Elastic wave device and preparation method therefor

Abstract

Provided in the present invention are an elastic wave device and a preparation method therefor. By means of providing an upper functional layer, the heat dissipation capability and the heat dissipation efficiency of the elastic wave device can be effectively improved, and the temperature of the elastic wave device can be reduced, thereby enhancing the power tolerance of the elastic wave device and prolonging the service life of the elastic wave device; the propagation sound velocity of an elastic wave can be effectively improved, and the energy of the elastic wave can be effectively confined within a piezoelectric layer and the upper functional layer, such that the operating frequency and the quality factor of the elastic wave device can be improved, thereby achieving a high frequency and a low loss at a greater interdigital line width, and achieving the effect of significantly improving the power tolerance; a low-velocity curve and a velocity profile curve of the elastic wave can be effectively adjusted, thereby suppressing or weakening the excitation of a transverse stray mode; the excitation intensity and the excitation frequency of a longitudinal stray mode can be adjusted, the resonance intensity of longitudinal high-order clutter can be weakened, and the longitudinal high-order clutter is away from a target elastic wave, so as to obtain a higher out-of-band suppression and a cleaner out-of-band response; therefore, the performance of the elastic wave device can be comprehensively improved.

Description

Elastic wave device and preparation method thereof Technical Field

[0001] The invention belongs to the field of microelectronic devices and relates to an elastic wave device and a preparation method thereof. Background Art

[0002] The application scenarios of fifth-generation mobile communication (5G) technology are gradually expanding to smart cities, smart homes, environmental monitoring, autonomous driving, telemedicine, and other aspects, reshaping people's lifestyles and accelerating people's communication and interconnection. For mobile terminal devices, in order to simultaneously meet the needs of multiple generations of communication, the number of frequency bands that RF front-end modules need to support continues to grow. With the large-scale use of multi-input and output antenna array technology, the use of filters will increase significantly. However, in response to the needs of mobile device battery life and the development of micro base stations, the size of devices is gradually decreasing, necessitating the integration of multiple filter components on a small chip. Due to the intense heat generation of electronic devices during operation, in order to ensure stable signal transmission, the requirements for filter performance such as heat dissipation, power tolerance, out-of-band suppression, passband flatness, and band edge steepness are constantly increasing.

[0003] For elastic surface wave filter devices, their operating frequency depends on the elastic wave phase velocity and the interdigital linewidth. Since the sound velocity of elastic waves in traditional piezoelectric single crystals is relatively low, in order to realize high-frequency devices, the interdigital linewidth can only be continuously compressed. In addition, the thermal conductivity of piezoelectric single crystals is very low, so the heat dissipation performance of the filter device is poor, which will cause the heat generated by the electronic device to be unable to dissipate in time, resulting in a significant temperature increase of the device structure. At the same time, the frequency temperature drift coefficient of the piezoelectric single crystal is large. The temperature increase of the device will not only lead to poor stability of the passband response and inability to provide sufficient out-of-band suppression for the adjacent band, but also cause heavy cyclic stress shock to the narrow interdigital electrodes at high temperatures, which will cause serious damage to the interdigital electrodes, thereby leading to rapid failure of the filter device and reducing the stability and service life of the device.

[0004] To address these issues, currently used surface acoustic wave (SAW) device structures compensate for the frequency-temperature drift coefficient by coating the piezoelectric single crystal with silicon oxide, but this still fails to address the device's heat dissipation and operating frequency. Alternatively, heat dissipation is enhanced by combining the piezoelectric single crystal with a supporting substrate. For the latter, to constrain the frequency-temperature drift coefficient of the SAW energy compensation device, most proposed structures insert a low-acoustic-velocity layer between the piezoelectric single crystal and the supporting substrate, which weakens the substrate's heat dissipation and acoustic-velocity compensation capabilities. Therefore, research is needed to address the issues of SAW device heat dissipation, power handling, operating frequency, and in-band and out-of-band spurious modes.

[0005] Therefore, it is necessary to provide an elastic wave device and a method for preparing the same.

[0006] Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an elastic wave device and a method for preparing the same, so as to solve the performance problems faced by the elastic wave device in the prior art.

[0008] To achieve the above and other related objectives, the present invention provides an elastic wave device, comprising:

[0009] a supporting substrate;

[0010] a piezoelectric layer, the piezoelectric layer being located on the supporting substrate, and the slow shear wave speed of the supporting substrate being greater than the speed of the target mode propagating in the piezoelectric layer;

[0011] an upper functional layer, the upper functional layer being located on the piezoelectric layer, and the thermal conductivity of the upper functional layer being greater than the thermal conductivity of the piezoelectric layer and / or the slow shear wave speed of the upper functional layer being greater than the speed of the target mode;

[0012] An interdigital electrode is located on the upper functional layer.

[0013] Optionally, the thermal conductivity of the upper functional layer is more than 3 times the thermal conductivity of the piezoelectric layer; and the slow shear wave speed of the upper functional layer is more than 1.2 times the speed of the target mode.

[0014] Optionally, the crystal type of the upper functional layer includes single crystal or polycrystalline; the upper functional layer includes one or a combination of an aluminum nitride layer, a silicon carbide layer, a diamond layer, a diamond-like carbon layer, a silicon nitride layer, a sapphire layer, a magnesium oxide layer, an aluminum oxide layer, a silicon layer, a gallium nitride layer, a boron carbide layer and a boron nitride layer.

[0015] Optionally, when the elastic wave wavelength is λ, the thickness range of the piezoelectric layer is 0.03λ~λ; the thickness range of the upper functional layer is greater than 0.02λ and less than the thickness of the piezoelectric layer; the thickness range of the interdigital electrode is 0.02λ~0.12λ.

[0016] Optionally, the piezoelectric layer includes a lithium tantalate layer, a lithium niobate layer, a quartz layer, a potassium niobate layer, an aluminum nitride layer, a scandium-doped aluminum nitride layer, a zinc oxide layer, a lead zirconate titanate layer, a lead magnesium niobate titanate layer, a gallium nitride layer, a gallium oxide layer or a gallium arsenide layer.

[0017] Optionally, the supporting substrate includes a silicon carbide substrate, a diamond substrate, a diamond-like carbon substrate, a gallium nitride substrate, a boron carbide substrate, a boron nitride substrate or an aluminum nitride substrate; or the supporting substrate includes a base located at the bottom and a lower functional layer located at the top, and the base includes a silicon substrate, a quartz substrate or a sapphire substrate, and the lower functional layer includes one or a combination of a polysilicon layer, a silicon oxide layer, a fluorine-containing silicon oxide layer, a silicon oxynitride layer, an aluminum nitride layer, a tantalum pentoxide layer and a tellurium dioxide layer.

[0018] Optionally, the material of the interdigital electrodes includes one of copper, silver, gold, aluminum, platinum, nickel, molybdenum, tungsten, chromium and titanium, or an alloy thereof, and the interdigital electrodes include a single-layer structure or a stacked-layer structure.

[0019] Optionally, in the direction of sound wave propagation, reflective gate electrodes are further included on both sides of the interdigital electrodes.

[0020] Optionally, the target mode includes horizontal shear waves, thickness shear waves, longitudinal waves, high-order horizontal shear waves, high-order thickness shear waves or high-order longitudinal waves; and the elastic wave device includes an elastic wave resonator and / or an elastic wave filter.

[0021] The present invention also provides a method for preparing any of the above elastic wave devices, comprising the following steps:

[0022] providing a supporting substrate;

[0023] forming a piezoelectric layer on the supporting substrate;

[0024] forming an upper functional layer on the piezoelectric layer;

[0025] Interdigital electrodes are formed on the upper functional layer.

[0026] Optionally, the method for forming the piezoelectric layer includes physical vapor deposition, chemical vapor deposition, magnetron sputtering, bonding transfer, ion implantation exfoliation transfer or Czochralski crystal growth; the method for forming the upper functional layer includes physical vapor deposition, chemical vapor deposition, magnetron sputtering, thermal oxidation, bonding transfer, ion implantation exfoliation transfer or Czochralski crystal growth.

[0027] As described above, the elastic wave device and preparation method of the present invention, by providing an upper functional layer with high thermal conductivity, can effectively improve the heat dissipation capacity and heat dissipation efficiency of the elastic wave device, reduce the temperature of the elastic wave device, and thus enhance the power tolerance and service life of the elastic wave device. The high sound velocity upper functional layer and supporting substrate can effectively increase the propagation speed of the elastic wave and effectively confine the energy of the elastic wave within the piezoelectric layer and the upper functional layer, thereby improving the operating frequency and quality factor of the elastic wave device, thereby achieving high frequency and low loss at a larger interdigital linewidth, and significantly improving the power tolerance. The provision of the upper functional layer can effectively adjust the slow speed curve and velocity profile curve of the elastic wave, thereby suppressing or weakening the excitation of the transverse stray mode. The upper functional layer can adjust the excitation intensity and excitation frequency of the longitudinal stray mode, and can weaken the resonance intensity of the longitudinal high-order stray waves and keep them away from the target elastic wave to obtain higher out-of-band suppression and cleaner out-of-band response.

