WO2020098481A1 - 具有粗糙面的体声波谐振器、滤波器和电子设备 - Google Patents

具有粗糙面的体声波谐振器、滤波器和电子设备 Download PDF

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WO2020098481A1
WO2020098481A1 PCT/CN2019/114001 CN2019114001W WO2020098481A1 WO 2020098481 A1 WO2020098481 A1 WO 2020098481A1 CN 2019114001 W CN2019114001 W CN 2019114001W WO 2020098481 A1 WO2020098481 A1 WO 2020098481A1
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bottom electrode
piezoelectric layer
air gap
acoustic wave
wave resonator
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PCT/CN2019/114001
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English (en)
French (fr)
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张孟伦
庞慰
刘伯华
杨清瑞
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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 WO2020098481A1 publication Critical patent/WO2020098481A1/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
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02047—Treatment of substrates
    • 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
    • H03H9/05—Holders; Supports
    • 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
    • H03H9/05—Holders; Supports
    • H03H9/0504—Holders; Supports for bulk acoustic wave devices
    • 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
    • H03H9/15—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
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/56—Monolithic crystal filters
    • 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
    • H03H9/56—Monolithic crystal filters
    • H03H9/564—Monolithic crystal filters implemented with thin-film techniques
    • 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
    • H03H9/58—Multiple crystal filters
    • 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
    • H03H9/58—Multiple crystal filters
    • H03H9/582—Multiple crystal filters implemented with thin-film techniques

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, and an electronic device with the filter.
  • multi-passband transceivers that can process large amounts of data simultaneously.
  • multi-passband transceivers have been widely used in positioning systems and multi-standard systems. These systems need to process signals in different frequency bands simultaneously to improve the overall performance of the system.
  • the number of frequency bands in a single chip continues to increase, consumers' demand for miniaturized and multi-functional portable devices is increasing. Miniaturization has become the development trend of chips, which puts forward a higher filter size Requirements.
  • a film bulk acoustic resonator (Film Bulk Acoustic Resonator, FBAR for short) has been used to replace the traditional waveguide technology to implement a multi-band filter.
  • FBAR mainly uses the piezoelectric effect and inverse piezoelectric effect of piezoelectric materials to generate bulk acoustic waves, thereby forming resonance in the device, because FBAR has high quality factor, large power capacity, high frequency (up to 2-10GHz or even higher) and A series of inherent advantages, such as good compatibility with standard integrated circuits (ICs), can be widely used in higher frequency RF application systems.
  • ICs integrated circuits
  • the main body of the FBAR structure is a "sandwich" structure composed of electrodes-piezoelectric films-electrodes, that is, a layer of piezoelectric material is sandwiched between two metal electrode layers.
  • FBAR uses the inverse piezoelectric effect to convert the input electrical signal into mechanical resonance, and then uses the piezoelectric effect to convert the mechanical resonance into electrical signal output.
  • FBAR mainly uses the longitudinal piezoelectric coefficient (d33) of the piezoelectric film to generate the piezoelectric effect, so its main working mode is the longitudinal wave mode (Thickness Extension Mode, TE mode for short) in the thickness direction.
  • the thin film bulk acoustic resonator excites only the thickness direction (TE) mode.
  • the TE thickness direction
  • the lateral parasitic mode For example, the Rayleigh-Ram mode is perpendicular to the direction of the TE mode. Mechanical wave.
  • These transverse mode waves will be reflected at the edge of the resonator to form a reflected wave and interfere with the incident wave, thereby forming a standing wave in the effective excitation area of the resonator.
  • these transverse mode waves are lost at the boundary of the resonator, thereby causing energy loss in the longitudinal mode required by the resonator.
  • the wave of the lateral parasitic mode eventually causes the resonator Q value to drop.
  • the present invention is proposed to alleviate or solve the drop in resonator Q value caused by the transverse mode wave in FBAR.
  • a bulk acoustic wave resonator including: a substrate; an acoustic mirror; a bottom electrode disposed above the substrate; a top electrode opposed to the bottom electrode; and a piezoelectric layer, It is arranged above the bottom electrode and between the bottom electrode and the top electrode, wherein: the area where the acoustic mirror, the bottom electrode, the piezoelectric layer, and the top electrode overlap in the thickness direction of the substrate is the effective area of the resonator; the resonator is adjacent to the The boundary of the effective area is provided with an air gap outside the boundary; at least one of the surfaces corresponding to the air gap is a rough surface, and the roughness of the rough surface is greater than that of the part of the surface around the rough surface of the component where the rough surface is Roughness.
  • the air gap is provided near the top electrode.
  • the top electrode has a body portion and a connection portion connected to the body portion; the air gap is provided below the connection portion and between the upper surface of the piezoelectric layer; and the piezoelectric layer corresponding to the air gap At least one of the surface, the lower surface of the connecting portion, and the upper surface of the connecting portion is the rough surface.
  • connection portion includes a first connection portion; the first connection portion forms a bridge wing structure adjacent to the boundary of the effective area, and the lower surface of the bridge wing structure and the upper surface of the piezoelectric layer form the Air gap.
  • connection portion includes a first connection portion and a second connection portion respectively connected to both sides of the main body portion;
  • the air gap includes a first air gap and a second air gap;
  • the first connection portion is adjacent to the The boundary of the effective area forms a first bridge wing structure, and the first air gap is formed between the lower surface of the first bridge wing structure and the upper surface of the piezoelectric layer;
  • the second connection portion is adjacent to the effective area The boundary forms a second bridge wing structure, and the second air gap is formed between the lower surface of the second bridge wing structure and the upper surface of the piezoelectric layer.
  • the upper surface of the piezoelectric layer corresponding to the air gap is the rough surface; the end edge of the bridge wing structure is located within the acoustic mirror in the thickness direction of the base and the bridge wing structure has a bridge in the lateral direction Wing width.
  • connection portion includes a first connection portion; the first connection portion forms a bridge structure adjacent to the boundary of the effective area, and the lower surface of the bridge structure and the upper surface of the piezoelectric layer form the bridge structure Air gap.
  • the upper surface of the piezoelectric layer corresponding to the air gap is the rough surface; in the thickness direction of the substrate, the connection between the main body part of the top electrode and the connection part is located within the acoustic mirror, and the connection There is a first lateral distance between the boundaries of the acoustic mirrors, and the bridge structure spans the bottom electrode, and there is a second lateral distance between the end of the connection portion of the top electrode and the corresponding end of the bottom electrode.
  • connection portion includes a first connection portion and a second connection portion respectively connected to both sides of the main body portion;
  • the air gap includes a first air gap and a second air gap;
  • the first connection portion is adjacent to the The boundary of the effective area forms a bridge structure, and the first air gap is formed between the lower surface of the bridge structure and the upper surface of the piezoelectric layer;
  • the second connection portion forms a bridge adjacent to the boundary of the effective area In the wing structure, the second air gap is formed between the lower surface of the bridge wing structure and the upper surface of the piezoelectric layer.
  • the upper surface of the piezoelectric layer corresponding to the air gap is the rough surface; in the thickness direction of the substrate, the connection between the main body part of the top electrode and the connection part is located within the acoustic mirror, and the connection There is a first lateral distance between the boundaries of the acoustic mirror, and the bridge structure spans the bottom electrode, and a second lateral distance between the end of the connection portion of the top electrode and the corresponding end of the bottom electrode; the end edge of the bridge wing structure is at the base
  • the thickness direction is within the acoustic mirror and the bridge wing structure has a bridge wing width in the lateral direction.
