WO2023202597A1 - 一种声表面波谐振器 - Google Patents

一种声表面波谐振器 Download PDF

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Publication number
WO2023202597A1
WO2023202597A1 PCT/CN2023/089108 CN2023089108W WO2023202597A1 WO 2023202597 A1 WO2023202597 A1 WO 2023202597A1 CN 2023089108 W CN2023089108 W CN 2023089108W WO 2023202597 A1 WO2023202597 A1 WO 2023202597A1
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Prior art keywords
finger
piezoelectric substrate
sound velocity
width
fingers
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PCT/CN2023/089108
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English (en)
French (fr)
Inventor
刘晓军
余泽
马阳阳
朱德进
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天通瑞宏科技有限公司
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Publication of WO2023202597A1 publication Critical patent/WO2023202597A1/zh

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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
    • H03H9/25—Constructional features of resonators using surface acoustic waves
    • 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
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02818—Means for compensation or elimination of undesirable effects
    • 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
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14544—Transducers of particular shape or position

Definitions

  • Embodiments of the present application relate to the technical field of surface acoustic wave devices, for example, to a surface acoustic wave resonator.
  • SAW Surface Acoustic Wave
  • IDT Inter Digital Transducer
  • the SAW resonator excites the main wave mode, it will generate unwanted transverse modes.
  • the transverse modes will introduce spurious responses, reduce the Q value of the IDT, and increase the insertion loss of the filter. , causing a greater impact on device performance, which is mainly caused by energy leakage, especially in heterogeneous semiconductor films.
  • Related art transverse mode suppression methods such as adding a dummy (dummy) finger to the bus bar on the opposite side of the inserted finger (electrode finger).
  • the width and thickness of the dummy finger are generally consistent with the inserted finger (electrode finger), but the transverse mode suppression not effectively.
  • Another example is the dummy method, which refers to the weighting method.
  • it is better at suppressing transverse modes, it may affect the Q value of the resonator and increase the filter loss. Therefore, how to effectively suppress the transverse modes excited by SAW resonators has always been a major challenge in engineering design.
  • Embodiments of the present application provide a surface acoustic wave resonator to effectively suppress transverse modes while ensuring the Q value of the resonator.
  • the embodiment of the present application provides a surface acoustic wave resonator, including:
  • the interdigital transducer structure is located on one side of the piezoelectric substrate; the interdigital transducer structure includes two oppositely arranged bus bars, and a plurality of electrode fingers arranged side by side between the two busbars; each electrodes refer to alternating electrical connections to one of said bus bars;
  • each false finger is correspondingly located between the end of one of the electrode fingers and the bus bar on the opposite side; in a direction parallel to the bus bar, the width of the false finger is equal to the width of the electrode finger;
  • a first sound velocity mutation structure the first sound velocity mutation structure is located on the side of the artificial finger away from the piezoelectric substrate, the side of the artificial finger close to the piezoelectric substrate and the layer where the artificial finger is located At least one of: in a direction parallel to the bus bar, the width of the first sound velocity mutation structure is greater than the width of the false finger.
  • Figure 1 is a schematic structural diagram of a surface acoustic wave resonator and the corresponding partial velocity spectrum provided by an embodiment of the present application;
  • Figure 2 is a schematic structural diagram of a surface acoustic wave resonator provided in the related art and its corresponding partial velocity spectrum;
  • Figure 3 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present application and its corresponding partial velocity spectrum;
  • Figure 4 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present application and its corresponding partial velocity spectrum;
  • Figure 5 is a comparison chart of the admittance curve amplitude values of a surface acoustic wave resonator with and without a load block provided by an embodiment of the present application;
  • Figure 6 is a comparison diagram of the real part of the admittance curve of a surface acoustic wave resonator with and without a load block provided by an embodiment of the present application;
  • Figure 7 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present application.
  • Figure 8 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present application.
  • Figure 9 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present application.
  • Figure 10 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present application.
  • Figure 11 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present application and a corresponding partial velocity spectrum;
  • FIG. 12 is a cross-sectional view along A-A1 of FIG. 11 .
  • FIG. 1 is a schematic structural diagram and a corresponding partial velocity spectrum of a surface acoustic wave resonator provided by an embodiment of the present application.
