Preparation method of lithium niobate film bulk acoustic resonator

Abstract

The invention relates to the technical field of film bulk acoustic resonators, and discloses a preparation method of a lithium niobate film bulk acoustic resonator, which comprises the following steps: carrying out ion implantation on a polished surface of a lithium niobate single crystal wafer, preparing a patterned bottom electrode layer on the surface of the lithium niobate single crystal wafer after ion implantation, and preparing a lithium niobate film bulk acoustic resonator on the patterned bottom electrode layer; depositing a supporting layer on the surface of the bottom electrode layer and carrying out polishing treatment; performing graphical etching on the SiC substrate layer to form a pre-etched structure and polishing the pre-etched structure; bonding the treated lithium niobate single crystal wafer with the treated SiC substrate layer, and carrying out high-temperature annealing to crack the lithium niobate single crystal wafer to form a lithium niobate single crystal piezoelectric layer; carrying out surface polishing on the lithium niobate single crystal piezoelectric layer, and forming an electrode through hole through photoetching and ICP etching processes; the patterned top electrode layer is prepared on the surface of the lithium niobate single crystal piezoelectric layer with the through hole, the top electrode layer is conducted with the bottom electrode layer through the through hole, and the resonator is prepared, the process steps are simplified, and the coupling coefficient and the heat dissipation performance are improved.

Description

Technical Field

[0001] This invention relates to the field of thin-film bulk acoustic resonator technology, specifically to a method for fabricating a lithium niobate thin-film bulk acoustic resonator. Background Technology

[0002] Thin-film bulk acoustic resonators (FBARs), with their high Q value, good frequency selectivity, and miniaturization, have become core components of radio frequency communication devices and are widely used in mobile communications, the Internet of Things, and other fields. With the rapid development of 5G communication technology, higher requirements are placed on the bandwidth and long-term reliability of filters, and the performance bottleneck of traditional aluminum nitride (AlN) based FBARs is becoming increasingly prominent.

[0003] Currently, mainstream FBARs employ a stacked structure of "silicon (Si) substrate + silicon dioxide (SiO2) support layer + molybdenum (Mo) bottom electrode + AlN piezoelectric layer + Mo top electrode," using a sacrificial layer method to create the air cavity. This involves depositing a sacrificial layer on the Si substrate, sequentially growing the electrode and AlN piezoelectric layer, and then releasing the sacrificial layer via wet etching to form the cavity. However, AlN material has a low electromechanical coupling coefficient, resulting in a narrow filter bandwidth that cannot meet the requirements of 5G ultra-wideband. While scandium-doped aluminum nitride (Sc-AlN) solutions have emerged, increasing the electromechanical coupling coefficient to 12%-15%, precise control of the doping concentration is required, making the process complex and costly, still insufficient for practical applications. Furthermore, the low thermal conductivity of the Si substrate used in traditional FBARs leads to heat accumulation during long-term high-frequency operation, causing piezoelectric layer performance degradation and resonant frequency drift, severely impacting long-term operational reliability. Summary of the Invention

[0004] In order to overcome the defects of the prior art, the present invention aims to provide a method for fabricating a lithium niobate thin film bulk acoustic resonator, so as to solve the technical problems of narrow bandwidth of AlN-based FBAR, complex and high cost of Sc-AlN scheme, and low reliability caused by poor heat dissipation of Si substrate in the prior art.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for fabricating a lithium niobate thin-film bulk acoustic resonator, comprising: Ion implantation is performed on the polished surface of a lithium niobate single crystal wafer. A patterned bottom electrode layer is then fabricated on the surface of the ion-implanted lithium niobate single crystal wafer. A support layer is deposited on the surface of the bottom electrode layer and then polished. Patterning and etching are performed on the SiC substrate to form a pre-etched structure, which is then polished. The treated lithium niobate single crystal wafer is bonded to the treated SiC substrate, and the lithium niobate single crystal wafer is cleaved by high-temperature annealing to form a lithium niobate single crystal piezoelectric layer. The surface of the lithium niobate single crystal piezoelectric layer is polished, and electrode vias are formed by photolithography and ICP etching processes. A patterned top electrode layer is fabricated on the surface of a lithium niobate single-crystal piezoelectric layer with through holes. The top electrode layer is connected to the bottom electrode layer through the through holes to complete the fabrication of the resonator.

