CN114614792A - Acoustic wave resonator and filter - Google Patents

Acoustic wave resonator and filter Download PDF

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Publication number
CN114614792A
CN114614792A CN202210231010.0A CN202210231010A CN114614792A CN 114614792 A CN114614792 A CN 114614792A CN 202210231010 A CN202210231010 A CN 202210231010A CN 114614792 A CN114614792 A CN 114614792A
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acoustic
layer
piezoelectric layer
acoustic wave
channel
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吴传贵
谭举
帅垚
罗文博
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University of Electronic Science and Technology of China
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/02118—Means for compensation or elimination of undesirable effects of lateral leakage between adjacent resonators
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02157—Dimensional parameters, e.g. ratio between two dimension parameters, length, width or thickness
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02637—Details concerning reflective or coupling arrays
    • H03H9/02653—Grooves or arrays buried in the substrate
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02637—Details concerning reflective or coupling arrays
    • H03H9/02653—Grooves or arrays buried in the substrate
    • H03H9/02661—Grooves or arrays buried in the substrate being located inside the interdigital transducers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/13—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/25—Constructional features of resonators using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6489—Compensation of undesirable effects

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  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

The application provides an acoustic wave resonator and wave filter for improve the quality factor Q value of syntonizer and wave filter, one of them acoustic wave resonator includes: a substrate; an acoustic reflection structure disposed on an upper surface of the substrate; a piezoelectric layer disposed on an upper surface of the acoustic reflection structure; an electrode structure disposed on an upper surface of the piezoelectric layer; wherein a channel is arranged outside the resonance area of the piezoelectric layer, the depth of the channel is smaller than the thickness of the piezoelectric layer, the width of the channel is larger than zero and smaller than or equal to the vertical distance from the boundary of the resonance area to the boundary of the piezoelectric layer, and the resonance area is an area corresponding to the electrode structure on the piezoelectric layer.

Description

Acoustic wave resonator and filter
Technical Field
The application belongs to the field of Micro-Electro-Mechanical Systems (MEMS) radio frequency devices, and particularly relates to an acoustic wave resonator and an acoustic wave filter.
Background
Since the development of analog rf communication technology in the early 90 th generation of the last century, rf front-end modules have gradually become the core components of communication devices. In all rf front-end modules, the filter has become the most fierce component to grow and have the greatest development prospect. The filter is a product with the highest production value in each field of the radio frequency front end, and the share of the filter in the market of the radio frequency front end reaches more than 50% in 2020. With the rapid development of wireless communication technology, the fifth Generation Mobile communication (5G) 5G communication protocol is becoming mature, and the market also puts forward more strict standards on various aspects of the performance of radio frequency filters. The performance of the filter is determined by the resonator elements that make up the filter.
In the existing filters, Acoustic filters are widely applied to various small devices (such as mobile phones, tablets, routers, bluetooth headsets) by virtue of the advantages of high selectivity, small size and the like, and are specifically divided into Surface Acoustic Wave (SAW) filters and Bulk Acoustic Wave (BAW) filters. The surface acoustic wave resonator occupies most of the sound wave filter in the fourth Generation Mobile communication (4th Generation Mobile Networks,4G) age due to the advantage of low cost, but with the rise of wireless communication frequency, the common surface acoustic wave filter cannot meet new requirements, but the updating of the surface acoustic wave filter technology is never stopped. The Temperature compensated surface acoustic wave (TC-SAW) filter improves the Temperature characteristics of the conventional SAW filter and improves the Temperature stability thereof. As an upgrading product of common Surface Acoustic Wave (TF-SAW), a Thin Film Surface Acoustic Wave (TF-SAW) filter has a higher Q value, better temperature stability and higher working frequency, makes up the defects of the SAW filter, but the cost is greatly increased. Compared with a surface acoustic wave filter, the bulk acoustic wave filter has the advantages of smaller insertion loss, better out-of-band rejection, higher working frequency, larger bandwidth, higher power capacity, better temperature stability and excellent anti-static impact capability, is one of the filters most suitable for 5G application, and the market occupation ratio is increased year by year. The future acoustic wave filter industry will be SAW and BAW complementary coexistence. The basic unit of the Bulk Acoustic wave filter is a Bulk Acoustic wave Resonator, and the basic unit is generally divided into two types, one is an air gap Bulk Acoustic wave Resonator (FBAR), and the other is a solid assembled Bulk Acoustic wave Resonator (BAW-SMR). The former uses the cavity as the sound wave reflection interface, and has more excellent Q value; the latter uses Bragg reflection layer as sound wave reflection interface, Q value is lower than the former, but has more efficient heat dissipation channel, can satisfy the demand of higher power. An improved resonator structure is proposed for low Q values of SAW and BAW-SMR. At the same time, SAW resonators also need to have further improved Q values to meet future higher demands and the challenges of BAW resonators.
