A preparation process of a gradual groove depth grating master, a preparation process of a diffractive grating waveguide and the diffractive grating waveguide

Abstract

This invention provides a process for fabricating a gradient groove deep grating master, a process for fabricating a diffraction grating waveguide, and a diffraction grating waveguide. The gradient groove deep grating master fabrication process includes: pre-etching a substrate in the gradient groove deep grating fabrication area to obtain a pre-etched substrate; spin-coating photoresist onto the pre-etched substrate to obtain a substrate with a photoresist mask; performing beam interference exposure on the photoresist mask on the substrate to obtain a photoresist mask with altered properties; developing the photoresist mask on the substrate to obtain a photoresist grating mask, resulting in a substrate with the photoresist grating mask; and performing a post-etching operation on the substrate with the photoresist grating mask in the gradient groove deep grating fabrication area to obtain the gradient groove deep grating master. The display clarity of the diffraction grating waveguide obtained using the gradient groove deep grating master nanoimprinting process of this invention is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of diffraction grating technology, specifically to a process for fabricating a gradient groove deep grating master, a process for fabricating a diffraction grating waveguide, and a diffraction grating waveguide. Background Technology

[0002] Augmented Reality (AR) technology refers to providing users with additional information in the real world through certain technical means (i.e., "enhancement"). This technology organically integrates images from the virtual world with scenes from the real world, providing users with richer information and an immersive experience by deeply integrating the calculated information with the real world.

[0003] Augmented reality (AR) technology can be implemented through many hardware platforms, with wearable AR devices offering the most immersive experience. AR glasses, as a type of wearable AR device, guide light into the eyes through the microstructures on the lens surface, providing a convenient way to achieve AR. Currently, mature AR glasses lens technologies mainly include prism solutions, birdbath solutions, freeform surface solutions, off-axis holographic lens solutions, and diffraction grating waveguide solutions. Among these, the diffraction grating waveguide solution is widely recognized as the mainstream AR glasses lens solution due to its advantages such as small size and light weight, large eye movement range, large field of view, and mass production feasibility.

[0004] like Figure 1 The diagram shown illustrates the basic principle of a diffraction grating waveguide scheme. The diffraction grating waveguide includes a waveguide substrate, an input grating, and an output grating. The input and output gratings are mounted on the waveguide substrate. Its basic principle is as follows: Figure 1 As shown, the light output from the optomechanical system 1 (imaging device) is coupled into the waveguide substrate 2 by the coupling grating 3. It propagates in the waveguide substrate 2 by total internal reflection. Whenever it encounters the coupling grating 4, a portion of the light is coupled out. The coupled-out light (the solid line in the direction of the human eye in the figure) enters the human eye, so that the same image as the output of the optomechanical system 1 can be seen. At the same time, the human eye can see the real world scene (the dashed line in the direction of the human eye in the figure). The superposition of the two parts can realize the function of augmented reality.

[0005] However, the diffraction grating waveguide scheme suffers from poor coupling imaging uniformity, such as... Figure 2As shown in the diagram, the thickness of the arrows represents the relative magnitude of light energy. The light emitted by the optomechanical system 1 is coupled into the waveguide substrate 2 by the coupling grating 3 and propagates through total internal reflection within the waveguide substrate. Whenever it encounters the output grating 4, a portion of the light is coupled out through the human eye 5. Therefore, the energy of the light coupled out at different positions along the total internal reflection propagation direction within the waveguide substrate decreases, resulting in inconsistent brightness of the image seen by the human eye at different positions of the output grating. For example, along the total internal reflection propagation direction within the waveguide substrate, the light energy received by the human eye at positions 1, 2, and 3 gradually decreases, causing inconsistent brightness of the image received by the human eye at different positions of the output grating during movement.

[0006] To address the issue of poor imaging uniformity in diffraction grating waveguide schemes, a gradually increasing groove depth structure is adopted for the coupling grating.

[0007] like Figure 3 As shown in Figure (a), the diffraction grating waveguide includes a waveguide substrate 2, an input grating 3, and an output grating 4. The output grating 4 adopts a unidirectional linearly tapered groove depth structure, and the groove depth of the output grating 4 changes linearly along the direction of light propagation.

[0008] like Figure 3 As shown in Figure (b), the diffraction grating waveguide includes a waveguide substrate 2, a coupling grating 3, and a coupling grating 4. The coupling grating 4 adopts a unidirectional stepped tapered groove depth structure, and the groove depth of the coupling grating 4 changes in a stepped manner along the direction of light propagation.

[0009] The fabrication methods for existing diffraction grating waveguides with gradient groove deep grating structures are generally as follows: 1. Prepare an imprint master with a gradient groove deep grating structure.

[0010] 2. The grating structure of the embossing master is transferred to the soft film substrate using a nanoimprinting process with a soft film adhesive to obtain a soft film plate with an inverse structure of grating structure.

[0011] Specifically, a soft film adhesive is uniformly spin-coated onto the imprinting master, the soft film substrate is bonded to the imprinting master, and pressure is applied to fill the grating structure of the imprinting master with the soft film adhesive, thus obtaining the inverse structure of the grating structure on the soft film adhesive. After curing and demolding with ultraviolet light, the soft film adhesive with the inverse structure of the grating structure is transferred to the soft film substrate to obtain a soft film plate with the inverse structure of the grating structure.

[0012] 3. The inverse structure of the grating structure on the flexible film plate is transferred to the imprinting adhesive on the waveguide substrate through a nanoimprinting process, thereby obtaining a diffraction grating waveguide with a gradient groove depth grating structure.

[0013] Specifically, an imprinting adhesive is spin-coated onto a waveguide substrate. A flexible film with an inverse grating structure is then bonded to the imprinting adhesive on the waveguide substrate. Pressure is applied to fill the inverse grating structure onto the flexible film with the imprinting adhesive, resulting in a grating structure on the imprinting adhesive. Ultraviolet light is used for curing and demolding, separating the flexible film with the inverse grating structure from the imprinting adhesive with the grating structure, thus obtaining a diffraction grating waveguide with a gradient groove depth grating structure (e.g., ...). Figure 4 (As shown).

