WO2025119255A1 - Elastic wave apparatus - Google Patents

Abstract

An elastic wave apparatus. A piezoelectric layer is configured to be a lithium niobate thin film with an Euler angle of (0°±10°, 122°±10°, 45°±10°) or (0°±10°, 122°±10°, 135°±10°); a conductive-material thin-film pattern is provided on the piezoelectric layer, a low acoustic velocity layer is provided under the piezoelectric layer, and a high acoustic velocity component is provided under the low acoustic velocity layer; when the thickness of the piezoelectric layer is set to be h_LN and the wavelength of an elastic wave is set to be λ, 0.1≤h_LN/λ≤0.3 is satisfied; and when the thickness of the low acoustic velocity layer is set to be h₁ and the wavelength of the elastic wave is set to be λ, 0.1≤h₁/λ≤0.3 is satisfied.

Description

Elastic wave device

This application claims priority to the Chinese patent application filed with the China Patent Office on December 6, 2023, with application number 202311659407.0, the entire contents of which are incorporated by reference into this application.

Technical Field

The present application relates to the field of elastic wave technology, for example, to an elastic wave device with a high Q value and a high operating frequency using a longitudinal leaky acoustic surface wave (LLSAW).

Background Art

Elastic wave devices have the characteristics of low cost, small size and multiple functions, and have been widely used in radar, communication and navigation. The most commonly used elastic wave devices in mobile phone and base station communications are elastic wave resonators, elastic wave filters composed of multiple elastic wave resonators, and elastic wave duplexers and elastic wave multiplexers composed of multiple elastic wave filters. In any type of elastic wave device, a conductive material film pattern is set on a piezoelectric multilayer substrate to determine multiple interdigital transducer electrodes and multiple reflective gate electrodes, and the frequency characteristics of the conversion function of converting the electrical signal of the interdigital transducer electrodes into elastic waves are used to obtain the bandpass characteristics.

Mobile communication systems are developing from the third generation of mobile communication technology (3G), the fourth generation of mobile communication technology (4G) to the fifth generation of mobile communication technology (5G), and their frequency bands are developing towards high frequency and large bandwidth. In order to make the elastic wave element high frequency, the elastic wave wavelength specified by the spacing of the interdigital transducer electrodes can be reduced. The global mobile 5G network deployment has included the sub-6G (below 6GHz) frequency band of 3 to 7 GHz, and the piezoelectric crystal materials such as lithium niobate and lithium tantalate that are currently widely used in the preparation of elastic wave elements have a sound velocity of about 3000 to 4000 meters per second (m/s). It is difficult to produce devices above 3GHz using conventional photolithography technology without significantly increasing costs. In addition, at high frequencies, the interdigital electrodes become narrower and thinner, the electrode ohmic loss increases, the quality factor (Q value) of the device decreases, and the electrode material is easily damaged, which seriously affects the performance and reliability of the device. Therefore, for the high frequency of elastic wave elements, the high sound velocity of elastic waves becomes particularly important.

In order to obtain a higher sound velocity, the industry is trying to use the Longitudinal Leaky Surface Acoustic Wave (LLSAW) as the working mode in elastic wave components. However, the Longitudinal Leaky Surface Acoustic Wave is a mode that propagates while leaking to the substrate containing the piezoelectric layer, so it has a low Q value and cannot meet the requirements of 5G communications for high-frequency and high-performance filters.

However, in the case where the main component of the elastic wave propagating in the elastic wave device disclosed in the Chinese patent application with application number CN112823473A is a longitudinal wave, the Euler angle of the piezoelectric layer does not cover all ranges, and the Q value, parasitic mode and other performance of the elastic wave device are limited by factors such as the electrode material of the interdigital transducer, the device structure and the tangent direction of the substrate material. Therefore, there are disadvantages such as high device manufacturing cost, poor stability and narrow application range.

Summary of the invention

The present application can provide an elastic wave device with a large device Q value and a high operating frequency, thereby solving the problem of too low Q value of longitudinal leaky acoustic surface wave (LLSAW) elastic wave devices.

In a first aspect, the present application provides an elastic wave device, comprising:

A piezoelectric layer, the piezoelectric layer comprising a lithium niobate film having an Euler angle of (0°±10°, 122°±10°, 45°±10°) or (0°±10°, 122°±10°, 135°±10°), and the piezoelectric layer having a first main surface and a second main surface opposite to each other;

an IDT electrode and a reflective gate electrode, wherein the IDT electrode and the reflective gate electrode are directly or indirectly formed on the first main surface, and the IDT electrode and the reflective gate electrode are made of a heavy metal material;

a low acoustic velocity layer, the low acoustic velocity layer being directly or indirectly formed on the second main surface; and

A high sound velocity component, wherein the high sound velocity component is located below the low sound velocity layer;

When the thickness of the piezoelectric layer is set to h _LN and the wavelength of the elastic wave is set to λ, 0.1≤h _LN /λ≤0.3 is satisfied; when the thickness of the low acoustic velocity layer is set to h ₁ and the wavelength of the elastic wave is set to λ, 0.1≤h ₁ /λ≤0.3 is satisfied.

