Surface acoustic wave devices, radio frequency front-end modules and electronic devices

Abstract

This application relates to a surface acoustic wave (SAW) device, a radio frequency (RF) front-end module, and an electronic device. The SAW device includes a piezoelectric layer and interdigitated electrodes disposed on a first surface of the piezoelectric layer, the interdigitated electrodes comprising multiple electrode fingers; the acoustic waves emitted during operation of the SAW device include SAW waves and volume waves, with the SAW waves propagating in the X-direction; the first characteristic thickness of the SAW device is T. y The thickness of the piezoelectric layer is D y The thickness of the piezoelectric layer satisfies the condition that the piezoelectric layer includes a piezoelectric crystal. The first characteristic thickness is determined based on the midline distance between two adjacent electrode fingers, the volume wave velocity of the piezoelectric crystal along the X-direction, and the operating frequency. Limiting the thickness of the piezoelectric layer by the first characteristic thickness avoids affecting the acoustic function of the remaining structures due to excessive piezoelectric layer thickness, thereby improving the performance of the surface acoustic wave device.

Description

Technical Field

[0001] This application relates to the field of radio frequency, and more particularly to a surface acoustic wave (SAW) device, a radio frequency front-end module including the SAW device, and an electronic device including the radio frequency front-end module. Background Technology

[0002] In the field of radio frequency, surface acoustic wave (SAW) devices typically consist of a piezoelectric substrate and interdigitated electrodes. The interdigitated electrodes on the piezoelectric substrate work in conjunction with the substrate to achieve the interconversion of electrical signals and acoustic signals.

[0003] In existing technologies, different functional layers can be placed beneath the piezoelectric substrate to control the performance of interdigital electrodes, achieving characteristics such as high quality factor (Q value) and low temperature coefficient of frequency (TCF). However, the theoretical basis for setting functional layers in existing technologies is not yet perfect, resulting in low development efficiency. Inappropriate functional layer placement can make it difficult for the interdigital electrodes to achieve the intended effects. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a solution to improve the working performance of surface acoustic wave devices, specifically including the following technical solution:

[0005] In a first aspect, embodiments of this application provide a surface acoustic wave device, including a piezoelectric layer and interdigitated electrodes disposed on a first surface of the piezoelectric layer, wherein the interdigitated electrodes include a plurality of electrode fingers;

[0006] The acoustic waves produced when a surface acoustic wave device is in operation include surface acoustic waves and volume waves, with the surface waves propagating in 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 thickness of the first feature satisfy the following condition:

[0008] The piezoelectric layer includes a piezoelectric crystal, and the size of the first characteristic thickness is determined based on the midline distance between two adjacent electrode fingers, the volume wave velocity of the piezoelectric crystal along the X direction, and the operating frequency.

[0009] Because the amplitude of the surface acoustic wave excited during operation of the surface acoustic wave device mainly acts on the first surface of the piezoelectric layer and a portion of the piezoelectric layer near the first surface, the surface acoustic wave device of this application also utilizes a first characteristic thickness T. yThe ratio range of the thickness of the piezoelectric layer to the thickness of the piezoelectric layer limits the thickness of the piezoelectric layer, ensuring that the energy of the surface acoustic wave can be effectively transferred to the remaining structure of the interdigitated electrodes. This ensures the acoustic performance of the surface acoustic wave device and improves the operating performance of the surface acoustic wave device of this application.

[0010] In one embodiment, the first feature thickness is: Wherein, the midline distance between two adjacent electrodes is P, and the volume wave velocity of the piezoelectric crystal along the X direction is V. b1 The operating frequency is f, and the bulk wavelength of the piezoelectric crystal along the X direction at the operating frequency is λ1.

[0011] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following condition:

[0012] In this embodiment, by setting the ratio of the piezoelectric layer thickness to the first feature thickness between 0.2 and 1.5, the piezoelectric layer thickness is avoided from being too thin due to an excessively small ratio, which would affect the stability of the surface acoustic wave device. Conversely, the piezoelectric layer thickness is avoided from being too thick due to an excessively large ratio, which would affect the acoustic performance of the remaining structures of the surface acoustic wave device. This improves the stability and performance of the surface acoustic wave device of this application.

[0013] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigital electrode 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 interdigitated electrode 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 following condition:

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

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

[0017] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 and the thickness of the piezoelectric layer is H, and the first characteristic thickness and the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfy the following condition:

[0018] In this embodiment, by limiting the ratio of the thickness of the first feature 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, ensuring 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 for the piezoelectric layer and realizing the acoustic effect of the temperature compensation layer on the surface acoustic wave device of this application.

[0019] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following 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 thickness of the first feature layer.

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

[0022] In one embodiment, when the angle between the propagation direction of the bulk wave excited by the interdigitated electrode into the piezoelectric layer and the first surface is equal to the first reinforcement angle θ, the bulk wave in the piezoelectric layer and the temperature compensation layer is in a reinforced state; the propagation speed of the bulk wave excited by the interdigitated electrode into the piezoelectric layer and the temperature compensation layer is V0, and the first reinforcement angle and the propagation speed of the bulk wave in the piezoelectric layer and the temperature compensation layer satisfy the following equation: The surface acoustic wave (SAW) frequency of the SAW device is f, and the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfies the following condition: Wherein, 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, by further limiting the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer, the influence of the waveguide mode generated by the body wave on the frequency of the surface acoustic wave is avoided after the reflection of the two surfaces of the piezoelectric layer and the temperature compensation layer that are opposite to each other.

[0024] In one embodiment, the thickness of the temperature compensation layer is D. w The thicknesses of the temperature compensation layer and the piezoelectric layer satisfy the following conditions:

[0025] In this embodiment, by limiting the range of the ratio between the thickness of the temperature compensation layer and the thickness of the piezoelectric layer, a matching setting for the thicknesses of the temperature compensation layer and the piezoelectric layer is achieved. This improves the operating performance of the surface acoustic wave device of this application.

[0026] In one embodiment, when the angle between the propagation direction of the bulk wave excited by the interdigitated electrode into the piezoelectric layer and the first surface is equal to a first reinforcement angle θ, the bulk wave in the piezoelectric layer is in a reinforced state; the wavelength λ of the bulk wave excited by the interdigitated electrode into the piezoelectric layer is... B1 The bulk wavelength is the wavelength of the piezoelectric layer in the enhanced state.

[0027] In one embodiment, the midline distance between two adjacent electrode fingers is P, and the first reinforcement angle is θ, which satisfies the following equation: Among them, V B1 λ is the volume wave velocity within the piezoelectric layer, f is the operating frequency, and λ is the velocity of sound. B1 Let θ be the bulk wave wavelength excited by the interdigitated electrodes within the piezoelectric layer, and let θ be the range of the first reinforcement angle θ, which satisfies the condition: 0° < θ < 180°.

[0028] In one embodiment, the surface acoustic wave device includes a functional layer disposed along the thickness direction of the piezoelectric layer on the side of the piezoelectric layer opposite to the interdigitated 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 thickness of the second feature satisfy the following condition: The thickness of the second feature is determined based on the volume wave velocity and operating frequency of the material of the functional layer along the X direction.

[0029] In this embodiment, a functional layer is provided on the side of the piezoelectric layer away from the interdigitated electrodes to reduce the loss of the surface acoustic wave (SAW) device of this application. The SAW device of this application also limits the thickness of the functional layer by the ratio range of the second feature thickness to the thickness of the functional layer, which is beneficial for reducing the leakage of high-frequency miscellaneous modes in the bulk wave. This improves the operating performance of the SAW device of this application.

[0030] In one embodiment, the thickness of the second feature satisfies the equation: Wherein, the midline distance between two adjacent electrodes is P, and the volume wave velocity of the functional layer material along the X direction is V. b2 The operating frequency is f, and λ2 is the wavelength corresponding to the volume wave velocity of the functional layer material along the X direction at the operating frequency.

[0031] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following condition:

[0032] In this embodiment, by setting the ratio of the functional layer thickness to the second feature thickness between 0.2 and 1.5, the excessively thin functional layer due to a ratio that is too small is avoided, which would affect the performance of the surface acoustic wave device. Conversely, an excessively large ratio would also prevent the functional layer from becoming too thick, which would affect the leakage of high-frequency miscellaneous modes in the bulk wave. This ensures the performance of the surface acoustic wave device of this application.

[0033] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 thickness of the second feature.

[0034] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following condition:

[0035] In one embodiment, the surface acoustic wave device includes a monocrystalline silicon layer disposed on the surface of the functional layer away from the piezoelectric layer along the thickness direction of the piezoelectric layer. <110> The spatial angle between the crystal group and the propagation direction of the surface acoustic wave excited by the multiple interdigitated electrodes on the first surface is less than or equal to 10°.

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

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

[0038] In one embodiment, the material of the functional layer is anisotropic or isotropic.

[0039] In one embodiment, the functional layer is a sound velocity layer or a polysilicon layer.

[0040] In one embodiment, the material of the piezoelectric layer is anisotropic.

[0041] Secondly, embodiments of this application provide a surface acoustic wave device, including a functional layer and a piezoelectric layer stacked along its own thickness direction, and an interdigitated electrode disposed on a first surface of the piezoelectric layer away from the functional layer, the interdigitated electrode including a plurality of electrode fingers;

[0042] The acoustic waves produced when a surface acoustic wave device is in operation include surface acoustic waves and volume waves, with the surface waves propagating in 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 thickness of the second feature satisfy the following condition:

[0044] The thickness of the second feature is determined based on the volume wave velocity and operating frequency of the material of the functional layer along the X direction.