Disclosure of Invention
The present application provides an acoustic wave resonator and an acoustic wave filter to provide a new technical solution for improving the Q value of the quality factor.
In a first aspect, the present application provides an acoustic wave resonator comprising:
a substrate;
an acoustic reflection structure disposed on an upper surface of the substrate;
a piezoelectric layer disposed on an upper surface of the acoustic reflection structure;
an electrode structure disposed on an upper surface of the piezoelectric layer;
wherein a channel is arranged outside a resonance area of the piezoelectric layer, the depth of the channel is smaller than the thickness of the piezoelectric layer, the width of the channel is larger than zero and smaller than or equal to the vertical distance from the boundary of the resonance area to the boundary of the piezoelectric layer, and the resonance area is an area corresponding to the electrode structure on the piezoelectric layer.
According to the piezoelectric resonator, the channel is arranged outside the resonance area of the piezoelectric layer and the upper electrode, the thickness of the piezoelectric layer outside the resonance area is changed through the channel, the boundary conditions of the resonance area and the external piezoelectric layer (the resonance state of the piezoelectric layer and the upper electrode boundary) are changed, the resonance mode is changed, transverse sound wave leakage is restrained, the sound wave energy loss is reduced, and the transmission coefficient of radio frequency signals is improved. The larger the channel width is, the larger the inhibition range of the resonance region to the design frequency acoustic wave vibration of the resonator is, and the better the limitation to the acoustic wave leakage is; the channel surface acoustic wave resonator is insensitive to the channel width. The depth of the channel is related to the sound wave frequency for limiting the lateral leakage of the bulk acoustic wave, the deeper the depth of the channel is, the higher the sound wave resonance frequency at the channel is, and the larger the frequency difference between the sound wave resonance frequency in the resonance region is, so the deeper the depth of the channel is, the better the sound wave limiting effect on the resonance frequency of the bulk acoustic wave resonator is; the deeper the channel depth, the larger the limit range of the transverse resonance sound wave of the surface acoustic wave resonator is, and the better effect is achieved. A new path is provided for the acoustic wave resonator in the direction of improving the quality factor Q value.
In one possible design, the method is characterized in that,
the electrode structure includes an upper electrode disposed on an upper surface of the piezoelectric layer and a lower electrode disposed between the piezoelectric layer and the acoustic reflection structure.
In one possible design, the channel is a recessed area of the piezoelectric layer disposed around the upper electrode, in an open or closed loop shape.
In one possible design, the acoustic wave resonator further includes:
and the protruding structure is arranged at the edge of the upper electrode, and the protruding structure surrounds the edge of the upper electrode to form a closed loop shape.
A layer of closed-loop protruding structure surrounding the edge of the upper electrode is arranged on the upper electrode within a limited range by taking the boundary of the upper electrode as a limiting range, so that steps are formed, the thickness of the edge of the upper electrode is changed, and the edge resonance of the upper electrode is inhibited. The step can enable the sound wave of the resonant frequency of the resonator to be attenuated at the boundary, resonance cannot be formed, and transverse leakage of the sound wave is reduced.
In one possible design, the acoustic wave resonator further includes:
and the deceleration layer is used for filling the channel.
In one possible design, the electrode structure is an interdigital transducer.
In one possible design, the acoustic reflection structure is:
a cavity structure; or
A Bragg reflector layer.
