WO2020177555A1 - 带凹陷和空气翼结构的体声波谐振器、滤波器及电子设备 - Google Patents

带凹陷和空气翼结构的体声波谐振器、滤波器及电子设备 Download PDF

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WO2020177555A1
WO2020177555A1 PCT/CN2020/076201 CN2020076201W WO2020177555A1 WO 2020177555 A1 WO2020177555 A1 WO 2020177555A1 CN 2020076201 W CN2020076201 W CN 2020076201W WO 2020177555 A1 WO2020177555 A1 WO 2020177555A1
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Prior art keywords
edge
recessed structure
resonator according
top electrode
resonator
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English (en)
French (fr)
Inventor
庞慰
张孟伦
杨清瑞
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Tianjin University
ROFS Microsystem Tianjin Co Ltd
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Tianjin University
ROFS Microsystem Tianjin Co Ltd
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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 elements; 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 elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/0211—Means for compensation or elimination of undesirable effects of reflections

Definitions

  • the embodiments of the present invention relate to the field of semiconductors, and in particular to a bulk acoustic wave resonator with a recess and an air wing structure, a filter with the resonator, and an electronic device with the resonator or the filter.
  • the thin-film bulk wave resonator made of the longitudinal resonance of the piezoelectric film in the thickness direction has become a viable alternative to surface acoustic wave devices and quartz crystal resonators in wireless communication systems.
  • the film bulk acoustic resonator (FBAR, film bulk acoustic resonator) includes: a substrate P00, an acoustic reflection structure P10 located on the substrate or embedded in the substrate (can be a cavity, a Bragg reflection layer, and other equivalent structures) , The bottom electrode P20 on the acoustic reflection structure P10 and the substrate P00, the piezoelectric layer film P30 covering the bottom electrode P20 and the upper surface of the substrate P00, and the top electrode P40 on the piezoelectric layer, etc., wherein the acoustic reflection structure
  • the overlapping area of P10, the bottom electrode P20, the piezoelectric layer P30 and the top electrode P40 in the thickness direction constitutes the effective acoustic area AR of the resonator, and the top electrode, the piezoelectric layer and the bottom electrode constitute a sandwich structure.
  • a bulk acoustic wave resonator including:
  • the bottom electrode is set above the substrate
  • the piezoelectric layer is arranged above the bottom electrode and between the bottom electrode and the top electrode,
  • the overlapping area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the resonator constitutes the effective area of the resonator;
  • One side of the top electrode has an electrode connection part, and the other side has an air wing structure;
  • the piezoelectric layer is provided with a recessed structure, and the recessed structure has an inner edge and an outer edge.
  • the concave structure is located inside the edge of the acoustic mirror.
  • the inner edge of the recess structure coincides with the edge of the air wing structure.
  • the edge of the air wing structure is located between the inner edge and the outer edge of the recessed structure, or the outer edge of the recessed structure coincides with the edge of the air wing structure, or The recessed structure is located between the edge of the air wing structure and the edge of the top electrode, or the inner edge of the recessed structure coincides with the edge of the top electrode.
  • the radial distance X between the inner edge of the recess structure and the edge of the top electrode is not greater than 10 ⁇ m.
  • the radial distance X between the recessed structure and the edge of the top electrode may be: 0-10 ⁇ m, further, 0 ⁇ m ⁇ X ⁇ 1 ⁇ m, or 2.5 ⁇ m ⁇ X ⁇ 4.5 ⁇ m, or 6 ⁇ m ⁇ X ⁇ 8 ⁇ m. Further optionally, the gap height of the air wing structure is 0.02 ⁇ m-0.5 ⁇ m.
  • the edge of the top electrode is located between the inner edge and the outer edge of the recessed structure; or the outer edge of the recessed structure coincides with the edge of the top electrode; or the recessed The outer edge of the structure is located inside the edge of the top electrode.
  • the recess structure includes a recess.
  • the depression may be a step depression.
  • the recess structure has at least two recesses.
  • the at least two recesses may be spaced apart from each other in the radial direction.
  • the outer edge of the concave structure is located inside the edge of the bottom electrode.
  • the outer edge of the concave structure is located inside the edge of the acoustic mirror.
  • the electrode connecting portion is formed with a bridge; and the recessed structure is a shaped recessed structure.
  • the width of the recessed structure ranges from 0.5 ⁇ m to 4 ⁇ m, or one quarter or an odd multiple of the wavelength of the S1 mode Lamb wave at the parallel resonance frequency; and the depth range of the recessed structure is 0.02 ⁇ m- 0.5 ⁇ m, or 5%-100% of the thickness of the piezoelectric layer, further, 10%-40%.
  • the embodiment of the present invention also relates to a filter including the above-mentioned bulk acoustic wave resonator.
  • the embodiment of the present invention also relates to an electronic device including the above-mentioned filter or the above-mentioned resonator.
