A filter and a method for preparing the same

Abstract

The embodiment of the present application provides a filter, including at least two resonators, the resonator including a top electrode, a piezoelectric layer and a bottom electrode; the resonators are stacked vertically, an acoustic reflection layer is arranged between adjacent resonators, the electrodes of the resonators extend to the surface of the filter, the at least two resonators are connected through a circuit, the circuit is arranged on the surface of the filter, and the surface is the plane where the acoustic reflection layer is located; the application also provides a method for preparing the filter, including preparing a substrate, preparing a first resonator, a support layer, an acoustic reflection layer and a second resonator in sequence, extending the electrode of the first resonator to the surface of the acoustic reflection layer, and connecting the first resonator and the second resonator through a circuit. The vertically integrated filter provided in the embodiment of the present application reduces the size of the filter, improves the integration of the filter, simplifies the structure of the resonator, and reduces the production cost of the filter.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of filters, and in particular to a filter and a method for preparing the same. Background Art

[0002] As an essential high-frequency component of the RF part of wireless terminals, the manufacture of RF filters requires at least two sets of resonators operating at different resonant frequencies. Current 4G / LTE and 5G mobile phone products need to support multiple frequency bands for communication at the same time. At the same time, the communication system structure needs to be smaller and more integrated. In this case, in order to achieve communication in multiple frequency bands, more filters need to be added to the space of the original RF front-end circuit, which puts forward new requirements for the size and integration of the filter itself.

[0003] In the prior art, SMR-BAW resonators (solidly mounted resonator-bulk acoustic wave) have high electromechanical coupling coefficient, mechanical quality factor, and high operating frequency performance, so SMR-BAW resonators are one of the current mainstream RF resonators. In existing filters, multiple resonators are interconnected on the same plane through expansion and integration in lateral dimensions to form filters, so the size of the filter formed is relatively large. In addition, for multiple resonators, for example, all use SMR-BAW resonators, because the thickness of the piezoelectric film of the SMR-BAW device on the wafer of each resonator is the same as each other, it is usually adopted to apply different sizes of loads to each resonator to adjust the resonant frequency of each resonator to obtain different resonant frequencies, which makes the process of multiple resonators complicated and restricts the miniaturization of RF filters. Summary of the invention

[0004] The embodiment of the present invention provides an optimized filter to reduce the size of the filter.

[0005] In a first aspect, an embodiment of the present application provides a filter, comprising at least two resonators, each of which comprises a top electrode, a piezoelectric layer, and a bottom electrode; the at least two resonators are stacked vertically, an acoustic reflection layer is arranged between two adjacent resonators of the at least two resonators, and the at least two resonators include a first resonator and a second resonator arranged adjacent to each other,

[0006] The first resonator is located at the top of the filter and the second resonator is located below the first resonator, and the top electrode and the bottom electrode of the second resonator extend to the surface of the sound reflection layer below the first resonator respectively;

[0007] Alternatively, the second resonator is located at the top of the filter and the first resonator is located below the second resonator, and the top electrode and the bottom electrode of the first resonator extend to the surface of the sound reflection layer below the second resonator respectively.

[0008] In the above embodiment, by integrating the resonator vertically, two adjacent filters share the same acoustic reflection structure, which saves the space size of the filter and enables multiple resonators to be prepared on the same wafer, thereby reducing the size of the filter and improving the integration of the filter.

[0009] In combination with the first aspect, in a possible implementation manner, the first resonator and the second resonator have different resonance frequencies.

[0010] In combination with the first aspect, in a possible implementation manner, the first resonator and the second resonator have different resonance frequencies, including: a thickness of a piezoelectric layer of the first resonator and a thickness of a piezoelectric layer of the second resonator are different.

[0011] In the above embodiments, this embodiment can realize the processing of piezoelectric films and electrodes of different thicknesses and materials on the same wafer, and can also adjust the resonator frequency by applying a pressure load, and then can design and process resonators with different resonant frequencies, thereby reducing the size of the filter and the process cost.

[0012] In combination with the first aspect, in a possible implementation, the acoustic reflection layer is a Bragg reflection structure, and the acoustic reflection layer includes a low acoustic impedance material and a high acoustic impedance material stacked alternately in a thickness direction.

[0013] In combination with the first aspect, in a possible implementation, the sound reflection layer is a phononic crystal structure, including low acoustic impedance materials and high acoustic impedance materials arranged in multiple directions.

[0014] In the above embodiment, low acoustic impedance materials and high acoustic impedance materials arranged in multiple directions are used, which has strong mechanical stability and good heat dissipation performance.

[0015] In combination with the first aspect, in a possible implementation, the filter is a ladder-type filter, the top electrode of the first resonator and the top electrode of the second resonator are both electrically connected to the first output end of the filter, the bottom electrode of the first resonator is grounded, and the bottom electrode of the second resonator is electrically connected to the first input end of the filter.

[0016] In the above embodiment, the ladder filter transmits the frequency band signals within the passband without attenuation and attenuates the out-of-band signals to the maximum extent, and can be used for single-ended (unbalanced) and differential (balanced) signals.

[0017] In combination with the first aspect, in a possible implementation, the filter is a multi-order Ladder-type filter including at least two Ladder-type filters, the at least two Ladder-type filters are connected in series, the first-order Ladder-type filter is connected to the first input end, and the last-order Ladder-type filter is connected to the first output end.

[0018] In combination with the first aspect, in a possible implementation manner, the at least two ladder filters are arranged on the same plane.

[0019] In combination with the first aspect, in a possible implementation manner, the at least two ladder type filters are stacked vertically, wherein an acoustic reflection layer is disposed between two adjacent ladder type filters.

[0020] In the above embodiment, the multi-order ladder filter includes at least two ladder filters. The vertically integrated structure can be used to process filters with complex structures, thereby improving the integration of complex filters and expanding the application range of filters using the vertically integrated structure.

[0021] In combination with the first aspect, in a possible implementation, the filter is a Lattice type filter, including a first resonator, a second resonator, a third resonator, and a fourth resonator, the third resonator and the fourth resonator are stacked vertically and an acoustic reflection layer is arranged between the two, the top electrode of the first resonator is electrically connected to the top electrode of the second resonator and then connected to the first input end of the filter, the bottom electrode of the third resonator is electrically connected to the bottom electrode of the fourth resonator and then connected to the second input end of the filter, the bottom electrode of the first resonator is electrically connected to the top electrode of the fourth resonator and then connected to the first output end of the filter, and the bottom electrode of the second resonator is electrically connected to the top electrode of the third resonator and then connected to the second output end of the filter.

