WO2022141392A1 - 滤波器以及滤波器的制备方法 - Google Patents

滤波器以及滤波器的制备方法 Download PDF

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Publication number
WO2022141392A1
WO2022141392A1 PCT/CN2020/142085 CN2020142085W WO2022141392A1 WO 2022141392 A1 WO2022141392 A1 WO 2022141392A1 CN 2020142085 W CN2020142085 W CN 2020142085W WO 2022141392 A1 WO2022141392 A1 WO 2022141392A1
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Prior art keywords
acoustic resistance
resistance structure
high acoustic
substrate
low
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PCT/CN2020/142085
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English (en)
French (fr)
Inventor
侯航天
杜波
刘鹏
高宗智
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华为技术有限公司
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Priority to CN202080108240.7A priority Critical patent/CN116671013A/zh
Priority to EP20967731.9A priority patent/EP4262088A4/en
Priority to PCT/CN2020/142085 priority patent/WO2022141392A1/zh
Publication of WO2022141392A1 publication Critical patent/WO2022141392A1/zh
Priority to US18/343,659 priority patent/US20230344412A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/56—Monolithic crystal filters
    • H03H9/564—Monolithic crystal filters implemented with thin-film techniques
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/56—Monolithic crystal filters
    • H03H9/566—Electric coupling means therefor
    • H03H9/568—Electric coupling means therefor consisting of a ladder configuration
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/58—Multiple crystal filters
    • H03H9/582—Multiple crystal filters implemented with thin-film techniques
    • H03H9/586—Means for mounting to a substrate, i.e. means constituting the material interface confining the waves to a volume
    • H03H9/589—Acoustic mirrors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
    • H03H2003/0414—Resonance frequency
    • H03H2003/0421—Modification of the thickness of an element
    • H03H2003/0442—Modification of the thickness of an element of a non-piezoelectric layer
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
    • H03H2003/0414—Resonance frequency
    • H03H2003/0471—Resonance frequency of a plurality of resonators at different frequencies

Definitions

  • the embodiments of the present application relate to the technical field of filters, and in particular, to a filter and a method for preparing the filter.
  • a combination of a filter formed by a thin film bulk acoustic wave resonator and an LC resonant circuit is usually used to achieve filtering in the radio frequency band.
  • the filter formed by the thin film bulk acoustic wave resonator and the LC resonant circuit are combined in a high-performance technical scenario, it is usually necessary to set the thin film bulk acoustic wave resonator in the filter in the high-performance radio frequency band.
  • the edge of the band is used to filter the edge of the passband of the 5G radio frequency band.
  • the value of the quality factor (Q, quality factor) of the filter is low, which reduces the filtering effect of the filter. Therefore, when the filter formed by the thin film bulk acoustic wave resonator is used in high-performance technical scenarios, how to improve the filtering performance of the filter becomes a problem that needs to be solved.
  • the filter and the preparation method of the filter provided by the present application can improve the performance of the filter.
  • an embodiment of the present application provides a filter, including: a substrate; and a series resonator, wherein the series resonator includes a first Bragg reflection layer and a first piezoelectric transducer sequentially stacked on the substrate. energy structure; a parallel resonator, the parallel resonator includes a second Bragg reflection layer and a second piezoelectric transducer structure stacked on the substrate in sequence, and the structure of the first Bragg reflection layer is the same as that of the first Bragg reflection layer.
  • a series branch includes the series resonator, and the series branch is coupled between the input end of the filter and the output end of the filter; a parallel branch , the parallel branch includes the parallel resonator, and the parallel branch is coupled between the series branch and the common ground.
  • the filter described in the embodiments of the present application may be a bare chip (ie, Die), which is an integrated circuit formed on a semiconductor through processes such as growth, doping, etching, or development, and the integrated circuit includes an input terminal, The output end, at least one series resonator, and at least one parallel resonator, so as to realize the filtering function.
  • the outside of the bare chip used to form the filter can be set in a package formed by the packaging material, and the above-mentioned input terminal, output terminal and ground terminal can be drawn out through the packaging case , so as to realize signal transmission with external devices.
  • the bare chip used to form the filter may not be packaged, and may be provided in the same chip with other devices (eg, capacitors, inductors, etc.).
  • the shear wave transmission coefficients of the series resonator and the parallel resonator can be changed, so that each resonator is effective in its The transverse wave transmission coefficient in the frequency band is low, which improves the reflection efficiency of each resonator, that is, the Q value of the quality factor of the resonator, thereby improving the filtering effect of the filter.
  • the filter further includes a low acoustic resistance structure for forming the first Bragg reflection layer and the second Bragg reflection layer; the first Bragg reflection The layer includes a first high acoustic resistance structure embedded in the low acoustic resistance structure; the second Bragg emission layer includes a second high acoustic resistance structure embedded in the low acoustic resistance structure; along the stacking direction, the The thickness of the first high acoustic resistance structure is different from the thickness of the second high acoustic resistance structure.
  • the low acoustic resistance structure is stacked on the surface of the substrate;
  • the filter further includes a structure for forming the first piezoelectric transducer and the The first electrode and the thin film structure of the second piezoelectric transducer structure are sequentially stacked on the surface of the low acoustic resistance structure away from the substrate;
  • the first piezoelectric transducer The structure further includes a second electrode, and the second piezoelectric transducer structure further includes a third electrode; the first electrode and the second electrode are both disposed on the surface of the thin film structure away from the substrate.
  • the first high acoustic resistance structure includes a first surface far away from the substrate
  • the low acoustic resistance structure includes a first surface far away from the substrate the first surface of the bottom
  • the second high acoustic resistance structure includes a first surface away from the substrate, between the first surface of the first high acoustic resistance structure and the first surface of the low acoustic resistance structure
  • the first surface of the first high acoustic resistance structure may also be referred to as the upper surface of the first high acoustic resistance structure
  • the first surface of the low acoustic resistance structure may also be referred to as the upper surface of the low acoustic resistance structure
  • the second high acoustic resistance structure A surface of the can also be referred to as the upper surface of the first high acoustic resistance structure.
  • the first Bragg reflection layer further includes a third high acoustic resistance structure buried in the low acoustic resistance structure, and along the stacking direction, the third The high acoustic resistance structure is disposed on a side of the first high acoustic resistance structure away from the substrate, and the low acoustic resistance structure is disposed between the first high acoustic resistance structure and the first high acoustic resistance structure; the second Bragg reflection The layer further includes a fourth high acoustic resistance structure buried in the low acoustic resistance structure, and along the stacking direction, the fourth high acoustic resistance structure is disposed at a distance of the second high acoustic resistance structure away from the substrate.
  • the low acoustic resistance structure is arranged between one side and the second high acoustic resistance structure; along the stacking direction, the thickness of the third high acoustic resistance structure is the same as the thickness of the fourth high acoustic resistance structure. Thickness varies.
  • the thickness of the first high acoustic resistance structure is the same as the thickness of the fourth high acoustic resistance structure; along the stacking direction, all The thickness of the second high acoustic resistance structure is the same as the thickness of the third high acoustic resistance structure.
  • the third high acoustic resistance structure includes a first surface away from the substrate, and an upper surface of the first surface of the third high acoustic resistance structure is connected to the There is a third distance between the first surfaces of the low acoustic resistance structure;
  • the fourth high acoustic resistance structure includes a first surface away from the substrate, the first surface of the third high acoustic resistance structure and the There is a fourth distance between the first surfaces of the low acoustic resistance structure; the third distance and the fourth distance are different.
  • the first surface of the third high acoustic resistance structure may also be referred to as the upper surface of the third high acoustic resistance structure
  • the first surface of the fourth high acoustic resistance structure may also be referred to as the upper surface of the fourth high acoustic resistance structure.
  • the third high acoustic resistance structure includes a second surface close to the substrate, and the second surface of the third high acoustic resistance structure is connected to the first There is a fifth distance between the first surfaces of the high acoustic resistance structure; the fourth high acoustic resistance structure includes a second surface close to the substrate, the second surface of the fourth structure and the second high acoustic resistance structure There is a sixth distance between the first surfaces of the resistance structures; the fifth distance is different from the sixth distance.
  • the second surface of the third high acoustic resistance structure may also be referred to as the lower surface of the third high acoustic resistance structure
  • the second surface of the fourth high acoustic resistance structure may also be referred to as the lower surface of the fourth high acoustic resistance structure.
  • the first high acoustic resistance structure includes a second surface close to the substrate, and the low acoustic resistance structure includes a second surface close to the substrate, There is a seventh distance between the second surface of the first high acoustic resistance structure and the second surface of the low acoustic resistance structure; the second high acoustic resistance structure includes a second surface close to the substrate, so There is an eighth distance between the second surface of the second high acoustic resistance structure and the second surface of the low acoustic resistance structure; the seventh distance and the eighth distance are different.
  • the second surface of the first high acoustic resistance structure may also be referred to as the lower surface of the first high acoustic resistance structure, and the second surface of the second high acoustic resistance structure may also be referred to as the lower surface of the second high acoustic resistance structure.
  • the second surface of the resistance structure may also be referred to as the lower surface of the low acoustic resistance structure.
  • the first high acoustic resistance structure, the second high acoustic resistance structure, the third high acoustic resistance structure, and the fourth high acoustic resistance structure Materials include one of the following: W (tungsten), Mo (molybdenum), ALN (aluminum nitride), or Ta 2 O 5 (tantalum pentoxide).
  • the material of the low acoustic resistance structure includes one of the following: silicon dioxide or silicon nitride.
  • an embodiment of the present application provides an electronic device, where the electronic device includes a transceiver, and the transceiver includes the filter according to the first aspect.
  • the electronic device further includes a circuit board, and the transceiver is disposed on the circuit board.
  • the circuit board may be a printed circuit board (PCB, Printed circuit boards).
  • an embodiment of the present application provides a method for fabricating a filter, the fabrication method comprising: providing a substrate; stacking a first Bragg reflection layer and a second Bragg reflection layer on the substrate; A first piezoelectric transducer structure is stacked on a Bragg reflection layer, and a second piezoelectric transducer structure is stacked on the second Bragg reflection layer; wherein the first Bragg reflection layer and the second Bragg reflection layer have The structure is different.
  • the stacking the first Bragg reflection layer and the second Bragg reflection layer on the substrate includes: depositing a low acoustic resistance material on the substrate to form a first low acoustic resistance layer; depositing a high acoustic resistance material on the surface of the first low acoustic resistance layer; patterning the high acoustic resistance material to form a first high acoustic resistance structure and a second high acoustic resistance structure, the The thicknesses of the first high acoustic resistance structure and the second high acoustic resistance structure along the deposition direction are different; a low acoustic resistance material is deposited on the surfaces of the first high acoustic resistance structure and the second high acoustic resistance structure to form the first high acoustic resistance structure.
  • Two low acoustic resistance layers, the second low acoustic resistance layer and the first low acoustic resistance layer have an integrated structure to form a low a
  • FIG. 1 is a schematic structural diagram of a filter provided by an embodiment of the present application.
  • FIG. 2 is another schematic structural diagram of a filter provided by an embodiment of the present application.
  • FIG. 3 is a cross-sectional view of a filter provided by an embodiment of the present application.
  • FIG. 4 is another cross-sectional view of a filter provided by an embodiment of the present application.
  • Fig. 5 is a sectional view of the filter in the conventional technology
  • FIG. 6 is a schematic diagram of the waveforms of the transverse wave transmission coefficient and the longitudinal wave transmission coefficient of the resonator in the filter in the conventional technology changing with frequency;
  • 7a is a schematic diagram of waveforms of the transverse wave transmission coefficient and the longitudinal wave transmission coefficient of the series resonator in the filter provided by the embodiment of the present application as a function of frequency;
  • 7b is a schematic diagram of waveforms of the transverse wave transmission coefficient and the longitudinal wave transmission coefficient of the parallel resonator in the filter provided by the embodiment of the present application as a function of frequency;
  • FIG. 8 is another cross-sectional view of a filter provided by an embodiment of the present application.
