Method for manufacturing diffractive optical waveguide, diffractive optical waveguide and AR display device

Abstract

The application provides a diffraction optical waveguide and a preparation method thereof and an AR display device, wherein, on the basis of defining a coupling-in grating area pattern and a coupling-out grating area pattern by using a patterned hard mask layer, nano-imprinting is performed on a liquid polymer resist based on a grating imprinting template; the patterned polymer resist after imprinting and solidification and the patterned hard mask layer are used to etch the coupling-in grating area and the coupling-out grating area at one time, so that the integration of the coupling-in grating area and the coupling-out grating area is realized, the relative position accuracy of the coupling-in grating area and the coupling-out grating area is effectively ensured, and the display effect of the AR device is further improved. Meanwhile, the second pattern area of the grating imprinting template is provided with grooves with different depths, so that the coupling-out grating units with different depths in the coupling-out grating area can be realized by one-time etching, and the modulation efficiency of the diffraction optical waveguide is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and in particular to a method for fabricating a diffractive waveguide, the diffractive waveguide, and an AR display device. Background Technology

[0002] With the rapid development of semiconductor technology, the interaction between humans and computers is evolving at an unprecedented pace. Augmented Reality (AR) displays offer humans more multidimensional information, and AR technology based on near-eye display devices is currently a hot research topic, attracting widespread attention. Waveguide technology, with its lossless transmission and high penetration, enables thin and light optical lenses while providing users with a large field of view (FOV), ensuring clear imaging. It is considered the mainstream optical solution for consumer-grade AR glasses. Diffractive waveguides are a relatively mainstream optical display solution for AR glasses, and many AR glasses utilize this method. Diffractive waveguides offer advantages such as high mass production capability and thinness, and are gradually gaining recognition in the AR display field, with the potential to become the mainstream technology development direction in the future AR field. The diffraction grating, obtained using micro-nano optical structure technology, is the core component of the diffractive waveguide. The diffraction grating can spatially modulate the phase or amplitude of incident light, and its working principle is based on the Fraunhofer multi-slit diffraction effect.

[0003] However, it is difficult to align the relative positions and angles of the input and output grating regions of a separately fabricated diffractive waveguide, while the quality of AR display depends heavily on the accuracy of the relative positions of the input and output grating regions.

[0004] In addition, based on traditional micro-nano fabrication technologies, such as mechanical scribing, photolithography, and ion etching, the trench depths obtained are all of uniform depth and periodicity, and large-area fabrication cannot be achieved efficiently. At the same time, the photolithography process in traditional micro-nano processes has many limiting factors that reduce resolution, ultimately resulting in the inability to improve the modulation efficiency of gratings or diffraction elements, and the optical waveguide performance not meeting expectations. Summary of the Invention

[0005] In view of the above problems, the present invention proposes a method for fabricating a diffractive optical waveguide to achieve integrated forming of the coupled-in grating region and the coupled-out grating region, effectively ensuring the relative positional accuracy of the coupled-in grating region and the coupled-out grating region, and the fabrication of grating structures of unequal depths in the coupled-out grating region can be achieved by a single etching process.

[0006] According to a first aspect of the present invention, a method for fabricating a diffractive optical waveguide is provided, comprising:

[0007] A grating embossing template is provided, wherein the grating embossing template has a first graphic area and a second graphic area, and the second graphic area is provided with grooves of varying depths;

[0008] A diffractive waveguide substrate is provided, and a patterned hard mask layer is formed on the diffractive waveguide substrate. The patterned hard mask layer defines a coupled-in grating region pattern and a coupled-out grating region pattern, wherein the coupled-in grating region pattern includes a plurality of coupled-in grating unit patterns, and the coupled-out grating region pattern includes a plurality of coupled-out grating unit patterns.

[0009] A liquid polymer resist is spin-coated onto the diffractive waveguide substrate, the liquid polymer resist covering the surface of the patterned hard mask layer and filling the gaps between adjacent hard mask patterns; wherein the thickness of the liquid polymer resist on the surface of the patterned hard mask layer is greater than or equal to the depth of the deepest groove in the second patterned region;

[0010] The grating imprint template is pressed onto the diffractive waveguide substrate so that the groove of the grating imprint template is filled with the liquid polymer resist, and the first pattern area on the grating imprint template is aligned with the pattern of the coupled grating area, and the second pattern area is aligned with the pattern of the coupled grating area.

