Preparation method of partition grating, diffraction optical waveguide and augmented reality equipment

Abstract

The invention discloses a partition grating preparation method, a diffraction optical waveguide and augmented reality equipment, and the method comprises the steps: providing a substrate; coating a first photoresist layer on the substrate; exposing the photoresist layer by using a first light mask to form a first exposure photoresist layer; the first exposure photoresist layer forms a first graphical mask layer, the first exposure photoresist layer at least comprises a first region and a second region of a plurality of exposure parts and a plurality of non-exposure parts, and the first development time of the first region is longer than the second development time of the second region; the first developing time is less than or equal to the time for completely developing the unexposed part or the exposed part of the first light mask; the substrate is etched according to the first graphical mask layer, the first photoresist layer is removed, a grating structure is formed, and the duty ratio of a first area of the grating structure is different from the duty ratio of a second area of the grating structure. Compared with a stepping photoetching or electron beam direct writing mode, the time cost and the processing cost are saved.

Description

Technical Field

[0001] The present invention relates to the field of optical process technology, and in particular to a method for preparing a partitioned grating, a diffraction optical waveguide and an augmented reality device. Background Art

[0002] At present, since diffraction grating waveguides mainly use photolithography technology to make surface relief gratings on the waveguide surface to achieve image coupling and decoupling, they have a large field of view, light weight, and their process is compatible with mature manufacturing technology in the semiconductor industry, with high mass production yield. As a result, they are widely used in augmented reality (AR) displays.

[0003] However, the problem is that the diffraction grating waveguide generally includes coupling-in grating, coupling-out grating, turning grating, etc. In order to meet the uniformity requirements of light propagation, the coupling-in grating, coupling-out grating, turning grating, duty cycle, height and other grating parameters in each grating will be set differently in different zones. At present, when preparing such partitioned gratings, either a stepper lithography machine is used to prepare gratings of different zones, or electron beam direct writing is used to prepare gratings of different zones. However, no matter which method is used, there are problems of long processing cycle and high processing cost. Summary of the invention

[0004] The present invention provides a method for preparing a partitioned grating, a diffraction optical waveguide and an augmented reality device, so as to solve the problems of long processing cycle and high processing cost in the related art.

[0005] In a first aspect, an embodiment of the present invention provides a method for preparing a partitioned grating, comprising:

[0006] providing a substrate;

[0007] coating a first photoresist layer on the substrate;

[0008] Exposing the first photoresist layer using a first photomask to form a first exposed photoresist layer, wherein the line widths of the light leakage parts of the first photomask are all the same, and the line widths of the light shielding parts of the first photomask are all the same;

[0009] Developing the first exposed photoresist layer to form a first patterned mask layer, wherein the first exposed photoresist layer at least includes a first region and a second region, the first region and the second region each include a plurality of exposed portions and a plurality of unexposed portions, and a first developing time of the first region is greater than a second developing time of the second region;

[0010] The substrate is etched according to the first patterned mask layer, and the first photoresist layer is removed to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region.

[0011] Optionally, after providing a substrate, the method further includes: forming a hard mask layer on the substrate;

[0012] The coating of the first photoresist layer on the substrate comprises: coating the first photoresist layer on the hard mask layer;

[0013] The step of etching the substrate according to the first graphic mask layer and removing the first photoresist layer to form a grating structure, wherein the duty cycle of the first region of the grating structure is different from the duty cycle of the second region comprises: etching the hard mask layer according to the first graphic mask layer, removing the first photoresist layer, and etching the substrate according to the hard mask layer to form a grating structure, wherein the duty cycle of the first region of the grating structure is different from the duty cycle of the second region.

[0014] Optionally, developing the first exposed photoresist layer to form a first patterned mask layer from the first exposed photoresist layer includes:

[0015] The first region is developed alone and maintained for a first time, and then the first region and the second region are simultaneously developed and maintained for a second time.

[0016] Optionally, after etching the hard mask layer according to the first patterned mask layer to remove the first photoresist layer, the method further includes:

[0017] Coating a second photoresist layer on the hard mask layer forming the first region and the second region;

[0018] Exposing the second photoresist layer using a second photomask to form a second exposed photoresist layer; wherein a light-transmitting portion of the second photomask covers one of the first region and the second region, and a light-shielding portion of the second photomask covers the other of the first region and the second region;

[0019] developing an exposed portion or an unexposed portion of the second exposure photoresist layer, and etching the substrate according to the hard mask layer;

[0020] The second exposure photoresist layer is removed, and the substrate is etched according to the hard mask layer to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region, and the height of the first region is different from the height of the second region.

[0021] Optionally, the substrate is one of a silicon substrate, a glass substrate, a lithium niobate substrate, a magnesium fluoride substrate, a zinc sulfide substrate, a gallium arsenide substrate, a silicon dioxide substrate, a silicon nitride substrate, a silicon carbide substrate, a gallium nitride substrate or an indium phosphide substrate.

