A bulk acoustic wave resonator and a method for manufacturing the same

Abstract

The present application provides a bulk acoustic wave resonator and a preparation method thereof, which relates to the field of resonator technology. By incorporating a first substrate and a single crystal thin film layer into the method, and making the single crystal thin film layer serve as the growth surface of a piezoelectric stacked film layer, and then utilizing the characteristics of the single crystal thin film layer, when a piezoelectric stacked film layer is formed on the single crystal thin film layer, a high-quality quasi-single crystal piezoelectric layer is obtained, which is then applied to a device to effectively improve the performance of the bulk acoustic wave resonator.

Description

Technical Field

[0001] The present application relates to the technical field of resonators, and in particular to a bulk acoustic wave resonator and a method for preparing the same. Background Art

[0002] Radio frequency filters are widely used in military and civilian applications such as radar communications and radio frequency front-ends. Film bulk acoustic wave resonators (FBARs), with their high quality factor, low loss, high reliability, and miniaturization, have become a key component in building radio frequency bandpass filters. Existing BAW resonators typically utilize piezoelectric thin films grown directly on silicon substrates. However, due to factors such as the lattice mismatch between the silicon substrate and the piezoelectric film, the quality of the piezoelectric film is low, affecting and restricting the resonator's performance.

[0003] At present, with the gradual deepening of research, we have developed a method to further improve the performance of resonators by preparing high-quality piezoelectric films starting from piezoelectric materials. However, how to apply high-quality crystal piezoelectric films to devices is a major problem. Summary of the Invention

[0004] The purpose of this application is to provide a bulk acoustic wave resonator and a method for manufacturing the same, in order to address the deficiencies in the above-mentioned prior art.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of the present application are as follows:

[0006] In one aspect of an embodiment of the present application, a method for preparing a bulk acoustic wave resonator is provided, the method comprising:

[0007] providing a first substrate and a single crystal thin film layer located on the first substrate;

[0008] forming a piezoelectric stacked film layer on a surface of the single crystal thin film layer facing away from the first substrate, wherein the piezoelectric stacked film layer comprises a top electrode, a piezoelectric layer, and a bottom electrode sequentially formed on the single crystal thin film layer;

[0009] Bonding a second substrate to a side of the piezoelectric stacked film layer facing away from the first substrate;

[0010] The first substrate is removed to suppress the stress release of the piezoelectric layer through the single crystal thin film layer.

[0011] Optionally, after removing the first substrate to suppress stress release of the piezoelectric layer through the single crystal thin film layer, the method further comprises:

[0012] The single crystal thin film layer is etched to form a microstructure located on the surface of the top electrode.

[0013] Optionally, etching the single crystal thin film layer to form a microstructure located on the surface of the top electrode includes:

[0014] Etching the entire surface of the single crystal thin film layer to a transition layer having a target thickness;

[0015] The transition layer having a target thickness is pattern-etched to form a microstructure located on the surface of the top electrode.

[0016] Optionally, after forming the piezoelectric stacked film layer on the surface of the single crystal thin film layer facing away from the first substrate, the method further includes:

[0017] A sacrificial layer is formed on a surface of the bottom electrode facing away from the piezoelectric layer, and the sacrificial layer is used for release to form a cavity between the bottom electrode and the second substrate.

[0018] Optionally, bonding the second substrate to a side of the piezoelectric stacked film layer facing away from the first substrate includes:

[0019] forming a covering layer on the sacrificial layer, covering the sacrificial layer and the piezoelectric stacked film layer;

[0020] polishing the cover layer to provide a first flat surface;

[0021] A second substrate is bonded to the first plane of the cover layer.

[0022] Optionally, providing a first substrate and a single crystal thin film layer located on the first substrate includes:

[0023] Providing a first substrate and a single crystal material layer, wherein the single crystal material layer has a damaged layer;

[0024] The single crystal material layer is bonded to the first substrate via a bonding layer;

[0025] The single crystal material layer is separated at the damaged layer to form a single crystal thin film layer located on the first substrate.

[0026] Optionally, bonding the single crystal material layer to the first substrate via a bonding layer includes:

[0027] forming a first bonding layer on the single crystal material layer, and forming a second bonding layer on the first substrate;

[0028] The first bonding layer and the second bonding layer form a bonding layer through hydrophilic bonding or metal bonding.

[0029] Optionally, the material of the single crystal thin film layer is silicon carbide.

