Cavity type film bulk acoustic resonator, preparation method thereof and filter

Abstract

The invention discloses a cavity type film bulk acoustic resonator, a preparation method thereof and a filter, and relates to the technical field of resonators, the cavity type film bulk acoustic resonator comprises a substrate silicon wafer, an AlN / Diamond film layer, top silicon and a cobweb-shaped transducer, and the middle of the top silicon is provided with a first through opening with an upward opening; the AlN / Diamond thin film layer is formed on the substrate silicon wafer, the middle part of the AlN / Diamond thin film layer is provided with a through hole II corresponding to the through hole I, the middle part of the substrate silicon wafer is provided with a bottom groove corresponding to the through hole II, and the through hole I, the through hole II and the bottom groove form a triangular beaker-shaped groove with a narrow upper part and a wide lower part; the cobweb-shaped transducer is formed on the top layer silicon and is positioned right above the through hole I; the bottom groove, the second penetrating opening, the first penetrating opening and the cobweb-shaped transducer jointly form a cavity. The film bulk acoustic resonator prepared by the invention can reduce acoustic energy loss, suppress a transverse vibration mode and improve a Q value.

Description

Technical Field

[0001] The present invention relates to the technical field of resonators, and particularly to a cavity-type thin film bulk acoustic wave resonator, a preparation method thereof, and a filter. Background Art

[0002] Currently, as a key device in communication systems, radio frequency filters are facing multiple challenges of integration, miniaturization, high frequency, and high performance. Thin film bulk acoustic wave resonators (FBARs) have gradually become a research hotspot in radio frequency filter technology due to their high quality factor (Q value), low insertion loss, high power handling capacity, and good frequency stability.

[0003] Existing thin film bulk acoustic wave resonators (FBARs) are mainly divided into three forms: solid-state packaged type, silicon back-etched type, and air-gap type. The solid-state packaged type FBAR directly encapsulates the piezoelectric stack structure in a solid material, enhancing the mechanical strength and environmental adaptability of the device. However, since acoustic waves may propagate to the substrate, increasing energy loss, the Q value is relatively low. The silicon back-etched type FBAR forms an acoustic wave propagation path by removing part of the silicon substrate to suspend the piezoelectric layer, having good mechanical stability. However, the etching process is complex and may reduce the device strength. The air-gap type FBAR forms an air gap between the piezoelectric layer and the substrate, restricting the acoustic wave propagation path, effectively reducing acoustic wave energy leakage, and improving the Q value.

[0004] However, in practical applications, traditional FBAR still has some problems: First, interference from the lateral vibration mode can lead to unnecessary acoustic wave energy loss, reducing signal selectivity and increasing insertion loss; Second, energy leakage during the propagation of acoustic waves and mechanical damping caused by the substrate further limit the efficiency of the device; In addition, at high frequencies, frequency drift and performance degradation caused by heat accumulation also seriously affect the reliability of FBAR. Some current improvement schemes mainly focus on material optimization and cavity structure design. For example, SiC / Diamond composite films are used to increase the sound velocity and mechanical strength. However, most existing cavity designs are limited to simple geometric shapes and do not fully optimize the acoustic wave propagation path and device lightweight performance. For example, the patent with the publication number CN109474252B: A cavity-type FBAR using SiC / Diamond composite film reduces interference from the lateral vibration mode by increasing the acoustic wave propagation rate and hardness, thereby improving the Q value and the electromechanical coupling coefficient. This scheme adopts a cavity structure with grooves and through-holes formed on the substrate, reducing mechanical damping and energy loss caused by the soft substrate. However, the cavity design is relatively simple and does not fully optimize the acoustic wave propagation path and lightweight performance. The patent with the publication number CN104202010A has made improvements in the application of multi-layer piezoelectric films and provides a scheme for controlling modal vibration through a multi-layer stacking structure. Although it enhances the frequency response and vibration control, its complex structure increases the manufacturing difficulty and poses challenges to cost and mass production. The patent with the publication number CN101977026A focuses on the influence of thermal effects on frequency drift and proposes to improve the temperature stability of FBAR by optimizing the heat dissipation design. Although it effectively improves the stability under high-frequency operation, its effect on reducing interference from the lateral vibration mode and energy loss is limited. In summary, although existing technologies have made some contributions in improving the Q value, reducing loss, and frequency stability, there is still room for optimization in suppressing the lateral vibration mode, device lightweight, and high-frequency adaptability.

