Surface acoustic wave device, radio frequency front-end module and electronic equipment

Abstract

The invention relates to a surface acoustic wave device, a radio frequency front-end module and electronic equipment. The surface acoustic wave device comprises a piezoelectric layer and an interdigital electrode arranged on the first surface of the piezoelectric layer, wherein the interdigital electrode comprises a plurality of electrode fingers; when the surface acoustic wave device works, acoustic waves comprise surface acoustic waves and bulk waves, and the propagation direction of the surface acoustic waves is the X direction; the first characteristic thickness of the surface acoustic wave device is Ty, the thickness of the piezoelectric layer is Dy, the thickness of the piezoelectric layer and the first characteristic thickness meet the condition: # imgabs0 #, the piezoelectric layer comprises a piezoelectric crystal, and the size of the first characteristic thickness is determined according to the midline distance between two adjacent electrode fingers, the bulk wave sound velocity of the piezoelectric crystal in the X direction and the working frequency. The thickness of the piezoelectric layer is limited through the first characteristic thickness, so that the influence on the acoustic function of other structures due to the too thick piezoelectric layer is avoided, and the working performance of the surface acoustic wave device is improved.

Description

Technical Field

[0001] The present application relates to the radio frequency field, and in particular to a surface acoustic wave device, a radio frequency front-end module including the surface acoustic wave device, and an electronic device including the radio frequency front-end module. Background Art

[0002] In the field of radio frequency, surface acoustic wave devices are usually composed of a piezoelectric substrate and interdigital electrodes. The mutual conversion between electrical signals and acoustic wave signals is achieved through the cooperation between the interdigital electrodes on the piezoelectric substrate and the piezoelectric substrate.

[0003] In the prior art, different functional layers are set under the piezoelectric substrate to achieve the regulation of the performance of the interdigital electrode, and to achieve characteristics such as high quality factor (Q value) and low temperature coefficient (TCF). However, the prior art is not perfect in the theory of setting the functional layer, and the development efficiency is low. If the functional layer is not set reasonably, it will make it difficult for the interdigital electrode to achieve the intended effect. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of this application is to provide a solution to improve the working performance of a surface acoustic wave device, which specifically includes the following technical solutions:

[0005] In a first aspect, an embodiment of the present application provides a surface acoustic wave device, comprising a piezoelectric layer, and an interdigital electrode disposed on a first surface of the piezoelectric layer, wherein the interdigital electrode comprises a plurality of electrode fingers;

[0006] The acoustic waves of the surface acoustic wave device when it is working include surface acoustic waves and body waves, and the direction of surface wave propagation is the X direction;

[0007] The first characteristic thickness of the surface acoustic wave device is T y , the thickness of the piezoelectric layer is D y , the thickness of the piezoelectric layer and the first characteristic thickness meet the conditions:

[0008] The piezoelectric layer includes a piezoelectric crystal, and the first characteristic thickness is determined according to the centerline spacing between two adjacent electrode fingers, the body wave velocity of the piezoelectric crystal along the X direction, and the operating frequency.

[0009] Since the amplitude of the surface acoustic wave excited by the surface acoustic wave device when working mainly acts on the first surface of the piezoelectric layer and a part of the piezoelectric layer close to the first surface, the surface acoustic wave device of the present application also has a first characteristic thickness T yThe ratio range to the thickness of the piezoelectric layer limits the thickness of the piezoelectric layer to ensure that the energy of the surface acoustic wave can be effectively transferred to the remaining structures of the interdigital electrodes, thereby ensuring the acoustic effect of the surface acoustic wave device and improving the working performance of the surface acoustic wave device of the present application.

[0010] In one embodiment, the first characteristic thickness is: Among them, the midline spacing between two adjacent electrode fingers is P, and the body wave speed of the piezoelectric crystal along the X direction is V b1 , the operating frequency is f, and the body wave wavelength of the piezoelectric crystal along the X direction at the operating frequency is λ 1 .

[0011] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer and the first characteristic thickness satisfy the condition:

[0012] In this embodiment, by setting the ratio of the thickness of the piezoelectric layer to the first characteristic thickness between 0.2 and 1.5, it is avoided that the thickness of the piezoelectric layer is too thin due to a too small ratio, thereby affecting the stability of the surface acoustic wave device. It is also avoided that the thickness of the piezoelectric layer is too thick due to a too large ratio, thereby affecting the acoustic effect of the remaining structures of the surface acoustic wave device. Thus, the stability and working performance of the surface acoustic wave device of the present application are improved.

[0013] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer is less than the first characteristic thickness.

[0014] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer and the first characteristic thickness satisfy the condition:

[0015] In one embodiment, the surface acoustic wave device further includes a temperature compensation layer, and along the thickness direction of the piezoelectric layer, the temperature compensation layer is arranged on a side of the piezoelectric layer away from the interdigital electrodes.

[0016] In this embodiment, a temperature compensation layer is provided on the side of the piezoelectric layer away from the interdigital electrodes to improve the temperature stability of the surface acoustic wave device of the present application and avoid affecting the performance of the surface acoustic wave device due to temperature changes.

[0017] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave antiresonant frequency, the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer is H, and the sum of the first characteristic thickness and the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfies the condition:

[0018] In this embodiment, by limiting the ratio of the first characteristic thickness to the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer, the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer is limited, it is ensured that the energy of the surface acoustic wave can be effectively transferred to the temperature compensation layer, thereby ensuring the temperature compensation function of the temperature compensation layer on the piezoelectric layer, and realizing the acoustic effect of the temperature compensation layer on the surface acoustic wave device of the present application.

[0019] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the sum of the first characteristic thickness, the thickness of the temperature compensation layer, and the thickness of the piezoelectric layer satisfies the condition:

[0020] In one embodiment, the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer is less than the first characteristic thickness.

[0021] In one embodiment, the sum of the first characteristic thickness, the thickness of the temperature compensation layer, and the thickness of the piezoelectric layer satisfies the condition:

[0022] In one embodiment, when the angle between the propagation direction of the body wave excited by the interdigital electrodes to the piezoelectric layer and the first surface is equal to the first enhancement angle θ, the body wave in the piezoelectric layer and the temperature compensation layer is in an enhanced state; the propagation speed of the body wave excited by the interdigital electrodes to the piezoelectric layer and the temperature compensation layer is V 0 , the first enhancement angle and the propagation velocity of the body wave in the piezoelectric layer and the temperature compensation layer satisfy the equation: The surface acoustic wave frequency of the surface acoustic wave device is f, and the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer meets the condition: The surface acoustic wave frequency f is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency.

[0023] In this embodiment, the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer is further limited to avoid the influence of the waveguide mode generated by the body wave on the frequency of the surface acoustic wave after the reflection between the two surfaces of the piezoelectric layer and the temperature compensation layer which are away from each other.

[0024] In one embodiment, the thickness of the temperature compensation layer is D w , where the thickness of the temperature compensation layer and the thickness of the piezoelectric layer meet the conditions:

[0025] In this embodiment, the ratio range of the thickness of the temperature compensation layer to the thickness of the piezoelectric layer is limited to achieve matching setting of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer, thereby improving the working performance of the surface acoustic wave device of the present application.

[0026] In one embodiment, when the angle between the propagation direction of the body wave excited by the interdigital electrodes to the piezoelectric layer and the first surface is equal to the first enhancement angle θ, the body wave in the piezoelectric layer is in an enhanced state; the wavelength λ of the body wave excited by the interdigital electrodes to the piezoelectric layer B1 is the wavelength of the bulk wave in the enhanced state within the piezoelectric layer.

[0027] In one embodiment, the midline distance between two adjacent electrode fingers is P, the first reinforcement angle is θ, and the first reinforcement angle satisfies the equation: Among them, V B1 is the body wave velocity in the piezoelectric layer, f is the operating frequency, λ B1 is the wavelength of the body wave excited by the interdigital electrodes in the piezoelectric layer, and the range of the first enhancement angle θ satisfies: 0°<θ<180°.

[0028] In one embodiment, the surface acoustic wave device comprises a functional layer, and along the thickness direction of the piezoelectric layer, the functional layer is arranged on a side of the piezoelectric layer away from the interdigital electrodes; the second characteristic thickness of the surface acoustic wave device is T d , the thickness of the functional layer is D d , the thickness of the functional layer and the second characteristic thickness meet the conditions: The second characteristic thickness is determined according to the body wave velocity of the material of the functional layer along the X direction and the operating frequency.

[0029] In this embodiment, a functional layer is provided on the side of the piezoelectric layer away from the interdigital electrodes to reduce the loss of the surface acoustic wave device of the present application. The surface acoustic wave device of the present application also limits the thickness of the functional layer by the ratio range of the second characteristic thickness to the thickness of the functional layer, which is beneficial to the leakage of high-frequency mixed modes in the body wave. Thereby, the working performance of the surface acoustic wave device of the present application is improved.

[0030] In one embodiment, the second characteristic thickness satisfies the equation: Among them, the midline spacing between two adjacent electrode fingers is P, and the body wave sound velocity of the material of the functional layer along the X direction is V b2 , the operating frequency is f,λ 2 is the wavelength corresponding to the body wave velocity of the material of the functional layer along the X direction at the operating frequency.

[0031] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness satisfy the condition:

[0032] In this embodiment, by setting the ratio of the thickness of the functional layer to the second characteristic thickness between 0.2 and 1.5, it is avoided that the thickness of the functional layer is too thin due to a too small ratio, thereby affecting the working performance of the surface acoustic wave device. It is also avoided that the thickness of the functional layer is too thick due to a too large ratio, thereby affecting the leakage of high-frequency heterogeneous modes in the body wave. Thus, the working performance of the surface acoustic wave device of the present application is guaranteed.

[0033] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer is less than the second characteristic thickness.

[0034] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness satisfy the condition:

[0035] In one embodiment, the surface acoustic wave device includes a single crystal silicon layer. Along the thickness direction of the piezoelectric layer, the single crystal silicon layer is arranged on the surface of the functional layer away from the piezoelectric layer. <110> A spatial angle between the crystal orientation family and a propagation direction of surface acoustic waves excited by the plurality of interdigital electrodes on the first surface is less than or equal to 10°.

[0036] In this embodiment, a single crystal silicon layer is provided on the surface of the functional layer away from the piezoelectric layer, and the <110> The spatial angle between the crystal orientation family and the propagation direction of the surface acoustic wave excited by the plurality of interdigital electrodes on the first surface is conducive to the leakage of the waveguide mode energy.

[0037] In one embodiment, the single crystal silicon layer <110> The crystal orientation family is parallel to a propagation direction of surface acoustic waves excited on the first surface by the plurality of interdigital electrodes.

[0038] In one embodiment, the material of the functional layer has anisotropy or isotropy.

[0039] In one embodiment, the functional layer is an acoustic layer or a polysilicon layer.

[0040] In one embodiment, the material of the piezoelectric layer has anisotropy.

[0041] In a second aspect, an embodiment of the present application provides a surface acoustic wave device, comprising a functional layer and a piezoelectric layer stacked along the thickness direction thereof, and an interdigitated electrode disposed on a first surface of the piezoelectric layer away from the functional layer, wherein the interdigitated electrode comprises a plurality of electrode fingers;

[0042] The acoustic waves of the surface acoustic wave device when it is working include surface acoustic waves and body waves, and the direction of surface wave propagation is the X direction;

[0043] The second characteristic thickness of the surface acoustic wave device is Td , the thickness of the functional layer is D d , the thickness of the functional layer and the second characteristic thickness meet the conditions:

[0044] The second characteristic thickness is determined according to the body wave velocity of the material of the functional layer along the X direction and the operating frequency.

[0045] The surface acoustic wave device of the present application reduces the loss of the surface acoustic wave device of the present application by arranging a functional layer on the side of the piezoelectric layer away from the interdigital electrodes. The surface acoustic wave device of the present application also limits the thickness of the functional layer by the ratio range of the second characteristic thickness to the thickness of the functional layer, thereby avoiding the leakage of high-frequency mixed modes in the bulk wave due to the excessive thickness of the functional layer. Thus, the working performance of the surface acoustic wave device of the present application is improved.