[0022] In combination with the first aspect, in a possible implementation manner, the third resonator is stacked vertically above the fourth resonator, the top electrode and the bottom electrode of the fourth resonator respectively extend to the surface of the sound reflection layer below the third resonator, the third resonator and the first resonator are arranged in the same plane, and the fourth resonator and the second resonator are arranged in the same plane;

[0023] Alternatively, the third resonator is stacked vertically above the fourth resonator, the top electrode and the bottom electrode of the fourth resonator extend to the surface of the sound reflection layer below the third resonator respectively, the third resonator and the second resonator are arranged in the same plane, and the fourth resonator and the first resonator are arranged in the same plane;

[0024] Alternatively, the fourth resonator is stacked vertically above the third resonator, the top electrode and the bottom electrode of the third resonator extend to the surface of the sound reflection layer below the fourth resonator respectively, the third resonator and the first resonator are arranged in the same plane, and the fourth resonator and the second resonator are arranged in the same plane;

[0025] Alternatively, the fourth resonator is stacked vertically above the third resonator, the top electrode and the bottom electrode of the third resonator respectively extend to the surface of the sound reflection layer below the fourth resonator, the third resonator and the second resonator are arranged in the same plane, and the fourth resonator and the first resonator are arranged in the same plane.

[0026] In combination with the first aspect, in a possible implementation manner, the first resonator, the second resonator, the third resonator and the fourth resonator are stacked vertically, and a sound reflection layer is arranged between adjacent resonators.

[0027] In the above embodiment, multiple resonators are vertically integrated, and two adjacent filters use the same acoustic reflection structure to achieve the process of piezoelectric films and electrodes of different thicknesses and materials on the same wafer, thereby designing filters with different resonant frequencies, thereby reducing the size and process cost of the filter.

[0028] In combination with the first aspect, in a possible implementation, the filter is a multi-order Lattice type filter including at least two Lattice type filters, the at least two Lattice type filters are connected in series, the first-order Lattice type filter is electrically connected to the first input end and the second input end, and the last-order Lattice type filter is electrically connected to the first output end and the second output end.

[0029] In combination with the first aspect, in a possible implementation manner, the at least two Lattice filters are arranged on the same plane.

[0030] In combination with the first aspect, in a possible implementation manner, the at least two Lattice filters are stacked vertically, and an acoustic reflection layer is disposed between two adjacent Lattice filters.

[0031] In the above embodiment, the multi-order Lattice filter includes at least two Lattice filters. The vertically integrated structure can be used to process filters with complex structures, thereby improving the integration of complex filters and expanding the application range of filters using the vertically integrated structure.

[0032] In a second aspect, the embodiments of the present application further provide a method for preparing any filter in the first aspect, comprising the following steps:

[0033] preparing a substrate, wherein the substrate is provided with a cavity;

[0034] growing a sacrificial layer in a cavity of a substrate so that the cavity is filled with the sacrificial layer;

[0035] Sequentially preparing a first bottom electrode, a first piezoelectric layer and a first top electrode of a first resonator on the upper surface of the substrate filled with the sacrificial layer, wherein at least a portion of the first bottom electrode, at least a portion of the first piezoelectric layer and at least a portion of the first top electrode are all disposed above the sacrificial layer;

[0036] Growing a support layer on the upper surface of the first top electrode, and grinding the support layer so that the upper surface of the support layer and the upper surface of the first top electrode are located in the same plane;

[0037] preparing an acoustic reflection layer on the upper surface of the first top electrode and the upper surface of the support layer;

[0038] On the upper surface of the acoustic reflection layer, a second bottom electrode, a second piezoelectric layer and a second top electrode of the second resonator are sequentially prepared;

[0039] The first resonator, the sound reflection layer, and the second resonator are sequentially etched to prepare at least one first release hole connected to the sacrificial layer, and the sacrificial layer is released through the at least one first release hole to form a cavity structure;

[0040] Sequentially etching the acoustic reflection structure and the support layer to prepare a second release hole connected to the first bottom electrode, and filling the second release hole with a conductive material;

[0041] The acoustic reflection structure and the support layer are sequentially etched to prepare a third release hole connected to the first top electrode, and a conductive material is filled in the third release hole; the first resonator and the second resonator are electrically connected through a circuit on the surface of the acoustic reflection layer.

[0042] In combination with the second aspect, in a possible implementation, the acoustic reflection layer is a Bragg reflection structure, and a magnetron sputtering method is used to sequentially deposit thin film materials with high and low acoustic impedances alternating in the thickness direction; or, the acoustic reflection layer is a phononic crystal structure, and a magnetron sputtering method is used to deposit high and low acoustic impedance materials periodically arranged along multiple directions.

[0043] In combination with the second aspect, in a possible implementation, the support layer is Si or SiC, the low acoustic impedance material is silicon dioxide, and the high acoustic impedance material is aluminum nitride, tungsten or molybdenum.

[0044] In the above embodiments, the material selected for the support layer can reduce energy loss and improve the performance of the resonator.

[0045] In a second aspect, an embodiment of the present application also provides a preparation method for preparing the above filter, comprising: preparing a substrate, wherein the substrate is provided with a cavity; growing a sacrificial layer in the cavity of the substrate; sequentially preparing a first bottom electrode, a first piezoelectric layer and a first top electrode of a first resonator; growing a supporting layer on the surface of the first top electrode, and mechanically grinding and flattening it to the first top electrode; preparing an acoustic reflection layer on the surface of the first top electrode supporting layer; sequentially preparing a second bottom electrode, a second piezoelectric layer and a second top electrode of a second resonator; sequentially etching the first resonator, the acoustic reflection layer and the second resonator, preparing a first release hole connected to the sacrificial layer, and releasing the sacrificial layer to form a cavity structure; sequentially etching the acoustic reflection structure and the supporting layer, preparing a second release hole connected to the first bottom electrode, and extending the first bottom electrode and the first top electrode to the surface of the acoustic reflection layer; and connecting the first resonator and the second resonator through a circuit on the surface of the acoustic reflection layer.

