Lithium niobate acoustic superlattice bulk acoustic wave resonator based on tilted domain structure and design method thereof

Abstract

The application discloses a lithium niobate acoustic superlattice bulk acoustic wave resonator based on a tilted domain structure and a design method thereof. The bulk acoustic wave resonator comprises an upper surface electrode, a lithium niobate acoustic superlattice and a lower surface electrode which are stacked in sequence from top to bottom. The lithium niobate acoustic superlattice comprises alternating positive domain regions and negative domain regions, and the positive domain regions and the negative domain regions are both tilted domains. The application further provides a design method of the bulk acoustic wave resonator. Firstly, simulation parameters are obtained through numerical simulation. Then, the lithium niobate acoustic superlattice with different cut types and with the tilted positive domain regions and the tilted negative domain regions which are periodically arranged alternately is designed according to the simulation parameters. Finally, appropriate electrodes are selected on the upper surface and the lower surface of the lithium niobate acoustic superlattice to form the bulk acoustic wave resonator. The application has a simple structure and realizes the bulk acoustic wave resonator with more working resonance modes and a higher electromechanical coupling coefficient.

Description

Technical Field

[0001] This invention relates to bulk acoustic wave devices and their design methods, and more particularly to a lithium niobate acoustic superlattice bulk acoustic wave resonator based on a tilted domain structure and its design method. Background Technology

[0002] Radio frequency (RF) acoustic devices, capable of signal processing by converting between RF signals and high-frequency sound waves, have been widely applied in mobile communications, industrial applications, and national defense. Innovations in the RF field, such as 5G and the Internet of Things (IoT), have increased the demand for high-performance, passive, and wide-bandwidth RF filters and resonators. Bulk acoustic devices have proven to be a reliable solution for RF signal processing from low to high frequencies. The increasingly diverse application scenarios also necessitate more diverse types, characteristics, and superior performance of bulk acoustic devices.

[0003] Currently widely used bulk acoustic wave (BAW) devices consist of a piezoelectric layer and upper and lower thin films, offering advantages such as small size, suitability for high operating frequencies, low insertion loss, and high power capacity. However, they also have limitations such as a low electromechanical coupling coefficient and complex manufacturing processes. Moreover, for conventional BAW resonators, higher operating frequencies can generally only be achieved by reducing the thickness of the piezoelectric layer, and the electromechanical coupling coefficient depends solely on the properties of the material itself, making it difficult to adjust.

[0004] Lithium niobate is C 3v Symmetrical negative uniaxial ferroelectric crystals possess two antiparallel spontaneous polarization orientations within their ferroelectric phases, meaning they contain only two ferroelectric domains with opposite spontaneous polarization directions along the z-axis. Lithium niobate acoustic superlattices are artificial microstructure materials composed of alternating ferroelectric domains, where the second-order tensors, such as the piezoelectric coefficient, are artificially modulated, while physical quantities like wave velocity and refractive index remain uniform. Due to the piezoelectric effect inherent in acoustic superlattices, stress and strain are generated within them under an electric field, which in turn produce polarization electric fields. Because of the superlattice microstructure, the interaction properties between acoustic superlattices and electromagnetic waves differ significantly from those of homogeneous crystals. Each domain boundary in the acoustic superlattice can also become a source of stress wave excitation, and the operating frequency of acoustic resonators made using this superlattice is inversely proportional to the distribution period of the piezoelectric coefficient. These properties allow acoustic superlattices to be used to realize novel, feature-rich bulk acoustic wave devices.

