CN118249775B - Acoustic wave resonator - Google Patents
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- CN118249775B CN118249775B CN202410668018.2A CN202410668018A CN118249775B CN 118249775 B CN118249775 B CN 118249775B CN 202410668018 A CN202410668018 A CN 202410668018A CN 118249775 B CN118249775 B CN 118249775B
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Abstract
The application provides an acoustic wave resonator, which is positioned on a release layer at one side of a substrate; a piezoelectric layer located on a side of the release layer away from the substrate; the tangential direction of the piezoelectric layer is X tangential direction; a cavity penetrating the release layer, the cavity part being located in the substrate, an outlet of the cavity penetrating the piezoelectric layer; a plurality of interdigital electrodes symmetrically arranged on the upper and lower surfaces of the piezoelectric layer; the ratio of the horizontal wavelength to the thickness wavelength is greater than or equal to 1 and less than or equal to 2; the included angle formed by the horizontal electric field direction formed by the interdigital electrodes and the +y axis direction under the coordinate system of the piezoelectric layer is used as the Euler angle, and the value range is [ -90 degrees, 90 degrees ]. The ratio of the horizontal wavelength to the thickness wavelength of the acoustic wave resonator is greater than or equal to 1 and less than or equal to 2. The Euler angle is within the range of [ -90 DEG, 90 DEG ]. The upper and lower interdigital electrodes excite horizontal and thickness-direction electric fields to form at least two coupling modes of first-order or multi-order and mutually orthogonal polarization. And the electromechanical coupling coefficient of the acoustic wave resonator is improved, and the large-bandwidth coupling mode resonator is realized.
Description
Technical Field
The application relates to the technical field of resonators, in particular to an acoustic wave resonator.
Background
Positive-valued cellular wireless communication technology is also rapidly adopting and commercializing the new Wi-Fi7 (seventh Generation wireless network communication technology, 7th Generation Wi-Fi) standard in the field of wireless local area networks (WLAN, wireless Local Area Network) when evolving from 5G (fifth Generation mobile communication technology, 5th Generation Mobile Communication Technology) to 5G-Advanced (enhanced fifth Generation mobile communication technology, 5th Generation Mobile Communication Technology Advanced) and 6G (sixth Generation mobile communication technology, 6th Generation Mobile Communication Technology).
The international consensus achieved at present is to make full use of the Frequency spectrum of the Radio Frequency (RF) of 6 GHz: for example, the n104 band (6425-7125 MHz) has been standardized by 3GPP (3 rd Generation Partnership Project, third generation partnership project), while in many countries the entire 6 GHz band (5925-7125 MHz) is beginning to be used for unlicensed Wi-Fi connections. In addition, the millimeter wave (MILLIMETER WAVE) spectrum of 6G will also be a very potential resource for future wireless communications, with a frequency range from 5 to 15 GHz guaranteeing a combination of good coverage and large bandwidth for high speed data propagation.
With the increasing frequency and relative bandwidth (FBW, fractional Band width), the evolving wireless communications need to be shifted to higher frequency bands and wider bandwidths to achieve faster data rates.
Since the electromechanical coupling coefficient (k 2) is one of important indexes for measuring the performances of the filter and the resonator, the high electromechanical coupling coefficient can ensure that the filter has enough passband bandwidth, so that the transmission of larger data volume can be realized.
The requirement of a large bandwidth for a radio frequency filter places very high demands on the electromechanical coupling coefficient (k 2) of the acoustic wave resonator, i.e. at least twice the relative bandwidth, e.g. the n77 band requires at least 48% of k 2. Thus, a series of techniques for increasing the electromechanical coupling coefficient at GHz frequencies arose, such as preparing first order antisymmetric lamb wave resonators on a Z-cut or 128 ° Y-cut lithium niobate substrate, which can achieve a high coupling resonator with an electromechanical coupling coefficient greater than 46% at 3.2 GHz; and the symmetrical mode S0 and horizontal shearing mode SH0 acoustic wave resonators with electromechanical coupling coefficients exceeding 30% and 35% are realized by utilizing the X-cut lithium niobate.
However, as a part of the vibration mode frequency of the first-order antisymmetric lamb wave is determined by the thickness of the piezoelectric film, the difficulty of preparing the first-order antisymmetric lamb wave resonator at the ultrathin piezoelectric film with higher frequency is great; there are a series of problems that the S0, SH0 mode cannot be applied to high frequencies, etc., and finally the above resonator is expected to be commercially heavy and far away at high frequencies.
