A lateral excitation bulk acoustic wave resonator and a method of fabrication

Abstract

A transverse excitation bulk acoustic wave resonator and a preparation method thereof, the structure of which comprises a piezoelectric layer, a top arc-shaped double electrode, a substrate and a cavity below the piezoelectric layer, the upper surface of the piezoelectric layer is configured with an arc-shaped double electrode interdigital structure connected by a bus perpendicular to the direction of the electrode. In addition, the resonator also adopts an electrode end region aperture region etched, by using an acoustic impedance mismatch to limit the acoustic wave reflection boundary, the stray mode of the resonator can be effectively suppressed and the side acoustic energy leakage of the resonator can be reduced, and the quality factor of the resonator is improved. The design of the arc-shaped double electrode can effectively suppress the parasitic mode and improve the spectral smoothness while realizing high quality factor (Q) and high electromechanical coupling coefficient (k t 2 ), so that the filter formed thereby has excellent characteristics of large bandwidth, low loss, low power consumption and steep roll-off.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency technology, specifically relating to a transverse exciter acoustic resonator and its fabrication method. Background Technology

[0002] In existing RF front-end systems, acoustic filters based on piezoelectric acoustic resonators are widely used to meet the requirements of 5G and future 6G wireless communication systems for low insertion loss, high selectivity, and compact size in the 3–7 GHz and higher frequency bands. These acoustic filters typically consist of multiple piezoelectric acoustic resonators arranged in a trapezoidal or lattice network structure to achieve bandpass or bandstop filtering. The resonant frequency, effective electromechanical coupling coefficient, and quality factor of each resonator determine the filter's center frequency, achievable relative bandwidth, and insertion loss performance, respectively. In recent years, lateral exciter acoustic resonators (XBARs) based on lithium niobate thin films have been considered an important technological approach for realizing high-frequency broadband acoustic filtering due to their high sound velocity and significant electromechanical coupling potential.

[0003] However, due to the significant anisotropy of lithium niobate materials and their tendency to simultaneously excite multiple acoustic modes in XBAR structures, traditional XBAR devices generally suffer from significant spurious responses and limited quality factors. These spurious modes not only introduce additional insertion losses but also disrupt the flatness of the filter passband and reduce out-of-band rejection, thus limiting their application in high-performance RF front-end systems. To alleviate these problems, existing research has focused on suppressing lateral parasitic modes and improving the quality factor by introducing trenches, vias, local thinning structures, or employing dual-electrode designs in thin films. However, these solutions often rely on complex micro / nano fabrication processes and strict manufacturing windows, increasing the difficulty and cost of the process. Furthermore, since the lateral boundary conditions in the IDT region have not been fundamentally improved, higher-order lateral modes may still accumulate along the aperture direction, making it difficult to completely eliminate residual spurious peaks. Therefore, achieving effective suppression of XBAR spurious modes and simultaneous improvement of the quality factor without significantly increasing manufacturing complexity remains a pressing issue that needs to be addressed in current technologies. Summary of the Invention

[0004] To address the problems of unreasonable acoustic energy distribution, high interface loss, and difficulty in effectively suppressing high-order A1 transverse stray modes in existing XBAR resonators due to the anisotropy and multimodal coexistence of lithium niobate material, this invention aims to provide an A1-mode resonator structure that can simultaneously improve stray mode suppression and quality factor without significantly increasing manufacturing complexity. To this end, this invention proposes a transverse exciter acoustic resonator and its fabrication method. By employing a dual-electrode configuration to re-regulate the acoustic energy distribution, the acoustic energy is preferentially localized in the gap region between adjacent electrodes, thereby reducing energy dissipation at the electrode-lithium niobate interface and improving the resonator's quality factor. Simultaneously, by introducing an arc-shaped boundary structure at the electrode edges, the local incident angle of the transverse acoustic wave is modulated and the transverse electric field distribution is reshaped to enhance the excitation efficiency of the target A1 mode and suppress the formation and accumulation of high-order A1 transverse stray modes. This improves the resonator's stray-free characteristics and overall performance indicators, meeting the requirements of high-frequency broadband acoustic filtering applications.

