CN116979925A

CN116979925A - Film bulk acoustic resonator, preparation method thereof and filter

Info

Publication number: CN116979925A
Application number: CN202311008006.9A
Authority: CN
Inventors: 高安明; 路晓明; 姜伟
Original assignee: Zhejiang Xingyao Semiconductor Co ltd
Current assignee: Zhejiang Xingyao Semiconductor Co ltd
Priority date: 2023-08-10
Filing date: 2023-08-10
Publication date: 2023-10-31

Abstract

The application discloses a film bulk acoustic resonator and a preparation method thereof, and a filter using the film bulk acoustic resonator.

Description

Film bulk acoustic resonator, preparation method thereof and filter

Technical Field

The application relates to the technical field of radio frequency, in particular to a film bulk acoustic resonator, a preparation method thereof and a filter applying the film bulk acoustic resonator.

Background

The film bulk acoustic resonator (FilmBulkAcoustics Resonator, FBAR) is a resonator widely used in the radio frequency field at present, is manufactured by using MEMS semiconductor surface technology and film technology, and can realize the effect of signal filtering by combining the piezoelectric effect and the inverse piezoelectric effect and the signal gating characteristic and adopting a topological structure formed by cascading a plurality of resonators.

The basic structure of the film bulk acoustic resonator comprises a piezoelectric layer and metal electrodes distributed on the upper surface and the lower surface of the piezoelectric layer, and a cavity is usually arranged on one side of the lower electrode, which is away from the piezoelectric layer, in order to inhibit acoustic energy leakage. Currently, in order to better limit energy to the active region of the resonator, it is proposed in the prior art to provide a gap structure, such as an air-bridge (air-wing), between the corresponding piezoelectric layer and the metal electrode at the boundary of the active region of the thin film bulk acoustic resonator, so as to reflect the acoustic wave back to the active region of the resonator, thereby reducing the energy loss and improving the performance of the resonator.

However, the above gap structure provided in the thin film bulk acoustic resonator in practice has a series of problems due to limitations in materials, processes, and the like: firstly, the mechanical strength is not high, and collapse is easy to occur; second, since the height of the gap cannot be too high due to the limit of the physical strength, the effect of reducing the energy leakage is relatively limited.

Disclosure of Invention

In order to solve the technical problems, embodiments of the present application provide a thin film bulk acoustic resonator, a method for manufacturing the same, and a filter using the thin film bulk acoustic resonator, so as to improve physical strength of a gap structure disposed between a metal electrode and a piezoelectric layer at a boundary of an active region of the thin film bulk acoustic resonator, so that a height of the gap can be set higher, and an effect of the gap on reducing energy leakage is improved.

In order to achieve the above purpose, the embodiment of the present application provides the following technical solutions:

the thin film bulk acoustic resonator comprises a substrate, and a first electrode, a piezoelectric layer and a second electrode which are sequentially stacked on one side of the substrate, wherein a dielectric cavity is arranged between the first electrode and the substrate, and the dielectric cavity, the first electrode, the piezoelectric layer and the second electrode are overlapped in a direction perpendicular to a plane of the substrate, and an area where adjacent layers are contacted with each other is an active area;

a first gap is arranged between the second electrode and the piezoelectric layer and/or between the first electrode and the piezoelectric layer, and at least one end of the first gap is the boundary of the active area;

At least one dielectric block is arranged in the first gap, the dielectric block is in contact with the piezoelectric layer, the dielectric block is in contact with a corresponding electrode on one side of the first gap, which is away from the piezoelectric layer, and the first gap is separated into at least two sub-gaps by at least one dielectric block.

Optionally, a plurality of medium blocks are disposed in the first gap, and at least two medium blocks have different volumes.

Optionally, in the first gap, the volumes of any two medium blocks are different.

Optionally, the different volumes of the two media blocks include:

the widths of the two dielectric blocks in the extending direction of the piezoelectric layer are different.

Optionally, in the first gap, the volumes of at least two of the sub-gaps are different.

Optionally, in the first gap, the volumes of any two sub-gaps are different.

Optionally, the difference in volume of the two sub-gaps includes:

the widths of the two sub-gaps in the extending direction of the piezoelectric layer are different.

Optionally, when one dielectric block is disposed in the first gap, the first gap is separated by one dielectric block into two sub-gaps, and a width a of any one of the two sub-gaps along an extending direction of the piezoelectric layer and a width b of the first gap along the extending direction of the piezoelectric layer satisfy: a/b is more than or equal to 10% and less than or equal to 90%;

When a plurality of dielectric blocks are arranged in the first gap, along the extending direction of the piezoelectric layer, the distance c between two adjacent dielectric blocks and the distance d between the far boundaries of the two adjacent dielectric blocks satisfy the following conditions: c/d is more than or equal to 10% and less than or equal to 90%.

Optionally, the dielectric block is made of metal.

Optionally, the dielectric block and the corresponding electrode material on the side of the first gap facing away from the piezoelectric layer are the same.

A preparation method of a film bulk acoustic resonator comprises the following steps:

providing a substrate;

forming a first electrode on one side of the substrate;

forming a piezoelectric layer on one side of the first electrode away from the substrate;

forming a second electrode on one side of the piezoelectric layer away from the substrate;

a dielectric cavity is arranged between the first electrode and the substrate, and the dielectric cavity, the first electrode, the piezoelectric layer and the second electrode are overlapped in the direction perpendicular to the plane of the substrate, and the area where adjacent layers are contacted with each other is an active area;

a first gap is arranged between the second electrode and the piezoelectric layer and/or between the first electrode and the piezoelectric layer, and at least one end of the first gap is a boundary with the active area;

Optionally, when the first gap is provided between the second electrode and the piezoelectric layer, before the second electrode is formed on a side of the piezoelectric layer facing away from the substrate, the method further includes:

forming a sacrificial layer on one side of the piezoelectric layer away from the substrate;

etching the sacrificial layer, reserving at least two sacrificial blocks in the area where the first gap is preformed on the surface of the piezoelectric layer, forming grooves between two adjacent sacrificial blocks, and removing the sacrificial layer in other areas on the surface of the piezoelectric layer;

filling a medium in the groove to form a medium block;

after forming the second electrode, the method further comprises:

the sacrificial block is removed to form the first gap between the second electrode and the piezoelectric layer, and at least one dielectric block is disposed in the first gap.