  • the bulk acoustic wave resonator further includes a flat layer disposed between the substrate and the piezoelectric layer and having the same thickness as the bottom electrode; the upper surface of the piezoelectric layer is flat.
  • the air gap may be provided between the lower surface of the piezoelectric layer and the upper surface of the bottom electrode near the edge of the bottom electrode.
  • An embodiment of the present invention also relates to a bulk acoustic wave resonator, including: a substrate; an acoustic mirror; a bottom electrode provided above the substrate; a top electrode opposed to the bottom electrode; and a piezoelectric layer provided above 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, and the effective area has the first acoustic impedance;
  • the resonator is adjacent to the boundary of the effective area and an air gap is provided outside the boundary, at least one of the surfaces corresponding to the air gap is a rough surface, and the area where the air gap is located has a different from the first acoustic impedance Second acoustic impedance.
  • Embodiments of the present invention also relate to a bulk acoustic wave resonator, including: a substrate; an acoustic mirror; a bottom electrode disposed above the substrate; a top electrode opposed to the bottom electrode; and a piezoelectric layer disposed above 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, and the effective area has the first acoustic impedance;
  • the resonator is adjacent to the boundary of the effective area and a rough surface is provided outside the boundary, and the area where the rough surface is located has a second acoustic impedance different from the first acoustic impedance.
  • the rough surface is provided at the upper surface or lower surface of the top electrode outside the effective boundary, or at the upper surface or lower surface of the piezoelectric layer, or at the upper surface or lower surface of the
  • the roughness of the rough surface is Further optionally, the roughness is about.
  • 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 aforementioned filter.
  • FIG. 1 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention
  • FIG. 1A is a cross-sectional view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, taken along the line 1B-1B in FIG. 1;
  • FIG. 1B is a cross-sectional view of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention, taken along the line 1B-1B in FIG. 1;
  • FIG. 1C is a cross-sectional view taken along the line 1B-1B in FIG. 1 of a bulk acoustic wave resonator according to still another exemplary embodiment of the present invention
  • 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 cross-sectional view taken along the line 1B-1B in FIG. 2 of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention
  • FIG. 2B is a cross-sectional view taken along the line 1B-1B in FIG. 2 of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention
  • FIG. 2C is a cross-sectional view taken along the line 1B-1B in FIG. 2 of a bulk acoustic wave resonator according to still another exemplary embodiment of the present invention
  • 2D is a cross-sectional view taken along the line 1B-1B in FIG. 2 of a bulk acoustic wave resonator according to still another exemplary embodiment of the present invention
  • FIG. 3 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention
  • 3A is a cross-sectional view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention taken along the line 1B-1B in FIG. 3;
  • 3B is a cross-sectional view taken along the line 1B-1B in FIG. 3 of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention
  • 3C is a cross-sectional view taken along the line 1B-1B in FIG. 3 of a bulk acoustic wave resonator according to still another exemplary embodiment of the present invention.
  • FIG. 4 is a cross-sectional SEM image of a thin film bulk acoustic resonator based on an exemplary embodiment of the present invention
  • FIG. 5 is a schematic cross-sectional view of a thin film bulk acoustic resonator according to another embodiment of the present invention.
  • the invention processes a bridge wing or a bridge structure containing roughness on one or more edges of the electrode of the resonator.
  • the bridge wing or the bridge structure can effectively reduce the influence of the lateral parasitic mode on the performance of the resonator and effectively improve the Q value.
  • FIG. 1 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention.
  • the embodiment shown in FIG. 1 is a top view of a piezoelectric resonance structure.
  • the bulk acoustic wave resonator includes a bottom electrode 105, a piezoelectric layer 107, a top electrode 109, and a bridge wing 113 including a rough structure or rough surface.
  • FIG. 1A it is a cross-sectional view of the bulk acoustic wave resonator taken along the top view of FIGS. 1B-1B.
  • the bulk acoustic wave resonator includes a substrate 101 and an acoustic mirror 103.
  • 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 105, a piezoelectric layer 107, and a top electrode 109.
  • the bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror.
  • the bottom electrode includes a first end portion, a second end portion, and a middle portion between the first end portion and the second end portion.
  • the first end portion and the second end portion of the bottom electrode may be etched into an inclined surface, and the inclined surface is located on the outer side of the acoustic mirror, and may also be stepped, vertical, or other similar structures.
  • the piezoelectric layer has a first end, a corresponding second end and a middle portion, and is located above the bottom electrode, and the two end portions extend to the substrate in opposite directions, so that the piezoelectric layer is on the oblique end surface Form a stepped edge.
  • the top electrode 109 is deposited on the piezoelectric layer 107, including the middle portion (ie, the body portion) above the piezoelectric layer and the bridge wing structure 111 and the second end of the first end spanning the piezoelectric layer Bridge wing structure 116.
  • An air gap 113 is provided between the first end of the top electrode and the piezoelectric layer, and an air gap 118 is provided between the corresponding second end and the piezoelectric layer.
  • the bridge wings at both ends of the top electrode are within the acoustic mirror, and the surface of the piezoelectric material under the first end of the top electrode and the corresponding second end has roughness.
  • the surfaces of the rough structures 115 and 117 are rougher than the surface of the surrounding piezoelectric layer area, and the typical roughness range can be Optional, can be Or in about.
  • the area where the bottom electrode 105, the piezoelectric layer 107, the top electrode 109, and the acoustic mirror 103 overlap in the thickness direction is the effective area of the resonator, that is, the area d2 in the figure, and has the first acoustic impedance.
  • the resonator has a second acoustic impedance at the air gap 113 under the first end bridge wing structure of the top electrode 109 and the air gap 118 under the second end bridge wing structure. Since the second acoustic impedance at the bridge wing structure does not match the first acoustic impedance, the transmission of the acoustic wave at the boundary is discontinuous. Therefore, at the boundary, a part of the acoustic energy is coupled and reflected into the effective excitation area d2, and is converted into a piston acoustic wave mode perpendicular to the surface of the piezoelectric layer.
  • the surfaces of the rough structures 115 and 117 are rougher than the surface of the surrounding piezoelectric layer area, the perimeter of the sound waves reflected in the rough structure becomes longer, thereby increasing the period of sound wave reflection, making part of the transverse mode sound waves Will be lost in the rough structure, thereby reducing the parasitic mode.
  • the bridge wing structure and the rough structure can increase the reflection coefficient of the acoustic wave reflected back from the lateral mode edge and the conversion efficiency from the lateral acoustic wave mode to the piston mode, thereby improving the Q value of the resonator. Because the bridge wing structure does not change the mechanical displacement distribution of the applied electric field in the effective excitation area, the Q value of the resonator will not be reduced, nor will it affect the strength of the parasitic mode.
  • the structure of the bulk acoustic wave resonator shown in FIG. 1B is similar to the structure of the embodiment shown in FIG. 1A, and they are all cross-sectional views taken along the top view of FIGS. 1B-1B. The difference is that the roughness is located on the upper and lower surfaces of the first end of the top electrode and the corresponding second end to form a rough structure.
