CN110994097A - High-frequency large-bandwidth thin-film bulk wave filter structure and preparation method thereof - Google Patents

High-frequency large-bandwidth thin-film bulk wave filter structure and preparation method thereof Download PDF

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CN110994097A
CN110994097A CN201911347704.5A CN201911347704A CN110994097A CN 110994097 A CN110994097 A CN 110994097A CN 201911347704 A CN201911347704 A CN 201911347704A CN 110994097 A CN110994097 A CN 110994097A
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substrate
interdigital transducer
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CN110994097B (en
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王为标
傅肃磊
沈君尧
苏荣宣
陆增天
潘峰
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Shoulder Electronics Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters
    • H01P1/20327—Electromagnetic interstage coupling
    • H01P1/20354—Non-comb or non-interdigital filters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P11/00—Apparatus or processes specially adapted for manufacturing waveguides or resonators, lines, or other devices of the waveguide type
    • H01P11/007—Manufacturing frequency-selective devices

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Abstract

The invention discloses a high-frequency large-bandwidth film bulk wave filter structure and a preparation method thereof, relating to the technical field of information electronic materials, the structure sequentially comprises a substrate, an interdigital transducer, an oxide protection layer and a piezoelectric thin film layer from bottom to top, wherein the interdigital transducer is arranged on the substrate, the oxide protection layer is arranged on the substrate and covers an adjacent interdigital gap of the interdigital transducer, the piezoelectric thin film layer is arranged on the oxide protection layer, the thickness of the oxide protection layer is larger than or equal to that of the interdigital transducer, the piezoelectric thin film layer with high crystal quality, good consistency and small propagation loss can be obtained by the preparation method, the bulk wave filter structure can obtain high sound velocity and large electromechanical coupling coefficient, the requirement of mobile communication on high frequency and large bandwidth is met, the preparation process used by the structure is easy to achieve, and the structure is easy to popularize on a large scale.

Description

High-frequency large-bandwidth thin-film bulk wave filter structure and preparation method thereof
Technical Field
The invention relates to the technical field of information electronic materials, in particular to a high-frequency large-bandwidth thin-film bulk wave filter structure and a preparation method thereof.
Background
As the basis and key of mobile communication, the radio frequency front end is a core component of a mobile intelligent terminal product. The radio frequency front end is a necessary path connected with an antenna and a communication transceiving chip and mainly comprises a switch, a filter/duplexer, a power amplifier, a low noise amplifier and other device units. The duplexer is used for isolating transmitting and receiving signals, has the function of radio frequency filtering and is a core device of a radio frequency front end. The surface acoustic wave filter and the bulk acoustic wave filter have the characteristics of small volume, excellent filtering performance, light weight, high reliability and the like, and are more suitable for the requirements of miniaturization, digitalization, high reliability and the like of the mobile terminal, so the surface acoustic wave filter and the bulk acoustic wave filter are two most mainstream radio frequency filters applied to the mobile terminal at present. From the 2G era to the 4G era, the increasing number of frequency bands causes the spectrum resources to be crowded. Meanwhile, the 5G era is approaching day by day, and in order to realize faster rate transmission and data traffic with sharply increased geometric grade, the application frequency of the mobile communication system is higher and higher, and the bandwidth is larger and larger, so that a radio frequency acoustic filter with high frequency and large bandwidth is urgently needed.
The frequency and bandwidth of the surface acoustic wave filter mainly depend on the sound velocity and electromechanical coupling coefficient of the piezoelectric substrate of the surface acoustic wave filter. The traditional surface acoustic wave filter is made of lithium tantalate (LiTaO)3) Lithium niobate (LiNbO)3) And finishing the preparation on the monocrystal material. The substrates have the advantages of good consistency, large electromechanical coupling coefficient, mature process conditions and the like, but LiTaO3And LiNbO3The sound speeds are all lower than 4000m/s, which limits the high frequency application. The piezoelectric material used for the bulk acoustic wave filter at present is an AlN piezoelectric film with higher sound velocity, which has certain advantages in high-frequency application, but because the AlN piezoelectric film has relatively smaller electromechanical coupling coefficient,limiting its application to wideband filters. In addition, grown AlN piezoelectric films are generally polycrystalline and are far less quality than single crystal substrates, and crystal defects in the film can degrade filter performance. According to the above, the application of the conventional rf filter in high frequency and large bandwidth has certain disadvantages. Therefore, in order to meet the requirement of 5G communication on a high-performance filter, a piezoelectric material and a piezoelectric substrate structure with high sound velocity and high electromechanical coupling coefficient are urgently needed to be found for preparing a high-frequency large-bandwidth filter.
