Manufacturing method of large-size diffraction optical waveguide element

Abstract

The manufacturing method of the large-size diffraction optical waveguide element comprises the following steps that a grating mother set is manufactured, silicon or quartz glass larger than or equal to 6 mm serves as a substrate, and the high-precision grating mother set is manufactured through the holographic-ion beam etching technology; the substrate is machined through the wafer back thinning technology to form a mold, and the thickness reduction value of the mold is smaller than 1 mm; the mold is copied by using a nanoimprint production process, and a sample of the mold is formed; performing waveguide bonding process treatment on the sample; the initial bonding sample is subjected to cutting process treatment, the grating is protected from being damaged, and cutting forming is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of waveguide element manufacturing technology, and in particular relates to a method for manufacturing a large-size diffraction optical waveguide element. Background Art

[0002] Diffraction waveguide technology is an emerging augmented reality optical technology. It achieves pupil expansion through holographic gratings, can significantly reduce the aperture of parts in the optical system, and realize the miniaturization of optical components. This technology is considered to be a mainstream AR optical solution due to its good display effect and mass production through photolithography.

[0003] At present, diffraction waveguide technology has been widely used in AR glasses. The thickness of diffraction waveguide elements in AR glasses can only be less than 1mm, and the size does not exceed 50mm. It can better fit the mainstream photolithography technology. The general manufacturing method is to obtain the grating master by holographic-ion beam etching or electron beam direct writing, and batch manufacture by nanoimprint lithography. The diffraction waveguide element in HUD has a larger diameter, generally up to about 280mm, and a thicker thickness, generally 6 to 10mm, which puts higher requirements on the diffraction wavefront of the diffraction grating, and cannot be produced using the mainstream diffraction waveguide manufacturing method, resulting in reduced manufacturing efficiency of diffraction waveguide elements. Summary of the invention

[0004] In view of this, the method for manufacturing a large-sized diffractive optical waveguide element provided by the present invention solves the problem that existing equipment and methods cannot manufacture large-sized diffractive optical waveguide elements.

[0005] A method for manufacturing a large-size diffractive optical waveguide element comprises the following steps:

[0006] Making a grating master, wherein silicon or quartz glass having a thickness of 6 mm or more is used as a substrate, and the grating master is made according to the substrate;

[0007] Thinning the grating master, wherein the substrate is processed by wafer back thinning technology to form a mold, and the thickness of the mold is reduced by less than 1 mm;

[0008] The mold is replicated using a nanoimprint production process, and a sample of the mold is formed;

[0009] The sample is subjected to a waveguide bonding process, wherein the sample is bonded to a flat glass having a thickness greater than or equal to 5 mm by a wafer bonding method to obtain an initial bonded sample;

[0010] The initial bonding sample is subjected to a cutting process, wherein the initial bonding sample is cut by a laser to obtain a waveguide element that meets the design requirements.

[0011] The technical beneficial effects of the present invention are:

[0012] In terms of substrate selection, the grating master uses thicker single crystal silicon or fused quartz as the substrate, and the thickness is generally selected to be 8mm to 10mm. The advantage of the thick substrate is that the surface shape of the grating to be produced is good and the impact on the subsequent photolithography process is small. In terms of production methods, the grating master adopts the technical solution of holographic-ion beam etching. Electron beam etching is suitable for the photolithography production of small-diameter masters, usually four inches, and cannot produce large-size grating masters. The holographic-ion beam etching solution uses the basic principle of light interference to form large-format, equidistant interference fringes, which is particularly suitable for the development of large-size, high-quality grating masters. The design concept of nanoimprint lithography equipment tends to be semiconductor-oriented, with a high degree of automation, but the thickness of the mold and substrate that can be processed is usually less than 2mm, so that the grating master can be processed and used by the nanoimprint lithography equipment. The wafer thinning technology is adopted to adjust the dilution ratio of the photoresist, and a thicker photoresist is spin-coated on the surface of the grating master by the spin coating method, and then the thicker grating master is thinned to a thickness range that can be handled by the nanoimprint lithography equipment. In addition, a roll-to-plane nanoimprint lithography equipment with a high degree of automation is used to batch-print a single grating master to obtain a working soft mold, and then a single working soft mold is batch-printed to obtain a thinner diffraction optical waveguide element, so as to realize large-scale manufacturing of waveguide graphics. The waveguide element obtained by printing is thin, which is far from the designed thickness. The wafer bonding technology is adopted to spin-coat bonding glue on a thicker flat glass, with the waveguide element on top. Under vacuum conditions, the thinner waveguide element is bonded to the thicker flat glass by the whole surface air pressure method to obtain a waveguide element of designed thickness. Finally, the quasi-circular waveguide element obtained in the above steps is cut by the laser cutting method to obtain a waveguide element of designed shape. The waveguide element to be cut is relatively thick and contains bonding glue in the middle. The bonding glue has a high absorption rate for cutting laser. The double-sided cutting method is selected. When the grating faces up, the waveguide is placed close to the workbench. When the grating faces down, the tooling is used to fix and clamp the waveguide element to protect the grating from damage and achieve cutting and cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0014] Figure 1 A large-sized diffractive optical waveguide element to be manufactured;

