An acoustic wave filter and a method of manufacturing the same

Abstract

The present application relates to the field of microelectronics, and particularly relates to a sound wave filter and a preparation method thereof. The sound wave filter comprises at least one series resonator and at least one parallel resonator; the series resonator and the parallel resonator each comprise a support substrate, a dielectric layer, a piezoelectric layer and an interdigital electrode; the dielectric layer and the piezoelectric layer are located on the support substrate, and the bottom of the piezoelectric layer has a preset distance from the support substrate; the interdigital electrode is arranged on the top of the piezoelectric layer; and a bottom electrode is arranged between the support substrate and the piezoelectric layer of at least one resonator in the series resonator and the parallel resonator. By selecting whether to have a bottom electrode or different in-plane orientations to select a target mode, local thinning of the piezoelectric layer is avoided, the advantages of high-order acoustic wave modes in high acoustic velocity and large electromechanical coupling coefficient are fully utilized, and this is conducive to batch production of high-performance high-frequency filters and improving yield.

Description

Technical Field

[0001] The present invention relates to the field of microelectronics technology, and in particular to an acoustic wave filter and a preparation method thereof. Background Art

[0002] With the development of wireless communication systems, higher requirements are placed on the operating frequency, insertion loss, bandwidth, power tolerance, and temperature stability of filters. The operating frequency of the bulk acoustic wave (BAW) filter is inversely proportional to the thickness of the piezoelectric layer, and its frequency can be increased by reducing the thickness of the film. For thin film bulk acoustic wave filters, a piezoelectric layer that is too thin has mechanical stability issues. For solid-state assembly-type BAW filters, the Bragg reflection layer not only causes processing difficulties, but also leads to other parasitic effects. Traditional surface acoustic wave (SAW) filters are limited by the speed of sound, and the frequency is difficult to increase. High-order acoustic wave mode resonators based on high-speed support substrates and single-crystal piezoelectric layers have advantages in frequency, bandwidth, and mechanical stability. However, the filter requires a certain frequency difference between the series and parallel resonators, that is, the resonant frequency fs of the series resonator is approximately equal to the anti-resonant frequency fp of the parallel resonator. High-order modes have strong dispersion characteristics. When the resonant frequency of the resonator is changed only by changing the electrode finger spacing λ of the interdigitated electrodes, the ratio of the thickness h of the piezoelectric layer between the series and parallel resonators to λ will vary greatly. Especially for the series resonator, when h / λ is too large, the frequency of the zero-order mode will surpass the high-order mode and become a parasitic mode. In order to maintain h / λ at a certain level, the series and parallel resonators often need to have different piezoelectric layer thicknesses, resulting in a more complex process. Therefore, achieving resonant frequency shift of series and parallel resonators in a simple process is the key to realizing high-performance, low-cost, high-frequency, large-bandwidth filters. Summary of the Invention

[0003] To solve the above technical problems, the present application discloses, in one aspect, an acoustic wave filter comprising at least one series resonator and at least one parallel resonator;

[0004] The series resonator and the parallel resonator each include a supporting substrate, a dielectric layer, a piezoelectric layer, and interdigital electrodes; the dielectric layer and the piezoelectric layer are located on the supporting substrate, and a preset distance exists between the bottom of the piezoelectric layer and the supporting substrate; the interdigital electrodes are located on top of the piezoelectric layer; a bottom electrode is provided between the supporting substrate and the piezoelectric layer of at least one of the series resonator and the parallel resonator; and the target mode of at least one of the series resonator and the parallel resonator is a high-order acoustic wave mode excited by a longitudinal electric field;

[0005] The acoustic wave filter contains at least two target modes;

[0006] In each resonator of the acoustic wave filter, the acoustic velocity of the slow shear wave of the supporting substrate is greater than the acoustic velocity of the target mode of the resonator; the acoustic velocity of the target mode of the resonator is determined by the electrode finger spacing of the interdigitated electrodes and the resonant frequency of the resonator;

[0007] In the acoustic wave filter, there is at least one target mode of a series resonator having a higher acoustic velocity than a target mode of a parallel resonator.

[0008] Furthermore, the acoustic velocity of the target mode of the resonator is equal to the product of the electrode finger spacing of the interdigitated electrodes and the resonant frequency of the resonator;

[0009] The electrode finger spacing of the interdigitated electrode is the distance between the centers of adjacent interdigitated electrode fingers on the same busbar of the interdigitated electrode;

[0010] The width of the bottom electrode is less than or equal to the width of the aperture region of the interdigital electrode; the aperture region of the interdigital electrode is the region where the electrode fingers of the interdigital electrode cross and overlap.

[0011] Furthermore, the target mode of the parallel resonator includes a zero-order horizontal shear mode, a zero-order longitudinal leakage surface acoustic wave mode, or a zero-order Rayleigh mode; the target mode of the series resonator includes a high-order horizontal shear mode or a high-order Lamb wave mode;

[0012] The bottom electrode is located in the series resonator.

[0013] Furthermore, the target mode of the parallel resonator is a high-order horizontal shear mode; the target mode of the series resonator is a high-order Lamb wave mode;

[0014] Bottom electrodes are provided in both the series resonator and the parallel resonator;

[0015] The series resonator and the parallel resonator correspond to different in-plane orientations; the in-plane orientation is a direction perpendicular to the extending direction of the interdigital electrodes.

[0016] Furthermore, different target modes are used between parallel resonators, and / or different target modes are used between series resonators.

[0017] Further, the piezoelectric layer is located on the dielectric layer;

[0018] The bottom electrode is buried in the dielectric layer, and the top of the bottom electrode is connected to the bottom of the piezoelectric layer.

[0019] Furthermore, the dielectric layer includes a first dielectric layer and a second dielectric layer stacked together;

[0020] The second dielectric layer is close to the supporting substrate;

[0021] The bottom electrode is located in the first dielectric layer;

[0022] The first dielectric layer and the second dielectric layer are made of different materials, or the first dielectric layer and the second dielectric layer are made of the same material, or the first dielectric layer, the second dielectric layer and the supporting substrate are made of the same material.