[0022] Optionally, the first light mask is a one-dimensional or two-dimensional light mask.

[0023] In a second aspect, an embodiment of the present invention provides a method for preparing a partitioned grating, comprising:

[0024] providing a substrate;

[0025] forming a hard mask layer on the substrate;

[0026] coating a third photoresist layer on the hard mask layer;

[0027] Exposing the third photoresist layer using a third photomask to form a third exposed photoresist layer, wherein the line widths of the light leakage parts of the third photomask are all the same, and the line widths of the light shielding parts of the third photomask are all the same;

[0028] Developing the third exposure photoresist layer, etching the hard mask layer, transferring the pattern of the third photomask to the hard mask layer, and removing the third exposure photoresist layer;

[0029] coating a fourth photoresist layer on the hard mask layer;

[0030] Exposing the fourth photoresist layer using a fourth photomask to form a fourth exposed photoresist layer, wherein the hard mask layer includes at least a first region and a second region, the fourth photomask includes a light-transmitting portion and a light-shielding portion, the light-transmitting portion of the fourth photomask covers one of the first region and the second region, and the light-shielding portion of the fourth photomask covers the other of the first region and the second region;

[0031] developing an exposed portion or an unexposed portion of the fourth exposure photoresist layer, and etching the substrate according to the hard mask layer;

[0032] The fourth exposure photoresist layer is removed, and the substrate is etched according to the hard mask layer to form a grating structure, wherein a height of the first region of the grating structure is different from a height of the second region.

[0033] Optionally, after the first region and the second region form partition gratings with different heights, the method further comprises:

[0034] Coating an organic film layer on the substrate, and coating a fifth photoresist layer on the organic film layer;

[0035] Exposing the fifth photoresist layer using a third photomask to form a fifth exposed photoresist layer;

[0036] Developing the fifth exposed photoresist layer; and performing O2 plasma shaping on the developed fifth exposed photoresist layer to form a shaped fifth exposed photoresist layer;

[0037] Etching the organic film layer with the shaped fifth exposure photoresist layer, and transferring the pattern of the shaped fifth exposure photoresist layer to the organic film layer;

[0038] removing the shaped fifth exposure photoresist layer, and coating a sixth photoresist layer on the organic film layer; exposing the sixth photoresist layer using a fourth photomask to form a sixth exposure photoresist layer;

[0039] Development, based on the organic film layer, etching the substrate to form a grating structure, the duty cycle of the first region of the grating structure is different from the duty cycle of the second region, and the height of the first region is different from the height of the second region.

[0040] Optionally, the substrate is one of a silicon substrate, a glass substrate, a lithium niobate substrate, a magnesium fluoride substrate, a zinc sulfide substrate, a gallium arsenide substrate, a silicon dioxide substrate, a silicon nitride substrate, a silicon carbide substrate, a gallium nitride substrate or an indium phosphide substrate.

[0041] In a third aspect, an embodiment of the present invention provides a diffraction optical waveguide, comprising an in-coupling grating region, a turning grating region and an out-coupling grating region, wherein each grating region is prepared based on the partitioned grating preparation method as described in any embodiment of the present invention.

[0042] In a fourth aspect, an embodiment of the present invention provides an augmented reality device, including the diffractive optical waveguide provided by an embodiment of the present invention.

[0043] According to the method for preparing a partitioned grating proposed in an embodiment of the present invention, first, a substrate is provided; a first photoresist layer is coated on the substrate; then the first photoresist layer is exposed using a first light mask to form a first exposure photoresist layer; then the first exposure photoresist layer is developed, and the first exposure photoresist layer forms a first graphic mask layer, wherein the first exposure photoresist layer includes at least a first region and a second region, the first region and the second region both include a plurality of exposure portions and a plurality of unexposed portions, and the first development time of the first region is greater than the second development time of the second region; finally, the substrate is etched according to the first graphic mask layer, and the first photoresist layer is removed to form a grating structure, and the duty cycle of the first region of the grating structure is different from the duty cycle of the second region. Thus, by setting the development time of the first region and the second region differently, the line width of the first graphic mask layer of the first region and the second region can be changed, so that the substrate is etched with the first graphic mask layer of different line widths located in the first region and the second region, so that the duty cycle of the first region and the second region is different. Furthermore, compared with the stepper lithography or electron beam direct writing method, time cost and processing cost are saved.