  • FIG. 9 is another cross-sectional view of a filter provided by an embodiment of the present application.
  • FIG 10 is another cross-sectional view of the filter provided by the embodiment of the present application.
  • FIG. 11 is a flowchart of a method for preparing a filter provided by an embodiment of the present application.
  • FIG. 12 is another flowchart of a method for preparing a filter provided by an embodiment of the present application.
  • 13a-13k are schematic structural diagrams in the process of preparing the filter provided by the embodiment of the present application.
  • FIG. 14 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.
  • FIG. 15 is a schematic structural diagram of a terminal device provided by an embodiment of the present application.
  • references herein to "first,” “second,” and similar terms do not denote any order, quantity, or importance, but are merely used to distinguish the various components. Likewise, words such as “a” or “an” do not denote a quantitative limitation, but rather denote the presence of at least one. Similar words “connected” or “connected” are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect, equivalent to coupling or communicating in a broad sense.
  • module mentioned in this document generally refers to a functional structure divided according to logic, and the “module” can be realized by pure hardware, or realized by a combination of software and hardware.
  • and/or describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and/or B, which can mean that A exists alone, A and B exist simultaneously, and B exists alone. three conditions.
  • words such as “exemplary” or “for example” are used to represent examples, illustrations or illustrations. Any embodiments or designs described in the embodiments of the present application as “exemplary” or “such as” should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as “exemplary” or “such as” is intended to present the related concepts in a specific manner.
  • the meaning of "plurality" refers to two or more. For example, multiple processing units refers to two or more processing units; multiple systems refers to two or more systems.
  • FIG. 1 is a schematic structural diagram of a filter provided by an embodiment of the present application.
  • the filter 100 includes an input end Vi, an output end Vo, a series branch C and a parallel branch P.
  • One end of the series branch C is coupled to the input end Vi and the other end is coupled to the output end Vo.
  • One end of the parallel branch P is coupled to the series branch C, and the other end is coupled to the common ground Gnd.
  • the series resonator 20 is provided on the series branch C, and the parallel resonator 30 is provided on the parallel branch P.
  • the series branch C of the filter 100 shown in FIG. 1 is provided with a series resonator 20, and a parallel branch P is coupled between the series branch C and the common ground Gnd.
  • a plurality of series resonators 20a, 20b . . . 20n may be arranged on the series branch C, and in addition, a plurality of parallel branches may be coupled between the series branch C and the common ground Gnd
  • each parallel branch may be provided with one parallel resonator 30, and each parallel branch may also be provided with multiple parallel resonators 30, which are not limited in this embodiment of the present application.
  • one end of the branch can be coupled to the position between every two series resonators on the series-connected branch C, and the other end It is coupled with the common ground Gnd, or one end of the branch is coupled with the output end Vo, and the other end is coupled with the common ground Gnd.
  • one end of the parallel branch P1 is coupled to the node a1 between the series resonator 20a and the series resonator 20b, the other end is connected to the common ground Gnd, and one end of the parallel branch P2 is connected to the series resonator 20b.
  • each parallel branch is provided with one parallel resonator 30 is schematically shown.
  • the filter described in the embodiments of the present application may be a bare chip (ie Die), and an integrated circuit is formed on a semiconductor through processes such as growth, doping, etching, or development. It includes the input end Vi, the output end Vo, at least one series resonator, and at least one parallel resonator, so as to realize the filtering function.
  • the outside of the filter 100 may be set in a package shell formed of packaging materials, and the input end Vi, the output end Vo and the ground end Gnd are drawn out through the package shell, So as to realize the signal transmission with external devices.
  • the filter 100 may also be provided in the same chip with other devices (eg, capacitors, inductors, etc.) without being packaged.
  • the filter 100 includes a parallel branch P, a parallel resonator 30 is arranged on the parallel branch P, and a series resonator 20 is arranged in the series branch.
  • a parallel branch P a parallel resonator 30 is arranged on the parallel branch P
  • a series resonator 20 is arranged in the series branch.
  • the filter 100 includes a series resonator 20 and a parallel resonator 30 .
  • the series resonator 20 and the parallel resonator 30 may share the same substrate 10 .
  • the series resonator 20 includes a Bragg reflection layer 201 and a piezoelectric transducer structure 202 disposed on the Bragg reflection layer 201 .
  • the parallel resonator 30 includes a Bragg reflection layer 301 and a piezoelectric transducer structure 302 disposed on the Bragg reflection layer 301 .
  • the piezoelectric transducer structure 202 includes an electrode 021 close to the Bragg reflection layer 201 , an electrode 2022 away from the Bragg reflection layer 201 , and a piezoelectric thin film 023 disposed between the electrode 021 and the electrode 2022 .
  • the piezoelectric transducer structure 302 includes an electrode 021 close to the Bragg reflection layer 301 , an electrode 3022 away from the Bragg reflection layer 301 , and a piezoelectric thin film 023 disposed between the electrode 021 and the electrode 3022 . As shown in FIG. 3 , the piezoelectric transducer structure 202 and the piezoelectric transducer structure 302 share the same layer of electrodes 021 and the same layer of piezoelectric film 023 .
  • the electrode 2022 and the electrode 3022 formed on the piezoelectric thin film 023 are separated from each other.
  • the piezoelectric transducer structure 202 and the piezoelectric transducer structure 302 are the same as the conventional piezoelectric transducer structures, and will not be repeated here.
  • the input terminal Vi can be drawn from the electrode 2022
  • the output terminal Vo can be drawn from the electrode 023
  • the ground terminal Gnd can be drawn from the electrode 3022 .
  • the Bragg reflection layer 201 of the series resonator 20 includes a low acoustic resistance structure D and a high acoustic resistance structure G1 buried in the low acoustic resistance structure D.
  • the Bragg reflection layer 301 of the parallel resonator 30 includes a low acoustic resistance structure D and a high acoustic resistance structure G2 buried in the low acoustic resistance structure D.
  • the low-acoustic resistance structure D is a continuous structure that wraps the high-acoustic-resistance structure G1 and the high-acoustic-resistance structure G2.
  • the material of the low acoustic resistance structure D may be a semiconductor oxide such as silicon dioxide (SiO 2 ).
  • the Bragg reflection layer 201 may include the high acoustic resistance structure G1 and the part of the low acoustic resistance structure D stacked with the high acoustic resistance structure G1; the Bragg reflection layer 301 may include the high acoustic resistance structure G2 and the low acoustic resistance structure The part of D stacked with the high acoustic resistance structure G2.
  • the low acoustic resistance structure and the high acoustic resistance structure are all aimed at the parameter of acoustic impedance, which refers to the resistance that needs to be overcome to displace the medium. It can also be expressed as "the product of the density of the medium and the speed of sound".
  • the low acoustic resistance structure refers to the structure formed by the material with lower acoustic impedance
  • the high acoustic impedance structure is the structure formed by the material with higher acoustic impedance. The acoustic impedance of the two is relative.
  • the materials for forming the high acoustic resistance structure G1 and the high acoustic resistance structure G2 may be metal materials, for example, including but not limited to tungsten (W), molybdenum (Mo), and the like.
  • the materials forming the high acoustic resistance structure G1 and the high acoustic resistance structure G2 may also be non-metallic materials, such as, but not limited to, aluminum nitride (ALN) or tantalum pentoxide (Ta 2 O 5 ).
  • the high acoustic resistance structure G1 and the high acoustic resistance structure G2 may be discontinuous structures, namely the structures shown in FIG. 3 ;
  • the material of the acoustic resistance structure is a non-metal oxide, along the second direction Y, the high acoustic resistance structure G1 and the high acoustic resistance structure G2 may be continuous structures, that is, the structures shown in FIG. 4 .
  • the high acoustic resistance structure G1 in the series resonator 20 and the high acoustic resistance structure in the parallel resonator 30 G2 has different thicknesses.
  • the thickness of the high acoustic resistance structure G1 in the series resonator 20 is greater than the thickness of the high acoustic resistance structure G2 in the parallel resonator 30, in other possible implementations, the parallel resonance
  • the thickness of the high acoustic resistance structure G2 in the resonator 30 may be greater than the thickness of the high acoustic resistance structure G1 in the series resonator 20, which is not limited in this embodiment of the present application.
  • the filter 100 described in the embodiments of the present application may be applied to scenarios of radio frequency bands such as 3G/4G, and may also be applied to scenarios of 5G radio frequency bands.
  • the 5G radio frequency band usually has the characteristics of large bandwidth and high frequency.
  • the BandN77 radio frequency band in the 5G communication protocol has a passband frequency between 3.3GHz-4.2GHz and a bandwidth of 900MHz.
  • the filtering of the above-mentioned large-bandwidth 5G frequency band is usually not realized.
  • the filtering of the above-mentioned 5G radio frequency band can be realized by a combination of a thin film bulk acoustic wave resonator and an LC resonant circuit.
  • the series resonators and the parallel resonators in the thin film bulk acoustic wave resonator usually need to be arranged at the edge of the above-mentioned passband to realize edge filtering of the passband.
  • the parallel resonator realizes the filtering of the low passband edge frequency of 3.3GHz
  • the series resonator realizes the filtering of the high pass band edge frequency of 4.2GHz, and then cooperates with the LC resonant circuit to realize the overall filtering of 3.3-4.2GHz, which can realize the passband frequency.
  • the Bragg reflection layer 401 in the series resonator 40 and the Bragg reflection layer 501 in the parallel resonator 50 have the same structure, that is, the high acoustic resistance structure 4011 in the series resonator 40 and the structure in the parallel resonator 50 are the same.
  • the thickness of the high acoustic resistance structure 5011 along the first direction Z is the same.
  • the distance h1 between the upper surface of the high acoustic resistance structure 4011 in the series resonator 40 and the upper surface of the low acoustic resistance structure 02 is the same as that of the high acoustic resistance structure in the parallel resonator 50.
  • the distance h2 between the upper surface of the resistance structure 5011 and the upper surface of the low acoustic resistance structure 02 is the same, and the distance h3 between the lower surface of the high acoustic resistance structure 4011 and the lower surface of the low acoustic resistance structure 02 in the series resonator 40 is the same as
  • the distance h4 between the lower surface of the high acoustic resistance structure 5011 and the lower surface of the low acoustic resistance structure 02 in the parallel resonator 50 is the same, as shown in FIG. 5 .
  • FIG. 6 A schematic diagram of the waveforms of the transmission coefficient and the longitudinal wave transmission coefficient varying with frequency is shown in FIG. 6 .
  • the abscissa is the frequency, and the unit is (GHz), and the ordinate is the transmission coefficient, and the unit is (dB). It should be noted that the lower the transmission coefficient, the lower the leakage of acoustic wave energy through the substrate, and the better the performance of the resonator. It can be seen from FIG.
  • both the parallel resonator 50 and the series resonator 40 have high shear wave transmission coefficients within their operating ranges.
  • the reflection efficiency of the resonator is low, that is, the value of the quality factor (Q, quality factor) of the resonator is low, which reduces the filtering effect of the filter.
  • the shear wave transmission coefficient and the longitudinal wave transmission coefficient of the series resonator 20 in the filter 100 shown in FIG. 3 or FIG. 4 vary with frequency as shown in FIG. 7a
  • the shear wave transmission coefficient and the longitudinal wave transmission coefficient of the parallel resonator 30 The waveform as a function of frequency is shown in Figure 7b. It can be seen from Fig. 7a that when the frequency is around 4.2GHz, the shear wave transmission coefficient of the series resonator 20 is around -20dB, and it can be seen from Fig. 7b that when the frequency is around 3.3GHz, the shear wave transmission coefficient of the parallel resonator 30 is around 3.3GHz. The coefficient is around -21dB.
  • the shear wave transmission coefficient of each resonator in the filter 100 according to the embodiment of the present application is significantly lower than the shear wave transmission coefficient of each resonator in the filter shown in FIG. 5 .
  • FIGS. 7 a and 6 , 7 b and 6 it can be seen that the longitudinal wave transmission coefficients of the series resonator 20 and the parallel resonator 30 are almost the same as those of the conventional resonator shown in FIG. 5 .