  • Figure 1 is a schematic cross-sectional view of a prior art bulk acoustic wave resonator
  • Fig. 2 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention
  • Fig. 2A is a schematic diagram exemplarily illustrating the acoustic reflection effect of a recessed structure
  • 3A to 3H are respectively partial cross-sectional views of the left part of the boundary S1 taken along A1-A2 in FIG. 2 according to an exemplary embodiment of the present invention
  • 4A to 4H are respectively partial cross-sectional views of the right part of the boundary S2 taken along A1-A2 in FIG. 2 according to an exemplary embodiment of the present invention
  • FIG. 5 is a schematic diagram illustrating the technical effect of the bulk acoustic wave resonator according to the exemplary embodiment of the present invention.
  • FIG. 6 is a structural diagram of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, wherein the width of the recessed structure is D1, the depth is H1, and the radial distance between the inner edge of the recessed structure and the edge of the top electrode is X1;
  • FIG. 7 is a graph showing the relationship between the parallel resonance impedance (Rp) and the radial distance X between the recess structure and the edge of the top electrode;
  • Figure 8 shows the dispersion curve of the S1 mode at the parallel resonance frequency of the bulk acoustic wave resonator.
  • Fig. 2 shows a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention.
  • the resonator includes a substrate 00, a bottom electrode 20 on the substrate, and a bottom electrode 20 between the bottom electrode and the substrate.
  • Figure 2 does not show the acoustic reflection structure (acoustic mirror) on the upper surface of the substrate and the pins of the bottom electrode.
  • the recessed structure As shown in FIG. 2A, the upper surface of the piezoelectric layer 30 has a recessed structure 31, which forms the boundary of two acoustic resistances B1 and B2 in the piezoelectric layer that do not match.
  • the sound wave propagates laterally from the effective acoustic area (not shown in the figure) on the right side of B1 to the B1 or B2 area, it will be reflected back to the effective area of the resonator, thereby reducing energy leakage.
  • FIG. 2 The embodiments of the present invention correspondingly propose the following technical solutions, as shown in FIG. 2, FIG. 3A to FIG. 3H, and FIG. 4A to FIG. 4H:
  • a bulk acoustic wave resonator including:
  • the bottom electrode 20 is arranged above the substrate 00;
  • the piezoelectric layer 30 is arranged above the bottom electrode and between the bottom electrode and the top electrode,
  • the overlapping area of the acoustic mirror, bottom electrode, piezoelectric layer and top electrode in the thickness direction of the resonator constitutes the effective area AR of the resonator (see FIG. 1);
  • top electrode One side of the top electrode has an electrode connection portion 43 (see FIG. 2), and the other side has an air wing structure (see, for example, FIG. 3A, the air wing structure has boundaries D1 and T1, and boundary T1 also constitutes the edge of the top electrode) ;
  • the piezoelectric layer is provided with a recessed structure 31 having an inner edge (the side of the recessed structure close to the effective area) and an outer edge (the side of the recessed structure away from the effective area).
  • FIG. 5 is a schematic diagram illustrating the technical effect of the bulk acoustic wave resonator according to an exemplary embodiment of the present invention.
  • the reflective structure A formed by the air wing and the reflective structure B formed by the recessed structure not only vibrate separately, but also can respectively leak part of the acoustic energy outside the boundary T1. (QA and QB) are reflected back to the effective area of the resonator.
  • the reflective structure A and B have a strong acoustic coupling relationship, the result of the mutual influence between the two leads to the formation of a resonance similar to a tuning fork.
  • the two structures are properly matched together
  • the combination of the air wing and the recess has a higher Q value improvement effect than the simple superposition of the suspended wing and the recessed sound wave reflection effect.
  • the recessed structure and the air wing structure can respectively reflect the sound waves propagating laterally beyond the boundary T1 back into the sandwich area, but also the recessed structure and the air wing structure together form a tuning fork structure, which can further reflect Acoustic wave and reduce energy leakage, improve Q value.
  • the material of the substrate 00 can be selected but not limited to: single crystal silicon, gallium arsenide, quartz, sapphire, silicon carbide, etc.
  • the materials of the electrodes 20 and 40 can be selected but not limited to: molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a combination of the above metals or their alloys.
  • the material of the piezoelectric layer 30 can be selected but not limited to: aluminum nitride, zinc oxide, lead zirconate titanate (PZT), lithium niobate, etc.
  • PZT lead zirconate titanate
  • a certain amount of material can be added to the material Proportion of rare earth element impurities.
  • the piezoelectric layer is a thin film with a thickness of less than 10 microns, has a single crystal or polycrystalline microstructure, and can be made by sputtering or deposition processes.
  • the acoustic mirror 10 is not limited to the acoustic mirror structure shown in the example.
  • 3A is a partial cross-sectional view of an exemplary embodiment according to the present invention of the left part of the boundary S1 taken along A1-A2 in FIG. 2.