[0046] It can be seen from the above technical solution that the embodiment of the present application stacks at least two resonators vertically, and through circuit connection, the vertically integrated resonator can be finally processed into a filter. Two adjacent filters share the same acoustic reflection structure, saving the spatial size of the filter. The vertically integrated filter can prepare multiple resonators on the same wafer, and can also design and process resonators with different resonant frequencies on the same wafer, reducing the size of the filter (such as the lateral size, or understood as the lateral area), improving the integration of the filter, and simplifying the structure of multiple resonators, which is conducive to increasing production and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The following will introduce the drawings related to the embodiments of the present application. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 A schematic diagram of the structure of a filter provided in one embodiment of the present application;

[0049] Figure 2 for Figure 1 A top view of the filter shown;

[0050] Figure 3 for Figure 1 A schematic diagram of the circuit structure of the filter shown;

[0051] Figure 4 for Figure 1 The circuit schematic diagram of the filter shown;

[0052] Figure 5 A schematic structural diagram of a filter including a first sound reflection layer provided in one embodiment of the present application;

[0053] Figure 6 for Figure 5 A cross-sectional view of the first acoustic reflection layer of the middle filter along the AA plane;

[0054] Figure 7-1 A schematic diagram of a circuit structure of a filter provided in one embodiment of the present application;

[0055] Figure 7-2 A schematic diagram of a circuit structure of a filter provided in one embodiment of the present application;

[0056] Figure 7-3 A circuit structure schematic diagram of a filter provided in one embodiment of the present application;

[0057] Figure 8 A schematic diagram of the structure of a filter provided in one embodiment of the present application;

[0058] Fig. 9 for Figure 8 A top view of the filter shown;

[0059] Fig.10 A schematic diagram of the structure of a filter provided in one embodiment of the present application;

[0060] Fig.11 for Figure 8 A schematic diagram of the circuit structure of the filter shown;

[0061] Fig.12 for Fig.10 A schematic diagram of the circuit structure of the filter shown;

[0062] Fig.13 for Figure 8 and Fig.10 The circuit schematic diagram of the filter shown;

[0063] Figure 14-1 A schematic diagram of a circuit structure of a filter provided in one embodiment of the present application;

[0064] Figure 14-2 A schematic diagram of a circuit structure of a filter provided in one embodiment of the present application;

[0065] Figure 15-1 to Figure 15-12 A schematic diagram of the steps of a method for preparing a filter provided in one embodiment of the present application. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] like Figure 1 As shown, it is a schematic diagram of the structure of a filter provided in an embodiment of the present application. The first filter 301 includes a first resonator 210, a second resonator 220, a substrate 100, a first support layer 103, and a first acoustic reflection layer 104. The first acoustic reflection layer 104 is arranged between the first resonator 210 and the second resonator 220, and the second resonator 220 and the first resonator 210 share the first acoustic reflection layer 104. The second resonator 220 is arranged adjacent to the first resonator 210, and the adjacent arrangement may mean that an acoustic reflection layer is arranged between the second resonator and the first resonator 210, and it is not required that the second resonator is adjacent to the first resonator. The second resonator 220 is disposed above the first resonator 210. The first resonator 210 and the second resonator 220 are stacked above the substrate 100. The first support layer 103 is disposed above the first resonator 210 to support the first acoustic reflection layer 104. The top electrode 213 and the bottom electrode 211 of the first resonator 210 extend to the surface of the first acoustic reflection layer 104 below the second resonator 220. At least one first release hole 130 is disposed on the first resonator 210, the second resonator 220 and the first acoustic reflection layer 104. The first release hole 130 is connected to the cavity of the substrate 100. The sacrificial layer is released through the at least one first release hole 130 to form a cavity structure.

[0068] In another embodiment provided in the present application, the first resonator 210 is disposed above the second resonator 220, the first resonator 210 and the second resonator 220 are stacked above the substrate 100, and the top electrode 223 and the bottom electrode 221 of the second resonator 220 extend to the surface of the first acoustic reflection layer 104 below the first resonator 210, respectively.

[0069] Below the first resonator 210 is the cavity 102 of the substrate 100. The first resonator 210 includes a first bottom electrode 211, a first piezoelectric layer 212, and a first top electrode 213. The first bottom electrode 211 and the first top electrode 213 are arranged opposite to each other, and the first piezoelectric layer 212 is located between the first bottom electrode 211 and the first top electrode 213. The thickness of the cavity, the electrode, and the piezoelectric layer can be set according to the actual needs. In a possible implementation provided in the embodiment of the present application, the thickness of the cavity is 0.5um to 2um, the thickness of the electrode is 0.01um to 1um, and the thickness of the piezoelectric layer is 0.1um to 3um.

[0070] The second resonator 220 includes a second bottom electrode 221, a second piezoelectric layer 222, and a second top electrode 223. The second bottom electrode 221 and the second top electrode 223 are arranged opposite to each other, and the second piezoelectric layer 222 is located between the second bottom electrode 221 and the second top electrode 223. The thickness of the cavity, the electrode and the piezoelectric layer can be set according to the actual needs. In a possible implementation provided in the embodiment of the present application, the thickness of the cavity is 0.5um to 2um, the thickness of the electrode is 0.01um to 1um, and the thickness of the piezoelectric layer is 0.1um to 3um.

[0071] A first acoustic reflection layer 104 provided in an embodiment of the present application is a Bragg reflection structure, which is made of a low acoustic impedance material 140 and a high acoustic impedance material 141 stacked alternately in the thickness direction. The thickness of each layer of the acoustic reflection structure is 1 / 4 of the wavelength, and the wavelength is the wavelength of an acoustic signal with a frequency equal to the center frequency of the filter when it is transmitted in the layer of material.

[0072] like Figure 5 and Figure 6 As shown, Figure 5 This is a schematic structural diagram of a filter including a first sound reflection layer provided in one embodiment of the present application. Figure 6 for Figure 5 A cross-sectional view of the first acoustic reflection layer 104 of the filter along the AA plane. In one embodiment, the first acoustic reflection layer 104 is a phononic crystal structure. Specifically, the phononic crystal structure includes high and low acoustic impedance materials periodically distributed in multiple directions, and the low acoustic impedance material 140 is embedded in the high acoustic impedance material 141. The shape and size of the phononic crystal can be set according to the needs of the actual situation. For example, in this embodiment, the shape of the phononic crystal is a rectangular parallelepiped or a columnar body. In this embodiment, a multi-layer acoustic reflection structure is adopted, and the resonator has strong mechanical stability and good heat dissipation performance.

