A filter thin film substrate and a method of manufacturing the same

Abstract

The application relates to a filter thin film substrate and a preparation method thereof. The method comprises the following steps: S100, providing a support substrate; S200, presetting a piezoelectric film with a thickness on one side surface of the support substrate; S300, performing heat treatment on the piezoelectric film, heating the piezoelectric film to above a Curie temperature, and keeping warm for a first preset time; a preset voltage is applied to the piezoelectric film in the process of the heat treatment; S400, energy pulses are applied to the piezoelectric film, so that the piezoelectric film is converted into a target piezoelectric layer, and the thin film substrate is obtained, and the target piezoelectric layer is a polycrystalline piezoelectric film with preferred orientation. The application realizes the conversion of the polycrystalline piezoelectric film with random polarization orientation into the high-quality polycrystalline piezoelectric film with preferred orientation, and the conversion of the amorphous piezoelectric film into the polycrystalline piezoelectric film, improves the material quality of the piezoelectric film, and is beneficial to the preparation of high-frequency and high-performance bulk acoustic wave devices.

Description

Technical Field

[0001] This application relates to the field of radio frequency device fabrication technology, and in particular to a filter thin film substrate and its fabrication method. Background Technology

[0002] With increasing demands for higher data transmission speeds, performance, and power consumption in telecommunications equipment, there is a growing need for acoustic filters operating at higher frequencies and with wider bandwidths to achieve enhanced data transmission. Currently, integrating piezoelectric materials with silicon provides a material-level integrated wafer substrate, offering a material platform for fabricating monolithically integrated modules. Filters fabricated using heterogeneous substrate wafers can effectively improve the filter's center frequency and bandwidth while reducing power consumption and heat dissipation. The resulting electro-optic modulators can significantly reduce half-wave voltage, increase operating bandwidth, and reduce device size. However, in practical applications, the significant difference in lattice types between the piezoelectric material and the substrate material limits the fabrication of piezoelectric thin films and the application scenarios of filters. Therefore, an improved fabrication scheme for filter thin film substrates is needed to address these issues. Summary of the Invention

[0003] To address the aforementioned problems in the prior art, this application provides a filter thin film substrate and its fabrication method, thereby resolving technical issues such as the difference in lattice types between the piezoelectric material and the substrate material in the prior art. The specific technical solution is as follows:

[0004] On one hand, this application provides a method for preparing a filter thin film substrate, the method comprising:

[0005] S100: Provides a supporting substrate;

[0006] S200: A piezoelectric thin film of a predetermined thickness is formed on one side surface of the support substrate;

[0007] S300: The piezoelectric film is heat-treated by heating it to above the Curie temperature and holding it at that temperature for a first preset time; a preset voltage is applied to the piezoelectric film during the heat treatment process.

[0008] S400: An energy pulse is applied to the piezoelectric thin film to transform it into a target piezoelectric layer, thereby obtaining the thin film substrate, wherein the target piezoelectric layer is a preferred-oriented polycrystalline piezoelectric thin film.

[0009] Furthermore, the piezoelectric film is a polycrystalline or amorphous material, and the material of the piezoelectric film includes at least one of lithium niobate, lithium tantalate, aluminum nitride, and barium titanate.

[0010] Furthermore, the method further includes: forming a thin layer between the supporting substrate and the piezoelectric thin film, wherein the lattice of the thin layer matches the lattice of the target piezoelectric layer; the thickness of the thin layer is greater than 0 μm and less than or equal to 100 μm.

[0011] Furthermore, the method further includes: forming an electrode layer between the thin layer and the piezoelectric film, applying a preset voltage to the electrode layer, wherein the thickness of the electrode layer is greater than 0 μm and less than or equal to 10 μm.

[0012] Furthermore, the preset voltage is greater than 0KV and less than or equal to 100KV, and the first preset time is 0.1-100h;

[0013] In S200, the preset thickness is 50nm-50um.

[0014] Furthermore, when the preset materials are lithium niobate and lithium tantalate, the materials of the thin layer or supporting substrate include at least one of sapphire, quartz and hexagonal crystal materials.

[0015] When the preset material is barium titanate, the thin layer or supporting substrate respectively includes a carbide layer or a cubic crystal material.

