CN118074651A

CN118074651A - Acoustic wave resonator and filter

Info

Publication number: CN118074651A
Application number: CN202211482949.0A
Authority: CN
Inventors: 庞慰; 杨清瑞
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2022-11-24
Filing date: 2022-11-24
Publication date: 2024-05-24

Abstract

Disclosed are an acoustic wave resonator and a filter, the acoustic wave resonator including: a piezoelectric layer; the first electrode and the second electrode are positioned on the first surface of the piezoelectric layer, the first electrode and the second electrode respectively comprise a trunk and a plurality of branches connected with the trunk, and the branches of the first electrode and the branches of the second electrode are staggered to form an interdigital structure; wherein the plurality of branches comprises: a connection portion connected to the trunk at a first side of the trunk; and an end distal to the first side of the backbone; at least one of the at least a portion of the first side region of the backbone, the end of at least one of the plurality of branches, and the connection of at least one of the plurality of branches is folded upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

Description

Acoustic wave resonator and filter

Technical Field

The present disclosure relates to semiconductor technology, and more particularly, to an acoustic resonator and a filter.

Background

Under the technical standard of fifth-generation mobile communication (5G), the new frequency band represented by n77, n78 and n79 has a frequency range of 3-5GHz and a relative bandwidth of 12% -24%, while the traditional radio frequency front-end filter is mostly realized by adopting a Surface Acoustic Wave (SAW) technology based on a bulk lithium niobate or lithium tantalate substrate and a Bulk Acoustic Wave (BAW) resonator technology based on an AlN or Sc doped AlN film, and the relative bandwidth is mostly below 10% or even not more than 5%, so that the radio frequency front-end filter facing 5G application faces double difficulties of frequency promotion and bandwidth expansion.

With the maturation of ion slicing technology, a single crystal piezoelectric film of lithium niobate (LiNbO ₃, abbreviated as LN) or lithium tantalate (LiTaO ₃, abbreviated as LT) with a thickness of hundreds of nanometers to several micrometers can be realized on a silicon substrate or other composite substrates, so that a high-frequency and large-bandwidth filter can be manufactured by utilizing the excellent piezoelectric characteristics of the single crystal piezoelectric film, and the resonator is generally excited by adopting an interdigital electrode structure.

In the interdigital electrode structure, electrode bus lines are generally used for connecting electrode strips with the same polarity, wherein parasitic modes are generated between the parts, except for the effective electrodes, of the interdigital electrode structure and the electrodes with opposite polarities. When the electrode spacing of opposite polarity is pulled to reduce coupling, the length of the electrode strip of the non-effective area is increased, so that series impedance is increased, high power capacity is not realized, and the area of the resonator is not reduced.

Disclosure of Invention

In view of the foregoing, it is an object of the present invention to provide an acoustic wave resonator and a filter that reduce parasitic mode generation by providing an air gap without increasing the electrode spacing of opposite polarity in the inactive region.

The present invention provides in a first aspect an acoustic wave resonator comprising:

a piezoelectric layer; and

The first electrode and the second electrode are positioned on the first surface of the piezoelectric layer, the first electrode and the second electrode respectively comprise a trunk and a plurality of branches connected with the trunk, and the branches of the first electrode and the branches of the second electrode are staggered to form an interdigital structure;

Wherein the plurality of branches comprises:

a connection portion connected to the trunk at a first side of the trunk; and

An end distal to the first side of the backbone;

at least one of the at least a portion of the first side region of the backbone, the end of at least one of the plurality of branches, and the connection of at least one of the plurality of branches is folded upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

Preferably, the height and length of the air gaps located on the different branches may be the same or different.

Preferably, the piezoelectric layer comprises a substrate, wherein the substrate comprises a base layer for providing support for the piezoelectric layer;

a first surface or a second surface of the piezoelectric layer is attached to the substrate; wherein the first surface and the second surface of the piezoelectric layer are opposite.

Preferably, the substrate further comprises a bonding layer via which the piezoelectric layer is attached to the substrate.

Preferably, a bragg reflective layer is further included, the bragg reflective layer being located between the piezoelectric layer and the base layer.

Preferably, the first and second electrodes are embedded in the substrate when the first surface of the piezoelectric layer is attached to the substrate, the bragg reflective layer being adapted to bend.

Preferably, the substrate has a cavity therein, the cavity extending from a surface of the substrate in contact with the piezoelectric layer toward the inside of the substrate and stopping in a groove inside the substrate, or a through hole penetrating the substrate.

Preferably, the piezoelectric layer includes:

A first region, opposite the cavity on the substrate, overhanging the cavity; and

A second region surrounding the first region, attached to the substrate.

Preferably, the connection parts of the branches are located in the first area, or are located in the second area.

Preferably, the first side region of the trunk is located either entirely in the first region, or is located partly in the first region, partly in the second region, or entirely in the second region.

Preferably, the ends of the plurality of branches are located either entirely in the first region, or partially in the first region, partially in the second region, or entirely in the second region.

Preferably, the first electrode and the second electrode further comprise pins connected with the trunk, respectively.

Preferably, the pins are located on any side of the trunk that is not connected to the branches.

Preferably, the entire backbone is lifted up on the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

Preferably, the piezoelectric element further comprises an additional layer, the additional layer covers the surface of the first electrode and the second electrode, which is far away from or near to the surface of the piezoelectric layer, and the additional layer is a metal layer.

Preferably, the additional layer is also located on the electrode bus.

Preferably, the piezoelectric layer is a lithium niobate layer or a lithium tantalate layer.

Preferably, the vibration modes excited by the first electrode and the second electrode include at least an antisymmetric lamb wave mode, a horizontal shear mode, and a symmetric lamb wave mode.

Preferably, the first electrode and the second electrode are further located on a second surface of the piezoelectric layer, and the first surface and the second surface of the piezoelectric layer are opposite.

Preferably, the first electrode and the second electrode located on the first surface and the second surface of the piezoelectric layer have the same or different structures.

Preferably, among the first electrode and the second electrode located on the first surface of the piezoelectric layer and the second surface of the piezoelectric layer, branches having the same polarity correspond in the thickness direction of the piezoelectric layer.

Preferably, the piezoelectric element further comprises a passivation layer covering the surface of the piezoelectric layer and/or the first electrode and/or the second electrode.

A second aspect of the invention provides a filter comprising an acoustic wave resonator as described above.

According to the acoustic wave resonator and the filter provided by the invention, the air gap between the first side edge area of the trunk, the end parts of the branches and the connecting parts of the branches and the first surface of the piezoelectric layer is formed, so that parasitic mode generation is reduced on the premise of not increasing electrode spacing.

