Elastic wave apparatus

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 hLN and the wavelength of an elastic wave is set to be λ, 0.1≤hLN / 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

[0001] 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

[0002] The present application relates to the field of elastic wave technology, and for example, to an elastic wave device utilizing a longitudinal leaky acoustic surface wave (LLSAW) with a high Q value and a high operating frequency. Background Art

[0003] Elastic wave devices, characterized by low cost, compact size, and versatility, have found widespread application in fields such as radar, communications, and navigation. The most commonly used elastic wave devices in mobile phone and base station communications include elastic wave resonators, elastic wave filters composed of multiple elastic wave resonators, and elastic wave duplexers and multiplexers composed of multiple elastic wave filters. In all types of elastic wave devices, a conductive thin film pattern is formed on a piezoelectric multilayer substrate to define multiple interdigital transducer electrodes and multiple reflective grating electrodes. Bandpass characteristics are achieved by exploiting the frequency characteristics of the conversion function of the electrical signals from the interdigital transducer electrodes into elastic waves.

[0004] Mobile communication systems are evolving from third-generation (3G) and fourth-generation (4G) to fifth-generation (5G) mobile communication technology, with their frequency bands moving toward higher frequencies and wider bandwidths. To achieve higher frequencies in elastic wave components, the elastic wave wavelength, defined by the spacing between the interdigital transducer electrodes, can be reduced. Global mobile 5G network deployments already include the sub-6GHz (below 6GHz) frequency band of 3 to 7 GHz. However, the piezoelectric crystal materials currently used in elastic wave component fabrication, such as lithium niobate and lithium tantalate, have an acoustic velocity of approximately 3000 to 4000 meters per second (m / s), making it difficult to fabricate devices above 3GHz using conventional photolithography techniques without significantly increasing costs. Furthermore, at higher frequencies, the interdigital electrodes become narrower and thinner, increasing electrode ohmic losses and reducing the device's quality factor (Q value). Furthermore, the electrode material is susceptible to damage, severely impacting device performance and reliability. Therefore, achieving higher acoustic velocities of elastic waves is crucial for achieving higher frequencies in elastic wave components.

[0005] To achieve higher sound speeds, the industry is experimenting with using longitudinal leaky surface acoustic waves (LLSAW) as an operating mode in elastic wave components. However, LLSAW propagates while leaking into the substrate containing the piezoelectric layer, resulting in a low Q factor and failing to meet the high-frequency, high-performance filter requirements of 5G communications.

[0006] However, in the elastic wave device disclosed in Chinese patent application CN112823473A, where the main component of the elastic wave propagating in the device is a longitudinal wave, the Euler angle of the piezoelectric layer does not cover the entire range, 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, the device has disadvantages such as high manufacturing cost, poor stability and a narrow scope of application. Summary of the Invention

[0007] 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.

[0008] In a first aspect, the present application provides an elastic wave device, comprising:

[0009] A piezoelectric layer, the piezoelectric layer comprising a lithium niobate thin 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;

[0010] an interdigital transducer electrode and a reflective gate electrode, wherein the interdigital transducer electrode and the reflective gate electrode are directly or indirectly formed on the first main surface, and the interdigital transducer electrode and the reflective gate electrode are made of a heavy metal material;

[0011] a low acoustic velocity layer formed directly or indirectly on the second main surface; and

[0012] a high-acoustic-velocity component, the high-acoustic-velocity component being located below the low-acoustic-velocity layer;

[0013] Wherein, when the thickness of the piezoelectric layer is set to h LN , under the premise that the wavelength of the elastic wave is set to λ, 0.1≤h LN / λ≤0.3; under the premise that the thickness of the low sound velocity layer is set to h1 and the wavelength of the elastic wave is set to λ, 0.1≤h1 / λ≤0.3 is satisfied.

[0014] 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

[0015] 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:

[0016] FIG1 shows a schematic plan view and a cross-sectional view of a typical surface acoustic wave (SAW) resonator 100 ;

[0017] FIG2 shows a cross-sectional view of an elastic wave device (a longitudinal-wave leaky surface wave resonator) 200 provided in Example 1 of the present application;

[0018] FIG3 shows a vibration mode diagram of two different acoustic modes in the piezoelectric layer of the elastic wave device (longitudinal-wave leaky surface wave resonator) 200 provided in Example 1 of the present application, and a diagram showing how the frequencies corresponding to the two different acoustic modes vary with wavelength;

[0019] 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 leaky surface wave resonator) 200 provided in the first embodiment of the present application as the Euler angles of the piezoelectric layer change;

[0020] FIG5 shows a frequency response diagram of an elastic wave device (longitudinal-wave type leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application;

[0021] FIG6 shows a frequency response diagram of another elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application;

[0022] FIG7 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;

