Elastic wave device

Abstract

An elastic wave device, comprising a quartz substrate (5), a piezoelectric layer (1), and interdigital transducer electrodes (2a). The horizontal shear wave curvature of the quartz substrate (5) is less than -4; the piezoelectric layer (1) is disposed on the quartz substrate (5), the Euler angle of the piezoelectric layer (1) is (0±2.5°, β±2.5°, 0±2.5°), and β satisfies 90°≤β≤130°; and the interdigital transducer electrodes (2a) are disposed on the side of the piezoelectric layer (1) away from the quartz substrate (5).

Description

Elastic wave device

[0001] This application claims priority to the Chinese patent application No. 202410629126.9 filed on May 21, 2024 with the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of elastic wave, for example, to an elastic wave device. BACKGROUND

[0003] Elastic wave devices have the characteristics of low cost, small size and multiple functions, and have been widely used in radar, communication, navigation and other fields. The most commonly used elastic wave devices in mobile phone and base station communication 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 thin film pattern of conductive material is provided on a piezoelectric multilayer substrate to determine multiple interdigital transducer (IDT) electrodes, and the frequency characteristics of the conversion function of the IDT electrode from an electrical signal to an elastic wave are used to obtain a bandpass characteristic.

[0004] Mobile communication systems are developing from the 3rd-Generation (3G), 4G to 5G. The 5G communication era has put forward more and more stringent requirements for the performance of elastic wave filters such as high frequency, high power, large bandwidth and low loss, and the use frequency band has moved to a frequency band above 3GHz. The traditional elastic wave device is limited by the piezoelectric material itself, with low Q value and coupling coefficient, which cannot fully meet the requirements of mobile communication for high performance devices. The elastic wave device based on the composite multilayer structure of lithium tantalate / lithium niobate piezoelectric thin film is concerned for its advantages of low insertion loss, low temperature drift, large bandwidth and large power.

[0005] As a frequency source device, the elastic wave filter usually has spurious waves caused by transverse modes, which causes large in-band fluctuations and large loss, i.e. leads to reduced filter performance. The industry usually uses different weighted forms of interdigital transducer electrodes to suppress the generation of transverse modes. However, this method has the following defects: first, the device itself will have a reduced Q value due to the weighting of the interdigital transducer electrodes, increasing the loss of the elastic wave filter and hindering its application in the radio frequency front end; second, the weighting method often leads to an increase in the size of the device, hindering the miniaturization development of the device; third, a part of the weighting method is complex and will increase the difficulty of device preparation.

[0006] SUMMARY

[0007] The present application provides an elastic wave device to solve the problems in the related art.

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

[0009] a quartz substrate, a horizontal shear wave curvature of the quartz substrate being less than -4;

[0010] a piezoelectric layer, the piezoelectric layer being disposed on the quartz substrate, an Euler angle of the piezoelectric layer being (0±2.5°, β±2.5°, 0±2.5°), and the β satisfying 90°≤β≤130°; and

[0011] an interdigital transducer electrode, the interdigital transducer electrode being disposed on a side of the piezoelectric layer away from the quartz substrate.

[0012] In a possible implementation, an Euler angle of the quartz substrate is (0±2.5°, θ±2.5°, 0±2.5°), and the θ satisfies 126°≤θ≤140°.

[0013] In a possible implementation, an Euler angle of the quartz substrate is (0±2.5°, θ±2.5°, 90±2.5°), and the θ satisfies 135°≤θ≤150°.

[0014] In a possible implementation, a material of the interdigital transducer electrode is aluminum, and a thickness h1 of the interdigital transducer electrode satisfies 0.01λ≤h1≤0.045λ, where λ represents a wavelength of an elastic wave.

[0015] In a possible implementation, a material of the interdigital transducer electrode is copper, and a thickness h2 of the interdigital transducer electrode satisfies 0.01λ≤h2≤0.02λ, where λ represents a wavelength of an elastic wave.

[0016] In a possible implementation, a material of the interdigital transducer electrode is a metal other than aluminum and copper, and a thickness h3 of the interdigital transducer electrode satisfies h3=h1ρ1 / ρ3 or h3=h2ρ2 / ρ3, where an electrode density of the interdigital transducer electrode is ρ3, a density of aluminum is ρ1, and a density of copper is ρ2.

[0017] In a possible implementation, the piezoelectric layer is lithium niobate.

[0018] In a possible implementation, a thickness h LN of the piezoelectric layer satisfies 0.05λ≤h LN ≤0.15λ, where λ represents a wavelength of an elastic wave.

[0019] In a possible implementation, a sound speed of sound propagation in the quartz substrate is higher than a sound speed of sound propagation in the piezoelectric layer.

[0020] In a possible implementation, the interdigital transducer electrode is stacked by at least one metal material thin film.

[0021] In a possible implementation, the interdigital transducer electrode further has a reflector electrode on both sides in the elastic wave propagation direction.

[0022] In a second aspect, the present application provides a filter device, comprising:

[0023] a series arm resonator; and

[0024] a parallel arm resonator;

[0025] At least one of the series arm resonator and the parallel arm resonator is the elastic wave device as described above.