[0011] The liquid polymer resist is cured to form a patterned solid polymer resist, the pattern of which corresponds to the pattern on the grating imprint template;

[0012] Remove the grating imprint template;

[0013] Using the patterned solid polymer resist and the patterned hard mask layer as a mask, the diffractive waveguide substrate is etched to integrally form a coupling grating region and a coupling grating region on the diffractive waveguide substrate, wherein the coupling grating region has coupling grating units of unequal depth.

[0014] Optionally, the bottom of the first graphic region is flattened so that the depth of the coupling grating units in the coupling grating region is equal.

[0015] Optionally, the area of ​​the liquid polymer resist spin-coated on the diffractive waveguide substrate is larger than the area of ​​the regions corresponding to the coupled-in grating region pattern and the coupled-out grating region pattern.

[0016] Optionally, providing a grating imprint template specifically includes:

[0017] Provide a grating embossing template substrate;

[0018] The grating imprint template substrate is subjected to multiple photolithography and etching processes to form the first patterned area and the second patterned area.

[0019] Optionally, the first patterned region and the second patterned region together include N grooves of different depths, and the second patterned region includes at least two grooves of different depths. The step of performing multiple photolithography and etching processes on the grating imprint template substrate to form the first patterned region and the second patterned region includes:

[0020] A Kth patterned mask layer is formed on the surface of the grating embossing template substrate; wherein the pattern of the Kth patterned mask layer corresponds to the pattern of a groove of Kth depth;

[0021] Using the Kth patterned mask layer as a mask, the surface of the grating imprint template substrate is etched for the Kth time to form a groove of the Kth depth corresponding to the first patterned region and / or the second patterned region;

[0022] Repeat the above steps until all grooves in the first graphic area and the second graphic area are formed; where K and N are positive integers, and N≥2, 1≤K≤N.

[0023] Optionally, the mask layer for the Kth patterning is a photoresist mask or a hard mask.

[0024] Optionally, a patterned hard mask layer is formed on the diffractive waveguide substrate. The patterned hard mask layer defines the coupling-in grating region pattern and the coupling-out grating region pattern, specifically including:

[0025] A hard mask layer is formed on the diffractive waveguide substrate;

[0026] A patterned photoresist is formed on the hard mask layer, wherein the pattern of the patterned photoresist corresponds to the pattern of the coupled-in grating region and the pattern of the coupled-out grating region;

[0027] Using the patterned photoresist as a mask, the hard mask layer is etched to form the patterned hard mask layer.

[0028] Optionally, the shape of the first graphic region and / or the second graphic region is a closed shape enclosed by curves and / or straight lines.

[0029] Optionally, the thickness of the liquid polymer resist on the surface of the patterned hard mask layer is 10-30 nm greater than the depth of the deepest groove in the second patterned region.

[0030] Optionally, the depth of the coupling grating unit in the coupling grating region is 100nm to 400nm.

[0031] According to a second aspect of the present invention, a diffractive optical waveguide is provided, which is prepared by the method for preparing a diffractive optical waveguide as described in the first aspect of the present invention.

[0032] According to a third aspect of the present invention, an AR display device is provided, comprising the diffractive waveguide as described in the second aspect of the present invention.

[0033] The method for fabricating diffractive waveguides provided by this invention defines the coupled-in grating region pattern and the coupled-out grating region pattern using a patterned hard mask layer. Based on the grating imprinting template, a liquid polymer resist is nanoimprinted. Using the imprinted and cured patterned polymer resist and the patterned hard mask layer, the coupled-in grating region and the coupled-out grating region can be etched in one step, thereby realizing the integrated forming of the coupled-in grating region and the coupled-out grating region. This effectively ensures the relative positional accuracy of the coupled-in grating region and the coupled-out grating region, which is beneficial to further improving the display effect of AR devices.

[0034] Meanwhile, because the second patterned region of the grating imprint template has grooves of varying depths, coupling grating units of varying depths can be fabricated in the coupling grating region with a single etching operation, effectively improving the modulation efficiency of the diffractive waveguide. Furthermore, since multiple etching operations are not required, the problem of inaccurate alignment that may result from repeated etching is avoided, facilitating the large-area, mass production of diffractive waveguide patterns.

