Lithium niobate / lithium tantalate bonding method and application

Abstract

The invention discloses a lithium niobate / lithium tantalate bonding method, and belongs to the technical field of single crystal thin film preparation. The method comprises the following steps: obtaining a lithium niobate / lithium tantalate slide and a substrate slide; the single-side surface of at least one of the lithium niobate / lithium tantalate slide and the substrate slide is uniformly covered with bonding glue; and aligning the lithium niobate / lithium tantalate slide with the substrate slide, positioning the bonding glue between the lithium niobate / lithium tantalate slide and the substrate slide, vacuumizing, pressurizing, defoaming and fixing, and irradiating the photoresist by using a light source to perform photochemical reaction to complete bonding. The problems of warping, fragmentation and the like of lithium niobate / lithium tantalate caused by high temperature and high pressure in a traditional hot gluing bonding process are solved, the bonding yield is improved, meanwhile, the process time is shortened, the energy consumption is reduced, the cost is reduced, and a reliable technical scheme is provided for batch preparation of large-size single crystal lithium niobate / lithium tantalate films.

Description

Technical Field

[0001] The present application relates to a lithium niobate / lithium tantalate bonding method and application, and belongs to the technical field of single crystal piezoelectric film preparation. Background Art

[0002] In recent years, single-crystal lithium niobate / lithium tantalate has attracted more and more attention due to its low dielectric loss and good piezoelectric properties in RF and piezoelectric applications. Among them, single-crystal lithium niobate / lithium tantalate thin films (LNOI / LTOI) inherit the excellent optoelectronic properties of single-crystal materials, such as low-loss transparent windows of 350nm-5μm, excellent second-order nonlinear optics, electro-optics, acousto-optics, piezoelectricity, pyroelectricity, etc., combined with the strong light field binding ability of thin film waveguides, high-speed electro-optic modulators, high-efficiency nonlinear frequency conversion devices and high-performance acousto-optic devices based on single-crystal lithium niobate / lithium tantalate thin films have demonstrated performance that traditional bulk materials cannot achieve. However, the main limiting factor of single-crystal lithium niobate / lithium tantalate thin films and various types is the bonding process in preparation and packaging. Before preparing single-crystal thin films, lithium niobate and lithium tantalate wafers need to be bonded with a protective substrate to solve the problem of cracking during thinning. At the same time, the integration of different devices on the chip also depends on bonding technology.

[0003] Temporary bonding technology plays a key role in semiconductor processing and microelectronic device manufacturing, especially in high-end manufacturing processes such as wafer-level packaging, three-dimensional integration and microsystem assembly. Although this technology brings many advantages, it also faces a series of technical challenges in practical applications, mainly including but not limited to the following aspects: (1) Bonding temperature and pressure: When bonding some piezoelectric and ferroelectric wafer materials, problems such as excessive bonding temperature causing wafer warping and deformation, and insufficient bonding strength of the bonding adhesive at low temperatures may occur; when encountering hard and brittle materials, excessive bonding pressure is prone to direct fragmentation and other problems; this greatly limits the application scope of thermal adhesive temporary bonding. (2) Mismatched thermal expansion coefficients: The difference in thermal expansion coefficients between the bonding material and the substrate may lead to stress concentration, causing fracture of the bonding interface, resulting in warping, deformation and even fragmentation. Designing a temporary bonding material with good compatibility or lowering the bonding temperature is a way to reduce such problems. (3) Bond strength control: Temporary bonding needs to ensure the stability of the wafer or chip during subsequent processing while being able to be easily and non-destructively debonded in the final stage. Therefore, how to accurately control the bonding strength to avoid being too strong and causing difficulty in debonding or too weak and causing debonding during processing is an important issue. (4) Interface contamination and residue: Due to the preheating and temperature rise process during thermal adhesive bonding and debonding, residual adhesive or contaminants may be generated at room temperature after debonding. These residues will affect device performance, especially for high-precision semiconductor devices. How to effectively remove these residues while protecting sensitive device structures is a technical challenge. (5) Cost and efficiency: Thermal adhesive temporary bonding requires matching bonding adhesive, preheating module, appropriate heating rate and cooling rate. The cost of materials, the time and energy consumption required for debonding, and the complexity of the entire process are directly related to production cost and efficiency.

