Piezoelectric resonator based on gallium oxide film

Abstract

According to the piezoelectric resonator, an epsilon-phase gallium oxide thin film is arranged on a substrate, an interdigital transducer composed of a first electrode and a second electrode is arranged on the epsilon-phase gallium oxide thin film, and reflecting gratings are arranged on the two sides of the interdigital transducer; the piezoelectric film resonator provided by the invention has the advantages of high frequency, high electromechanical coupling coefficient, high Q value, good temperature and mechanical stability, easiness in production and processing and low cost, and has great application prospects.

Description

Technical Field

[0001] The present invention relates to a piezoelectric resonator, and more particularly to a piezoelectric resonator based on a gallium oxide thin film. Background Art

[0002] Piezoelectric resonators have obvious advantages of small volume, low cost, and strong performance. Due to the low propagation loss of acoustic materials, piezoelectric resonators have a high Q value; since the acoustic wave velocity is four to five orders of magnitude smaller than the electromagnetic wave velocity, piezoelectric resonators have a smaller volume. Therefore, piezoelectric resonators have been widely used in the field of radio frequency communication and are commonly found in radio frequency filters and delay lines. Piezoelectric resonators are connected through a certain topological structure to form filters. According to the different electrode positions and the acoustic waves used, acoustic wave filters are further divided into surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. Due to high performance and low production cost, SAW occupies most of the share in 5G mobile phone filters. SAW filters are commonly used in frequency bands below 1.5 GHz. When the operating frequency exceeds 1.5 GHz, the quality factor Q of SAW begins to decline. By 2.5 GHz, the rejection ability of SAW filters significantly decreases.

[0003] Among them, the piezoelectric material directly affects the performance of the piezoelectric resonator. In the 1990s, the high piezoelectric coefficient material lead zirconate titanate (PZT) was widely studied. However, for higher frequency applications, aluminum nitride and zinc oxide have a higher quality factor (Q) than PZT and are easier to grow in the form of thin films than lithium niobate. Therefore, they are widely used in communication bandpass filters in the GHz frequency band. High-frequency and high-performance piezoelectric thin-film resonators that can be highly compatible with the CMOS process are the current research direction. In the prior art, piezoelectric resonators based on gallium oxide thin films are the current research hotspots. For example, in the patent with the publication number CN111510100A, the surface wave resonator based on the gallium oxide thin film from bottom to top is a middle hollowed-out substrate, a gallium oxide layer, and a metal electrode layer. The transducer electrode is placed on the gallium oxide thin film, and the transducer electrode is etched on the upper layer of gallium oxide and is in a interdigital structure. The excited surface acoustic wave is a Rayleigh wave. The center frequency of this resonator is about 1 GHz, and the effective electromechanical coupling coefficient is 1.09%. However, the structure of the middle hollowed-out substrate - gallium oxide thin film prevents the surface acoustic wave from being converted into a bulk acoustic wave by hollowing out the substrate, thereby increasing the Q value of the resonator. This structure has high processing difficulty, high cost, and at the same time, the structure is fragile and has low stability, and the practical applicability is poor. Therefore, the problem that the high quality factor (Q) value and high structural stability cannot be achieved simultaneously in the prior art of gallium oxide surface wave resonators needs to be solved urgently. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a piezoelectric resonator based on a gallium oxide thin film with stronger structural stability and a higher Q value.

[0005] Technical solution: The piezoelectric resonator based on gallium oxide thin film of the present invention is a surface acoustic wave piezoelectric thin film resonator. An ε-phase gallium oxide thin film is provided on a substrate, and an interdigital transducer composed of a first electrode and a second electrode is provided on the ε-phase gallium oxide thin film, and reflection gratings are provided on both sides of the interdigital transducer.

[0006] Among them, the first electrode, the second electrode and the reflection gratings are composed of two layers of metal. The layer in contact with the ε-phase gallium oxide thin film is a titanium layer, which plays an adhesive role. The upper layer of the titanium layer is a gold layer, which has a high conductivity.

[0007] Among them, for the interdigital transducer, the aperture W is 50λ - 90λ (λ is the wavelength), the interdigital width a is 0.2 - 0.8 microns, the finger pitch p is 0.8 - 1.4 microns, and the number of interdigital pairs n is 40 - 80.

[0008] Among them, the thickness of the titanium layer is 0.01λ - 0.06λ; the thickness of the gold layer is 0.07λ - 0.012λ (λ is the wavelength).