[0006] Preferably, the ion implantation energy is 100-400 keV and the implantation dose is 1×10⁻⁶. 16 -4×10 16 ions / cm 2 The injected ions are helium ions.

[0007] Preferably, the patterned bottom electrode layer is prepared using photolithography and magnetron sputtering processes.

[0008] Preferably, the lithium niobate single crystal piezoelectric layer is a 41°Y-cut lithium niobate single crystal piezoelectric layer, and the longitudinal wave electromechanical coupling coefficient of the 41°Y-cut lithium niobate single crystal piezoelectric layer is ≥22.37%.

[0009] Preferably, the material of the support layer includes silicon dioxide (SiO2) or silicon nitride (Si3N4).

[0010] Preferably, the etching pattern is defined by photolithography and patterned by RIE etching, and the pre-etched structure forms the air cavity of the resonator.

[0011] Preferably, the treated lithium niobate single crystal wafer is bonded to the treated SiC substrate layer, and then the lithium niobate single crystal wafer is cleaved by high-temperature annealing, wherein the high-temperature annealing temperature is 300-400°C and the annealing time is 1-2 hours. After annealing, the lithium niobate single crystal wafer is cleaved along the helium aggregation layer to form an ultrathin lithium niobate single crystal piezoelectric layer.

[0012] Preferably, the patterned top electrode layer is prepared using photolithography and magnetron sputtering; the materials of the bottom electrode layer and the top electrode layer include any one of aluminum (Al), copper (Cu), gold (Au), or molybdenum (Mo).

[0013] Preferably, the bottom electrode layer and the top electrode layer have shapes including any one of pentagon, rectangle, circle or ellipse; the input and output terminals of the top electrode layer and the bottom electrode layer are GSG structures.

[0014] Secondly, the present invention also provides a lithium niobate thin film bulk acoustic resonator, which is obtained by the above-described method for preparing a lithium niobate thin film bulk acoustic resonator, and includes, from bottom to top, a SiC substrate layer, a pre-etched air cavity, a support layer, a bottom electrode layer, a lithium niobate single crystal piezoelectric layer, and a top electrode layer.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a method for fabricating a lithium niobate thin-film bulk acoustic resonator. By selecting a 41°Y-cut lithium niobate single crystal wafer and performing ion implantation treatment with specific parameters, combined with subsequent bonding and cleaving processes to form an ultrathin lithium niobate single crystal piezoelectric layer, the longitudinal wave electromechanical coupling coefficient reaches 22.37%, which is much higher than that of traditional aluminum nitride materials and scandium-doped aluminum nitride schemes. The fourth-order filter constructed from this piezoelectric layer can achieve a 3dB bandwidth of 420MHz, significantly breaking through the bandwidth limitation of traditional thin-film bulk acoustic resonators and fully meeting the application requirements of broadband devices in fields such as 5G communication.

[0016] Furthermore, this invention uses a silicon carbide substrate instead of a traditional silicon substrate, which has a thermal conductivity approximately three times that of a silicon substrate. This effectively solves the problem of heat accumulation during long-term high-frequency operation of traditional devices, reduces the degradation of piezoelectric layer performance and resonant frequency drift, and significantly improves the long-term reliability and stability of the device.

[0017] Furthermore, the present invention replaces the traditional sacrificial layer method with an innovative route of ion implantation, preparation of bottom electrode and support layer, pre-etching of silicon carbide substrate, bonding, and annealing and splitting. This avoids the residual risks caused by wet etching to release the sacrificial layer. At the same time, it eliminates the need for precise control of doping concentration as in the scandium aluminum nitride scheme, simplifies the process steps, reduces production difficulty and cost, and improves production efficiency.

