A transversely excited film bulk acoustic wave filter and a method for preparing the same

Abstract

The present invention provides a lateral excitation membrane acoustic wave filter and a preparation method thereof, wherein the preparation method of the present invention solves the problems of irregular cavity of air cavity and inaccurate shape and size control existing in the prior art by pre-preparing an air cavity filled with sacrificial material in a wafer, realizes precise customization of the air cavity, and meets different design requirements; and the air cavity prepared by the preparation method of the present application causes little damage to the mechanical structure of the substrate, and will not have a negative impact on the mechanical structure strength of the device; it solves the problems existing in the prior art of preparing the air cavity, such as irregular cavity, inaccurate shape and size control of the air cavity, low production efficiency and high cost, unstable mechanical structure strength or complex structure. The overall performance and reliability of the lateral excitation membrane acoustic wave filter device are improved, providing strong support for the development of wireless communication technology.

Description

Technical Field

[0001] The invention relates to the technical field of electronic measuring instrument manufacturing, and in particular to a transversely excited film bulk acoustic wave filter and a preparation method thereof. Background Art

[0002] Compared with surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, film bulk acoustic wave resonators (FBAR) and other types of acoustic resonators, laterally excited film bulk acoustic wave filters (XBAR) can achieve high frequency and large bandwidth, better meeting the needs of future communication networks.

[0003] In the prior art, lithium niobate piezoelectric film is widely considered to be an ideal material for preparing transversely excited bulk acoustic wave filters (XBAR) because of its high acoustic velocity and large electromechanical coupling coefficient in the A1 mode. Smart-cut technology is a relatively mature process for preparing lithium niobate single crystal thin films. Through ion implantation and bonding technology, it can peel off a layer of high-quality piezoelectric film on the dielectric layer. However, the high-resistance silicon substrate used in the Smart-cut technology does not prepare the air cavity in advance, but prepares the air cavity in the subsequent wafer tape-out process. The prior art proposes three preparation schemes for reflective air cavities:

[0004] 1. Front etching release method: a release hole is formed on the front side of the wafer by dry etching, and then the substrate is released by wet chemical solution or gas. However, this method is isotropic during the release process, and the shape and size of the cavity are difficult to control, which limits its application in large-scale mass production.

[0005] 2. Backside dry etching method: The air cavity is directly formed on the substrate through backside dry etching technology. However, this method will reduce the mechanical strength of the device and affect its production and use.

[0006] 3. Bonding method: Bonding a substrate with a piezoelectric film to a substrate with an air cavity in advance. Although this method can achieve the preparation of an air cavity, the processing process is cumbersome and the cost is high.

[0007] In view of the limitations of the prior art, the present invention aims to provide a transversely excited film bulk acoustic wave filter and a preparation method thereof, so as to overcome the deficiencies in the prior art. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a laterally excited membrane acoustic wave filter and a method for preparing the same, which solves the problems in the prior art of preparing the air cavity, such as irregular cavity, inaccurate control of the shape and size of the air cavity, low production efficiency and high cost, unstable mechanical structure strength or complex structure.

[0009] On the one hand, an embodiment of the present invention provides a method for preparing a transversely excited film bulk acoustic wave filter, comprising:

[0010] Providing a single-side polished substrate, and performing photolithography, etching and desizing processes on the substrate according to a preset air cavity layout to form a desired air cavity;

[0011] Filling the air cavity with a sacrificial layer material, and performing a planarization process on the surface of the substrate after the sacrificial layer material is filled;

[0012] preparing a piezoelectric film on the dielectric layer;

[0013] preparing interdigital electrodes, a frequency modulation layer, electrode leads and a passivation layer on the piezoelectric film;

[0014] A release channel is formed by dry etching the piezoelectric film in the release hole area connected to the air cavity and the dielectric layer below the film;

[0015] releasing the sacrificial layer material to form an air cavity between the substrate and the dielectric layer;

[0016] The dielectric layer on the back of the piezoelectric film is removed to obtain a transversely excited film bulk acoustic wave filter.

[0017] Preferably, the air cavity pattern is a polygon, and any two sides of the polygon are not parallel.

[0018] Preferably, the edges of the air cavity layout include one or more combinations of curves and straight lines, and the angles of adjacent edges of the air cavity layout are greater than 90°.