[0009] Among them, for the interdigital transducer, the length directions of the first electrode and the second electrode are parallel to the cut-off edge of the sapphire substrate.

[0010] Among them, the thickness of the ε-phase gallium oxide thin film is 0.3λ - 2λ (λ is the wavelength).

[0011] Among them, the substrate is a sapphire substrate with a thickness of 400 - 600 microns.

[0012] Among them, the first electrode and the second electrode are interdigital electrodes with alternating polarities, and the interdigital electrodes are arranged periodically. The reflection gratings are symmetrically arranged on both sides of the interdigital transducer.

[0013] Principle of the invention: Aiming at the problems of low operating frequency, low electromechanical coupling coefficient, low Q value and unstable structure of surface acoustic wave resonators in the prior art, the present invention proposes a surface acoustic wave piezoelectric thin film resonator based on gallium oxide that maintains the structural stability of the resonator while increasing the Q value. The structure of this resonator from bottom to top is a sapphire substrate, an ε-phase gallium oxide piezoelectric layer, a metal with good adhesion to gallium oxide, and a metal with high conductivity. By optimizing the structure of the interdigital transducer, the effective electromechanical coupling coefficient and Q value of the gallium oxide surface acoustic wave resonator are further improved.

[0014] Among them, the present invention specially selects ε-phase gallium oxide as the gallium oxide thin film layer. The extremely high piezoelectricity and ultra-wide bandgap (4.9 eV) of the ε-phase among the isomers of gallium oxide enable the fabricated resonator to have excellent electromechanical coupling coefficient and power tolerance. Compared with traditional piezoelectric materials such as AlN and ZnO, this material has the advantages of both a high piezoelectric constant d33 = 10.8 - 11.2 pm / V and a wide bandgap Eg = 4.9 eV. The higher the piezoelectric constant, the better the piezoelectric performance. Piezoelectric materials with wide bandgaps are beneficial to improving the quality factor Q of the resonator. At the same time, due to the relatively simple lattice structure of gallium oxide, it is easier to integrate with other devices and be compatible with the process.

[0015] The resonator of the present invention also optimizes the structure of the interdigital transducer, and adjusts the structure, material, and placement angle of the interdigital transducer. A double-layer electrode is used. Titanium metal with good adhesion to gallium oxide is used for the lower layer, and gold metal with high conductivity is used for the upper layer, reducing the ohmic loss and capable of improving the Q value. According to the relationship between the natural axis of the gallium oxide crystal and the piezoelectric rectangular axis, the X-axis of the piezoelectric rectangular axis, the a-axis of gallium oxide, and the <11-20> crystal orientation of the sapphire substrate are parallel. The <11-20> crystal orientation of the sapphire substrate is perpendicular to its cut-off edge, as Figure 2 shown. The conclusion is as Figure 1 shown in that making the length directions of the first electrode 105, the second electrode 106, and the reflection grating 107 parallel to the cut-off edge 112 of the sapphire substrate can obtain a maximum Q value of the surface acoustic wave resonator based on the gallium oxide - sapphire structure and has the best spurious mode suppression performance. The present invention confirms its authenticity through simulation and experimental results. The ratio of a to p is called the metallization rate; the reflection gratings on both sides limit the excited surface acoustic wave in the transducer region. At the same time, waves with the same frequency, vibration direction, and opposite propagation directions interfere to form a standing wave, making the amplitude of the excited surface acoustic wave stronger to improve the Q value of the resonator.

[0016] Therefore, the piezoelectric resonator of the present invention overcomes the problem of reduced stability caused by the etching substrate operation in the prior art, ensuring that the resonator has higher quality factor Q while having structural stability. Since the interdigital electrodes are arranged periodically and their polarities are alternating, the elastic surface waves excited by each pair of electrodes can reinforce each other. The role of the reflection grating is to limit the acoustic wave in the interdigital transducer region.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: The piezoelectric thin film resonator of the present invention has the advantages of high frequency, high electromechanical coupling coefficient, high Q value, good temperature and mechanical stability, and is also easy to produce and process with low cost; specifically, the frequency of the processed sample reaches 2 GHz, which is twice that of the prior art; the electromechanical coupling coefficient is as high as 7%, which is 6 - 7 times that of the prior art. Description of the Drawings