  • the surface acoustic wave resonator includes :
  • the inserted finger transducing structure 20 is located on one side of the piezoelectric substrate; the inserted finger transducing structure 20 includes two bus bars 21 arranged oppositely, and a plurality of electrode fingers 22 arranged side by side between the two bus bars 21; and more The electrode fingers 22 are alternately electrically connected to one of the bus bars 21;
  • each false finger 30 is correspondingly located between the end of an electrode finger 22 and the bus bar 21 on the opposite side; along the direction parallel to the bus bar 21, the width of the false finger 30 is equal to the width of the electrode finger;
  • the first sound velocity mutation structure 40 is located at at least one of the side of the artificial finger 30 away from the piezoelectric substrate, the side of the artificial finger 30 close to the piezoelectric substrate, and the layer where the artificial finger 30 is located; along In the direction parallel to the bus bar 21 , the width of the first sound velocity mutation structure 40 is greater than the width of the dummy finger 30 .
  • FIG. 1 is a top view, and the piezoelectric substrate 10 is at the bottom of all the illustrated structures.
  • the piezoelectric substrate 10 is shown in FIG. 12 , and FIG. 12 is a side view of an embodiment.
  • the interdigital transducer structure 20 is an interdigital transducer, which can be understood as forming a metal pattern shaped like intersecting fingers of two hands on the surface of the piezoelectric substrate, and its function is to realize acoustic-electrical conversion. able.
  • the interdigital transducing structure 20 includes a first bus bar, a second bus bar and a plurality of electrode fingers 22; the first bus bar and the second bus bar are arranged oppositely; In the direction of the bus bar 21, a plurality of electrode fingers 22 are arranged side by side between the first bus bar 21 and the second bus bar 21, and are electrically connected to the first bus bar 21 and the second bus bar 21 alternately.
  • the electrodes that engage with each other Pointer 22 is used to excite sound waves. In the direction of sound wave propagation, the sound trajectory is usually limited by the resonator in order to reduce the energy loss caused by the sound wave emission in the horizontal direction.
  • the resonator may include a pair of reflection gratings 50 , the reflection gratings 50 and the interdigital transducing structure 20 are located on the same surface of the piezoelectric substrate 10 , and the reflection gratings 50 are located on opposite sides of the interdigital transducing structure 20 .
  • the dummy finger 30 is disposed between the end of each electrode finger 22 and the bus bar 21 to suppress the lateral leakage of energy, confine more energy in the resonator, and thereby improve the Q value of the resonator.
  • the speed of sound waves at the surface of the piezoelectric substrate depends on the mass distribution of the piezoelectric substrate, ie the mass of the layers arranged on the piezoelectric substrate.
  • the resonator is configured such that the sound waves have different transverse propagation velocities in a plurality of regions extending parallel to the sound path.
  • the transverse direction is a direction parallel to the bus bar 21 . Therefore, the widening of the false finger 30 is a simple but effective means in order to reduce the lateral speed in the inner edge region.
  • a first sound velocity mutation structure 40 is provided on at least one of the side of the dummy finger 30 away from the piezoelectric substrate, the side of the dummy finger 30 close to the piezoelectric substrate, and the layer where the dummy finger 30 is located, and is arranged parallel to the bus bar 21 direction, the width of the first sound velocity mutation structure 40 is set to be greater than the width of the artificial finger 30 .
  • a first sound velocity mutation structure 40 is provided on the side of the artificial finger 30 away from the piezoelectric substrate. The width of the first sound velocity mutation structure 40 is set to be greater than the width of the artificial finger 30.
  • the mass of the area of the first sound velocity mutation structure 40 is larger relative to its corresponding artificial finger 30 and the opposite gap area, so the first sound velocity mutation structure 40 has a larger width than its corresponding artificial finger 30 and the opposite gap area.
  • the lateral velocity at position 40 of the rapid mutation structure is the smallest.
  • the mass of the gap area facing the first sonic mutation structure 40 is the smallest, so the transverse velocity of the gap area is the largest.
  • Figure 2 is a schematic structural diagram of a surface acoustic wave resonator and the corresponding partial velocity spectrum provided in the related art. Comparing Figures 1 and 2, the setting of the first sound velocity mutation structure 40 can increase the amplitude of the sound velocity mutation, thereby Transverse modes can be suppressed by adjusting the transverse acoustic velocity distribution.
  • the first sound velocity mutation structure 40 may be a load block 41, a load bar or a load layer.
  • the material of the first sonic mutation structure 40 can be metal materials, oxide materials, polymer coating materials, etc., and can be selected from metal materials. material.
  • the first sonic mutation structure 40 is generally on a different layer than the artificial finger 30, and may also be on the same layer. Compared with the method of using only the dummy fingers 30 in the related art, the transverse mode can be suppressed more effectively, and the weighting method of the dummy fingers 30 can be avoided from affecting the Q value of the resonator. Therefore, the transverse mode is effectively suppressed while ensuring the Q value of the resonator.
