Preparation method of lithium niobate / lithium tantalate high-performance surface acoustic wave device

Abstract

The invention discloses a preparation method of a lithium niobate / lithium tantalate high-performance surface acoustic wave device, and belongs to the technical field of acoustic resonators / filters. The preparation method of the high-performance surface acoustic wave device comprises the following steps: depositing the energy limiting layer on the surface of one side of the piezoelectric layer; indirectly bonding the supporting substrate layer on one surface, far away from the piezoelectric layer, of the energy limiting layer to form a bonding device; thinning the piezoelectric layer on the bonding device to form a thin film piezoelectric layer; and depositing an electrode layer on the surface of the film piezoelectric layer on the bonding device to obtain the lithium niobate high-performance surface acoustic wave device. The piezoelectric layer is selected from a lithium niobate single crystal wafer and a lithium tantalate single crystal wafer. The preparation method is a general scheme of reverse manufacturing, ion implantation and direct bonding processes used in current mainstream processes are avoided, and precise thinning and indirect bonding processes are adopted. And under the condition of reducing the preparation difficulty and cost of the device, the device structure and product performance which are the same as those of a mainstream process can be achieved.

Description

Technical Field

[0001] The present application relates to a method for preparing a lithium niobate / lithium tantalate high-performance surface acoustic wave device, and belongs to the technical field of acoustic wave resonators / filters. Background Art

[0002] The rapid development of mobile communication technology requires devices with higher and wider communication frequency bands. Acoustic wave devices are key components of mobile communication terminals. For example, surface acoustic wave (SAW) devices used as filters have received widespread attention. Since it is difficult to grow high-quality highly oriented single crystal films of lithium niobate or lithium tantalate using traditional deposition techniques, the current preferred method for preparing high-performance surface acoustic wave resonators is the use of smart-cut and bonding technology. The general method can be described as: preparing lithium niobate on insulator (LNOI) (or lithium tantalate on insulator, LTOI) by smart-cut and bonding, followed by preparing electrodes by lift-off process, and finally forming a high-performance SAW device, in which the piezoelectric layer (such as lithium niobate or lithium tantalate, through Ion implantation and Smart-cut preparation) and substrate layer (such as SiO2 / Si, SiO2 / sapphire, SiO2 / SiC) need to be connected through a bonding process, that is, first grow a high acoustic velocity layer (such as sapphire, aluminum oxide, silicon carbide, etc.) on a supporting substrate (such as Si), or directly provide a high acoustic velocity layer substrate, and then grow a low acoustic velocity layer (for example, deposit SiO2 by magnetron sputtering or PECVD process), and then bond the lithium niobate piezoelectric layer to the low acoustic velocity layer by bonding, and polish the surface of the low acoustic velocity layer to prepare the electrode. In recent years, SAW devices have made a lot of progress in improving performance. For example, Takai et al. reported high-performance SAW devices (IHP SAW) with multilayer structures (LiTaO3 / SiO2 / AlN / Si) and (LiTaO3 / SiO2 / Si). Other similar structures have also been proposed, such as LiNbO3 / SiO2 / SiC, LiTaO3 / SiO2 / SiC, LiNbO3 / SiO2 / Sapphire, LiNbO3 / SiO2 / Si, and LiNbO3 / SiO2 / Si. These structures are realized by directly bonding submicron-thick LiNbO3 or LiTaO3 to SiO2 / SiC or other substrates through the Smart-cut process. However, the ion implantation link in the Smart-cut scheme used in the prior art to transfer (bond) piezoelectric films to low-acoustic-velocity materials requires expensive equipment worth tens of millions of yuan, and the traditional direct bonding process also requires extreme environmental requirements, which is difficult and has a low yield rate above 6 inches. At present, the mainstream wafers available for commercialization (such as Jinan Jingzheng, Shanghai New Silicon Polymerization, etc.) are 4-6 inch bonded wafers, and 8-inch bonding is expensive. Based on the above reasons, Smart-cut and traditional bonding have extremely high preparation costs and difficulties, which limits the large-scale low-cost preparation of such devices and is not suitable for large-scale commercial production. Summary of the invention

[0003] In order to solve the problems of high cost and difficulty of Smart-cut and traditional bonding technology in the existing technology for preparing high-performance acoustic wave devices, the present application provides a preparation scheme for high-performance surface acoustic wave devices based on "reverse manufacturing". First, the required energy limiting layer materials are deposited in sequence on the piezoelectric material, and then an indirect bonding process and thinning of the piezoelectric layer are used to achieve the same device structure and performance as the existing technology.

