Acoustic wave filter and preparation method thereof

Abstract

The invention relates to the technical field of microelectronics, in particular to an acoustic wave filter and a preparation method thereof. The acoustic wave filter comprises at least one series resonator and at least one parallel resonator; each of the series resonator and the parallel resonator comprises a supporting substrate, a dielectric layer, a piezoelectric layer and an interdigital electrode; 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 electrode is arranged at the top of the piezoelectric layer; and a bottom electrode is arranged between the support substrate and the piezoelectric layer of at least one of the series resonator and the parallel resonator. The target mode is selected by selecting whether a bottom electrode exists or different in-plane orientations exist, so that local thinning of the piezoelectric layer is avoided, the advantages of a high-order sound wave mode in the aspects of high sound velocity and large electromechanical coupling coefficient are fully utilized, and batch production of high-performance high-frequency filters and yield improvement are facilitated.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic 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 put forward for the operating frequency, insertion loss, bandwidth, power tolerance and temperature stability of filters. The operating frequency of bulk acoustic wave (BAW) filters 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, too thin piezoelectric layers have mechanical stability problems. For solid-state assembly BAW filters, the Bragg reflection layer not only causes processing difficulties, but also causes 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 formation of 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. The high-order mode has a strong dispersion characteristic. When the resonant frequency of the resonator is changed only by changing the electrode finger spacing λ of the forked electrode, the ratio of the thickness h of the piezoelectric layer between the series and parallel resonators will be quite different. Especially for the series resonator, h / λ is too large, and the frequency of the zero-order mode exceeds the high-order mode and becomes a parasitic mode. In order to maintain h / λ at a certain level, the series and parallel resonators are often required to have different piezoelectric layer thicknesses, resulting in a more complicated process. Therefore, realizing the resonant frequency offset of the series and parallel resonators under 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, which includes at least one series resonator and at least one parallel resonator;

[0004] The series resonator and the parallel resonator both 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 the bottom of the piezoelectric layer is at a preset distance from the supporting substrate; the interdigital electrodes are arranged on the top of the piezoelectric layer; a bottom electrode is arranged between the supporting substrate and the piezoelectric layer of at least one of the series resonator and the parallel resonator; 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] Further, 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 bus bar 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 in the interdigital electrode cross and overlap.

[0011] Further, 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] Further, 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] Further, the dielectric layer includes a first dielectric layer and a second dielectric layer stacked;

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

[0024] The thickness of the piezoelectric layer of each resonator in the acoustic wave filter is the same, and there is a preset interval 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] Further, 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 comprises a bottom electrode, and the in-plane orientation has an angle of -20 to 70° with the Y axis of the crystal;

[0029] The resonator whose target mode is a high-order Lamb wave mode comprises a bottom electrode, and the 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 include a bottom electrode, and the angle between the in-plane orientation and the Y axis is 150 to 200°;

[0031] 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;

[0032] The direction of rotation from the Y-axis of the crystal toward the Z-axis 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 of 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 a material that is easy to shape and process;

[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 in 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 preset region of the supporting substrate.

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

[0040] In another aspect, the present application also 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 preset area on the piezoelectric substrate;

[0043] Bonding the dielectric layer to the support substrate, removing the redundant area in the piezoelectric substrate, and forming interdigital electrodes to obtain the above-mentioned 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 cope with the problem that the high-order acoustic wave mode excited by the longitudinal electric field is difficult to achieve frequency shift under the same piezoelectric layer thickness, and to achieve the frequency difference between the series-parallel resonators under the premise of 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, so that the frequency shift between the series-parallel resonators is achieved under the premise of keeping the thickness of the piezoelectric layer the same, and the local etching of the piezoelectric layer is avoided. The resonator of the composed filter contains at least one high-order acoustic wave mode resonator excited by the longitudinal electric field, which makes full use of 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 that 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 will not be too small. Secondly, it avoids the situation that when the ratio of the thickness h of the piezoelectric layer to the electrode finger spacing λ of the forked electrode changes, the resonant frequency of the zero-order acoustic wave mode exceeds the high-order acoustic wave mode, thereby avoiding the related parasitic mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. 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 creative work.

[0047] Figure 1 is a schematic diagram of the structure of an existing resonator;

[0048] Figure 2 is a top view of a conventional 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 of simulated resonator frequencies of various acoustic wave modes of 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 of simulated resonator frequencies of various acoustic wave modes of Comparative Example 1 when h / λ is fixed to 0.155;

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

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

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

[0056] Fig.10 is a schematic diagram of the structure of another existing resonator;

[0057] Fig.11 It is a comparison diagram of the simulated admittance response of structure 1 and structure 2;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0076] Figure 30-36 It 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 attached 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 technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0080] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present application. In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may include one or more of the features explicitly or implicitly. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here.