  • the acoustic mirror (or acoustic reflection structure) 10 is located on the upper surface of the substrate 00 and has a left boundary C1
  • the top electrode 40 has a left boundary T1
  • the upper surface of the piezoelectric layer 30 is embedded with a concave structure 31.
  • the recessed structure is a rectangular ABCD. It should be pointed out that the shape of the recessed structure 31 is not limited to this. Based on actual applications or actual manufacturing processes, for example, it may be an inverted trapezoidal cross section.
  • the recessed structure 31 has a width W30 and a depth H30.
  • the right side CD (inner edge) of the recessed structure 31 coincides with the boundary D1 of the air wing structure.
  • the width W30 of the recessed structure ranges from 0.5 microns to 4 microns, and further from 1-3 microns. In addition to the above endpoints, it can also be 2 microns; or it is the S1 mode blue at the parallel resonance frequency. One quarter of the wavelength of the m wave or its odd multiples.
  • the depth H30 of the recessed structure ranges from 0.02 micrometers to 0.5 micrometers, and further ranges from 0.1 micrometers to 0.3 micrometers. In addition to the aforementioned endpoint values, it can also be 0.2 micrometers.
  • the depth of the recessed structure is the maximum depth of the recessed structure; and the width of the recessed structure is the width of the top opening of the recessed structure.
  • S1 mode Lamb wave wavelength ⁇ at the parallel resonance frequency of the resonator.
  • f frequency
  • k wave number
  • S1 mode the curves of the remaining modes are not shown in FIG. 8
  • the abscissa is the wave number
  • the ordinate is the vibration frequency.
  • the vibration frequency is the parallel resonance frequency f p
  • the corresponding wave number is k p
  • the wavelength ⁇ of the S1 mode is defined as the following formula:
  • the inner edge of the recessed structure coincides with the edge D1 of the air wing structure, but the recessed structure can also be in other positions.
  • the edge of the air wing structure is located within the recessed structure.
  • the outer edge of the recess structure coincides with the edge of the air wing structure.
  • the recessed structure is located between the edge of the air wing structure and the edge of the top electrode.
  • the inner edge of the concave structure coincides with the edge of the top electrode.
  • the edge of the top electrode is located between the inner edge and the outer edge of the recessed structure.
  • the outer edge of the concave structure coincides with the edge of the top electrode.
  • the outer edge of the concave structure is located inside the edge of the top electrode.
  • the inner edge of the recess structure may be located outside the edge D1 of the air wing structure.
  • the filling material can be non-metals such as silicon dioxide, silicon carbide, silicon nitride, etc., or metals such as titanium, molybdenum, magnesium, aluminum, and the like.
  • Fig. 6 is a schematic structural diagram of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, wherein the width of the recessed structure is D1, the depth is H1, and the distance between the inner edge of the recessed structure and the edge of the top electrode is X1, Fig. 7 shows the relationship between the parallel resonance impedance (Rp) and the radial distance X1 between the recess structure and the edge of the top electrode.
  • Rp parallel resonance impedance
  • the performance of the resonator with the recessed structure in the sense of the Q value is higher than the performance of the traditional resonator without the recessed structure in most of the range of X.
  • X1 is not greater than 10 ⁇ m, and a further range is 0 ⁇ m ⁇ X1 ⁇ 1 ⁇ m, or 2.5 ⁇ m ⁇ X1 ⁇ 4.5 ⁇ m, or 6 ⁇ m ⁇ X1 ⁇ 8 ⁇ m.
  • the gap height of the air wing structure is 0.02 ⁇ m-0.5 ⁇ m.
  • the recessed structure is not limited to being arranged on the upper side of the piezoelectric layer (as shown in FIG. 3B), and can also be arranged on the lower side of the piezoelectric layer, or between the upper and lower sides, or in the thickness of the resonator.
  • the piezoelectric layer penetrates in the direction (for example, similarly, see the recessed structure 31 in FIG. 4F).
  • the recessed structure may also be a stepped recess (for example, similarly, see the recessed structure 31 in FIG. 4G).
  • the recessed structure 31 has components with different depths.
  • the stepped recess not only increases the number of acoustic resistance mismatch boundaries, but also enriches the reflected wavelength.
  • the recessed structure is a single recessed structure, but the present invention is not limited to this.
  • the recess structure may also include at least two recesses (for example, similarly, see recesses 31 and 32 in FIG. 4H).
  • the two recesses may be spaced apart from each other by a distance in the radial direction. It should be noted that the width of the two recesses can be the same or different; in addition, the depth of the two recesses can also be different from each other.
  • FIG. 4A is a partial cross-sectional view of an exemplary embodiment of the present invention along the right side of the boundary S2 taken along A1-A2 in FIG. 2.
  • the electrode connecting portion 43 is formed with a bridge portion (that is, an arched portion in the figure); and the recessed structure 31 is a ring-shaped recessed structure passing through the electrode connecting portion 43 (see the ring-shaped structure in FIG. 2 shape).
