Elastic wave apparatus, filter apparatus, and multiplexer

Abstract

An elastic wave apparatus, a filter apparatus, and a multiplexer. In the present application, a silicon substrate (5) having horizontal shear wave curvature less than -0.58 is provided, a piezoelectric layer (1) is provided on the silicon substrate (5), the Euler angle of the piezoelectric layer (1) being (0±2.5°, β±2.5°, 0±2.5°), wherein β satisfies 90°≤β≤150°, and an interdigital transducer being provided on the piezoelectric layer (1).

Description

Elastic wave device, filter device, and multiplexer

[0001] This application claims priority to the Chinese patent application No. 202411306751.6, filed on September 19, 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 field of elastic wave technology, for example, to an elastic wave device, a filter device, and a multiplexer. 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 at least one interdigital transducer (IDT) electrode, 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), the 4th Generation mobile communication technology (4G) to the 5th Generation mobile communication technology (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. Traditional elastic wave devices are 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. Elastic wave devices based on the composite multilayer structure of lithium tantalate / lithium niobate piezoelectric thin film are attracting attention due to their 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 results in large in-band fluctuation and large loss, i.e. leads to the performance reduction of the filter. In the industry, the interdigital transducer electrodes in different weighting forms are usually used to suppress the generation of transverse modes, but this way also has some problems: first, the Q value of the device itself is reduced due to the weighting of the interdigital transducer electrodes, which increases the loss of the elastic wave filter and hinders its application in the radio frequency front end; second, the weighting method often leads to the increase of the size of the device, hindering the miniaturization development of the device; third, some weighting methods increase the difficulty of device preparation. SUMMARY

[0006] The present application provides an elastic wave device, a filter device and a multiplexer to solve the problems of the related art.

[0007] The present application provides an elastic wave device, comprising:

[0008] a silicon substrate with a horizontal shear wave curvature less than -0.58;

[0009] a piezoelectric layer disposed on the silicon substrate, with an Euler angle of (0±2.5°, β±2.5°, 0±2.5°), wherein β satisfies 90°≤β≤150°; and

[0010] an interdigital transducer disposed on the piezoelectric layer.

[0011] In a possible implementation, the Euler angle of the silicon substrate is set to (0°, 0°, ψ); wherein ψ satisfies -15°+n×90°≤ψ≤15°+n×90°, n is an integer.

[0012] In a possible implementation, the Euler angle of the silicon substrate is set to (135°, 90°, ψ); wherein ψ satisfies 80°+n×180°≤ψ≤100°+n×180°, n is an integer.

[0013] In a possible implementation, the sound speed of sound propagation in the silicon substrate is higher than the sound speed of sound propagation in the piezoelectric layer.

[0014] In a possible implementation, the interdigital transducer is laminated by one or more metal material thin films.

[0015] In a possible implementation, there is a low sound speed layer between the silicon substrate and the piezoelectric layer.

[0016] In a possible implementation, the low sound speed layer is composed of one or more combinations of silicon dioxide, glass, silicon oxynitride, tantalum oxide, or a material with a compound of fluorine, carbon, or boron as the main component.

[0017] In a possible implementation, the interdigital transducer further has reflectors on both sides along the elastic wave propagation direction.

[0018] The application provides a filter device, comprising:

[0019] a series arm resonator, and a parallel arm resonator;

[0020] At least one resonator among the series arm resonator and the parallel arm resonator is an elastic wave device as described above.

[0021] The application provides a multiplexer, comprising:

[0022] an antenna terminal connected with an antenna; and

[0023] a plurality of filter devices commonly connected to the antenna terminal, at least one of the filter devices being a filter device as described above. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1 shows a schematic top view and sectional view of an elastic wave device 100 based on a piezoelectric composite substrate;

[0025] Fig. 2 shows a schematic view of elastic wave propagation;

[0026] Fig. 3 shows a plot of admittance / conductance vs. frequency of the elastic wave device 100 based on the piezoelectric composite substrate;

[0027] Fig. 4 shows a plot of slowness of the elastic wave device 100 based on the piezoelectric composite substrate;