[0005] A transverse exciter acoustic resonator, comprising:

[0006] The substrate serves as the supporting base for the entire resonator; piezoelectric thin film layers are stacked on the substrate; arc-shaped interdigitated electrode systems (IDTs) are deposited on the upper surface of the piezoelectric thin film layers, including busbars and arc-shaped dual electrodes extending from the busbars; release windows are opened on the piezoelectric thin film layers; vias opened on the piezoelectric thin film layers serve as broadband piston modes, used to introduce etching gas to remove the underlying substrate to form a cavity, and also to suppress energy leakage; the suspended cavity is located below the piezoelectric thin film layers and is formed by etching the substrate.

[0007] The method for fabricating a transverse excitation body acoustic resonator includes the following steps:

[0008] Substrate preparation: Prepare Z-cut lithium niobate-silicon composite wafers and perform cleaning and drying processes;

[0009] Hard mask fabrication: Photoresist is coated on the surface of lithium niobate and developed into an electrode pattern, which serves as a mask for subsequent etching;

[0010] Electrode deposition: Using maskless photolithography, metal evaporation and lift-off processes, arc-shaped dual electrodes and busbars are fabricated on the thin film surface to obtain an arc-shaped dual interdigitated electrode system;

[0011] Piezoelectric layer etching: Lithium niobate is etched using inductively coupled plasma technology to form a release window;

[0012] Suspension release: XeF2 gas is used to etch away the underlying silicon substrate through the release window to form a cavity, thus suspending the resonant region.

[0013] The transverse excitation body acoustic resonator with an arc-shaped edge dual electrode structure proposed in this invention has significant technical advantages and social contributions compared with the prior art.

[0014] (1) The resonator structure effectively reduces the mass load of the electrode coverage area and weakens the acoustic impedance discontinuity by splitting the traditional single electrode into a double arc double electrode, so that the acoustic energy is more concentrated in the gap area between adjacent electrodes, significantly reducing the energy loss at the interface between the electrode and the piezoelectric layer, thereby greatly improving the quality factor (Q value) of the resonator.

[0015] (2) By introducing the arc-shaped electrode edge design, the incident angle and reflection phase of the lateral acoustic wave are modulated by the continuously changing local normal, which destroys the coherence condition for the formation of the lateral standing wave. Without increasing the complexity of the manufacturing process, the deep suppression of the high-order A1 lateral spurious mode is achieved, and a nearly spurious admittance spectrum is obtained.

[0016] (3) The arc-shaped edge optimizes the lateral electric field distribution and further enhances the excitation efficiency of the target A1 mode.

[0017] (4) Experimental data show that the device achieves a high coupling coefficient of 22.1% and a performance figure of 132 at a frequency of 4.5 GHz, with an overall performance improvement of about 3.2 times compared with the traditional structure.

[0018] (5) This invention provides a core radio frequency filter component solution for 5G and future 6G communication systems that combines high frequency, large bandwidth, low insertion loss and high selectivity. Its structural design achieves high performance while taking into account the feasibility of mass production, which helps to reduce the manufacturing threshold and cost of high-performance radio frequency front-end chips. It has great strategic significance for promoting the mobile communication industry chain to move towards high frequency bands and accelerating the localization process of high-end acoustic filters. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a transverse exciter acoustic resonator with an arc-shaped dual-electrode structure according to a specific embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the cross-section of the transverse exciter acoustic resonator in a specific embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram showing the dimensions of the arc-shaped dual electrodes in a specific embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of substrate preparation in the fabrication method of the transverse exciter acoustic resonator according to a specific embodiment of the present invention.

[0023] Figure 5This is a schematic diagram illustrating the hard mask preparation to form the electrode deposition region in the fabrication method of the transverse exciter acoustic resonator according to a specific embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram of electrode deposition in the fabrication method of the transverse exciter acoustic resonator according to a specific embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram illustrating the hard mask preparation to form the piezoelectric layer etching region in the fabrication method of the transverse exciter acoustic resonator in a specific embodiment of the present invention.

[0026] Figure 8 This is a schematic diagram of piezoelectric layer etching in the fabrication method of the transverse exciter acoustic resonator according to a specific embodiment of the present invention.

[0027] Figure 9 This is a schematic diagram of the suspension release in the preparation method of the transverse exciter acoustic resonator in a specific embodiment of the present invention.