[0005] Unlike ordinary isotropic materials, lithium niobate, as an anisotropic material, has crystal physical properties closely related to its crystal cut. Furthermore, unlike other isotropic piezoelectric materials, the acoustic properties of lithium niobate are closely related to its tangential orientation and the direction of sound wave propagation. Traditional lithium niobate acoustic superlattice devices are mostly Z-cut lithium niobate acoustic superlattices, which do not fully utilize different cuts of lithium niobate to achieve electroacoustic control. This type of cut lithium niobate acoustic superlattice has a low electromechanical coupling coefficient and a relatively limited range of usable acoustic resonance modes. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a lithium niobate acoustic superlattice acoustic resonator device based on a tilted domain structure and its design method, which has richer resonance modes and higher electromechanical coupling coefficient.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A lithium niobate acoustic superlattice acoustic resonator based on a tilted domain structure includes an upper surface electrode, a lithium niobate acoustic superlattice, and a lower surface electrode stacked from top to bottom. The lithium niobate acoustic superlattice includes alternating positive and negative domain regions. The piezoelectric coefficient of the positive domain region is positive, and the piezoelectric coefficient of the negative domain region is negative. Both the positive and negative domain regions are tilted domains, and the tilt angle θ between the positive and negative domain regions and the electrode surface is θ∈(0°, 90°)∪(90°, 180°).

[0009] A design method for the above-mentioned lithium niobate acoustic superlattice acoustic resonator based on tilted domain structure includes:

[0010] Step (1): Obtain simulation parameters of the lithium niobate acoustic superlattice acoustic resonator that can achieve the target performance, including the physical size parameters of the lithium niobate acoustic superlattice acoustic resonator and the tilt angle θ and ferroelectric domain distribution period T of the lithium niobate acoustic superlattice.

[0011] Step (2): Select the corresponding lithium niobate substrate based on the simulation parameters of step (1);

[0012] Step (3): Calculate the coercive field of lithium niobate based on the tilt angle θ:

[0013] E c (θ)=E c (90°) / cos(θ-90°)

[0014] In the formula, E c (θ) Coercive field of lithium niobate at a tilt angle of θ, E c (90°) represents the coercive field of lithium niobate when the tilt angle is 90°:

[0015] Step (4): According to the ferroelectric domain distribution period T, the thickness H of lithium niobate in the simulation parameters, and the coercive field E of lithium niobate when the tilt angle is θ. c (θ) Select the polarization method that makes the lithium niobate substrate a lithium niobate acoustic superlattice;

[0016] Step (5): Select electrode materials that meet the simulation parameters on the upper and lower surfaces of the lithium niobate acoustic superlattice to form the upper surface electrode and the lower surface electrode, respectively.

[0017] Furthermore, step (1) specifically includes:

[0018] Step (1.1): Set the preliminary simulation parameters of the lithium niobate acoustic superlattice acoustic resonator, including the physical size parameters of the lithium niobate acoustic superlattice acoustic resonator and the ferroelectric domain distribution period T of the lithium niobate acoustic superlattice.

[0019] Step (1.2): The Z-cut lithium niobate material coordinate system is transformed into the ZX-cut lithium niobate material coordinate system with an angle of θ using the Euler angle transformation (α, β, γ) of the ZXZ rotation method. The Euler angles of the positive domain region transformation are (0°, θ+90°, 0°) and the Euler angles of the negative domain region transformation are (0°, θ-90°, 0°).

[0020] Step (1.3): Establish a geometric model of the lithium niobate acoustic superlattice acoustic resonator in the simulation software, set the physical size parameters of the geometric model to the physical size parameters of the simulation parameters, set the ferroelectric domain distribution period of the lithium niobate acoustic superlattice in the geometric model to T in the simulation parameters, and perform meshing on the geometric model.

[0021] Step (1.4): Perform frequency domain calculations based on the geometric model after mesh generation, plot the admittance curve and mode shape diagram based on the frequency domain calculation results, and calculate the electrical coupling coefficient and resonant frequency.

[0022] Step (1.5): Determine whether the electromechanical coupling coefficient is higher than the threshold, whether the resonant frequency is within the resonant frequency range, and whether the parasitic mode is suppressed; if all the judgment results are yes, output the simulation parameters at this time; otherwise, readjust the simulation parameters and return to step (1.2).