[0023] Furthermore, the top of the bottom electrode contacts the piezoelectric layer, and the bottom of the bottom electrode contacts the supporting substrate;

[0024] The piezoelectric layers of each resonator in the acoustic wave filter have the same thickness, and there is a preset gap between the piezoelectric layers of adjacent resonators;

[0025] A dielectric layer is filled between adjacent resonators in the acoustic wave filter and between the piezoelectric layer and the supporting substrate in the resonator without the bottom electrode.

[0026] Furthermore, the piezoelectric layer is X-cut lithium niobate or lithium tantalate;

[0027] The thickness of the piezoelectric layer of each resonator in the acoustic wave filter is the same;

[0028] The resonator whose target mode is a high-order horizontal shear mode includes a bottom electrode with an in-plane orientation having an angle of -20 to 70° with respect to the Y axis of the crystal;

[0029] The resonator whose target mode is a high-order Lamb wave mode includes a bottom electrode whose in-plane orientation has an angle of 90 to 150 degrees with respect to the Y axis;

[0030] The resonator whose target mode is the zero-order horizontal shear mode does not contain a bottom electrode, and the angle between the in-plane orientation and the Y axis is 150 to 200 degrees;

[0031] The resonator whose target mode is the zero-order longitudinal leakage surface acoustic wave mode does not include a bottom electrode, and the angle between the in-plane orientation and the Y axis is 10 to 70 degrees;

[0032] The direction of rotation from the Y axis to the Z axis of the crystal is the positive direction.

[0033] Furthermore, the support substrate is a combination of one or more of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cut shapes.

[0034] Furthermore, the support substrate includes a stacked support layer and a high-acoustic-velocity layer; the support layer is made of a material that is easily formed and processed;

[0035] The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet;

[0036] The material of the high acoustic velocity layer is any one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cuts.

[0037] Furthermore, the material of the bottom electrode includes one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride.

[0038] Furthermore, the bottom electrode is a conductive region formed by doping or ion irradiation in a predetermined region of the supporting substrate.

[0039] Furthermore, at least one of a duty cycle, a thickness, and a material composition of the interdigital electrodes differs between different resonators in the acoustic wave filter.

[0040] In another aspect, the present application further discloses a method for preparing an acoustic wave filter, which comprises the following steps:

[0041] providing a piezoelectric substrate;

[0042] forming a bottom electrode and a dielectric layer in sequence on a predetermined area of ​​the piezoelectric substrate;

[0043] Bonding the dielectric layer to the supporting substrate, removing excess areas from the piezoelectric substrate, and forming interdigital electrodes to obtain the acoustic wave filter;

[0044] Wherein, the piezoelectric substrate is a piezoelectric crystal containing an ion-implanted damaged layer, or a heterostructure containing a piezoelectric film.

[0045] The acoustic wave filter provided in the embodiment of the present application is intended to address the problem that the high-order acoustic wave mode excited by the longitudinal electric field is difficult to achieve frequency offset under the same piezoelectric layer thickness, and to achieve the frequency difference between the series and parallel resonators while maintaining the uniform thickness of the piezoelectric layer. First, by in-plane orientation or the setting of the bottom electrode, the target mode with different sound speeds is excited, thereby achieving the frequency offset between the series and parallel resonators while maintaining the same thickness of the piezoelectric layer, avoiding local etching of the piezoelectric layer. The resonator of the filter comprises at least one high-order acoustic wave mode resonator excited by the longitudinal electric field, which fully utilizes the advantages of the high-order acoustic wave mode in terms of high sound speed and large electromechanical coupling coefficient. At the same time, it also avoids the situation where the sound speed of the target mode of the series resonator is significantly lower than that of the parallel resonator under the same piezoelectric layer thickness, ensuring that the electrode line width of the series resonator is not too small. Secondly, it avoids the situation where the resonant frequency of the zero-order acoustic wave mode exceeds the high-order acoustic wave mode when the ratio of the thickness h of the piezoelectric layer to the electrode finger spacing λ of the interdigital electrode changes, thereby avoiding the related parasitic modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0047] Figure 1 It is a structural schematic diagram of an existing resonator;

[0048] Figure 2 is a top view of an existing resonator;

[0049] Figure 3 is a cross-sectional view of an exemplary first acoustic wave filter of the present application;

[0050] Figure 4 is a graph showing the simulated resonator frequency of each acoustic wave mode in Comparative Example 1;

[0051] Figure 5 is a dispersion curve diagram of each acoustic wave mode of Comparative Example 1;

[0052] Figure 6 is a graph showing the simulated resonator frequency of each acoustic wave mode of Comparative Example 1 when h / λ is fixed at 0.155;

[0053] Figure 7 is a sound velocity variation curve of each sound wave mode of Comparative Example 1 when h / λ is fixed at 0.155;

[0054] Figure 8 This is a top view of an existing acoustic wave filter;

[0055] Figure 9 is a cross-sectional view of an existing acoustic wave filter;

[0056] Figure 10 It is a structural diagram of another existing resonator;

[0057] Figure 11 This is a comparison chart of the simulated admittance responses of structure 1 and structure 2;

[0058] Figure 12 is a cross-sectional view of a second exemplary acoustic wave filter of the present application;

[0059] Figure 13 is a cross-sectional view of a third exemplary acoustic wave filter of the present application;

[0060] Figure 14 is a top view of an exemplary acoustic wave filter of the present application;

[0061] Figure 15 This is an example of an Figure 14 Admittance response curve corresponding to the acoustic wave filter shown;

[0062] Figure 16 This is an example of an Figure 14 The transmission coefficient curve corresponding to the acoustic wave filter shown;

[0063] Figure 17 This is another comparison chart of the simulated admittance responses of Structure 1 and Structure 2;

[0064] Figure 18 is a top view of another exemplary acoustic wave filter of the present application;

[0065] Figure 19 This is an example of an Figure 18 Admittance response curve corresponding to the acoustic wave filter shown;

[0066] Figure 20 This is an example of an Figure 18 The transmission coefficient curve corresponding to the acoustic wave filter shown;

[0067] Figure 21 is a cross-sectional view of a fourth exemplary acoustic wave filter of the present application;

