Piezoelectric substrate, preparation method and acoustic wave device

Abstract

The invention provides a piezoelectric substrate, a preparation method and an acoustic wave device, the piezoelectric substrate comprises a piezoelectric layer, an oxygen-containing layer and a substrate layer, the oxygen-containing layer is located on the surface of one side of the substrate layer, and the piezoelectric layer is located on the surface of the side, away from the substrate layer, of the oxygen-containing layer; the oxygen-containing layer is of a porous structure, and the piezoelectric layer and the substrate layer are bonded through the oxygen-containing layer, so that by-products on a bonding interface can be discharged through the porous structure of the oxygen-containing layer, interface defects can be reduced, and the performance of the piezoelectric substrate is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a piezoelectric substrate, a preparation method and an acoustic wave device. Background Art

[0002] With the advent of the 5G era, the increase in communication frequency bands and the introduction of new technologies have led to an explosive growth in the demand for RF filters. Among them, thin-film surface acoustic wave filters not only have the low manufacturing cost of traditional surface acoustic wave filters, but also have device performance similar to or even better than that of bulk acoustic wave filters in all 4G and some 5G commonly used frequency bands, and have become one of the mainstream technical routes for RF filters today.

[0003] Composite substrates based on piezoelectric films are the basis for the preparation of thin-film surface acoustic wave filters. Piezoelectric wafers are usually directly bonded to substrates to prepare piezoelectric films. However, during the high-temperature annealing process after the piezoelectric wafer is combined with the silicon carbide substrate, the byproducts of the bonding interface cannot be discharged in time, and a large number of defects will be formed at the bonding interface, resulting in a significant decrease in the available area of ​​the heterogeneous substrate. At the same time, during the high-temperature annealing process, due to the concentration gradient effect, the oxygen atoms in the piezoelectric wafer area close to the bonding interface will move to the bonding interface, forming an amorphous layer of a certain thickness at the bonding interface, causing oxygen deficiency inside the piezoelectric wafer, generating vacancy defects, and affecting the performance of the piezoelectric film. During the high-temperature annealing process, the oxygen defects inside the piezoelectric wafer cannot be effectively restored. Summary of the invention

[0004] In view of the above problems in the prior art, the present application provides a piezoelectric substrate, a preparation method and an acoustic wave device. The specific technical solutions are as follows:

[0005] On the one hand, the present application provides a piezoelectric substrate, comprising: a piezoelectric layer, an oxygen-containing layer and a substrate layer, wherein the oxygen-containing layer is located on one side surface of the substrate layer, and the piezoelectric layer is located on one side surface of the oxygen-containing layer away from the substrate layer;

[0006] The oxygen-containing layer is a porous structure, and the piezoelectric layer and the substrate layer are bonded via the oxygen-containing layer.

[0007] In a possible implementation manner, the oxygen-containing layer satisfies at least one of the following characteristics:

[0008] The pore size of the oxygen-containing layer is 0.01-4 nm;

[0009] The oxygen content of the oxygen-containing layer is 15%-65%;

[0010] The thickness of the oxygen-containing layer is 5-800 nm;

[0011] The material of the oxygen-containing layer includes at least one of tantalum pentoxide, niobium pentoxide, silicon oxide, silicon oxynitride, and aluminum oxide.

[0012] In a possible implementation manner, the piezoelectric layer satisfies at least one of the following characteristics:

[0013] The thickness of the piezoelectric layer is 100-10000nm;

[0014] The oxygen content of the piezoelectric layer is 10%-35%;

[0015] The material of the piezoelectric layer is at least one of lithium tantalate and lithium niobate.

[0016] In a possible implementation manner, the substrate layer satisfies at least one of the following characteristics:

[0017] The thickness of the substrate layer is 300-1000 μm;

[0018] The substrate layer includes at least one of silicon carbide and diamond.

[0019] In another aspect, the present application provides a method for preparing a piezoelectric substrate, comprising:

[0020] S1: providing a piezoelectric wafer and a substrate layer;

[0021] S2: forming an oxygen-containing layer on a surface of at least one side of the substrate layer and the piezoelectric wafer;

[0022] S3: Bonding the piezoelectric wafer to the substrate layer via the oxygen-containing layer, performing a first annealing treatment to form a piezoelectric layer, and obtaining a piezoelectric substrate.

[0023] In a possible implementation manner, providing a piezoelectric wafer includes:

[0024] Providing an initial wafer, the initial wafer comprising an implantation surface;

[0025] Ions are implanted into the initial wafer from the implantation surface to form a damaged layer at a preset depth of the initial wafer to obtain the piezoelectric wafer. The implantation surface is used to bond with the substrate layer through the oxygen-containing layer.

