WO2020019246A1 - 体声波谐振器及其制作方法、滤波器 - Google Patents

体声波谐振器及其制作方法、滤波器 Download PDF

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WO2020019246A1
WO2020019246A1 PCT/CN2018/097237 CN2018097237W WO2020019246A1 WO 2020019246 A1 WO2020019246 A1 WO 2020019246A1 CN 2018097237 W CN2018097237 W CN 2018097237W WO 2020019246 A1 WO2020019246 A1 WO 2020019246A1
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acoustic wave
wave resonator
reflection unit
bulk acoustic
piezoelectric
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PCT/CN2018/097237
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English (en)
French (fr)
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李平
王伟
胡念楚
贾斌
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开元通信技术（厦门）有限公司
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Priority to PCT/CN2018/097237 priority Critical patent/WO2020019246A1/zh
Priority to US16/614,200 priority patent/US11336258B2/en
Publication of WO2020019246A1 publication Critical patent/WO2020019246A1/zh

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    • 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
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/13—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials
    • H03H9/131—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials consisting of a multilayered structure
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/0211—Means for compensation or elimination of undesirable effects of reflections
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/02125—Means for compensation or elimination of undesirable effects of parasitic elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02157—Dimensional parameters, e.g. ratio between two dimension parameters, length, width or thickness
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/205—Constructional features of resonators consisting of piezoelectric or electrostrictive material having multiple resonators
    • 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

Definitions

  • the present disclosure relates to the technical field of radio frequency chips, and in particular, to a bulk acoustic wave resonator, a manufacturing method thereof, and a filter.
  • SAW Surface Acoustic Wave Filter
  • BAW Film Bulk Acoustic Wave Filter
  • Bulk acoustic wave filters have been widely used in 4G communications due to their lower insertion loss, better roll-off characteristics, lower temperature coefficient, and greater power capability.
  • mobile communication data transmission speed is getting faster and faster, and spectrum resources are becoming more and more crowded.
  • the filter requires a wider bandwidth; on the other hand, the filter needs better roll-off characteristics and lower insertion loss.
  • the operating frequency of a bulk acoustic wave filter is inversely proportional to the thickness of the film, so at high frequencies, the electrodes of the bulk acoustic wave filter will become thinner and thinner, which will cause the connection resistance to increase, which will affect the bulk acoustic wave filter. Insertion loss, therefore, it is important to reduce the connection resistance of the bulk acoustic wave filter.
  • a bulk acoustic wave resonator is a basic unit constituting a bulk acoustic wave filter. Its basic structure includes a piezoelectric film, bottom and top electrodes sandwiched on both sides of the piezoelectric film, and an acoustic reflection unit located below the bottom electrode. The overlapping area between the acoustic reflection unit, the bottom electrode, the top electrode, and the piezoelectric film forms an effective area for the operation of the bulk acoustic wave resonator. When an RF signal is applied between the electrodes, the piezoelectric film will vibrate due to the inverse piezoelectric effect and generate sound waves.
  • the sound waves propagate in a direction perpendicular to the surface of the electrode and are reflected at the upper and lower interfaces.
  • the frequency of the applied radio frequency signal is the same as the frequency of the resonator of the piezoelectric film, the radio frequency signal can pass through to achieve the filtering effect.
  • the thin film piezoelectric resonator includes: a substrate E, an acoustic reflection structure D, a lower electrode B, a piezoelectric layer P, an upper electrode T, and a connection structure C.
  • the overlapping portion of the upper electrode T, the piezoelectric layer P, the lower electrode B, and the acoustic reflection structure D is defined as an effective area A of the thin film piezoelectric resonator.
  • the upper electrode T includes a portion T1 and a lead-out portion T2 in the effective area, as shown in FIG. 1.
  • the added connection structure C of the resonator is located outside the effective area of the resonator operation (d is greater than or equal to 0.1 um), and the resistance of the signal through the electrode terminal is not reduced, so the connection resistance of the resonator cannot be effectively reduced.
  • US20170346462A1 discloses a method for manufacturing a bulk acoustic wave resonator.
  • the bulk acoustic wave resonator 70 includes a substrate 71, a bottom electrode 72, a bottom electrode thickness increasing layer 73, an additional metal member 74, a PZ material layer 75, a first
  • the top electrode 76 and the second top electrode 77 are shown in FIG. 2.
  • the method for manufacturing a bulk acoustic wave resonator can prevent the bottom electrode from being etched too thin during the etching of the contact hole of the piezoelectric film to affect the electrical connection.
