Elastic wave device

Abstract

The application relates to an elastic wave device, and relates to the field of elastic waves. The application is characterized in that a quartz substrate with a horizontal shear wave curvature less than -4 is arranged, a piezoelectric layer is arranged on the quartz substrate, and an interdigital transducer electrode is arranged on the piezoelectric layer; wherein the Euler angle of the piezoelectric layer is (0+ / -2.5 DEG, beta+ / -2.5 DEG, 0+ / -2.5 DEG), and beta satisfies 90 DEG <= beta <= 130 DEG. In this case, by taking the quartz substrate as a supporting substrate, an elastic wave device with a large bandwidth capable of inhibiting an intrinsic transverse mode is realized.

Description

Technical Field

[0001] This application relates to the field of elastic wave technology, and in particular to an elastic wave device. Background Technology

[0002] Elastic wave devices, characterized by low cost, small size, and multiple functions, have found wide application in radar, communication, 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 any type of elastic wave device, a conductive material thin film pattern is formed on a piezoelectric multilayer substrate to define several interdigital transducer (IDT) electrodes, and the bandpass characteristic is obtained by utilizing the frequency characteristics of the conversion function of the electrical signal of the IDT electrodes into elastic waves.

[0003] Mobile communication systems are evolving from 3G and 4G to 5G. The 5G era places increasingly stringent demands on elastic wave filters, requiring high frequency, high power, large bandwidth, and low loss, while shifting the operating frequency band to above 3GHz. Traditional elastic wave devices are limited by the piezoelectric materials themselves, resulting in low Q-values ​​and coupling coefficients, which cannot fully meet the high-performance requirements of mobile communication devices. Elastic wave devices based on composite multilayer structures of lithium tantalate / lithium niobate piezoelectric films have attracted significant attention due to their advantages of low insertion loss, low temperature drift, large bandwidth, and high power.

[0004] Elastic wave filters, as frequency source devices, typically exhibit spurious waves caused by transverse modes, resulting in large in-band ripple and high loss, thus degrading filter performance. The industry commonly employs interdigitated transducer electrodes with different weighting schemes to suppress transverse modes. However, this approach has the following drawbacks: First, the Q-value of the device itself decreases due to the weighting of the interdigitated transducer electrodes, increasing the loss of the elastic wave filter and hindering its application in RF front-ends; second, the weighting method often leads to increased device size, hindering miniaturization; third, some weighting methods involve complex fabrication processes, increasing the difficulty of device manufacturing. Summary of the Invention

[0005] The purpose of this application is to provide an elastic wave device to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0007] In a first aspect, this application provides an elastic wave device, comprising:

[0008] Quartz substrate with a horizontal shear wave curvature of less than -4;

[0009] A piezoelectric layer is disposed on the quartz substrate, wherein the Euler angle of the piezoelectric layer is (0±2.5°, β±2.5°, 0±2.5°), and β satisfies 90°≤β≤130°; and

[0010] Interdigitated transducer electrodes are disposed on the piezoelectric layer.

[0011] In one possible implementation, when the Euler angles of the quartz substrate are (0±2.5°, θ±2.5°, 0±2.5°), the θ in the Euler angles satisfies 126°≤θ≤140°.

[0012] In one possible implementation, when the Euler angles of the quartz substrate are (0±2.5°, θ±2.5°, 90±2.5°), the θ in the Euler angles satisfies 135°≤θ≤150°.

[0013] In one possible implementation, the material of the interdigital transducer electrode is aluminum, and with the wavelength of the elastic wave set as λ, the thickness h1 of the interdigital transducer electrode satisfies 0.01λ≤h1≤0.045λ.

[0014] In one possible implementation, the material of the interdigital transducer electrode is copper, and with the wavelength of the elastic wave set as λ, the thickness h2 of the interdigital transducer electrode satisfies 0.01λ≤h2≤0.02λ.

[0015] In one possible implementation, the material of the interdigital transducer electrode is a metal other than aluminum and copper. Under the premise that the electrode density is set as ρ3, the density of aluminum is set as ρ1, and the density of copper is set as ρ2, the thickness h3 of the interdigital transducer electrode satisfies h3=h1ρ1 / ρ3 or h3=h2ρ2 / ρ3.

[0016] In one possible implementation, the piezoelectric layer is lithium niobate.

[0017] In one possible implementation, given that the wavelength of the elastic wave is λ, the thickness h of the piezoelectric layer is... LN Satisfying 0.05λ≤h LN ≤0.15λ.