Disclosure of Invention
The invention provides a high-frequency large-bandwidth thin-film bulk wave filter structure and a preparation method thereof, aiming at the problems and technical requirements, wherein the structure has high sound velocity and large electromechanical coupling coefficient so as to realize the application of high frequency and large bandwidth. The technical scheme of the invention is as follows:
a high-frequency large-bandwidth thin-film bulk wave filter structure comprises a substrate, an interdigital transducer, an oxide protective layer and a piezoelectric thin-film layer from bottom to top in sequence;
the interdigital transducer is arranged on the substrate, the oxide protection layer is arranged on the substrate and covers the adjacent interdigital gaps of the interdigital transducer, the piezoelectric film layer is arranged on the oxide protection layer, and the thickness of the oxide protection layer is larger than or equal to that of the interdigital transducer;
the substrate is made of a sapphire single crystal substrate or a SiC single crystal substrate;
the piezoelectric film layer is made of LiTaO3Single crystal thin film or LiNbO3A single crystal thin film.
The further technical scheme is that the thickness of the interdigital transducer is 100nm-200nm, the interdigital width is 100nm-2 μm, and the interdigital electrode period is 400nm-8 μm.
The interdigital transducer comprises an electrode priming layer and an electrode main body layer, wherein the electrode main body layer is arranged on the electrode priming layer;
the material of the electrode priming layer comprises at least one of Ti, Ni, Zr and Cr, and the thickness of the electrode priming layer is 1nm-20 nm;
the material of the electrode main body layer comprises at least one of Al, Cu, Pt and Mo.
The further technical proposal is that the thickness of the piezoelectric film layer is 0.2-2 μm. Confirmation of no problem
The further technical proposal is that the material of the oxide protective layer is SiO2Or TeO2Or SiOF, the thickness of the oxide protective layer is 100nm-250 nm.
The further technical scheme is that etching holes penetrating to the interdigital transducers are formed in the piezoelectric film layer and the oxide protection layer, the etching holes are located at electrode pads of the interdigital transducers, and the electrode pads of the interdigital transducers are exposed through the etching holes.
A preparation method of a high-frequency large-bandwidth film bulk wave filter comprises the following steps:
step 1, obtaining a substrate and cleaning the surface, wherein the substrate is made of a sapphire single crystal substrate or a SiC single crystal substrate;
step 2, preparing an interdigital transducer on the surface of the substrate by utilizing a photoetching technology and an electron beam evaporation method;
step 3, preparing an oxide film on the substrate by utilizing a magnetron sputtering method, wherein the oxide film uniformly and compactly covers the interdigital transducer and the adjacent interdigital gap of the interdigital transducer;
step 4, processing the surface of the oxide film by using a chemical mechanical polishing method to obtain an oxide protective layer, wherein the thickness of the oxide protective layer is more than or equal to that of the interdigital transducer, and the oxide protective layer covers the adjacent interdigital gaps of the interdigital transducer;
step 5, bonding a piezoelectric film and a substrate covered with an interdigital transducer and an oxide protective layer by using a wafer bonding method, wherein the piezoelectric film is arranged on the oxide protective layer and is made of LiTaO3Single crystal thin film or LiNbO3A single crystal thin film;
and 6, thinning the piezoelectric film by using a wafer grinding mode, and then performing surface treatment by using a chemical mechanical polishing mode to obtain the piezoelectric film.
The further technical scheme is that the method also comprises the following steps:
and etching the piezoelectric film layer and the oxide protective layer to expose the electrode pad of the interdigital transducer.