[0018] Furthermore, the materials for the bottom electrode layer and the top electrode layer can be flexibly selected from aluminum, copper, gold or molybdenum during the fabrication process, the support layer material can be replaced with silicon nitride, and the electrode shape can also be adopted in various forms such as rectangular, circular, and elliptical according to actual needs, adapting to the design and packaging requirements of different RF devices, and has strong compatibility and practicality. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the fabrication method of the lithium niobate thin film bulk acoustic resonator in this embodiment of the invention. Figure 2 This is a process diagram illustrating the fabrication method of the lithium niobate thin film bulk acoustic resonator in an embodiment of the present invention; Figure 3 This is a schematic diagram of the crystal tangential orientation in an embodiment of the present invention; Figure 4This is a schematic diagram illustrating the relationship between the electromechanical coupling coefficient and the cutting shape of lithium niobate in an embodiment of the present invention; Figure 5 This is an impedance-frequency diagram of 41°Y-cut lithium niobate in an embodiment of the present invention; Figure 6 This is a simulation result diagram of a fourth-order 41° Y-cut lithium niobate filter in an embodiment of the present invention; Figure 7 This is a schematic diagram of a model in an embodiment of the present invention; Figure 8 This is a cross-sectional view of the model in an embodiment of the present invention; Figure 9 This is a sectional front view of the model in an embodiment of the present invention; In the figure: 1. SiC substrate layer; 2. Air cavity; 3. Support layer; 4. Bottom electrode layer; 5. Lithium niobate single crystal piezoelectric layer; 6. Top electrode layer. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] The purpose of this invention is to provide a method for fabricating a lithium niobate thin film bulk acoustic resonator, in order to solve the technical problems of narrow bandwidth of AlN-based FBAR, complex and high cost of Sc-AlN scheme, and low reliability caused by poor heat dissipation of Si substrate in the prior art.

[0023] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 and Figure 2In one embodiment of the present invention, a method for fabricating a lithium niobate thin-film bulk acoustic resonator is provided, comprising: Step 1: Ion implantation is performed on the polished surface of the lithium niobate single crystal wafer. A patterned bottom electrode layer 4 is prepared on the surface of the lithium niobate single crystal wafer after ion implantation. A support layer 3 is deposited on the surface of the bottom electrode layer 4 and then polished. Specifically, the ion implantation energy is 300 keV, and the implantation dose is 2 × 10⁻⁶. 16 ions / cm 2 The injected ions are helium ions.

[0024] This embodiment clarifies the core parameters of ion implantation (implantation energy 300keV, implantation dose 2×10⁻⁶). 16 ions / cm 2 The design principle revolves around "precise control of thin film stripping." The implantation energy directly determines the implantation depth of helium ions within the lithium niobate single-crystal wafer; a parameter of 300 keV can form a uniform helium ion aggregation layer inside the single-crystal wafer; the implantation dose is 2 × 10⁻⁶. 16 ions / cm 2 This method balances the difficulty of subsequent dicing with the integrity of the thin film, ensuring smooth dicing during high-temperature annealing while avoiding premature breakage of the single crystal due to excessive dosage. Helium ions were chosen because of their small atomic radius and ease of diffusion and aggregation in the crystal lattice. At high temperatures, they can form bubbles to generate directional stress, providing the driving force for precise dicing of lithium niobate single crystals along the convergence layer. This ultimately achieves the transfer and preparation of an ultrathin, high-quality piezoelectric layer, solving the problems of difficult thickness control and easy film damage in traditional thin film transfer processes.

[0025] The patterned bottom electrode layer is prepared using photolithography and magnetron sputtering processes.

[0026] In this embodiment, magnetron sputtering technology offers advantages such as high film purity, good thickness uniformity, and strong adhesion, meeting the requirements of electrodes for electrical conductivity and structural stability. The photolithography process precisely defines the pattern dimensions of the bottom electrode using a mask, adapting to the acoustic design requirements of the resonator and preventing irregular electrode shapes from affecting sound wave propagation. The combined patterned bottom electrode provides a flat support interface for the subsequent piezoelectric layer and ensures reliable contact between the electrode and the piezoelectric layer. This solves the problem of device performance fluctuations caused by low pattern precision and poor film quality in traditional electrode fabrication processes, laying the foundation for the high-frequency characteristics of the resonator.

