Method of manufacturing large size diffractive optical waveguide elements

Abstract

The large-size diffraction optical waveguide element manufacturing method comprises the following steps: manufacturing a grating master, wherein silicon or quartz glass with a size greater than or equal to 6 mm is used as a substrate, and a high-precision grating master is manufactured by using a holographic-ion beam etching technology; thinning the grating master, wherein a wafer back thinning technology is used to process the substrate to form a mold, and the thickness of the mold is reduced by less than or equal to 1 mm; the mold is replicated by using a nano-imprint production process, and a sample of the mold is formed; the sample is subjected to a waveguide bonding process; and the initial bonding sample is subjected to a cutting process, so that the grating is protected from damage and cutting and forming are realized.

Description

Technical Field

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

[0002] Diffraction waveguide technology is an emerging augmented reality optical technology. It achieves pupil expansion through holographic gratings, which 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 ability to be mass-produced through photolithography.

[0003] Currently, diffraction waveguide technology is widely used in AR glasses. The diffraction waveguide components in AR glasses can be less than 1mm thick and no larger than 50mm in size, making them well-suited to mainstream lithography techniques. Typical manufacturing methods involve holographic-ion beam etching or electron beam direct writing to obtain the grating master, followed by nanoimprint lithography for mass production. However, the diffraction waveguide components used in HUDs have a larger diameter, typically around 280mm, and a relatively thick thickness, typically 6 to 10mm. This places higher demands on the diffraction grating's diffraction wavefront, making them difficult to manufacture using mainstream diffraction waveguide manufacturing methods, resulting in reduced manufacturing efficiency. 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-scale diffraction optical waveguide element comprises the following steps:

[0006] Making a grating master, wherein a silicon or quartz glass substrate having a thickness greater than or equal to 6 mm is used as the substrate, and the grating master is made based on the substrate;

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

[0008] The mold is replicated using a nanoimprint production process to form a sample of the mold;

[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 using 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 a thicker single crystal silicon or fused quartz substrate, generally with a thickness of 8mm to 10mm. The advantage of a 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 method, 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-scale grating masters. The holographic-ion beam etching solution uses the basic principle of light interference to form large-scale, equally spaced interference fringes, which is particularly suitable for the development of large-scale, high-quality grating masters. The design concept of nanoimprint lithography equipment tends to be semiconductor-oriented and has a high degree of automation, but the thickness of the molds and substrates that can be processed is usually less than 2mm. In order to enable the grating master to be processed and used by nanoimprint lithography equipment. Using a wafer thinning technique, the dilution ratio of the photoresist is adjusted. A thicker layer of photoresist is spin-coated onto the surface of the grating master, followed by rough grinding to reduce the thickness. This thin layer is then thinned to a thickness within the range that can be processed by nanoimprint lithography equipment. Furthermore, using a highly automated roll-to-plane nanoimprint lithography system, a single grating master is used for batch imprinting to produce a working soft mold. This single working soft mold is then used to batch imprint thinner diffractive optical waveguide components, enabling large-scale waveguide patterning. The resulting waveguide components are relatively thin, significantly different from the designed thickness. Using a wafer bonding technique, bonding adhesive is spin-coated onto a thicker flat glass plate, with the waveguide component positioned on top. Under vacuum conditions, the thinner waveguide component is bonded to the thicker flat glass plate using full-surface air pressure to achieve the designed thickness. Finally, the quasi-circular waveguide components obtained in the previous steps are cut using laser cutting to obtain the designed waveguide components. The waveguide component 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 component 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 following briefly introduces the drawings required for use in the embodiments. 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 any creative work.

[0014] Figure 1 A large-sized diffraction optical waveguide component 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 producing 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 component bonding method provided by an embodiment of the present invention;

[0020] Figure 7 A diagram of a waveguide element cutting method provided by 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, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this 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 this 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 an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0024] like Figures 1 to 7 The method for manufacturing a large-scale diffraction 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 greater is used as the substrate, and the grating master is made based on the substrate, for example, the substrate is formed by a holographic-ion beam etching process;