[0028] Fig. 5 shows a schematic sectional view of an elastic wave device 200 according to an embodiment of the application;

[0029] Fig. 6 shows a schematic view of the definition of silicon crystal axes and (100), (110), (111) orientations of silicon;

[0030] Fig. 7 shows a plot of slowness of a silicon substrate with a (100) main surface;

[0031] Fig. 8 shows a plot of slowness of a silicon substrate with a (110) main surface;

[0032] Fig. 9 shows a plot of slowness of a silicon substrate with a (111) main surface;

[0033] Fig. 10 shows plots of slowness of the elastic wave device 200 for different silicon substrates and different h Al / λ;

[0034] Fig. 11 shows plots of slowness of the elastic wave device 200 for a (0°, 0°, 45°) silicon substrate with respect to h Al / λ and h LT / λ and h

[0035] Fig. 12 shows the slow curve curvature map of the elastic wave device 200 of a (0°, 0°, 0°) silicon substrate with respect to h Al / λ and h LT / λ and h

[0036] Fig. 13 shows the slow curve curvature map of the elastic wave device 200 of a (135°, 90°, 90°) silicon substrate [surface orientation (110)] with respect to h Al / λ and h LT / λ and h

[0037] Fig. 14 shows the slow curve curvature of the elastic wave device 200 of a (0°, 0°, 0°) silicon substrate and the elastic wave device 200 of a (0°, 0°, 45°) silicon substrate as a function of h Al / λ and h

[0038] Fig. 15 shows a schematic view and a measurement of admittance / conductance of the actually produced elastic wave device 200 of a (0°, 0°, 45°) silicon substrate;

[0039] Fig. 16 shows a schematic view and a measurement of admittance / conductance of the actually produced elastic wave device 200 of a (0°, 0°, 0°) silicon substrate;

[0040] Fig. 17 shows a graph of the horizontal shear wave curvature of a silicon substrate with surface orientation (100) as a function of ψ;

[0041] Fig. 18 shows a graph of the horizontal shear wave curvature of a silicon substrate with surface orientation (110) as a function of ψ;

[0042] Fig. 19 shows a schematic cross-sectional view of the elastic wave device 300 according to the second embodiment of the present application;

[0043] Fig. 20 shows the slow curve curvature map of the elastic wave device 300 of a (0°, 0°, 45°) silicon substrate with respect to h SiO2 / λ and h LT / λ and h

[0044] Fig. 21 shows the slow curve curvature map of the elastic wave device 300 of a (0°, 0°, 0°) silicon substrate with respect to h SiO2 / λ and h LT / λ and h

[0045] Fig. 22 shows a schematic view and a measurement of admittance / conductance of the actually produced elastic wave device 200 of a (0°, 0°, 45°) silicon substrate;

[0046] Fig. 23 shows a schematic diagram of an actual manufactured elastic wave device 200 of a (0°, 0°, 0°) silicon substrate and an admittance / conductance test diagram;

[0047] Fig. 24 is a structural schematic diagram of a filter device according to an embodiment of the present application;

[0048] Fig. 25 is a structural schematic diagram of a multiplexer according to an embodiment of the present application. DETAILED DESCRIPTION

[0049] 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, not all the embodiments.

[0050] Wherein, the same parts are denoted by the same 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 specification, and the words "bottom" and "top", "inner" and "outer" refer to the directions towards or away from a particular part. In addition, the terms "first", "second" are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application specification, the meaning of "a plurality of" is two or more.

[0051] The present application will be described below with reference to the drawings and embodiments.

[0052] Device Description:

[0053] 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 piezoelectric composite substrates of piezoelectric layer 1 and non-piezoelectric substrate 3 have attracted wide attention due to their high Q value performance, and are applied to many fields such as radar, communication, navigation, etc.