[0026] In a third aspect, the present application provides a multiplexer, comprising:

[0027] an antenna terminal configured to be connected with an antenna; and

[0028] a plurality of filter devices commonly connected to the antenna terminal;

[0029] At least one of the plurality of filter devices is the filter device as described above. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application, and are used to explain the present application together with the embodiments of the present application to make the present application complete, and do not constitute a limitation to the present application. In the drawings:

[0031] FIG. 1 shows a schematic top view and sectional view of an elastic wave device 100 based on a piezoelectric composite substrate;

[0032] FIG. 2 shows a plot of admittance / conductance-frequency of an elastic wave device 100;

[0033] FIG. 3 shows a sectional view of an elastic wave device 200 according to an embodiment of the present application;

[0034] FIG. 4 shows a plot of comparison of admittance-frequency of the elastic wave device 200 and the elastic wave device 100 according to an embodiment of the present application;

[0035] FIG. 5 shows a displacement mode pattern of a resonance mode of the elastic wave device 200 according to an embodiment of the present application;

[0036] FIG. 6 shows a plot of variation of an admittance ratio of the elastic wave device 200 according to an embodiment of the present application with a cut angle θ in Euler angles of a quartz substrate;

[0037] Figure 7 shows the electromechanical coupling coefficient of the elastic wave device 200 of the present embodiment 1 as a function of the tilt angle β in the Euler angles of lithium niobate for different h LN Figure 8 shows the electromechanical coupling coefficient of the elastic wave device 200 of the present embodiment 1 as a function of the tilt angle β in the Euler angles of lithium niobate for different h

[0038] Figure 8 shows the electromechanical coupling coefficient of the elastic wave device 200 of the present embodiment 1 as a function of the tilt angle β in the Euler angles of lithium niobate for different h LN Figure 8 shows the electromechanical coupling coefficient of the elastic wave device 200 of the present embodiment 1 as a function of the tilt angle β in the Euler angles of lithium niobate for different h

[0039] Figure 9 shows the electromechanical coupling coefficient of the elastic wave device 200 of the present embodiment 1 as a function of the tilt angle β in the Euler angles of lithium niobate for different h

[0040] Figure 10 shows a cross-sectional view of the elastic wave device 300 of the present comparative example 1.

[0041] Figure 11 shows a slowness plot of the fast shear wave (SH), the slow shear wave (SV) and the longitudinal wave (L) of the components of the elastic wave device 300 of the present comparative example 1.

[0042] Figure 12 shows a slowness plot of the elastic wave device 300 of the present comparative example 1.

[0043] Figure 13 shows an admittance-frequency plot of the elastic wave device 300 of the present comparative example 1.

[0044] Figure 14 shows a slowness plot of the fast shear wave (SH), the slow shear wave (SV) and the longitudinal wave (L) of four materials which can be used as high acoustic velocity members.

[0045] Figure 15 shows an admittance-frequency plot of the elastic wave device of the four materials used as high acoustic velocity members.

[0046] Figure 16 shows a slowness plot of the elastic wave device 200 of different thicknesses of lithium niobate and patterned conductive material films.

[0047] Figure 17 shows a slowness plot of the elastic wave device 200 of different thicknesses of lithium niobate and patterned conductive material films.

[0048] Figure 18 shows the admittance / conductance-frequency plot of the elastic wave device 200 of the present embodiment 1 for different h Al Figure 18 shows the admittance / conductance-frequency plot of the elastic wave device 200 of the present embodiment 1 for different h

[0049] Figure 19 shows a cross-sectional view of the elastic wave device 400 of the present comparative example 2.

[0050] Figure 20 shows the admittance / conductance-frequency plot and the phase-frequency plot of the elastic wave device 200 and the elastic wave device 400.

[0051] Fig. 21 shows a graph of the admittance ratio of a quartz curvature and elastic wave device 200 as a function of the cut angle θ in the Euler angle of the quartz substrate;

[0052] Fig. 22 shows a graph of the admittance ratio of another quartz curvature and elastic wave device 200 as a function of the cut angle θ in the Euler angle of the quartz substrate;

[0053] Fig. 23 shows a graph of the slowness of an elastic wave device 200 as a function of the cut angle θ in the Euler angle of the lithium niobate for different lithium niobate cuts, different h Al / λ;

[0054] Fig. 24 shows a graph of the maximum h Al / λ for which there is no transverse mode of an elastic wave device 200 as a function of the cut angle β in the Euler angle of the lithium niobate for different lithium niobate cuts;

[0055] Fig. 25 shows a graph of the slowness of an elastic wave device 200 as a function of the cut angle θ in the Euler angle of the quartz for different quartz cuts, different h Al / λ;

[0056] Fig. 26 shows a graph of the maximum h Al / λ for which there is no transverse mode of an elastic wave device 200 as a function of the cut angle θ in the Euler angle of the quartz for different quartz cuts;

[0057] Fig. 27 shows a graph of the slowness of an elastic wave device 200 as a function of the cut angle θ in the Euler angle of the lithium niobate for different lithium niobate cuts, different h Al / λ;