[0081] For the purpose of the following detailed description, it should be understood that the present invention may adopt various alternative changes and step sequences, unless expressly specified to the contrary. In addition, except in any operating examples, or otherwise indicated, all numbers representing the amount of ingredients 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 attached 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 deemed to be continuous and includes the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. For example, a specified range from "1 to 10" should be deemed to include any and all sub-ranges between a minimum of 1 and a maximum of 10. Exemplary sub-ranges of ranges 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 existing filter scheme includes series-parallel resonators, see Figure 1 and 2 , the resonator it contains includes a supporting substrate 3, a dielectric layer 4, a bottom electrode 7, a piezoelectric layer 5 and a forked electrode 6 arranged in sequence from bottom to top, wherein the electrode finger spacing λ of the forked electrode 6 is the distance between the centers of adjacent forked electrode 6 fingers on the same bus bar 601 of the forked electrode 6, and h represents the thickness of the piezoelectric layer 5. The series-parallel resonators both utilize the high-order acoustic wave mode excited by the longitudinal electric field. Due to the strong dispersion characteristics of the high-order mode, as h / λ increases, the sound velocity νs of the target mode drops significantly and is lower than the zero-order mode. At this time, the zero-order mode will exist as a parasitic mode. In order to maintain the advantages of the high-order acoustic wave mode in high sound velocity and large electromechanical coupling coefficient, it is ensured that the νs of the zero-order mode is always smaller than the high-order mode. This scheme realizes the frequency shift between the series-parallel resonators by locally thinning the thickness of the piezoelectric layer 5 in the series resonator 1 area. This scheme requires precise control of the thinned thickness, which increases the process difficulty.

[0085] In view of 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 selecting whether to have a bottom electrode 7 or a different in-plane orientation. In this way, there is no need to change the thickness of the piezoelectric layer 5, and 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 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 a forked 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 forked electrode 6 is arranged on the top of the piezoelectric layer 5; a bottom electrode 7 is arranged 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 forked electrode 6 and the resonant frequency of the resonator; in the acoustic wave filter, there is at least one series resonator 1 whose target mode sound velocity is greater than the sound velocity of a parallel resonator. Therefore, the frequency shift required for constructing the filter can be achieved by using different sound velocities between the series-parallel resonators without changing the thickness of the piezoelectric layer 5. The local thinning of the piezoelectric layer 5 is avoided, and the advantages of the high-order acoustic wave mode in terms of high sound velocity and large electromechanical coupling coefficient are fully utilized, which is conducive to the mass production of high-performance high-frequency filters and improving the 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 region 603 of the interdigitated electrode 6; the aperture region 603 of the interdigitated electrode 6 is the region 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 of 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 shape 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 parallel resonators 2, and the same target mode is used between series resonators 1. Optionally, the same target mode is used between parallel resonators 2, and different target modes are used between series resonators 1. Optionally, different target modes are used between parallel resonators 2, and different target modes are used between 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; the resonator whose target mode is a high-order horizontal shear mode includes a bottom electrode 7, and optionally, the in-plane orientation and the Y-axis of the crystal are at an angle of -20 to 70°; the resonator whose target mode is a high-order Lamb wave mode includes a bottom electrode 7, and optionally, the in-plane orientation and the Y-axis are at an angle of 90 to 150°; the resonator whose target mode is a zero-order horizontal shear mode does not include a bottom electrode 7, and optionally, the in-plane orientation and the Y-axis are at an angle of 150 to 200°; the resonator whose target mode is a zero-order longitudinal leakage surface acoustic wave mode does not include a bottom electrode 7, and optionally, the in-plane orientation and the Y-axis are at an angle of 10 to 70°. The direction of rotation from the Y-axis of the crystal to the Z-axis is the positive direction.

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

[0094] Based on the different positions and structures of the dielectric layer 4 and the positions 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; 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 and realizes the frequency shift required for constructing the filter.