[0014] like Figure 4 As shown, in the gradient groove deep grating structure region of the waveguide substrate, there is a certain thickness of embossing adhesive between the contact surface of the waveguide substrate and the bottom surface of the grating structure at different positions (as shown by the dotted line area in the figure), which affects the display clarity of the diffraction grating waveguide. Summary of the Invention

[0015] To overcome the shortcomings of the prior art, the present invention provides a process for fabricating a gradient groove deep grating master, a process for fabricating a diffraction grating waveguide, and a diffraction grating waveguide.

[0016] This invention is achieved through the following technical solution: This invention provides a process for fabricating a gradient groove deep grating master, comprising the following steps: A pre-etching operation is performed on the substrate in the gradient groove deep grating fabrication area to obtain a pre-etched substrate. Photoresist is spin-coated onto a pre-etched substrate to obtain a substrate with a photoresist mask. A beam interference exposure operation is performed on the photoresist mask on the substrate to obtain a photoresist mask with altered properties on the substrate. The photoresist mask whose properties have changed on the substrate is developed to obtain a photoresist grating mask on the substrate, and a substrate with a photoresist grating mask is obtained. The substrate with the photoresist grating mask is subjected to a post-etching operation in the gradient groove deep grating fabrication area to obtain the gradient groove deep grating master.

[0017] Furthermore, the pre-etching operation on the substrate in the gradient groove deep grating fabrication area to obtain a pre-etched substrate includes the following steps: Determine the pre-etching depth distribution parameters of the substrate in the gradient groove deep grating fabrication region; The substrate is placed in an etching system, and the etching system is used to perform a pre-etching operation on the gradient groove deep grating fabrication area of ​​the substrate according to the pre-etching depth distribution parameters to obtain a pre-etched substrate.

[0018] Furthermore, determining the pre-etching depth distribution parameters of the substrate in the gradient groove deep grating fabrication region includes the following steps: The pre-etching depth distribution parameters of the substrate in the fabrication area of ​​the gradient groove deep grating are determined based on the maximum grating groove depth value and the gradient groove depth distribution parameters of the gradient groove deep grating.

[0019] Furthermore, based on the maximum grating groove depth value of the gradient groove depth grating and the gradient groove depth distribution parameters of the gradient groove depth grating, the pre-etching depth distribution parameters of the substrate in the fabrication region of the gradient groove depth grating are determined, including: The pre-etching depth distribution parameters of the substrate in the gradient groove grating fabrication area are obtained by subtracting the maximum grating groove depth value from the gradient groove depth distribution parameters of the gradient groove depth grating.

[0020] Furthermore, the gradient groove depth distribution parameters of the gradient groove depth grating are composed of the grating groove depth parameters at different positions within the gradient groove depth grating region; The pre-etching depth distribution parameters of the substrate in the gradient groove deep grating fabrication area are composed of the pre-etching depth parameters of the substrate at different positions in the gradient groove deep grating fabrication area.

[0021] Furthermore, the etching system includes an ion beam etching chamber, a movable stage, a first gradient etching direction limiting baffle, a gradient etching position limiting baffle, and an ion beam device; A movable stage is provided inside the ion beam etching chamber, and the opposite side of the etched surface of the substrate is detachably connected to the movable stage; the movable stage can drive the substrate to move within the ion beam etching chamber. An ion beam device is fixedly installed at the first position within the ion beam etching chamber; The second position within the ion beam etching chamber is detachably connected to a first gradient etching direction limiting baffle. The first gradient etching direction defines a first opening area within the baffle, and the opening length of the first opening area varies in different areas along the direction in which the moving base drives the substrate. The etching position limiting baffle is connected to the etching surface of the substrate within the ion beam etching chamber, and the etching position limiting baffle has a second through-hole area.

[0022] Furthermore, the substrate is placed in an etching system, and the etching system performs a pre-etching operation on the gradient groove deep grating fabrication area of ​​the substrate according to the pre-etching depth distribution parameters to obtain a pre-etched substrate, including: The opposite side of the etched surface of the substrate is connected to the movable stage in the ion beam etching chamber in a first set direction, the etching position limiting baffle is connected to one side of the etched surface of the substrate, and the first gradient etching direction limiting baffle is connected to the second position in the ion beam etching chamber. The mobile stage and ion beam equipment are started. The ion beam emitted by the ion beam equipment passes sequentially through the first opening area of ​​the first gradient etching direction limiting baffle and the second opening area of ​​the etching position limiting baffle. The substrate, which is moved by the mobile stage, is etched along the pre-etching depth distribution direction in the gradient groove deep grating fabrication area. The etching time and etching rate are controlled so that the substrate has pre-etching depth distribution parameters along the pre-etching depth distribution direction in the gradient groove deep grating fabrication area, thus obtaining a pre-etched substrate.

[0023] Furthermore, photoresist is spin-coated onto the pre-etched substrate to obtain a substrate with a photoresist mask, including: The pre-etched substrate is placed on the spin coater stage; Photoresist is dropped onto the surface of the pre-etched substrate; Rotate the photoresist spin coating stage to spin coat the surface of the pre-etched substrate, thereby obtaining a substrate with a photoresist mask.

[0024] Furthermore, a beam interference exposure operation is performed on the photoresist mask on the substrate to obtain a photoresist mask with altered properties on the substrate, including: A substrate with a photoresist mask is placed in a holographic exposure system. The substrate with the photoresist mask is irradiated by an exposure field formed by beam interference, resulting in a photoresist mask with altered properties on the substrate. In this system, the placement angle of the substrate with the photoresist mask in the holographic exposure system corresponds to the set grating line direction of the gradient groove depth grating; the beam interference period of the exposure field corresponds to the set grating period of the gradient groove depth grating.