[0004] This application adopts the following technical solutions: A method for preparing a lithium niobate / lithium tantalate high-performance surface acoustic wave device comprises the following steps: Depositing an energy confinement layer on one surface of the piezoelectric layer; indirectly bonding the support substrate layer to a side of the energy confinement layer away from the piezoelectric layer to form a bonded device; Thinning the piezoelectric layer on the bonded device to form a thin film piezoelectric layer; Depositing an electrode layer on the surface of the thin film piezoelectric layer on the bonding device to obtain the lithium niobate high-performance surface acoustic wave device; The piezoelectric layer is selected from lithium niobate single crystal wafer and lithium tantalate single crystal wafer.

[0005] In one embodiment, the energy confinement layer is selected from a high sound velocity layer and / or a low sound velocity layer. The high sound velocity and the low sound velocity are the sound velocity of the material relative to the sound velocity of the piezoelectric layer.

[0006] In one embodiment, the material of the low acoustic velocity layer is selected from at least one of SiO2, TiO2, Ta2O5, SiON, and SiO2F; In one embodiment, the material of the high acoustic velocity layer is selected from at least one of Al2O3, sapphire, SiN, AlN, SiC, and Si.

[0007] In one embodiment, the thickness of the low acoustic velocity layer is 0.1λ~1λ; for example, a SiO2 low acoustic velocity layer with a thickness of 0.1λ-1λ is deposited by a magnetron sputtering process or a PECVD process (where λ is the wavelength of the excited acoustic wave).

[0008] Preferably, the thickness of the high acoustic velocity layer is 0.1λ~1.5λ; for example, an Al2O3 high acoustic velocity layer with a thickness of 0.1λ-5λ is deposited by an atomic layer deposition process (ALD).

[0009] Where λ is the wavelength of the excited sound wave. In one embodiment, the material of the supporting substrate layer is selected from quartz or glass.

[0010] In one embodiment, the support substrate has a thickness of 300-800 μm.

[0011] In one embodiment, the thinning method is selected from precision thinning and / or chemical mechanical polishing.

[0012] In one embodiment, the thickness of the thin film piezoelectric layer is 0.1λ~0.5λ; for example, the bonded device is turned over and the top piezoelectric layer is thinned to 0.1λ~0.5λ.

[0013] Where λ is the wavelength of the excited sound wave.

[0014] In one embodiment, the deposition process is a lift-off process; The electrode layer is a metal electrode; The material of the metal electrode is selected from at least one of aluminum, titanium, gold, silver, copper and chromium; The electrode layer includes an interdigital transducer (IDT) electrode and a reflective gate electrode.

[0015] In one embodiment, the thickness of the electrode layer is 0.01λ-0.1λ.

[0016] In one embodiment, the high-performance surface acoustic wave device includes a supporting substrate layer, on which an energy confinement layer and a thin film piezoelectric layer are sequentially stacked; The energy confinement layer is selected from a high sound velocity layer and / or a low sound velocity layer. The high sound velocity and the low sound velocity are the sound velocity of the material relative to the sound velocity of the piezoelectric layer.

[0017] This application adopts the following technical solutions: S1. A method for preparing a lithium niobate / lithium tantalate high-performance surface acoustic wave device, comprising the following steps: S2, depositing an energy confinement layer on one surface of the piezoelectric layer; S3, indirectly bonding the supporting substrate layer to a side of the energy limiting layer away from the piezoelectric layer to form a bonding device; S4, thinning the piezoelectric layer on the bonding device to form a thin film piezoelectric layer; S5, depositing an electrode layer on the surface of the thin film piezoelectric layer on the bonding device to obtain the lithium niobate high-performance surface acoustic wave device; The piezoelectric layer is selected from lithium niobate single crystal wafer and lithium tantalate single crystal wafer.