[0068] Figure 22 is a cross-sectional view of a fifth exemplary acoustic wave filter of the present application;

[0069] Figure 23 is a cross-sectional view of a sixth exemplary acoustic wave filter of the present application;

[0070] Figure 24 is the simulated admittance response curve of structure 2 under different α;

[0071] Figure 25 is a top view of a sixth exemplary acoustic wave filter of the present application;

[0072] Figure 26 This is an example of an Figure 25 Admittance response curve corresponding to the acoustic wave filter shown;

[0073] Figure 27 This is an example of an Figure 25 The transmission coefficient curve corresponding to the acoustic wave filter shown;

[0074] Figure 28 is a cross-sectional view of a seventh exemplary acoustic wave filter of the present application;

[0075] Figure 29 is a cross-sectional view of an eighth exemplary acoustic wave filter of the present application;

[0076] Figures 30-36 This is a schematic diagram of an exemplary structure in the process of forming an acoustic wave filter in the present application.

[0077] The following is a supplementary description of the accompanying drawings:

[0078] 1-series resonator; 2-parallel resonator; 3-support substrate; 4-dielectric layer; 401-first dielectric layer; 402-second dielectric layer; 5-piezoelectric layer; 6-interdigitated electrodes; 601-bus bar; 602-electrode fingers; 603-aperture region; 7-bottom electrode; 8-conductive region; 9-first piezoelectric layer; 10-second piezoelectric layer; 11-damage layer; 12-third dielectric layer; 14-substrate. DETAILED DESCRIPTION

[0079] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0080] References to "one embodiment" or "embodiment" herein refer to specific features, structures, or characteristics that may be included in at least one implementation of the present application. Throughout the description of this application, it should be understood that the terms "upper," "lower," "top," and "bottom," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplification. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Thus, a feature designated "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, the terms "first," "second," etc. are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that such terms are interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0081] For the purpose of the following detailed description, it should be understood that the present invention may adopt various alternative variations and step sequences, unless expressly provided otherwise. In addition, except in any operating examples, or when otherwise indicated, all numerals representing the amount of the components used in the specification and claims should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and the appended claims are approximate values ​​that vary according to the desired performance to be obtained by the present invention. At least, it is not intended to limit the application of the doctrine of equivalents to the scope of the claims, and each numerical parameter should at least be interpreted according to the number of reported significant figures and by applying ordinary rounding techniques.

[0082] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0083] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein. For example, a specified range from "1 to 10" should be considered to include any and all subranges between a minimum of 1 and a maximum of 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0084] The filter in the existing solution contains series-parallel resonators, see Figure 1 and 2 The resonator includes a supporting substrate 3, a dielectric layer 4, a bottom electrode 7, a piezoelectric layer 5 and an interdigital electrode 6 arranged in sequence from bottom to top, wherein the electrode finger spacing λ of the interdigital electrode 6 is the distance between the centers of adjacent interdigital electrodes 6 on the same bus bar 601 of the interdigital electrode 6, and h represents the thickness of the piezoelectric layer 5. Both series and parallel resonators utilize high-order acoustic wave modes excited by the longitudinal electric field. Due to the strong dispersion characteristics of the high-order modes, as h / λ increases, the sound velocity νs of the target mode drops significantly and is lower than that of the zero-order mode. At this time, the zero-order mode will exist as a parasitic mode. In order to maintain the advantages of high-order acoustic wave modes in high sound velocity and large electromechanical coupling coefficient, it is ensured that νs of the zero-order mode is always smaller than that of the high-order mode. This solution achieves frequency offset between series and parallel resonators by locally thinning the thickness of the piezoelectric layer 5 in the series resonator 1 area. This solution requires precise control of the thinning thickness, which increases the process difficulty.

[0085] In response to the shortcomings of the existing scheme, this scheme proposes to use modes with different sound speeds to form series-parallel resonators. Different acoustic wave modes have different excitation methods and optimal in-plane orientations, so the target mode can be selected by choosing whether to have a bottom electrode 7 or a different in-plane orientation. In this way, without changing the thickness of the piezoelectric layer 5, the different sound speeds between the series-parallel resonators can achieve the frequency shift required to build the filter. It avoids local thinning of the piezoelectric layer 5 and fully utilizes the advantages of high-order acoustic wave modes in terms of high sound speed and large electromechanical coupling coefficient, which is conducive to the mass production of high-performance high-frequency filters and improves the yield.

[0086] See also Figure 3 The present application provides an acoustic wave filter, which includes at least one series resonator 1 and at least one parallel resonator 2; the series resonator 1 and the parallel resonator 2 both include a supporting substrate 3, a dielectric layer 4, a piezoelectric layer 5 and an interdigitated electrode 6; the dielectric layer 4 and the piezoelectric layer 5 are located on the supporting substrate 3, and the bottom of the piezoelectric layer 5 is at a preset distance from the supporting substrate 3; the interdigitated electrode 6 is arranged on the top of the piezoelectric layer 5; a bottom electrode 7 is provided between the supporting substrate 3 and the piezoelectric layer 5 of at least one resonator in the series resonator 1 and the parallel resonator 2; the target mode of at least one resonator in the series resonator 1 and the parallel resonator 2 is a high-order acoustic wave mode excited by a longitudinal electric field; the acoustic wave filter includes at least two target modes; in each resonator of the acoustic wave filter, the slow shear wave sound velocity of the supporting substrate 3 is greater than the sound velocity of the target mode of the resonator; the sound velocity of the target mode of the resonator is determined by the electrode finger spacing of the interdigitated electrode 6 and the resonant frequency of the resonator; in the acoustic wave filter, the sound velocity of the target mode of at least one series resonator 1 is greater than the sound velocity of the target mode of one parallel resonator. Without changing the thickness of the piezoelectric layer 5, the different acoustic velocities between the series and parallel resonators can achieve the frequency offset required to construct the filter. This avoids the need for local thinning of the piezoelectric layer 5 and fully utilizes the advantages of high-order acoustic modes in terms of high acoustic velocity and large electromechanical coupling coefficient, facilitating the mass production of high-performance high-frequency filters and improving yield.