[0023] FIG8 shows a cross-sectional view of an elastic wave device (longitudinal-wave type leaky surface wave resonator) 300 provided in Comparative Example 1 of the present application;

[0024] FIG9 shows a frequency response diagram of an elastic wave device (a longitudinal-wave type leaky acoustic surface wave resonator) 300 provided in Comparative Example 1 of the present application;

[0025] FIG10 shows a cross-sectional view of an elastic wave device (a longitudinal-wave type leaky surface wave resonator) 400 provided in Comparative Example 2 of the present application;

[0026] FIG11 shows a frequency response diagram of an elastic wave device (a longitudinal-wave type leaky acoustic surface wave resonator) 400 provided in Comparative Example 2 of the present application;

[0027] FIG12 shows a comparison of the displacement of the LLSAW mode in the supporting substrate of the elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application and the elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 300 provided in Comparative Example 1 as a function of the depth (thickness) of the supporting substrate;

[0028] FIG13 shows a frequency response curve of the elastic wave device (longitudinal-wave leaky surface wave resonator) 200 provided in the first embodiment of the present application as the propagation angle ψ of the piezoelectric layer changes;

[0029] FIG14 shows a graph of the electromechanical coupling coefficient of the elastic wave device (longitudinal-wave leaky surface wave resonator) 200 provided in the first embodiment of the present application as the piezoelectric layer propagation angle ψ changes;

[0030] FIG15 shows frequency response curves of an elastic wave device (a longitudinal-wave type leaky acoustic surface wave resonator) 200 having different materials and thicknesses of conductive film patterns;

[0031] FIG16 shows frequency response curves of another elastic wave device (longitudinal wave type leaky acoustic surface wave resonator) 200 with different materials and thicknesses of conductive material film patterns;

[0032] FIG17 shows a cross-sectional view of an elastic wave device (a longitudinal-wave type leaky surface wave resonator) 500 provided in Comparative Example 3 of the present application;

[0033] FIG18 shows a comparison of the frequency responses of an elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application and an elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 500 provided in Comparative Example 3;

[0034] FIG19 shows a comparison of the frequency responses of another elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application and another elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 500 provided in Comparative Example 3;

[0035] FIG20 shows a comparison of frequency responses of an elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 having different piezoelectric layer thicknesses;

[0036] FIG21 shows a trend diagram of the electromechanical coupling coefficient of an elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 with different piezoelectric layer thicknesses;

[0037] FIG22 shows a comparison of frequency responses of an elastic wave device (a longitudinal-wave leaky surface wave resonator) 200 having different low-acoustic-velocity layer thicknesses;

[0038] FIG23 shows a trend diagram of the electromechanical coupling coefficient of the elastic wave device (longitudinal-wave leaky surface wave resonator) 200 with different low-acoustic-velocity layer thicknesses;

[0039] FIG. 24 shows an elastic wave device (longitudinal-wave type leaky surface acoustic wave resonator) 200 (h LiNbO3 / λ=0.1) frequency response comparison diagram;

[0040] FIG. 25 shows an elastic wave device (longitudinal-wave type leaky surface acoustic wave resonator) 200 (h LiNbO3 / λ=0.15) frequency response comparison chart;

[0041] FIG. 26 shows an elastic wave device (longitudinal-wave type leaky surface acoustic wave resonator) 200 (h LiNbO3 / λ=0.2) frequency response comparison chart;

[0042] FIG. 27 shows an elastic wave device (longitudinal-wave type leaky surface acoustic wave resonator) 200 (h LiNbO3 / λ=0.3) frequency response comparison diagram;

[0043] 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;

[0044] FIG29 shows a measured frequency response and Q value curve of another elastic wave device (longitudinal-wave leaky surface wave resonator) 200 provided in Example 1 of the present application;

[0045] FIG30 shows the measured frequency response of the elastic wave device (longitudinal-wave leaky surface wave resonator) 200 provided in Example 1 of the present application and the vibration mode diagram corresponding to its transverse mode;

[0046] FIG31 shows a schematic diagram of an inclined IDT electrode 600;

[0047] FIG32 shows a graph of the measured frequency response of the elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 with different β values, as well as a graph of the measured impedance ratio and Q value trends;

[0048] Figure 33 shows a 5G communication-WIFI6 / 7 frequency band diagram;

[0049] FIG34 shows a schematic diagram of the topological structure of an elastic wave device (a longitudinal-wave leaky surface wave resonator) provided in Example 2 of the present application;

[0050] FIG35 shows a measured frequency response diagram of an elastic wave device (a longitudinal-wave leaky surface wave resonator) provided in Example 2 of the present application;

[0051] FIG36 shows a measured frequency response diagram of another elastic wave device (a longitudinal-wave leaky surface wave resonator) provided in Example 2 of the present application;

[0052] FIG37 shows a cross-sectional view of an elastic wave device (longitudinal-wave type leaky surface acoustic wave resonator) 700 provided in a first variation of the present application;

[0053] FIG38 shows a cross-sectional view of an elastic wave device (longitudinal-wave type leaky surface acoustic wave resonator) 800 provided in a second variation of the present application;

[0054] FIG39 shows a cross-sectional view of an elastic wave device (longitudinal-wave type leaky surface acoustic wave resonator) 900 provided in a third variation of the present application. DETAILED DESCRIPTION

[0055] The following describes the embodiments of the present application in conjunction with the accompanying drawings. The embodiments described are some related embodiments of the present application. Based on the embodiments of 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.