[0025] Further, a development operation is performed on the photoresist mask whose properties have changed on the substrate to obtain a photoresist grating mask on the substrate, resulting in a substrate with a photoresist grating mask, comprising: The substrate with the photoresist mask is immersed in the developing solution for development, so that the photoresist mask at the corresponding position is dissolved in the developing solution, thereby obtaining a photoresist mask with changed properties on the substrate.

[0026] Furthermore, the etching system also includes a second gradient etching direction defining baffle; The second position within the ion beam etching chamber is detachably connected to a second gradient etching direction limiting baffle. The second gradient etching direction defines a third opening area within the baffle, and the opening length of the third opening area varies in different regions along the direction in which the moving base drives the substrate.

[0027] Furthermore, a post-etching operation is performed on the substrate with the photoresist grating mask in the gradient groove deep grating fabrication area to obtain a gradient groove deep grating master, including: The opposite side of the etched surface of the substrate is connected to the movable stage in the ion beam etching chamber in a second set direction, the etching position limiting baffle is connected to one side of the etched surface of the substrate, and the second gradient etching direction limiting baffle is connected to the second position in the ion beam etching chamber. The moving stage and ion beam equipment are started. The ion beam emitted by the ion beam equipment passes sequentially through the third opening area of ​​the second gradient etching direction limiting baffle and the second opening area of ​​the etching position limiting baffle to etch the substrate, which is moved by the moving stage, along the gradient groove depth distribution direction in the gradient groove deep grating fabrication area. The etching time and etching rate are controlled so that the substrate has gradient groove depth distribution parameters along the gradient groove depth distribution direction in the gradient groove deep grating fabrication area, thus obtaining the gradient groove deep grating master.

[0028] Furthermore, the area where the substrate is pre-etched also includes the tolerance area; The tolerance region is the surrounding edge region of the gradient groove deep grating fabrication region.

[0029] This invention also provides a fabrication process for a diffraction grating waveguide, comprising the following steps: An imprinting master with a gradient groove deep grating structure is prepared; the imprinting master is prepared using the above-described gradient groove deep grating master preparation process. The grating structure of the embossing master is transferred to the soft film substrate using a nanoimprinting process with a soft film adhesive to obtain a soft film plate with an inverse structure of grating structure. The inverse structure of the grating structure of the flexible film plate is transferred to the imprinting adhesive of the waveguide substrate through a nanoimprinting process to obtain a diffractive waveguide with a gradient groove deep grating structure; wherein, the thickness parameter of the imprinting adhesive layer of the waveguide substrate is matched and set with the imprinting master plate with the gradient groove deep grating structure.

[0030] The present invention also provides a diffraction grating waveguide, which is prepared by the above-described fabrication process of the diffraction grating waveguide.

[0031] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: This invention provides a process for fabricating a gradient groove deep grating master. First, a pre-etching operation is performed on a substrate in the gradient groove deep grating fabrication area to obtain a pre-etched substrate. Then, photoresist is spin-coated onto the pre-etched substrate to obtain a substrate with a photoresist mask. Next, beam interference exposure is performed on the photoresist mask on the substrate to obtain a photoresist mask with altered properties. Then, the photoresist mask with altered properties on the substrate is developed to obtain a photoresist grating mask on the substrate, resulting in a substrate with a photoresist grating mask. Finally, a post-etching operation is performed on the substrate with the photoresist grating mask in the gradient groove deep grating fabrication area to obtain the gradient groove deep grating master. In the process of preparing the gradient groove deep grating master provided by this invention, before performing spin coating, exposure, development, and post-etching operations on the substrate to obtain the gradient groove deep grating in the gradient groove deep grating preparation area of ​​the substrate, a pre-etching operation is first performed on the substrate in the gradient groove deep grating preparation area to obtain a pre-etched substrate. The pre-etching depth distribution parameters of the substrate in the gradient groove deep grating preparation area are determined according to the maximum grating groove depth value on the substrate and the gradient groove depth distribution parameters of the gradient groove deep grating. Then, the pre-etched substrate is subjected to spin coating, exposure, development, and post-etching operations to obtain the gradient groove deep grating in the gradient groove deep grating preparation area. The deep grating fabrication area yields a gradient groove deep grating, ensuring that the bottom surfaces of the grating structures of the gradient groove deep grating fabricated on the substrate are on the same horizontal plane. Therefore, when transferring the gradient groove deep grating structure to the imprinting adhesive of the waveguide substrate using the gradient groove deep grating master provided by this invention via nanoimprinting, it is possible to achieve no residual imprinting adhesive between the contact surface between the waveguide substrate and the imprinting adhesive and the bottom surfaces of the grating structures at different locations within the gradient groove deep grating structure area of ​​the waveguide substrate simply by controlling the thickness parameters of the imprinting adhesive on the waveguide substrate. This improves the display clarity of the diffraction grating waveguide. Attached Figure Description

[0032] 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.