[0028] Therefore, the elastic wave device and the preparation method thereof of the present invention can comprehensively improve the performance of the elastic wave device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic structural diagram of an elastic wave device in Comparative Example 1 of the present invention.

[0030] FIG2 is a schematic structural diagram of an elastic wave device in Comparative Example 2 of the present invention.

[0031] FIG3 is a schematic structural diagram of an elastic wave device in Comparative Example 3 of the present invention.

[0032] FIG4 is a schematic diagram showing the structure of the elastic wave device in Example 1 of the present invention.

[0033] FIG5 is a schematic diagram showing the structure of the elastic wave device in Example 2 of the present invention.

[0034] FIG6 is a schematic diagram showing the structure of the elastic wave device in Example 3 of the present invention.

[0035] FIG7 shows a simulation diagram of the temperature distribution of the elastic wave device with upper functional layers of different thicknesses in the structure of Example 1 during stable operation.

[0036] FIG8 is a simulation diagram showing the temperature distribution of the elastic wave device in the structure of Comparative Example 1 during stable operation.

[0037] FIG9 is a simulation diagram showing the temperature distribution of the elastic wave device with upper functional layers of different thicknesses in the structure of Example 2 during stable operation.

[0038] FIG10 is a simulation diagram showing the temperature distribution of the elastic wave device in the structure of Comparative Example 2 during stable operation.

[0039] FIG11 is a simulation diagram showing the temperature distribution of the elastic wave device with upper functional layers of different thicknesses in the structure of Example 3 during stable operation.

[0040] FIG12 is a simulation diagram showing the temperature distribution of the elastic wave device in comparative example 3 during stable operation.

[0041] FIG13 is a schematic diagram showing a top view of the elastic wave device of the present invention.

[0042] FIG. 14 is a schematic top view of the elastic wave resonator with a reflective gate electrode according to the present invention.

[0043] FIG15 is a schematic diagram showing a top view of the elastic wave filter according to the present invention.

[0044] FIG16 shows a diagram of simulated admittance curves of excited horizontal shear waves in elastic wave devices corresponding to Example 2 and Comparative Example 2.

[0045] FIG17 is a graph showing a trend of a target elastic wave velocity versus the thickness of the upper functional layer of the elastic wave filter in Example 2 when the elastic wave wavelength λ is 1.2 μm.

[0046] FIG18 shows a graph showing the variation trend of the target elastic wave velocity of the elastic wave device corresponding to Example 2 and Comparative Example 2 with the thickness of the upper functional layer and the ratio of the piezoelectric layer thickness to the wavelength of the acoustic wave.

[0047] FIG19 is a graph showing a trend of the target elastic wave velocity versus the ratio of the piezoelectric layer thickness to the acoustic wave wavelength when the thickness of the upper functional layer of the elastic wave filter in Example 2 is 50 nm.

[0048] FIG20 shows a diagram of the simulated admittance curves of excited horizontal shear waves in the elastic wave devices corresponding to Example 3 and Comparative Example 3.

[0049] FIG21 is a graph showing a trend of a target elastic wave velocity versus the thickness of the upper functional layer of the elastic wave filter in Example 3 when the elastic wave wavelength λ is 1.2 μm.

[0050] FIG22 shows a graph showing the variation trend of the target elastic wave velocity of the elastic wave device corresponding to Example 3 and Comparative Example 3 with the ratio of the upper functional layer thickness and the piezoelectric layer thickness to the acoustic wave wavelength.

[0051] FIG23 shows a graph showing a trend of the target elastic wave velocity versus the ratio of the piezoelectric layer thickness to the acoustic wave wavelength for the elastic wave devices corresponding to Example 3 and Comparative Example 3 when the thickness of the upper functional layer is 50 nm.

[0052] FIG24 shows a slow velocity curve of the horizontal shear wave propagating through the elastic wave filter in Comparative Example 2. ...

[0053] FIG25 shows a comparison of the slow velocity curves of horizontal shear waves propagating through the elastic wave filters corresponding to Comparative Example 2 and Example 2. FIG.

[0054] FIG26 shows a simulated admittance curve corresponding to the horizontal shear wave propagating through the elastic wave filter in comparative example 2. FIG.

[0055] FIG27 shows a simulated admittance curve corresponding to the horizontal shear wave propagating through the elastic wave filter in Example 2. ...

[0056] FIG28 is a graph showing the slow velocity of the horizontal shear wave propagating through the elastic wave filter in Comparative Example 3. ...

[0057] FIG29 shows a comparison of slow velocity curves of horizontal shear waves propagating through elastic wave filters corresponding to comparative example 3 and example 3. FIG.

[0058] FIG30 shows a simulated admittance curve corresponding to the horizontal shear wave propagating through the elastic wave filter in comparative example 3. ...

[0059] FIG31 shows a simulated admittance curve corresponding to the horizontal shear wave propagating through the elastic wave filter in Example 3. ...

[0060] FIG32 shows a simulated graph of the longitudinal admittance corresponding to the horizontal shear wave propagating through the elastic wave filter in Example 3. ...

[0061] FIG33 shows a simulated graph of the longitudinal admittance corresponding to the horizontal shear wave propagating through the elastic wave filter in Example 3. FIG34 shows a simulated graph of the longitudinal admittance corresponding to the horizontal shear wave propagating through the elastic wave filter in Example 3.

[0062] FIG34 shows a test admittance curve corresponding to the horizontal shear wave propagating through the elastic wave filter in Example 1. ...

[0063] FIG35 shows a test admittance curve corresponding to the horizontal shear wave propagated by the elastic wave filter in comparative example 1. ...

[0064] FIG36 shows a test admittance curve corresponding to the horizontal shear wave propagating through the elastic wave filter in Example 1. ...

[0065] FIG37 shows a test admittance curve corresponding to the horizontal shear wave propagated by the elastic wave filter in comparative example 1. ...

[0066] Description of Reference Numerals

[0067] 100 Support substrate

[0068] 110 base

[0069] 200 Lower functional layer

[0070] 201 First lower functional layer

[0071] 202 Second lower functional layer

[0072] 300 piezoelectric layer

[0073] 400 Upper functional layer

[0074] 500 interdigitated electrodes

[0075] 600 reflective gate electrode

[0076] A Series Resonator

[0077] B Parallel Resonator DETAILED DESCRIPTION

[0078] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0079] For example, when describing the embodiments of the present invention, cross-sectional views of device structures may be partially enlarged to scale for ease of explanation. Furthermore, these schematic views are merely illustrative and should not limit the scope of the present invention. Furthermore, in actual manufacturing, three-dimensional dimensions, including length, width, and depth, should be included.

[0080] For convenience of description, spatially relative terms such as "under," "below," "below," "below," "over," and the like may be used herein to describe the relationship of one element or feature to other elements or features illustrated in the drawings. It will be understood that these spatially relative terms are intended to encompass orientations of the device in use or operation in addition to the orientation depicted in the drawings, and may include embodiments in which the first and second features are formed in direct contact, as well as embodiments in which additional features are formed between the first and second features so that the first and second features may not be in direct contact. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0081] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0082] As shown in Figure 4, the present invention provides an elastic wave device, which includes a supporting substrate 100, a piezoelectric layer 300, an upper functional layer 400 and an interdigitated electrode 500, wherein the piezoelectric layer 300 is located on the supporting substrate 100, and the slow shear wave sound velocity of the supporting substrate 100 is greater than the sound velocity of the target mode propagating in the piezoelectric layer 300; the upper functional layer 400 is located on the piezoelectric layer 300, and the thermal conductivity of the upper functional layer 400 is greater than the thermal conductivity of the piezoelectric layer 300 and / or the slow shear wave sound velocity of the upper functional layer 400 is greater than the sound velocity of the target mode; the interdigitated electrode 500 is located on the upper functional layer 400.

[0083] In the elastic wave device, the energy of the elastic wave is mainly concentrated in the piezoelectric layer 300, the upper functional layer 400, and the interdigitated electrodes 500. The heat generated by the excitation, propagation, and vibration of the elastic wave can be transmitted to the outside through two channels, the upper functional layer 400 with high thermal conductivity and the supporting substrate 100, effectively improving the heat dissipation capacity. The high sound velocity of the upper functional layer 400 can effectively increase the propagation speed of the elastic wave. The slow velocity curve of the elastic wave is determined by a combination of parameters such as the material, cut type, and thickness of each layer in the elastic wave device. The upper functional layer 400 can adjust the slow velocity curve of the elastic wave to be flatter. The flatter slow velocity curve can effectively reduce the transverse stray modes in the passband of the elastic wave resonator and elastic wave filter. The upper functional layer 400 has the characteristics of regulating the equivalent physical properties and anisotropy of the elastic wave device, can adjust the velocity profile curve of the target elastic wave in the transverse cavity direction, can effectively eliminate or weaken the transverse stray modes of the elastic wave, can effectively eliminate the longitudinal stray modes of the elastic wave, or increase the frequency spacing between the stray modes and the main mode.