  • the added extra metal is distributed outside the effective area of the resonator.
  • the bottom electrode resistance cannot be lowered, and because the bottom electrode and the top electrode of the bulk acoustic wave resonator are generally close in thickness in the design of a bulk acoustic wave filter, the top electrode still has a large resistance.
  • the existing bulk acoustic wave resonator has the following technical defects: Although the connection resistance is reduced to a certain extent, the connection resistance is still large, which affects the performance of the final bulk acoustic wave filter such as insertion loss. As the operating frequency becomes higher, The electrode thickness of a bulk acoustic wave resonator will become thinner and thinner, and the resistance will become larger and larger. The above-mentioned effects will be more pronounced in high-frequency bulk acoustic wave resonators and filters.
  • the present disclosure provides a bulk acoustic wave resonator, a manufacturing method thereof, and a filter, so as to at least partially solve the technical problems mentioned above.
  • a bulk acoustic wave resonator including:
  • the pad and the acoustic reflection unit have an overlapping area.
  • the piezoelectric stack structure includes:
  • a piezoelectric film on the bottom electrode A piezoelectric film on the bottom electrode
  • a top electrode on the piezoelectric film is A top electrode on the piezoelectric film.
  • the piezoelectric stacked structure further includes a conductive film, and the conductive film and the acoustic reflection unit have an overlapping area above or below the bottom electrode.
  • a contact hole is formed above the conductive film and the piezoelectric film, and the bulk acoustic wave resonator further includes another pad formed at the contact hole and in contact with the conductive film or the bottom electrode.
  • a filter including a plurality of the bulk acoustic wave resonators cascaded.
  • a method for manufacturing a bulk acoustic wave resonator including:
  • the pad and the acoustic reflection unit have an overlapping area.
  • the step of forming a piezoelectric stack structure on the acoustic reflection unit includes:
  • a top electrode is formed on the piezoelectric film.
  • the method before or after the step of forming the bottom electrode, the method further includes: forming a conductive film; the conductive film and the acoustic reflection unit have an overlapping area.
  • the bulk acoustic wave resonator, the manufacturing method thereof, and the filter of the present disclosure have at least one of the following beneficial effects:
  • the pad is extended into the effective area of the bulk acoustic wave resonator, and the electrodes of the bulk acoustic wave resonator bottom electrode and top electrode connection circuit are added.
  • the thickness effectively reduces the connection resistance of the bulk acoustic wave resonator, and can further reduce the insertion loss of filters and duplexers formed by cascading the resonator.
  • a discontinuous region of acoustic impedance is formed at the edge of the effective region of the bulk acoustic wave resonator, so that the acoustic wave energy leaked to the edge can be formed Reflection improves the figure of merit of a bulk acoustic resonator.
  • FIG. 1 is a schematic structural diagram of a conventional bulk acoustic wave resonator.
  • FIG. 2 is another schematic structural diagram of a conventional bulk acoustic wave resonator.
  • FIG. 3 is a top view of a bulk acoustic wave resonator according to an embodiment of the present disclosure.
  • FIG. 4 is a cross-sectional view of FIG. 3 along line 1A-1A.
  • 5A to 5H are flowcharts of manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.
  • FIG. 6 is a cross-sectional view of a bulk acoustic wave resonator according to another embodiment of the present disclosure.
  • FIGS. 7A to 7H are flowcharts of manufacturing a bulk acoustic wave resonator according to another embodiment of the present disclosure.
  • FIG. 8 is a schematic diagram of a filter structure of the present disclosure.
  • the present disclosure proposes a bulk acoustic wave resonator including:
  • the pad and the acoustic reflection unit have an overlapping area.
  • the bulk acoustic wave resonator includes:
  • the isolation layer may be selectively etched together when the bottom electrode is etched, or may be selectively not etched.
  • the bottom electrode 204 may be partially or completely covered on the acoustic reflection unit 202, and the piezoelectric film 205 is covered on the entire bottom electrode 204 except for the position of the contact hole 207.
  • the pads 208a and 208b are in contact with the top electrode 206 and the conductive film 209, respectively.
  • the conductive film 209 is covered on the bottom electrode 204 except for the connection terminal of the top electrode 206 (the end in contact with the pad 208a) and the bottom electrode 204 except for the M region shown in the figure, and is non-connected to the top electrode. edge) (the end that is not in contact with the pad 208a) has an overlapping area.
  • the width of the overlapping area of the conductive film 209 and the acoustic reflection unit 202 is d3, and the distance between the non-lead end of the top electrode 206 and the acoustic reflection unit 202 (the end of the acoustic reflection unit 202 away from the one pad 208a) is d4.