[0033] Figure 1 This is a schematic diagram illustrating the basic principle of a diffraction grating waveguide scheme. Figure 2 This is a schematic diagram of the energy distribution of the coupled rays from a diffraction grating waveguide. Figure 3 Schematic diagram of a diffraction grating waveguide with a gradually increasing groove depth structure for coupling out the grating; Figure 4 This is a schematic diagram of an existing imprinted adhesive transfer gradient groove deep grating structure on a waveguide substrate. Figure 5A schematic diagram of the overall process for fabricating the gradient groove deep grating master provided by the present invention; Figure 6 This is a schematic diagram of the connection structure between the etching system and the substrate; Figure 7 A schematic diagram of a first example structure for defining a baffle for a first gradient etching direction; Figure 8 A schematic diagram of a second example structure for defining a baffle for a first gradient etching direction; Figure 9 A schematic diagram of the baffle that defines the etching location; Figure 10 A schematic diagram of a first example structure for defining a baffle for a second gradient etching direction; Figure 11 A schematic diagram of a second example structure for defining a baffle for a second gradient etching direction; Figure 12 A schematic diagram of the first example structure of the pre-etched substrate obtained by performing a pre-etching operation on the substrate; Figure 13 A second example structural schematic diagram of a pre-etched substrate obtained by performing a pre-etching operation on the substrate; Figure 14 A schematic diagram of a third example structure of a pre-etched substrate obtained by performing a pre-etching operation on the substrate; Figure 15 A schematic diagram of a fourth example structure of a pre-etched substrate obtained by performing a pre-etching operation on the substrate; Figure 16 This is a schematic diagram of a dual-beam exposure system; Figure 17 This is a schematic diagram of a first example of a gradient groove deep grating master prepared using the gradient groove deep grating master preparation process of the present invention. Figure 18 This is a second example schematic diagram of a gradient groove deep grating master prepared using the gradient groove deep grating master preparation process of the present invention; Figure 19 This is a third example schematic diagram of a gradient groove deep grating master prepared using the gradient groove deep grating master preparation process of the present invention; Figure 20 This is a fourth example schematic diagram of a gradient groove deep grating master prepared using the gradient groove deep grating master preparation process of the present invention; Figure 21 This is a schematic diagram of the gradient groove deep grating structure transferred by the master plate of the present invention on the waveguide substrate.

[0034] Among them, 1-optical mechanism, 2-waveguide substrate, 3-coupled grating, 4-coupled grating, 5-human eye, 6-moving stage, 7-gradient etching direction limiting baffle, 7-1-first gradient etching direction limiting baffle, 7-1-1-first opening area, 7-2-second gradient etching direction limiting baffle, 7-2-1-third opening area, 8-gradient etching position limiting baffle, 8-1-second opening area, 9-ion beam equipment, 10-laser, 11-first waveplate, 12-beam splitter prism, 13-second waveplate, 14-first reflecting mirror, 15-second reflecting mirror, 16-third reflecting mirror, 17-first microscope objective, 18-second microscope objective, 19-first pinhole, 20-second pinhole, 21-first collimating lens, 22-second collimating lens. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0036] In this document, the terms "first," "second," and other similar words are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. The terms "one," "a," and other similar words are not intended to indicate the existence of only one of the stated things, but rather that the description refers only to one of the stated things, which may have one or more. The terms "comprising," "including," and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, "A includes B" means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms "comprising," "including," and other similar words should be considered open-ended, not closed. For example, "A includes B" means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.

[0037] In this document, the terms "embodiment," "this embodiment," "preferred embodiment," and "one embodiment" do not imply that the description applies only to one specific embodiment, but rather that such description may also be applicable to one or more other embodiments. Those skilled in the art will understand that any description made herein with respect to one embodiment can be substituted, combined, or otherwise incorporated with the descriptions in one or more other embodiments. Such substitutions, combinations, or other incorporations resulting in new embodiments are readily conceived by those skilled in the art and fall within the scope of protection of this invention.

[0038] In this description, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0039] This invention provides a fabrication process for a graded-groove deep grating master for a diffraction grating waveguide, such as... Figure 5 As shown, the overall technical concept is as follows: S1 performs a pre-etching operation on the substrate in the gradient groove deep grating fabrication area to obtain a pre-etched substrate.

[0040] S2 spin-coats photoresist onto the pre-etched substrate to obtain a substrate with a photoresist mask.

[0041] S3 performs beam interference exposure on the photoresist mask on the substrate, resulting in a photoresist mask with altered properties on the substrate.

[0042] S4 performs a development operation on the photoresist mask whose properties have changed on the substrate, and obtains a photoresist grating mask on the substrate, thus obtaining a substrate with a photoresist grating mask.

[0043] S5 performs a post-etching operation on the substrate with a photoresist grating mask in the gradient groove deep grating fabrication area to obtain the gradient groove deep grating master.

[0044] For example, the pre-etching operation performed on the substrate in the gradient groove deep grating fabrication area in step S1 above to obtain a pre-etched substrate specifically includes the following steps: S1-1 determines the pre-etching depth distribution parameters of the substrate in the gradient groove deep grating fabrication region. The gradient groove deep grating fabrication region of the substrate is a pre-defined region by those skilled in the art.

[0045] The pre-etching depth distribution parameters of the substrate in the graded-groove-depth grating fabrication area are determined based on the maximum grating groove depth value and the graded groove depth distribution parameters of the graded-groove-depth grating. The graded-groove-depth grating can employ a unidirectional linear graded groove depth structure or a unidirectional stepped graded groove depth structure. The graded groove depth distribution parameters of the graded-groove-depth grating consist of the grating groove depth parameters at different locations within the graded-groove-depth grating region.

[0046] Specifically, The pre-etching depth distribution parameters of the substrate in the gradient groove grating fabrication area are obtained by subtracting the maximum grating groove depth value from the gradient groove depth distribution parameters of the gradient groove depth grating.

[0047] That is, by subtracting the maximum grating groove depth value of the gradient groove depth grating from the grating groove depth parameters at different positions in the gradient groove depth distribution parameters of the gradient groove depth grating, the pre-etching depth parameters of the substrate at different positions in the gradient groove depth grating fabrication area are obtained. The pre-etching depth parameters of the substrate at different positions in the gradient groove depth grating fabrication area constitute the pre-etching depth distribution parameters of the substrate in the gradient groove depth grating fabrication area.

[0048] S1-2 The substrate is placed in the etching system, and the etching system is used to perform pre-etching operation on the gradient groove deep grating fabrication area of ​​the substrate according to the pre-etching depth distribution parameters to obtain the pre-etched substrate.