Therefore, how to realize a high-frequency large-bandwidth coupling mode acoustic wave resonator is a technical problem to be solved in the field.
Disclosure of Invention
In view of the above, this summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
The application aims to provide an acoustic wave resonator which can realize high-frequency large-bandwidth coupling mode acoustic wave resonators.
In order to achieve the above purpose, the application has the following technical scheme:
The embodiment of the application provides an acoustic wave resonator, which comprises:
A substrate;
a release layer located on one side of the substrate;
A piezoelectric layer located on a side of the release layer away from the substrate; the tangential direction of the piezoelectric layer is X tangential direction;
A cavity extending through the release layer, the cavity portion being located in the substrate, an outlet of the cavity extending through the piezoelectric layer;
a plurality of interdigital electrodes which are symmetrically arranged and are positioned on the upper surface and the lower surface of the piezoelectric layer;
Taking the sum of twice the width of the interdigital electrode and twice the interval between adjacent interdigital electrodes as a horizontal wavelength; taking twice the thickness of the piezoelectric layer as a thickness wavelength; the ratio of the horizontal wavelength to the thickness wavelength is greater than or equal to 1 and less than or equal to 2;
Taking an included angle formed by the horizontal electric field direction formed by the interdigital electrode and the +y axis direction under the coordinate system of the piezoelectric layer as an Euler angle; the value range of the Euler angle is [ -90 degrees, 90 degrees ].
In one possible implementation, the euler angle has a value in the range of [ -20 °,20 ° ] or [ -80 °, -40 ° ].
In one possible implementation, the euler angle is 0 °, and the ratio of the horizontal wavelength and the thickness wavelength is equal to 1.
In one possible implementation, the euler angle is-50 °, and the ratio of the horizontal wavelength to the thickness wavelength is equal to 1.5.
In one possible implementation, the material of the piezoelectric layer includes one of:
lithium niobate;
Lithium tantalate;
A composite layer material composed of lithium niobate and one or more selected from aluminum nitride, scandium-doped aluminum nitride and zinc oxide;
And a composite layer material composed of lithium tantalate and one or more selected from aluminum nitride, scandium-doped aluminum nitride and zinc oxide.
In one possible implementation, the material of the interdigital electrode is gold, silver, copper, aluminum, molybdenum, chromium, nickel, platinum, or an alloy composed of titanium gold, titanium aluminum, chromium gold, and chromium aluminum.
In one possible implementation, the number of interdigital electrodes ranges from [2, 500 ];
The thickness range of the interdigital electrode is [5, 500] nm;
The width range of the interdigital electrode is [0.001,5] mu m;
The length of the interdigital electrode ranges from [1, 500] mu m.
In one possible implementation, the release layer is one or more layers, and the material of each layer includes any one of silicon dioxide, silicon nitride, lithium niobate, and silicon;
the thickness of the release layer ranges from [0.01, 100] μm.
In one possible implementation, the material of the substrate includes one of: silicon, glass, quartz, sapphire, gallium nitride, and silicon carbide.
Compared with the prior art, the embodiment of the application has the following beneficial effects:
The embodiment of the application provides an acoustic wave resonator, which comprises: a substrate; a release layer located on one side of the substrate; a piezoelectric layer located on a side of the release layer away from the substrate; the tangential direction of the piezoelectric layer is X tangential direction; a cavity penetrating the release layer, the cavity part being located in the substrate, an outlet of the cavity penetrating the piezoelectric layer; a plurality of interdigital electrodes symmetrically arranged on the upper and lower surfaces of the piezoelectric layer; taking the sum of twice the width of the interdigital electrodes and twice the spacing of adjacent interdigital electrodes as a horizontal wavelength; taking twice the thickness of the piezoelectric layer as a thickness wavelength; the ratio of the horizontal wavelength to the thickness wavelength is greater than or equal to 1 and less than or equal to 2; taking an included angle formed by the horizontal electric field direction formed by the interdigital electrodes and the +y axis direction under the coordinate system of the piezoelectric layer as an Euler angle; the Euler angle is within the range of [ -90 DEG, 90 DEG ]. The ratio of the horizontal wavelength to the thickness wavelength of the acoustic wave resonator is greater than or equal to 1 and less than or equal to 2. Meanwhile, the value range of the Euler angle is controlled to be [ -90 degrees, 90 degrees ]. The upper and lower interdigital electrodes excite horizontal and thickness electric fields to form at least two coupling modes of one or more orders and mutually orthogonal polarization, wherein the coupling modes at least comprise one shearing mode. The electromechanical coupling coefficient of the acoustic wave resonator is improved, and the large-bandwidth coupling mode resonator with the working frequency from tens of MHz to tens of GHz is realized.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are some embodiments of the application and that other drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
The above and other features, advantages, and aspects of embodiments of the present disclosure will become more apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings. The same or similar reference numbers will be used throughout the drawings to refer to the same or like elements. It should be understood that the figures are schematic and that elements and components are not necessarily drawn to scale.