In one possible design, the bragg reflector layer is composed of alternating layers of high acoustic impedance and low acoustic impedance,
the thickness of the low-sound impedance layer is one fourth of the sound wave wavelength of the material of the low-sound impedance layer at the design frequency of the resonator, and the thickness of the high-sound impedance layer is one fourth of the sound wave wavelength of the material of the high-sound impedance layer at the design frequency of the resonator.
In one possible design, the bragg reflector layer has a low acoustic impedance layer as the topmost layer, the topmost layer low acoustic impedance layer being in direct contact with the piezoelectric layer.
It should be noted that, in addition to the above implementation, the bragg reflection layer may also be composed of high acoustic velocity layers and low acoustic velocity layers alternately, which is not limited in this application.
In one possible design, the low acoustic impedance layer of the bragg reflector layer is silicon dioxide and the high acoustic impedance layer is tungsten, molybdenum, platinum, aluminum nitride, hafnium oxide, and/or tantalum oxide.
Here and/or in the case that the bragg reflection layer is composed of a plurality of groups of high acoustic impedance layers and low acoustic impedance layers, taking two groups as an example, the material of the high acoustic impedance layer in one group is tungsten, and the material of the high acoustic impedance layer in the other group is molybdenum; or the material of the high acoustic impedance layer in one set is platinum and the material of the high acoustic impedance layer in the other set is tungsten, or other combinations, without limitation.
In one possible design, the material of the piezoelectric layer is quartz, lithium tantalate, or lithium niobate.
In one possible design, the substrate is greater than or equal to 500um and less than or equal to 1mm in thickness, and the material of the substrate is any one of monocrystalline silicon Si, quartz, lithium tantalate, lithium niobate, gallium arsenide, or gallium nitride.
In a second aspect, the present application provides an acoustic wave filter comprising an acoustic wave resonator as any one of the possible designs of the first aspect.
Drawings
Fig. 1 is a schematic structural diagram of an acoustic wave resonator according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of an acoustic reflection structure in an acoustic wave resonator according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of an acoustic reflection structure in an acoustic wave resonator according to an embodiment of the present disclosure, which is a bragg reflection layer;
fig. 4 is a schematic structural diagram of a bulk acoustic wave resonator according to an embodiment of the present disclosure;
fig. 5 is a schematic structural diagram of an acoustic wave filter according to an embodiment of the present application;
fig. 6 is a schematic structural diagram of another acoustic wave filter according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The present application will be described in detail with reference to the following examples and drawings.
The acoustic wave resonator and the acoustic wave filter designed by the application can be applied to base station equipment, terminal equipment, automobiles or other equipment. Wherein, the terminal equipment can be a smart phone and a smart wearable device (watch, bracelet, etc.).
Referring to fig. 1, an acoustic wave resonator provided in an embodiment of the present application includes:
a substrate;
an acoustic reflection structure disposed on an upper surface of the substrate;
a piezoelectric layer disposed on an upper surface of the acoustic reflection structure;
an electrode structure disposed on an upper surface of the piezoelectric layer;
wherein a channel is arranged outside a resonance area of the piezoelectric layer, the depth of the channel is smaller than the thickness of the piezoelectric layer, the width of the channel is larger than zero and smaller than or equal to the vertical distance from the boundary of the resonance area to the boundary of the piezoelectric layer, and the resonance area is an area corresponding to the electrode structure on the piezoelectric layer.
In the embodiment of the present application, the acoustic wave resonator includes a substrate, the material of the substrate may be any one of single crystal silicon Si, quartz, lithium tantalate, lithium niobate, gallium arsenide, or gallium nitride, and the thickness of the substrate ranges from greater than or equal to 500um to less than or equal to 1 mm.
Further, the acoustic wave resonator in the embodiment of the present application further includes an acoustic reflection structure disposed on the upper surface of the substrate. The implementation manners of the acoustic reflection structure include, but are not limited to, the following two, which are described below.
Mode-cavity structure
Referring to fig. 2A, in the structure, a sacrificial layer is generally grown on a lower surface of a piezoelectric layer, and then the sacrificial layer is removed by a later release method, so that an air gap is formed between the piezoelectric layer and a substrate, an air interface is formed on the lower surface, and an equivalent impedance of the air interface is approximately zero, so that the leakage of an acoustic wave in a bulk direction can be suppressed.