  • the acoustic mirror 10 has a right boundary C2
  • the top electrode 40 has a right boundary T2
  • the top electrode has an electrode connection structure (ie, a pin) 43
  • the electrode connection structure 43 has an arched bridge structure.
  • the upper surface of the layer 30 is provided with a recessed structure 31.
  • the edge or boundary T2 of the top electrode is located between the inner edge and the outer edge of the concave structure.
  • the recessed structure can also be in other positions.
  • the left edge of the recessed structure 31 coincides with the boundary C2.
  • the outer edge of the recessed structure coincides with the edge of the top electrode.
  • the outer edge of the recessed structure is inside the edge of the top electrode.
  • the inner edge of the recessed structure coincides with the edge of the top electrode.
  • the recessed structure is located between the edge of the top electrode and the edge of the acoustic mirror.
  • the inner edge of the recessed structure may be located outside the edge of the acoustic mirror.
  • the outer edge of the recessed structure is located inside the edge of the bottom electrode.
  • the outer edge of the recessed structure is located inside the edge of the bottom electrode
  • the outer edge of the concave structure is located inside the edge of the acoustic mirror.
  • the width of the recessed structure ranges from 0.5 ⁇ m to 4 ⁇ m, or one quarter or an odd multiple of the wavelength of the S1 mode Lamb wave at the parallel resonance frequency; and the depth range of the recessed structure It is 0.02 ⁇ m-0.5 ⁇ m.
  • the expression "vertical projection” is used. As shown in FIG. 3A, it should be understood as projecting in the thickness direction of the resonator.
  • the dashed lines or boundaries C1 and T1 can also be used. Think of it as a vertical projection line.
  • the "coincidence” in the present invention is on the same vertical projection line, or basically on the same vertical projection line.
  • the “edge” in the present invention refers to the outermost edge or the innermost edge of the corresponding component.