[0045] This application's surface acoustic wave (SAW) device reduces losses by setting a functional layer on the side of the piezoelectric layer away from the interdigitated electrodes. Furthermore, the thickness of the functional layer is limited by the ratio range of the second feature thickness to the thickness of the functional layer, preventing excessive thickness of the functional layer from affecting the leakage of high-frequency miscellaneous modes in the bulk wave. This improves the operating performance of the SAW device.

[0046] In one embodiment, the thickness of the second feature satisfies the equation: The midline distance between two adjacent electrodes is P, and the bulk acoustic velocity of the functional layer material along the X direction is V. b2 The operating frequency is f, and λ2 is the wavelength corresponding to the volume wave velocity of the functional layer material along the X direction at the operating frequency.

[0047] In one embodiment, when the angle between the propagation direction of the acoustic wave excited by the interdigitated electrode and the first surface is equal to the second reinforcement angle γ, the volume wave in the functional layer is in a reinforced state; the wavelength λ of the volume wave excited by the interdigitated electrode propagating into the functional layer is... B2 The bulk wavelength is the wavelength of the functional layer in the enhanced state.

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

[0049] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following condition:

[0050] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 thickness of the second feature.

[0051] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following 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 thickness of the first feature satisfy the following condition:

[0053] The thickness of the first feature is determined based on the midline distance between two adjacent electrode fingers, the volume wave velocity of the piezoelectric layer along the X direction, and the operating frequency.

[0054] In one embodiment, the thickness of the first feature 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 is anisotropic.

[0058] Thirdly, embodiments of this application provide a radio frequency front-end module, including a surface acoustic wave device.

[0059] Fourthly, embodiments of this application provide an electronic device, including a radio frequency front-end module.

[0060] Understandably, the RF front-end module provided in the third aspect and the electronic device provided in the fourth aspect of this application, due to the use of the surface acoustic wave device provided in the first and second aspects of this application, also possess better operating performance. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the structure of an electronic device provided in one embodiment of this application;

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

[0063] Figure 3 This is a schematic diagram of the filter structure provided in one embodiment of this application;

[0064] Figure 4 This is a schematic diagram of another structure of the filter provided in one embodiment of this application;

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

[0066] Figure 6 This is a schematic cross-sectional view of the surface acoustic wave device provided in one embodiment of this application.

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

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

[0069] Figure 9 This is a partial cross-sectional structural schematic diagram of a surface acoustic wave device provided in one embodiment of this application;

[0070] Figure 10 This is a partial cross-sectional structural schematic diagram of a surface acoustic wave device provided in one embodiment of this application;

[0071] Figure 11 This is a partial curve showing the relationship between the first reinforcement angle of the piezoelectric layer of the surface acoustic wave device provided in one embodiment of this application and the volume wave velocity;

[0072] Figure 12 This is another structural schematic diagram of the surface acoustic wave device provided in one embodiment of this application;

[0073] Figure 13 This is a schematic cross-sectional view of another surface acoustic wave device provided in one embodiment of this application.

[0074] Figure 14 This is another enlarged cross-sectional view of the surface acoustic wave device provided in one embodiment of this application;

[0075] Figure 15 This is a schematic diagram of the conductivity curve of a surface acoustic wave device provided in one embodiment of this application;

[0076] Figure 16 This is another partial cross-sectional structural schematic diagram of the surface acoustic wave device provided in one embodiment of this application. Detailed Implementation

[0077] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0078] The following descriptions of the embodiments are based on the accompanying illustrations and are used to illustrate specific embodiments in which this application can be implemented. The component designations used herein, such as "first," "second," etc., are merely for distinguishing the described objects and do not have any sequential or technical meaning. Unless otherwise specified, the terms "connection" and "linkage" used in this application include both direct and indirect connections (linkages). Directional terms used in this application, such as "up," "down," "front," "rear," "left," "right," "inner," "outer," "side," etc., are merely for reference to the accompanying drawings. Therefore, the use of directional terms is for better and clearer explanation and understanding of this application, and does not indicate or imply that the referred device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this application.

[0079] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application based on the 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, not to describe a specific order. Furthermore, the terms "comprising," "may include," "include," or "may include" used in this application indicate the presence of the corresponding disclosed function, operation, element, etc., and do not limit one or more other functions, operations, elements, etc. Moreover, the terms "comprising" or "include" indicate the presence of the corresponding features, numbers, steps, operations, elements, components, or combinations thereof disclosed in the specification, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, and are intended to cover non-exclusive inclusion.

[0080] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0081] Please see Figure 1 The diagram shown is a structural schematic of an electronic device 400 provided in one embodiment of this application.

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

[0083] In one embodiment, the substrate 401 is a printed circuit board to control the operation of the radio frequency front-end module 300. The electronic device 400 of this application receives and / or transmits signals through the radio frequency front-end module 300. Exemplarily, the electronic device 400 includes at least one of a computer, mobile phone, tablet computer, smartwatch, and navigator, etc., and this application does not impose any particular limitation on it.

[0084] Please see Figure 2 The diagram shown is a structural schematic of the radio frequency front-end module 300 provided in one embodiment of this 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. The signal terminal 301 is used to receive external signals or transmit RF signals. The switch 302 is communicatively connected between the signal terminal 301 and the filter 200 to control signal transmission between them. When the amplifier 303 is a low-noise amplifier, the filter 200 receives the external signal received by the signal terminal 301 when the switch 302 is closed and outputs 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 subsequent structures. When the amplifier 303 is a power amplifier, the filter 200 receives the amplified RF signal from the amplifier 303 when the switch 302 is closed, filters the received RF signal, and then transmits 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 one embodiment, the number of filters 200 can be multiple, and all multiple filters 200 are communicatively connected to the signal terminal 301.

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

[0088] Please see Figure 3 The diagram shown is a structural schematic of the filter 200 provided in one embodiment of this application.

[0089] like Figure 3 As shown, the filter 200 of this 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 this embodiment, the surface acoustic wave device 100 includes interdigitated electrodes 20. The interdigitated electrodes 20 are disposed on the piezoelectric substrate 204.

[0090] like Figure 3 As shown, there are three interdigitated electrodes 20. One end of one interdigitated electrode 20 is connected to the signal input terminal 201, and the other end is connected to the ground port 203. The remaining two interdigitated electrodes 20 are arranged on both sides of the interdigitated electrode 20 connected to the signal input terminal 201. One end of the two interdigitated electrodes 20 is connected to the signal output terminal 202, and the other end of the two interdigitated 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 interdigitated electrodes 20 inside the surface acoustic wave device 100 receive the electrical signal. The interdigitated electrodes 20 can internally realize the conversion between electroacoustic and acoustic-electric signals, and ultimately 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, meaning that the interdigital electrodes 20 must be fabricated on the piezoelectric substrate 204 to generate 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] Please see Figure 4 The diagram shown is another structural schematic of the filter 200 provided in one embodiment of this application.

[0095] like Figure 4 As shown, one group of resonators is connected in series between the signal input terminal 201 and the signal output terminal 202, while one end of another group of 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 series and parallel connection of multiple resonators enables the filter 200 of this application to filter signals of a preset frequency.

[0096] Please see Figure 5 The diagram shown is a structural schematic of the surface acoustic wave device 100 provided in one embodiment of this application.

[0097] like Figure 5As shown, the surface acoustic wave device 100 of this application includes a piezoelectric layer 10 and interdigitated electrodes 20. Along the thickness direction of the piezoelectric layer 10, the interdigitated electrodes 20 are disposed on the first surface 11 of the piezoelectric layer 10. The interdigitated electrodes 20 include two parallel and spaced-apart busbars 21 and a plurality of parallel and spaced-apart electrode fingers 22.

[0098] In this configuration, one of the two busbars 21 is used to receive external signals, while the other busbar 21 is used to output signals. Multiple electrode fingers 22 are located between the two busbars 21. Some of the electrode fingers 22 are connected to one busbar 21, while other electrode fingers 22 are connected to the other busbar 21.

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

[0100] Specifically, the first electrode finger 22a and the second electrode finger 22b both extend along the first direction 001 towards opposite sides of the piezoelectric layer 10. Along the second direction 002, the first electrode finger 22a and the second electrode finger 22b are arranged alternately. Specifically, as... 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] Both the first busbar 21a and the second busbar 21b extend along the second direction 002 to opposite sides of the piezoelectric layer 10, wherein the first direction 001 and the second direction 002 are perpendicular to each other. In practical applications, the surface acoustic wave device 100 of this application may have errors, and the angle between the first direction 001 and the second direction 002 may not be equal to 90°.

[0102] In this embodiment, due to the inverse piezoelectric effect of the piezoelectric layer 10, when an electrical signal is transmitted to each of the first electrode fingers 22a via the first busbar 21a, the electrical signal on each of the first electrode fingers 22a releases electrostatic force on the piezoelectric layer 10, causing deformation of the surface of the piezoelectric layer 10. Since the electrical signal is an alternating signal, it can be understood that the electrostatic force acting on the surface of the piezoelectric layer 10 by each of the first electrode fingers 22a exhibits periodic variation. Correspondingly, the amount of deformation of the surface of the piezoelectric layer 10 also varies with the periodic variation of the electrical signal, thereby generating outwardly released sound waves.

[0103] The acoustic waves emitted by the surface acoustic wave device 100 during operation include surface acoustic waves and volume waves. Specifically, when the component of the acoustic wave vector along the thickness direction of the piezoelectric layer 10 is imaginary, this type of acoustic wave can only propagate along the planar direction of the first surface 11, and is therefore a surface acoustic wave. The propagation direction of the surface acoustic wave is defined as the X-direction. When the acoustic wave vector has a real component along the thickness direction of the piezoelectric layer 10, it is a volume wave.