  • the pad 208a is in contact with the top electrode 206 and extends to overlap the acoustic reflection unit 202.
  • the electrode thickness of the connection circuit between the bottom electrode and the top electrode is increased, thereby effectively reducing the connection resistance of the bulk acoustic wave resonator; on the other hand, in the body An acoustic impedance discontinuity region is formed at the edge of the effective region of the acoustic wave resonator, and the sound wave energy leaked from the edge can form a better reflection, thereby improving the quality factor of the bulk acoustic wave resonator.
  • the material of the conductive film 209 can be the same as the electrodes 204 and 206 of the bulk acoustic wave resonator, such as molybdenum (Mo), tungsten (W), ruthenium (Ru), iridium (Ir), etc .; it can also be different, such as using resistivity. Small gold (Au), platinum (Pt), copper (Cu), aluminum (Al), graphene (Graphene), carbon nanotube (CNT), etc.
  • the method for manufacturing the bulk acoustic wave resonator includes:
  • An acoustic reflection unit 202 is produced. Specifically, an acoustic reflection unit 202 is formed on the substrate; wherein a Bragg reflection layer can be formed by alternately stacking materials with different acoustic impedances directly on the front surface of the substrate to form the acoustic reflection unit; Forming a groove in the substrate, filling the groove with a sacrificial material, and performing chemical mechanical polishing (CMP) to make the surface of the sacrificial material flush with the surface of the substrate, An acoustic reflection unit is formed; this embodiment is the latter; as shown in FIG. 5A.
  • CMP chemical mechanical polishing
  • an isolation layer 203 is formed on the acoustic reflection unit, and a bottom electrode 204 is formed on the isolation layer, as shown in FIG. 5B.
  • a conductive thin film 209 is deposited and patterned.
  • a stripping process is used: a pattern of 209 is made using a photolithography process (without a photoresist at the 209 position), a conductive film is deposited, and the conductive film on the photoresist and the photoresist is removed to form a conductive film 209, as shown in FIG. 5C.
  • the bottom electrode 204 is patterned, as shown in FIG. 5D.
  • a piezoelectric film 205 is deposited. Specifically, a piezoelectric film 205 is formed on the conductive thin film, as shown in FIG. 5E.
  • the top electrode 206 is deposited and patterned, as shown in FIG. 5F.
  • the pads 208a and 208b are fabricated.
  • the pad 208a is on the top electrode, and the pad 208b is at the contact hole, as shown in FIG. 5H.
  • the structure of the bulk acoustic wave resonator is shown in FIG. 6, and there is an acoustic reflection unit 302 on the substrate 301, and an isolation layer / support layer 303 and an isolation layer / There is a bottom electrode 304 on the support layer 303.
  • the bottom electrode 304 is partially or completely covered on the 302.
  • the bottom electrode 304 is covered by a piezoelectric film 305.
  • the piezoelectric film 305 covers the entire bottom electrode 304 except for the contact hole 307.
  • the top electrode 306 is partially covered on the piezoelectric film 305, and the pads 308a and 308b are in contact with the top electrode 306 and the bottom electrode 304, respectively.
  • the bulk acoustic wave resonator further includes a conductive film 309 under the bottom electrode 304.
  • the conductive film 309 is located on the bottom electrode 304 except for the top end of the top electrode 306 (the end in contact with the pad 308a) and the M area shown in the figure. under.
  • the width of the conductive film 309 and 302 overlap is d3 '
  • the distance between the non-lead-out end of the top electrode 306 and the acoustic reflection unit 302 is d4'
  • the width of the overlap of the conductive film 309 and the top electrode 306 is d5 '
  • d3' d4 ' + d5 '
  • ⁇ is an equivalent wavelength of the bulk acoustic wave resonator
  • k 1 is an odd number.
  • the pad 308a is in contact with the top electrode 306 and extends to overlap the acoustic reflection unit 302.
  • the material of the conductive film 309 can be the same as the electrodes 304 and 306 of the bulk acoustic wave resonator, such as molybdenum (Mo), tungsten (W), ruthenium (Ru), iridium (Ir), etc .; it can also be different, such as using resistivity Small gold (Au), platinum (Pt), copper (Cu), aluminum (Al), graphene (Graphene), carbon nanotube (CNT), etc.
  • the method for manufacturing the bulk acoustic wave resonator includes:
  • the acoustic reflection unit 302 is manufactured, as shown in FIG. 7A.
  • an etching process or a peeling process may be specifically used.