[0030] Another aspect of the present invention provides a method for preparing a bulk acoustic wave resonator, the method comprising:

[0031] Providing a first substrate and a single crystal material layer, wherein the single crystal material layer has a damaged layer;

[0032] The single crystal material layer is bonded to the first substrate via a bonding layer;

[0033] separating the single crystal material layer at the damaged layer to form a single crystal thin film layer on the first substrate;

[0034] Forming an annular isolation groove penetrating the single crystal thin film layer and the bonding layer by etching;

[0035] Filling the annular isolation groove with an isolation layer;

[0036] forming a piezoelectric stacked film layer on a surface of the single crystal thin film layer facing away from the first substrate;

[0037] The bonding layer on the inner circle of the annular isolation groove is released to form a cavity.

[0038] According to another aspect of the embodiments of the present application, a bulk acoustic wave resonator is provided, which is manufactured using any of the above-mentioned bulk acoustic wave resonator manufacturing methods.

[0039] The beneficial effects of this application include:

[0040] The present application provides a bulk acoustic wave resonator and a method for preparing the same, the method comprising: providing a first substrate and a single crystal thin film layer located on the first substrate; forming a piezoelectric stacked film layer on a surface of the single crystal thin film layer facing away from the first substrate, wherein the piezoelectric stacked film layer comprises a top electrode, a piezoelectric layer, and a bottom electrode sequentially formed on the single crystal thin film layer; bonding a second substrate to a side of the piezoelectric stacked film layer facing away from the first substrate; and removing the first substrate to suppress stress release in the piezoelectric layer through the single crystal thin film layer. This enables the application of high-quality quasi-single crystal piezoelectric layers in devices, and not only can the single crystal thin film layer provide protection for the piezoelectric stacked film layer, but also can suppress stress release in the piezoelectric layer in the piezoelectric stacked film layer through the single crystal thin film layer, thereby avoiding film rupture caused by stress release in the piezoelectric layer during the process of removing the temporary substrate by wet etching, thereby effectively improving the performance and yield of the bulk acoustic wave resonator.

[0041] The present application also provides a bulk acoustic wave resonator and a method for preparing the same, the method comprising: providing a first substrate and a single crystal material layer, wherein the single crystal material layer has a damage layer; bonding the single crystal material layer to the first substrate via a bonding layer; separating the single crystal material layer at the damage layer to form a single crystal thin film layer located on the first substrate; forming an annular isolation groove penetrating the single crystal thin film layer and the bonding layer by etching; filling the annular isolation groove with an isolation layer; forming a piezoelectric stacked film layer on the surface of the single crystal thin film layer facing away from the first substrate; releasing the bonding layer in the inner circle of the annular isolation groove to form a cavity. This enables the application of high-quality quasi-single crystal piezoelectric layers to the device, and also enables the use of the single crystal thin film layer in conjunction with the bottom electrode and the cavity to construct multiple acoustic reflection interfaces, thereby reflecting the acoustic wave multiple times, thereby effectively improving the Q value of the resonator. On this basis, the bonding layer is directly used as a sacrificial layer to release the cavity between the bottom electrode and the first substrate in conjunction with the annular isolation groove and the isolation layer, effectively simplifying the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 A schematic flow chart of a method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0044] Figure 2 This is one of the schematic diagrams of a method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0045] Figure 3 A second schematic diagram of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0046] Figure 4 The third state diagram of a method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0047] Figure 5 A fourth schematic diagram of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0048] Figure 6 A fifth schematic diagram of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0049] Figure 7 A sixth state diagram of a method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0050] Figure 8 The seventh state diagram of a method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0051] Figure 9 The eighth state diagram of a method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0052] Figure 10 A ninth state diagram of a method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0053] Figure 11 A tenth schematic diagram of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0054] Figure 12 11th schematic diagram of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0055] Figure 13 A schematic flow chart of another method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0056] Figure 14 One of the schematic diagrams of another method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application;

[0057] Figure 15 A second schematic diagram of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0058] Figure 16 A third schematic diagram of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0059] Figure 17 A fourth schematic diagram of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0060] Figure 18 A fifth schematic diagram of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present application;

[0061] Figure 19 This is a sixth state diagram of another method for preparing a bulk acoustic wave resonator provided in an embodiment of the present application.