  • the present application by setting the high acoustic resistance material layer G1 of the Bragg reflection layer 201 in the series resonator 20 and the high acoustic resistance material layer G2 of the Bragg reflection layer 302 of the parallel resonator 30 to different thicknesses, it is possible to Change the shear wave transmission coefficient of the series resonator 20 and the parallel resonator 30, so that the shear wave transmission coefficient of each resonator in its effective frequency band is lower, and the reflection efficiency of each resonator is improved, that is, the quality factor Q of the resonator is improved. value, thereby improving the filtering effect of the filter.
  • FIG. 8 shows a schematic diagram that the Bragg reflection layer 201 in the series resonator 20 and the Bragg reflection layer 301 in the parallel resonator 30 respectively include two high acoustic resistance structures.
  • the Bragg reflection layer 201 in the series resonator 20 includes a high acoustic resistance structure G1 and a high acoustic resistance structure G3, and the Bragg reflection layer 301 in the parallel resonator 30 includes a high acoustic resistance structure G2 and a high acoustic resistance structure G4 .
  • the high acoustic resistance structure G1 and the high acoustic resistance G3 are distributed in a parallel up and down manner in FIG. 8
  • a low acoustic resistance structure D is arranged between the high acoustic resistance structure G1 and the high acoustic resistance G3.
  • the high acoustic resistance structure G1 and the high acoustic resistance G3 are parallel, and along the opposite direction of the first direction Z, the high acoustic resistance structure G1 and the high acoustic resistance G3 are perpendicular to the dimensions of the stacking direction (that is, along the second direction).
  • the dimension extending in direction Y) gradually increases from top to bottom.
  • the high acoustic resistance structure G2 and the high acoustic resistance G4 in the Bragg reflection layer 301 are distributed in a parallel up and down manner in FIG. 8 , and a low acoustic resistance structure D is arranged between the high acoustic resistance structure G2 and the high acoustic resistance G4.
  • the high acoustic resistance structure G2 and the high acoustic resistance G4 are parallel, and along the opposite direction of the first direction Z, the high acoustic resistance structure G2 and the high acoustic resistance G4 are perpendicular to the dimensions of the stacking direction (that is, along the second direction).
  • the dimension extending in direction Y) gradually increases from top to bottom.
  • the high acoustic resistance structure G1 in the Bragg reflection layer 201 and the high acoustic resistance structure G2 in the Bragg reflection layer 301 have the same thickness along the first direction Z, and the high acoustic resistance structure G3 in the Bragg reflection layer 201 and The high acoustic resistance structures G4 in the Bragg reflection layer 301 have different thicknesses.
  • the materials for forming the high acoustic resistance structure G3 and the materials for forming the high acoustic resistance structure G4 are the same as the materials for forming the high acoustic resistance structure G1 . For details, please refer to the relevant description in FIG. 3 , which will not be repeated here.
  • the Bragg reflection layer 201 in the series resonator 20 and the Bragg reflection layer 301 in the parallel resonator 30 may further include a third high acoustic resistance structure, a fourth high acoustic resistance structure, and more high acoustic resistance structures, All the high acoustic resistance structures are embedded in the low acoustic resistance structures and are parallel to each other along the stacking direction.
  • the size of each high acoustic resistance structure extending along the second direction Y gradually increases from the electrode 021 to the direction of the substrate 10 .
  • a low-acoustic resistance structure is arranged between any two high-acoustic-resistance structures, so that each high-acoustic-resistance structure and low-acoustic-resistance structure are alternate layered structures, which facilitates sound propagation and reflection in each layered structure.
  • the high acoustic resistance structure closest to the electrode 021 in the series resonator 20 and the parallel resonator 30 closest to the electrode 021 Except the thickness of the high acoustic resistance structure along the first direction Z is different, for any one of the other high acoustic resistance structures in the series resonator 20 , the high acoustic resistance structure is the same as the high acoustic resistance structure in the parallel resonator 30 arranged on the same layer.
  • the thicknesses of the structures along the first direction Z are all the same.
  • the same layer setting here can be understood as: the same position in the Bragg reflection layer.
  • the high acoustic resistance structure G1 and the high acoustic resistance structure G2 shown in FIG. 8 can be understood as being arranged on the same layer, and the high acoustic resistance structure G3 and the high acoustic resistance structure G4 can be understood as being arranged on the same layer; when the Bragg reflection layer 201 further includes When the high acoustic resistance structure G5 located between the high acoustic resistance structure G1 and the high acoustic resistance structure G3, the Bragg reflection layer 301 further includes the high acoustic resistance structure G6 located between the high acoustic resistance structure G2 and the high acoustic resistance structure G4, the high acoustic resistance The structure G5 and the high acoustic resistance structure G6 can be understood as being arranged in the same layer (not shown in the figure).
  • both the series resonator 20 and the parallel resonator 30 in the filter 100 include two high acoustic resistance structures, and the high acoustic resistance structure G1 in the series resonator 20 is close to the substrate 10 This is the same as the thickness along the first direction Z of the high acoustic resistance structure G2 in the parallel resonator 30 close to the substrate 10 .
  • the thicknesses along the first direction Z of the high acoustic resistance structures disposed on the same layer of the series resonator 20 and the parallel resonator 30 are all different. Please refer to FIG.
  • FIG. 9 which shows that the thicknesses of the high acoustic resistance structure G1 near the substrate 10 in the series resonator 20 and the high acoustic resistance structure G2 near the substrate 10 in the parallel resonator 30 along the first direction Z are different .
  • the remaining structures and materials used in the resonators shown in FIG. 9 are the same as those shown in FIG. 2 , and details are not repeated here.
  • the thickness of the high acoustic resistance structure G3 in the series resonator 20 close to the electrode 021 along the first direction Z is the same as the thickness of the high acoustic resistance structure G2 in the parallel resonator 30 close to the substrate 10 along the first direction Z.
  • the thickness in the direction Z is the same; the thickness of the high acoustic resistance structure G4 near the electrode 021 in the parallel resonator 30 along the first direction Z is the same as the thickness of the high acoustic resistance structure G1 in the series resonator 20 near the substrate 10 along the first direction Z same.
  • the high acoustic resistance structure G3 and the high acoustic resistance structure G4 are also set along the first direction Z.
  • Different thicknesses are set in the direction Z, that is, the thicknesses of the high acoustic resistance structures arranged in the same layer of the series resonator 20 and the parallel resonator 30 are different along the first direction Z, so that the reflection efficiency of the resonator can be further improved, that is, further. Improve the quality factor Q value of the resonator and improve the filtering effect of the filter.
  • At least one layer of the high acoustic resistance structure disposed on the same layer is along the first layer.
  • the thickness in one direction Z is different.
  • the high acoustic resistance structures disposed on the same layer can also be set to the same thickness along the first direction Z, and the buried position of the high acoustic resistance structures in the series resonator 20 in the low acoustic resistance structures can be adjusted, At the same time, adjust the buried position of the high acoustic resistance structure in the parallel resonator 30 in the low acoustic resistance structure, so that the distance between the upper surface of the high acoustic resistance structure in the series resonator 20 and the upper surface of the low acoustic resistance structure, The distance between the upper surface of the high acoustic resistance structure and the upper surface of the low acoustic resistance structure in the parallel resonator 30 is different; or the lower surface of the high acoustic resistance structure in the series resonator 20 is different from the lower surface of the low acoustic resistance structure.
  • the distance between the surfaces is different from the distance between the lower surface of the high acoustic resistance structure and the lower surface of the low acoustic resistance structure in the parallel resonator 30, so that the shear wave transmission of the series resonator 20 and the parallel resonator 30 can also be reduced
  • the coefficient can improve the reflection efficiency of each resonator, that is, improve the quality factor Q value of the resonator, and then improve the filtering effect of the filter. A detailed description will be given below with reference to the embodiment shown in FIG. 10 .
  • the Bragg reflection layer 201 of the series resonator 20 includes a high acoustic resistance structure G1 and a high acoustic resistance structure G3 , and the high acoustic resistance structure G1 is disposed on a surface close to the substrate 10 On the side, the high acoustic resistance structure G3 is disposed on the side close to the electrode 021 .
  • the Bragg reflection layer 301 of the parallel resonator 30 includes a high acoustic resistance structure G2 and a high acoustic resistance structure G4 .
  • the high acoustic resistance structure G1 includes an upper surface close to the electrode 021 and a lower surface away from the electrode 021
  • the high acoustic resistance structure G3 includes an upper surface close to the electrode 021 and a lower surface away from the electrode 021
  • the high acoustic resistance structure G2 includes an upper surface close to the electrode 021 and a lower surface away from the electrode 021
  • the high acoustic resistance structure G4 includes an upper surface close to the electrode 021 and a lower surface away from the electrode 021
  • the low acoustic resistance structure D includes an upper surface close to the electrode 021 and a lower surface close to the substrate 10 .
  • first distance h1 between the upper surface of the high acoustic resistance structure G3 and the upper surface of the low acoustic resistance structure D
  • second distance h2 between the upper surface of the high acoustic resistance structure G3 and the upper surface of the low acoustic resistance structure D
  • the first distance h1 is different from the second distance h2.
  • the third distance h5 is different from the fourth distance h6.
  • an embodiment of the present application further provides a method for fabricating the filter 100 .
  • the process flow of fabricating the filter 100 may refer to the flow 1100 shown in FIG. 11 .
  • the process flow 1100 includes the following steps:
  • the substrate material here may be silicon.
  • first Bragg reflection layer and a second Bragg reflection layer Form a first Bragg reflection layer and a second Bragg reflection layer on the substrate; wherein the first Bragg reflection layer and the second Bragg reflection layer have different structures.
  • the first Bragg reflection layer includes a first low acoustic resistance structure and a first high acoustic resistance structure embedded in the first low acoustic resistance structure
  • the second Bragg reflection layer includes a second low acoustic resistance structure and a first low acoustic resistance structure embedded in the second low acoustic resistance structure.
  • the second high acoustic resistance structure in the acoustic resistance structure.
  • the thicknesses of the first high acoustic resistance structure and the second high acoustic resistance structure along the deposition direction are different.
  • the first Bragg reflection layer includes a first low acoustic resistance structure, a first high acoustic resistance structure and a third high acoustic resistance structure embedded in the first low acoustic resistance structure, and the third high acoustic resistance structure
  • the resistance structure is formed on the first high acoustic resistance structure and is parallel to the first high acoustic resistance structure along the stacking direction;
  • the second Bragg reflection layer includes a second low acoustic resistance structure and a second low acoustic resistance structure embedded in the second low acoustic resistance structure.
  • the high acoustic resistance structure and the fourth high acoustic resistance structure are formed on the second high acoustic resistance structure and are parallel to the second high acoustic resistance structure along the stacking direction.
  • the thicknesses of the first high acoustic resistance structure and the second high acoustic resistance structure along the deposition direction are different, and the thicknesses of the third high acoustic resistance structure and the fourth high acoustic resistance structure are different along the deposition direction.
  • the first high acoustic resistance structure and the fourth high acoustic resistance structure have the same thickness along the deposition direction; the second high acoustic resistance structure and the third high acoustic resistance structure have the same thickness along the deposition direction.
  • first distance between the surface of the first high acoustic resistance structure away from the substrate and the surface of the first low acoustic resistance structure away from the substrate, and the surface of the second high acoustic resistance away from the substrate
  • second distance between the surfaces of the second low acoustic resistance structure away from the substrate, and the length of the first distance and the second distance is different.
  • first piezoelectric transducer structure and a second piezoelectric transducer structure Form a first piezoelectric transducer structure and a second piezoelectric transducer structure on the first Bragg reflection layer and the second Bragg reflection layer, respectively.