[0084] Therefore, by providing the upper functional layer 400 with high thermal conductivity, the heat dissipation capacity and heat dissipation efficiency of the elastic wave device can be effectively improved, the temperature of the elastic wave device can be reduced, and the power tolerance and service life of the elastic wave device can be enhanced. The high sound velocity of the upper functional layer 400 and the supporting substrate 100 can effectively increase the propagation speed of the elastic wave and effectively confine the energy of the elastic wave within the piezoelectric layer 300 and the upper functional layer 400, thereby increasing the operating frequency and quality factor of the elastic wave device, thereby achieving high frequency and low loss at a larger interdigital linewidth, and significantly improving the power tolerance. The provision of the upper functional layer 400 can effectively adjust the slow speed curve and velocity profile curve of the elastic wave, thereby suppressing or weakening the excitation of the transverse stray mode. The upper functional layer 400 can adjust the excitation intensity and excitation frequency of the longitudinal stray mode, weaken the resonance intensity of the longitudinal high-order stray wave, and keep it away from the target elastic wave to obtain higher out-of-band suppression and cleaner out-of-band response, thereby comprehensively improving the performance of the elastic wave device.

[0085] As an example, the upper functional layer 400 may be a high thermal conductivity material, a high sound speed material, or a material with both high thermal conductivity and high sound speed, wherein the thermal conductivity of the upper functional layer 400 may be more than 3 times the thermal conductivity of the piezoelectric layer 300, such as 3 times, 5 times, 8 times, etc.; the slow shear wave sound speed of the upper functional layer 400 may be more than 1.2 times the sound speed of the target mode, such as 1.2 times, 1.5 times, 2 times, etc., and can be specifically set according to needs.

[0086] As an example, the crystal type of the upper functional layer 400 may include single crystal or polycrystalline, and the crystal direction is not limited.

[0087] As an example, the upper functional layer 400 may include one or a combination of an aluminum nitride layer, a silicon carbide layer, a diamond layer, a diamond-like carbon layer, a silicon nitride layer, a sapphire layer, a magnesium oxide layer, an aluminum oxide layer, a silicon layer, a gallium nitride layer, a boron carbide layer and a boron nitride layer.

[0088] Specifically, the upper functional layer 400 is formed on the upper surface of the piezoelectric layer 300 in a complete, uniform, planar shape covering the surface of the piezoelectric layer 300, as shown in FIG13 .

[0089] As an example, when the wavelength of the elastic wave is λ, the thickness range of the piezoelectric layer 300 may be 0.03λ~λ, such as 0.03λ, 0.1λ, 0.5λ, 0.8λ, λ, etc.; the thickness range of the upper functional layer 400 may be greater than 0.02λ and less than the thickness of the piezoelectric layer 300, such as 0.5λ, 0.8λ, etc.; the thickness range of the interdigitated electrode 500 may be 0.02λ~0.12λ, such as 0.02λ, 0.04λ, 0.08λ, 0.1λ, 0.12λ, etc.

[0090] As an example, the piezoelectric layer 300 may include a lithium tantalate layer, a lithium niobate layer, a quartz layer, a potassium niobate layer, an aluminum nitride layer, a scandium-doped aluminum nitride layer, a zinc oxide layer, a lead zirconate titanate layer, a lead magnesium niobate titanate layer, a gallium nitride layer, a gallium oxide layer, or a gallium arsenide layer.

[0091] As an example, the support substrate 100 can be a high-acoustic-velocity support substrate 100, i.e., the slow shear wave velocity of the support substrate 100 is greater than the acoustic velocity of the target mode propagating in the piezoelectric layer 300. The high-acoustic-velocity support substrate 100 can include a silicon carbide substrate, a diamond substrate, a diamond-like carbon substrate, a gallium nitride substrate, a boron carbide substrate, a boron nitride substrate, or an aluminum nitride substrate. The type and thickness of the support substrate 100 can be flexibly selected and are not excessively limited herein.

[0092] In another embodiment, the supporting substrate 100 may also include a base 110 located at the bottom and a lower functional layer 200 located at the top. As shown in Figure 5, the base 110 may include a silicon substrate, a quartz substrate or a sapphire substrate, and the lower functional layer 200 may include one or a combination of a polysilicon layer, a silicon oxide layer, a fluorine-containing silicon oxide layer, a silicon oxynitride layer, an aluminum nitride layer, a tantalum pentoxide layer and a tellurium dioxide layer.

[0093] Specifically, by combining the substrate 110 having a normal high acoustic velocity with the lower functional layer 200 to effectively reflect the target acoustic wave energy, this combination can replace the supporting substrate 100 having a high acoustic velocity. The lower functional layer 200 can also simultaneously have functions such as adsorbing free carriers within the material and interface of the contact layer, and / or reflecting and constraining elastic wave energy, and / or compensating for temperature stability. The lower functional layer 200 can be a single-layer film formed by a single layer of material, or a composite film structure composed of multiple layers of material. As shown in Figure 6, the lower functional layer 200 can be composed of a first lower functional layer 201 and a second lower functional layer 202.

[0094] The type and thickness of the substrate 110 can be flexibly selected without any excessive restrictions. The type, number of layers, and thickness of the lower functional layer 200 can be flexibly selected without any excessive restrictions.

[0095] As an example, the material of the interdigital electrode 500 may include one of copper, silver, gold, aluminum, platinum, nickel, molybdenum, tungsten, chromium and titanium or an alloy thereof, and the interdigital electrode 500 may include a single-layer structure or a stacked-layer structure.

[0096] Specifically, the thickness and stacking structure of the interdigitated electrode 500 depend on the specifically designed metal material and structure, and are also related to the specifically excited and utilized elastic wave frequency band. The type, number of layers, and thickness of the interdigitated electrode 500 can be flexibly selected and are not excessively restricted here.

[0097] Furthermore, it may also include reflective gate electrodes 600 located on both sides of the interdigitated electrode 500 to reflect the acoustic wave energy through the reflective gate electrode 600, thereby reducing the leakage of the acoustic wave in the horizontal propagation direction, as shown in Figure 14, wherein the metal material, stacking structure and electrode thickness used by the interdigitated electrode 500 and the reflective gate electrode 600 can be the same, or can be set separately.

[0098] As an example, the target mode may include horizontal shear waves, thickness shear waves, longitudinal waves, high-order horizontal shear waves, high-order thickness shear waves, or high-order longitudinal waves; the elastic wave device may include an elastic wave resonator and / or an elastic wave filter.

[0099] Specifically, as shown in Figure 15, an elastic wave filter is composed of a series elastic wave resonator A and a parallel elastic wave resonator B. In the elastic wave filter, the elastic wave resonators may all contain the upper functional layer 400, or only some of the elastic resonators may contain the upper functional layer 400. No specific restrictions are imposed here.

[0100] The present invention further provides a method for preparing the elastic wave device. The elastic wave devices can all be prepared using this method, but are not limited thereto. The preparation of the elastic wave device can include the following steps:

[0101] providing a supporting substrate 100;

[0102] forming a piezoelectric layer 300 on the supporting substrate;

[0103] forming an upper functional layer 400 on the piezoelectric layer 300;

[0104] Interdigital electrodes 500 are formed on the upper functional layer 400 .

[0105] Specifically, the method for forming the piezoelectric layer 300 may include but is not limited to physical vapor deposition, chemical vapor deposition, magnetron sputtering, bonding transfer, ion implantation stripping transfer or Czochralski crystal growth; the method for forming the upper functional layer 400 may include but is not limited to physical vapor deposition, chemical vapor deposition, magnetron sputtering, thermal oxidation, bonding transfer, ion implantation stripping transfer or Czochralski crystal growth; the method for forming the interdigital electrodes 500 on the upper functional layer 400 may include but is not limited to electron beam evaporation, thermal evaporation, magnetron sputtering, etc.; if patterning of the upper functional layer 400 is to be achieved, the patterning method may be to first pattern the upper functional layer 400 crystal (such as Alternatively, the upper functional layer 400 may be patterned and photolithographically patterned on the piezoelectric layer 300, and then the upper functional layer 400 may be patterned and transferred to the upper surface of the piezoelectric layer 300. Alternatively, the upper functional layer 400 may be patterned and photolithographically patterned on the upper surface of the piezoelectric layer 300, and then the upper functional layer 400 may be patterned and photolithographically patterned on the piezoelectric layer 300, and then the upper functional layer 400 may be peeled off to transfer the pattern to the upper functional layer 400. Alternatively, the upper functional layer 400 may be directly formed on the piezoelectric layer 300, and then patterned and ion-implanted to cause local damage to the piezoelectric layer 300, making it easier to corrode or etch, and then locally wet-etched or dry-etched. Methods for forming the lower functional layer 200 on the substrate 110 include, but are not limited to, physical vapor deposition, chemical vapor deposition, magnetron sputtering, thermal oxidation, bonding transfer followed by grinding and polishing to a target thickness, ion implantation followed by peeling transfer, and Czochralski crystal growth.