[0046] In one embodiment, the second characteristic thickness satisfies the equation: Among them, the midline spacing between two adjacent electrode fingers is P, and the body wave sound velocity of the material of the functional layer along the X direction is V b2 , the operating frequency is f,λ 2 is the wavelength corresponding to the body wave velocity of the material of the functional layer along the X direction at the operating frequency.

[0047] In one embodiment, when the angle between the propagation direction of the body wave propagated into the functional layer by the acoustic wave excited by the interdigital electrodes and the first surface is equal to the second enhancement angle γ, the body wave in the functional layer is in an enhanced state; the wavelength λ of the body wave propagated into the functional layer by the acoustic wave excited by the interdigital electrodes B2 is the wavelength of the body wave in the enhanced state within the functional layer.

[0048] In one embodiment, the midline distance between two adjacent electrode fingers is P, the second reinforcement angle is γ, and the second reinforcement angle γ satisfies the equation: Among them, V B2 is the body wave velocity in the functional layer, f is the operating frequency, λ B2 is the body wave wavelength of the acoustic wave excited by the interdigital electrodes and propagated into the functional layer, and the second reinforcement angle γ satisfies: 0°<γ<180°.

[0049] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness satisfy the condition:

[0050] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer is less than the second characteristic thickness.

[0051] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness satisfy the condition:

[0052] In one embodiment, the first characteristic thickness of the surface acoustic wave device is T y , the thickness of the piezoelectric layer is D y , the thickness of the piezoelectric layer and the first characteristic thickness meet the conditions:

[0053] The first characteristic thickness is determined according to the centerline distance between two adjacent electrode fingers, the body wave velocity of the piezoelectric layer along the X direction, and the operating frequency.

[0054] In one embodiment, the first characteristic thickness satisfies the equation:

[0055] In one embodiment, the thickness of the piezoelectric layer satisfies the condition: 0.4P≤D y ≤0.8P.

[0056] In one embodiment, the thickness of the functional layer satisfies the condition: 0.2P≤D d ≤0.6P.

[0057] In one embodiment, the material of the piezoelectric layer has anisotropy.

[0058] In a third aspect, an embodiment of the present application provides a radio frequency front-end module, including a surface acoustic wave device.

[0059] In a fourth aspect, an embodiment of the present application provides an electronic device, including a radio frequency front-end module.

[0060] It is understandable that the RF front-end module provided in the third aspect of the present application and the electronic device provided in the fourth aspect adopt the surface acoustic wave device provided in the first and second aspects of the present application. The RF front-end module and the electronic device of the present application also have better working performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 A schematic diagram of the structure of an electronic device provided in one embodiment of the present application;

[0062] Figure 2 This is a schematic diagram of the structure of a radio frequency front-end module provided in one embodiment of the present application;

[0063] Figure 3 A schematic diagram of the structure of a filter provided in one embodiment of the present application;

[0064] Figure 4 Another structural schematic diagram of a filter provided in an embodiment of the present application;

[0065] Figure 5 A schematic diagram of the structure of a surface acoustic wave device provided in one embodiment of the present application;

[0066] Figure 6 A schematic cross-sectional structure diagram of a surface acoustic wave device provided in one embodiment of the present application;

[0067] Figure 7 It is an enlarged cross-sectional schematic diagram of a surface acoustic wave device provided in one embodiment of the present application;

[0068] Figure 8 A comparison diagram of the admittance curves of a surface acoustic wave device provided in one embodiment of the present application;

[0069] Fig. 9 A schematic diagram of a partial cross-sectional structure of a surface acoustic wave device provided in one embodiment of the present application;

[0070] Fig.10 Another partial cross-sectional structural schematic diagram of a surface acoustic wave device provided in an embodiment of the present application;

[0071] Fig.11 A partial curve diagram of the relationship between the first reinforcement angle of the piezoelectric layer and the body wave speed of sound of the surface acoustic wave device provided in one embodiment of the present application;

[0072] Fig.12 Another schematic diagram of the structure of a surface acoustic wave device provided in one embodiment of the present application;

[0073] Fig.13 Another schematic cross-sectional structure diagram of a surface acoustic wave device provided in one embodiment of the present application;

[0074] Fig.14 Another enlarged cross-sectional schematic diagram of a surface acoustic wave device provided in one embodiment of the present application;

[0075] Fig.15 A schematic diagram of a conductance curve of a surface acoustic wave device provided in one embodiment of the present application;

[0076] Fig.16 This is another partial cross-sectional structural schematic diagram of a surface acoustic wave device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0077] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0078] The following descriptions of the embodiments are with reference to the attached diagrams to illustrate specific embodiments that the present application can be used to implement. The serial numbers for the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in the present application, unless otherwise specified, include direct and indirect connections (couplings). The directional terms mentioned in the present application, such as "upper", "lower", "front", "back", "left", "right", "inside", "outside", "side", etc., are only with reference to the directions of the attached drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0079] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be fixedly connected, detachably connected, or integrally connected; it can be mechanically connected; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances. It should be noted that the terms "first", "second", etc. in the specification, claims, and drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include", "may include", "include", or "may include" used in this application indicate the existence of the corresponding functions, operations, elements, etc. disclosed, and do not limit one or more other functions, operations, elements, etc. In addition, the terms "include" or "include" indicate the existence of the corresponding features, numbers, steps, operations, elements, components, or combinations thereof disclosed in the specification, and do not exclude the existence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, and are intended to cover non-exclusive inclusions.

[0080] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0081] See also Figure 1 A schematic diagram of the structure of an electronic device 400 provided in one embodiment of the present application is shown.

[0082] like Figure 1 As shown, the electronic device 400 of the present application includes a substrate 401 and a radio frequency front-end module 300, and the radio frequency front-end module 300 is mounted on the substrate 401. The substrate 401 is electrically connected to the radio frequency front-end module 300.

[0083] In one embodiment, the substrate 401 is a printed circuit board to realize the operation control of the RF front-end module 300. The electronic device 400 of the present application realizes signal reception and / or transmission through the RF front-end module 300. Exemplarily, the electronic device 400 includes at least one of a computer, a mobile phone, a tablet computer, a smart watch, and a navigator, etc., and the present application does not specifically limit this.

[0084] See also Figure 2 The figure shows a schematic diagram of the structure of a radio frequency front-end module 300 provided in one embodiment of the present application.

[0085] like Figure 2 As shown, the RF front-end module 300 includes a signal terminal 301, a switch 302, an amplifier 303 and a filter 200. Among them, the signal terminal 301 is used to receive an external signal or transmit a RF signal. The switch 302 is communicatively connected between the signal terminal 301 and the filter 200 to control the signal transmission between the signal terminal 301 and the filter 200. When the amplifier 303 is a low-noise amplifier, the filter 200 is used to receive the signal of the external signal received by the signal terminal 301 when the switch 302 is closed, and output a signal with a preset frequency. The amplifier 303 is electrically connected to the filter 200 to amplify the signal processed by the filter 200 and output it to the subsequent structure. When the amplifier 303 is a power amplifier, the filter 200 is used to receive the RF signal amplified by the amplifier 303 when the switch 302 is closed, and filter the received RF signal, and then transmit the filtered RF signal to the signal terminal 301 through the switch 302. In one embodiment, the signal terminal 301 is an antenna.

[0086] In an embodiment, there may be multiple filters 200 , and all of the multiple filters 200 are communicatively connected to the signal terminal 301 .

[0087] In one embodiment, the RF front-end module 300 further includes a multiplexer, and the multiplexer includes a filter 200 .

[0088] See also Figure 3 The structure diagram of the filter 200 provided in one embodiment of the present application is shown.

[0089] like Figure 3 As shown, the filter 200 of the present application includes a signal input terminal 201, a signal output terminal 202, a ground port 203, a piezoelectric substrate 204 and a surface acoustic wave device 100. In the embodiment of the present application, the surface acoustic wave device 100 includes interdigital electrodes 20. The interdigital electrodes 20 are arranged on the piezoelectric substrate 204.

[0090] like Figure 3 As shown, there are three interdigital electrodes 20, one end of one of the interdigital electrodes 20 is connected to the signal input terminal 201, and the other end is connected to the ground port 203. The remaining two interdigital electrodes 20 of the three interdigital electrodes 20 are arranged on both sides of the interdigital electrode 20 connected to the signal input terminal 201, one end of the two interdigital electrodes 20 is connected to the signal output terminal 202, and the other end of the two interdigital electrodes 20 is connected to the ground port 203.

[0091] When a signal enters the surface acoustic wave device 100 from the signal input terminal 201, the interdigital electrodes 20 in the surface acoustic wave device 100 receive the electrical signal. The interdigital electrodes 20 can realize the conversion of electricity to sound and sound to electricity, and finally realize the processing of the electrical signal.

[0092] In one embodiment, the piezoelectric substrate 204 and the interdigital electrodes 20 disposed on the piezoelectric substrate 204 can constitute an interdigital transducer, that is, the interdigital electrodes 20 must be made on the piezoelectric substrate 204 to stimulate the generation of sound waves. In another embodiment, the interdigital transducer can also be the interdigital electrodes 20 formed on the piezoelectric substrate 204.

[0093] In one embodiment, the surface acoustic wave device 100 includes a resonator.

[0094] See also Figure 4 Another structural schematic diagram of a filter 200 provided in an embodiment of the present application is shown.

[0095] like Figure 4 As shown, a part of the resonators are connected in series between the signal input terminal 201 and the signal output terminal 202, and one end of the other part of the resonators is connected to the ground port 203, and the other end is connected to the series circuit between the signal input terminal 201 and the signal output terminal 202. It can be understood that the mutual series and parallel connection of multiple resonators can realize the filtering function of the filter 200 of the present application for the signal of the preset frequency.

[0096] See also Figure 5 FIG. 1 is a schematic structural diagram of a surface acoustic wave device 100 provided in one embodiment of the present application.

[0097] like Figure 5As shown, the surface acoustic wave device 100 of the present application includes a piezoelectric layer 10 and an interdigital electrode 20. Along the thickness direction of the piezoelectric layer 10, the interdigital electrode 20 is arranged on the first surface 11 of the piezoelectric layer 10. The interdigital electrode 20 includes two bus bars 21 arranged in parallel and at intervals, and a plurality of electrode fingers 22 arranged in parallel and at intervals.

[0098] Among them, one bus bar 21 of the two bus bars 21 is used to receive external signals, and the other bus bar 21 of the two bus bars 21 is used to output signals. The plurality of electrode fingers 22 are located between the two bus bars 21. Some of the electrode fingers 22 of the plurality of electrode fingers 22 are conductively connected to one bus bar 21, and another part of the electrode fingers 22 of the plurality of electrode fingers 22 are conductively connected to the other bus bar 21.

[0099] For ease of description, the bus bar 21 for receiving external signals is defined as the first bus bar 21a, and the bus bar 21 for outputting signals is defined as the second bus bar 21b. The electrode fingers 22 connected to the first bus bar 21a are defined as the first electrode fingers 22a, and the electrode fingers 22 connected to the second bus bar 21b are defined as the second electrode fingers 22b.

[0100] Specifically, the first electrode fingers 22a and the second electrode fingers 22b extend toward opposite sides of the piezoelectric layer 10 along the first direction 001. Along the second direction 002, the first electrode fingers 22a and the second electrode fingers 22b are arranged alternately. Figure 5 As shown, along the second direction 002, there is a second electrode finger 22b between any two adjacent first electrode fingers 22a, and there is a first electrode finger 22a between any two adjacent second electrode fingers 22b.

[0101] The first bus bar 21a and the second bus bar 21b extend toward opposite sides of the piezoelectric layer 10 along the second direction 002, wherein the first direction 001 and the second direction 002 are perpendicular to each other. The surface acoustic wave device 100 of the present application may have errors during actual application, and the angle between the first direction 001 and the second direction 002 may not be equal to 90°.