Further, by forming an air gap between the connection portions of the plurality of branches and the first surface of the piezoelectric layer, the connection portions and the adjacent end portions of opposite polarity are prevented from generating electric field and acoustic field coupling through the piezoelectric layer, and parasitic modes are further prevented from being generated.

Further, by forming an air gap between the first side region of the backbone and the first surface of the piezoelectric layer, the end of the backbone and the opposite polarity branches are prevented from generating electric field and acoustic field coupling through the piezoelectric layer, further preventing spurious modes from being generated.

Further, by forming an air gap between the end of the branch and the first surface of the piezoelectric layer, the connection of the end of the branch with the branch of opposite polarity and the generation of electric field and acoustic field coupling of the trunk through the piezoelectric layer are avoided, further preventing parasitic modes from being generated.

Further, by providing the connection, the end and the relative position between the backbone and the first region of the piezoelectric layer, parasitic modes are further reduced.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1a shows a schematic top view of an acoustic wave resonator according to a first embodiment of the present invention;

FIG. 1b shows a cross-sectional view of FIG. 1a along the direction AA;

FIG. 1c shows a cross-sectional view along BB of FIG. 1 a;

FIG. 1d shows an enlarged view at S in FIG. 1 a;

FIG. 2 shows a schematic diagram of the internal electric field of a piezoelectric layer according to a first embodiment of the present invention;

FIG. 3a shows a schematic diagram of an antisymmetric lamb wave mode of a first embodiment of the present invention;

FIG. 3b shows a schematic view of a horizontal shear mode of a first embodiment of the present invention;

FIG. 3c shows a schematic diagram of a symmetrical lamb wave mode of a first embodiment of the present invention;

FIG. 4a shows a schematic top view of an acoustic wave resonator according to a second embodiment of the present invention;

FIG. 4b shows a cross-sectional view of FIG. 4a along the direction AA;

FIG. 5a shows a schematic top view of an acoustic wave resonator according to a third embodiment of the present invention;

FIG. 5b shows a cross-sectional view of FIG. 5a along the direction AA;

FIG. 6a is a schematic top view of an acoustic wave resonator according to a fourth embodiment of the present invention;

FIG. 6b shows a cross-sectional view of FIG. 6a along the direction AA;

FIG. 7a is a schematic top view of an acoustic wave resonator according to a fifth embodiment of the present invention;

FIG. 7b shows a cross-sectional view of FIG. 7a along the direction AA;

Fig. 8a shows a schematic top view of an acoustic wave resonator according to a sixth embodiment of the present invention;

FIG. 8b shows a cross-sectional view of FIG. 8a along the direction AA;

Fig. 9a shows a schematic top view of an acoustic wave resonator according to a seventh embodiment of the present invention;

FIG. 9b shows a cross-sectional view of FIG. 9a along the direction AA;

fig. 10a shows a schematic top view of an acoustic wave resonator according to an eighth embodiment of the present invention;

FIG. 10b shows a cross-sectional view of FIG. 10a along the direction AA;

fig. 11a shows a schematic top view of an acoustic wave resonator according to a ninth embodiment of the present invention;

FIG. 11b shows a cross-sectional view of FIG. 11a along the direction AA;

Fig. 12a shows a schematic top view of an acoustic wave resonator according to a tenth embodiment of the present invention;

FIG. 12b shows a cross-sectional view of FIG. 12a along the direction AA;

fig. 13a shows a schematic top view of an acoustic wave resonator according to an eleventh embodiment of the present invention;

FIG. 13b shows a cross-sectional view of FIG. 13a along the direction AA;

fig. 14a is a schematic top view showing a sound wave resonator according to a twelfth embodiment of the present invention;

FIG. 14b shows a cross-sectional view along AA of FIG. 14 a;

Fig. 14c shows a cross-sectional view along BB of fig. 14 a;

FIG. 15a is a schematic top view showing an acoustic wave resonator according to a thirteenth embodiment of the present invention, and FIG. 15b is a schematic cross-sectional view of FIG. 15a along AA

Fig. 16a is a schematic diagram showing a top view of an acoustic wave resonator according to a fourteenth embodiment of the present invention;

Fig. 16b-1 and 16b-2 show cross-sectional views of fig. 16a along the BB direction, wherein:

FIG. 16b-1 is a cross-sectional view of a transverse electric field excitation;

FIG. 16b-2 is a cross-sectional view of a longitudinal electric field excitation;

fig. 17a is a schematic diagram showing a top view of an acoustic wave resonator according to a fifteenth embodiment of the present invention;

fig. 17b shows a cross-sectional view along BB of fig. 16 a;

Fig. 18a is a schematic top view showing an acoustic wave resonator according to a sixteenth embodiment of the present invention;

Fig. 18b shows a cross-sectional view along BB of fig. 17 a;

fig. 19a is a schematic top view showing a sound wave resonator according to a seventeenth embodiment of the present invention;

Fig. 19b shows a cross-sectional view along BB of fig. 19 a;

FIG. 20a is a schematic top view of an acoustic wave resonator according to an eighteenth embodiment of the present invention;

FIG. 20b shows a cross-sectional view of FIG. 20a along the BB direction;

Fig. 21a shows a schematic structural view when the first surface of the piezoelectric layer is attached to the substrate or when the second surface of the piezoelectric layer is attached to the substrate, and the second surface of the piezoelectric layer also forms the first electrode and the second electrode;

FIG. 21b shows a schematic view of the structure of FIG. 21a along the direction AA;

Fig. 22a is a schematic diagram showing a top view of an acoustic wave resonator according to a nineteenth embodiment of the present invention;

FIG. 22b shows a cross-sectional view of FIG. 22a along the direction AA;

FIG. 23a is a schematic top view showing an acoustic wave resonator according to a twentieth embodiment of the present invention;

FIG. 23b shows a cross-sectional view of FIG. 23a along the direction AA;

FIG. 24a is a schematic top view showing an acoustic wave resonator according to a twenty-first embodiment of the invention;

Fig. 24b shows a cross-sectional view along AA of fig. 24 a.

Detailed Description

The invention will be described in more detail below with reference to the accompanying drawings. Like elements are denoted by like reference numerals throughout the various figures. For clarity, the various features of the drawings are not drawn to scale. Furthermore, some well-known portions may not be shown.

The invention may be embodied in various forms, some examples of which are described below.

FIG. 1a shows a schematic top view of an acoustic wave resonator according to a first embodiment of the present invention; FIG. 1b shows a cross-sectional view of FIG. 1a along the direction AA; FIG. 1c shows a cross-sectional view along BB of FIG. 1 a; FIG. 1d shows an enlarged view at S in FIG. 1 a; as shown in fig. 1a to 1d, the acoustic wave resonator 100 includes a substrate 110, a piezoelectric layer 120 on the substrate 110, and a first electrode 130 and a second electrode 150 on the piezoelectric layer 120.