  • a piezoelectric film 305 is deposited, as shown in FIG. 7E.
  • the top electrode 306 is deposited and patterned, as shown in FIG. 7F.
  • the piezoelectric film is etched to open the contact hole 307, as shown in FIG. 7G.
  • the conductive film in this embodiment is under the bottom electrode, while in the previous embodiment, the conductive film is on the bottom electrode, the rest is the same as in the previous embodiment.
  • the present disclosure also provides a filter including a plurality of the aforementioned bulk acoustic wave resonators 2 cascaded.
  • the bulk acoustic wave resonator may not include an isolation layer.
  • the bulk acoustic wave resonator may further include a passivation layer, which covers all areas where the top electrode is not contacted by the pad, and all areas where the bottom electrode is not covered by the pad and the piezoelectric film.
  • the shape of the effective region of the bulk acoustic wave resonator may be a square, a rectangle, an irregular polygon, a circle, or an ellipse.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

一种体声波谐振器及其制作方法、滤波器，其中，该体声波谐振器包括：一衬底（201）；在所述衬底（201）上的一声反射单元（202）；在所述声反射单元（202）上的一压电堆叠结构；以及在所述压电堆叠结构上的一焊盘（208a）；其中，所述焊盘（208a）与所述声反射单元（202）具有一重叠区域。该体声波谐振器及其制作方法、滤波器，有效降低了体声波谐振器的连接电阻，进而能够降低滤波器的插入损耗。

Description

体声波谐振器及其制作方法、滤波器 技术领域
本公开涉及射频芯片技术领域，尤其涉及一种体声波谐振器及其制作方法、滤波器。
背景技术
声表面波滤波器(Surface Acoustic Wave Filter，SAW)和薄膜体声波滤波器(Film Bulk Acoustic Wave Filter，BAW)是目前智能手机射频滤波器采用的两种重要技术。
随着4G(the 4th Generation mobile communication technology)/LTE(Long Term Evolution)多频段智能手机的普及，以及5G(the 5th Generation mobile communication technology)的试运行，移动通信频率越来越高，带宽越来越宽，对射频滤波器的性能要求越来越高。
体声波滤波器因其具有更低的插入损耗、更好的滚降特性、较低的温度系数、更大的功率承受能力，在4G通信中得到了广泛的应用。但随着5G的试运行，移动通信数据传输速度越来越快，而频谱资源越来越拥挤。这一方面要求滤波器需要有更宽的带宽，另一方面，需要滤波器具有更好的滚降特性、更低的插入损耗。而体声波滤波器的工作频率与薄膜的厚度成反比，因此在高频下，体声波滤波器的电极会越来越薄，电极变薄会导致连接电阻变大，从而影响体声波滤波器的插入损耗，因此，降低体声波滤波器的连接电阻具有重要意义。