[0056] Among them, the same parts are represented by the same figure marks. The words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom" and "top", "inside" and "outside" refer to directions toward or away from specific parts, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot 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.

[0057] An embodiment of the present application provides an elastic wave device, comprising: a piezoelectric layer, the piezoelectric layer comprising a lithium niobate thin film having Euler angles 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 facing each other; an interdigital transducer electrode and a reflection grid electrode, the interdigital transducer electrode and the reflection grid electrode being directly or indirectly formed on the first main surface, and being composed 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 acoustic velocity component, the high acoustic velocity component being located below the low acoustic velocity layer;

[0058] In which, when the thickness of the piezoelectric layer is set to h LN , under the premise that the wavelength of the elastic wave is set to λ, 0.1≤h LN / λ≤0.3; under the premise that the thickness of the low sound velocity layer is set to h1 and the wavelength of the elastic wave is set to λ, 0.1≤h1 / λ≤0.3 is satisfied.

[0059] In some embodiments, the front surface of the piezoelectric layer is the first main surface, and the back surface of the piezoelectric layer is the second main surface. For example, FIG2 shows the first main surface 2011 of the piezoelectric layer and the second main surface 2012 of the piezoelectric layer.

[0060] 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.

[0061] In some embodiments, the high acoustic velocity component includes: a supporting substrate, which is configured to support the low acoustic velocity layer; or, the high acoustic velocity component includes: a supporting substrate and a capture material layer, which is configured between the supporting substrate and the low acoustic velocity layer, and the capture material layer is configured to support the low acoustic velocity layer.

[0062] In some embodiments, the support substrate is composed of one or more materials having a sound velocity exceeding 6000 m / s.

[0063] 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 with a compound containing fluorine, carbon, or boron as a main component added thereto.

[0064] In some embodiments, the trapping material layer is formed of one or more of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium.

[0065] In some embodiments, under the premise that the thickness of the capture material layer is set to h2 and the wavelength of the elastic wave is set to λ, 0.1≤(h2+h1) / λ≤0.3 is satisfied.

[0066] In some embodiments, the heavy metal material is composed of one or more of copper, platinum, tungsten, gold, silver, molybdenum, and tantalum.

[0067] 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.

[0068] 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.

[0069] The elastic wave device provided in the embodiment of the present application is configured by setting the piezoelectric layer to a lithium niobate film having an Euler angle of (0°±10°, 122°±10°, 45°±10°) or (0°±10°, 122°±10°, 135°±10°); arranging a conductive material film pattern above the piezoelectric layer, arranging a low sound velocity layer below the piezoelectric layer, and arranging a high sound velocity component below the low sound velocity layer; and setting the thickness of the piezoelectric layer to h LN , under the premise that the wavelength of the elastic wave is set to λ, 0.1≤h LN / λ≤0.3; and, assuming the thickness of the low-acoustic-velocity layer is h1 and the wavelength of the elastic wave is λ, 0.1≤h1 / λ≤0.3. In this case, by using novel material Euler angles and a novel stacked piezoelectric structure, an elastic wave device with a high device Q and a high operating frequency is provided, addressing the low Q problem of longitudinal leaky acoustic surface wave (LLSAW) elastic wave devices.

[0070] The present application is described below with reference to the accompanying drawings and embodiments.

[0071] Figure 1 shows a schematic top view and 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, consisting of a piezoelectric layer 101 and a non-piezoelectric substrate 103, have garnered widespread attention due to their high Q performance and have been applied in numerous fields, including radar, communications, and navigation.

[0072] 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 piezoelectric material with a thickness of h LN , 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 Euler angles, for example, the Euler angles of the piezoelectric layer of Z cutting are (0°, 0°, 0°), the Euler angles of the piezoelectric layer of Y128° cutting are (0°, 38°, 0°), and the Euler angles of the piezoelectric layer of Y32°X45° cutting are (0°, 122°, 45°).

[0073] In acoustic resonators, the quality factor (Q) is typically defined as the ratio of the peak energy stored in one cycle of an applied RF signal to the energy dissipated or lost during that cycle. This energy dissipation and loss includes electrical losses, piezoelectric losses, and mechanical / elastic losses.

