WO2020258334A1 - 谐振器及其制备方法 - Google Patents

谐振器及其制备方法 Download PDF

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Publication number
WO2020258334A1
WO2020258334A1 PCT/CN2019/093920 CN2019093920W WO2020258334A1 WO 2020258334 A1 WO2020258334 A1 WO 2020258334A1 CN 2019093920 W CN2019093920 W CN 2019093920W WO 2020258334 A1 WO2020258334 A1 WO 2020258334A1
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WIPO (PCT)
Prior art keywords
bragg
top electrode
piezoelectric layer
ring
resonator
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Ceased
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PCT/CN2019/093920
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English (en)
French (fr)
Inventor
程诗阳
吴珂
李杨
王超
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AAC Technologies Holdings Shenzhen Co Ltd
AAC Technologies Pte Ltd
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AAC Acoustic Technologies Shenzhen Co Ltd
AAC Technologies Pte Ltd
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Application filed by AAC Acoustic Technologies Shenzhen Co Ltd, AAC Technologies Pte Ltd filed Critical AAC Acoustic Technologies Shenzhen Co Ltd
Priority to PCT/CN2019/093920 priority Critical patent/WO2020258334A1/zh
Priority to CN201910591563.5A priority patent/CN110324022B/zh
Priority to US16/993,198 priority patent/US11699988B2/en
Publication of WO2020258334A1 publication Critical patent/WO2020258334A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
    • H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
    • H03H9/175—Acoustic mirrors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
    • H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
    • H03H9/173—Air-gaps
    • 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 elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/02118—Means for compensation or elimination of undesirable effects of lateral leakage between adjacent resonators
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02543—Characteristics of substrate, 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 elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02614—Treatment of substrates, e.g. curved, spherical, cylindrical substrates ensuring closed round-about circuits for the acoustical waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/05—Holders or supports
    • H03H9/0538—Constructional combinations of supports or holders with electromechanical or other electronic elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
    • 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
    • H03H2003/021—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 the resonators or networks being of the air-gap type
    • 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
    • H03H2003/023—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 the resonators or networks being of the membrane type
    • 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
    • H03H2003/025—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 the resonators or networks comprising an acoustic mirror
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • This application relates to the technical field of resonators, and in particular to a resonator and a manufacturing method thereof.
  • Resonators refer to electronic components that generate resonant frequencies. Commonly used are quartz crystal resonators and ceramic resonators. The effect of the frequency generated by the resonator is stable and has good anti-interference performance. It is widely used in various electronic products.
  • quartz crystal resonators and ceramic resonators are no longer suitable for high-frequency and miniaturized products due to their large size and low frequency.
  • the film bulk acoustic resonator manufactured by the longitudinal wave resonance excited by the piezoelectric film material in its thickness direction has high frequency band, low power consumption, low temperature drift, low insertion loss, low noise, steep sideband, high power capacity, etc. Excellent performance, has become a new generation of resonators commonly used.
  • this type of piezoelectric thin film resonator can use a CMOS compatible process, which can effectively reduce production costs and facilitate the integration with CMOS circuits.
  • the piezoelectric film resonator includes an acoustic reflection layer, two metal electrodes, and a piezoelectric film layer located between the two electrodes.
  • the role of the metal electrode is to cause mechanical oscillation of the piezoelectric film to excite resonance in its thickness direction.
  • the function of the acoustic reflection structure is to form effective acoustic isolation between the two sides of the piezoelectric resonator in the thickness direction and the outside world and the substrate.
  • Fig. 1 is a structural cross-sectional view of a conventional resonator.
  • the resonator includes a silicon substrate 1, a bottom electrode 3, a piezoelectric layer 4, and a top electrode 5.
  • the piezoelectric layer is made of aluminum nitride.
  • the piezoelectric coefficient matrix diagram of the piezoelectric layer is shown in FIG. 2. It can be seen from Figure 2 that the piezoelectric coefficient matrix is not limited to the z-axis direction. There are also components in other directions, which causes the piezoelectric film to have compression, tension, and shear moduli at the same time when the resonator is working.
  • the longitudinally propagating sound waves also generate laterally propagating sound waves.
  • the laterally propagating sound waves will be reflected when they reach the edge of the top electrode.