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

[0097] Provide a comparative example 1, comparative example 1 is as follows Figure 1 In the structure shown in the comparative example 1, the support substrate 3 is 4H-SiC; the dielectric layer 4 is silicon oxide with a thickness of 200nm; the material of the bottom electrode 7 is tungsten with a thickness of 80nm; the material of the piezoelectric layer 5 is X-cut lithium niobate with a thickness defined as h; the interdigitated electrode 6 is 62 / 18nm aluminum / platinum, the electrode fingers 602 of the interdigitated electrode 6 have a spacing of λ, and the in-plane orientation is an angle ɑ=19° with the crystal Y axis. When the thickness of the piezoelectric layer 5 is fixed at 325nm, changing λ can obtain the following Figure 4 The simulated resonator frequencies fs of the acoustic modes are shown, from Figure 4 It can be seen that 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. Please refer to Figure 5 , which shows the dispersion curve corresponding to comparative example 1, the abscissa 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 ordinate is the product νs of the resonance frequency fs and λ. Figure 5 It can be seen that with the change of h / λ, the sound velocity νs of SH0 and LL-SAW changes little, and the dispersion effect is weak. On the contrary, 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 to 0.155, changing λ can be obtained as follows Figure 6 The simulated fs of each acoustic wave mode are shown. Figure 6It can be seen that the 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 you want to achieve a frequency shift above 600MHz, λ needs to change from 2.2μm to 1.6μm. When h / λ is fixed to 0.155, changing λ can get the following Figure 7 As shown in the figure, the corresponding sound wave modes νs. For SH1, when λ changes from 2.2μm to 1.6μm, its sound velocity νs is still as high as 5800m / s or more, while that of LL-SAW is 5200m / s. Therefore, by changing the thickness of the piezoelectric layer 5, h / λ can be maintained at a smaller value, ensuring that the sound velocity of the zero-order mode is always lower than that of the higher-order mode while achieving frequency shift. However, this method requires changing the thickness of the piezoelectric layer 5, which increases 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 In order to maintain h / λ at a small value and ensure that the 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 piezoelectric layer 5 of the parallel resonator 2. However, this will obviously increase the complexity of the process for preparing the acoustic wave filter.

[0099] The present application provides a structure 1 and a structure 2, wherein the structure 1 can be as follows Fig.10 The structure shown in FIG. 2 specifically includes a supporting substrate 3, a dielectric layer 4, a piezoelectric layer 5 and interdigital electrodes 6 arranged in sequence from bottom to top. The structure 2 may be as follows: Figure 1 As shown in the structure, it can be seen that the difference between structure 1 and structure 2 is only whether there is a 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, and the thickness of the dielectric layer 4 is 280nm; the interdigitated electrode 6 is 62 / 18nm aluminum / platinum, λ is 1.015μm, and the in-plane orientation is 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, and the remaining structural parameters are the same as those of structure 1. Please refer to Fig.11 , which shows the simulated admittance response comparison diagram 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 7 with bottom electrode 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 building 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 Fig.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 Fig.13 When the materials of the first dielectric layer 401 and the second dielectric layer 402 are the same, 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 Fig.14 , which is a top view of an exemplary acoustic wave filter of the present application, and the cross section of the acoustic wave filter is as follows Fig.13 The structure shown includes 7 resonators, namely, resonator 1, resonator 2, resonator 3, resonator 4, resonator 5, resonator 6 and resonator 7, wherein resonators 1, 3, 5 and 7 are series resonators 1 and all include bottom electrode 7, and the target mode is SH1 mode; resonators 2, 4 and 6 are parallel resonators 2 and do not include bottom electrode 7, and the target mode is SH0 mode. The parameters of resonators 1 and 7 are the same, the parameters of resonators 3 and 5 are the same, and the parameters of resonators 2 and 6 are the same. 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 245nm; the interdigital electrode 6 is 62 / 18nm aluminum / platinum, and the in-plane orientation is an angle α with the crystal Y axis; the material 7 of the bottom electrode is tungsten with a thickness of 80nm. The materials of the first dielectric layer 401 and the second dielectric layer 402 are both silicon oxide, and the thickness of the second dielectric layer 402 is 200nm. 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. Fig.14 The acoustic wave filter shown in the figure is simulated and tested, and the following results can be obtained: Fig.15From the simulation results shown, it can be seen that due to the huge difference in acoustic 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, and the maximum frequency shift between the series and parallel resonators reaches 625MHz. Fig.16 It can be seen from the transmission coefficient (S21) curve of the acoustic wave filter that its bandwidth is 805 MHz, basically covering the N77 frequency band.