[0058] Fig. 28 shows a graph of the maximum h Al / λ for which there is no transverse mode of an elastic wave device 200 as a function of the cut angle θ in the Euler angle of the lithium niobate for different lithium niobate cuts;

[0059] Fig. 29 shows an electron microscope image of an elastic wave device 200, and an admittance / conductance vs. frequency graph;

[0060] Fig. 30 shows graphs of the Bode-Q vs. frequency for an elastic wave device 200 for different wavelengths, and the electromechanical coupling coefficient, Q max vs. elastic wave wavelength for the elastic wave device, respectively;

[0061] Fig. 31 shows a three-dimensional view of a large bandwidth filter device 500 according to an embodiment of the present application;

[0062] Fig. 32 shows an insertion loss vs. frequency graph for the filter device 500 according to an embodiment of the present application;

[0063] Fig. 33 shows an insertion loss vs. frequency graph for a filter device according to an embodiment of the present application, in which a silicon substrate is used as a high acoustic velocity member;

[0064] Fig. 34 shows a structural schematic diagram of a multiplexer provided in Embodiment Two of the present application. DETAILED DESCRIPTION

[0065] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. The described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0066] In the drawings used in the following description, identical components are denoted by identical reference numerals. The words "front", "back", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application, and the words "bottom" and "top", "inner" and "outer" refer to directions towards or away from a particular component. In addition, the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or an indicated number of technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more.

[0067] Device Description:

[0068] Fig. 1 shows a schematic top view and cross-sectional view of an elastic wave device 100 based on a piezoelectric composite substrate. In recent years, elastic wave devices based on a piezoelectric composite substrate of a piezoelectric layer 1 and a non-piezoelectric substrate 3 have attracted wide attention due to their high Q value performance and have been applied to many fields such as radar, communication, navigation, etc. The elastic wave device 100 based on a piezoelectric composite substrate of a surface acoustic wave (SAW) resonator is composed of a pattern of thin film of conductive material formed on a piezoelectric composite substrate of a piezoelectric layer 1 and a non-piezoelectric substrate 3. The piezoelectric layer 1 is a thin single crystal layer made of a piezoelectric material such as lithium niobate, lithium tantalate, gallium nitride, aluminum nitride or zinc oxide. The piezoelectric layer 1 is cut so that the crystal axes of the front and back surfaces of the piezoelectric layer 1 are consistent, so that the piezoelectric layer 1 has different cut orientations, which can be defined by Euler angles, for example, the Euler angles of a 15°Y-cut piezoelectric layer are (0°, 105°, 0°), the Euler angles of a Z-cut piezoelectric layer are (0°, 0°, 0°), the Euler angles of a 128°Y-cut piezoelectric layer are (0°, 38°, 0°), and the Euler angles of a 32°Y45°X-cut piezoelectric layer are (0°, 122°, 45°).

[0069] Admittance is a physical quantity that describes the response of a circuit element to alternating current and voltage, and is usually represented by the symbol Y. For a circuit element, its admittance Y is equal to the ratio of its conductance G to its susceptance B, i.e., Y = G + jB, where j is the imaginary unit. In the present embodiment, the admittance (dB) can be obtained by the formula Y = 20 x log 10 |Y|.

[0070] Admittance ratio is a value obtained by the formula [admittance ratio = (20 x log 10 |Y1|) - (20 x log 10 |Y2|)], Y1 is the admittance at the resonant frequency of the circuit element, and Y2 is the admittance at the anti-resonant frequency of the circuit element. To some extent, the admittance ratio can measure the strength of resonance of the circuit element.

[0071] Quality factor (Q) is a measure of energy loss in a resonator, and when energy is converted from one form to another, a portion of the energy contained in the system directly escapes or repeatedly changes into an energy form that cannot be recovered.

[0072] Electromechanical coupling coefficient (K 2 ), under the premise that the resonant frequency of the resonator is set as f s , and the anti-resonant frequency is set as f p , the electromechanical coupling coefficient can be obtained by the formula K 2 = π 2 / 4 x (f p -f s ) / -f p .

[0073] The non-piezoelectric substrate 3 is a single-layer or multi-layer substrate made of a high-velocity material, and is also referred to as a high-velocity member. In the high-velocity member, the velocity of a bulk wave propagating therein is higher than the velocity of an elastic wave propagating in the piezoelectric layer, so that the velocity of the elastic wave in the piezoelectric layer can be increased, and the frequency of the device can be increased. In addition, the high-velocity member can effectively confine the elastic wave propagating in the piezoelectric layer within the piezoelectric layer without leakage, so that the Q value of the device can be increased.

[0074] The high-velocity member is composed of a material having a relatively high velocity, such as silicon, sapphire, silicon carbide, aluminum nitride, quartz, etc. Table 1 shows the velocities of three different modes of elastic waves in a plurality of materials.