[0005] Therefore, how to effectively solve the above problems by combining innovative piezoelectric layer materials with cavity structure design has become a key technical direction for further improving the performance of FBAR. Summary of the Invention

[0006] The object of the present invention is to provide a cavity-type thin film bulk acoustic resonator, its preparation method, and a filter. By adopting a spider web cavity structure and an AlN / Diamond composite film layer, it provides better thermal management performance and an efficient acoustic wave propagation path, significantly improves the Q value, and further enhances the overall performance of FBAR.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A cavity-type thin-film bulk acoustic resonator includes a substrate silicon wafer, and an AlN / Diamond thin-film layer, a top silicon layer, and a spider-shaped transducer sequentially arranged from bottom to top on the surface of the substrate silicon wafer;

[0009] The middle of the top silicon layer has a through hole one with an upward opening; the AlN / Diamond thin-film layer is formed on the substrate silicon wafer, and a through hole two corresponding to the through hole one is provided in the middle of the AlN / Diamond thin-film layer, and the cross-sectional dimensions of the through hole two and the through hole one are the same; a bottom groove corresponding to the through hole two is provided in the middle of the substrate silicon wafer, and the cross-sectional dimension of the bottom groove is larger than that of the through hole two, and the bottom groove is in an inverted horn shape, and the through hole one, the through hole two, and the bottom groove form a triangular beaker-shaped groove that is narrow at the top and wide at the bottom;

[0010] The spider-shaped transducer is formed in the middle of the top silicon layer and is located directly above the through hole one;

[0011] The bottom groove, the through hole two, the through hole one, and the spider-shaped transducer together form a cavity.

[0012] Further, the spider-shaped transducer sequentially includes a bottom electrode, a piezoelectric layer, and a top electrode from bottom to top.

[0013] Further, both the bottom electrode and the top electrode are metal thin films.

[0014] Further, the metal thin film is any one of gold, platinum, silver, tungsten, and molybdenum thin films.

[0015] Further, a plurality of release holes are evenly provided on the spider-shaped transducer to form a spider web shape.

[0016] Further, the cross-sections of the through hole one, the through hole two, and the bottom groove are circular, and the cross-sectional dimensions of the through hole one, the through hole two, and the bottom groove are the diameters of the circles.

[0017] The present invention provides a preparation method for preparing the cavity-type thin-film bulk acoustic resonator, including the following steps:

[0018] S1, depositing an AlN / Diamond thin-film layer on the substrate silicon wafer;

[0019] S2, etching a through hole two with a preset size on the AlN / Diamond thin-film layer;

[0020] S3, laying a top silicon layer on the AlN / Diamond thin-film layer, and thinning the bonded top silicon layer by a bonding and thinning method;

[0021] S4. Etch a through-hole 1 with a preset size on the thinned top silicon, and the cross-sectional size of the through-hole 1 is the same as that of the through-hole 2.

[0022] S5. Etch a bottom groove with a preset size on the substrate silicon wafer, and the cross-sectional size of the bottom groove is larger than that of the through-hole 2, so that the through-hole 1, the through-hole 2, and the bottom groove form a triangular beaker-shaped groove with a narrow top and a wide bottom.

[0023] S6. Deposit a bottom electrode, a piezoelectric layer, and a top electrode in sequence in the middle of the top silicon to form a transducer.

[0024] S7. Etch release holes on the transducer to obtain a spider-web-shaped transducer, and then obtain a spider-web cavity type thin film bulk acoustic wave resonator.

[0025] Further, in step S7, etching release holes on the transducer to obtain a spider-web-shaped transducer includes: performing spider-web patterning etching on the transducer, and the cross-section of the transducer after patterning etching is a regular octagon in the shape of a spider web.

[0026] Etch a plurality of release holes on the transducer to form a spider-web shape to obtain a spider-web-shaped transducer.

[0027] Further, the method further includes: using a wet etching method or a dry etching method to etch the top silicon.

[0028] The wet etching method is: using an HF-HN0 solution, a KOH solution, or a tetramethylammonium hydroxide solution to enter the cavity from the release hole (i.e., the etching window) to wet-etch the top silicon.

[0029] The present invention also provides a filter, including the cavity type thin film bulk acoustic wave resonator described in any one of the above.