Fig. 1 shows a schematic diagram of an acoustic wave resonator according to an embodiment of the present application.
Fig. 2 shows a three-dimensional schematic diagram of a euler angle α rotation provided by an embodiment of the present application;
FIG. 3 is a schematic cross-sectional view of a coupling mode resonator with a ratio of horizontal wavelength to thickness wavelength of 1/1 according to an embodiment of the present application;
FIG. 4 is a schematic view showing the tangential polarization displacement of a coupled mode resonator in which two first-order shear modes act together when the ratio of the horizontal wavelength to the thickness wavelength is 1/1 according to the embodiment of the present application;
FIG. 5 shows a simulated admittance curve of a coupled mode resonator operating at 2.4 GHz for a combined action of two first order shear modes for a horizontal wavelength to thickness wavelength ratio of 1/1 provided by an embodiment of the present application;
FIG. 6 shows a simulated admittance curve of a coupled mode resonator operating at 5 GHz with a combined action of two first order shear modes for a horizontal wavelength to thickness wavelength ratio of 1/1 provided by an embodiment of the present application;
FIG. 7 is a schematic cross-sectional view of a coupling mode resonator with a ratio of 3/2 of horizontal wavelength to thickness wavelength and a horizontal wavelength of 0.69 μm according to an embodiment of the present application;
FIG. 8 is a schematic view showing the polarization displacement of the section of a coupled mode resonator in which a first-order horizontal mode and a first-order shear mode act together when the ratio of the horizontal wavelength to the thickness wavelength is 3/2, according to an embodiment of the present application;
FIG. 9 shows simulated admittance curves for a coupled mode resonator having a first order horizontal mode and a first order shear mode acting together at a ratio of horizontal wavelength to thickness wavelength of 3/2 provided by embodiments of the present application;
FIG. 10 is a schematic cross-sectional view of a coupling mode resonator with a ratio of 3/2 of horizontal wavelength to thickness wavelength and 0.4 μm horizontal wavelength according to an embodiment of the present application;
FIG. 11 is a schematic view showing the polarization displacement of the section of a coupled mode resonator in which a first-order horizontal mode and a third-order shear mode act together when the ratio of the horizontal wavelength to the thickness wavelength is 3/2, according to the embodiment of the present application;
FIG. 12 shows simulated admittance curves for a coupled mode resonator with a first order horizontal mode and a third order shear mode acting together at a ratio of horizontal wavelength to thickness wavelength of 3/2 provided by embodiments of the present application.
Detailed Description
It should be noted that the acoustic wave resonator provided by the invention can be applied to the technical field of resonators. The foregoing is merely exemplary, and is not intended to limit the application field of the acoustic wave resonator provided by the present invention.
Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure have been shown in the accompanying drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are for illustration purposes only and are not intended to limit the scope of the present disclosure.
The term "including" and variations thereof as used herein are intended to be open-ended, i.e., including, but not limited to. The term "based on" is based at least in part on. The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments. Related definitions of other terms will be given in the description below.
It should be noted that the terms "first," "second," and the like in this disclosure are merely used to distinguish between different devices, modules, or units and are not used to define an order or interdependence of functions performed by the devices, modules, or units.
It should be noted that references to "one", "a plurality" and "a plurality" in this disclosure are intended to be illustrative rather than limiting, and those of ordinary skill in the art will appreciate that "one or more" is intended to be understood as "one or more" unless the context clearly indicates otherwise.