[0106] The present application is further introduced and illustrated below through specific embodiments.

[0107] Comparative Example 1

[0108] As shown in FIG1 , a silicon carbide (SiC) substrate is used as the supporting substrate 100, an X-tangent lithium niobate (LiNbO 3 ) layer is used as the piezoelectric layer 300, and metal Al is used as the interdigital electrode 500 to excite and generate a horizontal shear surface acoustic wave (SH-SAW) mode.

[0109] Comparative Example 2

[0110] As shown in FIG2 , the structure uses sapphire as the substrate 110 , a silicon oxide (SiO 2 ) layer as the lower functional layer 200 , a 42° YX LiTaO 3 layer as the piezoelectric layer 300 , and metal Al as the interdigital electrode 500 to generate the SH-SAW mode.

[0111] Comparative Example 3

[0112] As shown in FIG3 , the structure uses high-resistance silicon (Si) as the substrate 110, a polysilicon layer as the first lower functional layer 201, and a SiO2 layer as the second lower functional layer 202. That is, the lower functional layer 200 adopts a composite film layer, a 42° YX LiTaO3 layer as the piezoelectric layer 300, and metal Al as the interdigital electrode 500, which excites and generates the SH-SAW mode.

[0113] Example 1

[0114] The structure shown in FIG. 4 is different from that of Comparative Example 1 in that the elastic wave resonator has an upper functional layer 400 .

[0115] Example 2

[0116] The structure shown in FIG. 5 is different from that of Comparative Example 2 in that the elastic wave resonator has an upper functional layer 400 .

[0117] Example 3

[0118] The structure shown in FIG. 6 differs from that of Comparative Example 3 in that the elastic wave resonator has an upper functional layer 400 .

[0119] Example 1

[0120] The heat dissipation performance of the elastic wave resonator of this embodiment is described by comparing the steady-state temperature distributions of Figures 1 and 4. Compared with Figure 1, Figure 4 shows that the elastic wave resonator has an upper functional layer, AlN, with high thermal conductivity.

[0121] During stable operation, the interdigitated electrodes and piezoelectric layer in the device structure are the main heat-generating areas. Therefore, the interdigitated electrodes and the device surface are the locations with the highest temperature rise in the structure. The interdigitated electrodes are also the components most susceptible to device failure due to acoustic migration of metal atoms caused by high temperature and heavy cycle stress.

[0122] Among them, the thickness of the LiNbO3 layer is 400nm, the thickness of the Al interdigital electrode is 150nm, the interdigital period is 1.6μm, the duty cycle is 0.5, the room temperature is defined as 293.15K, and the temperature after the increase minus the room temperature is defined as the temperature increase (ΔT).

[0123] Figure 7 shows the steady-state temperature distribution of the elastic wave resonator in Example 1 for AlN layer thicknesses of 20nm, 50nm, 100nm, and 200nm. Because different device parameter settings can lead to different temperature rise simulation results, only the maximum temperature rise of the interdigital electrodes in the device structure shown in Comparative Example 1 and the structure shown in Example 1 is compared here, without evaluating the absolute temperature rise of any particular device structure. The steady-state temperature distribution shows that the interdigital electrodes are the hottest part of the entire device. Figure 7 extracts the maximum temperature rise of the interdigital electrodes for different structures.

[0124] As can be seen from FIG8 , in steady-state operation, in the device structure without an upper functional layer in Comparative Example 1, the temperature rise of the interdigital electrodes is 48K, that is, compared with the room temperature when not working, the temperature of the interdigital electrodes of the stably working device will increase by 48K.

[0125] Comparing Example 1 with Comparative Example 1, as shown in FIG7 (a), when the AlN layer is 20 nm, the maximum temperature rise of the interdigital electrode is 11.5 K, which is reduced to 1 / 4 of that in Comparative Example 1; as shown in FIG7 (b) to (d), when the thickness of the AlN layer gradually increases to 50 nm, 100 nm and 200 nm, the maximum temperature rise is further reduced to 4.8 K, 3.0 K and 0.3 K, respectively, which are 1 / 10, 1 / 16 and 1 / 160 of that in Comparative Example 1, respectively, showing efficient heat dissipation capability, indicating that when there is an upper functional layer with high thermal conductivity, an efficient high thermal conductivity heat dissipation plane and channel can be provided for the piezoelectric layer with lower thermal conductivity, thereby greatly improving the heat dissipation performance of the device, thereby reducing the operating temperature of the device, making the working environment of the interdigital electrode more friendly, lowering the temperature of the high-frequency vibration of the interdigital, and slowing down and reducing the acoustic migration and rupture of the electrode atoms, thereby effectively improving the power tolerance and the working life of the device.

[0126] Furthermore, as the thickness of the upper functional layer increases, the maximum temperature rise of the interdigital electrodes gradually decreases. Therefore, the thickness of the upper functional layer can be selected based on actual needs. When the AlN upper functional layer is only 20nm thick, the maximum temperature rise of the interdigital electrodes can be reduced to 1 / 4 of that in Comparative Example 1, achieving a significant heat dissipation effect and effectively improving the power capacity of the device.

[0127] Example 2

[0128] The heat dissipation performance of the elastic wave resonator of this embodiment is described by comparing the steady-state temperature distributions of Figures 2 and 5. Compared with Figure 2, the elastic wave resonator in Figure 5 has an upper functional layer of AlN with high thermal conductivity.

[0129] Among them, the thickness of the LiTaO3 layer is 400nm, the thickness of the SiO2 layer is 500nm, the thickness of the Al interdigital electrode is 150nm, the interdigital period is 1.6μm, the duty cycle is 0.5, the room temperature is defined as 293.15K, and the temperature after increase minus the room temperature is defined as the temperature increase (ΔT).

[0130] Figure 9 shows the steady-state temperature distributions of the elastic wave resonator in Example 2 for AlN layers of varying thicknesses: 20nm, 50nm, 100nm, and 200nm. Because different device parameter settings can lead to different temperature rise simulation results, only the maximum temperature rise of the interdigital electrodes in the device structures shown in Comparative Example 1 and Example 1 is compared here, without evaluating the absolute temperature rise of any particular device structure. Figure 9 extracts the maximum temperature rise of the interdigital electrodes for each structure.

[0131] As can be seen from Figure 10, in steady-state operation, in the device structure without an upper functional layer in Comparative Example 2, the temperature rise of the interdigital electrodes is 260K, that is, compared with the room temperature when not working, the temperature of the interdigital electrodes of the stably operating device will increase by 260K.

[0132] Comparing Example 2 with Comparative Example 2, as shown in FIG9 (a), when the AlN layer is 20 nm, the maximum temperature rise of the interdigital electrodes is 78 K, which is reduced to 1 / 3 of that in Comparative Example 2; as shown in FIG9 (b) to (d), when the thickness of the AlN layer gradually increases to 50 nm, 100 nm and 200 nm, the maximum temperature rise is further reduced to 43 K, 24 K and 6 K, respectively, which are 1 / 6, 1 / 10 and 1 / 40 of that in Comparative Example 2, respectively, demonstrating efficient heat dissipation capability. This indicates that in the presence of an upper functional layer with high thermal conductivity, an efficient high thermal conductivity heat dissipation plane and channel can be provided for the piezoelectric layer with lower thermal conductivity, thereby greatly improving the heat dissipation performance of the device, thereby reducing the operating temperature of the device, making the working environment of the interdigital electrodes more friendly, lowering the temperature of the high-frequency vibration of the interdigital electrodes, and slowing down and reducing the acoustic migration and rupture of the electrode atoms, thereby effectively improving the power tolerance and the service life of the device.

[0133] Furthermore, as the thickness of the upper functional layer increases, the maximum temperature rise of the interdigital electrodes gradually decreases. Therefore, the thickness of the upper functional layer can be selected based on actual needs. When the AlN layer is only 20nm thick, the maximum temperature rise of the interdigital electrodes can be reduced to one-third of that in Comparative Example 2, achieving a significant heat dissipation effect and effectively improving the power capacity of the device.

[0134] Example 3

[0135] The heat dissipation performance of the elastic wave resonator of this embodiment is described by comparing the steady-state temperature distributions of Figures 3 and 6. Compared with Figure 3, Figure 6 shows that the elastic wave resonator has an upper functional layer, AlN, with high thermal conductivity.

[0136] Among them, the thickness of the LiTaO3 layer is 400nm, the thickness of SiO2 is 500nm, the thickness of the polysilicon layer is 1μm, the thickness of the Al interdigital electrode is 150nm, the interdigital period is 1.6μm, the duty cycle is 0.5, the room temperature is defined as 293.15K, and the temperature after increase minus the room temperature is defined as the temperature increase (ΔT).