[0030] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: The cavity type thin film bulk acoustic wave resonator, its preparation method, and the filter provided by the present invention. Among them, in the cavity type thin film bulk acoustic wave resonator, the bottom groove, the through-hole 2, the through-hole 1, and the spider-web-shaped transducer jointly form a spider-web-shaped cavity structure, optimizing the cavity design. This can not only accurately optimize the acoustic wave propagation path, reduce energy loss, but also improve the device lightweight and high-frequency adaptability. Moreover, this structure can effectively limit the direction of acoustic wave propagation, making it propagate longitudinally and suppressing the generation of transverse vibration modes. The Q value is significantly improved, while the insertion loss is reduced, ensuring the high selectivity and high stability of the resonator. Using the AlN / Diamond composite thin film layer as the combined material of the piezoelectric layer and the substrate greatly reduces the influence of mechanical damping on acoustic wave propagation, improves the acoustic wave propagation efficiency, enhances the frequency stability and resonance performance of the FBAR, thereby improving the Q value.

[0031] In summary, through the combination of the innovative cobweb cavity structure and the AlN / Diamond composite thin film layer, the present invention overcomes the disadvantages in the prior art and improves the performance of the thin film bulk acoustic wave resonator (FBAR). Through the geometrically optimized cobweb cavity structure, the acoustic wave propagation is confined to the longitudinal mode, reducing energy leakage and transverse vibration interference. At the same time, by combining the characteristics of high sound velocity and low damping of the AlN / Diamond composite material, the acoustic wave propagation efficiency and the electromechanical coupling performance are enhanced. Utilizing the lightweight characteristics of the cobweb structure and the optimization of the manufacturing process, the device is ensured to adapt to the high-frequency working environment and has good structural stability and process feasibility. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a schematic cross-sectional structure diagram of the cavity-type thin film bulk acoustic wave resonator according to the embodiment of the present invention;

[0034] Figure 2 It is a flowchart of the preparation method of the cavity-type thin film bulk acoustic wave resonator according to the embodiment of the present invention;

[0035] Figure 3 It is a top view of each stage in the preparation process of the cavity-type thin film bulk acoustic wave resonator according to the embodiment of the present invention;

[0036] Figure 4 It is a top view of the spider-web-shaped regular octagon transducer according to the embodiment of the present invention;

[0037] Description of the reference numerals: 1. Substrate silicon wafer; 2. AlN / Diamond thin film layer; 3. Top silicon; 4. Bottom electrode; 5. Piezoelectric layer; 6. Top electrode; 7. Bottom groove. Detailed Embodiments

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0039] The object of the present invention is to provide a cavity-type thin-film bulk acoustic resonator, a preparation method thereof, and a filter. By adopting a spider-web cavity structure and an AlN / Diamond composite thin-film layer, better thermal management performance and an efficient acoustic wave propagation path are provided, the Q value is significantly improved, and the overall performance of the FBAR is further enhanced.

[0040] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] As Figure 1 - Figure 2 shown, a cavity-type thin-film bulk acoustic resonator provided by an embodiment of the present invention includes a substrate silicon wafer 1, and an AlN / Diamond thin-film layer 2, a top silicon layer 3, and a spider-web transducer sequentially arranged from bottom to top on the surface of the substrate silicon wafer 1.

[0043] The middle part of the top silicon layer 3 has a through hole one with an upward opening; the AlN / Diamond thin-film layer 2 is formed on the substrate silicon wafer 1, and a through hole two corresponding to the through hole one is provided in the middle of the AlN / Diamond thin-film layer 2, and the cross-sectional dimensions of the through hole two and the through hole one are the same; a bottom groove 7 corresponding to the through hole two is provided in the middle of the substrate silicon wafer 1, the cross-sectional dimension of the bottom groove 7 is larger than that of the through hole two, the bottom groove 7 is in an inverted horn shape, and the through hole one, the through hole two, and the bottom groove 7 form a triangular beaker-shaped groove that is narrow at the top and wide at the bottom.

[0044] The spider-web transducer is formed on the top silicon layer 3 and is located directly above the through hole two.

[0045] The bottom groove, the through hole two, the through hole one, and the spider-web transducer together form a cavity.

[0046] In this embodiment, the spider-web transducer sequentially includes a bottom electrode 4, a piezoelectric layer 5, and a top electrode 6 from bottom to top.

[0047] In this embodiment, both the bottom electrode 4 and the top electrode 6 are metal thin films.