  • the embodiment of the present application provides a surface acoustic wave resonator, which is provided on at least one of the side of the fake finger 30 away from the piezoelectric substrate, the side of the fake finger 30 close to the piezoelectric substrate, and the layer where the fake finger 30 is located.
  • the first sound velocity mutation structure 40 is thickened and widened according to the material parameters, providing the possibility of changing the mass distribution. By adjusting the thickness and width of the first sound velocity mutation structure 40, the sound velocity can be easily adjusted in order to obtain an improved piston mode.
  • the piston mode is characterized by the absence or minimal occurrence of transversely propagating sound waves.
  • realizing the piston mode is an effective means in order to reduce the energy loss due to the transverse emission of sound waves from the acoustic trajectory, and at the same time achieve an improvement in performance by suppressing the transverse mode.
  • the transverse mode can be effectively suppressed, and the weighting method of the dummy fingers 30 can be avoided from affecting the Q value of the resonator.
  • the surface acoustic wave resonator further includes:
  • the second sound velocity mutation structure 60 is located on the side of the electrode finger 22 away from the piezoelectric substrate, the side of the electrode finger 22 close to the piezoelectric substrate, and at least one place in the layer where the electrode finger 22 is located; along a line parallel to In the direction of the bus bar 21 , the width of the second sound velocity mutation structure 60 is greater than the width of the electrode fingers 22 .
  • the second sound velocity mutation structure 60 may be load blocks arranged at the ends of the electrode fingers 22 and corresponding lateral positions of the electrode fingers 22 of opposite polarity, thereby improving the acoustic characteristics of the resonator by establishing a piston mode.
  • the piston mode electroacoustic transducer structure can form a horizontal acoustic waveguide, reduce the sound waves propagating in the vertical direction, and achieve the effect of suppressing the transverse mode.
  • the structure shown in Figure 4 does not provide the false finger 30 and the first sound velocity mutation structure 40, and only provides the third finger at the end of the electrode finger 22 and the corresponding lateral position of the electrode finger 22 with opposite polarity.
  • the piston mode electroacoustic transducer structure of the bisonic mutation structure 60 It is known that the piston mode electroacoustic transducer structure can form a horizontal acoustic waveguide, reduce the sound waves propagating in the vertical direction, and achieve the suppression of lateral mold effect. However, due to wave diffraction, some sound waves can also excite transverse modes through the piston gap.
  • the structure shown in Figure 3 is a piston mode electroacoustic transducer structure that adds a first sound velocity mutation structure 40 of the false finger 30 to form a second acoustic waveguide structure to enhance the transverse mode suppression effect.
  • the width of the first sound velocity mutation structure 40 on the artificial finger 30 is greater than the width of the second sound velocity mutation structure 60 on the electrode finger 22 .
  • the surface acoustic wave resonator may also include a third sound velocity mutation structure 70.
  • the third sound velocity mutation structure 70 is located on the side of the reflection grating 50 away from the piezoelectric substrate, the side of the reflection grating 50 close to the piezoelectric substrate, and the reflection grating 50. At least one place in the layer; along the direction parallel to the bus bar 21 , the width of the third sound velocity mutation structure 70 is greater than the width of the electrode fingers of the reflection grid 50 .
  • Figure 5 is a comparison diagram of the admittance curve amplitude values of a surface acoustic wave resonator provided by an embodiment of the present application with and without a load block
  • Figure 6 is a comparison diagram of the admittance curve amplitude values of a surface acoustic wave resonator provided by an embodiment of the present application with and without a load block.
  • the solid line a corresponds to the structure shown in Figure 3
  • the dotted line a corresponds to the structure shown in Figure 3.
  • the structure of the present application has better amplitude-frequency characteristics. It can be seen that by setting the sound velocity mutation structure, the Q value can be significantly improved (the sharper the Q value, the higher the Q value), which illustrates that the structure of the present application It can better prevent the leakage of transverse mode energy.
  • the first sonic velocity mutation structure 40 includes a plurality of load blocks 41, each load block 41 is located correspondingly at the end of a false finger 30; located in the same row of false fingers 30 The distance between the end load block 41 and the end of the opposite electrode finger 22 is equal.
  • the first sonic velocity mutation structure 40 includes a plurality of load blocks 41 ; the vertical projection of each load block 41 on the piezoelectric substrate has a corresponding false finger 30 on the piezoelectric substrate.