Optionally, when the first gap is provided between the first electrode and the piezoelectric layer, before the piezoelectric layer is formed on the side of the first electrode facing away from the substrate, the method further includes:

Forming a sacrificial layer on one side of the first electrode away from the substrate;

etching the sacrificial layer, reserving at least two sacrificial blocks in the area where the first gap is preformed on the surface of the first electrode, forming grooves between two adjacent sacrificial blocks, and removing the sacrificial layer in other areas of the surface of the first electrode;

filling a medium in the groove to form a medium block;

after forming the second electrode, the method further comprises:

the sacrificial block is removed to form the first gap between the first electrode and the piezoelectric layer, and at least one dielectric block is disposed in the first gap.

A filter comprising a thin film bulk acoustic resonator as claimed in any preceding claim, or a thin film bulk acoustic resonator produced by a method as claimed in any preceding claim.

Compared with the prior art, the technical scheme has the following advantages:

the thin film bulk acoustic resonator provided by the embodiment of the application comprises a substrate, and a dielectric cavity, a first electrode, a piezoelectric layer and a second electrode which are sequentially arranged on one side of the substrate, wherein a first gap is arranged between the second electrode and the piezoelectric layer and/or between the first electrode and the piezoelectric layer, and the initial end of the first gap is overlapped with the tail end of an active area of the resonator, and at least one dielectric block is arranged in the first gap and simultaneously contacts with the piezoelectric layer and the electrode on one side of the first gap, which is away from the piezoelectric layer, so that the first gap is divided into at least two sub-gaps, and the following effects can be generated: in the first aspect, the physical strength of the first gap can be obviously improved, collapse in the manufacturing and using processes is avoided, and the product quality and yield are improved; in the second aspect, due to the improvement of the physical strength of the first gap, the first gap can be set to a higher height without worrying about structural collapse, and the higher first gap can reflect sound waves more effectively, reduce energy dissipation and improve the performance of the resonator; in the third aspect, at least one dielectric block is arranged in the first gap, an interface between the piezoelectric layer and the dielectric block is formed, and the acoustic impedance distribution of the interface between the piezoelectric layer and the dielectric block and the interface between the piezoelectric layer and the sub-gap and the interface between the piezoelectric layer and the second electrode is discontinuous, so that the reflection of sound waves can be further enhanced, parasitic modes are suppressed, meanwhile, the loss of expected longitudinal mechanical wave energy is reduced, the Q value of the resonator is improved, and the insertion loss is reduced.

Further, when a plurality of dielectric blocks are arranged in the first gap, the volumes of at least two dielectric blocks can be different, and similarly, the volumes of at least two sub-gaps can also be different, so that more discontinuous acoustic impedance changes are introduced at the boundary of the piezoelectric layer, the reflection of sound waves is further enhanced, the energy loss is reduced, and the performance of the resonator is improved.

And when the dielectric block arranged in the first gap is made of metal, the dielectric block made of metal can be directly contacted with the piezoelectric layer and the metal electrode at the same time, so that the heat dissipation effect of the first gap area can be improved, the heat generated by the piezoelectric layer during the working of the resonator is transmitted to the metal electrode through the dielectric block, the heat is effectively dissipated, and the performance of the resonator is improved by phase change.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic cross-sectional view of a prior art thin film bulk acoustic resonator with an air bridge structure;

FIG. 2 is a schematic cross-sectional view of a prior art thin film bulk acoustic resonator having both an air bridge and an air foil structure;

FIG. 3 is a schematic cross-sectional view of a thin film bulk acoustic resonator according to an embodiment of the present application;

FIG. 4 is a schematic cross-sectional view of another thin film bulk acoustic resonator according to an embodiment of the present application;

FIG. 5 is a schematic cross-sectional view of another thin film bulk acoustic resonator according to an embodiment of the present application;

FIG. 6 is a schematic cross-sectional view of another film bulk acoustic resonator according to an embodiment of the present application;

FIG. 7 is a schematic cross-sectional view of another thin film bulk acoustic resonator according to an embodiment of the present application;

FIG. 8 is a schematic cross-sectional view of another film bulk acoustic resonator according to an embodiment of the present application;

FIG. 9 is a schematic cross-sectional view of another thin film bulk acoustic resonator according to an embodiment of the present application;

FIG. 10 is a graph showing the Y parameter of a thin film bulk acoustic resonator with at least one dielectric block disposed in an air bridge versus the Y parameter of a conventional thin film bulk acoustic resonator with an air bridge structure according to an embodiment of the present application;

FIG. 11 is a graph showing the Q value of a thin film bulk acoustic resonator with at least one dielectric block disposed in an air bridge versus the Q value of a conventional thin film bulk acoustic resonator with an air bridge structure according to an embodiment of the present application;

fig. 12a to fig. 12j are schematic cross-sectional views of a device corresponding to each process step in a method for manufacturing a thin film bulk acoustic resonator according to an embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

As described in the background section, in the prior art, a design of disposing a gap structure between a corresponding piezoelectric layer and a metal electrode at a boundary of an active region of a thin film bulk acoustic resonator is proposed, and fig. 1 and fig. 2 respectively show schematic cross-sectional views of two thin film bulk acoustic resonators disposed with the gap structure in the prior art, it can be seen that the thin film bulk acoustic resonator includes, from bottom to top, a substrate 01, a cavity 02, a lower electrode 03, a piezoelectric layer 04, and an upper electrode 05, and optionally, a passivation layer 06 may be further covered on the upper electrode 05. In the thin film bulk acoustic resonator shown in fig. 1, an air bridge (air-bridge) 07 is further disposed between the piezoelectric layer 04 and the upper electrode 05, and the air bridge 07 may be located on one or more sides of the active area AA0 of the resonator, or may surround the active area AA0 of the resonator to form an air ring (air-ring); in the thin film bulk acoustic resonator shown in fig. 2, an air bridge (air-bridge) 07 and an air wing (air-wing) 08 are provided between the piezoelectric layer 04 and the upper electrode 05, and the air bridge 07 and the air wing 08 define the outer boundary of the active area AA0 of the resonator.