As described in the background art, the field of wireless local area networks (WLAN, wireless Local Area Network) is rapidly adopting and commercializing a new Wi-Fi7 (seventh Generation wireless network communication technology, 7th Generation Wi-Fi) standard upon development of positive-valued cellular wireless communication technology from 5G (fifth Generation mobile communication technology, 5th Generation Mobile Communication Technology) to 5G-Advanced (enhanced version of fifth Generation mobile communication technology, 5th Generation Mobile Communication Technology Advanced) and 6G (sixth Generation mobile communication technology, 6th Generation Mobile Communication Technology) as well as research by the applicant.
The international consensus achieved at present is to make full use of the Frequency spectrum of the Radio Frequency (RF) of 6 GHz: for example, the n104 band (6425-7125 MHz) has been standardized by 3GPP (3 rd Generation Partnership Project, third generation partnership project), while in many countries the entire 6 GHz band (5925-7125 MHz) is beginning to be used for unlicensed Wi-Fi connections. In addition, the millimeter wave (MILLIMETER WAVE) spectrum of 6G will also be a very potential resource for future wireless communications, with a frequency range from 5 to 15 GHz guaranteeing a combination of good coverage and large bandwidth for high speed data propagation.
With the increasing frequency and relative bandwidth (FBW, fractional Band width), the evolving wireless communications need to be shifted to higher frequency bands and wider bandwidths to achieve faster data rates.
Since the electromechanical coupling coefficient (k 2) is one of important indexes for measuring the performances of the filter and the resonator, the high electromechanical coupling coefficient can ensure that the filter has enough passband bandwidth, so that the transmission of larger data volume can be realized.
The requirement of a large bandwidth for a radio frequency filter places very high demands on the electromechanical coupling coefficient (k 2) of the acoustic wave resonator, i.e. at least twice the relative bandwidth, e.g. the n77 band requires at least 48% of k 2. Thus, a series of techniques for increasing the electromechanical coupling coefficient at GHz frequencies arose, such as preparing first order antisymmetric lamb wave resonators on a Z-cut or 128 ° Y-cut lithium niobate substrate, which can achieve a high coupling resonator with an electromechanical coupling coefficient greater than 46% at 3.2 GHz; and the symmetrical mode S0 and horizontal shearing mode SH0 acoustic wave resonators with electromechanical coupling coefficients exceeding 30% and 35% are realized by utilizing the X-cut lithium niobate.
However, as a part of the vibration mode frequency of the first-order antisymmetric lamb wave is determined by the thickness of the piezoelectric film, the difficulty of preparing the first-order antisymmetric lamb wave resonator at the ultrathin piezoelectric film with higher frequency is great; there are a series of problems that the S0, SH0 mode cannot be applied to high frequencies, etc., and finally the above resonator is expected to be commercially heavy and far away at high frequencies.
Therefore, how to realize a high-frequency large-bandwidth coupling mode acoustic wave resonator is a technical problem to be solved in the field.
In order to solve the above technical problems, an embodiment of the present application provides an acoustic wave resonator, including: a substrate; a release layer located on one side of the substrate; a piezoelectric layer located on a side of the release layer away from the substrate; the tangential direction of the piezoelectric layer is X tangential direction; a cavity penetrating the release layer, the cavity part being located in the substrate, an outlet of the cavity penetrating the piezoelectric layer; a plurality of interdigital electrodes symmetrically arranged on the upper and lower surfaces of the piezoelectric layer; taking the sum of twice the width of the interdigital electrodes and twice the spacing of adjacent interdigital electrodes as a horizontal wavelength; taking the thickness of the piezoelectric layer as a thickness wavelength; the ratio of the horizontal wavelength to the thickness wavelength is greater than or equal to 1 and less than or equal to 2; taking an included angle formed by the horizontal electric field direction formed by the interdigital electrodes and the +y axis direction under the coordinate system of the piezoelectric layer as an Euler angle; the Euler angle is within the range of [ -90 DEG, 90 DEG ]. The ratio of the horizontal wavelength to the thickness wavelength of the acoustic wave resonator is greater than or equal to 1 and less than or equal to 2. Meanwhile, the value range of the Euler angle is controlled to be [ -90 degrees, 90 degrees ]. The upper and lower interdigital electrodes excite horizontal and thickness electric fields to form at least two coupling modes of one or more orders and mutually orthogonal polarization, wherein the coupling modes at least comprise one shearing mode. The electromechanical coupling coefficient of the acoustic wave resonator is improved, and the large-bandwidth coupling mode resonator with the working frequency from tens of MHz to tens of GHz is realized.