[0104] Surface acoustic waves (SAWs) are used to realize the frequency selection and signal processing functions of the SAW device 100 of this application. During SAW propagation, the main propagation direction is the second direction 002, that is, the X direction is the second direction 002. However, in practice, due to edge effects and acoustic diffraction, the propagation direction of the SAW formed on the first surface 11 of the piezoelectric layer 10 may also be in other directions, corresponding to an angle between the X direction and the second direction 002. In one embodiment, SAWs propagating in other directions are absorbed by a sound-absorbing material (not shown in the figure).

[0105] In one embodiment, along the second direction 002, a reflective grating (not shown in the figure) is provided on both sides of the interdigital electrode 20. The reflective grating is used to confine the surface acoustic wave generated when the surface acoustic wave device 100 of this application is working within the interdigital electrode 20.

[0106] It is understood that this application can be applied to dual-mode surface acoustic wave (DMS) devices and filter devices formed by their interconnection through a certain topology, including interdigitated electrodes, and this application does not limit them.

[0107] Please see Figure 6 The diagram shown is a cross-sectional view of the surface acoustic wave device 100 provided in one embodiment of this application.

[0108] like Figure 6 As shown, the surface acoustic wave device 100 of this application has other structures on the side of the piezoelectric layer 10 away from the interdigitated electrode 20. Exemplarily, the surface acoustic wave device 100 of this application has a temperature compensation layer 30 on the side of the piezoelectric layer 10 away from the interdigitated electrode 20. For ease of description, in the embodiments of this application 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 change with temperature, thus affecting the propagation characteristics of surface acoustic waves on the first surface 11. The temperature compensation layer 30 is made of a material with a smaller or opposite temperature coefficient to that of 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 impact of temperature changes on the propagation of surface acoustic waves.

[0110] For surface acoustic waves (SAWs), the amplitude of the SAW can cause deformation of a portion of the structure within the piezoelectric layer 10. When the energy of the SAW can be effectively transferred to the temperature compensation layer 30 of the SAW device 100, the amplitude of the SAW 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 within which the amplitude of the SAW causes deformation of a portion of the structure within the piezoelectric layer 10 is defined as the acoustic field range of the SAW or the disturbance range of the SAW.

[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 changes on the first surface 11 of the piezoelectric layer 10. This improves the working performance of the surface acoustic wave device 100 of this application.

[0112] The amplitude of surface acoustic waves (SAWs) has a limited range of influence within the piezoelectric layer 10. In practical applications, the sound field of SAWs mainly acts on the first surface 11 of the piezoelectric layer 10, and a portion of the piezoelectric layer 10 near the first surface 11. Therefore, the SAW device 100 of this 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.

[0113] In the embodiments of this application, the surface acoustic wave device 100 of this application determines the size of the first characteristic thickness of the surface acoustic wave device 100 of this application, and defines 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 thickness of the first feature satisfy the following condition: That is, the ratio between the thickness of the piezoelectric layer 10 and the thickness of the first feature 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 midline distance between two adjacent electrode fingers 22, the volume wave velocity of the piezoelectric crystal along the X direction, and the operating frequency. In this embodiment, the volume 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 volume wave velocity of the piezoelectric crystal along the X direction is also determined.

[0116] It is worth noting that, in the embodiments of this application and subsequent embodiments, the two electrode fingers 22 of the interdigitated electrode 20 within one period length can refer to adjacent first electrode fingers 22a and second electrode fingers 22b, or to two adjacent first electrode fingers 22a or two adjacent second electrode fingers 22b. That is, the two electrode fingers 22 of the interdigitated electrode 20 within one period length can 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 embodiments of this application and subsequent embodiments, the two electrode fingers 22 of the interdigitated electrode 20 within one period length are used to represent two adjacent electrode fingers 22 with the same polarity.

[0117] For details, please refer to the following: Figure 7 The diagram shown is a cross-sectional enlarged schematic of the surface acoustic wave device 100 provided in one embodiment of this application.

[0118] like Figure 6 and Figure 7 As shown, the midline distance between two adjacent finger 22 of the interdigitated electrode 20 is P, and the volume wave velocity of the piezoelectric crystal along the X direction is V. b1 The operating frequency is f, and the bulk wavelength of the piezoelectric crystal along the X direction at the operating frequency is λ1. The first characteristic thickness satisfies the following equation:

[0119] Since, after the surface acoustic wave device 100 of this application is fabricated, the center-to-line distance P between two adjacent electrode fingers 22 of the interdigitated electrode 20, and the volume wave velocity V of the piezoelectric crystal along the X direction are... b1 And the operating frequency f are both measurable or determinable values. Therefore, the surface acoustic wave device 100 of this application can be based on the centerline spacing P and the volume wave velocity V. b1 The first feature thickness is obtained by using the operating frequency f.

[0120] Therefore, given a determined first characteristic thickness, 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 (SAW) device 100 of this application limits the thickness of the piezoelectric layer 10 by using a range of ratios between the first characteristic thickness and the thickness of the piezoelectric layer 10, thus avoiding a situation where the energy of the SAW cannot be effectively transferred to the temperature compensation layer 30 of the SAW device 100 due to excessive thickness of the piezoelectric layer 10. This ensures the acoustic function of the temperature compensation layer 30 of the SAW device 100 and guarantees the operating performance of the SAW device 100 of this application.

[0121] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following condition:

[0122] When the ratio of the thickness of the piezoelectric layer 10 to the thickness of the first feature is less than 0.2, the thickness of the piezoelectric layer 10 is too thin. On the one hand, an excessively thin piezoelectric layer 10 will reduce 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 this application. On the other hand, an excessively 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 this application are relatively poor.

[0123] When the ratio of the thickness of the piezoelectric layer 10 to the thickness of the piezoelectric feature is greater than 1.5, the thickness of the piezoelectric layer 10 is too thick, which leads to 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. This may cause the energy of the surface acoustic wave to be difficult to be effectively transferred to the temperature compensation layer 30 of the surface acoustic wave device 100, thereby affecting the acoustic function of the temperature compensation layer 30.

[0124] Here, the third direction 003 refers to the thickness direction of the piezoelectric layer 10. The third direction 003 is perpendicular to the first direction 001 and the second direction 002 respectively. In actual application, there may be errors. At least one of the angles between the third direction 003 and the first direction 001 and 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 this application sets the ratio of the thickness of the piezoelectric layer 10 to the thickness of the first feature between 0.2 and 1.5. This avoids the piezoelectric layer 10 becoming too thin due to an excessively small ratio, which would affect the working performance and stability of the surface acoustic wave device 100. It also avoids the piezoelectric layer 10 becoming too thick due to an excessively large ratio, which would affect the acoustic function of the temperature compensation layer 30 of the surface acoustic wave device 100. This ensures the stability and working performance of the surface acoustic wave device 100 of this application.

[0126] Specifically, admittance can be used to describe the response process of components and signals. In the surface acoustic wave device 100 of this application, admittance is used to measure the influence of clutter propagating on the surface of the piezoelectric layer 10 on the acoustic wave quality. Figure 8 This is a comparison chart showing the admittance curves of the surface acoustic wave (SAW) device 100 of this application and the SAW device in the comparative example, obtained based on different SAW frequencies. The horizontal axis is in GHz, and the vertical axis is in dB.

[0127] For the comparative example, the surface acoustic wave (SAW) device includes a piezoelectric layer and interdigitated electrodes disposed on the surface of the piezoelectric layer. The center-to-center distance between two adjacent interdigitated electrodes is P = 1.0 μm, the duty cycle of the interdigitated electrodes is 0.4, the piezoelectric layer is made of 42°YX-LiTaO3, the interdigitated electrodes are made of aluminum, and the thickness of the interdigitated electrodes is 0.16 μm. Along the thickness direction of the piezoelectric layer, a temperature compensation layer is disposed on the side of the piezoelectric layer opposite to the interdigitated electrodes. Ideally, the thickness of the piezoelectric layer is considered infinite, and correspondingly, the temperature compensation layer can be considered to be infinitely far from the interdigitated electrodes. Figure 8 As shown, the admittance curves corresponding to the comparative examples are represented by solid lines.

[0128] For the embodiments, there are four sets of embodiments. Each set of embodiments' surface acoustic wave device 100 includes a functional layer 40, a temperature compensation layer 30, a piezoelectric layer 10, and interdigitated electrodes 20 disposed on the first surface 11 of the piezoelectric layer 10, which are stacked sequentially. The centerline spacing P between two adjacent interdigitated electrodes 22 is 1.0 μm, the duty cycle of the interdigitated electrodes 20 is 0.4, the piezoelectric layer 10 is made of 42°YX-LiTaO3, the electrode fingers 22 are made of aluminum, and the thickness of the electrode fingers 22 is 0.16 μm.

[0129] The four sets of embodiments are Examples 1-4. Along the third direction 003, the thickness of the piezoelectric layer 10 in Example 1 is 0.2 μm. The thickness of the piezoelectric layer 10 in Example 2 is 0.6 μm. The thickness of the piezoelectric layer 10 in Example 3 is 1.0 μm. The thickness of the piezoelectric layer 10 in Example 4 is 1.4 μm. Figure 8 As shown, the admittance curves corresponding to Examples 1-4 are represented by different dashed lines.

[0130] Based on the material parameters of 42°YX-LiTaO3, the sound velocity of the bulk wave propagating along the second direction 002 in the piezoelectric layer 10 of Examples 1-4 and the comparative example piezoelectric layer can be calculated to be approximately 4230 m / s. The surface acoustic wave resonant frequency is 1.982 GHz, and the surface acoustic wave anti-resonant frequency is 2.058 GHz.