[0018] In one possible implementation, the speed of sound propagating in the quartz substrate is higher than the speed of sound propagating in the piezoelectric layer.

[0019] In one possible implementation, the interdigital transducer electrodes are formed by stacking one or more thin films of metallic materials.

[0020] In one possible implementation, the interdigital transducer electrodes also have reflector electrodes on both sides along the direction of elastic wave propagation.

[0021] Secondly, this application provides a filter device, comprising:

[0022] Series arm resonators; and

[0023] Parallel arm resonator;

[0024] Wherein, at least one of the series arm resonators and the parallel arm resonators is an elastic wave device as described above.

[0025] Thirdly, this application provides a multiplexer, comprising:

[0026] Antenna terminals, which are connected to the antenna; and

[0027] Multiple filter devices are connected to the antenna terminal in a common manner;

[0028] At least one of the filter devices is a filter device as described above.

[0029] The beneficial effects of the technical solution provided in this application include at least the following:

[0030] By setting a quartz substrate with a horizontal shear wave curvature less than -4, a piezoelectric layer on the quartz substrate, and interdigitated transducer electrodes 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°, a wide-bandwidth elastic wave device capable of suppressing intrinsic transverse modes is realized by using the quartz substrate as a support substrate. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the application and do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 A schematic top view and cross-sectional view of a typical elastic wave device 100 based on a piezoelectric composite substrate are shown.

[0033] Figure 2 The admittance / conductance-frequency curve of a typical elastic wave device 100 is shown.

[0034] Figure 3 A cross-sectional view of the elastic wave device 200 provided in Embodiment 1 of this application is shown;

[0035] Figure 4 This paper shows a comparison of admittance-frequency curves between the elastic wave device 200 and the elastic wave device 100 provided in Embodiment 1 of this application.

[0036] Figure 5 The displacement mode diagram of the resonant mode of the elastic wave device 200 provided in Embodiment 1 of this application is shown;

[0037] Figure 6 The graph shows the admittance ratio of the elastic wave device 200 provided in Embodiment 1 of this application as a function of the quartz tangent angle θ.

[0038] Figure 7 Different h provided in Embodiment 1 of this application are shown. LN The curve of the electromechanical coupling coefficient of the elastic wave device 200 with the change of lithium niobate chamfer β is shown.

[0039] Figure 8 This illustrates the electromechanical coupling coefficient of the elastic wave device 200 provided in Embodiment 1 of this application as a function of h. LN A graph showing the change in / λ.

[0040] Figure 9 The graphs showing the electromechanical coupling coefficient of elastic wave devices with different structures as a function of the piezoelectric layer chamfer angle β are presented.

[0041] Figure 10 A cross-sectional view of the elastic wave device 300 provided in Comparative Example 1 of this application is shown;

[0042] Figure 11 The diagram shows the slowness curves of fast shear wave (SH), slow shear wave (SV), and longitudinal wave (L) of each component in the elastic wave device 300 provided in Comparative Example 1 of this application.

[0043] Figure 12 The slowness curve of the elastic wave device 300 provided in Comparative Example 1 of this application is shown;

[0044] Figure 13 The admittance-frequency curve of the elastic wave device 300 provided in Comparative Example 1 of this application is shown.

[0045] Figure 14 The slowness curves of fast transverse waves (SH), slow transverse waves (SV), and longitudinal waves (L) for four materials that can be used as hypersonic components are shown.

[0046] Figure 15 Admittance-frequency plots of elastic wave devices using four different materials as hypersonic components are shown.

[0047] Figure 16 The slowness curves of an elastic wave device 200 with different lithium niobate thicknesses and conductive material thin film pattern thicknesses are shown.

[0048] Figure 17The slowness curves of another elastic wave device 200 with different lithium niobate thicknesses and conductive material thin film pattern thicknesses are shown.

[0049] Figure 18 Different h were shown Al Admittance / conductance-frequency curve of elastic wave device 200 with / λ;

[0050] Figure 19 A cross-sectional view of the elastic wave device 400 provided in Comparative Example 2 of this application is shown;

[0051] Figure 20 The admittance / conductance-frequency curves and phase-frequency curves of elastic wave devices 200 and 400 are shown.

[0052] Figure 21 and Figure 22 The graph shows the curves of the quartz curvature and the admittance ratio of the elastic wave device 200 as a function of the quartz tangent angle θ.

