WO2020125353A1 - 带沟槽的体声波谐振器、滤波器和电子设备 - Google Patents

带沟槽的体声波谐振器、滤波器和电子设备 Download PDF

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WO2020125353A1
WO2020125353A1 PCT/CN2019/121094 CN2019121094W WO2020125353A1 WO 2020125353 A1 WO2020125353 A1 WO 2020125353A1 CN 2019121094 W CN2019121094 W CN 2019121094W WO 2020125353 A1 WO2020125353 A1 WO 2020125353A1
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Prior art keywords
bottom electrode
groove
resonator
resonator according
upper side
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PCT/CN2019/121094
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English (en)
French (fr)
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杨清瑞
庞慰
张孟伦
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天津大学
诺思(天津)微系统有限责任公司
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Publication of WO2020125353A1 publication Critical patent/WO2020125353A1/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
    • H03H9/15—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 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
    • 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

  • Embodiments of the present invention relate to the field of semiconductors, and particularly to a bulk acoustic wave resonator, a filter with the resonator, an electronic device with the filter, and a method of increasing the parallel impedance of the resonator.
  • RF front-end filters composed of bulk acoustic wave resonators are widely used in RF communication systems.
  • Such filters usually have superior electrical performance, such as low insertion loss, steep transition band, large power capacity, and Strong anti-static discharge capability, and processing technology can be compatible with IC technology, which is suitable for large-scale low-cost manufacturing.
  • the quality of the filter is closely related to the performance indicators of the resonator.
  • Bulk acoustic wave resonators generally have two resonance frequencies.
  • the frequency point with the smallest impedance is defined as the series resonance frequency fs
  • the corresponding impedance is the series impedance Rs
  • the frequency point with the largest impedance is the parallel resonance frequency fp
  • the corresponding impedance is the parallel impedance Rp.
  • the electromechanical coupling coefficient measures the piezoelectric conversion efficiency in the resonator.
  • the series resonance frequency of the resonator determines the center frequency of the filter, and the effective electromechanical coupling coefficient of the resonator determines the maximum bandwidth that the filter can achieve.
  • the series and parallel impedances of the resonator determine the passband insertion loss and return Wave loss.
  • the invention proposes a technical solution for improving the parallel impedance of a bulk acoustic wave resonator by providing grooves.
  • a bulk acoustic wave resonator including: a substrate; an acoustic mirror; a bottom electrode provided on the upper side of the substrate; a top electrode; and a piezoelectric layer provided on the upper side of the bottom electrode and Between the bottom electrode and the top electrode, wherein: the area where the acoustic mirror, bottom electrode, piezoelectric layer, and top electrode overlap in the thickness direction of the substrate is the effective area of the resonator; the resonator further includes at least one groove, the The groove extends around the edge of the effective area.
  • the groove is an annular groove.
  • the lateral distance between the groove and the acoustic mirror remains unchanged.
  • the at least one groove includes one groove.
  • the trench is provided on the upper side of the substrate and completely covers the bottom electrode.
  • the depth H of the groove satisfies: 0.1 ⁇ m ⁇ H ⁇ 0.6 ⁇ m; and the distance from the groove to the acoustic mirror is D, and the width of the groove is W, where: 1 ⁇ m ⁇ D ⁇ 1.8 ⁇ m, and 1.2 ⁇ m ⁇ W ⁇ 2.5 ⁇ m.
  • the trench is provided on the upper side of the substrate and partially covers the bottom electrode.
  • the trench is provided on the upper side of the substrate and is spaced apart from the bottom electrode.
  • the depth H of the groove satisfies the condition: 0.6 ⁇ m ⁇ H ⁇ 1.1 ⁇ m, or 1.7 ⁇ m ⁇ H ⁇ 2.3 ⁇ m. Furthermore, it is 0.7 ⁇ m ⁇ H ⁇ 0.8 ⁇ m, or 1.9 ⁇ m ⁇ H ⁇ 2.1 ⁇ m.
  • the at least one groove includes two grooves.
  • the two trenches are provided on the upper side of the substrate and are completely covered by the bottom electrode.
  • the two trenches are provided on the upper side of the substrate and are spaced apart from the bottom electrode.
  • one of the two trenches is completely covered by the bottom electrode, and the other trench is partially covered by the bottom electrode or spaced apart from the bottom electrode.