[0131] Regarding proportions, according to It can be concluded that when the surface acoustic wave frequency is the surface acoustic wave resonant frequency, the first characteristic thickness T is... y =0.91μm. When the surface acoustic wave frequency is the surface acoustic wave anti-resonance frequency, the first characteristic thickness T is... y = 1.4 μm. For ease of description, the first characteristic thickness T is used. y Let's take 0.91μm as an example for introduction.

[0132] like Figure 8As shown, for Examples 1-4, the thicker the piezoelectric layer 10, the closer the admittance curve of the examples is to the admittance curve of the comparative examples. In the comparative examples, because the thickness of the piezoelectric layer can be considered infinite, the corresponding surface acoustic wave disturbance region does not overlap with the temperature compensation layer disposed on the piezoelectric layer. That is, the temperature compensation layer in the comparative examples does not play an acoustic role.

[0133] On the other hand, because of the 1.5T y = 1.365 μm. It can be seen that the thickness of the piezoelectric layer 10 corresponding to Examples 1-3 is less than 1.5 T. y The thickness of the piezoelectric layer 10 in Example 4 is greater than 1.5T. y It is evident that the admittance curves of Examples 1-3 are poorly consistent with the admittance curves of the comparative examples, and correspondingly, the acoustic effect of the temperature compensation layer 30 in Examples 1-3 is more pronounced.

[0134] In other words, compared to the comparative example, the surface acoustic wave device 100 of this application, by limiting the thickness of the piezoelectric layer 10, enables the energy of the surface acoustic wave to be effectively transferred to the temperature compensation layer 30, thereby ensuring the acoustic function of the temperature compensation layer 30. This improves the working performance of the surface acoustic wave device 100 of this application.

[0135] 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 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 interdigitated electrode 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 following condition:

[0137] In one embodiment, such as Figure 6 As shown, the surface acoustic wave device 100 of this application also includes a temperature compensation layer 30, which is disposed along the third direction 003 on the side of the piezoelectric layer 10 away from the interdigitated electrode 20. In the embodiments of this application, the temperature compensation layer 30 mainly improves the temperature stability of the surface acoustic wave device 100 of this application by its own response to temperature changes, thereby demonstrating its own acoustic function.

[0138] Specifically, during the use of the surface acoustic wave device 100 of this application, the acoustic properties of the piezoelectric layer 10 change with temperature variations. The temperature compensation layer 30 is made of a material with a temperature coefficient opposite to or smaller than that of the piezoelectric layer 10. In 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 interdigitated 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 first feature thickness and the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfy the following condition:

[0140] The value of the first characteristic thickness after the surface acoustic wave device 100 is fabricated can be calculated. It is understandable that the ratio of the first characteristic thickness to the sum of the thicknesses of the temperature compensation layer 30 and the piezoelectric layer 10 limits the sum of the thicknesses of the temperature compensation layer 30 and the piezoelectric layer 10, further ensuring that the energy of the surface acoustic wave can be effectively transferred to the temperature compensation layer 30. This ensures the temperature compensation function of the temperature compensation layer 30 on the piezoelectric layer 10, realizing the acoustic effect of the temperature compensation layer 30 on the surface acoustic wave device 100 of this application.

[0141] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following condition:

[0142] 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 less than the first characteristic thickness.

[0143] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following condition:

[0144] In one embodiment, when the angle between the propagation direction of the bulk wave excited by the interdigitated electrode 20 into the piezoelectric layer 10 and the first surface 11 is equal to the first reinforcement angle θ, the bulk wave in the piezoelectric layer 10 and the temperature compensation layer 30 is in a reinforced state. The propagation speed of the bulk wave excited by the two electrode fingers 22 of the interdigitated electrode 20 into the piezoelectric layer 10 and the temperature compensation layer 30 within one periodic segment length is V0, and the first angle satisfies the equation with respect to the propagation speed of the bulk wave in the piezoelectric layer 10 and the temperature compensation layer 30: The surface acoustic wave device 100 has a surface acoustic wave frequency of f, and the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 satisfies the following condition: Wherein, 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 thicknesses of the temperature compensation layer 30 and the piezoelectric layer 10, the refraction effect of the bulk wave at the interface between the piezoelectric layer 10 and the temperature compensation layer 30 is neglected for the sake of simplification. Correspondingly, the propagation speed of the bulk wave excited by the interdigitated electrode 20 into the piezoelectric layer 10 and the temperature compensation layer 30 is the propagation speed under the ideal condition of neglecting the difference in sound speed between the piezoelectric layer 10 and the temperature compensation layer 30.

[0146] In this embodiment, along the third direction 003, the temperature compensation layer 30 is disposed on the surface of the piezoelectric layer 10 facing away from the first surface 11, and the surface of the temperature compensation layer 30 facing away from the piezoelectric layer 10 is defined as the second surface 31. It is understood that when a volume wave propagates to the second surface 31, at least a portion of the volume wave will be reflected on the second surface 31. The reflected volume wave will also be reflected when it propagates to the first surface 11.

[0147] When the phases of the bulk wave after two reflections from the first surface 11 and the second surface 31 match, the bulk wave will form a waveguide mode within the piezoelectric layer 10 and the temperature compensation layer 30. The surface acoustic wave device 100 of this application further limits the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 by the above conditions, thereby reducing the influence of the waveguide mode frequency on the surface acoustic wave frequency. This ensures the operating performance of the surface acoustic wave device 100 of this application.

[0148] In one embodiment, the thickness of the temperature compensation layer 30 is D. w The thicknesses of the temperature compensation layer 30 and the piezoelectric layer 10 satisfy the following conditions: 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, then the thickness of the temperature compensation layer 30 is too thick. An excessively thick temperature compensation layer 30 will not significantly improve the frequency temperature coefficient of the device, but will cause deterioration in the device's operating frequency and noise characteristics, affecting the operating performance of the surface acoustic wave device 100 of this 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, then 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 this application achieves a matching setting of the thicknesses of the temperature compensation layer 30 and the piezoelectric layer 10 by limiting the range of the ratio between the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10. This improves the operating performance and temperature stability of the surface acoustic wave device 100 of this application.

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

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

[0153] In one embodiment, the midline distance between two adjacent electrode fingers is P, and the first reinforcement angle is θ, which satisfies the following equation: Among them, v B1 λ is the volume wave velocity within the piezoelectric layer 10, f is the operating frequency, and λ is the velocity of sound. B1 The first reinforcement angle θ is the bulk wave wavelength excited by the interdigitated 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 the following: Figure 9 ,in Figure 9 This is a partial cross-sectional structural diagram of the surface acoustic wave device 100 provided in one embodiment of this application. Figure 9 The solid line with arrows below the interdigitated electrode 20 indicates the volume wave propagating within the piezoelectric layer 10 and the direction of its propagation.

[0155] In this application, the surface acoustic wave (SAW) device 100 exhibits a surface acoustic wave intensity that gradually decreases with increasing depth along the third direction 003 as the surface acoustic wave propagates along the piezoelectric layer 10. The first characteristic thickness represents the decrease in SAW intensity to the point where the surface acoustic wave intensity attenuates to the first surface 11. The distance between the time and the first surface 11.

[0156] That is, the surface acoustic wave device 100 of this application obtains the surface acoustic wave intensity attenuated to the first surface 11 by acquiring the surface acoustic wave intensity. The distance between the piezoelectric layer 10 and the first surface 11 is used to define the thickness of the piezoelectric layer 10 and to 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 embodiments of this application, the acoustic wave vector generated by the surface acoustic wave device 100 when it is working has a real component along the thickness direction of the piezoelectric layer 10, which is a volume wave. The enhancement condition for volume wave excitation refers to the phase matching of the volume waves excited by the electrodes 22 of the same polarity in a specific direction. For example Figure 9 As shown, the two adjacent first electrode fingers 22a of the interdigitated electrode 20 excite the volume wave vector β within the piezoelectric layer 10. B1 The angle between the propagation direction and the first surface 11 is equal to the first reinforcing angle θ.

[0158] At this time, the wavelength λ of the bulk wave in the enhanced state within the piezoelectric layer 10 B1 The distance 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 this embodiment, the case where n=1 is considered. That is, The propagation speed of the bulk wave in the enhanced state within the piezoelectric layer 10 is v. B1 The volume wave vector β in the piezoelectric layer 10 is in an enhanced state. B1 The operating frequency is f.

[0160] In this embodiment, the magnitude of the first strengthening angle is determined by the operating frequency f. When When, cosθ=1.

[0161] When f <f c1 When cosθ > 1, the first reinforcement angle θ is a complex number, and correspondingly, the acoustic wave vector generated by the surface acoustic wave device 100 of this application does not have a real component along the thickness direction of the piezoelectric layer 10. That is, when the first reinforcement angle is complex, the acoustic wave vector component propagating in the piezoelectric layer 10 along the third direction θ03 away from the first surface 11 is imaginary, and the acoustic wave is an evanescent wave. Therefore, under ideal conditions, for the surface acoustic wave device 100 of this application, only the energy of the surface acoustic wave is concentrated on the surface of the device.

[0162] To facilitate the distinction between 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, β1 is used to represent the sound wave state when the first reinforcement angle is a complex number.

[0163] At this time, the intensity of the acoustic wave vector β1 rapidly attenuates along the third direction 003 in a direction away from the first surface 11. The surface acoustic wave device 100 of this application utilizes the attenuation characteristics of evanescent waves to characterize the distribution range of the surface acoustic waves. Specifically, the evanescent wave intensity attenuates to the evanescent wave intensity at the first surface 11... The distance between the time and the first surface 11 has a certain correspondence with the thickness of the piezoelectric layer 10 when the amplitude of the surface acoustic wave overlaps with the temperature compensation layer 30.