[0073] like Figure 2 As shown, Figure 1FIG. 1 is a top view of an embodiment of the filter shown in FIG. 1 . In this example, the circuit connection plane of the first resonator 210 and the second resonator 220 is the surface of the first acoustic reflection layer 104. The first output terminal 2, the first input terminal 1 and the ground terminal 3 are disposed on the surface of the first acoustic reflection layer 104, and the top and bottom electrodes of the second resonator 220 are disposed on the surface of the first acoustic reflection layer 104; Figure 15-11 and 15-12 As shown, the first bottom electrode 211 and the first top electrode 213 of the first resonator 210 are led out to the surface of the first acoustic reflection layer through the second release hole 131 , and the second release hole 131 penetrates the first acoustic reflection layer 104 and the first support layer 103 .

[0074] like Figure 3 and Figure 4 As shown, Figure 3 The circuit structure diagram of the ladder filter is shown in Figure 2. Figure 4 The circuit schematic diagram of the ladder type filter. In one embodiment of the present application, a filter is provided as a ladder type filter, and a ladder type filter 301 is formed by connecting the first resonator 210 and the second resonator 220 through a circuit. The first top electrode 213 of the first resonator 210 is connected to the second top electrode 223 of the second resonator 220 through the first circuit 11. The first top electrode 213 is connected to the first output terminal 2, the first bottom electrode 211 is grounded, and the second bottom electrode 221 is connected to the first input terminal 1. In another embodiment provided in the present application, the second top electrode 223, or the first circuit 11 is connected to the first output terminal 2.

[0075] The first resonator 210 and the second resonator 220 in the ladder filter 301 are connected in series. When the parallel resonant frequency of the first resonator 210 and the series resonant frequency of the second resonator 220 meet certain conditions, a passband is formed. In the ladder filter 301, the first input terminal 1 of the filter 301 receives an input signal; according to the impedance characteristics of the resonator 202 and the resonator 201, when the frequency of the input signal is within the passband of the filter 301, it will be output through the first output terminal 2 port; when the frequency of the input signal is outside the band of the filter 301, it will flow into the ground terminal through the ground terminal 3; thereby realizing the filter function of the filter, transmitting the frequency band signal within the passband without attenuation and maximally attenuating the out-of-band signal. The ladder filter 301 can be used on single-ended (single-ended / unbalanced) and differential (balanced) signals.

[0076] In the ladder-type filter 301 of this embodiment, the resonant frequency of the first resonator and the resonant frequency of the second resonator can be the same frequency or different frequencies. Since the resonant frequency is directly inversely proportional to the thickness of the piezoelectric film, the thickness of the piezoelectric film and the electrode of the resonator of different frequencies is different. In an embodiment provided in the present application, since the resonator is vertically integrated, there is no need to limit the thickness of the resonator in the vertical direction. Therefore, this embodiment can realize the processing of piezoelectric films and electrodes of different thicknesses and materials on the same wafer, and then the resonator with different resonant frequencies can be designed and processed, reducing the size and process cost of the filter.

[0077] A filter provided in one embodiment of the present application is a multi-order Ladder type filter. A plurality of Ladder type filters 301 with the same structure can form a multi-order Ladder type filter, wherein each order of Ladder type filter 301 includes a first resonator 210 and a second resonator 220, and the plurality of Ladder type filters 301 are connected in series, that is, the output end of the previous order Ladder type filter 301 is connected to the input end of the next order Ladder type filter 301.

[0078] like Figure 7-1 and Figure 7-2 As shown, it is a schematic diagram of the circuit structure of a two-order ladder filter provided by an embodiment of the present application, including two ladder filters 301 with the same structure; for the convenience of the following circuit structure description, the two ladder filters with the same structure are respectively recorded as the first-order ladder filter 301 and the second-order ladder filter 301'. The output terminal connection end (for example, the second top electrode 223) of the first-order ladder filter 301 is connected to the input terminal connection end of the second-order ladder filter 301' (for example, the second bottom electrode 221') through the second circuit 12, the input end (for example, the second bottom electrode 221) of the ladder filter 301 is connected to the first input end 1, the output end (for example, the first top electrode 213') of the second-order ladder filter 301' is connected to the first output end 2, and the first bottom electrodes 211 and 103' are respectively connected to the ground wire.

[0079] like Figure 7-1, which is a schematic diagram of the circuit structure of a two-order ladder filter provided in one embodiment of the present application. Specifically, the first ladder filter 301 and the second-order ladder filter 301' are arranged on the same plane, and the circuits of the first ladder filter 301 and the second-order ladder filter 301' are arranged on the surface of the first acoustic reflection layer 104 of the first ladder filter 301 and the first acoustic reflection layer 104' of the second-order ladder filter 301'.

[0080] like Figure 7-2 As shown, it is a schematic diagram of the circuit structure of a two-order ladder filter provided by an embodiment of the present application, wherein the second-order ladder filter 301' is longitudinally stacked and arranged above the ladder filter 301, and a second acoustic reflection layer 401 is arranged between the second-order ladder filter 301' and the ladder filter 301, and the second acoustic reflection layer 401 is a Bragg reflection structure or a phononic crystal structure. The structure of the second acoustic reflection layer 401 is similar to that of the first acoustic reflection layer, and will not be repeated here. The circuits of the first ladder filter 301 and the second-order ladder filter 301' are arranged on the surface of the first acoustic reflection layer 104' of the second-order ladder filter 301' at the top.