[0075] [Table 1]

[0076] The conductive material thin film pattern includes an interdigital transducer (IDT) electrode 2a, a reflector electrode 2b, an IDT bus bar 4a, and a reflector bus bar 4b, and the thickness of the conductive material thin film pattern is h mThe interdigital transducer electrode 2a includes a plurality of first electrode fingers and a plurality of second electrode fingers which are interlaced with each other, and a first bus bar and a second bus bar which are opposite to each other in the direction in which the fingers of the first electrode fingers and the second electrode fingers extend. The distance between adjacent first (or second) electrode fingers is usually referred to as the "wavelength" of the IDT. The distance by which the first electrode fingers and the second electrode fingers overlap is usually referred to as the "aperture" of the IDT. The reflector electrode 2b includes a plurality of third electrode fingers and a plurality of fourth electrode fingers which are interlaced with each other, and a third bus bar and a fourth bus bar which are opposite to each other in the direction in which the fingers of the third electrode fingers and the fourth electrode fingers extend.

[0077] The lateral mode is a fluctuation between the resonant frequency and the anti-resonant frequency of the resonator, which is usually caused by diffraction of the elastic wave during propagation.

[0078] Figure 2 shows a plot of the admittance / conductance-frequency curve of an elastic wave device 100. As can be seen from the plot, the elastic wave device 100 exhibits a lateral mode, which is manifested as a fluctuation in the admittance and the conductance between the resonant frequency and the anti-resonant frequency.

[0079] Embodiment One

[0080] Figure 3 shows a cross-sectional view of an elastic wave device 200 according to Embodiment One of the present application. The high acoustic velocity member is a quartz substrate 5 (Quartz, Qz), a piezoelectric layer 1 is formed above the quartz substrate 5 and supports the piezoelectric layer 1, and a thin film pattern of conductive material is formed above the piezoelectric layer 1, the thin film pattern of conductive material including an interdigital transducer electrode 2a, a reflector electrode 2b, an IDT bus bar (not shown in the figure) and a reflector bus bar (not shown in the figure). The direction parallel to the x-axis of the coordinate system is defined as the electrode finger arrangement direction, which is also the direction of propagation of the elastic wave, the direction parallel to the y-axis of the coordinate system is defined as the electrode finger extension direction (not shown in the figure), and the direction parallel to the z-axis of the coordinate system is defined as the height direction of the elastic wave device 200.

[0081] The piezoelectric layer 1 is lithium niobate (LiNbO3) with Euler angles (0°, β, 0°) and a thickness h LN ; the wavelength of the elastic wave is λ; the thin film pattern of conductive material is composed of aluminum electrodes with a thickness h m of 8%λ; and the high acoustic velocity member 5 is a quartz substrate with Euler angles (0°, θ, ψ).

[0082] Figure 4 shows a plot of the admittance-frequency curve of the elastic wave device 200 according to Embodiment One of the present application compared with that of a piezoelectric composite substrate-based elastic wave device 100 in the related art. The piezoelectric layer 1 is 32° YX lithium niobate with β of 122° and λ of 4 μm, and the thickness h LN (or hLiNbO3 ) is 0.15λ. From the curve, it can be seen that the elastic wave device 100 of the piezoelectric material has a small admittance because of the absence of the high acoustic velocity member, which leads to elastic wave leakage; when the Euler angle of the quartz substrate in the elastic wave device 200 (quartz Euler angle) is (0°, 100°, 0°), the elastic wave device 200 has a small admittance because the shear wave acoustic velocity of the quartz substrate with the Euler angle is low, which leads to elastic wave leakage from the lithium niobate into the substrate; when the Euler angle of the quartz substrate in the elastic wave device 200 is (0°, 126°, 0°) or (0°, 126°, 90°), the elastic wave device 200 has a large admittance because the shear wave acoustic velocity of the quartz substrate with the two Euler angles is high, which effectively confines the elastic wave in the piezoelectric layer.

[0083] Figure 5 shows a displacement mode diagram of the resonance mode of the elastic wave device 200 provided by the embodiment one of the present application. By observing the direction of elastic wave vibration and propagation, the elastic wave excited by the elastic wave device 200 is a horizontal shear wave (fast transverse wave).

[0084] Figure 6 shows a curve diagram of the admittance ratio of the elastic wave device 200 provided by the embodiment one of the present application varying with the cut angle θ in the Euler angle of the quartz substrate. The dashed line is the quartz with a propagation angle ψ of 90°, and the solid line is the quartz with a propagation angle ψ of 0°. From the curve, it can be seen that the admittance ratio of the elastic wave device 200 is different when the quartz substrate with different cut angles θ is used as the high acoustic velocity member; when θ satisfies 120°≤θ≤150°, the admittance ratio of the elastic wave device 200 is large.

[0085] Figure 7 shows a curve diagram of the electromechanical coupling coefficient of the elastic wave device 200 provided by the embodiment one of the present application varying with the cut angle β in the Euler angle of the lithium niobate when h LN / λ. By observing the curve, when β satisfies 90°≤β≤135°, the electromechanical coupling coefficient of the elastic wave device 200 is at a high level.

[0086] Figure 8 shows a curve diagram of the electromechanical coupling coefficient of the elastic wave device 200 provided by the embodiment one of the present application varying with h LN / λ. From the curve, it can be seen that when 0 LN / λ≤0.2, the electromechanical coupling coefficient of the elastic wave device 200 gradually increases; when h LN / λ>0.2, the electromechanical coupling coefficient of the elastic wave device 200 gradually tends to be stable and remains at about 30%.