The beneficial technical effects of the invention are as follows:
in the structure of the high-frequency large-bandwidth film bulk wave filter disclosed by the application, the substrate is made of a sapphire single crystal substrate or a SiC single crystal substrate, so that the structure has the advantages of high sound velocity, good chemical stability, high heat conductivity and the like; the oxide film adopted by the method can be densely filled in the substrate and the adjacent interdigital gaps of the interdigital transducer, and a flat surface is obtained by a chemical mechanical polishing method, so that a high-quality piezoelectric film can be prepared, and the temperature stability of the bulk wave filter is improved by the oxide film; the method for obtaining the LiTaO with high crystal quality, good consistency and small propagation loss by adopting the wafer bonding method3Single crystal thin film or LiNbO3The single crystal film can obtain high sound velocity and large electromechanical coupling coefficient by using the bulk wave filter structure, meets the requirement of mobile communication on high frequency and large bandwidth, and the preparation process used by the structure is easy to realize and is easy to popularize on a large scale.
Drawings
Fig. 1 is a block diagram of a high frequency large bandwidth thin film bulk wave filter as disclosed in the present application.
Fig. 2 is a flow chart of a method for manufacturing a high-frequency large-bandwidth thin-film bulk wave filter disclosed in the present application.
FIG. 3 is a block diagram of step 2 of the preparation method disclosed in the present application.
FIG. 4 is a block diagram of step 3 of the preparation method disclosed in the present application.
FIG. 5 is a block diagram of step 4 of the preparation method disclosed in the present application.
FIG. 6 is a block diagram of step 5 of the preparation method disclosed in the present application.
Fig. 7 is a graph of simulated admittance of a thin film bulk wave resonator in example 1 disclosed in the present application.
Fig. 8 is a graph of simulated admittance of a thin film bulk wave resonator in example 2 of the present disclosure.
Detailed Description
The following further describes the embodiments of the present invention with reference to the drawings.
The application discloses a high-frequency large-bandwidth thin-film bulk wave filter structure, as shown in fig. 1, the structure sequentially comprises a substrate 1, an interdigital transducer 2, an oxide protection layer 3 and a piezoelectric thin-film layer 4 from bottom to top.
The interdigital transducer 2 is arranged on the substrate 1, the oxide protection layer 3 is arranged on the substrate 1 and covers the adjacent interdigital gaps of the interdigital transducer 2, and the oxide protection layer 3 is used for filling the adjacent interdigital gaps to obtain a flat upper surface, so that the subsequent preparation is facilitated to obtain the high-quality piezoelectric thin film layer 4. Meanwhile, the temperature compensation effect is achieved, and the temperature stability of the bulk wave filter is improved. The piezoelectric thin film layer 4 is arranged on the oxide protective layer 3, the thickness of the piezoelectric thin film layer 4 is 0.2-2 mu m, and the thickness of the oxide protective layer 3 is larger than or equal to that of the interdigital transducer 2. Specifically, the thickness of the oxide protective layer is 100nm-250 nm.
The substrate material used in the application is a sapphire single crystal substrate or a SiC single crystal substrate, so that the structure has the advantages of high sound velocity, good chemical stability and high thermal conductivity.
The oxide protective layer material used in the application is SiO2Or TeO2Or SiOF.
The piezoelectric thin film layer used in the application is made of LiTaO3Single crystal thin film or LiNbO3The structure also has the advantages of high quality, good consistency and small propagation loss.
The interdigital transducer 2 used in the present application includes an electrode primer layer 5 and an electrode main body layer 6, and the electrode main body layer 6 is provided on the electrode primer layer 5. The material of the electrode priming layer 5 comprises at least one of Ti, Ni, Zr and Cr, and the thickness of the electrode priming layer 5 is 1nm-20 nm. The material of the electrode main body layer 6 includes at least one of Al, Cu, Pt, and Mo. Specifically, the thickness of the interdigital transducer 2 is 100nm-200nm, the interdigital width is 100nm-2 μm, and the interdigital electrode period λ is 400nm-8 μm.
Optionally, etching holes penetrating to the interdigital transducer 2 are formed in the piezoelectric thin film layer 4 and the oxide protection layer 3, the etching holes are located at electrode pads of the interdigital transducer 2, and the electrode pads of the interdigital transducer 2 are exposed through the etching holes.
The application also discloses a preparation method of the high-frequency large-bandwidth thin-film bulk wave filter, a preparation flow chart of which is shown in fig. 2, and the following description is given by two embodiments.