  • Both ends of the top electrode form rough structures on the upper and lower surfaces, that is, they have rough surfaces, which can further improve the degree of mismatch between the acoustic impedance and the first acoustic impedance, thereby further improving the reflection and conversion capabilities of the acoustic wave As well as the suppression of parasitic modes in the rough structure, the performance of the resonator is increased, and its Q value is further increased.
  • the structure of the bulk acoustic wave resonator shown in FIG. 1C is similar to the structure of the embodiment shown in FIG. 1A, and they are all cross-sectional views taken along the top view of FIGS. 1B-1B.
  • the difference is that a flat layer is added on both sides of the bottom electrode, and the added flat layer is aligned with the oblique end surfaces of the first end and the second end of the bottom electrode, thereby forming a flat and smooth surface, which is beneficial to the bottom electrode and flat
  • a piezoelectric film with good C-axis orientation is deposited on the junction of the layers.
  • suitable dielectric materials such as silicon dioxide, silicon nitride, and silicon carbide can be used.
  • FIG. 2 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention.
  • the bulk acoustic wave resonator shown in FIG. 2 includes a bottom electrode 205, a piezoelectric layer 207, a top electrode 209, and a bridge structure 213 including a rough structure.
  • FIG. 2A is a cross-sectional view of the bulk acoustic wave resonator taken along the top views 1B-1B of FIG. 2.
  • the bulk acoustic wave resonator includes a substrate 201 and an acoustic mirror 203.
  • 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 205, a piezoelectric layer 207, and a top electrode 209.
  • the bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror.
  • the bottom electrode includes a first end portion, a second end portion, and a middle portion between the first end portion and the second end portion.
  • the first end portion and the second end portion of the bottom electrode may be etched into an inclined surface, and the inclined surface is located on the outer side of the acoustic mirror, and may also be stepped, vertical, or other similar structures.
  • the piezoelectric layer has a first end, a corresponding second end and a middle portion, and is located above the bottom electrode, and the two end portions extend to the substrate in opposite directions, so that the piezoelectric layer is on the oblique end surface Form a stepped edge.
  • the top electrode 209 is deposited on the piezoelectric layer 207, including a main body portion on the piezoelectric layer and a bridge structure 211 spanning the second portion (connection portion) on the piezoelectric layer, on the second side of the top electrode There is an air gap 214 between the part and the piezoelectric layer.
  • connection between the main part of the top electrode and the second part is within the acoustic mirror, the distance between it and the acoustic mirror is d1, and the bridge structure spans the bottom electrode and is located above the piezoelectric layer.
  • the distance between the end and the end of the second part of the bottom electrode is d2.
  • the surface of the piezoelectric material under the second part of the top electrode has a roughness.
  • the surface of the rough structure 213 is rougher than the surface of the surrounding piezoelectric layer area, and its typical roughness range may be Optional, can be Or in about.
  • the area where the bottom electrode 205, the piezoelectric layer 207, the top electrode 209, and the acoustic mirror overlap in the thickness direction is the effective area of the resonator, that is, area d in the figure, and has the first acoustic impedance.
  • the air gap 214 under the bridge structure of the second part of the top electrode there is a second acoustic impedance. Since the second acoustic impedance at the bridge structure does not match the first acoustic impedance, the transmission of sound waves at the boundary is discontinuous.
  • a part of the acoustic energy will be coupled and reflected into the effective excitation area d, and converted into a piston acoustic wave mode perpendicular to the surface of the piezoelectric layer.
  • the surface of the rough structure 213 is rougher than the surface of the surrounding piezoelectric layer area, the perimeter of sound waves reflected in the rough structure becomes longer, thereby increasing the period of sound wave reflection, so that part of the transverse mode sound waves will be The rough structure is lost, thereby reducing the parasitic mode.
  • the bridge structure and the rough structure can increase the reflection coefficient of the acoustic wave reflected back from the edge of the lateral mode and the conversion efficiency from the lateral acoustic wave mode to the piston mode, thereby improving the Q value of the resonator. Because the bridge structure does not change the mechanical displacement distribution of the applied electric field in the effective excitation area, the Q value of the resonator will not be reduced, nor will it affect the strength of the parasitic mode.
  • the structure of the bulk acoustic wave resonator shown in FIG. 2B is similar to the structure of the embodiment shown in FIG. 2A, and they are all cross-sectional views taken along the top view of FIG. 2 in FIGS. 1B-1B.
  • the difference is that the roughness is located on the upper and lower surfaces of the second part of the top electrode to form a rough structure.
  • the rough structure formed on the upper and lower surfaces of the second part of the top electrode can further increase the degree of mismatch between the acoustic impedance and the first acoustic impedance and the suppression of parasitic modes in the rough structure, thereby further improving the reflection ability and conversion of the acoustic wave
  • the ability to increase the performance of the resonator increases its Q value further.
  • the structure of the bulk acoustic wave resonator shown in FIG. 2C is similar to the structure of the embodiment shown in FIG. 2A, and they are all cross-sectional views taken along the top view of FIGS. 2B-1B. The difference is that the bridge structure is located between the second portion of the bottom electrode and the second portion of the piezoelectric layer, and the rough structure is located above the second portion of the bottom electrode.
  • the structure of the bulk acoustic wave resonator shown in FIG. 2D is similar to the structure of the embodiment shown in FIG. 2A, and they are all cross-sectional views taken along the top views of FIGS. 2B-1B.
  • the difference is that a flat layer is added on both sides of the bottom electrode, and the added flat layer is aligned with the oblique end surfaces of the first end and the second end of the bottom electrode, thereby forming a flat and smooth surface, which is beneficial to the bottom electrode and flat
  • a piezoelectric film with good C-axis orientation is deposited on the junction of the layers.
  • suitable dielectric materials such as silicon dioxide, silicon nitride, and silicon carbide can be used.
  • FIG. 3 is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention.
  • the embodiment shown in FIG. 3 is a top view of a piezoelectric resonance structure.
  • the bulk acoustic wave resonator includes a bulk acoustic wave resonator including a bottom electrode 305, a piezoelectric layer 307, a top electrode 309, and a bridge structure 313 including a rough structure and a bridge wing structure 311 including a rough structure.
  • FIG. 3A it is a cross-sectional view of the bulk acoustic wave resonator taken along the top view of FIGS. 3B-1B.
  • the bulk acoustic wave resonator includes a substrate 301 and an acoustic mirror 303, 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 305, a piezoelectric layer 307, and a top electrode 309.
  • the bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror.
  • the bottom electrode includes a first end portion, a second end portion, and a middle portion between the first end portion and the second end portion.
  • the first end portion and the second end portion of the bottom electrode may be etched into a slope, and the slope is located outside the acoustic mirror, and may also be stepped, vertical, or other similar structures.
  • the piezoelectric layer has a first end, a corresponding second end and a middle portion, and is located above the bottom electrode, and the two end portions extend to the substrate in opposite directions, so that the piezoelectric layer is on the oblique end surface Form a stepped edge.
  • the top electrode is deposited on the piezoelectric layer, including the main body part on the piezoelectric layer, the first part of the bridge wing structure 311 and the second part of the bridge structure 313 on the piezoelectric layer, the first part of the top electrode
  • the air gaps 315 and 317 are between the second part and the piezoelectric layer.