  • the first piezoelectric transducer structure includes a first piezoelectric layer close to the first Bragg reflection layer, a second piezoelectric layer away from the first Bragg reflection layer, and a second piezoelectric layer located between the first piezoelectric layer and the second piezoelectric layer
  • the second piezoelectric transducer structure includes a first piezoelectric layer close to the second Bragg reflection layer, a second piezoelectric layer away from the second Bragg reflection layer, and a second piezoelectric layer located in the first piezoelectric layer and the second piezoelectric layer between the thin film layers.
  • first Bragg reflection layer and the first piezoelectric transducer structure form a series resonator
  • second Bragg reflection layer and the second piezoelectric transducer structure form a parallel resonator
  • the process flow 1200 includes the following steps:
  • Step 1201 providing a substrate 10; the substrate material here can be silicon.
  • Step 1202 growing a first low acoustic resistance material on the substrate.
  • the first low acoustic resistance material may be a semiconductor material, such as SiO 2 .
  • Step 1203 growing a first high acoustic resistance material on the first low acoustic resistance material. After this step is shown in Figure 13a.
  • the first high acoustic resistance material may be a metal material, including but not limited to: tungsten (W) and molybdenum (Mo).
  • Step 1204 growing a second acoustic resistance material on the first high acoustic resistance material and the first low acoustic resistance material to form a high acoustic resistance structure G1 and a high acoustic resistance structure G2.
  • the thickness of the high acoustic resistance structure G1 is greater than that of the high acoustic resistance structure G2, that is, the exposed upper surface of the high acoustic resistance structure G1 is higher than the upper surface of the high acoustic resistance structure G2. As shown in Figure 13b.
  • the second high acoustic resistance material may be etched by an etching method such as dry etching or wet etching.
  • the high acoustic resistance structure G1 is formed by growing the high acoustic resistance material twice.
  • the second high acoustic resistance material may be the same as the first high acoustic resistance material.
  • Step 1205 growing a second low acoustic resistance material and a third low acoustic resistance material on the exposed high acoustic resistance structure G1 and high acoustic resistance structure G2, respectively, so that the second low acoustic resistance material wraps the high acoustic resistance structure G1 and exposes The exposed part of the high-acoustic-resistance structure G2 is also wrapped by the third low-acoustic-resistance material.
  • the thickness of the second low acoustic resistance material grown on the high acoustic resistance structure G1 is the same as the thickness of the third low acoustic resistance material grown on the high acoustic resistance structure G2. As shown in Figure 13c.
  • the second low acoustic resistance material and the third low acoustic resistance material may be SiO2.
  • Step 1206 growing a third high acoustic resistance material on the third low acoustic resistance material. As shown in Figure 13d.
  • Step 1207 growing a fourth high acoustic resistance material on the third high acoustic resistance material and the second low acoustic resistance material to form a high acoustic resistance structure G3 and a high acoustic resistance structure G4, as shown in FIG. 13e.
  • the third high acoustic resistance material and the fourth high acoustic resistance material are the same.
  • the third high acoustic resistance material and the fourth high acoustic resistance material may be metal materials, including but not limited to: tungsten (W) and molybdenum (Mo).
  • the fourth high acoustic resistance material grown on the second low acoustic resistance material forms the high acoustic resistance structure G3, and the third high acoustic resistance material and the fourth high acoustic resistance material grown on the third low acoustic resistance material together form High acoustic resistance structure G4.
  • the thickness of the high acoustic resistance structure G4 is greater than that of the high acoustic resistance structure G3.
  • the thickness of the high acoustic resistance structure G3 along the stacking direction is the same as the thickness of the high acoustic resistance structure G2 along the stacking direction , so that the thickness of the high acoustic resistance structure G4 along the stacking direction is the same as the thickness of the high acoustic resistance structure G1 along the stacking direction.
  • Step 1208 grow a fourth low acoustic resistance material on the exposed parts of the high acoustic resistance structure G3, the high acoustic resistance structure G4, the first low acoustic resistance material, the second low acoustic resistance material and the third low acoustic resistance material, so that the first low acoustic resistance material is formed.
  • Four low acoustic resistance materials wrap the exposed parts of the high acoustic resistance structure G3, the high acoustic resistance structure G4, the first low acoustic resistance material, the second low acoustic resistance material and the third low acoustic resistance material, as shown in Figure 13f.
  • the fourth low acoustic resistance material may be SiO2.
  • Step 1209 planarizing the fourth low acoustic resistance material.
  • the redundant fourth low acoustic resistance material may be removed by a chemical mechanical polishing (CMP) process, so that the exposed surface of the fourth low acoustic resistance material is flat. As shown in Figure 13g.
  • CMP chemical mechanical polishing
  • Step 1210 continue to grow a fifth low acoustic resistance material on the fourth low acoustic resistance material, and planarize the fifth low acoustic resistance material to form a low acoustic resistance structure D. As shown in Figure 13h.
  • the redundant fifth low acoustic resistance material may be removed by a chemical mechanical polishing (CMP) process, so that the exposed surface of the fifth low acoustic resistance material is flat.
  • CMP chemical mechanical polishing
  • the first low acoustic resistance material, the second low acoustic resistance material, the third low acoustic resistance material, the fourth low acoustic resistance material and the fifth low acoustic resistance material are connected together to form a continuous low acoustic resistance structure.
  • the portion of the continuous low acoustic resistance structure stacked with the high acoustic resistance structure G1 and the high acoustic resistance structure G3 forms the Bragg reflection layer 201
  • the continuous low acoustic resistance structure is formed with the high acoustic resistance structure G2 and the high acoustic resistance structure G2 and the high acoustic resistance structure
  • the portion where G4 is stacked forms the Bragg reflection layer 301 .
  • Step 1211 depositing a first metal layer on the low acoustic resistance structure D to form an electrode 021 . As shown in Figure 13i.
  • step 1212 a piezoelectric thin film material is deposited on the electrode 021 to form a piezoelectric thin film 023 . As shown in Figure 13j.
  • Step 1213 depositing a second metal layer on the piezoelectric film 023 . As shown in Figure 13k.
  • Step 1214 patterning the second metal layer to form electrodes 2022 and 3022 separated from each other.
  • a patterned mask layer may be formed on the second metal layer, the second metal layer is etched by using the patterned mask layer as a mask, and the unetched portion forms the electrodes 2022 and Electrode 3022.
  • various etching methods such as dry etching or wet etching can be used to etch the second metal layer to form the electrode 2022 and the electrode 3022 .
  • the filters prepared through steps 1201 to 1214 are shown in FIG. 9 .
  • the electrode 2022 is disposed on the high acoustic resistance structure G1 and the high acoustic resistance structure G3, and its orthographic projection to the high acoustic resistance structure G3 overlaps with the high acoustic resistance structure G3 at least partially, and the electrode 3022 is disposed on the high acoustic resistance structure G2 and the high acoustic resistance structure G3. Above the acoustic resistance structure G4, its orthographic projection to the high acoustic resistance structure G4 at least partially overlaps with the high acoustic resistance structure G4.
  • the piezoelectric transducer structure 202 formed by the electrode 021, the piezoelectric thin film layer 023 and the electrode 2022 located on the high acoustic resistance structure G3, the electrode 021, the piezoelectric thin film layer 023 and the electrode 021 located on the high acoustic resistance structure G4.
  • the electrodes 3022 together form the piezoelectric transducer structure 302 .
  • the series resonator 20 is formed between the Bragg reflection layer 201 and the piezoelectric transducer structure 202
  • the resonator 20 is formed between the Bragg reflection layer 301 and the piezoelectric transducer structure 302 .
  • the shear wave transmission coefficient of the series resonator and the parallel resonator can be changed, so that the shear wave transmission coefficient of each resonator in its effective frequency band is relatively high. If the value is low, the reflection efficiency of each resonator is improved, that is, the quality factor Q value of the resonator is improved, and the filtering effect of the filter is further improved.
  • the process steps of forming the high acoustic resistance structure G1 and the high acoustic resistance structure G2 in the above steps 1203 and 1204 can also be replaced by the following steps:
  • a first high acoustic resistance material and a second high acoustic resistance material are grown on the first low acoustic resistance material, wherein the grown first high acoustic resistance material and the second high acoustic resistance material are discontinuous, and the first high acoustic resistance material
  • the upper surface of the material is flush with the upper surface of the second high acoustic resistance material; the second high acoustic resistance material is etched, so that the first high acoustic resistance material forms a high acoustic resistance structure G1, so that the etched second high acoustic resistance material
  • the resistive material forms a high acoustic resistance structure G2.
  • the process steps of forming the high acoustic resistance structure G3 and the high acoustic resistance structure G4 in the above steps 1206 and 1207 can also be replaced by the following steps:
  • a third high acoustic resistance material is grown on the second low acoustic resistance material, and a fourth high acoustic resistance material is grown on the third low acoustic resistance material, wherein the grown third high acoustic resistance material and the fourth high acoustic resistance material It is discontinuous, and the thickness of the grown third high acoustic resistance material along the stacking direction is the same as the thickness of the fourth high acoustic resistance material along the stacking direction; the third high acoustic resistance material is etched, so that the third high acoustic resistance material after etching is The acoustic resistance material forms the high acoustic resistance structure G3, so that the fourth high acoustic resistance material forms the high acoustic resistance structure G4.
  • the electronic device 1400 may include a transceiver 1401, a memory 1402, and a processor 1403.
  • the transceiver 1401 is provided with the above-mentioned filter 100.
  • the filter The structure of 100 may refer to one of the structures exemplified in FIG. 1 or FIG. 2 .
  • the electronic device 1400 here may specifically be a terminal device such as a smart phone, a computer, and a smart watch.
  • the terminal device may specifically include a processor 15102, a memory 15103, a control circuit, an antenna, and an input and output device.
  • the processor 15102 is mainly used to process communication protocols and communication data, control the entire smartphone, execute software programs, and process data of the software programs, for example, to support the smartphone 1510 to realize various communication functions (such as making calls, send a message or live chat, etc.).
  • the memory 15103 is mainly used to store software programs and data.
  • the control circuit is mainly used for the conversion of the baseband signal and the radio frequency signal and the processing of the radio frequency signal, and the control circuit includes the above-mentioned filter 100 .
  • the control circuit and the antenna together can also be called a transceiver 15101, which is mainly used for transmitting and receiving radio frequency signals in the form of electromagnetic waves.
  • Input and output devices such as touch screens, display screens, and keyboards, are mainly used to receive data input by users and output data to users.
  • the processor 15102 can read the software program in the memory 15103, interpret and execute the instructions of the software program, and process the data of the software program.
  • the processor 15102 performs baseband processing on the data to be sent, and outputs the baseband signal to the radio frequency circuit.
  • the radio frequency circuit performs radio frequency processing on the baseband signal and sends the radio frequency signal through the antenna in the form of electromagnetic waves.
  • the radio frequency circuit receives the radio frequency signal through the antenna, converts the radio frequency signal into a baseband signal, and outputs the baseband signal to the processor 15102, and the processor 15102 converts the baseband signal into data and sends the data to the data. to be processed.
  • FIG. 15 only shows one memory and one processor. In an actual terminal device, there may be multiple processors and multiple memories.
  • the memory may also be referred to as a storage medium or a storage device or the like. It should be noted that the embodiment of the present application does not limit the type of the memory.