[0081] like Figure 8 and Fig. 9As shown, it is a schematic diagram of the structure of a filter provided in an embodiment of the present application. The filter is a Lattice type filter 302, and the Lattice type filter 302 includes a first resonator 210, a second resonator 220, a third resonator 230, a fourth resonator 240, a substrate 100, a first support layer 103, a first acoustic reflection layer 104, a second support layer 105, and a third acoustic reflection layer 106. The first acoustic reflection layer 104 is arranged between the second resonator 220 and the first resonator 210, and the second resonator 220 is arranged adjacent to the first resonator 210. The adjacent arrangement can be that the second resonator and the first resonator 210 share the acoustic reflection layer, and it is not required that the second resonator is adjacent to the first resonator. The second resonator 220 is disposed above the first resonator 210. The second resonator 220 and the first resonator 210 are stacked above the substrate 100. The first supporting layer 103 is disposed above the first resonator 210 to support the first acoustic reflection layer 104. The top electrode 213 and the bottom electrode 211 of the first resonator 210 extend to the surface of the first acoustic reflection layer 104 below the second resonator 220. At least one first release hole 130 is disposed on the first resonator 210, the second resonator 220 and the first acoustic reflection layer 104. The first release hole 130 is connected to the cavity of the substrate 100. The sacrificial layer is released through the at least one first release hole 130 to form a cavity structure. The third acoustic reflection layer 106 is disposed between the fourth resonator 240 and the third resonator 230. The fourth resonator 240 is disposed adjacent to the third resonator 230. The adjacent arrangement may mean that the fourth resonator 240 and the third resonator 230 are provided with an acoustic reflection layer, and the fourth resonator 240 is not required to be adjacent to the third resonator 230. The fourth resonator 240 is disposed above the third resonator 230. The fourth resonator 240 is disposed above the third resonator 230 and is stacked above the substrate 100. The second supporting layer 105 is disposed above the third resonator 230 to support the third acoustic reflection layer 106. The top electrode 233 and the bottom electrode 231 of the third resonator 230 extend to the surface of the third acoustic reflection layer 106 below the fourth resonator 240, respectively. At least one first release hole 130 is disposed on the third resonator 230 , the fourth resonator 240 , and the third sound reflection layer 106 . The first release hole 130 is connected to the cavity of the substrate 100 . The sacrificial layer is released through the at least one first release hole 130 to form a cavity structure.

[0082] The first resonator 210 has a substrate cavity below it. The first resonator 210 includes a first bottom electrode 211, a first piezoelectric layer 212, and a third top electrode 213. The first bottom electrode 211 and the third top electrode 213 are arranged opposite to each other, and the first piezoelectric layer 212 is located between the first bottom electrode 211 and the third top electrode 213. The second resonator 220 is arranged above the first acoustic reflection layer 104. The second resonator 220 includes a second bottom electrode 221, a second piezoelectric layer 222, and a second top electrode 223. The second bottom electrode 221 and the second top electrode 223 are arranged opposite to each other, and the second piezoelectric layer 222 is located between the second bottom electrode 221 and the second top electrode 223.

[0083] The third resonator 230 has a substrate cavity below it. The third resonator 230 includes a third bottom electrode 231, a third piezoelectric layer 232, and a third top electrode 233. The third bottom electrode 231 and the third top electrode 233 are arranged opposite to each other, and the third piezoelectric layer 232 is located between the third bottom electrode 231 and the third top electrode 233. The fourth resonator 240 is arranged above the third acoustic reflection layer 106. The fourth resonator 240 includes a fourth bottom electrode 241, a fourth piezoelectric layer 242, and a fourth top electrode 243. The fourth bottom electrode 241 and the fourth top electrode 243 are arranged opposite to each other, and the fourth piezoelectric layer 242 is located between the fourth bottom electrode 241 and the fourth top electrode 243.

[0084] The thickness of the cavity, electrode and piezoelectric layer can be set according to actual needs. In a possible implementation provided in the embodiment of the present application, the cavity thickness is 0.5um to 2um, the electrode thickness is 0.01um to 1um, and the piezoelectric layer thickness is 0.1um to 3um.

[0085] In another embodiment provided in the present application, the first resonator 210 is disposed above the second resonator 220, the first resonator 210 and the second resonator 220 are stacked above the substrate 100, and the top electrode 223 and the bottom electrode 221 of the second resonator 220 extend to the surface of the first acoustic reflection layer 104 below the first resonator 210, respectively.

[0086] In another embodiment provided in the present application, the third resonator 230 is disposed above the fourth resonator 240, the third resonator 230 and the fourth resonator 240 are stacked above the substrate 100, and the top electrode 243 and the bottom electrode 241 of the fourth resonator 240 respectively extend to the surface of the third acoustic reflection layer 106 below the third resonator 230.

[0087] In one embodiment of the present application, the first acoustic reflection layer 104 and the third acoustic reflection layer 106 are Bragg reflection structures or phononic crystal structures, and the structure of the third acoustic reflection layer 106 is similar to that of the first acoustic reflection layer 104, which will not be described in detail. Fig. 9 In the filter shown, the first sound reflection layer 104 and the third sound reflection layer 106 can be different regions of the same sound reflection layer, and are distinguished by the first and the third for the convenience of description and reference. Other similar distinctions can be understood similarly.

[0088] like Fig. 9 As shown, Figure 8 A top view of the filter shown in the embodiment. The circuit connection planes of the first resonator 210, the second resonator 220, the third resonator 230, and the fourth resonator 240 are the surfaces of the first acoustic reflection layer 104 and the third acoustic reflection layer 106. The first input terminal 1, the first output terminal 2, the second input terminal 3, and the second output terminal 4 of the filter are arranged on the surfaces. The first bottom electrode 211, the first top electrode 213, the third bottom electrode 231, and the third top electrode 233 are connected through release holes (such as Figure 15-11 The release holes 131, 132) are shown leading to the surface.

[0089] like Fig.10 As shown, it is a schematic diagram of the structure of a filter provided by an embodiment of the present application. The lattice filter 302 includes a first resonator 210, a second resonator 220, a third resonator 230, and a fourth resonator 240 which are stacked vertically from bottom to top, and a fourth acoustic reflection layer 402 is arranged between the second resonator 220 and the third resonator 230, and the fourth acoustic reflection layer 402 is a Bragg reflection structure or a phononic crystal structure. The structure of the fourth acoustic reflection layer 402 is similar to that of the first acoustic reflection layer, and will not be repeated here. The circuit connection plane of the first resonator 210, the second resonator 220, the third resonator 230, and the fourth resonator 240 is the surface of the third acoustic reflection layer 106 located at the top. The first input terminal 1, the first output terminal 2, the second input terminal 3, and the second output terminal 4 of the filter are arranged on the surface, and the first bottom electrode 211, the third top electrode 213, the third bottom electrode 231, and the third top electrode 233 are led to the surface through the second release hole 131. In a possible implementation manner provided in the present application, the upper and lower positions of the first resonator 210, the second resonator 220, the third resonator 230, and the fourth resonator 240 stacked vertically can be swapped according to actual needs. For example, the fourth resonator 240, the third resonator 230, the second resonator 220, and the first resonator 210 are stacked vertically from top to bottom.