  • the embodiment of the present invention also relates to a filter including the above-mentioned bulk acoustic wave resonator.
  • the embodiment of the present invention also relates to an electronic device including the above-mentioned resonator or the above-mentioned filter.

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Abstract

本发明涉及一种体声波谐振器，包括：基底；声学镜；底电极，设置在基底上方；顶电极；和压电层，设置在底电极上方以及底电极与顶电极之间，其中：所述声学镜、底电极、压电层和顶电极在谐振器厚度方向上的重叠区域构成谐振器的有效区域；所述顶电极的一侧具有电极连接部，另一侧具有空气翼结构；且所述压电层设置有凹陷结构，所述凹陷结构具有内缘与外缘。本发明还涉及一种具有上述谐振器的滤波器，以及具有上述谐振器或者滤波器的电子设备。

Description

带凹陷和空气翼结构的体声波谐振器、滤波器及电子设备 技术领域
本发明的实施例涉及半导体领域，尤其涉及一种带凹陷和空气翼结构的体声波谐振器、一种具有该谐振器的滤波器，以及一种具有该谐振器或者该滤波器的电子设备。
背景技术
近年来，基于硅材料的半导体器件、尤其是集成电路芯片取得了飞速的发展，已经牢牢占据了产业的主流地位。利用压电薄膜在厚度方向的纵向谐振所制成的薄膜体波谐振器，在无线通信系统中己成为声表面波器件和石英晶体谐振器的一个可行的替代。
如图1所示，薄膜体声波谐振器(FBAR，film bulk acoustic resonator)包括：基底P00，位于基底上或嵌入基底的声反射结构P10(可以为空腔、布拉格反射层及其他等效结构)，位于声反射结构P10和基底P00之上的底电极P20，覆盖于底电极P20和基底P00上表面的压电层薄膜P30以及位于压电层之上的顶电极P40等，其中，声反射结构P10、底电极P20、压电层P30和顶电极P40在厚度方向上的重合区域构成所述谐振器的有效声学区域AR，顶电极、压电层和底电极构成三明治结构。
当所述体声波谐振器处于理想工作状态时，只存在活塞模式声波在三明治结构中传播，并且这种振动模式的能量被限制在有效声学区域AR之内。然而，实际情况中，谐振器的三明治结构中不仅存在活塞模式的振动还存在横向传播的振动模式，后者的能量会沿横向由三明治结构中的压电层向三明治结构(AR之内的电极和压电层组成的部分)之外的压电层及其它结构发生逸散(由箭头PE所示意)，从而导致谐振器的品质因数(Q值)下降，从而使谐振器性能劣化。
发明内容
为缓解或解决现有技术中的上述问题，提出本发明。
根据本发明的实施例的一个方面，提出了一种体声波谐振器，包括：
基底；
声学镜；
底电极，设置在基底上方；
顶电极；和
压电层，设置在底电极上方以及底电极与顶电极之间，
其中：
所述声学镜、底电极、压电层和顶电极在谐振器厚度方向上的重叠区域构成谐振器的有效区域；
所述顶电极的一侧具有电极连接部，另一侧具有空气翼结构；且
所述压电层设置有凹陷结构，所述凹陷结构具有内缘与外缘。
可选的，在垂直投影中，所述凹陷结构位于声学镜的边缘的内侧。
可选的，在垂直投影中，所述凹陷结构的内缘与所述空气翼结构的边缘重合。
可选的，在垂直投影中，所述空气翼结构的边缘位于所述凹陷结构的内缘与外缘之间，或者所述凹陷结构的外缘与所述空气翼结构的边缘重合，或者所述凹陷结构位于所述空气翼结构的边缘与所述顶电极的边缘之间，或者所述凹陷结构的内缘与所述顶电极的边缘重合。进一步可选的，在垂直投影中，所述凹陷结构的内缘与所述顶电极边缘之间的径向距离X不大于10μm。在垂直投影中，所述凹陷结构与所述顶电极边缘之间的径向距离X可为：0-10μm，进一步的，0μm≤X≤1μm，或者2.5μm≤X≤4.5μm，或者6μm≤X≤8μm。进一步可选的，所述空气翼结构的空隙高度为0.02μm-0.5μm。
可选的，在垂直投影中，所述顶电极的边缘位于所述凹陷结构的内缘与外缘之间；或者所述凹陷结构的外缘与所述顶电极的边缘重合；或者所述凹陷结构的外缘位于所述顶电极的边缘的内侧。
可选的，所述凹陷结构包括一个凹陷。所述凹陷可为阶梯凹陷。
可选的，所述凹陷结构具有至少两个凹陷。所述至少两个凹陷可在径向方向上彼此间隔开。
可选的，在垂直投影中，所述凹陷结构的外缘位于所述底电极的边缘 内侧。
可选的，在垂直投影中，所述凹陷结构的外缘位于所述声学镜的边缘内侧。
可选的，所述电极连接部形成有桥部；且所述凹陷结构为形凹陷结构。
可选的，凹陷结构的宽度的取值范围为0.5μm-4μm，或者为并联谐振频率处S1模式兰姆波波长的四分之一或其奇数倍；且凹陷结构的深度范围为0.02μm-0.5μm，或为所在压电层厚度的5％-100％，进一步的，10％-40％。
