to form a positioning pattern layer 40 and developed to form a positioning pattern 41. Then, the partition mask layer 30 is etched to form a positioning mask pattern 31 and the positioning pattern layer 40 is removed. Finally, the grating material layer 20 is etched to form a positioning mark 21.

[0128] (D) such as Figure 10D As shown, photoresist is coated to form a partitioned pattern layer 50 and the shape of the coupled grating region 22 is exposed to form a coupled grating region pattern 51. The partitioned mask layer 30 is etched through the coupled grating region pattern 51 to form a coupled grating region contour pattern 32. The grating material layer 20 is etched through the coupled grating region contour pattern 32 to form the coupled grating region 22. After the partitioned pattern layer 50 is removed, the coupled grating region 22 is formed.

[0129] (E) such as Figure 10E As shown, photoresist is coated to form a partitioned pattern layer 50 and the shape of the transition grating region 23 is exposed to form a transition grating region pattern 52. The partitioned mask layer 30 is etched through the transition grating region pattern 52 to form a transition grating region outline pattern 33. The grating material layer 20 is etched through the transition grating region outline pattern 33. After the transition grating region 23 is formed, the partitioned pattern layer 50 is removed.

[0130] (F) such as Figure 10F As shown, remove the partition mask layer 30;

[0131] (G) such as Figure 10G As shown, chromium (Cr) material is deposited on the grating material layer 20 to form a full grating mask layer 60;

[0132] (H) such as Figure 10HAs shown, photoresist is coated to form a full-grating pattern layer 70 and is subjected to imprinting or exposure to form a full-grating pattern 71 corresponding to the in-coupling grating region 24, the turning grating region 23 and the out-coupling grating region 22; the full-grating pattern 71 is used to etch the full-grating mask layer 60 to form a full-grating mask pattern 61 corresponding to the in-coupling grating region 24, the turning grating region 23 and the out-coupling grating region 22, and the full-grating pattern layer 70 is removed;

[0133] (I) As shown in FIG. 6, photoresist is coated to form a single-grating pattern layer 80 and is subjected to exposure to the out-coupling grating region 22; the out-coupling grating region 22 is etched to form a group of out-coupling gratings 221, and then the single-grating pattern layer 80 is removed; Figure 10I

[0134] (J) As shown in FIG. 7, photoresist is coated to form a single-grating pattern layer 80 and is subjected to exposure to the turning grating region 23; the turning grating region 23 is etched to form a group of turning gratings 231, and then the single-grating pattern layer 80 is removed; Figure 10J (K) As shown in FIG. 8, photoresist is coated to form a single-grating pattern layer 80 and is subjected to exposure to the in-coupling grating region 24; the in-coupling grating region 24 is etched to form a group of in-coupling gratings 241, and then the single-grating pattern layer 80 is removed;

[0135] Figure 10K (L) As shown in FIG. 9, the full-grating mask layer 60 is removed to form a bottom-alignment grating.

[0136] (L) As shown in FIG. 9, the full-grating mask layer 60 is removed to form a bottom-alignment grating. Figure 10L It is worth noting that the height of the in-coupling grating prepared in the present application is the highest, so the height of the in-coupling grating is taken as the height of the grating material layer in step (A) to save the step of etching the in-coupling grating region; if the height of the out-coupling grating or the height of the turning grating is higher in other embodiments, the height of the out-coupling grating or the height of the turning grating is taken as the height of the grating material layer, and the other two grating regions with lower height are etched respectively. The order of steps (D) and (E) can be interchanged, and the order of steps (I), (J) and (K) can be interchanged, that is, the order of etching the out-coupling grating region and the turning grating region is not fixed, and the order of etching the out-coupling grating, the turning grating and the in-coupling grating is not fixed.

[0137] The present application also provides a preparation method of a two-part bottom-alignment grating including an in-coupling grating and an out-coupling grating, and the specific preparation process is the same as the preparation process of the three-part bottom-alignment grating described above, wherein steps (E) and (J) are omitted, and only the full-grating pattern corresponding to the in-coupling grating region or the out-coupling grating region and the full-grating mask pattern corresponding to the in-coupling grating region or the out-coupling grating region are formed in step (H).

[0138] The present application also provides a preparation method of a two-part bottom-alignment grating including an in-coupling grating and an out-coupling grating, and the specific preparation process is the same as the preparation process of the three-part bottom-alignment grating described above, wherein steps (E) and (J) are omitted, and only the full-grating pattern corresponding to the in-coupling grating region or the out-coupling grating region and the full-grating mask pattern corresponding to the in-coupling grating region or the out-coupling grating region are formed in step (H).​​

[0139] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as there is no conflict, any combination of the technical features should be considered within the scope of the present disclosure.