[0062] Icons: 110-single crystal material layer; 111-single crystal thin film layer; 1111-microstructure; 112-separation part; 121-first bonding layer; 122-second bonding layer; 120-bonding layer; 130-first substrate; 140-piezoelectric stacked film layer; 141-top electrode; 142-piezoelectric layer; 143-bottom electrode; 150-sacrificial layer; 160-covering layer; 170-second substrate; 180-release hole; 210-annular isolation groove; 220-isolation layer. DETAILED DESCRIPTION

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of 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. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0064] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application as claimed, but merely represents selected embodiments of the present application. It should be noted that, unless there is a conflict, the various features of the embodiments of the present application may be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0065] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended only to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0066] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0067] In one aspect of the present invention, a method for preparing a bulk acoustic wave resonator is provided. Figure 1 As shown, the method includes:

[0068] S11 : providing a first substrate 130 and a single crystal thin film layer 111 located on the first substrate 130 .

[0069] like Figure 6 As shown, a stacked structure is first provided, which includes a first substrate 130 and a single crystal thin film layer 111, and the single crystal thin film layer 111 is located above the first substrate 130. In different embodiments, the first substrate 130 can be in direct contact with the surface of the single crystal thin film layer 111 to form a stacked structure, or the first substrate 130 and the single crystal thin film layer 111 are not in direct contact, and there is another layer between the two for connecting the two, such as Figure 6 In the embodiment, a bonding layer 120 is further provided between the first substrate 130 and the single crystal thin film layer 111 .

[0070] The single crystal thin film layer 111 can provide a good growth environment for the subsequent formation of the piezoelectric stacked film layer 140, facilitating the production of high-quality piezoelectric stacked film layers 140. The first substrate 130 can improve the support performance of the single crystal thin film layer 111, so the first substrate can serve as a temporary substrate, providing better support during the preparation of the piezoelectric stacked film layer 140.

[0071] S12: forming a piezoelectric stacked film layer 140 on the surface of the single crystal thin film layer 111 facing away from the first substrate 130, wherein the piezoelectric stacked film layer 140 includes a top electrode 141, a piezoelectric layer 142 and a bottom electrode 143 sequentially formed on the single crystal thin film layer.

[0072] On the basis of the structure provided in S11, a piezoelectric stacked film layer 140 is formed on the surface of the single crystal thin film layer 111 facing away from the first substrate 130, for example Figure 7 A piezoelectric stacked film layer 140 is formed on the single crystal film layer 111. The piezoelectric stacked film layer 140 is the layer in the resonator that can realize the conversion of mechanical energy and electrical energy, such as Figure 7 In the piezoelectric stack film 140, a stacked top electrode 141, a piezoelectric layer 142, and a bottom electrode 143 are formed. During the fabrication process, metal is first deposited on the surface of the single-crystal thin film layer 111 and patterned to form the top electrode 141. The entire piezoelectric layer 142 is then deposited on the top electrode 141. At this point, because the single-crystal thin film layer 111 and the piezoelectric layer 142 have highly matched lattice constants, thermal expansion coefficients, and excellent thermal conductivity, a high-quality piezoelectric layer 142, i.e., a quasi-single-crystal piezoelectric film, can be obtained. Metal is then deposited on the surface of the piezoelectric layer 142 and patterned to form the bottom electrode 143.

[0073] S13 : bonding the second substrate 170 to the side of the piezoelectric stacked film layer 140 facing away from the first substrate 130 .

[0074] S14: removing the first substrate 130.

[0075] Similar references Figure 9 After the preparation of the piezoelectric stacked film layer 140 is completed, the second substrate 170 is bonded to the side of the piezoelectric stacked film layer 140 facing away from the first substrate 130, so that the second substrate 170 can be used as a permanent substrate to provide basic support for the device.

[0076] like Figure 10As shown, the first substrate 130 formed in the aforementioned steps can be removed by etching. During the etching process of the first substrate 130, the single crystal thin film layer 111 can be used as an etch stop layer to facilitate the effective removal of the first substrate 130 while allowing the etching to stop promptly at the single crystal thin film layer 111 to avoid over-etching. Therefore, the single crystal thin film layer 111 and the first substrate 130 should meet an appropriate etching selectivity ratio. During the removal process of the first substrate 130, to avoid affecting the second substrate 170, the second substrate 170 can be first wax-sealed before the first substrate 130 is etched and removed.