[0044] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0046] Figure 1 is a flow chart of a method for preparing a partitioned grating according to an embodiment of the present invention;

[0047] Figure 2 is a process structure flow chart of a method for preparing a partitioned grating proposed in an embodiment of the present invention;

[0048] Figure 3 is a flow chart of a method for preparing a partitioned grating according to an embodiment of the present invention;

[0049] Figure 4 It is a process structure flow chart of a method for preparing a partitioned grating proposed in one embodiment of the present invention;

[0050] Figure 5 is a flow chart of a method for preparing a partitioned grating according to another embodiment of the present invention;

[0051] Figure 6 is a process structure flow chart of a method for preparing a partitioned grating according to another embodiment of the present invention;

[0052] Figure 7 is a flow chart of a method for preparing a partitioned grating according to another embodiment of the present invention;

[0053] Figure 8 is a process structure flow chart of a method for preparing a partitioned grating proposed in another embodiment of the present invention;

[0054] Fig. 9 is a flow chart of a method for preparing a partitioned grating according to another embodiment of the present invention;

[0055] Fig.10 is a process structure flow chart of a method for preparing a partitioned grating according to another embodiment of the present invention;

[0056] Fig.11 It is an electronic scanning diagram of the grating line width at different development times in the method for preparing the partitioned grating proposed in the embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0058] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0059] Augmented Reality (AR) technology is a technology that integrates computer-generated virtual information with the real world. AR near-eye display devices, represented by AR glasses, transmit the images of microdisplays to the human eye through a series of optical imaging elements, and its perspective characteristics allow the real scene to be reflected in the human eye at the same time, greatly enhancing the sense of reality. At present, the more mature optical imaging solutions mainly include prisms, free-form surfaces, off-axis holographic lenses, array waveguides, volume holographic grating waveguides, and diffraction grating waveguides. Among them, the diffraction grating waveguide mainly uses photolithography technology to make surface relief gratings on the surface of the waveguide to achieve image coupling and decoupling. It has a large field of view, light weight, and its process is compatible with the mature manufacturing technology of the semiconductor industry, with high mass production yield. Therefore, the diffraction grating waveguide is a popular AR display optical imaging solution. However, in the existing diffraction grating waveguide, the image light beam is transmitted forward in the output area while emitting light toward the human eye during display. Therefore, the light output efficiency may be high on the side of the output grating close to the input grating, while the light output efficiency may be low on the side far from the input grating, which in turn causes the problem of uneven overall exit pupil in the existing diffraction light waveguide.

[0060] In order to solve the problem of uneven pupil of the existing diffraction light waveguide, some people have proposed a method of partitioning the output grating area and / or the turning grating area on the waveguide substrate. By partitioning the output grating area and / or the turning grating area, and making the grating parameters (such as height, duty cycle, etc.) of different areas different, the problem of uniformity can be effectively solved. However, there are problems in preparing such partitioned gratings. Because the grating parameters of different partitions are different, during preparation, either a stepper lithography machine is used to prepare the gratings of different partitions, or an electron beam direct writing method is used. However, no matter which method is used, there are problems of long processing cycle and high processing cost.

[0061] Therefore, the present invention proposes a method for preparing a partitioned grating, which is described in detail below.

[0062] Figure 1 It is a flow chart of a method for preparing a partitioned grating proposed in an embodiment of the present invention. Figure 2 FIG. 1 is a process flow chart of a method for preparing a partitioned grating according to an embodiment of the present invention. Figure 1 and Figure 2 As shown, the preparation method comprises:

[0063] S101, providing a substrate.

[0064] The substrate 101 may be one of a silicon substrate, a glass substrate, a lithium niobate substrate, a magnesium fluoride substrate, a zinc sulfide substrate, a gallium arsenide substrate, a silicon dioxide substrate, a silicon nitride substrate, a silicon carbide substrate, a gallium nitride substrate or an indium phosphide substrate. The substrate 101 may be used as a material for making a grating, and in practical applications, a substrate material may be selected according to actual requirements of the grating, such as a refractive index.

[0065] S102, coating a first photoresist layer on the substrate.

[0066] Wherein, the first photoresist layer 102 can be coated on the substrate 101 by spin coating. And, before coating the first photoresist layer 102, the substrate 101 can be cleaned first, so that the first photoresist layer 102 can better contact with the substrate 101. In addition, the first photoresist layer 102 can be a positive photoresist layer, or a negative photoresist layer. After the positive photoresist layer is exposed and developed, the exposed part first reacts with the developer. After the negative photoresist layer is exposed and developed, the unexposed part first reacts with the developer. In the following embodiments, the positive photoresist layer is used as an example for description.

[0067] S103, exposing the first photoresist layer using a first photomask to form a first exposed photoresist layer, wherein the line widths of the light leakage parts of the first photomask are all the same, and the line widths of the light shielding parts of the first photomask are all the same.

[0068] It is understandable that the line width of the light leakage part and the light shielding part of the first light mask 103 can also be the same or different. The present invention does not make specific restrictions on this, and can select a suitable first light mask 103 according to actual needs. Exemplary, the first light mask with the following characteristics can be selected, and the line width of the first light mask 103 can be the line width of a certain area in the partition grating. After the first photoresist layer 102 is exposed, the pattern on the first light mask 103 is transferred to the first photoresist layer 102.