[0023] Compared with the prior art, the beneficial effects of this invention are:

[0024] 1. This invention can generate new resonant modes, thereby allowing the utilization of new resonant frequencies. For example... Figure 2As shown, a new A0-mode Lamb wave operating resonance mode was observed in lithium niobate with a 60° tilt angle, with a resonant frequency of 397 MHz, an anti-resonant frequency of 399 MHz, and an electromechanical coupling coefficient of 1.2%. In contrast, traditional non-tilted domain structure lithium niobate superlattices do not exhibit an A0-mode Lamb wave operating resonance mode.

[0025] 2. This invention can increase the electromechanical coupling coefficient of the resonant mode. For example... Figure 5 As shown, the S0 mode Lamb wave resonant frequency of a traditional non-tilted domain structure lithium niobate acoustic superlattice is 610 MHz, the anti-resonance frequency is 614 MHz, and the electromechanical coupling coefficient is 1.6%. In contrast, the 60° tilted domain structure lithium niobate acoustic superlattice exhibits a resonant frequency of 586 MHz and an anti-resonance frequency of 621 MHz in the same mode, with an electromechanical coupling coefficient of 15.1%. The resonance effect is improved while the electromechanical coupling coefficient is significantly enhanced.

[0026] 3. This invention can suppress existing resonant modes. For example... Figure 8 As shown, the S2 mode Lamb wave operating resonant mode of the non-tilted domain structure lithium niobate acoustic superlattice is 1186MHz, the anti-resonant frequency is 1188MHz, and the electromechanical coupling coefficient is 0.4%. In contrast, the 60° tilted domain structure lithium niobate acoustic superlattice effectively suppresses this resonant mode. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the lithium niobate acoustic superlattice acoustic resonator device based on the tilted domain structure provided by the present invention.

[0028] Figure 2 The simulated admittance curves of the lithium niobate acoustic superlattice at θ = 60° and θ = 90° are shown in the A0 mode Lamb wave resonant mode.

[0029] Figure 3 This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 90° and the resonant frequency is 397MHz;

[0030] Figure 4 This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 60° and the resonant frequency is 397MHz;

[0031] Figure 5 The simulated admittance curves of the lithium niobate acoustic superlattice at θ = 60° and θ = 90° are shown in the S0 mode Lamb wave coupled resonant mode.

[0032] Figure 6 This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 90° and the resonant frequency is 610MHz;

[0033] Figure 7This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 60° and the resonant frequency is 586MHz;

[0034] Figure 8 The simulated admittance curves of the lithium niobate acoustic superlattice at θ = 60° and θ = 90° are shown in the S2 mode Lamb wave resonant mode.

[0035] Figure 9 This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 90° and the resonant frequency is 1186MHz;

[0036] Figure 10 This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 60° and the resonant frequency is 1201MHz;

[0037] Figure 11 The simulated admittance curve of the lithium niobate acoustic superlattice at θ = 30° is shown in the S2 mode Lamb wave resonant mode.

[0038] Figure 12 This is the mode shape diagram of the lithium niobate acoustic superlattice with θ = 30° and a resonant frequency of 1128MHz. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0040] Before introducing the embodiments of the present invention, the following should be noted: Lithium niobate piezoelectric crystals are anisotropic materials, which leads to different propagation characteristics of different acoustic modes within the piezoelectric crystal. Therefore, when studying lithium niobate crystals, it is necessary to first specify which crystal plane is being "cut" for study, i.e., the cut type of the lithium niobate crystal. The initial parameters of the material properties of lithium niobate crystals can be represented by the relative positions of a coordinate system (X, Y, Z), called the material coordinate system. Correspondingly, there is a geometric coordinate system that reflects the material's orientation in real space, represented by the relative positions of (x, y, z). The coordinate system of a normally unrotated lithium niobate crystal is the Z-cut lithium niobate. The ZX-cut lithium niobate with an angle of θ corresponds to the lithium niobate crystal cutting plane with the normal direction of the Z-axis rotated counterclockwise by θ around the X-axis. At this time, the lithium niobate crystal coordinate system has already rotated relative to the default geometric coordinate system. Lithium niobate can only spontaneously polarize along the Z-axis of the material coordinate system to generate ferroelectric domains, thereby producing tilted domain structures that rotate θ relative to the z-axis of the geometric coordinate system. At this time, the domain interface makes an angle θ with the electrode plane.