[0087] Exemplarily, the sound velocity of the target mode of the resonator is equal to the product of the spacing between the electrode fingers 602 of the interdigitated electrode 6 and the resonant frequency of the resonator; the width of the bottom electrode 7 is less than or equal to the width of the aperture area 603 of the interdigitated electrode 6; the aperture area 603 of the interdigitated electrode 6 is the area where the electrode fingers 602 in the interdigitated electrode 6 cross and overlap.

[0088] Exemplarily, the support substrate 3 is a combination of one or more of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cut shapes.

[0089] Exemplarily, the supporting substrate 3 includes a stacked supporting layer and a high acoustic velocity layer; the supporting layer is a material that is easy to form and process; the material of the supporting layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity layer includes any one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide, and silicon nitride of different crystal forms and different cuts.

[0090] Exemplarily, the bottom electrode 7 can be one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride.

[0091] Exemplarily, different target modes are used between the parallel resonators 2, and the same target mode is used between the series resonators 1. Optionally, the same target mode may be used between the parallel resonators 2, and different target modes may be used between the series resonators 1. Optionally, different target modes are used between the parallel resonators 2, and different target modes are used between the series resonators 1.

[0092] Exemplarily, the piezoelectric layer 5 is X-cut lithium niobate or lithium tantalate; the thickness of the piezoelectric layer 5 of each resonator in the acoustic wave filter is the same; a resonator whose target mode is a high-order horizontal shear mode includes a bottom electrode 7, optionally with an in-plane orientation angle of -20 to 70 degrees with the Y-axis of the crystal; a resonator whose target mode is a high-order Lamb wave mode includes a bottom electrode 7, optionally with an in-plane orientation angle of 90 to 150 degrees with the Y-axis; a resonator whose target mode is a zero-order horizontal shear mode does not include a bottom electrode 7, optionally with an in-plane orientation angle of 150 to 200 degrees with the Y-axis; a resonator whose target mode is a zero-order longitudinal leakage surface acoustic wave mode does not include a bottom electrode 7, optionally with an in-plane orientation angle of 10 to 70 degrees with the Y-axis. The positive direction is the direction of rotation from the Y-axis of the crystal toward the Z-axis.

[0093] Illustratively, at least one of the duty cycle, thickness, and material composition of the interdigital electrodes 6 differs between different resonators in the acoustic wave filter.

[0094] Based on the position and structure of the dielectric layer 4 and the position of the bottom electrode 7 , the present application may specifically include the following feasible embodiments.

[0095] Please continue reading Figure 3In the first acoustic wave filter provided by the embodiment of the present application, the target mode of the parallel resonator 2 is a zero-order horizontal shear mode, a zero-order longitudinal leakage surface acoustic wave mode, or a zero-order Rayleigh mode; the target mode of the series resonator 1 is a high-order horizontal shear mode or a high-order Lamb wave mode; and the bottom electrode 7 is located in the series resonator 1. Optionally, the piezoelectric layer 5 is located on the dielectric layer 4; the bottom electrode 7 is buried in the dielectric layer 4, and the top of the bottom electrode 7 is connected to the bottom of the piezoelectric layer 5, and the bottom of the bottom electrode 7 is connected to the supporting substrate 3. In this way, the thickness of the piezoelectric layer 5 can be made uniform, which simplifies the process of preparing the acoustic wave filter while achieving the frequency shift required for constructing the filter.

[0096] In order to better illustrate the advantages of the acoustic wave filter provided by the embodiments of the present application, the performance of the existing structure is first described below.

[0097] Provide a pair of comparative examples 1, comparative example 1 is as follows Figure 1 In the structure shown in Comparative Example 1, the supporting substrate 3 is 4H-SiC; the dielectric layer 4 is silicon oxide with a thickness of 200nm; the bottom electrode 7 is made of tungsten with a thickness of 80nm; the piezoelectric layer 5 is made of X-cut lithium niobate with a thickness defined as h; the interdigitated electrodes 6 are made of 62 / 18nm aluminum / platinum, the electrode fingers 602 of the interdigitated electrodes 6 are spaced λ apart, and the in-plane orientation is at an angle ɑ=19° with respect to the crystal Y axis. When the thickness of the piezoelectric layer 5 is fixed at 325nm, changing λ can yield the following: Figure 4 The simulated resonator frequencies fs of the acoustic modes are shown, from Figure 4 As can be seen from the figure, the frequency of the zero-order horizontal shear mode SH0 and the zero-order longitudinal leakage surface acoustic wave mode LL-SAW in the zero-order mode changes rapidly with the change of λ, so the zero-order mode can easily achieve frequency shift. The frequency of the first-order horizontal shear mode SH1 changes less with λ. For example, to achieve a frequency shift of 600MHz, λ needs to change from 2.2μm to 1.2μm, and the corresponding h / λ changes from 0.148 to 0.27. Figure 5 , which shows the dispersion curve corresponding to comparative example 1, the horizontal axis is the ratio of the thickness of the piezoelectric layer 5 to the electrode finger spacing of the interdigitated electrode 6 h / λ, and the vertical axis is the product νs of the resonant frequency fs and λ. Figure 5 It can be seen from the figure that with the change of h / λ, the sound velocity νs of SH0 and LL-SAW changes little, and the dispersion effect is weak. In contrast, the νs of the SH1 mode decreases rapidly with the increase of h / λ. When h / λ≥0.2, the νs of the SH1 mode is smaller than that of the LL-SAW mode. This means that the SH1 mode no longer has the advantage of high sound velocity, and the LL-SAW mode will appear in the band of the SH1 mode as a parasitic mode. When h / λ is fixed at 0.155, changing λ can be obtained as follows Figure 6 The simulation fs of each acoustic wave mode is shown. Figure 6As can be seen from the figure, fs of the three modes decreases rapidly as λ increases, so the resonant frequency shift of the resonator can be achieved. For the SH1 mode, if we want to achieve a frequency shift above 600MHz, λ needs to be changed from 2.2μm to 1.6μm. When h / λ is fixed at 0.155, changing λ can produce the following Figure 7 The corresponding νs values ​​for each acoustic wave mode are shown. For SH1, when λ changes from 2.2μm to 1.6μm, its sound velocity νs remains as high as over 5800m / s, while that for LL-SAW is 5200m / s. Therefore, by varying the thickness of the piezoelectric layer 5, h / λ can be maintained at a relatively low value, ensuring that the sound velocity of the zero-order mode remains lower than that of higher-order modes while achieving frequency shift. However, this method requires varying the thickness of the piezoelectric layer 5, increasing the complexity of the process.