[0016] Furthermore, the energy of the energy pulse in S400 is 0.1-10 J / cm². 2 The duration of the energy pulse is 0.1-20 ns.

[0017] Furthermore, the method further includes: forming an insulating layer between the supporting substrate and the thin layer; the thickness of the insulating layer is 0.1-10 μm.

[0018] Furthermore, the material of the supporting substrate includes at least one of silicon, silicon oxide, sapphire, diamond, aluminum nitride, gallium nitride, silicon carbide, and silicon-on-insulator.

[0019] On the other hand, this application also provides a filter thin film substrate, which is prepared by any of the preparation methods described above.

[0020] On the other hand, this application also provides a filter, including the filter thin film substrate as described above.

[0021] Based on the above technical solution, this application has the following beneficial effects:

[0022] This application achieves the rearrangement of piezoelectric polarities by heat-treating the piezoelectric thin film and applying a preset voltage followed by an energy pulse. This enables the transformation of randomly polarized polycrystalline piezoelectric thin films into high-quality polycrystalline piezoelectric thin films with preferred polarization orientations, as well as the transformation of amorphous piezoelectric thin films into polycrystalline piezoelectric thin films. This application allows for the fabrication of arbitrary polycrystalline piezoelectric thin films located on a supporting substrate, improving the material quality of piezoelectric thin films and facilitating the fabrication of high-frequency and high-performance bulk acoustic wave devices. Attached Figure Description

[0023] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of the thin film substrate preparation method provided in the embodiments of this application;

[0025] Figure 2 This is a schematic diagram of the thin film substrate fabrication process provided in the embodiments of this application;

[0026] Figure 3 This is an X-ray diffraction pattern of the piezoelectric thin film provided in Embodiment 1 of this application;

[0027] Figure 4 This is an X-ray diffraction pattern of the target piezoelectric layer provided in Embodiment 1 of this application;

[0028] In the figure, the corresponding reference numerals are: 100 - support substrate; 200 - piezoelectric thin film; 300 - target piezoelectric layer; 400 - metal patterned electrode. Detailed Implementation

[0029] The technical solutions of this disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0030] The following definitions shall apply unless a different definition is given elsewhere in the claims or this specification. All numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about". The term "about" generally refers to a range of numerical values ​​that a person skilled in the art would consider equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A range of numerical values ​​indicated by a low value and a high value is defined as including all numerical values ​​within that range and all subranges included within that range.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0032] The following describes the preparation method of the thin film substrate provided in the embodiments of this application. Please refer to [the relevant documentation]. Figure 1 , Figure 1 This is a schematic diagram of the process for preparing a thin film substrate. Figure 2 This is a schematic diagram of the thin film substrate fabrication process. This specification provides method operation steps as shown in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operation steps may be included. The order of steps listed in the embodiments is merely one possible order of execution among many steps and does not represent the only possible order. In actual fabrication, the method can be executed in the order shown in the embodiments or figures, or in parallel. The method includes:

[0033] S100: Provides a support substrate 100;

[0034] In some embodiments, the material of the support substrate 100 includes at least one of silicon, silicon oxide, sapphire, diamond, aluminum nitride, gallium nitride, silicon carbide, and silicon-on-insulator.

[0035] S200: A piezoelectric thin film 200 of a predetermined thickness is formed on one side surface of a support substrate; wherein the method of forming the piezoelectric thin film 200 of the predetermined thickness includes at least one of chemical vapor deposition, physical vapor deposition and atomic layer deposition.

[0036] In some embodiments, the preset thickness is 50nm-50um;

[0037] In other embodiments, the preset thickness is 70nm-50um;

[0038] In other embodiments, the preset thickness is 50nm-10um;

[0039] In other embodiments, the preset thickness is 90nm-1um.

[0040] In some embodiments, the piezoelectric film 200 is a polycrystalline material or an amorphous material, and the material of the piezoelectric film 200 includes at least one of lithium niobate, lithium tantalate, aluminum nitride, and barium titanate.