[0054] The surface acoustic wave (SAW) resonator elastic wave device 100 based on piezoelectric composite substrate is composed of a piezoelectric layer 1 and a piezoelectric composite substrate of a non-piezoelectric substrate 3, and a thin film pattern of conductive material formed on the piezoelectric composite substrate. The piezoelectric layer 1 is a thin single crystal layer made of piezoelectric material, including lithium niobate, lithium tantalate, gallium nitride, aluminum nitride or zinc oxide, and the thickness is h. The piezoelectric layer 1 is cut so as to be consistent with the crystal axis of the front and back surfaces of the piezoelectric layer 1, so that the piezoelectric layer 1 has different cutting directions, and the cutting direction of the piezoelectric layer 1 is often defined by Euler angles, for example, the Euler angles of the 42°Y-cut piezoelectric layer are (0°, 132°, 0°), the Euler angles of the Z-cut piezoelectric layer are (0°, 0°, 0°), the Euler angles of the 128°Y-cut piezoelectric layer are (0°, 38°, 0°), and the Euler angles of the 32°Y45°X-cut piezoelectric layer are (0°, 122°, 45°).

[0055] Admittance is a physical quantity describing the response of a circuit element to alternating current and voltage, 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, that is, 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|).

[0056] 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 of the circuit element at the resonant frequency, and Y2 is the admittance of the circuit element at the anti-resonant frequency. To some extent, the admittance ratio can measure the strength of the resonance of the circuit element.

[0057] 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 directly escape or repeatedly change into a form that cannot be recovered.

[0058] Electromechanical coupling coefficient (K 2 ), under the premise that the resonant frequency of the resonator is f s and the anti-resonant frequency is f p , the electromechanical coupling coefficient can be obtained by the formula K 2 = π 2 / 4 x (f p -f s ) / f p .

[0059] The non-piezoelectric substrate 3 is a single layer or multi-layer substrate made of high acoustic velocity material, and is also called high acoustic velocity member. In the high acoustic velocity member, the acoustic velocity of the bulk wave propagating therein is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer, so that the acoustic 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 acoustic 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.

[0060] The high acoustic velocity member is made of material having high acoustic velocity, such as silicon, sapphire, silicon carbide, aluminum nitride, quartz, etc. Table 1 shows the acoustic velocities of longitudinal wave (L), fast shear wave (SH), and slow shear wave (SV) in various materials.

[0061] [Table 1]

[0062] The conductive material thin film pattern includes the electrodes 2a of the IDT, the electrodes 2b of the reflector, the bus bars 4a of the interdigital transducer, and the bus bars 4b of the reflector. The thickness of the conductive material thin film pattern is h m The electrodes 2a of the interdigital transducer include a plurality of first electrode fingers and a plurality of second electrode fingers which are alternately inserted, and a first bus bar and a second bus bar which are opposite to each other in the direction in which the electrode fingers extend. The distance between adjacent first (or second) electrode fingers is λ, which is commonly referred to as the "wavelength" of the IDT. The distance by which the first electrode fingers and the second electrode fingers overlap is AP, which is commonly referred to as the "aperture" of the IDT. The electrodes 2b of the reflector include a plurality of third electrode fingers and a plurality of fourth electrode fingers which are alternately inserted, and a third bus bar and a fourth bus bar which are opposite to each other in the direction in which the electrode fingers extend.

[0063] The lateral mode is a fluctuation between the resonance frequency and the anti-resonance frequency of the resonator, which is usually caused by the diffraction of the elastic wave during propagation. FIG. 2 shows a schematic diagram of the propagation of the elastic wave, in which the acoustic wave 11 is a normally propagating acoustic wave, and the acoustic wave 10 is an acoustic wave in which lateral diffraction occurs.

[0064] FIG. 3 shows the admittance / conductance-frequency curve of the elastic wave device 100 based on the piezoelectric composite substrate. The main excitation mode is a horizontal shear wave. As can be seen from the curve, the elastic wave device exhibits a lateral mode, which is manifested as a fluctuation in the admittance and the conductance between the resonance frequency and the anti-resonance frequency.