Referring to fig. 1, a schematic diagram of an acoustic wave resonator according to an embodiment of the present application includes:
a substrate 1; a release layer 2 located on one side of the substrate 1; a piezoelectric layer 3 located on a side of the release layer 2 remote from the substrate 1; the tangential direction of the piezoelectric layer 3 is X tangential direction.
A cavity 5 penetrating the release layer 2, the cavity 5 being partially located in the substrate 1, an outlet of the cavity 5 penetrating the piezoelectric layer 3; a plurality of interdigital electrodes 4 symmetrically disposed on the upper and lower surfaces of the piezoelectric layer 3.
The sum of twice the width of the interdigital electrode 4 and twice the pitch of the adjacent interdigital electrodes 4 is taken as the horizontal wavelength; Taking twice the thickness of the piezoelectric layer 3 as a thickness wavelength lambda y; horizontal wavelengthAnd the thickness wavelength lambda y is greater than or equal to 1 and less than or equal to 2.
Referring to fig. 2, a three-dimensional schematic diagram of a rotation of an euler angle α according to an embodiment of the present application is shown.
According to the embodiment of the application, the included angle formed by the horizontal electric field direction +y' formed by the interdigital electrode 4 and the +y axis direction under the coordinate system of the piezoelectric layer 3 can be used as the Euler angle alpha; the Euler angle alpha has a value range of [ -90 DEG, 90 DEG ].
Namely, in order to obtain the acoustic wave resonator with high frequency and large bandwidth, the embodiment of the application can design horizontal wavelengthThe ratio of the thickness wavelength lambda y to the thickness wavelength lambda y is more than or equal to 1 and less than or equal to 2, the cross polarization of the upper interdigital electrode and the lower interdigital electrode is adopted, the specific tangential piezoelectric film, the specific Euler angle [ -90 DEG, 90 DEG ] and the coupling modes of at least two first-order or multi-order and mutually orthogonal polarization in the specific propagation direction at least comprise one shearing mode, the electromechanical coupling coefficient of the acoustic wave resonator is improved, and the large-bandwidth coupling mode resonator with the working frequency from tens of MHz to tens of GHz is realized.
Specifically, the material of the substrate 1 provided in the embodiment of the present application may include one of the following: silicon, glass, quartz, sapphire, gallium nitride, and silicon carbide.
The material of the piezoelectric layer 3 may include one of the following: lithium Niobate (LN), lithium Tantalate (LT), composite layer material composed of lithium niobate and one or more selected from aluminum nitride, scandium-doped aluminum nitride and zinc oxide, composite layer material composed of lithium tantalate and one or more selected from aluminum nitride, scandium-doped aluminum nitride and zinc oxide. According to an embodiment of the present invention, the thickness of the piezoelectric layer 3 may be 50 nm to 300 nm; for example, the thickness of the piezoelectric layer 3 may be 50 nm, 100 nm, 200 nm, 210 nm, 220 nm, 240 nm, 250 nm, 270 nm, 300 nm.
The anisotropic piezoelectric material provided by the embodiment of the application has rich piezoelectric coefficient (e), relative dielectric constant (ɛ) and elastic coefficient (c), and the physical parameters can be further changed by adjusting the tangential direction, euler angle and propagation direction of the crystal. When the tangential direction and the Euler angle of the crystal are highly uniform, polarization modes with different phase velocities can appear in specific propagation directions, and each mode can work at the same frequency, so that coupling is realized, and a higher electromechanical coupling coefficient is obtained. Thus, the present application is achieved by designing the horizontal wavelengthAnd the ratio of the thickness wavelength lambda y is equal to that of the coupling mode resonator, and the upper interdigital electrode and the lower interdigital electrode are adopted for cross polarization, so that a plurality of acoustic wave modes are well coupled, and the coupling mode resonator with large bandwidth is realized.
Optionally, in order to further improve the electromechanical coupling coefficient of the acoustic wave resonator, the embodiment of the present application may set the range of values of euler angles to [ -20 °,20 ° ] or [ -80 °, -40 ° ].
In one possible implementation, referring to fig. 3, a schematic cross-sectional view of a coupling mode resonator with a ratio of horizontal wavelength to thickness wavelength of 1/1 is provided in an embodiment of the present application.
I.e. in the embodiment of the application, the Euler angle can be set to 0 DEG, the horizontal wavelengthWhen the ratio of the thickness wavelength lambda y is 1/1 and is equal to 2.08 mu m or 0.94 mu m, the two first-order shearing modes can jointly act to realize a coupling mode resonator with the electromechanical coupling coefficient of 40% and 2.4 GHz or 5 GHz.