[0098] See also Figure 8-9 , which are respectively a top view and a cross-sectional view of an existing acoustic wave filter. The existing acoustic wave filter may include 7 resonators, wherein the series resonator 1 has 4 ( Figure 8 The four resonators in the dashed box are shown in Figure 1, while the parallel resonator 2 has three. To maintain h / λ at a small value and ensure that frequency shift is achieved, the piezoelectric layer 5 of the series resonator 1 needs to be etched and thinned so that the thickness of the piezoelectric layer 5 of the series resonator 1 is smaller than that of the parallel resonator 2. However, this will obviously increase the complexity of the process for manufacturing the acoustic wave filter.

[0099] The present application provides a structure 1 and a structure 2, wherein the structure 1 can be as follows Figure 10 The structure shown in FIG2 specifically includes a supporting substrate 3, a dielectric layer 4, a piezoelectric layer 5 and an interdigital electrode 6 arranged in sequence from bottom to top. The structure 2 can be as follows: Figure 1 As shown in the structure, it can be seen that the only difference between Structure 1 and Structure 2 is the presence or absence of bottom electrode 7. In Structure 1, the material of the supporting substrate 3 is 4H-SiC; the material of the piezoelectric layer 5 is X-cut lithium niobate, with a thickness of 245nm; the material of the dielectric layer 4 is silicon oxide, with a thickness of 280nm; the interdigitated electrodes 6 are 62 / 18nm aluminum / platinum, with a λ of 1.015μm and an in-plane orientation of 172° with the crystal Y axis. In Structure 2, the thickness of the dielectric layer 4 is 200nm; the material of the bottom electrode 7 is tungsten, with a thickness of 80nm. The remaining structural parameters are the same as those of Structure 1. Figure 11 , which shows the comparison of the simulated admittance responses of structure 1 and structure 2. The SH0 mode is mainly excited by the transverse electric field. When there is no bottom electrode 7, the electromechanical coupling coefficient k of the SH0 mode is 2 As high as 48.7%, far exceeding the k of the bottom electrode 7 2This shows that in order to utilize the SH0 mode, the corresponding resonator region should not have the bottom electrode 7, which shows that the embodiment of the present application provides Figure 3 The structure shown can achieve the frequency shift required for constructing a filter by taking advantage of the different sound velocities between the series and parallel resonators without changing the thickness of the piezoelectric layer 5 .

[0100] In another exemplary embodiment, see Figure 12 The dielectric layer 4 includes a stacked first dielectric layer 401 and a second dielectric layer 402 ; the second dielectric layer 402 is close to the supporting substrate 3 ; the bottom electrode 7 is located in the first dielectric layer 401 ; the materials of the first dielectric layer 401 and the second dielectric layer 402 are different.

[0101] In another exemplary embodiment, see Figure 13 When the first dielectric layer 401 and the second dielectric layer 402 are made of the same material, dielectric layers 4 of the same material are filled between the bottom of the bottom electrode 7 and the supporting substrate 3, and between the piezoelectric layer 5 and the supporting substrate 3.

[0102] See also Figure 14 , which is a top view of an exemplary acoustic wave filter of the present application, the cross section of the acoustic wave filter is as follows Figure 13 The structure shown includes seven resonators: resonator 1, resonator 2, resonator 3, resonator 4, resonator 5, resonator 6, and resonator 7. Resonators 1, 3, 5, and 7 are series resonators 1 and all include a bottom electrode 7, targeting the SH1 mode. Resonators 2, 4, and 6 are parallel resonators 2 and do not include a bottom electrode 7, targeting the SH0 mode. Resonators 1 and 7 have the same parameters, resonators 3 and 5 have the same parameters, and resonators 2 and 6 have the same parameters. Specifically, the resonator parameters in this acoustic wave filter are as follows: the support substrate 3 is made of 4H-SiC; the piezoelectric layer 5 is made of X-cut lithium niobate with a thickness of 245 nm; the interdigitated electrodes 6 are made of 62 / 18 nm aluminum / platinum, with an in-plane orientation of α with the crystal's Y-axis; and the bottom electrode 7 is made of tungsten with a thickness of 80 nm. The first dielectric layer 401 and the second dielectric layer 402 are both made of silicon oxide, with a thickness of 200 nm. The λ of resonators 1 and 3 in series resonator 1 is 1.67μm, the duty ratio (2w / λ) of resonators 1 and 3 is 0.64 and 0.372, α is 22° and 17°, and νs is 6004m / s and 6212m / s. The λ of resonators 2 and 4 in parallel resonator 2 is 1.015μm and 1μm, the duty ratio (2w / λ) is 0.5, α is 172°, and νs is 3095m / s and 3182m / s. Figure 14 The acoustic wave filter shown in the figure is simulated and tested, and the following results can be obtained: Figure 15From the simulation results shown, it can be seen that due to the huge difference in sound velocity between the series and parallel connections, the frequency shift between the series and parallel resonators can be achieved without changing the thickness of the piezoelectric layer 5. The maximum frequency shift between the series and parallel resonators reaches 625MHz. Figure 16 As can be seen from the transmission coefficient (S21) curve of the acoustic wave filter, its bandwidth is 805 MHz, basically covering the N77 frequency band.