[0065] FIG. 4 shows the slowness curve of the elastic wave device 100 based on the piezoelectric composite substrate. In general, the slowness curve can predict the case in which the elastic wave device generates a lateral mode, in which S x represents the slowness of the device in the x direction, and S yThe slowness of the device in the y direction. When the curvature γ of the slowness curve is greater than 0 (convex), the elastic wave device generates a lateral mode; when the curvature γ of the slowness curve is less than or equal to 0 (concave), the elastic wave device does not generate a lateral mode. Thus, as can be seen from the curve in the figure, the curvature γ of the slowness curve of the typical elastic wave device 100 is greater than 0, and a lateral mode is generated.

[0066] Embodiment One

[0067] The elastic wave device provided in the present application includes a silicon substrate 5, the horizontal shear wave curvature of which is less than -0.58; a piezoelectric layer 1 disposed on the silicon substrate 5, the Euler angle of which is (0±2.5°, β±2.5°, 0±2.5°), wherein β satisfies 90°≤β≤150°; and an interdigital transducer disposed on the piezoelectric layer 1.

[0068] The acoustic velocity of acoustic propagation in the silicon substrate 5 is higher than that in the piezoelectric layer 1. The interdigital transducer also has reflectors on both sides along the elastic wave propagation direction.

[0069] Figure 5 shows a schematic sectional view of the elastic wave device 200 provided in Embodiment One of the present application. The high acoustic velocity member is a silicon substrate 5 (Silicon, Si), on which a piezoelectric layer 1 is formed, the silicon substrate 5 supports the piezoelectric layer 1, and on the piezoelectric layer 1, a thin film pattern of conductive material is formed, which includes the electrodes 2a of the interdigital transducer, the electrodes 2b of the reflectors, the bus bars of the interdigital transducer and the bus bars of the reflectors. 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, and the direction parallel to the z axis of the coordinate system is defined as the height direction of the elastic wave device 200. The interdigital transducer is composed of one or more layers of thin film of metal material.

[0070] The piezoelectric layer 1 is 42°Y-cut lithium tantalate (42°YX-LiTaO3), the Euler angle of which is (0°, 132°, 0°), and the thickness of which is h LT ; the wavelength of the elastic wave is λ; the thin film pattern of conductive material is composed of aluminum electrodes, and the thickness of the electrodes is h Al .

[0071] Figure 6 shows the definition of the silicon crystal axis and the schematic diagram of the (100), (110), (111) orientations of silicon. Silicon is a single crystal with tetragonal structure, and under the premise that the crystal axis of silicon is set as (X, Y, Z), the X axis, the Y axis and the Z axis are equivalent due to the symmetry of the crystal structure.

[0072] The main surface of the silicon substrate 5 can be a (100) surface, a (110) surface, or a (111) surface. In the case where the main surface of the silicon substrate 5 is a (100) surface, the main surface on the piezoelectric layer 1 side in the silicon substrate 5 becomes a (100) surface. The (100) surface is a surface orthogonal to a crystal axis represented by Miller indices

[0100] in the crystal structure. In this state, the propagation angle ψ of the elastic wave in the silicon substrate 5 is an angle formed by the propagation direction of the elastic wave and the crystal orientation

[0001] of silicon of Miller indices when viewed from the main surface side of the electrode 2a of the interdigital transducer formed in the piezoelectric layer 1. Here, the Euler angles of the silicon substrate 5 are set to In addition, ψ in the Euler angles is the above-described propagation angle ψ. In the case where the (100) surface is expressed by Euler angles, it is (0°, 0°, ψ).

[0073] In the case where the main surface of the silicon substrate 5 is a (110) surface, the main surface on the piezoelectric layer 1 side in the silicon substrate 5 becomes a (110) surface. In this state, the propagation angle ψ of the silicon substrate 5 is an angle formed by the propagation direction of the elastic wave and the crystal orientation

[0001] of silicon of Miller indices when viewed from the main surface side of the electrode 2a of the interdigital transducer formed in the piezoelectric layer 1. In the case where the (110) surface is expressed by Euler angles, it is (135°, 90°, ψ).