In a second aspect, the present application provides an elastic wave filter or multiplexer, comprising a resonator located on a series arm and a resonator located on a parallel arm, wherein at least one of the resonators adopts any of the elastic wave devices described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide an understanding of the present application and constitute a part of the specification, and together with the embodiments of the present application, are used to explain the present application. In the accompanying drawings:

FIG1 shows a schematic plan view and a cross-sectional view of a typical surface acoustic wave (SAW) resonator 100;

FIG2 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application;

FIG3 shows a vibration mode diagram of two different acoustic modes in the piezoelectric layer of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application, and a diagram showing the variation of the frequencies corresponding to the two different acoustic modes with the wavelength;

FIG4 shows a graph showing the piezoelectric coupling coefficients of two different acoustic modes in the piezoelectric layer of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application as the Euler angles of the piezoelectric layer change;

FIG5 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application;

FIG6 shows a frequency response diagram of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in the first embodiment of the present application;

FIG. 7 shows a frequency response diagram of another elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application;

FIG8 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 300 provided in Comparative Example 1 of the present application;

FIG9 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 300 provided in Comparative Example 1 of the present application;

FIG10 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 400 provided in Comparative Example 2 of the present application;

FIG. 11 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 400 provided in Comparative Example 2 of the present application;

FIG12 is a comparison diagram showing the displacement of the LLSAW mode in the supporting substrate of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application and the elastic wave device (longitudinal wave type leaky surface wave resonator) 300 provided in Comparative Example 1 as a function of the depth (thickness) of the supporting substrate;

FIG. 13 shows a frequency response curve of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application as the propagation angle ψ of the piezoelectric layer changes;

FIG14 shows a graph of the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application as the piezoelectric layer propagation angle ψ changes;

FIG. 15 shows frequency response curves of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 of conductive material film patterns of different materials and thicknesses;

FIG. 16 shows a frequency response curve of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 of conductive material thin film patterns of different materials and thicknesses;

FIG. 17 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 500 provided in Comparative Example 3 of the present application;

FIG18 shows a frequency response comparison diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application and an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 500 provided in Comparative Example 3;

FIG19 shows a frequency response comparison diagram of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application and another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 500 provided in Comparative Example 3;

FIG20 shows a comparison of frequency responses of an elastic wave device (a longitudinal wave type leaky acoustic surface wave resonator) 200 with different piezoelectric layer thicknesses;

FIG. 21 shows a trend diagram of the electromechanical coupling coefficient of an elastic wave device (a longitudinal wave type leaky acoustic surface wave resonator) 200 with different piezoelectric layer thicknesses;

FIG22 shows a comparison of the frequency responses of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 with different low acoustic velocity layer thicknesses;

FIG23 shows a trend diagram of the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with different low acoustic velocity layer thicknesses;

FIG. 24 is a graph showing a comparison of frequency responses of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 (h _{LiNbO 3} /λ=0.1) with different supporting substrates;

FIG. 25 is a graph showing a comparison of frequency responses of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 (h _{LiNbO 3} /λ=0.15) with different supporting substrates;

FIG. 26 is a graph showing a comparison of frequency responses of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 (h _{LiNbO 3} /λ=0.2) with different supporting substrates;

FIG. 27 is a graph showing a comparison of frequency responses of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 (h _{LiNbO 3} /λ=0.3) with different supporting substrates;

FIG28 shows a measured frequency response and Q value curve of an elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application;

FIG29 shows a measured frequency response and Q value curve of another elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application;

FIG30 shows the measured frequency response of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application and the vibration mode diagram corresponding to its transverse mode;

FIG31 shows a schematic diagram of an inclined interdigital transducer electrode 600;

FIG32 shows a graph of measured frequency responses of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with different β values, as well as a graph of measured impedance ratio and Q value trends;

FIG33 shows a 5G communication-WIFI6/7 frequency band diagram;

FIG34 shows a schematic diagram of the topological structure of an elastic wave device (longitudinal wave type leaky surface wave resonator) provided in Embodiment 2 of the present application;

FIG35 shows a measured frequency response diagram of an elastic wave device (longitudinal wave type leaky surface wave resonator) provided in Embodiment 2 of the present application;

FIG36 shows a measured frequency response diagram of another elastic wave device (longitudinal wave type leaky surface wave resonator) provided in Embodiment 2 of the present application;

FIG37 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 700 provided in the first variant of the present application;

FIG38 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 800 provided in the second variation of the present application;

FIG39 shows a cross-sectional view of an elastic wave device (longitudinal-wave type leaky surface wave resonator) 900 provided in a third variation of the present application.

DETAILED DESCRIPTION

The following will describe the embodiments of the present application in conjunction with the drawings in the embodiments of the present application, and the described embodiments are some embodiments related to the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

Among them, the same parts are represented by the same figure marks. The words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom surface" and "top surface", "inside" and "outside" refer to the direction towards or away from a specific component, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application specification, the meaning of "multiple" is two or more.

The embodiment of the present application provides an elastic wave device, comprising: a piezoelectric layer, the piezoelectric layer comprises a lithium niobate film having an Euler angle of (0°±10°, 122°±10°, 45°±10°) or (0°±10°, 122°±10°, 135°±10°), and the piezoelectric layer has a first main surface and a second main surface opposite to each other; an interdigital transducer electrode and a reflection gate electrode, the interdigital transducer electrode and the reflection gate electrode are directly or indirectly formed on the first main surface, and the interdigital transducer electrode and the reflection gate electrode are made of a heavy metal material; a low sound velocity layer, the low sound velocity layer is directly or indirectly formed on the second main surface; and a high sound velocity component, the high sound velocity component is located below the low sound velocity layer;

When the thickness of the piezoelectric layer is set to h _LN and the wavelength of the elastic wave is set to λ, 0.1≤h _LN /λ≤0.3 is satisfied; when the thickness of the low acoustic velocity layer is set to h ₁ and the wavelength of the elastic wave is set to λ, 0.1≤h ₁ /λ≤0.3 is satisfied.

In some embodiments, the front side of the piezoelectric layer is the first main side, and the back side of the piezoelectric layer is the second main side. Exemplarily, FIG2 shows the first main side 2011 of the piezoelectric layer and the second main side 2012 of the piezoelectric layer.

In some embodiments, the acoustic velocity of the bulk wave propagating in the high acoustic velocity member is higher than the acoustic velocity of the bulk wave propagating in the piezoelectric layer.

In some embodiments, the high acoustic speed component includes: a supporting substrate, which is configured to support the low acoustic speed layer; or, the high acoustic speed component includes: a supporting substrate and a capture material layer, which is configured between the supporting substrate and the low acoustic speed layer, and the capture material layer is configured to support the low acoustic speed layer.

In some embodiments, the support substrate is composed of one or more materials having a sound velocity exceeding 6000 m/s.