[0019] Preferably, the depth of the air cavity is 0.1 micrometer to 5 micrometers, and the angle between the sidewall and the bottom of the air cavity is greater than 80° and less than 125°.

[0020] Preferably, the piezoelectric film prepared on the dielectric layer includes a single-layer or multi-layer structure, and each layer of the piezoelectric film is made of the same or different materials.

[0021] Preferably, the material of the piezoelectric film includes lithium niobate, lithium tantalate, aluminum nitride or scandium-doped aluminum nitride, the material of the interdigitated electrodes includes two or more of titanium, aluminum, copper, silver, molybdenum, tungsten, platinum, aluminum-copper alloy and titanium-tungsten alloy, the material of the sacrificial layer material includes one or more of PSG, polycrystalline silicon, ferrocrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, porous silicon, carbon-doped oxide and diamond; the material of the substrate includes silicon, silicon carbide, gallium nitride, aluminum oxide or diamond.

[0022] Preferably, the dielectric layer includes a single dielectric layer made of a single material or a multi-layer dielectric layer made of two or more different materials, and the dielectric layer has a thickness of 30 nanometers to 1 micrometer.

[0023] Preferably, the material of the dielectric layer includes one or more combinations of aluminum oxide, PSG, polysilicon, ferrocrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, porous silicon, carbon-doped oxide and diamond.

[0024] On the other hand, an embodiment of the present invention also provides a lateral excitation membrane bulk acoustic wave filter using a method for preparing a lateral excitation membrane bulk acoustic wave filter as described in any of the above steps, comprising a substrate, a dielectric layer, a piezoelectric film stacked in sequence, and interdigitated electrodes, a frequency modulation layer, electrode leads and a passivation layer respectively arranged on the piezoelectric film.

[0025] Preferably, an air cavity is formed between the substrate and the dielectric layer, the depth of the air cavity is 0.1 micrometer to 5 micrometers, and the angle between the side wall and the bottom of the air cavity is greater than 80° and less than 125°.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention solves the problems of irregular air cavity and inaccurate shape and size control in the prior art by pre-preparing an air cavity filled with sacrificial material in the wafer, and realizes precise customization of the air cavity to meet different design requirements. At the same time, the air cavity mentioned in this patent is usually only a few microns deep. Compared with the substrate thickness maintained at 150 to 200 microns after thinning, the damage to the mechanical structure of the substrate caused by the air cavity in this patent is basically negligible. Compared with the traditional back-side etching process, it will not have a negative impact on the mechanical structure strength of the device.

[0028] In addition, the air cavity preparation method proposed in the present invention can not only prepare any air cavity shape, size, and depth required by the design, but also the process can be repeated and mass-produced, ensuring production efficiency and device consistency. At the same time, by precisely controlling the formation of the air cavity, the overall performance and reliability of the lateral excitation film bulk acoustic wave filter device are improved, providing strong support for the development of wireless communication technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the front etching release method of the air cavity preparation scheme in the background technology of the present invention;

[0030] Figure 2 It is a structural schematic diagram of a backside dry etching method of an air cavity preparation scheme in the background technology of the present invention;

[0031] Figure 3 A flowchart of the steps of a method for preparing a transversely excited film bulk acoustic wave filter provided by the present invention;

[0032] Figure 4 A schematic diagram of a structure for forming a required air cavity on a substrate provided by the present invention;

[0033] Figure 5 A schematic diagram of a structure of filling a sacrificial layer material in an air cavity provided by the present invention;

[0034] Figure 6 A schematic diagram of a structure for depositing a dielectric layer on a substrate surface provided by the present invention;

[0035] Figure 7 A schematic diagram of a structure for forming a piezoelectric film on a substrate provided by the present invention;

[0036] Figure 8 A schematic diagram of a structure for preparing interdigital electrodes on a piezoelectric film provided by the present invention;

[0037] Fig. 9 A schematic diagram of a structure for forming a release channel by dry etching provided by the present invention;

[0038] Fig.10 A schematic diagram of a structure for forming an air cavity between a substrate and a dielectric layer provided by the present invention;

[0039] Fig.11 A schematic diagram of a structure for removing a dielectric layer on the back of a piezoelectric film provided by the present invention;

[0040] Fig.12 The present invention provides a schematic diagram of the composition structure of a dielectric layer.