[0049] For example, such as Figure 6 As shown, the etching system includes an ion beam etching chamber (not shown), a movable stage 6, a gradient etching direction limiting baffle 7, a gradient etching position limiting baffle 8, and an ion beam device 9. The gradient etching direction limiting baffle 7 includes a first gradient etching direction limiting baffle 7-1 and a second gradient etching direction limiting baffle 7-2. The first gradient etching direction limiting baffle 7-1 is used in the pre-etching operation, and the second gradient etching direction limiting baffle 7-2 is used in the post-etching operation.

[0050] A movable stage is installed inside the ion beam etching chamber. The opposite side of the etched surface of the substrate is detachably connected to the movable stage. The movable stage can drive the substrate to move within the ion beam etching chamber.

[0051] An ion beam device is fixedly installed at the first position within the ion beam etching chamber.

[0052] The second position within the ion beam etching chamber is detachably connected to either a first gradient etching direction limiting baffle or a second gradient etching direction limiting baffle.

[0053] A first aperture region is formed within a baffle defined by a first gradient etching direction. The aperture length varies in different regions of the first aperture region along the direction in which the moving base drives the substrate. For example... Figure 7 The diagram shows a schematic of the first gradient etching direction limiting baffle used in the fabrication process of a unidirectional linear gradient groove deep grating. The first gradient etching direction limiting baffle 7-1 has a first opening region 7-1-1. Figure 8 The diagram shows the structure of the first gradient etching direction limiting baffle used in the fabrication process of a gradient groove deep grating with a unidirectional stepped gradient groove deep structure. The first gradient etching direction limiting baffle 7-1 is provided with a first opening area 7-1-1.

[0054] An etching position limiting baffle is connected to the etching surface of the substrate within the ion beam etching chamber, and the etching position limiting baffle has a second through-hole area. For example... Figure 9The diagram shows the structure of the etching position limiting baffle 8, in which a second through hole region 8-1 is formed.

[0055] The second gradient etching direction defines a third opening region within the baffle. The opening length of this third opening region varies in different areas along the direction in which the moving base drives the substrate. For example... Figure 10 The diagram shows a schematic of the second gradient etching direction limiting baffle used in the fabrication process of a unidirectional linear gradient groove depth grating. A third opening region 7-2-1 is provided within the second gradient etching direction limiting baffle 7-2. Figure 11 The diagram shows a schematic of the second gradient etching direction limiting baffle used in the fabrication process of a gradient groove depth grating with a unidirectional stepped gradient groove depth structure. A third opening region 7-2-1 is provided inside the second gradient etching direction limiting baffle 7-2.

[0056] Using the etching system described above, a pre-etching substrate is obtained by pre-etching the gradient trench deep grating fabrication area of ​​the substrate according to the pre-etching depth distribution parameters. Specifically, the process includes the following steps: The opposite side of the etched surface of the substrate is connected to a movable stage within the ion beam etching chamber in a first predetermined direction. An etching position limiting baffle is connected to one side of the etched surface of the substrate, and a first gradient etching direction limiting baffle is connected to a second position within the ion beam etching chamber. Here, the first predetermined direction is consistent with the pre-etching depth distribution direction of the substrate.

[0057] The mobile stage and ion beam equipment are started. The ion beam emitted by the ion beam equipment passes sequentially through the first opening area of ​​the first gradient etching direction limiting baffle and the second opening area of ​​the etching position limiting baffle. The substrate, which is moved by the mobile stage, is etched along the pre-etching depth distribution direction in the gradient groove deep grating fabrication area. The etching time and etching rate are controlled so that the substrate has pre-etching depth distribution parameters along the pre-etching depth distribution direction in the gradient groove deep grating fabrication area, thus obtaining a pre-etched substrate.

[0058] The etching time here is the single etching time multiplied by the number of etching cycles. The single etching time can be determined based on the moving speed of the substrate driven by the moving stage and the length of the first opening area of ​​the baffle defined by the first gradient etching direction.

[0059] The etching rate here can be determined by the substrate material, the voltage and current of the ion beam equipment, and the ion beam gas used.

[0060] like Figure 12 The diagram shows a pre-etched substrate obtained by pre-etching the substrate in the grating fabrication area during the fabrication process of a unidirectional linear gradient groove depth grating. Figure 13The diagram shows a pre-etched substrate obtained by performing a pre-etching operation on the substrate in the fabrication area of ​​the gradient groove deep grating using a unidirectional stepped gradient groove deep structure.

[0061] In a preferred embodiment, the area where the substrate is pre-etched may further include a tolerance region, which is the surrounding edge region of the gradient groove deep grating fabrication region. That is, during the pre-etching operation of the substrate in the gradient groove deep grating fabrication region, the surrounding edge region (i.e., the tolerance region) of the gradient groove deep grating fabrication region is simultaneously pre-etched. This pre-etched substrate reduces the height difference between the peripheral region of the gradient groove deep grating fabrication region and the edge grating structure of the gradient groove deep grating fabrication region, thereby avoiding any impact on subsequent processes such as spin coating, exposure, and development of the pre-etched substrate.

[0062] like Figure 14 The diagram shows a pre-etched substrate structure obtained by pre-etching the substrate in the grating fabrication region and tolerance region during the fabrication process of a unidirectional linear gradient groove depth grating. Figure 15 The diagram shows a pre-etched substrate obtained by performing pre-etching operations on the substrate in the grating fabrication area and the tolerance area during the fabrication process of a unidirectional stepped gradient groove depth grating.

[0063] For example, the spin coating of photoresist onto the pre-etched substrate in step S2 above to obtain a substrate with a photoresist mask specifically includes the following steps: Place the pre-etched substrate on the spin coater's spin coater stage.

[0064] Photoresist is dropped onto the surface of the pre-etched substrate.

[0065] Rotate the photoresist carrier to spin-coat the surface of the pre-etched substrate, thereby obtaining a substrate with a photoresist mask.