[0053] Figure 23 It shows different lithium niobate tangentials and different h Al The slowness curve of the elastic wave device 200 with / λ;

[0054] Figure 24 The maximum h of the elastic wave device 200 with different lithium niobate Euler angles β is shown to have no transverse mode. Al / λ curve;

[0055] Figure 25 It shows different quartz tangents and different h Al The slowness curve of the elastic wave device 200 with / λ;

[0056] Figure 26 The maximum h of the elastic wave device 200 without a transverse mode is shown for different quartz Euler angles θ. Al / λ curve;

[0057] Figure 27 It shows different quartz tangents and different h Al The slowness curve of the elastic wave device 200 with / λ;

[0058] Figure 28 The maximum h of the elastic wave device 200 without a transverse mode is shown for different quartz Euler angles θ. Al / λ curve;

[0059] Figure 29 Electron microscope images of the elastic wave device 200 and admittance / conductance-frequency graphs are shown.

[0060] Figure 30The curves showing the Bode-Q of the elastic wave device 200 as a function of the elastic wave wavelength and the electromechanical coupling coefficient, Q are respectively shown. max A graph showing the variation of elastic wave wavelength;

[0061] Figure 31 A three-dimensional view of the high-bandwidth filter device 500 provided in Embodiment 2 of this application is shown;

[0062] Figure 32 The insertion loss-frequency curve of the filter device 500 provided in Embodiment 2 of this application is shown.

[0063] Figure 33 The insertion loss-frequency curve of the filter device with a silicon substrate as a high-speed acoustic component provided in Embodiment 2 of this application is shown. Detailed Implementation

[0064] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0065] In this specification, identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions towards or away from a specific component, respectively. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "multiple" means two or more.

[0066] Device Description:

[0067] Figure 1A schematic top view and cross-sectional view of a typical elastic wave device 100 based on a piezoelectric composite substrate are shown. In recent years, elastic wave devices based on piezoelectric composite substrates (piezoelectric layer 1 and non-piezoelectric substrate 3) have gained widespread attention due to their high Q-value performance and have been applied in numerous fields such as radar, communication, and navigation. The SAW resonator elastic wave device 100 based on a piezoelectric composite substrate consists of a conductive material thin film pattern formed on a piezoelectric composite substrate (piezoelectric layer 1 and non-piezoelectric substrate 3). The piezoelectric layer 1 is a thin single-crystal layer made of a piezoelectric material with a thickness of h, such as lithium niobate, lithium tantalate, gallium nitride, aluminum nitride, or zinc oxide. As is common knowledge, the piezoelectric layer 1 is cut to align with the crystal axes of the front and back sides of the piezoelectric layer 1, thus allowing for different tangential choices. We often use Euler angles to define its tangential direction. For example, the Euler angles of a piezoelectric layer cut at 15°Y are (0°, 105°, 0°), the Euler angles of a piezoelectric layer cut at Z are (0°, 0°, 0°), the Euler angles of a piezoelectric layer cut at 128°Y are (0°, 38°, 0°), and the Euler angles of a piezoelectric layer cut at 32°Y and 45°X are (0°, 122°, 45°).

[0068] Admittance is a physical quantity describing the response of a circuit element to alternating current and voltage, usually denoted 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 this embodiment, admittance (dB) can be expressed by the formula Y = 20 × log0 10 |Y| is obtained.

[0069] The admittance ratio is calculated using the formula [Admittance Ratio = (20 × log...]. 10 |Y1|)-(20×log 10 The values ​​obtained from |Y2| are: 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 a certain extent, the admittance ratio can measure the strength of the resonance of the circuit element.

[0070] The quality factor (Q) is a measure of energy loss in a resonator. When energy is converted from one form to another, a portion of the energy contained in the system will either escape directly or be repeatedly converted into an unrecoverable energy form.

[0071] Electromechanical coupling coefficient (K) 2 ), when the resonant frequency of the resonator is set to f s Let the anti-resonant frequency be f. p Under the premise that the electromechanical coupling coefficient can be obtained by formula K 2 =π 2 / 4×(f p -f s ) / -f p To obtain.

[0072] The non-piezoelectric substrate 3 is a single-layer or multi-layer substrate made of a high-velocity acoustic material, and is therefore also called a high-velocity acoustic component. The sound speed of bulk waves propagating in the high-velocity acoustic component is higher than that of elastic waves propagating in the piezoelectric layer, thereby increasing the sound speed of elastic waves in the piezoelectric layer and increasing the frequency of the device. In addition, the high-velocity acoustic component can effectively confine the elastic waves propagating in the piezoelectric layer within the piezoelectric layer to prevent leakage, thereby improving the Q value of the device.

[0073] High-speed components are made of materials with high sound velocities, such as silicon, sapphire, silicon carbide, aluminum nitride, and quartz. Table 1 shows the sound velocities of three different modes of elastic waves in various materials.