[0041] In the above figures: 1. substrate; 2. air cavity; 3. sacrificial layer material; 4. dielectric layer; 5. piezoelectric film; 6. dielectric layer; 7. interdigitated electrodes; 8. release channel. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0043] like Figure 3 As shown, an embodiment of the present invention provides a method for preparing a transversely excited film bulk acoustic wave filter, comprising:

[0044] S101, providing a single-side polished substrate 1, and performing photolithography, etching and desizing processes on the substrate 1 according to a preset air cavity layout to form a required air cavity 2;

[0045] S102, filling the air cavity 2 with a sacrificial layer material 3, and performing a planarization process on the surface of the substrate 1 after the sacrificial layer material 3 is filled;

[0046] S103, depositing a dielectric layer 4 on the surface of the substrate 1 after the planarization treatment, and performing planarization treatment on the surface of the dielectric layer 4;

[0047] S104, preparing a piezoelectric film 5 on the dielectric layer 4;

[0048] S105, preparing interdigital electrodes 7, a frequency modulation layer, electrode leads and a passivation layer on the piezoelectric film 5;

[0049] S106, forming a release channel 8 by dry etching the piezoelectric film 5 in the release hole area connected to the air cavity 2 and the dielectric layer 4 below the film;

[0050] S107, releasing the sacrificial layer material 3 to form an air cavity 2 between the substrate 1 and the dielectric layer 4;

[0051] S108, removing the dielectric layer 4 on the back side of the piezoelectric film 5 to obtain a transversely excited film bulk acoustic wave filter.

[0052] It should be noted that the preparation method of the laterally excited membrane acoustic wave filter proposed in this embodiment solves the problems of irregular air cavity and inaccurate shape and size control existing in the prior art, realizes precise customization of the air cavity 2, and meets different design requirements. First, a single-sided polished substrate 1 is used, and the required air cavity 2 is accurately manufactured according to a preset air cavity layout through photolithography, etching and degumming processes, ensuring that the geometric parameters of the air cavity 2 meet the design requirements. Next, a sacrificial layer material 3 is filled in the air cavity 2 and a flattening treatment is performed to provide a uniform surface for the subsequent deposition of the dielectric layer 4. The deposition and flattening of the dielectric layer 4 further ensure the adhesion quality of the piezoelectric film 5 and the uniformity of the overall structure. Then, a coating technology or a bonding process is used to prepare the piezoelectric film 5 on the dielectric layer 4;

[0053] Prepare interdigital electrodes 7, frequency modulation layer, electrode leads and passivation layer on the piezoelectric film 5, and form release channels 8 by dry etching the piezoelectric film 5 in the release hole area connected to the air cavity 2 and the dielectric layer 4 under the film, so as to prepare for the release of the sacrificial layer material 3; after releasing the sacrificial layer material 3, form the air cavity 2 between the substrate 1 and the dielectric layer 4, the shape design of the air cavity 2 can reduce the parasitic effect caused by the standing wave oscillation of the reflected sound wave, and is also conducive to the sacrificial material to fully fill the cavity, and no abnormal conditions such as gaps and voids will occur; finally, remove the dielectric layer 4 on the back of the piezoelectric film 5 to complete the preparation of the transverse excitation film body acoustic wave filter. The air cavity preparation method proposed in the present invention can not only prepare the air cavity shape, size and depth required by any design, but also the process can be repeated and mass-produced, ensuring the production efficiency and consistency of the device. At the same time, by accurately controlling the formation of the air cavity, the overall performance and reliability of the transverse excitation film body acoustic wave filter device are improved, providing strong support for the development of wireless communication technology.

[0054] like Figure 4 As shown, Figure 4 A schematic diagram of a structure for forming a required air cavity on a substrate provided by the present invention is provided. A single-side polished substrate 1 is provided, and photolithography, etching and desizing are performed on the substrate 1 according to a preset air cavity layout to form a required air cavity 2.

[0055] It should be noted that the air cavity 2 filled with sacrificial material is pre-prepared in the wafer, which solves the problem of irregular cavity, unstable structure or complex structure. First, a suitable single-crystal silicon substrate 1 is selected, and the substrate 1 is single-sided polished to ensure surface flatness. According to the pre-designed air cavity layout, photoresist is coated on the substrate 1 using photolithography technology and exposed, and then dry etching is performed to remove unnecessary parts to form a predetermined air cavity 2 structure, and then the residual photoresist is removed by a stripping process, so that the shape and size of the air cavity 2 can be precisely controlled, and the production efficiency can be improved and the manufacturing cost can be reduced.