In some embodiments, the low acoustic velocity layer is made of one or more of silicon dioxide, glass, silicon oxynitride, tantalum oxide, or silicon oxide added with a compound mainly composed of fluorine, carbon, or boron.

In some embodiments, the trapping material layer is formed of one or more combinations of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium.

In some embodiments, under the premise that the thickness of the capture material layer is set to h ₂ and the wavelength of the elastic wave is set to λ, 0.1≤(h ₂ +h ₁ )/λ≤0.3 is satisfied.

In some embodiments, the heavy metal material is composed of one or more of copper, platinum, tungsten, gold, silver, molybdenum, and tantalum.

In some embodiments, the elastic wave device also includes a dielectric layer, which is composed of silicon dioxide, silicon nitride, or a material with fluorine, carbon, or boron compounds added to silicon oxide as the main component. The dielectric layer is arranged on the piezoelectric layer and covers the interdigital transducer electrode and the reflective gate electrode.

In some embodiments, the present application also provides an elastic wave filter or multiplexer, including a resonator located on a series arm and a resonator located on a parallel arm, wherein at least one resonator adopts the elastic wave device described in any of the above embodiments.

The elastic wave device provided in the embodiment of the present application is provided by setting the piezoelectric layer to a lithium niobate film with an Euler angle of (0°±10°, 122°±10°, 45°±10°) or (0°±10°, 122°±10°, 135°±10°); setting a conductive material film pattern above the piezoelectric layer, setting a low acoustic velocity layer below the piezoelectric layer, and setting a high acoustic velocity component below the low acoustic velocity layer; and under the premise that the thickness of the piezoelectric layer is set to h _LN and the wavelength of the elastic wave is set to λ, 0.1≤h _LN /λ≤0.3 is satisfied; and under the premise that the thickness of the low acoustic velocity layer is set to h ₁ and the wavelength of the elastic wave is set to λ, 0.1≤h ₁ /λ≤0.3 is satisfied. In this case, by using new material Euler angles and new stacked piezoelectric structures, an elastic wave device with a large device Q value and a high operating frequency is provided, solving the problem of too low Q value of longitudinal leaky acoustic surface wave (LLSAW) elastic wave devices.

The present application is described below with reference to the accompanying drawings and embodiments.

Fig. 1 shows a schematic top view and a cross-sectional view of a typical piezoelectric composite substrate-based surface acoustic wave (SAW) resonator 100. In recent years, SAW resonators based on piezoelectric composite substrates of a piezoelectric layer 101 and a non-piezoelectric substrate 103 have received widespread attention due to their high Q-value performance and have been applied to many fields such as radar, communication, and navigation.

The SAW resonator 100 based on a piezoelectric composite substrate is composed of a piezoelectric layer 101 and a conductive material thin film pattern formed on a piezoelectric composite substrate of a non-piezoelectric substrate 103. The piezoelectric layer 101 is a thin single crystal layer made of a piezoelectric material with a thickness of h _LN , and the piezoelectric material may include lithium niobate, lithium tantalate, gallium nitride, aluminum nitride or zinc oxide. The piezoelectric layer 101 is cut so as to be consistent with the front and back crystal axes of the relative piezoelectric layer 101, so that the piezoelectric layer 101 has different tangent options. The tangent of the piezoelectric layer 101 is defined by the Euler angle, for example, the Euler angle of the piezoelectric layer of the Z cut is (0°, 0°, 0°), the Euler angle of the piezoelectric layer of the Y128° cut is (0°, 38°, 0°), and the Euler angle of the piezoelectric layer of the Y32°X45° cut is (0°, 122°, 45°).

In an acoustic resonator, the quality factor Q is usually defined as the ratio of the peak energy stored in one cycle of an applied RF signal to the energy dissipated or lost in that cycle. These dissipated and lost energies include: electrical losses, piezoelectric losses, and mechanical/elastic losses.

The non-piezoelectric substrate 103 is a single-layer or multi-layer substrate made of a high-acoustic-velocity material, and is therefore also referred to as a high-acoustic-velocity component. The acoustic velocity of the body wave propagating in the high-acoustic-velocity component is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer, thereby increasing the acoustic velocity of the elastic wave in the piezoelectric layer and the frequency of the device. In addition, the high-acoustic-velocity component can effectively seal the elastic wave propagating in the piezoelectric layer in the piezoelectric layer without leakage, thereby increasing the Q value of the device.

The conductive material film pattern includes an IDT electrode 102a, a reflective grid electrode 102b, an IDT bus bar 104a and a reflective grid bus bar 104b, and the thickness of the conductive material film pattern is h _m . The IDT electrode 102a includes a plurality of first electrode fingers and a plurality of second electrode fingers interlaced with each other, and a first bus bar and a second bus bar facing each other in the extending direction of the first electrode fingers and the second electrode fingers. The distance λ between adjacent first (or second) electrode fingers is usually referred to as the "wavelength" of the IDT. A distance AP where the first electrode fingers and the second electrode fingers overlap is usually referred to as the "aperture" of the IDT. The reflective grid electrode 102b includes a plurality of third electrode fingers and a plurality of fourth electrode fingers interlaced with each other, and a third bus bar and a fourth bus bar facing each other in the extending direction of the third electrode fingers and the fourth electrode fingers.

Embodiment 1:

FIG2 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application. In this embodiment, the high acoustic velocity component 205 is implemented as a supporting substrate 204, on which a low acoustic velocity layer 203 is formed, and the piezoelectric layer 201 is supported, and a conductive material film pattern is formed on the piezoelectric layer 201. The conductive material film pattern includes an interdigital transducer electrode 202a, a reflective grid electrode 202b, an interdigital transducer bus bar, and a reflective grid bus bar. The direction parallel to the x-axis in the coordinate system is defined as the electrode finger arrangement direction, which is also the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system is defined as the electrode finger extension direction, and the direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 200.

In this embodiment, the support substrate 204 is made of a material with a relatively high longitudinal wave velocity, such as sapphire, silicon carbide or aluminum nitride, etc. Table 1 shows the acoustic velocities of three different modes of elastic waves in various materials.