Mode two Bragg reflection layer
In the specific implementation process of the bragg reflector, two different implementation manners are also included, which are described below:
(1) the Bragg reflection layer is formed by alternately forming high acoustic velocity layers and low acoustic velocity layers
The high acoustic velocity layer is a film in which the acoustic velocity of the acoustic wave in the high acoustic velocity layer is higher than the acoustic velocity of the acoustic wave propagating on the piezoelectric layer, and the low acoustic velocity layer is a film in which the acoustic velocity of the acoustic wave in the low acoustic velocity layer is lower than the acoustic velocity of the acoustic wave propagating on the piezoelectric layerThe material of the high sound velocity layer can be silicon carbide or diamond film, and the material of the low sound velocity layer can be silicon dioxide SiO2。
(2) The Bragg reflection layer is formed by alternately forming high acoustic impedance layer and low acoustic impedance layer
Referring to fig. 2B, the bragg reflector may be formed by one or more sets of high acoustic impedance layers and low acoustic impedance layers, where the sets may be specifically 2 sets, 3 sets, or any number of sets from 2 to 10 sets, which is not limited herein. The material of the high acoustic impedance layer may be a metal, such as molybdenum Mo, platinum Pt, etc., although the material of the high acoustic impedance layer may also be an insulating material, such as an oxide, which may be tantalum Ta oxide2O5Hafnium oxide HfO2Aluminum oxide Al2O3Zinc oxide ZnO or nitride, and can be aluminum nitride AlN or silicon nitride Si3N4Or carbide, which may be silicon carbide SiC, or other insulating material having an acoustic impedance greater than that of the low acoustic impedance layer, without limitation in this application. It should be noted here that, when the bragg reflection layer is formed by alternately forming a plurality of groups of high acoustic impedance layers and low acoustic impedance layers, the materials of the high acoustic impedance layers in each group may be the same or different, and similarly, the materials of the low acoustic impedance layers in each group may be the same or different.
Further, in order to better suppress the acoustic wave leakage, in the embodiment of the present application, the thickness of the low acoustic impedance layer is one fourth of the acoustic wave wavelength of the material of the low acoustic impedance layer at the design frequency of the resonator, and the thickness of the high acoustic impedance layer is one fourth of the acoustic wave wavelength of the material of the high acoustic impedance layer at the design frequency of the resonator. If silicon dioxide is selected as the low-sound-impedance layer and tantalum pentoxide is selected as the high-sound-impedance layer, a 7.5 GHz bulk acoustic wave resonator is designed, wherein the thickness of the silicon dioxide is 195 nm, and the thickness of the tantalum pentoxide is 127 nm.
In this embodiment of the application, the alternating order of the high acoustic impedance layer and the low acoustic impedance layer may also be from bottom to top, one low acoustic impedance layer, one high acoustic impedance layer, or from bottom to top, one high acoustic impedance layer, one low acoustic impedance layer. When from up being one deck high sound impedance layer and one deck low sound impedance layer down, the topmost layer of Bragg reflection stratum is low sound impedance layer, and low sound impedance layer can be directly contact with the piezoelectric layer, because the temperature coefficient of low sound impedance layer is positive, the temperature coefficient of piezoelectric layer is the burden, low sound impedance layer and piezoelectric layer contact like this, can reduce the temperature coefficient of acoustic wave syntonizer to play temperature compensation's effect.
The above-described acoustic reflection structure includes two implementations of a cavity structure and a bragg reflection layer, but when the following technical solutions are specifically described, the implementation of the acoustic reflection structure as a bragg reflection layer is taken as an example.
After the description of the acoustic reflection structure, the piezoelectric layer is described next, and the piezoelectric layer is disposed on the upper surface of the acoustic reflection structure. In the embodiment of the present application, the piezoelectric layer may be a bulk material or a thin film, and the material of the piezoelectric layer may be any one of quartz, lithium tantalate, or lithium niobate.