[0103] This embodiment of the present application provides structures 1 and 2 with alternative structural parameters. In structure 1, the support substrate 3 is made of 4H-SiC; the piezoelectric layer 5 is made of X-cut lithium niobate with a thickness of 210nm; the dielectric layer 4 is made of silicon oxide; the interdigitated electrodes 6 are made of 60 / 20nm aluminum / copper, with a λ of 1.145μm and an in-plane orientation of 42° with respect to the crystal's Y-axis. In structure 2, the dielectric layer 4 is 100nm thick, the bottom electrode 7 is made of tungsten with a thickness of 30nm, and the remaining structural parameters are the same as those of structure 1. Figure 17 , which shows the comparison of the simulated admittance response of another structure 1 and structure 2. The LL-SAW mode is mainly excited by the transverse electric field. When there is no bottom electrode 7, the electromechanical coupling coefficient k of the LL-SAW mode is 2 It is 24.8%, and only 3.1% when there is a bottom electrode 7. Therefore, in order to utilize the LL-SAW mode, the bottom electrode 7 should not exist in the corresponding resonator region.

[0104] See also Figure 18 , an embodiment of the present application provides another acoustic wave filter, the cross section of the acoustic wave filter is as follows Figure 13The structure shown includes seven resonators: resonator 1, resonator 2, resonator 3, resonator 4, resonator 5, resonator 6, and resonator 7. Resonators 1, 3, 5, and 7 are series resonators 1 and all include a bottom electrode 7, with the target mode being the SH1 mode. Resonators 2, 4, and 6 are parallel resonators 2 and do not include a bottom electrode 7, with the target mode being the LL-SAW mode. The parameters of resonators 1 and 7 are the same, as are the parameters of resonators 3 and 5, and the parameters of resonators 2 and 6. Specifically, the resonator parameters in this acoustic wave filter are as follows: the material of the supporting substrate 3 is 4H-SiC; the material of the piezoelectric layer 5 is X-cut lithium niobate with a thickness of 210 nm; the interdigitated electrode 6 is 60 / 20 nm aluminum / copper, with an in-plane orientation of an angle α with the crystal Y axis; and the material of the bottom electrode 7 is tungsten with a thickness of 30 nm. The material of dielectric layer 4 is silicon oxide, the thickness of second dielectric layer 402 is 100nm, the λ of resonators 1 and 3 in series resonator 1 are 1.178μm and 1.102μm respectively, the duty ratio (2w / λ) is 0.57 and 0.5 respectively, α is 37° and 35° respectively, and νs is 6332m / s and 6061m / s respectively. The λ of resonators 2 and 4 in parallel resonator 2 are 1.145μm and 1.128μm respectively, the duty ratio (2w / λ) is 0.5, α is 42°, and νs is 5662m / s and 5646m / s respectively. Figure 18 The acoustic wave filter shown in the figure is simulated and tested, and the following results can be obtained: Figure 19 The simulation results show that due to the acoustic velocity difference between the series and parallel resonators, the thickness of the piezoelectric layer 5 does not need to be changed, and the λ between the series and parallel resonators is basically the same, achieving a frequency offset between the series and parallel resonators. The maximum frequency offset between the series and parallel resonators reaches 555MHz.

[0105] Furthermore, by Figure 20 As can be seen from the transmission coefficient (S21) curve of the acoustic wave filter shown, the bandwidth is 730MHz, which fully covers the 5G WiFi frequency band.

[0106] In another exemplary embodiment, Figure 12 In the structure shown, when the first dielectric layer 401, the second dielectric layer 402 and the supporting substrate 3 are made of the same material, the following can be obtained: Figure 21 The structure shown.

[0107] In another exemplary embodiment, see Figure 22 The bottom electrode 7 is a conductive region 8 formed by doping in a predetermined region of the support substrate 3 , and may also be a conductive region 8 formed by ion irradiation in a predetermined region of the support substrate 3 .

[0108] The above is an explanation of the case where only the series resonator 1 has the bottom electrode 7 . The following will explain the case where both the series and parallel resonators have the bottom electrode 7 .

[0109] In another exemplary embodiment, see Figure 23 , the target mode of the parallel resonator 2 is a high-order horizontal shear mode; the target mode of the series resonator 1 is a high-order Lamb wave mode; both the series resonator 1 and the parallel resonator 2 are provided with a bottom electrode 7; the series resonator 1 and the parallel resonator 2 correspond to different in-plane orientations; the in-plane orientation is a direction perpendicular to the extension direction of the interdigital electrode 6.

[0110] In another exemplary embodiment, at least one of the duty cycle, thickness, and material composition of the interdigital electrodes 6 differs between different resonators in the acoustic wave filter.

[0111] See also Figure 24 , which shows the simulated admittance response curve of structure 2 under different α. In this structure 2, specifically, the material of the supporting substrate 3 is 4H-SiC; the material of the piezoelectric layer 5 is X-cut lithium niobate with a thickness of 200nm; the material of the dielectric layer 4 is silicon oxide; the interdigitated electrode 6 is 62 / 18nm aluminum / platinum, λ is 1.211μm, the duty cycle (2w / λ) is 0.58, and the in-plane orientation is an angle α with the Y axis of the crystal. The material of the bottom electrode 7 is platinum with a thickness of 95nm. When α=19°, the target mode is SH1 mode, and when α=119.5°, the target mode is A1 mode. From Figure 24 As can be seen in the figure, simply by changing the in-plane orientation, the target mode shifts from the SH1 mode to the A1 mode, achieving a 475MHz frequency difference while maintaining all other parameters identical. Subsequent adjustments only require fine-tuning λ and the duty cycle to meet the required frequency offset. This demonstrates that adjusting λ and the duty cycle can adjust the frequency offset between different resonators.