[0066] The amount of photoresist applied to the pre-etched substrate surface is related to the spin coating thickness of the photoresist on the substrate. There are no specific requirements for the spin coating thickness of the photoresist on the substrate, and those skilled in the art can set it according to actual needs.

[0067] For example, the beam interference exposure operation performed on the photoresist mask on the substrate in step S3 above to obtain a photoresist mask with changed properties on the substrate specifically includes the following steps: A substrate with a photoresist mask is placed in a holographic exposure system. The substrate with the photoresist mask is irradiated by an exposure field formed by beam interference, resulting in a photoresist mask with altered properties on the substrate.

[0068] Holographic exposure systems can employ either dual-beam exposure systems or Loewe mirror exposure systems.

[0069] like Figure 16 The diagram shows the optical path of a dual-beam exposure system. The incident beam emitted by the laser 10 enters the first waveplate 11. After the polarization state is adjusted by the first waveplate, it enters the beam-splitting prism 12. The beam-splitting prism 12 splits the beam into two beams. The first beam is reflected by the third mirror 16 and enters the first microscope objective 17. After being focused by the first microscope objective 17, it enters the first pinhole 19. After being filtered by the first pinhole 19, it enters the first collimating lens 21 and becomes the first parallel beam. The second beam is polarized by the second waveplate 13 and then reflected by the first mirror 14 and the second mirror 15 in sequence. After being focused by the second microscope objective 18, it enters the second pinhole 20. After being filtered by the second pinhole 20, it enters the second collimating lens 22 and becomes the second parallel beam. The first and second parallel beams are adjusted so that the interference period of the exposure field formed by the interference of the first and second parallel beams corresponds to the set grating period of the gradient groove depth grating to be prepared.

[0070] The substrate (sample to be exposed) with the photoresist mask is fixed in the exposure field at a set placement angle (the placement angle corresponds to the set grating line direction of the gradient groove deep grating to be prepared) and a beam interference exposure operation is performed to obtain a photoresist mask with changed properties on the substrate.

[0071] For example, the development operation of the photoresist mask whose properties have changed on the substrate in step S4 above, to obtain a photoresist grating mask on the substrate, and to obtain a substrate with a photoresist grating mask, specifically includes the following steps: The substrate with the photoresist mask is immersed in the developing solution for development, so that the photoresist mask at the corresponding position is dissolved in the developing solution, thereby obtaining a photoresist mask with changed properties on the substrate.

[0072] Taking positive photoresist as an example, After the photoresist mask with altered properties on the substrate is immersed in a developing solution for development, the light-exposed portion of the photoresist mask is eroded and dissolved by the developing solution, resulting in a substrate with a photoresist grating mask.

[0073] For example, the post-etching operation on the substrate with the photoresist grating mask in the gradient groove deep grating fabrication area in step S5 above to obtain the gradient groove deep grating master image specifically includes the following steps: The opposite side of the etched surface of the substrate is connected to the movable stage within the ion beam etching chamber in a second predetermined direction. An etching position limiting baffle is connected to one side of the etched surface of the substrate, and a second gradient etching direction limiting baffle is connected to a second position within the ion beam etching chamber. Here, the second predetermined direction is consistent with the gradient groove depth distribution direction of the gradient groove depth grating to be fabricated on the substrate.

[0074] The moving stage and ion beam equipment are started. The ion beam emitted by the ion beam equipment passes sequentially through the third opening area of ​​the second gradient etching direction limiting baffle and the second opening area of ​​the etching position limiting baffle to etch the substrate, which is moved by the moving stage, along the gradient groove depth distribution direction in the gradient groove deep grating fabrication area. The etching time and etching rate are controlled so that the substrate has gradient groove depth distribution parameters along the gradient groove depth distribution direction in the gradient groove deep grating fabrication area, thus obtaining the gradient groove deep grating master.

[0075] The etching time here is the single etching time multiplied by the number of etching cycles. The single etching time can be determined based on the moving speed of the substrate driven by the moving stage and the length of the third opening area of ​​the baffle defined by the second gradient etching direction.

[0076] The etching rate here can be determined by the substrate material, the voltage and current of the ion beam equipment, and the ion beam gas used.

[0077] like Figure 17 The diagram shows a first structural schematic of a gradient groove depth grating master with a unidirectional linear gradient groove depth structure, prepared using the gradient groove depth grating master fabrication process of the present invention. Figure 12 The diagram shows a gradient groove depth grating master structure with a unidirectional linear gradient groove depth, obtained by performing homogenization, exposure, and post-etching operations on the pre-etched substrate.

[0078] like Figure 18 The diagram shows a second structural schematic of a gradient groove depth grating master with a unidirectional stepped gradient groove depth structure, prepared using the gradient groove depth grating master fabrication process of the present invention. Figure 13 The diagram shows a gradient groove deep grating master structure with a unidirectional stepped gradient groove depth structure obtained by performing homogenization, exposure and post-etching operations on the pre-etched substrate.

[0079] like Figure 19 The diagram shown is a third structural schematic of a gradient groove depth grating master with a unidirectional linear gradient groove depth structure, prepared using the gradient groove depth grating master fabrication process of the present invention. Figure 14 The diagram shows a gradient groove depth grating master structure with a unidirectional linear gradient groove depth, obtained by performing homogenization, exposure, and post-etching operations on the pre-etched substrate.

[0080] like Figure 20 The diagram shown is a fourth structural schematic of a gradient groove depth grating master with a unidirectional stepped gradient groove depth structure, prepared using the gradient groove depth grating master fabrication process of the present invention. Figure 15 The diagram shows a gradient groove deep grating master structure with a unidirectional stepped gradient groove depth structure obtained by performing homogenization, exposure and post-etching operations on the pre-etched substrate.