[0102] In the embodiment of the present application, due to the inverse piezoelectric effect of the piezoelectric layer 10. When the electrical signal is transmitted to each first electrode finger 22a via the first bus bar 21a, the electrical signal on each first electrode finger 22a will release electrostatic force to the piezoelectric layer 10, and the electrostatic force will cause the surface of the piezoelectric layer 10 to deform. And because the electrical signal is an alternating signal. It can be understood that the electrostatic force of each first electrode finger 22a acting on the surface of the piezoelectric layer 10 presents periodic changes, and correspondingly, the deformation amount of the surface of the piezoelectric layer 10 also changes with the periodic changes of the electrical signal, thereby forming an outwardly released sound wave.

[0103] The acoustic waves of the surface acoustic wave device 100 of the present application when working include surface acoustic waves and body waves. Among them, when the component of the acoustic wave vector along the thickness direction of the piezoelectric layer 10 is an imaginary number, this acoustic wave can only propagate along the plane direction of the first surface 11, that is, a surface acoustic wave. Among them, the propagation direction of the surface acoustic wave is defined as the X direction. When the acoustic wave vector has a real number component along the thickness direction of the piezoelectric layer 10, it is a body wave.

[0104] The surface acoustic wave is used to realize the frequency selection function and signal processing function of the surface acoustic wave device 100 of the present application. During the propagation of the surface acoustic wave, the main propagation direction of the surface acoustic wave is the second direction 002, that is, the X direction is the second direction 002. However, in the actual process, due to the edge effect and the diffraction of the sound wave, the propagation direction of the surface acoustic wave formed on the first surface 11 of the piezoelectric layer 10 may also be other directions, and correspondingly, there is an angle between the X direction and the second direction 002. In one embodiment, the surface acoustic wave propagating in the other directions will be absorbed by the sound absorbing material (not shown in the figure).

[0105] In one embodiment, along the second direction 002 , reflection gratings (not shown in the figure) are respectively provided on both sides of the interdigital electrodes 20 , and the reflection gratings are used to confine the surface acoustic waves generated when the surface acoustic wave device 100 of the present application is working within the interdigital electrodes 20 .

[0106] It is understandable that the present application can be applied to dual-mode surface acoustic wave devices (DMS) and filter devices formed by interconnecting them through a certain topology, etc., which include interdigital electrodes, and the present application does not limit this.

[0107] See also Figure 6 FIG. 1 is a schematic cross-sectional structure diagram of a surface acoustic wave device 100 provided in an embodiment of the present application.

[0108] like Figure 6 As shown, the surface acoustic wave device 100 of the present application is provided with other structures on the side of the piezoelectric layer 10 away from the interdigital electrodes 20. Exemplarily, the surface acoustic wave device 100 of the present application is provided with a temperature compensation layer 30 on the side of the piezoelectric layer 10 away from the interdigital electrodes 20. For ease of description, in the present embodiment and subsequent embodiments, the temperature compensation layer 30 is used to refer to the other structures of the surface acoustic wave device 100.

[0109] The material parameters of the piezoelectric layer 10 will change with the temperature, thereby affecting the propagation characteristics of the surface acoustic wave on the first surface 11. The temperature compensation layer 30 is made of a material with a smaller or opposite temperature coefficient than the piezoelectric layer 10. When the temperature changes, the temperature compensation layer 30 can compensate for the temperature effect of the piezoelectric layer 10. This reduces the influence of temperature changes on the propagation of the surface acoustic wave.

[0110] For surface acoustic waves, the amplitude of the surface acoustic waves can cause deformation of some structures in the piezoelectric layer 10. When the energy of the surface acoustic waves can be effectively transferred to the temperature compensation layer 30 of the surface acoustic wave device 100, the amplitude of the surface acoustic waves can also cause deformation of the temperature compensation layer 30. Correspondingly, the temperature compensation layer 30 can also act on the first surface 11 through the piezoelectric layer 10. The range in which the amplitude of the surface acoustic wave causes deformation of some structures in the piezoelectric layer 10 is the sound field range of the surface acoustic wave or the disturbance range of the surface acoustic wave.

[0111] That is, when the acoustic field range of the surface acoustic wave overlaps with the temperature compensation layer 30 of the surface acoustic wave device 100, the acoustic effect of the temperature compensation layer 30 can compensate for the influence of temperature change on the first surface 11 of the piezoelectric layer 10, thereby improving the working performance of the surface acoustic wave device 100 of the present application.

[0112] The amplitude of the surface acoustic wave acts on a limited range of structures in the piezoelectric layer 10. In actual use, the acoustic field range of the surface acoustic wave mainly acts on the first surface 11 of the piezoelectric layer 10 and a portion of the piezoelectric layer 10 close to the first surface 11. Therefore, the surface acoustic wave device 100 of the present application needs to limit the thickness of the piezoelectric layer 10 to ensure that the temperature compensation layer 30 and the piezoelectric layer 10 can interact with each other.

[0113] In the embodiment of the present application, the surface acoustic wave device 100 of the present application determines the size of the first characteristic thickness of the surface acoustic wave device 100 of the present application, and limits the thickness of the piezoelectric layer 10 by the ratio range of the first characteristic thickness to the thickness of the piezoelectric layer 10.

[0114] Specifically, the first characteristic thickness of the surface acoustic wave device 100 is T y , the thickness of the piezoelectric layer 10 is D y , the thickness of the piezoelectric layer 10 and the first characteristic thickness satisfy the condition: That is, the ratio between the thickness of the piezoelectric layer 10 and the first characteristic thickness is less than or equal to 1.5.

[0115] The piezoelectric layer 10 includes a piezoelectric crystal, and the first characteristic thickness is determined by the centerline spacing between two adjacent electrode fingers 22, the body wave velocity of the piezoelectric crystal along the X direction, and the operating frequency. In the embodiment of the present application, the body wave velocity of the piezoelectric crystal along the X direction is determined by the material of the piezoelectric layer 10. When the crystal material of the piezoelectric layer 10 is determined, the body wave velocity of the piezoelectric crystal along the X direction is also determined.

[0116] It is worth pointing out that in the embodiment of the present application and the subsequent embodiments, the two electrode fingers 22 of the interdigitated electrode 20 within one period segment length may refer to the adjacent first electrode finger 22a and the second electrode finger 22b, or may refer to the adjacent two first electrode fingers 22a or the adjacent two second electrode fingers 22b. That is, the two electrode fingers 22 of the interdigitated electrode 20 within one period segment length may be two adjacent electrode fingers 22 with the same polarity, or two adjacent electrode fingers 22 with different polarities. For ease of description, in the embodiment of the present application and the subsequent embodiments, the two electrode fingers 22 of the interdigitated electrode 20 within one period segment length are used to represent two adjacent electrode fingers 22 with the same polarity.

[0117] For details, please refer to Figure 7 The figure shows an enlarged cross-sectional schematic diagram of a surface acoustic wave device 100 provided in one embodiment of the present application.

[0118] like Figure 6 and Figure 7 As shown, the midline spacing between two adjacent electrode fingers 22 of the interdigitated electrode 20 is P, and the body wave velocity of the piezoelectric crystal along the X direction is V b1 , the operating frequency is f, and the body wave wavelength of the piezoelectric crystal along the X direction at the operating frequency is λ 1 , the first characteristic thickness satisfies the equation:

[0119] After the surface acoustic wave device 100 of the present application is manufactured, the midline spacing P between two adjacent electrode fingers 22 of the interdigital electrode 20 and the body wave velocity of the piezoelectric crystal along the X direction are V b1 and the operating frequency f, which are all measurable or determinable values. Therefore, the surface acoustic wave device 100 of the present application can be based on the centerline spacing P, the body wave speed V b1 And the operating frequency f obtains the first characteristic thickness.

[0120] Therefore, when the first characteristic thickness is determined, the thickness of the piezoelectric layer 10 can be determined based on the relationship between the first characteristic thickness and the thickness of the piezoelectric layer 10. The surface acoustic wave device 100 of the present application limits the thickness of the piezoelectric layer 10 through the ratio range of the first characteristic thickness to the thickness of the piezoelectric layer 10, thereby avoiding the situation where the energy of the surface acoustic wave cannot be effectively transmitted to the temperature compensation layer 30 of the surface acoustic wave device 100 due to the excessive thickness of the piezoelectric layer 10. In this way, the acoustic effect of the temperature compensation layer 30 of the surface acoustic wave device 100 is guaranteed, and the working performance of the surface acoustic wave device 100 of the present application is guaranteed.

[0121] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer 10 and the first characteristic thickness satisfy the condition:

[0122] When the ratio of the thickness of the piezoelectric layer 10 to the first characteristic thickness is less than 0.2, the thickness of the piezoelectric layer 10 is too thin. On the one hand, an overly thin piezoelectric layer 10 will lead to a decrease in the acoustic-to-electric conversion efficiency of the surface acoustic wave device 100, thereby affecting the working performance of the surface acoustic wave device 100 of the present application. On the other hand, an overly thin piezoelectric layer 10 is more sensitive to temperature changes and has relatively poor mechanical strength. As a result, the stability and reliability of the surface acoustic wave device 100 of the present application are relatively poor.

[0123] When the ratio of the thickness of the piezoelectric layer 10 to the piezoelectric characteristic thickness is greater than 1.5, the thickness of the piezoelectric layer 10 is too thick, resulting in an increase in the distance between the temperature compensation layer 30 of the surface acoustic wave device 100 and the first surface 11 along the third direction 003. It may make it difficult for the energy of the surface acoustic wave to be effectively transmitted to the temperature compensation layer 30 of the surface acoustic wave device 100, thereby affecting the acoustic effect of the temperature compensation layer 30.

[0124] Among them, the third direction 003 refers to the thickness direction of the piezoelectric layer 10, and the third direction 003 is perpendicular to the first direction 001 and the second direction 002 respectively. There may be errors in actual application. At least one of the angles between the third direction 003 and the first direction 001 and the angle between the third direction 003 and the second direction 002 may not be equal to 90°.

[0125] Therefore, the surface acoustic wave device 100 of the present application sets the ratio of the thickness of the piezoelectric layer 10 to the first characteristic thickness between 0.2 and 1.5, thereby avoiding the piezoelectric layer 10 being too thin due to a too small ratio, thereby affecting the working performance and stability of the surface acoustic wave device 100 of the present application. It also avoids the piezoelectric layer 10 being too thick due to a too large ratio, thereby affecting the acoustic effect of the temperature compensation layer 30 of the surface acoustic wave device 100. Thus, the stability and working performance of the surface acoustic wave device 100 of the present application are guaranteed.

[0126] Specifically, admittance can be used to describe the response process of components and signals. In the surface acoustic wave device 100 of the present application, admittance is used to measure the influence of the clutter propagating on the surface of the piezoelectric layer 10 on the quality of the acoustic wave. Figure 8 This is a comparison diagram of the admittance curves of the surface acoustic wave device 100 of the present application and the surface acoustic wave device in the comparative example based on different surface acoustic wave frequencies, wherein the unit of the abscissa is GHz and the unit of the ordinate is dB.

[0127] For the comparative example, the surface acoustic wave device includes a piezoelectric layer and an interdigital electrode disposed on the surface of the piezoelectric layer. The centerline spacing P between two adjacent interdigital electrodes of the interdigital electrode is 1.0 μm, the duty cycle of the interdigital electrode is 0.4, and the piezoelectric layer is made of 42° YX-LiTaO3 The material of the interdigital electrodes is aluminum, and the thickness of the interdigital electrodes is 0.16 μm. Along the thickness direction of the piezoelectric layer, the temperature compensation layer is arranged on the side of the piezoelectric layer away from the interdigital electrodes. In an ideal state, the thickness of the piezoelectric layer is considered to be infinite, and correspondingly, the temperature compensation layer can be considered to be infinitely far away from the interdigital electrodes. Figure 8 As shown, the admittance curve corresponding to the comparative example is represented by a solid line.