When an electric signal is applied to one electrode of the thin film bulk acoustic resonator, the piezoelectric layer is deformed longitudinally due to the inverse piezoelectric effect to generate a bulk acoustic wave which propagates longitudinally and vibrates, and the bulk acoustic wave is reflected back and forth between the upper electrode and the lower electrode of the thin film bulk acoustic resonator by the arrangement of a dielectric cavity such as the cavity 02 to form a standing wave in the piezoelectric layer, so as to generate resonance, and then the piezoelectric effect of the piezoelectric layer is utilized to convert the bulk acoustic wave into the electric signal on the other electrode to output, so that the area where the cavity 02, the lower electrode 03, the piezoelectric layer 04 and the upper electrode 05 overlap in the direction perpendicular to the plane of the substrate 01 and the adjacent layers are in contact with each other is an active area AA0, which is also called an effective resonance area.

In the propagation path of the acoustic wave, the acoustic impedance value, thickness and structural changes of the metal electrode and the piezoelectric layer as propagation media affect the acoustic impedance change of the propagation structure, so that after a gap structure (such as an air bridge 07 and an air wing 08) is introduced between the piezoelectric layer 04 and the metal electrode (03 or 05), an interface between the piezoelectric layer 04 and air is formed at the gap, and the acoustic impedance distribution of the interface between the piezoelectric layer 04 and the upper electrode 05 is discontinuous, so that the acoustic wave is reflected back to the active area AA0 of the resonator, as shown by an arrow on the piezoelectric layer 04 in reference to fig. 2, so that energy loss is reduced, and the performance of the resonator is improved.

However, the above gap structure provided in the thin film bulk acoustic resonator in practice has a series of problems due to limitations in materials, processes, and the like:

(1) The mechanical strength is not high, and the gap structures such as an air bridge, an air wing and the like are easy to collapse in the manufacturing and using processes, so that the quality and the yield of products are affected;

(2) Because the physical strength limit is limited, the height of the gap structure such as the air bridge, the air foil, etc. cannot be raised excessively, so the effect of reducing the energy leakage is relatively limited.

In view of this, an embodiment of the present application provides a thin film bulk acoustic resonator, and fig. 3 is a schematic cross-sectional view of the thin film bulk acoustic resonator provided in the embodiment of the present application, as shown in fig. 3, the thin film bulk acoustic resonator includes a substrate 10, and a first electrode 20, a piezoelectric layer 30, and a second electrode 40 that are sequentially stacked on one side of the substrate 10, a dielectric cavity 50 is disposed between the first electrode 20 and the substrate 10, and a region where the dielectric cavity 50, the first electrode 20, the piezoelectric layer 30, and the second electrode 40 overlap in a direction perpendicular to a plane of the substrate 10 and adjacent layers contact each other is an active region AA.

In specific operation, after an electrical signal is applied to one of the first electrode 20 and the second electrode 40, the piezoelectric layer 30 is deformed longitudinally due to the inverse piezoelectric effect to generate a bulk acoustic wave that propagates longitudinally and vibrates, the surface of the second electrode 40 facing away from the substrate 10 contacts with air, or a passivation layer 60 is provided to enable the bulk acoustic wave to be reflected on the surface of the second electrode 40 facing away from the substrate 10, meanwhile, a dielectric cavity 50 is provided on the surface of the first electrode 20 facing towards the substrate 10 to reflect the bulk acoustic wave, so that energy cannot leak to the substrate 10, and thus the bulk acoustic wave is reflected back and forth between the first electrode 20 and the second electrode 40 to form a standing wave in the piezoelectric layer 30 to generate resonance, and then the bulk acoustic wave is converted into an electrical signal by the piezoelectric effect of the piezoelectric layer on the other electrode to be output. As can be seen, the area where the dielectric cavity 50, the first electrode 20, the piezoelectric layer 30, and the second electrode 40 overlap in a direction perpendicular to the plane of the substrate 10 and adjacent layers contact each other is an active area AA, which is also referred to as an effective resonance area.

Alternatively, the material of the substrate 10 may be any material known to those skilled in the art, such as at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III/V compound semiconductors, may also include multilayer structures composed of these semiconductors, or the like, or be silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-on-insulator (S-SiGeOI), silicon-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or may also be double-sided polished silicon wafers (Double Side Polished Wafers, DSP), or may also be ceramic substrates such as alumina, quartz, or glass substrates, or the like.

Alternatively, the dielectric cavity 50 may be a cavity or may be filled with a dielectric material of high acoustic impedance, such as to form a Bragg reflector structure. Also, the dielectric cavity 50 may alternatively be located on the surface of the substrate 10, or may be embedded in the substrate 10, i.e., by etching the substrate 10 to form a recess, where the dielectric cavity 50 is formed. Fig. 3 illustrates the dielectric cavity 50 as a cavity, and is positioned on the surface of the substrate 10. When the dielectric cavity 50 is a cavity, a sacrificial material may be formed in the area where the cavity is preformed, and finally, after the first electrode 20, the piezoelectric layer 30, and the second electrode 40 are formed, the sacrificial material is removed, thereby forming the cavity. When the dielectric cavity 50 is a Bragg reflector structure, the Bragg reflector structure may be formed directly on the surface of the substrate 10 or in a recess formed by etching the substrate 10.

The first electrode 20 and the second electrode 40 are made of a metal material, and alternatively, the metal material may be copper (Cu), tungsten (W), platinum (Pt), aluminum (Al), ruthenium (Ru), molybdenum (Mo), gold (Au), or the like.

The piezoelectric layer 30 is made of a piezoelectric material, which may be aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN), zinc oxide (ZnO), lead zirconate titanate (PZT), or the like

In the thin film bulk acoustic resonator provided in the embodiment of the present application, optionally, as shown in fig. 3, a first gap K1 is disposed between the second electrode 40 and the piezoelectric layer 30, and at least one end of the first gap K1 is a boundary of the active area AA.

The first gap K1 may be air or may be filled with a dielectric material. Taking the first gap K1 as air as an example, an interface between the piezoelectric layer 30 and air is formed in the first gap K1, and the acoustic impedance of the interface between the piezoelectric layer 30 and the second electrode 40 is discontinuous, so that the acoustic wave is reflected back to the active area AA, thereby reducing energy loss and improving the performance of the resonator. Similarly, when the first gap K1 is filled with a dielectric material, it also functions to reflect sound waves back to the active area AA.