[0026] In a possible implementation manner, bonding the piezoelectric wafer to the substrate layer via the oxygen-containing layer and performing a first annealing process to form a piezoelectric layer includes:

[0027] Bonding the implantation surface of the piezoelectric wafer to the substrate layer through the oxygen-containing layer, and performing a first annealing treatment to obtain a first bonding structure;

[0028] The first bonding structure is peeled off at the damaged layer, a second annealing treatment is performed, and the damaged layer is subjected to a first planarization treatment to form a piezoelectric layer.

[0029] In a possible implementation manner, the bonding of the piezoelectric wafer and the substrate layer through the oxygen-containing layer and performing a first annealing treatment to form a piezoelectric layer includes:

[0030] The piezoelectric wafer and the substrate layer are bonded through the oxygen-containing layer, the first annealing treatment is performed, and the surface of the piezoelectric wafer away from the substrate layer is thinned and subjected to a second planarization treatment to form a piezoelectric layer.

[0031] In a possible implementation manner, the formation method of the oxygen-containing layer includes at least one of chemical vapor deposition, physical vapor deposition, and thermal oxidation.

[0032] In a possible implementation manner, the heat treatment satisfies at least one of the following characteristics:

[0033] The temperature of the heat treatment is greater than or equal to a preset temperature, and the preset temperature is the formation temperature of the oxygen-containing layer;

[0034] The time of the heat treatment is 1-12 h.

[0035] In a possible implementation manner, the second annealing treatment is gradient annealing, including a first step temperature and a second step temperature, and the second annealing treatment satisfies at least one of the following characteristics:

[0036] The first step temperature is 200-300 °C;

[0037] The heating rate of the first step temperature is 1-5 °C / min;

[0038] The second step temperature is 300-950 °C;

[0039] The heating rate of the second step temperature is 5-10 °C / min.

[0040] On the other hand, the present application provides an acoustic wave device, including a surface electrode and a piezoelectric substrate as described in any one of claims 1-5, and the surface electrode is located on the piezoelectric layer.

[0041] Based on the above technical solutions, the present application has the following beneficial effects:

[0042] The present application provides a piezoelectric substrate, comprising a piezoelectric layer, an oxygen-containing layer and a substrate layer, wherein the piezoelectric layer and the substrate layer are bonded via the oxygen-containing layer, wherein the oxygen-containing layer is a porous structure, and can discharge byproducts generated at the bonding interface during high-temperature annealing through the gaps, thereby effectively reducing interface defects; and the oxygen-containing layer can eliminate the oxygen atom concentration gradient effect between the piezoelectric layer and the substrate layer, block the oxygen atoms in the piezoelectric layer from diffusing to the substrate layer, and avoid the formation of vacancy defects inside the piezoelectric layer, which is beneficial to improving the performance of the piezoelectric substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 : A schematic diagram of the structure of a piezoelectric substrate provided in an embodiment of the present application;

[0045] Figure 2 : A schematic diagram of a process for forming a piezoelectric wafer provided in an embodiment of the present application;

[0046] Figure 3 : A schematic diagram of a formation process of an oxygen-containing layer provided in an embodiment of the present application;

[0047] Figure 4 : A schematic diagram of another process for forming an oxygen-containing layer provided in an embodiment of the present application;

[0048] Figure 5 : A schematic diagram of the structure of a piezoelectric substrate during a formation process provided in an embodiment of the present application;

[0049] Figure 6 : A schematic diagram of the structure of a piezoelectric substrate during another formation process provided in an embodiment of the present application;

[0050] Figure 7 : A schematic diagram of the structure of a piezoelectric substrate during another formation process provided in an embodiment of the present application;

[0051] Figure 8 : A schematic diagram of a process for forming a piezoelectric layer provided in an embodiment of the present application;

[0052] Fig. 9 : TEM image of a piezoelectric substrate provided in an embodiment of the present application;

[0053] Reference numerals:

[0054] 1-piezoelectric layer, 2-oxygen-containing layer, 3-substrate layer, 4-piezoelectric wafer, 5-damaged layer. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. 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 making creative work are within the scope of protection of this application.

[0056] It should be noted that in the description of the present application, for the following defined terms, unless a different definition is given in the claims or elsewhere in this specification, these definitions should be applied. All numerical values, whether or not explicitly indicated, are defined herein as being modified by the term "about". The term "about" generally refers to a numerical range that a person of ordinary skill in the art would consider to be equivalent to the stated value to produce substantially the same properties, functions, results, etc. A numerical range indicated by a low value and a high value is defined to include all numerical values ​​included in the numerical range and all subranges included in the numerical range.