  • one of the two trenches is partially covered by the bottom electrode, and the other trench is spaced apart from the bottom electrode.
  • the groove is provided on the lower or upper side of the piezoelectric layer; or the groove is provided on the upper or lower side of the bottom electrode.
  • the at least one groove includes a plurality of groove segments, the plurality of groove segment grooves are spaced apart from each other and are disposed along the effective area.
  • a filter including the bulk acoustic wave resonator described above.
  • an electronic device including the above-mentioned filter or the above-mentioned resonator.
  • the invention also relates to a method for increasing the parallel impedance of a bulk acoustic wave resonator, comprising the steps of forming at least one annular groove on the upper side of the resonator base around the effective area of the resonator.
  • FIG. 1A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, in which only one annular groove is provided;
  • Fig. 1B is a cross-sectional view of the bulk acoustic wave resonator in Fig. 1A along the A-A' direction according to an exemplary embodiment of the present invention
  • FIG. 1C is an exemplary relationship curve diagram of the bulk acoustic wave resonator in FIG. 1B with respect to the depth of the groove (that is, the height H of the circular swimming pool) and the parallel impedance of the resonator;
  • 1D is a cross-sectional view of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention.
  • FIG. 1E is an exemplary relationship diagram of the bulk acoustic wave resonator in FIG. 1D with respect to the depth of the groove (that is, the height H of the circular swimming pool) and the parallel impedance of the resonator;
  • 1F is a cross-sectional view of a bulk acoustic wave resonator according to still another exemplary embodiment of the present invention.
  • FIG. 1G is an exemplary relationship diagram of the bulk acoustic wave resonator in FIG. 1F with respect to the depth of the groove (that is, the height H of the circular swimming pool) and the parallel impedance of the resonator;
  • FIG. 2A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, in which only two annular grooves are provided;
  • FIG. 2B is a cross-sectional view of the bulk acoustic wave resonator in FIG. 2A along the B-B' direction according to an exemplary embodiment of the present invention
  • 2C is a cross-sectional view of a bulk acoustic wave resonator according to still another exemplary embodiment of the present invention.
  • 2D is a cross-sectional view of a bulk acoustic wave resonator according to yet another exemplary embodiment of the present invention.
  • FIG. 1A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention
  • FIG. 1B is a cross section of the bulk acoustic wave resonator in FIG. 1A along the AA' direction according to an exemplary embodiment of the present invention.
  • the bulk acoustic wave resonator includes a bottom electrode 120, a piezoelectric layer 130, a top electrode 140, and a first annular groove 150.
  • the bulk acoustic wave resonator includes a substrate 100 and an acoustic mirror 110.
  • the acoustic mirror is located on the upper surface of the substrate or embedded inside the substrate.
  • the acoustic mirror is composed of a cavity embedded in the substrate, but any other acoustic mirror structure The same applies to Bragg reflectors.
  • the bulk acoustic wave resonator further includes a bottom electrode 120, a piezoelectric layer 130, and a top electrode 140.
  • the bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror.
  • the ends of the two sides of the bottom electrode 120 may be etched into inclined planes, and the inclined planes are located on the outer side of the acoustic mirror, and may also be stepped, vertical, or other similar structures.
  • the piezoelectric layer 130 has a first end, a corresponding second end, and an intermediate portion, and is located above the bottom electrode. The two end portions extend to the substrate in opposite directions, respectively.
  • the top electrode 140 is deposited on the piezoelectric layer 130.
  • the ring-shaped grooves 150 are located on both sides of the acoustic mirror 110 with a certain interval from the acoustic mirror, and in the non-slope area at the bottom of the bottom electrode.
  • the area where the top electrode, piezoelectric layer, bottom electrode, and cavity overlap in the thickness direction is the effective area of the resonator, that is, the area d2 in the figure.
  • the sound wave leaks from the effective area, it propagates in the surrounding medium in the form of traveling waves.
  • the annular groove 150 is added, the air impedance is 0 due to the introduction of the air interface, and the corresponding area is d1 and d3 in the figure.