[0164] The wave vector component of the acoustic wave vector β1 on 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 this application only manifests as an acoustic wave along the X direction. At this time, the modulus of the acoustic wave vector β1 satisfies the equation: Where λ1 is the bulk wavelength of the piezoelectric crystal along the X direction at the operating frequency f.

[0165] The wave vector component β1 on the third direction 003 is β 1z Satisfying the equation:

[0166] In the above equation, the first enhancement angle θ is selected as the operating frequency f = f c1 At that time, the value of the first strengthening angle.

[0167] The intensity of the surface acoustic wave propagating along the third direction 003 in the piezoelectric layer 10 towards the direction away from the first surface 11 is denoted by u, wherein the intensity of the surface acoustic wave in the piezoelectric layer 10 satisfies the equation The body wave component of the acoustic wave vector β1 in the second direction 002 is β 1x z represents the distance between any point within 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 between the time and the first surface 11. That is,

[0169] Will Substituting into the equation for the acoustic wave intensity within the piezoelectric layer 10, the z-value in the above equation is obtained. The calculated z-value is the first characteristic thickness. Since V B1 The volume wave velocity within the piezoelectric layer 10 is given. When the first reinforcement angle is a complex number, the sound wave velocity of the surface acoustic wave device in this application depends only on the material of the piezoelectric layer 10. Therefore, the first characteristic thickness... Wherein, the volume wave velocity of the piezoelectric crystal along the X direction is V. b1 .

[0170] In this embodiment, after calculating the first characteristic thickness based on the above equation, the thickness of the piezoelectric layer 10 is determined by the range of the ratio between the thickness of the piezoelectric layer 10 and the first characteristic thickness. For a 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 that of the temperature compensation layer 30.

[0171] Please refer to the following: Figure 10 ,in Figure 10 This is a partial cross-sectional structural schematic diagram of the surface acoustic wave device 100 provided in one embodiment of this application. Wherein, Figure 10 The solid lines with arrows in the figure represent the bulk waves propagating within the piezoelectric layer 10 and the temperature compensation layer 30, and the direction of propagation of the bulk waves.

[0172] like Figure 10 As shown, the first reinforcement angle is a real number, the propagation speed of the bulk wave inside the piezoelectric layer 10 and the temperature compensation layer 30 is V0, the operating frequency of the interdigitated electrode 20 is f, and the thickness of the temperature compensation layer 30 is the sum of the thickness of the piezoelectric layer 10 and H.

[0173] It is worth noting that the propagation speed of the bulk wave excited by the interdigitated electrode 20 into the piezoelectric layer 10 and the temperature compensation layer 30 is the propagation speed under ideal conditions where the difference in sound speed between the piezoelectric layer 10 and the temperature compensation layer 30 is ignored. That is, the propagation speed V0 of the bulk wave in the piezoelectric layer 10 and the temperature compensation layer 30 is V0. B1 The values ​​are equal, but different superscripts are used in the embodiments of this application for easy distinction.

[0174] When the phase difference between the two reflections of the bulk wave on the first surface 11 and the second surface 31 is 2nπ, the bulk wave will form a waveguide mode within the piezoelectric layer 10 and the temperature compensation layer 30. Here, 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] Where 2n represents the ratio of the path length of the volume wave between the reflections on the first surface 11 and the second surface 31 to the wavelength of the volume wave. This represents the ratio of the phase introduced by the body wave when reflected from the first surface 11 and the second surface 31 to π.

[0177] In practical use of the surface acoustic wave (SAW) device 100 of this application, the waveguide mode may affect the ripple of the SAW filter passband. Typically, the waveguide mode frequency f is required to be... g The surface acoustic wave frequency f (e.g., the surface acoustic wave resonant frequency f) rIt is η times the value of 1.07. Where η > 1.07 or η = 1.05. For ease of description, we will take η > 1.07 as an example.

[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 seen that in order to determine 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, The minimum value should be taken. That is, n = 1. The phase difference introduced by the body wave when reflected from the first surface 11 and the second surface 31 is 0, that is, Therefore, we obtain

[0180] The first reinforcement angle is defined to satisfy the equation with respect to the propagation velocity of the bulk wave within the piezoelectric layer 10 and the temperature compensation layer 30: Therefore, we obtain

[0181] In this embodiment, during the fabrication of the surface acoustic wave (SAW) device 100, the range of the sum of the thicknesses H of the temperature compensation layer 30 and the piezoelectric layer 10 can be calculated by obtaining the first reinforcement angle D, the propagation velocity V0 of the bulk wave excited by the interdigitated electrode 20 into the piezoelectric layer 10 and the temperature compensation layer 30 when in the reinforcement state, and the SAW frequency f. This limits the range of the sum of the thicknesses H of the temperature compensation layer 30 and the piezoelectric layer 10, facilitating the selection of the thickness D of the piezoelectric layer 10. y and the thickness D of the temperature compensation layer w .

[0182] Wherein, for the first strengthening angle θ. Since the first strengthening angle is a real number, according to And with Christoph's formula, we can obtain the following: Figure 11 The diagram shows a partial curve illustrating the relationship between F(θ) and the first strengthening angle θ. The horizontal axis represents the first strengthening angle θ, in degrees. The vertical axis represents F(θ), in m / s.

[0183] Based on the equation relationship between G(θ) and F(θ), it can be known that, That is, when calculating G(θ), it can be done by... Figure 11 Obtain F(θ) and the first strengthening angle θ to calculate G(θ).

[0184] Therefore, in the process of fabricating the surface acoustic wave device 100 of this application, the distance P between the midlines of two adjacent electrode fingers 22 and the volume wave velocity V of the piezoelectric crystal along the X direction can be obtained. b1The first characteristic thickness T is calculated based on the operating frequency f. y .

[0185] The first characteristic thickness T is calculated. y On this premise, it is necessary to further limit the selection range of the sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10. Specifically, this can be achieved by obtaining the midline distance P between two adjacent electrode fingers 22 and the volume wave velocity V within the piezoelectric layer 10. B1 The first strengthening angle θ is calculated based on the operating frequency f.

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

[0187] In this embodiment, the body wave includes longitudinal waves and transverse waves, and the transverse waves include fast shear waves and slow shear waves. When obtaining the first reinforcement angle θ, different intersection points can be selected to choose different first reinforcement angles θ based on actual needs.

[0188] Based on the first reinforcement angle θ, 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 by obtaining the propagation velocity V0 of the bulk wave in the piezoelectric layer 10 and the temperature compensation layer 30, as well as the surface acoustic wave frequency f (surface acoustic wave resonant frequency or surface acoustic wave anti-resonant frequency) selected in the embodiment of this application.

[0189] During the fabrication of the surface acoustic wave device 100 of this application, the first characteristic thickness T can be used. y The sum H of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 is limited, and The range of the sum H of the thickness of the temperature compensation layer 30 and the piezoelectric layer 10 is defined, thereby limiting the range of the sum H of the thickness of the temperature compensation layer 30 and the piezoelectric layer 10. This facilitates the selection of the thickness D of the piezoelectric layer 10. y and the thickness D of the temperature compensation layer w .

[0190] In one embodiment, the surface acoustic wave device 100 further includes a functional layer 40, which is disposed on the side of the piezoelectric layer 10 away from the interdigitated electrode 20 along the thickness direction of the piezoelectric layer 10. For details, please refer back to... Figure 6 Along the third direction 003, the functional layer 40 is located on the side of the temperature compensation layer 30 away from the piezoelectric layer 10 to block the leakage of bulk waves and reduce the loss of the surface acoustic wave device 100.

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

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

[0193] The thickness of the second feature is determined by the volume wave velocity and operating frequency of the material of the pressure functional layer 40 along the X direction.

[0194] Specifically, in one embodiment, the wavelength of a bulk wave in the enhanced state within the piezoelectric layer 10 refracted into the functional layer 40 is λ2, and the second characteristic thickness satisfies the equation:

[0195] Since, after the surface acoustic wave device 100 of this application is fabricated, the center-to-center distance between two adjacent electrode fingers 22 is P, and the volume wave velocity of the material of the functional layer 40 along the X direction is V. b2 The operating frequency is f, and both are measurable or calculable values. Therefore, the surface acoustic wave device 100 of this application can be based on the volume wave velocity V. b2 The wavelength λ2 corresponding to the bulk sound velocity of the material of functional layer 40 along the X direction at the operating frequency is calculated using the operating frequency f, and the second characteristic thickness is obtained based on the bulk wave wavelength λ2 and the centerline spacing P.

[0196] Therefore, given the second characteristic thickness, 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 this application limits the thickness of the functional layer 40 by defining the range of the ratio between the second characteristic thickness and the functional layer 40, allowing high-frequency bulk waves in the bulk wave to leak outwards, thereby reducing the quality factor (Q value) of high-frequency miscellaneous modes. This reduces the impact of high-frequency miscellaneous modes in practical applications and ensures the operating performance of the surface acoustic wave device 100 of this application.

[0197] In one embodiment, the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following condition: When the ratio of the thickness of the functional layer 40 to the thickness of the second feature is less than 0.2, the thickness of the functional layer 40 is too thin. An excessively thin functional layer 40 is more sensitive to temperature changes and has relatively poor mechanical strength. This results in relatively poor stability and reliability of the surface acoustic wave device 100 of this application.

[0198] When the ratio of the thickness of the functional layer 40 to the thickness of the second feature 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 bulk wave leakage is enhanced, which may make it difficult for high-frequency noise modes in the bulk wave to leak out, thereby causing high-frequency noise modes to affect the working performance of the surface acoustic wave device 100 of this application.