[0057] It should be noted that, in the description of the present application, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0058] It should be noted that, in the description of the present application, the meanings of the terms "on", "above", "above", and "over" should be interpreted in the broadest sense, meaning that the description containing these terms is interpreted as "a component can be set on another component in direct contact, or there can be intermediate components or layers between the components". In addition to the orientations described in the figures, spatially relative terms are also intended to cover different orientations of the device in use or operation. The device can be oriented in other ways (rotated 90° or in other orientations), and the spatially relative descriptors used in the present application can be interpreted accordingly.

[0059] The term "layer" as used in this application refers to a portion of a material that includes an area with a certain thickness. A layer can extend over the entire underlying or superstructure, or can extend over a local area of ​​the underlying or superstructure. In addition, a layer can be an area of ​​a homogeneous or inhomogeneous continuous structure, whose thickness is less than the thickness of the continuous structure. For example, a layer can be located between the top and bottom surfaces of the continuous structure or between any pair of horizontal planes therebetween. A layer can extend horizontally, vertically and / or along a tapered surface. A layer can include multiple layers.

[0060] It should be understood that the "surface" used in this application, such as "first surface", "second surface", etc., refers to the XY plane of the piezoelectric layer, etc., and the "thickness direction" refers to the Z direction perpendicular to the XY plane. The "thickness" or "height" mentioned in this application all refer to the Z-direction thickness or Z-direction height.

[0061] The present application provides a piezoelectric substrate, referring to Figure 1 , including a piezoelectric layer 1, an oxygen-containing layer 2 and a substrate layer 3, wherein the oxygen-containing layer 2 is located on one side of the substrate layer 3, and the piezoelectric layer 1 is located on the side of the oxygen-containing layer 2 away from the substrate layer 3; the oxygen-containing layer 2 is a porous structure, and the piezoelectric layer 1 and the substrate layer 3 are bonded through the oxygen-containing layer 2. In this way, the oxygen-containing layer 2 is arranged between the piezoelectric layer 1 and the substrate layer 3, which is conducive to improving the bonding effect between the piezoelectric layer 1 and the substrate layer 3, and can discharge the byproducts generated at the bonding interface during the high-temperature annealing process through the gaps in the oxygen-containing layer 2, effectively reducing interface defects; and the oxygen-containing layer 2 can eliminate the oxygen atom concentration gradient effect between the piezoelectric layer 1 and the substrate layer 3, block the oxygen atoms in the piezoelectric layer 1 from diffusing to the substrate layer 3, and avoid the formation of vacancy defects inside the piezoelectric layer 1, which is conducive to improving the performance of the piezoelectric substrate.

[0062] Among them, the porous structure contains a large number of pores, which can be closed, connected, or a combination of closed and connected pores; the distribution of the pores can be regular or irregular; it can be understood that the pore shape and pore distribution of the porous structure can be set according to actual application requirements to achieve the effect of discharging by-products from the bonding interface.

[0063] In some embodiments, the pore size of the oxygen-containing layer 2 is 0.01-4 nm; it can be understood that the pore size of the oxygen-containing layer 2 is any point value in the range of 0.01-4 nm; illustratively, the pore size of the oxygen-containing layer 2 can be 0.01 nm, 1 nm, 2 nm, 3 nm, 4 nm, etc. In this way, the pore size of the oxygen-containing layer 2 is controlled within the above range, which is conducive to the discharge of by-products generated during the preparation process and avoids defects in the bonding interface. Preferably, the pore size of the oxygen-containing layer 2 is 0.01-2 nm.

[0064] Specifically, the oxygen content of the oxygen-containing layer 2 is 15%-65%; it can be understood that the oxygen content of the oxygen-containing layer 2 is any point value between 15%-65%; illustratively, the oxygen content of the oxygen-containing layer 2 can be 15%, 20%, 35%, 55%, 65%, etc. In this way, controlling the oxygen content of the oxygen-containing layer 2 within the above range is conducive to eliminating the oxygen atom concentration gradient effect between the piezoelectric layer 1 and the substrate layer 3, avoiding the oxygen atoms in the piezoelectric layer 1 from moving to the substrate layer 3, and can effectively improve the performance of the piezoelectric substrate.

[0065] Specifically, the thickness of the oxygen-containing layer 2 is 5-800 nm; it can be understood that the thickness of the oxygen-containing layer 2 is any value in the range of 5-800 nm; illustratively, the thickness of the oxygen-containing layer 2 can be 5 nm, 50 nm, 100 nm, 400 nm, 800 nm, etc. In this way, the thickness of the oxygen-containing layer 2 is controlled within the above range, and the oxygen-containing layer 2 can provide mechanical support between the piezoelectric layer 1 and the substrate layer 3, which is beneficial to improving the stability of the piezoelectric substrate. Preferably, the thickness of the oxygen-containing layer 2 is 10-300 nm.