[0140] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the present application, and these are within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for fabricating a bottom-aligned grating, characterized in that, The method comprises the steps of: depositing a grating material on a light-transmitting substrate to form a grating material layer on the light-transmitting substrate; etching the grating material layer to form a plurality of grating regions with different heights on the grating material layer; and respectively etching each of the grating regions to the light-transmitting substrate to form a plurality of groups of gratings with different heights, thereby obtaining bottom-aligned gratings.

2. The method of claim 1, wherein, The step of etching the grating material layer to form a plurality of grating regions with different heights on the grating material layer comprises the steps of: depositing a mask material on the grating material layer to form a partitioned mask layer on the grating material layer; etching the partitioned mask layer to form a first region profile pattern on the grating material layer; etching, through the first region profile pattern, a region on the grating material layer corresponding to the first region profile pattern to a first predetermined height, thereby forming a first grating region with the first predetermined height on the grating material layer; and removing the partitioned mask layer.

3. The method of claim 2, wherein the method further comprises: The step of etching, through the first region profile pattern, a region on the grating material layer corresponding to the first region profile pattern to a first predetermined height, thereby forming a first grating region with the first predetermined height on the grating material layer, and the step of removing the partitioned mask layer comprise the steps of: etching, in a second region different from the first grating region, the partitioned mask layer to form a second region profile pattern on the grating material layer; and etching, through the second region profile pattern, a region on the grating material layer corresponding to the second region profile pattern to a second predetermined height, thereby forming a second grating region with the second predetermined height on the grating material layer. The step of depositing a mask material on the grating material layer to form a partitioned mask layer on the grating material layer, and the step of etching the partitioned mask layer to form a first region profile pattern on the grating material layer comprise the steps of:

4. The method of claim 2, wherein the method further comprises: etching the partitioned mask layer to form a plurality of positioning mask patterns on the grating material layer; and etching, through the positioning mask patterns, the grating material layer to form a plurality of positioning marks. The step of etching the partitioned mask layer to form a first region profile pattern on the grating material layer comprises the steps of: coating a photoresist on the partitioned mask layer to form a partitioned pattern layer; 5. The method of claim 2, wherein the photoresist is exposed to light through the bottom alignment mask. defining a pattern of the partitioned pattern layer, thereby obtaining a first region pattern; etching, through the first region pattern, a region on the partitioned mask layer corresponding to the first region pattern to the grating material layer, thereby forming a first region profile pattern on the grating material layer; and removing the partitioned pattern layer. In the step of etching the grating material layer to form a plurality of grating regions with different heights on the grating material layer, the height of the grating regions is controlled by controlling the etching time. In the step of depositing a grating material on a light-transmitting substrate to form a grating material layer on the light-transmitting substrate, the height of the grating material layer is the highest grating height of the prepared gratings.

6. The method of claim 2, wherein, The step of respectively etching each of the grating regions to the light-transmitting substrate to form a plurality of groups of gratings with different heights, thereby obtaining bottom-aligned gratings comprises the steps of:

7. The method of claim 1, wherein, depositing a mask material on all the grating regions to form a full-grating mask layer; 8. The method according to any one of claims 1 to 7, wherein ​ ​ etching the full grating mask layer to obtain a full grating mask pattern corresponding to the full grating area; etching the area corresponding to the full grating mask pattern of each grating area to the transparent substrate through the full grating mask pattern to form a plurality of groups of gratings, respectively; and removing the full grating mask layer to obtain the bottom-aligned gratings.

9. The method of claim 8, wherein, The step of etching the full grating mask layer to obtain a full grating mask pattern includes steps of: coating photoresist on the full grating mask layer to form a full grating pattern layer; defining a pattern on the full grating pattern layer to obtain a full grating pattern; etching the full grating mask layer to form a full grating mask pattern through the full grating pattern; and removing the full grating pattern layer. The step of etching the area corresponding to the full grating mask pattern of each grating area to the transparent substrate through the full grating mask pattern to form a plurality of groups of gratings, respectively, includes steps of:

10. The method of claim 8, wherein, coating photoresist on the full grating mask layer to form a single group of grating pattern layer; defining a pattern on the single group of grating pattern layer to expose a single group of grating pattern of the full grating mask pattern; etching the area corresponding to the single group of grating pattern of the grating area to the transparent substrate through the single group of grating pattern to form a group of gratings; removing the single group of grating pattern layer; and repeating the above steps to form a plurality of groups of gratings. The bottom-aligned gratings are prepared according to the bottom-aligned grating preparation method of any one of claims 1 to 10. ​ 11. A bottom alignment grating, characterized by, ​

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