  • the connection between the main part of the top electrode and the second part is within the acoustic mirror, the distance between it and the acoustic mirror is d1, and the bridge structure spans the bottom electrode and is located above the piezoelectric layer.
  • the distance between the end and the end of the second part of the bottom electrode is d2.
  • the edge of the bridge wing structure of the first part of the top electrode is located inside the acoustic mirror, and its width is d3.
  • the surface of the piezoelectric material under the first part and the second part of the top electrode has a roughness.
  • the surface of the rough structures 319 and 321 is rougher than the surface of the surrounding piezoelectric layer area, and the typical roughness range can be Optional, can be Or in about.
  • the area where the bottom electrode, the piezoelectric layer, the top electrode, and the acoustic mirror overlap in the thickness direction is the effective area of the resonator, that is, area d in the figure, which has the first acoustic impedance.
  • the air gap 214 under the first partial bridge wing structure and the second partial bridge structure of the top electrode has a second acoustic impedance. Since the second acoustic impedance at the bridge wing and the bridge structure does not match the first acoustic impedance, the acoustic wave will be discontinuously transmitted at the boundary.
  • the surface of the rough structures 319 and 321 is rougher than the surface of the surrounding piezoelectric layer area, so that the perimeter of the sound wave reflected in the rough structure becomes longer, thereby increasing the period of sound wave reflection, making part of the transverse mode sound waves Will be lost in the rough structure, thereby reducing the parasitic mode.
  • the wing structure, the bridge structure and the rough structure can increase the reflection coefficient of the acoustic wave reflected back from the lateral mode edge and the conversion efficiency from the lateral acoustic wave mode to the piston mode, thereby improving the Q value of the resonator. Because the structure of the bridge wing and the bridge part does not change the mechanical displacement distribution of the applied electric field in the effective excitation area, the Q value of the resonator will not be reduced, nor will it affect the strength of the parasitic mode.
  • the structure of the bulk acoustic wave resonator shown in FIG. 3B is similar to the structure of the embodiment shown in FIG. 3A, and they are all cross-sectional views taken along the top view of FIG. 3 in FIGS. 1B-1B. The difference is that the roughness is located on the upper and lower surfaces of the first and second parts of the top electrode to form a rough structure.
  • the rough structure formed on the upper and lower surfaces of the first and second parts of the top electrode can further increase the degree of mismatch between the acoustic impedance and the first acoustic impedance and the suppression of parasitic modes in the rough structure, thereby further enhancing the reflection of the acoustic wave
  • the ability and conversion ability make the performance of the resonator increase, and its Q value further increases.
  • the structure of the bulk acoustic wave resonator shown in FIG. 3C is similar to the structure of the embodiment shown in FIG. 3A, and they are all cross-sectional views taken along the top view of FIG. 3 in FIGS. 1B-1B.
  • the difference is that a flat layer is added on both sides of the bottom electrode, and the added flat layer is aligned with the oblique end surfaces of the first end and the second end of the bottom electrode, thereby forming a flat and smooth surface, which is beneficial to the bottom electrode and flat
  • a piezoelectric film with good C-axis orientation is deposited on the junction of the layers.
  • suitable dielectric materials such as silicon dioxide, silicon nitride, and silicon carbide can be used.
  • the resonator includes a piezoelectric layer 401, a top electrode 403, a passivation layer 405, and a layer of foil 407 sprayed to make the device picture clearer, the bridge structure 409, and the rough structure 411 are located In the bridge structure above the piezoelectric layer.
  • an embodiment of the present invention proposes a bulk acoustic wave resonator, including: a substrate; an acoustic mirror; a bottom electrode disposed above the substrate; a top electrode opposed to the bottom electrode; and a piezoelectric layer disposed at Above the bottom electrode and between the bottom electrode and the top electrode, where: 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 is adjacent to the effective area An air gap is provided outside the boundary; at least one of the surfaces corresponding to the air gap is a rough surface, and the roughness of the rough surface is greater than the roughness of a part of the surface around the rough surface of the part where the rough surface is located .
  • an embodiment of the present invention further proposes a bulk acoustic wave resonator, including: a substrate; an acoustic mirror; a bottom electrode disposed above the substrate; a top electrode opposed to the bottom electrode; and a piezoelectric layer disposed Above 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, and the effective area has the first sound Impedance; the resonator is adjacent to the boundary of the effective area and an air gap is provided outside the boundary, at least one of the surfaces corresponding to the air gap is a rough surface, and the area where the air gap is located has a different One acoustic impedance is the second acoustic impedance.
  • the bulk acoustic wave resonator includes a substrate 501 and an acoustic mirror 503, 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 Structures such as Bragg reflectors are also suitable.
  • the bulk acoustic wave resonator further includes a bottom electrode 505, a piezoelectric layer 507 and a top electrode 509, and a rough structure 515.
  • the bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror.
  • the rough structure 515 is located on the upper surface of the piezoelectric layer in the area around the edge of the top electrode.
  • the surface of the rough structure 515 is rougher than the surface of the surrounding piezoelectric layer area, and its typical roughness range can be Optional, can be Or in
  • the area where the bottom electrode, the piezoelectric layer, the top electrode, and the acoustic mirror overlap in the thickness direction is the effective area of the resonator, and has the first acoustic impedance.
  • the rough structure 515 has a second acoustic impedance. Due to the mismatch between the second acoustic impedance and the first acoustic impedance in the rough structure, the transmission of sound waves at the boundary is discontinuous. Therefore, at the boundary, part of the acoustic energy is coupled and reflected into the effective excitation area, and is converted into a piston acoustic wave mode perpendicular to the surface of the piezoelectric layer.
  • the surface of the rough structure 515 is rougher than the surface of the surrounding piezoelectric layer area, the perimeter of sound waves reflected in the rough structure becomes longer, thereby increasing the period of sound wave reflection, so that part of the transverse mode sound waves will be in The rough structure is lost, thereby reducing the parasitic mode.
  • the rough structure or rough surface may also be directly provided on the upper or lower surface of the top electrode or the upper or lower surface of the piezoelectric layer or the bottom electrode outside the effective boundary At the upper or lower surface.
  • the present invention proposes a bulk acoustic wave resonator including: a substrate; an acoustic mirror; a bottom electrode provided above the substrate; a top electrode opposed to the bottom electrode; and a piezoelectric layer provided above 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, and the effective area has the first acoustic impedance;
  • the resonator is adjacent to the boundary of the effective area and a rough surface is provided outside the boundary, and the area where the rough surface is located has a second acoustic impedance different from the first acoustic impedance.
  • the electrode composition material may be gold (Au), tungsten (W), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), titanium tungsten (TiW), aluminum (Al) , Titanium (Ti) and similar metals.
  • the piezoelectric layer material may be aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO 3 ), quartz (Quartz), potassium niobate (KNbO 3 ) or lithium tantalate (LiTaO 3 ) and other materials.
  • 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 aforementioned filter.
  • 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.