In this embodiment, the substrate 110 includes a base layer 111 and a bonding layer 112 that are stacked, and the piezoelectric layer 120 is located on a surface of the bonding layer 112 away from the base layer 111. The base layer 111 is a support layer that provides mechanical support for the piezoelectric layer 120, and the bonding layer 112 is a connection layer between the piezoelectric layer 120 and the base layer 111. The underlayer 111 is a material layer such as single crystal silicon, lithium tantalate (LiTaO ₃, LT), lithium niobate (LiNbO ₃, LN), silicon carbide (SiC), sapphire (sapphire), or Quartz (Quartz). In a specific embodiment, the base layer 111 is, for example, a layer of high-resistance silicon material having a resistivity >1000Ω·cm, and further having a resistivity >5000 Ω·cm. The bonding layer 120 is a material layer such as silicon dioxide, silicon nitride, polysilicon, amorphous silicon, and the like, and a composite material layer thereof. In other embodiments, the piezoelectric layer 120 may also be attached to the base layer 111 via other intermediate material layers, or directly to the base layer 111.

The piezoelectric layer 120 has opposite first and second surfaces, and may have a convex or concave structure on the first and second surfaces of the piezoelectric layer, or have a curved structure, which is not limited in this embodiment. The first surface of the piezoelectric layer 120 forms a first electrode 130 and a second electrode 150, the second surface being attached to the substrate 110. The piezoelectric layer 120 is a thin single crystal layer made of a piezoelectric material such as lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, aluminum nitride, doped aluminum nitride, lead zirconate titanate (PZT), or the like.

The first electrode 130 and the second electrode 150 have opposite polarities, and the first electrode 130 and the second electrode 150 respectively include a trunk extending in a first direction (for example, an x-axis direction in fig. 1 a) and a plurality of branches connected to the trunk and extending in a second direction (for example, a y-axis direction in fig. 1 a), and the plurality of branches of the first electrode and the plurality of branches of the second electrode are staggered to form an interdigital structure. Wherein the first direction and the second direction are perpendicular to each other.

Specifically, the first electrode 130 includes a first trunk 131 and a plurality of first branches 132 connected to the first trunk 131, and the second electrode 150 includes a second trunk 151 and a second branch 152 connected to the second trunk 151, wherein the first trunk 131 and the second trunk 152 extend in a first direction (for example, an x-axis direction in fig. 1 a), the first branches 132 and the second branches 152 extend in a second direction (for example, a y-axis direction in fig. 1 a), and the plurality of first branches 132 and the plurality of second branches 152 are staggered to form an interdigital structure. The material of the first electrode 130 and the second electrode 150 may be one or more of metal materials such as aluminum (Al), copper (Cu), gold (Au), molybdenum (Mo), tungsten (W), ruthenium (Ru), platinum (Pt), and the like, and a composite structure including an appropriate seed layer or an adhesion layer such as titanium (Ti), chromium (Cr), and the like, but is not limited thereto.

Fig. 2 shows a schematic diagram of an internal electric field of the piezoelectric layer 120 according to the first embodiment of the present invention; FIG. 3a shows a schematic diagram of an antisymmetric lamb wave mode of a first embodiment of the present invention; FIG. 3b shows a schematic view of a horizontal shear mode of a first embodiment of the present invention; FIG. 3c shows a schematic diagram of a symmetrical lamb wave mode of a first embodiment of the present invention; as shown in fig. 2 and 3a to 3c, different vibration modes can be excited by forming the first electrode 130 and the second electrode 150 on the piezoelectric layer 120, and the vibration modes include at least an antisymmetric Lamb Wave (FIRST ANTISYMMETRIC Lamb Wave) mode, a shear horizontal mode, and a symmetric Lamb Wave (SYMMETRIC LAMB WAVE) mode.

Specifically, when the piezoelectric coupling coefficient is E15 (or d 15), for example, the acoustic Wave resonator can excite a first-order antisymmetric Lamb Wave (FIRST ANTISYMMETRIC Lamb Wave) mode, abbreviated as A1 mode, by using a transverse electric field component E1 (parallel to the direction of the piezoelectric layer 120, for example, the x-axis direction) formed in the piezoelectric layer 120, and the minimum resonance unit is an xz in-plane shear mode; when the piezoelectric coupling coefficient is E16 (or d 16), for example, the acoustic wave resonator can be excited to a zero-order horizontal shear (SH 0) mode by using a transverse electric field component E1 formed in the piezoelectric layer 120, and the minimum resonance unit is an xy-plane in-shear mode; when the piezoelectric coupling coefficient is E11 (or d 11), for example, by forming the transverse electric field component E1 in the piezoelectric layer 120, the acoustic resonator can excite a zero-order symmetric lamb wave (SYMMETRIC LAMB WAVE) mode, abbreviated as S0 mode, the minimum resonance unit is an xz in-plane longitudinal wave, that is, stretching-compression vibration is generated along the x-axis direction, and the adjacent units are at the same time, and the stretching and compression directions are opposite. Other suitable electromechanical coupling coefficients may be used to excite the vibration modes as described above, depending on the characteristics of the piezoelectric material used.

With continued reference to fig. 1 a-1 d, the backbone includes a first side and a second side, and the plurality of branches includes a connection portion connected to the backbone at the first side of the backbone and an end portion remote from the backbone. Specifically, the first trunk 131 includes a first side 131a and a second side 131b, and the first branch 132 includes a first connection portion 132a and a first end portion 132b, wherein the first connection portion 132a is connected to the first trunk 131 at the first side 131a of the first trunk 131, and the first end portion 132b is far from the first trunk 131. The second trunk 151 includes a first side 151a and a second side 151b, and the second branch 152 includes a second connection portion 152a and a second end portion 152b, wherein the second connection portion 152a is connected to the second trunk 151 at the first side 151a of the second trunk 151, and the second end portion 152b is far from the second trunk 151.

Further, the overlapping area of the first branch 132 and the second branch 152 projected in the first direction is defined as the electrode aperture. In the second direction, the first connection portion 132a extends from an end connected to the first trunk 131 in a direction away from the first trunk 131, and may extend to the outside of the electrode aperture edge, or the inside of the electrode aperture edge; similarly, in the second direction, the second connection portion 152a extends from an end connected to the second trunk 151 toward a direction away from the second trunk 161, and may extend to the outside of the electrode aperture edge, or the inside of the electrode aperture edge. In the second direction, the first end 132b and the second end 152b are generally inside the edges of the electrode aperture.

Further, the substrate 110 has a cavity 101 inside, and the cavity 101 is a groove extending from a surface of the substrate 110 in contact with the piezoelectric layer 120 toward the inside of the substrate 110 and stopping inside the base layer 111. The piezoelectric layer 120 includes a first region 120a and a second region 120b surrounding the first region 120a. Wherein the first region 120a is opposite the cavity 101 of the substrate 110, and is suspended above the cavity 101; a second region 120b of the piezoelectric layer is attached to the substrate 110, surrounding said first region 120a outside said first region 120a.