[0128] For the embodiments, there are four groups of embodiments, and the surface acoustic wave device 100 of each group of embodiments includes a functional layer 40, a temperature compensation layer 30, a piezoelectric layer 10, and a forked electrode 20 provided on the first surface 11 of the piezoelectric layer 10. Among them, the center line spacing P of two adjacent electrode fingers 22 of the forked electrode 20 is 1.0 μm, the duty cycle of the forked electrode 20 is 0.4, and the piezoelectric layer 10 adopts 42°YX-LiTaO 3 The material of the electrode finger 22 is aluminum, and the thickness of the electrode finger 22 is 0.16 μm.

[0129] The four groups of embodiments are respectively Embodiment 1 to Embodiment 4. Among them, along the third direction 003, the thickness of the piezoelectric layer 10 of Embodiment 1 is 0.2 μm. The thickness of the piezoelectric layer 10 of Embodiment 2 is 0.6 μm. The thickness of the piezoelectric layer 10 of Embodiment 3 is 1.0 μm. The thickness of the piezoelectric layer 10 of Embodiment 4 is 1.4 μm. Figure 8 As shown, the admittance curves corresponding to Embodiment 1 to Embodiment 4 are represented by different dotted lines respectively.

[0130] According to 42°YX-LiTaO 3 The material parameters can be calculated to show that in the piezoelectric layer 10 of Examples 1 to 4 and the piezoelectric layer of the comparative example, the sound velocity of the body wave propagating along the second direction 002 is about 4230 m / s. The surface acoustic wave resonant frequency is 1.982 GHz, and the surface acoustic wave antiresonant frequency is 2.058 GHz.

[0131] For the comparative example, according to It can be concluded that when the surface acoustic wave frequency is the surface acoustic wave resonance frequency, at this time, the first characteristic thickness T y =0.91 μm. When the surface acoustic wave frequency is the surface acoustic wave antiresonance frequency, at this time, the first characteristic thickness T y =1.4 μm. For ease of description, the first characteristic thickness T y =0.91μm as an example.

[0132] like Figure 8As shown, for Examples 1 to 4, the thicker the piezoelectric layer 10 is, the closer the admittance curve of the example is to the admittance curve of the comparative example. In the comparative example, because the thickness of the piezoelectric layer can be regarded as infinite, the disturbance area of ​​the corresponding surface acoustic wave will not overlap with the temperature compensation layer set on the piezoelectric layer. That is, the temperature compensation layer in the comparative example will not play an acoustic role.

[0133] On the other hand, because 1.5T y =1.365 μm. It can be seen that the thickness of the piezoelectric layer 10 corresponding to Examples 1 to 3 is less than 1.5T y The thickness of the piezoelectric layer 10 corresponding to the fourth embodiment is greater than 1.5T. y It is obvious that the admittance curves of Examples 1 to 3 are less consistent with the admittance curve of the comparative example, and correspondingly, the acoustic effect of the temperature compensation layer 30 of Examples 1 to 3 is more obvious.

[0134] That is, compared with the comparative example, the surface acoustic wave device 100 of the present application limits the thickness of the piezoelectric layer 10, so that the energy of the surface acoustic wave can be effectively transferred to the temperature compensation layer 30, thereby ensuring the acoustic effect of the temperature compensation layer 30. Thus, the working performance of the surface acoustic wave device 100 of the present application is improved.

[0135] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer 10 is less than the first characteristic thickness.

[0136] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer 10 and the first characteristic thickness satisfy the condition:

[0137] In one embodiment, if Figure 6 As shown, the surface acoustic wave device 100 of the present application further includes a temperature compensation layer 30, which is arranged on a side of the piezoelectric layer 10 away from the interdigital electrodes 20 along the third direction 003. In the embodiment of the present application, the temperature compensation layer 30 mainly improves the temperature stability of the surface acoustic wave device 100 of the present application by its own response to temperature changes, thereby reflecting its own acoustic effect.

[0138] Specifically, during the use of the surface acoustic wave device 100 of the present application, the acoustic characteristics of the piezoelectric layer 10 change when the temperature changes. The temperature compensation layer 30 is made of a material having a temperature coefficient opposite to or smaller than that of the piezoelectric layer 10. During actual operation, the temperature compensation layer 30 can partially or completely offset the temperature effect of the piezoelectric layer 10.

[0139] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrode 20 is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 is H, and the sum of the first characteristic thickness and the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the condition:

[0140] The value of the first characteristic thickness can be obtained by calculation after the surface acoustic wave device 100 is prepared. It can be understood that the ratio of the first characteristic thickness to the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 realizes the limitation of the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10, further ensuring that the energy of the surface acoustic wave can be effectively transferred to the temperature compensation layer 30, thereby ensuring the temperature compensation function of the temperature compensation layer 30 on the piezoelectric layer 10, and realizing the acoustic effect of the temperature compensation layer 30 on the surface acoustic wave device 100 of the present application.

[0141] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the sum of the first characteristic thickness, the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the condition:

[0142] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 is less than the first characteristic thickness.

[0143] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the sum of the first characteristic thickness, the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the condition:

[0144] In one embodiment, when the angle between the propagation direction of the body wave excited by the interdigital electrode 20 into the piezoelectric layer 10 and the first surface 11 is equal to the first enhancement angle θ, the body wave in the piezoelectric layer 10 and the temperature compensation layer 30 is in an enhanced state. The propagation speed of the body wave excited by two electrode fingers 22 in one period of the interdigital electrode 20 into the piezoelectric layer 10 and the temperature compensation layer 30 is V 0 , the first angle and the propagation velocity of the body wave in the piezoelectric layer 10 and the temperature compensation layer 30 satisfy the equation: The surface acoustic wave frequency of the surface acoustic wave device 100 is f, and the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the condition: The surface acoustic wave frequency f is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency.

[0145] In the above description of the relationship satisfied by the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10, in order to simplify the problem, the refraction effect of the body wave at the interface between the piezoelectric layer 10 and the temperature compensation layer 30 is ignored. Correspondingly, the propagation speed of the body wave excited by the interdigital electrodes 20 into the piezoelectric layer 10 and the temperature compensation layer 30 is the propagation speed under the ideal condition where the difference in the speed of sound between the piezoelectric layer 10 and the temperature compensation layer 30 is ignored.

[0146] In the embodiment of the present application, along the third direction 003, the temperature compensation layer 30 is disposed on the surface of the piezoelectric layer 10 away from the first surface 11, and the surface of the temperature compensation layer 30 away from the piezoelectric layer 10 is defined as the second surface 31. It can be understood that when the body wave propagates to the second surface 31, at least part of the body wave will be reflected on the second surface 31. When the reflected body wave propagates to the first surface 11, it will also be reflected.

[0147] When the phases of the body wave after two reflections on the first surface 11 and the second surface 31 match, the body wave will form a waveguide mode in the piezoelectric layer 10 and the temperature compensation layer 30. The surface acoustic wave device 100 of the present application further limits the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 through the above conditions to reduce the influence of the frequency of the waveguide mode on the frequency of the surface acoustic wave, thereby ensuring the working performance of the surface acoustic wave device 100 of the present application.

[0148] In one embodiment, the thickness of the temperature compensation layer 30 is D w , wherein the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfy the condition: When the thickness of the piezoelectric layer 10 is determined, if the ratio of the thickness of the piezoelectric layer 10 to the thickness of the temperature compensation layer 30 is less than 0.5, the thickness of the temperature compensation layer 30 is too thick. An overly thick temperature compensation layer 30 will not significantly improve the frequency temperature coefficient of the device, but will cause the device operating frequency and hybrid mode characteristics to deteriorate, affecting the working performance of the surface acoustic wave device 100 of the present application.

[0149] When the thickness of the piezoelectric layer 10 is determined, if the ratio of the thickness of the piezoelectric layer 10 to the thickness of the temperature compensation layer 30 is greater than 2, the thickness of the temperature compensation layer 30 is too thin, which may make it difficult for the temperature compensation layer 30 to achieve the predetermined temperature stability of the surface acoustic wave device 100.

[0150] Therefore, the surface acoustic wave device 100 of the present application limits the ratio range of the thickness of the temperature compensation layer 30 to the thickness of the piezoelectric layer 10 to achieve matching setting of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10, thereby improving the working performance and temperature stability of the surface acoustic wave device 100 of the present application.

[0151] In one embodiment, when the angle between the propagation direction of the body wave excited by the interdigital electrodes 20 into the piezoelectric layer 10 and the first surface 11 is equal to the first reinforcement angle θ, the body wave in the piezoelectric layer 10 is in a reinforcement state; the wavelength λ of the body wave excited by the interdigital electrodes 20 into the piezoelectric layer 10 is B1 is the wavelength of the bulk wave in the piezoelectric layer 10 in the enhanced state.

[0152] When the body wave excited by the interdigital electrodes 20 in the piezoelectric layer 10 propagates along the third direction 003 at a certain inclination angle, the angle between the propagation direction of the body wave and the first surface 11 is the propagation angle. For any two different propagation angles, the intensity of the body wave corresponding to one propagation angle may be different from the intensity of the body wave corresponding to another propagation angle. When the propagation angle is equal to the first reinforcement angle, the intensity of the body wave in the piezoelectric layer 10 is the largest compared to the intensities of the body waves corresponding to other propagation angles.

[0153] In one embodiment, the midline distance between two adjacent electrode fingers is P, the first reinforcement angle is θ, and the first reinforcement angle satisfies the equation: Among them, v B1 is the body wave velocity in the piezoelectric layer 10, f is the operating frequency, λ B1 is the wavelength of the body wave excited by the interdigital electrode 20 in the piezoelectric layer 10 , and the range of the first reinforcement angle θ satisfies: 0°<θ<180°.

[0154] Based on the limitations of the above embodiments, please refer to Fig. 9 ,in Fig. 9 FIG. 1 is a schematic diagram of a partial cross-sectional structure of a surface acoustic wave device 100 provided in an embodiment of the present application. Fig. 9 The solid line with arrows below the interdigital electrodes 20 in FIG. 1 represents the body wave propagating in the piezoelectric layer 10 and the propagation direction of the body wave.

[0155] When the surface wave of the surface acoustic wave device 100 of the present application propagates along the surface of the piezoelectric layer 10, the intensity of the surface acoustic wave gradually decreases as the depth along the third direction 003 gradually increases. The first characteristic thickness represents the time at which the intensity of the surface acoustic wave decays to the intensity of the surface acoustic wave at the first surface 11. The distance from the first surface 11.

[0156] That is, the surface acoustic wave device 100 of the present application obtains the surface acoustic wave intensity attenuated to the surface acoustic wave intensity at the first surface 11. The distance from the first surface 11 is set to limit the thickness of the piezoelectric layer 10 and ensure that the characteristic depth of the surface acoustic wave can cover the temperature compensation layer or overlap with the temperature compensation layer 30 below the thickness of the piezoelectric layer 10.

[0157] Specifically, in the embodiment of the present application, the acoustic wave vector generated by the surface acoustic wave device 100 of the present application when working has a real number component along the thickness direction of the piezoelectric layer 10, that is, a body wave, and the enhancement condition for body wave excitation means that the body waves excited by the electrode fingers 22 of the same polarity are phase-matched in a specific direction. Fig. 9 As shown, two adjacent first electrode fingers 22a of the interdigital electrode 20 excite the body wave vector β in the piezoelectric layer 10. B1 The angle between the propagation direction of and the first surface 11 is equal to the first reinforcement angle θ.

[0158] At this time, the wavelength λ of the bulk wave in the enhanced state in the piezoelectric layer 10 is B1 , the spacing P between the central axes of two adjacent electrode fingers 22, and the first reinforcement angle θ satisfy the condition: 2Pcosθ=nλ B1 . Where n is a positive integer.

[0159] In the embodiment of the present application, the case of n=1 is considered. That is, The propagation speed of the body wave in the enhanced state in the piezoelectric layer 10 is v B1 , the wave vector β of the body wave in the enhanced state in the piezoelectric layer 10 B1 The operating frequency is f.

