CN110868170A - Acoustic resonator - Google Patents

Acoustic resonator Download PDF

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Publication number
CN110868170A
CN110868170A CN201910328539.2A CN201910328539A CN110868170A CN 110868170 A CN110868170 A CN 110868170A CN 201910328539 A CN201910328539 A CN 201910328539A CN 110868170 A CN110868170 A CN 110868170A
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substrate
resonator
curved surface
bridge
cavity
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CN201910328539.2A
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CN110868170B (en
Inventor
李亮
吕鑫
梁东升
刘青林
马杰
高渊
丁现朋
冯利东
商庆杰
钱丽勋
李丽
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CETC 13 Research Institute
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CETC 13 Research Institute
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic 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
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/02149—Means for compensation or elimination of undesirable effects of ageing changes of characteristics, e.g. electro-acousto-migration
    • 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
    • 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 piezo-electric or electrostrictive material
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H03H2003/023—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the membrane type
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H2009/02165—Tuning
    • H03H2009/02173—Tuning of film bulk acoustic resonators [FBAR]

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

The invention relates to the technical field of semiconductors, and particularly discloses an acoustic resonator, which comprises: a substrate; the multilayer structure is formed on the substrate and sequentially comprises a lower electrode layer, a piezoelectric layer and an upper electrode layer from bottom to top; a cavity is formed between the substrate and the multilayer structure, and comprises a lower half cavity below the upper surface of the substrate and an upper half cavity which exceeds the upper surface of the substrate and protrudes towards the multilayer structure; an edge of the lower electrode layer abuts the planarization layer; the multilayer structure is provided with a bridge portion. The acoustic resonator has good performance, firm structure and difficult damage through the combination of the cavity body with a special structure and the bridge part.