[0087] Figure 9 shows a graph of the electromechanical coupling coefficient of the elastic wave device with different structures varying with the cut angle β in the Euler angle of lithium niobate. The Euler angle of the quartz substrate is (0°, 126°, 0°). By observing the curve, the electromechanical coupling coefficient of the elastic wave device 200 (in the figure: LiNbO3(0.075λ) / Qz, LiNbO3(0.1λ) / Qz) of the present embodiment can exceed 15%, and the electromechanical coupling coefficient of the elastic wave device 200 can be as high as 22% when the thickness of lithium niobate (LiNbO3) is 0.1λ. The electromechanical coupling coefficient of the elastic wave device 200 of the present embodiment is much larger than that of the conventional elastic wave device based on lithium tantalate film (in the figure: LiTaO3 / SiO2 / Si), so the elastic wave device 200 of the present embodiment is more suitable for the preparation of a large-bandwidth filter.

[0088] Comparative Example 1

[0089] Figure 10 shows a cross-sectional view of the elastic wave device 300 provided by Comparative Example 1 of the present application. The difference between the elastic wave device 300 and the elastic wave device 200 is that there is no high acoustic velocity member under the piezoelectric layer 1. 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 (not shown in the figure), and the direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 300.

[0090] The piezoelectric layer 1 is implemented as 32°YX lithium niobate, and the conductive material film pattern is implemented as aluminum or copper.

[0091] Figure 11 shows a slowness curve graph of the fast transverse wave (SH), the slow transverse wave (SV) and the longitudinal wave (L) of the various components in the elastic wave device 300 provided by Comparative Example 1 of the present application. For the elastic wave device 300 with the main mode as the fast transverse wave, the curvature γ of the 32°YX lithium niobate is -0.91, while the curvature γ of both copper and aluminum is 1.

[0092] Figure 12 shows a slowness curve graph of the elastic wave device 300 provided by Comparative Example 1 of the present application. The slowness curve can predict the transverse mode condition of the elastic wave device. When the curvature of the slowness curve is greater than 0, the elastic wave device will generate a transverse mode; when the curvature of the slowness curve is less than or equal to 0, the elastic wave device will not generate a transverse mode. Therefore, according to the slowness curve of the elastic wave device 300, the elastic wave device 300 will generate a transverse mode.

[0093] Figure 13 shows an admittance-frequency curve graph of the elastic wave device 300 provided by Comparative Example 1 of the present application. By observing the curve, regular fluctuations occur between the resonance frequency and the anti-resonance frequency of the elastic wave device 300, i.e. the transverse mode, which is consistent with the prediction of the above-mentioned slowness curve.

[0094] Figure 14 shows the slowness curves of the fast shear wave (SH), the slow shear wave (SV) and the longitudinal wave (L) of four materials that can be used as high-velocity components. For the elastic wave device 300 whose main mode is the fast shear wave, the curvature γ of silicon (Si) is 2.82, the curvature γ of silicon carbide (SiC) is 1, the curvature γ of quartz with Euler angles (0°, 150°, 0°) is -4.1, and the curvature γ of quartz with Euler angles (0°, 126°, 0°) is -5.62.

[0095] Figure 15 shows the admittance-frequency curves of the elastic wave devices using the above four materials as high-velocity components. As can be seen from the curves, the elastic wave device 300 using silicon and silicon carbide as high-velocity components will generate a lateral mode, while the elastic wave device 200 using quartz with Euler angles (0°, 126°, 0°) and (0°, 150°, 90°) as high-velocity components will not generate a lateral mode.

[0096] From Figures 14 and 15, it can be concluded that when the main mode of the elastic wave device is the fast shear wave, the curvature of the fast shear wave slowness curve of the high-velocity component can predict whether the elastic wave device will generate a lateral mode. When the curvature of the fast shear wave slowness curve of the high-velocity component is greater than 0, the elastic wave device will generate a lateral mode; when the curvature of the fast shear wave slowness curve of the high-velocity component is less than 0, the elastic wave device will not generate a lateral mode.

[0097] The reason for the above phenomenon is that the curvature of the fast shear wave slowness curve of the conductive material thin film pattern of the elastic wave device is greater than 0, so a material with a fast shear wave slowness curve less than 0 is needed to compensate for the slowness curve of the conductive material thin film pattern, while the curvature of the fast shear wave slowness curve of the piezoelectric layer is also less than 0, but the curvature value is too small to compensate for the slowness curve of the conductive material thin film pattern.