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Abstract

一种滤波器（100）和滤波器（100）的制备方法，该滤波器（100）包括：衬底（10）；串联谐振器（20），串联谐振器（20）包括依次堆叠于衬底（10）之上的第一布拉格反射层（201）和第一压电换能结构（202）；并联谐振器（30），并联谐振器（30）包括依次堆叠于衬底（10）之上的第二布拉格反射层（301）和第二压电换能结构（302），第一布拉格反射层（201）的结构与第二布拉格反射层（301）的结构不同；串联支路（C），所述串联支路（C）包括所述串联谐振器（20），所述串联支路（C）耦合于所述滤波器输入端（Vi）和所述滤波器输出端（Vo）之间；并联支路（P），所述并联支路（P）包括所述并联谐振器（30），所述并联支路（P）耦合于所述串联支路（C）与公共地（Gnd）之间；该结构可以提高滤波器（100）的滤波性能。

Description

滤波器以及滤波器的制备方法 技术领域
本申请实施例涉及滤波器技术领域，尤其涉及一种滤波器以及滤波器的制备方法。
背景技术
随着通信技术发展，射频滤波器的需求量日益增大。当滤波器应用于高性能要求的场景，比如5G技术场景时，通常采用薄膜体声波谐振器所形成的滤波器和LC谐振电路相结合的方式实现射频频段的滤波。
当前技术中，当薄膜体声波谐振器所形成的滤波器和LC谐振电路相结合应用于高性能技术场景中时，通常需要将滤波器中的薄膜体声波谐振器设置于高性能射频频段的通频带的边缘，用于实现5G射频频段的通频带边缘的滤波。此时，滤波器的品质因数(Q，quality factor)的值较低，降低了滤波器的滤波效果。由此，当薄膜体声波谐振器所形成的滤波器应用于高性能技术场景中时，如何提高滤波器的滤波性能成为需要解决的问题。
发明内容
本申请提供的滤波器以及滤波器的制备方法，可以提高滤波器的性能。
为达到上述目的，本申请采用如下技术方案：
第一方面，本申请实施例提供一种滤波器，包括：衬底；串联谐振器，所述串联谐振器包括依次堆叠于所述衬底之上的第一布拉格反射层和第一压电换能结构；并联谐振器，所述并联谐振器包括依次堆叠于所述衬底之上的第二布拉格反射层和第二压电换能结构，所述第一布拉格反射层的结构与所述第二布拉格反射层的结构不同；串联支路，所述串联支路包括所述串联谐振器，所述串联支路耦合于所述滤波器输入端和所述滤波器输出端之间；并联支路，所述并联支路包括所述并联谐振器，所述并联支路耦合于所述串联支路与公共地之间。
本申请实施例所述的滤波器，可以为裸芯片(也即Die)，其是在半导体上通过生长、掺杂、刻蚀、或显影等工艺形成集成电路，该集成电路中包括输入端、输出端、至少一个串联谐振器、至少一个并联谐振器，从而实现滤波功能。需要说明的是，在一种可能的实现方式中，用于形成滤波器的裸芯片的外部可以设置于封装材料所形成的封装壳中，并通过封装壳引出上述输入端、输出端和接地端，从而实现与外部各器件之间的信号传输。在另外一种可能的实现方式中，用于形成滤波器的裸芯片还可以不经过封装，与其他器件(例如电容、电感等)设置于同一个芯片中。
本申请实施例通过将串联谐振器中的布拉格反射层与并联谐振器的布拉格反射层设置成不同的厚度，可以改变串联谐振器和并联谐振器的横波透射系数，从而使得各谐振器在其有效频带范围内的横波透射系数较低，提高各谐振器的反射效率，也即提高谐振器的品质因数Q值，进而提高滤波器的滤波效果。
基于第一方面，在一种可能的实现方式中，所述滤波器还包括用于形成所述第一布拉格反射层和所述第二布拉格反射层的低声阻结构；所述第一布拉格反射层包括埋设于所述低声阻结构中的第一高声阻结构；所述第二布拉格发射层包括埋设于所述低声阻结构中的第二高声阻结构；沿堆叠方向，所述第一高声阻结构的厚度与所述第二高声阻结构的厚度不同。
基于第一方面，在一种可能的实现方式中，所述低声阻结构堆叠于所述衬底的表面；所述滤波器还包括用于形成所述第一压电换能结构和所述第二压电换能结构的第一电极和薄膜结构，所述第一电极和所述薄膜结构依次堆叠于所述低声阻结构远离所述衬底的表面；所述第一压电换能结构还包括第二电极，所述第二压电换能结构还包括第三电极；所述第一电极和所述第二电极均设置于所述薄膜结构远离所述衬底的表面。
基于第一方面，在一种可能的实现方式中，沿所述堆叠方向，所述第一高声阻结构包括远离所述衬底的第一表面，所述低声阻结构包括远离所述衬底的第一表面，所述第二高声阻结构包括远离所述衬底的第一表面，所述第一高声阻结构的第一表面与所述低声阻结构的第一表面之间具有第一距离，所述第二高声阻结构的第一表面与所述低声阻结构的第一表面之间具有第二距离，所述第一距离和所述第二距离不同。
第一高声阻结构的第一表面也可以称为第一高声阻结构的上表面，低声阻结构的第一表面也可以称为低声阻结构的上表面，第二高声阻结构的一表面也可以称为第一高声阻结构的上表面。
基于第一方面，在一种可能的实现方式中，所述第一布拉格反射层还包括埋设于所述低声阻结构中的第三高声阻结构，沿所述堆叠方向，所述第三高声阻结构设置于所述第一高声阻结构远离所述衬底的一侧、且与所述第一高声阻结构之间设置有所述低声阻结构；所述第二布拉格反射层还包括埋设于所述低声阻结构中的第四高声阻结构，沿所述堆叠方向，所述第四高声阻结构设置于所述第二高声阻结构远离所述衬底的一侧、且与所述第二高声阻结构之间设置有所述低声阻结构；沿所述堆叠方向，所述第三高声阻结构的厚度与所述第四高声阻结构的厚度不同。
基于第一方面，在一种可能的实现方式中，沿所述堆叠方向，所述第一高声阻结构的厚度与所述第四高声阻结构的厚度相同；沿所述堆叠方向，所述第二高声阻结构的厚度与所述第三高声阻结构的厚度相同。
基于第一方面，在一种可能的实现方式中，所述第三高声阻结构包括远离所述衬底的第一表面，所述第三高声阻结构的第一表面的上表面与所述低声阻结构的第一表面之间具有第三距离；所述第四高声阻结构包括远离所述衬底的第一表面，所述第三高声阻结构的第一表面与所述低声阻结构的第一表面之间具有第四距离；所述第三距离和所述第四距离不同。
第三高声阻结构的第一表面也可以称为第三高声阻结构的上表面，第四高声阻结构的第一表面也可以称为第四高声阻结构的上表面。
基于第一方面，在一种可能的实现方式中，所述第三高声阻结构包括靠近所述衬底的第二表面，所述第三高声阻结构的第二表面与所述第一高声阻结构的第一表面之间具有第五距离；所述第四高声阻结构包括靠近所述衬底的第二表面，所述第四结构的第二表面与所述第二高声阻结构的第一表面之间具有第六距离；所述第五距离与所述第六距离不同。
第三高声阻结构的第二表面也可以称为第三高声阻结构的下表面，第四高声阻结构的第二表面也可以称为第四高声阻结构的下表面。
基于第一方面，在一种可能的实现方式中，所述第一高声阻结构包括靠近所述衬底的第二表面，所述低声阻结构包括靠近所述衬底的第二表面，所述第一高声阻结构的第二表面与所述低声阻结构的第二表面之间具有第七距离；所述第二高声阻结构包括靠近所述衬底的第二表面，所述第二高声阻结构的第二表面与所述低声阻结构的第二表面之间具有第八距离；所述第七距离和所述第八距离不同。
第一高声阻结构的第二表面也可以称为第一高声阻结构的下表面，第二高声阻结构的第二表面也可以称为第二高声阻结构的下表面，低声阻结构的第二表面也可以称为低声阻结构的下表面。
基于第一方面，在一种可能的实现方式中，所述第一高声阻结构、所述第二高声阻结构、所述第三高声阻结构和所述第四高声阻结构的材料包括以下之一：W(钨)、Mo(钼)、ALN(氮化铝)或者Ta 2O 5(五氧化二钽)。
基于第一方面，在一种可能的实现方式中，所述低声阻结构的材料包括以下之一：二氧化硅或者氮化硅。
第二方面，本申请实施例提供一种电子设备，该电子设备包括收发机，该收发机包括如第一方面所述的滤波器。
基于第二方面，在一种可能的实现方式中，电子设备还包括电路板，所述收发机设置于所述电路板。具体实现中，该电路板可以为印刷电路版(PCB,Printed circuit boards)。
第三方面，本申请实施例提供一种滤波器的制备方法，该制备方法包括：提供一衬底；在所述衬底上堆叠第一布拉格反射层和第二布拉格反射层；在所述第一布拉格反射层上堆叠第一压电换能结构，在所述第二布拉格反射层上堆叠第二压电换能结构；其中，所述第一布拉格发射层和所述第二布拉格反射层的结构不同。
基于第三方面，在一种可能的实现方式中，所述在所述衬底上堆叠第一布拉格反射层和第二布拉格反射层，包括：在所述衬底上沉积低声阻材料以形成第一低声阻层；在所述第一低声阻层的表面沉积高声阻材料；图案化所述高声阻材料以形成第一高声阻结构和第二高声阻结构，所述第一高声阻结构和所述第二高声阻结构沿沉积方向的厚度不同；在所述第一高声阻结构和所述第二高声阻结构的表面沉积低声阻材料以形成第二低声阻层，所述第二低声阻层与所述第一低声阻层具有一体式结构以形成低声阻结构。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例的描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的滤波器的一个结构示意图；
图2是本申请实施例提供的滤波器的又一个结构示意图；
图3是本申请实施例提供的滤波器的一个剖视图；
图4是本申请实施例提供的滤波器的又一个剖视图；
图5是传统技术中滤波器的一个剖视图；
图6是传统技术中滤波器中的谐振器的横波透射系数以及纵波透射系数随频率变化的波形的示意图；
图7a是本申请实施例提供的滤波器中的串联谐振器的横波透射系数以及纵波透射系数随频率变化的波形的示意图；
图7b是本申请实施例提供的滤波器中的并联谐振器的横波透射系数以及纵波透射系数随频率变化的波形的示意图；
图8是本申请实施例提供的滤波器的又一个剖视图；
图9是本申请实施例提供的滤波器的又一个剖视图；
图10是本申请实施例提供的滤波器的又一个剖视图；
图11是本申请实施例提供的滤波器的制备方法的一个流程图；
图12是本申请实施例提供的滤波器的制备方法的又一个流程图；
图13a-图13k是本申请实施例提供的滤波器的制备过程中的结构示意图；
图14是本申请实施例提供的电子设备的一个结构示意图；
图15是本申请实施例提供的终端设备的一个结构示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
本文所提及的"第一"、"第二"以及类似的词语并不表示任何顺序、数量或者重要性，而只是用来区分不同的组成部分。同样，"一个"或者"一"等类似词语也不表示数量限制，而是表示存在至少一个。"连接"或者"相连"等类似的词语并非限定于物理的或者机械的连接，而是可以包括电性的连接，不管是直接的还是间接的，等同于广义上的耦合或联通。
在本文中提及的"模块"通常是指按照逻辑划分的功能性结构，该"模块"可以由纯硬件实现，或者，软硬件的结合实现。在本申请实施中，“和/或”描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示:单独存在A，同时存在A和B，单独存在B这三种情况。