本发明的实施例还涉及一种滤波器，包括上述的体声波谐振器。
本发明的实施例也涉及一种电子设备，包括上述的滤波器或者上述的谐振器。
附图说明
以下描述与附图可以更好地帮助理解本发明所公布的各种实施例中的这些和其他特点、优点，图中相同的附图标记始终表示相同的部件，其中：
图1为现有技术的体声波谐振器的剖面示意图；
图2为根据本发明的一个示例性实施例的体声波谐振器的俯视示意图；
图2A为示例性说明凹陷结构的声波反射作用的示意图；
图3A至3H分别为沿图2中的A1-A2剖得的边界S1左侧部分的根据本发明的示例性实施例的局部剖视图；
图4A至4H分别为沿图2中的A1-A2剖得的边界S2右侧部分的根据本发明的示例性实施例的局部剖视图；
图5为说明根据本发明的示例性实施例的体声波谐振器的技术效果的示意图；
图6为根据本发明的一个示例性实施例的体声波谐振器的结构示意图，其中凹陷结构的宽度为D1，深度为H1，凹陷结构的内缘与顶电极的边缘之间的径向距离为X1；
图7为示出并联谐振阻抗(Rp)随凹陷结构与顶电极的边缘之间的径向距离X的关系图；
图8为体声波谐振器并联谐振频率处S1模式的色散曲线。
具体实施方式
下面通过实施例，并结合附图，对本发明的技术方案作进一步具体的说明。在说明书中，相同或相似的附图标号指示相同或相似的部件。下述参照附图对本发明实施方式的说明旨在对本发明的总体发明构思进行解释，而不应当理解为对本发明的一种限制。
下面参照附图示例性描述根据本发明的实施例的压电层带凹陷结构的体声波谐振器。
图2给出了本发明的一个示例性实施例的体声波谐振器的俯视示意图，如图2所示，该谐振器包括基底00，位于基底之上的底电极20，位于底电极和基底之上的压电层30，位于压电层的上表面的凹陷结构31(阴影所示的沟道部分)，位于压电层之上的顶电极40以及顶电极的引脚(即电极连接部)43。
图2中并未示出位于基底上表面的声反射结构(声学镜)和底电极的引脚。
下面参照图2A示例性说明凹陷结构的作用。如图2A所示，压电层30的上表面具有凹陷结构31，该结构在压电层中形成了B1和B2两个声阻不匹配的边界。当声波从位于B1右侧的有效声学区域(图中未示出)横向传播至B1或B2区域时，会被反射回谐振器有效区域，从而减少了能量泄漏。
本发明的实施例相应提出了如下技术方案，如图2，图3A至图3H以及图4A至图4H所示：
一种体声波谐振器，包括：
基底00；
声学镜10；
底电极20，设置在基底00上方；
顶电极40；和
压电层30，设置在底电极上方以及底电极与顶电极之间，
其中：
所述声学镜、底电极、压电层和顶电极在谐振器厚度方向上的重叠区域构成谐振器的有效区域AR(参见图1)；
所述顶电极的一侧具有电极连接部43(参见图2)，另一侧具有空气翼结构(例如参见图3A，该空气翼结构具有边界D1和T1，边界T1也构成顶电极的边缘)；且
所述压电层设置有凹陷结构31，所述凹陷结构31具有内缘(凹陷结构靠近有效区域的一侧)与外缘(凹陷结构远离有效区域的一侧)。
图5为说明根据本发明的示例性实施例的体声波谐振器的技术效果的示意图。如图5所示，在本发明中，谐振器工作时，空气翼形成的反射结构A和凹陷结构形成的反射结构B不仅分别振动，并能够分别将横向泄露至边界T1之外的部分声波能量(QA和QB)反射回谐振器有效区域，同时由于反射结构A和B结构间属于强声学耦合关系，两者相互影响的结果导致最终形成类似音叉的共振，在适当配合在一起后两种结构形成耦合结构还会另外反射一份能量QA+B,那么总反射能量Q＝QA+QB+QA+B要大于QA+QB。这样空气翼和凹陷结合后对Q值的提升效果要高于悬翼与凹陷声波反射效果的单纯叠加。
因此，在本发明中，不仅凹陷结构和空气翼结构能够分别将横向传播到边界T1之外的声波反射回三明治区域内，同时凹陷结构和空气翼结构还共同构成类似音叉结构，这样可进一步反射声波并减少能量泄漏，提高Q值。
在本发明中，基底00的材料可选用但不限于：单晶硅，砷化镓，石英，蓝宝石，碳化硅等。
在本发明中，电极20和40的材料可选用但不限于：钼、钌、金、铝、镁、钨、铜，钛、铱、锇、铬或以上金属的复合或其合金。
在本发明中，压电层30的材料可选但不限于：氮化铝，氧化锌，钛锆酸铅(PZT)，铌酸锂等，可选的，还可对所述材料掺入一定比例的稀土元素杂质。
在本发明中，所述压电层为厚度小于10微米的薄膜，具有单晶或多 晶微观结构，并可由溅射或沉积工艺制成。
在本发明中，声学镜10不限于示例中示出的声学镜结构。
图3A为沿图2中的A1-A2剖得的边界S1左侧部分的根据本发明的示例性实施例的局部剖视图。
图3A中的结构中，声学镜(或者声反射结构)10位于基底00的上表面，并具有左侧边界C1，顶电极40具有左侧边界T1，压电层30的上表面嵌有凹陷结构31，所述凹陷结构为矩形ABCD。需要指出的是，凹陷结构31的形状不限于此，基于实际应用或者实际制造工艺，例如可以为倒梯形截面。
凹陷结构31具有宽度W30和深度H30。此外，在图3A中，凹陷结构31的右侧边CD(内缘)与空气翼结构的边界D1重合。