Example 1:
a high-frequency large-bandwidth thin-film bulk wave filter structure is prepared, and the preparation method comprises the following steps:
step 1, obtaining a substrate 1 which is made of a 6H-SiC single crystal substrate and has the thickness of 500 microns, ultrasonically cleaning the surface of the substrate for 5 minutes by using acetone, alcohol and deionized water, then flushing the substrate for 2 minutes by using the deionized water, and finally drying the substrate by using nitrogen.
And 2, preparing the interdigital transducer 2 on the surface of the substrate 1 by utilizing a photoetching technology and an electron beam evaporation method, wherein the structure is shown in figure 3. The interdigital transducer 2 selects an electrode bottom layer 5 with the thickness of 10nm Ti and an electrode main body layer 6 with the thickness of 90nm Cu, the thickness of the interdigital transducer 2 is 100nm, the interdigital width is 260nm, and the interdigital electrode period lambda is 1.45 mu m. The preparation method comprises the following specific steps: firstly, carrying out a photoetching process, wherein the photoetching process comprises the specific steps of surface cleaning and drying, priming, photoresist spinning, soft drying, exposure, post-drying, developing and hard drying, and after photoetching is finished, the pattern of the interdigital transducer 2 on the substrate 1 is already formed. And then putting the sample into an electron beam evaporation machine for film coating, wherein the electron beam evaporation method comprises the following specific experimental conditions: background vacuum degree superior to 9 x 10-9torr, Ti deposition rate
Figure BDA0002333854060000051
Deposition of 10nm, evaporation rate of Cu
Figure BDA0002333854060000052
Deposit 90 nm. After completion of the evaporation, the sample was taken out from the evaporator and peeled off in acetone, thereby completing the preparation of the interdigital transducer 2.
Step 3, preparing SiO on the substrate by using a magnetron sputtering method2An oxide thin film 7 of 500nm in thickness, an oxideThe thin film 7 is uniformly and densely covered on the interdigital transducer 2 and the adjacent interdigital gap thereof, and the structure is shown in figure 4. The specific experimental conditions were as follows: background vacuum degree superior to 7 x 10-5Pa, adopting silicon target reactive sputtering, a direct current power supply, the power supply power is 1000W, the flow rate of sputtering gas Ar is 18sccm, and the reaction gas O2The flow rate is 12sccm, the film is coated at normal temperature, the film coating pressure is 0.5Pa, and the growth rate of the oxide film 7 is
Figure BDA0002333854060000053
And 4, processing the surface of the oxide film 7 by using a chemical mechanical polishing method to obtain an oxide protection layer 3, wherein the thickness of the oxide protection layer 3 is greater than or equal to that of the interdigital transducer 2, the oxide protection layer covers the adjacent interdigital gaps of the interdigital transducer, and the structure is shown in fig. 5. In the present application, the oxide thin film 7 is polished to a thickness of 100nm, and thus the thickness of the oxide protective layer 3 is equal to that of the interdigital transducer 2.
Step 5, utilizing a wafer bonding method to enable the tangential sum material to be 15-degree YX-LiNbO3The piezoelectric film 8 is bonded to the substrate 1 covered with the interdigital transducer 2 and the oxide protective layer 3, and the structure is as shown in fig. 6, the piezoelectric film 8 being provided on the oxide protective layer 3. The specific experimental conditions of the wafer bonding method are as follows: under the vacuum degree of 9.0X 10-5Pa and the pressure of 800N, and annealing at 250 ℃ for 8h, and the bonding force between the substrate 1 and the piezoelectric film 8 can be enhanced through the steps.
And 6, thinning the piezoelectric film 8 to 20 microns by utilizing a wafer grinding mode, and then performing surface treatment by adopting a chemical mechanical polishing mode to obtain the piezoelectric film layer 4. In the present application, the piezoelectric film 8 is polished to a thickness of 400 nm. The structure of the high-frequency large-bandwidth thin-film bulk wave filter obtained through the preparation steps is shown in fig. 1.
Optionally, finally, the piezoelectric film layer 4 and the oxide protective layer 3 are etched to expose the electrode pads of the interdigital transducer 2.
The simulation results of the thin film bulk wave resonator prepared according to the scheme described in this example 1 are shown in fig. 7. The resonator presents a high frequency signal with a resonant frequency of 5.191GHz and an anti-resonant frequency of 5.358GHz, corresponding to a speed of sound of 7486m/s and an electromechanical coupling coefficient of 7.9%.