[0098] Figure 16 shows the slowness curves of an elastic wave device 200 with different thicknesses of lithium niobate and conductive material thin film pattern. In the figure, the wavelength λ of the elastic wave is 4 μm, the thickness of the lithium niobate is h LN (or h LiNbO3 ), and the conductive material thin film pattern is aluminum with a thickness of h Al . As can be seen from the curves, as the thickness of the lithium niobate decreases, the curvature of the slowness curve of the elastic wave device 200 gradually decreases from greater than 0 to less than 0. To ensure that the curvature is less than 0, the thickness h LN needs to satisfy 0.05λ≤h LN ≤0.15λ; as the thickness of the conductive material thin film pattern decreases, the curvature of the slowness curve of the elastic wave device 200 gradually decreases from greater than 0 to less than 0. To ensure that the curvature is less than 0, the thickness h Al needs to satisfy h Al≤0.04λ. Thus, the thinner the thickness of the lithium niobate and the thinner the thickness of the conductive material film pattern of the elastic wave device 200, the more conducive to the transverse mode suppression of the elastic wave device 200.

[0099] Fig. 17 shows the slowness curves of another elastic wave device 200 with different thicknesses of lithium niobate and conductive material film pattern. Wherein, the wavelength λ of the elastic wave is 4 μm, the thickness of the lithium niobate is h LN (or h LiNbO3 ), and the conductive material film pattern is copper, and the thickness is h Cu . It can be seen from the curve that as the thickness of the lithium niobate decreases, the curvature of the slowness curve of the elastic wave device 200 gradually decreases from greater than 0 to less than 0, and to ensure that the curvature is less than 0, the thickness h LN needs to satisfy 0.05λ≤h LN ≤0.15λ; as the thickness of the conductive material film pattern decreases, the curvature of the slowness curve of the elastic wave device 200 gradually decreases from greater than 0 to less than 0, and to ensure that the curvature is less than 0, the thickness h Cu needs to satisfy h Cu ≤0.015λ. Thus, the thinner the thickness of the lithium niobate and the thinner the thickness of the conductive material film pattern of the elastic wave device 200, the more conducive to the transverse mode suppression of the elastic wave device 200.

[0100] Under the premise of ensuring the performance of the elastic wave device, the greater h Al / λ, the lower the ohmic loss of the device, the more conducive to the preparation and performance improvement of the actual device, and thus h Al / λ needs to be greater than 0.005.

[0101] Fig. 18 shows the admittance / conductance-frequency curves of the elastic wave device 200 with different h Al / λ. Based on the same reasons as above, the elastic wave device 200 with h Al / λ of 0.04 has a thinner thickness of the conductive material film pattern, and there is no transverse mode, and the elastic wave device 200 with h Al / λ of 0.08 has a thicker thickness of the conductive material film pattern, and there is a transverse mode.

[0102] Comparative Example Two:

[0103] Figure 19 shows a cross-sectional view of the elastic wave device 400 according to Comparative Example 2 of the present application. The high acoustic velocity member is a silicon substrate 7, a low acoustic velocity layer 6 is formed above the silicon substrate 7, a piezoelectric layer 1 is formed above the low acoustic velocity layer 6, and a thin film pattern of conductive material is formed above the piezoelectric layer 1, which includes the IDT electrodes 2a, the reflector electrodes 2b, the IDT bus bars (not shown in the figure), and the reflector bus bars (not shown in the figure). The direction parallel to the x-axis of 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 of the coordinate system is defined as the electrode finger extension direction (not shown in the figure), and the direction parallel to the z-axis of the coordinate system is defined as the height direction of the elastic wave device 400.

[0104] Figure 20 shows the admittance / conductance-frequency curve and the phase-frequency curve of the elastic wave device 200 and the elastic wave device 400. The Euler angle of the quartz substrate is (0°, 126°, 0°). According to the curves, the elastic wave device 200 does not have a lateral mode, and there is basically no fluctuation between the resonant frequency and the anti-resonant frequency, while the elastic wave device 400 has a lateral mode, and there is a regular fluctuation between the resonant frequency and the anti-resonant frequency. Therefore, the quartz substrate as the high acoustic velocity member can suppress the lateral mode of the elastic wave device.

[0105] According to the conclusions of Figures 14 and 15, when the fast shear wave curvature of the high acoustic velocity member is less than 0, the elastic wave device does not have a lateral mode. In order to further determine the range of the Euler angle of the quartz substrate, Figures 21 and 22 show the curves of the quartz curvature and the admittance ratio of the elastic wave device 200 with respect to the cut angle θ in the Euler angle of the quartz substrate. In Figure 21, the propagation angle ψ of the quartz is 90°, and in Figure 22, the propagation angle ψ of the quartz is 0°. In order to ensure that the curvature of the quartz is less than 0 while the admittance ratio of the elastic wave device 200 remains at a high level, when the propagation angle of the quartz is 90°, θ satisfies 135°≤θ≤150°, and when the propagation angle of the quartz is 0°, θ satisfies 126°≤θ≤140°.

[0106] Figure 23 shows the slowness curves of the elastic wave device 200 with different lithium niobate cut angles and different h Al / λ. In the figure, the thin film pattern of conductive material is aluminum, h Al is the thickness of aluminum, and the Euler angle of the quartz substrate is (0°, 126°, 0°). By observing the curves, it can be found that when the cut angle β in the Euler angle of the lithium niobate satisfies 90°≤β≤140°, h Al / λ≤4.5% needs to be satisfied to ensure that the curvature of the slowness curve of the elastic wave device 200 is less than 0 and there is no lateral mode.