[0035] In a further preferred embodiment, by setting the area range of the liquid polymer resist spin-coated on the diffractive waveguide substrate to be larger than the area range corresponding to the coupled-in grating region and the coupled-out grating region, the alignment accuracy requirements between the grating imprint template and the diffractive waveguide substrate are reduced, that is, the alignment accuracy requirements between the coupled-in grating region and the coupled-out grating region and the diffractive waveguide substrate are reduced. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic flowchart of a method for fabricating a diffractive optical waveguide according to an embodiment of the present invention;

[0038] Figure 2A-2G This is a schematic cross-sectional view of the device structure at different process stages according to the fabrication method of the diffractive waveguide provided in an embodiment of the present invention;

[0039] Figure 2H This is a schematic diagram of the structure of a grating embossing template provided in one embodiment of the invention;

[0040] Figure 3 This is a top view schematic diagram showing that, during the fabrication of a diffractive optical waveguide according to an embodiment of the present invention, the area of ​​the liquid polymer resist on the diffractive optical waveguide substrate is larger than the area of ​​the grating imprint template.

[0041] Explanation of reference numerals in the attached figures:

[0042] 201 - Grating Imprinting Template;

[0043] 202 - First graphic area;

[0044] 203 - Second graphic area;

[0045] 204-Diffraction waveguide substrate;

[0046] 205 - A patterned hard mask layer;

[0047] 206 - Coupled grating unit pattern;

[0048] 207 - Coupled-out grating unit pattern;

[0049] 208 - Coupled into the grating region;

[0050] 209 - Coupling grating region;

[0051] 210 - Liquid polymer resist;

[0052] 211 - Cured polymer resist;

[0053] 212-Coupled grating unit;

[0054] 213-Coupled grating unit. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0057] Given that the relative positions of the separately fabricated coupling grating regions and coupling grating regions are difficult to align in traditional diffractive waveguide fabrication processes, and that traditional micro / nano fabrication techniques such as mechanical scribing, photolithography, and ion etching produce trenches of uniform depth and periodicity, this invention proposes a method for fabricating diffractive waveguides. Based on defining the coupling grating region and coupling grating region patterns using a patterned hard mask layer, a liquid polymer resist is nanoimprinted using a grating imprinting template. Utilizing the imprinted and cured patterned polymer resist and the patterned hard mask layer, the coupling grating region and coupling grating region can be etched in a single step, achieving integrated forming of the coupling grating region and coupling grating region, effectively ensuring the relative positional accuracy of the coupling grating region and coupling grating region. Meanwhile, because the second patterned region of the grating imprint template has grooves of varying depths, coupling grating units of varying depths can be fabricated in the coupling grating region with a single etching operation, effectively improving the modulation efficiency of the diffractive waveguide. Furthermore, since multiple etching operations are not required, the problem of inaccurate alignment that may result from repeated etching is avoided, facilitating the large-area, mass production of diffractive waveguide patterns.

[0058] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0059] Please refer to Figure 1 and combined Figure 2A-2G The fabrication method of the diffractive optical waveguide provided in this embodiment of the invention includes S1-S7, as detailed below:

[0060] S1: A lenticular impression template 201 is provided, wherein the lenticular impression template has a first graphic area 202 and a second graphic area 203, and the second graphic area 203 is provided with grooves of varying depths, such as... Figure 2A As shown. Of course, it should be understood that the present invention is not limited thereto, and the first graphic area 202 may also be provided with grooves of varying depths, and this embodiment is also within the protection scope of the present invention.

[0061] As an example, S1 may specifically include the following steps S11-S13:

[0062] S11: Provides a grating embossing template substrate;

[0063] S12: Perform multiple photolithography and etching processes on the grating imprint template substrate to form the first pattern area 202 and the second pattern area 203;

[0064] As an example, the substrate material of the grating embossing template can be SiO2. Of course, it should be understood that this invention is not limited to this, and other materials used in grating embossing templates are also within the scope of this invention.