[0081] from Figures 17-20 As can be seen, the bottom surfaces of the gradient groove deep grating structures fabricated on the substrate are on the same horizontal plane. Therefore, when the gradient groove deep grating structure is transferred to the imprinting adhesive of the waveguide substrate using the gradient groove deep grating master provided by this invention through nanoimprinting, it is possible to achieve no residual imprinting adhesive between the contact surface of the waveguide substrate and the imprinting adhesive and the bottom surface of the grating structure at different positions in the gradient groove deep grating area of ​​the waveguide substrate by simply controlling the thickness parameter of the imprinting adhesive of the waveguide substrate. This improves the display clarity of the diffraction grating waveguide.

[0082] This invention also provides a fabrication process for a diffraction grating waveguide, comprising the following steps: An imprinting master with a gradient groove deep grating structure is prepared; the imprinting master is prepared using the above-described gradient groove deep grating master preparation process.

[0083] The grating structure of the embossing master is transferred to the soft film substrate using a nanoimprinting process with a soft film adhesive, resulting in a soft film plate with an inverse structure of grating structure.

[0084] The inverse structure of the grating structure of the flexible film plate is transferred to the imprinting adhesive of the waveguide substrate through nanoimprinting process to obtain a diffractive waveguide with a gradient groove deep grating structure.

[0085] The thickness parameters of the imprinting adhesive layer on the waveguide substrate are matched with the imprinting master plate having a gradient groove depth grating structure. For example, when the height difference between the top surface of the imprinting master plate and the bottom surface of the grating structure is greater than the maximum groove depth of the gradient groove depth grating structure, the thickness parameters of the imprinting adhesive layer on the waveguide substrate are equal to the height difference between the top surface of the imprinting master plate and the bottom surface of the grating structure. When the height difference between the top surface of the imprinting master plate and the bottom surface of the grating structure is equal to the maximum groove depth of the gradient groove depth grating structure, the thickness parameters of the imprinting adhesive layer on the waveguide substrate are equal to the maximum groove depth of the gradient groove depth grating structure.

[0086] like Figure 21 The diagram shows a schematic of the gradient groove deep grating structure transferred by the master plate of the present invention on the waveguide substrate. Figure 21 Figure (a) in the middle corresponds to Figure 17 Gradient groove deep raster master, Figure 21 Figure (b) in the middle corresponds to Figure 18 Gradient groove deep raster master, Figure 21 Figure (c) in the middle corresponds to Figure 19 Gradient groove deep raster master, Figure 21 The corresponding diagram (d) in the middle Figure 20 Gradient groove deep raster master. Through... Figure 21 As can be seen, when the gradient groove deep grating master provided by the present invention is used to transfer the gradient groove deep grating structure to the imprinting adhesive of the waveguide substrate through nanoimprinting process, no residual imprinting adhesive can be set between the contact surface of the waveguide substrate and the imprinting adhesive and the bottom surface of the grating structure at different positions in the gradient groove deep grating area of ​​the waveguide substrate, thereby greatly improving the display clarity of the diffraction grating waveguide.

[0087] The present invention also provides a diffraction grating waveguide, which is prepared by the above-described fabrication process of the diffraction grating waveguide.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A process for fabricating a gradient groove deep grating master, characterized in that, Includes the following steps: A pre-etching operation is performed on the substrate in the gradient groove deep grating fabrication area to obtain a pre-etched substrate. Photoresist is spin-coated onto a pre-etched substrate to obtain a substrate with a photoresist mask. A beam interference exposure operation is performed on the photoresist mask on the substrate to obtain a photoresist mask with altered properties on the substrate. The photoresist mask whose properties have changed on the substrate is developed to obtain a photoresist grating mask on the substrate, and a substrate with a photoresist grating mask is obtained. The substrate with the photoresist grating mask is subjected to a post-etching operation in the gradient groove deep grating fabrication area to obtain the gradient groove deep grating master.

2. The process for fabricating a gradient groove deep grating master according to claim 1, characterized in that, The step of performing a pre-etching operation on the substrate in the gradient groove deep grating fabrication area to obtain a pre-etched substrate includes the following steps: Determine the pre-etching depth distribution parameters of the substrate in the gradient groove deep grating fabrication region; The substrate is placed in an etching system, and the etching system is used to perform a pre-etching operation on the gradient groove deep grating fabrication area of ​​the substrate according to the pre-etching depth distribution parameters to obtain a pre-etched substrate.

3. The process for fabricating a gradient groove deep grating master according to claim 2, characterized in that, Determining the pre-etching depth distribution parameters of the substrate in the gradient groove deep grating fabrication region includes the following steps: The pre-etching depth distribution parameters of the substrate in the fabrication area of ​​the gradient groove deep grating are determined based on the maximum grating groove depth value and the gradient groove depth distribution parameters of the gradient groove deep grating.

4. The process for fabricating a gradient groove deep grating master according to claim 3, characterized in that, The pre-etching depth distribution parameters of the substrate in the graded groove depth grating fabrication area are determined based on the maximum grating groove depth value and the graded groove depth distribution parameters of the graded groove depth grating, including: The pre-etching depth distribution parameters of the substrate in the gradient groove grating fabrication area are obtained by subtracting the maximum grating groove depth value from the gradient groove depth distribution parameters of the gradient groove depth grating.

5. The process for fabricating a gradient groove deep grating master according to claim 3 or 4, characterized in that, The gradient groove depth distribution parameters of the gradient groove depth grating are composed of the grating groove depth parameters at different positions within the gradient groove depth grating region; The pre-etching depth distribution parameters of the substrate in the gradient groove deep grating fabrication area are composed of the pre-etching depth parameters of the substrate at different positions in the gradient groove deep grating fabrication area.