[0004] At present, the bonding process of lithium niobate / lithium tantalate materials has the following main difficulties: (1) Lithium niobate / lithium tantalate crystals integrate piezoelectric, ferroelectric, pyroelectric and other properties, and are very sensitive to temperature and pressure. The heating and pressurization during the bonding process can easily lead to fragmentation; (2) The thermal expansion coefficient of lithium niobate / lithium tantalate is large, and the large difference in thermal expansion between the carrier and the heating element after heating can easily cause large warping or even direct fragmentation. Therefore, the bonding process has always been a technical problem that restricts the preparation and application of single-crystal lithium niobate / lithium tantalate films. Summary of the invention

[0005] In order to solve the warping and fragmentation problems existing in the prior art of lithium niobate / lithium tantalate wafer bonding process, the present application provides a lithium niobate / lithium tantalate bonding method, which uses a commonly used bonding adhesive as a bonding medium to bond the lithium niobate / lithium tantalate material to the substrate through a photochemical reaction. Specifically, a light source of appropriate wavelength is irradiated through the lithium niobate / lithium tantalate or the substrate carrier and the bonding adhesive is allowed to undergo a photochemical reaction, thereby achieving rapid bonding.

[0006] This application adopts the following technical solutions: A lithium niobate / lithium tantalate bonding method comprises the following steps: Provide lithium niobate / lithium tantalate carriers and substrate carriers; Uniformly covering the single-side surface of the lithium niobate / lithium tantalate carrier and / or substrate carrier with bonding glue; Align the lithium niobate / lithium tantalate carrier with the substrate carrier so that the bonding glue is located between the lithium niobate / lithium tantalate carrier and the substrate carrier, apply pressure for bonding, and then use a light source to irradiate the bonding glue for photochemical reaction to complete the bonding.

[0007] The choice of bonding adhesive is not strictly limited in this application, and any bonding adhesive that can be cured by a light-triggered chemical reaction can be used, such as epoxy resin, polyurethane, acrylate, silicone, etc.

[0008] The bonding method adopted in the present application is an optimization of the method of use, that is, curing is achieved through a light-triggered chemical reaction. By irradiating light of a specific wavelength, the photoinitiator (photosensitizer) in the glue liquid is triggered to produce free radicals or cations, thereby initiating chain polymerization and cross-linking chemical reactions between the prepolymer and the active diluent, so that the adhesive is converted from liquid to solid within a few seconds, and the bonding between the bonding materials is completed. Compared with the conventional bonding method in the prior art, the method of use is directly optimized. For example, compared with the use of photosensitive bonding glue in the prior art, the present application does not require processes such as photolithography and development, nor does it require a heating process.

[0009] In one embodiment, a lithium niobate / lithium tantalate bonding method comprises the following steps: Obtaining a lithium niobate / lithium tantalate coated carrier with a surface uniformly covered with bonding glue; Obtaining a substrate-coated carrier sheet with the surface uniformly covered with bonding glue; The lithium niobate / lithium tantalate coated carrier is aligned with the cover adhesive surface of the substrate coated carrier and pressure bonded, and then a light source is used to irradiate the bonding adhesive to carry out a photochemical reaction to complete the bonding.

[0010] In one embodiment, the covering method is selected from the group consisting of coating.

[0011] In one embodiment, the pressure bonding process includes: vacuuming for pressurization, degassing and fixing.

[0012] Lithium niobate / lithium tantalate refers to lithium niobate or lithium tantalate materials. In the present application, the lithium niobate or lithium tantalate materials are selected from lithium niobate or lithium tantalate wafers or films.

[0013] In one embodiment, the pressure bonding conditions include: the pressure is 10 g / cm 2 ~1000g / cm 2The pressurization time is 10s ~300s.

[0014] In one embodiment, the bonding is a permanent bonding or a temporary bonding; When the bonding is permanent bonding, the bonding adhesive is a permanent bonding adhesive; for example, CV2001 bonding adhesive.

[0015] When the bonding is temporary bonding, the bonding adhesive is a self-debonding adhesive, such as TBM-01L bonding adhesive, 8002 bonding adhesive, 3311 bonding adhesive, and after the bonding is completed, a debonding process is also included to remove the substrate and the bonding adhesive.

[0016] In one embodiment, the debonding method is selected from at least one of laser debonding, thermal debonding, hydrothermal debonding, and chemical solvent debonding.

[0017] In one embodiment, the bonding adhesives are all traditional commercially available bonding adhesives to which different debonding agents are added.

[0018] In one embodiment, the bonding adhesive has a coverage thickness of 5 μm to 100 μm.

[0019] In one embodiment, the bonding adhesive on the lithium niobate / lithium tantalate coated wafer and the substrate coated wafer has a coverage thickness of 5 μm to 100 μm.

[0020] In one embodiment, the covering condition is: spreading the glue at a speed of 1000 rpm / min to 9000 rpm / min.

[0021] In one embodiment, the conditions of the photochemical reaction include: the wavelength of the light source is 5nm~1mm, the intensity of the light source is 10 mw / cm 2 ~1000mw / cm 2 The irradiation time is 10 s ~300 s.