[0027] Step 2: Perform patterned etching on SiC substrate layer 1 to form a pre-etched structure and polish it; Specifically, the lithium niobate single crystal piezoelectric layer 5 is a 41°Y-cut lithium niobate single crystal piezoelectric layer, and the longitudinal wave electromechanical coupling coefficient of the 41°Y-cut lithium niobate single crystal piezoelectric layer is ≥22.37%.

[0028] In this embodiment, the piezoelectric properties of lithium niobate depend on the crystal tangent. Simulation verification shows that the electromechanical coupling coefficient of lithium niobate in the 18°-45° range is greater than 20%, with a 41° Y-cut being the optimal cut, achieving a longitudinal wave electromechanical coupling coefficient of 22.37%, far exceeding that of traditional aluminum nitride (AlN) and scandium-doped aluminum nitride (Sc-AlN). By locking this specific cut and its corresponding performance parameters, the high bandwidth potential of the resonator can be directly guaranteed, enabling the cascaded filter to achieve a 3dB bandwidth of 420MHz, precisely addressing the requirements of 5G communication for ultra-wideband devices. Furthermore, the clearly defined performance indicators provide a quantitative basis for the repeatability and effectiveness of the technical solution.

[0029] Specifically, the material of the support layer 3 includes silicon dioxide (SiO2) or silicon nitride (Si3N4).

[0030] In this embodiment, SiO2 is a commonly used support material in RF devices, offering advantages such as mature deposition processes, easy polishing, and good compatibility with other layers. Silicon nitride (Si3N4), on the other hand, possesses higher mechanical strength and high-temperature resistance, making it suitable for more complex working environments. Providing two material options retains the process convenience of traditional materials while expanding the application scenarios of the technical solution. This avoids the limitations of a single material not meeting the requirements of different operating conditions, ensuring the structural stability of the device during subsequent bonding, annealing, and long-term operation.

[0031] Step 3: Bond the treated lithium niobate single crystal wafer to the treated SiC substrate layer 1, and anneal at high temperature to cleave the lithium niobate single crystal wafer to form a lithium niobate single crystal piezoelectric layer 5. Specifically, the etching pattern is defined using photolithography and patterned etching is performed using RIE (reactive ion etching) technology. The pre-etched structure forms the air cavity 2 of the resonator.

[0032] Specifically, the treated lithium niobate single crystal wafer is bonded to the treated SiC substrate layer 1, and then the lithium niobate single crystal wafer is split into pieces by high-temperature annealing. The high-temperature annealing temperature is 300-400℃ and the annealing time is 1-2 hours. After annealing, the lithium niobate single crystal wafer is split along the helium aggregation layer to form an ultrathin lithium niobate single crystal piezoelectric layer.

[0033] Step 4: Polish the surface of the lithium niobate single crystal piezoelectric layer 5, and form electrode vias by photolithography and ICP etching processes; Step 5: A patterned top electrode layer 6 is fabricated on the surface of the lithium niobate single crystal piezoelectric layer 5 with through holes. The top electrode layer 6 is connected to the bottom electrode layer 4 through the through holes, thus completing the fabrication of the resonator.

[0034] Specifically, the patterned top electrode layer 6 is prepared using photolithography and magnetron sputtering; the materials of the bottom electrode layer 4 and the top electrode layer 6 include any one of aluminum (Al), copper (Cu), gold (Au), or molybdenum (Mo).

[0035] The bottom electrode layer 4 and the top electrode layer 6 can be any one of pentagon, rectangle, circle or ellipse; the input and output terminals of the top electrode layer 6 and the bottom electrode layer 4 are GSG structures.

[0036] In this embodiment, as shown... Figure 3 As shown, crystal cut, also known as wafer orientation or tangential orientation, refers to the specific orientation of the cutting plane relative to the crystal's own lattice coordinate axes when cutting a single-crystal material. For example... Figure 3 As shown in (a), a crystal cutting plane perpendicular to the Z-axis is called a Z-cut. A plane perpendicular to the Y-axis, rotated θ° around the X-axis, is used as a cross-section to cut the crystal; this is called an θ° Y-cut. Figure 3 As shown in (b), simulations of lithium niobate of various cuts were performed using COMSOL, and the simulation results are as follows. Figure 4 As shown.