[0041] In the simulation, the material coordinate system of Z-cut lithium niobate was transformed into the ZX-cut lithium niobate material coordinate system with an angle of θ using a ZXZ rotation Euler angle transformation. The Euler angles (α, β, γ) using the ZXZ rotation method are defined as follows: starting from the spatial coordinate system (x, y, z), first rotate counterclockwise by α around the z-axis to obtain the coordinate system (x1, y1, z1), then rotate counterclockwise by β around the x1-axis to obtain the coordinate system (x2, y2, z2), and finally rotate counterclockwise around the z2-axis to obtain the material coordinate system (X, Y, Z). The transformation matrix defined by the Euler angles can transform the vectors (v) in the material coordinate system (X, Y, Z). X ,v Y ,v Z Convert ) to a vector (v) in the spatial coordinate system (x, y, z). x ,v y ,v z ), represented as:

[0042]

[0043] The electromechanical coupling coefficient represents the conversion efficiency between mechanical energy and electrical energy. A larger electromechanical coupling coefficient means higher conversion efficiency. In the actual performance of a resonator, it reflects the frequency bandwidth between the resonant frequency and the anti-resonant frequency. The electromechanical coupling coefficient is defined as the energy conversion efficiency, but in actual calculations, it is difficult to directly apply the definition of energy conversion to calculate the electromechanical coupling coefficient. Therefore, several calculation formulas are commonly used in practical electromechanical coupling coefficient calculations. The calculation form used in this invention is as follows: Where k t It is the electromechanical coupling coefficient, f r It is the resonant frequency, f a It is the anti-resonant frequency.

[0044] Example 1

[0045] This embodiment provides a lithium niobate acoustic superlattice acoustic resonator device based on a tilted domain structure, such as... Figure 1 As shown, it includes an upper surface electrode 1, a lithium niobate acoustic superlattice 2, and a lower surface electrode 3 stacked sequentially from top to bottom. The lithium niobate acoustic superlattice 2 includes alternating positive domain regions 21 and negative domain regions 22. The piezoelectric coefficient of the positive domain regions is positive, and the piezoelectric coefficient of the negative domain regions is negative. Both the positive and negative domain regions are tilted domains with a tilt angle θ = 60°, i.e., ZX-cut lithium niobate with a cut of 60°.

[0046] The upper surface electrode 1 and the lower surface electrode 3 are both single-layer flat aluminum electrodes with a thickness h1 of 200 nm, the lithium niobate acoustic superlattice has a thickness H of 5 μm, and the ferroelectric domain distribution period T of the lithium niobate acoustic superlattice is 8 μm.

[0047] Example 2

[0048] This embodiment provides another acoustic resonator based on a tilted domain structure, which differs from Embodiment 1 in that the tilt angle θ of the positive and negative domain regions is 30°, while other parameters are the same.

[0049] It is understood that in other embodiments, the upper and lower surface electrodes may also be multilayer metals, specifically at least one of Au, Pt, Cr, W, Mo, Ni, Fe, and Ti. The tilt angle θ can be set to any value within (0°, 90°) ∪ (90°, 180°).