[0022] In one embodiment, the light source is selected from infrared light with a wavelength of 0.16 to 1000 μm or ultraviolet light with a wavelength of 10 nm to 400 nm.

[0023] In one embodiment, the substrate is selected from a silicon wafer, a glass wafer, a sapphire wafer, a silicon carbide wafer, and a ceramic wafer.

[0024] In one embodiment, the lithium niobate / lithium tantalate bonding method comprises the following steps: Obtaining a coated carrier, wherein the coated carrier is a lithium niobate / lithium tantalate carrier and a substrate carrier whose surface is uniformly covered with photoresist; The lithium niobate or lithium tantalate substrate is aligned with the glue-coated surface of the glue-coated carrier and fixed under pressure, and then the bonding glue is irradiated with a light source to cause a photochemical reaction to obtain a bonding sheet; Temporary bonding is to debond the bonded wafer to remove the carrier wafer and photoresist.

[0025] Permanent bonding does not involve debonding.

[0026] According to another aspect of the present application, there is also provided an application of the above-mentioned lithium niobate / lithium tantalate bonding method in a thin film preparation process or a device packaging process.

[0027] The beneficial effects of this application include: The lithium niobate / lithium tantalate bonding method provided in the present application, compared with traditional hot-coating bonding, does not require heating and high-pressure bonding, and can avoid the problems of lithium niobate / lithium tantalate warping and fragmentation caused by high temperature and high pressure in traditional bonding processes, thereby improving the bonding yield and providing a reliable technical solution for the batch preparation of large-size single-crystal lithium niobate / lithium tantalate films; the bonding method can be applied to temporary bonding before lithium niobate / lithium tantalate wafer thinning to achieve more extreme wafer thinning, and can also be applied to packaging bonding for integration of different devices and chips to provide a reliable technical solution for heterogeneous integration of different functional materials and devices; the bonding method selects conventional commercially available bonding glue as the bonding medium, undergoes a photochemical reaction under light irradiation, and cures to complete the bonding, which not only shortens the process time, reduces energy consumption, and reduces costs, but also can select the corresponding bonding glue type according to needs to determine whether debonding is required, and the debonding method can be flexibly selected according to the type of bonding glue used, such as laser debonding, heating debonding, hydrothermal debonding, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the photochemical reaction bonding method of lithium niobate / lithium tantalate wafers in this application.

[0029] Figure 2 This is a schematic diagram of the photochemical reaction bonding used in the packaging bonding structure of this application.

[0030] Figure 3 This is a schematic diagram of a temporary bonding structure in which photochemical reaction bonding that can be laser debonded is used in the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0033] In the prior art, lithium niobate / lithium tantalate crystals integrate piezoelectric, ferroelectric, pyroelectric and other properties, and are very sensitive to temperature and pressure. The heating and pressurization during the bonding process can easily lead to fragmentation, and the thermal expansion coefficient of lithium niobate / lithium tantalate is large. After heating, the thermal expansion difference with the carrier is large, which can easily cause large warping or even direct fragmentation. Therefore, the bonding process has always been a technical problem that restricts the preparation and application of single crystal lithium niobate / lithium tantalate thin films. In view of the problems of warping and fragmentation in the prior art of lithium niobate / lithium tantalate wafer bonding process, the inventors found that a layer of bonding glue is spin-coated on a clean carrier (lithium niobate / lithium tantalate or substrate), aligned and placed, pressurized and fixed, and a light source of appropriate wavelength is selected to irradiate the bonding glue to cause a photochemical reaction, so as to quickly complete the bonding, and the corresponding bonding glue type can be selected according to the needs to determine whether debonding is required. The debonding method can be flexibly selected according to the type of bonding glue used, such as laser debonding, heating debonding, hydrothermal debonding, etc.

[0034] In one embodiment, a lithium niobate / lithium tantalate bonding method comprises the following steps: Provide lithium niobate / lithium tantalate carriers and substrate carriers; Uniformly covering the single-side surface of the lithium niobate / lithium tantalate carrier and / or substrate carrier with bonding glue; Align the lithium niobate / lithium tantalate carrier with the substrate carrier so that the bonding glue is located between the lithium niobate / lithium tantalate carrier and the substrate carrier, apply pressure for bonding, and then use a light source to irradiate the bonding glue for photochemical reaction to complete the bonding.

[0035] The coverage thickness of the bonding adhesive is independently 5 to 100 μm.

[0036] In one embodiment, a lithium niobate / lithium tantalate bonding method comprises the following steps: Obtaining a lithium niobate / lithium tantalate coated carrier with a surface uniformly covered with bonding glue; Obtaining a substrate-coated carrier sheet with the surface uniformly covered with bonding glue; The coated surfaces of the lithium niobate / lithium tantalate glue carrier and the substrate glue carrier are aligned and pressure-bonded, and then a light source is used to irradiate the photoresist to carry out a photochemical reaction to complete the bonding.