Example 2:
the preparation method of another high-frequency large-bandwidth film bulk wave filter structure comprises the following steps:
step 1, obtaining a substrate 1 which is made of a sapphire single crystal substrate and has the thickness of 500 microns, ultrasonically cleaning the surface of the substrate for 5 minutes by using acetone, alcohol and deionized water respectively, then flushing the substrate for 2 minutes by using the deionized water, and finally drying the substrate by using nitrogen.
And 2, preparing the interdigital transducer 2 on the surface of the substrate 1 by utilizing a photoetching technology and an electron beam evaporation method, wherein the structure is shown in figure 3. The interdigital transducer 2 selects an electrode bottom layer 5 with the thickness of 10nm Ti and an electrode main body layer 6 with the thickness of 90nm Al, the thickness of the interdigital transducer 2 is 100nm, the interdigital width is 250nm, and the interdigital electrode period lambda is 1 mu m. The preparation method comprises the following specific steps: firstly, carrying out a photoetching process, wherein the photoetching process comprises the specific steps of surface cleaning and drying, priming, photoresist spinning, soft drying, exposure, post-drying, developing and hard drying, and after photoetching is finished, the pattern of the interdigital transducer 2 on the substrate 1 is already formed. And then putting the sample into an electron beam evaporation machine for film coating, wherein the electron beam evaporation method comprises the following specific experimental conditions: background vacuum degree superior to 9 x 10-9torr, Ti deposition rate
Figure BDA0002333854060000061
Deposition of 10nm, evaporation rate of Al
Figure BDA0002333854060000062
Deposit 90 nm. After completion of the evaporation, the sample was taken out from the evaporator and peeled off in acetone, thereby completing the preparation of the interdigital transducer 2.
Step 3, preparing SiO on the substrate by using a magnetron sputtering method2And an oxide film 7 with the thickness of 800nm, wherein the oxide film 7 uniformly and densely covers the interdigital transducer 2 and the adjacent interdigital gaps thereof, and the structure is shown in fig. 4. The specific experimental conditions were as follows: background trueThe hollowness is better than 7 multiplied by 10-5Pa, adopting silicon target reactive sputtering, a direct current power supply, the power supply power is 1000W, the flow rate of sputtering gas Ar is 18sccm, and the reaction gas O2The flow rate is 12sccm, the film is coated at normal temperature, the film coating pressure is 0.5Pa, and the growth rate of the oxide film 7 is
Figure BDA0002333854060000063
And 4, processing the surface of the oxide film 7 by using a chemical mechanical polishing method to obtain an oxide protection layer 3, wherein the thickness of the oxide protection layer 3 is greater than or equal to that of the interdigital transducer 2, the oxide protection layer covers the adjacent interdigital gaps of the interdigital transducer, and the structure is shown in fig. 5. In the present application, the oxide film 7 is polished to a thickness of 110nm, and thus the thickness of the oxide protective layer 3 is equal to that of the interdigital transducer 2.
Step 5, utilizing a wafer bonding method to enable the tangential sum material to be 128-degree YX-LiNbO3The piezoelectric film 8 is bonded to the substrate 1 covered with the interdigital transducer 2 and the oxide protective layer 3, and the structure is as shown in fig. 6, the piezoelectric film 8 being provided on the oxide protective layer 3. The specific experimental conditions of the wafer bonding method are as follows: under the vacuum degree of 9.0X 10-5Pa and the pressure of 800N, and annealing at 250 ℃ for 8h, and the bonding force between the substrate 1 and the piezoelectric film 8 can be enhanced through the steps.
And 6, thinning the piezoelectric film 8 to 30 microns by utilizing a wafer grinding mode, and then performing surface treatment by adopting a chemical mechanical polishing mode to obtain the piezoelectric film layer 4. In the present application, the piezoelectric film 8 is polished to a thickness of 250 nm. The structure of the high-frequency large-bandwidth thin-film bulk wave filter obtained through the preparation steps is shown in fig. 1.
Optionally, finally, the piezoelectric film layer 4 and the oxide protective layer 3 are etched to expose the electrode pads of the interdigital transducer 2.