[0074] 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 bulk waves propagating in the high-acoustic-velocity component is higher than the acoustic velocity of elastic waves propagating in the piezoelectric layer. This increases the acoustic velocity of the elastic waves in the piezoelectric layer and the device's frequency. Furthermore, the high-acoustic-velocity component effectively confines the elastic waves propagating in the piezoelectric layer, preventing them from leaking, thereby improving the device's Q factor.

[0075] The conductive material film pattern includes the IDT electrode 102a, the reflective grid electrode 102b, the IDT bus bar 104a and the reflective grid bus bar 104b. 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 that are interlaced with each other, and a first bus bar and a second bus bar that are opposite to each other in the direction in which the first electrode fingers and the second electrode fingers extend. The distance λ between adjacent first (or second) electrode fingers is usually referred to as the "wavelength" of the IDT. The distance AP where the first electrode finger and the second electrode finger 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 that are interlaced with each other, and a third bus bar and a fourth bus bar that are opposite to each other in the direction in which the third electrode finger and the fourth electrode finger extend.

[0076] Example 1:

[0077] Figure 2 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 200 provided in Example 1 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 above the piezoelectric layer 201. The conductive material film pattern includes an interdigital transducer electrode 202a, a reflection grid electrode 202b, an interdigital transducer bus bar and a reflection 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.

[0078] In this embodiment, the support substrate 204 is made of a material having a relatively high longitudinal wave velocity, such as sapphire, silicon carbide, or aluminum nitride, etc. Table 1 shows the acoustic velocities of three different elastic wave modes in various materials.

[0079] Table 1

[0080] In this embodiment, piezoelectric layer 201 is lithium niobate. The conductive film material pattern is composed of a heavy metal material such as copper, molybdenum, gold, silver, platinum, tantalum, or tungsten. Low acoustic velocity layer 203 is composed of silicon dioxide. Alternatively, low acoustic velocity layer 203 may be composed primarily of materials such as glass, silicon oxynitride, tantalum oxide, or compounds containing fluorine, carbon, or boron added to silicon oxides such as silicon dioxide. The material of low acoustic velocity layer 203 can be any material with a relatively low acoustic velocity.

[0081] Figure 3 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 Example 1 of the present application, as well as the frequency variation diagrams corresponding to the two different acoustic modes with wavelength. Among them, the SH0 mode is a transverse wave mode, the vibration direction of this mode is along the y-axis direction, the propagation direction of this 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 this mode is along the x-axis direction, the propagation direction of this 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 SH0 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 of h. LN It is 300 nanometers (nm).

[0082] 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.

[0083] In some drawings of the embodiments, “LN” is used to represent lithium niobate.

[0084] The piezoelectric constant in the electric field direction and mechanical stress direction of the piezoelectric layer is set to e, and the stiffness under zero electric field is set to c. E , the dielectric constant in the electric field direction under zero stress is set to ε T Under the premise of 2 / c E ε T Unlike the electromechanical coupling coefficient of the resonator, the piezoelectric coupling coefficient is completely dependent on the material properties and is not determined by the design and manufacture of the resonator.

[0085] As can be seen from Figure 4, for the SH0 mode, the piezoelectric layer has a large piezoelectric coupling coefficient when 90°≤θ≤150°, 0°≤ψ≤15°, or 165°≤ψ≤180°. For example, when θ=120° and ψ=0°, the SH0 mode has a better piezoelectric coupling coefficient. For the LLSAW mode, the piezoelectric layer has a large piezoelectric coupling coefficient when 90°≤θ≤150°, 30°≤ψ≤60°, or 120°≤ψ≤150°, or when 15°≤θ≤45° and 105°≤ψ≤135°. For example, when θ=122° and ψ=45° or 135°, the LLSAW mode has a better piezoelectric coupling coefficient.

[0086] Figure 5 shows a frequency response diagram of an elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application. For example, the piezoelectric layer 201 is implemented as a 200nm thick lithium niobate (LiNbO3) film with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200nm thick silicon dioxide (SiO2) film, the supporting substrate 204 is implemented as a 500 micron (μm) thick silicon carbide (SiC), and the conductive material film pattern is implemented as a 60nm thick copper film with a wavelength λ of 1 μm.

[0087] Figure 6 shows a frequency response diagram of another elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application. 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, the supporting substrate 204 is implemented as a 500μm thick sapphire, and the conductive material film pattern is implemented as a 60nm thick copper film with a wavelength λ of 1μm.

[0088] Figure 7 shows a frequency response diagram of another elastic wave device (a longitudinal-wave leaky acoustic surface wave resonator) 200 provided in Example 1 of the present application. 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, the supporting substrate 204 is implemented as a 500μm thick aluminum nitride (AlN), and the conductive material film pattern is implemented as a 60nm thick copper film with a wavelength λ of 1μm.