[0074] [Table 1]:

[0075]

[0076] The conductive material thin film pattern includes an interdigital transducer (IDT) electrode 2a, a reflector electrode 2b, an interdigital transducer busbar 4a, and a reflector busbar 4b, with a thickness of h. m The interdigitated transducer electrode 2a includes multiple first electrode fingers and multiple second electrode fingers inserted in an alternating manner, and a first busbar and a second busbar opposing each other in the extension direction of the first and second electrode fingers. The distance λ between adjacent first (or second) electrode fingers is commonly referred to as the "wavelength" of the IDT. The overlap distance AP between the first and second electrode fingers is commonly referred to as the "aperture" of the IDT. The reflector electrode 2b includes multiple third electrode fingers and multiple fourth electrode fingers inserted in an alternating manner, and a third busbar and a fourth busbar opposing each other in the extension direction of the third and fourth electrode fingers.

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

[0078] Figure 2 The admittance / conductance-frequency curve of a typical elastic wave device 100 is shown. The curve reveals a transverse mode in the elastic wave device 100, specifically characterized by fluctuations in admittance and conductance between the resonant and anti-resonant frequencies.

[0079] Example 1:

[0080] Figure 3A cross-sectional view of the elastic wave device 200 provided in Embodiment 1 of this application is shown. The high-speed acoustic component is a quartz substrate 5 (Quartz, Qz), on which a piezoelectric layer 1 is formed and supported. A conductive material thin film pattern is formed on the piezoelectric layer 1, including interdigitated transducer electrodes 2a, reflector electrodes 2b, IDT busbars (not shown in the figure), and reflector busbars (not shown in the figure). 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). The direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 200.

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

[0082] Figure 4 This paper presents a comparison of admittance-frequency curves between the elastic wave device 200 provided in Embodiment 1 of this application and a typical elastic wave device 100 based on a piezoelectric composite substrate. Specifically, the piezoelectric layer 1 is a 32°YX lithium niobate, with β = 122°, λ = 4 μm, and the thickness h of the lithium niobate is... LN (or h) LiNbO3 The value is 0.15λ. As can be seen from the curve, the elastic wave device 100 made of piezoelectric material has a relatively small admittance due to the absence of a high-velocity component, resulting in elastic wave leakage. When the Euler angle of the quartz substrate in the elastic wave device 200 is (0°, 100°, 0°), the admittance of the elastic wave device 200 is also relatively small. This is because the shear wave velocity of the quartz substrate at this Euler angle is low, causing the elastic wave in the lithium niobate to leak 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 shear wave velocity of the quartz substrate at these two Euler angles is high, effectively confining the elastic wave in the piezoelectric layer, resulting in a relatively large admittance of the elastic wave device 200.

[0083] Figure 5 The diagram shows the displacement mode shape of the resonant mode of the elastic wave device 200 provided in Embodiment 1 of this 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 6The graph shows the admittance ratio of the elastic wave device 200 provided in Embodiment 1 of this application as a function of the quartz cutting angle θ. The dashed line represents quartz with a propagation angle ψ of 90°, and the solid line represents quartz with a propagation angle ψ of 0°. As can be seen from the graph, the admittance ratio of the elastic wave device 200 varies when the quartz substrate has different cutting angles θ as a high-speed acoustic component. The admittance ratio of the elastic wave device 200 is larger when θ satisfies 120°≤θ≤150°.

[0085] Figure 7 Different h provided in Embodiment 1 of this application are shown. LN The graph shows the electromechanical coupling coefficient of the elastic wave device 200 as a function of the lithium niobate cutting angle β. By observing the curve, it can be seen that when the lithium niobate cutting angle β satisfies 90°≤β≤135°, the electromechanical coupling coefficient of the elastic wave device 200 is at a relatively high level.

[0086] Figure 8 This illustrates the electromechanical coupling coefficient of the elastic wave device 200 provided in Embodiment 1 of this application as a function of h. LN A graph showing the change in / λ. The curve shows that when 0 < h... LN When / λ≤0.2, the electromechanical coupling coefficient of the elastic wave device 200 gradually increases, and when h LN When / λ>0.2, the electromechanical coupling coefficient of the elastic wave device 200 gradually stabilizes and remains at around 30%.