  • a number of resonance points of clutter are generated, forming
  • the parasitic mode causes fluctuations in the phase in the working frequency band, which affects the performance of the resonator, thereby increasing the ripple in the filter band.
  • the purpose of this application is to provide a resonator and a manufacturing method thereof, aiming to improve the frequency response curve of the resonator.
  • a resonator comprising a silicon substrate, a bottom electrode stacked on a part of the silicon substrate, a piezoelectric layer covering the bottom electrode and a part of the silicon substrate, and a piezoelectric layer stacked on the piezoelectric layer
  • the top electrode on the upper electrode and the Bragg reflection ring, the Bragg reflection ring is arranged on the side where the piezoelectric layer is connected to the top electrode, and the Bragg reflection ring is arranged around the top electrode, and the Bragg reflection ring includes an edge
  • the Bragg high resistance layer and the Bragg low resistance layer are alternately arranged in the radial direction of the Bragg reflection ring, wherein the acoustic impedance of the Bragg high resistance layer is greater than the acoustic impedance of the Bragg low resistance layer.
  • the plurality of Bragg reflection rings are sleeved and placed along the radial direction of the Bragg reflection ring.
  • the material of the Bragg high resistance layer includes tungsten and carbon.
  • the material of the Bragg low resistance layer includes silicon oxide.
  • the thickness of the Bragg high resistance layer is smaller than the thickness of the Bragg low resistance layer, and the thickness of the Bragg low resistance layer is smaller than the thickness of the top electrode.
  • the silicon substrate is provided with a cavity on the side facing the bottom electrode.
  • the projection of the Bragg reflection ring along the direction from the top electrode to the piezoelectric layer is located in the cavity.
  • this application also provides a method for manufacturing a resonator, which includes the following steps:
  • a Bragg reflection ring is deposited and patterned on the piezoelectric layer and the top electrode, and the Bragg reflection ring is arranged around the top electrode.
  • the sacrificial material in the cavity needs to be released before depositing and patterning the Bragg reflector ring on the piezoelectric layer and the top electrode;
  • the sacrificial material in the cavity needs to be released after depositing and patterning the Bragg reflector ring on the piezoelectric layer.
  • the Bragg reflection ring includes Bragg high resistance layers and Bragg low resistance layers alternately arranged along the radial direction of the Bragg reflection ring, wherein the acoustic impedance of the Bragg high resistance layer is greater than that of the Bragg low resistance layer.
  • Acoustic impedance, the step of depositing and patterning the Bragg reflection ring on the piezoelectric layer and the top electrode specifically includes:
  • the resonator of the present application includes a silicon substrate, a bottom electrode, a piezoelectric layer, a top electrode, and a Bragg reflection ring formed in sequence, and the silicon substrate is provided with a cavity on the side facing the bottom electrode, and the Bragg reflection
  • the ring is arranged on the side where the piezoelectric layer and the top electrode are connected, and the Bragg reflection ring is arranged around the top electrode.
  • the Bragg reflection ring includes Bragg high resistance layers and Bragg low resistance layers alternately arranged along the radial direction of the Bragg reflection ring.
  • the Bragg high-resistance layer and the Bragg low-resistance layer have different acoustic impedances.
  • the Bragg reflection rings with alternating acoustic impedances can produce several reflecting surfaces.
  • the laterally propagating clutter will be partially reflected on these reflecting surfaces.
  • Each reflected clutter They cancel each other out, thereby suppressing the parasitic modes in the working range, improving the frequency response curve of the resonator, reducing filtering, and improving the overall performance of the resonator.
  • Figure 1 is a cross-sectional view of a conventional resonator
  • FIG. 2 is a matrix diagram of piezoelectric coefficients of the piezoelectric layer when aluminum nitride is used as the piezoelectric layer in the existing resonator;
  • Figure 3 is a simulation diagram of a frequency response curve of an existing resonator
  • Fig. 4 is a simulation diagram of the phase angle of the existing resonator
  • FIG. 5 is a cross-sectional view of a resonator according to an embodiment of the application.
  • FIG. 6 is a cross-sectional view of a resonator according to another embodiment of the application.
  • FIG. 7 is a simulation diagram of a frequency response curve of a resonator according to an embodiment of the application.
  • Fig. 8 is a phase angle simulation diagram of a resonator according to an embodiment of the application.
  • FIG. 9 is a manufacturing flow chart of a resonator according to an embodiment of the application.