[0065] Specifically, as an example, the lenticular embossing template also has a third region in addition to the first graphic region 202 and the second graphic region 203, which includes a groove of a certain depth, such as... Figure 2A As shown, the third region includes three grooves c1-c3, and the three grooves c1-c3 have the same depth. The depth of the three grooves c1-c3 is equal to the depth of the deepest groove in the first patterned region 202 and the second patterned region 203. Of course, it should be understood that the present invention is not limited thereto. The groove depth of the third region can also be greater than or less than the depth of the deepest groove in the first patterned region 202 and the second patterned region 203, as long as it satisfies the requirement that after the diffractive waveguide substrate 204 is imprinted with spin-coated solid polymer resist 211 using the grating imprint template 201, the hard mask layer corresponding to the third region is not completely etched when the diffractive waveguide substrate 204 is etched using the patterned solid polymer resist 211 and the patterned hard mask layer 205 as masks. However, it should be noted that, practically, the groove depth of the third region is equal to the depth of one of the grooves in the first patterned region 202 and the second patterned region 203; wherein, when the groove depth of the third region is equal to the depth of the shallowest groove in the first patterned region 202 and the second patterned region 203, the number of etching steps in the fabrication process of the grating imprint template is minimized. The third region can be understood as including the interval region used to separate the first patterned region 202 and the second patterned region 203 (specifically corresponding to...). Figure 2A c1), and the region located at the edge of the grating imprint template substrate (specifically corresponding to c1). Figure 2A(c2 and c3 in the example). Of course, it should be understood that the third region is only one example. In other embodiments, the third region may not be provided. The focus of this invention is on the setting of the first graphic region 202 and the second graphic region 203. Whether or not the third region is provided and how it is set should not be regarded as a limitation of this invention.

[0066] As an example, the first graphic region 202 and the second graphic region 203 together include N grooves of different depths, and the second graphic region 203 includes at least two grooves of different depths. Therefore, the above-mentioned S12 may further include the following steps S121-S123:

[0067] S121: A patterned mask layer of the Kth degree is formed on the surface of the grating imprint template substrate; wherein the pattern of the patterned mask layer of the Kth degree corresponds to the pattern of the groove of the Kth depth;

[0068] S122: Using the Kth patterned mask layer as a mask, the Kth etching is performed on the surface of the grating imprint template substrate to form a groove of the Kth depth corresponding to the first patterned region 202 and / or the second patterned region 203.

[0069] The number of grooves at each depth can be one or more.

[0070] S123: Repeat the above steps until all the grooves in the first graphic region 202 and the second graphic region 203 are formed; where K and N are positive integers, and N≥2, 1≤K≤N.

[0071] The value of N depends on the number of grooves, and is used as follows: Figure 2A For example, the second graphic region 203 includes six grooves, specifically a11-a16. Figure 2A In the illustrated case, the first groove a11, the fourth groove a14, and the sixth groove a16 have the same depth, thus the six grooves correspond to four different depths; Figure 2A In the illustrated scenario, a third region is also included. The depth of the grooves (c1-c3) in the third region is equal to the depth of the deepest groove (a15) in the second pattern region 203. The first pattern region 202 includes one groove, specifically b11. The depth of this groove is different from the depth of the groove in the second pattern region 203. Therefore, N is 5, meaning that the mask layer needs to be formed and etched 5 times to form grooves of 5 different depths. Of course, as a preferred method, it can be understood that the shallowest groove does not need to be etched. The thickness of the grating imprint template at this groove is the original thickness of the grating imprint template substrate. That is, the groove b11 does not need to be etched. Therefore, N is 5, meaning that the mask layer needs to be formed and etched 4 times to form grooves of 5 different depths.

[0072] Specifically, the depth of the groove can be determined by the etching time. Deep grooves require a longer etching time, while shallow grooves require a shorter etching time. By controlling the different etching times, grooves of different depths can be formed.

[0073] Of course, it should be recognized that the grating imprint template of the present invention may also include only the first graphic area 202 and the second graphic area 203, without providing the third area, specifically as follows: Figure 2H As shown, the grooves on the second graphic area 203 can be different; Figure 2F In the illustrated case, the first pattern area 202 has 1 groove (b21), and the second pattern area 203 has 6 grooves, specifically a21-a26, and the depth of each groove is different. In this case, the value of N is 7, that is, it is necessary to repeat the formation of the mask layer and etching 7 times to form grooves of 7 different depths.

[0074] In one feasible approach, when the thickness of the grating imprint template is greatest in the first pattern region 202 and / or the second pattern region 203, N≥2, 1≤K≤N-1, this is equivalent to the presence of a groove with a depth of 0 in the first pattern region 202 and / or the second pattern region 203, which can reduce one etching step.