[0074] In the case where the main surface of the silicon substrate 5 is a (111) surface, the main surface on the piezoelectric layer 1 side in the silicon substrate 5 becomes a (111) surface. In this state, the propagation angle ψ of the silicon substrate 5 is an angle formed by the propagation direction of the elastic wave and the crystal orientation [-1-12] of silicon of Miller indices when viewed from the main surface side of the electrode 2a of the interdigital transducer formed in the piezoelectric layer 1. In the case where the (111) surface is expressed by Euler angles, it is (135°, 54.7°, ψ).

[0075] FIGS. 7 to 9 show the slowness curves of the silicon substrate whose main surface is a (100), (110), or (111) surface, respectively. As can be seen from the curves, the curvatures γ of the slowness curves of the silicon substrate 5 differ depending on the main surface and the propagation angle ψ. Therefore, the main surface and ψ have an influence on the lateral mode of the elastic wave device 200.

[0076] FIG. 10 shows the slowness curves of the elastic wave device 200 of different silicon substrates and different h Al / λ. As can be seen from the curves, when the main surface of the silicon substrate 5 is a (100) surface and the propagation angle ψ is 45°, the curvature of the slowness curve of the elastic wave device 200 is greater than 0 regardless of the value of h Al / λ, the elastic wave device 200 generates a lateral mode, and the horizontal shear wave curvature of the silicon substrate 5 is greater than 0 (γ = 2.82). When the main surface of the silicon substrate 5 is a (100) surface and the propagation angle ψ is 0°, the curvature of the slowness curve of the elastic wave device 200 is greater than 0 when h Al / λ is in the range of 0 to 6%, the curvature of the slowness curve of the elastic wave device 200 is less than or equal to 0, the elastic wave device 200 does not generate a transverse mode, and the horizontal shear wave curvature of the silicon substrate 5 is less than 0 (γ = -0.94); when the main surface of the silicon substrate 5 is (110) and the propagation angle ψ is 90°, the curvature of the slowness curve of the elastic wave device 200 is greater than 0, the elastic wave device 200 generates a transverse mode, and the horizontal shear wave curvature of the silicon substrate 5 is greater than 0 (γ = 0.21). Al / λ is in the range of 0 to 6%, the curvature of the slowness curve of the elastic wave device 200 is less than or equal to 0, the elastic wave device 200 does not generate a transverse mode, and the horizontal shear wave curvature of the silicon substrate 5 is less than 0 (γ = -0.58); when the main surface of the silicon substrate 5 is (111) and the propagation angle ψ is 0°, the curvature of the slowness curve of the elastic wave device 200 is greater than 0, the elastic wave device 200 generates a transverse mode, and the horizontal shear wave curvature of the silicon substrate 5 is greater than 0 (γ = 0.21).

[0077] Therefore, from the above results, it can be seen that the curvature of the slowness curve of the elastic wave device 200 is related to the curvature of the slowness curve of the silicon substrate 5, and in order to avoid the generation of a transverse mode in the elastic wave device 200, the horizontal shear wave curvature of the silicon substrate 5 should be less than 0.

[0078] Figure 11 shows the slowness curve curvature heat map of the elastic wave device 200 of the (0°, 0°, 45°) silicon substrate with respect to h Al / λ and h LT / λ. The abscissa is h Al / λ, and the ordinate is h LT / λ. In order to ensure that the curvature of the slowness curve is less than 0 and does not generate a transverse mode, h Al / λ and h LT / λ should be ensured to be in the area outside the dashed line in the upper left corner of the figure.

[0079] Figure 12 shows the slowness curve curvature heat map of the elastic wave device 200 of the (0°, 0°, 0°) silicon substrate with respect to h Al / λ and h LT / λ. The abscissa is h Al / λ, and the ordinate is h LT / λ. In order to ensure that the curvature of the slowness curve is less than 0 and does not generate a transverse mode, h Al / λ and h LT / λ should be ensured to be in the area outside the dashed line on the left side of the figure.

[0080] By comparing Figure 11 and Figure 12, the area in which the elastic wave device 200 of the (0°, 0°, 0°) silicon substrate does not generate a transverse mode is larger, and the selectivity of h Al / λ and h LT / λ is better.