凹陷结构的宽度W30(参见图3A)的取值范围为0.5微米-4微米，进一步为1-3微米，除了上述端点值之外，还可为2微米；或者为并联谐振频率处S1模式兰姆波波长的四分之一或其奇数倍。
凹陷结构的深度H30(参见图3A)的范围为0.02微米-0.5微米，进一步的为0.1微米-0.3微米，除了上述端点值之外，还可为0.2微米。
在本发明中，凹陷结构的深度为凹陷结构的最大深度；而凹陷结构的宽度为凹陷结构的顶部开口宽度。
下面简单说明谐振器并联谐振频率处S1模式兰姆波波长λ。在体声波谐振器工作时，三明治结构中会产生大量的振动，若将这些振动按照其频率(f)和波数(k)的关系绘制成色散曲线，则可获得多种模式的曲线，其中1种模式的曲线称为S1模式(其余模式的曲线未在图8中示出)，其具有图8示形状的色散曲线，其中横坐标为波数，纵坐标为振动频率。振动频率为并联谐振频率f p时，对应的波数为k p，而S1模式的波长λ定义为下式：
Figure PCTCN2020076201-appb-000001
在图3A中，凹陷结构的内缘与空气翼结构的边缘D1重合，不过，凹陷结构也可以处于其它的位置。
如图3B所示，在垂直投影中，所述空气翼结构的边缘位于所述凹陷 结构之内。
如图3C所示，在垂直投影中，所述凹陷结构的外缘与所述空气翼结构的边缘重合。
如图3D所示，在垂直投影中，所述凹陷结构位于所述空气翼结构的边缘与所述顶电极的边缘之间。
如图3E所示，在垂直投影中，所述凹陷结构的内缘与所述顶电极的边缘重合。
如图3F所示，在垂直投影中，所述顶电极的边缘位于所述凹陷结构的内缘与外缘之间。
如图3G所示，在垂直投影中，所述凹陷结构的外缘与顶电极的边缘重合。
如图3H所示，在垂直投影中，所述凹陷结构的外缘位于所述顶电极的边缘的内侧。
此外，虽没有示出，在垂直投影中，所述凹陷结构的内缘可位于所述空气翼结构的边缘D1外侧。
此外，虽未示出，凹陷结构内还可以填充其他材料，填充材料可以是非金属如二氧化硅，碳化硅，氮化硅等，或金属如钛、钼、镁、铝等。
下面描述凹陷结构与顶电极的边缘之间的距离对于谐振器Q值的影响。图6为根据本发明的一个示例性实施例的体声波谐振器的结构示意图，其中凹陷结构的宽度为D1，深度为H1，凹陷结构的内缘与顶电极的边缘之间的距离为X1，图7示出了并联谐振阻抗(Rp)随凹陷结构与顶电极的边缘之间的径向距离X1的关系图。
在图7中，X1变化范围为0-7微米，每次变化步进0.5微米。另外2个参数D和H则被固定为2组。每次X1变化时，D1和H1均保持不变，具体的，图5示出了如下三组变化数据：
(1)D＝1um，H＝1000A，并联谐振阻抗Rp1随X1的变化数据。
(2)D＝1um，H＝3000A，并联谐振阻抗Rp2随X1的变化数据。
将上述数据与已知的无凹陷结构的谐振器的并联谐振阻抗的结果Rp0进行比较并绘图，可得到图7所示的曲线图(Rp值越高说明谐振器的 Q值越高，性能越好)。
由图7结果可知，具有凹陷结构的谐振器在Q值意义下的性能，在X大多数范围内，都要高于没有凹陷结构的传统谐振器性能。并且在一些X的取值区间内，凹陷结构可显著提高谐振器的Q值，例如在X1＝0微米处，以及X1＝3.5微米附近等。
鉴于以上，在本发明的实施例中，X1不大于10微米，进一步的范围为0μm≤X1≤1μm，或者2.5μm≤X1≤4.5μm，或者6μm≤X1≤8μm。相应的，所述空气翼结构的空隙高度为0.02μm-0.5μm。
需要说明的是，所述凹陷结构不限于设置在压电层的上侧(如图3B所示)，也可以设置在压电层的下侧，或上下侧之间，或者在谐振器的厚度方向上贯穿压电层(例如，类似的，参见图4F中的凹陷结构31)。
此外，凹陷结构也可以为阶梯型凹陷(例如，类似的，参见图4G中的凹陷结构31)。具体的，该凹陷结构31具有不同深度的组成部分。阶梯型凹陷不仅增加了声阻不匹配边界的数量，而且丰富了反射波长。
在图3A至3H的示例中，凹陷结构为单凹陷结构，但本发明不限于此。凹陷结构也可以包括至少两个凹陷(例如，类似的，参见图4H中的凹陷31与32)。两个凹陷可以在径向方向上彼此间隔开一个距离。需要指出的是，该两个凹陷的宽度可以相同，也可以不同；此外，两个凹陷的深度也可以彼此不同。
图4A为沿图2中的A1-A2剖得的边界S2右侧部分的根据本发明的示例性实施例的局部剖视图。如图所示，所述电极连接部43形成有桥部(即图中拱形部)；且所述凹陷结构31为穿过所述电极连接部43的环形凹陷结构(参见图2中的环形形状)。
如图4A所示，声学镜10具有右侧边界C2，顶电极40具有右侧边界T2，顶电极具有电极连接结构(即引脚)43，电极连接结构43具有拱起的桥结构，压电层30的上表面设置有凹陷结构31。在图4A中,在垂直投影中,顶电极的边缘或者边界T2位于所述凹陷结构的内缘与外缘之间。不过，凹陷结构也可以处于其它的位置。
凹陷结构31的左侧边缘(凹陷结构的内缘)与边界C2重合。
如图4B所示，在垂直投影中,凹陷结构的外缘与顶电极的边缘重合。
如图4C所示，在垂直投影中,凹陷结构的外缘处于顶电极的边缘的内侧。
如图4D所示，在垂直投影中,凹陷结构的内缘与顶电极的边缘重合。