[0090] like Figure 11-13 As shown, Fig.11 for Figure 8 The circuit structure diagram of the filter shown in the figure is as follows: Fig.12 for Fig.10 The circuit structure diagram of the filter shown in FIG. Fig.13 for Figure 8 and Fig.10 The circuit schematic diagram of the filter shown. The first top electrode 213 of the first resonator 210 is connected to the second top electrode 223 of the second resonator 220 through the third circuit 13; the third bottom electrode 231 of the third resonator 230 is connected to the fourth bottom electrode 241 of the fourth resonator 240 through the sixth circuit 16, the first bottom electrode 211 is connected to the second top electrode 223 through the fifth circuit 15, and the second bottom electrode 221 is connected to the third top electrode 233 through the fourth circuit 14. The first top electrode 213 (or the second top electrode 223 or the third circuit 13) is connected to the first input terminal 1, the third top electrode 233 (or the second bottom electrode 221 or the fourth circuit 14) is connected to the first output terminal 2, the third bottom electrode 231 (or the fourth bottom electrode 241 or the sixth circuit 16) is connected to the second input terminal 3, and the second bottom electrode 221 (or the third top electrode 233 or the fourth circuit 14) is connected to the second output terminal 4. The first resonator 210 , the second resonator 220 , the third resonator 230 , and the fourth resonator 240 are connected by a circuit to form a lattice filter 302 .

[0091] In the Lattice filter 302, the input electrical signal is received by the first input terminal 1 and the second input terminal 3. When the frequency of the input signal is within the passband of the filter 302, it will be output through the first output terminal 2 and the seventh output terminal 7 port. In the Lattice filter 302 in this embodiment, the resonance frequencies of the first resonator 210, the second resonator 220, the third resonator 230, and the fourth resonator 240 can be the same frequency or different frequencies. Since the resonance frequency is directly inversely proportional to the thickness of the piezoelectric film, the thickness of the piezoelectric film and the electrode of the resonator with different resonance frequencies is different. In an embodiment provided in the present application, since the resonator is vertically integrated, there is no need to limit the thickness of the resonator in the vertical direction. Therefore, this embodiment can realize the processing of piezoelectric films and electrodes of different thicknesses and materials on the same wafer, and then the resonator with different resonance frequencies can be designed and processed, which reduces the size and process cost of the filter.

[0092] A filter provided in an embodiment of the present application includes a multi-order Lattice filter, including a plurality of Lattice filters 302, wherein the plurality of Lattice filters 302 are connected in series to form a multi-order Lattice filter. Figure 14-1 and 14-2 As shown, the circuit structure diagram of the two-order Lattice filter in the embodiment of the present application, in order to facilitate the following circuit structure description, the two Lattice filters 302 with the same structure are respectively recorded as the first-order Lattice filter 302 and the second-order Lattice filter 302'. The connection mode of the multi-order Lattice filter is that the Lattice filter 302 is connected in series with the second-order Lattice filter 302', that is, the two output ends of the Lattice filter 302 are connected to the two input ends of the second-order Lattice filter 302'. In an embodiment provided in the present application, the fourth circuit 14 (or output end) of the Lattice filter 301 is connected to the third circuit 13' (or input end) of the second-order Lattice filter 301' through the seventh circuit 17, and the fifth circuit 15 (or output end) of the Lattice filter 301 is connected to the sixth circuit 16' (or input end) of the second-order Lattice filter 301' through the eighth circuit 18. The third circuit 13 of the first-order Lattice filter 302 is connected to the first input terminal 1, the sixth circuit 16 is connected to the second input terminal 3, the fourth circuit 14' of the second-order Lattice filter 302' is connected to the first output terminal 2, and the fifth circuit 15' of the second-order Lattice filter 302' is connected to the second output terminal 4.

[0093] In other embodiments of the present application, since the circuits 13 to 16 are connected to a plurality of resonators, the electrodes of the resonators may be directly connected to the output end or the input end.

[0094] like Figure 14-1 As shown, a circuit structure diagram of a two-order Lattice filter provided by an embodiment of the present application, wherein a first-order Lattice filter 302 and a second-order Lattice filter 302' are arranged on the same plane, the surface of the acoustic reflection layer of the first-order Lattice filter 302 and the second-order Lattice filter 302' is a plane for circuit connection, and the seventh circuit 17 and the eighth circuit 18 are arranged on the plane.

[0095] like Figure 14-2As shown, it is a schematic diagram of the circuit structure of a two-order Lattice filter provided in an embodiment of the present application, wherein the second-order Lattice filter 302' is stacked vertically above the first-order Lattice filter 302, and the fifth sound reflection layer 403 and the sixth sound reflection layer 404 are arranged between the second-order Lattice filter 301' and the first-order Lattice filter 301. The structures of the fifth sound reflection layer 403 and the sixth sound reflection layer 404 are similar to those of the first sound reflection layer, and are not repeated here. The fifth sound reflection layer 403 and the sixth sound reflection layer 404 are Bragg reflection structures or phononic crystal structures. The surface of the sound reflection layer of the second-order Lattice filter 302' located at the top is a plane for circuit connection, and the seventh circuit 17 and the eighth circuit 18 are arranged on the plane.

[0096] A second-order Lattice filter 302' provided in an embodiment of the present application is stacked vertically above a first-order Lattice filter 302, and the Lattice filter 302 includes a first resonator 210, a second resonator 220, a third resonator 230, and a fourth resonator 240 stacked sequentially from bottom to top, and an acoustic reflection layer is arranged between adjacent resonators. A tenth acoustic reflection layer is arranged between the second-order Lattice filter 301' and the Lattice filter 301. The tenth acoustic reflection layer is a Bragg reflection structure or a phononic crystal structure. The surface of the acoustic reflection layer of the second-order Lattice filter 302' located at the top is a plane for circuit connection.

[0097] A filter provided in one embodiment of the present application includes a plurality of resonators, and the number of the resonators may be two or more. The resonators are stacked longitudinally, and an acoustic reflection layer is provided between adjacent resonators, and the electrodes of the resonators extend to the surface of the acoustic reflection layer of the top filter through a second release hole. According to a preset circuit design, the plurality of resonators are connected according to a preset circuit on the surface of the acoustic reflection layer. The plurality of resonators may have the same resonant frequency or different resonant frequencies. The acoustic reflection layer is a Bragg reflection structure or a phononic crystal structure.

[0098] As shown in FIG15 , a method for preparing a filter provided in an embodiment of the present application is as follows:

[0099] S100, such as Figure 15-1 As shown, a groove is etched on the upper surface of the prepared silicon wafer to form a substrate 100 with a cavity 102; the substrate 100 is made of silicon material.