[0056] like Figure 5 As shown, Figure 5 A schematic diagram of a structure of filling a sacrificial layer material in an air cavity provided by the present invention is shown in FIG. A sacrificial layer material 3 is filled in the air cavity 2, and a surface of the substrate 1 after being filled with the sacrificial layer material 3 is planarized.

[0057] It should be noted that in order to release the air cavity 2 later, it is necessary to fill the formed air cavity 2 with a sacrificial layer material 3, such as phosphosilicate glass PSG or silicon dioxide. After the filling is completed, the surface of the substrate 1 is flattened using chemical mechanical polishing (CMP) technology to ensure the flatness of the entire surface for subsequent deposition processes. For example, after filling the sacrificial layer material 3, the sacrificial material will bulge or sink relative to the substrate 1 in the Z-axis direction, forming a height difference. At this time, it is necessary to use CMP technology to smooth the surface to ensure that the subsequently deposited dielectric layer 4 is uniform. This process can effectively avoid subsequent process problems caused by surface unevenness, and also help to improve the performance stability of the device.

[0058] like Figure 6 As shown, Figure 6 A schematic diagram of a structure of depositing a dielectric layer on a substrate surface provided by the present invention is shown in FIG. A dielectric layer 4 is deposited on a flattened surface of a substrate 1 , and the surface of the dielectric layer 4 is flattened.

[0059] It should be noted that a dielectric layer 4, such as silicon dioxide or silicon nitride, is deposited on the planarized surface of the substrate 1 to isolate the piezoelectric film 5 from the substrate 1; after the deposition is completed, the surface of the dielectric layer 4 is planarized again using CMP technology to ensure surface flatness, providing a good foundation for subsequent bonding processes.

[0060] like Figure 7 As shown, Figure 7 The schematic diagram of the structure of forming a piezoelectric film on a substrate provided by the present invention is as follows: The piezoelectric film 3 prepared on the dielectric layer 4 includes a single layer or a multi-layer structure, and each layer of the piezoelectric film 3 is made of the same or different materials.

[0061] like Figure 8 As shown, Figure 8 The schematic diagram of the structure of preparing interdigital electrodes on a piezoelectric film provided by the present invention is as follows: on the piezoelectric film 5, interdigital electrodes 7, a frequency modulation layer, electrode leads and a passivation layer are prepared.

[0062] It should be noted that a metal layer is deposited on the piezoelectric film 5 and patterned to form interdigital electrodes 7, and then a frequency modulation layer, electrode leads and a passivation layer are prepared; wherein the frequency modulation layer, the passivation layer and the electrode leads are not shown in the figure.

[0063] like Fig. 9 As shown, Fig. 9 A schematic diagram of a structure of forming a release channel by dry etching provided by the present invention. The release channel 8 is formed by dry etching the piezoelectric film 5 in the release hole area connected to the air cavity 2 and the dielectric layer 4 under the film.

[0064] It should be noted that in a specific implementation, for example, the position and shape of the release hole can be defined on the piezoelectric film 5 and the dielectric layer 4 using photolithography technology, and then the material is removed along these defined patterns through a dry etching process, penetrating the piezoelectric film 5 and the dielectric layer 4 until the air cavity 2, so that the release hole is connected to the air cavity 2 through the etched channel.

[0065] like Fig.10 As shown, Fig.10 The schematic diagram of the structure of forming an air cavity between a substrate and a dielectric layer provided by the present invention is as follows: the sacrificial layer material 3 is released, and an air cavity 2 is formed between the substrate 1 and the dielectric layer 4.

[0066] It should be noted that after the release channel 8 is formed, the sacrificial material release operation is performed. The sacrificial material can be dissolved by a liquid medicine, or a specific gas can be used to react with the sacrificial material to vaporize or decompose it, thereby removing it from the air cavity 2. After completing this step, the space originally occupied by the sacrificial material becomes the air cavity 2, providing the necessary cavity structure for the normal operation of the acoustic wave filter.

[0067] like Fig.11 As shown, Fig.11 The schematic diagram of the structure of removing the dielectric layer on the back of the piezoelectric film provided by the present invention is as follows: The dielectric layer 4 on the back of the piezoelectric film 5 is removed to obtain a transversely excited film bulk acoustic wave filter.