[0081] Figure 13 shows the slow curve curvature of the elastic wave device 200 of a (135°, 90°, 90°) silicon substrate [the surface orientation is (110)] with respect to h Al / λ LT / λ. The horizontal axis is h Al / λ, and the vertical axis is h LT / λ. In order to ensure that the slow curve curvature is less than 0 and no transverse mode is generated, h Al / λ and h LT / λ must be ensured to be in the area outside the dashed line on the left side of the figure.

[0082] In order to verify the suppression of the two silicon substrates 5 on the elastic wave device 200, Figure 14 shows the slow curve curvature of the elastic wave device 200 of a (0°, 0°, 0°) silicon substrate and a (0°, 0°, 45°) silicon substrate with respect to h Al / λ. It can be seen from the curve that no matter what value h Al / λ is, the slow curve curvature of the elastic wave device 200 of the (0°, 0°, 0°) silicon substrate 5 is smaller than that of the (0°, 0°, 45°) silicon substrate 5, and the slow curve curvature of the elastic wave device 200 of the (0°, 0°, 0°) silicon substrate 5 basically remains below 0. Therefore, the former is more conducive to the suppression of the transverse mode.

[0083] Figure 15 shows a schematic diagram and an admittance / conductance test diagram of the actually prepared elastic wave device 200 of a (0°, 0°, 45°) silicon substrate. Wherein, h Al / λ is 7%, and h LT / λ is 0.3. As the same as the above analysis, it can be seen from the test curve that the (0°, 0°, 45°) silicon substrate 5 generates fluctuations between the resonance frequency and the anti-resonance frequency of the elastic wave device 200, which indicates that the (0°, 0°, 45°) silicon substrate 5 has a transverse mode.

[0084] Figure 16 shows a schematic diagram and an admittance / conductance test diagram of the actually prepared elastic wave device 200 of a (0°, 0°, 0°) silicon substrate. Wherein, h Al / λ is 7%, and h LT / λ is 0.3. As the same as the above analysis, it can be seen from the test curve that the (0°, 0°, 0°) silicon substrate 5 does not generate fluctuations between the resonance frequency and the anti-resonance frequency of the elastic wave device 200, which indicates that the (0°, 0°, 0°) silicon substrate 5 does not have a transverse mode.

[0085] In one or more embodiments, the Euler angles of the silicon substrate 5 are set as (0°, 0°, ψ); wherein ψ satisfies -15°+n×90°≤ψ≤15°+n×90°, n is an integer.

[0086] In one or more embodiments, Euler angles of the silicon substrate 5 are set as (135°, 90°, ψ); wherein ψ satisfies 80°+n×180°≤ψ≤100°+n×180°, n is an integer.

[0087] FIG. 17 and FIG. 18 respectively show the curves of the horizontal shear wave curvature of the silicon substrate with the surface orientation of (100) and (110) varying with ψ. Wherein, the period of the silicon substrate with the surface orientation of (100) is 90°, and the period of the silicon substrate with the surface orientation of (110) is 180°.

[0088] Therefore, for the silicon substrate 5 with the surface orientation of (100), the propagation angle ψ needs to ensure that the horizontal shear wave curvature of the silicon substrate 5 is less than 0, i.e. -15°+n×90°≤ψ≤15°+n×90° (n is an integer), so that the elastic wave device will not generate the lateral mode; for the silicon substrate 5 with the surface orientation of (110), the propagation angle ψ needs to ensure that the horizontal shear wave curvature of the silicon substrate 5 is less than 0, i.e. 80°+n×180°≤ψ≤100°+n×180° (n is an integer), so that the elastic wave device will not generate the lateral mode.

[0089] Exemplarily, for the silicon substrate 5 with the surface orientation of (100), the propagation angle ψ is 0°+n×90° (n is an integer), i.e. the horizontal shear wave curvature of the silicon substrate 5 is -0.94, the elastic wave device 200 reaches the best effect of lateral mode suppression; for the silicon substrate 5 with the surface orientation of (110), the propagation angle ψ is 90°+n×180° (n is an integer), i.e. the horizontal shear wave curvature of the silicon substrate 5 is -0.58, the elastic wave device 200 reaches the best effect of lateral mode suppression.