[0028] Figure 10 This is an admittance curve of a transverse exciter acoustic resonator with an arc-shaped dual-electrode structure according to a specific embodiment of the present invention.

[0029] Figure 11 The figure shows the admittance curve of a conventional single-electrode transverse exciter acoustic resonator in a specific embodiment of the present invention.

[0030] Figure 12 This is an admittance curve of a transverse exciter acoustic resonator with only two electrodes and no arc structure in a specific embodiment of the present invention.

[0031] In the figure: 10-substrate, 20-piezoelectric thin film layer, 30-Pad region, 40-arc dual electrode, 50-release window, 60-wideband piston mode, 70-suspended cavity, 80-photoresist, 100-resonator. Detailed Implementation

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] This embodiment provides a transverse excitation volume acoustic resonator and its fabrication method, belonging to the field of radio frequency microelectromechanical systems (MEMS) devices. It presents a transverse excitation volume acoustic resonator (arched-edge double-electrode, AED-XBAR) with an arc-shaped double-electrode structure. The transverse excitation volume acoustic resonator includes: a substrate; a piezoelectric layer located on the substrate; a cavity structure configured as a release cavity extending downwards from the upper surface of the substrate, with the top of the release cavity covered by the piezoelectric layer; and an arc-shaped interdigitated double-electrode structure located on the piezoelectric layer. In this embodiment, by setting the arc-shaped interdigitated double-electrode structure in the transverse excitation volume acoustic resonator, the purpose of suppressing stray modes can be achieved, thus exhibiting the performance characteristics of fewer stray modes and enabling the realization of a high-frequency, large-bandwidth filter with extremely low in-band ripple.

[0034] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] refer to Figure 1 and Figure 2 The AED-XBAR resonator 100 provided in this embodiment mainly consists of the following parts:

[0036] Substrate 10: Serves as the supporting substrate for the entire device and is typically made of a 4-inch silicon (Si) wafer. The silicon substrate is 400µm thick.

[0037] Piezoelectric thin film layer 20: Stacked on substrate 10, in this embodiment a Z-cut lithium niobate single crystal thin film with a thickness of 400nm is used.

[0038] Arc-shaped interdigitated electrode (IDT) system: deposited on the upper surface of the piezoelectric thin film layer 20, including a busbar in the Pad region 30 and arc-shaped dual electrodes 40 extending from the busbar.

[0039] Busbars are metal strips that directly connect to the interdigital electrodes (IDTs) and are responsible for evenly distributing the electrical excitation signal to the IDTs. They are typically located above or at the edge of the cavity and form the core path for signal transmission. They employ a peripheral surround structure (full anchor point structure), meaning a ring of structure surrounding the resonator outside the cavity boundary. In AED-XBAR designs, to prevent signal leakage through the substrate, the signal busbars are usually insulated from or disconnected from the surrounding mechanical support rings.

[0040] The main functions of the surrounding structure include: 1. Mechanical support and improved yield. Firstly, it prevents collapse. Since the lithium niobate film is only 400nm thick and has a completely hollowed-out cavity underneath, without the robust anchor points around it, the film is prone to collapse or damage during the fabrication process (especially the release etching stage). Secondly, it balances stress. The surrounding structure helps disperse residual stress inside the film, ensuring the flatness of the resonator surface. 2. Defining acoustic boundary conditions. The cavity structure provides a free boundary for sound waves, thus suppressing energy leakage. The design of the anchor point structure directly affects the impedance mismatch as sound waves diffuse outward from the resonant region. Combined with the arc-shaped edge design, it achieves efficient localization of acoustic energy. 3. Probe testing support: The pad area needs to withstand the mechanical pressure when the probe is pressed down. The surrounding support structure enhances the local mechanical strength of the chip, ensuring that the probe will not crush the suspended film structure during vector network analyzer (VNA) testing.

[0041] Release window 50: A through hole formed in the piezoelectric thin film layer 20 for introducing etching gas to remove the underlying substrate to form a cavity.

[0042] Broadband piston mode 60: Through holes opened on the busbar in the piezoelectric thin film layer 20 and Pad region 30 can be used to introduce etching gas to remove the underlying substrate to form a cavity, and also to suppress energy leakage.