It should be further noted that, in the present application, at least one end of the first gap K1 is a boundary of the active area AA, that is, the first gap K1 is located outside the active area AA, and an end of the first gap K1 near the active area AA defines at least a part of an outer boundary of the active area AA. Specifically, considering that the shape of the thin film bulk acoustic resonator tends to be polygonal, such as pentagon, if the first gap K1 is located at one side of the active area AA, one end of the first gap K1 adjacent to the active area AA defines a partial outer boundary of the active area AA, if the first gap K1 is located at multiple sides of the active area AA, each end of the first gap K1 adjacent to the active area AA defines a partial outer boundary of the active area AA, and if the first gap K1 is disposed around the active area AA, each end of the first gap K1 adjacent to the active area AA defines a full outer boundary of the active area AA.

Alternatively, as shown in fig. 3, the first gap K1 between the second electrode 40 and the piezoelectric layer 30 may be an air bridge. Alternatively, as shown in fig. 4, the first gap K1 between the second electrode 40 and the piezoelectric layer 30 may be an air foil. As can be seen from fig. 3 and 4, the second electrode 40 needs to extend outwardly from the active area AA for electrical connection, an air bridge may be provided on the side of the second electrode 40 near its connection end, while an air foil is typically provided on the non-connection end of the second electrode 40; the air bridge is formed by projecting the second electrode 40 away from the piezoelectric layer 30, and the air wing is a cantilever structure or a projecting structure formed by raising the non-connection end of the second electrode 40.

Similarly, alternatively, the first electrode 20 and the piezoelectric layer 30 may be provided with a first gap K1, at least one end of the first gap K1 is a boundary of the active area AA, where the first gap K1 between the first electrode 20 and the piezoelectric layer 30 may be an air bridge, and the first electrode 20 also needs to extend outward from the active area AA to be electrically connected, so the air bridge may be disposed on a side of the first electrode 20 near the connection section thereof. However, since the dielectric cavity 50 and the piezoelectric layer 30 are provided on the upper and lower sides of the first electrode 20, respectively, the first gap K1 between the first electrode 20 and the piezoelectric layer 30 is not a cantilever structure.

Alternatively, the first gap K1 may be disposed between the second electrode 40 and the piezoelectric layer 30, and the first gap K1 may be disposed between the first electrode 20 and the piezoelectric layer 30, where at least one end of any first gap K1 is a boundary of the active area AA.

In summary, in the thin film bulk acoustic resonator provided in the embodiment of the present application, the first gap K1 is disposed between the second electrode 40 and the piezoelectric layer 30 and/or between the first electrode 20 and the piezoelectric layer 30, and at least one end of any first gap K1 is a boundary of the active area AA.

In order to solve the above-mentioned problems of the gap structure provided between the corresponding piezoelectric layer 30 and the metal electrode (20 or 40) at the boundary of the active area AA of the thin film bulk acoustic resonator, as shown in fig. 3 and 4, in the thin film bulk acoustic resonator provided by the embodiment of the present application, at least one dielectric block D1 is provided in the first gap K1, the dielectric block D1 is in contact with the piezoelectric layer 30, and the dielectric block D1 is in contact with the corresponding electrode on the side of the first gap K1 facing away from the piezoelectric layer 30, and the first gap K1 is separated into at least two sub-gaps K11 by at least one dielectric block D1.

If the first gap K1 is located between the second electrode 40 and the piezoelectric layer 30, as shown in fig. 3, the dielectric block D1 within the first gap K1 is in contact with both the piezoelectric layer 30 and the second electrode 40; if the first gap K1 is located between the first electrode 20 and the piezoelectric layer 30, the dielectric block D1 within the first gap K1 is in contact with both the piezoelectric layer 30 and the first electrode 20.

If only one dielectric block D1 is arranged in the first gap K1, the first gap K1 is divided into two sub-gaps K11 by the dielectric block D1; if two dielectric blocks D1 are disposed in the first gap K1, the first gap K1 is divided into three sub-gaps K11 by the two dielectric blocks D1, and so on.

It can be seen that, in the thin film bulk acoustic resonator provided by the embodiment of the present application, at least one dielectric block D1 is disposed in the first gap K1 between the piezoelectric layer 30 and the metal electrode (20 or 40) at the boundary of the active area AA of the resonator, and the dielectric block D1 contacts the piezoelectric layer 30 and the metal electrode (20 or 40) on the side of the first gap K1 facing away from the piezoelectric layer 30 at the same time, so as to divide the first gap K1 into at least two sub-gaps K11, which can generate the following effects: in the first aspect, the physical strength of the first gap K1 can be obviously improved, collapse in the manufacturing and using processes is avoided, and the product quality and yield are improved; in the second aspect, due to the improvement of the physical strength of the first gap K1, the first gap K1 can be set to a higher height without worrying about structural collapse, and the higher first gap K1 can reflect sound waves more effectively, reduce energy dissipation, and improve the performance of the resonator; in the third aspect, at least one dielectric block D1 is disposed in the first gap K1, and an interface between the piezoelectric layer 30 and the dielectric block D1 is formed, and the acoustic impedance distribution of the interface between the piezoelectric layer 30 and the dielectric block D1 and the interface between the piezoelectric layer 30 and the sub-gap K11 and the interface between the piezoelectric layer 30 and the second electrode 40 is discontinuous, so that reflection of acoustic waves is further enhanced, parasitic modes are suppressed, and meanwhile, loss of expected longitudinal mechanical wave energy is reduced, Q value of the resonator is increased, and insertion loss is reduced.

Since the case where the first gap K1 is located between the first electrode 20 and the piezoelectric layer 30 is similar to the case where the first gap K1 is located between the second electrode 40 and the piezoelectric layer 30, the following description will be continued taking as an example the case where the first gap K1 is located between the second electrode 40 and the piezoelectric layer 30. Since the case where the medium block D1 is provided in the air foil is similar to the case where the medium block D1 is provided in the air bridge, the following description will be given by taking the case where the medium block D1 is provided in the air bridge as an example.

As known from the foregoing, in the propagation path of the acoustic wave, the acoustic impedance changes are affected by the changes in the acoustic impedance values, thicknesses and structures of the metal electrode and the piezoelectric layer as the propagation medium, and then, in the first gap K1, the changes in the material, number, volume and shape of the dielectric block D1 may introduce discontinuous acoustic impedance changes at the boundary of the piezoelectric layer, so as to further enhance the reflection of the acoustic wave and reduce the energy loss.