[0066] Specifically, the material of the oxygen-containing layer 2 includes at least one of tantalum pentoxide, niobium pentoxide, silicon oxide, silicon oxynitride, and aluminum oxide, which can form an oxygen-containing layer 2 with a preset oxygen content and pore size, so that the oxygen-containing layer 2 has stable chemical properties and can provide mechanical support for the piezoelectric substrate.

[0067] In some embodiments, the thickness of the piezoelectric layer 1 is 100-10000nm; it can be understood that the thickness of the piezoelectric layer 1 is any point value in the range of 100-10000nm; illustratively, the thickness of the piezoelectric layer 1 can be 100nm, 500nm, 1000nm, 4000nm, 10000nm, etc. In this way, if the thickness of the piezoelectric layer 1 is less than the above range, it may cause an increase in short-circuit current and leakage current, thereby causing a decrease in capacitance; controlling the thickness of the piezoelectric layer 1 within the above range can maintain the mechanical strength and stability of the piezoelectric layer 1, which is conducive to improving the sensitivity and rapid response performance of the piezoelectric layer 1. Preferably, the thickness of the piezoelectric layer 1 is 100-1000nm.

[0068] Specifically, the oxygen content of the piezoelectric layer 1 is 10%-35%; it can be understood that the oxygen content of the piezoelectric layer 1 is any point value between 10%-35%; illustratively, the oxygen content of the piezoelectric layer 1 can be 10%, 20%, 25%, 30%, 35%, etc. Exemplarily, the oxygen content of the piezoelectric layer 1 is less than or equal to the oxygen content of the oxygen-containing layer 2, which is conducive to eliminating the oxygen atom concentration gradient effect between the piezoelectric layer 1 and the substrate layer 3, avoiding the oxygen atoms in the piezoelectric layer 1 from moving to the substrate layer 3, forming vacancy defects in the piezoelectric layer 1, and thus affecting the performance of the piezoelectric layer 1.

[0069] Specifically, the material of the piezoelectric layer 1 is at least one of lithium tantalate and lithium niobate. In this way, the piezoelectric layer 1 can have stable chemical properties, low dielectric loss and good piezoelectric properties, which is conducive to the preparation of piezoelectric devices.

[0070] In some embodiments, the thickness of the substrate layer 3 is 300-1000 μm; it is understandable that the thickness of the substrate layer 3 is any point value in the range of 300-1000 μm; illustratively, the thickness of the substrate layer 3 can be 300 μm, 500 μm, 700 μm, 900 μm, 1000 μm, etc. In this way, the thickness of the substrate layer 3 is controlled within the above range, and the substrate layer 3 can provide a certain mechanical support. The substrate layer 3 of different thicknesses may change the charge distribution and electric field distribution of the piezoelectric substrate, thereby affecting the performance of its piezoelectric effect. It is understandable that the thickness of the substrate layer 3 can be changed according to actual application requirements.

[0071] Specifically, the material of the substrate layer 3 includes at least one of silicon carbide and diamond, so that the substrate layer 3 has good oxidation resistance, and prevents the surface of the substrate layer 3 from being oxidized to form an oxide layer, which affects the performance of the piezoelectric substrate; and silicon carbide and diamond have a large shear shear wave speed, high thermal conductivity and low dielectric loss, which is beneficial to improving the performance of the piezoelectric substrate. Applying the piezoelectric substrate to radio frequency acoustic devices is beneficial to improving the performance of the acoustic devices from multiple angles such as the sound field, electric field, and thermal field.

[0072] The following combination Figure 2-8 A method for preparing a piezoelectric substrate provided in an embodiment of the present application is introduced. This specification provides the method operation steps as in the embodiment, but more or fewer operation steps may be included based on conventional or non-creative labor. The order of steps listed in the embodiment is only one way of executing the order of many steps and does not represent the only execution order. When the actual preparation method is executed, it can be executed in the order of the method shown in the embodiment or the accompanying drawings or in parallel. The steps of the preparation method include:

[0073] S1: providing a piezoelectric wafer 4 and a substrate layer 3;

[0074] In some embodiments, reference Figure 2 Providing a piezoelectric wafer 4 includes: providing an initial wafer, the initial wafer including an implantation surface; performing ion implantation from the implantation surface to the initial wafer to form a damaged layer 5 at a preset depth of the initial wafer, thereby obtaining the piezoelectric wafer 4, wherein the implantation surface is used to bond with the substrate layer 3 through the oxygen-containing layer 2.