[0112] See also Figure 25 , the embodiment of the present application provides an acoustic wave filter, the cross section of the acoustic wave filter is as follows Figure 23The structure shown includes seven resonators, each of which includes a bottom electrode 7. Resonators 1, 3, 5, and 7 are series resonators 1, targeting the SH1 mode; resonators 2, 4, and 6 are parallel resonators 2, targeting the A1 mode. Resonators 1 and 7 have the same parameters, as do resonators 3 and 5, and resonators 2 and 6. Specifically, the resonator parameters in the acoustic wave filter are as follows: the material of the supporting substrate 3 is 4H-SiC; the material of the piezoelectric layer 5 is X-cut lithium niobate with a thickness of 200 nm; the interdigitated electrode 6 is 62 / 18 nm aluminum / platinum, and the in-plane orientation is at an angle α with the crystal Y axis; the material of the bottom electrode 7 is platinum with a thickness of 95 nm, and there is no dielectric layer 4 under the bottom electrode 7; the λ of resonators 1 and 3 in the series resonator 1 are 1.243 μm and 1.211 μm, respectively, the duty cycle (2w / λ) are 0.59 and 0.58, α are 119° and 119.5°, respectively, and νs are 5774 m / s and 5704 m / s, respectively. The λ of resonators 2 and 4 in the parallel resonator 2 are 1.366μm and 1.348μm, respectively, the duty ratio (2w / λ) is 0.6 and 0.54, respectively, α is 21.5° and 21°, respectively, and νs is 5498m / s and 5473m / s, respectively. Figure 25 The acoustic wave filter shown in the figure is simulated and tested, and the following results can be obtained: Figure 26 From the simulation results shown, it can be seen that the acoustic velocity of series resonator 1 is higher than that of parallel resonator 2, thus avoiding the situation where the acoustic velocity of a single high-order mode of series resonator 1 is lower than that of parallel resonator 2 when the thickness is the same. In this case, the maximum frequency offset between the series and parallel resonators reaches 685MHz. Figure 27 As can be seen from the transmission coefficient (S21) curve of the acoustic wave filter, the bandwidth is 647 MHz, which completely covers the N79 frequency band.

[0113] In another exemplary embodiment, when both the series-parallel resonators have a bottom electrode 7, the dielectric layer 4 includes a stacked first dielectric layer 401 and a second dielectric layer 402; the second dielectric layer 402 is close to the supporting substrate 3; the bottom electrode 7 is located in the first dielectric layer 401; the first dielectric layer 401 and the second dielectric layer 402 are made of different materials. Optionally, when the first dielectric layer 401 and the second dielectric layer 402 are made of the same material, they can be as follows: Figure 28 The structure shown.

[0114] In another exemplary embodiment, regardless of whether the bottom electrode 7 is present only in the series resonator 1 or in both series-parallel resonators, in the structure of the acoustic wave filter, the top of the bottom electrode 7 may be in contact with the piezoelectric layer 5, and the bottom of the bottom electrode 7 may be in contact with the supporting substrate 3; the thickness of the piezoelectric layer 5 of each resonator in the acoustic wave filter is the same, and there is a preset gap between the piezoelectric layers 5 in adjacent resonators, specifically, in each resonator, the width of the piezoelectric layer 5 is equal to the width of the bottom electrode 7 or equal to the width of the aperture region 603; the dielectric layer 4 is filled between adjacent resonators in the acoustic wave filter and between the piezoelectric layer 5 and the supporting substrate 3 in the resonator without the bottom electrode 7. Of course, if both series-parallel resonators have a bottom electrode 7, please refer to Figure 29 , the dielectric layer 4 fills the spacing area between adjacent resonators.

[0115] The above is only an exemplary embodiment of the present application. In fact, the acoustic wave filter is not limited to the above exemplary types and combinations. As long as the idea is to bury the bottom electrode 7 in the dielectric layer 4 or the supporting substrate 3, and avoid local etching of the piezoelectric layer 5 by the presence or absence of the bottom electrode 7 or the in-plane orientation, and can achieve frequency offset between series and parallel resonators while maintaining the same thickness of the piezoelectric layer 5, it falls within the protection scope of this solution.

[0116] See also Figures 30-36 , an embodiment of the present application provides a method for preparing an acoustic wave filter, which comprises the following steps:

[0117] 1) Provide a piezoelectric substrate.

[0118] For example, the piezoelectric substrate may be a piezoelectric crystal containing an ion implantation damage layer, and the piezoelectric substrate may be prepared by providing a Figure 30 The piezoelectric crystal shown in FIG. is ion-implanted to form a damaged layer 11 at a preset depth in the piezoelectric crystal, and the piezoelectric crystal is obtained as shown in FIG. Figure 31 The piezoelectric substrate shown in FIG. 1 includes a first piezoelectric layer 9 , a damaged layer 11 , and a second piezoelectric layer 10 stacked in sequence from bottom to top.

[0119] In another exemplary embodiment, the piezoelectric substrate may be a heterostructure containing a piezoelectric film. Specifically, the structure of the piezoelectric substrate may be as follows: Figure 32 The structure shown in FIG. 1 includes a stacked substrate 14 and a piezoelectric layer 5. In another exemplary embodiment, the structure of the piezoelectric substrate can also be as follows: Figure 33 The structure shown includes a laminated substrate 14 , a third dielectric layer 12 and a piezoelectric layer 5 .

[0120] 2) A bottom electrode 7 and a dielectric layer 4 are sequentially formed on a predetermined area on the piezoelectric substrate.

[0121] For example, the specific implementation of step 2) can be that a metal layer can be first deposited on the piezoelectric substrate, and then the metal layer is patterned to form the bottom electrode 7, and then a dielectric material layer is deposited and the surface of the dielectric material layer is polished to form the bottom electrode 7. Figure 35 The structure shown in FIG, the polishing thickness can be selected according to the needs, for example, if the desired preparation is as follows Figure 13 The thickness of the polished dielectric layer 4 is greater than the thickness of the bottom electrode 7. Figure 3 In the acoustic wave filter shown, the thickness of the polished dielectric layer 4 is equal to the thickness of the bottom electrode 7 .

[0122] 3) The dielectric layer 4 is bonded to the supporting substrate 3, and then the redundant area in the piezoelectric substrate is removed and interdigital electrodes 6 are formed to obtain the above-mentioned acoustic wave filter.

[0123] Exemplarily, a specific implementation of step 3) may be to provide a supporting substrate 3, and to connect the supporting substrate 3 with the supporting substrate 3. Figure 35 The dielectric layer 4 in the structure is bonded, and then annealed, peeled, and polished to obtain the following Figure 36 The structure shown in FIG. 1 is further obtained by forming interdigital electrodes 6 on the second piezoelectric layer 10. Figure 13 The acoustic wave filter shown.

[0124] The materials and dimensions of each layer in the process of preparing the acoustic wave filter are detailed in the above description of the structure of the acoustic wave filter, and will not be repeated here.