[0107] Figure 24 shows the maximum hAl Figure 25 shows the slowness curves of the elastic wave device 200 with different quartz cut, different h Al / λmax, the maximum value is more than 4.3%.

[0108] Figure 25 shows the slowness curves of the elastic wave device 200 with different quartz cut, different h Al / λ. In which, the conductive thin film material pattern is aluminum, h Al is the thickness of aluminum, the Euler angle of lithium niobate is (0°, 122°, 0°) (i.e. 32° YX cut), and the propagation angle ψ of quartz is 0°. By observing the curve, it can be found that when the cut angle θ in the Euler angle of the quartz substrate satisfies 110°≤θ≤170°, it needs to satisfy 0<h Al / λ≤4% to ensure that the curvature of the slowness curve of the elastic wave device 200 is less than 0, and there is no transverse mode.

[0109] Figure 26 shows the maximum h Al / λof the elastic wave device 200 without transverse mode with different cut angle θ in the Euler angle of quartz substrate, and the curve of the electromechanical coupling coefficient of the elastic wave device 200 with the change of θ. In which, the conductive thin film material pattern is aluminum, h Al is the thickness of aluminum, the Euler angle of lithium niobate is (0°, 122°, 0°) (i.e. 32° YX cut), and the propagation angle ψ of quartz is 0°. The electromechanical coupling coefficient of the elastic wave device 200 decreases with the increase of θ, and when θ satisfies 130°≤θ≤150°, the maximum h Al / λof the elastic wave device 200 without transverse mode is the maximum, and the maximum value is more than 3.75%.

[0110] Figure 27 shows the slowness curves of the elastic wave device 200 with different quartz cut, different h Al / λ. In which, the conductive thin film material pattern is aluminum, h Al is the thickness of aluminum, the Euler angle of lithium niobate is (0°, 122°, 0°) (i.e. 32° YX cut), and the propagation angle ψ of quartz is 90°. By observing the curve, it can be found that the cut angle θ in the Euler angle of the quartz substrate is 120° and 150° respectively, when θ is 120°, h Al / λneeds to satisfy 0<h Al / λ≤0.0375% to ensure that the curvature of the slowness curve of the elastic wave device 200 is less than 0, and no transverse mode exists; when θ is 150°, h Al / λ needs to satisfy 0 < h Al / λ≤4% to ensure that the curvature of the slowness curve of the elastic wave device 200 is less than 0, and no transverse mode exists.

[0111] Figure 28 shows a curve of the maximum h Al / λ of the elastic wave device 200 without transverse mode in the cut angle θ in the Euler angle of different quartz substrates, and a curve of the electromechanical coupling coefficient of the elastic wave device 200 varying with θ. In the figure, the conductive thin film material pattern is aluminum, h Al is the thickness of aluminum, the Euler angle of lithium niobate is (0°, 122°, 0°) (i.e. 32° YX cut), and the propagation angle ψ of quartz is 90°. When θ satisfies 120°≤θ≤130°, the electromechanical coupling coefficient of the elastic wave device 200 increases with the increase of the cut angle β in the Euler angle of lithium niobate; when θ satisfies 130°<θ≤140°, the electromechanical coupling coefficient of the elastic wave device 200 remains basically unchanged with the increase of β; when θ satisfies 140°<θ≤155°, the electromechanical coupling coefficient of the elastic wave device 200 decreases with the increase of β. In addition, when θ satisfies 140°≤θ≤155°, the maximum h Al / λ of the elastic wave device 200 without transverse mode is the largest, and the maximum value exceeds 3%.

[0112] In order to further verify the suppression effect of the quartz substrate on the transverse mode of the elastic wave device, the actual preparation of the elastic wave device 200 is continued. The elastic wave device 200 is processed under the condition of Micro-Electro-Mechanical System (MEMS) technology, and the device is tested by using a Ground Signal Ground (GSG) probe.

[0113] Figure 29 shows an optical microscope image of the elastic wave device 200, and a curve of admittance / conductance-frequency. In the figure, the elastic wave wavelength λ of the elastic wave device 200 is 3 μm-4 μm, the conductive thin film material pattern is aluminum, the thickness is 160 nm, the aperture is 30λ, the number of interdigital transducer electrodes is 200, and the number of reflector electrodes is 20. By observing the curve, the elastic wave device 200 has no transverse mode response, and there is basically no fluctuation between the resonance frequency and the anti-resonance frequency.

[0114] Figure 30 shows a curve of Bode-Q of the elastic wave device 200 varying with frequency and a curve of the electromechanical coupling coefficient, Q maxA graph of the curvature with respect to the wavelength of the elastic wave. When the wavelength of the elastic wave is 3 μm to 4 μm, the Q factor of the elastic wave device 200 is increased slightly with an increase in the wavelength of the elastic wave. max The electromechanical coupling coefficient of the elastic wave device 200 is increased slightly with an increase in the wavelength of the elastic wave, while the value of the electromechanical coupling coefficient is maintained at around 800 to 900.