[0137] Figure 11 shows the steady-state temperature distributions corresponding to the elastic wave resonator structure in Example 3 with different AlN layer thicknesses: 20nm, 50nm, 100nm, and 200nm. Because different device parameter settings can lead to different temperature rise simulation results, only the maximum temperature rise of the interdigital electrodes in the device structures shown in Comparative Example 3 and Example 3 is compared here, without evaluating the absolute temperature rise of each device structure individually. Figure 11 extracts the maximum temperature rise of the interdigital electrodes in different structures.

[0138] As can be seen from Figure 12, in steady-state operation, in the device structure without an upper functional layer in Comparative Example 3, the temperature rise of the interdigital electrodes is 60K, that is, compared with the room temperature when not working, the temperature of the interdigital electrodes of the stably operating device will increase by 60K.

[0139] Comparing Example 3 with Comparative Example 3, as shown in (a) of FIG11 , when the AlN layer is 20 nm, the maximum temperature rise of the interdigital electrodes is reduced to 1 / 2 of that of Comparative Example 3, with a maximum temperature rise of only 38 K. As shown in (b) to (d) of FIG11 , when the thickness of the AlN layer gradually increases to 50 nm, 100 nm, and 200 nm, the maximum temperature rise is further reduced to 18 K, 3 K, and 0.9 K, respectively, which are 1 / 3, 1 / 20, and 1 / 70 of that of Comparative Example 3, respectively, demonstrating efficient heat dissipation capability. This indicates that when an upper functional layer with high thermal conductivity is present, an efficient high thermal conductivity heat dissipation plane and channel can be provided for the piezoelectric layer with lower thermal conductivity, thereby greatly improving the heat dissipation performance of the device. This reduces the operating temperature of the device, makes the working environment of the interdigital electrodes more friendly, lowers the temperature of the high-frequency vibration of the interdigital electrodes, and slows down and reduces the acoustic migration and rupture of the electrode atoms, thereby effectively improving the power tolerance and the service life of the device.

[0140] Furthermore, as the thickness of the upper functional layer increases, the maximum temperature rise of the interdigital electrodes gradually decreases. Therefore, the thickness of the upper functional layer can be adjusted based on actual needs. When the AlN layer is only 20 nm, the maximum temperature rise of the interdigital electrodes is reduced to half that of Comparative Example 3, demonstrating a significant heat dissipation effect.

[0141] Example 4

[0142] FIG13 shows a schematic diagram of the top-down structure of the elastic wave device, that is, the upper functional layer can evenly and completely cover the surface of the piezoelectric layer to ensure that the upper functional layer regulates the performance of the resonant body for elastic wave excitation and transmission, and accelerates heat dissipation.

[0143] FIG14 is a schematic diagram showing a top view of an elastic wave resonator having a reflective gate electrode.

[0144] FIG15 is a top view schematic diagram of an elastic wave filter. The filter in the figure is an electronic device composed of series resonators and parallel resonators connected in cascade via a circuit. Since the frequency of the series resonator is relatively high and the power it withstands is relatively large, in order to ensure the finger line width of the series resonator, its elastic wave sound velocity can be increased by means of an upper functional layer. The heat dissipation of the elastic wave filter is accelerated, which is beneficial to improving the power tolerance of high-frequency filter devices. Taking the elastic wave filter shown in FIG15 (b) as an example, the central resonator has the highest operating frequency, so only the upper functional layer can be set for it to further increase the sound velocity, facilitate reducing the finger line width, and enhance heat dissipation. The specific structure of the series resonator and the parallel resonator can be selected according to specific needs.

[0145] Example 5

[0146] The improvement in acoustic velocity and resonant frequency performance of the elastic wave resonator of this embodiment is described in conjunction with Figures 2 and 5. Compared with Figure 2, the elastic wave resonator in Figure 5 has an upper functional layer of AlN.

[0147] Among them, the thickness of the LiTaO3 layer is 360nm, the thickness of the SiO2 layer is 400nm, the thickness of the Al interdigital electrode is 110nm, the interdigital period is 1.2μm, the duty cycle is 0.5, the thickness of the AlN layer is 20nm, and the target mode is SH-SAW. The simulated admittance curves of the resonator unit model are compared, and the resonant frequency point and sound velocity are extracted.

[0148] FIG16 shows the frequency response simulation results of elastic wave resonators corresponding to the structures of Example 2 and Comparative Example 2, where (a) corresponds to the structure of Example 2 and (b) corresponds to the structure of Comparative Example 2.

[0149] From the comparison of the simulation results of (a) and (b) in Figure 16, it can be seen that the resonant frequency of the elastic wave resonator corresponding to Example 2 is 3268MHz, and the sound speed is 3922m / s; the resonant frequency corresponding to Comparative Example 2 is 3134MHz, and the sound speed is 3760m / s, and the sound speed is increased by 160m / s. Therefore, under the same finger line width, the frequency is increased by 134MHz, which shows the effect of the AlN layer on the improvement of the sound speed of the acoustic wave. The improvement in sound speed means that to achieve the same operating frequency, the line width of the device structure of Example 2 is larger, which helps to increase the finger width, relax the process requirements, reduce resistance loss, and enhance power capacity. For the production process with a fixed line width, the operating frequency of the device structure of Example 2 is relatively higher, which is suitable for the setting and application of high-frequency devices. Therefore, compared with Comparative Example 2, the device structure of Example 2 has a beneficial effect in improving the device frequency and sound speed.

[0150] Example 6

[0151] The acoustic velocity and resonant frequency performance of the elastic wave resonator of this embodiment are described in conjunction with Figure 2 and Figure 5. Compared with Figure 2, the elastic wave resonator in Figure 5 has an upper functional layer of AlN.

[0152] Among them, the thickness of the LiTaO3 layer is 360nm, the thickness of the SiO2 layer is 400nm, the thickness of the Al interdigital electrode is 110nm, the interdigital period is 1.2μm, and the duty cycle is 0.5. The sound velocity change trends of the target mode SH-SAW in the device structures of Figure 2 and Figure 5 are compared. Here, the sound velocity is the sound velocity corresponding to the resonant frequency point.

[0153] FIG17 shows the acoustic velocity variation trend of the target mode SH-SAW in the device structure of the elastic wave resonator corresponding to Comparative Example 2 and Example 2 when the wavelength λ is determined to be 1.2 μm and the AlN layer thickness is 20 nm, 50 nm, 100 nm, and 200 nm.

[0154] First, at a certain wavelength, compared with the structure of Comparative Example 2, the high-sound-velocity AlN layer significantly improves the sound velocity of the target elastic wave SH-SAW, reflecting the improvement and effective regulation of the elastic wave sound velocity by the high-sound-velocity upper functional layer; second, with the increase of the thickness of the AlN layer, the elastic wave sound velocity increases significantly, thereby being able to relax the manufacturing process requirements of the line width when the frequency is determined by the interdigital line width; and under the same line width requirements, this device structure can obtain a higher elastic wave operating frequency.

[0155] In addition, it can be seen from FIG17 that the sound velocity enhancement effect of the AlN layer with a thickness of 20 nm is already very significant. In practice, when setting the thickness of the structural layer, the thickness of the AlN layer can be set according to the target elastic wave sound velocity or frequency.

[0156] FIG18 shows the acoustic velocity enhancement of AlN layers of different thicknesses for the elastic wave resonators corresponding to Comparative Example 2 and Example 2 at multiple piezoelectric layer thickness / acoustic wave wavelength ratios.

[0157] First, for Comparative Example 2, as the piezoelectric layer thickness / acoustic wave wavelength ratio decreases, the elastic wave velocity increases rapidly, demonstrating a strong dispersion characteristic. However, when the high-acoustic-velocity AlN layer is present, as in the structure described in Example 2, the velocity dispersion characteristic remains. As the piezoelectric layer thickness / acoustic wave wavelength ratio decreases, the elastic wave velocity increases rapidly, and the velocity-enhancing effect is maintained at all piezoelectric layer thickness / acoustic wave wavelength ratios (hereinafter referred to as "thickness-wavelength ratio"). This demonstrates the universality of the AlN layer covering the piezoelectric layer surface in increasing the elastic wave velocity at all thickness-wavelength ratios, while maintaining the dispersion characteristic of the acoustic wave velocity in the structure without invalidating the dispersion effect.

[0158] Secondly, when the AlN layer is 20nm, the acoustic velocity of the acoustic wave in the structure of Example 2 increases to 1.05 times that of Comparative Example 2; when the AlN layer is 50nm, the acoustic velocity increases to 1.08 times that of Comparative Example 2; when the AlN layer is 100nm, the acoustic velocity increases to 1.13 times that of Comparative Example 2; and when the AlN layer is 200nm, the acoustic velocity increases to 1.17 times that of Comparative Example 2. For the device structure of Example 2, at any thickness-to-wavelength ratio, the elastic wave acoustic velocity increases more significantly with increasing AlN layer thickness. This exponential increase in acoustic velocity means that to achieve the same operating frequency, the line width of the device structure of Example 2 can be expanded exponentially, which helps to increase the interdigital width, relax process requirements, reduce resistance losses, and enhance power capacity. For a production process with a fixed line width, the operating frequency of the device structure of Example 2 can be increased exponentially. Therefore, compared to Comparative Example 2, the device structure of Example 2 has beneficial effects in improving device frequency and acoustic velocity, helping to promote the development of high-frequency devices.