[0015] Figure 2 A process flow chart of a method for manufacturing a large-size diffractive optical waveguide element provided by an embodiment of the present invention;

[0016] Figure 3 A diagram of a method for making a grating master provided by an embodiment of the present invention;

[0017] Figure 4 A diagram of a method for thinning the back of a grating master provided in an embodiment of the present invention;

[0018] Figure 5 A flow chart of the nanoimprint lithography process provided by an embodiment of the present invention;

[0019] Figure 6 A diagram of a waveguide element bonding method provided by an embodiment of the present invention;

[0020] Figure 7 A diagram of a waveguide element cutting method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0022] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0023] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0024] like Figures 1 to 7 The method for manufacturing a large-size diffractive optical waveguide element includes the following steps:

[0025] S1: making a grating master, wherein a silicon or quartz glass substrate having a thickness of 6 mm or more is used as a substrate, and the grating master is made according to the substrate, for example, the substrate is processed and formed in a holographic-ion beam etching process;

[0026] S2: thinning the grating master, wherein the substrate is processed by wafer back thinning technology to form a mold, the thickness of the mold is reduced to less than 1 mm, and the mold is placed in a nanoimprint lithography device for batch replication under the premise of protecting the holographic grating, and the thickness of the grating master is reduced so that the master can be placed in the nanoimprint lithography device for operation, wherein the mold is roughly ground to ensure that the thickness is 0.7 mm-1 mm;

[0027] S3: The mold is replicated using the nanoimprint production process, and the mold sample is formed. The thinned grating master can achieve large-scale nanoimprint production;

[0028] S4: The sample is subjected to a waveguide bonding process, wherein the sample is bonded to a flat glass having a thickness greater than or equal to 5 mm by a wafer bonding method to obtain an initial bonded sample. The sample is processed by air pressure during the waveguide bonding process and subjected to surface glue coating. The purpose of the glue coating is to protect the holographic grating on the surface of the processed sample, ensure that the groove of the holographic grating is not damaged, and improve the processing yield, that is, the two pieces of glass are bonded by glue;

[0029] S5: The initial bonding sample is subjected to a cutting process, wherein the initial bonding sample is cut by a laser to obtain a waveguide element that meets the design requirements. For example, the initial bonding sample is cut by a double-sided laser to obtain a waveguide element that meets the design requirements.

[0030] Nanoimprint lithography is used on large-sized, thick glass substrates to manufacture large-sized diffractive optical waveguides. Holographic-ion beam etching technology is used to develop large-sized, thick glass or silicon-based grating masters. The wafer back thinning technology is used to thin the grating master to less than 2mm. Nanoimprint lithography is used to achieve batch imprint manufacturing of thin substrates. Then wafer bonding technology is used to thicken the thin substrate to the ideal design thickness, realizing batch manufacturing of large-sized diffractive optical waveguide components.

[0031] Example

[0032] Figure 1The large-sized diffraction optical waveguide element to be manufactured has a diagonal aperture of 280mm, a thickness of 8mm, a glass substrate refractive index of 1.75, and a surface including a coupling-in grating and a coupling-out grating. The coupling-in grating aperture is Φ20mm, the grating period is 400nm, the coupling-out grating aperture is 160mm×140mm, the coupling-in grating is generally a blazed grating or a beveled grating, and the coupling-out grating is generally a dot lattice grating. The thickness and single grating size of this element are more than ten times that of the diffraction optical waveguide element used in AR glasses, and it is impossible to use existing mature processes and equipment for large-scale manufacturing. In order to solve the difficulties in manufacturing large-sized diffraction optical waveguide elements with existing technologies, a technology combining wafer thinning and wafer bonding is proposed to realize large-scale manufacturing of large-sized, thick glass substrate diffraction optical waveguide elements, see. Figures 2 to 7 As shown, specifically,

[0033] Process step 1: Grating master production

[0034] The grating master was made using holographic-ion beam etching technology, and the substrate was made of fused quartz glass with a thickness of 8 mm and an aperture of Φ300 mm.

[0035] The specific process includes:

[0036] (1) Substrate coating: After cleaning and viscosity increasing, the glass substrate is spin-coated with positive photoresist AZ4562.

[0037] (2) Exposure and development. In the interference light field, shield the out-coupling grating area, expose the in-coupling grating area, shield the in-coupling grating area, rotate 45°, expose the out-coupling grating area once, rotate 90° in the opposite direction, expose the out-coupling grating area once, and the exposure time of the out-coupling grating area is equal to half of the exposure time of the in-coupling grating area. After development, the mask to be etched is obtained.