[0087] Figure 9 The graphs show the electromechanical coupling coefficient of elastic wave devices with different structures as a function of the piezoelectric layer chamfer angle β. The Euler angles of the quartz substrate are (0°, 126°, 0°). Observing the curves, the electromechanical coupling coefficient of the elastic wave device 200 in this embodiment (LiNbO3(0.075λ) / Qz, LiNbO3(0.1λ) / Qz in the figure) can exceed 15%, and when the thickness of lithium niobate (LiNbO3) is 0.1λ, the electromechanical coupling coefficient of the elastic wave device 200 can reach up to 22%. The electromechanical coupling coefficient of the elastic wave device 200 in this embodiment is much larger than that of traditional elastic wave devices based on lithium tantalate thin films (LiTaO3 / SiO2 / Si in the figure). Therefore, the elastic wave device 200 in this embodiment is more suitable for the fabrication of wideband filters.

[0088] Comparative Example 1:

[0089] Figure 10A cross-sectional view of the elastic wave device 300 provided in Comparative Example 1 of this application is shown. The difference between the elastic wave device 300 and the elastic wave device 200 is that there is no high-velocity acoustic component below 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). The direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 300.

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

[0091] Figure 11 The diagram shows the slowness curves of the fast shear wave (SH), slow shear wave (SV), and longitudinal wave (L) of each component in the elastic wave device 300 provided in Comparative Example 1 of this application. For the elastic wave device 300, where the main mode is fast shear wave, the curvature γ of 32°YX lithium niobate is -0.91, while the curvature γ of copper and aluminum is 1.

[0092] Figure 12 The diagram shows the slow-motion curve of the elastic wave device 300 provided in Comparative Example 1 of this application. The slow-motion curve can predict the transverse mode of the elastic wave device. When the curvature of the slow-motion curve is greater than 0, the elastic wave device will generate a transverse mode; when the curvature of the slow-motion curve is less than or equal to 0, the elastic wave device will not generate a transverse mode. Therefore, according to the slow-motion curve of the elastic wave device 300, the elastic wave device 300 will generate a transverse mode.

[0093] Figure 13 The admittance-frequency curve of the elastic wave device 300 provided in Comparative Example 1 of this application is shown. By observing the curve, a regular fluctuation, i.e., a transverse mode, appears between the resonant frequency and the anti-resonant frequency of the elastic wave device 300, which is consistent with the prediction of the slow curve mentioned above.

[0094] Figure 14 The slowness curves of fast transverse waves (SH), slow transverse waves (SV), and longitudinal waves (L) for four materials that can be used as hypersonic components are shown. For the elastic wave device 300 with fast transverse waves as the dominant mode, 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 of (0°, 150°, 90°) is -4.1, and the curvature γ of quartz with Euler angles of (0°, 126°, 0°) is -5.62.

[0095] Figure 15Admittance-frequency curves of elastic wave devices using the four materials mentioned above as hypersonic components are shown. The curves show that the elastic wave device 300 using silicon and silicon carbide as hypersonic components produces a transverse mode, while the elastic wave device 200 using quartz as a hypersonic component with Euler angles of (0°, 126°, 0°) and (0°, 150°, 90°) does not produce a transverse mode.

[0096] according to Figure 14 and Figure 15 We can conclude that when the dominant mode of the elastic wave device is a fast shear wave, the curvature of the fast shear wave slowness curve of the hypersonic component can predict whether the elastic wave device will exhibit a transverse mode. When the curvature of the fast shear wave slowness curve of the hypersonic component is greater than 0, the elastic wave device will exhibit a transverse mode; when the curvature of the fast shear wave slowness curve of the hypersonic component is less than 0, the elastic wave device will not exhibit a transverse mode.

[0097] The reason for the above phenomenon is that the curvature of the fast transverse wave slow curve of the conductive material thin film pattern of the elastic wave device is greater than 0. Therefore, it is necessary to have a material with a fast transverse wave slow curve less than 0 to compensate for it. Although the curvature of the fast transverse wave slow curve of the piezoelectric layer is also less than 0, the curvature value is too small and insufficient to compensate for the curvature of the slow curve of the conductive material thin film pattern.

[0098] Figure 16 The slowness curves of an elastic wave device 200 with different lithium niobate thicknesses and conductive material thin film pattern thicknesses are shown. The wavelength λ of the elastic wave is 4 μm, and the thickness of the lithium niobate is h. LN (or h) LiNbO3 The conductive material thin film pattern is aluminum, and its thickness is h. Al As can be seen from the curve, as the thickness of 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 It is required that 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 h needs to be satisfied Al ≤0.04λ. Therefore, the thinner the lithium niobate thickness and the thinner the conductive material thin film pattern thickness of the elastic wave device 200, the better it is for the transverse mode suppression of the elastic wave device 200.