[0041] In some embodiments, the method further includes: forming a thin layer between the support substrate (100) and the piezoelectric thin film (200), the lattice of the thin layer matching the lattice of the target piezoelectric layer (300); the thickness of the thin layer being greater than 0 μm and less than or equal to 100 μm.

[0042] In some embodiments, the thickness of the thin layer is greater than 50 μm and less than or equal to 100 μm; in some embodiments, the thickness of the thin layer is greater than 50 μm and less than or equal to 80 μm; in some embodiments, the thickness of the thin layer is greater than 0 μm and less than or equal to 60 μm.

[0043] In some embodiments, the thin layer is formed by at least one of physical vapor deposition and chemical vapor deposition, wherein physical vapor deposition may specifically be sputtering and evaporation, and chemical vapor deposition may specifically be MOCVD, LPCVD and PECVD.

[0044] In some embodiments, the method further includes: forming an electrode layer between the thin layer and the piezoelectric film (200), applying a preset voltage to the electrode layer, wherein the thickness of the electrode layer is greater than 0 μm and less than or equal to 10 μm. By providing an electrode layer, this application enables the piezoelectric film to be directly grounded, which facilitates the application of voltage to be fully effective within the piezoelectric film.

[0045] It should be noted that when the material of the electrode layer matches the lattice of the target piezoelectric layer 300, the electrode layer is both an electrode layer and a thin layer.

[0046] In some embodiments, the method further includes forming an insulating layer between the support substrate (100) and the thin layer; the thickness of the insulating layer is 0.1-10 μm. The material of the insulating layer includes at least one of silicon oxide and germanium oxide.

[0047] S300: Heat treatment is performed on the piezoelectric film 200 by heating the piezoelectric film 200 to above the Curie temperature and holding it at that temperature for a first preset time; a preset voltage is applied to the piezoelectric film 200 during the heat treatment process;

[0048] In some embodiments, the first preset time is 0.1-100h; in other embodiments, the first preset time is 10-100h; in other embodiments, the first preset time is 0.1-50h; in other embodiments, the first preset time is 60-75h.

[0049] In some embodiments, when the preset materials are lithium niobate and lithium tantalate, the material of the thin layer or support substrate (100) includes at least one of sapphire, quartz and hexagonal crystal system materials;

[0050] In other embodiments, when the preset material is barium titanate, the thin layer or support substrate (100) respectively includes a carbide layer or a cubic crystal material.

[0051] Preferably, an ultrashort high-energy pulse is added during heat treatment.

[0052] In some embodiments, the preset voltage is greater than 0KV and less than or equal to 100KV, and the first preset time is 0.1-100h; in S200, the preset thickness is 50nm-50um.

[0053] In some embodiments, the preset voltage is greater than 50KV and less than or equal to 100KV; in some embodiments, the preset voltage is greater than 0KV and less than or equal to 60KV; in some embodiments, the preset voltage is greater than 30KV and less than or equal to 70KV.

[0054] S400: An energy pulse is applied to the piezoelectric thin film (200) to transform the piezoelectric thin film (200) into a target piezoelectric layer (300) to obtain the thin film substrate, wherein the target piezoelectric layer (300) is a preferred-oriented polycrystalline piezoelectric thin film.

[0055] This application achieves the rearrangement of piezoelectric polarity by heat-treating the piezoelectric thin film and applying a preset voltage followed by an energy pulse. This enables the transformation of randomly polarized polycrystalline piezoelectric thin films into high-quality polycrystalline piezoelectric thin films with preferred polarization orientation, as well as the transformation of amorphous piezoelectric thin films into polycrystalline piezoelectric thin films. This application allows for the fabrication of arbitrary polycrystalline piezoelectric thin films located on a supporting substrate, improves the material quality of the target piezoelectric layer, and is beneficial for the fabrication of high-frequency and high-performance bulk acoustic wave devices.

[0056] In some embodiments, the energy of the energy pulse in S400 is 0.1-10 J / cm². 2 The duration of the energy pulse is 0.1-20 ns.

[0057] In some embodiments, the duration of the energy pulse is 10-20 ns; in other embodiments, the duration of the energy pulse is 0.1-15 ns; and in still other embodiments, the duration of the energy pulse is 3-13 ns.