[0043] Suspended cavity 70: Located below the piezoelectric thin film layer 20, it is formed by etching the substrate 10. Its function is to provide a free boundary and prevent acoustic energy from leaking into the substrate. The size of the suspended cavity 70 is larger than the resonant region driven by the upper arc-shaped dual electrodes 40.

[0044] The core improvement in this embodiment lies in the geometric design of the electrodes, specifically the combination of dual electrodes and curved edges. (Reference) Figure 3The traditional single electrode is split into two symmetrical arc-shaped dual electrodes 40, with a small gap between them. Arc-shaped dual electrodes on the same side (i.e., the same group) are connected to the same busbar 30 and subjected to the same voltage signal. This design alters the mass distribution over the electrode coverage area, reducing the mass load in the central portion. One edge of each arc-shaped dual electrode 40 remains straight, while the other edge (typically the side facing the adjacent arc-shaped dual electrode) is designed as an inwardly concave arc-shaped boundary. This arched edge typically incorporates a portion of an elliptical curve, with its radius of curvature continuously varying along the aperture direction. The piezoelectric thin film layer 20 of this resonator is a Z-cut lithium niobate single-crystal thin film with a thickness of approximately 400 nm. The aluminum arc-shaped dual electrodes 40 deposited on its surface have a thickness of approximately 200 nm. The design period of the electrode system, i.e., the grid spacing (P), is set to 20 µm. In the core dual-electrode structure, each electrode unit is split into two equally wide arc-shaped dual electrodes, with a gap width W between the two arc-shaped dual electrodes. a The width is set to 2µm. Due to the introduction of an arc-shaped edge design, the width of the arc-shaped dual electrode varies continuously along the aperture direction, with the narrowest part of the arc-shaped dual electrode having a width W. b As a key design variable, its value ranges from 1µm to 3µm. Experiments and simulations show that when W... b At a value of 2, the device achieves the optimal balance between suppressing spurious modes and maintaining a high Q value. The lateral length L of the arc-shaped fingers is designed to be 60 μm. Through simulation and experimental comparison, a curvature radius R of 150 μm is found to balance both the quality factor (Q) and the electromechanical coupling coefficient (k). t 2 The optimal size is found at which the parasitic modes of the resonator are significantly suppressed, and the Q value is significantly improved.

[0045] This device utilizes a transverse electric field excitation effect. When a voltage of opposite polarity is applied to adjacent IDT electrodes, a horizontal electric field is generated in the piezoelectric thin film layer 20. Due to the high piezoelectric coefficient of Z-cut lithium niobate, this electric field effectively excites a thickness shear wave, i.e., a first-order asymmetric Lamb mode (A1 mode).

[0046] The dual-electrode structure improves the Q-value by mitigating acoustic impedance discontinuities: In traditional XBARs, significant displacement distribution exists beneath the electrodes, leading to energy loss at the electrode-piezoelectric layer interface. By splitting the structure into a dual-electrode configuration, the removal of some metal in the central region makes the equivalent acoustic impedance of that area closer to the uncovered region, reducing scattering losses caused by impedance abrupt changes. Experiments show that the Bode-Q can be increased from 301 in the traditional structure to 653.

[0047] The stray mode (I-VI) is essentially a higher-order longitudinal overtone of the A1 mode, caused by coherent standing waves formed by multiple reflections of lateral sound waves between parallel electrode edges.

[0048] The curved edge disrupts the parallelism of the edges, causing changes in the local normal direction at different locations. The phase increment acquired by the lateral wave during reflection varies with position, making it impossible to satisfy a uniform standing wave formation condition across the entire aperture region, thus suppressing the interference enhancement of stray modes. According to the Airy function, the curved boundary alters the local transmission coefficient. At the end of the IDT, the increased radius of curvature increases transmission, reduces the acoustic energy reflected back to the resonant region, and further weakens stray peaks. The curved design modulates the metallization ratio (c), making the transverse electric field E... x With non-target electric field (E) y E z The ratio (γ) of W reaches its optimum (when W) b When the value is 2 micrometers and c≈0.24, the excitation efficiency of the main mode is improved and parasitic vibrations are suppressed.

[0049] The manufacturing process of the aforementioned transverse exciter acoustic resonator is as follows:

[0050] Substrate preparation: Prepare Z-cut lithium niobate-silicon (LNOS) composite wafers, and perform cleaning and drying processes, such as... Figure 4 As shown.