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Abstract

一种体声波谐振器，包括：基底（101）；声学镜（103）；底电极（105），设置在基底（101）上方；顶电极（109），与所述底电极（105）对置；和压电层（107），设置在底电极（105）上方以及底电极（105）与顶电极（109）之间，其中：声学镜（103）、底电极（105）、压电层（107）、顶电极（109）在基底（101）的厚度方向重叠的区域为谐振器的有效区域（d）；所述谐振器邻近所述有效区域（d）的边界且在边界之外设置有空气隙（113）；所述空气隙（113）对应的表面中的至少一个表面为粗糙面，该粗糙面的粗糙度大于该粗糙面所在部件的该粗糙面周围部分表面的粗糙度。还涉及一种具有上述谐振器的滤波器，一种具有该滤波器的电子设备。

Description

具有粗糙面的体声波谐振器、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，以及一种具有该滤波器的电子设备。
背景技术
随着无线通信技术的快速发展，人们对于能同步处理大量数据的多通带收发器的需求与日俱增。近年来，多通带收发器已被广泛地应用在定位系统和多标准的系统中，这些系统需要同时处理不同频段的信号以提高系统的整体性能。虽然单个芯片中频率带的个数不断增加，但消费者对小型化、多功能的便携式设备的需求越来越高，小型化成为芯片的发展趋势，这就对滤波器的尺寸提出了更高的要求。
为此，现有技术中已经采用薄膜体声波谐振器(Film Bulk Acoustic Resonator，简称FBAR)取代传统的波导技术实现多频带滤波器。
FBAR主要利用压电材料的压电效应与逆压电效应产生体声波，从而在器件内形成谐振，因为FBAR具有品质因数高、功率容量大、频率高(可达2-10GHz甚至更高)以及与标准集成电路(IC)的兼容性好等一系列的固有优势，可广泛应用于频率较高的射频应用系统中。
FBAR的结构主体为由电极-压电薄膜-电极组成的“三明治”结构，即两层金属电极层之间夹一层压电材料。通过在两电极间输入正弦信号，FBAR利用逆压电效应将输入电信号转换为机械谐振，并且再利用压电效应将机械谐振转换为电信号输出。FBAR主要利用压电薄膜的纵向压电系数(d33)产生压电效应，所以其主要工作模式为厚度方向上的纵波模式(Thickness Extensional Mode，简称TE模式)。
理想地，薄膜体声波谐振器仅激发厚度方向(TE)模。但是体声波谐振器在工作状态下，除了会激发在厚度方向的(TE)模式或者活塞模式外，还会产生横向寄生模式的波，如瑞利-拉姆模是与TE模的方向相垂直的机械波。这些横向模式的波会在谐振器的边缘经反射形成反射波并与入射波干涉，从而会在谐振器的有效激励区域内形成驻波。此外，这些横向模式的波会在谐振器的边界处损失掉，从而使得谐振器所需 的纵模的能量损失。横向寄生模式的波最终导致谐振器Q值下降。
发明内容
为缓解或解决FBAR中横向模式的波所导致的谐振器Q值下降，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，与所述底电极对置；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；所述谐振器邻近所述有效区域的边界且在边界之外设置有空气隙；所述空气隙对应的表面中的至少一个表面为粗糙面，该粗糙面的粗糙度大于该粗糙面所在部件的该粗糙面周围部分表面的粗糙度。
在可选的实施例中，空气隙设置在顶电极附近。具体的，所述顶电极具有主体部以及与主体部连接的连接部；所述空气隙设置在所述连接部的下方以及压电层的上表面之间；与空气隙对应的压电层上表面、连接部下表面、连接部上表面中的至少一个表面为所述粗糙面。
可选的，所述连接部包括第一连接部；所述第一连接部邻近所述有效区域的边界形成桥翼结构，所述桥翼结构下表面以及压电层上表面之间形成所述空气隙。
可选的，所述连接部包括分别连接在主体部两侧的第一连接部和第二连接部；所述空气隙包括第一空气隙和第二空气隙；所述第一连接部邻近所述有效区域的边界形成第一桥翼结构，所述第一桥翼结构下表面与所述压电层上表面之间形成所述第一空气隙；所述第二连接部邻近所述有效区域的边界形成第二桥翼结构，所述第二桥部翼结构下表面与所述压电层上表面之间形成所述第二空气隙。
进一步可选的，与空气隙对应的压电层的上表面为所述粗糙面；所述桥翼结构的末端边缘在基底的厚度方向上位于声学镜之内且桥翼结构在横向上具有桥翼宽度。
可选的，所述连接部包括第一连接部；所述第一连接部邻近所述有效区域的边界形成桥部结构，所述桥部结构下表面以及压电层上表面之间形成所述空气隙。进一步可选的，与空气隙对应的压电层的上表面为所述粗糙面；在基底的厚度方向上顶电极的主体部与连接部的连接处位于声学镜之内，所述连接处与声学镜边界之间具有第一横向距离，并且桥部结构跨越底电极，顶电极的连接部的末端与底电极的对应末端之间具有第二横向距离。
可选的，所述连接部包括分别连接在主体部两侧的第一连接部和第二连接部；所 述空气隙包括第一空气隙和第二空气隙；所述第一连接部邻近所述有效区域的边界形成桥部结构，所述桥部结构下表面与所述压电层上表面之间形成所述第一空气隙；所述第二连接部邻近所述有效区域的边界形成桥翼结构，所述桥翼结构下表面与所述压电层上表面之间形成所述第二空气隙。进一步可选的，与空气隙对应的压电层的上表面为所述粗糙面；在基底的厚度方向上顶电极的主体部与连接部的连接处位于声学镜之内，所述连接处与声学镜边界之间具有第一横向距离，并且桥部结构跨越底电极，顶电极的连接部的末端与底电极的对应末端之间具有第二横向距离；所述桥翼结构的末端边缘在基底的厚度方向上位于声学镜之内且桥翼结构在横向上具有桥翼宽度。
可选的，所述体声波谐振器还包括平坦层，所述平坦层设置在所述基底与所述压电层之间且与底电极厚度相同；所述压电层上表面是平坦的。
在可选的实施例中，所述空气隙可以在底电极的边缘附近设置在压电层下表面与底电极上表面之间。
本发明的实施例还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，与所述底电极对置；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，所述有效区域具有第一声阻抗；所述谐振器邻近所述有效区域的边界且在边界之外设置有空气隙，与所述空气隙对应的表面中的至少一个表面为粗糙面，所述空气隙所在区域具有不同于第一声阻抗的第二声阻抗。
本发明的实施例也涉及一种体声波谐振器，包括：基底；声学镜；底电极，置在基底上方；顶电极，与所述底电极对置；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，所述有效区域具有第一声阻抗；所述谐振器邻近所述有效区域的边界且在边界之外设置有粗糙面，所述粗糙面所在区域具有不同于第一声阻抗的第二声阻抗。可选的，所述粗糙面设置在有效边界之外的顶电极的上表面或者下表面处、或者压电层的上表面或者下表面处、或者底电极的上表面或者下表面处。
可选的，上述体声波谐振器中，所述粗糙面的粗糙度为
Figure PCTCN2019114001-appb-000001
进一步可选的，所述粗糙度为
Figure PCTCN2019114001-appb-000002
左右。
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。
本发明的实施例还涉及一种电子设备，包括上述的滤波器。
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为根据本发明的一个示例性实施例的体声波谐振器的示意性俯视图；
图1A为根据本发明的一个示例性实施例的体声波谐振器沿图1中的1B-1B向的截面图；
图1B为根据本发明的另一个示例性实施例的体声波谐振器沿图1中的1B-1B向的截面图；