[0160] In the embodiment of the present application, the magnitude of the first enhancement angle is determined by the operating frequency f. , cosθ=1.

[0161] When f <f c1 When cosθ>1. At this time, the first reinforcement angle θ is a complex number, and correspondingly, the acoustic wave vector generated when the surface acoustic wave device 100 of the present application is working does not have a real component along the thickness direction of the piezoelectric layer 10. That is, when the first reinforcement angle is a complex number, the acoustic wave vector component propagating along the third direction 003 in the piezoelectric layer 10 away from the first surface 11 is an imaginary number, and the acoustic wave is an evanescent wave. Therefore, under ideal conditions, for the surface acoustic wave device 100 of the present application, there is only the energy of the surface acoustic wave concentrated on the surface layer of the device.

[0162] In order to distinguish the sound wave state when the first reinforcement angle is a real number and the sound wave state when the first reinforcement angle is a complex number, β 1 This shows the state of the sound wave when the first reinforcement angle is plural.

[0163] At this time, the sound wave vector β 1 The intensity of the evanescent wave decays rapidly in the direction away from the first surface 11 along the third direction 003. The surface acoustic wave device 100 of the present application uses the attenuation characteristics of the evanescent wave to characterize the distribution range of the surface acoustic wave. Specifically, the evanescent wave intensity decays to the evanescent wave intensity at the first surface 11. There is a certain corresponding relationship between the distance from the first surface 11 and the thickness of the piezoelectric layer 10 when the amplitude of the surface acoustic wave overlaps with the temperature compensation layer 30.

[0164] Acoustic wave vector β 1 The wave vector component in the third direction 003 is β 1z Since the first reinforcement angle is a complex number, the acoustic wave of the surface acoustic wave device 100 of the present application is only manifested as an acoustic wave along the X direction. At this time, the acoustic wave vector β 1 The modulus satisfies the equation: Among them, λ 1 is the body wave wavelength of the piezoelectric crystal along the X direction at the operating frequency f.

[0165] Wave vector β 1 The wave vector component in the third direction 003 is β 1z Satisfies the equation:

[0166] In the above equation, the first reinforcement angle θ is selected as the operating frequency f=f c1 , the value of the first reinforcement angle.

[0167] The intensity of the surface acoustic wave propagating in the piezoelectric layer 10 along the third direction 003 away from the first surface 11 is u, wherein the intensity of the surface acoustic wave in the piezoelectric layer 10 satisfies the equation Acoustic wave vector β 1 The body wave component in the second direction 002 is β 1x , z represents the distance between any point in the piezoelectric layer 10 and the first surface 11 .

[0168] In this embodiment, the first characteristic thickness represents the surface acoustic wave intensity attenuated to the surface acoustic wave intensity at the first surface 11. The distance from the first surface 11. That is,

[0169] Will Substituting the equation for the acoustic wave intensity in the piezoelectric layer 10, the z value in the above equation is obtained. The calculated z value is the first characteristic thickness. B1 is the body wave velocity in the piezoelectric layer 10, and when the first reinforcement angle is a complex number, the acoustic wave velocity of the surface acoustic wave device of the present application is only related to the material of the piezoelectric layer 10. Therefore, the first characteristic thickness Among them, the body wave speed of the piezoelectric crystal along the X direction is V b1 .

[0170] In the embodiment of the present application, after the first characteristic thickness is calculated based on the above equation, the thickness of the piezoelectric layer 10 is determined by the ratio range of the thickness of the piezoelectric layer 10 to the first characteristic thickness. For the piezoelectric layer 10 with this thickness, the energy of the surface acoustic wave can act on the temperature compensation layer 30 through the piezoelectric layer 10. That is, the amplitude of the surface acoustic wave overlaps with the temperature compensation layer 30.

[0171] Please refer to Fig.10 ,in Fig.10 FIG. 1 is another partial cross-sectional structural diagram of a surface acoustic wave device 100 provided in an embodiment of the present application. Fig.10 The solid lines with arrows in FIG. 5 represent the bulk waves propagating in the piezoelectric layer 10 and the temperature compensation layer 30 and the propagation direction of the bulk waves.

[0172] like Fig.10 As shown, the first reinforcement angle is a real number, and the propagation speed of the body wave in the piezoelectric layer 10 and the temperature compensation layer 30 is V 0 , the operating frequency of the interdigital electrode 20 is f, and the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 is H.

[0173] It is worth pointing out that the propagation speed of the body wave excited by the interdigital electrodes 20 into the piezoelectric layer 10 and the temperature compensation layer 30 is the propagation speed under the ideal condition of ignoring the difference in the speed of sound between the piezoelectric layer 10 and the temperature compensation layer 30. That is, the propagation speed V of the body wave in the piezoelectric layer 10 and the temperature compensation layer 30 is 0 The propagation speed of the bulk wave in the piezoelectric layer 10 is V B1 The values ​​are equal, and the embodiments of the present application use different superscripts for easy distinction.

[0174] When the phase difference of the bulk wave after two reflections on the first surface 11 and the second surface 31 is 2nπ, the bulk wave will form a waveguide mode in the piezoelectric layer 10 and the temperature compensation layer 30. Wherein, n is a positive integer.

[0175] The frequency of the waveguide mode is f g The frequency of the waveguide mode satisfies the equation:

[0176] Wherein, 2n represents the ratio of the distance between the body wave reflected on both sides of the first surface 11 and the second surface 31 to the wavelength of the body wave, It represents the ratio of the phase introduced when the body wave is reflected by the first surface 11 and the second surface 31 to π.

[0177] In the actual use of the surface acoustic wave device 100 of the present application, the waveguide mode may affect the ripple of the passband of the surface acoustic wave filter. It is usually required that the frequency f of the waveguide mode g is the surface acoustic wave frequency f (for example: the surface acoustic wave resonant frequency fr ). Wherein, η>1.07, or η=1.05. For ease of description, η>1.07 is taken as an example for introduction.

[0178] That is, the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the condition:

[0179] Based on the above conditions, it can be known that in order to obtain the maximum range of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10, Correspondingly, It should take the minimum value. That is, n = 1. The phase difference introduced by the body wave when it is reflected on the first surface 11 and the second surface 31 is 0, that is, From this we get

[0180] The first reinforcement angle and the propagation velocity of the body wave in the piezoelectric layer 10 and the temperature compensation layer 30 satisfy the equation: From this we get

[0181] In the embodiment of the present application, in the process of preparing the surface acoustic wave device 100 of the present application, the propagation speed of the body wave excited by the interdigital electrode 20 to the piezoelectric layer 10 and the temperature compensation layer 30 in the enhanced state can be V 0 , and the surface acoustic wave frequency f are used to calculate the range of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10. Thus, the range of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 is limited. In order to select the thickness D of the piezoelectric layer 10 y and the thickness of the temperature compensation layer D w .

[0182] Among them, for the first reinforcement angle θ. Since the first reinforcement angle is a real number, according to and Christoph's formula, we can get Fig.11 The local curve diagram of the relationship between F(θ) and the first reinforcement angle θ shown in FIG. The horizontal axis is the first reinforcement angle θ, in degrees, and the vertical axis is F(θ), in m / s.

[0183] Based on the equation relationship between G(θ) and F(θ), we can know that That is, when calculating G(θ), we can use Fig.11 F(θ) and the first reinforcement angle θ are obtained to calculate G(θ).

[0184] It can be seen that in the process of preparing the surface acoustic wave device 100 of the present application, the midline spacing P between two adjacent electrode fingers 22, the body wave sound velocity V of the piezoelectric crystal along the X direction can be obtained. b1 and the operating frequency f, the first characteristic thickness T is calculated y .

[0185] The first characteristic thickness T is calculated y On the premise of , it is necessary to further limit the selection range of the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10. Specifically, on the one hand, by obtaining the midline spacing P of two adjacent electrode fingers 22, the body wave sound velocity V in the piezoelectric layer 10 B1 and the operating frequency f, the first reinforcement angle θ is calculated.

[0186] On the other hand, the F(θ) value corresponding to the first reinforcement angle θ can also be calculated by using the operating frequency f and the spacing P between the central axes of two adjacent electrode fingers 22, and the F(θ) value can be calculated by using the operating frequency f and the spacing P between the central axes of two adjacent electrode fingers 22. Fig.11 (like Fig.11 The first reinforcement angle θ is obtained as shown by the double-dotted line parallel to the horizontal axis.

[0187] In the embodiment of the present application, body waves include longitudinal waves and transverse waves, and transverse waves include fast shear waves and slow shear waves. When the first enhancement angle θ is obtained, different intersection points can be selected based on actual needs to select different first enhancement angles θ.

[0188] On the basis of obtaining the first reinforcement angle θ, the propagation velocity V of the body wave in the piezoelectric layer 10 and the temperature compensation layer 30 is obtained. 0 , and the surface acoustic wave frequency f (surface acoustic wave resonant frequency or surface acoustic wave anti-resonant frequency) selected in the embodiment of the present application, another limited range of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 is calculated.

[0189] In the process of preparing the surface acoustic wave device 100 of the present application, the first characteristic thickness T y The obtained range of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10, and The obtained limited range of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 realizes the range limitation of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10. In order to select the thickness D of the piezoelectric layer 10 y and the thickness of the temperature compensation layer D w .

[0190] In one embodiment, the surface acoustic wave device 100 further includes a functional layer 40. Along the thickness direction of the piezoelectric layer 10, the functional layer 40 is disposed on a side of the piezoelectric layer 10 away from the interdigital electrodes 20. Figure 6 Along the third direction 003 , the functional layer 40 is disposed on a side of the temperature compensation layer 30 away from the piezoelectric layer 10 to block leakage of the bulk wave and reduce the loss of the surface acoustic wave device 100 .

[0191] The bulk wave generated when the surface acoustic wave device 100 of the present application is in operation will propagate into the functional layer 40 through the temperature compensation layer 30 after being released to the piezoelectric layer 10 , and propagate in a direction away from the second surface 31 .

[0192] The second characteristic thickness of the surface acoustic wave device 100 of the present application is T d , the thickness of the functional layer 40 is D d , the thickness of the functional layer 40 and the second characteristic thickness satisfy the condition: That is, the ratio of the thickness of the functional layer 40 to the second characteristic thickness is less than or equal to 1.5.

[0193] The size of the second characteristic thickness is determined by the body wave velocity of the material of the compressive functional layer 40 along the X direction and the operating frequency.

[0194] Specifically, in one embodiment, the wavelength of the bulk wave in the enhanced state in the piezoelectric layer 10 after being refracted into the functional layer 40 is λ 2 , the second characteristic thickness satisfies the equation:

[0195] After the surface acoustic wave device 100 of the present application is manufactured, the centerline spacing between two adjacent electrode fingers 22 is P, and the body wave velocity of the material of the functional layer 40 along the X direction is V b2 , the operating frequency is f, which are all measurable or calculable values. Therefore, the surface acoustic wave device 100 of the present application can be based on the body wave sound velocity V b2 The wavelength λ corresponding to the body wave velocity of the material of the functional layer 40 along the X direction at the working frequency is calculated as f 2 , and based on the body wave wavelength λ 2 And the centerline spacing P obtains the second characteristic thickness.

[0196] Therefore, when the second characteristic thickness is determined, the thickness of the functional layer 40 can be determined based on the relationship between the second characteristic thickness and the thickness of the functional layer 40. The surface acoustic wave device 100 of the present application limits the thickness of the functional layer 40 through the ratio range of the second characteristic thickness to the functional layer 40, so that the high-frequency body wave in the body wave can leak outward to reduce the quality factor (Q value) of the high-frequency stray mode, thereby reducing the influence of the high-frequency stray mode in practical applications and ensuring the working performance of the surface acoustic wave device 100 of the present application.