[0018] In one embodiment, the structure of the high-performance surface acoustic wave device is, from top to bottom, an electrode layer, a piezoelectric layer, an energy limiting layer, and a supporting substrate layer. The preparation method of the high-performance surface acoustic wave device, the energy limiting layer is a high sound velocity layer and a low sound velocity layer deposited in layers, the high sound velocity and the low sound velocity are the sound velocity of the material relative to the sound velocity of the piezoelectric layer, and the preparation of the structure of the high-performance surface acoustic wave device includes the following steps: (1) Obtain lithium niobate single crystal wafers and lithium tantalate single crystal wafers as piezoelectric layers. This step does not require the tangent direction and thickness of the wafers.

[0019] (2) Depositing a low acoustic velocity layer on the surface of the piezoelectric layer. For example, a layer of SiO2 low acoustic velocity layer with a thickness of 0.1λ~1λ (where λ is the wavelength of the excited acoustic wave) is deposited by magnetron sputtering or PECVD process. TiO2, Ta2O5, SiON, SiO2F and other materials can also replace SiO2 as the low acoustic velocity layer material.

[0020] (3) Deposit a high acoustic velocity layer on the surface of the low acoustic velocity layer. For example, use the ALD process to deposit a layer of Al2O3 high acoustic velocity layer with a thickness of 0.1λ~5λ. Sapphire, SiN, AlN, SiC, Si and other materials can also replace Al2O3 as the high acoustic velocity layer material.

[0021] (4) Indirect bonding: quartz or glass is used as a supporting substrate layer and bonded to the surface of the high acoustic velocity layer. The thickness of the bonding substrate is 300~800μm.

[0022] (5) Flip the bonded device over and perform precision thinning and CMP process on the piezoelectric layer material to the required thickness, which can range from 0.1λ to 0.5λ.

[0023] (6) Depositing electrodes, using a lift-off process to set metal electrodes on the surface of the piezoelectric material. The electrodes include an IDT electrode and a reflective gate electrode. The electrode thickness is 0.01λ~0.1λ. The electrode material is selected from at least one of aluminum, titanium, gold, silver, copper, and chromium.

[0024] The beneficial effects of this application include: The preparation method of high-performance surface acoustic wave devices provided in this application is a general solution for "reverse manufacturing" of surface acoustic wave piezoelectric resonators, which avoids the ion implantation and direct bonding processes used in the current mainstream processes and instead adopts precision thinning and indirect bonding processes. Compared with the direct bonding process, the cost and difficulty of the indirect bonding process are greatly reduced, and the same device structure and product performance as the mainstream process can be achieved while reducing the difficulty and cost of device preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the steps of the method for preparing a high-performance surface acoustic wave device in this application. DETAILED DESCRIPTION

[0026] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0027] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0028] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0029] Explanation of key terms and technical abbreviations in this application: Smart-cut: Wafer Smart Cut is a semiconductor manufacturing technology used to manufacture thin film wafers. This technology allows thin layers of material to be transferred from one wafer to another while maintaining high crystal quality and flatness. The core principle is to form a brittle layer between the contact surfaces of the two wafers and induce stress to peel off the film from one wafer and transfer it to another. The following is the general process of wafer Smart Cut technology: 1. Prepare wafers: Prepare two wafers, one as the source wafer for the thin film and the other as the target wafer for receiving the thin film. These two wafers are usually silicon wafers, but can also be other materials.

[0030] 2. Ion implantation: On the source wafer, dopant ions (usually hydrogen or helium) are implanted into the surface by ion implantation. These dopant ions will be implanted into the crystal lattice to form a brittle layer, usually located at a depth of about a few hundred nanometers to a few microns in the wafer.

[0031] 3. Contact and bonding: Align and contact the surfaces of the source wafer and the target wafer. While in contact, bond the two wafer surfaces together by pressure or heat pressing, so that the brittle layer is located at the contact interface of the two wafers.

[0032] 4. Stripping the film: By applying mechanical or thermal stress and / or stress induction at the appropriate temperature, the brittle layer on the source wafer is peeled off and the film is transferred to the target wafer. This step usually requires precise control to ensure the quality and flatness of the film.

[0033] 5. Thin film processing: The transferred film on the target wafer may require subsequent processing, such as surface cleaning, polishing, etching, etc., to obtain the desired final characteristics.