[0100] S101, such as Figure 15-2As shown, a sacrificial layer 101 is grown on the surface of the substrate 100 by plasma enhanced chemical vapor deposition (PECVD). The sacrificial layer 101 is deposited on the surface of the substrate 100 so that the cavity is filled with the sacrificial layer. Figure 15-3 As shown, a chemical mechanical polishing method is used to grind the sacrificial layer to the substrate surface. The sacrificial layer includes silicon dioxide.

[0101] S102, such as Figure 15-4 As shown, the first bottom electrode, the first piezoelectric layer and the first top electrode of the first resonator are sequentially prepared on the upper surface of the substrate filled with the sacrificial layer. At least a portion of the first bottom electrode, at least a portion of the first piezoelectric layer and at least a portion of the first top electrode are all arranged above the sacrificial layer. In a possible implementation provided by the present invention, magnetron sputtering is sequentially used for deposition, and a photolithography method is used for patterning to prepare the first bottom electrode 211, the first piezoelectric layer 212 and the first top electrode 213. The first bottom electrode 211, the first piezoelectric layer 212 and the first top electrode 213 are made into the first resonator 101. The first piezoelectric layer has piezoelectric properties, and the piezoelectric layer material can be a piezoelectric film such as piezoelectric ceramic (PZT), aluminum nitride (AlN), zinc oxide (ZnO), etc. The top electrode and the bottom electrode can be metal films such as tungsten, molybdenum, aluminum, gold, platinum, etc.

[0102] S103, such as Figure 15-5 As shown, an atmospheric pressure chemical vapor deposition (APCVD) method is used to grow a support layer (eg, first support layer 103) on the upper surface of the first top electrode, as shown in FIG. Figure 15-6 As shown, the upper surface of the support layer and the upper surface of the first top electrode are located in the same plane by using a chemical mechanical grinding method. The support layer can be made of silicon, silicon carbide, etc. Silicon and silicon carbide materials can reduce energy loss.

[0103] S104, preparing an acoustic reflection layer 107 on the upper surface of the first top electrode and the upper surface of the support layer. If the acoustic reflection layer is a Bragg reflection structure, such as Figure 15-7 As shown, a thin film material with alternating high and low acoustic impedance in the thickness direction is sequentially deposited by magnetron sputtering. If the acoustic reflection layer is a phononic crystal structure, a magnetron sputtering method is used to deposit high and low acoustic impedance materials periodically arranged in multiple directions; the low acoustic impedance material can be silicon dioxide, etc.; the high acoustic impedance material can be aluminum nitride, tungsten, molybdenum, etc.

[0104] S105, such as Figure 15-8As shown, the second bottom electrode, the second piezoelectric layer and the second top electrode of the second resonator are sequentially prepared on the upper surface of the acoustic reflection layer; in a possible implementation mode provided in the present application, the second bottom electrode 109, the second piezoelectric layer 110 and the second top electrode 111 are sequentially deposited by magnetron sputtering method, and the second bottom electrode 109, the second piezoelectric layer 110 and the second top electrode 111 are patterned by photolithography and etching method, and the second bottom electrode 109, the second piezoelectric layer 110 and the second top electrode 111 are made into the second resonator 220. The second piezoelectric layer has piezoelectric properties, and the piezoelectric layer material can be piezoelectric films such as piezoelectric ceramics (PZT), aluminum nitride (AlN), zinc oxide (ZnO), etc. The top electrode and the bottom electrode can be all metal films such as tungsten, molybdenum, aluminum, gold, platinum, etc.

[0105] S106, such as Figure 15-9 and 15-10 As shown, the first resonator, the sound reflection layer, and the second resonator are etched in sequence to prepare at least one first release hole 130 connected to the sacrificial layer, and the sacrificial layer is released through the at least one first release hole 130 to form a cavity structure.

[0106] S107, such as Figure 15-11 and 15-12 As shown, the acoustic reflection structure and the support layer are etched in sequence to form a second release hole 131 connected to the first bottom electrode 211, and a third release hole 132 connected to the first top electrode is prepared. A conductive material is filled in the second release hole 131 or the third release hole 132. In one embodiment of the present invention, the first bottom electrode 211 and the first top electrode 213 are extended to the surface of the acoustic reflection layer 107 by electroplating the inner wall of the second release hole 131 or the third release hole 132. The conductive material or the electroplating material can be copper, nickel, aluminum, gold and other conductive materials. The figure shows a circuit connection method, which is not limited to the top electrode or bottom electrode material being the same as the conductive material.

[0107] S108 , according to the preset circuit design, on the surface of the sound reflection layer 107 , the first resonator 210 and the second resonator 220 are connected according to the circuit to form the vertically integrated filter in the above embodiment.

[0108] It should also be understood that the first, second and various numerical numbers involved in this document are only distinguished for the convenience of description and are not used to limit the scope of the present application.

[0109] In this application, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0110] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0111] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms of "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used in this article refers to and includes any or all possible combinations of one or more associated listed items. The character " / " herein generally indicates that the objects associated before and after are in an "or" relationship.

[0112] It should be understood that, although the terms first, second, third, etc. may be used to describe various messages, requests, and terminals in the embodiments of the present invention, these messages, requests, and terminals should not be limited to these terms. These terms are only used to distinguish messages, requests, and terminals from each other. For example, without departing from the scope of the embodiments of the present invention, the first terminal may also be referred to as the second terminal, and similarly, the second terminal may also be referred to as the first terminal.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A filter comprising at least two resonators, each of the resonators comprising a top electrode, a piezoelectric layer and a bottom electrode; Features: The at least two resonators are stacked vertically, an acoustic reflection layer is arranged between two adjacent resonators of the at least two resonators, and the at least two resonators include a first resonator and a second resonator arranged adjacent to each other; The second resonator is located at the top of the filter and the first resonator is located below the second resonator, and the top electrode and the bottom electrode of the first resonator extend to the surface of the sound reflection layer below the second resonator respectively; The filter further comprises a support layer, which is arranged around the side of the first resonator; at least a portion of the top electrode and at least a portion of the bottom electrode of the first resonator are arranged below the support layer, and an upper surface of the support layer and an upper surface of the top electrode of the first resonator are located in the same plane; At least part of the sound reflection layer is arranged on the supporting layer; parts of the top electrode and the bottom electrode of the first resonator arranged below the supporting layer both penetrate the supporting layer and the sound reflection layer and extend to the surface of the sound reflection layer; the top electrode and the bottom electrode of the second resonator also extend to the surface of the sound reflection layer.