[0197] In one embodiment, the frequency of the surface acoustic wave excited by the interdigital electrode 20 is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, and the thickness of the functional layer 40 and the second characteristic thickness meet the condition: When the ratio of the thickness of the functional layer 40 to the second characteristic thickness is less than 0.2, the thickness of the functional layer 40 is too thin. An overly thin functional layer 40 is more sensitive to temperature changes and has relatively poor mechanical strength, which results in relatively poor stability and reliability of the surface acoustic wave device 100 of the present application.

[0198] When the ratio of the thickness of the functional layer 40 to the second characteristic thickness is greater than 1.5, the thickness of the functional layer 40 is too thick, and the blocking effect of the functional layer 40 on the leakage of body waves is enhanced, which may cause the high-frequency stray modes in the body waves to be difficult to leak, thereby causing the high-frequency stray modes to affect the working performance of the surface acoustic wave device 100 of the present application.

[0199] Therefore, the surface acoustic wave device 100 of the present application sets the ratio of the thickness of the functional layer 40 to the second characteristic thickness between 0.2 and 1.5, thereby avoiding the functional layer 40 being too thin due to the ratio being too small, thereby affecting the working performance and stability of the surface acoustic wave device 100 of the present application. It also avoids the functional layer 40 being too thick due to the ratio being too large, thereby affecting the leakage of high-frequency heterogeneous modes of the surface acoustic wave device 100. Thus, the stability and working performance of the surface acoustic wave device 100 of the present application are guaranteed.

[0200] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer 40 is less than the second characteristic thickness.

[0201] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrode 20 is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer 40 and the second characteristic thickness meet the condition:

[0202] In one embodiment, if Figure 6 As shown, the surface acoustic wave device 100 of the present application includes a single crystal silicon layer 50 . Along the third direction 003 , the single crystal silicon layer 50 is disposed on the surface of the functional layer 40 away from the piezoelectric layer 10 .

[0203] The bulk wave generated by the surface acoustic wave device 100 of the present application during operation is released to the piezoelectric layer 10, and then leaks to the single crystal silicon layer 50 through the temperature compensation layer 30 and the functional layer 40 in sequence. <110> The spatial angle between the crystal orientation group and the propagation direction of the surface acoustic wave excited by the plurality of electrode fingers 22 on the first surface 11 is less than or equal to 10°. <110> A spatial angle between the crystal orientation group and the second direction 002 is less than or equal to 10°.

[0204] Since the acoustic velocity of the functional layer 40 is greater than that of the single crystal silicon layer 50, <110> The speed of sound propagating in the direction of the single crystal silicon layer 50 is greater than that of the single crystal silicon layer 50. It can be understood that the functional layer 40 is a wave-sparse medium compared to the single crystal silicon layer 50. When the body wave is incident on the interface between the single crystal silicon layer 50 and the functional layer 40 at a certain incident angle, the refraction angle of the body wave refracted into the single crystal silicon layer 50 is smaller than the incident angle. Correspondingly, the angle between the propagation direction of the body wave refracted into the single crystal silicon layer 50 and the second direction 002 is greater than the angle between the propagation direction of the body wave incident on the single crystal silicon layer 50 and the second direction 002.

[0205] Since the single crystal silicon layer 50 <110> The crystal orientation family has a lower acoustic wave propagation speed and lower acoustic loss. It can be understood that the single crystal silicon layer 50 <110> The spatial angle between the crystal orientation group and the second direction 002 is less than or equal to 10°, which is beneficial to the leakage of the bulk wave from the functional layer 40 to the single crystal silicon layer 50 .

[0206] That is, the matching arrangement of the single crystal silicon layer 50 and the functional layer 40 can facilitate the leakage of high-frequency heterogeneous modes (including waveguide modes) in the bulk wave, thereby reducing the interference of high-frequency heterogeneous modes on the surface acoustic wave in practical applications and improving the working performance of the surface acoustic wave device 100 of the present application.

[0207] In one embodiment, the single crystal silicon layer 50 <110> The crystal orientation group is parallel to the propagation direction of the surface acoustic waves excited by the plurality of electrode fingers 22 on the first surface 11 .

[0208] See also Fig.12 and Fig.13 ,in Fig.12 FIG. 1 is another schematic diagram of the structure of a surface acoustic wave device 100 provided in an embodiment of the present application. Fig.13 FIG. 1 is another schematic cross-sectional structure diagram of a surface acoustic wave device 100 provided in an embodiment of the present application.

[0209] like Fig.12 and Fig.13 As shown, the surface acoustic wave device 100 of the present application includes a functional layer 40 and a piezoelectric layer 10 stacked along the thickness direction thereof, and at least one interdigital electrode 20 disposed on a first surface 11 of the piezoelectric layer 10 facing away from the functional layer 40 .

[0210] The interdigitated electrode 20 includes two bus bars 21 arranged in parallel and at intervals, and a plurality of electrode fingers 22 arranged in parallel and at intervals. Among them, one bus bar 21 of the two bus bars 21 is used to receive external signals, and the other bus bar 21 of the two bus bars 21 is used to output signals. The plurality of electrode fingers 22 are located between the two bus bars 21. Some of the plurality of electrode fingers 22 are connected to one bus bar 21, and another part of the plurality of electrode fingers 22 are connected to the other bus bar 21.

[0211] For ease of description, the bus bar 21 for receiving external signals is defined as the first bus bar 21a, and the bus bar 21 for outputting signals is defined as the second bus bar 21b. The electrode fingers 22 connected to the first bus bar 21a are defined as the first electrode fingers 22a, and the electrode fingers 22 connected to the second bus bar 21b are defined as the second electrode fingers 22b.

[0212] Specifically, the first electrode fingers 22a and the second electrode fingers 22b extend toward opposite sides of the piezoelectric layer 10 along the first direction 001. Along the second direction 002, the first electrode fingers 22a and the second electrode fingers 22b are arranged alternately. Fig.12 As shown, along the second direction 002, there is a second electrode finger 22b between any two adjacent first electrode fingers 22a, and there is a first electrode finger 22a between any two adjacent second electrode fingers 22b.

[0213] The first bus bar 21a and the second bus bar 21b extend toward opposite sides of the piezoelectric layer 10 along the second direction 002, wherein the first direction 001 and the second direction 002 are perpendicular to each other. The surface acoustic wave device 100 of the present application may have errors during actual application, and the angle between the first direction 001 and the second direction 002 may not be equal to 90°.

[0214] In the embodiment of the present application, based on the inverse piezoelectric effect of the piezoelectric layer 10, the electrical signal can act on the piezoelectric layer 10 via the first bus bar 21a and each first electrode finger 22a in sequence, and cause the surface of the piezoelectric layer 10 to deform periodically, thereby forming an acoustic wave released outward.

[0215] The acoustic waves of the surface acoustic wave device 100 of the present application when working include surface acoustic waves and body waves. Among them, when the component of the acoustic wave along the thickness direction of the piezoelectric layer 10 is an imaginary number, this acoustic wave can only propagate along the plane direction of the first surface 11, that is, a surface acoustic wave. Among them, the propagation direction of the surface acoustic wave is defined as the X direction. When the acoustic wave vector has a real number component along the thickness direction of the piezoelectric layer 10, it is a body wave.

[0216] The surface acoustic wave is used to realize the frequency selection function and signal processing function of the surface acoustic wave device 100 of the present application. During the propagation of the surface acoustic wave, the main propagation direction of the surface acoustic wave is the second direction 002. That is, the X direction is the second direction 002. However, in the actual process, due to the edge effect and the diffraction of the sound wave, the propagation direction of the surface acoustic wave formed on the first surface 11 of the piezoelectric layer 10 may also be other directions, and correspondingly, there is an angle between the X direction and the second direction 002. In one embodiment, the surface acoustic waves propagating in the other directions will be absorbed by the sound absorbing material (not shown in the figure).

[0217] In the embodiment of the present application, the bulk waves generated when the surface acoustic wave device 100 of the present application is in operation will be released to the piezoelectric layer 10 and propagate into the functional layer 40 . The bulk waves in the functional layer 40 will propagate in a direction away from the first surface 11 .

[0218] The second characteristic thickness of the surface acoustic wave device 100 of the present application is T d , the thickness of the functional layer 40 is D d , the thickness of the functional layer 40 and the second characteristic thickness satisfy the condition: That is, the ratio of the thickness of the functional layer 40 to the second characteristic thickness is less than or equal to 1.5.

[0219] The size of the second characteristic thickness is determined by the body wave acoustic velocity of the material of the functional layer 40 along the X direction and the operating frequency. In the embodiment of the present application, the body wave acoustic velocity of the material of the functional layer 40 along the X direction is determined by the material of the functional layer 40. When the material of the functional layer 40 is determined, the body wave acoustic velocity of the material of the functional layer 40 along the X direction is also determined.

[0220] For details, please refer to Fig.14 Another enlarged cross-sectional schematic diagram of a surface acoustic wave device 100 provided in one embodiment of the present application is shown.

[0221] like Fig.14 As shown, the midline spacing between two adjacent electrode fingers 22 is P, and the body wave acoustic velocity of the material of the functional layer 40 along the X direction is V b2 , the operating frequency is f, and the second characteristic thickness satisfies the equation:

[0222] Therefore, the surface acoustic wave device 100 of the present application can be based on the body wave sound velocity V b2 The wavelength λ corresponding to the body wave velocity of the material of the functional layer 40 along the X direction at the working frequency is calculated as f. 2 , and based on the body wave wavelength λ 2 And the centerline spacing P obtains the second characteristic thickness.

[0223] Therefore, when the second characteristic thickness is determined, the thickness of the functional layer 40 can be determined based on the relationship between the second characteristic thickness and the thickness of the functional layer 40. The surface acoustic wave device 100 of the present application limits the thickness of the functional layer 40 through the ratio range of the second characteristic thickness to the functional layer 40, so that the high-frequency body wave in the body wave can leak outward to reduce the quality factor (Q value) of the high-frequency stray mode, thereby reducing the influence of the high-frequency stray mode in practical applications and ensuring the working performance of the surface acoustic wave device 100 of the present application.

[0224] Specifically, admittance can be used to describe the response process of components and signals. In the surface acoustic wave device 100 of the present application, admittance is used to measure the influence of the clutter propagating on the surface of the piezoelectric layer 10 on the quality of the acoustic wave. Fig.15 This is a schematic diagram of the conductivity curves of the surface acoustic wave device 100 of the present application and the surface acoustic wave device in the comparative example based on different surface acoustic wave frequencies, wherein the unit of the abscissa is GHz and the unit of the ordinate is dB.

[0225] For the comparative examples, there are two groups of comparative examples, and the surface acoustic wave devices of each group of comparative examples include a piezoelectric layer and an interdigital electrode disposed on the surface of the piezoelectric layer. Among them, the centerline spacing P of two adjacent interdigital electrodes of the interdigital electrode is 1.0 μm, the duty cycle of the interdigital electrode is 0.4, and the piezoelectric layer adopts 0.6 μm 42° YX-LiTaO 3 The material of the interdigital electrode is aluminum, and the thickness of the interdigital electrode is 0.16 μm.

[0226] The two groups of comparative examples are comparative example 1 and comparative example 2. For comparative example 1, a single crystal silicon layer is provided on the side of the piezoelectric layer away from the interdigital electrodes along the thickness direction of the piezoelectric layer. The upper surface of the single crystal silicon layer is (111), wherein the [1-10] crystal direction is parallel to the second direction 002. For comparative example 2, a functional layer is provided on the side of the piezoelectric layer away from the interdigital electrodes along the thickness direction of the piezoelectric layer. Fig.15 As shown, the conductivity curves corresponding to Comparative Example 1 and Comparative Example 2 are represented by solid lines with different line widths.