[0018] Figure 1 Schematic diagram of the gallium oxide-based piezoelectric thin film resonator structure of the present invention; Figure 2 Schematic diagram of the relationship between sapphire, the natural axis of gallium oxide crystal and the piezoelectric rectangular axis; Figure 3 Electron microscope image of the resonator prepared by the present invention; Figure 4 For Figure 1 Cross-sectional view taken along the A-A direction in Figure 5 Simplified two-dimensional model of the resonator in COMSOL; Figure 6 Q-value curve of the resonator with the electrodes of the ε-phase gallium oxide device parallel to the cut-off edge of sapphire and at a 60° angle; Figure 7 Admittance curve when the electrodes of the ε-phase gallium oxide device are parallel to the cut-off edge of sapphire; Figure 8 Admittance curve when the electrodes of the ε-phase gallium oxide device are not parallel to the cut-off edge of sapphire; Figure 9 Relationship curve of the phase velocity, effective electromechanical coupling coefficient and normalized thickness of the ε-phase gallium oxide device; Figure 10 Relationship curve of the phase velocity, electromechanical coupling coefficient and finger gap p of the ε-phase gallium oxide device; Figure 11 Relationship curve of the phase velocity, electromechanical coupling coefficient and finger width a of the ε-phase gallium oxide device; Figure 12 Two-dimensional contour plot of the phase velocity varying with the normalized thickness of titanium and gold; Figure 13 Two-dimensional contour plot of the effective electromechanical coupling coefficient varying with the normalized thickness of titanium and gold; Figure 14 Simulation results of the admittance of the working mode of the ε-phase gallium oxide device with the acoustic aperture being different multiples of the wavelength; Figure 15 Two-dimensional cross-sectional model of the entire device in COMSOL; Figure 16 Admittance curve of the resonator with different numbers of interdigital transducers; Reference numerals: 101 - substrate, 102 - ε-phase gallium oxide thin film, 103 - titanium layer, 104 - gold layer, 105 - first electrode, 106 - second electrode, 107 - reflection grating, 108 - periodic boundary condition, 109 - perfectly matched layer, 110 - applied excitation boundary, 111 - ground boundary, 112 - cut-off edge. Detailed implementation manners

[0019] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

[0020] Example 1

[0021] For the piezoelectric resonator based on gallium oxide thin film of the present invention, as shown in Figure 1 and Figure 4 shown, an ε-phase gallium oxide thin film 102 is provided on the substrate 101, and an interdigital transducer composed of a first electrode 105 and a second electrode 106 is provided on the ε-phase gallium oxide thin film 102, and reflection gratings 107 are provided on both sides of the interdigital transducer.

[0022] Among them, the first electrode 105, the second electrode 106 and the reflection grating 107 are composed of two layers of metal, and the layer in contact with the ε-phase gallium oxide thin film 102 is a titanium layer 103, and the upper layer of the titanium layer 103 is a gold layer 104.

[0023] Among them, for the interdigital transducer, the aperture W is 72 microns, the interdigital finger width a is 0.3 microns, the finger pitch p is 0.5 microns, and the number of interdigital fingers n is 60; for the interdigital transducer, the length directions of the first electrode 105 and the second electrode 106 are parallel to the cut-off edge 112 of the substrate 101.

[0024] Among them, the thickness of the ε-phase gallium oxide thin film 102 is 1 micron; the thickness of the titanium layer is 50 microns; the thickness of the gold layer is 140 microns; the substrate 101 is a sapphire substrate with a thickness of 500 microns.

[0025] Among them, the first electrode 105 and the second electrode 106 are interdigital electrodes with alternating polarities, and the interdigital electrodes are arranged periodically; the reflection gratings 107 are symmetrically arranged on both sides of the interdigital transducer.

[0026] For the piezoelectric resonator based on gallium oxide thin film of the present invention, its electron microscope image is as shown in Figure 3 shown.

[0027] The working principle is that when an alternating voltage is applied to the interdigital transducer through the busbars of the first electrode and the second electrode, an electric field distribution with a period of a pair of interdigital spacings (2p) is established in the substrate. Due to the inverse piezoelectric effect, the alternating electric field excites corresponding elastic vibrations in the substrate, and the propagation of the vibrations in the substrate forms elastic waves.