[0038] (3) Etching: In an ion beam etcher, oblique etching is used to obtain a blazed grating or a slanted grating in the coupling-in region, and forward etching is used to obtain a rectangular grating in the coupling-out region.

[0039] Process step 2: Grating master thinning

[0040] The wafer thinning technology is adopted, the holographic grating is protected by photoresist, and the grating master is rough-ground and thinned on the back. The specific process includes:

[0041] (1) Spin-coat the photoresist on the surface of the grating master. The photoresist does not need to be diluted and can be directly spin-coated on the surface of the grating master and baked to fix. This process should be repeated several times to ensure that the thickness of the photoresist exceeds 20um to protect the grating.

[0042] (2) Rough grinding and thinning of the back side. Place the grating master facing downward, fix it on the rough grinding disc, and slowly rough grind until the thickness is reduced to less than 2 mm.

[0043] Process step 3: Nanoimprint production

[0044] Nanoimprint lithography is used to replicate the thinned grating master on a large scale to obtain thinner waveguide components. The specific process includes:

[0045] (1) Production of working soft mold. Spin-coat soft film glue on the quartz grating master, and then perform batch embossing to obtain the PET working soft mold;

[0046] (2) Imprinting of waveguide components: Spin-coat an imprinting glue on a relatively small glass substrate. In this embodiment, the glass substrate has a diameter of Φ290 mm and a thickness of 2 mm. The waveguide components are obtained by batch imprinting.

[0047] Process step 4: Waveguide bonding

[0048] The wafer bonding technology is used to bond a thinner waveguide component to a thicker flat glass to obtain a waveguide component of designed thickness. The specific process includes:

[0049] (1) Glue coating on glass substrate: Spin-coat bonding glue on a glass substrate with a thickness of 6 mm and a diameter of 290 mm. The thickness of the bonding glue should not exceed 15 μm, the refractive index range should be 1.75 ± 0.01, and the thickness uniformity should be better than 3%.

[0050] (2) Vacuum pressure bonding: In a high vacuum environment, the waveguide element is placed on a glass substrate coated with glue to avoid bubbles. Then, high air pressure is used to evenly apply pressure on the waveguide surface to achieve a firm bond.

[0051] Process step 5: cutting and forming.

[0052] The quasi-circular waveguide element is cut into a designed shape by using a laser cutting technical solution. Laser cutting is not easy to generate dust and impurities, and will not cause damage to the waveguide element or degradation of the surface quality.

[0053] The specific process includes:

[0054] (1) Front cutting: With the grating facing upward, place the waveguide component on the cutting machine workbench and complete the front cutting according to the CAD drawing.

[0055] (2) Back cutting. With the grating surface facing downward, place the waveguide element on the workbench of the cutting machine, making sure that the grating surface does not touch the workbench, and complete the back cutting according to the CAD drawing.

[0056] (3) Split. With the grating facing upward, place the waveguide element on the cutting machine workbench to form the split.

[0057] Thanks to the embodiments of the present invention, large-size, thick-base diffractive optical waveguide elements can be manufactured on a large scale with high quality and applied in the HUD field.

[0058] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for manufacturing a large-size diffractive optical waveguide element, characterized in that: The following steps are included: Making a grating master, wherein silicon or quartz glass having a thickness of 6 mm or more is used as a substrate, and the grating master is made according to the substrate; Thinning the grating master, wherein the substrate is processed by wafer back thinning technology to form a mold, and the thickness of the mold is reduced by less than 1 mm; The mold is replicated using a nanoimprint production process to form a sample of the mold; The sample is subjected to a waveguide bonding process, wherein the sample is bonded to a flat glass having a thickness greater than or equal to 5 mm using a wafer bonding method to obtain an initial bonding sample; The initial bonding sample is subjected to a cutting process, wherein the initial bonding sample is cut by a laser to obtain a waveguide element that meets the design requirements.

2. The method for manufacturing a large-size diffractive optical waveguide element according to claim 1, characterized in that: The substrate is processed and shaped in a holographic-ion beam etching process.

3. The method for manufacturing a large-size diffractive optical waveguide element according to claim 1, characterized in that: The mold is roughly ground to ensure a thickness of 0.7 mm to 1 mm.

4. The method for manufacturing a large-size diffractive optical waveguide element according to claim 1, characterized in that: The mold is placed in a nanoimprint lithography device for batch replication.

5. The method for manufacturing a large-size diffractive optical waveguide element according to claim 1, characterized in that: The sample is processed by air pressure during the waveguide bonding process and subjected to surface glue coating.

6. The method for manufacturing a large-size diffractive optical waveguide element according to claim 1, characterized in that: The initial bonding sample adopts a double-sided laser cutting method to obtain a waveguide element that meets the design requirements.

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