[0227] For the embodiments, there are six groups of embodiments, and the surface acoustic wave device 100 of each group of embodiments includes a monocrystalline silicon layer 50, a functional layer 40, a temperature compensation layer 30, a piezoelectric layer 10, and a forked electrode 20 provided on the first surface 11 of the piezoelectric layer 10. Among them, the centerline spacing P of two adjacent electrode fingers 22 of the forked electrode 20 is 1.0 μm, the duty cycle of the forked electrode 20 is 0.4, and the piezoelectric layer 10 adopts 0.6 μm 42° YX-LiTaO 3 The electrode finger 22 is made of aluminum and has a thickness of 0.16 μm. The upper surface of the single crystal silicon layer 50 is (111), wherein the [1-10] crystal direction is parallel to the second direction 002 .

[0228] The six groups of embodiments are respectively Embodiment 5 to Embodiment 10. Among them, along the third direction 003, the thickness of the functional layer 40 of Embodiment 5 is 0.6 μm. The thickness of the functional layer 40 of Embodiment 6 is 1.0 μm. The thickness of the functional layer 40 of Embodiment 7 is 1.4 μm. The thickness of the functional layer 40 of Embodiment 8 is 1.8 μm. The thickness of the functional layer 40 of Embodiment 9 is 2.2 μm. The thickness of the functional layer 40 of Embodiment 10 is 2.6 μm. Fig.15 As shown, the conductivity curves corresponding to Examples 5 to 10 are represented by different line segments, respectively.

[0229] According to 42°YX-LiTaO 3 The material parameters can be calculated. For the embodiment, the shear wave velocity of the body wave in the functional layer 40 is about 5340 m / s. According to the local curve diagram and the relationship between the second reinforcement angle of the functional layer 40 of the surface acoustic wave device and the body wave velocity The second characteristic thickness T of the body wave with a body wave frequency of 2.4 GHz is calculated as d =0.73μm.

[0230] like Fig.15 is the change of harmonic conductance and the thickness of the functional layer 40, wherein the conductance is directly related to the loss of the system. For comparative example 1, at 2.34 GHz, the harmonic conductance curve has a turning point, which indicates that the body wave released by the interdigital electrode 20 into the piezoelectric layer 10 leaks from 2.34 GHz to the single crystal silicon layer 50. For comparative example 2, the harmonic conductance curve has this turning point at 2.67 GHz.

[0231] For SAW devices, the leakage of high-frequency noise in the body wave can reduce the Q value of the high-frequency noise mode and reduce the interference of the high-frequency noise mode on the operation of the SAW device. Therefore, SAW devices usually need to control the leakage frequency to avoid the phenomenon that the leakage frequency is too high and the high-frequency noise is difficult to leak.

[0232] like Fig.15 As shown, for Examples 5 to 10, the thinner the thickness of the functional layer 40 is, the closer the conductance curve is to that of Comparative Example 1. The thicker the thickness of the functional layer 40 is, the closer the conductance curve is to that of Comparative Example 2.

[0233] On the other hand, because 1.5T d =1.095 μm. It can be seen that the thickness of the functional layer 40 corresponding to Examples 5 and 6 is less than 1.5T d The thickness of the functional layer 40 corresponding to Examples 7 to 10 is greater than 1.5T. dIt is obvious that the turning points of Examples 5 and 6 are relatively close to the turning point of Comparative Example 1. That is, the surface acoustic wave devices 100 corresponding to Examples 5 and 6 can better achieve leakage of high-frequency clutter in the bulk wave.

[0234] That is, compared with Comparative Examples 1 and 2, the surface acoustic wave device 100 of the present application limits the thickness of the functional layer 40, so that the body wave can pass through the functional layer 40 and leak to the single crystal silicon layer 50, thereby reducing the interference of high-frequency heterogeneous modes in practical applications. Thus, the working performance of the surface acoustic wave device 100 of the present application is improved.

[0235] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrode 20 is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer 40 and the second characteristic thickness meet the condition: The surface acoustic wave device 100 of the present application sets the ratio of the thickness of the functional layer 40 to the second characteristic thickness between 0.2 and 1.5, thereby preventing the thickness of the functional layer 40 from being too thin due to a too small ratio, thereby affecting the working performance and stability of the surface acoustic wave device 100 of the present application. It also prevents the thickness of the functional layer 40 from being too thick due to a too large ratio, thereby affecting the leakage of high-frequency heterogeneous modes of the surface acoustic wave device 100. Thus, the stability and working performance of the surface acoustic wave device 100 of the present application are guaranteed.

[0236] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrodes 20 is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer 40 is less than the second characteristic thickness.

[0237] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrode 20 is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer 40 and the second characteristic thickness meet the condition:

[0238] In one embodiment, the first characteristic thickness of the surface acoustic wave device 100 is T y , the thickness of the piezoelectric layer 10 is D y , the thickness of the piezoelectric layer 10 and the first characteristic thickness satisfy the condition: The first characteristic thickness is determined according to the centerline distance between two adjacent electrode fingers 22 and the body wave velocity and the operating frequency of the piezoelectric layer 10 along the X direction.

[0239] In one embodiment, the first characteristic thickness satisfies the equation:

[0240] In one embodiment, please refer to Fig.13The surface acoustic wave device 100 of the present application further includes a temperature compensation layer 30 and a single crystal silicon layer 50. Along the third direction 003, the temperature compensation layer 30 is located between the piezoelectric layer 10 and the functional layer 40 to improve the temperature stability of the surface acoustic wave device 100 of the present application. The single crystal silicon layer 50 is arranged on a side of the functional layer 40 away from the temperature compensation layer 30 to facilitate the leakage of the waveguide mode capacity.

[0241] In one embodiment, when the angle between the propagation direction of the acoustic wave excited by the interdigital electrode 20 and the first surface 11 is equal to the second enhancement angle γ, the body wave in the functional layer 40 is in an enhanced state; when the acoustic wave excited by the interdigital electrode 20 propagates to the body wave wavelength λ in the functional layer B2 is the wavelength of the bulk wave in the functional layer 40 in the enhanced state.

[0242] When the body wave excited by the interdigital electrodes 20 into the functional layer 40 propagates along the third direction 003 at a certain inclination angle, the angle between the propagation direction of the body wave and the first surface 11 is the propagation angle. For any two different propagation angles, the intensity of the body wave corresponding to one propagation angle may be different from the intensity of the body wave corresponding to another propagation angle. When the propagation angle is equal to the second enhancement angle, the intensity of the body wave in the functional layer 40 is the largest compared to the intensities of the body waves corresponding to other propagation angles.

[0243] In one embodiment, the midline distance between two adjacent electrode fingers is P, the second reinforcement angle is γ, and the second reinforcement angle γ satisfies the equation: Among them, V B2 is the body wave velocity in the functional layer, f is the operating frequency, λ B2 is the body wave wavelength of the acoustic wave excited by the interdigital electrodes and propagated into the functional layer, and the second reinforcement angle γ satisfies: 0°<γ<180°.

[0244] Based on the limitations of the above embodiments, please refer to Fig.16 ,in Fig.16 FIG. 1 is another partial cross-sectional structural diagram of a surface acoustic wave device 100 provided in an embodiment of the present application. Fig.16 The solid line with arrows below the interdigital electrodes 20 in FIG. 1 represents the bulk waves propagating in the piezoelectric layer 10 , the temperature compensation layer 30 , and the functional layer 40 and the propagation direction of the bulk waves.

[0245] For ease of description, the refraction effect of the bulk wave at the interface between the piezoelectric layer 10 and the temperature compensation layer 30 is ignored. The surface where the temperature compensation layer 30 and the functional layer 40 are attached is defined as the second surface 31 .

[0246] During the propagation of the body wave of the surface acoustic wave device 100 in the functional layer 40, as the propagation depth of the body wave along the third direction 003 gradually increases, the intensity of the body wave will gradually decrease. The second characteristic thickness represents the time when the body wave intensity decays to the second surface 31. The distance from the second surface 31.

[0247] That is, the surface acoustic wave device 100 of the present application obtains the body wave intensity attenuated to the body wave intensity at the second surface 31. The distance from the second surface 31 is set to limit the thickness of the functional layer 40 and ensure that the body wave can leak into the single crystal silicon layer 50 below the thickness of the functional layer 40.

[0248] Specifically, in the embodiment of the present application, the acoustic wave vector generated by the surface acoustic wave device 100 of the present application when working has a real number component along the thickness direction of the functional layer 40, that is, a body wave, and the enhancement condition of body wave excitation means that the body waves excited by the electrode fingers 22 of the same polarity are phase-matched in a specific direction. Fig.16 As shown, the body wave vector β of two adjacent first electrode fingers 22a of the interdigital electrode 20 is excited into the piezoelectric layer 10 and enters the functional layer 40 through the temperature compensation layer 30. B2 The angle between the propagation direction of and the second surface 31 is equal to the second reinforcement angle γ.

[0249] At this time, the wavelength λ of the bulk wave in the enhanced state in the functional layer 40 is B2 , the spacing P between the central axes of two adjacent electrode fingers 22, and the second reinforcement angle γ satisfy the condition: 2Pcosγ=nλ B2 . Where n is a positive integer.

[0250] In the embodiment of the present application, the case of n=1 is considered. That is, The propagation speed of the body wave in the enhanced state in the functional layer 40 is V B2 , the body wave vector β in the enhanced state in the functional layer 40 B2 The operating frequency is f.

[0251] In the embodiment of the present application, the magnitude of the second reinforcement angle is determined by the operating frequency f. , cosγ=1.

[0252] When f <f c2 When cosγ>1. At this time, the second reinforcement angle γ is a complex number. Correspondingly, when the body wave generated by the surface acoustic wave device 100 of the present application is in operation, it will be fully emitted from the second surface 31 when entering the functional layer 40 from the piezoelectric layer 10 and the temperature compensation layer 30.

[0253] That is, the acoustic wave vector component propagating along the third direction 003 in the functional layer 40 away from the first surface 11 is an imaginary number, and the acoustic wave at this time is an evanescent wave. Therefore, in an ideal case, for the surface acoustic wave device 100 of the present application, only the acoustic wave propagating along the X direction on the second surface 31 acts on the functional layer 40.

[0254] In order to distinguish the sound wave state when the refraction angle is a real number and the sound wave state when the refraction angle is a complex number, β 2 This shows the state of the sound wave when the second reinforcement angle is plural.

[0255] At this time, the sound wave vector β 2 The attenuation of the evanescent wave is rapidly reduced along the third direction 003 away from the first surface 11. The surface acoustic wave device 100 of the present application uses the attenuation characteristics of the evanescent wave to characterize the leakage of high-frequency body waves. Specifically, the evanescent wave intensity is reduced to the evanescent wave intensity at the second surface 31. There is a certain corresponding relationship between the distance from the second surface 31 and the leakage of high-frequency body waves.

[0256] Define the acoustic wave vector β 2 The body wave component in the third direction 003 is β 2z Since the refraction angle is a complex number, the acoustic wave of the surface acoustic wave device 100 of the present application is manifested as an acoustic wave along the X direction. At this time, the acoustic wave vector β 2 The modulus satisfies the equation: Among them, λ 2 is the wavelength corresponding to the body wave velocity of the material of the functional layer 40 along the X direction at the operating frequency f.

[0257] Acoustic wave vector β 2 The component β in the third direction 003 2z Satisfies the equation:

[0258] In the above equation, the second enhancement angle γ is selected as the operating frequency f=f c2 , the value of the second reinforcement angle.

[0259] The intensity of the sound wave in the functional layer 40 is ν, and the sound wave β 2 The body wave component in the second direction 002 is β 2x , z represents the distance between the body wave at any point in the functional layer 40 and the second surface 31 .

[0260] The body wave intensity in the functional layer 40 satisfies the equation:

[0261]

[0262] In this embodiment, the second characteristic thickness represents the thickness of the body wave intensity attenuated to the body wave intensity at the second surface 31. The distance from the second surface 31. That is,

[0263] Will Substituting the equation of the acoustic wave intensity in the functional layer 40, the z value in the above equation is obtained. The calculated z value is the second characteristic thickness. B2 is the body wave velocity in the functional layer 40, and when the second enhancement angle is a plural number, the acoustic wave velocity of the surface acoustic wave device of the present application is only related to the material of the functional layer 40.