在本申请实施例中，“示例性的”或者“例如”等词用于表示作例子、例证或说明。本申请实施例中被描述为“示例性的”或者“例如”的任何实施例或设计方案不应被解释为比其它实施例或设计方案更优选或更具优势。确切而言，使用“示例性的”或者“例如”等词旨在以具体方式呈现相关概念。在本申请实施例的描述中，除非另有说明，“多个”的含义是指两个或两个以上。例如，多个处理单元是指两个或两个以上的处理单元；多个系统是指两个或两个以上的系统。
请参考图1，图1是本申请实施例提供的滤波器的结构示意图。
在图1中，滤波器100包括输入端Vi、输出端Vo、串联支路C和并联支路P，串联支路C的一端耦合至输入端Vi，另一端耦合至输出端Vo。并联支路P的一端耦合至串联支路C、另一端耦合至公共地Gnd。其中，串联支路C上设置有串联谐振器20，并联支路 P上设置有并联谐振器30。如图1所示的滤波器100的串联支路C设置有一个串联谐振器20，在串联支路C和公共地Gnd之间耦合有一条并联支路P。
在其他一种可能的实现方式中，串联支路C上可以设置有多个串联谐振器20a、20b…20n，此外，在串联支路C与公共地Gnd之间还可以耦合有多条并联支路P1、P2、…Pn，其中每一条并联支路上可以设置有一个并联谐振器30，每一条并联支路也可以设置多个并联谐振器30，本申请实施例对此不做限定。具体实现中，对于上述多条并联支路P1、P2、…Pn的其中一条，该条支路的一端可以耦合于串联联支路C上每两个串联谐振器之间的位置处，另一端与公共地Gnd耦合，或者该条支路的一端与输出端Vo耦合，另外一端与公共地Gnd耦合。具体如图2所示，并联支路P1的一端与串联谐振器20a和串联谐振器20b之间的结点a1耦合，另一端连接至公共地Gnd，并联支路P2的一端与串联谐振器20b和串联谐振器20c之间的结点a2耦合，另一端耦合至公共地Gnd，并联支路Pn的一端与输出端Vo耦合，另一端耦合至公共地Gnd。在图2中，示意性的示出了每条并联支路均设置有一个并联谐振器30的情况。
需要说明的是，本申请实施例所述的滤波器，可以为裸芯片(也即Die)，是在半导体上通过生长、掺杂、刻蚀、或显影等工艺形成集成电路，该集成电路中包括上述输入端Vi、输出端Vo、至少一个串联谐振器、至少一个并联谐振器，从而实现滤波功能。需要说明的是，在一种可能的实现方式中，上述滤波器100的外部可以设置于封装材料所形成的封装壳中，并通过封装壳引出上述输入端Vi、输出端Vo和接地端Gnd，从而实现与外部各器件之间的信号传输。在另外一种可能的实现方式中，滤波器100还可以不经过封装，与其他器件(例如电容、电感等)设置于同一个芯片中。
基于图1和图2所示的滤波器100，下面以滤波器100中包括一个并联支路P、该并联支路P上设置一个并联谐振器30、并且串联支路中设置一个串联谐振器20为例(也即以如图1所示的滤波器100为例)，结合图3，对滤波器100的具体结构进行详细描述。
请参考图3，其示出了滤波器100的一个剖视图。如图3所示，滤波器100包括串联谐振器20和并联谐振器30。其中，串联谐振器20和并联谐振器30可以共用同一衬底10。沿第一方向Z，也即堆叠方向，串联谐振器20包括布拉格反射层201和设置于布拉格反射层201之上的压电换能结构202。同样，沿第一方向Z，并联谐振器30包括布拉格反射层301和设置于布拉格反射层301之上的压电换能结构302。压电换能结构202包括靠近布拉格反射层201的电极021、远离布拉格反射层201的电极2022和设置于电极021和电极2022之间的压电薄膜023。压电换能结构302包括靠近布拉格反射层301的电极021、远离布拉格反射层301的电极3022和设置于电极021和电极3022之间的压电薄膜023。如图3所示，压电换能结构202和压电换能结构302共用同一层电极021和共用同一层压电薄膜023。在压电薄膜023之上所形成的电极2022和电极3022之间相互分离。其中，压电换能结构202和压电换能结构302与传统压电换能结构相同，在此不再赘述。需要说明的是，可以在电极2022上引出输入端Vi，可以在电极023上引出输出端Vo，可以在电极3022上引出接地端Gnd。
在图3中，串联谐振器20的布拉格反射层201包括低声阻结构D和埋设于低声阻结构D中的高声阻结构G1。同样，并联谐振器30的布拉格反射层301包括低声阻结构D和埋设于低声阻结构D中的高声阻结构G2。如图3所示，低声阻结构D为连续的结构， 其将高声阻结构G1和高声阻结构G2包裹。在本申请实施例中，低声阻结构D的材料可以为二氧化硅(SiO2)等半导体氧化物。需要说明的是，布拉格反射层201可以包括高声阻结构G1以及低声阻结构D中与高声阻结构G1层叠设置的部分；布拉格反射层301可以包括高声阻结构G2以及低声阻结构D中与高声阻结构G2层叠设置的部分。
应当理解，低声阻结构和高声阻结构针对的都是声波阻抗这一参数，阻抗指的是将介质位移所需克服的阻力，此处的声波阻抗即可以定义为“声压/介质流过一面积的速度”，亦可表示为“介质密度与声速的乘积”。低声阻结构即指的是由声波阻抗较低的材料形成的结构，高声阻结构则是由声波阻抗较高的材料形成的结构，二者的声波阻抗高低是相对而言的。本申请实施例中，形成高声阻结构G1和高声阻结构G2的材料可以为金属材料，例如包括但不限于钨(W)、钼(Mo)等。此外，形成高声阻结构G1和高声阻结构G2的材料也可以为非金属材料，例如可以包括但不限于氮化铝(ALN)或者五氧化二钽(Ta 2O 5)。当形成高声阻结构的材料为金属氧化物时，沿第二方向Y，高声阻结构G1和高声阻结构G2可以为不连续的结构，也即图3所示的结构；当形成高声阻结构的材料为非金属氧化物时，沿第二方向Y，高声阻结构G1和高声阻结构G2可以为连续的结构，也即图4所示的结构。
继续参看图3和图4，在图3和图4所示的滤波器100中，沿第一方向Z，串联谐振器20中的高声阻结构G1与并联谐振器30中的高声阻结构G2具有不同的厚度。图3和图4中示意性的示出了串联谐振器20中的高声阻结构G1的厚度大于并联谐振器30中的高声阻结构G2的厚度，在其他可能的实现方式中，并联谐振器30中的高声阻结构G2的厚度可以大于串联谐振器20中的高声阻结构G1的厚度，本申请实施例对此不做限定。
需要说明的是，本申请实施例所述的滤波器100可以应用于3G/4G等射频频段的场景中，也可以应用于5G射频频段的场景中。5G射频频段通常具有带宽大、频率高的特点。例如，5G通信协议中的BandN77射频频段，其通带频率在3.3GHz-4.2GHz之间，带宽为900MHz。在5G射频频段中，当采用薄膜体声波谐振器所组成的滤波器该单一器件时，通常无法实现上述大带宽的5G频段的滤波。也即是说，在5G射频频段中，可以采用薄膜体声波谐振器和LC谐振电路相结合的方式实现上述5G射频频段的滤波。该实现方式中，通常需要将薄膜体声波谐振器中的串联谐振器和并联谐振器，设置于上述通频带的边缘，用于实现通频带的边缘滤波。以BandN77为例，并联谐振器实现低通带边缘频率3.3GHz的滤波，串联谐振器实现高通带边缘频率4.2GHz的滤波，再配合LC谐振电路实现3.3-4.2GHz的整体滤波，可以实现通带边缘的高抑制度。这就要求薄膜体声波谐振器中的串联谐振器在频率4.2GHz附近具有较高的横波与纵波的反射性能，同样要求薄膜体声波谐振器中的并联谐振器在频率3.3GHz附近具有较高的横波与纵波反射性能。
传统滤波器中，串联谐振器40中的布拉格反射层401和并联谐振器50中的布拉格反射层501的结构相同，也即串联谐振器40中的高声阻结构4011和并联谐振器50中的高声阻结构5011沿第一方向Z的厚度相同，此外，串联谐振器40中高声阻结构4011的上表面与低声阻结构02的上表面之间的距离h1，与并联谐振器50中高声阻结构5011的上表面与低声阻结构02的上表面之间的距离h2相同，串联谐振器40中高声阻结构4011的下表面与低声阻结构02的下表面之间的距离h3，与并联谐振器50中高声阻结构5011的下表面与低声阻结构02的下表面之间的距离h4相同，如图5所示。当如图5所示的薄膜 体声波谐振器所形成的滤波器应用于5G射频频段的场景中时，基于薄膜体声波谐振器的结构和材料特性，串联谐振器40和并联谐振器50的横波透射系数以及纵波透射系数随频率变化的波形的示意图如图6所示。在图6中，横坐标为频率，其单位为(GHz)，纵坐标为透射系数，单位为(dB)。需要说明的是，透射系数越低，声波能量通过衬底泄露越低，谐振器的性能越好。从图6中可以看出，频率在3.3GHz附近时，并联谐振器50的横波透射系数在-12dB附近；频率在4.2GHz附近时，串联谐振器40的横波透射系数在-17dB附近。也即是说，当前技术中，并联谐振器50和串联谐振器40在其工作范围内均具有较高的横波透射系数。在横波高透射系数的情况下，谐振器的反射效率较低，也即谐振器的品质因数(Q，quality factor)的值较低，降低了滤波器的滤波效果。
而如图3或图4所示的滤波器100中的串联谐振器20的横波透射系数和纵波透射系数随频率变化的波形如图7a所示，并联谐振器30的横波透射系数和纵波透射系数随频率变化的波形如图7b所示。从图7a中可以看出，频率在4.2GHz附近时，串联谐振器20的横波透射系数在-20dB附近，从图7b中可以看出，频率在3.3GHz附近时，并联谐振器30的横波透射系数在-21dB附近。由此，本申请实施例所述的滤波器100中的各谐振器的横波透射系数与图5所示的滤波器中的各谐振器的横波透射系数相比，明显降低。对比图7a和图6、图7b和图6，可以看出，串联谐振器20和并联谐振器30的纵波透射系数与如图5所示的传统谐振器的纵波透射系数几乎相同。由此，本申请实施例通过将串联谐振器20中的布拉格反射层201的高声阻材料层G1与并联谐振器30的布拉格反射层302的高声阻材料层G2设置成不同的厚度，可以改变串联谐振器20和并联谐振器30的横波透射系数，从而使得各谐振器在其有效频带范围内的横波透射系数较低，提高各谐振器的反射效率，也即提高谐振器的品质因数Q值，进而提高滤波器的滤波效果。
图3和图4示意性的示出了串联谐振器20和并联谐振器30中设置有一个高声阻结构，在其他可能的实现方式中，串联谐振器20和并联谐振器30中均可以设置有多个高声阻结构，例如两个、三个等。请参考图8，其示出了串联谐振器20中的布拉格反射层201和并联谐振器30中的布拉格反射层301分别包括两个高声阻结构的示意图。
如图8所示，串联谐振器20中的布拉格反射层201包括高声阻结构G1和高声阻结构G3，并联谐振器30中布拉格反射层301包括高声阻结构G2和高声阻结构G4。其中，高声阻结构G1和高声阻G3在图8中以上下平行的方式分布，高声阻结构G1和高声阻G3之间设置有低声阻结构D。沿第一方向Z，高声阻结构G1和高声阻G3平行，且沿第一方向Z的反方向，高声阻结构G1和高声阻G3垂直于堆叠方向的尺寸(也即沿第二方向Y延伸的尺寸)自上而下逐渐增大，在整个谐振器中，尺寸越小的高声阻结构G3越靠近电极021一侧，尺寸越大的高声阻结构G1越靠近衬底10一侧，从而可以使得声音自电极021的一侧向衬底10一侧传播时，波形范围逐渐增大，从而能够与声波实现匹配，满足谐振需求。同样，布拉格反射层301中的高声阻结构G2和高声阻G4在图8中以上下平行的方式分布，高声阻结构G2和高声阻G4之间设置有低声阻结构D。沿第一方向Z，高声阻结构G2和高声阻G4平行，且沿第一方向Z的反方向，高声阻结构G2和高声阻G4垂直于堆叠方向的尺寸(也即沿第二方向Y延伸的尺寸)自上而下逐渐增大。在图8中，布拉格反射层201中的高声阻结构G1与布拉格反射层301中的高声阻结构G2沿第一方向Z具有相同的厚度，布拉格反射层201中的高声阻结构G3与布拉格反射层301 中的高声阻结构G4具有不同的厚度。其中，形成高声阻结构G3的材料、形成高声阻结构G4与形成高声阻结构G1的材料相同，具体参考图3中的相关描述，在此不再赘述。