  • the equivalent acoustic impedance of the area will be lower than the acoustic impedance of the two adjacent sides, thereby forming two impedance mismatch interfaces, so that the sound waves can form reflections at these two interfaces, so that part of the leaked sound wave energy can return to the resonant cavity d2 , Thereby increasing the parallel resistance Rp.
  • the depth of the annular groove and the depth of the cavity 110 may be the same or different. Referring to FIG. 1B, it is defined that H is the depth of the annular groove, W is the width of the annular groove, D is the distance from the inner edge of the annular groove to the edge of the cavity, and the distance of the bottom electrode beyond the cavity is E.
  • FIG. 1B it is defined that H is the depth of the annular groove
  • W is the width of the annul
  • the abscissa is the depth H of the annular groove, and the ordinate is the parallel impedance Rp.
  • the depth H of the trench satisfies: 0.1 ⁇ m ⁇ H ⁇ 0.6 ⁇ m; and the trench reaches the The distance of the acoustic mirror is D, and the width of the groove is W, where: 1 ⁇ m ⁇ D ⁇ 1.8 ⁇ m, and 1.2 ⁇ m ⁇ W ⁇ 2.5 ⁇ m.
  • the annular groove 150 may also be disposed outside the bottom electrode 120, as shown in FIG. 1D.
  • the structure of Figure 1D is simulated, and the simulation results are shown in Figure 1E.
  • the abscissa is the depth H of the annular groove, and the ordinate is the parallel impedance Rp.
  • the end of the bottom electrode 120 is located above the annular groove 150, but does not completely cover the annular groove 150, as shown in FIG. 1F.
  • the structure of Figure 1F is simulated, and the simulation results are shown in Figure 1G.
  • the abscissa is the depth H of the annular groove, and the ordinate is the parallel impedance Rp.
  • the depth H of the trench satisfies the condition: 0.6 ⁇ m ⁇ H ⁇ 1.1 ⁇ m, Or 1.7 ⁇ m ⁇ H ⁇ 2.3 ⁇ m. Further, it is 0.7 ⁇ m ⁇ H ⁇ 0.8 ⁇ m, or 1.9 ⁇ m ⁇ H ⁇ 2.1 ⁇ m.
  • the bulk acoustic wave resonator includes a bottom electrode 220, a piezoelectric layer 230, a top electrode 240, a first annular groove 250, and a second annular groove 260.
  • FIG. 2B a cross-sectional view of the bulk acoustic wave resonator taken along the top view B-B' of FIG. 2A.
  • the bulk acoustic wave resonator includes a substrate 200 and an acoustic mirror 210, which is located on the upper surface of the substrate or embedded inside the substrate.
  • the acoustic mirror is composed of a cavity embedded in the substrate, but any other acoustic mirror structure The same applies to Bragg reflectors.
  • the bulk acoustic wave resonator further includes a bottom electrode 220, a piezoelectric layer 230, and a top electrode 240.
  • the bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror.
  • the ends of the two sides of the bottom electrode 220 may be etched into inclined planes, and the inclined planes are located on the outer side of the acoustic mirror, and may also be stepped, vertical, or other similar structures.
  • the piezoelectric layer 230 has a first end, a corresponding second end, and an intermediate portion, and is located above the bottom electrode. The two end portions extend to the substrate in opposite directions, respectively.
  • the top electrode 240 is deposited on the piezoelectric layer 230.
  • the first annular groove 250 and the second annular groove 260 are located on both sides of the acoustic mirror 210 with a certain interval from the acoustic mirror, and in a non-slope area at the bottom of
  • the first annular groove 250 and the second annular groove 260 may not all be disposed in the non-slope region at the bottom of the bottom electrode.
  • the first ring-shaped trench 250 is disposed outside the bottom electrode 220
  • the second ring-shaped trench 260 is disposed in the slope area at the bottom of the bottom electrode, as shown in FIG. 2C.
  • the end of the bottom electrode 220 is located above the first annular groove 250 but does not cover the first annular groove 250, and the second annular groove 260 is disposed under the bottom electrode 220, as shown in FIG. 2D.
  • FIGS. 2A-2D Although only two grooves are shown in FIGS. 2A-2D, three or more grooves may be provided based on needs, and these are all within the protection scope of the present invention.