Regarding the material of the dielectric block D1 in the first gap K1, optionally, the dielectric block D1 may be made of metal. The inventor researches and discovers that in the existing film bulk acoustic resonator with the gap structures such as the air bridge, the air wing and the like, the piezoelectric layer and the metal electrode are separated at the gap positions such as the air bridge, the air wing and the like, so that heat during the operation of the resonator cannot be effectively dissipated through metal, and additional challenges are caused to the heat dissipation of the resonator. Therefore, if the dielectric block D1 in the first gap K1 is made of metal, the dielectric block D1 made of metal can directly contact the piezoelectric layer 30 and the metal electrode (20 or 40) at the same time, so that the heat dissipation effect in the area of the first gap K1 can be improved, the heat generated by the piezoelectric layer 30 during the operation of the resonator is transmitted to the metal electrode (20 or 40) through the metal block D1, the heat is effectively dissipated, and the phase change improves the performance of the resonator. Of course, if the dielectric block D1 in the first gap K1 is made of a material that is non-metal but has a high thermal conductivity, the same can be achieved.

Further alternatively, considering that the shape of the thin film bulk acoustic resonator tends to be an irregular polygon, such as a pentagon, the dielectric block D1 may be the same as the corresponding electrode material on the side of the first gap K1 facing away from the piezoelectric layer 30, i.e., if the first gap K1 is located between the second electrode 40 and the piezoelectric layer 30, the dielectric block D1 in the first gap K1 may be the same as the second electrode 40 material, and similarly, if the first gap K1 is located between the first electrode 20 and the piezoelectric layer 30, the dielectric block D1 in the first gap K1 may be the same as the first electrode 20 material, thereby making the process preparation easier. Of course, alternatively, the dielectric block D1 may be different from the corresponding electrode material on the side of the first gap K1 facing away from the piezoelectric layer 30, as the case may be.

The number of the dielectric blocks D1 in the first gap K1 may be one or plural, for example, in the thin film bulk acoustic resonator shown in fig. 3, five dielectric blocks D1 are provided in the first gap K1; for another example, in the thin film bulk acoustic resonator shown in fig. 4, five dielectric blocks D1 are provided in the first gap K1 as an air bridge, and one dielectric block D1 is provided in the first gap K1 as an air wing; for another example, in the thin film bulk acoustic resonator shown in fig. 5, four dielectric blocks are provided in the first gap K1. It should be noted that, in the first gap K1, there is a sub-gap K11 between two adjacent dielectric blocks D1 and between the dielectric blocks D1 and the boundary of the first gap K1, that is, the two dielectric blocks D1 will not contact together, and the dielectric blocks D1 will not contact the boundary of the first gap K1.

Regarding the volume of the dielectric blocks D1 in the first gap K1, optionally, when a plurality of dielectric blocks D1 are disposed in the first gap K1, the volumes of at least two dielectric blocks D1 may be different, and at this time, dielectric blocks D1 with different volumes may introduce more discontinuous acoustic impedance changes at the boundary of the piezoelectric layer 30, thereby further enhancing reflection of the acoustic wave, reducing energy loss, and improving performance of the resonator. According to this idea, further optionally, when a plurality of dielectric blocks D1 are disposed in the first gap K1, the volumes of any two dielectric blocks may be different, that is, the volumes of all the dielectric blocks are different, so as to further introduce more discontinuous acoustic impedance changes at the boundary of the piezoelectric layer 30, thereby further enhancing reflection of the acoustic wave, reducing energy loss, and improving performance of the resonator.

In the first gap K1, the dielectric block D1 is simultaneously in contact with the piezoelectric layer 30 and the metal electrode on the side of the first gap K1 facing away from the piezoelectric layer 30, that is, the height of the dielectric block D1 is the same as the height of the corresponding position of the first gap K1, so that the width of the dielectric block D1 along the extending direction of the piezoelectric layer 30 and the extending length of the dielectric block D1 can be changed to change the volume of the dielectric block D1.

Considering that the width variation of the dielectric block D1 along the extension direction of the piezoelectric layer 30 may introduce more discontinuous acoustic impedance variation at the boundary of the piezoelectric layer 30, therefore, optionally, the different volumes of the two dielectric blocks D1 include different widths of the two dielectric blocks D1 along the extension direction of the piezoelectric layer 30, thereby introducing more discontinuous acoustic impedance variation at the boundary of the piezoelectric layer 30, further enhancing the reflection of the acoustic wave, reducing the energy loss, and improving the performance of the resonator.

Specifically, as shown in fig. 6, four dielectric blocks D1 are sequentially arranged in the first gap K1 along the direction away from the active area AA, and widths of the four dielectric blocks D1 along the extending direction of the piezoelectric layer 30 are sequentially D1, D2, D3, and D4, and optionally, widths of at least two dielectric blocks D1 along the extending direction of the piezoelectric layer 30 are different from each other in the four dielectric blocks D1, for example, a width D3 of a third dielectric block D1 along the extending direction of the piezoelectric layer 30 is different from widths D1, D2, and D4 of other three dielectric blocks D1 along the extending direction of the piezoelectric layer 30, so that volumes of the third dielectric block D1 and the other three dielectric blocks D1 are different; further alternatively, the four dielectric blocks D1 are different in width D1, D2, D3, and D4 in the extending direction of the piezoelectric layer 30, so that the four dielectric blocks D1 are different in volume.

Of course, in other embodiments of the present application, when a plurality of dielectric blocks D1 are disposed in the first gap K1, the volumes of the dielectric blocks D1 may be the same, for example, the widths of the dielectric blocks D1 in the extending direction of the piezoelectric layer 30 may be the same.

The width of the dielectric block D1 in the extending direction of the piezoelectric layer 30 refers to the width of the projection of the dielectric block D1 on the surface of the piezoelectric layer 30 facing away from the substrate 10. Also, since the dielectric block D1 may vary in width in its own extending direction, the width of the dielectric block D1 in the extending direction of the piezoelectric layer 30 may refer to the minimum width of the dielectric block D1 in the extending direction of the piezoelectric layer 30, or refer to the maximum width of the dielectric block D1 in the extending direction of the piezoelectric layer 30, or alternatively, the minimum or maximum width of the dielectric block D1 in the extending direction of the piezoelectric layer 30 in a section parallel to the surface of the piezoelectric layer 30 facing away from the substrate 10. That is, in the case of comparing the widths of the different dielectric blocks D1, the width standard is not limited to the specific one, as long as the width standard is the same.