[0048] In this embodiment, the metal thin film is any one of gold, platinum, silver, tungsten, and molybdenum thin films.

[0049] In this embodiment, a plurality of release holes are uniformly arranged on the spider-web transducer to form a spider-web shape.

[0050] In this embodiment, the piezoelectric layer 5 is a piezoelectric thin film.

[0051] Exemplarily, the cross-sections of the through-hole 1, the through-hole 2, and the bottom groove are circular, and the cross-sectional dimensions of the through-hole 1, the through-hole 2, and the bottom groove are the diameters of the circles. Specifically, in the embodiments of the present invention, the cross-sections of the through-hole 1, the through-hole 2, and the bottom groove are circular, the cross-sectional diameters of the through-hole 1 and the through-hole 2 are the same, and the cross-sectional diameter of the bottom groove is slightly larger than the cross-sectional diameter of the through-hole 2.

[0052] Embodiment 2

[0053] As Figure 2 and Figure 3 shown, the embodiments of the present invention provide a preparation method for preparing the cavity-type thin-film bulk acoustic wave resonator described in Embodiment 1, including the following steps:

[0054] S1. Deposit an AlN / Diamond thin film layer 2 on the substrate silicon wafer 1;

[0055] S2. Etch a through-hole 2 with a preset size on the AlN / Diamond thin film layer 2;

[0056] S3. Lay a top silicon layer 3 on the AlN / Diamond thin film layer 2, and perform a thinning treatment on the bonded top silicon layer 3 by a bonding and thinning method; wherein, step S3-1 is to lay the top silicon layer 3, and step S3-2 is the bonding and thinning treatment;

[0057] S4. Etch a through-hole 1 with a preset size on the thinned top silicon layer 3, and the cross-sectional dimensions of the through-hole 1 are the same as the cross-sectional dimensions of the through-hole 2;

[0058] S5. Etch a bottom groove 7 with a preset size on the substrate silicon wafer, and the cross-sectional dimensions of the bottom groove 7 are larger than the cross-sectional dimensions of the through-hole 2, so that the through-hole 1, the through-hole 2, and the bottom groove 7 form a triangular beaker-shaped groove that is narrow at the top and wide at the bottom;

[0059] S6. Deposit a bottom electrode 4, a piezoelectric layer 5, and a top electrode 6 on the middle of the top silicon layer in sequence to form a transducer; wherein, S6-1 is to deposit the bottom electrode 4, S6-2 is to deposit the piezoelectric layer 5, and S6-3 is to deposit the top electrode 6;

[0060] S7. Etch release holes on the transducer to obtain a spider-web-shaped transducer, and further obtain a spider-web cavity-type thin-film bulk acoustic wave resonator.

[0061] Specifically, in step S7, etching release holes on the transducer to obtain a spider-web-shaped transducer includes: S7-1. Perform spider-web patterning etching on the transducer with a sandwich structure composed of the bottom electrode 4, the piezoelectric layer 5, and the top electrode 6. After the patterning etching, the cross-section of the transducer is a spider-web-shaped regular octagon;

[0062] S7-2. Etch corresponding release holes on the transducer to form a spider web shape, obtaining a spider web-shaped transducer, as Figure 4 shown.

[0063] In this embodiment, the method further includes: using wet etching or dry etching to etch the top silicon. Specifically:

[0064] Use HF-HN0 solution, KOH solution or TMAH (tetramethylammonium hydroxide) solution to enter the cavity from the release hole (i.e., the etching window) to wet-etch the top silicon, or directly use dry etching to etch the top silicon. By controlling the etching time, the thickness of the top silicon is adjusted, so as to achieve the purpose of adjusting the resonance frequency of the resonator. The entire top silicon in the cavity is etched away, forming a complete cavity structure.

[0065] Embodiment 3

[0066] An embodiment of the present invention provides a filter, including a cavity-type thin film bulk acoustic wave resonator described in Embodiment 1.