[0050] Example 3

[0051] This embodiment provides a design method for a lithium niobate acoustic superlattice acoustic resonator based on a tilted domain structure, specifically including:

[0052] Step (1): Obtain simulation parameters of the lithium niobate acoustic superlattice acoustic resonator that can achieve the target performance, including the physical size parameters of the lithium niobate acoustic superlattice acoustic resonator and the ferroelectric domain distribution period T of the lithium niobate acoustic superlattice; the physical size parameters of the lithium niobate acoustic superlattice acoustic resonator include the upper surface electrode material m1, thickness h1 and shape s1, the lower surface electrode material m2, thickness h2 and shape s2, tilt angle θ, and thickness H of the lithium niobate acoustic superlattice; the lithium niobate acoustic superlattice can convert radio frequency signals into sound waves under the action of a periodic electric field of a specific frequency f, and the excitation frequency of the sound wave is the same as the frequency of the radio frequency signal. The relationship between its resonant frequency f and period T is: f = v / T, where v is the wave velocity corresponding to the resonant mode in the lithium niobate acoustic superlattice.

[0053] This step specifically includes:

[0054] Step (1.1): Set the preliminary simulation parameters of the lithium niobate acoustic superlattice acoustic resonator, including the physical size parameters of the lithium niobate acoustic superlattice acoustic resonator and the tilt angle θ and ferroelectric domain distribution period T of the lithium niobate acoustic superlattice.

[0055] Step (1.2): The Z-cut lithium niobate material coordinate system is transformed into the ZX-cut lithium niobate material coordinate system with an angle of θ using the Euler angle transformation (α, β, γ) of the ZXZ rotation method. The Euler angles for the positive domain region transformation are (0°, θ+90°, 0°), and the Euler angles for the negative domain region transformation are (0°, θ-90°, 0°).

[0056] Step (1.3): Establish a geometric model of the lithium niobate acoustic superlattice acoustic resonator in the simulation software, set the physical size parameters of the geometric model to the physical size parameters of the simulation parameters, set the ferroelectric domain distribution period of the lithium niobate acoustic superlattice in the geometric model to T in the simulation parameters, and perform meshing on the geometric model.

[0057] Step (1.4): Perform frequency domain calculations based on the geometric model after mesh generation, plot the admittance curve and mode shape diagram based on the frequency domain calculation results, and calculate the electrical coupling coefficient and resonant frequency.

[0058] Step (1.5): Determine whether the electromechanical coupling coefficient is higher than the threshold, whether the resonant frequency is within the resonant frequency range, and whether the parasitic mode is suppressed; if all the judgment results are yes, output the simulation parameters at this time; otherwise, readjust the simulation parameters and return to execute step (1.2);

[0059] Step (2): Based on the simulation parameters in step (1), select the corresponding lithium niobate substrate with a cut angle of θ.

[0060] Step (3): Calculate the coercive field of lithium niobate based on the tilt angle θ:

[0061] E c (θ)=E c (90°) / cos(θ-90°)

[0062] In the formula, E c (θ) Coercive field of lithium niobate at a tilt angle of θ, E c (90°) represents the coercive field of lithium niobate when the tilt angle is 90°;

[0063] Step (4): According to the ferroelectric domain distribution period T, the thickness H of lithium niobate in the simulation parameters, and the coercive field E of lithium niobate when the tilt angle is θ. c (θ) Select the polarization method that makes the lithium niobate substrate a lithium niobate acoustic superlattice;

[0064] Step (5): Select electrode materials that meet the simulation parameters on the upper and lower surfaces of the lithium niobate acoustic superlattice to form the upper surface electrode and the lower surface electrode, respectively.

[0065] Comparative Example

[0066] This comparative example provides another lithium niobate acoustic superlattice acoustic resonator device. The difference from Example 1 is that the tilt angle θ of the positive domain region and the negative domain region is 90°, which is the traditional non-tilted domain structure of the lithium niobate acoustic superlattice. Other parameters are the same.