Table 1

In this embodiment, the piezoelectric layer 201 is lithium niobate. The conductive film material pattern is composed of heavy metal materials, such as copper, molybdenum, gold, silver, platinum, tantalum or tungsten. The low acoustic velocity layer 203 is composed of silicon dioxide. In addition, the low acoustic velocity layer 203 can also be composed of a material with glass, silicon oxynitride, tantalum oxide, or a compound of fluorine, carbon, or boron added to silicon oxide such as silicon dioxide as a main component. Among them, the material of the low acoustic velocity layer 203 can be any material with a relatively low acoustic velocity.

FIG3 shows the vibration modal diagrams of two different acoustic modes in the piezoelectric layer 201 of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application, and the frequency corresponding to the two different acoustic modes varies with the wavelength. Among them, the SH ₀ mode is a transverse wave mode, the vibration direction of the mode is along the y-axis direction, the propagation direction of the mode is along the x-axis direction, and the two directions are perpendicular to each other; the LLSAW mode is a longitudinal wave mode, the vibration direction of the mode is along the x-axis direction, the propagation direction of the mode is along the x-axis direction, and the two directions are the same. By observing the frequency variation diagrams of the two modes with wavelength, it can be found that for a fixed wavelength, the frequency of the LLSAW mode is approximately 1.5 times the frequency of the SH ₀ mode. Therefore, the LLSAW mode has a unique advantage in realizing a longitudinal wave type leaky surface wave resonator in the high frequency band. Exemplarily, the piezoelectric layer 201 is implemented as a lithium niobate film with an Euler angle of (0°, 122°, 45°), and a thickness h _LN of 300 nanometers (nm).

FIG4 shows a graph showing the piezoelectric coupling coefficients of two different acoustic modes in the piezoelectric layer of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application as the Euler angle of the piezoelectric layer changes. Under the premise that the Euler angle of the piezoelectric layer 201 is set to (0°, θ, ψ), the horizontal axis in FIG4 represents the value of the propagation angle ψ of the piezoelectric layer 201, and the vertical axis represents the value of the cutting angle θ of the piezoelectric layer 201. The darker the color of the area in FIG4, the greater the piezoelectric coupling coefficient of the piezoelectric layer corresponding to the Euler angle of this area.

In some embodiment drawings, “LN” is used to represent lithium niobate.

Under the premise that the piezoelectric constant of the piezoelectric layer in the electric field direction and the mechanical stress direction is set to e, the stiffness under zero electric field is set to c ^E , and the dielectric constant in the electric field direction under zero stress is set to ε ^T , the piezoelectric coupling coefficient can be obtained by the formula e ² /c ^E ε ^T. Unlike the electromechanical coupling coefficient of the resonator, the piezoelectric coupling coefficient is completely dependent on the material properties, rather than being determined by the design and manufacture of the resonator.

As can be seen from FIG4, for the SH ₀ mode, when 90°≤θ≤150°, 0°≤ψ≤15° or 165°≤ψ≤180°, the piezoelectric layer has a larger piezoelectric coupling coefficient. For example, when θ＝120°, ψ＝0°, the piezoelectric coupling coefficient of the SH ₀ mode is better; for the LLSAW mode, when 90°≤θ≤150°, 30°≤ψ≤60° or 120°≤ψ≤150°, or when 15°≤θ≤45°, 105°≤ψ≤135°, the piezoelectric layer has a larger piezoelectric coupling coefficient. For example, when θ＝122°, ψ＝45° or 135°, the piezoelectric coupling coefficient of the LLSAW mode is better.

Fig. 5 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in the first embodiment of the present application. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate (LiNbO ₃ ) film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide (SiO ₂ ) film, the supporting substrate 204 is implemented as a 500 micrometer (μm) thick silicon carbide (SiC), and the conductive material film pattern is implemented as a 60nm thick copper, and the wavelength λ is 1μm.

Fig. 6 shows a frequency response diagram of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 204 is implemented as a 500μm thick sapphire, the conductive material film pattern is implemented as a 60nm thick copper, and the wavelength λ is 1μm.

7 shows a frequency response diagram of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 204 is implemented as a 500μm thick aluminum nitride (AIN), and the conductive material film pattern is implemented as a 60nm thick copper, and the wavelength λ is 1μm.

Comparative Example 1:

FIG8 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 300 provided in the first comparative example of the present application. In this embodiment, the high acoustic velocity component 305 is implemented as a supporting substrate 304, on which a low acoustic velocity layer 303 is formed, and the piezoelectric layer 301 is supported. A conductive material film pattern is formed on the piezoelectric layer 301, and the conductive material film pattern includes an interdigital transducer electrode 302a, a reflective grid electrode 302b, an interdigital transducer bus bar and a reflective grid bus bar. The direction parallel to the x-axis in the coordinate system is defined as the electrode finger arrangement direction, which is also the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system is defined as the electrode finger extension direction, and the direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 300.

Fig. 9 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 300 provided in Comparative Example 1 of the present application. For example, the piezoelectric layer 301 is implemented as a 200nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 303 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 304 is implemented as a 500μm thick silicon (Si), and the conductive material film pattern is implemented as a 60nm thick copper, and the wavelength λ is 1μm.

Comparative Example 2:

FIG10 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 400 provided in the second comparative example of the present application. The elastic wave device has no high-acoustic-velocity components, and the piezoelectric bulk material 401 serves as both a piezoelectric layer and a supporting function. A conductive material film pattern is formed above the piezoelectric layer 401, and the conductive material film pattern includes an interdigital transducer electrode 402a, a reflective grid electrode 402b, an interdigital transducer bus 600 and a reflective grid bus bar. The direction parallel to the x-axis in the coordinate system is defined as the electrode finger arrangement direction, which is also the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system is defined as the electrode finger extension direction, and the direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 400.