[0077] During the process of etching and removing the first substrate 130, since the single crystal thin film layer 111 covers the piezoelectric stacked film layer 140, not only can the single crystal thin film layer 111 provide protection for the piezoelectric stacked film layer 140, but the single crystal thin film layer 111 can also suppress the stress release of the piezoelectric layer 142 in the piezoelectric stacked film layer 140, thereby avoiding the film rupture of the piezoelectric layer 142 caused by stress release, and effectively improving the performance and yield of the bulk acoustic wave resonator.

[0078] The above-mentioned process method can realize the application of high-quality quasi-single crystal piezoelectric layer 142 to the device, and on this basis, not only can the piezoelectric stacked film layer 140 be protected by the single crystal thin film layer 111, but the stress release of the piezoelectric layer 142 in the piezoelectric stacked film layer 140 can also be suppressed by the single crystal thin film layer 111, thereby avoiding the film rupture of the piezoelectric layer 142 caused by stress release during the process of removing the temporary substrate by wet etching, thereby effectively improving the performance and yield of the bulk acoustic wave resonator.

[0079] In the process of etching and removing the first substrate 130 , dry etching or wet etching may be used.

[0080] Optionally, after removing the first substrate 130 to suppress the stress release of the piezoelectric layer 142 through the single crystal thin film layer 111, the method further includes:

[0081] S15 : etching the single crystal thin film layer 111 to form a microstructure 1111 on the surface of the top electrode 141 .

[0082] Specifically, the single crystal thin film layer 111 in the device obtained in S14 can be utilized as follows: Figure 11 or Figure 12 As shown, by etching the single crystal thin film layer 111, the remaining portion is left as a microstructure 1111 on the surface of the top electrode 141. The microstructure 1111 can effectively construct an acoustic reflection interface, thereby improving the Q value of the resonator.

[0083] The microstructure 1111 can be an annular protrusion, for example, arranged along the periphery of the effective working area of ​​the resonator. Of course, there can be multiple annular protrusions, and they can be arranged in sequence, that is, a large circle within a small circle distribution. Of course, the protrusion can also be a columnar protrusion, and there can be multiple columnar protrusions, and the multiple columnar protrusions can be evenly or unevenly distributed along the periphery of the effective working area of ​​the resonator.

[0084] During the etching process of the single crystal thin film layer 111 , the top electrode 141 may be used as a hard mask to protect the piezoelectric layer 142 .

[0085] Optionally, etching the single crystal thin film layer 111 to form a microstructure 1111 located on the surface of the top electrode 141 includes:

[0086] S1501: Etching the entire surface of the single crystal thin film layer 111 to a transition layer having a target thickness.

[0087] S1502 : performing pattern etching on the transition layer having a target thickness to form a microstructure 1111 located on the surface of the top electrode 141 .

[0088] Specifically, such as Figure 11 or Figure 12 As shown, since the thickness of the single crystal thin film layer 111 is significantly different from that of the final microstructure 1111, the single crystal thin film layer 111 can first be etched through a full-surface etching method to a transition layer having a target thickness. The target thickness can be the same or approximately the same as the thickness of the microstructure 1111. Then, through a photolithography process, the transition layer is patterned and etched with the aid of a mask to form the microstructure 1111 located on the surface of the top electrode 141. This method preferably obtains a microstructure 1111 having a specific thickness.

[0089] Optionally, after forming the piezoelectric stacked film layer 140 on the surface of the single crystal thin film layer 111 facing away from the first substrate 130, the method further includes: forming a sacrificial layer 150 on the surface of the bottom electrode 143 facing away from the piezoelectric layer 142, and the sacrificial layer 150 is used to release to form a cavity between the bottom electrode 143 and the second substrate 170.

[0090] Specifically, in order to further improve the Q value of the resonator, a cavity for reflecting sound waves can be formed by the sacrificial layer 150: Figure 7 As shown, between S12 and S13, a sacrificial layer 150 may be deposited on the surface of the bottom electrode 143 of the piezoelectric stacked film layer 140. The shape and size of the sacrificial layer 150 should be the same or substantially the same as the shape and size of the cavity required in the end. Figure 11 and Figure 12As shown, a release hole 180 extending from the device surface to the sacrificial layer 150 can be formed by etching the piezoelectric stacked film layer 140 to the sacrificial layer 150. The sacrificial layer 150 is then released through the release hole 180, ultimately forming a cavity between the bottom electrode 143 and the second substrate 170. The cavity should be located in the effective working area of ​​the resonator so that the cavity can effectively reflect longitudinal acoustic waves, thereby improving the Q value of the resonator.