[0099] Figure 17 The slowness curves of another elastic wave device 200 with different lithium niobate thicknesses and conductive material thin film pattern thicknesses are shown. The wavelength λ of the elastic wave is 4 μm, and the thickness of the lithium niobate is h. LN (or h)LiNbO3 The conductive material thin film pattern is copper, and its thickness is h. Cu As can be seen from the curve, as the thickness of 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 It is required that 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... Cu h needs to be satisfied Cu ≤0.015λ. Therefore, the thinner the lithium niobate thickness and the thinner the conductive material thin film pattern thickness of the elastic wave device 200, the better it is for the transverse mode suppression of the elastic wave device 200.

[0100] While ensuring the performance of the elastic wave device, h Al A larger h / λ value reduces the ohmic loss of the device, which is more beneficial for the fabrication and performance improvement of the actual device. Al / λ needs to be greater than 0.005.

[0101] Figure 18 Different h were shown Al The admittance / conductance-frequency curve of the elastic wave device 200 with / λ. For the same reason mentioned above, h Al The elastic wave device 200 with a / λ of 0.04 has a thin conductive material film pattern and no lateral mode. Al The elastic wave device 200 with a / λ of 0.08 has a relatively thick conductive material thin film pattern and exhibits a transverse mode.

[0102] Comparative Example 2:

[0103] Figure 19 A cross-sectional view of the elastic wave device 400 provided in Comparative Example 2 of this application is shown. The high-velocity component is a silicon substrate 7, on which a low-velocity layer 6 is formed. A piezoelectric layer 1 is formed above the low-velocity layer 6, and a conductive material thin film pattern is formed above the piezoelectric layer 1. The conductive material thin film pattern includes interdigitated transducer electrodes 2a, reflector electrodes 2b, IDT busbars (not shown in the figure), and reflector busbars (not shown in the figure). 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). The direction parallel to the z-axis in the coordinate system is defined as the height direction of the elastic wave device 400.

[0104] Figure 20The admittance / conductance-frequency and phase-frequency curves of elastic wave devices 200 and 400 are shown. The Euler angles of the quartz substrate are (0°, 126°, 0°). According to the curves, elastic wave device 200 has no transverse mode, and there is essentially no fluctuation between the resonant frequency and the anti-resonant frequency. Elastic wave device 400, however, exhibits a transverse mode, with a clear and regular fluctuation between the resonant frequency and the anti-resonant frequency. Therefore, the quartz substrate, as a hypersonic component, can suppress the transverse mode of the elastic wave device.

[0105] according to Figure 14 and Figure 15 The conclusion is that when the fast transverse wave curvature of the hypersonic component is less than 0, the elastic wave device will not exhibit a transverse mode. To further determine the Euler angle range of the quartz substrate, Figure 21 and Figure 22 The graph shows the curves of the quartz curvature and the admittance ratio of the elastic wave device 200 as a function of the quartz tangent angle θ. Figure 20 The propagation angle ψ of quartz is 90°. Figure 21 The propagation angle ψ of the quartz is 0°. To ensure that the curvature of the quartz is less than 0 while maintaining a high admittance ratio of the elastic wave device 200, when the propagation angle of the quartz is 90°, the tangent angle θ of the quartz satisfies 135°≤θ≤150°, and when the propagation angle of the quartz is 0°, the tangent angle θ satisfies 126°≤θ≤140°.

[0106] Figure 23 It shows different lithium niobate tangentials and different h Al The slowness curve of the elastic wave device 200 with / λ. The conductive thin film material is aluminum, h. Al Given the thickness of the aluminum substrate, the Euler angles of the quartz substrate are (0°, 126°, 0°). Observing the curves, it can be found that for the tangent angle β in the lithium niobate Euler angles to satisfy 90°≤β≤140°, h must also be satisfied. Al Only when / λ≤4.5% can the curvature of the slow curve of the elastic wave device 200 be guaranteed to be less than 0, and the transverse mode not exist.

[0107] Figure 24 The maximum h of the elastic wave device 200 with different lithium niobate Euler angles β is shown to have no transverse mode. AlThe graphs show the relationship between / λ and the electromechanical coupling coefficient of the elastic wave device 200 as a function of the Euler angle β of lithium niobate. When the tangent angle β in the lithium niobate Euler angle satisfies 90°≤β≤110°, the electromechanical coupling coefficient of the elastic wave device 200 remains essentially constant with increasing Euler angle β. When the tangent angle β satisfies 110°<β≤150°, the electromechanical coupling coefficient of the elastic wave device 200 increases with increasing Euler angle β. Furthermore, when the tangent angle β in the lithium niobate Euler angle satisfies 120°≤β≤135°, the elastic wave device 200 does not exhibit a maximum h in the transverse mode. Al / λ is the largest, exceeding 4.3%.