  • the present invention proposes a bulk acoustic wave resonator, including:
  • Substrate 100 or 200 are Substrate 100 or 200;
  • the bottom electrode 120 or 220 is provided on the upper side of the substrate 100 or 200;
  • Top electrode 140 or 240
  • the piezoelectric layer 130 or 230 is provided on the upper side of the bottom electrode and between the bottom electrode and the top electrode,
  • the area where the acoustic mirror, bottom electrode, piezoelectric layer, and top electrode overlap in the thickness direction of the substrate is the effective area of the resonator;
  • the resonator further includes a trench 150 or 250 or 260 that extends around the edge of the effective area (in FIG. 1A, for example, it can be considered to correspond to the boundary area d2 of the top electrode 140).
  • a groove structure is processed on, for example, the substrate at one or more edges of the effective area of the resonator.
  • Rp value the resonator parallel resistance
  • the groove is a micro groove structure.
  • the groove is an annular groove.
  • the groove may also be a plurality of groove segments that are spaced apart from each other and are arranged along the effective area.
  • the groove segment may be one or more groove segments disposed on one side or multiple sides of the polygonal effective area shown in FIG. 1A.
  • the lateral distance between the groove and the acoustic mirror remains unchanged.
  • the trenches are all formed on the substrate.
  • the present invention is not limited to this, and the groove may be formed at the lower surface of the piezoelectric layer opposed to the substrate, or provided at the upper surface of the piezoelectric layer. Or the trench is provided on the upper side or the lower side of the bottom electrode.
  • the trench or the trench segment may be filled with other materials or may not be filled, which are all within the protection scope of the present invention.
  • one of the two trenches is completely covered by the bottom electrode, and the other trench is partially covered by the bottom electrode or spaced apart from the bottom electrode.