[0069] S104, developing the first exposed photoresist layer to form a first patterned mask layer, wherein the first exposed photoresist layer includes at least a first region and a second region, each of the first region and the second region includes a plurality of exposed portions and a plurality of unexposed portions, and a first development time of the first region is greater than a second development time of the second region.

[0070] Optionally, developing the first exposed photoresist layer to form a first patterned mask layer includes:

[0071] The first region is developed alone and maintained for a first time, and then the first region and the second region are simultaneously developed and maintained for a second time.

[0072] When developing the first exposed photoresist layer, a developer (exemplarily, TMAH 2.38% developer) may be used. If the first photoresist layer is a positive photoresist, the exposed portion will react with the developer first, and the unexposed portion will also react slowly as the first exposed photoresist layer is immersed in the developer.

[0073] It can be understood that in order to make the duty ratios of the first area 01 and the second area 02 different, the first area 01 can be located in the developer (for example, the substrate is vertically immersed in the developer), and then developed for a preset time (for example, 20 seconds). Then, the substrate is controlled to move into the developer so that the second area 02 is completely located in the developer. At this time, the first area 01 is still in the developer. The developer is developed for a preset time (such as 30 seconds), and then the substrate is taken out to form masks (i.e., partitions) with two different duty ratios on the substrate. That is, when the substrate is taken out, the first area 01 is developed in the developer for 50 seconds, and the second area 02 is developed in the developer for 30 seconds, thereby obtaining two grating masks with different duty ratios.

[0074] In other embodiments, multiple regions may be included, and each region enters the developer at a different time, so that grating masks with different duty cycles can be obtained.

[0075] In addition to obtaining grating masks with different duty ratios by using different development times, the development speed can also be increased by adjusting the developer concentration and the development temperature. Different exposure areas or different development areas of the same exposure area use different process conditions for development, and the line width after development will also be different, resulting in different duty ratios.

[0076] Among them, in order to ensure the effectiveness of the photoresist layer, the development time of each area shall not exceed the time for the photoresist to completely dissolve or fall off. And the preset development time can be determined in advance according to the concentration of the developer, the thickness of the photoresist, the baking temperature, the line width of the partition grating, the line width of the first light mask, etc. For example, according to the preset development time of the first area 01, it is 60s, the TMAH concentration is 2.38%, and the development temperature is 23°C; the preset development time of the second area 02 is 40s, the TMAH concentration is 2.38%, and the temperature is 21°C. The line width of the first area obtained after development is smaller than the line width of the second area, that is, the duty cycle is small. Fig.11 1 is an electronic scanning diagram of the grating line width at different development times in the method for preparing the partitioned grating according to the embodiment of the present invention. Fig.11 As shown, Fig.11 (a) is the electronic scanning diagram of the grating line width with a preset time of 50s. Fig.11 (b) is the electronic scanning diagram of the grating line width with a preset time of 60s. Fig.11(c) is an electronic scanning diagram of the grating line width with a preset time of 80s. Fig.11 (d) To display the electronic scanning image of the grating line width with a preset time of 120s, you can Fig.11 It can be seen that the longer the development time, the narrower the grating line width.

[0077] S105, etching the substrate according to the first patterned mask layer and removing the first photoresist layer to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region.

[0078] Therefore, by controlling the development time of different areas in the development step, the different duty ratios of the grating mask are controlled, and then when the pattern is transferred and the substrate is etched, a partitioned grating with different duty ratios is formed. Compared with the preparation of gratings of different partitions by stepper lithography or electron beam direct writing, a certain process step is saved, thereby saving time cost and corresponding equipment cost.

[0079] Figure 3 It is a flow chart of a method for preparing a partitioned grating proposed in one embodiment of the present invention. Figure 4 FIG. 1 is a process flow chart of a method for preparing a partitioned grating according to an embodiment of the present invention. Figure 3 and Figure 4 As shown, the preparation method comprises:

[0080] S201, providing a substrate.

[0081] After providing a substrate, the method further includes: S202, forming a hard mask layer on the substrate.

[0082] The material of the hard mask layer 104 may be one of silicon dioxide, silicon nitride, silicon carbide, aluminum oxide, metal chromium, metal tungsten or metal molybdenum. The hard mask layer 104 may be formed on the substrate 101 by deposition.

[0083] S203, coating a first photoresist layer on the substrate includes: coating the first photoresist layer on the hard mask layer.

[0084] S204, exposing the first photoresist layer using a first photomask to form a first exposed photoresist layer, wherein the line widths of the light leakage parts of the first photomask are all the same, and the line widths of the light shielding parts of the first photomask are all the same.

[0085] S205, developing the first exposed photoresist layer to form a first patterned mask layer, wherein the first exposed photoresist layer includes at least a first region and a second region, each of the first region and the second region includes a plurality of exposed portions and a plurality of unexposed portions, and a first development time of the first region is greater than a second development time of the second region.