图1C为根据本发明的再一个示例性实施例的体声波谐振器沿图1中的1B-1B向的截面图；
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示意性俯视图；
图2A为根据本发明的一个示例性实施例的体声波谐振器沿图2中的1B-1B向的截面图；
图2B为根据本发明的另一个示例性实施例的体声波谐振器沿图2中的1B-1B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沿图2中的1B-1B向的截面图；
图2D为根据本发明的再一个示例性实施例的体声波谐振器沿图2中的1B-1B向的截面图；
图3为根据本发明的一个示例性实施例的体声波谐振器的示意性俯视图；
图3A为根据本发明的一个示例性实施例的体声波谐振器沿图3中的1B-1B向的截面图；
图3B为根据本发明的另一个示例性实施例的体声波谐振器沿图3中的1B-1B向的截面图；
图3C为根据本发明的再一个示例性实施例的体声波谐振器沿图3中的1B-1B向的截面图；
图4为基于本发明的一个示例性实施例的薄膜体声波谐振器的截面SEM图；
图5为根据本发明的另一个实施例的薄膜体声波谐振器的截面示意图。
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。
本发明在谐振器的电极的一边或多边边缘处加工一种包含粗糙度的桥翼或桥部结构，桥翼或桥部结构能够有效减小横向寄生模式对谐振器性能的影响，有效提高其Q值。
下面参照附图1-4描述根据本发明的实施例的体声波谐振器。
图1为根据本发明的一个示例性实施例的体声波谐振器的示意性俯视图。图1所示的实施例中，为压电谐振结构的俯视图。体声波谐振器包括底电极105，压电层107，顶电极109以及包含粗糙结构或粗糙面的桥翼113。
图1A所示的实施例中，为体声波谐振器沿着图1俯视图1B-1B所取的截面图。体声波谐振器包括基底101和声学镜103，此声学镜位于基底的上表面或嵌于基底的内部，在图1A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器也同样适用。
体声波谐振器还包括底电极105，压电层107和顶电极109。底电极沉积在声学镜的上表面，并覆盖声学镜。所述的底电极包含第一末端部、第二末端部、以及位于第一末端部和第二末端部的中间部分。可以将底电极的第一末端部和第二末端部刻蚀成斜面，并且该斜面位于声学镜的外边，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，从而使压电层在斜端面上形成阶梯型边缘。
顶电极109沉积在压电层107之上，包括位于压电层之上的中间的部分(即主体部)以及跨于压电层之上的第一末端的桥翼结构111和第二末端的桥翼结构116。在顶电极的第一末端与压电层之间设置有空气隙113，在对应的第二末端与压电层之间设置有空气隙118。
所述顶电极的两末端的桥翼结构在声学镜之内，同时在顶电极的第一末端和对应的第二末端下的压电材料表面有粗糙度。粗糙结构115和117的表面要比其周围压电层区域的表面粗糙，其典型的粗糙度范围可以为
Figure PCTCN2019114001-appb-000003
可选的，可以为
Figure PCTCN2019114001-appb-000004
Figure PCTCN2019114001-appb-000005
或者在
Figure PCTCN2019114001-appb-000006
左右。
底电极105、压电层107、顶电极109和声学镜103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，具有第一声阻抗。
谐振器在顶电极109的第一末端桥翼结构下的空气隙113和第二末端桥翼结构下的空气隙118处，具有第二声阻抗。由于在桥翼结构处的第二声阻抗与第一声阻抗不匹配，会使得声波在边界处传输不连续。因此在边界处，一部分声能就会耦合且反射到有效激励区域d2中，并且转换成与压电层表面垂直的活塞声波模式。同时由于粗糙结构115和117的表面与其周围压电层区域的表面相比更为粗糙，使得声波在粗糙结构中反射的周长变长，从而提高了声波反射的周期，使得一部分横向模式的声波会在粗糙结构中损失掉，从而降低了寄生模式。
桥翼结构以及粗糙结构可以增大横向模式边缘反射回来的声波的反射系数和从横向声波模式转换为活塞模式的转换效率，从而提高谐振器的Q值。因为桥翼结构没有改变有效激励区域外加电场方向的机械位移分布，因此不会降低谐振器的Q值，也不会对寄生模式强度有影响。
在图1B所示的体声波谐振器结构与图1A所示的实施例结构类似，它们都是沿着图1俯视图1B-1B所取的截面图。不同之处在于粗糙度位于顶电极的第一末端和对应的第二末端的上下表面形成粗糙结构。顶电极两末端部在上、下表面均形成粗糙结构，即都具有粗糙面，这能够进一步提升其声阻抗与第一声阻抗之间的不匹配程度，从而进一步提升声波的反射能力和转换能力以及在粗糙结构中对寄生模式的抑制作用，使得谐振器的性能增加，其Q值进一步增加。
在图1C所示的体声波谐振器结构与图1A所示的实施例结构类似，它们都是沿着图1俯视图1B-1B所取的截面图。不同之处在于在底电极的两侧加入了平坦层，加入的平坦层与底电极的第一末端和第二末端的斜端面对齐，从而形成平整光滑的表面，这样有利于在底电极与平坦层的连接处上沉积有良好C-轴取向的压电薄膜。平坦层可以采用二氧化硅、氮化硅、碳化硅等合适的介质材料。
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示意性俯视图。图2所 示的体声波谐振器包括底电极205，压电层207，顶电极209，以及包含粗糙结构的桥部结构213。
图2A所示的实施例，为体声波谐振器沿着图2俯视图1B-1B所取的截面图。体声波谐振器包括基底201和声学镜203，此声学镜位于基底的上表面或嵌于基底的内部，在图2A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器也同样适用。
体声波谐振器还包括底电极205，压电层207和顶电极209。底电极沉积在声学镜的上表面，并覆盖声学镜。所述的底电极包含第一末端部、第二末端部、以及位于第一末端部和第二末端部的中间部分。可以将底电极的第一末端部和第二末端部刻蚀成斜面，并且该斜面位于声学镜的外边，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，从而使压电层在斜端面上形成阶梯型边缘。
顶电极209沉积在压电层207之上，包括位于压电层之上的主体部以及跨于压电层之上的第二部分(连接部)的桥部结构211，在顶电极的第二部分与压电层之间为空气隙214。
顶电极的主体部与第二部分的连接处位于声学镜之内，其与声学镜之间的距离为d1，并且桥部结构跨越底电极并位于压电层上方，顶电极的第二部分的末端与底电极第二部分末端之间的距离为d2。同时在顶电极的第二部分下的压电材料表面有一粗糙度。粗糙结构213的表面要比其周围压电层区域的表面粗糙，其典型的粗糙度范围可以为
Figure PCTCN2019114001-appb-000007
可选的，可以为
Figure PCTCN2019114001-appb-000008
或者在
Figure PCTCN2019114001-appb-000009
左右。
底电极205、压电层207、顶电极209和声学镜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d，具有第一声阻抗。在顶电极的第二部分桥部结构下的空气隙214处，具有第二声阻抗。由于在桥部结构处的第二声阻抗与第一声阻抗不匹配，会使得声波在边界处传输不连续。因此在边界处，一部分声能就会耦合且反射到有效激励区域d中，并且转换成与压电层表面垂直的活塞声波模式。同时由于粗糙结构213的表面与其周围压电层区域的表面相比更为粗糙，使得声波在粗糙结构中反射的周长变长，从而提高了声波反射的周期，使得一部分横向模式的声波会在粗糙结构中损失掉，从而降低了寄生模式。