[0068] It should be noted that the dielectric layer 4 in the back area of ​​the piezoelectric film can be removed by liquid or gas reaction, thereby exposing the back side of the piezoelectric film 5. After removing the dielectric layer 4, some parts of the piezoelectric film 5 will be in direct contact with the air or other media, which helps to adjust the resonant frequency and bandwidth characteristics of the filter. After the dielectric layer 4 is removed, the structure of the entire transverse excitation film body acoustic wave filter is basically completed, and subsequent performance testing and packaging can be carried out, ultimately forming a high-performance acoustic wave filter that can be used in various wireless communication devices.

[0069] Preferably, the depth of the air cavity 2 is 0.1 micrometer to 5 micrometers, and the angle between the side wall and the bottom of the air cavity 2 is greater than 80° and less than 125°.

[0070] It should be noted that, in the specific design, the depth range of the air cavity 2 is precisely controlled between 0.1 microns and 5 microns. This size range allows the air cavity 2 to provide the necessary space for sound wave propagation while maintaining the mechanical stability of the wafer as a whole. In addition, the angle between the side wall and the bottom of the air cavity 2 is also designed to be greater than 80° and less than 125°, which helps to reduce the multiple reflections and scattering of sound waves inside the cavity. At the same time, since the depth of the air cavity 2 is usually only a few microns, the destructive effect of the air cavity 2 on the mechanical structure is very small compared to the thickness of the substrate 1 maintained at 150 to 200 microns after thinning, and the effect of the air cavity 2 on the mechanical structure strength of the entire wafer is also very limited. Compared with the traditional back-side etching process, the solution of preparing the air cavity 2 in advance at the wafer production end will not have a negative impact on the mechanical structure strength of the device, and improves the overall quality and service life of the device.

[0071] Preferably, the material of the piezoelectric film 5 includes lithium niobate, lithium tantalate, aluminum nitride or scandium-doped aluminum nitride, the material of the interdigitated electrode 7 includes two or more combinations of titanium, aluminum, copper, silver, molybdenum, tungsten, platinum, aluminum-copper alloy and titanium-tungsten alloy, the material of the sacrificial layer material 3 includes one or more combinations of PSG, polycrystalline silicon, ferrocrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, porous silicon, carbon-doped oxide and diamond; the material of the substrate includes silicon, silicon carbide, gallium nitride, aluminum oxide or diamond.

[0072] Preferably, the dielectric layer includes a single dielectric layer made of a single material, and also includes a multi-layer dielectric layer made of two or more different materials. The dielectric layer 4 has a thickness of 30 nanometers to 1 micrometer.

[0073] Preferably, the material of the dielectric layer 4 includes one or more combinations of aluminum oxide, PSG, polysilicon, ferrocrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, porous silicon, carbon-doped oxide and diamond.

[0074] like Fig.12 As shown, Fig.12 The present invention provides a schematic diagram of the composition structure of a dielectric layer. In the figure, reference numerals 4 and 6 are both dielectric layers. It should be noted that the dielectric layer can be composed of a single material or a combination of two or more different materials. For example, silicon dioxide SiO2 can be selected as a dielectric layer of a single material, or a combination of silicon dioxide and silicon nitride Si3N4 can be used to obtain the desired performance.

[0075] Another embodiment of the present invention provides a lateral excitation film bulk acoustic wave filter using the method for preparing a lateral excitation film bulk acoustic wave filter described in the above steps, comprising a substrate 1, a dielectric layer 4, a piezoelectric film 5 stacked in sequence, and interdigital electrodes 7, a frequency modulation layer, an electrode lead and a passivation layer respectively arranged on the piezoelectric film 5. An air cavity 2 is formed between the substrate 1 and the dielectric layer 4, the depth of the air cavity 2 is 0.1 microns to 5 microns, and the angle between the side wall and the bottom of the air cavity 2 is greater than 80° and less than 125°.

[0076] Since the manufacturing method of the present application pre-prepares the air cavity 2 filled with sacrificial material in the wafer, the problem of irregular cavity and unstable structure is solved; at the same time, the air cavity 2 mentioned in this patent is usually only a few microns deep. Compared with the thickness of the substrate 1 maintained at 150 to 200 microns after thinning, the damage to the mechanical structure of the substrate 1 caused by the air cavity 2 in this patent is basically negligible, and compared with the traditional back-side etching process, it will not have a negative impact on the mechanical structure strength of the device.