  • one of the two trenches is partially covered by the bottom electrode, and the other trench is spaced apart from the bottom electrode.
  • the "upper side” in the orientation means the side away from the substrate in the thickness direction of the resonator, and the “lower side” means the side close to the substrate in the thickness direction of the resonator.
  • the embodiments of the present invention also relate to a filter including the bulk acoustic wave resonator described above.
  • Embodiments of the present invention also relate to an electronic device, including the above-mentioned filter or resonator.
  • the electronic devices here include but are not limited to intermediate products such as radio frequency front-ends, filter amplification modules, and terminal products such as mobile phones, WIFI, and drones.
  • the present invention also proposes a method for increasing the parallel impedance of a bulk acoustic wave resonator, comprising the steps of forming at least one annular groove on the upper side of the resonator base around the effective area of the resonator.

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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，设置在基底上侧；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：声学镜、底电极、压电层、顶电极在基底的厚度方向重叠的区域为谐振器的有效区域；所述谐振器还包括至少一个沟槽，所述沟槽围绕所述有效区域延伸设置。所述沟槽可设置于所述压电层的下侧或者上侧；或者所述沟槽可设置于所述底电极的上侧或者下侧。本发明还涉及一种具有该谐振器的滤波器，一种具有上述滤波器或者谐振器的电子设备，一种提高体声波谐振器的并联阻抗的方法。

Description

带沟槽的体声波谐振器、滤波器和电子设备 技术领域
本发明的实施例涉及半导体领域，尤其涉及一种体声波谐振器，一种具有该谐振器的滤波器，一种具有该滤波器的电子设备，以及一种提高谐振器的并联阻抗的方法。
背景技术
当前，由体声波谐振器构成的射频前端滤波器在射频通讯系统中被广泛应用，这种滤波器通常具有优越的电性能，如低插入损耗、陡峭的过渡带、较大的功率容量、较强的抗静电放电能力，以及加工工艺能够与IC工艺相兼容，从而适宜大规模低成本制造。而滤波器的好坏与谐振器的各项性能指标息息相关。
体声波谐振器一般具有两个谐振频率，定义阻抗最小的频率点为串联谐振频率fs，相应阻抗为串联阻抗Rs，阻抗最大的频率点为并联谐振频率fp，相应阻抗为并联阻抗Rp，通过有效机电耦合系数衡量谐振器中压电转换效率。通常，谐振器的串联谐振频率决定了滤波器的中心频率，而谐振器的有效机电耦合系数决定了滤波器可实现的最大带宽，谐振器的串联阻抗和并联阻抗决定了通带插入损耗及回波损耗。一般而言，谐振器的并联阻抗Rp越高，串联阻抗Rs越低，相应滤波器的通带插入损耗越好。因此，如何提高谐振器的性能，特别是提高谐振器的并联阻抗Rp，是滤波器设计中的一个重要而基础的问题。
发明内容
本发明提出了一种通过设置沟槽提高体声波谐振器的并联阻抗的技术方案。
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，设置在基底上侧；顶电极；和压电层，设置在底电极上侧以及底电极与顶电极之间，其中：声学镜、底电极、压电层、顶电极在基底的厚度方向重叠的区域为谐振器的有效区域；所述谐振器还包括至少一个沟槽，所述沟槽围绕所述有效区域边缘延伸设置。