The connection portions of the plurality of branches may be located entirely within the first region, partially within the second region, or entirely within the second region; similarly, the ends of the plurality of branches may be located entirely within the first region, partially within the second region, or entirely within the second region, and the first side of the trunk may be located entirely within the first region, partially within the second region, or entirely within the second region.

In this embodiment, the connection portions of the branches, the end portions of the branches, and the first side of the trunk are all located in the first area 120a, and the second side of the trunk is located in the second area 120 b. Specifically, the first connection portions 132a of the plurality of first branches 132, the first end portions 132b of the plurality of first branches 132, the first side 131a of the first trunk 131, the second connection portions 152a of the plurality of second branches 152, the second end portions 152b of the plurality of second branches 152, and the first side 151a of the second trunk 151 are located within the first region 120 a; the second side 131b of the first backbone 131 and the second side 151b of the second backbone 151 are located within the second region 120 b.

In this embodiment, the first connection portions 132a of the first branches 132, the first end portions 132b of the first branches 132, the first side 131a of the first trunk 131, the second connection portions 152a of the second branches 152, the second end portions 152b of the second branches 152, and the first side 151a of the second trunk 151 are disposed in the first region 120a, so that the first connection portions 132a of the first branches 132, the first end portions 132b of the first branches 132, the first side 131a of the first trunk 131, the second connection portions 152a of the second branches 152, and the first side 151a of the second trunk 151 are opposite to the cavity 101 in the substrate 110, thereby avoiding coupling between the parts and the substrate and forming leakage currents, parasitic capacitances, and acoustic parasitic modes, and further improving the overall performance of the acoustic resonator.

Further, the connection portion of at least one of the plurality of branches is bent upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer. The present embodiment does not limit the distribution of the air gaps and the number of branches where the air gaps are provided.

In a particular embodiment, the connection of any one of the plurality of first branches 132 and the plurality of second branches 152 forms an air gap. For example, the first connection portion 132a of any one of the plurality of first branches 132 forms an air gap with the first surface of the piezoelectric layer; or the second connection portion 152a of any one of the plurality of second branches 152 forms an air gap with the first surface of the piezoelectric layer.

In another particular embodiment, the connection of any of the plurality of first branches 132 and the plurality of second branches 152 forms an air gap. For example, the first connection portion 132a of any three first branches 132 of the plurality of first branches 132 forms an air gap with the first surface of the piezoelectric layer; or the second connection portion 152a of any five second branches 152 among the plurality of second branches 152 forms an air gap with the first surface of the piezoelectric layer; or the first connection portion 132a of any one of the plurality of first branches 132 forms an air gap with the first surface of the piezoelectric layer, and the second connection portion 152a of any three of the plurality of second branches 152 forms an air gap with the first surface of the piezoelectric layer.

In yet another specific embodiment, the connection of all of the plurality of branches is folded upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer. Specifically, the first connection portions 132a of all the first branches 132 of the plurality of first branches 132 and the second connection portions 152a of all the second branches 152 of the plurality of second branches 152 are bent upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

In this embodiment, the first connection portion 132a and the second end portion 152b of the adjacent second branch 152 have opposite polarities, and the first connection portion 132a and the second end portion 152b having opposite polarities generate electric field and acoustic field coupling through the piezoelectric layer 120, so as to further generate parasitic modes. The present embodiment prevents the first connection portion 132a and the second end portion 152b having opposite polarities from generating electric field and acoustic field coupling through the piezoelectric layer 120 by forming an air gap between the first connection portion 132a and the first surface of the piezoelectric layer 120, thereby further preventing parasitic modes from being generated. Similarly, by forming an air gap between the second connection portion 152a and the first surface of the piezoelectric layer 120, the second connection portion 152a and the first end portion 132b, which are opposite in polarity, are prevented from generating electric field and acoustic field coupling through the piezoelectric layer 120, and generation of parasitic modes is further prevented.

Further, the height and length of the air gaps located on the different branches may be the same or different. For example, an air gap having a first length and a first height is formed at a connection portion of one of the plurality of first branches 132, and an air gap having a second length and a second height is formed at a connection portion of another one of the plurality of first branches 132, wherein the first length and the second length may be the same or different, and the first height and the second height may be the same or different.

Further, when the length of the branch connection portion is too long (for example, when the end of the branch connection portion remote from the corresponding trunk extends to the inside of the electrode aperture edge), the effective length of the branch (i.e., the length within the electrode aperture) is lost, and in order to prevent the loss of the effective electrode length of the branch, the length of the branch connection portion is as small as possible. When the length of the connection portion is too short (for example, when the end of the branch connection portion away from the corresponding trunk extends to the outside of the electrode aperture edge), a parasitic mode still exists, and in order to reduce the parasitic mode, the length of the branch connection portion may be appropriately set according to need, which is not limited in this embodiment. In a preferred embodiment, the end of the connection remote from the respective stem extends to the edge of the electrode aperture, i.e. is flush with the edge of the electrode aperture. The effective electrode length without losing branches is ensured, and the parasitic mode is reduced as much as possible. Specifically, an end of the first connection portion 132a remote from the first trunk 131 is flush with an edge of the electrode aperture, and an end of the second connection portion 152a remote from the second trunk 151 is flush with an edge of the electrode aperture.

FIG. 4a shows a schematic top view of an acoustic wave resonator according to a second embodiment of the present invention; FIG. 4b shows a cross-sectional view of FIG. 4a along the direction AA; unlike the first embodiment, in this embodiment, the end of at least one of the plurality of branches is bent upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

In a particular embodiment, the ends of any of the plurality of first branches 132 and the plurality of second branches 152 form an air gap. For example, the first end 132b of any one of the plurality of first branches 132 forms an air gap with the first surface of the piezoelectric layer; or the second end 152b of any one of the plurality of second branches 152 forms an air gap with the first surface of the piezoelectric layer.

In another particular embodiment, the ends of any of the plurality of first branches 132 and the plurality of second branches 152 form an air gap. For example, the first end 132b of any three first branches 132 of the plurality of first branches 132 forms an air gap with the first surface of the piezoelectric layer; or the second ends 152b of any five second branches 152 of the plurality of second branches 152 form an air gap with the first surface of the piezoelectric layer; or the first end 132b of any one of the plurality of first branches 132 forms an air gap with the first surface of the piezoelectric layer, and the second end 152b of any three of the plurality of second branches 152 forms an air gap with the first surface of the piezoelectric layer.