[0067] The following simulation experiments were conducted on Examples 1, 2, and the comparative example under different resonance modes. Figure 2 As shown, the lithium niobate acoustic superlattice does not have an A0 mode working resonance mode when θ = 90°, but exhibits an A0 mode Lamb wave working resonance mode when θ = 60°, with a resonant frequency of 397MHz, an anti-resonant frequency of 399MHz, and an electromechanical coupling coefficient of 1.2%. Figure 3 This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 90° and the resonant frequency is 397MHz; Figure 4 This is the mode shape diagram of the lithium niobate acoustic superlattice at θ = 60° and a resonant frequency of 397MHz. (Example:) Figure 5 As shown, when θ = 90°, the resonant frequency of the S0 mode Lamb wave operating resonant mode of the lithium niobate acoustic superlattice is 610 MHz, the anti-resonant frequency is 614 MHz, and the electromechanical coupling coefficient is 1.6%; when θ = 60°, the resonant frequency of the S0 mode Lamb wave operating resonant mode of the lithium niobate acoustic superlattice is 586 MHz, the anti-resonant frequency is 621 MHz, and the electromechanical coupling coefficient is 15.1%. The resonance effect is improved while the electromechanical coupling coefficient is significantly enhanced. Figure 6 This is the mode shape diagram of the lithium niobate acoustic superlattice at θ = 90° and a resonant frequency of 610MHz. Figure 7 This is the mode shape diagram of the lithium niobate acoustic superlattice at θ = 60° and a resonant frequency of 586 MHz. As shown in Figure 8, at θ = 90°, the resonant frequency of the S2 mode Lamb wave operating resonant mode of the lithium niobate acoustic superlattice is 1186 MHz, the anti-resonant frequency is 1188 MHz, and the electromechanical coupling coefficient is 0.4%. At θ = 60°, the resonant frequency of the S2 mode Lamb wave operating resonant mode of the lithium niobate acoustic superlattice is 1201 MHz, the anti-resonant frequency is 1202 MHz, and the electromechanical coupling coefficient is 0.2%. Figure 9 This is the mode shape diagram of the lithium niobate acoustic superlattice when θ = 90° and the resonant frequency is 1186MHz; Figure 10 This is the mode shape diagram of the lithium niobate acoustic superlattice at θ = 60° and a resonant frequency of 1201MHz. Here, the 60° tilted domain structure of the lithium niobate acoustic superlattice effectively suppresses this resonant mode. Figure 11 As shown, when θ = 30°, the resonant frequency of the S2 mode Lamb wave working resonant mode of the lithium niobate acoustic superlattice is 1128 MHz, the anti-resonant frequency is 1178 MHz, and the electromechanical coupling coefficient is 11.7%. Figure 12 This is the mode shape diagram of the lithium niobate acoustic superlattice with θ = 30° and a resonant frequency of 1128MHz.

[0068] Among them, the lithium niobate acoustic superlattice acoustic resonator with θ = 60° and θ = 120° has a symmetrical structure and the data is consistent, so it will not be described again. The lithium niobate acoustic superlattice acoustic resonator with θ = 30° and θ = 150° has a symmetrical structure and the data is consistent, so it will not be described again.