可选的，所述沟槽为环形沟槽。
可选的，所述沟槽与所述声学镜的横向距离保持不变。
可选的，所述至少一个沟槽包括一个沟槽。
可选的，所述沟槽设置在基底上侧且为所述底电极完全覆盖。可选的，所述沟槽的深度H满足：0.1μm≤H≤0.6μm；且所述沟槽到所述声学镜的距离为D，所述沟槽的宽度为W，其中：1μm≤D≤1.8μm，且1.2μm≤W≤2.5μm。
可选的，所述沟槽设置在基底上侧且为所述底电极部分覆盖。或者可选的，所述沟槽设置在基底上侧且与底电极间隔开。进一步的，所述沟槽的深度H满足条件：0.6μm≤H≤1.1μm，或者1.7μm≤H≤2.3μm。更进一步的，在0.7μm≤H≤0.8μm，或者1.9μm≤H≤2.1μm。
可选的，所述至少一个沟槽包括两个沟槽。
进一步的，所述两个沟槽设置在基底上侧且均被所述底电极完全覆盖。
可选的，所述两个沟槽设置在基底上侧且均与所述底电极间隔开。
可选的，所述两个沟槽中的一个沟槽被所述底电极完全覆盖，另一个沟槽被所述底电极部分覆盖或者与所述底电极间隔开。可选的，所述两个沟槽中的一个沟槽被所述底电极部分覆盖，另一个沟槽被与所述底电极间隔开。
可选的，所述沟槽设置于所述压电层的下侧或者上侧；或者所述沟槽设置于所述底电极的上侧或者下侧。
可选的，所述至少一个沟槽包括多个沟槽段，所述多个沟槽段槽彼此之间间隔开且沿围绕所述有效区域设置。
根据本发明的实施例的另一方面，提出了一种滤波器，包括上述的体声波谐振器。
根据本发明的实施例的再一方面，提出了一种电子设备，包括上述的滤波器或者上述的谐振器。
本发明还涉及一种提高体声波谐振器的并联阻抗的方法，包括步骤：围绕所述谐振器的有效区域在谐振器的基底上侧形成至少一个环形沟槽。
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1A为根据本发明的一个示例性实施例的体声波谐振器示意性俯视图，其中，仅设置了一个环形沟槽；
图1B为根据本发明的一个示例性实施例的图1A中的体声波谐振器沿A-A’向的截面图；
图1C为图1B中的体声波谐振器的关于沟槽的深度(即环形泳池高度H)与谐振器的并联阻抗的示例性关系曲线图；
图1D为根据本发明的另一个示例性实施例的体声波谐振器的截面图；
图1E为图1D中的体声波谐振器的关于沟槽的深度(即环形泳池高度H)与谐振器的并联阻抗的示例性关系曲线图；
图1F为根据本发明的再一个示例性实施例的体声波谐振器的截面图；
图1G为图1F中的体声波谐振器的关于沟槽的深度(即环形泳池高度H)与谐振器的并联阻抗的示例性关系曲线图；
图2A为根据本发明的一个示例性实施例的体声波谐振器示意性俯视图，其中，仅设置了两个环形沟槽；
图2B为根据本发明的一个示例性实施例的图2A中的体声波谐振器沿B-B’向的截面图；
图2C为根据本发明的再一个示例性实施例的体声波谐振器的截面图；
图2D为根据本发明的又一个示例性实施例的体声波谐振器的截面图。
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。
下面参照附图描述根据本发明的实施例的体声波谐振器。
图1A为根据本发明的一个示例性实施例的体声波谐振器示意性俯视图；图1B为根据本发明的一个示例性实施例的图1A中的体声波谐振器沿A-A’向的截面图。
参见图1A和1B，体声波谐振器包括底电极120，压电层130，顶电极140，第一环形沟槽150。体声波谐振器包括基底100和声学镜110，此声学镜位于基底的上表面或嵌于基底的内部，在图1B中声学镜为嵌入基底中的空腔所构成，但是任何其它 的声学镜结构如布拉格反射层也同样适用。
体声波谐振器还包括底电极120、压电层130、顶电极140。底电极沉积在声学镜的上表面，并覆盖声学镜。可将底电极120的两侧末端部刻蚀成斜面，并且该斜面位于声反射镜的外边，此外还可以为阶梯状、垂直状或是其它相似的结构。所述的压电层130具有第一末端和对应的第二末端以及中间部分，并且位于底电极之上，两个末端部分分别向相反方向延伸到基底之上。顶电极140沉积在压电层130之上。环形沟槽150位于声学镜110的两侧，与声学镜有一定的间隔，且在底电极底部的非斜坡区域。
顶电极、压电层、底电极、空腔在厚度方向重叠的区域为谐振器的有效区域，即图中的区域d2。当声波从有效区域泄露出来时，以行波形式在周围介质中传播，当增加了环形沟槽150时，由于引入空气界面，而空气的声阻抗为0，对应区域即图中的d1和d3区域的等效声阻抗会比相邻两侧声阻抗低，从而形成两个阻抗不匹配界面，使得声波在这两个界面处可以形成反射，使得一部分泄漏出的声波能量可以回到谐振腔d2中，从而提高并联阻抗Rp。