2. The filter according to claim 1, Features: The first resonator and the second resonator have different resonant frequencies.

3. The filter according to claim 2, Features: The first resonator and the second resonator having different resonance frequencies comprises: a thickness of the piezoelectric layer of the first resonator and a thickness of the piezoelectric layer of the second resonator are different.

4. The filter according to claim 1, Features: The acoustic reflection layer is a Bragg reflection structure, and the acoustic reflection layer includes a low acoustic impedance material and a high acoustic impedance material which are alternately stacked in a thickness direction.

5. The filter according to claim 1, Features: The acoustic reflection layer is a phononic crystal structure, including low acoustic impedance materials and high acoustic impedance materials arranged in multiple directions.

6. The filter according to any one of claims 1 to 5, Features: The filter is a ladder type filter, the top electrode of the first resonator and the top electrode of the second resonator are both electrically connected to the first output end of the filter, the bottom electrode of the first resonator is grounded, and the bottom electrode of the second resonator is electrically connected to the first input end of the filter.

7. The filter according to claim 6, Features: The filter is a multi-order Ladder type filter including at least two Ladder type filters, wherein the at least two Ladder type filters are connected in series, the first order Ladder type filter is connected to the first input end, and the last order Ladder type filter is connected to the first output end.

8. The filter according to claim 7, Features: The at least two ladder-type filters are arranged on the same plane.

9. The filter according to claim 7, Features: The at least two ladder type filters are stacked vertically, wherein an acoustic reflection layer is arranged between two adjacent ladder type filters.

10. The filter according to any one of claims 1 to 5, Features: The filter is a Lattice type filter, comprising a first resonator, a second resonator, a third resonator, and a fourth resonator. The third resonator and the fourth resonator are stacked vertically and an acoustic reflection layer is arranged between the third resonator and the fourth resonator. The top electrode of the first resonator is electrically connected to the top electrode of the second resonator and then connected to the first input end of the filter. The bottom electrode of the third resonator is electrically connected to the bottom electrode of the fourth resonator and then connected to the second input end of the filter. The bottom electrode of the first resonator is electrically connected to the top electrode of the fourth resonator and then connected to the first output end of the filter. The bottom electrode of the second resonator is electrically connected to the top electrode of the third resonator and then connected to the second output end of the filter.

11. The filter according to claim 10, Features: The third resonator is stacked vertically above the fourth resonator, the top electrode and the bottom electrode of the fourth resonator extend to the surface of the sound reflection layer below the third resonator respectively, the third resonator and the first resonator are arranged in the same plane, and the fourth resonator and the second resonator are arranged in the same plane; Alternatively, the third resonator is stacked vertically above the fourth resonator, the top electrode and the bottom electrode of the fourth resonator extend to the surface of the sound reflection layer below the third resonator respectively, the third resonator and the second resonator are arranged in the same plane, and the fourth resonator and the first resonator are arranged in the same plane; Alternatively, the fourth resonator is stacked vertically above the third resonator, the top electrode and the bottom electrode of the third resonator extend to the surface of the sound reflection layer below the fourth resonator respectively, the third resonator and the first resonator are arranged in the same plane, and the fourth resonator and the second resonator are arranged in the same plane; Alternatively, the fourth resonator is stacked vertically above the third resonator, the top electrode and the bottom electrode of the third resonator respectively extend to the surface of the sound reflection layer below the fourth resonator, the third resonator and the second resonator are arranged in the same plane, and the fourth resonator and the first resonator are arranged in the same plane.

12. The filter according to claim 10, Features: The first resonator, the second resonator, the third resonator and the fourth resonator are stacked vertically, and a sound reflection layer is arranged between adjacent resonators.

13. The filter according to claim 10, Features: The filter is a multi-order Lattice filter including at least two Lattice filters, wherein the at least two Lattice filters are connected in series, the first-order Lattice filter is electrically connected to the first input end and the second input end, and the last-order Lattice filter is electrically connected to the first output end and the second output end.

14. The filter according to claim 13, Features: The at least two Lattice filters are arranged on the same plane.

15. The filter according to claim 13, Features: The at least two Lattice filters are stacked vertically, and an acoustic reflection layer is arranged between two adjacent Lattice filters.

16. A method for preparing the filter according to any one of claims 1 to 15, It is characterized in that The following steps are involved: preparing a substrate, wherein the substrate is provided with a cavity; growing a sacrificial layer in a cavity of a substrate so that the cavity is filled with the sacrificial layer; Sequentially preparing a first bottom electrode, a first piezoelectric layer and a first top electrode of a first resonator on the upper surface of the substrate filled with the sacrificial layer, wherein at least a portion of the first bottom electrode, at least a portion of the first piezoelectric layer and at least a portion of the first top electrode are all disposed above the sacrificial layer; Growing a support layer on the upper surface of the first top electrode, and grinding the support layer so that the upper surface of the support layer and the upper surface of the first top electrode are located in the same plane; preparing an acoustic reflection layer on the upper surface of the first top electrode and the upper surface of the support layer; On the upper surface of the acoustic reflection layer, a second bottom electrode, a second piezoelectric layer and a second top electrode of the second resonator are sequentially prepared; The first resonator, the sound reflection layer, and the second resonator are sequentially etched to prepare at least one first release hole connected to the sacrificial layer, and the sacrificial layer is released through the at least one first release hole to form a cavity structure; Sequentially etching the acoustic reflection structure and the support layer to prepare a second release hole connected to the first bottom electrode, and filling the second release hole with a conductive material; The acoustic reflection structure and the support layer are sequentially etched to prepare a third release hole connected to the first top electrode, and a conductive material is filled in the third release hole; The first resonator and the second resonator are electrically connected to each other through a circuit on the surface of the sound reflecting layer.

17. The method for preparing the filter according to claim 16, Features: The acoustic reflection layer is a Bragg reflection structure, and a thin film material with high and low acoustic impedance alternating in the thickness direction is deposited in sequence by a magnetron sputtering method; or, the acoustic reflection layer is a phononic crystal structure, and a high and low acoustic impedance material periodically arranged in multiple directions is deposited by a magnetron sputtering method.

18. The method for preparing the filter according to claim 17, Features: The support layer is Si or SiC, the low acoustic impedance material is silicon dioxide, and the high acoustic impedance material is aluminum nitride, tungsten or molybdenum.

Images