[0115] The elastic wave device provided by the present application includes a quartz substrate with a horizontal shear wave curvature less than -4, a piezoelectric layer disposed on the quartz substrate, and an interdigital transducer electrode disposed on the piezoelectric layer; wherein the Euler angle of the piezoelectric layer is (0±2.5°, β±2.5°, 0±2.5°), and β satisfies 90°≤β≤130°. In this case, by using the quartz substrate as a support substrate, a large-bandwidth elastic wave device capable of suppressing the intrinsic transverse mode is realized.

[0116] Embodiment Two

[0117] FIG. 31 shows a three-dimensional view of a large-bandwidth filter device 500 provided by Embodiment Two of the present application. The filter device 500 includes a series arm resonator and a parallel arm resonator, at least one resonator of the series arm resonator and the parallel arm resonator being the elastic wave device 200 provided by Embodiment One of the present application. A direction parallel to the x-axis of the coordinate system is defined as the electrode finger arrangement direction, which is also the elastic wave propagation direction, a direction parallel to the y-axis of the coordinate system is defined as the electrode finger extension direction, and a direction parallel to the z-axis of the coordinate system is defined as the height direction of the filter device 500.

[0118] FIG. 32 shows an insertion loss-frequency graph of the filter device 500 provided by Embodiment Two of the present application. Based on the same reason as the elastic wave device, since the fast transverse wave slowness curve of quartz has a curvature less than 0, the intrinsic suppression of the transverse mode of the filter device can be achieved. As can be seen from the graph, the filter has a small in-band fluctuation, a flat passband, and substantially no transverse mode.

[0119] FIG. 33 shows an insertion loss-frequency graph of a filter device provided by Embodiment Two of the present application, in which a silicon substrate is used as a high acoustic velocity member. Since the fast transverse wave slowness curve of silicon has a curvature greater than 0, the suppression of the transverse mode of the filter device cannot be achieved. As can be seen from the graph, the filter has a large in-band fluctuation, most of which is regular fluctuation, and a significant transverse mode.

[0120] FIG. 34 shows a structural schematic diagram of a multiplexer provided by Embodiment Two of the present application, which includes an antenna terminal 600 configured to be connected to an antenna 700, and a plurality of filter devices commonly connected to the antenna terminal 600, at least one of the plurality of filter devices being the filter device 500 described above.

[0121] In the embodiments of the present application, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, "connecting" can be fixedly connected, or can be detachably connected, or integrally connected; "connecting" can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

Claims

1. An elastic wave device comprising: a quartz substrate, a horizontal shear wave curvature of which is less than -4; a piezoelectric layer provided on the quartz substrate, an Euler angle of which is (0±2.5°, β±2.5°, 0±2.5°), and the β satisfies 90°≤β≤130°; and an interdigital transducer electrode provided on a side of the piezoelectric layer distal from the quartz substrate.

2. The elastic wave device according to claim 1, wherein an Euler angle of the quartz substrate is (0±2.5°, θ±2.5°, 0±2.5°), and the θ satisfies 126°≤θ≤140°.

3. The elastic wave device according to claim 1, wherein an Euler angle of the quartz substrate is (0±2.5°, θ±2.5°, 90±2.5°), and the θ satisfies 135°≤θ≤150°.

4. The elastic wave device according to claim 1, wherein a material of the interdigital transducer electrode is aluminum, and a thickness h1 of the interdigital transducer electrode satisfies 0.01λ≤h1≤0.045λ, where the λ represents a wavelength of an elastic wave.

5. The elastic wave device according to claim 1, wherein a material of the interdigital transducer electrode is copper, and a thickness h2 of the interdigital transducer electrode satisfies 0.01λ≤h2≤0.02λ, where the λ represents a wavelength of an elastic wave.

6. The elastic wave device according to claim 1, wherein a material of the interdigital transducer electrode is a metal other than aluminum and copper, and a thickness h3 of the interdigital transducer electrode satisfies h3=h1ρ1 / ρ3 or h3=h2ρ2 / ρ3, where an electrode density of the interdigital transducer electrode is ρ3, a density of aluminum is ρ1, and a density of copper is ρ2.

7. The elastic wave device according to claim 1, wherein the piezoelectric layer is lithium niobate.

8. The elastic wave device according to claim 1, wherein The thickness h of the piezoelectric layer LN satisfies 0.05λ≤h LN ≤0.15λ, the λ representing the wavelength of the elastic wave.

9. The elastic wave device according to claim 1, wherein a sound velocity of sound propagation in the quartz substrate is higher than a sound velocity of sound propagation in the piezoelectric layer.

10. The elastic wave device according to claim 1, wherein the interdigital transducer electrode is laminated from at least one metal material thin film.

11. The elastic wave device according to claim 1, wherein both sides of the interdigital transducer electrode in an elastic wave propagation direction further have reflector electrodes.

12. A filter device comprising: a series arm resonator; and a parallel arm resonator; wherein at least one of the series arm resonator and the parallel arm resonator is the elastic wave device according to any one of claims 1 to 11.

13. A multiplexer comprising: an antenna terminal provided to be connected to an antenna; and a plurality of filter devices commonly connected to the antenna terminal; wherein at least one of the plurality of filter devices is the filter device according to claim 12. ​ ​

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