环形沟槽的深度可以和空腔110深度可以相同或不同。参见图1B，定义H是环形沟槽的深度，W是环形沟槽的宽度，D是环形沟槽内边缘距离空腔边缘的距离，底电极超出空腔的距离为E。采用有限元法对上述结构进行二维仿真，其仿真结果如图1C所示。仿真中，设定E为5μm，分别计算了W＝1μm，D＝1μm；W＝1μm，D＝2μm；W＝2μm，D＝1μm和W＝2μm，D＝1μm四种情况。图1C中横坐标为环形沟槽的深度H，纵坐标为并联阻抗Rp。H＝0的情况是没有沟槽的情况；从图1C中可以看出，在W＝2μm，D＝1μm的情况下，当H＝0.3μm时，并联阻抗Rp可以达到2477，增大约250(约11.2％)。
相应的，在根据本发明的示例性实施例中，对于沟槽被底电极完全覆盖的情况，所述沟槽的深度H满足：0.1μm≤H≤0.6μm；且所述沟槽到所述声学镜的距离为D，所述沟槽的宽度为W，其中：1μm≤D≤1.8μm，且1.2μm≤W≤2.5μm。在进一步的实施例中，0.1μm≤H≤0.6μm。更进一步的，1μm≤D≤1.2μm，且1.8μm≤W≤2.0μm。
环形沟槽150也可设置在底电极120的外侧,如图1D所示。对图1D结构进行仿真，其仿真结果如图1E所示。仿真中，设定E为5μm，分别计算了W＝1μm，D＝5μm； W＝1μm，D＝7μm；W＝1μm，D＝9μm三种情况。图中横坐标为环形沟槽的深度H，纵坐标为并联阻抗Rp。H＝0的情况是没有环形沟槽的情况；在W＝1μm，D＝7μm的情况下，当H＝0.7μm时，并联阻抗Rp达到2929，增大约700(约31.5％)。在W＝1μm，D＝9μm的情况下，当H＝2μm时，并联阻抗Rp达到2977，增大约750(33.7％)。
可选的，底电极120的末端位于环形沟槽150之上，但不全部覆盖环形沟槽150，如图1F所示。对图1F结构进行仿真，其仿真结果如图1G所示。仿真中，设定E为5μm，分别计算了W＝1μm，D＝4.25μm；W＝1μm，D＝4.5μm；W＝1μm，D＝4.75μm三种情况。图中横坐标为环形沟槽的深度H，纵坐标为并联阻抗Rp。H＝0的情况是没有环形沟槽的情况；在W＝1μm，D＝4.5μm的情况下，当H＝0.8μm时，并联阻抗Rp达到3015，增大约790(约35.6％)。对比图1C、1E、1G的仿真结果，可以看到，当沟槽宽度固定时，如W＝1μm时，当环形沟槽横跨底电极末端(第三种结构情况时)可以取得最好的提升并联阻抗Rp的效果。
相应的，在根据本发明的示例性实施例中，对于沟槽没有被底电极覆盖或者没有完全被底电极覆盖的情况，所述沟槽的深度H满足条件：0.6μm≤H≤1.1μm，或者1.7μm≤H≤2.3μm。进一步的，在0.7μm≤H≤0.8μm，或者1.9μm≤H≤2.1μm。
以上以单个沟槽为例进行说明，下面参照附图2A-2D以两个沟槽为例示例性说明根据本发明的谐振器。
如图2A-2D所示，体声波谐振器包括底电极220，压电层230，顶电极240，第一环形沟槽250和第二环形沟槽260。
图2B所示的实施例中，为体声波谐振器沿着图2A俯视图B-B’所取的截面图。体声波谐振器包括基底200和声学镜210，此声学镜位于基底的上表面或嵌于基底的内部，在图2B中声学镜为嵌入基底中的空腔所构成，但是任何其它的声学镜结构如布拉格反射层也同样适用。
体声波谐振器还包括底电极220，压电层230、顶电极240。底电极沉积在声学镜的上表面，并覆盖声学镜。可将底电极220的两侧末端部刻蚀成斜面，并且该斜面位于声反射镜的外边，此外还可以为阶梯状、垂直状或是其它相似的结构。所述的压电层230具有第一末端和对应的第二末端以及中间部分，并且位于底电极之上，两个末端部分分别向相反方向延伸到基底之上。顶电极240沉积在压电层230之上。第一环形沟槽250和第二环形沟槽260位于声学镜210的两侧，与声学镜有一定的间隔， 且在底电极底部的非斜坡区域。
通过设置多个环形沟槽，相比图1A中给出的实施例，可以形成更多声阻抗不匹配界面，从而将泄露声波多次反射回有效区域，以增强谐振器的并联阻抗Rp。
第一环形沟槽250和第二环形沟槽260也可不全部设置在底电极底部的非斜坡区域。例如第一环形沟槽250设置在底电极220的外侧，第二环形沟槽260设置在底电极底部的斜坡区域，如图2C所示。
可选的，底电极220的末端位于第一环形沟槽250之上但不覆盖第一环形沟槽250，第二环形沟槽260设置在底电极220之下，如图2D所示。
虽然在附图2A-2D中，仅仅示出了两个沟槽，但是基于需要，也可以设置三个或更多沟槽，这些均在本发明的保护范围之内。
基于以上，本发明提出了一种体声波谐振器，包括：
基底100或200；
声学镜110或210；
底电极120或220，设置在基底100或200上侧；
顶电极140或240；和
压电层130或230，设置在底电极上侧以及底电极与顶电极之间，
其中：
声学镜、底电极、压电层、顶电极在基底的厚度方向重叠的区域为谐振器的有效区域；
所述谐振器还包括沟槽150或250或260，所述沟槽围绕所述有效区域(在图1A中，示例性的，可以认为对应于顶电极140的边界区域d2)边缘延伸设置。