[0037] Within the 18° to 45° range, the electromechanical coupling coefficient of lithium niobate materials is greater than 20%. 41° Y-cut lithium niobate, with a relatively high longitudinal wave electromechanical coupling coefficient, was selected as the piezoelectric material for this invention. Figure 5 and Figure 6 As shown, the simulation yielded a longitudinal wave electromechanical coupling coefficient of 22.37%. The fourth-order filter constructed from it achieved a 3dB bandwidth of 420MHz.

[0038] In this embodiment, lithium niobate (LiNbO3) is a material with significant piezoelectric properties, which are strongly dependent on the crystal cutting orientation. Certain cuts exhibit extremely high electromechanical coupling coefficients. Furthermore, with breakthroughs in thin film fabrication technologies such as smart-cut, LiNbO3 single-crystal thin films can be transferred to various substrates with high quality, providing a material basis for addressing the shortcomings of traditional AlN-based FBARs and becoming a key research direction for broadband, high-reliability FBARs. By utilizing lithium niobate as a piezoelectric material in device design, a significant expansion of the filter bandwidth is achieved. By selecting SiC, which has a higher thermal conductivity, as the substrate, heat dissipation is optimized to ensure the long-term stability of the device. Using a 41° Y-cut LiNbO3 piezoelectric layer significantly improves the electromechanical coupling coefficient compared to AlN, thereby expanding the filter bandwidth.

[0039] Example 2 according to Figure 7 , Figure 8 and Figure 9 As shown, this embodiment also provides a lithium niobate thin film bulk acoustic resonator, which is obtained by the above-described method for fabricating a lithium niobate thin film bulk acoustic resonator. From bottom to top, it includes a SiC substrate layer 1, a pre-etched air cavity 2, a support layer 3, a bottom electrode layer 4, a lithium niobate single crystal piezoelectric layer 5, and a top electrode layer 6.

[0040] In this embodiment, the SiC substrate utilizes its high thermal conductivity to address the poor heat dissipation problem of traditional Si substrates, ensuring the long-term stability of the device. A pre-etched air cavity provides an acoustic resonance environment; a support layer ensures structural stability; a 41° Y-cut lithium niobate piezoelectric layer provides a high electromechanical coupling coefficient, overcoming bandwidth limitations; and upper and lower electrodes enable electrical conduction and signal transmission. The overall structure forms a technical closed loop of "high bandwidth + high reliability," precisely addressing the invention's objective and solving the core defects of traditional AlN-based FBARs, such as narrow bandwidth and poor heat dissipation, ultimately meeting the high-performance requirements of RF devices in fields such as 5G communication.

[0041] The lithium niobate thin-film bulk acoustic resonator prepared in this application has an electromechanical coupling coefficient greater than 20%, far exceeding that of resonators based on AlN materials. The resulting fourth-order ladder filter has a bandwidth greater than 400MHz, representing a significant bandwidth improvement. The thermal conductivity of the SiC substrate is approximately three times that of Si, resulting in a lower long-term high-frequency operating temperature, less temperature drift, and more stable performance.

[0042] In summary, this invention provides a method for fabricating a lithium niobate thin-film bulk acoustic resonator. By selecting a 41°Y-cut lithium niobate single crystal wafer and performing ion implantation treatment with specific parameters, combined with subsequent bonding and cleaving processes to form an ultrathin lithium niobate single crystal piezoelectric layer, the longitudinal wave electromechanical coupling coefficient reaches 22.37%, which is far higher than that of traditional aluminum nitride materials and scandium-doped aluminum nitride schemes. The fourth-order filter constructed from this piezoelectric layer can achieve a 3dB bandwidth of 420MHz, significantly breaking through the bandwidth limitation of traditional thin-film bulk acoustic resonators and fully meeting the application requirements of broadband devices in fields such as 5G communication.

[0043] Furthermore, this invention uses a silicon carbide substrate instead of a traditional silicon substrate, which has a thermal conductivity approximately three times that of a silicon substrate. This effectively solves the problem of heat accumulation during long-term high-frequency operation of traditional devices, reduces the degradation of piezoelectric layer performance and resonant frequency drift, and significantly improves the long-term reliability and stability of the device.