  • an embodiment of the present application provides a resonator, which includes a silicon substrate 1, a bottom electrode 3 stacked on a part of the silicon substrate 1, a piezoelectric device covering the bottom electrode 3 and a part of the silicon substrate 1.
  • the material of the piezoelectric layer 4 is aluminum nitride, and the aluminum nitride film is an excellent piezoelectric material with high temperature resistance, stable chemical properties, and good insulation performance.
  • the aluminum nitride film has large electromechanical coupling coefficient, high sound velocity, and good high-frequency performance, which is suitable for making surface acoustic wave devices.
  • the Bragg reflection ring 6 is arranged on the side where the piezoelectric layer 4 and the top electrode 5 are connected, and the Bragg reflection ring 6 is arranged around the top electrode 5.
  • the Bragg reflection ring 6 includes Bragg high resistance layers 61 and Bragg low resistance layers 62 alternately arranged along the radial direction of the Bragg reflection ring 6.
  • the Bragg high resistance layer 61 and the Bragg low resistance layer 62 have different acoustic impedances, and the acoustic impedance of the Bragg high resistance layer 61 is greater than that of the Bragg low resistance layer 62.
  • the Bragg reflector ring 6 with alternating acoustic impedance can produce several reflecting surfaces.
  • the laterally propagating clutter will be partially reflected on these reflecting surfaces, and the reflected clutter will cancel each other out, thereby suppressing the parasitic mode in the working range.
  • the Bragg reflection ring 6 applies the principle of Bragg reflection, which refers to periodic reflection points on the interface of two different media to generate periodic reflections. This makes the laterally propagating clutter cancel each other out.
  • the Bragg reflector ring 6 is added in the present application.
  • the working frequency band is suppressed.
  • the parasitic mode makes the phase angle in the working frequency band smoother than that of the existing resonator.
  • the number of Bragg reflection rings 6 is one. In other embodiments, as shown in FIG. 6, two Bragg reflection rings 6 may also be provided. Of course, the Bragg reflection rings 6 The number can also be more than three.
  • the material of the Bragg high resistance layer 61 includes tungsten and carbon
  • the material of the Bragg low resistance layer 62 includes at least silicon oxide.
  • the chemical properties of tungsten, carbon and silicon oxide are all relatively stable to improve the stability of the resonator. .
  • the storage capacity of tungsten, carbon and silicon oxide is relatively large to reduce manufacturing costs.
  • the thickness of the Bragg high resistance layer 61 is smaller than the thickness of the Bragg low resistance layer 62; the thickness of the Bragg low resistance layer 62 is smaller than the thickness of the top electrode 6.
  • the Bragg radiation ring with alternating high and low acoustic impedance can produce several reflecting surfaces, and the laterally propagating clutter will be partially reflected on these reflecting surfaces.
  • the structure of the reflective ring with staggered heights can also increase the total reflection area in the vertical direction to offset more laterally propagating clutter.
  • the reflected clutter can be canceled each other, thereby suppressing the parasitic mode in the working range.
  • the thickness of the Bragg high resistance layer 61 of the Bragg reflection ring 6 can also be equal to or greater than the thickness of the Bragg low resistance layer 62, and the number of layers of the Bragg high resistance layer 61 and the Bragg low resistance layer 62 is The width of the layer can also be determined according to actual needs to suppress parasitic modes in the working range.
  • the silicon substrate 1 is provided with a cavity 11 on the side facing the bottom electrode 3, and the Bragg reflection ring 6 is projected in the cavity 11 along the direction from the top electrode 5 to the piezoelectric layer 4.
  • the projection of the Bragg reflection ring 6 along the direction from the top electrode 5 to the piezoelectric layer 4 may also be outside the region of the cavity 11.
  • the projection of the Bragg reflector ring 6 along the direction from the top electrode 5 to the piezoelectric layer 4 can also be partly inside the cavity 11 and the remaining part outside the cavity 11.
  • this application also provides a method for manufacturing a resonator. As shown in FIG. 9, the method includes the following steps:
  • Step S1 Provide a silicon substrate 1, etch a recessed cavity 11 on the silicon substrate 1, and fill the cavity 11 with a sacrificial material;
  • Step S2 depositing and patterning the bottom electrode 3 on the side of the silicon substrate 1 where the cavity 11 is etched;
  • Step S3 Depositing and patterning the piezoelectric layer 4 on the bottom electrode 3;
  • Step S4 depositing and patterning the top electrode 5 on the piezoelectric layer 4;
  • Step S5 Depositing and patterning the Bragg reflection ring 6 on the piezoelectric layer 4 and the top electrode 5, and the Bragg reflection ring 6 is arranged around the top electrode 5.