[0089] Comparative Example 1:

[0090] FIG8 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 300 provided in Comparative Example 1 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 supports the piezoelectric layer 301. A conductive material thin film pattern is formed above the piezoelectric layer 301, and the conductive material thin 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. The direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 300.

[0091] Figure 9 shows a frequency response diagram of an elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 300 provided in Comparative Example 1 of this application. For example, the piezoelectric layer 301 is implemented as a 200nm thick lithium niobate film with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 303 is implemented as a 200nm thick silicon dioxide film, the support substrate 304 is implemented as 500μm thick silicon (Si), and the conductive material film pattern is implemented as 60nm thick copper with a wavelength λ of 1μm.

[0092] Comparative Example 2:

[0093] 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. The elastic wave device has no high-acoustic-velocity components. The piezoelectric bulk material 401 serves as both a piezoelectric layer and a support. A conductive material thin film pattern is formed above the piezoelectric layer 401. The conductive material thin 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. The direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 400.

[0094] Figure 11 shows a frequency response diagram of an elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 400 provided in Comparative Example 2 of this application. For example, piezoelectric layer 401 is implemented as 350 μm thick lithium niobate with Euler angles of (0, 122°, 45°), and the conductive material film pattern is implemented as 60 nm thick copper with a wavelength λ of 1 μm.

[0095] Comparative Example 3:

[0096] 17 shows a cross-sectional view of an elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 500 provided in Comparative Example 3 of the present application. Comparative Example 3 differs from Example 1 in that no intermediate layer (silicon dioxide) is provided between the piezoelectric layer and the supporting substrate.

[0097] Effect verification:

[0098] By comparing Figures 5 to 7, Figure 9, and Figure 11, it can be seen that the impedance ratio of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 exceeds 70 decibels (dB) and has fewer parasitic modes, which shows that it has better impedance characteristics than the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 and the elastic wave device (longitudinal wave type leaky surface acoustic 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| is obtained. The impedance ratio is the difference between the impedance (dB) at the resonant frequency and the impedance (dB) at the antiresonant frequency. The impedance ratio represents the magnitude of the resonant response. A larger value indicates a stronger resonance and a higher Q value.

[0099] FIG12 shows a comparison of the displacement of the LLSAW mode in the supporting substrates of the elastic wave device (longitudinal-wave leaky surface wave resonator) 200 provided in Example 1 of the present application and the elastic wave device (longitudinal-wave leaky surface wave resonator) 300 provided in Comparative Example 1, as a function of the depth (thickness) of the supporting substrate. FIG12 shows that when the supporting substrate is thicker, the displacement of the LLSAW mode in the supporting substrate of sapphire, silicon carbide, or aluminum nitride is essentially zero, indicating that when sapphire, silicon carbide, or aluminum nitride is used as the supporting substrate, the longitudinal-wave leaky surface wave resonator can better confine the acoustic wave in the piezoelectric layer, resulting in a high Q value of the resonator. However, in the supporting substrate of the elastic wave device (longitudinal-wave leaky surface wave resonator) 300, the Si substrate has a low sound velocity, and the acoustic wave energy leaks into the substrate, resulting in a low Q value of the resonator.

[0100] 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 vertical axis in FIG13 represents the value of the propagation angle ψ of the piezoelectric layer 201. For example, 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.

[0101] FIG14 shows a graph showing the electromechanical coupling coefficient 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 horizontal axis in FIG14 represents the value of the propagation angle ψ of the piezoelectric layer 201. For example, 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 ). When the resonant frequency of the resonator is set to f s , the anti-resonance frequency is set to f p Under the premise of t 2 =π 2 / 4×(f p -f s ) / f p Obtain.

[0102] Figure 15 shows frequency response curves for an elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 made of conductive thin film patterns of various materials and thicknesses. For example, the piezoelectric layer 201 is implemented as a 200 nm thick lithium niobate film with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200 nm thick silicon dioxide film, and the support substrate 204 is implemented as a 500 μm thick silicon carbide film with a wavelength λ of 1 μm.

[0103] Figure 16 shows frequency response curves for another elastic wave device (a longitudinal-wave leaky acoustic surface wave resonator) 200 made of conductive thin film patterns of varying materials and thicknesses. For example, the piezoelectric layer 201 is implemented as a 200 nm thick lithium niobate film with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200 nm thick silicon dioxide film, and the supporting substrate 204 is implemented as 500 μm thick sapphire with a wavelength λ of 1 μm.