[0075] As another way of describing it, in this application, the first patterned region 202 and / or the second patterned region 203 are provided with grooves of varying depths. Alternatively, the first patterned region 202 and / or the second patterned region 203 may include several sub-regions, where the grating imprint template has N different thicknesses. The sub-regions within the second patterned region 203 have at least two different thicknesses, and the thickness of the third region is the minimum thickness within the second patterned region 203. A Kth patterned mask layer is formed on the surface of the grating imprint template substrate; wherein the pattern of the Kth patterned mask layer corresponds to the pattern of the sub-region of the Kth thickness; using the Kth patterned mask layer as a mask, the surface of the grating imprint template substrate is etched for the Kth time to form the sub-region of the Kth thickness corresponding to the first patterned region 202 and / or the second patterned region 203; wherein the number of sub-regions of each thickness may be one or more. Repeat the above steps until all depth sub-regions of the first graphic region 202 and the second graphic region 203 are formed; where K and N are positive integers, and N≥2, 1≤K≤N.

[0076] In one specific implementation, the thickness of the grating imprint template in the first patterned region 202 is the same; the second patterned region 203 includes several sub-regions, and the grating imprint templates in these sub-regions have M different thicknesses, all of which are less than the thickness of the first patterned region 202; the thickness of the grating imprint template in the third region is the minimum thickness in the second patterned region 203. Specifically, the fabrication process includes: forming an i-th patterned mask layer on the surface of the grating imprint template substrate; wherein the pattern of the i-th patterned mask layer corresponds to the pattern on the grating imprint template of the i-th thickness; using the i-th patterned mask layer as a mask, performing an i-th etching on the surface of the grating imprint template substrate to form a sub-region of the i-th thickness corresponding to the second patterned region 203; wherein the number of sub-regions of each thickness in the second patterned region 203 can be one or more. The above steps are repeated until sub-regions of all thicknesses in the second patterned region 203 are formed; wherein i and M are positive integers, and M≥2, 1≤i≤M. Thus, when fabricating a diffractive waveguide using the grating imprint template prepared in this manner, both the coupling-in structure and the coupling-out structure can be etched simultaneously. The etching depth of the coupling-in structure is equal, while the etching depth of different partitions within the coupling-out structure varies. (Refer to...) Figure 2G As shown.

[0077] In one specific implementation, the mask layer for the Kth patterning step described above is either a photoresist mask or a hard mask. For vertical etching, either a photoresist mask or a hard mask can be used; however, when the etching depth is too deep, using a photoresist mask would result in excessive thickness, especially when the etching rate of the material being etched is low. In such cases, a hard mask is relatively superior, as its thickness is significantly reduced compared to a photoresist mask. Furthermore, for inclined etching, since the mask thickness cannot be too thick, otherwise it will affect the etching morphology, a hard mask is preferred for inclined etching.

[0078] As one specific implementation method, the above-mentioned etching refers to dry etching.

[0079] As an example, the bottom of the first graphic area 202 is flat, such as... Figure 2A As shown, this is done so that the depths of the coupling grating units 212 in the coupling grating region 208 after the diffraction waveguide is finally fabricated are equal, such as... Figure 2G As shown, it should be understood that the present invention is not limited thereto, and the unevenness of the bottom of the first graphic area 202 is also within the scope of protection of the present invention. That is, the first graphic area 202 may also include several grooves of different depths.

[0080] As an example, the first graphic area 202 and / or the second graphic area 203 are closed shapes enclosed by curves and / or straight lines. As a specific embodiment, the first graphic area 202 and / or the second graphic area 203 are any one of rectangle, circle, trapezoid, hexagon and octagon. Of course, it should be understood that the present invention is not limited thereto, and other graphics are also within the protection scope of the present invention.

[0081] S2: A diffractive waveguide substrate 204 is provided, and a patterned hard mask layer 205 is formed on the diffractive waveguide substrate 204. The patterned hard mask layer 205 defines a coupling-in grating region pattern 208 and a coupling-out grating region pattern 209. The coupling-in grating region pattern 208 includes several coupling-in grating unit patterns 206, and the coupling-out grating region pattern 209 includes several coupling-out grating unit patterns 207, such as... Figure 2B As shown.