桥部结构以及粗糙结构可以增大横向模式边缘反射回来的声波的反射系数和从横向声波模式转换为活塞模式的转换效率，从而提高谐振器的Q值。因为桥部结构没有改变有效激励区域外加电场方向的机械位移分布，因此不会降低谐振器的Q值，也不会对寄生模式强度有影响。
在图2B所示的体声波谐振器结构与图2A所示的实施例结构类似，它们都是沿着图2俯视图1B-1B所取的截面图。不同之处在于粗糙度位于顶电极的第二部分的上下表面形成粗糙结构。顶电极第二部分上下表面形成的粗糙结构，能够进一步提升其声阻抗与第一声阻抗之间的不匹配程度以及在粗糙结构中对寄生模式的抑制作用，从而进一步提升声波的反射能力和转换能力，使得谐振器的性能增加，其Q值进一步增加。
在图2C所示的体声波谐振器结构与图2A所示的实施例结构类似，它们都是沿着图2俯视图1B-1B所取的截面图。不同之处在于桥部结构位于底电极的第二部分和压电层的第二部分之间，且粗糙结构位于底电极的第二部分之上。
在图2D所示的体声波谐振器结构与图2A所示的实施例结构类似，它们都是沿着图2俯视图1B-1B所取的截面图。不同之处在于在底电极的两侧加入了平坦层，加入的平坦层与底电极的第一末端和第二末端的斜端面对齐，从而形成平整光滑的表面，这样有利于在底电极与平坦层的连接处上沉积有良好C-轴取向的压电薄膜。平坦层可以采用二氧化硅、氮化硅、碳化硅等合适的介质材料。
图3为根据本发明的一个示例性实施例的体声波谐振器的示意性俯视图。图3所示的实施例中，为压电谐振结构的俯视图。体声波谐振器包括体声波谐振器包括底电极305，压电层307，顶电极309，以及包含粗糙结构的桥部结构313和包含粗糙结构的桥翼结构311。
图3A所示的实施例中，为体声波谐振器沿着图3俯视图1B-1B所取的截面图。体声波谐振器包括基底301和声学镜303，此声学镜位于基底的上表面或嵌于基底的内部，在图3A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器也同样适用。
体声波谐振器还包括底电极305，压电层307和顶电极309。底电极沉积在声学镜的上表面，并覆盖声学镜。所述的底电极包含第一末端部、第二末端部、以及位于第一末端部和第二末端部的中间部分。可以将底电极的第一末端部和第二末端部刻蚀成斜面，并且该斜面位于声学镜的外边，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，从而使压电层在斜端面上形成阶梯型边缘。
顶电极沉积在压电层之上，包括位于压电层之上的主体部、第一部分桥翼结构311以及跨于压电层之上的第二部分桥部结构313，在顶电极的第一、第二部分与压电层之间为空气隙315和317。顶电极的主体部与第二部分的连接处位于声学镜之内，其与声学镜之间的距离为d1，并且桥部结构跨越底电极并位于压电层上方，顶电极的第二部分的末端与底电极第二部分末端之间的距离为d2。顶电极的第一部分桥翼结构的边缘位于声学镜之内，其宽度为d3。同时，在顶电极第一部分下和第二部分下的压电材料表面有一粗糙度。粗糙结构319和321的表面要比其周围压电层区域的表面粗糙，其典型的粗糙度范围可以为
Figure PCTCN2019114001-appb-000010
可选的，可以为
Figure PCTCN2019114001-appb-000011
或者在
Figure PCTCN2019114001-appb-000012
左右。
底电极、压电层、顶电极和声学镜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d，具有第一声阻抗。在顶电极的第一部分桥翼结构下和第二部分桥部结构下的空气隙214，具有第二声阻抗。由于在桥翼、桥部结构处的第二声阻抗与第一声阻抗不匹配，会使得声波在边界处传输不连续。因此在边界处，一部分声能就会耦合且反射到有效激励区域d中，并且转换成与压电层表面垂直的活塞声波模式。同时由于粗糙结构319和321的表面与其周围压电层区域的表面相比更为粗糙，使得声波在粗糙结构中反射的周长变长，从而提高了声波反射的周期，使得一部分横向模式的声波会在粗糙结构中损失掉，从而降低了寄生模式。
桥翼结构、桥部结构以及粗糙结构可以增大横向模式边缘反射回来的声波的反射系数和从横向声波模式转换为活塞模式的转换效率，从而提高谐振器的Q值。因为桥翼、桥部结构没有改变有效激励区域外加电场方向的机械位移分布，因此不会降低谐振器的Q值，也不会对寄生模式强度有影响。
在图3B所示的体声波谐振器结构与图3A所示的实施例结构类似，它们都是沿着图3俯视图1B-1B所取的截面图。不同之处在于粗糙度位于顶电极的第一、第二部分的上下表面形成粗糙结构。顶电极第一、第二部分上下表面形成的粗糙结构，能够进一步提升其声阻抗与第一声阻抗之间的不匹配程度以及在粗糙结构中对寄生模式的抑制作用，从而进一步提升声波的反射能力和转换能力，使得谐振器的性能增加，其 Q值进一步增加。
在图3C所示的体声波谐振器结构与图3A所示的实施例结构类似，它们都是沿着图3俯视图1B-1B所取的截面图。不同之处在于在底电极的两侧加入了平坦层，加入的平坦层与底电极的第一末端和第二末端的斜端面对齐，从而形成平整光滑的表面，这样有利于在底电极与平坦层的连接处上沉积有良好C-轴取向的压电薄膜。平坦层可以采用二氧化硅、氮化硅、碳化硅等合适的介质材料。
图4为基于本发明的一个示例性实施例的薄膜体声波谐振器的截面SEM图。如图4所示，谐振器包括压电层401，顶电极403，钝化层405，以及为了方便将器件图片拍的更清楚而喷涂的一层箔407，桥部结构409，粗糙结构411位于压电层的上方桥部结构中。
在图4中，由于粗糙结构的表面与其周围压电层区域的表面相比更为粗糙，使得声波在粗糙结构中反射的周长变长，从而提高了声波反射的周期，使得一部分横向模式的声波会在粗糙结构中损失掉，从而降低了寄生模式。
基于以上，本发明的实施例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，与所述底电极对置；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；所述谐振器邻近所述有效区域的边界且在边界之外设置有空气隙；所述空气隙对应的表面中的至少一个表面为粗糙面，该粗糙面的粗糙度大于该粗糙面所在部件的该粗糙面周围部分表面的粗糙度。
基于以上，本发明的实施例还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，与所述底电极对置；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、顶电极在基板的厚度方向重叠的区域为谐振器的有效区域，所述有效区域具有第一声阻抗；所述谐振器邻近所述有效区域的边界且在边界之外设置有空气隙，与所述空气隙对应的表面中的至少一个表面为粗糙面，所述空气隙所在区域具有不同于第一声阻抗的第二声阻抗。
图5为根据本发明的一个示例性实施例的体声波谐振器的截面图。体声波谐振器包括：基底501、声学镜503，此声学镜位于基底的上表面或嵌于基底的内部，在图5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器也同样适用。
体声波谐振器还包括底电极505，压电层507和顶电极509以及粗糙结构515。底电极沉积在声学镜的上表面，并覆盖声学镜。粗糙结构515位于顶电极边缘周围区域压电层的上表面。粗糙结构515的表面要比其周围压电层区域的表面粗糙，其典型的粗糙度范围可以为
Figure PCTCN2019114001-appb-000013
可选的，可以为
Figure PCTCN2019114001-appb-000014