[0104] Comparing Figures 15 and 16, it can be seen that using aluminum (Al) electrodes as the conductive material thin film pattern, due to its low density, generates more parasitic modes, relatively low impedance, and low device Q, making it unfavorable for the realization of high-performance elastic wave components. However, using heavy metal electrodes (copper (Au), molybdenum (Mo), platinum (Pt)) as the conductive material thin film pattern, the elastic wave device (longitudinal-wave leaky acoustic surface wave resonator) 200 has a cleaner frequency response, fewer parasitic modes, and a higher impedance ratio, making it more suitable as a material for longitudinal-wave leaky acoustic surface wave resonator electrodes.

[0105] In Figures 15 and 16, “h Al " is used to express the thickness of the aluminum electrode as a conductive material film pattern, and "h Au " is used to express the thickness of the copper electrode as a conductive material film pattern, and "h Pt " is used to express the thickness of the platinum electrode as a conductive material film pattern, and "h Mo " is used to indicate the thickness of the molybdenum electrode when it is used as a conductive material film pattern.

[0106] FIG18 shows a frequency response comparison diagram of an elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application and an elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 500 provided in Comparative Example 3.

[0107] Exemplarily, the piezoelectric layer 201 and the piezoelectric layer 501 are implemented as a lithium niobate film with a thickness of 100 nm, 150 nm, 200 nm, or 300 nm, and the Euler angle is (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a silicon dioxide film with a thickness of 200 nm, and the supporting substrate 204 and the supporting substrate 503 are implemented as a sapphire with a thickness of 500 μm and a wavelength λ of 1 μm.

[0108] FIG19 shows a comparison of the frequency responses of another elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 provided in Example 1 of the present application and another elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 500 provided in Comparative Example 3. For example, the piezoelectric layers 201 and 501 are implemented as lithium niobate films with a thickness of 100 nm, 200 nm, or 300 nm, with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200 nm thick silicon dioxide film, and the supporting substrates 204 and 503 are implemented as 500 μm thick silicon carbide, with a wavelength λ of 1 μm.

[0109] As shown in Figures 18 and 19, regardless of whether the substrate is sapphire or silicon carbide, the acoustic wave device (longitudinal-wave leaky surface acoustic wave resonator) 500 lacking an intermediate layer (silicon dioxide) generally exhibits a low impedance ratio, preventing acoustic waves from being trapped in the piezoelectric layer and leaking energy into the substrate. In contrast, the acoustic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 with an intermediate layer (silicon dioxide) generally exhibits a high impedance ratio, effectively trapping acoustic waves in the piezoelectric layer and preventing them from leaking into the substrate.

[0110] FIG20 shows a comparison of the frequency responses of elastic wave devices (longitudinal-wave leaky surface acoustic wave resonators) 200 with different piezoelectric layer thicknesses. FIG21 shows a trend diagram of the electromechanical coupling coefficient of elastic wave devices (longitudinal-wave leaky surface acoustic wave resonators) 200 with different piezoelectric layer thicknesses. For example, 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 200 nm thick silicon dioxide film, the supporting substrate 204 is implemented as 500 μm thick silicon carbide, and the wavelength λ is 1.5 μm.

[0111] It can be seen from Figures 20 and 21 that when the thickness of the piezoelectric layer (h LN ) and the wavelength λ satisfies 0.1≤h LN When / 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 When / λ≤0.35, the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 is large. For example, when the ratio of the thickness of the piezoelectric layer to the wavelength λ satisfies 0.16≤h LN When / λ≤0.23, the elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 has both a large electromechanical coupling coefficient and a relatively clean frequency response, and has excellent performance.

[0112] FIG22 shows a comparison of the frequency responses of elastic wave devices (longitudinal-wave leaky surface wave resonators) 200 with different low-acoustic-velocity layer thicknesses. FIG23 shows a trend diagram of the electromechanical coupling coefficient of elastic wave devices (longitudinal-wave leaky surface wave resonators) 200 with different low-acoustic-velocity layer thicknesses. For example, the piezoelectric layer 201 is implemented as a 200 nm thick lithium niobate film with Euler angles of (0, 122°, 45°), the low-acoustic-velocity layer 203 is implemented as a silicon dioxide film, and the supporting substrate 204 is implemented as 500 μm thick silicon carbide with a wavelength λ of 1.5 μm.

[0113] It can be seen from Figures 22 and 23 that when the thickness of the low sound velocity layer h SiO2 The ratio to the wavelength λ satisfies 0.067≤h SiO2When / λ≤0.2, the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 does not have acoustic 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 When / λ≤0.2, the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface wave resonator) 200 is large. For example, when the ratio of the thickness of the low acoustic velocity layer to the wavelength λ satisfies 0.1≤h SiO2 When / λ≤0.17, the elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 has both a large electromechanical coupling coefficient and a relatively clean frequency response, and has excellent performance.