  • the vertical projections partially overlap; the distance from the load block 41 located at the end of the artificial finger 30 in the same row to the end of the opposite electrode finger 22 increases or decreases.
  • the first sound velocity mutation structure 40 includes a plurality of load blocks 41 ; the vertical projection of each load block 41 on the piezoelectric substrate and the corresponding false finger 30 on the piezoelectric substrate of The vertical projections partially overlap; the distance from the load block 41 located at the end of the artificial finger 30 in the same row to the end of the opposite electrode finger 22 is alternately equal.
  • each load block 41 is less than or equal to the width between two adjacent electrode fingers 22 located on both sides of the load block 41 .
  • the width of each load block 41 is smaller than the width between two adjacent electrode fingers 22 located on both sides thereof.
  • the width of each load block 41 extends horizontally to be equal to the distance between two adjacent electrode fingers 22 located on both sides thereof, so that sound wave diffraction can be better reduced.
  • the first sound velocity mutation structure 40 includes two load bars 42 , the two load bars 42 are arranged oppositely, and are both parallel to the bus bar 21 ; direction, the width of the load bar 42 is greater than or equal to the width of the bus bar 21 . It can be understood that in order to reduce sound wave diffraction, the load block can be extended in the horizontal direction to form a load bar 42 parallel to the bus bar 21 .
  • the surface acoustic wave resonator further includes a passivation layer 90 , and the passivation layer 90 covers the side of the electrode finger 22 and the dummy finger 30 away from the piezoelectric substrate 10 , and the piezoelectric substrate 10 not covered by the electrode fingers 22 and the dummy fingers 30; the first sound velocity mutation structure 40 is located on the side of the passivation layer 90 away from the piezoelectric substrate 10; the material of the first sound velocity mutation structure 40 includes a polymer coating application material.
  • the passivation layer 90 may be made of silicon dioxide or silicon nitride, and the polymer coating material may be polyimide or the like.
  • the first sound velocity mutation structure 40 includes two load layers 43.
  • the vertical projection of each load layer 43 on the piezoelectric substrate covers a corresponding dummy finger 30 area; along the direction parallel to the bus bar 21, the dummy finger 30 area
  • the width is greater than or equal to the width of the bus bar 21
  • the length of the dummy finger 30 region in the direction perpendicular to the bus bar 21 is equal to the length of the dummy finger 30 .
  • the load settles in the entire false finger 30 area to increase the difference in sound speed mutation, which can suppress the transverse mode while ensuring the Q value of the resonator.
  • the resonator may be a Thin Film-Surface Acoustic Wave (TF-SAW) filter.
  • the piezoelectric substrate 10 includes a silicon layer 11 and a polysilicon layer 12, a silicon oxide layer 13 and a lithium tantalate crystal layer 14 formed on the silicon layer in sequence.
  • TF-SAW filters can provide a relatively large bandwidth while providing good temperature compensation performance and an effective path for multi-band integration.
  • the technical solution provided by the embodiments of the present application is to provide a first sound velocity mutation structure at at least one of the side of the artificial finger away from the piezoelectric substrate, the side of the artificial finger close to the piezoelectric substrate, and the layer where the artificial finger is located, thereby
  • the transverse mode can be suppressed by adjusting the transverse acoustic velocity distribution.