[0159] FIG19 is an example of FIG18 when the thickness of the AlN layer is 50 nm, showing the trend of the change of the elastic wave speed with the ratio of the piezoelectric film thickness to the acoustic wave wavelength when the thickness of the AlN layer is determined.

[0160] When the thickness of the AlN layer in the structure of Example 2 is 50nm, the elastic wave speed is generally increased by 1.08 times, which means that for the two structures to achieve the same operating frequency, the line width of the device structure of Example 2 can be relaxed to 1.08 times that of Comparative Example 2. This helps to increase the interdigital width, reduce process difficulty and resistance loss, and at the same time enhance the electrode quality, thereby improving power capacity. When considering the fixed line width, the operating frequency of the device structure of Example 2 can be increased to 1.08 times that of Comparative Example 2. Therefore, compared with Comparative Example 2, the device structure of Example 2 has a strong beneficial effect in improving device frequency and speed of sound.

[0161] Example 7

[0162] The improvement in acoustic velocity and resonant frequency performance of the elastic wave resonator of this embodiment is described in conjunction with Figure 3 and Figure 6. Compared with Figure 3, the elastic wave resonator in Figure 6 has an upper functional layer of AlN.

[0163] Among them, the thickness of the LiTaO3 layer is 360nm, the thickness of the SiO2 layer is 400nm, the thickness of the polysilicon is 1μm, the thickness of the Al interdigital electrode is 110nm, the interdigital period is 1.2μm, the duty cycle is 0.5, the thickness of the AlN layer is 20nm, and the target mode is SH-SAW. The simulated admittance curves of the resonator unit model are compared, and the resonant frequency point and sound velocity are extracted.

[0164] Refer to the comparison of simulation results of (a) and (b) in Figure 20, where (a) corresponds to the structure of Example 3 and (b) corresponds to the structure of Example 3.

[0165] From the comparison of the simulation results of (a) and (b) in Figure 20, it can be seen that the resonant frequency of the elastic wave resonator corresponding to Example 3 is 3256MHz, and the sound speed is 3907m / s; the resonant frequency of the elastic wave resonator corresponding to Comparative Example 3 is 3126MHz, and the sound speed is 3751m / s, which is an increase of 156m / s in sound speed. At the same interdigital line width, the frequency is increased by 130MHz, indicating the effect of the AlN layer on the sound speed of the acoustic wave. The increase in sound speed means that to achieve the same operating frequency, the line width of the device structure of Example 3 is larger, which helps to increase the interdigital width, relax process requirements, reduce resistance loss, and enhance power capacity. For a production process with a fixed line width, the operating frequency of the device structure of Example 3 is relatively higher, which is suitable for the setting and application of high-frequency devices. Therefore, compared with Comparative Example 3, the device structure of Example 3 has a beneficial effect in improving the device frequency and sound speed.

[0166] Example 8

[0167] The improvement in acoustic velocity and resonant frequency performance of the elastic wave resonator of this embodiment is described in conjunction with Figure 3 and Figure 6. Compared with Figure 3, the elastic wave resonator in Figure 6 has an upper functional layer of AlN.

[0168] Among them, the thickness of the LiTaO3 layer is 360nm, the thickness of the SiO2 layer is 400nm, the thickness of the polysilicon is 1μm, the thickness of the Al interdigital electrode is 110nm, the interdigital period is 1.2μm, and the duty cycle is 0.5. The sound velocity change trends of the target mode SH-SAW in the device structures of Figures 3 and 6 are compared. Here, the sound velocity is the sound velocity corresponding to the resonant frequency point.

[0169] FIG21 shows the acoustic velocity change trend of the target mode SH-SAW in the device structure of the elastic wave resonator corresponding to Comparative Example 3 and Example 3 at a certain wavelength of λ of 1.2 μm and AlN layer thicknesses of 20 nm, 50 nm, 100 nm, and 200 nm.

[0170] First, at a certain wavelength, compared with the structure of Comparative Example 3, the high-acoustic-velocity AlN layer significantly improves the acoustic velocity of the target elastic wave SH-SAW, reflecting the regulation and improvement of the acoustic velocity of the elastic wave by the high-acoustic-velocity upper functional layer; second, as the AlN thickness increases, the elastic wave acoustic velocity increases more significantly, thereby relaxing the manufacturing process requirements of the line width when the frequency is determined by the interdigital line width; and under the same line width requirements, this device structure can achieve a higher elastic wave operating frequency.

[0171] In addition, it can be seen from FIG21 that the sound velocity enhancement effect of the AlN layer with a thickness of 20 nm is already very significant. In practice, when setting the thickness of the structural layer, the thickness of the AlN layer can be set according to the target elastic wave sound velocity or frequency.

[0172] FIG22 shows the acoustic velocity enhancement of AlN layers of different thicknesses for the elastic wave resonators corresponding to Comparative Example 3 and Example 3 at multiple ratios of the piezoelectric layer thickness to the acoustic wave wavelength.

[0173] First, in Comparative Example 3, as the piezoelectric layer thickness / acoustic wave wavelength ratio decreases, the elastic wave velocity increases rapidly, demonstrating a strong dispersion characteristic. However, when the high-acoustic-velocity AlN layer is present, as in the structure described in Example 3, the velocity dispersion characteristic remains. As the thickness-to-wavelength ratio decreases, the elastic wave velocity increases rapidly, and the velocity-enhancing effect persists at all thickness-to-wavelength ratios. This demonstrates the universality of the AlN layer's increased velocity across all thickness-to-wavelength ratios, while maintaining the dispersion characteristic of the acoustic wave velocity in the structure without negating the dispersion effect.

[0174] Secondly, when the AlN layer is 20nm, the acoustic velocity of the acoustic wave in the structure of Example 3 increases to 1.05 times that of Comparative Example 3; when the AlN layer is 50nm, the acoustic velocity increases to 1.08 times that of Comparative Example 3; when the AlN layer is 100nm, the acoustic velocity increases to 1.13 times that of Comparative Example 3; and when the AlN layer is 200nm, the acoustic velocity increases to 1.17 times that of Comparative Example 3. For the device structure of Example 3, at any thickness-to-wavelength ratio, the elastic wave acoustic velocity increases more significantly with the increase in the thickness of the AlN layer. The exponential increase in acoustic velocity means that to achieve the same operating frequency, the line width of the device structure of Example 3 can be relaxed exponentially, which helps to increase the interdigital width, relax process requirements, reduce resistance loss, and enhance power capacity. For a production process with a fixed line width, the operating frequency of the device structure of Example 3 can be increased exponentially. Therefore, compared with Comparative Example 3, the device structure of Example 3 has a beneficial effect in improving device frequency and acoustic velocity.

[0175] FIG23 is an example of FIG22 when the thickness of the AlN layer is 50 nm, showing the trend of the change of the elastic wave speed with the ratio of the piezoelectric film thickness to the acoustic wave wavelength when the thickness of the AlN layer is determined.

[0176] When the thickness of the AlN layer in the Example 3 structure is 50nm, the elastic wave speed generally increases by 1.08 times. This means that to achieve the same operating frequency for both structures, the line width of the Example 3 device structure can be relaxed to 1.08 times that of the Comparative Example 3. This helps to increase the interdigital width, reduce process difficulty and resistance loss, and enhance electrode quality, thereby increasing power capacity. When considering the fixed line width, the operating frequency of the Example 3 device structure can be increased to 1.08 times that of the Comparative Example 3. Therefore, compared with the Comparative Example 3, the device structure of Example 3 has a strong beneficial effect in improving device frequency and speed.

[0177] Example 9

[0178] The intra-band noise problem of the elastic wave resonator of this embodiment is described with reference to Figures 2 and 5. Compared with Figure 2, the elastic wave resonator in Figure 5 has an upper functional layer of AlN.

[0179] Among them, the thickness of the LiTaO3 layer is 360nm, the thickness of the SiO2 layer is 400nm, the thickness of the Al interdigital electrode is 110nm, the interdigital period is 1.2μm, the duty cycle is 0.5, and the target mode is SH-SAW.

[0180] Figure 24 shows the slow speed curve of SH-SAW in the elastic wave resonator corresponding to Comparative Example 2; Figure 25 shows a comparison of the slow speed curves of SH-SAW under different AlN layer thicknesses in the elastic wave resonators corresponding to Comparative Example 2 and Example 2.