[0058] In other embodiments, the energy pulse has an energy of 7-10 J / cm². 2 In other embodiments, the energy pulse has an energy of 0.1-5 J / cm². 2 In other embodiments, the energy pulse has an energy of 1-6 J / cm². 2 .

[0059] In some embodiments, the stoichiometric ratio of the elements in the piezoelectric film is consistent with the desired preset material. Specifically, when the preset material is lithium niobate, the stoichiometric ratio of Li:Nb:O in the piezoelectric film is 1:1:3; when the preset material is lithium tantalate, the stoichiometric ratio of Li:Ta:O in the piezoelectric film is 1:1:3.

[0060] The thin film substrate of this application can be detected by X-ray diffraction and Raman spectroscopy.

[0061] On the other hand, this application also provides a filter thin film substrate, which is prepared by any of the preparation methods described above.

[0062] On the other hand, this application also provides a filter, including: a support substrate 100, a target piezoelectric layer 300 and a metal patterned electrode 400; the support substrate 100 has a first surface and a second surface opposite to each other; the target piezoelectric layer 300 is located on the second surface; the metal patterned electrode 400 is located on the side surface of the target piezoelectric layer away from the support substrate.

[0063] The following are some specific embodiments of the above technical solutions listed in this specification.

[0064] Example 1:

[0065] This embodiment discloses a method for preparing a thin film substrate, the method including...

[0066] S001: Provides a support substrate 100;

[0067] Specifically, the material of the support substrate 100 is silicon.

[0068] In some embodiments, the support substrate 100 includes an insulating layer located on one side close to the piezoelectric film 200. The insulating layer is made of at least one of silicon oxide and germanium oxide, and has a thickness of 0.1-10 μm.

[0069] S002: An electrode layer is placed on one side of the supporting substrate. Specifically, the electrode layer is a molybdenum metal electrode with a thickness of 1 μm.

[0070] It should be noted that the aforementioned electrode layer is also a thin layer.

[0071] S003: A piezoelectric thin film 200 of a predetermined thickness is deposited or epitaxially formed on the surface of the electrode layer on the side away from the supporting substrate 100; wherein the deposition method includes at least one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition. In some embodiments, the predetermined thickness is 0.3 μm; in some embodiments, the material of the piezoelectric thin film 200 is polycrystalline, and the material of the piezoelectric thin film 200 is aluminum nitride.

[0072] S004: The piezoelectric film 200 is heat-treated by heating it to above the Curie temperature of aluminum nitride, specifically 450°C, and holding it at that temperature for a first preset time; a preset voltage is applied to the piezoelectric film 200 during the heat treatment process; in some embodiments, the first preset time is 10 hours.

[0073] In some implementations, the preset voltage is a DC voltage of 100V.

[0074] In some implementations, the voltage applied without an electrode layer is greater than the voltage applied with an electrode layer.

[0075] S005: An energy pulse is applied to the piezoelectric thin film 200 to transform the piezoelectric thin film 200 into a target piezoelectric layer 300, thereby obtaining a thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film.

[0076] In some implementations, the duration of the energy pulse is 0.1-20 ns;

[0077] In some implementations, the energy pulse has an energy of 0.1-10 J / cm². 2 ;

[0078] It should be noted that the above-mentioned heat treatment of the piezoelectric film 200 and the application of a preset voltage to the piezoelectric film 200 during the heat treatment process can be replaced by heat treatment of the entire structure of the prepared silicon-molybdenum electrode-aluminum nitride film or the supporting substrate 100 and the application of voltage.

[0079] X-ray diffraction test:

[0080] like Figure 3 As shown, Figure 3The X-ray diffraction pattern of the piezoelectric thin film of aluminum nitride material before the heat treatment, voltage application, and energy pulse application of this application is shown. The crystal diffraction peaks show three crystal planes with small tilt angles to the Z-direction (0 0 0 1), and one crystal direction (1 0-1 2) with a large angle difference from the Z-direction (0 0 0 1). Figure 4 As shown, Figure 4 This is an X-ray diffraction pattern of the target piezoelectric layer of the aluminum nitride material after treatment in Example 1 of this application. As shown in the figure, the crystal orientations are significantly reduced, and their angles are not significantly different and are basically consistent.