[0103] The present application provides another structure 1 and structure 2 with different structural parameters. In structure 1, the material of the support substrate 3 is 4H-SiC; the material of the piezoelectric layer 5 is X-cut lithium niobate with a thickness of 210nm; the material of the dielectric layer 4 is silicon oxide; the interdigitated electrode 6 is 60 / 20nm aluminum / copper, λ is 1.145μm, and the in-plane orientation is 42° with the crystal Y axis. In structure 2, the thickness of the dielectric layer 4 is 100nm, the material of the bottom electrode 7 is tungsten with a thickness of 30nm, and the remaining structural parameters are the same as those of the above structure 1; please refer to Fig.17 , which shows the simulated admittance response comparison diagram 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 Fig.18 , the present application embodiment provides another acoustic wave filter, the cross section of the acoustic wave filter is as follows Fig.13The structure shown includes 7 resonators, namely, resonator 1, resonator 2, resonator 3, resonator 4, resonator 5, resonator 6 and resonator 7, wherein resonators 1, 3, 5 and 7 are series resonators 1 and all include bottom electrode 7, and the target mode is SH1 mode; resonators 2, 4 and 6 are parallel resonators 2 and do not include bottom electrode 7, and the target mode is LL-SAW mode. The parameters of resonators 1 and 7 are the same, the parameters of resonators 3 and 5 are the same, and the parameters of resonators 2 and 6 are the same. 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 210nm; the interdigitated electrode 6 is 60 / 20nm aluminum / copper, and the in-plane orientation is an angle α with the crystal Y axis; the material of the bottom electrode 7 is tungsten with a thickness of 30nm. 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, the duty ratio (2w / λ) are 0.57 and 0.5, α are 37° and 35°, and νs are 6332m / s and 6061m / s. The λ of resonators 2 and 4 in parallel resonator 2 are 1.145μm and 1.128μm, the duty ratio (2w / λ) are 0.5, α are 42°, and νs are 5662m / s and 5646m / s. Fig.18 The acoustic wave filter shown in the figure is simulated and tested, and the following results can be obtained: Fig.19 From the simulation results shown, it can be seen that due to the difference in acoustic velocity between the series-parallel resonators, the thickness of the piezoelectric layer 5 does not need to be changed, and the λ between the series-parallel resonators is basically the same, so the frequency shift between the series-parallel resonators is achieved. The maximum frequency shift between the series-parallel resonators reaches 555MHz.

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

[0106] In another exemplary embodiment, Fig.12 In the structure shown in FIG. 1 , when the materials of the first dielectric layer 401, the second dielectric layer 402 and the supporting substrate 3 are the same, the following can be obtained: Fig.21 The structure shown.

[0107] In another exemplary embodiment, see Fig. 22 The bottom electrode 7 is a conductive region 8 formed by doping in a preset region of the support substrate 3 , and may also be a conductive region 8 formed by ion irradiation in a preset 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 , and the following will explain the case where both the series-parallel resonators have the bottom electrode 7 .

[0109] In another exemplary embodiment, see Fig.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 Fig.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 the SH1 mode, and when α=119.5°, the target mode is the A1 mode. From Fig.24 It can be seen that by simply changing the in-plane orientation, the target mode changes from SH1 mode to A1 mode, and a frequency difference of 475MHz is achieved under the premise that other parameters are exactly the same. Then only λ and duty cycle need to be fine-tuned to meet the frequency offset requirements. This shows that the frequency offset between different resonators can be adjusted by adjusting λ and duty cycle.

[0112] See also Fig.25 , the present application embodiment provides an acoustic wave filter, the cross section of the acoustic wave filter is as follows Fig.23The structure shown includes 7 resonators, each of which includes a bottom electrode 7, wherein resonators 1, 3, 5, and 7 are series resonators 1, and the target mode is SH1 mode; resonators 2, 4, and 6 are parallel resonators 2, and the target mode is A1 mode. The parameters of resonators 1 and 7 are the same, the parameters of resonators 3 and 5 are the same, and the parameters of resonators 2 and 6 are the same. 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 200nm; the interdigitated electrode 6 is 62 / 18nm aluminum / platinum, and the in-plane orientation is an angle α with the crystal Y axis; the material of the bottom electrode 7 is platinum with a thickness of 95nm, 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 1.243μm and 1.211μm, respectively, the duty cycle (2w / λ) are 0.59 and 0.58, respectively, α are 119° and 119.5°, respectively, and νs are 5774m / s and 5704m / s, respectively. The λ of resonators 2 and 4 in 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°, and νs is 5498m / s and 5473m / s, respectively. Fig.25 The acoustic wave filter shown in the figure is simulated and tested, and the following results can be obtained: Fig.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, which avoids 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. Fig. 27 It can be seen from the transmission coefficient (S21) curve of the acoustic wave filter that the bandwidth is 647MHz, which completely covers the N79 frequency band.