[0075] Specifically, the initial wafer is ion-implanted with gas ions, the gas ions include at least one of hydrogen ions, helium ions and argon ions, the ion implantation energy is 20-300 KeV, and the ion implantation dose is 1E14 ions / cm 2 -1 E17 ions / cm 2 It can be understood that the implantation energy of the ion implantation can be any value in the range of 20-300KeV, and the implantation dose of the ion implantation is 1E14 ions / cm 2 -1 E17ions / cm 2 In this way, a piezoelectric wafer 4 with a damaged layer 5 can be formed, which is conducive to subsequent peeling of the piezoelectric wafer 4 through the damaged layer 5, thereby obtaining a piezoelectric layer 1 with a heterogeneous structure.

[0076] S2: forming an oxygen-containing layer 2 on a surface of at least one of the substrate layer 3 and the piezoelectric wafer 4;

[0077] In some embodiments, reference Figure 3 In step S2 , an oxygen-containing layer 2 is formed on one side surface of the piezoelectric wafer 4 , which can effectively prevent the element overflow from occurring during the surface treatment of the piezoelectric wafer 4 , and is beneficial to protecting the surface of the piezoelectric wafer 4 .

[0078] In some embodiments, reference Figure 4 , an oxygen-containing layer 2 is formed on one side surface of the substrate layer 3; optionally, a first oxygen-containing layer 2 can be formed on one side surface of the substrate layer 3, and a second oxygen-containing layer 2 can be formed on one side surface of the piezoelectric wafer 4, and the first oxygen-containing layer 2 and the second oxygen-containing layer 2 are bonded. This is beneficial to enhance the bonding strength and prevent the piezoelectric layer 1 from cracking or even falling off in the subsequent peeling or thinning steps.

[0079] Specifically, the method for forming the oxygen-containing layer 2 includes at least one of chemical vapor deposition, physical vapor deposition, and thermal oxidation, which can form an oxygen-containing layer 2 with a certain thickness, and can control the structure of the oxygen-containing layer 2 by controlling the conditions of the preparation process to form a porous structure with a preset pore size.

[0080] In some embodiments, the material of the substrate layer 3 is silicon carbide material, and the oxygen-containing layer 2 can be obtained by thermally oxidizing the silicon carbide substrate. The prepared oxygen-containing layer 2 has higher density and thus better insulation and can better balance the temperature effect generated by the piezoelectric layer 1 during operation, thereby improving the performance of the acoustic wave device; and the oxygen-containing layer 2 is obtained by oxidizing silicon carbide, which has lower cost than other methods of forming the oxygen-containing layer 2, thereby reducing the cost of structural preparation.

[0081] In some embodiments, step S2 includes heat treating the oxygen-containing layer 2. Specifically, the heat treatment time is 1-12 hours; it can be understood that the heat treatment temperature is any point value in 1-12 hours; exemplarily, the heat treatment temperature can be 1 hour, 5 hours, 7 hours, 10 hours, 12 hours, etc. The temperature of the heat treatment is greater than or equal to the preset temperature, and the preset temperature is the formation temperature of the oxygen-containing layer 2; it can be understood that the formation method of the oxygen-containing layer 2 is different, and the range of the preset temperature is different. Exemplarily, the oxygen-containing layer 2 is formed by plasma chemical vapor deposition, and the formation temperature of the oxygen-containing layer 2 is 50-450°C. Exemplarily, the oxygen-containing layer 2 is formed by low-pressure chemical vapor deposition, and the formation temperature of the oxygen-containing layer 2 is 400-800°C. Exemplarily, the oxygen-containing layer 2 is formed by magnetron sputtering, and the formation temperature of the oxygen-containing layer 2 is 50-200°C. In another example, when thermal oxidation is used to form the oxygen-containing layer 2 and the material of the substrate layer 3 is silicon carbide, the formation temperature of the oxygen-containing layer 2 is 800-1300° C. Thus, heat treatment of the oxygen-containing layer 2 is beneficial for removing byproducts generated during the preparation of the oxygen-containing layer 2 .

[0082] Specifically, the gas atmosphere of the heat treatment is at least one of nitrogen, vacuum and inert gas, so as to prevent the materials of each layer of the piezoelectric substrate from generating byproducts in a high temperature environment.

[0083] In some embodiments, step S2 further includes performing a third planarization treatment on the oxygen-containing layer 2. Specifically, after the third planarization treatment, the root mean square roughness of the oxygen-containing layer 2 is less than a preset roughness, and the preset roughness is 0.4-0.6 nm. It can be understood that the preset roughness is any point value in 0.4-0.6 nm. Exemplarily, the preset roughness is 0.4 nm, 0.45 nm, 0.5 nm, 0.55 nm, 0.6 nm, etc. In this way, the roughness of the oxygen-containing layer 2 is controlled within the above range, which is conducive to the bonding of the substrate layer 3 and the piezoelectric layer 1 through the oxygen-containing layer 2.

[0084] S3: Bonding the piezoelectric wafer 4 and the substrate layer 3 via the oxygen-containing layer 2, performing a first annealing treatment to form a piezoelectric layer 1, and obtaining a piezoelectric substrate.