[0034] The main problem with the existing technology is that the preparation method is costly and difficult, because the preparation process involves intelligent cutting and bonding to transfer the piezoelectric layer to the desired substrate. The application proposes a general solution for "reverse manufacturing" of surface acoustic wave piezoelectric resonators, that is, first depositing the required materials on the piezoelectric material in sequence (such as depositing SiO2 and SiC in sequence on a 6-inch lithium niobate wafer), and then using an indirect bonding process to bond the product to the supporting substrate. Compared with the direct bonding process, the cost and difficulty of the indirect bonding process are greatly reduced. The piezoelectric material is then precisely thinned and polished to the required thickness. Finally, the electrode process is completed on the piezoelectric surface, and the electrode process is the same as the mainstream technology solution.

[0035] In one embodiment, the present application provides a preparation scheme for high-performance surface acoustic wave devices based on "reverse manufacturing" to solve the problems of high cost and difficulty of Smart-cut and traditional bonding technology in the prior art of preparing high-performance acoustic wave devices, including the following steps: Step (1), depositing an energy confinement layer on one surface of the piezoelectric layer; Step (2), indirectly bonding the supporting substrate layer to a side of the energy limiting layer away from the piezoelectric layer to form a bonding device; Step (3), thinning the piezoelectric layer on the bonding device to form a thin film piezoelectric layer; Step (4), depositing an electrode layer on the surface of the thin film piezoelectric layer on the bonding device to obtain the lithium niobate high-performance surface acoustic wave device; The piezoelectric layer is selected from lithium niobate single crystal wafer and lithium tantalate single crystal wafer. In this application, no requirements are made on the wafer tangent and thickness, and those skilled in the art can purchase commercially available lithium niobate single crystal wafer and lithium tantalate single crystal wafer according to their selection.

[0036] In one embodiment, the energy confinement layer is selected from a high sound velocity layer and / or a low sound velocity layer. The high sound velocity and the low sound velocity are the sound velocity of the material relative to the sound velocity of the piezoelectric layer.

[0037] High acoustic velocity materials refer to those materials with higher acoustic wave propagation speed. In SAW technology, high acoustic velocity materials are often used to form acoustic wave confinement structures to improve device performance and efficiency. Low acoustic velocity materials refer to those materials with slower acoustic wave propagation speed. In SAW technology, low acoustic velocity materials are often used in acoustic wave coupling and matching layers to improve the interaction between acoustic waves and electrodes or other materials.

[0038] In one embodiment, the material of the low acoustic velocity layer is selected from at least one of TiO2, Ta2O5, SiON, and SiO2F.

[0039] In one embodiment, the material of the low acoustic velocity layer is preferably at least one of SiO2 and Ta2O5.

[0040] In one embodiment, the material of the high acoustic velocity layer is selected from at least one of Al2O3, sapphire, SiN, AlN, SiC, and Si.

[0041] In one embodiment, the material of the high acoustic velocity layer is preferably at least one of Al2O3, SiN, AlN, SiC, and Si.

[0042] In the present application, the method for depositing the energy limiting layer on the surface of one side of the piezoelectric layer is not specifically limited. Those skilled in the art can select a suitable deposition method based on the aforementioned specific low acoustic velocity layer materials and high acoustic velocity layer materials. For example, it can be chemical vapor deposition (CVD): using a gas phase precursor to undergo a chemical reaction under specific conditions to deposit the desired thin film material on a specific substrate; physical vapor deposition (PVD): using physical means (such as evaporation or sputtering) to transfer the material from the target material to the substrate; pulsed laser deposition technology: using a pulsed laser to evaporate the target material and deposit the material on the substrate; molecular beam epitaxy (MBE): using an ultra-high vacuum environment to deposit atoms or molecules on the substrate by means of a molecular beam to form a thin film; atomic layer deposition (ALD): growing a thin film layer by layer on a substrate, and depositing a layer of atomic thick material in each growth cycle by precisely controlling the chemical reaction.

[0043] In one embodiment, the thickness of the low acoustic velocity layer is 0.1λ~1λ, where λ is the wavelength of the excited acoustic wave; for example, a layer of SiO2 low acoustic velocity layer with a thickness of 0.1λ-1λ (where λ is the wavelength of the excited acoustic wave) is deposited using a magnetron sputtering process or a PECVD process.