[0181] As shown in Figure 24, for the structure shown in Comparative Example 2, the target elastic wave SH-SAW excited and propagating therein exhibits a convex slow-speed curve. According to coupled-mode theory, a resonant device with this elastic wave as the primary mode will exhibit multiple high-order transverse spurious modes within the passband from the resonant frequency to the antiresonant frequency. This results in severe in-band jitter in the frequency response of the filter composed of such a resonator. When the slow-speed curve of the elastic wave is perpendicular to the horizontal axis within a certain angle (θ), transverse spurious modes corresponding to certain angular positions within this angle range are no longer excited. The number of transverse spurious modes within the passband of the main mode decreases. The specific number of transverse spurious modes reduced depends on the angle θ at which the curve is perpendicular. The larger the angle θ, the fewer transverse spurious modes are excited, and the further the high-order transverse spurious modes are from the main mode's resonant and antiresonant frequencies, resulting in a relatively flatter and cleaner passband. When the slow-speed curve of the elastic wave is constantly perpendicular to the horizontal axis, no transverse spurious modes exist within the passband of the main mode, achieving perfect suppression of high-order transverse spurious modes.

[0182] As shown in Curve III of Figure 25 , when the functional AlN layer is present, the convex shape of the slow velocity curve of the elastic wave is relatively mitigated. By designing the thickness of the AlN layer, the slow velocity curve can be perpendicular to the horizontal axis within a certain angle, which directly reduces the number of lateral stray mode excitations within the passband, thereby mitigating the filter's in-band jitter. Generally, methods for suppressing lateral stray modes begin with electrode design, evolving from conventional duty-cycle, uniform, single-layer interdigitated electrode designs to other variations or multi-layer electrodes. This can lead to a decrease in device quality factor, increased manufacturing difficulty, and reduced product yield. By adopting the structure shown in Example 2, the lateral stray modes within the passband are intrinsically unexcited or weakly excited. Based on this structure, elastic wave devices can be directly designed and fabricated, eliminating the need for complex electrode design. This can mitigate the adverse effects of lateral stray mode responses on the filter's passband performance, simplifying the design approach for suppressing lateral stray modes.

[0183] By simulating the in-band spurious modes of the elastic wave resonator, we can visually compare the excitation and suppression of transverse spurious modes. Figures 26 and 27 show the simulated frequency responses of the resonator passband for the structures of Comparative Example 2 and Example 2, respectively.

[0184] Compared to the convex slow-speed curve of the structure in Comparative Example 2, the slow-speed curve of the main mode in the structure shown in Example 2 can be adjusted to be perpendicular to the horizontal axis within a certain angle by adjusting the thickness of each layer. In Figure 27, the corresponding AlN layer thickness is 50 nm.

[0185] FIG26 shows the passband response of the device based on comparative example 2. There are many spurious modes between the resonant and anti-resonant frequency bands, and the resonance is strong. When the filter is built, strong in-band jitter will be introduced into the filter passband, causing signal distortion and increased loss.

[0186] Figure 27 shows the simulation results of the passband response of the device based on Example 2 with an AlN layer thickness of 50nm. Compared with the strong multi-order lateral noise excited in Comparative Example 2, the order of the lateral stray mode in this structure is reduced by more than half, and the resonance intensity of each stray mode is also reduced, which can significantly reduce the jitter and loss problems caused by in-band strays, confirming the advantages of the Example 2 structure in suppressing lateral noise. Since the intrinsic excitation of the lateral stray mode is very weak, only simple interdigitation is required when designing the device to weaken the interference of lateral noise. In addition, when the slow speed curve can be perpendicular to the horizontal axis within a certain angle, the weak lateral stray mode is easier to remove or suppress. For example, the use of a universal noise suppression solution can achieve more efficient and lower-loss lateral noise suppression.

[0187] Example 10

[0188] The intra-band noise problem of the elastic wave resonator of this embodiment is described with reference to Figures 3 and 6. Compared with Figure 3, the elastic wave resonator in Figure 6 has an upper functional layer of AlN.

[0189] Among them, the thickness of the LiTaO3 layer is 360nm, the thickness of the SiO2 layer is 400nm, the thickness of the Al interdigital electrode is 110nm, the interdigital period is 1.2μm, the duty cycle is 0.5, and the target mode is SH-SAW.

[0190] Figure 28 shows the slow speed curve of SH-SAW in the elastic wave resonator corresponding to Comparative Example 3; Figure 29 shows a comparison of the slow speed curves of SH-SAW under different AlN layer thicknesses in the elastic wave resonators corresponding to Comparative Example 3 and Example 3.

[0191] As shown in FIG28 , for the structure shown in Comparative Example 3, the target elastic wave SH-SAW excited and propagated therein has a convex slow velocity curve. When an AlN layer is present, as shown in Curve III of FIG29 , the convex shape of the slow velocity curve of the elastic wave is mitigated. That is, by designing the thickness of the AlN layer, the slow velocity curve can be perpendicular to the horizontal axis within a certain angle, which can directly reduce the number of lateral stray mode excitations within the passband, thereby reducing the in-band jitter of the filter. Therefore, by adopting the structure shown in Example 3, the lateral stray modes within the passband are intrinsically non-excited or weakly excited. Based on this structure, elastic wave devices can be directly designed and manufactured without the need for complex electrode design. This can achieve the goal of weakening the adverse effects of the lateral stray mode response on the filter passband performance, simplifying the design scheme for suppressing lateral stray modes.

[0192] By simulating the in-band spurious modes of the elastic wave resonator, we can visually compare the excitation and suppression of the transverse spurious modes. Figures 30 and 31 show the simulation results of the resonator's passband frequency response for the structures of Comparative Example 3 and Example 3, respectively.

[0193] Compared to the convex slow-speed curve of the structure in Comparative Example 3, based on the structure shown in Example 3, by individually designing the thickness of each layer, the slow-speed curve of the main mode in the structure can be adjusted to be perpendicular to the horizontal axis within a certain angle. In Figure 31, the corresponding AlN layer thickness is 50 nm.

[0194] FIG30 shows the passband response of the device based on comparative example 3. There are many spurious modes between the resonant and anti-resonant frequency bands and the resonance intensity is high. When building the filter, strong in-band jitter will be introduced into the filter passband, causing signal distortion and increased loss.

[0195] Figure 31 shows the simulation results of the passband response of a device based on Example 3, with an AlN layer thickness of 50nm. Compared to the strong multi-order lateral spurious waves excited in Comparative Example 3, the order of lateral spurious modes in the new substrate structure is reduced by more than half, and the resonant intensity of each spurious mode is also reduced, significantly reducing the jitter and loss caused by in-band spurious waves. This demonstrates the advantages of the new substrate design in suppressing lateral spurious waves. Because the intrinsic excitation of lateral spurious modes is weak, the device design only requires the use of simple interdigitation to eliminate lateral spurious interference.

[0196] Example 11

[0197] The high-order longitudinal noise problem of the elastic wave resonator of this embodiment is described in conjunction with Figure 3 and Figure 6. Compared with Figure 3, the elastic wave resonator in Figure 6 has an upper functional layer of AlN.

[0198] Among them, the thickness of the LiTaO3 layer is 360nm, the thickness of the SiO2 layer is 400nm, the thickness of the polysilicon is 1μm, the thickness of the Al interdigital electrode is 110nm, the interdigital period is 1.2μm, and the duty cycle is 0.5.

[0199] FIG32 shows a simulation curve of the longitudinal admittance corresponding to the horizontal shear wave propagating in the elastic wave resonator corresponding to Comparative Example 3. ...

[0200] FIG33 shows a simulation graph of the longitudinal admittance corresponding to the horizontal shear wave propagating in the elastic wave resonator corresponding to Example 3. FIG34 shows a simulation graph of the longitudinal admittance corresponding to the horizontal shear wave propagating in the elastic wave resonator corresponding to Example 3.

[0201] As shown in the black dotted box in Figure 32, the frequency response admittance curve of Example 3 shows a cluster of high-order longitudinal spurious mode responses far away from the antiresonance frequency point. When building the filter, jitter may be introduced within the band or at the edge of the passband. Therefore, special consideration should be given to moving this cluster of spurious peaks away from the passband during design.

[0202] As shown in Figure 33, the resonant frequency point of the frequency response admittance curve of Example 3 shows a significant improvement, which corresponds to the sound velocity enhancement effect of the structure. Secondly, compared with Comparative Example 3, the number of a cluster of longitudinal high-order clutter in Example 3 is reduced, and the vibration intensity is significantly weakened, showing the effect of suppressing longitudinal clutter. Finally, the frequency spacing between the anti-resonance frequency point of the main mode in Comparative Example 3 and the nearest high-order clutter is 150MHz, and the frequency spacing between the anti-resonance frequency point of the main mode in Example 3 and the nearest high-order clutter is 166MHz, indicating that the frequency position of the longitudinal high-order clutter is farther away from the main mode, providing a margin for the flat filter passband design.

[0203] Example 12

[0204] The performance of the elastic wave resonator of this embodiment is described in conjunction with Figures 1 and 4. Compared to Figure 1, Figure 4 shows the elastic wave resonator having an upper functional layer of AlN. It should be noted that in this embodiment, the interdigital electrodes in the structure of Comparative Example 1 are replaced with Al-Cu alloy interdigital electrodes.