在本发明中，在谐振器的有效区域的一边或多边边缘处，在例如基底上加工一种沟槽结构，实践中通过选择合适的沟槽尺寸，能够有效反射泄露到基底中的声波，从而有效提高谐振器并联阻抗Rp值。
沟槽为微槽结构。在本发明的附图中，沟槽为环形沟槽。不过，沟槽也可以为多个沟槽段，所述多个沟槽段彼此之间间隔开且沿围绕所述有效区域设置。例如，沟槽段可以为设置在图1A中所示的多边形的有效区域的一条边或多条边的一个或多个沟槽段。
在本发明中，如附图所示，在可选的实施例中，所述沟槽与所述声学镜的横向距 离保持不变。
在本发明的一个示例性实施例中，沟槽均形成在基底上。但是，本发明不限于此，沟槽也可以形成在与基底相对的压电层的下表面处，或者设置在压电层的上表面处。或者所述沟槽设置于所述底电极的上侧或者下侧。
在本发明中，沟槽或者沟槽段内可以填充其他材料，也可以不填充，均在本发明的保护范围之内。
在本发明的可选实施例中，所述两个沟槽中的一个沟槽被所述底电极完全覆盖，另一个沟槽被所述底电极部分覆盖或者与所述底电极间隔开。可选的，所述两个沟槽中的一个沟槽被所述底电极部分覆盖，另一个沟槽被与所述底电极间隔开。
在本发明中，方位中的“上侧”表示在谐振器的厚度方向上远离基底的一侧，而“下侧”表示在谐振器的厚度方向上靠近基底的一侧。
基于以上，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，包括上述的滤波器或者谐振器。需要指出的是，这里的电子设备，包括但不限于射频前端、滤波放大模块等中间产品，以及手机、WIFI、无人机等终端产品。
相应的，本发明还提出了一种提高体声波谐振器的并联阻抗的方法，包括步骤：围绕所述谐振器的有效区域在谐振器的基底上侧形成至少一个环形沟槽。
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 (20)

  1. 一种体声波谐振器，包括：
    基底；
    声学镜；
    底电极，设置在基底上侧；
    顶电极；和
    压电层，设置在底电极上侧以及底电极与顶电极之间，
    其中：
    声学镜、底电极、压电层、顶电极在基底的厚度方向重叠的区域为谐振器的有效区域；
    所述谐振器还包括至少一个沟槽，所述沟槽围绕所述有效区域边缘延伸设置。
  2. 根据权利要求1所述的谐振器，其中：
    所述沟槽为环形沟槽。
  3. 根据权利要求2所述的谐振器，其中：
    所述沟槽与所述声学镜的横向距离保持不变。
  4. 根据权利要求1-3中任一项所述的谐振器，其中：
    所述至少一个沟槽包括一个沟槽。
  5. 根据权利要求4所述的谐振器，其中：
    所述沟槽设置在基底上侧且为所述底电极完全覆盖。
  6. 根据权利要求5所述的谐振器，其中：
    所述沟槽的深度H满足：0.1μm≤H≤0.6μm；且
    所述沟槽到所述声学镜的距离为D，所述沟槽的宽度为W，其中：1μm≤D≤1.8μm，且1.2μm≤W≤2.5μm。
  7. 根据权利要求4所述的谐振器，其中：
    所述沟槽设置在基底上侧且为所述底电极部分覆盖。
  8. 根据权利要求4所述的谐振器，其中：
    所述沟槽设置在基底上侧且与底电极间隔开。
  9. 根据权利要求7或8所述的谐振器，其中：
    所述沟槽的深度H满足条件：0.6μm≤H≤1.1μm，或者1.7μm≤H≤2.3μm。
  10. 根据权利要求9所述的谐振器，其中：
    在0.7μm≤H≤0.8μm，或者1.9μm≤H≤2.1μm。
  11. 根据权利要求1-3中任一项所述的谐振器，其中：
    所述至少一个沟槽包括两个沟槽。
  12. 根据权利要求11所述的谐振器，其中：
    所述两个沟槽设置在基底上侧且均被所述底电极完全覆盖。
  13. 根据权利要求11所述的谐振器，其中：
    所述两个沟槽设置在基底上侧且均与所述底电极间隔开。
  14. 根据权利要求11所述的谐振器，其中：
    所述两个沟槽中的一个沟槽被所述底电极完全覆盖，另一个沟槽被所述底电极部分覆盖或者与所述底电极间隔开。
  15. 根据权利要求11所述的谐振器，其中：
    所述两个沟槽中的一个沟槽被所述底电极部分覆盖，另一个沟槽被与所述底电极间隔开。
  16. 根据权利要求1-3中任一项所述的谐振器，其中：
    所述沟槽设置于所述压电层的下侧或者上侧；或者
    所述沟槽设置于所述底电极的上侧或者下侧。
  17. 根据权利要求1-3中任一项所述的谐振器，其中：
    所述至少一个沟槽包括多个沟槽段，所述多个沟槽段彼此之间间隔开且沿围绕所述有效区域设置。
  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。
  20. 一种提高体声波谐振器的并联阻抗的方法，包括步骤：
    围绕所述谐振器的有效区域在谐振器的基底上侧形成至少一个环形沟槽。
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