[0082] As an example, in step S2, a patterned hard mask layer is formed on the diffractive waveguide substrate. The patterned hard mask layer defines the coupled-in grating region pattern and the coupled-out grating region pattern, which may specifically include the following steps S21-S23:

[0083] S21: A hard mask layer is formed on the diffractive waveguide substrate 204;

[0084] S22: A patterned photoresist is formed on a hard mask layer, wherein the pattern of the patterned photoresist corresponds to the coupled-in grating region pattern 208 and the coupled-out grating region pattern 209;

[0085] S23: Using patterned photoresist as a mask, the hard mask layer is etched to form a patterned hard mask layer 205.

[0086] In one example, the hard mask layer is made of Cr. Of course, it should be understood that this invention is not limited to this, and other materials for hard mask layers are also within the scope of this invention.

[0087] In one example, the material of the diffractive waveguide substrate 204 is Si. Of course, it should be understood that the present invention is not limited to this, and other materials of diffractive waveguide substrates are also within the protection scope of the present invention.

[0088] S3: A liquid polymer resist 210 is spin-coated onto the diffractive waveguide substrate 204. The liquid polymer resist 210 covers the surface of the patterned hard mask layer 205 and fills the gaps between adjacent hard mask patterns, such as... Figure 2C As shown; wherein the thickness of the liquid polymer resist 210 on the surface of the patterned hard mask layer 205 is greater than or equal to the depth of the deepest groove in the second patterned region 203.

[0089] Of course, if the first patterned region 202 also includes several grooves of different depths, then the thickness of the liquid polymer resist 210 on the surface of the patterned hard mask layer 205 is greater than or equal to the depth of the deepest groove in the second patterned region 203 and the first patterned region 202.

[0090] In one embodiment of the present invention, the thickness of the liquid polymer resist 210 on the surface of the patterned hard mask layer 205 is 10-30 nm greater than the depth of the deepest groove of the second patterned region 203. Of course, it should be understood that the present invention is not limited thereto, and other numerical ranges in which the thickness of the liquid polymer resist 210 is greater than the maximum value of the groove depth range on the surface of the imprint template 201 are also within the protection scope of the present invention.

[0091] In one embodiment of the present invention, the liquid polymer resist 210 is a hot stamping adhesive or a UV stamping adhesive, wherein the hot stamping adhesive is, for example, PMMA or PDMS; and the UV stamping adhesive is, for example, acrylate or vinyl ether. It should be understood that the present invention is not limited thereto, and other hot stamping adhesive materials are also within the scope of protection of the present invention. The liquid polymer resist 210 is acceptable as long as it has good flowability, low shrinkage, and good etching resistance.

[0092] S4: Press the grating imprint template 201 onto the diffractive waveguide substrate 204, so that the grooves of the grating imprint template 201 are filled with liquid polymer resist 210, and the first patterned region 202 on the grating imprint template is aligned with the coupled grating region pattern 208, and the second patterned region 203 is aligned with the coupled grating region pattern 209. Figure 2D As shown.

[0093] In a further preferred embodiment, the area of ​​the liquid polymer resist 210 spin-coated on the diffractive waveguide substrate is set to be larger than the area of ​​the region corresponding to the grating imprint template 201 (in this case, the area of ​​the liquid polymer resist 210 spin-coated on the diffractive waveguide substrate is correspondingly larger than the area of ​​the coupled-in grating region 208 and the coupled-out grating region pattern 209). Figure 3 As shown, this reduces the alignment accuracy requirements between the grating imprint template 201 and the diffractive waveguide substrate 204, that is, it reduces the alignment accuracy requirements between the coupled-in grating region 208 and the coupled-out grating region 209 and the diffractive waveguide substrate 204.

[0094] S5: The liquid polymer resist 210 is cured to form a patterned solid polymer resist 211, the pattern of which corresponds to the pattern on the lenticular imprint stencil 201, such as... Figure 2E As shown.

[0095] If the liquid polymer resist 210 is a hot-press printing adhesive, the curing process can be a cooling process, where the liquid polymer resist 210 is cured by cooling. If the liquid polymer resist 210 is a UV printing adhesive, the curing process can be a UV exposure process, where the liquid polymer resist 210 is cross-linked and cured by UV irradiation. Of course, the above are just examples; different types of liquid polymer resist 210 will have different curing processes.

[0096] Through steps S4 and S5, the shapes of the first graphic region 202 and the second graphic region 203 on the lenticular imprinting template 201 are transferred to the liquid polymer resist, and the depth of the grooves is also transferred accordingly. Specifically, the deeper the grooves on the lenticular imprinting template 201, the thicker the liquid polymer resist filling them; conversely, the shallower the grooves on the lenticular imprinting template 201, the thinner the liquid polymer resist filling them. Once the liquid polymer resist has cured, the pattern on it is fixed.