[0081] This application achieves the rearrangement of piezoelectric polarity by heat treatment and the application of a preset voltage followed by the addition of an energy pulse. This transforms a polycrystalline aluminum nitride piezoelectric film with randomly arranged polarization orientation into a high-quality polycrystalline aluminum nitride piezoelectric film with preferred orientation, thereby improving the material quality of the piezoelectric film and facilitating the fabrication of high-frequency and high-performance bulk acoustic wave devices.

[0082] Example 2:

[0083] This embodiment discloses a method for preparing a thin film substrate, the method including...

[0084] S10: Provides a support substrate 100;

[0085] Specifically, the material of the support substrate 100 is sapphire.

[0086] A thin layer is formed on the supporting substrate (100), the lattice of the thin layer being matched with the lattice of the target piezoelectric layer (300); the thickness of the thin layer is greater than 0 μm and less than or equal to 100 μm.

[0087] In some embodiments, the thin layer is formed by at least one of physical vapor deposition and chemical vapor deposition, specifically sputtering and evaporation, and MOCVD, LPCVD, and PECVD. The material of the thin layer is specifically strontium titanate.

[0088] S20: A piezoelectric thin film 200 of a predetermined thickness is formed by molecular beam epitaxy on the surface of the thin film away from the supporting substrate 100; in some embodiments, the predetermined thickness is 0.4-0.6 μm; in some embodiments, the material of the piezoelectric thin film 200 is barium titanate.

[0089] S30: Heat treatment is performed on the piezoelectric film 200, heating the piezoelectric film 200 to above the Curie temperature of barium titanate, specifically 130°C, and holding it at that temperature for a first preset time; a preset voltage is applied to the piezoelectric film 200 during the heat treatment process; in some embodiments, the first preset time is 0.1-100h; in some embodiments, the preset voltage is 210V.

[0090] S40: An energy pulse is applied to the piezoelectric thin film 200 to transform it into the target piezoelectric layer 300, thus obtaining a thin film substrate. In some embodiments, the duration of the energy pulse is 0.1-20 ns; in some embodiments, the energy of the energy pulse is 0.1-10 J / cm². 2 .

[0091] It should be noted that the above-mentioned heat treatment of the piezoelectric film 200 and the application of a preset voltage to the piezoelectric film 200 during the heat treatment process can be replaced by heat treatment of the entire structure of the prepared sapphire-strontium titanate-barium titanate film or the supporting substrate 100 and the application of voltage.

[0092] Example 3:

[0093] This embodiment discloses a method for preparing a thin film substrate, the method comprising the following steps:

[0094] S1: Provides a support substrate 100;

[0095] S2: A piezoelectric thin film 200 of a predetermined thickness of 1µm is placed on one side surface of the supporting substrate.

[0096] S3: Heat treatment is performed on the piezoelectric film 200. The piezoelectric film 200 is heated to above the Curie temperature and kept at that temperature for a first preset time. During the heat treatment, a preset voltage is applied to the piezoelectric film 200. The first preset time is 48 hours and the preset voltage is 210 kV.

[0097] S4: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 0.1-10 J / cm². 2 The duration of the energy pulse is 10 ns.

[0098] Example 4:

[0099] This embodiment discloses a method for preparing a thin film substrate, the method comprising the following steps:

[0100] S1: A support substrate 100 is provided, the support substrate 100 having opposing first and second surfaces;

[0101] S2: A piezoelectric thin film 200 of a predetermined thickness is placed on one side surface of the supporting substrate; the predetermined thickness is 20 μm.

[0102] S3: Heat treatment is performed on the piezoelectric film 200. The piezoelectric film 200 is heated to above the Curie temperature and kept at that temperature for a first preset time. During the heat treatment, a preset voltage is applied to the piezoelectric film 200. The first preset time is 0.1-100h. The preset voltage is 280KV.

[0103] S4: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 5 J / cm². 2 The duration of the energy pulse is 0.1-20 ns.

[0104] Example 5:

[0105] This embodiment discloses a method for preparing a thin film substrate, the method comprising the following steps:

[0106] S1: A support substrate 100 is provided, the support substrate 100 having opposing first and second surfaces;

[0107] S2: A piezoelectric thin film 200 of a predetermined thickness is placed on one side surface of the supporting substrate; the predetermined thickness is 600 nm.

