Multi-piezoelectric-coefficient coupled-mode surface acoustic wave resonator and manufacturing method therefor

Abstract

The present disclosure provides a multi-coefficient coupled-mode surface acoustic wave resonator and a manufacturing method therefor. During operation of the surface acoustic wave resonator, at least two different piezoelectric coefficients are coupled and jointly excite acoustic waves. The multi-coefficient coupled-mode surface acoustic wave resonator comprises: a substrate; a piezoelectric layer, provided on the substrate; an electrode unit, provided on the surface of the piezoelectric layer and comprising at least one interdigital electrode pair; and a reflective grating unit, comprising at least two grating structures which are symmetrically arranged on the two sides of the electrode unit, wherein the equivalent density of the electrode unit is greater than 4000kg / m3. The electric field distribution is changed by changing the mass loading effect of the interdigital electrode pair and the ratio of the electrode wavelength to the thickness of the piezoelectric layer, such that at least two piezoelectric coefficients are mutually coupled to jointly excite acoustic waves, thus achieving the surface acoustic wave resonator having an electromechanical coupling coefficient exceeding 25%.

Description

Surface acoustic wave resonator with multiple piezoelectric coefficient coupled modes and preparation method thereof TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of resonators, and in particular to a surface acoustic wave resonator with multiple piezoelectric coefficient coupled modes and a preparation method thereof. BACKGROUND

[0002] With the wide application of mobile wireless communication devices, SAW (Surface Acoustic Wave) devices have been an important part of signal filtering in radio frequency modules for decades. However, with the rapid development of the fifth generation mobile communication protocol, the newly emerging frequency band requires greater bandwidth, which poses new challenges to the traditional surface acoustic wave resonator in terms of frequency and bandwidth. In order to solve the challenges brought by the new communication protocol, some solutions have been proposed, such as AlScN bulk acoustic wave devices, Lamb wave resonators, and new solutions are proposed to improve the electromechanical coupling coefficient k 2 . This is mainly because the electromechanical coupling coefficient k 2 is considered to be the most important performance indicator, which directly determines the bandwidth of the filter. However, the complex manufacturing process of bulk acoustic wave devices and the need to individually trim the thickness of the piezoelectric film, and the doping of the piezoelectric film will reduce the quality factor of the resonator, are not the most cost-effective solutions.

[0003] On the other hand, piezoelectric waveguides based on suspended films such as Lamb wave resonators. The film is lithium tantalate (LT) or lithium niobate (LN), both of which have been proven to have high Q values or large electromechanical coupling characteristics. In addition, by using periodically poled LN, it also provides a way to alleviate the internal charge cancellation and performance loss during frequency scaling, and preliminary results show good RF performance. However, this requires precise control of the thickness of lithium niobate to achieve a certain frequency, and lacks flexibility in single-chip frequency scaling design; another problem is that the mechanical stability of suspended resonators still needs to be improved in large-scale manufacturing.

[0004] Relatively speaking, the surface acoustic wave resonator is still the most economical solution, and the currently commercially prepared surface acoustic wave devices also follow the above development trend, i.e. to meet higher frequency bands and larger bandwidths. So far, the most mature is the surface acoustic wave resonator with horizontal shear mode, which has a relatively large k 2 , but it mainly works below 3GHz and has many nearby spurious modes.

[0005] SUMMARY

[0006] Therefore, the present disclosure provides a surface acoustic wave resonator with improved electromechanical coupling coefficient and a preparation method thereof, which realizes an electromechanical coupling coefficient of more than 25%.

[0007] In one aspect of the present disclosure, a multi-coefficient coupled mode surface acoustic wave resonator is provided, at least two different piezoelectric coefficients are coupled and jointly excited to generate acoustic waves, the multi-coefficient coupled mode surface acoustic wave resonator comprises: a substrate; a piezoelectric layer disposed on the substrate; an electrode unit disposed on the surface of the piezoelectric layer, the electrode unit comprising at least one pair of interdigital electrodes; a reflective grating unit comprising at least two groups of grating structures symmetrically disposed on both sides of the electrode unit; wherein the equivalent density of the electrode unit is greater than 4000 kg / m 3 By changing the mass loading effect of the interdigital electrode pair and the ratio of the electrode wavelength to the piezoelectric layer thickness to change the electric field distribution, at least two piezoelectric coefficients are coupled to jointly excite acoustic waves, and a surface acoustic wave resonator with an electromechanical coupling coefficient exceeding 25% is realized.