  • the transverse mode can be further effectively suppressed and the use of false finger weighting method can be avoided to affect the Q value of the resonator. Therefore, the transverse mode is effectively suppressed while ensuring the Q value of the resonator.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

本申请实施例公开了一种声表面波谐振器，包括：压电基板(10)；插指换能结构(20)，位于压电基板(10)的一侧；插指换能结构(20)包括相对设置的两个汇流条(21)，以及并排设置在两个汇流条(21)之间的多个电极指(22)；每个电极指(22)交替电连接到汇流条(21)中的一个汇流条(21)；多个假指(30)，每一假指(30)对应位于一电极指(22)末端与对侧的汇流条(21)之间；沿平行于汇流条(21)的方向，假指(30)的宽度等于电极指(22)的宽度；在假指(30)、电极指(22)以及反射栅(50)的栅格导体靠近压电基板(10)的一侧、远离压电基板(10)的一侧，或者在假指(30)、电极指(22)以及反射栅(50)的所在层设置有声速突变结构。

Description

一种声表面波谐振器
本申请要求在2022年4月19日提交中国专利局、申请号为202210410191.3的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及声表面波器件技术领域，例如涉及一种声表面波谐振器。
背景技术
在现代通信系统中，滤波器常被用来过滤目标通信频段之外的不必要信号。声表面波(Surface Acoustic Wave，SAW)谐振器由于高品质因子(Q factor，Q)值、体积小、高可靠性、易于大批量生产等优势，已被广泛应用于高频滤波器设计。SAW一般由压电基板、插指换能器(Inter Digital Transducter，IDT)、反射栅组成，采用半导体工艺生产制备。
通常，SAW谐振器在激发主要波模的同时，会产生不需要的横模，在SAW滤波器的频率响应上，横模会引入杂散响应，降低IDT的Q值，增加滤波器的插入损耗，对器件性能造成较大影响，这主要是由于能量泄露引起的，例如在异质半导体薄膜中尤为突出。相关技术的横模抑制方法，如在插指(电极指)对侧的汇流条上增加假(dummy)指，dummy指的宽度和厚度一般与插指(电极指)保持一致，但是横模抑制效果不佳。再比如dummy指加权的方法，虽然抑制横模效果较好，但是可能会影响谐振器Q值，增大滤波器损耗。因此如何有效抑制SAW谐振器激发的横模，一直是工程设计中的一大挑战。
发明内容
本申请实施例提供了一种声表面波谐振器，以有效抑制横向模式的同时，保证谐振器的Q值。
本申请实施例提供了一种声表面波谐振器，包括：
压电基板；
插指换能结构，位于所述压电基板的一侧；所述插指换能结构包括相对设置的两个汇流条，以及并排设置在两个汇流条之间的多个电极指；每个电极指交替电连接到所述汇流条中的一个汇流条；
多个假指，每一假指对应位于一所述电极指末端与对侧的汇流条之间；沿平行于汇流条的方向，所述假指的宽度等于所述电极指的宽度；
第一声速突变结构，所述第一声速突变结构位于所述假指远离所述压电基板的一侧、所述假指靠近所述压电基板的一侧和所述假指所在层中的至少一处；沿平行于汇流条的方向，所述第一声速突变结构的宽度大于所述假指的宽度。
附图说明
图1是本申请实施例提供的一种声表面波谐振器的结构示意图及对应的部分速度谱；
图2是相关技术中提供的一种声表面波谐振器的结构示意图及对应的部分速度谱；
图3是本申请实施例提供的另一种声表面波谐振器的结构示意图及对应的部分速度谱；
图4是本申请实施例提供的另一种声表面波谐振器的结构示意图及对应的部分速度谱；
图5是本申请实施例提供的一种声表面波谐振器有无负载块的导纳曲线幅度值对比图；
图6是本申请实施例提供的一种声表面波谐振器有无负载块的导纳曲线中导纳实部对比图；
图7是本申请实施例提供的另一种声表面波谐振器的结构示意图；
图8是本申请实施例提供的另一种声表面波谐振器的结构示意图；
图9是本申请实施例提供的另一种声表面波谐振器的结构示意图；
图10是本申请实施例提供的另一种声表面波谐振器的结构示意图；
图11是本申请实施例提供的另一种声表面波谐振器的结构示意图及对应的部分速度谱；
图12是图11沿A-A1的截面图。
具体实施方式