[0028] The preparation method includes the following detailed steps: Preparation of the piezoelectric layer: A high-performance ε-Ga2O3 single crystal thin film is prepared on the substrate 101 by metalorganic chemical vapor deposition (MOCVD), and the thickness is controlled within the preferred range; Fabrication of the first electrode 105, the second electrode 106, and the reflection grating 107: Before photolithography, use L-edit software to draw the layout gds file of the electrode parts, namely the first electrode 105, the second electrode 106, and the reflection grating 107. Spin-coat electron beam resist and bake it; Deposit the conductive layer using an electron beam evaporation equipment Ei-5z to deposit 10 nm of Cr on the sample; After importing the gds file, perform electron beam exposure to define the interdigital pattern; Remove the conductive layer and wet-etch the Cr layer using a Cr etching solution; Place the sample in the developer for 120 s, and then place it in IPA for fixing; Use the electron beam evaporation equipment Ei-5z to deposit Ti / Au on the sample; Place the sample in acetone and heat it in a 70 °C water bath, and then ultrasonically strip it to complete the pattern metallization, and the fabrication is completed.

[0029] The test method includes the following detailed steps: For the resonator sample in this embodiment, use a GSG probe station for testing. The excitation signal is applied to the first electrode 105 and the second electrode 106 through leads with a line width of 50 μm. Considering cost reduction, the test part and the resonator part are fabricated using different processes, and the test part is fabricated using laser direct writing.

[0030] Fabrication of the test structure: Use L-edit to draw the layout of the test structure, spin-coat photoresist and bake it, put it into a laser direct writing equipment Microwriter ML3, expose it with the best parameters, and then develop it; Use the electron beam evaporation equipment Ei-5z to deposit Ti / Au on the sample; Place the sample in acetone and heat it in a 70 °C water bath and then ultrasonically strip it to complete the pattern metallization, and the fabrication of the test metal electrode is completed.

[0031] The SEM image of the fabricated surface acoustic wave resonator sample is as Figure 3 shown.

[0032] Test process: Connect the Cascade SUMMIT200 probe station to the network analyzer, set the sweep frequency range and the number of points, first perform calibration at room temperature, then adsorb the sample on the probe station, and align the probe to the test pad to start the test. The S-parameter characteristic curve of the sample is obtained through the test for subsequent calculations.

[0033] Process errors will greatly affect the Q value of the sample, so the comparability of the Q values of samples from different batches is poor. Therefore, in this embodiment, within the same batch of samples, the method of controlling variables is adopted to fabricate samples with only the angles between the lengths of the first electrode 105 and the second electrode 106 and the cut-off edge of the sapphire substrate 101 being different. Their angles with the sapphire cut-off edge are 0°, 60°, 90°, and 120° respectively.

[0034] Table 1 Q values at different angles under the condition of controlling variables

[0035] As shown in Table 1, the resonator of the present invention has a special structure and constituent materials, and further improves the effective electromechanical coupling coefficient and Q value of the gallium oxide surface acoustic wave resonator by optimizing the structure of the interdigital transducer. In the interdigital transducer, when the length directions of the first electrode 105 and the second electrode 106 are parallel to the cutoff edge 112 of the substrate 101, an unexpected improvement in the Q value is achieved.

[0036] Example 2

[0037] The design method of the gallium oxide thin film-based piezoelectric resonator based on the present invention includes the finite element simulation step of the surface acoustic wave resonator; the design step of the geometric parameters of the resonator structure. A two-dimensional cross-sectional model of a single-period electrode pair and the entire device is established in COMSOL, and the relationship curves between the geometric parameters of the interdigital transducer and the core performance parameters of the resonator are obtained by simulation. Finally, the geometric parameters of the surface acoustic wave resonator structure based on gallium oxide thin film with better performance are obtained.

[0038] First, the simulation of the surface acoustic wave resonator includes: using a two-dimensional model to establish a two-dimensional simplified model of a single period of the surface acoustic wave resonator in COMSOL. Set the two interdigital electrodes, and use the characteristic frequency to solve for the characteristic modes generated by the resonator and the corresponding frequencies; use the frequency domain solver to calculate the admittance and frequency response of the entire model. Using the two-dimensional simplified model greatly reduces the simulation calculation amount. Establish a two-dimensional cross-sectional model of the entire resonator in COMSOL, change the number of reflection gratings, balance the number of electrode pairs and admittance characteristics, and obtain the optimized number of reflection gratings.