[0008] According to the embodiments of the present disclosure, the thickness of the piezoelectric layer is 10 nm to 10000 nm; the ratio of the wavelength of the interdigital electrode pair to the thickness of the piezoelectric layer is between 0.2 and 20.

[0009] According to the embodiments of the present disclosure, the piezoelectric layer is X-cut or Y-cut lithium niobate; the performance of the surface acoustic wave resonator is improved by changing the related parameters of the piezoelectric layer and / or changing the related parameters of the interdigital electrode; the related parameters of the piezoelectric layer include the tangential direction and the thickness of the piezoelectric layer. The related parameters of the interdigital electrode include the wavelength, material, thickness, length, width, and extension direction of the interdigital electrode.

[0010] According to the embodiments of the present disclosure, the distance between the interdigital electrode pairs is 0.001 um to 50 um; the thickness of the interdigital electrode is 5 nm to 500 nm; the width of the interdigital electrode is 0.001 um to 10 um; the length of the interdigital electrode is 1 um to 500 um.

[0011] According to the embodiments of the present disclosure, each group of grating structures comprises 2 to 100 reflective gratings.

[0012] According to the embodiments of the present disclosure, the preparation material of the interdigital electrode and / or the reflective grating unit is selected from at least one of Pt, Au, W, Ag, Mo, Cu, Ni, Fe, Cr, Ti.

[0013] According to the embodiments of the present disclosure, the preparation material of the substrate is selected from at least one of silicon, sapphire, gallium nitride, or silicon carbide; or the substrate is a composite substrate composed of any one of silicon, sapphire, gallium nitride, silicon carbide and SiO2.

[0014] According to the embodiments of the present disclosure, the piezoelectric layer is X-cut lithium niobate, and the Euler angle α is in the range of -40° to 40°, the Euler angle α being the included angle between the extension direction of the interdigital electrode and the +z axis direction in the X-cut lithium niobate coordinate system.

[0015] According to the embodiment of the present disclosure, the piezoelectric layer is Y-cut lithium niobate, and an Euler angle a is in a range of -40° to 40°, where the Euler angle a is an angle between an extension direction of the interdigital electrode and a +z axis direction in a coordinate system of the Y-cut lithium niobate.

[0016] In another aspect of the present disclosure, a preparation method of a multi-coefficient coupled mode surface acoustic wave resonator is provided, and the preparation method is used for preparing the surface acoustic wave resonator described above, and the preparation method comprises the following steps: providing a substrate; preparing a piezoelectric layer on the substrate; preparing an electrode unit in a middle region of the substrate; and preparing a reflective grating unit symmetrically on both sides of the electrode unit, so as to complete the preparation of the surface acoustic wave resonator.

[0017] In the surface acoustic wave resonator and the preparation method thereof provided by the present disclosure, the proportion of the electrode wavelength and the piezoelectric layer thickness is adjusted, so that the resonator forms mode coupling to generate a large bandwidth, and the equivalent density of the resonator is greater than 4000 kg / m 3 The metal is thickened to obtain a large quality factor, and finally a multi-piezoelectric coefficient coupled mode surface acoustic wave resonator with a high quality factor and an electromechanical coupling coefficient greater than 25% and a preparation method thereof are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0018] FIG. 1 schematically shows a top view of a multi-coefficient coupled mode surface acoustic wave resonator provided by an embodiment of the present disclosure;

[0019] FIG. 2 schematically shows a cross-sectional view of a multi-coefficient coupled mode surface acoustic wave resonator provided by an embodiment of the present disclosure;

[0020] FIG. 3 schematically shows a three-dimensional view (right-handed system) of Euler angle a rotation when the piezoelectric layer adopts X-cut lithium niobate according to an embodiment of the present disclosure;

[0021] FIG. 4 schematically shows a three-dimensional view (right-handed system) of Euler angle a rotation when the piezoelectric layer adopts Y-cut lithium niobate according to an embodiment of the present disclosure;

[0022] FIG. 5 schematically shows a ratio structure schematic diagram of an interdigital electrode wavelength (λ) and a piezoelectric layer thickness (T LN ) according to an embodiment of the present disclosure;

[0023] FIG. 6 schematically shows a simulation performance diagram of a surface acoustic wave resonator with an interdigital electrode width of 150 nm and a wavelength of 600 nm using a 15-nm Mo electrode when the Euler angle is 0° based on 300-nm X-cut lithium niobate according to an embodiment of the present disclosure;