Fig. 11 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 400 provided in Comparative Example 2 of the present application. For example, the piezoelectric layer 401 is implemented as lithium niobate with a thickness of 350 μm, the Euler angle is (0, 122°, 45°), the conductive material film pattern is implemented as copper with a thickness of 60 nm, and the wavelength λ is 1 μm.

Comparative Example 3:

17 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 500 provided in Comparative Example 3 of the present application. The difference between Comparative Example 3 and Example 1 is that there is no intermediate layer (silicon dioxide) between the piezoelectric layer and the supporting substrate.

Effect verification:

By comparing Figures 5 to 7, Figure 9, and Figure 11, it can be found that the impedance ratio of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 exceeds 70 decibels (dB), and has fewer parasitic modes, and has better impedance characteristics than the elastic wave device (longitudinal wave type leaky surface wave resonator) 300 and the elastic wave device (longitudinal wave type leaky surface wave resonator) 400. Under the premise that the impedance of the resonator is set to Z, the impedance (dB) can be obtained by the formula 20×log ₁₀ |Z|. The impedance ratio is the difference between the impedance (dB) at the resonant frequency of the resonator and the impedance (dB) at the anti-resonance frequency. The impedance ratio represents the size of the resonant response of the resonator. The larger its value, the stronger the resonance of the resonator and the larger the Q value.

FIG12 shows a comparison of the displacement of the LLSAW mode in the supporting substrate of the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application and the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 300 provided in Comparative Example 1 as a function of the depth (thickness) of the supporting substrate. It can be seen from FIG12 that when there is a thicker supporting substrate, the displacement of the LLSAW mode in the supporting substrate of sapphire, silicon carbide or aluminum nitride is basically 0, which indicates that when sapphire, silicon carbide or aluminum nitride is used as the supporting substrate, the longitudinal wave type leaky acoustic surface wave resonator can better bind the sound wave in the piezoelectric layer, and the Q value of the resonator is large; while in the supporting substrate of the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 300, the sound velocity of the Si substrate is relatively low, and the sound wave energy leaks into the substrate, so the resonator Q value is relatively low.

FIG13 shows a frequency response curve of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application as the propagation angle ψ of the piezoelectric layer changes. Under the premise that the Euler angle of the piezoelectric layer 201 is set to (0, 122°, ψ), the ordinate in FIG13 represents the value of the propagation angle ψ of the piezoelectric layer 201. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 204 is implemented as a 500μm thick silicon carbide, the conductive material film pattern is implemented as a 60nm thick copper, and the wavelength λ is 1.5μm. It can be seen from FIG13 that when the propagation angle ψ of the piezoelectric layer satisfies 25°≤ψ≤65°, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 has a larger impedance ratio, and the amplitude of the existing parasitic mode is smaller.

FIG14 shows a graph of the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in the first embodiment of the present application as the propagation angle ψ of the piezoelectric layer changes. Under the premise that the Euler angle of the piezoelectric layer 201 is set to (0, 122°, ψ), the horizontal axis in FIG14 represents the value of the propagation angle ψ of the piezoelectric layer 201. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 204 is implemented as a 500μm thick silicon carbide, the conductive material film pattern is implemented as a 60nm thick copper, and the wavelength λ is 1μm. It can be seen from FIG14 that when the propagation angle ψ of the piezoelectric layer satisfies 30°≤ψ≤65°, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 has a larger electromechanical coupling coefficient (K _t ² ). Assuming that the resonant frequency of the resonator is f _s and the anti-resonant frequency is f _p , the electromechanical coupling coefficient can be obtained by the formula K _t ² =π ² /4×(f _p -f _s )/f _p .

Fig. 15 shows the frequency response curves of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 of different materials and thicknesses of conductive material film patterns. For example, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 204 is implemented as a 500μm thick silicon carbide, and the wavelength λ is 1μm.

Fig. 16 shows the frequency response curve of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 of different materials and thicknesses of conductive material film patterns. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 204 is implemented as a 500μm thick sapphire, and the wavelength λ is 1μm.

By comparing FIG. 15 and FIG. 16, it can be found that when aluminum (Al) electrodes are used as conductive material thin film patterns, due to their low density, more parasitic modes are generated, the impedance is relatively small, and the device Q value is low, which is not conducive to the realization of high-performance elastic wave components. When heavy metal electrodes (copper (Au), molybdenum (Mo), platinum (Pt)) are used as conductive material thin film patterns, the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 has a cleaner frequency response, fewer parasitic modes, and a larger impedance ratio, which is more suitable as the material for the longitudinal wave type leaky acoustic surface wave resonator electrode.

In Figures 15 and 16, "h _Al " is used to represent the thickness of the aluminum electrode when it is used as a conductive material thin film pattern, "h _Au " is used to represent the thickness of the copper electrode when it is used as a conductive material thin film pattern, "h _Pt " is used to represent the thickness of the platinum electrode when it is used as a conductive material thin film pattern, and "h _Mo " is used to represent the thickness of the molybdenum electrode when it is used as a conductive material thin film pattern.

FIG18 shows a frequency response comparison diagram of an elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application and an elastic wave device (longitudinal wave type leaky surface wave resonator) 500 provided in Comparative Example 3.

Exemplarily, the piezoelectric layer 201 and the piezoelectric layer 501 are implemented as a lithium niobate film with a thickness of 100nm, 150nm, 200nm, or 300nm, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a silicon dioxide film with a thickness of 200nm, and the supporting substrate 204 and the supporting substrate 503 are implemented as a sapphire with a thickness of 500μm, and the wavelength λ is 1μm.

19 shows a frequency response comparison diagram of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application and another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 500 provided in Comparative Example 3. Exemplarily, the piezoelectric layer 201 and the piezoelectric layer 501 are implemented as a lithium niobate film with a thickness of 100nm, 200nm, or 300nm, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a silicon dioxide film with a thickness of 200nm, the supporting substrates 204 and 503 are implemented as silicon carbide with a thickness of 500μm, and the wavelength λ is 1μm.