In yet another specific embodiment, the ends of all of the plurality of branches are bent upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer. Specifically, the first ends 132b of all of the first branches 132 of the plurality of first branches 132 and the second ends 152b of all of the second branches 152 of the plurality of second branches 152 are bent upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

The present embodiment further prevents parasitic modes from being generated by forming an air gap between the first end portion 132b and the first surface of the piezoelectric layer 120, avoiding the second connection portion 152a and the first end portion 132b having opposite polarities from generating electric field and acoustic field coupling through the piezoelectric layer 120. Similarly, by forming an air gap between the second end 152b and the first surface of the piezoelectric layer 120, the first connection portion 132a and the second end 152b, which are opposite in polarity, are prevented from generating electric field and acoustic field coupling through the piezoelectric layer 120, further preventing parasitic modes from being generated.

Further, the first side 131a of the first trunk 131 and the second terminal 152b of the second branch 152 have opposite polarities, and the first side 131a and the second terminal 152b of the first trunk 131 generate electric field and acoustic field coupling through the piezoelectric layer 120, so as to further generate parasitic modes. The present embodiment prevents electric field and acoustic field coupling between the ends of the branches and the opposite-polarity backbone through the piezoelectric layer 120 by forming an air gap with the first surface of the piezoelectric layer at the ends of the branches, and further avoids parasitic modes.

Further, the height and length of the air gaps located on the different branches may be the same or different. For example, an air gap having a third length and a third height is formed at an end of one of the plurality of first branches 132, and an air gap having a fourth length and a fourth height is formed at a connection of one of the plurality of second branches 152, wherein the third length and the fourth length may be the same or different, and the third height and the fourth height may be the same or different.

Further, since the ends of the branches are located inside the edges of the electrode aperture, the effective length of the branches is lost when the length of the ends of the branches is too long, and the length of the ends of the branches is as small as possible in order to prevent the loss of the effective electrode length of the branches.

FIG. 5a shows a schematic top view of an acoustic wave resonator according to a third embodiment of the present invention; FIG. 5b shows a cross-sectional view of FIG. 5a along the direction AA; unlike the first embodiment, in this embodiment, at least a portion of the first side of the backbone is folded upward on the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer. The specific location of the air gap in the first side region of the backbone is not limited in this embodiment.

In a specific embodiment, any one or any several of the first side 131a region of the first backbone 131 and the first side 151a region of the second backbone 151 form an air gap with the first surface of the piezoelectric layer, wherein the portions forming the air gap may or may not be in communication with each other when the first side 131a region of the first backbone 131 and any several of the first side 151a region of the second backbone 151 form an air gap with the first surface of the piezoelectric layer.

In another specific embodiment, the entire area of the first side of the backbone is folded upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer. Specifically, the entire area of the first side 131a of the first backbone 131 and the entire area of the first side 151a of the second backbone 151 are bent upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

The first side 131a of the first trunk 131 and the second terminal 152b of the second branch 152 have opposite polarities, and the first side 131a and the second terminal 152b of the first trunk 131 generate electric field and acoustic field coupling through the piezoelectric layer 120, further generating parasitic modes. The present embodiment further prevents parasitic modes from being generated by forming an air gap between the region of the first side 131a of the first trunk 131 and the first surface of the piezoelectric layer 120, such that there is a gap between the first side 131a of the first trunk 131 and the first surface of the piezoelectric layer 120, thereby avoiding the electric field and acoustic field coupling between the first side 131a of the first trunk 131 and the second terminal 152b of the opposite second branch 152 through the piezoelectric layer 120. Similarly, by forming an air gap between the first side 151a of the second backbone 151 and the first surface of the piezoelectric layer such that there is a gap between the first side 151a of the second backbone 151 and the first surface of the piezoelectric layer 120, the first side 151a of the second backbone 151 and the first terminal 132b of the opposite first branch 132 are prevented from generating electric field and acoustic field coupling through the piezoelectric layer 120, further preventing parasitic modes from being generated.

FIG. 6a is a schematic top view of an acoustic wave resonator according to a fourth embodiment of the present invention; FIG. 6b shows a cross-sectional view of FIG. 6a along the direction AA; unlike the first embodiment, in this embodiment, the connection portion of at least one of the plurality of branches and the end portion of at least one of the plurality of branches are bent upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

In a specific embodiment, the connection of any one of the plurality of first branches 132 and the plurality of second branches 152, and the end of any one of the plurality of first branches 132 and the plurality of second branches 152 are bent upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

In another specific embodiment, the connection of any one of the plurality of first branches 132 and the plurality of second branches 152, and the ends of any several of the plurality of first branches 132 and the plurality of second branches 152 form an air gap with the first surface of the piezoelectric layer.

In yet another specific embodiment, the connection of any of the plurality of first branches 132 and the plurality of second branches 152, and the end of any of the plurality of first branches 132 and the plurality of second branches 152 form an air gap with the first surface of the piezoelectric layer.

In yet another specific embodiment, the connection of any of the plurality of first branches 132 and the plurality of second branches 152, and the ends of any of the plurality of first branches 132 and the plurality of second branches 152 form an air gap with the first surface of the piezoelectric layer.

In yet another specific embodiment, the connection of all of the plurality of first branches 132 and the plurality of second branches 152, and the ends of all of the plurality of first branches 132 and the plurality of second branches 152 are bent upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

The length and the height of the air gap arranged at the branch connecting part and the air gap arranged at the branch end part can be the same or different.

FIG. 7a is a schematic top view of an acoustic wave resonator according to a fifth embodiment of the present invention; FIG. 7b shows a cross-sectional view of FIG. 7a along the direction AA; unlike the first embodiment, in this embodiment, the connection portion of at least one of the plurality of branches and at least a portion of the area of the first side of the trunk are bent upward on the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

In a specific embodiment, the connection of any one of the plurality of first branches 132 and the plurality of second branches 152 forms an air gap, and any one or several partial areas of the first side 131a area of the first trunk 131 and the first side 151a area of the second trunk 151 form an air gap with the first surface of the piezoelectric layer.

In another specific embodiment, the connection portions of any of the plurality of first branches 132 and the plurality of second branches 152 form an air gap, and any one or any several partial areas of the first side 131a area of the first trunk 131 and the first side 151a area of the second trunk 151 form an air gap with the first surface of the piezoelectric layer.

In yet another specific embodiment, the connection of all of the plurality of first branches 132 and the plurality of second branches 152, and all of the areas of the first sides 131a of the first and second stems 131 and 151 are bent upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

Further, in the present embodiment, the air gap between the first connection portion 132a of the first branch 132 and the first surface and the air gap between the first trunk 131 and the first surface are communicated; the air gap between the second connection 152a of the second branch 152 and the first surface communicates with the air gap between the second trunk 151 and the first surface. In other embodiments, the air gap between the first connecting portion 132a and the first surface and the air gap between the first trunk 131 and the first surface may be independent, which is not limited in this embodiment.