[0024] Fig. 7 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 300 nm X-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 60 nm Mo electrode, and an Euler angle of 0°;

[0025] Fig. 8 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 300 nm X-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 130 nm Mo electrode, and an Euler angle of 0°;

[0026] Fig. 9 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 300 nm X-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 20 nm Au electrode, and an Euler angle of 0°;

[0027] Fig. 10 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 300 nm X-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 20 nm Au electrode, and an Euler angle of 5°;

[0028] Fig. 11 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 300 nm X-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 90 nm Pt electrode, and an Euler angle of 5°;

[0029] Fig. 12 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 300 nm X-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 85 nm Cu electrode, and an Euler angle of 0°;

[0030] Fig. 13 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 300 nm X-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 190 nm Cr electrode, and an Euler angle of 0°;

[0031] Fig. 14 schematically shows a simulation performance diagram of a surface acoustic wave resonator based on 400 nm Y-cut lithium niobate, with an interdigital electrode width of 150 nm and a wavelength of 600 nm, using a 20 nm Fe electrode, and an Euler angle of 0°;

[0032] Fig. 15 schematically shows a flowchart of a surface acoustic wave resonator with multi-coefficient coupling modes according to an embodiment of the present disclosure.

[0033] Reference signs:

[0034] 1 - substrate; 2 - piezoelectric layer; 3 - electrode unit; 4 - gate structure. DETAILED DESCRIPTION

[0035] The present disclosure provides a multi-piezoelectric coefficient coupled mode surface acoustic wave resonator and a preparation method thereof. By changing the mass loading effect of the metal electrode, i.e., designing the ratio of the electrode width, thickness and piezoelectric layer thickness to change the electric field distribution, at least two piezoelectric coefficients (e.g., piezoelectric coefficients with the same positive coefficient or the same negative coefficient), i.e., piezoelectric coefficients with similar or the same vibration direction, are utilized to realize a high electromechanical coupling coefficient surface acoustic wave resonator structure with an electromechanical coupling coefficient exceeding 10%. The present disclosure couples all piezoelectric coefficients with the same direction vibration to realize a surface acoustic wave resonator with an ultra-large bandwidth.

[0036] In order to make the objects, technical solutions and advantages of the present disclosure clearer, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the drawings.

[0037] In the embodiments of the present disclosure, a multi-piezoelectric coefficient coupled mode surface acoustic wave resonator is provided, which is shown in FIGS. 1-4. The multi-piezoelectric coefficient coupled mode surface acoustic wave resonator comprises:

[0038] A multi-coefficient coupled mode surface acoustic wave resonator is provided. At least two different piezoelectric coefficients are coupled and jointly excite acoustic waves during operation. The multi-coefficient coupled mode surface acoustic wave resonator comprises:

[0039] a substrate 1;

[0040] a piezoelectric layer 2 disposed on the substrate;

[0041] an electrode unit 3 disposed on the surface of the piezoelectric layer, the electrode unit comprising at least one pair of interdigital electrodes;

[0042] a reflective grating unit comprising at least two groups of grating structures 4 symmetrically disposed on both sides of the electrode unit; wherein the equivalent density of the electrode unit 3 is greater than 4000 kg / m 3 By changing the mass loading effect of the interdigital electrode pair and the ratio of the electrode wavelength and the piezoelectric layer thickness to change the electric field distribution, at least two piezoelectric coefficients are coupled to jointly excite acoustic waves, and a surface acoustic wave resonator with an electromechanical coupling coefficient exceeding 25% is realized.

[0043] According to the embodiments of the present disclosure, the substrate 1 can be one or more layers, for example, the substrate 1 is a silicon substrate, a sapphire substrate (Al2O3), a gallium nitride substrate (GaN) or a silicon carbide substrate (SiC); or the substrate is a composite substrate composed of any one of silicon, sapphire, gallium nitride, silicon carbide and SiO2.

[0044] According to the embodiments of the present disclosure, the plurality of periodically arranged reflective gratings in the grating structure 4 (e.g., 3 reflective gratings in each grating structure as shown in FIG. 1) can be separated into completely independent states, or the ends of the plurality of reflective gratings in the grating structure can be connected to each other. The grating structure is used to isolate the interference of the piezoelectric layer between different electrodes, to maximize the piezoelectric strain of a specific vibration mode, and to reduce the loss of acoustic waves.