[0037] In the present application, the bonding glue may be covered on only one side of the lithium niobate / lithium tantalate carrier and the substrate carrier, or may be covered on one side of both carriers.

[0038] In one embodiment, the covering method is selected from the group consisting of coating.

[0039] In one embodiment, the pressure bonding conditions include: the pressure is 10-1000 g / cm 2 , the pressurization time is 10~300s.

[0040] The bonding method of the present application does not require heating and can be performed in a clean room, thus avoiding the negative impact of bonding pressure and temperature on wafer materials. At the same time, due to the short bonding time, no preheating is required, which shortens the process time and energy consumption, greatly improving the bonding efficiency.

[0041] In one embodiment, the bonding is a permanent bonding and the bonding glue is a permanent bonding glue.

[0042] In one embodiment, the bonding is temporary bonding, the bonding adhesive is a self-debonding adhesive, and after the bonding is completed, a debonding process is also included to remove the substrate and the bonding adhesive.

[0043] In this application, temporary bonding refers to temporarily bonding a wafer or a thin film material to a carrier substrate to provide support and protection in subsequent process steps, especially for thin wafers and three-dimensional integration and other high-precision operations. Glue coating temporary bonding technology plays a key role in semiconductor processing and microelectronic device manufacturing, especially in high-end manufacturing processes such as wafer-level packaging, three-dimensional integration and microsystem assembly. The technical solution of this application can overcome the problems in the prior art that when bonding some piezoelectric and ferroelectric wafer materials, the bonding temperature may be too high, causing the wafer to warp and deform, the bonding strength of the bonding glue at low temperatures is insufficient, and when encountering hard and brittle materials, the bonding pressure is too high and direct fragments are prone to occur. The technical solution of this application can greatly avoid the application scope limitation of traditional hot glue temporary bonding. In addition, the technical solution of this application can also overcome the problem that the difference in thermal expansion coefficients between the bonding material and the substrate in the conventional hot glue temporary bonding process in the prior art may cause stress concentration and cause fracture, warping, deformation and even fragmentation of the bonding interface.

[0044] In one embodiment, the debonding method is selected from at least one of laser debonding, thermal debonding, hydrothermal debonding, and chemical solvent debonding.

[0045] In this application, the debonding method is based on the type of debonding agent in the bonding glue, and the specific meaning of the debonding method is as follows: Laser debonding: Laser uses a laser beam to scan the cured bonding adhesive to age it and achieve debonding.

[0046] Pyrolysis bonding: The cured bonding adhesive decomposes or degrades due to heat, losing its adhesiveness and achieving debonding.

[0047] Hydrothermolysis bonding: The chemical decomposition process of the cured bonding adhesive after absorbing water causes changes in the molecular structure, thereby affecting the performance, such as reduced strength and loss of adhesiveness. Chemical solvent debonding: Chemical solvents penetrate into the adhesive layer and react with the chemical bonds therein, thereby softening or dissolving the bonding adhesive and achieving debonding.

[0048] In one embodiment, the photopermanent bonding is performed without any debonding; In one embodiment, the coverage thickness of the bonding glue on the lithium niobate / lithium tantalate coated carrier and the substrate coated carrier is independently 5-100 μm. In the present application, the photochemical reaction bonding has the following characteristics: low cost, the bonding glue is conventionally available on the market; fast bonding, the bonding glue can react rapidly in a short time under light irradiation, thereby improving production efficiency; environmentally friendly, usually does not contain solvents or volatiles, and is relatively friendly to the environment; diverse performance, the bonding glue can adjust the debonding agent according to different needs to obtain different debonding methods; a wide range of applications, and can be used to bond a variety of materials, such as glass, plastic, metal, etc.

[0049] In one embodiment, the covering condition is: spreading the glue at a rotation speed of 1000-9000 rpm / min.

[0050] The type of bonding glue in the present application and the single dosage can be adjusted according to the type of actual bonding material, application, and glue thickness; in the specific embodiment of the present application, it is preferred to select the type of bonding glue according to the bonding material and bonding application, and the speed of glue spreading, the dosage of bonding glue and the viscosity jointly determine the thickness of the glue. The faster the speed, the smaller the dosage, the lower the viscosity, and the smaller the thickness of the bonding glue.

[0051] In one embodiment, the conditions of the photochemical reaction include: the wavelength of the light source is 5nm~1mm, the intensity of the light source is 10~1000mw / cm 2 , the irradiation time is 10~300s.

[0052] In one embodiment, the light source is selected from infrared light with a wavelength of 0.16-1000 μm or ultraviolet light with a wavelength of 10-400 nm.