本申请实施例提供了一种声表面波谐振器，图1是本申请实施例提供的一种声表面波谐振器的结构示意图及对应的部分速度谱，参考图1，声表面波谐振器包括：
压电基板10；
插指换能结构20，位于压电基板的一侧；插指换能结构20包括相对设置的两个汇流条21，以及并排设置在两个汇流条21之间的多个电极指22；多个电极指22交替电连接到汇流条21中的一个汇流条21；
多个假指30，每一假指30对应位于一电极指22末端与对侧的汇流条21之间；沿平行于汇流条21的方向，假指30的宽度等于电极指的宽度；
第一声速突变结构40，第一声速突变结构40位于假指30远离压电基板的一侧、假指30靠近压电基板的一侧和假指30所在层中的至少一处；沿平行于汇流条21的方向，第一声速突变结构40的宽度大于假指30的宽度。
其中，图1为俯视图，压电基板10在所有图示结构的底部，压电基板10在图12中有示出，图12为一种实施例的侧视图。示例性的，插指换能结构20即为插指换能器，可以理解为在压电基板表面上形成形状像两只手的手指交叉状的金属图案，它的作用是实现声-电换能。插指换能结构20包括第一汇流条、第二汇流条以及多个电极指22；第一汇流条与第二汇流条相对设置；沿平行于 汇流条21的方向，多个电极指22并排设置在第一汇流条21与第二汇流条21之间，并依次交替与第一汇流条21和第二汇流条21电连接，彼此咬合的电极指22以用于激励声波。在声波传播方向上，声轨迹通常受到谐振器的限制，以便减小由于声波在水平方向上发射造成的能量损耗。谐振器可以包括一对反射栅50，反射栅50与插指换能结构20的位于压电基板10的同一表面上，且反射栅50位于插指换能结构20的相对两侧。假指30设置于每个电极指22末端与汇流条21之间，设置为抑制能量的横向泄露，将能量更多的约束在谐振器内，进而提高谐振器的Q值。
声波在压电基板表面处的速度取决于压电基板的质量分布、即布置在压电基板上的层的质量。在此，该质量分布越高则声波越慢，并且质量分布的材料的弹性常数越高则声波越快。在垂直于汇流条21的方向上，该谐振器被构造为声波在多个与声轨迹平行延伸的区域中具有不同的横向传播速度。横向为平行于汇流条21的方向。因此，假指30加宽是简单但有效的手段，以便减小内边缘区域中的横向速度。
在假指30远离压电基板的一侧、假指30靠近压电基板的一侧和假指30所在层中的至少一处，设置第一声速突变结构40，并且沿平行于汇流条21的方向，设置第一声速突变结构40的宽度大于假指30的宽度。图1中示例性的画出在假指30远离压电基板的一侧设置第一声速突变结构40。设置第一声速突变结构40的宽度大于假指30的宽度，第一声速突变结构40的区域的质量相对于其对应的假指30，以及正对的空隙区域较大，因此第一声速突变结构40位置的横向速度最小。第一声速突变结构40正对的空隙区域质量最小，因此空隙区域的横向速度最大。图2是相关技术中提供的一种声表面波谐振器的结构示意图及对应的部分速度谱，对比图1和图2，第一声速突变结构40的设置可以增大声速突变的幅度，从而可以通过调整横向声学速度分布来抑制横向模式。
第一声速突变结构40可以为负载块41、负载条或负载层。第一声速突变结构40的材质可为金属材料、氧化物材料、高分子涂敷材料等，可选为金属材 料。第一声速突变结构40一般与假指30不同层，也可在同一层。相对于相关技术中只采用假指30的方式，可以更有效地抑制横向模式，并且避免采用假指30加权的方法而影响谐振器Q值。因此，有效抑制了横向模式的同时，保证了谐振器的Q值。
本申请实施例提供的一种声表面波谐振器，通过在假指30远离压电基板的一侧、假指30靠近压电基板的一侧和假指30所在层中的至少一处，设置第一声速突变结构40，根据材料参数对第一声速突变结构40加厚变宽，提供了改变质量分布的可能性。通过调节第一声速突变结构40的厚度和宽度，可以容易地调节声速度，以便获得改善的活塞模态。活塞模态的特点在于，不出现或者出现最小的在横向上传播的声波。因此，实现活塞模态是有效的手段，以便减小由于声波从声轨迹横向发射造成的能量损耗，并且同时通过抑制横向模态实现性能的改善。相对于相关技术中只采用假指30的方式，可以有效抑制横向模式，并且避免采用假指30加权的方法而影响谐振器Q值。
在本申请的一个实施例中，参考图3、图4和图7～图11，声表面波谐振器，还包括：
第二声速突变结构60，第二声速突变结构60位于电极指22远离压电基板的一侧、电极指22靠近压电基板的一侧和电极指22所在层中的至少一处；沿平行于汇流条21的方向，第二声速突变结构60的宽度大于电极指22的宽度。
第二声速突变结构60可以为负载块，这些负载块布置在电极指22的端和极性相反的电极指22的对应横向位置处，从而通过建立活塞模式来改善谐振器的声学特性。采用活塞模式电声换能器结构可以形成水平方向的声学波导，减小在垂直方向传播的声波，达到抑制横向模的效果。