[0264] In the embodiment of the present application, after the second characteristic thickness is calculated based on the above equation, the thickness of the functional layer 40 is determined by the ratio range of the thickness of the functional layer 40 to the second characteristic thickness. For the functional layer 40 having the thickness of the functional layer 40, the high-frequency heterogeneous mode in the body wave can leak into the single crystal silicon layer 50.

[0265] Therefore, in the process of preparing the surface acoustic wave device 100 of the present application, on the one hand, by obtaining the centerline spacing P between two adjacent electrode fingers 22, the body wave sound velocity V in the functional layer 40 along the X direction, b2 and the operating frequency f, the second reinforcement angle γ is calculated.

[0266] On the other hand, the F(γ) value corresponding to the second enhancement angle γ can also be calculated by obtaining the frequency of the body wave in the functional layer 40 and the spacing P between the midlines of two adjacent electrode fingers 22, and the F(γ) value corresponding to the functional layer 40 can be calculated based on the Fig.11 The illustrated example results in a second reinforcement angle γ.

[0267] On the basis of obtaining the second reinforcement angle γ, the propagation velocity V of the body wave of the material of the functional layer 40 along the X direction is obtained. b2 , and the surface acoustic wave frequency f (surface acoustic wave resonant frequency or surface acoustic wave anti-resonant frequency) selected in the embodiment of the present application, the second characteristic thickness T is calculated d Thus, the thickness D of the functional layer 40 is obtained. d limited scope.

[0268] In one embodiment, when the thickness of the piezoelectric layer 10 and the first characteristic thickness satisfy the condition: When the thickness of the piezoelectric layer 10 satisfies the condition: 0.4P≤D y ≤0.8P.

[0269] In one embodiment, when the sum of the first characteristic thickness, the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the condition: When the thickness of the temperature compensation layer 30 satisfies the condition: 0.4P≤D w ≤0.8P.

[0270] In one embodiment, when the sum of the first characteristic thickness, the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the condition: When , the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 can satisfy the condition: H<1.4P.

[0271] In one embodiment, when the thickness of the functional layer 40 and the second characteristic thickness satisfy the condition: When the thickness of the functional layer 40 satisfies the condition: 0.2P≤D d ≤0.6P.

[0272] In one embodiment, the material of the functional layer 40 has anisotropy or isotropy.

[0273] In one embodiment, the functional layer 40 is an acoustic layer or a polysilicon layer.

[0274] In one embodiment, the material of the piezoelectric layer 10 has anisotropy.

[0275] It should be understood that the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0276] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0277] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in the field, improvements or changes can be made according to the above description, and all these improvements and changes should fall within the scope of protection of the claims attached to this application. Ordinary technicians in the field can understand that all or part of the processes of the above embodiments are implemented, and equivalent changes made according to the claims of the present invention still fall within the scope of the present invention.

Claims

1. A surface acoustic wave device, characterized in that: A piezoelectric layer and an interdigital electrode disposed on a first surface of the piezoelectric layer, wherein the interdigital electrode comprises a plurality of electrode fingers; The acoustic waves of the surface acoustic wave device when working include surface acoustic waves and body waves, and the propagation direction of the surface acoustic wave is the X direction; The first characteristic thickness of the surface acoustic wave device is T y , the thickness of the piezoelectric layer is D y , the thickness of the piezoelectric layer and the first characteristic thickness satisfy the condition: The piezoelectric layer includes a piezoelectric crystal, and the first characteristic thickness is determined according to the centerline spacing between two adjacent electrode fingers, the body wave velocity of the piezoelectric crystal along the X direction, and the operating frequency.

2. The surface acoustic wave device according to claim 1, characterized in that: The first characteristic thickness: The midline spacing between two adjacent electrode fingers is P, and the body wave velocity of the piezoelectric crystal along the X direction is V b1 , the operating frequency is f, and the body wave wavelength of the piezoelectric crystal along the X direction at the operating frequency is λ1.

3. The surface acoustic wave device according to claim 2, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer and the first characteristic thickness satisfy the condition:

4. The surface acoustic wave device according to claim 2, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer is less than the first characteristic thickness.

5. The surface acoustic wave device according to claim 2, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the piezoelectric layer and the first characteristic thickness satisfy the condition:

6. The surface acoustic wave device according to claim 2, characterized in that: The surface acoustic wave device further comprises a temperature compensation layer. Along the thickness direction of the piezoelectric layer, the temperature compensation layer is arranged on a side of the piezoelectric layer away from the interdigital electrodes.

7. The surface acoustic wave device according to claim 6, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave antiresonant frequency, the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer is H, and the sum of the first characteristic thickness and the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfies the condition:

8. The surface acoustic wave device according to claim 7, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the sum of the first characteristic thickness, the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfies the condition:

9. The surface acoustic wave device according to claim 6, characterized in that: When the angle between the propagation direction of the body wave excited by the interdigital electrodes into the piezoelectric layer and the first surface is equal to the first reinforcement angle θ, the body wave in the piezoelectric layer and the temperature compensation layer is in an enhanced state; the propagation speed of the body wave excited by the interdigital electrodes into the piezoelectric layer and the temperature compensation layer is V0, and the first reinforcement angle and the propagation speed of the body wave in the piezoelectric layer and the temperature compensation layer satisfy the equation: The surface acoustic wave frequency of the surface acoustic wave device is f, and the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfies the condition: The surface acoustic wave frequency f is a surface acoustic wave resonant frequency or a surface acoustic wave anti-resonant frequency.

10. The surface acoustic wave device according to claim 9, characterized in that: The thickness of the temperature compensation layer is D w , where the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfy the condition:

11. The surface acoustic wave device according to any one of claims 1 to 10, characterized in that: When the angle between the propagation direction of the body wave excited by the interdigital electrodes into the piezoelectric layer and the first surface is equal to the first reinforcement angle θ, the body wave in the piezoelectric layer is in a reinforcement state; the wavelength λ of the body wave excited by the interdigital electrodes into the piezoelectric layer B1 is the wavelength of the bulk wave in the enhanced state in the piezoelectric layer.

12. The surface acoustic wave device according to claim 11, characterized in that: The midline distance between two adjacent electrode fingers is P, the first reinforcement angle is θ, and the first reinforcement angle satisfies the equation: Among them, V B1 is the body wave velocity in the piezoelectric layer, f is the operating frequency, λ B1 is the wavelength of the bulk wave excited by the interdigitated electrodes in the piezoelectric layer, and the range of the first reinforcement angle θ satisfies: 0°<θ<180°.

13. The surface acoustic wave device according to any one of claims 1 to 10, characterized in that: The surface acoustic wave device comprises a functional layer, and along the thickness direction of the piezoelectric layer, the functional layer is arranged on a side of the piezoelectric layer away from the interdigital electrodes; The second characteristic thickness of the surface acoustic wave device is T d , the thickness of the functional layer is D d , the thickness of the functional layer and the second characteristic thickness satisfy the condition: The second characteristic thickness is determined according to the body wave velocity of the material of the functional layer along the X direction and the operating frequency.

14. The surface acoustic wave device according to claim 13, characterized in that: The second characteristic thickness satisfies the equation: The midline spacing between two adjacent electrode fingers is P, and the body wave velocity of the material of the functional layer along the X direction is V. b2 , the operating frequency is f, and λ2 is the wavelength corresponding to the body wave sound velocity of the material of the functional layer along the X direction at the operating frequency.

15. The surface acoustic wave device according to claim 14, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness meet the condition:

16. The surface acoustic wave device according to claim 14, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer is less than the second characteristic thickness.

17. The surface acoustic wave device according to claim 14, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness meet the condition:

18. The surface acoustic wave device according to claim 13, characterized in that: The surface acoustic wave device comprises a single crystal silicon layer, and along the thickness direction of the piezoelectric layer, the single crystal silicon layer is arranged on the surface of the functional layer away from the piezoelectric layer. <110> A spatial angle between the crystal orientation family and a propagation direction of surface acoustic waves excited on the first surface by the plurality of interdigital electrodes is less than or equal to 10°.

19. The surface acoustic wave device according to claim 18, characterized in that: The single crystal silicon layer <110> The crystal orientation family is parallel to a propagation direction of surface acoustic waves excited on the first surface by the plurality of interdigital electrodes.

20. The surface acoustic wave device according to claim 13, characterized in that: The material of the functional layer has anisotropy or isotropy.

21. The surface acoustic wave device according to claim 13, characterized in that: The functional layer is an acoustic layer or a polysilicon layer.

22. The surface acoustic wave device according to any one of claims 1 to 10, characterized in that: The material of the piezoelectric layer has anisotropy.

23. A surface acoustic wave device, characterized in that: It includes a functional layer and a piezoelectric layer stacked along its thickness direction, and an interdigital electrode arranged on a first surface of the piezoelectric layer away from the functional layer, wherein the interdigital electrode includes a plurality of electrode fingers; The acoustic waves of the surface acoustic wave device when working include surface acoustic waves and body waves, and the propagation direction of the surface wave is the X direction; The second characteristic thickness of the surface acoustic wave device is T d , the thickness of the functional layer is D d , the thickness of the functional layer and the second characteristic thickness satisfy the condition: The second characteristic thickness is determined according to the body wave velocity of the material of the functional layer along the X direction and the operating frequency.

24. The surface acoustic wave device according to claim 23, characterized in that: The second characteristic thickness satisfies the equation: The distance between the center lines of two adjacent electrode fingers is P, and the body wave acoustic velocity of the material of the functional layer along the X direction is V. b2 , the operating frequency is f, and λ2 is the wavelength corresponding to the body wave sound velocity of the material of the functional layer along the X direction at the operating frequency.

25. The surface acoustic wave device according to claim 23, characterized in that: When the angle between the propagation direction of the body wave excited by the interdigital electrodes and the first surface is equal to the second reinforcement angle γ, the body wave in the functional layer is in a reinforcement state; the wavelength λ of the body wave excited by the interdigital electrodes is B2 is the wavelength of the body wave in the enhanced state in the functional layer.

26. The surface acoustic wave device according to claim 25, characterized in that: The midline distance between two adjacent electrode fingers is P, the second reinforcement angle is γ, and the second reinforcement angle γ satisfies the equation: Among them, V B2 is the body wave velocity in the functional layer, f is the operating frequency, λ B2 is the body wave wavelength of the acoustic wave excited by the interdigital electrodes and propagated into the functional layer, and the second reinforcement angle γ satisfies: 0°<γ<180°.

27. The surface acoustic wave device according to claim 23, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness meet the condition:

28. The surface acoustic wave device according to claim 23, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer is less than the second characteristic thickness.

29. The surface acoustic wave device according to claim 23, characterized in that: When the frequency of the surface acoustic wave excited by the interdigital electrodes is greater than or equal to the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency, the thickness of the functional layer and the second characteristic thickness meet the condition:

30. The surface acoustic wave device according to any one of claims 23 to 29, characterized in that: The first characteristic thickness of the surface acoustic wave device is T y , the thickness of the piezoelectric layer is D y , the thickness of the piezoelectric layer and the first characteristic thickness satisfy the condition: The first characteristic thickness is determined according to the distance between the center lines of two adjacent electrode fingers, the body wave velocity of the piezoelectric layer along the X direction, and the operating frequency.

31. The surface acoustic wave device according to claim 30, characterized in that: The first characteristic thickness satisfies the equation:

32. The surface acoustic wave device according to claim 31, characterized in that: The thickness of the piezoelectric layer satisfies the condition: 0.4P≤D y ≤0.8P.

33. The surface acoustic wave device according to claim 31, characterized in that The thickness of the functional layer meets the condition: 0.2P≤D d ≤0.6P.

34. The surface acoustic wave device according to any one of claims 23 to 29, characterized in that: The material of the piezoelectric layer has anisotropy.

35. A radio frequency front-end module, characterized in that: Comprising a surface acoustic wave device as described in any one of claims 1-34.

36. An electronic device, characterized in that: Comprising a radio frequency front-end module as described in claim 35.

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