[0053] The principle of photochemical reaction bonding is to induce the photoinitiator in the adhesive to produce free radicals or cations through light irradiation of a specific wavelength, thereby initiating chain polymerization and cross-linking chemical reactions between the prepolymer and the reactive diluent, so that the adhesive is converted from liquid to solid within a few seconds to produce a stable adhesive effect. In the embodiment of the present application, the wavelength, energy and duration of the light source are determined by the selected curing adhesive component, and the components of the light curing adhesive are adjusted according to different requirements.

[0054] In one embodiment, the substrate is selected from a silicon wafer, a glass wafer, a sapphire wafer, a silicon carbide wafer, and a ceramic wafer.

[0055] In one embodiment, the lithium niobate / lithium tantalate bonding method comprises the following steps: Obtaining a lithium niobate / lithium tantalate coated carrier with a surface uniformly covered with bonding glue; A substrate-coated carrier with a surface uniformly covered with bonding glue is obtained.

[0056] The lithium niobate / lithium tantalate coated carrier is aligned with the cover adhesive surface of the substrate coated carrier and pressure bonded, and then a light source is used to irradiate the photoresist for photochemical reaction to complete the bonding, and then debonding is performed to remove the substrate and bonding adhesive.

[0057] The lithium niobate / lithium tantalate bonding method of the present application omits the steps of matching bonding glue and preheating module required for traditional hot-coating temporary bonding in the prior art, and can achieve bonding at room temperature with appropriate heating rate and cooling rate. The cost of materials, the time and energy consumption required for debonding, and the complexity of the entire process are directly related to production cost and efficiency.

[0058] In order to solve the warping and fragmentation problems existing in the prior art of lithium niobate / lithium tantalate wafer bonding process, in one embodiment, the present application provides a lithium niobate / lithium tantalate bonding method, as shown in the schematic diagram Figure 1 As shown in the figure, the bonding glue is located between the substrate carrier and the lithium niobate / lithium tantalate wafer. Light passes through the lithium niobate / lithium tantalate wafer and reacts with the bonding glue to complete the solidification bonding. The process flow chart of lithium niobate / lithium tantalate wafer photochemical bonding is shown in the figure. Figure 3 As shown in the first three steps, the specific steps are: Step 1: Glue spreading. Take a clean lithium niobate / lithium tantalate carrier and a substrate carrier, place the carrier with the smooth side facing up on the glue spreading plate of the bonding machine, and align it mechanically. Select a suitable bond, set the required glue amount, adjust the appropriate glue spreading speed, and start glue spreading. The type of bonding glue in this application and the single amount can be adjusted according to the type, application, and glue thickness of the actual bonding material; in the specific embodiment of the present application, the type of bonding glue is preferably selected according to the bonding material and the bonding application. The glue spreading speed, the amount of bonding glue, and the viscosity jointly determine the thickness of the glue. The faster the speed, the smaller the amount, the lower the viscosity, and the smaller the thickness of the bonding glue.

[0059] Photochemical reaction bonding has the following characteristics: (1) Low cost, the bonding glue is commonly available on the market; (2) Fast bonding, the bonding glue can react rapidly under light exposure in a short time, thus improving production efficiency; (3) Environmental protection, usually does not contain solvents or volatiles, and is relatively environmentally friendly; (4) Diverse performance, the bonding glue can adjust the debonding agent according to different needs to obtain different debonding methods; (5) Wide range of applications, it can be used to bond a variety of materials, such as glass, plastic, metal, etc.

[0060] Step 2: Alignment and fixation. The coated carrier is transferred to the bonding plate, and the coated surface is automatically aligned by the machine for pressure bonding to obtain a bonded sheet. Before pressure bonding, set the appropriate bonding pressure and bonding time to complete the fixation, and the pressure is less than 1000g / cm 2 , the pressurization time is less than 300s. The bonding method of the present application does not require heating, and bonding can be performed at room temperature in a clean room, avoiding the negative impact of bonding pressure and temperature on wafer materials. At the same time, due to the short bonding time, no preheating is required, shortening the process time and energy consumption, greatly improving the bonding efficiency.

[0061] Step 3: Photochemical reaction bonding. Transfer the bonding sheet into the reaction chamber, and set the wavelength of the light source, the energy level of the illumination, and the illumination time. The bonding principle of the photochemical reaction is to induce the photoinitiator in the glue to produce free radicals or cations through light irradiation of a specific wavelength, thereby initiating chain polymerization and cross-linking chemical reactions between the prepolymer and the active diluent, so that the adhesive is converted from liquid to solid within a few seconds to produce a stable adhesive effect. In the embodiment of the present application, the wavelength of the illumination source, the energy level of the illumination, and the illumination time are determined by the selection of the bonding adhesive, and the composition of the bonding adhesive can be adjusted according to different needs.