  • the material of the Bragg reflector ring 6 includes a sacrificial material
  • the sacrificial material in the cavity 11 needs to be released before depositing and patterning the Bragg reflector ring 6 on the piezoelectric layer 4 and the top electrode 5.
  • the sacrificial material in the cavity 11 is released after the Bragg reflection ring 6 is deposited and patterned on the piezoelectric layer 4 and the top electrode 5.
  • the Bragg low resistance layer 62 is fabricated before the Bragg high resistance layer 61. Specifically, the Bragg low resistance layer 62 is deposited and patterned on the piezoelectric layer 4 and the top electrode 5, and then the Bragg high resistance layer 61 is deposited and patterned on the piezoelectric layer 4, the top electrode 5 and the Bragg low resistance layer 62.
  • the sacrificial material is silicon dioxide.
  • the electrode materials of the bottom electrode 3 and the top electrode 5 include molybdenum and titanium, which can effectively extend the service life of the bottom electrode 3 and the top electrode 5. At the same time, the power consumption of the titanium electrode is small, which can effectively save resources.

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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

一种谐振器及其制备方法，谐振器包括硅衬底（1）、叠设于部分硅衬底（1）上的底电极（3）、覆盖底电极（3）及部分硅衬底（1）的压电层（4）、叠设于压电层（4）上的顶电极（5）和布拉格反射环（6），布拉格反射环（6）设置于压电层（4）与顶电极（5）连接的一面，且布拉格反射环（6）环绕顶电极（5）设置，布拉格反射环（6）包括沿布拉格反射环（6）的径向交替设置的布拉格高阻层（61）和布拉格低阻层（62），其中所述布拉格高阻层（61）的声阻抗大于所述布拉格低阻层（62）的声阻抗。布拉格高阻层（61）和布拉格低阻层（62）具有不同的声阻抗，声阻抗高低相间的布拉格反射环（6）能够产生若干反射面，横向传播的杂波在这些反射面上均会发生部分反射，各个反射的杂波相互抵消，从而抑制工作区间上的寄生模态，以改善谐振器的频响曲线，减少滤波，从而提升谐振器的整体性能。

Description

谐振器及其制备方法 技术领域
本申请涉及谐振器技术领域，尤其涉及一种谐振器及其制备方法。
 背景技术