[0199] Therefore, the surface acoustic wave (SAW) device 100 of this application sets the ratio of the thickness of the functional layer 40 to the thickness of the second feature between 0.2 and 1.5. This avoids the functional layer 40 becoming too thin due to an excessively small ratio, which would affect the working performance and stability of the SAW device 100. It also avoids the functional layer 40 becoming too thick due to an excessively large ratio, which would affect the leakage of high-frequency miscellaneous modes in the SAW device 100. This ensures the stability and working performance of the SAW device 100 of this application.

[0200] 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 is less than the second feature thickness.

[0201] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following condition:

[0202] In one embodiment, such as Figure 6 As shown, the surface acoustic wave device 100 of this 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 during operation, after being released to the piezoelectric layer 10, leaks sequentially through the temperature compensation layer 30 and the functional layer 40 to the monocrystalline silicon layer 50. In the embodiments of this application, the monocrystalline silicon layer 50... <110> The spatial angle between the crystal orientation and the propagation direction of the surface acoustic waves excited on the first surface 11 by the multiple electrode fingers 22 is less than or equal to 10°. That is, the single-crystal silicon layer 50... <110> The space angle between the crystal orientation group and the second orientation 002 is less than or equal to 10°.

[0204] Because the sound velocity of functional layer 40 is greater than that of monocrystalline silicon layer 50 along... <110> The speed of sound propagation in the direction of propagation. Understandably, functional layer 40 is a less dense medium than the monocrystalline silicon layer 50. When a bulk wave is incident at a certain angle to the interface between the monocrystalline silicon layer 50 and functional layer 40, the angle of refraction of the bulk wave refracted into the monocrystalline silicon layer 50 is smaller than the angle of incidence. Correspondingly, the angle between the propagation direction of the bulk wave refracted into the monocrystalline silicon layer 50 and the second direction 002 is greater than the angle between the propagation direction of the bulk wave incident into the monocrystalline silicon layer 50 and the second direction 002.

[0205] Furthermore, due to the 50% of the single-crystal silicon layer <110> Crystalline orientations exhibit lower sound wave propagation speeds and lower acoustic losses. Understandably, a 50-layer monocrystalline silicon crystal... <110> The space angle between the crystal orientation group and the second orientation 002 is less than or equal to 10°, which is conducive to the leakage of bulk waves through the functional layer 40 to the single crystal silicon layer 50.

[0206] In other words, the matching arrangement of the monocrystalline silicon layer 50 and the functional layer 40 can facilitate the leakage of high-frequency miscellaneous modes (including waveguide modes) in the bulk wave, thereby reducing the interference of high-frequency miscellaneous modes on the surface acoustic wave in practical applications and improving the working performance of the surface acoustic wave device 100 of this application.

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

[0208] Please see Figure 12 and Figure 13 ,in Figure 12 This is another structural schematic diagram of the surface acoustic wave device 100 provided in one embodiment of this application. Figure 13 This is another cross-sectional structural schematic diagram of the surface acoustic wave device 100 provided in one embodiment of this application.

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

[0210] The interdigitated electrode 20 includes two parallel and spaced-apart busbars 21 and a plurality of parallel and spaced-apart electrode fingers 22. One of the two busbars 21 is used to receive external signals, and the other busbar 21 is used to output signals. The plurality of electrode fingers 22 are located between the two busbars 21. Some of the electrode fingers 22 are connected to one busbar 21, and other electrode fingers 22 are connected to the other busbar 21.

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

[0212] Specifically, the first electrode finger 22a and the second electrode finger 22b both extend along the first direction 001 towards opposite sides of the piezoelectric layer 10. Along the second direction 002, the first electrode finger 22a and the second electrode finger 22b are arranged alternately. Specifically, as... Figure 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 busbar 21a and the second busbar 21b both extend along the second direction 002 to opposite sides of the piezoelectric layer 10, wherein the first direction 001 and the second direction 002 are perpendicular to each other. In practical applications, the surface acoustic wave device 100 of this application may have errors, and the angle between the first direction 001 and the second direction 002 may not be equal to 90°.

[0214] In this embodiment, based on the inverse piezoelectric effect of the piezoelectric layer 10, an electrical signal can be sequentially applied to the piezoelectric layer 10 via the first busbar 21a and each of the first electrode fingers 22a, causing periodic deformation of the surface of the piezoelectric layer 10. This generates an outwardly released sound wave.

[0215] The acoustic waves emitted by the surface acoustic wave device 100 during operation include surface acoustic waves and volume waves. Specifically, when the component of the acoustic wave along the thickness direction of the piezoelectric layer 10 is imaginary, this type of acoustic wave can only propagate along the plane of the first surface 11, and is therefore a surface acoustic wave. The propagation direction of the surface acoustic wave is defined as the X-direction. When the acoustic wave vector has a real component along the thickness direction of the piezoelectric layer 10, it is a volume wave.

[0216] Surface acoustic waves (SAWs) are used to realize the frequency selection and signal processing functions of the SAW device 100 of this application. During SAW propagation, the main propagation direction is the second direction 002. That is, the X direction is the second direction 002. However, in practice, due to edge effects and acoustic diffraction, the propagation direction of the SAW formed on the first surface 11 of the piezoelectric layer 10 may also be in other directions, corresponding to an angle between the X direction and the second direction 002. In one embodiment, SAWs propagating in other directions are absorbed by a sound-absorbing material (not shown in the figure).

[0217] In this embodiment, the bulk wave generated when the surface acoustic wave device 100 is working will be released to the piezoelectric layer 10 and propagate into the functional layer 40. The bulk wave 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 in this application is T. d The thickness of functional layer 40 is D. d The thickness of functional layer 40 and the thickness of the second feature satisfy the following condition: That is, the ratio between the thickness of the functional layer 40 and the thickness of the second feature is less than or equal to 1.5.

[0219] The thickness of the second feature is determined by the volume wave velocity and operating frequency of the material of the functional layer 40 along the X direction. In this embodiment, the volume wave 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 volume wave velocity of the material of the functional layer 40 along the X direction is also determined.

[0220] For details, please refer to the following: Figure 14 The diagram shown is an enlarged cross-sectional view of another surface acoustic wave device 100 provided in one embodiment of this application.

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

[0222] Therefore, the surface acoustic wave device 100 of this application can be based on the volume wave velocity V. b2 The wavelength λ2 corresponding to the bulk wave velocity of the material of functional layer 40 along the X direction at the operating frequency is calculated using the operating frequency f, and the second characteristic thickness is obtained based on the bulk wave wavelength λ2 and the midline spacing P.

[0223] Therefore, given the second characteristic thickness, 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 this application limits the thickness of the functional layer 40 by defining the range of the ratio between the second characteristic thickness and the functional layer 40, allowing high-frequency bulk waves in the bulk wave to leak outwards, thereby reducing the quality factor (Q value) of high-frequency miscellaneous modes. This reduces the impact of high-frequency miscellaneous modes in practical applications and ensures the operating performance of the surface acoustic wave device 100 of this application.

[0224] Specifically, admittance can be used to describe the response process of components and signals. In the surface acoustic wave device 100 of this application, admittance is used to measure the influence of clutter propagating on the surface of the piezoelectric layer 10 on the acoustic wave quality. Figure 15 This diagram illustrates the conductance curves of the surface acoustic wave (SAW) device 100 and the comparative SAW device based on different SAW frequencies. The horizontal axis is in GHz, and the vertical axis is in dB.

[0225] For the comparative examples, there are two sets, and the surface acoustic wave devices in each set include a piezoelectric layer and interdigitated electrodes disposed on the surface of the piezoelectric layer. The centerline spacing P between two adjacent interdigitated electrodes is 1.0 μm, the duty cycle of the interdigitated electrodes is 0.4, the piezoelectric layer is 0.6 μm thick 42°YX-LiTaO3, the interdigitated electrodes are made of aluminum, and the thickness of the interdigitated electrodes is 0.16 μm.

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

[0227] For the embodiments, there are six sets of embodiments. The surface acoustic wave device 100 in each set of embodiments includes a single crystal silicon layer 50, a functional layer 40, a temperature compensation layer 30, a piezoelectric layer 10, and interdigitated electrodes 20 disposed on the first surface 11 of the piezoelectric layer 10, which are stacked sequentially. Among them, the midline spacing P between two adjacent electrode fingers 22 of the interdigitated electrodes 20 is 1.0 μm, the duty cycle of the interdigitated electrodes 20 is 0.4, the piezoelectric layer 10 is made of 0.6 μm 42°YX-LiTaO3, the electrode fingers 22 are made of aluminum, and the electrode fingers 22 have a thickness of 0.16 μm. The upper surface of the single crystal silicon layer 50 is (111), wherein the crystal orientation of [1-10] is parallel to the second direction 002.

[0228] The six sets of embodiments are Examples 5 through 10. Along the third direction 003, the thickness of the functional layer 40 in Example 5 is 0.6 μm. The thickness of the functional layer 40 in Example 6 is 1.0 μm. The thickness of the functional layer 40 in Example 7 is 1.4 μm. The thickness of the functional layer 40 in Example 8 is 1.8 μm. The thickness of the functional layer 40 in Example 9 is 2.2 μm. The thickness of the functional layer 40 in Example 10 is 2.6 μm. Figure 15 As shown, the conductivity curves corresponding to Examples 5-10 are represented by different line segments.

[0229] Based on the material parameters of 42°YX-LiTaO3, the transverse wave velocity within the functional layer 40 can be calculated to be approximately 5340 m / s for this embodiment. This is further supported by a local curve showing the relationship between the second reinforcement angle of the functional layer 40 of the surface acoustic wave device and the volume wave velocity. The second characteristic thickness T for a body wave with a frequency of 2.4 GHz was calculated. d =0.73μm.