6. The process for fabricating a gradient groove deep grating master according to claim 2, characterized in that, The etching system includes an ion beam etching chamber, a movable stage, a first gradient etching direction limiting baffle, a gradient etching position limiting baffle, and an ion beam device. A movable stage is provided inside the ion beam etching chamber, and the opposite side of the etched surface of the substrate is detachably connected to the movable stage; the movable stage can drive the substrate to move within the ion beam etching chamber. An ion beam device is fixedly installed at the first position within the ion beam etching chamber; The second position within the ion beam etching chamber is detachably connected to a first gradient etching direction limiting baffle. The first gradient etching direction defines a first opening area within the baffle, and the opening length of the first opening area varies in different areas along the direction in which the moving base drives the substrate. The etching position limiting baffle is connected to the etching surface of the substrate within the ion beam etching chamber, and the etching position limiting baffle has a second through-hole area.

7. The process for fabricating a gradient groove deep grating master according to claim 6, characterized in that, The substrate is placed in an etching system, and the etching system performs a pre-etching operation on the gradient groove deep grating fabrication area of ​​the substrate according to the pre-etching depth distribution parameters to obtain a pre-etched substrate, comprising: The opposite side of the etched surface of the substrate is connected to the movable stage in the ion beam etching chamber in a first set direction, the etching position limiting baffle is connected to one side of the etched surface of the substrate, and the first gradient etching direction limiting baffle is connected to the second position in the ion beam etching chamber. The mobile stage and ion beam equipment are started. The ion beam emitted by the ion beam equipment passes sequentially through the first opening area of ​​the first gradient etching direction limiting baffle and the second opening area of ​​the etching position limiting baffle. The substrate, which is moved by the mobile stage, is etched along the pre-etching depth distribution direction in the gradient groove deep grating fabrication area. The etching time and etching rate are controlled so that the substrate has pre-etching depth distribution parameters along the pre-etching depth distribution direction in the gradient groove deep grating fabrication area, thus obtaining a pre-etched substrate.

8. The process for fabricating a gradient groove deep grating master according to claim 1, characterized in that, Spin-coating photoresist onto a pre-etched substrate to obtain a substrate with a photoresist mask, comprising: The pre-etched substrate is placed on the spin coater stage; Photoresist is dropped onto the surface of the pre-etched substrate; Rotate the photoresist spin coating stage to spin coat the surface of the pre-etched substrate, thereby obtaining a substrate with a photoresist mask.

9. The process for fabricating a gradient groove deep grating master according to claim 1, characterized in that, Performing beam interference exposure on the photoresist mask on the substrate to obtain a photoresist mask with altered properties on the substrate includes: A substrate with a photoresist mask is placed in a holographic exposure system. The substrate with the photoresist mask is irradiated by an exposure field formed by beam interference, resulting in a photoresist mask with altered properties on the substrate. In this system, the placement angle of the substrate with the photoresist mask in the holographic exposure system corresponds to the set grating line direction of the gradient groove depth grating; the beam interference period of the exposure field corresponds to the set grating period of the gradient groove depth grating.

10. The process for fabricating a gradient groove deep grating master according to claim 1, characterized in that, A development operation is performed on the photoresist mask whose properties have changed on the substrate to obtain a photoresist grating mask on the substrate, resulting in a substrate with a photoresist grating mask, comprising: The substrate with the photoresist mask is immersed in the developing solution for development, so that the photoresist mask at the corresponding position is dissolved in the developing solution, thereby obtaining a photoresist mask with changed properties on the substrate.

11. The process for fabricating a gradient groove deep grating master according to claim 6, characterized in that, The etching system also includes a second gradient etching direction limiting baffle; The second position within the ion beam etching chamber is detachably connected to a second gradient etching direction limiting baffle. The second gradient etching direction defines a third opening area within the baffle, and the opening length of the third opening area varies in different regions along the direction in which the moving base drives the substrate.

12. The process for fabricating a gradient groove deep grating master according to claim 11, characterized in that, The substrate with the photoresist grating mask is subjected to a post-etching operation in the gradient groove deep grating fabrication area to obtain a gradient groove deep grating master, comprising: The opposite side of the etched surface of the substrate is connected to the movable stage in the ion beam etching chamber in a second set direction, the etching position limiting baffle is connected to one side of the etched surface of the substrate, and the second gradient etching direction limiting baffle is connected to the second position in the ion beam etching chamber. The moving stage and ion beam equipment are started. The ion beam emitted by the ion beam equipment passes sequentially through the third opening area of ​​the second gradient etching direction limiting baffle and the second opening area of ​​the etching position limiting baffle to etch the substrate, which is moved by the moving stage, along the gradient groove depth distribution direction in the gradient groove deep grating fabrication area. The etching time and etching rate are controlled so that the substrate has gradient groove depth distribution parameters along the gradient groove depth distribution direction in the gradient groove deep grating fabrication area, thus obtaining the gradient groove deep grating master.

13. The process for fabricating a gradient groove deep grating master according to claim 1, characterized in that, The area where the substrate is pre-etched also includes the tolerance area; The tolerance region is the surrounding edge region of the gradient groove deep grating fabrication region.

14. A fabrication process for a diffraction grating waveguide, characterized in that, Includes the following steps: An imprint master with a gradient groove deep grating structure is prepared; the imprint master is prepared using the gradient groove deep grating master preparation process described in any one of claims 1-13; The grating structure of the embossing master is transferred to the soft film substrate using a nanoimprinting process with a soft film adhesive to obtain a soft film plate with an inverse structure of grating structure. The inverse structure of the grating structure of the flexible film plate is transferred to the imprinting adhesive of the waveguide substrate through a nanoimprinting process to obtain a diffractive waveguide with a gradient groove deep grating structure; wherein, the thickness parameter of the imprinting adhesive layer of the waveguide substrate is matched and set with the imprinting master plate with the gradient groove deep grating structure.

15. A diffraction grating waveguide, characterized in that, The diffraction grating waveguide is fabricated using the fabrication process of the diffraction grating waveguide described in claim 14.

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