谐振器就是指产生谐振频率的电子元件，常用的分为石英晶体谐振器和陶瓷谐振器。谐振器产生的频率的作用，具有稳定，且抗干扰性能良好的特点，其广泛应用于各种电子产品中。
随技术发展，石英晶体谐振器及陶瓷谐振器由于体积大、频率低等缺陷不再适用于高频、小型化的产品。而利用压电薄膜材料在其厚度方向激发的纵波谐振所制造的薄膜体声波谐振器，具有高频带、低功耗、低温漂、低插损、低噪声、陡峭边带、大功率容量等优异性能，已成为普遍使用的新一代谐振器。此外，这类压电薄膜谐振器可使用与CMOS兼容的工艺，可有效降低生产成本，并利于与CMOS电路的集成。
压电薄膜谐振器包含声反射层和两个金属电极，及位于两电极间的压电薄膜层。金属电极的作用是引起压电薄膜的机械振荡从而在其厚度方向激发谐振。声反射结构的作用在于在压电谐振器厚度方向两侧与外界及衬底之间形成有效声学隔离。
 技术问题
图1为现有的谐振器的结构剖面图，该谐振器包括硅衬底1、底电极3、压电层4和顶电极5，压电层的材料为氮化铝。此时，压电层的压电系数矩阵图如图2所示。由图2可知，压电系数矩阵并不局限于z轴方向，在其他方向也存在分量，导致谐振器在工作状态下，压电膜同时存在压缩、拉伸和剪切模量，从而在产生纵向传播的声波的同时也产生横向传播的声波。如图3及图4所示，横向传播的声波传播到顶电极的边缘会发生反射，在谐振器的阻抗曲线，尤其是两个谐振峰之间的工作频段内产生了若干杂波的谐振点，形成寄生模态，造成工作频段内的相位出现波动，影响谐振器的性能，进而使滤波器带内纹波增加。
因此，有必要提供一种谐振器及其制备方法。
 技术解决方案
本申请的目的在于提供一种谐振器及其制备方法，旨在改善谐振器的频响曲线。
本申请的技术方案如下：
提供一种谐振器，包括硅衬底、叠设于部分所述硅衬底上的底电极、覆盖所述底电极和部分所述硅衬底的压电层、叠设于所述压电层上的顶电极和布拉格反射环，所述布拉格反射环设置于所述压电层与所述顶电极连接的一面，且所述布拉格反射环环绕所述顶电极设置，所述布拉格反射环包括沿所述布拉格反射环的径向交替设置的布拉格高阻层和布拉格低阻层，其中所述布拉格高阻层的声阻抗大于所述布拉格低阻层的声阻抗。
可选地，所述布拉格反射环设有多个，多个所述布拉格反射环沿所述布拉格反射环的径向套设放置。
可选地，所述布拉格高阻层的材料包括钨和碳。
可选地，所述布拉格低阻层的材料包括氧化硅。
可选地，所述布拉格高阻层的厚度小于所述布拉格低阻层厚度，所述布拉格低阻层的厚度小于所述顶电极的厚度。
可选地，所述硅衬底朝向所述底电极的一面设有空腔。
可选地，所述布拉格反射环沿所述顶电极至所述压电层的方向的投影位于所述空腔内。
另外，本申请还提供一种谐振器的制备方法，该方法包括以下步骤：
提供硅衬底，在所述硅衬底上刻蚀出凹陷的空腔，并在所述空腔内填充牺牲材料；
在所述硅衬底刻蚀有所述空腔的一面上沉积并图形化底电极；
在所述底电极上沉积并图形化压电层；
在所述压电层上沉积并图形化顶电极；
在所述压电层及所述顶电极上沉积并图形化布拉格反射环，且所述布拉格反射环环绕所述顶电极设置。
可选地，当所述布拉格反射环的材料包含牺牲材料时，在所述压电层及所述顶电极上沉积并图形化所述布拉格反射环之前需要释放所述空腔内的牺牲材料；
当所述布拉格反射环的材料不包含牺牲材料时，在所述压电层上沉积并图形化所述布拉格反射环之后需要释放所述空腔内的牺牲材料。
可选地，所述布拉格反射环包括沿所述布拉格反射环的径向交替设置的布拉格高阻层及布拉格低阻层，其中所述布拉格高阻层的声阻抗大于所述布拉格低阻层的声阻抗，在所述压电层及所述顶电极上沉积并图形化所述布拉格反射环的步骤具体包括：
在所述压电层及所述顶电极上沉积并图形化所述布拉格低阻层；及
在所述压电层、所述顶电极及所述布拉格低阻层上沉积并图形化所述布拉格高阻层。
 有益效果