Further, the acoustic wave resonator in the embodiment of the present application further includes an electrode structure disposed on an upper surface of the piezoelectric layer. And a channel is arranged outside the resonance area of the piezoelectric layer, the thickness of the piezoelectric layer outside the resonance area is changed through the channel, the difference value of the acoustic wave resonance frequency in the resonance area and the acoustic wave resonance frequency outside the resonance area is further increased, transverse acoustic wave leakage is inhibited, acoustic wave energy loss is reduced, and the transmission coefficient of radio frequency signals is improved.
Wherein the depth of the channels is less than the thickness of the piezoelectric layer, for example the depth of the channels can be greater than zero and less than or equal to the thickness of the piezoelectric layer. However, the setting of the channel depth also needs to be according to the specific type of the acoustic wave resonator, since the acoustic wave resonator in the embodiment of the present application may be a bulk acoustic wave resonator, a surface acoustic wave resonator, or another type. For the bulk acoustic wave resonator, the depth of the channel does not exceed half of the thickness of the piezoelectric layer, because the transverse acoustic wave exists, the transverse acoustic wave is a clutter for the bulk acoustic wave resonator, the channel is too deep, the leakage of the transverse acoustic wave and even the resonance of the transverse acoustic wave can be limited, and the Q value of the device is reduced. The deeper the channel depth, the better the saw resonator, because the surface wave which is required by the saw resonator and propagates transversely is limited by the channel to leak out of the resonance area, which is beneficial to improving the Q value of the saw resonator.
The width of the channel is greater than zero and less than or equal to the vertical distance from the boundary of the resonance region to the boundary of the piezoelectric layer. For the bulk acoustic wave resonator, the wider the channel width, the larger the area in which leakage is suppressed, but the increase in width has a boundary diminishing effect, and after half the size of the resonance area is reached, there is little benefit in increasing the width. The surface acoustic wave resonator is insensitive to the channel width, and the channel width is arbitrary.
Further, the embodiment of the application further comprises:
a deceleration layer for filling the trench;
the material of the deceleration layer may be a metal, such as copper Cu, aluminum Al, silver Au, platinum Pt, or other metal material, and of course, the material of the deceleration layer may also be an oxide.
In this embodiment of the application, specific implementation forms of the electrode structure include the following two, and when the specific form of the electrode structure is different, types of the corresponding acoustic wave resonator are also different, for example, when the electrode structure includes an upper electrode and a lower electrode, the corresponding acoustic wave resonator is a bulk acoustic wave resonator, and when the electrode structure is an interdigital transducer, the corresponding acoustic wave resonator is a surface acoustic wave resonator, which is described below:
the first electrode structure comprises an upper electrode and a lower electrode
Referring to fig. 3, when the electrode structure includes an upper electrode and a lower electrode, the upper electrode is disposed on the upper surface of the piezoelectric layer, and the lower electrode is disposed on the lower surface of the piezoelectric layer and directly contacts the acoustic reflection structure. The shape of the upper and lower electrodes here may be rectangular, square, circular or other polygonal shapes. The material of the upper electrode and the lower electrode may be a metal such as aluminum, copper, gold, or an aluminum-copper alloy.
When the electrode structure comprises an upper electrode and a lower electrode, the channel surrounds a piezoelectric layer concave area arranged on the upper electrode and is in an open loop or closed loop shape. If the recessed area is a closed loop, the shape of the recessed area may be the same as or different from that of the upper electrode, for example, the recessed area may be rectangular, square, circular, or other shapes, and may be specifically set according to actual needs.
In order to further suppress the transverse wave leakage, referring to fig. 4, the acoustic wave resonator provided in the embodiment of the present application further includes:
and the protruding structure is arranged at the edge of the upper electrode, and the protruding structure surrounds the edge of the upper electrode to form a closed loop shape.
The material of the protruding structure is the same as that of the upper electrode, and the thickness of the protruding structure can be set according to the requirement of the subsequent actual packaging size, and no specific requirement is made in the embodiment of the application.
It should be noted here that when the electrode structure includes an upper electrode and a lower electrode, the acoustic wave resonator may be a bulk acoustic wave resonator, such as an air gap bulk acoustic wave resonator, a diaphragm bulk acoustic wave resonator, a solid mount bulk acoustic wave resonator, or another type of bulk acoustic wave resonator.