[0085] Specifically, the bonding methods include but are not limited to hydrophilic direct bonding, dielectric layer indirect bonding, surface activated bonding, etc., which can realize the integration of heterogeneous piezoelectric substrates.

[0086] In some embodiments, the temperature of the first annealing treatment is 100-250°C; it can be understood that the temperature of the first annealing treatment is any point value in the range of 100-250°C; illustratively, the temperature of the first annealing treatment can be 100°C, 150°C, 200°C, 225°C, 250°C, etc. In this way, controlling the annealing temperature within the above range is conducive to releasing the stress generated during the bonding process, and improving the bonding strength, which is conducive to improving the stability and reliability of the bonding structure.

[0087] In some embodiments, the piezoelectric wafer 4 is bonded to the substrate layer 3 via the oxygen-containing layer 2, and a first annealing process is performed to form the piezoelectric layer 1, including: Figure 5 , the injection surface of the piezoelectric wafer 4 is bonded to the substrate layer 3 through the oxygen-containing layer 2, and a first annealing treatment is performed to obtain a first bonding structure; Figure 6 , the first bonding structure is peeled off at the damaged layer 5, and a second annealing treatment is performed; Figure 7 The damaged layer 5 is subjected to a first planarization process to form the piezoelectric layer 1. In this way, the damaged layer 5 formed by ion implantation can be peeled off to obtain a piezoelectric substrate.

[0088] Specifically, during the process of high-energy ion bombardment of the piezoelectric wafer 4 during ion implantation, the implantation surface may be punctured and deformed due to the pyroelectric effect. Bonding the implantation surface of the piezoelectric wafer 4 to the substrate layer 3 through the oxygen-containing layer 2 can reduce the impact of temperature changes on the morphology of the surface of the piezoelectric wafer 4.

[0089] In some embodiments, the second annealing treatment is a gradient annealing, including a first step temperature and a second step temperature. Specifically, the first step temperature is 200-300°C; it can be understood that the first step temperature is any point value in 200-300°C; illustratively, the first step temperature can be 200°C, 220°C, 250°C, 275°C, 300°C, etc. Specifically, the heating rate of the first step temperature is 1-5°C / min; it can be understood that the heating rate of the first step temperature is any point value in 1-5°C / min; illustratively, the heating rate of the first step temperature can be 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, etc.

[0090] Specifically, the second step temperature is 300-950°C; it can be understood that the second step temperature is any point value in the range of 300-950°C; illustratively, the second step temperature can be 300°C, 400°C, 500°C, 700°C, 950°C, etc. Specifically, the heating rate of the second step temperature is 5-10°C / min; it can be understood that the heating rate of the second step temperature is any point value in the range of 5-10°C / min; illustratively, the heating rate of the second step temperature can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, etc. In this way, the atoms at the bonding interface can be rearranged through gradient annealing, the crystal quality can be restored, and a more stable chemical bond can be formed, thereby improving the bonding strength, and reducing the defects and voids at the bonding interface, thereby improving the stability of the bonding structure.

[0091] Specifically, the first planarization process includes but is not limited to chemical mechanical polishing, which can remove defects on the surface of the damaged layer 5 and reduce the generation of resistance and leakage current, thereby improving the reliability and stability of the piezoelectric substrate.

[0092] In some other embodiments, reference Figure 8 , bonding the piezoelectric wafer 4 to the substrate layer 3 through the oxygen-containing layer 2, performing a first annealing treatment, and forming a piezoelectric layer 1 includes: bonding the piezoelectric wafer 4 to the substrate layer 3 through the oxygen-containing layer 2, performing a first annealing treatment, thinning the surface of the side of the piezoelectric wafer 4 away from the substrate layer 3, and performing a second flattening treatment to form a piezoelectric layer 1.

[0093] Specifically, the thinning method includes but is not limited to mechanical grinding thinning, chemical mechanical grinding thinning, wet etching, plasma dry chemical etching, etc. The second planarization treatment includes but is not limited to chemical mechanical polishing, which can remove irregular shapes and defects on the surface of the piezoelectric layer 1, reduce the generation of resistance and leakage current, and thus improve the reliability and stability of the piezoelectric substrate.

[0094] In summary, the piezoelectric substrate prepared by the above-mentioned preparation method can form an oxygen-containing layer 2 with a preset thickness and a preset pore size between the substrate layer 3 and the piezoelectric layer 1, and the substrate layer 3 and the piezoelectric layer 1 are bonded through the oxygen-containing layer 2. The by-products generated during the bonding process can be discharged through the oxygen-containing layer 2, and the defects generated at the bonding interface can be effectively reduced, thereby improving the bonding strength of the piezoelectric substrate, which is beneficial to improving the performance of the piezoelectric substrate, and then improving the performance of the acoustic wave device.