[0044] In one embodiment, the thickness of the high acoustic velocity layer is 0.1λ~1.5λ, where λ is the wavelength of the excited acoustic wave; for example, an Al2O3 high acoustic velocity layer with a thickness of 0.1λ-5λ is deposited using the ALD process.

[0045] In one embodiment, the material of the supporting substrate layer is selected from quartz or glass.

[0046] In one embodiment, the support substrate has a thickness of 300-800 μm.

[0047] In one embodiment, the support substrate has a thickness of 500 μm.

[0048] In one embodiment, the thinning method is selected from precision thinning and / or chemical mechanical polishing.

[0049] In one embodiment, the thickness of the thin film piezoelectric layer is 0.1λ~0.5λ, where λ is the wavelength of the excited acoustic wave; for example, the bonded device is turned over and the top piezoelectric layer is thinned to 0.1λ~0.5λ.

[0050] λ is the wavelength of the excited sound wave, which refers to the wavelength of the sound wave in the aforementioned high-speed layer material and low-speed layer material. Those skilled in the art can adjust the thickness of the energy limiting layer through design and material selection as needed to meet the needs of different SAW devices.

[0051] In one embodiment, the deposition process is a lift-off process; The electrode layer is a metal electrode; The material of the metal electrode is selected from at least one of aluminum, titanium, gold, silver, copper and chromium; The electrode layer includes an interdigital transducer (IDT) electrode and a reflective gate electrode.

[0052] The lift-off process in this application is a commonly used technology in microelectronics manufacturing, mainly used to make metal interconnects, wires and other structures. This process uses the patterning and solvent dissolution of photoresist to form the required structure without the need for traditional etching steps, thereby simplifying the process flow and reducing costs. Its basic steps include: first using photoresist to form a pattern on a substrate, then depositing metal or other materials on the photoresist pattern through a coating process, and finally using a solvent to remove the photoresist, while taking away the thin film material covering the photoresist, thereby leaving the required metal pattern on the substrate.

[0053] In this application, IDT electrodes and reflection gate electrodes are key components in surface acoustic wave (SAW) devices. IDT is a structure composed of two sets of intersecting metal electrodes, which converts electrical signals into sound waves, or converts sound waves into electrical signals. In SAW devices, IDT electrodes are usually used to generate and receive sound waves; the reflection gate electrode is a structure composed of periodically arranged metal strips or gaps, which is used to reflect sound waves. In SAW filters and sensors, the reflection gate can be used to form a standing wave pattern, thereby achieving selective reflection and transmission of sound waves of a specific frequency; the structure and material of the IDT electrode and the reflection gate electrode are not specifically limited in this application, and those skilled in the art can select them as needed and optimize them according to specific application requirements to achieve the best device performance.

[0054] In one embodiment, the thickness of the electrode layer is 0.01λ-0.1λ.

[0055] In one embodiment, the thickness of the electrode layer is 0.01λ-0.5λ.

[0056] In one embodiment, the high-performance surface acoustic wave device includes a supporting substrate layer, on which an energy confinement layer and a thin film piezoelectric layer are sequentially stacked; The energy confinement layer is selected from a high sound velocity layer and / or a low sound velocity layer. The high sound velocity and the low sound velocity are the sound velocity of the material relative to the sound velocity of the piezoelectric layer.

[0057] In one embodiment, when the energy limiting layer is a high acoustic velocity layer, a preparation scheme of a high-performance surface acoustic wave device based on "reverse manufacturing" comprises the following steps: step (1), depositing a high acoustic velocity layer on one surface of the piezoelectric layer as the energy limiting layer; step (2), indirectly bonding a supporting substrate layer to a side of the energy limiting layer away from the piezoelectric layer to form a bonded device; step (3), thinning the piezoelectric layer on the bonded device to form a thin film piezoelectric layer; step (4), depositing an electrode layer on the surface of the thin film piezoelectric layer on the bonded device to obtain the lithium niobate high-performance surface acoustic wave device; In one embodiment, when the energy limiting layer is a low acoustic velocity layer, a preparation scheme for a high-performance surface acoustic wave device based on "reverse manufacturing" comprises the following steps: step (1), depositing a low acoustic velocity layer energy limiting layer on one side of the piezoelectric layer; step (2), indirectly bonding a supporting substrate layer to a side of the energy limiting layer away from the piezoelectric layer to form a bonded device; step (3), thinning the piezoelectric layer on the bonded device to form a thin film piezoelectric layer; step (4), depositing an electrode layer on the surface of the thin film piezoelectric layer on the bonded device to obtain the lithium niobate high-performance surface acoustic wave device; the piezoelectric layer is selected from lithium niobate single crystal wafers and lithium tantalate single crystal wafers.