Specifically, referring to fig. 4, a schematic diagram of the tangential polarization displacement of a coupling mode resonator under the combined action of two first-order shearing modes is shown when the ratio of the horizontal wavelength to the thickness wavelength is 1/1.
The polarization displacement of the coupling mode, in which the two first-order shearing modes act together, is in-plane shearing (in the length direction of the electrode), and the periodicity of the first-order modes is exhibited in the horizontal and thickness directions.
Referring to fig. 5, a simulation admittance curve of 2.4 GHz is shown for a coupling mode resonator with two first-order shearing modes acting together when the ratio of the horizontal wavelength to the thickness wavelength is 1/1. In FIG. 5, the Frequency (Frequency/GHz) is on the abscissa and the admittance (ADMITTANCE/dB) is on the ordinate.
In fig. 5, the frequency of the coupling mode resonator under the combined action of the two first-order shearing modes is 2.4 GHz, the electromechanical coupling coefficient is greater than 40%, and the large-bandwidth coupling mode resonator is realized. The electromechanical coupling coefficient k 2 can be calculated by the following formula:
k2=(π2/4)×(1-/fp)
Wherein f p is the frequency of the lowest point of the admittance of the simulated admittance curve (parallel resonance frequency), The frequency of the highest point of the admittance curve (series resonance frequency) is simulated.
In one possible implementation, referring to fig. 6, a coupling mode resonator with two first order shear modes acting together operates at a simulated admittance curve of 5 GHz when the ratio of horizontal wavelength to thickness wavelength is 1/1, which is provided for embodiments of the present application.
The coupling mode resonator frequency of the combined action of the two first-order shearing modes can be 5 GHz, and the electromechanical coupling coefficient is more than 40%.
In one possible implementation, referring to fig. 7, a schematic cross-sectional view of a coupling mode resonator with a ratio of a horizontal wavelength to a thickness wavelength of 3/2 and a horizontal wavelength of 0.69 μm is provided in an embodiment of the present application.
The tangential direction of the piezoelectric layer can be X-cut lithium niobate, the Euler angle is-50 DEG, and the horizontal wavelength is the sameWhen the ratio of the thickness wavelength lambda y to the thickness wavelength lambda y is 3/2 and the horizontal wavelength is equal to 0.69 mu m, a coupling mode resonator with 7.87 GHz and an electromechanical coupling coefficient of 35% can be realized by the combined action of a first-order horizontal mode and a first-order shearing mode.
Specifically, referring to fig. 8, a schematic diagram of the tangential polarization displacement of a coupling mode resonator under the combined action of a first-order horizontal mode and a first-order shearing mode is shown when the ratio of the horizontal wavelength to the thickness wavelength is 3/2.
The arrow direction in the figure represents the tangential polarization displacement direction of the resonator, i.e., the acoustic vibration direction. The polarization displacement of the coupling mode which is acted by a first-order horizontal mode and a first-order shearing mode is shearing in the horizontal and thickness directions, and the periodicity of the first-order mode is shown in the horizontal and thickness directions.
Referring to fig. 9, a simulated admittance curve of a coupling mode resonator with a first order horizontal mode and a first order shear mode acting together is provided for an embodiment of the present application with a ratio of horizontal wavelength to thickness wavelength of 3/2.
The coupling mode resonator of fig. 9, in which a first-order horizontal mode and a first-order shearing mode cooperate, has a frequency of 7.87 GHz, and an electromechanical coupling coefficient of greater than 35%, so that a large-bandwidth coupling mode resonator is realized.
In one possible implementation, referring to fig. 10, a schematic cross-sectional view of a coupling mode resonator with a ratio of a horizontal wavelength to a thickness wavelength of 3/2 and a horizontal wavelength of 0.4 μm is provided in an embodiment of the present application.
The tangential direction of the piezoelectric layer can be X-cut lithium niobate, the Euler angle is-50 DEG, and the horizontal wavelength is the sameA ratio to the thickness wavelength lambda y of 3/2, and a horizontal wavelengthWhen the coupling mode resonator is equal to 0.69 mu m, a coupling mode resonator with 7.87 GHz and an electromechanical coupling coefficient of 35% can be realized by the combined action of a first-order horizontal mode and a first-order shearing mode.