As for the shape of the dielectric block D1 in the first gap K1, alternatively, the shape of the dielectric block D1 may be a cuboid, and as shown in fig. 3 to 6, the cross-sectional shape of the dielectric block D1 is rectangular, but the present application is not limited thereto, and the cross-sectional shape of the dielectric block D1 may be other shapes such as a trapezoid.

Similarly, in the first gap K1, the discontinuous acoustic impedance change may be introduced at the boundary of the piezoelectric layer due to the change of the material, the number, the volume and the shape of the sub-gap K11, so as to further enhance the reflection of the acoustic wave and reduce the energy loss.

Regarding the material of the sub-gap K11 within the first gap K1, optionally, the sub-gap K11 is air; alternatively, the sub-gap K11 is a dielectric material, and the reflection efficiency of the sound wave at the air interface is higher, so that the sound wave can be reflected more effectively when the sub-gap K11 is air.

Regarding the number of the sub-gaps K11 in the first gap K1, which is related to the number of the dielectric blocks D1 disposed in the first gap K1, it is understood that the number of the dielectric blocks D1 disposed in the first gap K1 is N, and the number of the sub-gaps K11 in the first gap K1 is n+1.

Regarding the volume of the sub-gap K11 in the first gap K1, similar to the design thought of the volume of the dielectric block D1 in the first gap K1, optionally, in the first gap K1, the volumes of at least two sub-gaps K11 may be different, and at this time, the sub-gaps K11 with different volumes may introduce more discontinuous acoustic impedance changes at the boundary of the piezoelectric layer 30, thereby further enhancing the reflection of the acoustic wave, reducing the energy loss, and improving the performance of the resonator. According to this idea, further optionally, in the first gap K1, the volumes of any two sub-gaps K11 are different, that is, the volumes of all the sub-gaps K11 are different, so that more discontinuous acoustic impedance changes are further introduced at the boundary of the piezoelectric layer 30, thereby further enhancing reflection of the acoustic wave, reducing energy loss, and improving performance of the resonator.

In the first gap K1, since the height of the sub-gap K11 is the same as the height of the corresponding position of the first gap K1, the width of the sub-gap K11 in the extending direction of the piezoelectric layer 30 and the extending length of the sub-gap K11 may be changed to change the volume of the sub-gap K11.

Considering that the variation of the width of the sub-gap K11 along the extension direction of the piezoelectric layer 30 may introduce more discontinuous acoustic impedance variation at the boundary of the piezoelectric layer 30, the difference in volume of the two sub-gaps K11 may alternatively include the difference in width of the two sub-gaps K11 along the extension direction of the piezoelectric layer 30. Specifically, as shown in fig. 7, four dielectric blocks D1 are sequentially arranged in the first gap K1 along the direction away from the active area AA, so that the first gap K1 is divided into five sub-gaps K11, and widths w1, w2, w3, w4 and w5 of the five sub-gaps K11 in the extending direction of the piezoelectric layer 30 are different, so that volumes of the five sub-gaps K11 are also different, and further more discontinuous acoustic impedance changes are introduced at the boundary of the piezoelectric layer 30, thereby further enhancing reflection of acoustic waves, reducing energy loss and improving performance of the resonator.

Of course, in other embodiments of the present application, the volumes of the respective sub-gaps K11 may be the same within the first gap K1, for example, the widths of the respective sub-gaps K11 in the extending direction of the piezoelectric layer 30 may be equal.

The width of the sub-gap K11 in the extending direction of the piezoelectric layer 30 means the width of the projection of the sub-gap K11 onto the surface of the piezoelectric layer 30 facing away from the substrate 10. Also, since the sub-gap K11 may vary in width in the extending direction thereof, the width of the sub-gap K11 in the extending direction of the piezoelectric layer 30 may refer to the minimum width of the sub-gap K11 in the extending direction of the piezoelectric layer 30, or refer to the maximum width of the sub-gap K11 in the extending direction of the piezoelectric layer 30, or alternatively, the minimum or maximum width of the sub-gap K11 in the extending direction of the piezoelectric layer 30 in a section parallel to the surface of the piezoelectric layer 30 facing away from the substrate 10. That is, in the case of comparing the widths of the different sub-gaps K11, the width standard is not limited to the specific one, as long as the widths are compared with the same standard.

It will be appreciated that the spacing between the boundaries of the dielectric block D1 and the first gap K1, and the spacing between two adjacent dielectric blocks D1 are the widths of the sub-gaps K11 along the extending direction of the piezoelectric layer 30, and therefore, the design of the widths of the sub-gaps K11 along the extending direction of the piezoelectric layer 30 is actually the setting of the spacing between the boundaries of the dielectric blocks D1 and the first gap K1, and the spacing between two adjacent dielectric blocks D1.

Alternatively, in one embodiment of the present application, when one dielectric block D1 is disposed in the first gap K1, as shown in fig. 8, the first gap K1 is divided into two sub-gaps K11 by one dielectric block D1, and a width a of any one of the two sub-gaps K11 in the extending direction of the piezoelectric layer 30 and a width b of the first gap K1 in the extending direction of the piezoelectric layer 30 satisfy: a/b is more than or equal to 10% and less than or equal to 90%;

when a plurality of dielectric blocks D1 are disposed in the first gap K1, as shown in fig. 9, a distance c between two adjacent dielectric blocks D1 and a distance D between the far boundaries of the two adjacent dielectric blocks D1 along the extending direction of the piezoelectric layer 30 satisfy: c/d is more than or equal to 10% and less than or equal to 90%.

This is because if the width of the sub-gap K11 in the first gap K1 in the extending direction of the piezoelectric layer 30 is too narrow, most of the area in the first gap K1 is filled with the dielectric block D1, and the effect of the first gap K1 as an air bridge or an air wing is impaired. If the width of the sub-gap K11 in the first gap K1 along the extending direction of the piezoelectric layer 30 is too wide, the first gap K1 is very close to a traditional air bridge or air wing without a dielectric block D1, and the effect of introducing discontinuous acoustic impedance change at the boundary of the piezoelectric layer 30 is relatively insignificant, so that when one dielectric block D1 is arranged in the first gap K1, 10% +.a/b+.ltoreq.90%; when a plurality of dielectric blocks D1 are arranged in the first gap K1, c/D is 10% -90%, so that the first gap K1 can not only keep the effect of an air bridge or an air wing, but also introduce more discontinuous acoustic impedance changes at the boundary of the piezoelectric layer 30, the reflection of acoustic waves is enhanced, parasitic modes are suppressed, meanwhile, the loss of expected longitudinal mechanical wave energy is reduced, the Q value of the resonator is improved, and the insertion loss is reduced.