[0058] In one embodiment, when the energy confinement layer is a high sound velocity layer and a low sound velocity layer, a preparation scheme of a high performance surface acoustic wave device based on "reverse manufacturing" is shown in the schematic diagram of the steps. Figure 1 As shown, the following steps are included: Step (1), depositing a low sound velocity layer and a high sound velocity layer in sequence on one side surface of the piezoelectric layer as an energy limiting layer, wherein the high sound velocity and the low sound velocity are the sound velocity of the material relative to the sound velocity of the piezoelectric layer; Step (2), indirectly bonding the supporting substrate layer to a side of the energy limiting layer away from the piezoelectric layer to form a bonding device; Step (3), thinning the piezoelectric layer on the bonding device to form a thin film piezoelectric layer; Step (4), depositing an electrode layer on the surface of the thin film piezoelectric layer on the bonding device to obtain the lithium niobate high-performance surface acoustic wave device; The piezoelectric layer is selected from lithium niobate single crystal wafer and lithium tantalate single crystal wafer.

[0059] In one embodiment, the thinning is performed by precision thinning and polishing to a desired thickness.

[0060] In one embodiment, the technical solution of the present application adopts precision thinning and indirect bonding processes to avoid the ion implantation and direct bonding processes used in the current mainstream processes, and can achieve the same device structure and product performance as the mainstream processes while reducing the difficulty and cost of device preparation. The specific process steps of the technical solution of the present application are as follows: (1) The structure is composed of an IDT electrode, a piezoelectric layer, an energy confinement layer, and a support substrate from top to bottom. First, a commercially available LiNbO3 or LiTaO3 single crystal wafer is provided as the piezoelectric layer, and no requirements are made on the wafer tangent and thickness.

[0061] (2) Depositing an energy limiting layer on the surface of the wafer. The energy limiting layer is at least one of a high sound velocity layer and (or) a low sound velocity layer (the high sound velocity and low sound velocity are the sound velocity of the material relative to the sound velocity of the piezoelectric layer). For example, a layer of SiO2 low sound velocity layer with a thickness of 0.1-1λ (where λ is the wavelength of the excited sound wave) is deposited using a magnetron sputtering process or a PECVD process. Materials such as TiO2, Ta2O5, SiON, and SiO2F can be used.

[0062] (3) Continue to deposit a high acoustic velocity layer on the upper surface of SiO2 as an energy limiting layer. For example, use the ALD process to deposit a layer of Al2O3 high acoustic velocity layer with a thickness of 0.1-5λ. Sapphire, SiN, AlN, SiC, Si and other materials can be used.

[0063] (4) Indirect bonding. Bond quartz or glass to a high acoustic velocity substrate as a support layer. The thickness of the bonded substrate is 500 microns.

[0064] (5) Flip the bonded device over and perform precision thinning and CMP process on the top piezoelectric layer material to the required thickness, which can range from 0.1-0.5λ.

[0065] (6) Depositing electrodes. A metal electrode is disposed on the surface of the piezoelectric material by a lift-off process. The electrode includes an IDT electrode and a reflective gate electrode. The electrode thickness is 0.01-0.1λ. The electrode material can be at least one of aluminum, titanium, gold, silver, copper, and chromium.

[0066] The main advantage of the technical solution of the present application is that it reduces the difficulty of preparing a high-performance surface acoustic wave device, thereby reducing the production cost. This high-performance device requires a piezoelectric layer of about submicron thickness. The method adopted by the mainstream solution is to use the Smart-cut process at the beginning of the process, which requires an expensive ion implanter, and the ion implantation process will inevitably cause lattice damage to the required submicron thickness piezoelectric layer, and ultimately affect the performance of the device. This solution uses a thinning machine thinning process to thin the piezoelectric layer to the required thickness at the end of the process. The mainstream solution requires the submicron thick piezoelectric layer to be directly bonded to a SiO2 substrate wafer, followed by CMP polishing, in which the bonding process is difficult and costly. This solution is to directly deposit materials such as SiO2 on the piezoelectric material through a process such as magnetron sputtering, and use CMP polishing after thinning the piezoelectric layer in the later stage of the process. It avoids the direct bonding process and reduces the difficulty and cost of preparation.