[0067] In summary, the cavity-type thin film bulk acoustic wave resonator, its preparation method, and the filter provided by the present invention have the following characteristics:

[0068] 1. In traditional FBARs, especially cavity-type and silicon back-etched FBARs, the spurious modes adopted usually interfere with the longitudinal vibration mode, often resulting in the loss of acoustic wave energy, leading to a decrease in the Q value, an increase in the insertion loss, a reduction in the efficiency and frequency selectivity of the device, and unstable performance. However, the present invention adopts a spider web cavity structure. By precisely designing the geometric shape and size of the cavity, the direction of acoustic wave propagation is effectively restricted, making it mainly propagate longitudinally. The spider web structure suppresses the generation of spurious modes by optimizing the local shape of the cavity. This design not only reduces the interference of spurious vibrations but also improves the effective propagation efficiency of acoustic waves in the piezoelectric layer by reducing unnecessary energy loss. Therefore, the Q value of the FBAR is significantly improved, and at the same time, the insertion loss is reduced, ensuring the high selectivity and high stability of the resonator.

[0069] 2. Conventional FBAR designs typically use silicon or other softer substrate materials. The material properties of these substrate materials (such as density, elastic modulus, mechanical damping, etc.) can cause loss of acoustic wave energy, limiting the performance of the device. In high-frequency applications, the damping effect of the substrate is particularly evident, reducing the performance of the FBAR, especially reducing the Q value, resulting in unstable signal quality, increasing insertion loss, and thus reducing the overall efficiency of the resonator. In contrast, the present invention uses an AlN / Diamond composite thin film layer as the combined material for the piezoelectric layer and the substrate. Diamond has extremely high hardness and sound velocity, which can effectively reduce the damping effect introduced by the substrate material; while AlN provides excellent piezoelectric properties, ensuring efficient generation and conversion of acoustic waves. Through this high-performance composite material structure, the influence of mechanical damping on the propagation of acoustic waves is greatly reduced, the propagation efficiency of acoustic waves is improved, the frequency stability and resonance performance of the FBAR are enhanced, and thus the Q value is increased.

[0070] 3. In the prior art, FBARs operating at high frequencies are prone to the influence of thermal effects, resulting in heat accumulation inside the device, which in turn causes frequency drift. Frequency drift can lead to unstable frequency response of the filter, affecting the reliability and accuracy of the system; in addition, high temperatures may also cause material expansion or thermal stress, further affecting the performance of the piezoelectric layer and the electrodes.

[0071] To address this heat dissipation problem, the present invention uses Diamond material as part of it. This material has extremely high thermal conductivity, which is three times that of silicon. The Diamond layer can quickly and effectively dissipate heat from the piezoelectric layer and the electrodes to the substrate, significantly improving the thermal management ability of the FBAR. By incorporating an efficient heat dissipation structure in the design of the thin film bulk acoustic resonator, the thermal stress caused by temperature fluctuations can be effectively reduced, and frequency drift can be minimized. In this way, the FBAR can still maintain stable operating performance in high-frequency and high-power applications, enhancing its reliability and stability during long-term operation.

[0072] 4. Existing FBAR cavity designs often rely on simple grooves or traditional silicon backside etching methods. Although these designs can form cavities, they do not fully consider the requirements for high-frequency operation and device lightweighting; moreover, the cavity structures in traditional designs are either too complex or too heavy, affecting the high-frequency response and structural strength of the FBAR, resulting in inefficient energy propagation and failure to effectively improve the lightweight characteristics of the device.

[0073] The solution of the present invention to solve this problem is as follows: By adopting a cobweb cavity structure, not only can the acoustic wave propagation path be precisely optimized to reduce energy loss, but also the weight of the device can be reduced by reducing the mass of the cavity part. The cobweb structure design can effectively reduce the mass of the overall structure while maintaining the strength of the structure, adapting to high-frequency applications. Since the acoustic wave energy is more concentrated in the longitudinal mode, the geometric design of the cavity can make the acoustic wave more concentrated, reduce attenuation, and improve the high-frequency response of the FBAR. Through this innovative design, the present invention not only meets the requirements of high-frequency applications, but also improves the mechanical strength and stability of the FBAR, ensuring the performance of the device during long-term operation.

[0074] In summary, by designing a cobweb cavity structure and adopting an AlN / Diamond composite thin film layer, the present invention can solve the above problems, provide a higher Q value, lower energy loss, better thermal management performance, and a more efficient acoustic wave propagation path, further improving the overall performance of the FBAR.

[0075] For the remaining technical features in this embodiment, those skilled in the art can flexibly select them according to the actual situation to meet different specific actual needs. However, it is obvious to those of ordinary skill in the art that these specific details do not have to be adopted to implement the present invention. In other instances, in order to avoid confusing the present invention, well-known components, structures, or parts have not been specifically described, and all are within the scope of the technical solutions claimed in the claims of the present invention.