可以理解的是，串联谐振器20中的布拉格反射层201和并联谐振器30中布拉格反射层301还可以包括第三高声阻结构、第四高声阻结构以及更多的高声阻结构，所有的高声阻结构都是埋设在低声阻结构中且沿堆叠方向相互平行，各个高声阻结构沿第二方向Y延伸的尺寸自电极021指向衬底10的方向逐渐增大。当然，任意两个高声阻结构之间均设置有低声阻结构，使得各个高声阻结构和低声阻结构呈相互交替的层状结构，方便声音在各层结构中传播反射。在包括第三高声阻结构、第四高声阻结构以及更多的高声阻结构时，串联谐振器20中最靠近电极021的高声阻结构与并联谐振器30中最靠近电极021的高声阻结构沿第一方向Z的厚度不同之外，对于串联谐振器20中其余各高声阻结构中的任一个，该高声阻结构与并联谐振器30中同层设置的高声阻结构沿第一方向Z的厚度均相同。这里的同层设置可以理解为：在布拉格反射层中的位置相同。例如，图8所示的高声阻结构G1与高声阻结构G2可以理解为同层设置，高声阻结构G3与高声阻结构G4可以理解为同层设置；当布拉格反射层201还包括位于高声阻结构G1和高声阻结构G3中间的高声阻结构G5、布拉格反射层301还包括位于高声阻结构G2和高声阻结构G4中间的高声阻结构G6时，高声阻结构G5和高声阻结构G6可以理解为同层设置(图中未示出)。
在图8中示意性的示出了滤波器100中的串联谐振器20和并联谐振器30均包括两个高声阻结构、且串联谐振器20中的靠近衬底10的高声阻结构G1与并联谐振器30中的靠近衬底10的高声阻结构G2沿第一方向Z的厚度相同的情况。在其他一些可能的实现方式中，串联谐振器20和并联谐振器30同层设置的高声阻结构沿第一方向Z的厚度均不相同。请参考图9，其示出了串联谐振器20中靠近衬底10的高声阻结构G1与并联谐振器30中靠近衬底10的高声阻结构G2沿第一方向Z的厚度不同的情况。图9中所示的各谐振器的其余结构以及所采用的材料与图2所示的各谐振器的结构以及采用的材料相同，在此不再赘述。进一步的，如图9所示，串联谐振器20中靠近电极021的高声阻结构G3沿第一方向Z的厚度，与并联谐振器30中靠近衬底10的高声阻结构G2沿第一方向Z的厚度相同；并联谐振器30中靠近电极021的高声阻结构G4沿第一方向Z的厚度与串联谐振器20中靠近衬底10的高声阻结构G1沿第一方向Z的厚度相同。
如图9所示的实施例中，除了将高声阻结构G1与高声阻结构G2沿第一方向Z设置不同的厚度外，还将高声阻结构G3与高声阻结构G4沿第一方向Z设置不同的厚度，也即串联谐振器20和并联谐振器30同层设置的高声阻结构沿第一方向Z的厚度均不相同，从而可以进一步提高谐振器的反射效率，也即进一步提高谐振器的品质因数Q值，提高滤波器的滤波效果。
从图2-图9所示的实施例中可以看出，串联谐振器20的布拉格反射层201与并联谐振器30的布拉格反射层301中，至少一层同层设置的高声阻结构沿第一方向Z的厚度不同。在其他可能的实现方式中，还可以将同层设置的高声阻结构沿第一方向Z设置相同的厚度，调整串联谐振器20中的高声阻结构在低声阻结构中的埋设位置，同时调整并联谐振器30中的高声阻结构在在低声阻结构中的埋设位置，使得串联谐振器20中的高声阻结构的上表面与低声阻结构的上表面之间的距离，与并联谐振器30中的高声阻结构的上表面与低声阻结构的上表面之间的距离不同；或者使得串联谐振器20中的高声阻结构的下 表面与低声阻结构的下表面之间的距离，与并联谐振器30中的高声阻结构的下表面与低声阻结构的下表面之间的距离不同，从而也可以降低串联谐振器20和并联谐振器30的横波透射系数，提高各谐振器的反射效率，也即提高谐振器的品质因数Q值，进而提高滤波器的滤波效果。下面结合图10所示的实施例进行详细描述。
在图10中，如图10所示的滤波器100中，串联谐振器20的布拉格反射层201包括高声阻结构G1和高声阻结构G3，高声阻结构G1设置于靠近基板10的一侧，高声阻结构G3设置于靠近电极021的一侧。并联谐振器30的布拉格反射层301包括高声阻结构G2和高声阻结构G4，高声阻结构G2设置于靠近基板10的一侧，高声阻结构G4设置于靠近电极021的一侧。其中，高声阻结构G1包括靠近电极021的上表面和远离电极021的下表面，高声阻结构G3包括靠近电极021的上表面和远离电极021的下表面。同样，高声阻结构G2包括靠近电极021的上表面和远离电极021的下表面，高声阻结构G4包括靠近电极021的上表面和远离电极021的下表面。低声阻结构D包括靠近电极021的上表面和靠近衬底10的下表面。高声阻结构G3的上表面与低声阻结构D的上表面之间具有第一距离h1，高声阻结构G3的上表面与低声阻结构D的上表面之间具有第二距离h2，其中第一距离h1与第二距离h2不同。高声阻结构G3的下表面与高声阻结构G1的上表面之间具有第三距离h5，高声阻结构G4的下表面与高声阻结构G2的上表面之间具有第四距离h6，其中第三距离h5与第四距离h6不同。
基于如上所述的各滤波器100的结构，本申请实施例还提供一种制作滤波器100的方法。该制作滤波器100的工艺流程可以参考图11所示的流程1100。该工艺流程1100包括如下步骤：
1101：提供一衬底；此处的衬底材质可以为硅。
1102：在衬底上形成第一布拉格反射层和第二布拉格反射层；其中第一布拉格反射层和第二布拉格反射层具有不同的结构。
其中，第一布拉格反射层包括第一低声阻结构和埋设于第一低声阻结构中的第一高声阻结构，第二布拉格反射层包括第二低声阻结构和埋设于第二低声阻结构中的第二高声阻结构。
在一种可能的实现方式中，第一高声阻结构和第二高声阻结构沿沉积方向的厚度不同。
在一种可能的实现方式中，第一布拉格反射层包括第一低声阻结构和埋设于第一低声阻结构中的第一高声阻结构和第三高声阻结构，第三高声阻结构形成于第一高声阻结构之上，沿堆叠方向与第一高声阻结构平行；第二布拉格反射层包括第二低声阻结构和埋设于第二低声阻结构中的第二高声阻结构和第四高声阻结构，第四高声阻结构形成于第二高声阻结构之上，沿堆叠方向与第二高声阻结构平行。第一高声阻结构和第二高声阻结构沿沉积方向的厚度不同，第三高声阻结构和第四高声阻结构沿沉积方向的厚度不同。进一步的，第一高声阻结构和第四高声阻结构沿沉积方向的厚度相同；第二高声阻结构和第三高声阻结构沿沉积方向的厚度相同。
在一种可能的实现方式中，第一高声阻结构远离衬底的表面与第一低声阻结构远离衬底的表面之间具有第一距离，第二高声阻远离衬底的表面与第二低声阻结构远离衬底的表面之间具有第二距离，该第一距离与第二距离的长度不同。
在一种可能的实现方式中，第一高声阻结构靠近衬底的表面与第一低声阻结构靠近衬 底的表面之间具有第三距离，第二高声阻靠近衬底的表面与第二低声阻结构靠近衬底的表面之间具有第四距离，该第三距离与第四距离的长度不同。
在一种可能的实现方式中，第一高声阻结构远离衬底的表面与第三高声阻结构靠近衬底的表面之间具有第五距离，第二高声阻结构远离衬底的表面与第四高声阻结构靠近衬底的表面之间具有第六距离，第五距离与第六距离的长度不同。
1103：在第一布拉格反射层和第二布拉格反射层上分别形成第一压电换能结构和第二压电换能结构。
其中，第一压电换能结构包括靠近第一布拉格反射层的第一压电层、远离第一布拉格反射层的第二压电层和位于第一压电层和第二压电层之间的薄膜层；第二压电换能结构包括靠近第二布拉格反射层的第一压电层、远离第二布拉格反射层的第二压电层和位于第一压电层和第二压电层之间的薄膜层。
从而，第一布拉格反射层和第一压电换能结构形成串联谐振器，第二布拉格反射层和第二压电换能结构形成并联谐振器。
下面以制备如图9所示的滤波器100为例，对滤波器100的制备方法进行详细描述。制备如图9所示的滤波器100的工艺流程可以参考图12所示的流程1200。该工艺流程1200包括如下步骤：
步骤1201，提供一衬底10；此处的衬底材质可以为硅。
步骤1202，在衬底上生长第一低声阻材料。该第一低声阻材料可以为半导体材料，例如可以为SiO 2。
步骤1203，在第一低声阻材料上生长第一高声阻材料。该步骤后如图13a所示。
具体实现中，第一高声阻材料可以为金属材料，包括但不限于：钨(W)、钼(Mo)。
步骤1204，在第一高声阻材料和第一低声阻材料上生长第二声阻材料，以形成高声阻结构G1和高声阻结构G2。
具体的，在第一高声阻材料和暴露出的第一低声阻材料上继续沉积第二高声阻材料，刻蚀第二高声阻材料，从而形成高声阻结构G1和高声阻结构G2。其中，沿沉积方向，高声阻结构G1的厚度大于高声阻结构G2的厚度，也即高声阻结构G1的暴露出的上表面高于高声阻结构G2的上表面。如图13b所示。
其中，可以采用干刻或者湿刻等刻蚀方法对第二高声阻材料进行刻蚀。
通过步骤1203和步骤1204可以看出，高声阻结构G1是通过两次生长高声阻材料形成的。第二高声阻材料可以与第一高声阻材料相同。
步骤1205，在暴露出的高声阻结构G1和高声阻结构G2上分别生长第二低声阻材料和第三低声阻材料，从而使得第二低声阻材料包裹高声阻结构G1暴露出的部分，第三低声阻材料同样也包裹高声阻结构G2暴露出的部分。其中，沿堆叠方向，高声阻结构G1之上生长的第二低声阻材料的厚度，与高声阻结构G2之上生长的第三低声阻材料的厚度相同。如图13c所示。
第二低声阻材料和第三低声阻材料可以为SiO2。
步骤1206，在第三低声阻材料上生长第三高声阻材料。如图13d所示。
步骤1207，在第三高声阻材料和第二低声阻材料上生长第四高声阻材料，以形成高声阻结构G3和高声阻结构G4，如图13e所示。
这里，第三高声阻材料和第四高声阻材料相同。其中，第三高声阻材料和第四高声阻材料可以为金属材料，包括但不限于：钨(W)、钼(Mo)。
从而，第二低声阻材料之上生长的第四高声阻材料形成高声阻结构G3，第三低声阻材料之上生长的第三高声阻材料和第四高声阻材料共同形成高声阻结构G4。其中，沿堆叠方向，高声阻结构G4的厚度大于高声阻结构G3的厚度。此外，还可以通过控制第三高声阻材料和第四高声阻材料的生长量和刻蚀量，使得高声阻结构G3沿堆叠方向的厚度与高声阻结构G2沿堆叠方向的厚度相同，使得高声阻结构G4沿堆叠方向的厚度与高声阻结构G1沿堆叠方向的厚度相同。
步骤1208，在高声阻结构G3、高声阻结构G4、第一低声阻材料、第二低声阻材料和第三低声阻材料暴露出的部分生长第四低声阻材料，使得第四低声阻材料包裹高声阻结构G3、高声阻结构G4、第一低声阻材料、第二低声阻材料和第三低声阻材料暴露出的部分，如图13f所示。其中，第四低声阻材料可以为SiO2。
步骤1209，平坦化第四地低声阻材料。
具体的，可以通过化学机械抛光(CMP)工艺去除多余的第四低声阻材料，从而使得第四低声阻材料暴露出的表面平坦。如图13g所示。
步骤1210，在第四低声阻材料上继续生长第五低声阻材料，以及平坦化第五低声阻材料，以形成低声阻结构D。如图13h所示。
具体的，可以通过化学机械抛光(CMP)工艺去除多余的第五低声阻材料，从而使得第五低声阻材料暴露出的表面平坦。