如图4E所示，在垂直投影中,凹陷结构位于顶电极的边缘与声学镜的边缘之间。
此外，虽没有示出，所述凹陷结构的内缘可位于所述声学镜的边缘外侧。
参见图3A-图3H，在可选的实施例中，在垂直投影中，所述凹陷结构的外缘位于所述底电极的边缘内侧。
在可选的实施例中，所述凹陷结构的外缘位于所述底电极的边缘内侧
可选的，在垂直投影中，所述凹陷结构的外缘位于所述声学镜的边缘内侧。
在本发明的实施例中，凹陷结构的宽度的取值范围为0.5μm-4μm，或者为并联谐振频率处S1模式兰姆波波长的四分之一或其奇数倍；且凹陷结构的深度范围为0.02μm-0.5μm。
在本发明中，使用了“垂直投影”的表述，如附图3A所示，应理解为在与谐振器的厚度方向上进行投影，例如，在图3A中，虚线或边界C1和T1也可以认为是垂直投影线。而本发明中的“重合”则是处于同一垂直投影线上，或者基本处于同一垂直投影线上。本发明中的“边缘”则为对应部件的最外侧缘或者最内侧缘。
虽然没有示出，本发明的实施例也涉及一种滤波器，包括上述的体声波谐振器。
本发明的实施例也涉及一种电子设备，包括上述的谐振器或者上述的滤波器。
尽管已经示出和描述了本发明的实施例，对于本领域的普通技术人员而言，可以理解在不脱离本发明的原理和精神的情况下可以对这些实施例进行变化，本发明的范围由所附权利要求及其等同物限定。

Claims (19)

  1. 一种体声波谐振器，包括：
    基底；
    声学镜；
    底电极，设置在基底上方；
    顶电极；和
    压电层，设置在底电极上方以及底电极与顶电极之间，
    其中：
    所述声学镜、底电极、压电层和顶电极在谐振器厚度方向上的重叠区域构成谐振器的有效区域；
    所述顶电极的一侧具有电极连接部，另一侧具有空气翼结构；且
    所述压电层设置有凹陷结构，所述凹陷结构具有内缘与外缘。
  2. 根据权利要求1所述的谐振器，其中：
    在垂直投影中，所述凹陷结构位于声学镜的边缘的内侧。
  3. 根据权利要求2所述的谐振器，其中：
    在垂直投影中，所述凹陷结构的内缘与所述空气翼结构的边缘重合。
  4. 根据权利要求2所述的谐振器，其中：
    在垂直投影中，所述空气翼结构的边缘位于所述凹陷结构的内缘与外缘之间，或者所述凹陷结构的外缘与所述空气翼结构的边缘重合，或者所述凹陷结构位于所述空气翼结构的边缘与所述顶电极的边缘之间，或者所述凹陷结构的内缘与所述顶电极的边缘重合。
  5. 根据权利要求3或4所述的谐振器，其中：
    在垂直投影中，所述凹陷结构的内缘与所述顶电极边缘之间的径向距离X不大于10μm。
  6. 根据权利要求5所述的谐振器，其中：
    在垂直投影中，所述凹陷结构与所述顶电极边缘之间的径向距离X为：0μm≤X≤1μm，或者2.5μm≤X≤4.5μm，或者6μm≤X≤8μm。
  7. 根据权利要求6所述的谐振器，其中：
    所述空气翼结构的空隙高度为0.02μm–0.5μm。
  8. 根据权利要求2所述的谐振器，其中：
    在垂直投影中，所述顶电极的边缘位于所述凹陷结构的内缘与外缘之间；或者所述凹陷结构的外缘与所述顶电极的边缘重合；或者所述凹陷结构的外缘位于所述顶电极的边缘的内侧。
  9. 根据权利要求1所述的谐振器，其中：
    所述凹陷结构包括一个凹陷。
  10. 根据权利要求9所述的谐振器，其中：
    所述凹陷为阶梯凹陷。
  11. 根据权利要求1所述的谐振器，其中：
    所述凹陷结构具有至少两个凹陷。
  12. 根据权利要求11所述的谐振器，其中：
    所述至少两个凹陷在径向方向上彼此间隔开。
  13. 根据权利要求1所述的谐振器，其中：
    在垂直投影中，所述凹陷结构的外缘位于所述底电极的边缘内侧。
  14. 根据权利要求1所述的谐振器，其中：
    在垂直投影中，所述凹陷结构的外缘位于所述声学镜的边缘内侧。
  15. 根据权利要求1所述的谐振器，其中：
    所述电极连接部形成有桥部；且
    所述凹陷结构为环形凹陷结构。
  16. 根据权利要求1-15中任一项所述的谐振器，其中：
    凹陷结构的宽度的取值范围为0.5μm-4μm，或者为并联谐振频率处S1模式兰姆波波长的四分之一或其奇数倍；且
    凹陷结构的深度范围为0.02μm-0.5μm，或者为所在压电层厚度的5％-100％。
  17. 根据权利要求16所述的谐振器，其中：
    凹陷结构的深度范围为所在压电层厚度的10％-40％。
  18. 一种滤波器，包括根据权利要求1-17中任一项所述的体声波谐振器。
  19. 一种电子设备，包括根据权利要求18所述的滤波器或者根据权利要求1-17中任一项所述的谐振器。
PCT/CN2020/076201 2019-03-02 2020-02-21 带凹陷和空气翼结构的体声波谐振器、滤波器及电子设备 Ceased WO2020177555A1 (zh)

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