As can be seen from Figures 18 and 19, regardless of whether sapphire or silicon carbide is used as the supporting substrate, the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 500 lacking an intermediate layer (silicon dioxide) generally has a smaller impedance ratio, the acoustic wave cannot be bound in the piezoelectric layer, and the energy leaks to the supporting substrate. However, the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with an intermediate layer (silicon dioxide) generally has a larger impedance, the acoustic wave is well bound in the piezoelectric layer, and does not leak to the supporting substrate.

FIG20 shows a frequency response comparison diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with different piezoelectric layer thicknesses. FIG21 shows a trend diagram of the electromechanical coupling coefficient of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with different piezoelectric layer thicknesses. Exemplarily, the piezoelectric layer 201 is implemented as a lithium niobate film with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, the supporting substrate 204 is implemented as 500μm thick silicon carbide, and the wavelength λ is 1.5μm.

As can be seen from FIG. 20 and FIG. 21, when the ratio of the thickness of the piezoelectric layer (h _LN ) to the wavelength λ satisfies 0.1≤h _LN /λ≤0.23, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 has a relatively clean frequency response, fewer parasitic modes, and relatively large impedance; when the ratio of the thickness of the piezoelectric layer to the wavelength λ satisfies 0.16≤h _LN /λ≤0.35, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 has a large electromechanical coupling coefficient. Exemplarily, when the ratio of the thickness of the piezoelectric layer to the wavelength λ satisfies 0.16≤h _LN /λ≤0.23, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 has both a large electromechanical coupling coefficient and a relatively clean frequency response, and has excellent performance.

FIG22 shows a frequency response comparison diagram of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with different low acoustic velocity layer thicknesses. FIG23 shows a trend diagram of the electromechanical coupling coefficient of an elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with different low acoustic velocity layer thicknesses. Exemplarily, the piezoelectric layer 201 is implemented as a 200 nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a silicon dioxide film, the supporting substrate 204 is implemented as a 500 μm thick silicon carbide, and the wavelength λ is 1.5 μm.

It can be seen from FIG. 22 and FIG. 23 that when the ratio of the thickness of the low acoustic velocity layer h _SiO2 to the wavelength λ satisfies 0.067≤h _SiO2 /λ≤0.2, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 does not have the acoustic wave leakage phenomenon and has a relatively clean frequency response; when the ratio of the thickness of the low acoustic velocity layer to the wavelength λ satisfies 0.1≤h _SiO2 /λ≤0.2, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 has a large electromechanical coupling coefficient. Exemplarily, when the ratio of the thickness of the low acoustic velocity layer to the wavelength λ satisfies 0.1≤h _SiO2 /λ≤0.17, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 has both a large electromechanical coupling coefficient and a relatively clean frequency response, and has excellent performance.

Figures 24 to 27 show frequency response comparison diagrams of elastic wave devices (longitudinal wave type leaky acoustic surface wave resonators) 200 with different supporting substrates. For example, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, and the supporting substrate 204 is implemented as 500μm thick silicon carbide, sapphire and aluminum nitride, respectively, with a wavelength λ of 1μm. By comparison, it can be found that the impedance characteristics of the LLSAW main mode of the three high acoustic velocity substrates silicon carbide, sapphire and aluminum nitride are similar, and the impedance ratio exceeds 70dB, with excellent performance. The elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with silicon carbide and aluminum nitride as supporting substrates has a large parasitic mode on the right side of the passband, while the parasitic mode on the right side of the passband of the elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with sapphire as the supporting substrate is successfully suppressed.

In FIGS. 24 to 27 , the thickness of the lithium niobate thin film is represented by “h _LiNbO3 ”.

In some embodiments, the parasitic mode of the longitudinal-wave leaky acoustic surface wave resonator with silicon carbide as the supporting substrate is farther away from the main LLSAW mode than that of the longitudinal-wave leaky acoustic surface wave resonator with aluminum nitride as the supporting substrate.

In some embodiments, sapphire is a better support substrate material than silicon carbide and aluminum nitride. Silicon carbide is a better support substrate material than aluminum nitride. Exemplarily, support substrate 204 is sapphire.

FIG28 shows the measured frequency response and Q value curve of an elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application. Exemplarily, the piezoelectric layer 201 is implemented as a 300nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, and the supporting substrate 204 is implemented as a 500μm thick silicon carbide with a wavelength λ of 1.5μm. After calculation, the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 actually prepared is 13.65%, and the Q _max value is 1022.

FIG29 shows the measured frequency response and Q value curve of another elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application. Exemplarily, the piezoelectric layer 201 is implemented as a 180nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, and the supporting substrate 204 is implemented as a 250μm thick sapphire with a wavelength λ of 1μm. After calculation, the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 actually prepared is 14.65%, and the Q _max value is 850.

By observing the measured frequency response of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200, it can be found that there are regular and small parasitic modes (transverse modes) in the passband of the resonator. If these transverse modes are not suppressed, the performance of the resonator will deteriorate.

Figure 30 shows the measured frequency response of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 of the present application and the vibration mode diagram corresponding to its transverse mode. As the order of the transverse mode increases, the number of sound waves in the transverse direction also gradually increases.

Figure 31 shows a schematic diagram of an inclined IDT electrode 600. Exemplarily, the IDT bus bar 604a and the reflector bus bar 604b are inclined relative to the direction of elastic wave propagation, and the angle of inclination is β. Thus, the lateral mode can be suppressed. The IDT bus bar 604a and the reflector bus bar 604b extend in parallel. In addition, the IDT bus bar 604a and the reflector bus bar 604b may not necessarily extend in parallel. Similarly, the IDT electrode 602a and the reflector electrode 602b are also inclined relative to the direction of elastic wave propagation, and the angle of inclination is β.

FIG32 shows the measured frequency response diagram of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 with different β, as well as the measured impedance ratio and Q value trend diagram. By comparison, it can be found that when β is greater than 16°, the transverse mode in the resonator passband is basically suppressed. When β satisfies 16°≤ψ≤20°, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 can achieve a larger impedance ratio and ensure a higher Q value.