[0045] The distance between adjacent reflective gratings and reflective gratings can be 0.01-5um, for example, 150nm or 1um.

[0046] According to the embodiments of the present disclosure, the equivalent density of the electrode unit and / or the reflective grating unit is greater than 4000kg / m 3 The preparation material is selected from Pt, Au, W, Ag, Mo, Cu, Ni, Fe, Cr, Ti, or an alloy thereof.

[0047] Preferably, the ratio of the wavelength (λ) of the interdigital electrode to the thickness (T LN ) of the piezoelectric layer is between 1.5-3.

[0048] The thickness of the interdigital electrode can be 1-500nm, preferably, the thickness of the interdigital electrode is between 1-200nm, for example, 20nm or 90nm.

[0049] The thickness of the interdigital electrode can be 5-500nm, for example, 20nm or 90nm.

[0050] The width of the interdigital electrode is 0.01-5um, for example, 150nm or 1um.

[0051] The length of the interdigital electrode is 1-500um, for example, 20um or 30um.

[0052] Optionally, the distance between adjacent interdigital electrodes (interdigital electrode pairs) is 0.01-5um.

[0053] In the embodiments of the present disclosure, the piezoelectric layer 2 can be an X-cut or Y-cut lithium niobate layer (LN), and the thickness of the piezoelectric layer 2 can be 10-10000nm, for example, 300nm or 600nm.

[0054] According to the embodiments of the present disclosure, when the piezoelectric layer film is X-cut lithium niobate, the preferred Euler angle value range is -40°-40°, when the electrode is Mo and the thickness is 10-130nm, k 2 is greater than 40%. When the piezoelectric layer film is Y-cut lithium niobate, the preferred Euler angle value range is -40°-40°, when the electrode is Fe and the thickness is 20nm, k 2greater than 50%. The Euler angle a is the included angle between the direction of the interdigital electrode (i.e. the extension direction of the interdigital electrode) and the +z axis direction under the X-cut lithium niobate coordinate system (right-handed system).

[0055] According to the embodiment of the present disclosure, FIG. 4 is a three-dimensional schematic diagram of Euler angle a rotation under Y-cut lithium niobate, the Euler angle a ranges from -40° to 40°, and the Euler angle a is the included angle between the direction of the interdigital electrode and the +z axis direction under the Y-cut lithium niobate coordinate system (right-handed system).

[0056] According to the embodiment of the present disclosure, FIG. 5 is a schematic diagram of the ratio of the interdigital electrode wavelength to the thickness of the piezoelectric layer (T LN ) provided by the embodiment of the present disclosure. The interdigital electrode wavelength λ is twice the distance between the centers of two adjacent interdigital electrodes. When the ratio of the interdigital electrode wavelength to the thickness of the piezoelectric layer is 1.5-3, the resonant frequency can be changed by changing the thickness of the metal electrode and the Euler angle a, and the resonant frequencies of multiple modes can be made the same and coupled, so that the resonator has a very large electromechanical coupling coefficient.

[0057] According to the embodiment of the present disclosure, FIGS. 6-8 are simulation results of the surface acoustic wave resonator provided by the embodiment of the present disclosure based on 300nm X-cut lithium niobate, with an interdigital electrode width of 150nm and a wavelength of 600nm, i.e. the ratio of the interdigital electrode wavelength to the thickness of the piezoelectric layer is 2. As shown in FIG. 6, a 15nm Mo electrode is used, and the Euler angle is 0°. As shown in FIG. 7, a 60nm Mo electrode is used, and the Euler angle is 0°. As shown in FIG. 8, a 130nm Mo electrode is used, and the Euler angle is 0°. As shown in FIGS. 6-8, through multiple simulation verifications, there are two resonant peaks near the resonant frequency, and by thickening the electrode, both resonant peaks can be moved to low frequency, and the second resonant peak moves faster, gradually reaches the same frequency as the first resonant peak and is coupled, which is manifested as the reduction and disappearance of the in-band spur. After the in-band spur disappears, the thickness of the electrode is continuously increased to adjust the resonant frequency of the resonator, so that there is no spur in the resonant frequency band, and the quality factor of the resonator is improved under the premise of ensuring the electromechanical coupling coefficient.