The second electrode structure being an interdigital transducer
When the electrode structure is an interdigital transducer, the acoustic wave resonator may be a surface acoustic wave resonator such as an air gap type surface acoustic wave resonator, a solid mount type surface acoustic wave resonator, or other type of surface acoustic wave resonator.
When the electrode structure is an interdigital transducer, in order to further inhibit the leakage of transverse waves, a groove can be formed between adjacent interdigital electrodes in the interdigital electrodes, the depth of the groove is smaller than the thickness of the piezoelectric layer, and the width of the groove can be the width between the adjacent interdigital electrodes.
It should be noted here that the acoustic wave resonators described above all have an acoustic reflection structure, but the technical solution provided in the present application can also be applied to a surface acoustic wave resonator without an acoustic reflection structure.
Second aspect of the invention
After the introduction of the acoustic wave resonator, embodiments of the present application further provide an acoustic wave filter including the acoustic wave resonator provided in the above embodiments.
The filter is composed of a plurality of resonators, and the structure generally includes a plurality of series resonators and a plurality of parallel resonators, and the sum of the number of series resonators and the number of parallel resonators is referred to as the order of the filter. An example of the topology of the filter is shown in figure 5.
The optimization of the power capacity for a bulk acoustic wave filter can be done by increasing the number of resonators without changing their impedance. Referring to fig. 6, one resonator is changed into two resonators, the impedance of the resonator is not changed while the area is increased, because the area of the bulk acoustic wave resonator is doubled, the impedance of the resonator is halved according to a capacitance and capacitive reactance calculation formula, the two resonators with halved impedance are connected in series, and the impedance is kept unchanged.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. An acoustic wave resonator, comprising:
a substrate;
an acoustic reflection structure disposed on an upper surface of the substrate;
a piezoelectric layer disposed on an upper surface of the acoustic reflection structure;
an electrode structure disposed on an upper surface of the piezoelectric layer;
wherein a channel is arranged outside a resonance area of the piezoelectric layer, the depth of the channel is smaller than the thickness of the piezoelectric layer, the width of the channel is larger than zero and smaller than or equal to the vertical distance from the boundary of the resonance area to the boundary of the piezoelectric layer, and the resonance area is an area corresponding to the electrode structure on the piezoelectric layer.
2. The acoustic resonator according to claim 1,
the electrode structure includes an upper electrode disposed on an upper surface of the piezoelectric layer and a lower electrode disposed between the piezoelectric layer and the acoustic reflection structure.
3. The acoustic resonator according to claim 2, wherein the channel is a recessed area of the piezoelectric layer disposed around the upper electrode, and is in an open loop or a closed loop shape.
4. The acoustic resonator according to claim 2, further comprising: and the protruding structure is arranged at the edge of the upper electrode, and the protruding structure surrounds the edge of the upper electrode to form a closed loop shape.
5. The acoustic resonator according to claim 1, further comprising: and the deceleration layer is used for filling the channel.
6. The acoustic resonator according to claim 1, wherein the electrode structure is an interdigital transducer.
7. The acoustic resonator of claim 1, wherein the acoustic reflection structure is: a cavity structure; or a bragg reflector.
8. The acoustic resonator according to claim 7, wherein the bragg reflective layers are composed of alternating layers of high acoustic impedance and low acoustic impedance;
the thickness of the low-sound impedance layer is one fourth of the sound wave wavelength of the material of the low-sound impedance layer at the design frequency of the resonator, and the thickness of the high-sound impedance layer is one fourth of the sound wave wavelength of the material of the high-sound impedance layer at the design frequency of the resonator.
9. The acoustic resonator according to claim 7, wherein the bragg reflective layer has the low acoustic impedance layer as a topmost layer.
10. An acoustic wave filter comprising the acoustic wave resonator according to any one of claims 1 to 9.
CN202210231010.0A 2022-03-10 2022-03-10 Acoustic wave resonator and filter Pending CN114614792A (en)

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CN116032236A (en) * 2023-02-15 2023-04-28 成都频岢微电子有限公司 Bulk acoustic wave ear-shaped channel resonator
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