[0108] S3: Heat treatment is performed on the piezoelectric film 200. The piezoelectric film 200 is heated to above the Curie temperature and held at that temperature for a first preset time. During the heat treatment, a preset voltage is applied to the piezoelectric film 200. The first preset time is 0.1-100h. The preset voltage is 170KV.

[0109] S4: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 3 J / cm². 2 The duration of the energy pulse is 0.1-20 ns.

[0110] Example 6:

[0111] This embodiment discloses a method for preparing a thin film substrate, the method comprising the following steps:

[0112] S1: A support substrate 100 is provided, the support substrate 100 having opposing first and second surfaces;

[0113] The second surface of the supporting substrate 100 has a thin layer whose lattice matches that of the target piezoelectric layer 300; the thickness of the thin layer is 100 μm.

[0114] S2: A piezoelectric thin film 200 of a predetermined thickness is placed on one side surface of the supporting substrate; the predetermined thickness is 50 nm.

[0115] S3: Heat treatment is performed on the piezoelectric film 200. The piezoelectric film 200 is heated to above the Curie temperature and kept at that temperature for a first preset time. During the heat treatment, a preset voltage is applied to the piezoelectric film 200. The first preset time is 0.1-100h. The preset voltage is 160KV.

[0116] S4: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 5 J / cm². 2 The duration of the energy pulse is 20 ns.

[0117] Example 7:

[0118] This embodiment discloses a method for preparing a thin film substrate, the method comprising the following steps:

[0119] S1: A support substrate 100 is provided, the support substrate 100 having opposing first and second surfaces;

[0120] The second surface of the supporting substrate 100 has a thin layer whose lattice matches that of the target piezoelectric layer 300; the thickness of the thin layer is 100 nm.

[0121] S2: A piezoelectric thin film 200 of a predetermined thickness is placed on one side surface of the supporting substrate; the predetermined thickness is 600 nm.

[0122] S3: Heat treatment is performed on the piezoelectric film 200. The piezoelectric film 200 is heated to above the Curie temperature and held at that temperature for a first preset time. During the heat treatment, a preset voltage is applied to the piezoelectric film 200. The first preset time is 0.1-100h. The preset voltage is 170KV.

[0123] S4: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 5 J / cm². 2 The duration of the energy pulse is 20 ns.

[0124] Example 8:

[0125] This embodiment discloses a method for preparing a thin film substrate, the method comprising the following steps:

[0126] S1: A support substrate 100 is provided, the support substrate 100 having opposing first and second surfaces;

[0127] The second surface of the support substrate 100 has a thin layer whose lattice matches the lattice of the target piezoelectric layer (300); the thickness of the thin layer is 20 μm.

[0128] S2: An electrode layer is formed on the surface of the thin layer away from the support substrate 100, and a preset voltage is applied to the electrode layer. The thickness of the electrode layer is y (0um < y ≤ 10um).

[0129] S3: A piezoelectric film 200 of a predetermined thickness is placed on one side surface of the support substrate; the predetermined thickness is 0.5 μm.

[0130] S4: Heat treatment is performed on the piezoelectric film 200. The piezoelectric film 200 is heated to above the Curie temperature and kept at that temperature for a first preset time. During the heat treatment, a preset voltage is applied to the piezoelectric film 200. The first preset time is 0.1-100h. The preset voltage is 1KV.

[0131] S5: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 0.5 J / cm². 2 The duration of the energy pulse is 20 ns.

[0132] Example 9:

[0133] This embodiment discloses a method for preparing a thin film substrate, the method comprising the following steps:

[0134] S1: A support substrate 100 is provided, the support substrate 100 having opposing first and second surfaces;

[0135] The second surface of the supporting substrate 100 has a thin layer whose lattice matches that of the target piezoelectric layer 300; the thickness of the thin layer is 10 μm.

[0136] S2: An electrode layer is formed on the surface of the thin layer away from the support substrate 100, and a preset voltage is applied to the electrode layer. The thickness of the electrode layer is 1µm.