Alternatively, in each of the above embodiments, as shown in fig. 3-9, a passivation layer 60 may be further disposed on the second electrode 40 and the piezoelectric layer 30 on the side facing away from the substrate 10, to protect the overall resonator structure, and specifically, the passivation layer may be made of, for example, silicon dioxide (SiO ₂ ) Gallium nitride (GaN), silicon nitride (Si) ₃ N ₄ ) Dielectric materials such as aluminum nitride (AlN) and the like are formed, and meanwhile, the thickness of passivation layers of certain specific materials is finely adjusted by using a trimming process, so that the effect of finely adjusting the resonance performance of the device can be achieved.

Fig. 10 shows a comparison of a frequency-dependent Y parameter of a thin film bulk acoustic resonator provided with at least one dielectric block in an air bridge and a thin film bulk acoustic resonator having an air bridge structure according to an embodiment of the present application, and it can be seen that, compared with the thin film bulk acoustic resonator provided by the embodiment of the present application, the thin film bulk acoustic resonator provided by the present application has a higher Q value due to less spurious interference, and more sharp and distinct resonance peaks and antiresonance peaks. Fig. 11 further shows a graph of Q values of the two thin film bulk acoustic resonators as a function of frequency, and it can be seen that, compared with the prior art, the Q values of the thin film bulk acoustic resonators provided by the embodiments of the present application are significantly improved.

The embodiment of the application also provides a preparation method of the film bulk acoustic resonator, which is shown by referring to fig. 3-8, and comprises the following steps:

s100: providing a substrate 10;

s200: forming a first electrode 20 on one side of the substrate 10;

s300: forming a piezoelectric layer 30 on a side of the first electrode 20 facing away from the substrate 10;

s400: forming a second electrode 40 on a side of the piezoelectric layer 30 facing away from the substrate 10;

wherein a dielectric cavity 50 is disposed between the first electrode 20 and the substrate 10, and a region where the dielectric cavity 50, the first electrode 20, the piezoelectric layer 30, and the second electrode 40 overlap in a direction perpendicular to a plane on which the substrate 10 is located and adjacent layers contact each other is an active region AA;

a first gap K1 is disposed between the second electrode 40 and the piezoelectric layer 30 and/or between the first electrode 20 and the piezoelectric layer 30, at least one end of the first gap K1 being a boundary with the active area AA;

at least one dielectric block D1 is arranged in the first gap K1, the dielectric block D1 is in contact with the piezoelectric layer 30, the dielectric block D1 is in contact with a corresponding electrode on one side, away from the piezoelectric layer 30, of the first gap K1, and the first gap K1 is separated into at least two sub-gaps K11 by the at least one dielectric block D1.

Alternatively, the dielectric cavity 50 may be a cavity or may be filled with a dielectric material of high acoustic impedance, such as to form a Bragg reflector structure. Also, the dielectric cavity 50 may alternatively be located on the surface of the substrate 10, or may be embedded in the substrate 10, i.e., by etching the substrate 10 to form a recess, where the dielectric cavity 50 is formed. Fig. 3-8 each illustrate a dielectric cavity 50 as a cavity and positioned on a surface of the substrate 10. When the dielectric cavity 50 is a cavity, a sacrificial material may be formed in the area where the cavity is preformed, and finally, after the first electrode 20, the piezoelectric layer 30, and the second electrode 40 are formed, the sacrificial material is removed, thereby forming the cavity. When the dielectric cavity 50 is a Bragg reflector structure, the Bragg reflector structure may be formed directly on the surface of the substrate 10 or in a recess formed by etching the substrate 10.

In an embodiment of the present application, as shown in fig. 3 to 8, optionally, a first gap K1 is disposed between the second electrode 40 and the piezoelectric layer 30, and at least one end of the first gap K1 is a boundary of the active area AA.

To summarize, in the embodiment of the present application, a first gap K1 is provided between the second electrode 40 and the piezoelectric layer 30, and/or between the first electrode 20 and the piezoelectric layer 30, and at least one end of any first gap K1 is a boundary of the active area AA.

In the embodiment of the present application, if the first gap K1 is located between the second electrode 40 and the piezoelectric layer 30, as shown in fig. 3 to 8, the dielectric block D1 in the first gap K1 contacts both the piezoelectric layer 30 and the second electrode 40; if the first gap K1 is located between the first electrode 20 and the piezoelectric layer 30, the dielectric block D1 within the first gap K1 is in contact with both the piezoelectric layer 30 and the first electrode 20.

Specifically, when the first gap K1 is provided between the second electrode 40 and the piezoelectric layer 30, the method for manufacturing the thin film bulk acoustic resonator according to the embodiment of the present application includes:

s1: as shown in fig. 12a, a substrate 10 is provided.

S2: as shown in fig. 12b, a sacrificial layer 11 is formed on the substrate 10 in a region where the cavity 50 is preformed.

S3: as shown in fig. 12c, a first electrode 20 is formed on the substrate 10 and the sacrificial layer 11.

S4: as shown in fig. 12d, a piezoelectric layer 30 is deposited on the side of the first electrode 20 facing away from the substrate 10.

S5: as shown in fig. 12e, the sacrificial layer 12 is formed on the side of the piezoelectric layer 30 facing away from the substrate 10.

S6: as shown in fig. 12f, the sacrificial layer 12 is etched, at least two sacrificial blocks 120 remain in the area where the first gap K1 is preformed on the surface of the piezoelectric layer 30, and a groove U1 is provided between two adjacent sacrificial blocks 120, so that the sacrificial layer 12 in other areas on the surface of the piezoelectric layer 30 is removed.

In fig. 12f, a sacrificial block 121 is also remained on the surface of the piezoelectric layer 30, and the sacrificial block 121 is used for forming an air foil later.