[0062] The bonding process from step 1 to step 3 is permanent bonding, which can realize the application of lithium niobate / lithium tantalate wafers in packaging bonding for the integration of different devices and chips, and provide a reliable technical solution for the heterogeneous integration of different functional materials and devices.

[0063] In order to temporarily bond the lithium niobate / lithium tantalate wafer before thinning, overcome the warping and fragmentation problems existing in the prior art of lithium niobate / lithium tantalate wafer bonding process, and achieve more extreme wafer thinning, in one embodiment, the present application provides a lithium niobate / lithium tantalate bonding method, select a desolvable bonding glue to temporarily bond the lithium niobate / lithium tantalate wafer to the carrier, and the specific steps are: Step 1: Glue spreading. Take a clean lithium niobate / lithium tantalate carrier and a substrate carrier, place the carrier with the smooth side facing up on the glue spreading plate of the bonding machine, and align it mechanically. Select a suitable bond, set the required glue amount, adjust the appropriate glue spreading speed, and start glue spreading. The type of bonding glue in this application and the single amount can be adjusted according to the type, application, and glue thickness of the actual bonding material; in the specific embodiment of the present application, the type of bonding glue is preferably selected according to the bonding material and the bonding application. The glue spreading speed, the amount of bonding glue, and the viscosity jointly determine the thickness of the glue. The faster the speed, the smaller the amount, the lower the viscosity, and the smaller the thickness of the bonding glue.

[0064] Step 2: Alignment and fixation. The coated carrier is transferred to the bonding plate, and the coated surface is automatically aligned by the machine for pressure bonding to obtain a bonded sheet. Before pressure bonding, set the appropriate bonding pressure and bonding time to complete the fixation, and the pressure is less than 1000g / cm 2 , the pressurization time is less than 300s. The bonding method of the present application does not require heating, and bonding can be performed at room temperature in a clean room, avoiding the negative impact of bonding pressure and temperature on wafer materials. At the same time, due to the short bonding time, no preheating is required, shortening the process time and energy consumption, greatly improving the bonding efficiency.

[0065] Step 3: Photochemical reaction bonding. Transfer the bonding sheet into the reaction chamber, and set the wavelength of the light source, the energy level of the illumination, and the illumination time. The bonding principle of the photochemical reaction is to induce the photoinitiator in the glue to produce free radicals or cations through light irradiation of a specific wavelength, thereby initiating chain polymerization and cross-linking chemical reactions between the prepolymer and the active diluent, so that the adhesive is converted from liquid to solid within a few seconds to produce a stable adhesive effect. In the embodiment of the present application, the wavelength of the illumination source, the energy level of the illumination, and the illumination time are determined by the selection of the bonding adhesive, and the composition of the bonding adhesive can be adjusted according to different needs.

[0066] Step 4: Debonding. After the temporarily bonded lithium niobate / lithium tantalate wafer is thinned, debonding is performed. The debonding methods include: (1) laser debonding: the laser uses a laser beam to scan the cured j-bonding glue to age it and achieve debonding; (2) thermal debonding: the bonding glue decomposes or degrades due to heat, loses its adhesiveness and achieves debonding; (3) hydrothermal debonding: the chemical decomposition process of the bonding glue when it absorbs water causes changes in the molecular structure, thereby affecting the performance of the cured glue, such as reduced strength and loss of adhesiveness; (4) chemical solvent debonding: the chemical solvent penetrates into the interior of the cured glue layer and reacts with the chemical bonds therein, thereby softening or dissolving the bonding glue and achieving debonding.

[0067] The bonding process of steps 1 to 4 is temporary bonding, which can realize thinning after the lithium niobate / lithium tantalate is bonded. The obtained lithium niobate / lithium tantalate thick film is applied to different piezoelectric MEMS devices (piezoelectric ultrasonic transducers, piezoelectric micropumps, etc.), without the need for heating and high-pressure bonding, avoiding the warping and fragmentation of lithium niobate / lithium tantalate caused by high temperature and high pressure, improving the bonding yield, and providing a reliable technical solution for the batch preparation of large-size single-crystal lithium niobate / lithium tantalate films.

[0068] In order to realize the application of lithium niobate / lithium tantalate wafers in packaging bonding for the integration of different devices and chips, and to provide a reliable technical solution for the heterogeneous integration of different functional materials and devices, the photochemical reaction bonding of permanent bonding (without debonding) is applied to the packaging bonding structure diagram as shown in the figure. Figure 2 As shown, the selected bonding adhesive cannot be debonded after solidification. After the lithium niobate / lithium tantalate wafer is further processed into a device, it can be applied to the packaging bonding of chips and devices, such as Example 1.