Fig. 8a shows a schematic top view of an acoustic wave resonator according to a sixth embodiment of the present invention; FIG. 8b shows a cross-sectional view of FIG. 8a along the direction AA; unlike the first embodiment, in this embodiment, the end portion of at least one of the plurality of branches and at least a portion of the area of the first side of the trunk are bent upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

In a specific embodiment, the ends of any one of the plurality of first branches 132 and the plurality of second branches 152 form an air gap, and any one or several partial areas of the first side 131a area of the first trunk 131 and the first side 151a area of the second trunk 151 form an air gap with the first surface of the piezoelectric layer.

In another specific embodiment, the ends of any of the plurality of first branches 132 and the plurality of second branches 152 form an air gap, and any one or any few of the first side 131a region of the first stem 131 and the first side 151a region of the second stem 151 form an air gap with the first surface of the piezoelectric layer.

In yet another specific embodiment, the ends of all of the plurality of first branches 132 and the plurality of second branches 152, and all of the areas of the first sides 131a of the first and second stems 131, 151 are bent upward at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer.

Fig. 9a shows a schematic top view of an acoustic wave resonator according to a seventh embodiment of the present invention; FIG. 9b shows a cross-sectional view of FIG. 9a along the direction AA; unlike the first embodiment, in this embodiment, the connection portion of at least one of the plurality of branches, the end portion of at least one of the plurality of branches, and at least a portion of the area of the first side of the backbone are bent upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

In a specific embodiment, the connection of any one or more of the plurality of first branches 132 and the plurality of second branches 152 forms an air gap, the end of any one or more of the plurality of first branches 132 and the plurality of second branches 152 forms an air gap, and any one or more of the first side 131a region of the first backbone 131 and the first side 151a region of the second backbone 151 forms an air gap with the first surface of the piezoelectric layer.

In another specific embodiment, the connection of all of the plurality of first branches 132 and the plurality of second branches 152, the ends of all of the plurality of first branches 132 and the plurality of second branches 152, and all of the areas of the first sides 131a of the first and second stems 131 and 151 are bent upward at the first surface of the piezoelectric layer to form an air gap with the first surface of the piezoelectric layer.

Fig. 10a shows a schematic top view of an acoustic wave resonator according to an eighth embodiment of the present invention; FIG. 10b shows a cross-sectional view of FIG. 10a along the direction AA; unlike any one of the first to seventh embodiments, in this embodiment, the plurality of branches are located in the first area, and the first side area of the trunk is located partially in the first area and partially in the second area. Specifically, the first branch 132 and the second branch 152 are located within the first region 120 a; the first side 131a region of the backbone 131 is partially within the first region 120a and partially within the second region 120b, and the first side 151a region of the backbone 151 is partially within the first region 120a and partially within the second region 120 b.

In this embodiment, coupling is generated between the first side 151a of the trunk located in the second region and the substrate, so as to form leakage current, parasitic capacitance and acoustic parasitic mode, thereby affecting the overall performance of the resonator and further improving the performance of the acoustic wave resonator. When an air gap is formed between the first side region of the backbone and the first surface of the piezoelectric layer, the first side region of the backbone located in the second region is prevented from being coupled with the substrate.

Fig. 11a shows a schematic top view of an acoustic wave resonator according to a ninth embodiment of the present invention; FIG. 11b shows a cross-sectional view of FIG. 11a along the direction AA; unlike any one of the first to seventh embodiments, in the present embodiment, the end portions of the plurality of branches and a part of the connecting portion of the plurality of branches are located within the first region 120 a; another portion of the connection of the plurality of branches and the trunk are located within the second region 120 b. Specifically, the first end 132b of the first branch 132, a portion of the first connection 132a of the first branch 132 proximate to the first end 132b, the second end 152b of the second branch 152, and a portion of the second connection 152a of the second branch 152 proximate to the second end 152b are located within the first region 120 a; the first connection portion 132a of the first branch 132 is located away from a portion of the first end 132b, the trunk 131, a portion of the second connection portion 152a of the second branch 152 is located away from the second end 152b, and the trunk 151 is located within the second region 120 b.

In this embodiment, coupling is generated between the branched connection portion located in the second region and the substrate, so as to form leakage current, parasitic capacitance and acoustic parasitic mode. When the branched connection portions form an air gap with the first surface of the piezoelectric layer, coupling between the connection portions located in the second region 120b and the substrate is avoided, and leakage current, parasitic capacitance and acoustic parasitic modes are further avoided, so that performance of the acoustic wave resonator is improved.

Further, coupling is generated between the trunk and the substrate in the second region, and when the first side region of the trunk forms an air gap with the first surface of the piezoelectric layer, coupling is avoided between the trunk and the substrate in the second region 120b, so that leakage current, parasitic capacitance and acoustic parasitic mode are further avoided, and performance of the acoustic wave resonator is improved.

Fig. 12a shows a schematic top view of an acoustic wave resonator according to a tenth embodiment of the present invention; FIG. 12b shows a cross-sectional view of FIG. 12a along the direction AA; unlike any one of the first to seventh embodiments, in this embodiment, a part of the ends of the plurality of branches is located in the first region, another part is located in the second region, and the connection portions of the plurality of branches and the trunk are located in the second region 120 b. Specifically, a portion of the first end 132b of the first branch 132 is located in a first region, another portion is located in a second region, and a portion of the second end 152b of the second branch 152 is located in the first region, another portion is located in the second region; the first connection portion 132a of the first branch 132, the second connection portion 152a of the second branch 152, the trunk 131, and the trunk 151 are located in the second region 120 b.

In this embodiment, when the ends of the branches form an air gap with the first surface of the piezoelectric layer, on one hand, the connection portion of the branches opposite to the polarity and the trunk are prevented from generating electric field and acoustic field coupling through the piezoelectric layer 120, so as to further prevent parasitic modes. On the other hand, the coupling between the end portion located in the second region 120b and the substrate is avoided, and the formation of leakage current, parasitic capacitance and acoustic parasitic mode is further avoided, so as to improve the performance of the acoustic wave resonator.

Further, coupling is generated between the branched connection part and the substrate in the second area, so that leakage current, parasitic capacitance and acoustic parasitic modes are formed. When the branched connection portions form an air gap with the first surface of the piezoelectric layer, coupling between the connection portions located in the second region 120b and the substrate is avoided, and leakage current, parasitic capacitance and acoustic parasitic modes are further avoided, so that performance of the acoustic wave resonator is improved.