由此，第一低声阻材料、第二低声阻材料、第三低声阻材料、第四低声阻材料和第五低声阻材料连接在一起，形成连续的低声阻结构。此外，该连续的低声阻结构中与高声阻结构G1和高声阻结构G3层叠的部分形成布拉格反射层201，该连续的低声阻结构中与高声阻结构G2和高声阻结构G4层叠的部分形成布拉格反射层301。
步骤1211，在低声阻结构D上沉积第一金属层，形成电极021。如图13i所示。
步骤1212，在电极021上沉积压电薄膜材料，形成压电薄膜023。如图13j所示。
步骤1213，在压电薄膜023上沉积第二金属层。如图13k所示。
步骤1214，图案化第二金属层，形成相互分离的电极2022和电极3022。
具体工艺中，可以在第二金属层上形成图案化的掩膜层，以该图案化的掩膜层作为掩膜，对第二金属层进行刻蚀，未被刻蚀的部分形成电极2022和电极3022。具体可以采用干刻或湿刻等各种刻蚀方法对上述第二金属层进行刻蚀以形成电极2022和电极3022。
通过步骤1201-步骤1214所制备出的滤波器如图9所示。
其中电极2022设置于高声阻结构G1和高声阻结构G3之上，其向高声阻结构G3的正投影与高声阻结构G3至少部分重叠，电极3022设置于高声阻结构G2和高声阻结构G4之上，其向高声阻结构G4的正投影与高声阻结构G4至少部分重叠。从而，电极021、压电薄膜层023和位于高声阻结构G3之上的电极2022共同形成的压电换能结构202，电极021、压电薄膜层023和位于高声阻结构G4之上的电极3022共同形成的压电换能结构302。由此，布拉格反射层201和压电换能结构202之间形成串联谐振器20，布拉格反射层301和压电换能结构302之间形成谐振器20。
本申请实施例通过采用如图12所示的工艺步骤所制造的滤波器，可以改变串联谐振 器和并联谐振器的横波透射系数，从而使得各谐振器在其有效频带范围内的横波透射系数较低，提高各谐振器的反射效率，也即提高谐振器的品质因数Q值，进而提高滤波器的滤波效果。
在一种可能的实现方式中，上述步骤1203和步骤1204中形成高声阻结构G1和高声阻结构G2的工艺步骤还可以被如下步骤替换：
在第一低声阻材料上生长第一高声阻材料和第二高声阻材料，其中，所生长的第一高声阻材料和第二高声阻材料不连续，且第一高声阻材料的上表面与第二高声阻材料的上表面平齐；刻蚀第二高声阻材料，从而使得第一高声阻材料形成高声阻结构G1，使得刻蚀后的第二高声阻材料形成高声阻结构G2。
此外，在一种可能的实现方式中，上述步骤1206和步骤1207中形成高声阻结构G3和高声阻结构G4的工艺步骤还可以被如下步骤替换：
在第二低声阻材料上生长第三高声阻材料、在第三低声阻材料上生长第四高声阻材料，其中，所生长的第三高声阻材料和第四高声阻材料不连续，且所生长的第三高声阻材料沿堆叠方向的厚度与第四高声阻材料沿堆叠方向的厚度相同；刻蚀第三高声阻材料，从而使得刻蚀后的第三高声阻材料形成高声阻结构G3，使得第四高声阻材料形成高声阻结构G4。
本申请实施例还提供一种电子设备1400，请参照图14，该电子设备1400可以包括收发器1401、存储器1402和处理器1403，此处的收发器1401内设置有上述滤波器100，滤波器100的结构可以参照图1或图2所示例的其中一种结构。
应当理解，此处的电子设备1400可以具体为智能手机、电脑、智能手表等终端设备。将终端设备以图15所示的智能手机1510进行示例，其具体可以包括处理器15102、存储器15103、控制电路、天线以及输入输出装置。处理器15102主要用于对通信协议以及通信数据进行处理，以及对整个智能手机进行控制，执行软件程序，处理软件程序的数据，例如用于支持智能手机1510实现各种通信功能(例如打电话、发送消息或者即时聊天等)。存储器15103主要用于存储软件程序和数据。控制电路主要用于基带信号与射频信号的转换以及对射频信号的处理，控制电路则包括有上述滤波器100。控制电路和天线一起也可以叫做收发器15101，主要用于收发电磁波形式的射频信号。输入输出装置，例如触摸屏、显示屏，键盘等主要用于接收用户输入的数据以及对用户输出数据。
当上述智能手机1510开机后，处理器15102可以读取存储器15103的软件程序，解释并执行软件程序的指令，处理软件程序的数据。当需要通过无线发送数据时，处理器15102对待发送的数据进行基带处理后，输出基带信号至射频电路，射频电路将基带信号进行射频处理后将射频信号通过天线以电磁波的形式向外发送。当有数据发送到智能手机1510时，射频电路通过天线接收到射频信号，将射频信号转换为基带信号，并将基带信号输出至处理器15102，处理器15102将基带信号转换为数据并对该数据进行处理。
本领域技术人员可以理解，为了便于说明，图15仅示出了一个存储器和一个处理器。在实际的终端设备中，可以存在多个处理器和多个存储器。存储器也可以称为存储介质或者存储设备等。需要说明的是，本申请实施例对存储器的类型不做限定。
以上，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (15)

  1. 一种滤波器，其特征在于，包括：
    衬底；
    串联谐振器，所述串联谐振器包括依次堆叠于所述衬底之上的第一布拉格反射层和第一压电换能结构；
    并联谐振器，所述并联谐振器包括依次堆叠于所述衬底之上的第二布拉格反射层和第二压电换能结构，所述第一布拉格反射层的结构与所述第二布拉格反射层的结构不同；
    串联支路，所述串联支路包括所述串联谐振器，所述串联支路耦合于所述滤波器输入端和所述滤波器输出端之间；
    并联支路，所述并联支路包括所述并联谐振器，所述并联支路耦合于所述串联支路与公共地之间。
  2. 根据权利要求1所述的滤波器，其特征在于，
    所述滤波器还包括用于形成所述第一布拉格反射层和所述第二布拉格反射层的低声阻结构；
    所述第一布拉格反射层包括埋设于所述低声阻结构中的第一高声阻结构；
    所述第二布拉格发射层包括埋设于所述低声阻结构中的第二高声阻结构；
    沿堆叠方向，所述第一高声阻结构的厚度与所述第二高声阻结构的厚度不同。
  3. 根据权利要求2所述的滤波器，其特征在于，
    所述低声阻结构堆叠于所述衬底的表面；
    所述滤波器还包括用于形成所述第一压电换能结构和所述第二压电换能结构的第一电极和薄膜结构，所述第一电极和所述薄膜结构依次堆叠于所述低声阻结构远离所述衬底的表面；
    所述第一压电换能结构还包括第二电极，所述第二压电换能结构还包括第三电极；
    所述第一电极和所述第二电极均设置于所述薄膜结构远离所述衬底的表面。
  4. 根据权利要求2或3所述的滤波器，其特征在于，
    沿所述堆叠方向，所述第一高声阻结构包括远离所述衬底的第一表面，所述低声阻结构包括远离所述衬底的第一表面，所述第一高声阻结构的第一表面与所述低声阻结构的第一表面之间具有第一距离；
    沿所述堆叠方向，所述第二高声阻结构包括远离所述衬底的第一表面，所述第二高声阻结构的第一表面与所述低声阻结构的第一表面之间具有第二距离；
    其中，所述第一距离和所述第二距离不同。
  5. 根据权利要求2-4任一项所述的滤波器，其特征在于，
    所述第一布拉格反射层还包括埋设于所述低声阻结构中的第三高声阻结构，沿所述堆叠方向，所述第三高声阻结构平行设置于所述第一高声阻结构远离所述衬底的一侧、且与所述第一高声阻结构之间设置有所述低声阻结构；
    所述第二布拉格反射层还包括埋设于所述低声阻结构中的第四高声阻结构，沿所述堆叠方向，所述第四高声阻结构平行设置于所述第二高声阻结构远离所述衬底的一侧、且与所述第二高声阻结构之间设置有所述低声阻结构；
    沿所述堆叠方向，所述第三高声阻结构的厚度与所述第四高声阻结构的厚度不同。
  6. 根据权利要求5所述的滤波器，其特征在于，
    沿所述堆叠方向，所述第一高声阻结构的厚度与所述第四高声阻结构的厚度相同；
    沿所述堆叠方向，所述第二高声阻结构的厚度与所述第三高声阻结构的厚度相同。
  7. 根据权利要求5或6所述的滤波器，其特征在于，
    沿所述堆叠方向，所述第三高声阻结构包括远离所述衬底的第一表面，所述低声阻结构包括远离所述衬底的第一表面，所述第三高声阻结构的第一表面与所述低声阻结构的第一表面之间具有第三距离；
    沿所述堆叠方向，所述第四高声阻结构包括远离所述衬底的第一表面，所述第四高声阻结构的第一表面与所述低声阻结构的第一表面之间具有第四距离；
    所述第三距离与所述第四距离不同。
  8. 根据权利要求5-7任一项所述的滤波器，其特征在于，
    沿所述堆叠方向，所述第三高声阻结构包括靠近所述衬底的第二表面，所述第一高声阻结构包括远离所述衬底的第一表面，所述第三高声阻结构的第二表面与所述第一高声阻结构的第一表面之间具有第五距离；
    沿所述堆叠方向，所述第四高声阻结构包括靠近所述衬底的第二表面，所述第二高声阻结构包括远离所述衬底的第一表面，所述第四高声阻结构的第二表面与所述第二高声阻结构的第一表面之间具有第六距离；
    所述第五距离和所述第六距离不同。
  9. 根据权利要求2-8任一项所述的滤波器，其特征在于，
    所述第一高声阻结构包括靠近所述衬底的第二表面，所述低声阻结构包括靠近所述衬底的第二表面，所述第一高声阻结构的第二表面与所述低声阻结构的第二表面之间具有第七距离；
    所述第二高声阻结构包括靠近所述衬底的第二表面，所述第二高声阻结构的第二表面与所述低声阻结构的第二表面之间具有第八距离；
    所述第七距离和所述第八距离不同。
  10. 根据权利要求2-9任一项所述的滤波器，其特征在于，所述低声阻结构的材料包括以下之一：二氧化硅或者氮化硅。
  11. 根据权利要求5-8任一项所述的滤波器，其特征在于，所述第一高声阻结构、所述第二高声阻结构、所述第三高声阻结构和所述第四高声阻结构的材料包括以下之一：钨、钼、氮化铝或者五氧化二钽。
  12. 一种电子设备，其特征在于，所述电子设备包括收发机，所述收发机包括如权利要求1-11任一项所述的滤波器。
  13. 根据权利要求12所述的电子设备，其特征在于，所述电子设备还包括电路板，所述收发机设置于所述电路板。
  14. 一种滤波器的制备方法，其特征在于，包括：
    提供一衬底；
    在所述衬底上堆叠第一布拉格反射层和第二布拉格反射层；
    在所述第一布拉格反射层上堆叠第一压电换能结构，在所述第二布拉格反射层上堆叠 第二压电换能结构；其中，
    所述第一布拉格发射层和所述第二布拉格反射层的结构不同。
  15. 根据权利要求14所述的制备方法，其特征在于，所述在所述衬底上堆叠第一布拉格反射层和第二布拉格反射层，包括：
    在所述衬底上沉积低声阻材料以形成第一低声阻层；
    在所述第一低声阻层的表面沉积高声阻材料；
    图案化所述高声阻材料以形成第一高声阻结构和第二高声阻结构，所述第一高声阻结构和所述第二高声阻结构沿沉积方向的厚度不同；
    在所述第一高声阻结构和所述第二高声阻结构的表面沉积低声阻材料以形成第二低声阻层，所述第二低声阻层与所述第一低声阻层具有一体式结构以形成低声阻结构。
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