[0069] Example 1 Permanent bonding (no debonding) photochemical reaction bonding is used for packaging bonding structures, and its specific process flow is: Step 1: Glue Take a clean 8-inch lithium niobate (500 µm) and place it on the bonding machine with the smooth surface facing up. Automatically align the machine. Select CV2001 non-debondable bonding glue, set the glue volume to 5mL, adjust the glue speed to 5000rmp / min, and start glue spreading. After the end, the actual thickness measured by the thickness gauge is about 15um.

[0070] Step 2: Align and fix Transfer the lithium niobate with glue to the bonding plate, place an 8-inch silicon wafer on the top of the lithium niobate through the mechanical tray, with the smooth surface facing the lithium niobate glue surface, and align it automatically. Set the fixed pressure to 10g / cm², quickly evacuate, pressurize for 30s to eliminate bubbles, and remove the sample after completion.

[0071] Step 3: Reaction Bonding The sample was transferred to a light curing device, whose light source was ultraviolet light with a wavelength of 365nm. The light intensity of the device was 30mw / cm 2 , curing time 60s. After curing, no bubbles or cracks were observed on the surface of the sample.

[0072] In order to realize the application of thinned lithium niobate / lithium tantalate wafers in different piezoelectric MEMS devices (piezoelectric ultrasonic transducers, piezoelectric micropumps, etc.), and to provide a reliable technical solution for the batch preparation of large-size single-crystal lithium niobate / lithium tantalate films, the photochemical reaction bonding that can be laser debonded is applied to the temporary bonding structure diagram as shown in the figure. Figure 3 As shown in the structure after the photochemical reaction in the third step, the selected curing adhesive can be debonded by laser, hydrothermal debonding or chemical reagent debonding after curing bonding to peel off the lithium niobate / lithium tantalate wafer, which can be applied to temporary bonding before wafer thinning, such as Examples 2 to 4.

[0073] Example 2 Photochemical bonding by laser debonding is applied to temporary bonded structures. The specific process flow is as follows: Step 1: Glue Take a clean 8-inch lithium niobate wafer (350 µm) and place it on the bonding machine with the smooth surface facing up, and align it automatically. Select TBM-01L bonding adhesive, set the adhesive volume to 5mL, adjust the adhesive speed to 8000rmp / min, start adhesive spreading, and the average thickness of the adhesive measured by the thickness gauge is about 5um.

[0074] Step 2: Align and fix Transfer the lithium niobate with glue to the bonding plate, place the 8-inch silicon wafer on the top of the lithium niobate through the mechanical tray, with the smooth surface facing the lithium niobate glue surface, and align it automatically. Set the fixed pressure to 20g / cm², quickly evacuate, pressurize for 30s to eliminate bubbles, and remove the sample after completion.

[0075] Step 3: Reaction Bonding The sample is transferred to a light curing device, whose light source is ultraviolet light with a wavelength of 405nm. The light intensity of the device is 50mw / cm 2 The reaction was completed in 10 seconds. No bubbles or cracks were observed on the sample surface.

[0076] Step 4: Debonding The bonded sample was transferred to the debonding machine for laser debonding. The laser power was set to 3.5W and the wavelength was 355nm. The laser beam was focused on the bonded sample and the entire sample was scanned. It was observed that the photocurable adhesive was melted by heat after being scanned by the laser beam and lost its adhesiveness. The silicon wafer substrate was fixed, the upper lithium niobate wafer was removed, and then the residual adhesive on the surface of the wafer was cleaned with acetone and alcohol.

[0077] Example 3 Photochemical reaction bonding via hydrothermal bonding is applied to temporary bonding structures, and the specific process flow is as follows: Step 1: Glue Take a clean 8-inch lithium tantalate (350 µm) wafer and place it on the bonding machine with the smooth surface facing up, and align it automatically. Select hydrolyzed 8002 bonding glue, set the glue volume to 10mL, and drip it on the smooth surface of the glass wafer. Adjust the glue speed to 4000rmp / min, start glue spreading, and the measured thickness is about 12um.

[0078] Step 2: Align and fix Transfer the lithium tantalate wafer with glue to the bonding plate, place the 8-inch sapphire wafer on the top of the lithium tantalate through the mechanical tray, with the smooth surface facing the lithium tantalate glue surface, and align it automatically. Set the fixed pressure to 15g / cm², quickly evacuate the chamber, pressurize for 40s to expel bubbles, and remove the sample.

[0079] Step 3: Reaction Bonding The sample is transferred to a light curing device, whose light source is infrared light with a wavelength of 500µm. The light intensity of the device is 100mw / cm 2 The reaction was completed in 300s. No bubbles or cracks were observed on the sample surface.