[0069] It should be understood that the embodiments and descriptions above are only the principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope of the invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on tilted domain structure, characterized by, The lithium niobate acoustic superlattice bulk acoustic wave resonator device comprises an upper surface electrode, a lithium niobate acoustic superlattice and a lower surface electrode which are sequentially stacked from top to bottom, wherein the lithium niobate acoustic superlattice comprises positive domain regions and negative domain regions which are alternately arranged, the positive domain regions have positive piezoelectric coefficients, the negative domain regions have negative piezoelectric coefficients, and the positive domain regions and the negative domain regions are both tilt domains, and the method comprises the following steps: Step (1), obtaining simulation parameters of the lithium niobate acoustic superlattice bulk acoustic wave resonator device capable of achieving target performance, including physical size parameters of the lithium niobate acoustic superlattice bulk acoustic wave resonator device, a tilt angle θ of the lithium niobate acoustic superlattice and a ferroelectric domain distribution period T of the lithium niobate acoustic superlattice; Step (2), selecting a lithium niobate substrate corresponding to a cut type according to the simulation parameters in step (1); Step (3), calculating a coercive field size of the lithium niobate according to the tilt angle θ as follows: ， wherein the coercive field of lithium niobate when the tilt angle is θ, denotes the coercive field of lithium niobate when the tilt angle is θ. Step (4), the coercive field of the lithium niobate when the thickness H and the tilt angle θ of the lithium niobate in the simulation parameters are θ selecting a polarization method for making the lithium niobate substrate into a lithium niobate acoustic superlattice; Step (5), selecting electrode materials on the upper surface and the lower surface of the lithium niobate acoustic superlattice respectively to form an upper surface electrode and a lower surface electrode respectively, wherein the electrode materials satisfy the simulation parameters; Step (1) specifically comprises the following steps: Step (1.1), setting preliminary simulation parameters of the lithium niobate acoustic superlattice bulk acoustic wave resonator device, including physical size parameters of the lithium niobate acoustic superlattice bulk acoustic wave resonator device and a ferroelectric domain distribution period T of the lithium niobate acoustic superlattice; Step (1.2), converting a material coordinate system of Z-cut lithium niobate into a material coordinate system of ZX-cut lithium niobate with an angle θ by Euler angle transformation (α, β, γ) in Z-X-Z rotation mode, wherein the Euler angles of the positive domain region are (0°, θ+90°, 0°), and the Euler angles of the negative domain region are (0°, θ-90°, 0°); Step (1.3), establishing a geometric model of the lithium niobate acoustic superlattice bulk acoustic wave resonator device in a simulation software, setting physical size parameters of the geometric model as the physical size parameters in the simulation parameters, setting a ferroelectric domain distribution period of the lithium niobate acoustic superlattice in the geometric model as T in the simulation parameters, and performing mesh division on the geometric model; Step (1.4), performing frequency domain calculation based on the mesh-divided geometric model, drawing a admittance curve and a mode shape diagram according to the frequency domain calculation result, and calculating an electromechanical coupling coefficient, a resonance frequency; Step (1.5), judging whether the electromechanical coupling coefficient is higher than a threshold value, whether the resonance frequency is within a resonance frequency interval range, and whether a parasitic mode is suppressed; if all the judgment results are yes, outputting the simulation parameters at this time; otherwise, adjusting the simulation parameters again and returning to step (1.2).

2. The design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on a tilted domain structure according to claim 1, characterized in that, The physical size parameters of the lithium niobate acoustic superlattice bulk acoustic wave resonator device include an upper surface electrode material m1, a thickness h1 and a shape s1, a lower surface electrode material m2, a thickness h2 and a shape s2, a tilt angle θ, a ferroelectric domain distribution period T and a lithium niobate acoustic superlattice thickness H.

3. The design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on a tilted domain structure according to claim 1, characterized in that, The cut type of the lithium niobate substrate in step (2) is specifically a ZX-cut type with an angle θ.

4. The design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on a tilted domain structure according to claim 1, characterized in that: The upper surface electrode is single-layer metal or multi-layer metal.

5. The design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on a tilted domain structure according to claim 1, characterized in that: The upper surface electrode is at least one of Al, Au, Pt, Cr, W, Mo, Ni, Fe and Ti.

6. The design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on a tilted domain structure according to claim 1, wherein: The lower surface electrode is single-layer metal or multi-layer metal.

7. The design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on tilted domain structure according to claim 1, wherein: The lower surface electrode is at least one of Al, Au, Pt, Cr, W, Mo, Ni, Fe, Ti. The lower surface electrode is at least one of Al, Au, Pt, Cr, W, Mo, Ni, Fe, Ti.

8. The design method of a lithium niobate acoustic superlattice bulk acoustic wave resonator device based on a tilted domain structure according to claim 1, wherein: The positive domain region and the negative domain region have an inclination angle θ∈(0°, 90°) with the electrode surface (90°, 180°).

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