Referring to fig. 11, a schematic diagram of the tangential polarization displacement of a coupling mode resonator with a first-order horizontal mode and a third-order shearing mode acting together is shown when the ratio of the horizontal wavelength to the thickness wavelength is 3/2.
The arrow direction in the figure represents the tangential polarization displacement direction of the resonator, i.e., the acoustic vibration direction. The polarization displacement of the coupling mode under the combined action of the first-order horizontal mode and the third-order shearing mode provided by the embodiment of the application is shearing in the horizontal and thickness directions, and the polarization displacement of the coupling mode shows the periodicity of the first-order mode in the horizontal direction and the periodicity of the third-order mode in the thickness direction.
Referring to fig. 12, a simulated admittance curve of a coupling mode resonator with a first order horizontal mode and a third order shear mode acting together is provided for an embodiment of the present application when the ratio of the horizontal wavelength to the thickness wavelength is 3/2.
In fig. 12, the frequency of the coupling mode resonator which is jointly acted by a first-order horizontal mode and a third-order shearing mode is 10.2 GHz, and the electromechanical coupling coefficient is greater than 24%, so that the large-bandwidth coupling mode resonator is realized.
As can be seen from the description, in the large-bandwidth coupling mode resonator provided by the technical scheme of the invention, when the tangential direction of the piezoelectric layer is X-cut lithium niobate, the Euler angle is-20 degrees or-80-40 degrees, and the horizontal wavelength is the same as that of the piezoelectric layerWhen the ratio of the thickness wavelength lambda y to the thickness wavelength lambda y is more than or equal to 1 and less than or equal to 2, the upper interdigital electrode and the lower interdigital electrode excite the horizontal electric field and the thickness direction electric field to form at least two coupling modes of one or more orders and mutually orthogonal polarization, wherein the coupling modes at least comprise one shearing mode, so that the large-bandwidth coupling mode resonator with the working frequency from tens of MHz to tens of GHz is realized, and the performance requirements of the current GHz frequency band on the high frequency and the large bandwidth of the filter can be well met.
Alternatively, the material of the interdigital electrode 4 provided in the embodiment of the present application may be gold, silver, copper, aluminum, molybdenum, chromium, nickel, platinum, or an alloy composed of titanium gold, titanium aluminum, chromium gold and chromium aluminum. The interdigital electrode 4 is an electrode having a periodic pattern in a plane such as a finger or comb.
The number of the interdigital electrodes 4 is in the range of [2, 500 ]; the thickness range of the interdigital electrode 4 is [5, 500] nm; the width range of the interdigital electrode 4 is [0.001,5] mu m; the length of the interdigital electrode 4 ranges from [1, 500] μm.
Optionally, the release layer 2 provided in the embodiment of the present application may be one or more layers, and the material of each layer includes any one of silicon dioxide, silicon nitride, lithium niobate, and silicon; the thickness of the release layer 2 may range from 0.01 to 100 μm.
The release layer 2 is adapted to form a cavity 5 to release the space between the substrate 1 and the piezoelectric layer 3 and thereby avoid the substrate 1 from contacting the piezoelectric layer 3.
By forming the cavity 5 between the substrate 1 and the piezoelectric layer 3, since the cavity 5 is an empty space and has an impedance close to infinity, the formation of the cavity 5 can confine the acoustic wave generated in the piezoelectric layer 3, thereby reducing the loss or loss of the acoustic wave.
The above-mentioned horizontal wavelengthThe values of the thickness wavelength lambda y are merely examples, and the specific values are not limited thereto, but may be other specific values, and may be specifically set by those skilled in the art according to actual situations.
The embodiment of the application provides an acoustic wave resonator, which comprises: a substrate; a release layer located on one side of the substrate; a piezoelectric layer located on a side of the release layer away from the substrate; the tangential direction of the piezoelectric layer is X tangential direction; a cavity penetrating the release layer, the cavity part being located in the substrate, an outlet of the cavity penetrating the piezoelectric layer; a plurality of interdigital electrodes symmetrically arranged on the upper and lower surfaces of the piezoelectric layer; taking the sum of twice the width of the interdigital electrodes and twice the spacing of adjacent interdigital electrodes as a horizontal wavelength; taking twice the thickness of the piezoelectric layer as a thickness wavelength; the ratio of the horizontal wavelength to the thickness wavelength is greater than or equal to 1 and less than or equal to 2; taking an included angle formed by the horizontal electric field direction formed by the interdigital electrodes and the +y axis direction under the coordinate system of the piezoelectric layer as an Euler angle; the Euler angle is within the range of [ -90 DEG, 90 DEG ]. The ratio of the horizontal wavelength to the thickness wavelength of the acoustic wave resonator is greater than or equal to 1 and less than or equal to 2. Meanwhile, the value range of the Euler angle is controlled to be [ -90 degrees, 90 degrees ]. The upper and lower interdigital electrodes excite horizontal and thickness electric fields to form at least two coupling modes of one or more orders and mutually orthogonal polarization, wherein the coupling modes at least comprise one shearing mode. The electromechanical coupling coefficient of the acoustic wave resonator is improved, and the large-bandwidth coupling mode resonator with the working frequency from tens of MHz to tens of GHz is realized.