[0086] S206, etching the substrate according to the first graphic mask layer, and removing the first photoresist layer to form a grating structure, wherein the duty cycle of the first region of the grating structure is different from the duty cycle of the second region, comprises: etching the hard mask layer according to the first graphic mask layer, removing the first photoresist layer, and etching the substrate according to the hard mask layer to form a grating structure, wherein the duty cycle of the first region of the grating structure is different from the duty cycle of the second region.

[0087] After etching the substrate, the hard mask layer may be cleaned.

[0088] In this embodiment, by setting the hard mask layer 104, the pattern can be first transferred to the hard mask layer 104, and then the pattern of the hard mask layer 104 can be transferred to the substrate, so as to avoid the pattern from breaking when etching the substrate. This is beneficial to improving the product yield. The contents of the remaining steps are the same as those of the previous embodiment and have the same technical effects, and will not be repeated here.

[0089] Figure 5 It is a flow chart of a method for preparing a partitioned grating proposed in another embodiment of the present invention. Figure 6 FIG. 1 is a process flow chart of a method for preparing a partitioned grating according to another embodiment of the present invention. Figure 5 and Figure 6 As shown, after etching the hard mask layer according to the first patterned mask layer to remove the first photoresist layer, that is, after etching the hard mask layer in step S206 of the previous embodiment, the following steps are also included:

[0090] S301, coating a second photoresist layer on the hard mask layer.

[0091] The material of the second photoresist layer 105 can be the same as that of the first photoresist layer 102. The coating of the second photoresist layer 105 needs to cover the hard mask layer 104.

[0092] S302, exposing the second photoresist layer using a second photomask to form a second exposed photoresist layer; wherein the light-transmitting portion of the second photomask covers one of the first region and the second region, and the light-shielding portion of the second photomask covers the other of the first region and the second region;

[0093] The second light mask 106 may be set in advance according to the size and shape of the required area.

[0094] S303, developing the exposed portion or the unexposed portion of the second exposure photoresist layer, and etching the substrate according to the hard mask layer.

[0095] Wherein, in this embodiment, the second photoresist layer 105 can be a positive photoresist layer or a negative photoresist layer. When the second photoresist layer 105 is a positive photoresist layer, the exposed portion of the second exposure photoresist layer can be developed, and the substrate is etched according to the hard mask layer. When the second photoresist layer 105 is a negative photoresist layer, the unexposed portion of the second exposure photoresist layer can be developed, and the substrate is etched according to the hard mask layer. In addition, when developing, whether the first area is exposed or the second area is exposed, it depends on actual needs. Exemplarily, if the second photoresist layer 105 is a positive photoresist, if the height of the grating in the first area is higher than the height of the grating in the second area, the second light mask 106 can expose the first area 01, and the second area 01 is shielded, so that the first area 01 is exposed after development. If the height of the grating in the first region 01 is required to be lower than the height of the grating in the second region 02 , the second photomask 106 can expose the second region 02 and shield the first region 01 , so that the second region 02 is exposed after development.

[0096] Figure 6 In the example, the second photoresist layer 105 is a positive photoresist layer and the second region 02 is exposed. It can be seen from step S303 that the exposed part is developed, and the hard mask layer of the second region is exposed. The substrate is etched according to the pattern of the hard mask layer, and the pattern on the hard mask layer is transferred to the substrate. At this time, the first region 01 is still blocked by the second photoresist layer 105, and thus the first region 01 cannot be etched, and the first region 01 of the substrate remains original.

[0097] S304, removing the second exposure photoresist layer, etching the substrate according to the hard mask layer to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region, and the height of the first region is different from the height of the second region.

[0098] After removing the second exposure photoresist layer, the substrate can be etched according to the hard mask layer, and after etching the substrate, the hard mask layer can be cleaned, so that the first region 01 and the second region 02 form partitioned gratings with different duty ratios and heights. Figure 6 As can be seen from S304, the grating line width of the first region 01 is smaller than that of the second region 02 due to the different first development time, that is, the duty cycle is different. The grating height of the first region 01 is smaller than that of the second region 02 due to the different etching depths, that is, the heights are different.

[0099] Thus, through this embodiment, a partition grating with different duty cycles and different heights can be formed. In this process, the first photoresist layer 102 is exposed by using the first light mask 103, and the development time is controlled to be different, so that a photoresist layer with different duty cycles is formed above the hard mask layer 104. And by etching the hard mask layer 104, the pattern is transferred to the hard mask layer 104. Then, through the setting of the second photoresist layer 105 and the exposure of the second light mask 106, by controlling the different exposure areas, the part that needs to be higher in height is first exposed, developed and etched to form a pattern transfer, and then the part with lower height is etched to form a final partition grating. Among them, the first light mask 103 and the second light mask 104 can both use a universal light mask, and there is no need to customize according to the specific size of the partition grating, thereby improving the utilization rate of the first light mask 103 and the second light mask 104. In addition, the provision of the hard mask layer 104 protects the pattern transfer process, so that the top heights of the patterns finally formed on the substrate 101 are all the same.