Fig. 13a shows a schematic top view of an acoustic wave resonator according to an eleventh embodiment of the present invention; FIG. 13b shows a cross-sectional view of FIG. 13a along the direction AA; unlike any one of the first to seventh embodiments, in this embodiment, the ends of the branches, the connection portions of the branches, and the trunk are located in the second region 120 b. Specifically, the first end 132b of the first branch 132, the first connection 132a of the first branch 132, the second end 152b of the second branch 152, the second connection 152a of the second branch 152, the trunk 131, and the trunk 151 are located within the second region 120 b.

In this embodiment, the connection portions of the branches form an air gap with the first surface of the piezoelectric layer, so that on one hand, the electric field and the acoustic field coupling generated by the ends of the branches opposite to the polarity through the piezoelectric layer 120 are avoided, and the parasitic mode is further prevented from being generated. On the other hand, the coupling between the connection portion located in the second region 120b and the substrate is avoided, and the formation of leakage current, parasitic capacitance and acoustic parasitic mode is further avoided, so as to improve the performance of the acoustic wave resonator.

Fig. 14a shows a schematic top view of an acoustic wave resonator according to a twelfth embodiment of the present invention, fig. 14b shows a cross-sectional view along AA direction of fig. 14a, and fig. 14c shows a cross-sectional view along BB direction of fig. 14 a; the present embodiment is located in the first region 120a with the ends of the plurality of branches and a portion of the connection of the plurality of branches; another part of the connection portion of the branches and the trunk are located in the second area 120b is described as an example. Unlike any one of the first to eleventh embodiments, in this embodiment, the first surface of the piezoelectric layer 120 is attached to the substrate 110. Wherein, the portions of the first electrode 130 and the second electrode 150 located in the first region 120a are located in the cavity 101, and the portions located in the second region 120b are embedded in the substrate.

Further, an air gap between the backbone and the piezoelectric layer communicates with the cavity of the substrate.

Fig. 15a shows a schematic top view of an acoustic wave resonator according to a twelfth embodiment of the present invention, and fig. 15b shows a cross-sectional view along AA direction of fig. 15a, unlike the twelfth embodiment, in this embodiment, an air gap between a backbone and a piezoelectric layer is not in communication with a cavity of a substrate.

Fig. 16a is a schematic diagram showing a top view of an acoustic wave resonator according to a fourteenth embodiment of the present invention, fig. 16b-1 and fig. 16b-2 are cross-sectional views along the BB direction of fig. 16a, wherein fig. 16b-1 is a cross-sectional view when excited with a transverse electric field (e.g., component E1 in fig. 2), and fig. 16b-2 is a cross-sectional view when excited with a longitudinal electric field (e.g., component E3 in fig. 2); unlike any one of the first to eleventh embodiments, in this embodiment, the first and second electrodes are also formed on the second surface of the piezoelectric layer 120.

In particular, when the piezoelectric layer is lithium niobate or lithium tantalate and the operation mode is a transverse electric field excitation A1, SH0 or S0, then among the first electrode and the second electrode located on the first surface of the piezoelectric layer 120 and the second surface of the piezoelectric layer 120, the electrodes having the same polarity correspond to each other in the thickness direction of the piezoelectric layer 120, specifically, in the thickness direction of the piezoelectric layer 120, the first branch 132 located on the first surface of the piezoelectric layer 120 corresponds to the first branch 132 located on the second surface of the piezoelectric layer 120, and the second branch 152 located on the first surface of the piezoelectric layer 120 corresponds to the second branch 152 located on the second surface of the piezoelectric layer 120.

When the vibration modes of the first and second electrodes are the longitudinal electric field excitation modes, among the first and second electrodes located on the first surface of the piezoelectric layer 120 and the second surface of the piezoelectric layer 120, the electrodes having opposite polarities correspond in the thickness direction of the piezoelectric layer 120, specifically, in the thickness direction of the piezoelectric layer 120, the first branch 132 located on the first surface of the piezoelectric layer 120 corresponds to the second branch 152 located on the second surface of the piezoelectric layer 120, and the second branch 152 located on the first surface of the piezoelectric layer 120 corresponds to the first branch 132 located on the second surface of the piezoelectric layer 120.

Further, the first electrode and the second electrode on the second surface of the piezoelectric layer 120 may have the same or different structures (e.g., electrode width, period, interdigital electrode arrangement, etc.) as the first electrode and the second electrode on the first surface of the piezoelectric layer.

Further, the distribution, length, and height of the air gaps on the first electrode and the second electrode on the second surface of the piezoelectric layer 120 may be the same or different from those on the first electrode and the second electrode on the first surface of the piezoelectric layer.

Further, the portion of the first electrode and the second electrode located on the second surface of the piezoelectric layer 120 located in the first region 120a is located in the cavity 101, and the portion located in the second region 120b is embedded in the substrate.

Fig. 17a shows a schematic top view of an acoustic wave resonator according to a fifteenth embodiment of the present invention, and fig. 17b shows a cross-sectional view along the BB direction of fig. 17 a; unlike any of the first to thirteenth embodiments, in the present embodiment, the cavity 101 extends from the surface of the substrate 110 in contact with the piezoelectric layer 120 toward the inside of the substrate 110, stopping inside the bonding layer 112.

Fig. 18a shows a schematic top view of an acoustic wave resonator according to a sixteenth embodiment of the present invention, and fig. 18b shows a cross-sectional view along the BB direction of fig. 18 a; unlike any of the first to thirteenth embodiments, in the present embodiment, the cavity 101 extends from the surface of the substrate 110 in contact with the piezoelectric layer 120 toward the inside of the substrate 110, stopping at the surface of the bonding layer 112 in contact with the base layer 111, i.e., penetrating the bonding layer 112.

Fig. 19a shows a schematic top view of an acoustic wave resonator according to a seventeenth embodiment of the present invention, and fig. 19b shows a cross-sectional view along the BB direction of fig. 19 a; unlike any of the first to thirteenth embodiments, in this embodiment, the cavity 101 is a through hole penetrating the substrate 110 (i.e., penetrating the bonding layer 112 and the base layer 111).

The present embodiment is not limited to the structure of the cavity, as long as the cavity structure can be formed on one or both side surfaces of the piezoelectric layer.

Fig. 20a shows a schematic top view of an acoustic wave resonator according to an eighteenth embodiment of the present invention, and fig. 20b shows a cross-sectional view along the BB direction of fig. 20 a; unlike any of the first to thirteenth embodiments, in the present embodiment, the piezoelectric layer 120 is attached to the base layer 111 via the bragg reflection layer 113, and a cavity does not need to be provided in the bragg reflection layer.

Fig. 21a shows a schematic structural view when the first surface of the piezoelectric layer is attached to the substrate or when the second surface of the piezoelectric layer is attached to the substrate, and the second surface of the piezoelectric layer also forms the first electrode and the second electrode; FIG. 21b shows a schematic view of the structure of FIG. 21a along the direction AA; as shown in fig. 21a and 21b, when the first surface of the piezoelectric layer 120 is attached to the substrate 110, or when the second surface of the piezoelectric layer 120 is attached to the substrate 110, and the second surface of the piezoelectric layer 120 also forms the first electrode and the second electrode, the bragg reflection layer is adaptively curved according to the first electrode and the second electrode.