体声波谐振器是构成体声波滤波器的基本单元，其基本结构包含一层压电膜、夹持在压电膜两侧的底电极和顶电极，以及位于底电极下方的声反射单元。声反射单元、底电极、顶电极以及压电膜之间的重叠区域，形成了体声波谐振器工作的有效区。当在电极之间施加射频信号时，压电膜因逆压电效应会产生振动，产生声波，声波在垂直于电极表面的方向传播， 并且在上下界面处发生反射。当施加的射频信号频率与压电膜的谐振器频率相同时，射频信号可以通过，从而达到滤波的作用。
CN103166596A号中国专利公开了一种谐振器和滤波器，其中，薄膜压电谐振器包括：基底E，声反射结构D，下电极B，压电层P，上电极T以及连接结构C。上电极T、压电层P、下电极B以及声反射结构D的重叠部分定义为薄膜压电谐振器的有效区域A。上电极T包括在有效区域的部分T1和引出部分T2，如图1所示。该谐振器增加的连接结构C，位于谐振器工作的有效区域之外(d大于或等于0.1um)，而信号通过电极端的电阻并未减小，因此，无法有效降低谐振器的连接电阻。
US20170346462A1号美国专利公开了一种体声波谐振器制造方法，所述体声波谐振器70包括基板71，底电极72，底电极厚度增加层73，附加的金属部件74，PZ材料层75，第一顶电极76，第二顶电极77，如图2所示。该体声波谐振器制造方法可以避免压电膜接触孔刻蚀时底电极被刻蚀太薄影响电连接，但其增加的额外金属分布在谐振器有效区以外，因此，额外金属与有效区之间的底电极电阻无法被降低，并且，因为通常体声波滤波器的设计中，体声波谐振器的底电极和顶电极具有接近的厚度，因此，顶电极依然存在较大的电阻。
综上，现有体声波谐振器存在如下技术缺陷：虽然在一定程度上降低了连接电阻，但连接电阻仍然较大，影响最终体声波滤波器的插入损耗等性能，随着工作频率变高，体声波谐振器的电极厚度会越来越薄，电阻会越来越大，上述影响在高频体声波谐振器、滤波器中更为明显。
发明内容
(一)要解决的技术问题
本公开提供了一种体声波谐振器及其制作方法、滤波器，以至少部分解决以上所提出的技术问题。
(二)技术方案
根据本公开的一个方面，提供了一种体声波谐振器，包括：
一衬底；
在所述衬底上的一声反射单元；
在所述声反射单元上的一压电堆叠结构；以及
在所述压电堆叠结构上的一焊盘；其中，
所述焊盘与所述声反射单元具有一重叠区域。
在一些实施例中，所述压电堆叠结构包括：
一底电极；
在所述底电极上的一压电膜；以及
在所述压电膜上的一顶电极。
在一些实施例中，所述压电堆叠结构还包括导电薄膜，在所述底电极上方或所述底电极下方，所述导电薄膜与所述声反射单元具有一重叠区域。
在一些实施例中，所述顶电极与所述导电薄膜具有一宽度为d5的重叠区域；所述导电薄膜与所述声反射单元的重叠区域的宽度为d3；所述顶电极非引出端与所述声反射单元的距离为d4；d3＝d4+d5，d4≥0，d5＝k 1λ/4，其中，λ为所述体声波谐振器等效波长，k 1为奇数。
在一些实施例中，在所述顶电极引出端，所述一焊盘与顶电极接触，并且所述焊盘与所述声反射单元的重叠区域的宽度为d6，d6＝k 2λ/4，其中，λ为所述体声波谐振器等效波长，k 2为奇数，且k 1≥k 2；
在所述导电薄膜上方、所述压电膜形成有一接触孔，所述体声波谐振器还包括另一焊盘，形成于所述接触孔处，与所述导电薄膜或者底电极接触。
根据本公开的另一个方面，提供了一种滤波器，其包括级联的多个所述体声波谐振器。
根据本公开的另一个方面，提供了一种体声波谐振器的制作方法，包括：
在一衬底上形成一声反射单元；
在所述声反射单元上形成一压电堆叠结构；以及
在所述压电堆叠结构上制作一焊盘；其中，
所述焊盘与所述声反射单元具有一重叠区域。
在一些实施例中，在所述声反射单元上形成一压电堆叠结构的步骤包括：
在所述声反射单元上形成一底电极；
在所述底电极上的形成一压电膜；以及
在所述压电膜上形成一顶电极。
在一些实施例中，在形成底电极的步骤之前或之后，还包括：形成一导电薄膜；该导电薄膜与所述声反射单元具有一重叠区域。
在一些实施例中，所述顶电极与所述导电薄膜具有一宽度为d5的重叠区域；所述导电薄膜与所述声反射单元的重叠区域的宽度为d3；所述顶电极非引出端与所述声反射单元的距离为d4；d3＝d4+d5，d4≥0，d5＝k 1λ/4，其中，λ为所述体声波谐振器等效波长，k 1为奇数；
所述焊盘与声反射单元的重叠区域的宽度为d6，d6＝k 2λ/4，其中，λ为体声波谐振器等效波长，k 2为奇数，且k 1≥k 2。
(三)有益效果
从上述技术方案可以看出，本公开体声波谐振器及其制作方法、滤波器至少具有以下有益效果其中之一：
(1)本公开通过引入导电薄膜，及焊盘与声反射单元具有重叠区域，将焊盘延伸至体声波谐振器的有效区域内，增加了体声波谐振器底电极和顶电极连接电路的电极厚度，有效降低了体声波谐振器的连接电阻，进而能够降低用该谐振器级联形成的滤波器、双工器的插入损耗。