[0091] The present application does not limit the shape of the sacrificial layer 150. For example, it can be Figure 7 The trapezoid in .

[0092] Optionally, bonding the second substrate 170 to a side of the piezoelectric stacked film layer 140 facing away from the first substrate 130 includes:

[0093] S1301 : forming a covering layer 160 on the sacrificial layer 150 to cover the sacrificial layer 150 and the piezoelectric stacked film layer 140 .

[0094] S1302: Polishing the cover layer 160 to provide a first plane.

[0095] S1303 : Bonding the second substrate 170 to the first plane of the cover layer 160 .

[0096] Specifically, such as Figure 7 As shown, after the sacrificial layer 150 is formed on the bottom electrode 143, the side surface ( Figure 7 The upper surface of the device is relatively uneven, so Figure 8 As shown, a whole covering layer 160 can be deposited on the side surface of the device first, and then the surface of the covering layer 160 facing away from the piezoelectric stacked film layer 140 is polished to obtain a relatively flat first plane, as shown in FIG. Figure 9 As shown, when the second substrate 170 is bonded on the first plane, plane bonding can be used to improve a good bonding effect.

[0097] In the embodiment combined with S15: after completing the bonding of the second substrate 170 according to S1303, the Figure 9 Then, according to S14, the first substrate 130 is removed until the single crystal thin film layer 111 is stopped. Figure 10 The device structure shown. According to S15, the single crystal thin film layer 111 is etched to form a microstructure 1111 to obtain Figure 11 Next, the top electrode 141, the piezoelectric layer 142 and the bottom electrode 143 are sequentially etched to form a release hole 180 connected to the sacrificial layer 150, and then the sacrificial layer 150 is released through the release hole 180 to form a cavity, thereby obtaining Figure 12 The device structure shown.

[0098] Optionally, providing the first substrate 130 and the single crystal thin film layer 111 located on the first substrate 130 includes:

[0099] S1101: providing a first substrate 130 and a single crystal material layer 110, wherein the single crystal material layer 110 has a damaged layer therein.

[0100] S1102 : The single crystal material layer 110 is bonded to the first substrate 130 via the bonding layer 120 .

[0101] S1103 : separating the single crystal material layer 110 at the damaged layer to form a single crystal thin film layer 111 located on the first substrate 130 .

[0102] Specifically, first provide a first substrate 130 and Figure 2 The single crystal material layer 110 is shown, wherein a damaged layer ( Figure 2 The damaged layer is formed by using H + Ions are implanted from one side of the single crystal material layer 110 to form a damaged layer in the single crystal material layer 110. Figure 5 As shown, the single crystal material layer 110 is bonded to the first substrate 130 via the bonding layer 120. Figure 6 As shown, Figure 5 The device structure shown is subjected to heat treatment so that the single crystal material layer 110 is at the damaged layer ( Figure 6 The single crystal material layer 110 is separated from the single crystal thin film layer 111 below the dotted line at the dotted line. The thinner portion of the single crystal material layer 110 below the dotted line (the single crystal thin film layer 111) is still connected to the first substrate 130 via the bonding layer 120. Polishing can then be performed to make the surface of the single crystal thin film layer 111 facing away from the first substrate 130 relatively flat, facilitating the subsequent formation of a high-quality piezoelectric stacked film layer 140.

[0103] By forming a damaged layer through ion implantation, when the single crystal material layer 110 is separated, the separated and fallen portion can be reused, thereby reducing the preparation cost.

[0104] Optionally, bonding the single crystal material layer 110 to the first substrate 130 via the bonding layer 120 includes:

[0105] S11021 : forming a first bonding layer 121 on the single crystal material layer 110 , and forming a second bonding layer 122 on the first substrate 130 .

[0106] S11022: The first bonding layer 121 and the second bonding layer 122 are formed into a bonding layer 120 through hydrophilic bonding or metal bonding.

[0107] Specifically, such as Figure 3 As shown, in order to facilitate bonding, a first bonding layer 121 may be formed on the single crystal material layer 110, as shown in FIG. Figure 4 As shown, a second bonding layer 122 is formed on the surface of the first substrate 130, and then the bonding layer 120 is formed by hydrophilic bonding or metal bonding between the first bonding layer 121 and the second bonding layer 122, so that the single crystal material layer 110 is bonded to the first substrate 130.