对比图4和图3，图4所示的结构为未设置假指30以及第一声速突变结构40，只在电极指22的末端和极性相反的电极指22的对应横向位置处设置第二声速突变结构60的活塞模式电声换能器结构。已知采用活塞模式电声换能器结构可以形成水平方向的声学波导，减小在垂直方向传播的声波，达到抑制横向 模的效果。然而由于波的衍射，部分声波还可以通过活塞间隙激发横向模式。图3所示的结构为在活塞模式电声换能器结构中，增加假指30的第一声速突变结构40，可以形成第二个声学波导结构，增强横向模式抑制效果。图3中示例性的画出假指30上的第一声速突变结构40的宽度大于电极指22上的第二声速突变结构60的宽度。
另外，声表面波谐振器还可以包括第三声速突变结构70，第三声速突变结构70位于反射栅50远离压电基板的一侧、反射栅50靠近压电基板的一侧和反射栅50所在层中的至少一处；沿平行于汇流条21的方向，第三声速突变结构70的宽度大于反射栅50的电极指的宽度。通过在声表面波谐振器的假指30和电极指22上、反射栅50的栅格导体上均构造声速突变结构，可更有效地抑制横向模产生。
图5是本申请实施例提供的一种声表面波谐振器有无负载块的导纳曲线幅度值对比图；图6是本申请实施例提供的一种声表面波谐振器有无负载块的导纳曲线中导纳实部对比图。其中，实线a对应图3所示结构，虚线a对应图3所示结构。相比于没有声速突变结构的谐振器，本申请的结构具有更好的幅频特性，可见通过设置声速突变结构，可以显著地提升Q值(越尖锐Q值越高)，说明本申请的结构能够更好的防止横向模式能量的泄露。
在本申请的一个实施例中，参考图1和图3，第一声速突变结构40包括多个负载块41，每一负载块41对应位于一假指30的末端；位于同一排假指30末端的负载块41到对侧电极指22末端的距离相等。
在本申请的另一个实施例中，参考图7，第一声速突变结构40包括多个负载块41；每一负载块41在压电基板的垂直投影与对应的假指30在压电基板的垂直投影部分重叠；位于同一排假指30末端的负载块41到对侧电极指22末端的距离递增或递减。
在本申请的另一个实施例中，参考图8，第一声速突变结构40包括多个负载块41；每一负载块41在压电基板的垂直投影与对应的假指30在压电基板的 垂直投影部分重叠；位于同一排假指30末端的负载块41到对侧电极指22末端的距离交替相等。
沿平行于汇流条21的方向，每一负载块41的宽度小于或等于位于该负载块41两侧相邻的两个电极指22之间的宽度。参考图3、图7以及图8，示例性的画出每一负载块41的宽度小于位于其两侧相邻的两个电极指22之间的宽度。参考图9，示例性的画出每一负载块41的宽度水平延伸至等于位于其两侧相邻的两个电极指22之间的距离，这样可以更好地减小声波衍射。
在本申请的一个实施例中，参考图10，第一声速突变结构40包括两个负载条42，两个负载条42相对设置，并均与汇流条21平行；沿平行于汇流条21的方向，负载条42的宽度大于或等于汇流条21的宽度。可以理解为，为减小声波衍射，可将负载块沿水平方向延伸形成平行于汇流条21的负载条42。
相对于图1为俯视图，图12则为侧视截面图。在本申请的一个实施例中，参考图3和图12，声表面波谐振器还包括钝化层90，钝化层90覆盖在电极指22和假指30远离压电基板10的一侧，以及电极指22和假指30未覆盖的压电基板10；第一声速突变结构40位于钝化层90远离压电基板10的一侧；第一声速突变结构40的材料包括高分子涂敷材料。其中钝化层90的材料可以为二氧化硅或氮化硅，高分子涂敷材料可以为聚亚酰胺等。
第一声速突变结构40包括两个负载层43，每一负载层43在压电基板上的垂直投影覆盖对应的一假指30区域；沿平行于汇流条21的方向，假指30区域的宽度大于或等于汇流条21的宽度，沿垂直于汇流条21的方向，假指30区域的长度等于假指30的长度。负载沉降在整个假指30区域，实现增大声速突变的差值，可以抑制横向模式的同时，保证了谐振器的Q值。
参考图12，谐振器可以为薄膜声表面波(Thin Film-Surface Acoustic Wave，TF-SAW)滤波器。其中，压电基板10包括硅层11以及依次形成在硅层上的多晶硅层12、氧化硅层13和钽酸锂晶体层14。TF-SAW滤波器能提供相对较大的带宽，同时提供良好的温度补偿性能和多频带集成的有效路径。
本申请实施例提供的技术方案，通过在假指远离压电基板的一侧、假指靠近压电基板的一侧和假指所在层中的至少一处，设置第一声速突变结构，从而可以通过调整横向声学速度分布来抑制横向模式，相对于相关技术中只采用假指的方式，可以进一步有效抑制横向模式，并且避免采用假指加权的方法而影响谐振器Q值。因此，有效抑制了横向模式的同时，保证了谐振器的Q值。