[0114] Figures 24 to 27 show a comparison of the frequency responses of elastic wave devices (longitudinal-wave leaky surface acoustic 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 substrates 204 are implemented as 500μm-thick silicon carbide, sapphire, and aluminum nitride, respectively, with a wavelength λ of 1μm. Comparison reveals that the impedance characteristics of the LLSAW main mode for the three high-acoustic-velocity substrates—silicon carbide, sapphire, and aluminum nitride—are similar, with impedance ratios exceeding 70dB, demonstrating excellent performance. The elastic wave devices (longitudinal-wave leaky surface acoustic wave resonators) 200 with silicon carbide and aluminum nitride as supporting substrates exhibit a large parasitic mode to the right of their passband, while the elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) 200 with sapphire as its supporting substrate successfully suppresses this parasitic mode to the right of its passband.

[0115] In Figures 24 to 27, “h LiNbO3 " is used to indicate the thickness of lithium niobate film.

[0116] In some embodiments, the parasitic mode of the longitudinal-wave leaky surface acoustic wave resonator using silicon carbide as the supporting substrate is farther away from the main LLSAW mode than that of the longitudinal-wave leaky surface acoustic wave resonator using aluminum nitride as the supporting substrate.

[0117] 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.

[0118] 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. For example, the piezoelectric layer 201 is implemented as a 300nm thick lithium niobate film with an Euler angle 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 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 Q max The value is 1022.

[0119] 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. For example, the piezoelectric layer 201 is implemented as a 180nm thick lithium niobate film with an Euler angle 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 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 Q max The value is 850.

[0120] 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.

[0121] 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 acoustic waves in the transverse direction also gradually increases.

[0122] 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 propagation of the elastic wave, and the inclination angle is β. As a result, the transverse 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 propagation of the elastic wave, and the inclination angle is β.

[0123] Figure 32 shows the measured frequency response of an elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 for different β angles, as well as trends in the measured impedance ratio and Q value. A comparison reveals that when β is greater than 16°, the transverse modes within the resonator's passband are substantially suppressed. When β satisfies 16° ≤ ψ ≤ 20°, the elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) 200 achieves both a large impedance ratio and a high Q value.

[0124] Example 2:

[0125] Figure 33 shows a 5G communication - sixth / seventh generation wireless network technology (WIFI6 / 7) frequency band diagram. The longitudinal wave leaky acoustic surface wave of this 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, large-bandwidth longitudinal wave leaky acoustic surface wave filter.

[0126] FIG34 shows a schematic diagram of the topological structure of the elastic wave device (longitudinal-wave leaky surface acoustic wave resonator) provided in Example 2 of the present application. S1 to S4 are series-arm resonators, and P1 to P5 are parallel-arm resonators. For example, all series-arm resonators and parallel-arm resonators are elastic wave devices (longitudinal-wave leaky surface acoustic wave resonators) 200 provided in Example 1 of the present application.

[0127] Figure 35 shows the measured frequency response of an elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) provided in Example 2 of this application. 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 a 500μm thick silicon carbide.

[0128] As shown in FIG35 , 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.

[0129] Figure 36 shows the measured frequency response of another elastic wave device (a longitudinal-wave leaky surface acoustic wave resonator) provided in Example 2 of this application. For example, the piezoelectric layer 201 is implemented as a 200 nm thick lithium niobate film with Euler angles of (0, 122°, 45°), the low acoustic velocity layer 203 is implemented as a 200 nm thick silicon dioxide film, and the supporting substrate 204 is implemented as a 500 μm thick sapphire.

[0130] As shown in Figure 36, 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.

[0131] In the above embodiment, 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-wave leaky surface acoustic wave of this application can also be designed and prepared to meet the requirements of other 5G communication-WIFI6 / 7 frequency bands.

[0132] 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 embodiment for application.

[0133] Modification 1:

[0134] FIG37 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface wave resonator) 700 provided in a 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. A conductive material film pattern is formed above the piezoelectric layer 701. 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. 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.

[0135] In this variation, support substrate 704 is made of a material with a relatively high L-wave acoustic velocity, such as sapphire, silicon carbide, or aluminum nitride. Piezoelectric layer 701 is lithium niobate. The conductive thin film material pattern is made of a heavy metal material, such as copper, molybdenum, gold, silver, platinum, tantalum, or tungsten. Low acoustic velocity layer 703 is made of silicon dioxide. Alternatively, low acoustic velocity layer 703 may be made of a material primarily composed of glass, silicon oxynitride, tantalum oxide, or a compound containing fluorine, carbon, or boron added to silicon oxide, such as silicon dioxide. The material of low acoustic velocity layer 703 can be any material with a relatively low acoustic velocity.

[0136] For example, the ratio of the thickness of the piezoelectric layer 701 to the wavelength λ satisfies 0.16≤h LN / λ≤0.23.