[0108] Optionally, the single crystal material layer 110 and the single crystal thin film layer 111 are made of silicon carbide.

[0109] Optionally, the bonding layer 120 may be made of silicon dioxide, and the first substrate 130 and the second substrate 170 may be made of silicon. The bonding layer 120 has a thickness ranging from 500 nm to 4000 nm, and the single crystal thin film layer 111 has a thickness ranging from 10 nm to 1500 nm. S1103 yields a heterogeneous substrate: silicon / silicon dioxide / silicon carbide.

[0110] Another aspect of the present invention provides a method for preparing a bulk acoustic wave resonator. Figure 13 As shown, the method includes:

[0111] S21: providing a first substrate 130 and a single crystal material layer 110, wherein the single crystal material layer 110 has a damaged layer therein.

[0112] S22 : The single crystal material layer 110 is bonded to the first substrate 130 via the bonding layer 120 .

[0113] S23 : separating the single crystal material layer 110 at the damaged layer to form a single crystal thin film layer 111 on the first substrate 130 .

[0114] S21 to S23 can refer to Figures 1 to 4 The process shown is to provide a first substrate 130 and a single crystal material layer 110, bond the single crystal material layer 110 to the first substrate 130 via the bonding layer 120, and then perform heat treatment to separate the single crystal material layer 110 at the damaged layer. Figure 14 The thickness of the single crystal thin film layer 111 obtained is relatively thin, so as to avoid a large thickness of the entire device structure.

[0115] S24 : forming an annular isolation groove 210 penetrating the single crystal thin film layer 111 and the bonding layer 120 by etching.

[0116] like Figure 15As shown, etching is performed on the surface of the single crystal thin film layer 111 facing away from the first substrate 130, thereby forming an annular isolation groove 210 that sequentially passes through the single crystal thin film layer 111 and the bonding layer 120. The annular isolation groove 210 can divide the bonding layer 120 into two spaced-apart portions, one located within the annular isolation groove 210 and the other located outside the annular isolation groove 210. The area enclosed by the annular isolation groove 210 should be consistent with the effective operating area of ​​the resonator.

[0117] S25 : filling the annular isolation groove 210 with an isolation layer 220 .

[0118] like Figure 16 As shown, in Figure 15 The isolation layer 220 is further deposited on the upper surface of the device shown, so that the isolation layer 220 fills the annular isolation groove 210. In this way, the isolation layer 220 can be used as a barrier for the subsequent release of the bonding layer 120 in the inner circle of the annular isolation groove 210, thereby preventing the bonding layer 120 outside the outer circle of the annular isolation groove 210 from being affected. The isolation layer 220 is then polished to the single crystal thin film layer 111, as shown in FIG. Figure 17 As shown, a relatively flat device surface is obtained. The material of the isolation layer 220 is polysilicon.

[0119] S26 : forming a piezoelectric stacked film layer 140 on the surface of the single crystal thin film layer 111 facing away from the first substrate 130 .

[0120] S27 : releasing the bonding layer 120 on the inner circle of the annular isolation groove 210 to form a cavity.

[0121] like Figure 18 As shown, a piezoelectric stacked film layer 140 is formed on the surface of the single crystal thin film layer 111 away from the first substrate 130. The piezoelectric stacked film layer 140 is also a layer in the resonator that can realize the conversion of mechanical energy and electrical energy. For example, the piezoelectric stacked film layer 140 includes a stacked top electrode 141, a piezoelectric layer 142 and a bottom electrode 143. Figure 19 As shown, the piezoelectric stacked membrane layer 140 and the single crystal thin film layer 111 are then etched to form a bonding layer 120 surface extending into the inner circle of the annular isolation groove 210, and the bonding layer 120 within the inner circle of the annular isolation groove 210 is removed through the release hole 180 to form a cavity.

[0122] The above-described process method enables the application of a high-quality quasi-single-crystal piezoelectric layer 142 to the device. Furthermore, the single-crystal thin film layer 111, in conjunction with the bottom electrode 143 and the cavity, can be used to construct multiple acoustic reflection interfaces, thereby reflecting the acoustic waves multiple times and effectively improving the resonator's Q value. Furthermore, by combining the annular isolation groove 210 and the isolation layer 220, the bonding layer 120 can be directly used as a sacrificial layer 150 to release and form a cavity between the bottom electrode 143 and the first substrate 130, effectively simplifying the process.