[0080] Step 4: Debonding The bonded sample was transferred to a water bath for hydrothermal bonding. The water in the water bath was heated to 80°C, and the bonded sample was immersed in the bath. It was observed that the bonding glue began to hydrolyze and melt. After 15 minutes, the bonding glue completely detached from the wafer surface. The lithium tantalate wafer was taken out and then cleaned to remove the residual glue.

[0081] Example 4 Light-curing bonding by chemical reagent debonding is applied to temporary bonding structures. The specific process flow is: Step 1: Glue Take a clean 8-inch lithium tantalate wafer (500 µm) and place it on the bonding machine with the smooth surface facing up, and align it automatically. Select 3311 chemical photocurable adhesive, set the amount of adhesive to 3mL, and drip it on the smooth surface of the glass wafer. Adjust the adhesive speed to 9000rmp / min, start adhesive spreading, and the measured thickness is about 12um.

[0082] Step 2: Align and fix Transfer the lithium tantalate wafer with glue to the bonding plate, place an 8-inch glass wafer on the top of the lithium tantalate through the mechanical tray, with the smooth surface facing the lithium tantalate glue surface, and align it automatically. Set the fixed pressure to 15g / cm², quickly evacuate the chamber, pressurize for 40s to expel bubbles, and remove the sample.

[0083] Step 3: Reaction Bonding The sample was transferred to a light curing device, whose light source was infrared light with a wavelength of 100µm. The light intensity of the device was 50mw / cm2, and the curing was completed in 200s. No bubbles or cracks were observed on the surface of the sample.

[0084] Step 4: Debonding The chemical reagent debonding method is to drip the corresponding debonding agent on the bonding glue at the edge of the bonding, wait for the outermost bonding glue to react and age, and then clean the residual glue. Then continue to drip the debonding agent on the newly exposed light-curing glue, clean it after the reaction, and repeatedly remove all the bonding glue of the entire sample. Finally, the entire lithium tantalate wafer is cleaned.

[0085] In summary, the production process of conventional bonding adhesives is mature and has diverse performance. The formula can be adjusted according to different bonding requirements (such as temporary bonding, permanent bonding) to obtain different properties such as hardness, flexibility, bonding strength, etc.

[0086] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A lithium niobate / lithium tantalate bonding method, characterized in that: The steps include: Provide lithium niobate / lithium tantalate carriers and substrate carriers; Uniformly covering the single-side surface of the lithium niobate / lithium tantalate carrier and / or substrate carrier with bonding glue; Align the lithium niobate / lithium tantalate carrier with the substrate carrier so that the bonding glue is located between the lithium niobate / lithium tantalate carrier and the substrate carrier, apply pressure for bonding, and then use a light source to irradiate the bonding glue for photochemical reaction to complete the bonding.

2. The lithium niobate / lithium tantalate bonding method according to claim 1, characterized in that: The conditions for the pressurized bonding include: the pressurized pressure is 10 g / cm 2 ~1000g / cm 2 The pressurization time is 10s~300s.

3. The lithium niobate / lithium tantalate bonding method according to claim 1, characterized in that: The bonding is permanent bonding or temporary bonding; When the bonding is permanent bonding, the bonding glue is permanent bonding glue; When the bonding is temporary bonding, the bonding adhesive is a self-debonding adhesive, and after the bonding is completed, a debonding process is also included to remove the substrate and the bonding adhesive.

4. The lithium niobate / lithium tantalate bonding method according to claim 3, characterized in that: The debonding method is selected from at least one of laser debonding, thermal debonding, hydrothermal debonding, and chemical solvent debonding.

5. The lithium niobate / lithium tantalate bonding method according to claim 1, characterized in that: The bonding adhesive has a covering thickness of 5 μm to 100 μm.

6. The lithium niobate / lithium tantalate bonding method according to claim 1, characterized in that: The covering condition is: spreading the glue at a speed of 1000 rpm / min to 9000 rpm / min.

7. The lithium niobate / lithium tantalate bonding method according to claim 1, characterized in that: The conditions of the photochemical reaction include: the wavelength of the light source is 5nm~1mm, the intensity of the light source is 10mw / cm 2 ~1000mw / cm 2 The irradiation time is 10s~300s.

8. The lithium niobate / lithium tantalate bonding method according to claim 1, characterized in that: The light source is selected from infrared light with a wavelength of 0.16 μm to 1000 μm or ultraviolet light with a wavelength of 10 nm to 400 nm.

9. The lithium niobate / lithium tantalate bonding method according to claim 1, characterized in that: The substrate is selected from one of a silicon wafer, a glass wafer, a sapphire wafer, a silicon carbide wafer, and a ceramic wafer.

10. Application of the lithium niobate / lithium tantalate bonding method according to any one of claims 1 to 9 in a thin film preparation process or a device packaging process.

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