[0044] The present invention replaces the traditional sacrificial layer method with an innovative process of ion implantation, preparation of bottom electrode and support layer, pre-etching of silicon carbide substrate, bonding, and annealing and splitting. This avoids the residual risk caused by wet etching to release the sacrificial layer. At the same time, it eliminates the need for precise control of doping concentration as in the scandium aluminum nitride scheme, simplifies the process steps, reduces production difficulty and cost, and improves production efficiency.

[0045] During the fabrication process, the materials for the bottom electrode layer and the top electrode layer can be flexibly selected from aluminum, copper, gold or molybdenum, the support layer material can be replaced with silicon nitride, and the electrode shape can also be adopted in various forms such as rectangle, circle, and ellipse according to actual needs, adapting to the design and packaging requirements of different RF devices, and has extremely strong compatibility and practicality.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for fabricating a lithium niobate thin-film bulk acoustic resonator, characterized in that, include: Ion implantation was performed on the polished surface of the lithium niobate single crystal wafer, and a patterned bottom electrode layer (4) was prepared on the surface of the lithium niobate single crystal wafer after ion implantation. A support layer (3) was deposited on the surface of the bottom electrode layer (4) and then polished. Patterning etching is performed on the SiC substrate (1) to form a pre-etched structure and then polished; The treated lithium niobate single crystal wafer was bonded to the treated SiC substrate (1), and the lithium niobate single crystal wafer was cleaved by high-temperature annealing to form a lithium niobate single crystal piezoelectric layer (5). The surface of the lithium niobate single crystal piezoelectric layer (5) is polished, and electrode vias are formed by photolithography and ICP etching processes; A patterned top electrode layer (6) is prepared on the surface of a lithium niobate single crystal piezoelectric layer (5) with through holes. The top electrode layer is connected to the bottom electrode layer (4) through the through holes to complete the fabrication of the resonator.

2. The method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, Ion implantation energy is 100-400 keV, and implantation dose is 1×10⁻⁶. 16 -4×10 16 ions / cm 2 The injected ions are helium ions.

3. The method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, The patterned bottom electrode layer was fabricated using photolithography and magnetron sputtering processes.

4. The method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, The lithium niobate single crystal piezoelectric layer (5) is a 41°Y cut lithium niobate single crystal piezoelectric layer, and the longitudinal wave electromechanical coupling coefficient of the 41°Y cut lithium niobate single crystal piezoelectric layer is ≥22.37%.

5. The method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, The material of the support layer (3) includes silicon dioxide (SiO2) or silicon nitride (Si3N4).

6. The method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, The etching pattern is defined by photolithography and etched by RIE etching. The pre-etched structure forms the air cavity (2) of the resonator.

7. A method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, The treated lithium niobate single crystal wafer is bonded to the treated SiC substrate layer (1), and the lithium niobate single crystal wafer is split into pieces by high-temperature annealing, wherein the high-temperature annealing temperature is 300-400℃ and the annealing time is 1-2 hours. After annealing, the lithium niobate single crystal wafer is split along the helium aggregation layer to form an ultrathin lithium niobate single crystal piezoelectric layer.

8. The method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, The patterned top electrode layer (6) is prepared by photolithography and magnetron sputtering; the materials of the bottom electrode layer (4) and the top electrode layer (6) include any one of aluminum (Al), copper (Cu), gold (Au) or molybdenum (Mo).

9. A method for fabricating a lithium niobate thin-film bulk acoustic resonator according to claim 1, characterized in that, The bottom electrode layer (4) and the top electrode layer (6) have shapes including any one of pentagon, rectangle, circle or ellipse; the input and output terminals of the top electrode layer (6) and the bottom electrode layer (4) are GSG structures.

10. A lithium niobate thin-film bulk acoustic resonator, characterized in that, The lithium niobate thin film bulk acoustic resonator is obtained by any one of claims 1-9, and from bottom to top includes a SiC substrate layer (1), a pre-etched air cavity (2), a support layer (3), a bottom electrode layer (4), a lithium niobate single crystal piezoelectric layer (5), and a top electrode layer (6).

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