[0108] Figure 25 It shows different quartz tangents and different h Al The slowness curve of the elastic wave device 200 with / λ.

[0109] The conductive thin film material pattern is aluminum, h Al Given the thickness of aluminum, the Euler angles of lithium niobate are (0°, 122°, 0°) (i.e., 32° tangentially in the YX direction), and the propagation angle ψ of quartz is 0°. Observing the curves, it can be found that for the tangential angle θ in the quartz Euler angles to satisfy 110° ≤ θ ≤ 170°, 0 < h must be satisfied. Al Only when / λ≤4% can the curvature of the slow curve of the elastic wave device 200 be guaranteed to be less than 0, and the transverse mode not exist.

[0110] Figure 26 The maximum h of the elastic wave device 200 without a transverse mode is shown for different quartz Euler angles θ. Al The graphs show the curves of / λ and the electromechanical coupling coefficient of the elastic wave device 200 as a function of the quartz Euler angle θ. The conductive thin film material is aluminum, h Al Given the thickness of aluminum, the Euler angles of lithium niobate are (0°, 122°, 0°) (i.e., 32° tangential to the YX direction), and the propagation angle ψ of quartz is 0°. The electromechanical coupling coefficient of the elastic wave device 200 decreases as the Euler angle θ of the quartz increases, and when θ in the Euler angle of the quartz satisfies 130°≤θ≤150°, the elastic wave device 200 does not have a maximum h in the transverse mode. Al / λ is the largest, exceeding 3.75%.

[0111] Figure 27 It shows different quartz tangents and different h Al The slowness curve of the elastic wave device 200 with / λ.

[0112] The conductive thin film material pattern is aluminum, h AlGiven the thickness of aluminum, the Euler angles of lithium niobate are (0°, 122°, 0°) (i.e., 32° tangential to the YX direction), and the propagation angle ψ of quartz is 90°. Observing the curves, it can be found that the tangential angle θ in the quartz Euler angle is 120° and 150° respectively. When θ in the quartz Euler angle is 120°, h... Al / λ needs to satisfy 0 < h Al / λ≤0.0375% to ensure that the curvature of the slow curve of the elastic wave device 200 is less than 0 and that there is no transverse mode; when the tangent angle θ in the quartz Euler angle is 150°, h Al / λ needs to satisfy 0 < h Al Only when / λ≤4% can the curvature of the slow curve of the elastic wave device 200 be guaranteed to be less than 0, and the transverse mode not exist.

[0113] Figure 28 The maximum h of the elastic wave device 200 without a transverse mode is shown for different quartz Euler angles θ. Al The graphs show the curves of / λ and the electromechanical coupling coefficient of the elastic wave device 200 as a function of the quartz Euler angle θ. The conductive thin film material is aluminum, h Al Given the thickness of aluminum, the Euler angles of lithium niobate are (0°, 122°, 0°) (i.e., 32° tangential to Y and X), and the propagation angle ψ of quartz is 90°. When the tangent angle θ in the quartz Euler angle satisfies 120° ≤ θ ≤ 130°, the electromechanical coupling coefficient of the elastic wave device 200 increases with the increase of the lithium niobate Euler angle β. When the tangent angle θ in the quartz Euler angle satisfies 130° < θ ≤ 140°, the electromechanical coupling coefficient of the elastic wave device 200 remains essentially unchanged with the increase of the lithium niobate Euler angle θ. When the tangent angle θ in the lithium niobate Euler angle satisfies 140° < θ ≤ 155°, the electromechanical coupling coefficient of the elastic wave device 200 decreases with the increase of the lithium niobate Euler angle θ. Furthermore, when the tangent angle θ in the quartz Euler angle satisfies 140° ≤ θ ≤ 155°, the elastic wave device 200 does not have a maximum h in the transverse mode. Al / λ is the maximum, exceeding 3%.

[0114] To further verify the effect of the quartz substrate on suppressing the lateral mode of the elastic wave device, the actual fabrication of the elastic wave device 200 was continued. The elastic wave device 200 was fabricated under MEMS process conditions, and the device was tested using GSG probes.