[0067] Example 1 Prepare a 4-inch 15° Y-cut LiNbO3 wafer with a thickness of 525 microns. Use a magnetron sputtering process to grow SiO2 with a thickness of 0.3λ on the surface of LiNbO3, and then use a CVD process to deposit SiC with a thickness of 1.2λ on the surface of SiO2. Use a bonding process to bond one side of SiC to a supporting substrate. The specific method is as follows: prepare a 4-inch glass wafer (thickness greater than 50λ), apply a photocurable bonding adhesive, bond it to one side of SiC, and perform UV treatment to accelerate the curing of the adhesive. Use a thinner and grinder to thin the LiNbO3 layer of the bonded device, and then perform precision thinning after rough thinning to less than 50 microns, and then polish it to a thickness of 0.15λ. Then use standard photolithography and lift-off processes to pattern and prepare the IDT electrode.

[0068] Comparative Example 1 First, a 0.3λ thick SiO2 film was grown on a 4-inch 4H-SiC substrate (thickness greater than 50λ) using a magnetron sputtering device. Hydrogen ion implantation was performed on a 4-inch 15° Y-cut LiNbO3 wafer, and the implanted wafer was then directly bonded to a SiO2 / SiC substrate, with the implanted surface bonded to one side of the SiO2. The lithium niobate film was peeled off by an annealing process, and the peeled surface was smoothed using CMP and the thickness was reduced to 0.15λ. The IDT electrode was then patterned and prepared using standard photolithography and lift-off processes.

[0069] The device structures finally formed in Example 1 and Comparative Example 1 are the same, and do not affect the performance of the final product, that is, the final products of the two schemes are consistent, but Example 1 adopts the general scheme of "reverse manufacturing" of surface acoustic wave piezoelectric resonators, that is, first depositing the required materials on the piezoelectric material in sequence, then using an indirect bonding process to bond the product to the supporting substrate, and thinning the piezoelectric material to the required thickness. Compared with Comparative Example 1, the cost and difficulty of the indirect bonding process are greatly reduced, avoiding the currently used ion implantation and direct bonding processes, and achieving the same device structure and product performance as the mainstream process while reducing the difficulty and cost of device preparation.

[0070] Example 2 Prepare a 6-inch LiNbO3 wafer with a thickness of 675 microns. Use plasma enhanced chemical vapor deposition to grow SiO2 with a thickness of 0.4λ on the surface of LiNbO3. Then use magnetron sputtering to deposit AlN with a thickness of 1.0λ on the surface of SiO2. Use a bonding process to bond the AlN side to the supporting substrate. The specific method is as follows: prepare a 6-inch glass wafer (thickness greater than 50λ), apply a photocurable bonding adhesive, bond it to the AlN side, and perform UV treatment to accelerate the curing of the adhesive. The LiNbO3 layer of the bonded device is thinned to less than 50 microns, then finely thinned, and then polished to a thickness of 0.15λ. Then use standard photolithography and lift-off processes to pattern and prepare the IDT electrode.

[0071] Example 3 Prepare an 8-inch LiNbO3 wafer with a thickness of 750 microns. Use plasma enhanced chemical vapor deposition to grow SiO2 with a thickness of 0.35λ on the surface of LiNbO3. Then use ALD process to deposit Al2O3 with a thickness of 1.3λ on the surface of SiO2. Use bonding process to bond one side of Al2O3 to the supporting substrate. The specific method is as follows: prepare an 8-inch glass wafer (thickness greater than 50λ), apply photocurable bonding glue, bond it to one side of Al2O3, and perform UV treatment to accelerate the curing of the glue. The LiNbO3 layer of the bonded device is thinned to less than 50 microns, then fine-thinned, and then polished to a thickness of 0.15λ. Then use standard photolithography and lift-off processes to pattern and prepare the IDT electrode.