S7: as shown in fig. 12g, the medium is filled in the groove U1 to form a medium block D1.

S8: as shown in fig. 12h, the second electrode 40 is formed on the piezoelectric layer 30, the dielectric block D1, the sacrifice block 120 (and the sacrifice block 121) on the side facing away from the substrate 10.

S9: as shown in fig. 12i, a passivation layer 60 is formed on the second electrode 40 and the piezoelectric layer 30 on the side facing away from the substrate 10.

S10: as shown in fig. 12j, the sacrificial block 120 (and the sacrificial block 121) is removed to form a first gap K1 between the second electrode 40 and the piezoelectric layer 30, and at least one dielectric block D1 is disposed in the first gap K1, the dielectric block D1 is simultaneously in contact with the piezoelectric layer 30 and the second electrode 40, and the first gap K1 is partitioned into at least two sub-gaps K11 by the at least one dielectric block D1; at the same time, the sacrificial layer 11 is removed to form a dielectric cavity 50 (i.e., cavity) between the first electrode 20 and the substrate 10.

It can be seen that, in the method for manufacturing a thin film bulk acoustic resonator according to the embodiment of the present application, when the first gap K1 is provided between the second electrode 40 and the piezoelectric layer 30, before the second electrode 40 is formed on the side of the piezoelectric layer 30 facing away from the substrate 10, the method further includes:

S400: forming a sacrificial layer 12 on a side of the piezoelectric layer 30 facing away from the substrate 10;

s410: etching the sacrificial layer 12, reserving at least two sacrificial blocks 120 in the area where the first gap K1 is preformed on the surface of the piezoelectric layer 30, forming a groove U1 between every two adjacent sacrificial blocks 120, and removing the sacrificial layer 12 in other areas on the surface of the piezoelectric layer 30;

s420: filling a medium in the groove U1 to form a medium block D1;

after forming the second electrode 40, the method further comprises:

s430: the sacrificial block 12 is removed to form a first gap K1 between the second electrode 40 and the piezoelectric layer 30, and at least one dielectric block D1 is disposed within the first gap K1.

Similarly, when the first gap K1 is provided between the first electrode 20 and the piezoelectric layer 30, before the piezoelectric layer 30 is formed on the side of the first electrode 20 facing away from the substrate 10, the method further includes:

s500: forming a sacrificial layer on a side of the first electrode 20 facing away from the substrate 10;

s510: etching the sacrificial layer, reserving at least two sacrificial blocks in the area where the first gap K1 is preformed on the surface of the first electrode 20, forming grooves between two adjacent sacrificial blocks, and removing the sacrificial layer in other areas on the surface of the first electrode 20;

s520: filling a medium in the groove to form a medium block D1;

After forming the second electrode, the method further comprises:

s530: the sacrificial block is removed to form a first gap K1 between the first electrode 20 and the piezoelectric layer 30, and at least one dielectric block D1 is disposed within the first gap K1.

The embodiment of the application also provides a filter, which comprises the film bulk acoustic resonator provided by any embodiment or the film bulk acoustic resonator prepared by the method provided by any embodiment. Since the thin film bulk acoustic resonator has been described in detail in the foregoing embodiments, a detailed description thereof is omitted.

In the description, each part is described in a parallel and progressive mode, and each part is mainly described as a difference with other parts, and all parts are identical and similar to each other.

The features described in the various embodiments of the present disclosure may be interchanged or combined with one another in the description to enable those skilled in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The thin film bulk acoustic resonator is characterized by comprising a substrate, a first electrode, a piezoelectric layer and a second electrode, wherein the first electrode, the piezoelectric layer and the second electrode are sequentially stacked on one side of the substrate, a dielectric cavity is arranged between the first electrode and the substrate, and the dielectric cavity, the first electrode, the piezoelectric layer and the second electrode are overlapped in the direction perpendicular to the plane of the substrate, and the area where adjacent layers are contacted with each other is an active area;

2. The thin film bulk acoustic resonator of claim 1, wherein a plurality of dielectric blocks are disposed in the first gap, and wherein at least two of the dielectric blocks have different volumes.

3. The thin film bulk acoustic resonator of claim 2, wherein any two of said dielectric blocks have different volumes within said first gap.

4. A thin film bulk acoustic resonator as claimed in claim 2 or 3, wherein the difference in volume of the two dielectric blocks comprises:

5. The thin film bulk acoustic resonator of claim 1, wherein at least two of said sub-gaps differ in volume within said first gap.

6. The thin film bulk acoustic resonator of claim 5, wherein any two of said sub-gaps differ in volume within said first gap.

7. The thin film bulk acoustic resonator of claim 5 or 6, wherein the difference in volume of the two sub-gaps comprises:

8. The thin film bulk acoustic resonator according to claim 1, wherein when one of the dielectric blocks is provided in the first gap, the first gap is partitioned by one of the dielectric blocks into two of the sub-gaps, and a width a of either one of the two sub-gaps in an extending direction of the piezoelectric layer and a width b of the first gap in the extending direction of the piezoelectric layer satisfy: a/b is more than or equal to 10% and less than or equal to 90%;

9. The thin film bulk acoustic resonator of claim 1 wherein the dielectric block is a metal material.

10. The thin film bulk acoustic resonator of claim 9, wherein the dielectric block and the corresponding electrode material on a side of the first gap facing away from the piezoelectric layer are the same.

11. A method of making a thin film bulk acoustic resonator comprising:

providing a substrate;

forming a first electrode on one side of the substrate;

12. The method of manufacturing a thin film bulk acoustic resonator according to claim 11, characterized in that when the first gap is provided between the second electrode and the piezoelectric layer, the method further comprises, before the second electrode is formed on a side of the piezoelectric layer facing away from the substrate:

Filling a medium in the groove to form a medium block;

after forming the second electrode, the method further comprises:

13. The method of manufacturing a thin film bulk acoustic resonator according to claim 11, characterized in that when the first gap is provided between the first electrode and the piezoelectric layer, before the piezoelectric layer is formed on the side of the first electrode facing away from the substrate, the method further comprises:

filling a medium in the groove to form a medium block;

after forming the second electrode, the method further comprises:

14. A filter comprising a thin film bulk acoustic resonator according to any one of claims 1 to 10 or a thin film bulk acoustic resonator produced by a method according to any one of claims 11 to 13.