Embodiment 2:

Figure 33 shows the 5G communication-sixth/seventh generation wireless network technology (WIFI6/7) frequency band diagram. The longitudinal wave type leaky acoustic surface wave of the present application has the advantages of high sound velocity and large electromechanical coupling coefficient, and is a suitable solution for preparing filters that meet the 5G communication-WIFI6/7 frequency band. This embodiment builds a high-frequency and large-bandwidth longitudinal wave type leaky acoustic surface wave filter.

FIG34 shows a schematic diagram of the topological structure of the elastic wave device (longitudinal wave type leaky surface wave resonator) provided in the second embodiment of the present application. Among them, S1 to S4 are series arm resonators, and P1 to P5 are parallel arm resonators. Exemplarily, all series arm resonators and parallel arm resonators are elastic wave devices (longitudinal wave type leaky surface wave resonators) 200 provided in the first embodiment of the present application.

Figure 35 shows a measured frequency response diagram of an elastic wave device (longitudinal wave type leaky surface wave resonator) provided in Embodiment 2 of the present application. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, and the supporting substrate 204 is implemented as a 500μm thick silicon carbide.

As can be seen from FIG. 35 , the filter has a center frequency of 5250 MHz and a 3 dB bandwidth of 300 MHz, a minimum insertion loss of -1 dB, and an out-of-band suppression greater than 40 dB.

Figure 36 shows a measured frequency response diagram of another elastic wave device (longitudinal wave type leaky surface wave resonator) provided in Embodiment 2 of the present application. Exemplarily, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate film, the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide film, and the supporting substrate 204 is implemented as a 500μm thick sapphire.

As shown in FIG36 , the filter has a center frequency of 5625 MHz and a 3 dB bandwidth of 450 MHz, a minimum insertion loss of -1 dB, and an out-of-band suppression greater than 30 dB.

In the above embodiments, the filter can meet the requirements of the Unlicensed National Information Infrastructure band 1 (UNII-1) and the Unlicensed Mobile Information Infrastructure band 2C (UMII-2C) in the 5G communication-WIFI6/7 frequency band. In some embodiments, the longitudinal acoustic leakage surface wave of the present application can also be designed and prepared to meet the requirements of other frequency bands of 5G communication-WIFI6/7.

In order to better understand the present application, the present application is described below in conjunction with the accompanying drawings and three modified examples. It should be noted that the modified examples can be appropriately combined with the above-mentioned embodiments for application.

Modification 1:

FIG37 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 700 provided in the first variant of the present application. The high acoustic velocity component 705 is implemented as a supporting substrate 704, on which a low acoustic velocity layer 703 is formed to support the piezoelectric layer 701, and a conductive material film pattern is formed on the piezoelectric layer 701, and the conductive material film pattern includes an interdigital transducer electrode 702a, a reflective grid electrode 702b, an interdigital transducer bus bar and a reflective grid bus bar. The direction parallel to the x-axis in the coordinate system is defined as the electrode finger arrangement direction, which is also the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system is defined as the electrode finger extension direction, and the direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device (longitudinal wave type leaky surface wave resonator) 700.

In this variation, the support substrate 704 is made of a material having a relatively high L-wave acoustic velocity, such as sapphire, silicon carbide, aluminum nitride, etc. The piezoelectric layer 701 is lithium niobate. The conductive film material pattern is made of a heavy metal material, such as copper, molybdenum, gold, silver, platinum, tantalum, tungsten, etc. The low acoustic velocity layer 703 is made of silicon dioxide. In addition, the low acoustic velocity layer 703 may be made of a material having glass, silicon oxynitride, tantalum oxide, or a compound having fluorine, carbon, or boron added to silicon oxide such as silicon dioxide as a main component. The material of the low acoustic velocity layer 703 may be any material having a relatively low acoustic velocity.

Exemplarily, the ratio of the thickness of the piezoelectric layer 701 to the wavelength λ satisfies 0.16≤h _LN /λ≤0.23.

Exemplarily, the ratio of the thickness of the low acoustic velocity layer 703 to the wavelength λ satisfies 0.1≤h _{SiO 2} /λ≤0.2.

The above structure is defined in the same manner as in the first embodiment. The difference between the two is that a dielectric layer 706 is formed on the conductive material film pattern. The dielectric layer 706 is made of silicon dioxide. In addition, the dielectric layer 706 may also be made of a material having silicon nitride or a compound in which fluorine, carbon, or boron is added to silicon oxide such as silicon dioxide as a main component. The dielectric layer 706 may be made of a temperature compensation material or a non-temperature compensation material.

Based on the same reasons as those of the first embodiment, the structure of this variation can exhibit high-frequency characteristics and achieve a high Q value.

Modification 2:

FIG38 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 800 provided in the second variant of the present application. The high acoustic velocity component 805 includes a capture material layer 807 and a supporting substrate 804 below the capture material layer 807. A low acoustic velocity layer 803 is formed above the capture material layer 807 to support the piezoelectric layer 801. A conductive material film pattern is formed above the piezoelectric layer 801. The conductive material film pattern includes an interdigital transducer electrode 802a, a reflective grid electrode 802b, an interdigital transducer bus bar, and a reflective grid bus bar. The direction parallel to the x-axis in the coordinate system is defined as the electrode finger arrangement direction, which is also the elastic wave propagation direction. The direction parallel to the y-axis in the coordinate system is defined as the electrode finger extension direction. The direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device (longitudinal wave type leaky surface wave resonator) 800.

In this variation, the support substrate 804 is made of a material having a relatively high L-wave acoustic velocity, such as sapphire, silicon carbide, aluminum nitride, etc. The piezoelectric layer 801 is lithium niobate. The conductive film material pattern is made of a heavy metal material, such as copper, molybdenum, gold, silver, platinum, tantalum, tungsten, etc. The low acoustic velocity layer 803 is made of silicon dioxide. In addition, the low acoustic velocity layer 803 may be made of a material having glass, silicon oxynitride, tantalum oxide, or a compound having fluorine, carbon, or boron added to silicon oxide such as silicon dioxide as a main component. The material of the low acoustic velocity layer 803 may be any material having a relatively low acoustic velocity.