[0125] The above description is merely an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An acoustic wave filter, characterized in that comprising at least one series resonator and at least one parallel resonator; The series resonator and the parallel resonator each include a supporting substrate, a dielectric layer, a piezoelectric layer, and interdigital electrodes; the dielectric layer and the piezoelectric layer are located on the supporting substrate, and a preset distance exists between the bottom of the piezoelectric layer and the supporting substrate; the interdigital electrodes are located on the top of the piezoelectric layer; The piezoelectric layer of each resonator in the acoustic wave filter has the same thickness; the target mode of at least one of the series resonator and the parallel resonator is a high-order acoustic wave mode excited by a longitudinal electric field; In the series resonator and the parallel resonator, a bottom electrode is provided between the supporting substrate and the piezoelectric layer of at least one resonator, and the bottom electrode is not provided between the supporting substrate and the piezoelectric layer of at least one resonator, the target mode of the parallel resonator includes a zero-order horizontal shear mode, a zero-order longitudinal leakage surface acoustic wave mode, or a zero-order Rayleigh mode; the target mode of the series resonator includes a high-order horizontal shear mode or a high-order Lamb wave mode; or; the series resonator and the parallel resonator are both provided with the bottom electrode, and the series resonator and the parallel resonator have different corresponding in-plane orientations, the in-plane orientation is a direction perpendicular to the extension direction of the interdigitated electrodes, the target mode of the parallel resonator is a high-order horizontal shear mode; the target mode of the series resonator is a high-order Lamb wave mode; The acoustic wave filter comprises at least two target modes; In each resonator of the acoustic wave filter, the slow shear wave velocity of the supporting substrate is greater than the velocity of the target mode of the resonator; the velocity of the target mode of the resonator is determined by the electrode finger spacing of the interdigitated electrodes and the resonant frequency of the resonator; In the acoustic wave filter, there is at least one series resonator whose target mode has a higher acoustic velocity than that of one parallel resonator.

2. The acoustic wave filter according to claim 1, wherein The acoustic velocity of the target mode of the resonator is equal to the product of the electrode finger spacing of the interdigitated electrodes and the resonant frequency of the resonator; The electrode finger spacing of the interdigitated electrode is the distance between the centers of adjacent interdigitated electrode fingers on the same bus bar of the interdigitated electrode; The width of the bottom electrode is less than or equal to the width of the aperture region of the interdigital electrode; the aperture region of the interdigital electrode is the region where the electrode fingers of the interdigital electrode cross and overlap.

3. The acoustic wave filter according to claim 2, wherein The bottom electrode is located in the series resonator.

4. The acoustic wave filter according to claim 1, wherein The parallel resonators use different target modes, and / or the series resonators use different target modes.

5. The acoustic wave filter according to claim 1, wherein The piezoelectric layer is located on the dielectric layer; The bottom electrode is buried in the dielectric layer, and the top of the bottom electrode is connected to the bottom of the piezoelectric layer.

6. The acoustic wave filter according to claim 5, wherein The dielectric layer includes a first dielectric layer and a second dielectric layer stacked together; The second dielectric layer is close to the supporting substrate; The bottom electrode is located in the first dielectric layer; The first dielectric layer and the second dielectric layer are made of different materials, or the first dielectric layer and the second dielectric layer are made of the same material, or the first dielectric layer, the second dielectric layer and the supporting substrate are made of the same material.

7. The acoustic wave filter according to claim 1, wherein The top of the bottom electrode contacts the piezoelectric layer, and the bottom of the bottom electrode contacts the supporting substrate; The thickness of the piezoelectric layer of each resonator in the acoustic wave filter is the same, and there is a preset gap between the piezoelectric layers of adjacent resonators; The dielectric layer is filled between adjacent resonators in the acoustic wave filter and between the piezoelectric layer and the supporting substrate in the resonator without the bottom electrode.

8. The acoustic wave filter according to claim 2, wherein The piezoelectric layer is X-cut lithium niobate or lithium tantalate; The thickness of the piezoelectric layer of each resonator in the acoustic wave filter is the same; The resonator whose target mode is a high-order horizontal shear mode includes a bottom electrode, and the angle between the in-plane orientation and the Y axis of the crystal is -20° to 70°; The resonator whose target mode is a high-order Lamb wave mode includes a bottom electrode, and the angle between the in-plane orientation and the Y axis is 90 to 150 degrees; The resonator whose target mode is the zero-order horizontal shear mode does not include a bottom electrode, and the angle between the in-plane orientation and the Y axis is 150-200 degrees; The resonator whose target mode is a zero-order longitudinal leakage surface acoustic wave mode does not include a bottom electrode, and the angle between the in-plane orientation and the Y axis is 10 to 70 degrees; The direction of rotation from the Y axis to the Z axis of the crystal is the positive direction.

9. The acoustic wave filter according to claim 1, wherein The support substrate is a combination of one or more of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cut shapes.

10. The acoustic wave filter according to claim 1, wherein The support substrate comprises a stacked support layer and a high acoustic velocity layer; the support layer is made of a material that is easy to shape and process; The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; The material of the high acoustic velocity layer is any one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride in different crystal forms and cut shapes.

11. The acoustic wave filter according to claim 1, wherein The material of the bottom electrode includes one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride.

12. The acoustic wave filter according to claim 2, wherein The bottom electrode is a conductive region formed by doping or ion irradiation in a predetermined region of the supporting substrate.

13. The acoustic wave filter according to claim 1, wherein At least one of a duty ratio, a thickness, and a material composition of the interdigital electrodes differs between different resonators in the acoustic wave filter.

14. A method for preparing an acoustic wave filter, characterized in that: The following steps are involved: providing a piezoelectric substrate; forming a bottom electrode and a dielectric layer in sequence on a predetermined area on the piezoelectric substrate; Bonding the dielectric layer to a supporting substrate, removing excess regions from the piezoelectric substrate, and forming interdigital electrodes to obtain the acoustic wave filter according to any one of claims 1 to 13; Wherein, the piezoelectric substrate is a piezoelectric crystal containing an ion-implanted damaged layer, or a heterostructure containing a piezoelectric film.

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