[0051] Maskless photolithography: A photoresist 80 is coated onto the surface of lithium niobate and developed into a specific pattern, which serves as a mask for subsequent etching, such as... Figure 5 As shown.

[0052] Electrode deposition: Using metal evaporation and lift-off processes, a 200 nm thick aluminum (Al) interdigitated arc-shaped dual electrode 40 and busbar 30 are fabricated on the thin film surface. The geometry of the arc-shaped dual electrode 40 is then defined, as follows: Figure 6 As shown. Specifically, the LNOS wafer is first degreased, cleaned, and dried. Then, a layer of photoresist 80 is uniformly coated on the lithium niobate surface. Exposure is performed using MLA, followed by development. At this point, the photoresist is removed where electrodes need to be formed, exposing the underlying lithium niobate surface. A 200 nm thick layer of aluminum (Al) is deposited on the entire wafer surface. At this point, the aluminum simultaneously covers the exposed lithium niobate surface and the remaining photoresist surface. The wafer is then immersed in an organic solvent such as acetone. As the solvent dissolves the photoresist, the metal above the photoresist is detached, while the metal directly deposited on the lithium niobate (i.e., electrode 40 and Pad region 30) is retained.

[0053] Piezoelectric layer etching: The lithium niobate film was etched using inductively coupled plasma (ICP) technology to form a release window 50, such as... Figure 8As shown. Specifically, the ICP etching process for forming the release window 50 of the lithium niobate film includes the following sub-steps: Mask preparation: A layer of photoresist 80 is spin-coated again onto the wafer with the pre-processed electrodes (or a hard mask, such as metal or silicon oxide), and the pattern of the "release window" is defined. Sample introduction and vacuum deposition: The wafer is fed into the ICP etching chamber and evacuated to a high vacuum. Plasma excitation: A reactive gas (typically a mixture of SF6 or Ar) is introduced. Etching process: A high-density plasma is generated by an induction coil, which removes the lithium niobate film in the window area through physical bombardment and chemical reaction. Endpoint detection and photoresist removal: Etching stops after penetrating the lithium niobate layer, and the remaining mask is then removed by cleaning.

[0054] Suspension Release: XeF2 gas is used to etch away the underlying silicon substrate through the release window 50, forming a cavity 70, thus suspending the resonant region. Figure 9 As shown. Specifically, the gas etching operation process is as follows: Sample placement: The wafer with the etched release window is placed into the reaction chamber of the XeF2 etching system. Pulsed etching: The system typically uses a pulsed approach to introduce XeF2 gas. Gas molecules enter below through the release window 50 and wideband piston mode 60 on the lithium niobate layer. Isotropic etching: The XeF2 gas reacts chemically with the underlying silicon substrate. Because this reaction is isotropic (etching in all directions simultaneously), the silicon is gradually hollowed out. Cavity formation: As the etching depth and lateral distance increase, a cavity 70 is eventually formed below the resonant region, thus suspending the lithium niobate resonator. Venting and cleaning: After etching, the reaction byproducts are vented, and the wafer is removed.

[0055] Through the above structural design, the AED-XBAR realized by this invention has the following excellent performance: resonant frequency (f s ): Approximately 4.47 GHz. Electromechanical coupling coefficient (k t 2 Bode-Q score: Up to 22.1%. Quality factor: Maximum Bode-Q value of 599. Performance figure of merit (FOM): 132, approximately 3.2 times higher than conventional structures.

[0056] refer to Figure 11 The AED-XBAR presented in this embodiment is compared with a traditional linear XBAR: The traditional XBAR adopts a standard parallel linear interdigital transducer (IDT) structure, with the electrode fingers extending directly to the busbar or reflection boundary at both ends. This structure has a physical bottleneck. Because the fingers are straight, acoustic energy propagates unimpeded along the longitudinal direction of the fingers, causing a large amount of acoustic energy to leak from the ends of the fingers into the non-resonant region, thus generating significant lateral parasitic modes.

[0057] refer to Figure 12Comparing the AED-XBAR presented in this embodiment with a conventional unoptimized dual-electrode resonator: Although the conventional dual-electrode resonator adopts a dual-electrode configuration to improve electromechanical coupling, it does not perform geometric modulation (such as curvature adjustment) on the electrode shape. Its boundary conditions are usually simple mechanical fixed or free boundaries, thus having performance limitations. In the high-frequency band above 5 GHz, dense parasitic peaks appear in its frequency response curve, which seriously reduces the phase purity within the effective bandwidth.