本申请的有益效果在于：本申请的谐振器包括依次形成的硅衬底、底电极、压电层、顶电极和布拉格反射环，且硅衬底朝向底电极的一面设有空腔，布拉格反射环设置于压电层与顶电极连接的一面，且布拉格反射环环绕设置于顶电极，布拉格反射环包括沿布拉格反射环的径向交替设置的布拉格高阻层和布拉格低阻层。布拉格高阻层和布拉格低阻层具有不同的声阻抗，声阻抗高低相间的布拉格反射环能够产生若干反射面，横向传播的杂波在这些反射面上均会发生部分反射，各个反射的杂波相互抵消，从而抑制工作区间上的寄生模态，以改善谐振器的频响曲线，减少滤波，从而提升谐振器的整体性能。
 附图说明
图1是现有谐振器的剖面图；
图2为现有谐振器采用氮化铝作为压电层时的压电层的压电系数矩阵图；
图3为现有谐振器的频响曲线仿真图；
图4为现有谐振器的相位角仿真图；
图5为本申请一实施例的谐振器的剖面图；
图6为本申请另一实施例的谐振器的剖面图；
图7为本申请一实施例的谐振器的频响曲线仿真图；
图8为本申请一实施例的谐振器的相位角仿真图；
图9为本申请一实施例的谐振器的制备流程图。
说明书中附图标记如下：
1、硅衬底；11、空腔；3、底电极；4、压电层；5、顶电极；6、布拉格反射环；61、布拉格高阻层；62、布拉格低阻层。
 本发明的实施方式
下面结合附图和实施方式对本申请作进一步说明。
如图5所示，本申请一实施例提供一种谐振器，包括硅衬底1、叠设于部分硅衬底1上的底电极3、覆盖底电极3和部分硅衬底1的压电层4、叠设于压电层4上的顶电极5和布拉格反射环6。
压电层4的材料为氮化铝，氮化铝薄膜耐高温、化学性质稳定、绝缘性能好,是优良的压电材料。且氮化铝薄膜机电耦合系数大、声速高、高频性能好,适合于制作声表面波器件。
布拉格反射环6设置于压电层4与顶电极5连接的一面，且布拉格反射环6环绕顶电极5设置。布拉格反射环6包括沿布拉格反射环6的径向交替设置的布拉格高阻层61和布拉格低阻层62。布拉格高阻层61和布拉格低阻层62具有不同的声阻抗，其中布拉格高阻层61的声阻抗大于布拉格低阻层62的声阻抗。声阻抗高低相间的布拉格反射环6能够产生若干反射面，横向传播的杂波在这些反射面上均会发生部分反射，各个反射的杂波相互抵消，从而抑制工作区间上的寄生模态，以改善谐振器的频响曲线，减少滤波，从而提升谐振器的整体性能。
具体地，布拉格反射环6应用了布拉格反射的原理，布拉格反射是指在两种不同介质的交界面上,具有周期性的反射点,以产生周期性的反射。从而使得横向传播的杂波相互抵消。
如图7及图8所示，从仿真结果可以看出，相比现有的谐振器的结构，本申请增加布拉格反射环6后，通过让横向传播的杂波多次反射，抑制了工作频段内的寄生模态，使得工作频段内的相位角相比现有谐振器的相位角更加平滑。
如图5所示，在本实施例中，布拉格反射环6的数量为一个，在其他实施例中，如图6所示，布拉格反射环6也可以设有两个，当然，布拉格反射环6的数量还可以为三个以上。
在本实施例中，布拉格高阻层61的材料包括钨和碳，布拉格低阻层62的材料至少包括氧化硅，钨、碳和氧化硅的化学性能均较为稳定，以提高谐振器的稳定性。而且，钨、碳和氧化硅的存储量较大，以降低制造成本。
如图5所示，布拉格高阻层61的厚度小于布拉格低阻层62的厚度；布拉格低阻层62的厚度小于顶电极6的厚度。声阻抗高低相间的布拉格放射环可以产生若干反射面，横向传播的杂波在这些反射面上均会发生部分反射。与此同时，构造高低错落的反射环也可以增加竖直方向上的总反射面积，以抵消更多的横向传播的杂波。而且，通过适当调整各布拉格反射环的厚度和宽度，可以使各个反射的杂波相互抵消，从而抑制工作区间上的寄生模态。
当然，在其他实施例中，布拉格反射环6的布拉格高阻层61的厚度也可以等于或大于布拉格低阻层62的厚度，且布拉格高阻层61和布拉格低阻层62的层数及每层的宽度也可以根据实际需要确定，以抑制工作区间上的寄生模态。
在本实施例中，硅衬底1朝向底电极3的一面设有空腔11，布拉格反射环6沿顶电极5至压电层4的方向的投影在空腔11的区域内。在其他实施例中，布拉格反射环6沿顶电极5至压电层4的方向的投影也可以在空腔11的区域外。当然，布拉格反射环6沿顶电极5至压电层4的方向的投影还可以一部分在空腔11内，剩余部分在空腔11外。
此外，本申请还提供一种谐振器的制备方法，如图9所示，该方法包括以下步骤：
步骤S1:提供硅衬底1，在硅衬底1上刻蚀出凹陷的空腔11，并在空腔11内填充牺牲材料；