[0077] By adopting the air cavity preparation method proposed in the present invention, not only can the air cavity shape, size, and depth required by any design be prepared, but also it can be repeatedly and mass-produced. By precisely controlling the formation of the air cavity, the overall performance and reliability of the laterally excited membrane bulk acoustic wave filter device are improved, providing strong support for the development of wireless communication technology.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a transversely excited film bulk acoustic wave filter, characterized in that: include: Providing a single-side polished substrate, and performing photolithography, etching and desizing processes on the substrate according to a preset air cavity layout to form a desired air cavity; Filling the air cavity with a sacrificial layer material, and performing a planarization process on the surface of the substrate after the sacrificial layer material is filled; Depositing a dielectric layer on the flattened surface of the substrate, and flattening the surface of the dielectric layer; preparing a piezoelectric film on the dielectric layer; preparing interdigital electrodes, a frequency modulation layer, electrode leads and a passivation layer on the piezoelectric film; A release channel is formed by dry etching the piezoelectric film in the release hole area connected to the air cavity and the dielectric layer below the film; releasing the sacrificial layer material to form an air cavity between the substrate and the dielectric layer; The dielectric layer on the back of the piezoelectric film is removed to obtain a transversely excited film bulk acoustic wave filter.

2. The method for preparing a transversely excited film bulk acoustic wave filter according to claim 1, characterized in that: The air cavity pattern is a polygon, and any two sides of the polygon are not parallel.

3. The method for preparing a transversely excited film bulk acoustic wave filter according to claim 1, characterized in that: The edges of the air cavity layout include one or more combinations of curves and straight lines, and the angles of adjacent edges of the air cavity layout are greater than 90°.

4. The method for preparing a transversely excited film bulk acoustic wave filter according to claim 1, characterized in that: The depth of the air cavity is 0.1 micrometer to 5 micrometers, and the angle between the side wall and the bottom of the air cavity is greater than 80 degrees and less than 125 degrees.

5. The method for preparing a transversely excited film bulk acoustic wave filter according to claim 1, characterized in that: The piezoelectric film prepared on the dielectric layer includes a single-layer or multi-layer structure, and each layer of the piezoelectric film is made of the same or different materials.

6. The method for preparing a transversely excited film bulk acoustic wave filter according to claim 1, characterized in that: The material of the piezoelectric film includes lithium niobate, lithium tantalate, aluminum nitride or scandium-doped aluminum nitride; the material of the interdigitated electrodes includes two or more of titanium, aluminum, copper, silver, molybdenum, tungsten, platinum, aluminum-copper alloy and titanium-tungsten alloy; the material of the sacrificial layer material includes one or more of PSG, polycrystalline silicon, ferrocrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, porous silicon, carbon-doped oxide and diamond; the material of the substrate includes silicon, silicon carbide, gallium nitride, aluminum oxide or diamond.

7. The method for preparing a transversely excited film bulk acoustic wave filter according to claim 1, characterized in that: The dielectric layer includes a single dielectric layer made of a single material, and also includes a multi-layer dielectric layer made of two or more different materials. The thickness of the dielectric layer is 30 nanometers to 1 micrometer.

8. The method for preparing a transversely excited film bulk acoustic wave filter according to claim 1, characterized in that: The material of the dielectric layer includes one or more combinations of aluminum oxide, PSG, polysilicon, ferrocrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, porous silicon, carbon-doped oxide and diamond.

9. A transversely excited film bulk acoustic wave filter, using the method for preparing a transversely excited film bulk acoustic wave filter according to any one of claims 1 to 8, characterized in that: The invention comprises a substrate, a dielectric layer, a piezoelectric film which are stacked in sequence, and interdigital electrodes, a frequency modulation layer, an electrode lead and a passivation layer which are respectively arranged on the piezoelectric film.

10. The transversely excited film bulk acoustic wave filter according to claim 9, characterized in that: An air cavity is formed between the substrate and the dielectric layer, the depth of the air cavity is 0.1 micrometer to 5 micrometers, and the angle between the side wall and the bottom of the air cavity is greater than 80° and less than 125°.

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