[0058] As can be seen, the AED-XBAR presented in this embodiment possesses the following technical advantages: 1. Performance breakthrough: The FOM value of the AED-XBAR reaches 132, achieving a leap of 3.2 times compared to the traditional structure. This is crucial for developing broadband, low insertion loss 5G and 6G filters. 2. Dynamic phase control: The arc-shaped design achieves geometric modulation of the acoustic wave phase by changing the propagation path of the acoustic wave in the piezoelectric layer, without sacrificing the electromechanical coupling coefficient k. t 2 Under the premise of ensuring high-frequency resonators, the problem of "lateral parasitic waves" is solved. 3. Process compatibility: Under the same processing precision (such as the 2μm linewidth mentioned above), huge performance gains can be obtained simply by changing the drawing pattern, without the need to introduce complex doping or multilayer thin film processes.

[0059] It can be seen that the proposed AED-XBAR achieves near-spurious-free response characteristics and extremely high FOM at the resonator level, demonstrating its application potential in 5G / 6G RF filters.

[0060] The above description is only a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present invention should be included within the scope of protection set forth in the claims.

Claims

1. A transverse exciter acoustic resonator, characterized in that: The resonator includes: The substrate serves as the supporting base for the entire resonator; piezoelectric thin film layers are stacked on the substrate; arc-shaped interdigitated electrode systems (IDTs) are deposited on the upper surface of the piezoelectric thin film layers, including busbars and arc-shaped dual electrodes extending from the busbars; release windows are opened on the piezoelectric thin film layers; vias opened on the piezoelectric thin film layers serve as broadband piston modes, used to introduce etching gas to remove the underlying substrate to form a cavity, and also to suppress energy leakage; the suspended cavity is located below the piezoelectric thin film layers and is formed by etching the substrate.

2. The transverse exciter acoustic resonator according to claim 1, characterized in that: The substrate is a 4-inch silicon wafer.

3. The transverse exciter acoustic resonator according to claim 1, characterized in that: The piezoelectric thin film layer is a Z-cut lithium niobate single crystal thin film with a thickness of 400 nm.

4. The transverse exciter acoustic resonator according to claim 1, characterized in that: The arc-shaped dual interdigital electrode system is made of aluminum with a thickness of 200nm. It includes two sets of symmetrical arc-shaped dual electrodes with a 2µm gap between them. The pair of arc-shaped dual electrodes in the same set are connected to the bus bar on the same side and are subjected to the same voltage signal. The grid spacing is set to 20µm. One edge of each arc-shaped dual electrode is kept straight, while the other edge, that is, the side facing the adjacent arc-shaped dual electrode, is an inwardly concave arc-shaped boundary.

5. The transverse exciter acoustic resonator according to claim 1, characterized in that: The release window is used to introduce etching gas to remove the underlying substrate and form a cavity.

6. The transverse exciter acoustic resonator according to claim 1, characterized in that: The vias in the broadband piston pattern are used to introduce etching gas to remove the underlying substrate and form cavities, and also to suppress energy leakage.

7. The transverse exciter acoustic resonator according to claim 1, characterized in that: The suspended cavity provides a free boundary to prevent acoustic energy from leaking into the substrate.

8. A method for fabricating a transverse exciter acoustic resonator as described in any one of claims 1-7, characterized in that: The preparation method includes the following steps: Substrate preparation: Prepare Z-cut lithium niobate-silicon composite wafers and perform cleaning and drying processes; Hard mask fabrication: Photoresist is coated on the surface of lithium niobate and developed into an electrode pattern, which serves as a mask for subsequent etching; Electrode deposition: Using maskless photolithography, metal evaporation and lift-off processes, arc-shaped dual electrodes and busbars are prepared on the thin film surface to obtain an arc-shaped dual interdigitated electrode system; Piezoelectric layer etching: Lithium niobate is etched using inductively coupled plasma technology to form a release window; Suspension release: XeF2 gas is used to etch away the underlying silicon substrate through the release window to form a cavity, thus suspending the resonant region.

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