[0097] S6: Remove the lenticular imprint template 201. A schematic diagram after removal is shown below. Figure 2F As shown;

[0098] S7: Using a patterned solid polymer resist 211 and a patterned hard mask layer 205 as a mask, the diffraction waveguide substrate 204 is etched to integrally form a coupling grating region 208 and a coupling grating region 209 on the diffraction waveguide substrate 204. The coupling grating region 208 has coupling grating units 212, and the coupling grating region 209 has coupling grating units 213 of varying depths. Figure 2G As shown.

[0099] The thicker part of the solid polymer resist corresponds to a shallower etching depth on the diffraction waveguide substrate, while the thinner part corresponds to a deeper etching depth on the diffraction waveguide substrate. This allows for the creation of grating units with varying depths in a single etching operation.

[0100] As one specific implementation method, the above-mentioned etching refers to dry etching.

[0101] In one embodiment of the present invention, the depth of the coupling grating unit 213 of the coupling grating region 209 is 100nm to 400nm. Of course, it should be understood that the present invention is not limited thereto, and other depth values ​​of the coupling grating unit are also within the protection scope of the present invention.

[0102] In one embodiment of the present invention, the depth of the coupling grating unit 212 of the coupling grating region 208 is 400 nm. Of course, it should be understood that the present invention is not limited thereto, and other depth values ​​of the coupling grating unit are also within the protection scope of the present invention.

[0103] As can be seen, the fabrication method of the diffractive waveguide provided in this embodiment, based on defining the coupled-in grating region pattern and the coupled-out grating region pattern using a patterned hard mask layer, performs nanoimprinting of liquid polymer resist based on a grating imprinting template. Using the imprinted and cured patterned polymer resist and the patterned hard mask layer, the coupled-in grating region and the coupled-out grating region can be etched in one step, thereby realizing the integrated forming of the coupled-in grating region and the coupled-out grating region, effectively ensuring the relative positional accuracy of the coupled-in grating region and the coupled-out grating region, which is conducive to further improving the display effect of AR devices.

[0104] Meanwhile, because the second patterned region of the grating imprint template has grooves of varying depths, coupling grating units of varying depths can be fabricated in the coupling grating region with a single etching operation, effectively improving the modulation efficiency of the diffractive waveguide. Furthermore, since multiple etching operations are not required, the problem of inaccurate alignment that may result from repeated etching is avoided, facilitating the large-area, mass production of diffractive waveguide patterns.

[0105] Furthermore, this embodiment of the invention employs nanoimprinting technology to transfer the pattern on the grating imprint template 201 through mechanical force. This avoids many of the limitations that reduce resolution in traditional micro-nano fabrication processes such as photolithography, including exposure wavelength, objective lens numerical aperture, light reflection and scattering by the photoresist, and developer. This effectively improves the pattern resolution. On the other hand, due to its unique imprinting process, it eliminates the need for expensive optical systems and lenses required by other photolithography techniques. This also facilitates the large-scale, low-cost fabrication of diffractive waveguides.

[0106] According to one embodiment of the present invention, a diffractive optical waveguide is also provided, such as Figure 2G As shown, the diffractive waveguide is fabricated using the method described in the specific embodiment above. Because the diffractive waveguide has an integrally formed coupling grating region 208 and coupling out grating region 209, the relative positional accuracy of the coupling grating region 208 and coupling out grating region 209 is effectively guaranteed, improving the display effect of the AR device. Furthermore, the coupling out grating units 213 at different depths in the coupling out grating region 209 also improve the modulation efficiency of the diffractive waveguide, thereby further enhancing the display performance of the AR device.