[0039] Secondly, the design steps of the geometric parameters of the resonator structure include: (1) Determine the electrode placement angle of the interdigital transducer. First, add a rotating coordinate system in the component definition, select appropriate Euler angles, and use the rotating coordinate system in the piezoelectric material of the solid mechanics field. Perform parametric scanning on the Euler angles to obtain the admittance results, observe the number of spurious modes at this placement angle and calculate the Q value, and comprehensively select the electrode placement angle; (2) Determine the thickness of the ε-phase gallium oxide. Perform parametric scanning on the thickness, solve the characteristic frequency and frequency domain, and calculate the effective electromechanical coupling coefficient and phase velocity. Determine whether the acoustic wave mode is the required working mode by analyzing the vibration mode, and comprehensively judge and determine the thickness of the ε-phase gallium oxide; (3) Determine the finger width p of the interdigital transducer. Here, h is the thickness of the ε-phase gallium oxide layer, which has been determined in the second step. is the spatial period length of the interdigital transducer, which is equal to the wavelength of the excited surface acoustic wave. Therefore, once λ is determined, p is determined. Extract information from the admittance curve and S11 curve obtained by simulation to obtain the effective electromechanical coupling coefficient and phase velocity of the resonator, and comprehensively judge and determine p; (4) Determine the finger width a of the interdigital electrode, perform a parametric scan on a, calculate the phase velocity and the electromechanical coupling factor, and comprehensively judge to determine p, from which the metallization rate η of the resonator is determined.

[0040] (5) Change the thickness combination of the double-layer electrode and calculate the resonance frequency; (6) Then change the acoustic aperture length W and the number of pairs n of the interdigital electrodes of the transducer, calculate the Q value, and select the combination that maximizes the Q value under the premise of meeting the size requirements and process allowances.

[0041] The design method includes the following detailed steps: Establish a simplified two-dimensional single-period electrode pair model of the resonator in COMSOL, as Figure 5 shown, where 108 - periodic boundary condition, 109 - perfectly matched layer, 110 - applied excitation boundary, 111 - grounded boundary. Set the periodic boundary condition 108 on both sides of the boundary and set the perfectly matched layer 109. Set a voltage of 1V and ground on the applied excitation boundary 110 and the grounded boundary 111 surfaces where the electrode contacts the gallium oxide. By using the frequency domain solver, the admittance of the resonator can be obtained; by using the characteristic frequency solver, the characteristic mode of the resonator can be obtained. Set the applied excitation boundary 110 and the grounded boundary 111 surfaces to 1W power and ground respectively, and by using the frequency domain solver, the frequency response curve S11 of the resonator can be obtained.

[0042] The key performance parameters of the resonator, the phase velocity and the effective electromechanical coupling factor and the quality factor Q are calculated as follows: ; ; ; Among them, is the surface acoustic wave wavelength, is the resonance frequency, is the anti-resonance frequency, is the phase of the impedance, is the frequency.

[0043] First, determine the electrode placement angle of the interdigital transducer. Under the same resonator geometric structure, Figure 6 is the Q-value curve of the resonator with the electrode parallel to the cut-off edge of the sapphire and at a 60° angle. It can be seen that for the same acoustic wave mode, the placement angle of the interdigital transducer does have an impact on the Q value. This is because gallium oxide is anisotropic, with different polarization intensities in different directions and different acoustic wave intensities excited. Figure 7 shows the admittance curve when the electrode is parallel to the cut-off edge of the sapphire, while Figure 8The admittance curve when it is non - parallel. It can be seen that there are no spurious modes when it is parallel.

[0044] Next, optimize the normalized thickness h / λ. Figure 9 The curves showing the phase velocity and the effective electromechanical coupling coefficient of the ε - phase gallium oxide device varying with the normalized thickness are presented. When the normalized thickness increases, the phase velocity decreases first and then stabilizes, while the effective electromechanical coupling coefficient increases first and then stabilizes. This is because the acoustic wave mode used in the resonator designed in the present invention is the surface acoustic wave, and its vibration range is only on the surface of the piezoelectric material. So when the thickness is much larger than the wavelength, the device performance hardly changes. However, considering the growth difficulty and cost of the gallium oxide thick film, the thickness of the ε - phase gallium oxide is between 0.3λ and 2λ.

[0045] Figure 10 The curves showing the relationship between the phase velocity, electromechanical coupling coefficient of the ε - phase gallium oxide resonator and the interdigital electrode distance p. It can be observed that the phase velocity increases with the increase of p. This is because the phase velocity is proportional to the wavelength, and in the surface acoustic wave resonator, the wavelength is twice of p. The electromechanical coupling coefficient shows a trend of decreasing first and then increasing. In order to obtain a resonator with balanced performance, the value of p should be in the range near the intersection of the two curves, that is, between 0.8um - 1.6um.