[0100] Optionally, the first light mask is a one-dimensional or two-dimensional light mask. When the partitioned grating to be prepared is a one-dimensional grating, a one-dimensional first light mask can be used, and when the partitioned grating to be prepared is a two-dimensional grating, a two-dimensional first light mask can be used.

[0101] Among them, the one-dimensional or two-dimensional preparation of the grating is achieved by changing the first light mask, avoiding the complicated preparation method of first preparing one dimension and then preparing another dimension, and simplifying the process steps.

[0102] Figure 7 It is a flow chart of a method for preparing a partitioned grating proposed in yet another embodiment of the present invention. Figure 8 It is a process structure flow chart of a method for preparing a partitioned grating proposed in yet another embodiment of the present invention.

[0103] like Figure 7 and Figure 8 As shown, the method for preparing a partitioned grating provided in an embodiment of the present invention comprises:

[0104] S401, providing a substrate.

[0105] The substrate 201 may be one of a silicon substrate, a glass substrate, a lithium niobate substrate, a magnesium fluoride substrate, a zinc sulfide substrate, a gallium arsenide substrate, a silicon dioxide substrate, a silicon nitride substrate, a silicon carbide substrate, a gallium nitride substrate or an indium phosphide substrate. The substrate 201 may be used as a material for making a grating, and in practical applications, a substrate material may be selected according to actual requirements of the grating, such as a refractive index.

[0106] S402, forming a hard mask layer on the substrate.

[0107] The material of the hard mask layer 204 may be one of silicon dioxide, silicon nitride, silicon carbide, aluminum oxide, metal chromium, metal tungsten or metal molybdenum. The hard mask layer 204 may be formed on the substrate 201 by deposition.

[0108] S403, coating a third photoresist layer on the hard mask layer.

[0109] The third photoresist layer 202 may be made of the same material as the first photoresist layer and the second photoresist layer. For example, the third photoresist layer 202 may be a positive photoresist.

[0110] S404, exposing the third photoresist layer using a third photomask to form a third exposed photoresist layer, wherein the line widths of the light leakage parts of the third photomask are all the same, and the line widths of the light shielding parts of the third photomask are all the same.

[0111] The third light mask 203 may be the same as the first light mask 103 .

[0112] S405, developing the third exposure photoresist layer, etching the hard mask layer, transferring the pattern of the third photomask to the hard mask layer, and removing the third exposure photoresist layer.

[0113] S406, coating a fourth photoresist layer on the hard mask layer;

[0114] S407, exposing the fourth photoresist layer using a fourth photomask to form a fourth exposed photoresist layer, wherein the hard mask layer includes at least a first region and a second region, the fourth photomask includes a light-transmitting portion and a light-shielding portion, the light-transmitting portion of the fourth light mask covers one of the first region and the second region, and the light-shielding portion of the fourth light mask covers the other of the first region and the second region.

[0115] The fourth light mask 206 may be the same as the second light mask 106 .

[0116] S408, developing the exposed portion or the unexposed portion of the fourth exposure photoresist layer, and etching the substrate according to the hard mask layer;

[0117] S409, removing the fourth exposure photoresist layer, etching the substrate according to the hard mask layer to form a grating structure, wherein the height of the first region of the grating structure is different from the height of the second region.

[0118] Therefore, in this embodiment, the fourth photoresist layer 205 can be made of the same material as the third photoresist layer 202, both of which are positive photoresists. The fourth photoresist layer is coated on the hard mask layer 204 forming the pattern, and is exposed through the fourth photoresist mask 206. After development, the portion to be etched is exposed. During etching in step S408, the unexposed portion of the fourth photoresist layer is not developed, and then another area can be covered. Finally, during etching in step S409, a partitioned grating with different grating heights is formed.

[0119] Optionally, Fig. 9 It is a flow chart of a method for preparing a partitioned grating proposed in yet another embodiment of the present invention. Fig.10 The process structure flow chart of the method for preparing the partitioned grating proposed in another embodiment of the present invention is as follows. After forming the partitioned gratings with different heights in the first area and the second area of ​​the previous embodiment, the method further includes:

[0120] S410, coating an organic film layer on the substrate, and coating a fifth photoresist layer on the organic film layer.

[0121] The purpose of coating the organic film layer is to flatten the pattern already formed on the substrate, and the purpose of coating the fifth photoresist layer on the organic film layer is to etch the organic film layer in the subsequent process steps.

[0122] S411, the fifth photoresist layer is exposed using the third photomask to form a fifth exposed photoresist layer. The third photomask is used to expose the fifth photoresist layer, and the size of the exposed portion may correspond to the pattern previously left on the substrate.

[0123] S412, developing the fifth exposed photoresist layer; and performing O2 plasma shaping on the developed fifth exposed photoresist layer to form a shaped fifth exposed photoresist layer.