(2)本公开通过各重叠区域宽度及顶电极非引出端与声反射单元的距离的设置，在体声波谐振器有效区的边缘形成声阻抗不连续区域，从而可以对边缘泄露的声波能量形成反射，提升体声波谐振器的品质因数。
附图说明
为了更清楚地说明本公开实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简要介绍，显而易见地，下面描述中的附图仅仅是本公开的一些实施例，对于本领域的普通技术人员来讲，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现有体声波谐振器的结构示意图。
图2现有体声波谐振器的另一结构示意图。
图3所示为本公开一实施例体声波谐振器俯视图。
图4所示为图3沿1A-1A线的截面图。
图5A～5H所示为本公开一实施例体声波谐振器制作流程图。
图6所示为本公开另一实施例体声波谐振器的截面图。
图7A～7H所示为本公开另一实施例体声波谐振器制作流程图。
图8所示为本公开滤波器结构示意图。
具体实施方式
为使本公开的目的、技术方案和优点更加清楚明白，以下结合具体实施例，并参照附图，对本公开进一步详细说明。
具体实施例及附图仅用于更好理解本公开的内容而非限制本公开的保护范围。实施例附图的结构中各组成部分非按正常比例缩放，故不代表实施例中各结构的实际相对大小。
本公开提出了一种体声波谐振器，包括：
一衬底；
在所述衬底上的一声反射单元；
在所述声反射单元上的一压电堆叠结构；以及
在所述压电堆叠结构上的一焊盘；其中，
所述焊盘与所述声反射单元具有一重叠区域。
在一具体实施例中，请结合图3和4所示，该体声波谐振器包括：
衬底201；
形成于所述衬底上的一声反射单元202；其中，可直接在所述衬底的前表面利用声阻抗不同的材料交替堆叠制作布拉格反射层，从而形成所述声反射单元；也可以刻蚀所述衬底，在衬底上形成一凹槽，在所述凹槽内填充牺牲材料，再进行化学机械抛光(Chemical Mechanical Polish，CMP)，使牺牲材料表面与所述衬底的表面齐平，从而形成所述声反射单元；本实施例为后者；
形成于所述声反射单元上的隔离层/支撑层203；其中，该隔离层可完整覆盖所述衬底及声反射单元的前表面，或者只部分覆盖在所述衬底的前表面，即所述隔离层可选择性的在底电极刻蚀的时候一起被刻蚀，也可以选择性的不刻蚀。
形成于所述隔离层上的底电极204；其中，所述底电极部分覆盖所述 隔离层的前表面，或者全部覆盖所述隔离层的前表面；
形成于所述底电极上的导电薄膜209；其中，所述导电薄膜部分覆盖所述底电极的前表面；
形成于所述导电薄膜上的压电膜205；其中，刻蚀所述压电膜，在压电膜上形成一接触孔207，该接触孔形成于所述导电薄膜上方；
形成于所述压电膜上的顶电极206，所述顶电极206部分覆盖所述压电膜；以及
在所述顶电极上的一焊盘208a和在所述接触孔207处的另一焊盘208b。
请进一步参照图4所示，底电极204可部分或全部覆盖在声反射单元202之上，压电膜205覆盖在除接触孔207位置之外的整个底电极204上。焊盘208a和208b分别与顶电极206、导电薄膜209接触。所述导电薄膜209覆盖在除了顶电极206引出端(connect edge)(与焊盘208a接触的一端)及图示M区域以外的底电极204上，并且与顶电极的非引出端(non-connect edge)(不与焊盘208a接触的一端)具有一个重叠区域。
导电薄膜209与声反射单元202重叠区域的宽度为d3，顶电极206非引出端距离声反射单元202(声反射单元202远离所述一焊盘208a的一端)的距离为d4，导电薄膜209与顶电极206的重叠区域的宽度为d5，其中，d3＝d4+d5，d4≥0，d5＝k 1λ/4，λ为所述体声波谐振器等效波长，k 1为奇数。在所述顶电极引出端，焊盘208a与顶电极206接触，并且延伸至与声反射单元202重叠，重叠区域宽度为d6，d6＝k 2λ/4，其中，λ为体声波谐振器等效波长，k 2为奇数，且k 1≥k 2。由此，在不影响有效工作区域面积的同时，一方面增加了底电极和顶电极连接电路的电极厚度，从而有效降低了所述体声波谐振器的连接电阻；另一方面，在所述体声波谐振器有效区的边缘形成声阻抗不连续区域，对边缘泄露的声波能量可形成较好的反射，从而提升了所述体声波谐振器的品质因数。
导电薄膜209的材料可以与体声波谐振器的电极204，206相同，如采用钼(Mo)、钨(W)、钌(Ru)、铱(Ir)等；也可以不同，如采用电阻率更小的金(Au)、铂(Pt)、铜(Cu)、铝(Al)、石墨烯(Graphene)、碳纳米管(CNT)等。