或者在
Figure PCTCN2019114001-appb-000015
底电极、压电层、顶电极和声学镜在厚度方向重叠的区域为谐振器的有效区域，具有第一声阻抗。在粗糙结构515中具有第二声阻抗。由于在粗糙结构中的第二声阻抗与第一声阻抗不匹配，会使得声波在边界处传输不连续。因此在边界处，一部分声能就会耦合且反射到有效激励区域中，并且转换成与压电层表面垂直的活塞声波模式。同时由于粗糙结构515的表面与其周围压电层区域的表面相比更为粗糙，使得声波在粗糙结构中反射的周长变长，从而提高了声波反射的周期，使得一部分横向模式的声波会在粗糙结构中损失掉，从而降低了寄生模式。
需要指出的是，虽然没有示出，粗糙结构或者粗糙面也可以直接设置在有效边界之外的顶电极的上表面或者下表面处、或者压电层的上表面或者下表面处、或者底电极的上表面或者下表面处。
基于以上，本发明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，与所述底电极对置；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，所述有效区域具有第一声阻抗；所述谐振器邻近所述有效区域的边界且在边界之外设置有粗糙面，所述粗糙面所在区域具有不同于第一声阻抗的第二声阻抗。
在本发明中，电极组成材料可以是金(Au)、钨(W)、钼(Mo)、铂(Pt)，钌(Ru)、铱(Ir)、钛钨(TiW)、铝(Al)、钛(Ti)等类似金属。
在本发明中，压电层材料可以为氮化铝(AlN)、氧化锌(ZnO)、锆钛酸铅(PZT)、铌酸锂(LiNbO 3)、石英(Quartz)、铌酸钾(KNbO 3)或钽酸锂(LiTaO 3)等材料。
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。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。
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 (18)

  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，与所述底电极对置；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；
    所述谐振器邻近所述有效区域的边界且在边界之外设置有空气隙；
    所述空气隙对应的表面中的至少一个表面为粗糙面，该粗糙面的粗糙度大于该粗糙面所在部件的该粗糙面周围部分表面的粗糙度。
  2. 根据权利要求1所述的体声波谐振器，其中：
    所述顶电极具有主体部以及与主体部连接的连接部；
    所述空气隙设置在所述连接部的下方以及压电层的上表面之间；
    与空气隙对应的压电层上表面、连接部下表面、连接部上表面中的至少一个表面为所述粗糙面。
  3. 根据权利要求2所述的体声波谐振器，其中：
    所述连接部包括第一连接部；
    所述第一连接部邻近所述有效区域的边界形成桥翼结构，所述桥翼结构下表面以及压电层上表面之间形成所述空气隙。
  4. 根据权利要求2所述的体声波谐振器，其中：
    所述连接部包括分别连接在主体部两侧的第一连接部和第二连接部；
    所述空气隙包括第一空气隙和第二空气隙；
    所述第一连接部邻近所述有效区域的边界形成第一桥翼结构，所述第一桥翼结构下表面与所述压电层上表面之间形成所述第一空气隙；
    所述第二连接部邻近所述有效区域的边界形成第二桥翼结构，所述第二桥部翼结构下表面与所述压电层上表面之间形成所述第二空气隙。
  5. 根据权利要求3或4所述的体声波谐振器，其中：
    与空气隙对应的压电层的上表面为所述粗糙面；
    所述桥翼结构的末端边缘在基底的厚度方向上位于声学镜之内且桥翼结构在横向上具有桥翼宽度。
  6. 根据权利要求2所述的体声波谐振器，其中：
    所述连接部包括第一连接部；
    所述第一连接部邻近所述有效区域的边界形成桥部结构，所述桥部结构下表面以及压电层上表面之间形成所述空气隙。
  7. 根据权利要求6所述的体声波谐振器，其中：
    与空气隙对应的压电层的上表面为所述粗糙面；
    在基底的厚度方向上顶电极的主体部与连接部的连接处位于声学镜之内，所述连接处与声学镜边界之间具有第一横向距离，并且桥部结构跨越底电极，顶电极的连接部的末端与底电极的对应末端之间具有第二横向距离。
  8. 根据权利要求2所述的体声波谐振器，其中：
    所述连接部包括分别连接在主体部两侧的第一连接部和第二连接部；
    所述空气隙包括第一空气隙和第二空气隙；
    所述第一连接部邻近所述有效区域的边界形成桥部结构，所述桥部结构下表面与所述压电层上表面之间形成所述第一空气隙；
    所述第二连接部邻近所述有效区域的边界形成桥翼结构，所述桥翼结构下表面与所述压电层上表面之间形成所述第二空气隙。
  9. 根据权利要求8所述的体声波谐振器，其中：
    与空气隙对应的压电层的上表面为所述粗糙面；
    在基底的厚度方向上顶电极的主体部与连接部的连接处位于声学镜之内，所述连接处与声学镜边界之间具有第一横向距离，并且桥部结构跨越底电极，顶电极的连接部的末端与底电极的对应末端之间具有第二横向距离；
    所述桥翼结构的末端边缘在基板的厚度方向上位于声学镜之内且桥翼结构在横向上具有桥翼宽度。
  10. 根据权利要求2-9中任一项所述的体声波谐振器，其中：
    所述体声波谐振器还包括平坦层，所述平坦层设置在所述基底与所述压电层之间且与底电极厚度相同；
    所述压电层上表面是平坦的。
  11. 根据权利要求1所述的体声波谐振器，其中：
    所述空气隙在底电极的边缘附近设置在压电层下表面与底电极上表面之间。
  12. 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，与所述底电极对置；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，所述有效区域具有第一声阻抗；
    所述谐振器邻近所述有效区域的边界且在边界之外设置有空气隙，与所述空气隙对应的表面中的至少一个表面为粗糙面，所述空气隙所在区域具有不同于第一声阻抗的第二声阻抗。
  13. 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，与所述底电极对置；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，所述有效区域具有第一声阻抗；
    所述谐振器邻近所述有效区域的边界且在边界之外设置有粗糙面，所述粗糙面所在区域具有不同于第一声阻抗的第二声阻抗。
  14. 根据权利要求13所述的体声波谐振器，其中：
    所述粗糙面设置在有效边界之外的顶电极的上表面或者下表面处、或者压电层的上表面或者下表面处、或者底电极的上表面或者下表面处。
  15. 根据权利要求1-14中任一项所述的体声波谐振器，其中：
    所述粗糙面的粗糙度为
    Figure PCTCN2019114001-appb-100001
  16. 根据权利要求15所述的体声波谐振器，其中：
    所述粗糙度为
    Figure PCTCN2019114001-appb-100002
    左右。
  17. 一种滤波器，包括根据权利要求1-16中任一项所述的体声波谐振器。
  18. 一种电子设备，包括根据权利要求17所述的滤波器。
PCT/CN2019/114001 2018-11-14 2019-10-29 具有粗糙面的体声波谐振器、滤波器和电子设备 WO2020098481A1 (zh)

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