Exemplarily, the ratio of the thickness of the piezoelectric layer 801 to the wavelength λ satisfies 0.16≤h _LN /λ≤0.23.

Exemplarily, the ratio of the sum of the thicknesses of the low acoustic velocity layer 803 and the capture material layer 807 to the wavelength λ satisfies 0.1≤h/λ≤0.2.

Based on the same reasons as those of the first embodiment, the structure of this variation can exhibit high-frequency characteristics and achieve a high Q value.

Modification 3:

FIG39 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 900 provided in the third variant of the present application. The high acoustic velocity component 905 includes a capture material layer 907 and a supporting substrate 904 below the capture material layer 907. A low acoustic velocity layer 903 is formed above the capture material layer 907 to support the piezoelectric layer 901. A conductive material film pattern is formed above the piezoelectric layer 901. The conductive material film pattern includes an interdigital transducer electrode 902a, a reflective grid electrode 902b, an interdigital transducer bus bar, and a reflective grid bus bar. The direction parallel to the x-axis in the coordinate system is defined as the electrode finger arrangement direction, which is also the elastic wave propagation direction. The direction parallel to the y-axis in the coordinate system is defined as the electrode finger extension direction. The direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device (longitudinal wave type leaky surface wave resonator) 900.

In this variation, the support substrate 904 is made of a material having a relatively high L-wave acoustic velocity, such as sapphire, silicon carbide, aluminum nitride, etc. The piezoelectric layer 901 is lithium niobate. The conductive film material pattern is made of a heavy metal material, such as copper, molybdenum, gold, silver, platinum, tantalum, tungsten, etc. The low acoustic velocity layer 903 is made of silicon dioxide. In addition, the low acoustic velocity layer 903 may be made of a material having glass, silicon oxynitride, tantalum oxide, or a compound having fluorine, carbon, or boron added to silicon oxide such as silicon dioxide as a main component. The material of the low acoustic velocity layer 903 may be any material having a relatively low acoustic velocity.

Exemplarily, the ratio of the thickness of the piezoelectric layer 901 to the wavelength λ satisfies 0.16≤h _LN /λ≤0.23.

Exemplarily, the ratio of the sum of the thicknesses of the low acoustic velocity layer 903 and the capture material layer 907 to the wavelength λ satisfies 0.1≤h/λ≤0.2.

The above structure is limited in the same way as in the second modification. The difference between the two is that a dielectric layer 906 is formed on the conductive material film pattern. The dielectric layer 906 is made of silicon dioxide. In addition, the dielectric layer 906 may also be made of a material mainly composed of silicon nitride or a compound in which fluorine, carbon, or boron is added to silicon oxide such as silicon dioxide. The dielectric layer 906 may be made of a temperature compensation material or a non-temperature compensation material.

Based on the same reasons as those of the first embodiment, the structure of this comparative example can exhibit high frequency characteristics and achieve a high Q value.

Claims (10)

An elastic wave device, comprising: A piezoelectric layer, the piezoelectric layer comprising a lithium niobate film having an Euler angle of (0°±10°, 122°±10°, 45°±10°) or (0°±10°, 122°±10°, 135°±10°), and having a first main surface and a second main surface opposite to each other; an IDT electrode and a reflective gate electrode, wherein the IDT electrode and the reflective gate electrode are directly or indirectly formed on the first main surface, and the IDT electrode and the reflective gate electrode are made of a heavy metal material; a low acoustic velocity layer, the low acoustic velocity layer being directly or indirectly formed on the second main surface; and A high sound velocity component, the high sound velocity component is located below the low sound velocity layer; When the thickness of the piezoelectric layer is set to h _LN and the wavelength of the elastic wave is set to λ, 0.1≤h _LN /λ≤0.3 is satisfied; when the thickness of the low acoustic velocity layer is set to h ₁ and the wavelength of the elastic wave is set to λ, 0.1≤h ₁ /λ≤0.3 is satisfied. The elastic wave device according to claim 1, wherein an acoustic velocity of a bulk wave propagating in the high-acoustic-velocity member is higher than an acoustic velocity of a bulk wave propagating in the piezoelectric layer. The elastic wave device according to claim 1, wherein the high acoustic velocity member comprises: a supporting substrate, the supporting substrate being configured to support the low acoustic velocity layer; or, The high acoustic velocity component comprises: a supporting substrate and a capture material layer, wherein the capture material layer is disposed between the supporting substrate and the low acoustic velocity layer, and the capture material layer is configured to support the low acoustic velocity layer. The elastic wave device according to claim 3, wherein the support substrate is made of one or more materials having a sound velocity exceeding 6000 meters per second. The elastic wave device according to claim 3, wherein the low acoustic velocity layer is composed of one or more materials selected from silicon dioxide, glass, silicon oxynitride, tantalum oxide, or silicon oxide to which a compound containing fluorine, carbon, or boron as a main component is added. The elastic wave device according to claim 3, wherein the capture material layer is formed of one or more combinations of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium. The elastic wave device according to claim 3, wherein, assuming that the thickness of the trapping material layer is h ₂ and the wavelength of the elastic wave is λ, 0.1≤(h ₂ +h ₁ )/λ≤0.3 is satisfied. The elastic wave device according to claim 1, wherein the heavy metal material is composed of one or more of copper, platinum, tungsten, gold, silver, molybdenum, and tantalum. The elastic wave device according to any one of claims 1 to 8 further includes a dielectric layer, which is composed of silicon dioxide, silicon nitride, or a material in which a compound with fluorine, carbon, or boron as a main component is added to silicon oxide, and the dielectric layer is arranged on the piezoelectric layer and covers the interdigital transducer electrode and the reflection gate electrode. An elastic wave filter or multiplexer comprises a resonator located on a series arm and a resonator located on a parallel arm, wherein at least one of the resonators adopts an elastic wave device as claimed in any one of claims 1 to 9.