在本实施例中，还提出了一种制作本实施例上述体声波谐振器的方法，请结合图5A～5H所示，该体声波谐振器的制作方法包括：
S1，制作声反射单元202。具体的，在所述衬底上形成一声反射单元202；其中，可直接在所述衬底的前表面利用声阻抗不同的材料交替堆叠制作布拉格反射层，形成声反射单元；也可以刻蚀所述衬底，在衬底上形成一凹槽，在所述凹槽内填充牺牲材料，再进行化学机械抛光(Chemical Mechanical Polish，CMP)，使牺牲材料表面与所述衬底的表面齐平，形成声反射单元；本实施例为后者；如图5A所示。
S2，沉积隔离层203及底电极204。具体的，在所述声反射单元上形成隔离层203，在所述隔离层上形成底电极204，如图5B所示。
S3，沉积并图形化导电薄膜209。优选的，采用剥离工艺：利用光刻工艺制作出209的图形(209位置无光阻覆盖)，沉积一层导电薄膜，以及去除光阻及光阻上的导电薄膜，形成导电薄膜209，如图5C所示。
S4，图形化底电极204，如图5D所示。
S5，沉积压电膜205。具体的，在所述导电薄膜上形成压电膜205，如图5E所示。
S6，沉积并图形化顶电极206，如图5F所示。
S7，刻蚀压电膜打开接触孔207，如图5G所示。
S8，制作焊盘208a及208b。焊盘208a在所述顶电极上，焊盘208b在所述接触孔处，如图5H所示。
在另一具体实施例中，所述体声波谐振器的结构如图6所示，在衬底301之上有声反射单元302，声反射单元302之上有隔离层/支撑层303，隔离层/支撑层303之上有底电极304，底电极304部分或全部覆盖在302之上，底电极304之上有压电膜305，压电膜305中除接触孔307外，覆盖整个底电极304，顶电极306部分覆盖在压电膜305之上，焊盘308a和308b分别与顶电极306、底电极304接触。所述体声波谐振器还包括位于底电极304之下的导电薄膜309，该导电薄膜309位于在除了顶电极306引出端(与焊盘308a接触的一端)及图示M区域以外的底电极304之下。
导电薄膜309与302重叠的宽度为d3’，顶电极306非引出端距离声反射单元302的距离为d4’，导电薄膜309与顶电极306的重叠宽度为d5’， 其中，d3’＝d4’+d5’，d4’≥0，d5’＝k 1λ/4，λ为所述体声波谐振器等效波长，k 1为奇数。
在所述顶电极引出端，焊盘308a与顶电极306接触，并且延伸至与声反射单元302重叠，重叠区域宽度为d6’，d6’＝k 2λ/4，其中，λ为体声波谐振器等效波长，k 2为奇数，且k 1≥k 2。
导电薄膜309的材料可以与体声波谐振器的电极304，306相同，如采用钼(Mo)、钨(W)、钌(Ru)、铱(Ir)等；也可以不同，如采用电阻率更小的金(Au)、铂(Pt)、铜(Cu)、铝(Al)、石墨烯(Graphene)、碳纳米管(CNT)等。
在本实施例中，还提出了一种制作本实施例上述体声波谐振器的方法，请结合图7A～7H所示，该体声波谐振器的制作方法包括：
S1，制作声反射单元302，如图7A所示。
S2，沉积隔离层303及导电薄膜309，如图7B所示。
S3，图形化导电薄膜309，如图7C所示，具体可以采用刻蚀工艺，也可以采用剥离工艺。
S4，沉积并图形化底电极304，如图7D所示。
S5，沉积压电膜305，如图7E所示。
S6，沉积并图形化顶电极306，如图7F所示。
S7，刻蚀压电膜打开接触孔307，如图7G所示。
S8，制作焊盘308a及308b，如图7H所示。
相较而言，与前述实施例不同的是，本实施例导电薄膜在所述底电极下，而前一实施例，导电薄膜在所述底电极上，其余与前述实施例相同。
如图8所示，本公开还提供了一种滤波器，其包括级联的多个前述体声波谐振器2。
此外，上述对各元件和方法的定义并不仅限于实施例中提到的各种具体结构、形状或方式，本领域普通技术人员可对其进行简单地更改或替换，例如：
(1)体声波谐振器可以不包含隔离层。
(2)体声波谐振器还可以包含钝化层，钝化层覆盖在顶电极不被焊盘接触的所有面积，以及底电极不被焊盘和压电膜覆盖的所有面积即可。
(3)体声波谐振器有效区的形状可以为正方形、矩形、不规则多边形、圆形或椭圆形。
至此，已经结合附图对本公开实施例进行了详细描述。依据以上描述，本领域技术人员应当对本公开有了清楚的认识。