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments.
The foregoing is merely a preferred embodiment of the present application, and the present application has been disclosed in the above description of the preferred embodiment, but is not limited thereto. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present application or modifications to equivalent embodiments using the methods and technical contents disclosed above, without departing from the scope of the technical solution of the present application. Therefore, any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present application still fall within the scope of the technical solution of the present application.
Claims (7)
1. An acoustic wave resonator, comprising:
A substrate;
a release layer located on one side of the substrate;
A piezoelectric layer located on a side of the release layer away from the substrate; the tangential direction of the piezoelectric layer is X tangential direction;
A cavity extending through the release layer, the cavity portion being located in the substrate, an outlet of the cavity extending through the piezoelectric layer;
a plurality of interdigital electrodes which are symmetrically arranged and are positioned on the upper surface and the lower surface of the piezoelectric layer;
taking the sum of twice the width of the interdigital electrode and twice the interval between adjacent interdigital electrodes as a horizontal wavelength; taking twice the thickness of the piezoelectric layer as a thickness wavelength; the ratio of the horizontal wavelength to the thickness wavelength is greater than or equal to 1 and less than or equal to 1.5;
Taking an included angle formed by the horizontal electric field direction formed by the interdigital electrode and the +y axis direction under the coordinate system of the piezoelectric layer as an Euler angle; the Euler angle is in the range of [ -20 degrees, 20 degrees ] or [ -80 degrees, -40 degrees);
The method comprises the steps of sufficiently exciting a specific tangential piezoelectric film, a specific Euler angle, and at least two coupling modes of first order or multiple orders and mutually orthogonal polarization in a specific propagation direction by designing the numerical value of the horizontal wavelength or the thickness wavelength, the ratio of the horizontal wavelength to the thickness wavelength and the Euler angle, wherein at least one shearing mode is included, so as to adjust the working frequency and the electromechanical coupling coefficient of the acoustic wave resonator;
the material of the piezoelectric layer comprises one of the following:
lithium niobate;
Lithium tantalate;
A composite layer material composed of lithium niobate and one or more selected from aluminum nitride, scandium-doped aluminum nitride and zinc oxide;
And a composite layer material composed of lithium tantalate and one or more selected from aluminum nitride, scandium-doped aluminum nitride and zinc oxide.
2. The acoustic wave resonator according to claim 1, characterized in that the euler angle is 0 °, and the ratio of the horizontal wavelength and the thickness wavelength is equal to 1.
3. The acoustic wave resonator according to claim 1, characterized in that the euler angle is-50 °, and the ratio of the horizontal wavelength and the thickness wavelength is equal to 1.5.
4. The acoustic wave resonator according to claim 1, characterized in that the material of the interdigital electrode is gold, silver, copper, aluminum, molybdenum, chromium, nickel, platinum, or an alloy of titanium gold, titanium aluminum, chromium gold and chromium aluminum.
5. The acoustic wave resonator according to claim 1, characterized in that the number of interdigital electrodes ranges from [2, 500 ];
The thickness range of the interdigital electrode is [5, 500] nm;
the width range of the interdigital electrode is [0.001,5] mu m;
the length of the interdigital electrode ranges from [1, 500] mu m.
6. The acoustic wave resonator according to claim 1, characterized in that the release layer is one or more layers, the material of each layer comprising any one of silicon dioxide, silicon nitride, lithium niobate and silicon;
the thickness of the release layer ranges from [0.01, 100] μm.
7. The acoustic wave resonator of claim 1 wherein the material of the substrate comprises one of: silicon, glass, quartz, sapphire, gallium nitride, and silicon carbide.
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