步骤S2:在硅衬底1刻蚀有空腔11的一面上沉积并图形化底电极3；
步骤S3:在底电极3上沉积并图形化压电层4；
步骤S4:在压电层4上沉积并图形化顶电极5；
步骤S5:在压电层4及顶电极5上沉积并图形化布拉格反射环6，且布拉格反射环6环绕顶电极5设置。
应当注意的是，当布拉格反射环6的材料包含牺牲材料时，在压电层4及顶电极5上沉积并图形化布拉格反射环6之前需要释放空腔11内的牺牲材料。
当布拉格反射环6的材料不包含牺牲材料时，在压电层4及顶电极5上沉积并图形化布拉格反射环6之后释放空腔11内的牺牲材料。
值得一提的是，在本实施例中，布拉格低阻层62先于布拉格高阻层61制作。具体地，在压电层4及顶电极5上沉积并图形化布拉格低阻层62，再在压电层4、顶电极5及布拉格低阻层62上沉积并图形化布拉格高阻层61。
在本实施例中，牺牲材料为二氧化硅，通过在空腔11内填充二氧化硅，便于在硅衬底1上沉积并图形化底电极3。
底电极3和顶电极5的电极材料包括钼和钛，能够有效地延长底电极3和顶电极5的使用寿命。同时，钛电极电能消耗小，能有效节约资源。
以上所述的仅是本申请的实施方式，在此应当指出，对于本领域的普通技术人员来说，在不脱离本申请创造构思的前提下，还可以做出改进，但这些均属于本申请的保护范围。

Claims (10)

  1. 一种谐振器，其特征在于：包括硅衬底、叠设于部分所述硅衬底上的底电极、覆盖所述底电极和部分所述硅衬底的压电层、叠设于所述压电层上的顶电极和布拉格反射环，所述布拉格反射环设置于所述压电层与所述顶电极连接的一面，且所述布拉格反射环环绕所述顶电极设置，所述布拉格反射环包括沿所述布拉格反射环的径向交替设置的布拉格高阻层和布拉格低阻层，其中所述布拉格高阻层的声阻抗大于所述布拉格低阻层的声阻抗。
  2. 根据权利要求1所述的一种谐振器，其特征在于：所述布拉格反射环设有多个，多个所述布拉格反射环沿所述布拉格反射环的径向套设放置。
  3. 根据权利要求1所述的一种谐振器，其特征在于：所述布拉格高阻层的材料包括钨和碳。
  4. 根据权利要求1所述的一种谐振器，其特征在于：所述布拉格低阻层的材料包括氧化硅。
  5. 根据权利要求1所述的一种谐振器，其特征在于：所述布拉格高阻层的厚度小于所述布拉格低阻层厚度，所述布拉格低阻层的厚度小于所述顶电极的厚度。
  6. 根据权利要求1所述的一种谐振器，其特征在于：所述硅衬底朝向所述底电极的一面设有空腔。
  7. 根据权利要求6所述的一种谐振器，其特征在于：所述布拉格反射环沿所述顶电极至所述压电层的方向的投影位于所述空腔内。
  8. 一种谐振器的制备方法，其特征在于：该方法包括以下步骤：
    提供硅衬底，在所述硅衬底上刻蚀出凹陷的空腔，并在所述空腔内填充牺牲材料；
    在所述硅衬底刻蚀有所述空腔的一面上沉积并图形化底电极；
    在所述底电极上沉积并图形化压电层；
    在所述压电层上沉积并图形化顶电极；及
    在所述压电层及所述顶电极上沉积并图形化布拉格反射环，且所述布拉格反射环环绕所述顶电极设置。
  9. 如权利要求8所述的一种谐振器的制备方法，其特征在于：当所述布拉格反射环的材料包含牺牲材料时，在所述压电层及所述顶电极上沉积并图形化所述布拉格反射环之前需要释放所述空腔内的牺牲材料；
    当所述布拉格反射环的材料不包含牺牲材料时，在所述压电层上沉积并图形化所述布拉格反射环之后需要释放所述空腔内的牺牲材料。
  10. 如权利要求8所述的一种谐振器的制备方法，其特征在于：所述布拉格反射环包括沿所述布拉格反射环的径向交替设置的布拉格高阻层及布拉格低阻层，其中所述布拉格高阻层的声阻抗大于所述布拉格低阻层的声阻抗，在所述压电层及所述顶电极上沉积并图形化所述布拉格反射环的步骤具体包括：
    在所述压电层及所述顶电极上沉积并图形化所述布拉格低阻层；及
    在所述压电层、所述顶电极及所述布拉格低阻层上沉积并图形化所述布拉格高阻层。
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