需要说明的是，在附图或说明书正文中，未绘示或描述的实现方式，均为所属技术领域中普通技术人员所知的形式，并未进行详细说明。此外，上述对各元件的定义并不仅限于实施例中提到的各种具体结构、形状，本领域普通技术人员可对其进行简单地更改或替换；本文可提供包含特定值的参数的示范，但这些参数无需确切等于相应的值，而是可在可接受的误差容限或设计约束内近似于相应值；实施例中提到的方向用语，例如“上”、“下”、“前”、“后”、“左”、“右”等，仅是参考附图的方向，并非用来限制本公开的保护范围；上述实施例可基于设计及可靠度的考虑，彼此混合搭配使用或与其他实施例混合搭配使用，即不同实施例中的技术特征可以自由组合形成更多的实施例。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本申请。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本申请的精神或范围的情况下，在其它实施例中实现。因此，本公开将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。
需要说明的是，在附图或说明书正文中，未绘示或描述的实现方式，均为所属技术领域中普通技术人员所知的形式，并未进行详细说明。此外，上述对各元件和方法的定义并不仅限于实施例中提到的各种具体结构、形状或方式，本领域普通技术人员可对其进行简单地更改或替换。
以上所述的具体实施例，对本公开的目的、技术方案和有益效果进行了进一步详细说明，所应理解的是，以上所述仅为本公开的具体实施例而已，并不用于限制本公开，凡在本公开的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本公开的保护范围之内。

Claims (10)

  1. 一种体声波谐振器，包括：
    一衬底；
    在所述衬底上的一声反射单元；
    在所述声反射单元上的一压电堆叠结构；以及
    在所述压电堆叠结构上的一焊盘；其中，
    所述焊盘与所述声反射单元具有一重叠区域。
  2. 根据权利要求1所述的体声波谐振器，其中，所述压电堆叠结构包括：
    一底电极；
    在所述底电极上的一压电膜；以及
    在所述压电膜上的一顶电极。
  3. 根据权利要求2所述的体声波谐振器，其中，所述压电堆叠结构还包括导电薄膜，在所述底电极上方或所述底电极下方，所述导电薄膜与所述声反射单元具有一重叠区域。
  4. 根据权利要求3所述的体声波谐振器，其中，所述顶电极与所述导电薄膜具有一宽度为d5的重叠区域；所述导电薄膜与所述声反射单元的重叠区域的宽度为d3；所述顶电极非引出端与所述声反射单元的距离为d4；d3＝d4+d5，d4≥0，d5＝k 1λ/4，其中，λ为所述体声波谐振器等效波长，k 1为奇数。
  5. 根据权利要求4所述的体声波谐振器，其中，
    在所述顶电极引出端，所述一焊盘与顶电极接触，并且所述焊盘与所述声反射单元的重叠区域的宽度为d6，d6＝k 2λ/4，其中，λ为所述体声波谐振器等效波长，k 2为奇数，且k 1≥k 2；
    在所述导电薄膜上方、所述压电膜形成有一接触孔，所述体声波谐振器还包括另一焊盘，形成于所述接触孔处，与所述导电薄膜或者底电极接触。
  6. 一种滤波器，其包括级联的多个如权利要求1-5中任一项所述体声波谐振器。
  7. 一种体声波谐振器的制作方法，包括：
    在一衬底上形成一声反射单元；
    在所述声反射单元上形成一压电堆叠结构；以及
    在所述压电堆叠结构上制作一焊盘；其中，
    所述焊盘与所述声反射单元具有一重叠区域。
  8. 根据权利要求7所述的体声波谐振器的制作方法，其中，在所述声反射单元上形成一压电堆叠结构的步骤包括：
    在所述声反射单元上形成一底电极；
    在所述底电极上的形成一压电膜；以及
    在所述压电膜上形成一顶电极。
  9. 根据权利要求8所述的体声波谐振器的制作方法，其中，在形成底电极的步骤之前或之后，还包括：形成一导电薄膜；该导电薄膜与所述声反射单元具有一重叠区域。
  10. 根据权利要求9所述的体声波谐振器的制作方法，其中，所述顶电极与所述导电薄膜具有一宽度为d5的重叠区域；所述导电薄膜与所述声反射单元的重叠区域的宽度为d3；所述顶电极非引出端与所述声反射单元的距离为d4；d3＝d4+d5，d4≥0，d5＝k 1λ/4，其中，λ为所述体声波谐振器等效波长，k 1为奇数；
    所述焊盘与声反射单元的重叠区域的宽度为d6，d6＝k 2λ/4，其中，λ为体声波谐振器等效波长，k 2为奇数，且k 1≥k 2。
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