[0230] like Figure 15 The diagram illustrates the variation of harmonic conductance with the thickness of functional layer 40, where conductance is directly related to system losses. For Comparative Example 1, a turning point in the harmonic conductance curve occurs at 2.34 GHz, indicating that the bulk wave released from the interdigitated electrode 20 into the piezoelectric layer 10 leaks from 2.34 GHz into the monocrystalline silicon layer 50. For Comparative Example 2, this turning point only appears at 2.67 GHz.

[0231] For surface acoustic wave (SAW) devices, leakage of high-frequency clutter in the bulk wave can reduce the Q value of high-frequency clutter modes and weaken their interference with the operation of the SAW device. Therefore, SAW devices typically require control of the leakage frequency to avoid excessively high leakage frequencies that would hinder the leakage of high-frequency clutter.

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

[0233] On the other hand, because of the 1.5T d =1.095μm. 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 7-10 is greater than 1.5T. d It is evident that the inflection points of Embodiments 5 and 6 are relatively close to the inflection point of Comparative Example 1. That is, the surface acoustic wave devices 100 corresponding to Embodiments 5 and 6 are better able to achieve leakage of high-frequency clutter in the volume wave.

[0234] In other words, compared to Comparative Examples 1 and 2, the surface acoustic wave device 100 of this application, by limiting the thickness of the functional layer 40, allows bulk waves to leak across the functional layer 40 to the single-crystal silicon layer 50, thereby reducing interference from high-frequency noise modes in practical applications. This improves the operating performance of the surface acoustic wave device 100 of this application.

[0235] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following condition: The surface acoustic wave (SAW) device 100 of this application sets the ratio of the thickness of the functional layer 40 to the thickness of the second feature between 0.2 and 1.5. This avoids the functional layer 40 becoming too thin due to an excessively small ratio, which would affect the working performance and stability of the SAW device 100. It also avoids the functional layer 40 becoming too thick due to an excessively large ratio, which would affect the leakage of high-frequency miscellaneous modes in the SAW device 100. This ensures the stability and working performance of the SAW device 100 of this application.

[0236] 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 is less than the second feature thickness.

[0237] In one embodiment, when the frequency of the surface acoustic wave excited by the interdigitated 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 thickness of the second feature satisfy the following 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 thickness of the first feature satisfy the following condition: The thickness of the first feature is determined based on the midline spacing between two adjacent electrode fingers 22, the volume wave velocity of the piezoelectric layer 10 along the X direction, and the operating frequency.

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

[0240] In one embodiment, please refer back. Figure 13 The surface acoustic wave device 100 of this 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 this application. The single-crystal silicon layer 50 is disposed on the side of the functional layer 40 away from the temperature compensation layer 30 to facilitate the leakage of waveguide mode capability.

[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 reinforcement angle γ, the bulk wave in the functional layer 40 is in a reinforced state; the bulk wave wavelength λ of the acoustic wave excited by the interdigital electrode 20 propagating into the functional layer is... B2The bulk wavelength within functional layer 40 in the enhanced state.

[0242] When the interdigitated electrode 20 excites a bulk wave within the functional layer 40, which propagates at a certain angle along the third direction 003, the angle between the propagation direction of the bulk wave and the first surface 11 is the propagation angle. For any two different propagation angles, the intensity of the bulk wave corresponding to one propagation angle may differ from the intensity of the bulk wave corresponding to the other propagation angle. When the propagation angle is equal to the second reinforcement angle, the intensity of the bulk wave within the functional layer 40 is the greatest compared to the intensity of the bulk wave corresponding to other propagation angles.

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

[0244] Based on the limitations of the above embodiments, please refer to the following: Figure 16 ,in Figure 16 This is another partial cross-sectional structural schematic diagram of the surface acoustic wave device 100 provided in one embodiment of this application. Wherein, Figure 16 The solid line with arrows below the interdigitated electrode 20 indicates the bulk wave and its propagation direction within the piezoelectric layer 10, the temperature compensation layer 30, and the functional layer 40.

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

[0246] During the propagation of the bulk wave in the surface acoustic wave device 100 of this application within the functional layer 40, the intensity of the bulk wave gradually decreases as the propagation depth along the third direction 003 gradually increases. The second characteristic thickness represents the attenuation of the bulk wave intensity to the point where it decreases to the second surface 31. The distance between the second surface 31 and the time.

[0247] That is, the surface acoustic wave device 100 of this application obtains the volume wave intensity attenuated to the volume wave intensity at the second surface 31. The distance between the second surface 31 and the second surface 31 is used to define the thickness of the functional layer 40 and to ensure that the bulk wave can leak into the monocrystalline silicon layer 50 below the thickness of the functional layer 40.

[0248] Specifically, in the embodiments of this application, the acoustic wave vector generated by the surface acoustic wave device 100 during operation has a real component along the thickness direction of the functional layer 40, which is a volume wave. The enhancement condition for volume wave excitation refers to the phase matching of the volume waves excited by the electrodes 22 of the same polarity in a specific direction. For example... Figure 16 As shown, the volume wave vector β of the two adjacent first electrode fingers 22a of the interdigitated electrode 20 is excited into the piezoelectric layer 10 and enters the functional layer 40 via the temperature compensation layer 30. B2 The angle between the propagation direction and the second surface 31 is equal to the second reinforcing angle γ.

[0249] At this time, the wavelength λ of the volume wave in the enhanced state within functional layer 40 B2 The distance 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 this embodiment, the case where n=1 is considered. That is, The propagation speed of the body wave in the enhanced state within functional layer 40 is V. B2 The volume wave vector β in the enhanced state within functional layer 40 B2 The operating frequency is f.

[0251] In this embodiment, the magnitude of the second strengthening angle is determined by the operating frequency f. When When, cosγ=1.

[0252] When f <f c2 When cosγ > 1, the second reinforcement angle γ is a complex number. Correspondingly, the bulk wave generated by the surface acoustic wave device 100 of this application will undergo total emission on the second surface 31 when it enters the functional layer 40 from the piezoelectric layer 10 and the temperature compensation layer 30.

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

[0254] To facilitate the distinction between 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, β2 is used to represent the sound wave state when the second reinforcement angle is a complex number.

[0255] At this time, the acoustic wave vector β2 rapidly attenuates along the third direction 003 in a direction away from the first surface 11. The surface acoustic wave device 100 of this application utilizes the attenuation characteristics of evanescent waves to characterize the leakage of high-frequency volume waves. Specifically, the evanescent wave intensity attenuates to the evanescent wave intensity at the second surface 31. The distance between the time and the second surface 31 has a certain correlation with the leakage of high-frequency body waves.

[0256] Define the body wave component of the acoustic wave vector β2 in the third direction 003 as β 2z Since the refraction angle is complex, the acoustic wave of the surface acoustic wave device 100 of this application manifests as an acoustic wave along the X direction. In this case, the modulus of the acoustic wave vector β2 satisfies the equation: Wherein, λ2 is the wavelength corresponding to the volume wave velocity of the material of functional layer 40 along the X direction at the operating frequency f.

[0257] The component β of the acoustic wave vector β2 in the third direction 003 2z Satisfying the equation:

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

[0259] The intensity of the sound wave within functional layer 40 is ν, and the volume wave component of the sound wave β2 in the second direction 002 is β. 2x z represents the distance between the volume wave at any point within the functional layer 40 and the second surface 31.

[0260] The volume wave intensity within functional layer 40 satisfies the following equation:

[0261]

[0262] In this embodiment, the second characteristic thickness represents the volume wave intensity attenuated to the volume wave intensity at the second surface 31. The distance between the time and the second surface 31. That is,

[0263] Will Substituting into the equation for the acoustic wave intensity within functional layer 40, the z-value in the above equation is obtained. The calculated z-value is the second characteristic thickness. Since V B2 The volume wave velocity within the functional layer 40 is given. When the second reinforcement angle is complex, the sound wave velocity of the surface acoustic wave device in this application depends only on the material of the functional layer 40. The second characteristic thickness...

[0264] In this embodiment, after calculating the second characteristic thickness based on the above equation, the thickness of the functional layer 40 is determined by the range of the ratio between the thickness of the functional layer 40 and the second characteristic thickness. For the functional layer 40 with this thickness, high-frequency noise modes in the bulk wave can leak into the single-crystal silicon layer 50.

[0265] Therefore, in the process of fabricating the surface acoustic wave device 100 of this application, on the one hand, the midline distance P between two adjacent electrode fingers 22 and the volume wave velocity V along the X direction in the functional layer 40 can be obtained. b2 Based on the operating frequency f, the second strengthening angle γ is calculated.

[0266] On the other hand, the value of F(γ) corresponding to the second reinforcement angle γ can also be calculated by obtaining the frequency of the bulk wave within the functional layer 40 and the distance P between the midlines of two adjacent electrode fingers 22, and then relying on the functional layer 40 corresponding to a similar value. Figure 11 The diagram shows the second strengthening angle γ.

[0267] Based on the second reinforcement angle γ, the propagation velocity V of the bulk wave along the X direction of the material in the functional layer 40 is obtained. b2 The second characteristic thickness T is calculated using the surface acoustic wave frequency f (surface acoustic wave resonant frequency or surface acoustic wave anti-resonant frequency) selected in the embodiments of this application. d Thus, the thickness D of functional layer 40 is obtained. d The limited scope.

[0268] In one embodiment, the thickness of the piezoelectric layer 10 and the thickness of the first feature satisfy the following condition: At this time, the thickness of the piezoelectric layer 10 can satisfy the condition: 0.4P≤D y ≤0.8P.