[0115] Figure 29An optical microscope image of the elastic wave device 200 and its admittance / conductance-frequency curves are shown. The elastic wave wavelength λ of the elastic wave device 200 is 3 μm to 4 μm. The conductive thin film material is aluminum with a thickness of 160 nm and an aperture of 30λ. The interdigital transducer has 200 electrodes, and the reflector has 20 electrodes. Observation of the curves shows that the elastic wave device 200 has no transverse mode response, and there is essentially no fluctuation between the resonant and anti-resonant frequencies.

[0116] Figure 30 The curves showing the Bode-Q of the elastic wave device 200 as a function of the elastic wave wavelength and the electromechanical coupling coefficient, Q are respectively shown. max A graph showing the variation of elastic wave wavelength. When the elastic wave wavelength is 3μm to 4μm, the Q of the elastic wave device 200... max The electromechanical coupling coefficient of the elastic wave device 200 is maintained at around 800-900, while the electromechanical coupling coefficient of the elastic wave device 200 increases slightly with the increase of the elastic wave wavelength.

[0117] Example 2:

[0118] Figure 31 A three-dimensional view of a high-bandwidth filter device 500 provided in Embodiment 2 of this application is shown. The filter device 500 includes a series arm resonator and a parallel arm resonator, at least one of which is the elastic wave device 200 provided in Embodiment 1 of this application. 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 filter device 500.

[0119] Figure 32 The insertion loss-frequency curve of the filter device 500 provided in Embodiment 2 of this application is shown. For the same reason as the elastic wave device, since the curvature of the fast transverse wave slow curve of quartz is less than 0, intrinsic suppression of the transverse modes of the filter device can be achieved. As can be seen from the curve, the filter exhibits small in-band ripple, a flat passband, and virtually no transverse modes.

[0120] Figure 33 The insertion loss-frequency curve of the filter device using a silicon substrate as a hypersonic component, according to Embodiment 2 of this application, is shown. Since the curvature of the fast transverse wave slow curve of silicon is greater than 0, it cannot suppress the transverse mode of the filter device. As can be seen from the curve, the filter band exhibits large fluctuations, mostly regular fluctuations, with a clear transverse mode.

[0121] In the embodiments disclosed in this application, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this application according to the specific circumstances.

[0122] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An elastic wave device, characterized in that, include: Quartz substrate, The Euler angles of the quartz substrate are (0±2.5°, θ±2.5°, 0±2.5°), and θ in the Euler angles satisfies 126°≤θ≤140°; A piezoelectric layer is disposed on the quartz substrate, wherein the Euler angle of the piezoelectric layer is (0±2.5°, β±2.5°, 0±2.5°), and β satisfies 90°≤β≤130°; and Interdigitated transducer electrodes are disposed on the piezoelectric layer; The material of the interdigital transducer electrode is aluminum. Under the premise that the wavelength of the elastic wave is set as λ, the thickness h1 of the interdigital transducer electrode satisfies 0.01λ≤h1≤0.045λ. The material of the interdigital transducer electrode is copper. Assuming the wavelength of the elastic wave is λ, the thickness h2 of the interdigital transducer electrode satisfies 0.01λ≤h2≤0.02λ. Assuming the wavelength of the elastic wave is λ, the thickness h of the piezoelectric layer... LN Satisfying 0.05λ≤h LN ≤0.15λ; Its horizontal shear wave curvature is less than -4.

2. The elastic wave device according to claim 1, characterized in that: The material of the interdigital transducer electrode is a metal other than aluminum and copper. Under the premise that the electrode density is set as ρ3, the density of aluminum is set as ρ1, and the density of copper is set as ρ2, the thickness h3 of the interdigital transducer electrode satisfies h3=h1ρ1 / ρ3 or h3=h2ρ2 / ρ3.

3. The elastic wave device according to claim 1, characterized in that: The piezoelectric layer is lithium niobate.

4. The elastic wave device according to claim 1, characterized in that: The speed of sound propagating in the quartz substrate is higher than the speed of sound propagating in the piezoelectric layer.

5. The elastic wave device according to claim 1, characterized in that: The interdigital transducer electrode is formed by stacking one or more thin films of metallic materials.

6. The elastic wave device according to claim 1, characterized in that: The interdigitated transducer electrodes also have reflector electrodes on both sides along the direction of elastic wave propagation.

7. A filter device, comprising: Series arm resonator; as well as Parallel arm resonator; Wherein, at least one of the series arm resonators and the parallel arm resonators is an elastic wave device according to any one of claims 1 to 6.

8. A multiplexer, comprising: Antenna terminal, which connects to the antenna; as well as Multiple filter devices are connected to the antenna terminal in a common manner; Wherein, at least one of the filter devices is the filter device according to claim 7.

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