[0137] S3: A piezoelectric film 200 of a predetermined thickness is placed on one side surface of the support substrate; the predetermined thickness is 20 μm.

[0138] S4: Heat treatment is performed on the piezoelectric film 200. The piezoelectric film 200 is heated to above the Curie temperature and kept at that temperature for a first preset time. During the heat treatment, a preset voltage is applied to the piezoelectric film 200. The first preset time is 0.1-100h. The preset voltage is 40KV.

[0139] S5: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 5 J / cm². 2 The duration of the energy pulse is 8 ns.

[0140] Due to the above technical solution, this application has the following beneficial effects:

[0141] This application achieves the rearrangement of piezoelectric polarities by heat-treating the piezoelectric thin film and applying a preset voltage followed by an energy pulse. This enables the transformation of randomly polarized polycrystalline piezoelectric thin films into high-quality polycrystalline piezoelectric thin films with preferred polarization orientations, as well as the transformation of amorphous piezoelectric thin films into polycrystalline piezoelectric thin films. This application allows for the fabrication of arbitrary polycrystalline piezoelectric thin films located on a supporting substrate, improving the material quality of piezoelectric thin films and facilitating the fabrication of high-frequency and high-performance bulk acoustic wave devices.

[0142] The foregoing description has fully disclosed the specific embodiments of this application. It should be noted that any modifications made by those skilled in the art to the specific embodiments of this application do not depart from the scope of the claims. Accordingly, the scope of the claims of this application is not limited to the foregoing specific embodiments.

Claims

1. A method for preparing a filter thin film substrate, characterized in that, The method includes: S100: Provides a support substrate (100); S200: A piezoelectric film (200) of a predetermined thickness is formed on one side surface of the support substrate (100); S300: The piezoelectric film (200) is heat-treated by heating it to above the Curie temperature and holding it at that temperature for a first preset time; during the heat treatment, a preset voltage is applied to the piezoelectric film (200); the preset voltage is greater than 0 kV and less than or equal to 100 kV, and the first preset time is 0.1 kV. 100h; S400: An energy pulse is applied to the piezoelectric thin film (200) to transform it into a target piezoelectric layer (300), thereby obtaining the thin film substrate. The target piezoelectric layer (300) is a preferentially oriented polycrystalline piezoelectric thin film. The energy of the energy pulse is 0.1 kJ / m³. 10J / cm 2 The duration of the energy pulse is 0.1 seconds. 20ns.

2. The method according to claim 1, characterized in that, The piezoelectric film (200) is a polycrystalline or amorphous material, and the material of the piezoelectric film (200) includes at least one of lithium niobate, lithium tantalate, aluminum nitride and barium titanate.

3. The method according to claim 1, characterized in that, The method further includes: forming a thin layer between the supporting substrate (100) and the piezoelectric thin film (200), wherein the lattice of the thin layer matches the lattice of the target piezoelectric layer (300); the thickness of the thin layer is greater than 0 μm and less than or equal to 100 μm.

4. The method according to claim 3, characterized in that, The method further includes: forming an electrode layer between the thin layer and the piezoelectric film (200), applying a preset voltage to the electrode layer, wherein the thickness of the electrode layer is greater than 0 μm and less than or equal to 10 μm.

5. The method according to claim 4, characterized in that, In step S200, the preset thickness is 50nm. 50um.

6. The method according to claim 3, characterized in that, When the preset materials are lithium niobate and lithium tantalate, the material of the thin layer or support substrate (100) includes at least one of sapphire, quartz and hexagonal crystal system materials; When the preset material is barium titanate, the thin layer or support substrate (100) respectively includes a carbide layer or a cubic crystal material.

7. The method according to claim 3, characterized in that, The method further includes forming an insulating layer between the supporting substrate (100) and the thin layer; the thickness of the insulating layer is 0.

1. 10um.

8. The method according to claim 1, characterized in that, The material of the support substrate (100) includes at least one of silicon, silicon oxide, sapphire, diamond, aluminum nitride, gallium nitride, silicon carbide, and silicon-on-insulator.

9. A filter thin film substrate, characterized in that, The filter thin film substrate adopts the method described in claim 1. Prepared by any of the preparation methods described in 8.

Images