[0269] In one embodiment, the first feature thickness is satisfied when the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 meets the following condition: At that time, the thickness of the temperature compensation layer 30 can satisfy the condition: 0.4P≤D w ≤0.8P.

[0270] In one embodiment, the first feature thickness is satisfied when the sum of the thickness of the temperature compensation layer 30 and the thickness of the piezoelectric layer 10 meets the following condition: At that time, 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, the thickness of the functional layer 40 and the thickness of the second feature satisfy the following condition: At that time, the thickness of functional layer 40 can satisfy the condition: 0.2P≤D d ≤0.6P.

[0272] In one embodiment, the material of the functional layer 40 is anisotropic or isotropic.

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

[0274] In one embodiment, the material of the piezoelectric layer 10 is anisotropic.

[0275] It should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0276] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0277] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Those skilled in the art will understand that implementing all or part of the processes of the above embodiments, and making equivalent changes according to the claims of this invention, still falls within the scope of this invention.

Claims

1. A surface acoustic wave device, characterized in that, It includes a piezoelectric layer and interdigitated electrodes disposed on a first surface of the piezoelectric layer, wherein the interdigitated electrodes include a plurality of electrode fingers; The acoustic waves emitted by the surface acoustic wave device during operation include surface acoustic waves and volume waves, and the surface acoustic waves propagate in 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 satisfies the condition that the thickness of the first feature is: The piezoelectric layer includes a piezoelectric crystal, and the thickness of the first feature is determined based on the midline distance between two adjacent electrode fingers, the volume wave velocity of the piezoelectric crystal along the X direction, and the operating frequency. First feature thickness: Wherein, the midline distance between two adjacent electrode fingers is P, and the volume wave velocity of the piezoelectric crystal along the X direction is V. b1 The operating frequency is f, and the bulk wavelength of the piezoelectric crystal along the X direction at the operating frequency is λ1.

2. The surface acoustic wave device according to claim 1, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following condition:

3. The surface acoustic wave device according to claim 1, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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.

4. The surface acoustic wave device according to claim 1, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following condition:

5. The surface acoustic wave device according to claim 1, characterized in that, The surface acoustic wave device further includes a temperature compensation layer, which is disposed on the side of the piezoelectric layer away from the interdigitated electrodes along the thickness direction of the piezoelectric layer.

6. The surface acoustic wave device according to claim 5, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 and the thickness of the piezoelectric layer is H, and the first characteristic thickness and the sum of the thickness of the temperature compensation layer and the thickness of the piezoelectric layer satisfy the following condition:

7. The surface acoustic wave device according to claim 6, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 following condition:

8. The surface acoustic wave device according to claim 5, characterized in that, When the angle between the propagation direction of the bulk wave excited by the interdigitated electrode into the piezoelectric layer and the first surface is equal to the first reinforcement angle θ, the bulk wave in the piezoelectric layer and the temperature compensation layer is in a reinforced state; the propagation speed of the bulk wave excited by the interdigitated electrode into the piezoelectric layer and the temperature compensation layer is V0, and the first reinforcement angle and the propagation speed of the bulk wave in the piezoelectric layer and the temperature compensation layer satisfy the following 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 following condition: Wherein, the surface acoustic wave frequency f is the surface acoustic wave resonant frequency or the surface acoustic wave anti-resonant frequency.

9. The surface acoustic wave device according to claim 8, characterized in that, The thickness of the temperature compensation layer is D. w The thicknesses of the temperature compensation layer and the piezoelectric layer satisfy the following conditions:

10. The surface acoustic wave device according to any one of claims 1-9, characterized in that, When the propagation direction of the bulk wave excited by the interdigitated electrode into the piezoelectric layer makes an angle equal to the first reinforcement angle θ with the first surface, the bulk wave in the piezoelectric layer is in a reinforced state; the wavelength λ of the bulk wave excited by the interdigitated electrode into the piezoelectric layer is... B1 The bulk wavelength is the wavelength of the piezoelectric layer in the enhanced state.

11. The surface acoustic wave device according to claim 10, characterized in that, The distance between the centerlines of two adjacent electrode fingers is P, and the first reinforcement angle is θ. The first reinforcement angle satisfies the following equation: Among them, V B1 λ is the volume wave velocity within the piezoelectric layer, f is the operating frequency, and λ is the velocity of sound. B1 The first reinforcement angle θ is the bulk wave wavelength excited by the interdigitated electrode within the piezoelectric layer, and the range of the first reinforcement angle θ satisfies: 0° < θ < 180°.

12. The surface acoustic wave device according to any one of claims 1-9, characterized in that, The surface acoustic wave device includes a functional layer, which is disposed on the side of the piezoelectric layer away from the interdigitated electrodes along the thickness direction of the piezoelectric layer. 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 thickness of the second feature satisfy the following condition: The thickness of the second feature is determined based on the volume wave velocity and operating frequency of the material of the functional layer along the X direction.

13. The surface acoustic wave device according to claim 12, characterized in that, The second characteristic thickness satisfies the following equation: Wherein, the midline distance between two adjacent electrode fingers is P, and the volume 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 volume wave velocity of the material of the functional layer along the X direction at the operating frequency.

14. The surface acoustic wave device according to claim 13, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 feature thickness satisfy the following condition:

15. The surface acoustic wave device according to claim 13, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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.

16. The surface acoustic wave device according to claim 13, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 feature thickness satisfy the following condition:

17. The surface acoustic wave device according to claim 12, characterized in that, The surface acoustic wave device includes a monocrystalline silicon layer. Along the thickness direction of the piezoelectric layer, the monocrystalline silicon layer is disposed on the surface of the functional layer opposite to the piezoelectric layer. <110> The spatial angle between the crystal orientation group and the propagation direction of the surface acoustic wave excited on the first surface by the plurality of interdigitated electrodes is less than or equal to 10°.

18. The surface acoustic wave device according to claim 17, characterized in that, The single-crystal silicon layer <110> The crystal orientation is parallel to the propagation direction of the surface acoustic waves excited by the multiple interdigitated electrodes on the first surface.

19. The surface acoustic wave device according to claim 12, characterized in that, The material of the functional layer is either anisotropic or isotropic.

20. The surface acoustic wave device according to claim 12, characterized in that, The functional layer is a sound velocity layer or a polycrystalline silicon layer.

21. The surface acoustic wave device according to any one of claims 1-9, characterized in that, The material of the piezoelectric layer is anisotropic.

22. A surface acoustic wave device, characterized in that, It includes a functional layer and a piezoelectric layer stacked along its own thickness direction, and an interdigitated electrode disposed on a first surface of the piezoelectric layer away from the functional layer, wherein the interdigitated electrode includes a plurality of electrode fingers; The acoustic waves emitted by the surface acoustic wave device during operation include surface acoustic waves and volume waves, with the surface waves propagating in 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 thickness of the second feature satisfy the following condition: The thickness of the second feature is determined based on the volume wave velocity and operating frequency of the material of the functional layer along the X direction. The second characteristic thickness satisfies the following equation: Wherein, the midline distance between two adjacent electrode fingers is P, and the bulk 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 volume wave velocity of the material of the functional layer along the X direction at the operating frequency.

23. The surface acoustic wave device according to claim 22, characterized in that, When the angle between the propagation direction of the acoustic wave excited by the interdigitated electrode and the first surface is equal to the second reinforcement angle γ, the volume wave in the functional layer is in a reinforced state; the wavelength λ of the volume wave of the acoustic wave excited by the interdigitated electrode propagating into the functional layer is... B2 The bulk wavelength is the wavelength of the functional layer in the enhanced state.

24. The surface acoustic wave device according to claim 23, characterized in that, The midline distance between two adjacent electrode fingers is P, and the second reinforcement angle is γ, which satisfies the following equation: Among them, V B2 Let f be the volume wave velocity within the functional layer, f be the operating frequency, and λ be the velocity of sound. B2 The second reinforcement angle γ is the bulk wavelength of the acoustic wave excited by the interdigital electrode that propagates into the functional layer, and satisfies: 0° < γ < 180°.

25. The surface acoustic wave device according to claim 22, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 feature thickness satisfy the following condition:

26. The surface acoustic wave device according to claim 22, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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.

27. The surface acoustic wave device according to claim 22, characterized in that, When the frequency of the surface acoustic wave excited by the interdigitated electrode 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 feature thickness satisfy the following condition:

28. The surface acoustic wave device according to any one of claims 22-27, 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 satisfies the condition that the thickness of the first feature is: The thickness of the first feature is determined based on the midline distance between two adjacent electrode fingers, the volume wave velocity of the piezoelectric layer along the X direction, and the operating frequency.

29. The surface acoustic wave device according to claim 28, characterized in that, The piezoelectric layer includes a piezoelectric crystal, and the volume wave velocity of the piezoelectric crystal along the X direction is V. b1 At the operating frequency, the bulk wavelength of the piezoelectric crystal along the X direction is λ1, and the first characteristic thickness satisfies the equation:

30. The surface acoustic wave device according to claim 29, characterized in that, The thickness of the piezoelectric layer satisfies the condition: 0.4P≤D y ≤0.8P.

31. The surface acoustic wave device according to claim 29, characterized in that, The thickness of the functional layer satisfies the condition: 0.2P≤D d ≤0.6P.

32. The surface acoustic wave device according to any one of claims 22-27, characterized in that, The material of the piezoelectric layer is anisotropic.

33. A radio frequency front-end module, characterized in that, Includes the surface acoustic wave device as described in any one of claims 1-32.

34. An electronic device, characterized in that, Includes the radio frequency front-end module as described in claim 33.

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