[0095] The present application also provides an acoustic wave device, comprising a surface electrode and the piezoelectric substrate as described above, wherein the surface electrode is located on the piezoelectric layer 1 .

[0096] Specifically, the surface electrodes are interdigital electrodes, and the interdigital electrodes are arranged on the surface of the piezoelectric layer 1 .

[0097] The following is combined with the above Figure 1-9 Specific embodiments of the present application are introduced. The following embodiments describe the technical scheme of the present application in more detail, and these embodiments are only for illustrative purposes, because various modifications and changes within the scope of the disclosure of the present application are obvious to those skilled in the art. The reagents used in the embodiments can be obtained by commercial purchase or synthesized according to conventional methods, and can be used directly without further treatment, and the instruments and devices used in the embodiments can be obtained by commercial purchase.

[0098] Example 1

[0099] This embodiment provides a piezoelectric substrate, a preparation method and an acoustic wave device. The preparation method of the piezoelectric substrate includes the following steps: Figure 2-7 :

[0100] 1. Providing a substrate layer 3 and an initial wafer, wherein the initial wafer includes an implantation surface;

[0101] 2. Perform ion implantation on the initial wafer from the implantation surface to form a damaged layer 5 at a preset depth of the initial wafer to obtain a piezoelectric wafer 4, wherein the implantation surface is used to bond with the substrate layer 3 through the oxygen-containing layer 2;

[0102] 3. forming an oxygen-containing layer 2 on one side surface of the substrate layer 3;

[0103] 4. Bonding the implantation surface of the piezoelectric wafer 4 to the substrate layer 3 via the oxygen-containing layer 2, and performing a first annealing treatment to obtain a first bonding structure;

[0104] 5. The first bonding structure is peeled off from the damaged layer 5, a second annealing treatment is performed, and a first planarization treatment is performed on the damaged layer 5 to form a piezoelectric layer 1, thereby obtaining a piezoelectric substrate.

[0105] Specifically, the second annealing process is a secondary gradient annealing.

[0106] The piezoelectric substrate prepared in this embodiment comprises a piezoelectric layer 1, an oxygen-containing layer 2 and a substrate layer 3, the oxygen-containing layer 2 is located on one side surface of the substrate layer 3, the piezoelectric layer 1 is located on the side surface of the oxygen-containing layer 2 facing away from the substrate layer 3, and the side surface of the piezoelectric layer 1 facing away from the substrate layer 3 comprises a damaged layer 5; specifically, the oxygen-containing layer 2 has a porous structure, and the pore size of the oxygen-containing layer 2 is 0.01-2 μm, which is conducive to the discharge of by-products at the bonding interface; specifically, the oxygen content of the oxygen-containing layer 2 is 15%-65%, which can eliminate the oxygen atom concentration gradient effect between the piezoelectric layer 1 and the substrate layer 3, and is conducive to improving the performance of the piezoelectric substrate.

[0107] This embodiment also provides an acoustic wave device, including interdigital electrodes and the above-mentioned piezoelectric substrate.

[0108] Example 2

[0109] This embodiment provides a piezoelectric substrate, a preparation method and an acoustic wave device. The preparation method of the piezoelectric substrate includes the following steps: Figure 3 , Figure 4 and Figure 8 :

[0110] 1. Providing a piezoelectric wafer 4 and a substrate layer 3;

[0111] 2. forming an oxygen-containing layer 2 on a surface of at least one of the substrate layer 3 and the piezoelectric wafer 4;

[0112] Specifically, an oxygen-containing layer 2 may be formed on one side surface of the substrate layer 3; optionally, an oxygen-containing layer 2 may be formed on one side surface of the piezoelectric wafer 4; optionally, an oxygen-containing layer 2 may be formed on both one side surface of the substrate layer 3 and one side surface of the piezoelectric wafer 4.

[0113] 3. Bond the piezoelectric wafer 4 to the substrate layer 3 via the oxygen-containing layer 2, perform a first annealing treatment, perform a thinning treatment and a second flattening treatment on the surface of the piezoelectric wafer 4 away from the substrate layer 3 to form a piezoelectric layer 1 and obtain a piezoelectric substrate.

[0114] The piezoelectric substrate prepared in this embodiment has a piezoelectric layer 1, an oxygen-containing layer 2 and a substrate layer 3. Figure 1 and Fig. 9 The oxygen-containing layer 2 is located on one side of the substrate layer 3, the piezoelectric layer 1 is located on the side of the oxygen-containing layer 2 away from the substrate layer 3, the pore size of the oxygen-containing layer 2 is 0.01-2μm, and the oxygen content of the oxygen-containing layer 2 is 15%-65%.