[0124] Among them, performing O2 plasma shaping on the fifth exposed photoresist layer after development can make the fifth exposed photoresist layer smaller, thereby reducing the line width of subsequent etching and reducing the duty cycle.

[0125] S413, etching the organic film layer with the shaped fifth exposure photoresist layer, and transferring the pattern of the shaped fifth exposure photoresist layer to the organic film layer.

[0126] In this step, the etching depth of the organic film layer cannot be lower than the original height of the substrate.

[0127] S414, removing the shaped fifth exposure photoresist layer, coating a sixth photoresist layer on the organic film layer, and exposing the sixth photoresist layer using a fourth photomask to form a sixth exposure photoresist layer.

[0128] S415, developing, etching the substrate based on the organic film layer to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region, and the height of the first region is different from the height of the second region.

[0129] By setting the sixth photoresist layer and using the fourth light mask, after development in step S415, when etching the substrate based on the organic film layer, the unexposed portion of the sixth photoresist layer protects the covered portion of the substrate, so that it will not be etched. Finally, the organic film layer and the unexposed sixth photoresist layer are cleaned off to obtain partitioned gratings with different duty cycles and different heights. Furthermore, there is no need for stepper lithography or electron beam direct writing, which saves time cost and processing cost compared to these two methods.

[0130] In one embodiment, a substrate may be provided first, and then an organic mask layer may be formed, and then a seventh photoresist layer may be formed, and the seventh photoresist layer may be exposed and developed through a first photomask, and then the organic mask layer may be etched to remove the seventh photoresist layer. Then an eighth photoresist layer may be formed, and the eighth photoresist layer may be exposed and developed through a second photomask, and the organic mask layer may be exposed through O2plasma shaping, and the substrate may be etched using the shaped organic mask layer to form a pattern on the substrate. Then, the eighth photoresist layer may be stripped and removed to expose another portion of the organic mask layer, and the substrate may be further etched through the organic mask layer to form patterns with different duty ratios and heights on the substrate.

[0131] Based on the same inventive concept, an embodiment of the present invention provides a diffractive optical waveguide, including an in-coupling grating region, a turning grating region and an out-coupling grating region, each grating region being prepared based on a partitioned grating preparation method as in any embodiment of the present invention. The diffractive optical waveguide provided by the embodiment of the present invention has the technical effect of the technical solution in any of the above embodiments, and the explanation of the structures and terms that are the same or corresponding to the above embodiments will not be repeated here.

[0132] Based on the same inventive concept, an embodiment of the present invention proposes an augmented reality device, including the diffractive optical waveguide proposed in the embodiment of the present invention. The augmented reality device provided by the embodiment of the present invention has the technical effect of the technical solution in any of the above embodiments, and the explanation of the structures and terms that are the same or corresponding to the above embodiments will not be repeated here. The augmented reality device can be a device such as AR glasses.

[0133] In summary, according to the method for preparing a partitioned grating proposed in an embodiment of the present invention, first, a substrate is provided; a first photoresist layer is coated on the substrate; then the first photoresist layer is exposed using a first photomask to form a first exposure photoresist layer; then the first exposure photoresist layer is developed, and the first exposure photoresist layer forms a first graphic mask layer, wherein the first exposure photoresist layer includes at least a first region and a second region, the first region and the second region both include a plurality of exposure portions and a plurality of unexposed portions, the first development time of the first region is greater than the second development time of the second region, and the first development time is less than or equal to the time for completely developing the unexposed portion or the exposed portion of the first photomask; finally, the substrate is etched according to the first graphic mask layer, and the first photoresist layer is removed to form a grating structure, and the duty cycle of the first region of the grating structure is different from the duty cycle of the second region. Thus, by setting the development time of the first region and the second region differently, the line width of the first graphic mask layer in the first region and the second region can be changed, so that the substrate is etched with the first graphic mask layer with different line widths located in the first region and the second region, so that the duty cycle of the first region and the second region is different. Furthermore, compared with stepper lithography or electron beam direct writing, time and processing costs are saved.

[0134] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0135] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a partitioned grating, characterized in that: include: providing a substrate; coating a first photoresist layer on the substrate; Exposing the first photoresist layer using a first photomask to form a first exposed photoresist layer, wherein the line widths of the light leakage parts of the first photomask are all the same, and the line widths of the light shielding parts of the first photomask are all the same; Developing the first exposed photoresist layer to form a first patterned mask layer, wherein the first exposed photoresist layer at least includes a first region and a second region, the first region and the second region each include a plurality of exposed portions and a plurality of unexposed portions, and a first developing time of the first region is greater than a second developing time of the second region; The substrate is etched according to the first patterned mask layer, and the first photoresist layer is removed to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region.