The simulation results of the thin film bulk wave resonator prepared according to the scheme described in this example 2 are shown in fig. 8. The resonator generates a high-frequency signal, the resonant frequency of the high-frequency signal is 4.434GHz, the anti-resonant frequency of the high-frequency signal is 4.890GHz, the corresponding sound velocity is 4662m/s, and the electromechanical coupling coefficient is 22.9%.
According to the two embodiments, the structure of the high-frequency large-bandwidth film bulk wave filter has the characteristics of high acoustic velocity and large electromechanical coupling coefficient, the requirements of high-frequency and large-bandwidth mobile communication can be met, and the preparation process used by the structure is easy to realize and easy to popularize on a large scale.
What has been described above is only a preferred embodiment of the present application, and the present invention is not limited to the above embodiment. It is to be understood that other modifications and variations directly derivable or suggested by those skilled in the art without departing from the spirit and concept of the present invention are to be considered as included within the scope of the present invention.

Claims (8)

1. A high-frequency large-bandwidth thin-film bulk wave filter structure is characterized by comprising a substrate, an interdigital transducer, an oxide protective layer and a piezoelectric thin-film layer from bottom to top in sequence;
the interdigital transducer is arranged on the substrate, the oxide protection layer is arranged on the substrate and covers adjacent interdigital gaps of the interdigital transducer, the piezoelectric film layer is arranged on the oxide protection layer, and the thickness of the oxide protection layer is larger than or equal to that of the interdigital transducer;
the substrate is made of a sapphire single crystal substrate or a SiC single crystal substrate;
the piezoelectric film layer is made of LiTaO3Single crystal thin film or LiNbO3A single crystal thin film.
2. The structure of claim 1 wherein the interdigital transducer has a thickness of 100nm to 200nm, an interdigital width of 100nm to 2 μm, and an interdigital electrode period of 400nm to 8 μm.
3. The structure of claim 1, wherein the interdigital transducer comprises an electrode primer layer and an electrode body layer, the electrode body layer being disposed on the electrode primer layer;
the material of the electrode priming layer comprises at least one of Ti, Ni, Zr and Cr, and the thickness of the electrode priming layer is 1nm-20 nm;
the material of the electrode main body layer comprises at least one of Al, Cu, Pt and Mo.
4. The structure of claim 1, wherein the thickness of the piezoelectric thin film layer is 0.2 μm to 2 μm.
5. The structure of claim 1, wherein the material of the oxide protective layer is SiO2Or TeO2Or SiOF, the thickness of the oxide protective layer is 100nm-250 nm.
6. The structure according to claim 1, wherein etching holes penetrating to the interdigital transducers are formed in the piezoelectric thin film layer and the oxide protective layer, the etching holes are located at electrode pads of the interdigital transducers, and the electrode pads of the interdigital transducers are exposed through the etching holes.
7. A preparation method of a high-frequency large-bandwidth film bulk wave filter is characterized by comprising the following steps:
step 1, obtaining a substrate and cleaning the surface, wherein the substrate is made of a sapphire single crystal substrate or a SiC single crystal substrate;
step 2, preparing an interdigital transducer on the surface of the substrate by utilizing a photoetching technology and an electron beam evaporation method;
step 3, preparing an oxide film on the substrate by utilizing a magnetron sputtering method, wherein the oxide film uniformly and compactly covers the interdigital transducer and an adjacent interdigital gap of the interdigital transducer;
step 4, processing the surface of the oxide film by using a chemical mechanical polishing method to obtain an oxide protective layer, wherein the thickness of the oxide protective layer is more than or equal to that of the interdigital transducer, and the oxide protective layer covers the adjacent interdigital gaps of the interdigital transducer;
step 5, bonding a piezoelectric film and the substrate covered with the interdigital transducer and the oxide protective layer by using a wafer bonding method, wherein the piezoelectric film is arranged on the oxide protective layer and is made of LiTaO3Single crystal thin film or LiNbO3A single crystal thin film;
and 6, thinning the piezoelectric film by using a wafer grinding mode, and then performing surface treatment by using a chemical mechanical polishing mode to obtain the piezoelectric film.
8. The method of claim 7, further comprising:
and etching the piezoelectric film layer and the oxide protective layer to expose the electrode pad of the interdigital transducer.
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