[0115] This embodiment also provides an acoustic wave device, including interdigital electrodes and the above-mentioned piezoelectric substrate.

[0116] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0117] The above description has fully disclosed the specific implementation methods of the present application. It should be pointed out that any changes made by technicians familiar with the field to the specific implementation methods of the present application do not deviate from the scope of the claims of the present application. Accordingly, the scope of the claims of the present application is not limited to the above specific implementation methods.

Claims

1. A piezoelectric substrate, characterized in that: It comprises a piezoelectric layer, an oxygen-containing layer and a substrate layer, wherein the oxygen-containing layer is located on one side surface of the substrate layer, and the piezoelectric layer is located on one side surface of the oxygen-containing layer away from the substrate layer; The oxygen-containing layer is a porous structure, and the piezoelectric layer and the substrate layer are bonded via the oxygen-containing layer.

2. The piezoelectric substrate according to claim 1, characterized in that The oxygen-containing layer satisfies at least one of the following characteristics: The pore size of the oxygen-containing layer is 0.01-4 nm; The oxygen content of the oxygen-containing layer is 15%-65%; The thickness of the oxygen-containing layer is 5-800 nm; The material of the oxygen-containing layer includes at least one of tantalum pentoxide, niobium pentoxide, silicon oxide, silicon oxynitride, and aluminum oxide.

3. The piezoelectric substrate according to any one of claims 1 to 3, characterized in that The piezoelectric layer satisfies at least one of the following characteristics: The thickness of the piezoelectric layer is 100-10000nm; The oxygen content of the piezoelectric layer is 10%-35%; The material of the piezoelectric layer is at least one of lithium tantalate and lithium niobate.

4. The piezoelectric substrate according to any one of claims 1 to 3, characterized in that The substrate layer satisfies at least one of the following characteristics: The thickness of the substrate layer is 300-1000 μm; The substrate layer includes at least one of silicon carbide and diamond.

5. A method for preparing a piezoelectric substrate, characterized in that: include: S1: providing a piezoelectric wafer and a substrate layer; S2: forming an oxygen-containing layer on a surface of at least one side of the substrate layer and the piezoelectric wafer; S3: Bonding the piezoelectric wafer to the substrate layer via the oxygen-containing layer, performing a first annealing treatment to form a piezoelectric layer, and obtaining a piezoelectric substrate.

6. The preparation method according to claim 5, characterized in that: Providing a piezoelectric wafer comprises: Providing an initial wafer, the initial wafer comprising an implantation surface; Ions are implanted into the initial wafer from the implantation surface to form a damaged layer at a preset depth of the initial wafer to obtain the piezoelectric wafer. The implantation surface is used to bond with the substrate layer through the oxygen-containing layer.

7. The preparation method according to claim 6, characterized in that: The step of bonding the piezoelectric wafer to the substrate layer via the oxygen-containing layer and performing a first annealing process to form a piezoelectric layer comprises: Bonding the implantation surface of the piezoelectric wafer to the substrate layer through the oxygen-containing layer, and performing a first annealing treatment to obtain a first bonding structure; The first bonding structure is peeled off from the damaged layer, a second annealing treatment is performed, and a first planarization treatment is performed on the damaged layer to form a piezoelectric layer.

8. The preparation method according to claim 5, characterized in that: The step of bonding the piezoelectric wafer to the substrate layer via the oxygen-containing layer and performing a first annealing process to form a piezoelectric layer comprises: The piezoelectric wafer is bonded to the substrate layer via the oxygen-containing layer, the first annealing treatment is performed, and a surface of the piezoelectric wafer on a side away from the substrate layer is thinned and flattened to form a piezoelectric layer.

9. The preparation method according to claim 5 or 6, characterized in that: The method for forming the oxygen-containing layer includes at least one of chemical vapor deposition, physical vapor deposition, and thermal oxidation.

10. The preparation method according to claim 5 or 6, characterized in that: The heat treatment satisfies at least one of the following characteristics: The temperature of the heat treatment is greater than or equal to a preset temperature, and the preset temperature is the formation temperature of the oxygen-containing layer; The heat treatment time is 1-12h.

11. The preparation method according to claim 6, characterized in that: The second annealing process is a gradient annealing process including a first step temperature and a second step temperature, and the second annealing process satisfies at least one of the following characteristics: The first step temperature is 200-300°C; The heating rate of the first step temperature is 1-5°C / min; The second step temperature is 300-950°C; The heating rate of the second step temperature is 5-10°C / min.

12. An acoustic wave device, characterized in that: The piezoelectric substrate comprises a surface electrode and the piezoelectric substrate as claimed in any one of claims 1 to 5, wherein the surface electrode is located on the piezoelectric layer.

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