[0058] According to the embodiments of the present disclosure, FIGS. 9-10 are simulation results of the surface acoustic wave resonator based on 300nm X-cut lithium niobate, with an interdigital electrode width of 150nm and a wavelength of 600nm, as shown in FIG. 9, the simulation is performed using a 20nm Au electrode and an Euler angle of 0°; as shown in FIG. 10, the simulation is performed using a 20nm Au electrode and an Euler angle of 5°. In combination with FIGS. 9-10, it is verified through multiple simulations that, similar to thickening the electrode, rotating the Euler angle can make both resonance peaks move to low frequencies and produce coupling, so that the in-band spurs disappear. However, both schemes will cause the electromechanical coupling coefficient of the resonator to decrease. In order to achieve better performance, the Euler angle and the electrode thickness need to be adjusted and selected in a compromise manner according to different metals.

[0059] The above results show that, by changing the Euler angle and adjusting the electrode thickness, the in-band spurs can be removed, and a surface acoustic wave resonator with an electromechanical coupling coefficient greater than 25% and a high quality factor can be obtained in a very large frequency range.

[0060] According to the embodiments of the present disclosure, FIGS. 11-13 are simulation results of the surface acoustic wave resonator based on 300nm X-cut lithium niobate, with an interdigital electrode width of 150nm and a wavelength of 600nm, as shown in FIG. 11, the simulation is performed using a 90nm Pt electrode and an Euler angle of 5°; as shown in FIG. 12, the simulation is performed using an 85nm Cu electrode and an Euler angle of 0°; as shown in FIG. 13, the simulation is performed using a 190nm Cr electrode and an Euler angle of 0°. In combination with FIGS. 11-13, the results show that, by using this structure, a variety of electrode metals can be used to obtain a surface acoustic wave resonator with an electromechanical coupling coefficient greater than 25% and a high quality factor.

[0061] FIG. 14 is a simulation result of a surface acoustic wave resonator based on 400nm Y-cut lithium niobate, with an interdigital electrode width of 150nm and a wavelength of 600nm, i.e., the ratio of the electrode wavelength to the thickness of the piezoelectric layer is 1.5. The simulation is performed using a 20nm Fe electrode and an Euler angle of 0°. The results show that the surface acoustic wave resonator obtained by using this structure has a working frequency greater than 6GHz and an electromechanical coupling coefficient greater than 50%.

[0062] The present disclosure also provides a preparation method of a multi-coefficient coupling mode surface acoustic wave resonator, which is used to prepare the surface acoustic wave resonator described above, in combination with FIGS. 1, 2 and 15, the preparation method comprises the following steps:

[0063] Operation S1: providing a substrate;

[0064] Operation S2: preparing a piezoelectric layer on the substrate;

[0065] Operation S3: preparing an electrode unit in the middle region of the substrate;

[0066] Operation S4: preparing a reflection grating unit symmetrically on both sides of the electrode unit, and completing the preparation of the surface acoustic wave resonator.

[0067] In operation S3 and operation S4, the electrode unit and the reflection grating unit can be manufactured by using a lift off process or an etching process.

[0068] As can be seen from the above description, the surface acoustic wave resonator with multiple coefficient coupled modes and the preparation method thereof provided by the technical scheme of the present disclosure can form mode coupling to generate a large bandwidth by designing a special ratio of electrode wavelength to piezoelectric layer thickness, and can obtain a large equivalent density greater than 4000 kg / m 3 a metal and thicken the electrode to obtain a large quality factor, and finally obtain a surface acoustic wave resonator with multiple piezoelectric coefficient coupled modes and an electromechanical coupling coefficient greater than 40%.

[0069] Hereinbefore, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that the implementation manners not shown or described in the drawings or the text of the specification are known to those skilled in the art, and are not described in detail. In addition, the definitions of the elements and methods described above are not limited to the various specific structures, shapes or manners mentioned in the embodiments, and can be simply changed or replaced by those skilled in the art.

[0070] According to the above description, those skilled in the art should have a clear understanding of the surface acoustic wave resonator with multiple piezoelectric coefficient coupled modes and the preparation method thereof.