[0205] In the structure of Example 1, the thickness of the LiNbO3 layer is 330 nm, the thickness of the Al interdigital electrode is 130 nm, the interdigital period is 1.5 μm, the interdigital duty cycle is 0.5, and the thickness of the AlN layer is 100 nm.

[0206] In the structure of Comparative Example 1, the thickness of the LiNbO 3 layer is 300 nm, the thickness of the Al—Cu alloy interdigital electrode is 72 nm, the interdigital period is 1.5 μm, the interdigital duty cycle is 0.5, and there is no AlN layer.

[0207] Figures 34 and 35 show the measured admittance response curves of the elastic wave resonator at multiple wavelengths and compare their electromechanical coupling coefficients. and resonance conditions.

[0208] Due to the varying metal thicknesses, mass loading significantly impacts the acoustic velocity, so a comparison of acoustic velocities is not performed here. Regarding the resonance intensity, both data sets show a similar admittance ratio of 60 dB, indicating that the 100 nm AlN layer does not affect the excitation and transmission of the elastic wave. The elastic wave energy remains within the piezoelectric layer, transmitting with low loss, demonstrating excellent device performance.

[0209] Table 1 below shows the electromechanical coupling coefficients for two elastic wave device structures, covering an elastic wave wavelength range of 1.2 to 1.6 μm. Compared to Comparative Example 1, the electromechanical coupling coefficient of the device based on Example 1 decreases by approximately 0.8% to 1.9%, a very slight decrease. However, the device structure of Example 1 still exhibits effective elastic wave excitation and energy confinement, demonstrating significant potential for high-frequency and wide-bandwidth applications.

[0210] Table 1

[0211] Example 13

[0212] The longitudinal high-order noise suppression of the elastic wave resonator according to this embodiment is described in conjunction with Figure 1 and Figure 4. Compared with Figure 1, the elastic wave resonator in Figure 4 has an upper functional layer of AlN.

[0213] In the structure of Example 1, the thickness of the LiNbO3 layer is 330 nm, the thickness of the Al interdigital electrode is 130 nm, the interdigital period is 1.5 μm, the duty cycle is 0.5, and the thickness of the AlN layer is 100 nm.

[0214] In the structure of Comparative Example 1, the thickness of the LiNbO 3 layer is 300 nm, the thickness of the Al interdigital electrode is 100 nm, the interdigital period is 1.5 μm, the duty cycle is 0.5, and there is no AlN layer.

[0215] FIG36 shows the test admittance curve corresponding to the horizontal shear wave propagating in the structure corresponding to Comparative Example 1; FIG37 shows the test admittance curve corresponding to the horizontal shear wave propagating in the structure corresponding to Example 1.

[0216] As shown in Figure 37, the resonant frequency of the frequency response admittance curve of Example 1 shows a significant improvement, corresponding to the sound velocity enhancement effect of the structure. Secondly, as shown in the black dashed box in Figure 36, the frequency response admittance curve of Comparative Example 1 has a cluster of high-order longitudinal spurious modes far away from the antiresonant frequency point. However, as shown in Figure 37, the number of this cluster of longitudinal high-order clutter in Example 1 has decreased, the vibration intensity has significantly weakened, and the frequency position of the longitudinal high-order clutter is farther away from the main mode, demonstrating an effective suppression effect on longitudinal clutter, providing margin for flat filter passband design. Finally, as shown in the black dashed circles in Figures 36 and 37, the resonant intensity of the high-frequency clutter of the Example 1 device has also weakened, which can effectively increase the out-of-band suppression level. Therefore, the Example 1 structure has the advantage of suppressing longitudinal and high-frequency clutter.

[0217] In summary, the elastic wave device and its preparation method of the present invention, by providing an upper functional layer with high thermal conductivity, can effectively improve the device's heat dissipation capacity and efficiency, reduce the device's temperature, and thus enhance the device's power tolerance and operating life. The high-acoustic-velocity upper functional layer and supporting substrate can effectively increase the propagation velocity of the elastic wave and effectively confine the elastic wave energy within the piezoelectric layer and upper functional layer, thereby increasing the device's operating frequency and quality factor. This allows for high frequency and low loss at a larger interdigital linewidth, significantly improving power tolerance. The upper functional layer effectively adjusts the slow velocity curve and velocity profile of the elastic wave, thereby suppressing or weakening the excitation of transverse spurious modes. The upper functional layer can adjust the excitation intensity and frequency of longitudinal spurious modes, weakening the resonance intensity of longitudinal high-order spurious waves and moving them away from the target elastic wave, resulting in higher out-of-band suppression and cleaner out-of-band response. Therefore, the elastic wave device and its preparation method of the present invention can comprehensively improve the performance of the elastic wave device.

[0218] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An elastic wave device, characterized in that, the elastic wave device includes: a supporting substrate; a piezoelectric layer, the piezoelectric layer is located on the supporting substrate, and the slow shear wave sound velocity of the supporting substrate is greater than the sound velocity of the target mode propagating in the piezoelectric layer; an upper functional layer, the upper functional layer is located on the piezoelectric layer, and the thermal conductivity of the upper functional layer is greater than the thermal conductivity of the piezoelectric layer and / or the slow shear wave sound velocity of the upper functional layer is greater than the sound velocity of the target mode; interdigital electrodes, the interdigital electrodes are located on the upper functional layer.

2. The elastic wave device according to claim 1, characterized in that: the thermal conductivity of the upper functional layer is more than 3 times that of the piezoelectric layer; the slow shear wave sound velocity of the upper functional layer is more than 1.2 times that of the target mode.

3. The elastic wave device according to claim 1, characterized in that: the crystal type of the upper functional layer includes single crystal or polycrystal; the upper functional layer includes one or a combination of aluminum nitride layer, silicon carbide layer, diamond layer, diamond-like carbon layer, silicon nitride layer, sapphire layer, magnesium oxide layer, aluminum oxide layer, silicon layer, gallium nitride layer, boron carbide layer and boron nitride layer.

4. The elastic wave device according to claim 1, characterized in that: when the elastic wave wavelength is λ, the thickness range of the piezoelectric layer is 0.03λ to λ; the thickness range of the upper functional layer is greater than 0.02λ and less than the thickness of the piezoelectric layer; the thickness range of the interdigital electrodes is 0.02λ to 0.12λ.

5. The elastic wave device according to claim 1, characterized in that: the piezoelectric layer includes lithium tantalate layer, lithium niobate layer, quartz layer, potassium niobate layer, aluminum nitride layer, scandium-doped aluminum nitride layer, zinc oxide layer, lead zirconate titanate layer, lead magnesium niobate titanate layer, gallium nitride layer, gallium oxide layer or gallium arsenide layer.

6. The elastic wave device according to claim 1, characterized in that: the supporting substrate includes silicon carbide substrate, diamond substrate, diamond-like carbon substrate, gallium nitride substrate, boron carbide substrate, boron nitride substrate or aluminum nitride substrate; or the supporting substrate includes a substrate at the lower part and a lower functional layer at the upper part, and the substrate includes a silicon substrate, a quartz substrate or a sapphire substrate, and the lower functional layer includes one or a combination of polysilicon layer, silicon oxide layer, fluorine-containing silicon oxide layer, silicon oxynitride layer, aluminum nitride layer, tantalum pentoxide layer and tellurium dioxide layer.

7. The elastic wave device according to claim 1, characterized in that: the material of the interdigital electrodes includes one or an alloy composed of copper, silver, gold, aluminum, platinum, nickel, molybdenum, tungsten, chromium and titanium, and the interdigital electrodes include a single-layer structure or a stacked structure.

8. The elastic wave device according to claim 1, characterized in that: in the sound wave propagation direction, there are also reflection grating electrodes located on both sides of the interdigital electrodes.

9. The elastic wave device according to claim 1, characterized in that: the target mode includes horizontal shear wave, thickness shear wave, longitudinal wave, higher-order horizontal shear wave, higher-order thickness shear wave or higher-order longitudinal wave; the elastic wave device includes an elastic wave resonator and / or an elastic wave filter.

10. A method for manufacturing an elastic wave device according to any one of claims 1 to 9, characterized in that, it comprises the following steps: providing a support substrate; forming a piezoelectric layer on the support substrate; forming an upper functional layer on the piezoelectric layer; forming interdigital electrodes on the upper functional layer.

11. The method for manufacturing an elastic wave device according to claim 10, characterized in that: the method for forming the piezoelectric layer includes physical vapor deposition, chemical vapor deposition, magnetron sputtering, bonding transfer method, ion implantation stripping transfer method or Czochralski crystal growth method; the method for forming the upper functional layer includes physical vapor deposition, chemical vapor deposition, magnetron sputtering, thermal oxidation, bonding transfer method, ion implantation stripping transfer method or Czochralski crystal growth method.

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