[0107] In addition, the present invention also provides an AR display device, including the diffractive waveguide involved in the above embodiments.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a diffractive optical waveguide, characterized in that, The method includes: A grating embossing template is provided, wherein the grating embossing template has a first graphic area and a second graphic area, and the second graphic area is provided with grooves of varying depths; A diffractive waveguide substrate is provided, and a patterned hard mask layer is formed on the diffractive waveguide substrate. The patterned hard mask layer defines a coupled-in grating region pattern and a coupled-out grating region pattern, wherein the coupled-in grating region pattern includes a plurality of coupled-in grating unit patterns, and the coupled-out grating region pattern includes a plurality of coupled-out grating unit patterns. A liquid polymer resist is spin-coated onto the diffractive waveguide substrate, the liquid polymer resist covering the surface of the patterned hard mask layer and filling the gaps between adjacent hard mask patterns; wherein the thickness of the liquid polymer resist on the surface of the patterned hard mask layer is greater than or equal to the depth of the deepest groove in the second patterned region; The grating imprint template is pressed onto the diffractive waveguide substrate so that the groove of the grating imprint template is filled with the liquid polymer resist, and the first pattern area on the grating imprint template is aligned with the pattern of the coupled grating area, and the second pattern area is aligned with the pattern of the coupled grating area. The liquid polymer resist is cured to form a patterned solid polymer resist, the pattern of which corresponds to the pattern on the grating imprint template; Remove the grating imprint template; Using the patterned solid polymer resist and the patterned hard mask layer as a mask, the diffractive waveguide substrate is etched to integrally form a coupling grating region and a coupling grating region on the diffractive waveguide substrate, wherein the coupling grating region has coupling grating units of unequal depth.

2. The method for fabricating a diffractive optical waveguide according to claim 1, characterized in that, The bottom of the first graphic region is flat so that the depth of the coupling grating units in the coupling grating region is equal.

3. The method for fabricating a diffractive optical waveguide according to claim 1, characterized in that, The area of ​​the liquid polymer resist spin-coated on the diffractive waveguide substrate is larger than the area of ​​the regions corresponding to the coupled-in grating region pattern and the coupled-out grating region pattern.

4. The method for fabricating a diffractive optical waveguide according to any one of claims 1-3, characterized in that, The provision of a grating imprint template specifically includes: Provide a grating embossing template substrate; The grating imprint template substrate is subjected to multiple photolithography and etching processes to form the first patterned area and the second patterned area.

5. The method for fabricating a diffractive optical waveguide according to claim 4, characterized in that, The first and second patterned regions together include N grooves of different depths, and the second patterned region includes at least two grooves of different depths. The process of performing multiple photolithography and etching processes on the grating imprint template substrate to form the first and second patterned regions includes: A Kth patterned mask layer is formed on the surface of the grating embossing template substrate; wherein the pattern of the Kth patterned mask layer corresponds to the pattern of a groove of Kth depth; Using the Kth patterned mask layer as a mask, the surface of the grating imprint template substrate is etched for the Kth time to form a groove of the Kth depth corresponding to the first patterned region and / or the second patterned region; Repeat the above steps until all grooves in the first graphic area and the second graphic area are formed; where K and N are positive integers, and N≥2, 1≤K≤N.

6. The method for fabricating a diffractive optical waveguide according to claim 5, characterized in that, The mask layer for the Kth patterning is a photoresist mask or a hard mask.

7. The method for fabricating a diffractive optical waveguide according to any one of claims 1-3, characterized in that, A patterned hard mask layer is formed on the diffractive waveguide substrate. This patterned hard mask layer defines the coupling-in grating region pattern and the coupling-out grating region pattern, specifically including: A hard mask layer is formed on the diffractive waveguide substrate; A patterned photoresist is formed on the hard mask layer, wherein the pattern of the patterned photoresist corresponds to the pattern of the coupled-in grating region and the pattern of the coupled-out grating region; Using the patterned photoresist as a mask, the hard mask layer is etched to form the patterned hard mask layer.

8. The method for fabricating a diffractive optical waveguide according to any one of claims 1-3, characterized in that, The first graphic region and / or the second graphic region are closed shapes enclosed by curves and / or straight lines.

9. The method for fabricating a diffractive optical waveguide according to any one of claims 1-3, characterized in that, The thickness of the liquid polymer resist on the surface of the patterned hard mask layer is 10-30 nm greater than the depth of the deepest groove in the second patterned region.

10. The method for fabricating a diffractive optical waveguide according to any one of claims 1-3, characterized in that, The depth of the coupling grating unit in the coupling grating region is 100nm to 400nm.

11. A diffractive optical waveguide, characterized in that, It is prepared by the method of any one of claims 1-10 for the fabrication of diffractive optical waveguide.

12. An AR display device, characterized in that, Including the diffractive waveguide as described in claim 11.

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