[0071] In summary, the present disclosure provides a surface acoustic wave resonator with multiple piezoelectric coefficient coupled modes and a preparation method thereof. By selecting a metal electrode that meets certain density requirements, adjusting the ratio of the horizontal wavelength of the interdigital electrode to the thickness wavelength, and distributing the horizontal and thickness direction electric fields in proportion, at least two first-order or multi-order, mutually orthogonal polarized coupled modes of acoustic waves are excited under specific tangential piezoelectric thin films, specific Euler angles, and specific propagation directions, at least one of which contains a shear mode, thereby realizing a high-frequency, large-bandwidth coupled mode resonator. When the horizontal wavelength and the thickness wavelength are increased or shortened synchronously while maintaining the ratio, the resonator operating frequency can range from tens of MHz to tens of GHz, and the electromechanical coupling coefficient remains high. The coupled mode resonator is almost suitable for all current communication frequency bands, and meets the high-frequency, large-bandwidth requirements of future 6G frequency bands and millimeter wave communication.

[0072] It should be further understood that the above-described specific examples are intended to be illustrative only and not limiting of the present disclosure, and that any modifications, equivalents, improvements, and the like that incorporate the principles of the present disclosure are intended to be included within the scope of the present disclosure.

Claims

1.A surface acoustic wave resonator with multi-coefficient coupled modes, at least two different piezoelectric coefficients are coupled and acoustic waves are excited together during operation, the surface acoustic wave resonator with multi-coefficient coupled modes comprising: a substrate; a piezoelectric layer disposed on the substrate; an electrode unit disposed on the surface of the piezoelectric layer, the electrode unit comprising at least one pair of interdigital electrodes; and a reflective grating unit comprising at least two groups of grating structures symmetrically disposed on both sides of the electrode unit. 2.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1, wherein the thickness of the piezoelectric layer is 10 nm to 10,000 nm; and the ratio of the wavelength of the interdigital electrodes to the thickness of the piezoelectric layer is 0.2 to 20. 3.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1 or 2, wherein the piezoelectric layer is X-cut or Y-cut lithium niobate; and the performance of the surface acoustic wave resonator is improved by changing the relevant parameters of the piezoelectric layer and / or changing the relevant parameters of the interdigital electrodes. The relevant parameters of the piezoelectric layer include the thickness and the cut direction of the piezoelectric layer. The relevant parameters of the interdigital electrodes include the wavelength, material, thickness, length, width and extension direction of the interdigital electrodes. The equivalent density of the electrode unit is greater than 4000 kg / m 3 By changing the mass loading effect of the interdigital electrode pair and the ratio of the electrode wavelength to the thickness of the piezoelectric layer to change the electric field distribution, at least two piezoelectric coefficients are coupled to each other to jointly excite the acoustic wave, and an acoustic surface wave resonator with an electromechanical coupling coefficient exceeding 25% is realized. 4.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1, wherein the distance between the interdigital electrodes is 0.001 um to 50 um; the thickness of the interdigital electrodes is 5 nm to 500 nm; the width of the interdigital electrodes is 0.001 um to 10 um; and the length of the interdigital electrodes is 1 um to 500 um. 5.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1, wherein each group of grating structures comprises 2 to 100 reflective gratings. 6.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1, wherein the material of the interdigital electrodes and / or the reflective grating unit is selected from at least one of Pt, Au, W, Ag, Mo, Cu, Ni, Fe, Cr and Ti. 7.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1, wherein the material of the substrate is selected from at least one of silicon, sapphire, gallium nitride and silicon carbide; or the substrate is a composite substrate composed of any one of silicon, sapphire, gallium nitride and silicon carbide and SiO 2. 8.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1, wherein the piezoelectric layer is X-cut lithium niobate, and the Euler angle α is in the range of -40° to 40°, the Euler angle α being the angle between the extension direction of the interdigital electrodes and the +z axis direction in the coordinate system of the X-cut lithium niobate. 9.The surface acoustic wave resonator with multi-coefficient coupled modes according to claim 1, wherein the piezoelectric layer is Y-cut lithium niobate, and the Euler angle α is in the range of -40° to 40°, the Euler angle α being the angle between the extension direction of the interdigital electrodes and the +z axis direction in the coordinate system of the Y-cut lithium niobate. 10.A method for preparing a surface acoustic wave resonator with multi-coefficient coupled modes, the method being used for preparing the surface acoustic wave resonator according to any one of claims 1 to 9, the method comprising: providing a substrate; and preparing a piezoelectric layer on the substrate. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ An electrode unit is prepared in the middle region of the substrate; A reflective grating unit is prepared symmetrically on both sides of the electrode unit, and the preparation of the surface acoustic wave resonator is completed.

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