[0026] S2: Thinning the grating master. The substrate is processed using wafer backside thinning technology to form a mold. The mold thickness is reduced to less than 1 mm. While protecting the holographic grating, the mold is placed in a nanoimprint lithography apparatus for batch replication. This reduces the thickness of the grating master so that the master can be placed in the nanoimprint lithography apparatus for operation. The mold is then coarsely ground to ensure a thickness of 0.7 mm to 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 undergoes a waveguide bonding process, wherein the sample is bonded to a flat glass sheet with a thickness greater than or equal to 5 mm using a wafer bonding method to obtain an initial bonded sample. The sample is processed using air pressure during the waveguide bonding process and then 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 shape of the holographic grating is not damaged, and improve the processing yield. That is, the two pieces of glass are bonded together by glue;

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

[0030] Nanoimprint lithography is used to fabricate large-scale diffractive waveguides on large, thick glass substrates. Holographic-ion beam etching is used to develop large, thick glass or silicon grating masters. Wafer back thinning is used to thin the grating masters to less than 2 mm. Nanoimprint lithography is used to achieve batch imprint manufacturing of thin substrates. Wafer bonding is then used to thicken the thin substrates to the desired design thickness, enabling batch manufacturing of large-scale diffractive waveguide components.

[0031] Examples

[0032] Figure 1The large-scale diffraction optical waveguide component to be manufactured has a diagonal aperture of 280mm and a thickness of 8mm. The refractive index of the glass substrate is 1.75. The surface contains a coupling-in grating and a coupling-out grating. The coupling-in grating aperture is Φ20mm, the grating period is 400nm, and the coupling-out grating aperture is 160mm×140mm. The coupling-in grating is generally a blazed grating or a skewed grating, and the coupling-out grating is generally a dot matrix grating. The thickness and single grating size of this component are more than ten times that of the diffraction optical waveguide component used in AR glasses, and it cannot be mass-produced using existing mature processes and equipment. In order to solve the difficulties in manufacturing large-scale diffraction optical waveguide components with existing technologies, a technology combining wafer thinning and wafer bonding is proposed to achieve large-scale manufacturing of large-scale, thick glass substrate diffraction optical waveguide components, see [1]. 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. 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 tackifying the glass substrate, spin-coat the positive photoresist AZ4562.

[0037] (2) Exposure and development. In the interference light field, block the out-coupling grating area, expose the in-coupling grating area, block 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 two exposure times of the out-coupling grating area are equal and 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 solution 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 grating master. The photoresist does not need to be diluted and is directly spin-coated on the grating master surface and baked to fix. This process should be repeated several times to ensure that the photoresist thickness exceeds 20μm to protect the grating.

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

[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 molds. Spin-coat soft film glue on the quartz grating master and batch-print to obtain PET working soft molds;

[0046] (2) Waveguide component imprinting: Spin-coat an imprinting adhesive onto a relatively small glass substrate. In this embodiment, the glass substrate has a diameter of Φ290 mm and a thickness of 2 mm, and batch imprints are used to obtain waveguide components.

[0047] Process step 4: Waveguide bonding

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

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

[0050] (2) Vacuum bonding: In a high vacuum environment, the waveguide component 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 strong bond.

[0051] Process step 5: cutting and shaping.

[0052] The quasi-circular waveguide element is cut into the designed shape by using the laser cutting technology. 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. Place the waveguide component on the cutting machine workbench with the grating facing upwards and complete the front cutting according to the CAD drawing.

[0055] (2) Back cutting. Place the waveguide component on the workbench of the cutting machine with the grating surface facing down, ensuring 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-sized, thick-substrate diffractive optical waveguide components 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 scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A method for manufacturing a large-scale diffraction optical waveguide element, characterized in that: The following steps are included: Making a grating master, wherein a silicon or quartz glass substrate having a thickness of 6 mm or greater is used as the substrate, and the grating master is made based on the substrate, wherein the substrate is formed by a holographic-ion beam etching process; Grating master thinning, wherein the substrate is processed using wafer back thinning technology to form a mold, and the thickness of the mold is reduced to less than 1mm; 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 bonded sample, wherein the sample is processed using an air pressure method during the waveguide bonding process and subjected to a surface glue coating process; The initial bonding sample is subjected to a cutting process, wherein the initial bonding sample is subjected to a laser cutting method to obtain a waveguide element that meets the design requirements, wherein the initial bonding sample is subjected to a double-sided laser cutting method to obtain a waveguide element that meets the design requirements.

2. The method for manufacturing a large-scale diffractive optical waveguide element according to claim 1, wherein: The mold is coarsely ground to ensure a thickness of 0.7 mm to 1 mm.

3. The method for manufacturing a large-scale diffractive optical waveguide element according to claim 1, wherein: The mold is placed in a nanoimprint lithography device for batch replication.

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