Fig. 22a shows a schematic top view of an acoustic wave resonator according to a nineteenth embodiment of the invention, and fig. 22b shows a cross-sectional view along AA direction of fig. 22 a; as shown in fig. 22a and 22b, unlike any one of the first to seventeenth embodiments, in the present embodiment, the first and second electrodes further include pins including a first pin 137 and a first pin 138, the first pin 137 being connected to the first stem 131 at a second side of the first stem 131, and the second pin 138 being connected to the second stem 151 at a second side of the second stem 151.

Further, the second side area of the backbone is also bent upwards at the first surface of the piezoelectric layer, forming an air gap with the first surface of the piezoelectric layer, i.e. the entire backbone forms an air gap with the first surface of the piezoelectric layer.

In this embodiment, the second side region of the stem forms an air gap with the first surface of the piezoelectric layer, further reducing parasitics between the stem and the substrate.

Fig. 23a is a schematic top view showing a sound wave resonator according to a twentieth embodiment of the present invention, and fig. 23b is a cross-sectional view along AA direction of fig. 23 a; as shown in fig. 23a and 23b, unlike the eighteenth embodiment, in the present embodiment, the first pin 137 is located at any one side adjacent to the first side of the first trunk 131, and the second pin 138 is located at any one side adjacent to the first side of the second trunk 151.

Fig. 24a is a schematic diagram showing a top view of an acoustic wave resonator according to a twenty-first embodiment of the present invention, and fig. 24b is a sectional view along AA direction of fig. 24 a; as shown in fig. 24a and 24b, unlike any one of the first to nineteenth embodiments, in this embodiment, the first and second electrodes further include an additional layer 139, so that the acoustic wave resonator series impedance is further reduced. The additional layer 139 is located on any part forming the air gap, e.g. the connection, the end, the first side area of the trunk and the second side area of the main root, etc. of the branches forming the air gap.

In other embodiments, when the backbone does not form an air gap, an additional layer is also overlaid on the backbone. Further, the material of the additional layer 139 is a metal with high conductivity, for example, any one or more of gold (Au), aluminum (Al), copper (Cu), molybdenum (Mo), tungsten (W), ruthenium (Ru), platinum (Pt), or an alloy containing the above materials as a main component.

Further, in other embodiments, the acoustic wave resonator further comprises a passivation layer covering the surface of the piezoelectric layer and/or the first electrode and/or the second electrode for protecting the piezoelectric layer and/or the first electrode and/or the second electrode from air oxidation or moisture corrosion. The passivation layer is made of dielectric material, and the passivation layer is made of silicon dioxide, silicon nitride, aluminum oxide, aluminum nitride and the like.

Further, the invention also provides a filter comprising the acoustic wave resonator in any of the above embodiments.

Embodiments in accordance with the present invention, as described above, are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and the full scope and equivalents thereof.

Claims

1. An acoustic wave resonator comprising:

a piezoelectric layer; and

Wherein the plurality of branches comprises:

a connection portion connected to the trunk at a first side of the trunk; and

An end distal to the first side of the backbone;

2. The acoustic wave resonator of claim 1, wherein the height and length of the air gaps located on different branches may be the same or different.

3. The acoustic wave resonator of claim 1 further comprising a substrate including a base layer providing support for the piezoelectric layer;

4. The acoustic wave resonator of claim 3 wherein the substrate further comprises a bonding layer via which the piezoelectric layer is attached to the base layer.

5. The acoustic wave resonator according to claim 3 or 4, further comprising a bragg reflective layer located between the piezoelectric layer and the substrate layer.

6. The acoustic wave resonator of claim 5 wherein the first and second electrodes are embedded in the substrate when the first surface of the piezoelectric layer is attached to the substrate, the bragg reflective layer being adapted to flex.

7. The acoustic wave resonator according to claim 3, wherein the substrate has a cavity therein, the cavity being a groove extending from a surface of the substrate in contact with the piezoelectric layer toward an inside of the substrate and stopping inside of the substrate, or a through hole penetrating through the substrate.

8. The acoustic wave resonator of claim 7 wherein the piezoelectric layer comprises:

A second region surrounding the first region, attached to the substrate.

9. The acoustic wave resonator of claim 8 wherein the connections of the plurality of branches are either entirely located in the first region, or are partially located in the first region, partially located in the second region, or are entirely located in the second region.

10. The acoustic wave resonator of claim 8 wherein the first side region of the backbone is either entirely located in the first region, or is partially located in the first region, partially located in the second region, or is entirely located in the second region.

11. The acoustic wave resonator of claim 8 wherein ends of the plurality of branches are located either entirely in the first region, or partially in the first region, partially in the second region, or entirely in the second region.

12. The acoustic wave resonator of claim 1 wherein the first and second electrodes further comprise pins, respectively, connected to the backbone.

13. The acoustic wave resonator of claim 12 wherein the pin is located on any side of the stem not connected to the branch.

14. The acoustic wave resonator of claim 12 wherein the entire backbone is raised upward at the first surface of the piezoelectric layer forming an air gap with the first surface of the piezoelectric layer.

15. The acoustic wave resonator of claim 1 further comprising an additional layer covering a surface of the first and second electrodes where the air gap is formed away from or near the piezoelectric layer, the additional layer being a metal layer.

16. The acoustic wave resonator of claim 15 wherein the additional layer is further located on an electrode bus.

17. The acoustic wave resonator of claim 1, wherein the piezoelectric layer is a lithium niobate layer or a lithium tantalate layer.

18. The acoustic wave resonator of claim 17 wherein the vibrational modes excited by the first and second electrodes comprise at least an antisymmetric lamb wave mode, a horizontal shear mode, and a symmetric lamb wave mode.

19. The acoustic wave resonator of claim 1 wherein the first and second electrodes are further located on a second surface of the piezoelectric layer, the first and second surfaces of the piezoelectric layer being opposite.

20. The acoustic wave resonator of claim 19 wherein the first and second electrodes at the first and second surfaces of the piezoelectric layer are the same or different in structure.

21. The acoustic wave resonator of claim 19 wherein the same polarity branches in the piezoelectric layer thickness direction correspond in the first and second electrodes at the piezoelectric layer first surface and at the piezoelectric layer second surface.

22. The acoustic wave resonator according to claim 1, further comprising a passivation layer covering a surface of the piezoelectric layer and/or the first electrode and/or the second electrode.

23. A filter comprising the acoustic wave resonator of any one of claims 1 to 22.