[0123] Optionally, the single crystal material layer 110 and the single crystal thin film layer 111 are made of silicon carbide.

[0124] Optionally, the bonding layer 120 may be made of silicon dioxide, and the first substrate 130 and the second substrate 170 may be made of silicon. The bonding layer 120 has a thickness ranging from 500 nm to 4000 nm, and the single crystal thin film layer 111 has a thickness ranging from 10 nm to 1500 nm. S1103 yields a heterogeneous substrate: silicon / silicon dioxide / silicon carbide.

[0125] In another aspect of the present invention, a bulk acoustic wave resonator is provided, which is prepared by any of the above-mentioned bulk acoustic wave resonator preparation methods. The bulk acoustic wave resonator prepared by the above-mentioned method can have good performance, and will not be described in detail here.

[0126] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a bulk acoustic wave resonator, characterized in that: The method comprises: Providing a first substrate and a single crystal thin film layer located on the first substrate; forming a piezoelectric stacked film layer on a surface of the single crystal thin film layer facing away from the first substrate, wherein the piezoelectric stacked film layer comprises a top electrode, a piezoelectric layer, and a bottom electrode sequentially formed on the single crystal thin film layer; bonding a second substrate to a side of the piezoelectric stacked film layer facing away from the first substrate; The single crystal thin film layer is used as an etching stop layer, and the first substrate is removed by wet etching, so that the single crystal thin film layer is used to suppress the stress release of the piezoelectric layer.

2. The method according to claim 1, wherein After removing the first substrate by wet etching using the single crystal thin film layer as an etch stop layer so as to suppress stress release of the piezoelectric layer by the single crystal thin film layer, the method further includes: The single crystal thin film layer is etched to form a microstructure located on the surface of the top electrode.

3. The method according to claim 2, wherein The etching of the single crystal thin film layer to form a microstructure on the surface of the top electrode comprises: Etching the entire surface of the single crystal thin film layer to a transition layer having a target thickness; The transition layer having a target thickness is pattern-etched to form a microstructure located on the surface of the top electrode.

4. The method according to claim 1, wherein After forming a piezoelectric stacked film layer on a surface of the single crystal thin film layer facing away from the first substrate, the method further includes: A sacrificial layer is formed on a surface of the bottom electrode facing away from the piezoelectric layer, and the sacrificial layer is used for releasing to form a cavity between the bottom electrode and the second substrate.

5. The method according to claim 4, wherein Bonding the second substrate on a side of the piezoelectric stacked film layer facing away from the first substrate includes: forming a covering layer on the sacrificial layer, covering the sacrificial layer and the piezoelectric stacked film layer; polishing the cover layer to provide a first plane; The second substrate is bonded to the first plane of the cover layer.

6. The method according to any one of claims 1 to 5, characterized in that Providing a first substrate and a single crystal thin film layer on the first substrate includes: Providing the first substrate and a single crystal material layer, wherein the single crystal material layer has a damaged layer; The single crystal material layer is bonded to the first substrate via a bonding layer; The single crystal material layer is separated at the damaged layer to form the single crystal thin film layer located on the first substrate.

7. The method according to claim 6, wherein Bonding the single crystal material layer to the first substrate via a bonding layer comprises: forming a first bonding layer on the single crystal material layer, and forming a second bonding layer on the first substrate; The first bonding layer and the second bonding layer are formed into the bonding layer through hydrophilic bonding or metal bonding.

8. The method according to claim 1, wherein The material of the single crystal thin film layer is silicon carbide.

9. A method for preparing a bulk acoustic wave resonator, characterized in that: The method comprises: Providing a first substrate and a single crystal material layer, wherein the single crystal material layer has a damaged layer; The single crystal material layer is bonded to the first substrate via a bonding layer; separating the single crystal material layer at the damaged layer to form a single crystal thin film layer on the first substrate; forming an annular isolation groove penetrating the single crystal thin film layer and the bonding layer by etching; Filling an isolation layer in the annular isolation groove; forming a piezoelectric stacked film layer on a surface of the single crystal thin film layer facing away from the first substrate; The bonding layer on the inner circle of the annular isolation groove is released to form a cavity.

10. A bulk acoustic wave resonator, characterized in that: The bulk acoustic wave resonator is prepared using the bulk acoustic wave resonator preparation method according to any one of claims 1 to 8 or claim 9.

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