[0113] In another exemplary embodiment, in the case where both the series-parallel resonators have the 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 may be as follows: Fig.28 The structure shown.

[0114] In another exemplary embodiment, whether the bottom electrode 7 is present only in the series resonator 1 or in both the 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 interval 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 the series-parallel resonators have the bottom electrode 7, please refer to Fig.29 , the dielectric layer 4 fills the spacing area between adjacent resonators.

[0115] The above are only exemplary embodiments of the present application. In fact, the acoustic wave filter is not limited to the above exemplary types and combinations. As long as the concept 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 shifts between series and parallel resonators while maintaining the same thickness of the piezoelectric layer 5, they all fall within the protection scope of this solution.

[0116] See also Figure 30-36 The present invention provides a method for preparing an acoustic wave filter, which comprises the following steps:

[0117] 1) Provide a piezoelectric substrate.

[0118] Exemplarily, the piezoelectric substrate may be a piezoelectric crystal containing an ion-implanted damaged layer, and the preparation method of the piezoelectric substrate may be to provide a Fig.30 The piezoelectric crystal shown in FIG. 1 is ion-implanted to form a damaged layer 11 at a preset depth in the piezoelectric crystal to obtain a piezoelectric crystal having a predetermined depth. Fig.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: Fig.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: Fig.33 The structure shown includes a stacked 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] Exemplarily, a specific implementation of step 2) may be to first deposit a metal layer on the piezoelectric substrate, then pattern the metal layer to form a bottom electrode 7, then deposit a dielectric material layer, and polish the surface of the dielectric material layer to form a bottom electrode 7 as shown in FIG. Fig.35 The structure shown in FIG. 1 can be polished to a thickness that can be selected as required. For example, if the desired preparation is as follows: Fig.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 in FIG. 1 , the thickness of the dielectric layer 4 after polishing 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 support substrate 3, and to connect the support substrate 3 with Fig.35 The dielectric layer 4 in the structure is bonded, and then annealed, peeled, and polished to obtain the following Fig.36 By forming the structure shown in FIG. 1 and then forming the interdigitated electrodes 6 on the second piezoelectric layer 10, the structure shown in FIG. 1 can be obtained. Fig.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 only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope 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 both 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 arranged on the top of the piezoelectric layer; a bottom electrode is arranged between the supporting substrate and the piezoelectric layer of at least one of the series resonator and the parallel resonator; a 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; The acoustic wave filter comprises at least two target modes; In each resonator of the acoustic wave filter, the slow shear wave acoustic velocity of the support 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; In the acoustic wave filter, there is at least one series resonator whose target mode has a higher acoustic velocity than a parallel resonator.

2. The acoustic wave filter according to claim 1, characterized in that 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 electrodes is the distance between the centers of adjacent interdigitated electrode fingers on the same bus bar of the interdigitated electrodes; 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, characterized in that 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; The bottom electrode is located in the series resonator.

4. The acoustic wave filter according to claim 2, characterized in that 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 bottom electrode is provided in both the series resonator and the parallel resonator; 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.

5. The acoustic wave filter according to claim 1, characterized in that The parallel resonators use different target modes, and / or the series resonators use different target modes.

6. The acoustic wave filter according to claim 1, characterized in that 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.

7. The acoustic wave filter according to claim 6, characterized in that The dielectric layer comprises 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.

8. 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 interval 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.

9. The acoustic wave filter according to claim 2, characterized in that 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 comprises a bottom electrode, and the in-plane orientation has an angle of -20 to 70° with the Y-axis of the crystal; The resonator whose target mode is a high-order Lamb wave mode comprises 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 a 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 to 200°; 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 of the crystal toward the Z-axis is the positive direction.

10. The acoustic wave filter according to claim 1, characterized in that 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 of different crystal forms and different cut shapes.

11. The acoustic wave filter according to claim 1, characterized in that The support substrate comprises a stacked support layer and a high acoustic velocity layer; the support layer is 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 different cuts.

12. The acoustic wave filter according to claim 1, characterized in that 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.

13. The acoustic wave filter according to claim 2, characterized in that The bottom electrode is a conductive region formed by doping or ion irradiation in a preset region of the supporting substrate.

14. 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.

15. A method for preparing an acoustic wave filter, characterized in that: The following steps are involved: providing a piezoelectric substrate; Sequentially forming a bottom electrode and a dielectric layer on a preset area on the piezoelectric substrate; Bonding the dielectric layer to the supporting substrate, removing the redundant area in the piezoelectric substrate, and forming interdigital electrodes to obtain the acoustic wave filter according to any one of claims 1 to 14; 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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