[0072] Example 4 Prepare a 6-inch LiNbO3 wafer with a thickness of 675 microns. Use magnetron sputtering to grow Ta2O5 with a thickness of 0.25λ on the surface of LiNbO3. Then deposit AlN with a thickness of 1.1λ on the surface of Ta2O5 using magnetron sputtering. Bond the AlN side to the supporting substrate using a bonding process. The specific method is as follows: prepare a 6-inch glass wafer (thickness greater than 50λ), apply a photocurable bonding adhesive, bond it to the AlN side, and perform UV treatment to accelerate the curing of the adhesive. The LiNbO3 layer of the bonded device is thinned to less than 50 microns, then finely thinned and polished to a thickness of 0.15λ. Then use standard photolithography and lift-off processes to pattern and prepare the IDT electrode.

[0073] Example 5 Prepare a 6-inch LiNbO3 wafer with a thickness of 675 microns. Use magnetron sputtering to grow Ta2O5 with a thickness of 0.3λ on the surface of LiNbO3. Then use chemical vapor deposition to deposit SiC with a thickness of 1.2λ on the surface of Ta2O5. Use a bonding process to bond one side of SiC to a supporting substrate. The specific method is as follows: prepare a 6-inch glass wafer (thickness greater than 50λ), apply a photocurable bonding adhesive, bond it to one side of SiC, and perform UV treatment to accelerate the curing of the adhesive. The LiNbO3 layer of the bonded device is thinned to less than 50 microns, then finely thinned, and then polished to a thickness of 0.15λ. Then use standard photolithography and lift-off processes to pattern and prepare the IDT electrode.

[0074] Embodiment 6-10 The preparation of high-performance surface acoustic wave devices in Examples 6 to 10 is the same as that in Examples 1 to 5, with the only difference being that LiNbO 3 can also be replaced with LiTaO 3 .

[0075] 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 method for preparing a lithium niobate / lithium tantalate high-performance surface acoustic wave device, characterized in that: The steps include: Depositing an energy confinement layer on one surface of the piezoelectric layer; indirectly bonding the support substrate layer to a side of the energy confinement layer away from the piezoelectric layer to form a bonded device; Thinning the piezoelectric layer on the bonded device to form a thin film piezoelectric layer; Depositing an electrode layer on the surface of the thin film piezoelectric layer on the bonding device to obtain the lithium niobate high-performance surface acoustic wave device; The piezoelectric layer is selected from lithium niobate single crystal wafer and lithium tantalate single crystal wafer.

2. The method for preparing a high-performance surface acoustic wave device according to claim 1, characterized in that: The energy confinement layer is selected from a high sound velocity layer and / or a low sound velocity layer.

3. The method for preparing a high-performance surface acoustic wave device according to claim 2, characterized in that: The material of the low acoustic velocity layer is selected from at least one of SiO2, TiO2, Ta2O5, SiON, and SiO2F; Preferably, the material of the high acoustic velocity layer is selected from at least one of Al2O3, sapphire, SiN, AlN, SiC, and Si.

4. The method for preparing a high-performance surface acoustic wave device according to claim 2, characterized in that: The thickness of the low sound velocity layer is 0.1λ~1λ; Preferably, the thickness of the high acoustic velocity layer is 0.1λ~1.5λ; Where λ is the wavelength of the excited sound wave.

5. The method for preparing a high-performance surface acoustic wave device according to claim 1, characterized in that: The material of the supporting substrate layer is selected from quartz or glass.

6. The method for preparing a high-performance surface acoustic wave device according to claim 1, characterized in that: The thickness of the support substrate is 300-800 μm.

7. The method for preparing a high-performance surface acoustic wave device according to claim 1, characterized in that: The thinning method is selected from precision thinning and / or chemical mechanical grinding.

8. The method for preparing a high-performance surface acoustic wave device according to claim 1, characterized in that: The thickness of the thin film piezoelectric layer is 0.1λ~0.5λ; Where λ is the wavelength of the excited sound wave.

9. The method for preparing a high-performance surface acoustic wave device according to claim 1, characterized in that: The deposition process is a lift-off process; The electrode layer is a metal electrode; The material of the metal electrode is selected from at least one of aluminum, titanium, gold, silver, copper and chromium; The electrode layer includes an interdigital transducer electrode and a reflective gate electrode.

10. The method for preparing a high-performance surface acoustic wave device according to claim 1, characterized in that: The thickness of the electrode layer is 0.01λ-0.1λ.

Images