2. The method for preparing a partitioned grating according to claim 1, characterized in that: After providing a substrate, the method further includes: forming a hard mask layer on the substrate; The coating of the first photoresist layer on the substrate comprises: coating the first photoresist layer on the hard mask layer; The step of etching the substrate according to the first graphic mask layer and removing the first photoresist layer to form a grating structure, wherein the duty cycle of the first region of the grating structure is different from the duty cycle of the second region comprises: etching the hard mask layer according to the first graphic mask layer, removing the first photoresist layer, and etching the substrate according to the hard mask layer to form a grating structure, wherein the duty cycle of the first region of the grating structure is different from the duty cycle of the second region.

3. The method for preparing a partitioned grating according to claim 1 or 2, characterized in that: The developing the first exposed photoresist layer to form a first patterned mask layer from the first exposed photoresist layer comprises: The first region is developed alone and maintained for a first time, and then the first region and the second region are simultaneously developed and maintained for a second time.

4. The method for preparing a partitioned grating according to claim 2, characterized in that: After etching the hard mask layer according to the first patterned mask layer to remove the first photoresist layer, the method further includes: Coating a second photoresist layer on the hard mask layer forming the first region and the second region; Exposing the second photoresist layer using a second photomask to form a second exposed photoresist layer; wherein a light-transmitting portion of the second photomask covers one of the first region and the second region, and a light-shielding portion of the second photomask covers the other of the first region and the second region; developing an exposed portion or an unexposed portion of the second exposure photoresist layer, and etching the substrate according to the hard mask layer; The second exposure photoresist layer is removed, and the substrate is etched according to the hard mask layer to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region, and the height of the first region is different from the height of the second region.

5. The method for preparing a partitioned grating according to claim 1, characterized in that: The substrate is one of a silicon substrate, a glass substrate, a lithium niobate substrate, a magnesium fluoride substrate, a zinc sulfide substrate, a gallium arsenide substrate, a silicon dioxide substrate, a silicon nitride substrate, a silicon carbide substrate, a gallium nitride substrate or an indium phosphide substrate.

6. The method for preparing a partitioned grating according to claim 1, characterized in that: The first light mask is a one-dimensional or two-dimensional light mask.

7. A method for preparing a partitioned grating, characterized in that: include: providing a substrate; forming a hard mask layer on the substrate; coating a third photoresist layer on the hard mask layer; Exposing the third photoresist layer using a third photomask to form a third exposed photoresist layer, wherein the line widths of the light leakage parts of the third photomask are all the same, and the line widths of the light shielding parts of the third photomask are all the same; Developing the third exposure photoresist layer, etching the hard mask layer, transferring the pattern of the third photomask to the hard mask layer, and removing the third exposure photoresist layer; coating a fourth photoresist layer on the hard mask layer; Exposing the fourth photoresist layer using a fourth photomask to form a fourth exposed photoresist layer, wherein the hard mask layer includes at least a first region and a second region, the fourth photomask includes a light-transmitting portion and a light-shielding portion, the light-transmitting portion of the fourth photomask covers one of the first region and the second region, and the light-shielding portion of the fourth photomask covers the other of the first region and the second region; developing an exposed portion or an unexposed portion of the fourth exposure photoresist layer, and etching the substrate according to the hard mask layer; The fourth exposure photoresist layer is removed, and the substrate is etched according to the hard mask layer to form a grating structure, wherein a height of the first region of the grating structure is different from a height of the second region.

8. The method for preparing a partitioned grating according to claim 7, characterized in that: After the first region and the second region form partition gratings with different heights, the method further includes: Coating an organic film layer on the substrate, and coating a fifth photoresist layer on the organic film layer; Exposing the fifth photoresist layer using a third photomask to form a fifth exposed photoresist layer; Developing the fifth exposed photoresist layer; and performing O2 plasma shaping on the developed fifth exposed photoresist layer to form a shaped fifth exposed photoresist layer; Etching the organic film layer with the shaped fifth exposure photoresist layer, and transferring the pattern of the shaped fifth exposure photoresist layer to the organic film layer; removing the shaped fifth exposure photoresist layer, and coating a sixth photoresist layer on the organic film layer; exposing the sixth photoresist layer using a fourth photomask to form a sixth exposed photoresist layer, and developing the layer; Based on the organic film layer, the substrate is etched to form a grating structure, wherein the duty ratio of the first region of the grating structure is different from the duty ratio of the second region, and the height of the first region is different from the height of the second region.

9. The method for preparing a partitioned grating according to claim 7, characterized in that: The substrate is one of a silicon substrate, a glass substrate, a lithium niobate substrate, a magnesium fluoride substrate, a zinc sulfide substrate, a gallium arsenide substrate, a silicon dioxide substrate, a silicon nitride substrate, a silicon carbide substrate, a gallium nitride substrate or an indium phosphide substrate.

10. A diffractive optical waveguide, characterized in that: It comprises a coupling-in grating region, a turning grating region and an coupling-out grating region, and each grating region is prepared based on the partitioned grating preparation method as described in any one of claims 1-9.

11. An augmented reality device, characterized in that: Comprising the diffractive optical waveguide as claimed in claim 10.

Images