[0076] Modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention. In the above description, in order to provide a thorough understanding of the present invention, a large number of specific details have been set forth. However, it is obvious to those of ordinary skill in the art that these specific details do not have to be adopted to implement the present invention. In other instances, in order to avoid confusing the present invention, well-known technologies, such as specific construction details, operating conditions, and other technical conditions, have not been specifically described.

[0077] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A cavity-type film bulk acoustic resonator, characterized in that: It includes a substrate silicon wafer and an AlN / Diamond thin film layer, a top silicon layer and a spider web-shaped transducer arranged in sequence from bottom to top on the surface of the substrate silicon wafer; The middle of the top silicon layer has a through hole 1 which opens upward; the AlN / Diamond thin film layer is formed on the substrate silicon wafer, the middle of the AlN / Diamond thin film layer is provided with a through hole 2 which corresponds to the through hole 1, and the cross-sectional dimensions of the through hole 2 and the through hole 1 are the same; the middle of the substrate silicon wafer is provided with a bottom groove which corresponds to the through hole 2, and the cross-sectional dimension of the bottom groove is larger than the cross-sectional dimension of the through hole 2, and the bottom groove is in an inverted trumpet shape, and the through hole 1, the through hole 2, and the bottom groove form a triangular beaker-shaped groove which is narrow at the top and wide at the bottom; The spider web-shaped transducer is formed in the middle of the top silicon layer and is located directly above the through hole 1; The bottom groove, the second through-hole, the first through-hole and the spider-web-shaped transducer together form a cavity.

2. The cavity type thin film bulk acoustic resonator according to claim 1, characterized in that: The spider web-shaped transducer comprises, from bottom to top, a bottom electrode, a piezoelectric layer and a top electrode.

3. The cavity type film bulk acoustic resonator according to claim 2, characterized in that: The bottom electrode and the top electrode are both metal films.

4. The cavity type thin film bulk acoustic resonator according to claim 3, characterized in that: The metal film is any one of gold, platinum, silver, tungsten and molybdenum films.

5. The cavity type film bulk acoustic resonator according to claim 1, characterized in that: The spider web-shaped transducer is evenly provided with a plurality of release holes to form a spider web shape.

6. The cavity type film bulk acoustic resonator according to claim 1, characterized in that: The cross-sections of the through-opening 1, the through-opening 2 and the bottom groove are circular, and the cross-section dimensions of the through-opening 1, the through-opening 2 and the bottom groove are the diameters of the circles.

7. A method for preparing the cavity type thin film bulk acoustic resonator according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, depositing an AlN / Diamond thin film layer on a substrate silicon wafer; S2, etching a second through hole of a preset size on the AlN / Diamond thin film layer; S3, laying a top layer of silicon on the AlN / Diamond thin film layer, and thinning the bonded top layer of silicon using a bonding thinning method; S4, etching a through hole 1 of a preset size on the thinned top silicon layer, wherein the cross-sectional size of the through hole 1 is the same as the cross-sectional size of the through hole 2; S5, etching a bottom groove of a preset size on the substrate silicon wafer, wherein the cross-sectional dimension of the bottom groove is larger than the cross-sectional dimension of the second through-hole, so that the first through-hole, the second through-hole and the bottom groove form a triangular beaker-shaped groove that is narrow at the top and wide at the bottom; S6, depositing a bottom electrode, a piezoelectric layer and a top electrode in sequence in the middle of the top silicon layer to form a transducer; S7, etching a release hole on the transducer to obtain a spider web-shaped transducer, and then obtaining a spider web cavity type thin film bulk acoustic resonator.

8. The preparation method according to claim 7, characterized in that: The step S7, etching a release hole on the transducer to obtain a spider web-shaped transducer, comprises: performing spider web-shaped patterned etching on the transducer, wherein the cross section of the transducer after the patterned etching is a spider web-shaped regular octagon; A plurality of release holes are etched on the transducer to form a spider web shape, thereby obtaining a spider web-shaped transducer.

9. The preparation method according to claim 7, characterized in that: The method further comprises: etching the top silicon layer by wet etching or dry etching; The wet etching method is: using HF-HNO solution, KOH solution or tetramethylammonium hydroxide solution to enter the cavity from the release hole to wet etch the top layer of silicon.

10. A filter, characterized in that: A cavity-type thin film bulk acoustic resonator comprising any one of claims 1 to 6.

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