[0137] For example, the ratio of the thickness of the low acoustic velocity layer 703 to the wavelength λ satisfies 0.1≤hSiO2 / λ≤0.2.

[0138] The above structure is defined in the same manner as in Example 1. The difference between the two is that a dielectric layer 706 is formed above the conductive material thin film pattern. Dielectric layer 706 is composed of silicon dioxide. Alternatively, dielectric layer 706 may be composed, for example, of a material primarily composed of silicon nitride or a compound containing fluorine, carbon, or boron added to silicon oxide, such as silicon dioxide. Dielectric layer 706 may be composed of either a temperature-compensating material or a non-temperature-compensating material.

[0139] 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.

[0140] Modification 2:

[0141] 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 and supports the piezoelectric layer 801. A conductive material thin film pattern is formed above the piezoelectric layer 801. The conductive material thin 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.

[0142] In this variation, support substrate 804 is made of a material with a relatively high L-wave acoustic velocity, such as sapphire, silicon carbide, or aluminum nitride. Piezoelectric layer 801 is lithium niobate. The conductive thin film material pattern is made of a heavy metal material, such as copper, molybdenum, gold, silver, platinum, tantalum, or tungsten. Low acoustic velocity layer 803 is made of silicon dioxide. Alternatively, low acoustic velocity layer 803 may be made of a material primarily composed of glass, silicon oxynitride, tantalum oxide, or a compound containing fluorine, carbon, or boron added to silicon oxide, such as silicon dioxide. The material of low acoustic velocity layer 803 can be any material with a relatively low acoustic velocity.

[0143] For example, the ratio of the thickness of the piezoelectric layer 801 to the wavelength λ satisfies 0.16≤h LN / λ≤0.23.

[0144] 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.

[0145] 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.

[0146] Modification 3:

[0147] 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 and supports 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.

[0148] In this variation, support substrate 904 is made of a material with a relatively high L-wave acoustic velocity, such as sapphire, silicon carbide, or aluminum nitride. Piezoelectric layer 901 is lithium niobate. The conductive thin film material pattern is made of a heavy metal material, such as copper, molybdenum, gold, silver, platinum, tantalum, or tungsten. Low acoustic velocity layer 903 is made of silicon dioxide. Alternatively, low acoustic velocity layer 903 may be made of a material primarily composed of glass, silicon oxynitride, tantalum oxide, or a compound containing fluorine, carbon, or boron added to silicon oxide, such as silicon dioxide. The material of low acoustic velocity layer 903 can be any material with a relatively low acoustic velocity.

[0149] For example, the ratio of the thickness of the piezoelectric layer 901 to the wavelength λ satisfies 0.16≤h LN / λ≤0.23.

[0150] 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.

[0151] The above structure is similar to that of Modification 2. The difference between the two is that a dielectric layer 906 is formed above the conductive material thin film pattern. Dielectric layer 906 is composed of silicon dioxide. Alternatively, dielectric layer 906 may be composed, for example, of a material primarily composed of silicon nitride or a compound containing fluorine, carbon, or boron added to silicon oxide, such as silicon dioxide. Dielectric layer 906 may be composed of either a temperature-compensating material or a non-temperature-compensating material.

[0152] 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

1. 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 sound velocity layer, the low sound velocity layer being directly or indirectly formed on the second main surface; as well as A high sound velocity component, the high sound velocity component is located below the low sound velocity layer; Wherein, when the thickness of the piezoelectric layer is set to h LN , under the premise that the wavelength of the elastic wave is set to λ, 0.1≤h LN / λ≤0.3; under the premise that the thickness of the low acoustic velocity layer is set to h1 and the wavelength of the elastic wave is set to λ, 0.1≤h1 / λ≤0.3 is satisfied.

2. The elastic wave device according to claim 1, wherein: 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.

3. The elastic wave device according to claim 1, wherein: The high acoustic velocity component comprises: a supporting substrate, wherein the supporting substrate is 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.

4. The elastic wave device according to claim 3, wherein: The support substrate is composed of one or more materials having a sound velocity exceeding 6000 meters per second.

5. 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 added with a compound containing fluorine, carbon, or boron as a main component.

6. 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.

7. The elastic wave device according to claim 3, wherein: On the premise that the thickness of the capture material layer is set to h2 and the wavelength of the elastic wave is set to λ, 0.1≤(h2+h1) / λ≤0.3 is satisfied.

8. 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.

9. The elastic wave device according to any one of claims 1 to 8, further comprising a dielectric layer, wherein the dielectric layer is composed of silicon dioxide, silicon nitride, or a material having fluorine, carbon, or boron compounds added to silicon oxide as a main component, and the dielectric layer is arranged on the piezoelectric layer and covers the interdigital transducer electrode and the reflective gate electrode.

10. 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 employs the elastic wave device as claimed in any one of claims 1 to 9.

Images