[0090] Embodiment Two:

[0091] FIG. 19 shows a schematic sectional view of the elastic wave device 300 provided by the present application. The high acoustic velocity member is a silicon substrate 5 (Silicon, Si), a low acoustic velocity layer 6 is formed above the silicon substrate 5, a piezoelectric layer 1 is formed above the low acoustic velocity layer 6, the low acoustic velocity layer 6 supports the piezoelectric layer 1, a conductive material thin film pattern is formed above the piezoelectric layer 1, and the conductive material thin film pattern includes electrodes 2a of an interdigital transducer, electrodes 2b of a reflector, bus bars of the interdigital transducer, and bus bars of the reflector. A direction parallel to the x-axis of the coordinate system is defined as an 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 an electrode finger extension direction, and a direction parallel to the z-axis of the coordinate system is defined as a height direction of the elastic wave device 300.

[0092] The difference between the elastic wave device 300 and the elastic wave device 200 is that the low acoustic velocity layer 6 exists between the silicon substrate 5 and the piezoelectric layer 1.

[0093] The low-velocity layer 6 is made of one or more combinations of materials having relatively low acoustic velocity, such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, or a material in which a compound of fluorine, carbon, or boron is added to silicon dioxide as a main component. The low-velocity layer 6 can improve the temperature stability and frequency selectivity of the device.

[0094] For example, the piezoelectric layer 1 is 42° Y-cut lithium tantalate (42° YX-LiTaO3) having Euler angles of (0°, 132°, 0°) and a thickness of h LT ; the low-velocity layer 6 is silicon dioxide having a thickness of h SiO2 ; the wavelength of the elastic wave is λ; and the pattern of the conductive thin film material is made of an aluminum electrode having a thickness of h Al .

[0095] Fig. 20 shows a slowness curve curvature thermal map of the elastic wave device 300 of a (0°, 0°, 45°) silicon substrate with respect to h SiO2 / λ and h LT / λ. Here, h Al / λ is 6%, the abscissa is h SiO2 / λ, and the ordinate is h LT / λ. To ensure that the slowness curve curvature is less than 0 and no transverse mode is generated, h SiO2 / λ and h LT / λ must be ensured to be in the area above the dashed line of the figure.

[0096] Fig. 21 shows a slowness curve curvature thermal map of the elastic wave device 300 of a (0°, 0°, 0°) silicon substrate with respect to h SiO2 / λ and h LT / λ. Here, h Al / λ is 6%, the abscissa is h SiO2 / λ, and the ordinate is h LT / λ. To ensure that the slowness curve curvature is less than 0 and no transverse mode is generated, h SiO2 / λ and h LT / λ must be ensured to be in the area above the dashed line of the figure.

[0097] By comparing Fig. 20 and Fig. 21, the elastic wave device 300 of a (0°, 0°, 0°) silicon substrate 5 has a larger area in which no transverse mode is generated, and has better selectivity for h SiO2 / λ and h LT / λ.

[0098] Fig. 22 shows a schematic diagram and an admittance / conductance test diagram of an actually manufactured elastic wave device 200 of a (0°, 0°, 45°) silicon substrate. Here, h Al / λ is 6%, h LT / λ is 0.27. As the same analysis as above, it can be seen from the test curve that the fluctuation between the resonance frequency and the anti-resonance frequency of the elastic wave device 300 of the (0°, 0°, 45°) silicon substrate 5 is generated, which indicates that the elastic wave device 300 of the (0°, 0°, 45°) silicon substrate 5 has the lateral mode.

[0099] Fig. 23 shows a schematic diagram and an admittance / conductance test chart of an actually manufactured elastic wave device 200 of a (0°, 0°, 0°) silicon substrate. In the figure, h Al / λ is 6%. h LT / λ is 0.27. As the same analysis as above, it can be seen from the test curve that the fluctuation between the resonance frequency and the anti-resonance frequency of the elastic wave device 300 of the (0°, 0°, 45°) silicon substrate 5 is generated, which indicates that the elastic wave device 300 of the (0°, 0°, 45°) silicon substrate 5 has the lateral mode.