Claims (10)

  1. 一种声表面波谐振器，包括：
    压电基板(10)；
    插指换能结构(20)，位于所述压电基板(10)的一侧；所述插指换能结构(20)包括相对设置的两个汇流条(21)，以及并排设置在两个汇流条(21)之间的多个电极指(22)；每个电极指(22)交替电连接到所述汇流条(21)中的一个汇流条(21)；
    多个假指(30)，每一假指(30)对应位于一所述电极指(22)末端与对侧的汇流条(21)之间；沿平行于汇流条(21)的方向，所述假指(30)的宽度等于所述电极指(22)的宽度；
    第一声速突变结构(40)，所述第一声速突变结构(40)位于所述假指(30)远离所述压电基板(10)的一侧、所述假指(30)靠近所述压电基板(10)的一侧和所述假指(30)所在层中的至少一处；沿平行于汇流条(21)的方向，所述第一声速突变结构(40)的宽度大于所述假指(30)的宽度。
  2. 根据权利要求1所述的声表面波谐振器，其中，所述第一声速突变结构(40)包括多个负载块(41)，每一负载块(41)对应位于一假指(30)的末端；位于同一排假指(30)末端的负载块(41)到对侧电极指(22)末端的距离相等。
  3. 根据权利要求1所述的声表面波谐振器，其中，所述第一声速突变结构(40)包括多个负载块(41)；每一负载块(41)在压电基板(10)的垂直投影与对应的假指(30)在压电基板(10)的垂直投影部分重叠；位于同一排假指(30)末端的负载块(41)到对侧电极指(22)末端的距离递增或递减。
  4. 根据权利要求1所述的声表面波谐振器，其中，所述第一声速突变结构(40)包括多个负载块(41)；每一负载块(41)在压电基板(10)的垂直投影与对应的假指(30)在压电基板(10)的垂直投影部分重叠；位于同一排假指(30)末端的负载块(41)到对侧电极指(22)末端的距离交替相等。
  5. 根据权利要求2～4任一所述的声表面波谐振器，其中，沿平行于汇流条 (21)的方向，每一负载块(41)的宽度小于或等于位于所述负载块(41)两侧相邻的两个电极指(22)之间的宽度。
  6. 根据权利要求1所述的声表面波谐振器，其中，所述第一声速突变结构(40)包括两个负载条(42)，两个负载条(42)相对设置，并均与所述汇流条(21)平行；沿平行于所述汇流条(21)的方向，所述负载条(42)的宽度大于或等于所述汇流条(21)的宽度。
  7. 根据权利要求1所述的声表面波谐振器，还包括钝化层(90)，所述钝化层(90)覆盖在所述电极指(22)和假指(30)远离所述压电基板(10)的一侧，以及电极指(22)和假指(30)未覆盖的压电基板(10)上；所述第一声速突变结构(40)位于所述钝化层(90)远离所述压电基板(10)的一侧；所述第一声速突变结构(40)的材料包括高分子涂敷材料。
  8. 根据权利要求7所述的声表面波谐振器，其中，所述第一声速突变结构(40)包括两个负载层(43)，每一所述负载层(43)在所述压电基板(10)上的垂直投影覆盖对应的一假指(30)区域；沿平行于所述汇流条(21)的方向，所述假指(30)区域的宽度大于或等于所述汇流条(21)的宽度，沿垂直于所述汇流条(21)的方向，所述假指(30)区域的长度等于所述假指(30)的长度。
  9. 根据权利要求1所述的声表面波谐振器，还包括：
    第二声速突变结构(60)，所述第二声速突变结构(60)位于所述电极指(22)远离所述压电基板(10)的一侧、所述电极指(22)靠近所述压电基板(10)的一侧和所述电极指(22)所在层中的至少一处；沿平行于汇流条(21)的方向，所述第二声速突变结构(60)的宽度大于所述电极指(22)的宽度；
    一对反射栅(50)，所述一对反射栅(50)与所述插指换能结构(20)位于所述压电基板(10)的同一表面上，且所述一对反射栅(50)位于所述插指换能结构(20)的相对两侧；
    第三声速突变结构(70)，所述第三声速突变结构(70)位于所述反射栅(50) 远离所述压电基板(10)的一侧、所述反射栅(50)靠近所述压电基板(10)的一侧和所述反射栅(50)所在层中的至少一处；沿平行于汇流条(21)的方向，所述第三声速突变结构(70)的宽度大于所述反射栅(50)的电极指的宽度。
  10. 根据权利要求1所述的声表面波谐振器，其中，所述压电基板(10)包括硅层(11)以及依次形成在硅层(11)上的多晶硅层(12)、氧化硅层(13)和钽酸锂晶体层(14)。
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