[0046] After determining the value of p, change the size of the interdigital electrode finger width a and calculate the phase velocity and electromechanical coupling factor. Figure 11 The curves showing the relationship between the phase velocity, electromechanical coupling coefficient of the ε - phase gallium oxide device and the finger width a. The phase velocity decreases slightly with the increase of a. The relationship between the electromechanical coupling coefficient and a has a Gaussian distribution characteristic, and the illustrated results are based on p = 1um. So when the metallization rate is 50%, the electromechanical coupling coefficient reaches the maximum. The value range of a is 0.2um - 0.8um.

[0047] Change the electrode thickness and calculate the admittance and S - parameters. Figure 12 It is a two - dimensional contour plot of the phase velocity varying with the normalized thickness of titanium and gold. Figure 13 It is a two - dimensional contour plot of the effective electromechanical coupling coefficient varying with the normalized thickness of titanium and gold. It can be concluded that the electrode thickness, especially the thickness of gold, has a greater influence on the operating mode frequency of the surface acoustic wave device, while has little influence on the effective electromechanical coupling coefficient. Therefore, the thickness of the lower electrode (titanium layer 103) should be 0.01λ - 0.06λ; the thickness of the upper electrode (gold layer 104) should be 0.07λ - 0.12λ.

[0048] Finally, change the acoustic aperture length W. The variation law of the Q - value with W and n can be qualitatively investigated to save computing resources. Figure 14The simulation results of the working wave mode admittance of the ε-phase gallium oxide device when the acoustic aperture is different multiples of the wavelength. The larger the acoustic aperture, the larger the absolute value of the admittance, the sharper the resonance peak, and the larger the Q value. The acoustic aperture ranges from 50λ to 90λ.

[0049] After completing the design of the interdigital transducer, a two-dimensional cross-sectional model of the entire device is established in COMSOL, as Figure 15 shown. The symmetric short-circuit reflection gratings on both sides are set to be grounded, and the intersections of the interdigital transducer electrodes are set to terminal 1V and ground. By running the frequency-domain solution, the admittance curve of the resonator can be obtained. When the terminal is set to power and the frequency-domain solution is run, the frequency response curve of the resonator can be obtained. Set the number of pairs of interdigital electrodes n. Figure 16 The admittance curves when n is 40, 60, and 80 are shown. When n is greater than 80, the device performance improvement is not significant. Therefore, the number of pairs of interdigital electrodes is taken between 40 and 80 pairs.

[0050] Therefore, the piezoelectric thin-film resonator of the present invention, by setting the special structure of the sapphire substrate, the ε-phase gallium oxide piezoelectric layer, the metal with good adhesion to gallium oxide, and the metal with high conductivity, and by optimizing the interdigital transducer, brings the effects of high frequency, high electromechanical coupling coefficient, high Q value, and good temperature and mechanical stability, and has great application prospects.

Claims

1. A piezoelectric resonator based on a gallium oxide thin film, characterized in that: The piezoelectric resonator is provided with an ε-phase gallium oxide film (102) on a substrate (101), an interdigital transducer consisting of a first electrode (105) and a second electrode (106) is provided on the ε-phase gallium oxide film (102), and reflection gratings (107) are provided on both sides of the interdigital transducer.

2. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The first electrode (105), the second electrode (106) and the reflective grid (107) are composed of two layers of metal, the titanium layer (103) connected to the epsilon-phase gallium oxide film (102), and the upper layer of the titanium layer (103) is a gold layer (104).

3. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The interdigital transducer has an aperture W of 50λ-90λ, where λ is the wavelength, an interdigital width a of 0.2-0.8 micrometers, an interdigital spacing p of 0.8-1.4 micrometers, and an interdigital logarithm n of 40-80.

4. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The thickness of the titanium layer (103) is 0.01λ-0.06λ; the thickness of the gold layer (104) is 0.07λ-0.012λ, where λ is the wavelength.

5. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: In the interdigital transducer, the length directions of the first electrode (105) and the second electrode (106) are parallel to the cutoff edge (112) of the substrate (101).

6. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The thickness of the ε-phase gallium oxide thin film (102) is 0.3λ-2λ, where λ is the wavelength.

7. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The substrate (101) is a sapphire substrate.

8. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The thickness of the substrate (101) is 400-600 micrometers.

9. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The first electrode (105) and the second electrode (106) are interdigitated electrodes with alternating polarities, and the interdigitated electrodes are arranged periodically.

10. The piezoelectric resonator based on gallium oxide thin film according to claim 1, characterized in that: The reflection grating (107) is symmetrically arranged on both sides of the interdigital transducer.

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