[0100] Therefore, for the silicon substrate 5 having the surface orientation of (100), the propagation angle ψ needs to satisfy the horizontal shear wave curvature of the silicon substrate 5 being less than 0, i.e., -15° + n x 90° ≤ ψ ≤ 15° + n x 90° (n is an integer), so that the elastic wave device does not generate the lateral mode.

[0101] Exemplarily, for the silicon substrate 5 having the surface orientation of (100), the propagation angle ψ is 0° + n x 90° (n is an integer), i.e., the horizontal shear wave curvature of the silicon substrate 5 is -0.94, so that the elastic wave device 300 achieves the best effect of the lateral mode suppression.

[0102] In summary, the present application provides a silicon substrate having a horizontal shear wave curvature less than -0.58, a piezoelectric layer disposed on the silicon substrate, the piezoelectric layer having Euler angles of (0 ± 2.5°, β ± 2.5°, 0 ± 2.5°), wherein β satisfies 90° ≤ β ≤ 150°, and an interdigital transducer disposed on the piezoelectric layer. In this case, a large-bandwidth elastic wave device capable of suppressing the intrinsic lateral mode is provided.

[0103] As shown in Fig. 24, the present application further provides a filter device, comprising: a series arm resonator 1000, and a parallel arm resonator 2000;

[0104] At least one resonator among the series arm resonator 1000 and the parallel arm resonator 2000 is the elastic wave device as described above.

[0105] As shown in Fig. 25, the present application further provides a multiplexer, comprising: an antenna terminal 3000 connected to an antenna 5000; and a plurality of filter devices 4000 commonly connected to the antenna terminal 3000, at least one of the filter devices 4000 being the filter device as described above.

[0106] In the embodiments of the present application, the terms "mounting", "connection", "connecting", "fixing" and the like are to be understood in a broad sense and for example, "connecting" can be fixed connecting, detachable connecting, or integrally connecting; "connection" can be direct connection, or indirect connection through an intermediate medium. 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 silicon substrate having a horizontal shear wave curvature of less than -0.58; a piezoelectric layer disposed on the silicon substrate, the piezoelectric layer having Euler angles of (0±2.5°, β±2.5°, 0±2.5°), where β satisfies 90°≤β≤150°; and an interdigital transducer disposed on the piezoelectric layer.

2. The elastic wave device according to claim 1, wherein the Euler angles of the silicon substrate are set to (0°, 0°, ψ); where ψ satisfies -15°+n×90°≤ψ≤15°+n×90°, n being an integer.

3. The elastic wave device according to claim 1, wherein the Euler angles of the silicon substrate are set to (135°, 90°, ψ); where ψ satisfies 80°+n×180°≤ψ≤100°+n×180°, n being an integer.

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

5. The elastic wave device according to claim 1, wherein the interdigital transducer is laminated by one or more thin films of a metal material.

6. The elastic wave device according to claim 1, wherein a low sound velocity layer is further provided between the silicon substrate and the piezoelectric layer.

7. The elastic wave device according to claim 6, wherein the low sound velocity layer is composed of one or more combinations of the following relatively low sound velocity materials: silicon dioxide, glass, silicon oxynitride, tantalum oxide, or a material in which a compound of fluorine, carbon, or boron is added as a main component to silicon dioxide.

8. The elastic wave device according to claim 1, wherein the interdigital transducer further has reflectors on both sides in an elastic wave propagation direction.

9. A filter device comprising: a series arm resonator, and a parallel arm resonator; at least one resonator among the series arm resonator and the parallel arm resonator being the elastic wave device according to any one of claims 1 to 8.

10. A multiplexer comprising: an antenna terminal connected to an antenna; and a plurality of filter devices commonly connected to the antenna terminal, at least one filter device being the filter device according to claim 9.

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