Description

Acoustic resonator
Technical Field
The invention relates to the technical field of semiconductors, in particular to an acoustic resonator.
Background
Resonators may be used in various electronic applications to implement signal processing functions, for example, some cellular telephones and other communication devices use resonators to implement filters for transmitted and/or received signals. Several different types of resonators may be used depending on different applications, such as Film Bulk Acoustic Resonators (FBAR), coupled resonator filters (SBAR), Stacked Bulk Acoustic Resonators (SBAR), Dual Bulk Acoustic Resonators (DBAR), and solid-State Mounted Resonators (SMR).
A typical acoustic resonator includes an upper electrode, a lower electrode, a piezoelectric material between the upper and lower electrodes, an acoustic reflection structure below the lower electrode, and a substrate below the acoustic reflection structure. The area where the three materials of the upper electrode, the piezoelectric layer and the lower electrode are overlapped in the thickness direction is generally defined as the effective area of the resonator. When a voltage signal with a certain frequency is applied between the electrodes, due to the inverse piezoelectric effect of the piezoelectric material, a sound wave which is vertically transmitted can be generated between the upper electrode and the lower electrode in the effective area, and the sound wave is reflected back and forth between the interface of the upper electrode and the air and the sound reflection structure below the lower electrode and generates resonance under a certain frequency. When an acoustic resonator is excited by an applied transformer plant, it generates acoustic waves that can propagate along all possible lateral directions and higher order harmonic mixing products that adversely affect the function of the acoustic resonator and increase energy losses.
Disclosure of Invention
Based on the above problems, embodiments of the present invention provide an acoustic resonator to solve the problems in the prior art that a resonator has low performance and is prone to generate energy loss.
A first aspect of an embodiment of the present invention provides an acoustic resonator, including:
a substrate;
the multilayer structure is formed on the substrate and sequentially comprises a lower electrode layer, a piezoelectric layer and an upper electrode layer from bottom to top;
a planarization layer adjacent to an edge of the lower electrode layer;
a cavity is formed between the substrate and the multilayer structure, and comprises a lower half cavity below the upper surface of the substrate and an upper half cavity which exceeds the upper surface of the substrate and protrudes towards the multilayer structure;
the bridge part is arranged in the piezoelectric layer adjacent to one side of the lower electrode layer and is arranged along the periphery of the cavity; the bridge is partially disposed on the substrate and extends across an edge of the cavity.
Preferably, the lower half cavity is enclosed by a bottom wall and a first side wall, the bottom wall is entirely parallel to the substrate surface, and the first side wall is a first smooth curved surface extending from the edge of the bottom wall to the upper surface of the substrate.
Preferably, the first smoothly curved surface comprises a first curved surface and a second curved surface which are smoothly and transitionally connected.
Preferably, the upper half cavity is defined by a lower side surface of the multilayer structure, a portion of the multilayer structure corresponding to the upper half cavity is defined by a top wall and a second side wall, and the second side wall is a second smooth curved surface extending from an edge of the top wall to an upper surface of the substrate.
Preferably, the second round curved surface comprises a third curved surface and a fourth curved surface which are in round transition connection.
Preferably, the bridge is an unfilled bridge containing air therein.
Preferably, the bridge is a filled bridge filled with a dielectric material.
Preferably, the dielectric material is one of non-etchable silicon borosilicate glass, carbon doped silica glass, silicon carbide.
Preferably, the bridge is a filled bridge filled with a metal material inside.
Preferably, the metal material is one of copper, tungsten, molybdenum and iridium.
Preferably, the vertical cross-section of the bridge part is shuttle-shaped.
A second aspect of an embodiment of the present invention provides an acoustic resonator, including:
a substrate;
the multilayer structure is formed on the substrate and sequentially comprises a lower electrode layer, a piezoelectric layer and an upper electrode layer from bottom to top;
a planarization layer adjacent to an edge of the lower electrode layer;
a cavity is formed between the substrate and the multilayer structure, and comprises a lower half cavity below the upper surface of the substrate and an upper half cavity which exceeds the upper surface of the substrate and protrudes towards the multilayer structure;
the first bridge part is arranged in the piezoelectric layer adjacent to one side of the lower electrode layer and is arranged along the periphery of the cavity; the first bridge portion is partially disposed on the substrate and extends across an edge of the cavity.
The second bridge part is arranged in the upper electrode layer adjacent to one side of the piezoelectric layer and is arranged along the periphery of the cavity; the second bridge portion is partially disposed on the substrate and extends across an edge of the cavity.
Preferably, the lower half cavity is enclosed by a bottom wall and a first side wall, the bottom wall is entirely parallel to the substrate surface, and the first side wall is a first smooth curved surface extending from the edge of the bottom wall to the upper surface of the substrate.
Preferably, the first smoothly curved surface comprises a first curved surface and a second curved surface which are smoothly and transitionally connected.
Preferably, the upper half cavity is defined by a lower side surface of the multilayer structure, a portion of the multilayer structure corresponding to the upper half cavity is defined by a top wall and a second side wall, and the second side wall is a second smooth curved surface extending from an edge of the top wall to an upper surface of the substrate.
Preferably, the second round curved surface comprises a third curved surface and a fourth curved surface which are in round transition connection.
Preferably, the first bridge part and the second bridge part are internally provided with cavities containing air.
Preferably, the inside of the first and second bridge portions is filled with a filling material having acoustic impedance.
Preferably, the first bridge part is internally provided with a cavity containing air; the inside of the second bridge portion is filled with a filling material having an acoustic impedance.
Preferably, an inside of the first bridge portion is filled with a filling material having an acoustic impedance; the second bridge part is internally provided with a cavity containing air.
Preferably, the first and second bridge portions have a shuttle-shaped vertical cross section.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: according to the embodiment of the invention, the cavity with the lower half cavity and the upper half cavity is arranged, the lower half cavity is integrally positioned below the upper surface of the substrate, the upper half cavity is integrally positioned above the upper surface of the substrate, and the bridge part is arranged between the piezoelectric layer and the electrode layer, so that a novel resonator structure is formed.
Drawings
FIG. 1 is a schematic diagram of a structure with unfilled bridges between a voltage layer and a lower electrode layer of a resonator according to the present invention;
FIG. 2 is a schematic diagram of a structure with a filling bridge portion between a voltage layer and a lower electrode layer of a resonator according to the present invention;
fig. 3 is a schematic structural view of a resonator multilayer structure of the present invention provided with unfilled first and second bridge portions;
fig. 4 is a schematic structural view of a resonator multilayer structure of the present invention with filled first and second bridges disposed;
fig. 5 is a schematic structural view of a resonator multilayer structure of the present invention provided with an unfilled first bridge portion and a filled second bridge portion;
fig. 6 is a schematic structural view of a resonator multilayer structure of the present invention with a filled first bridge portion and an unfilled second bridge portion;
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1, an embodiment of the present invention provides an acoustic resonator including a substrate 100 and a multilayer structure 200. The multilayer structure 200 is formed on the substrate 100, and the multilayer structure 200 sequentially includes a lower electrode layer 203, a piezoelectric layer 202, and an upper electrode layer 201 from bottom to top. Wherein a cavity 300 is formed between the substrate 100 and the multi-layer structure 200, the cavity 300 including a lower half cavity below the upper surface of the substrate 100 and an upper half cavity protruding beyond the upper surface of the substrate 100 and protruding toward the multi-layer structure 200; the edge of the lower electrode layer abuts the planarization layer 204; a bridge 401 is provided in the piezoelectric layer 202 adjacent to the side of the lower electrode layer 203, the bridge 401 being provided along the periphery of the cavity 300, the bridge 401 being partially provided on the substrate 100 and extending across the edge of the cavity 300.
Wherein the planarization layer 204 is also disposed above the substrate 100, the planarization layer 204 may be made of non-etchable borate glass, and the disposition of the planarization layer 204 can improve the growth quality of the subsequent layers and simplify their processing.
Referring to fig. 1, in one embodiment, the lower half cavity is defined by a bottom wall 301 and a first side wall, the bottom wall 301 is entirely parallel to the surface of the substrate 100, and the first side wall is a first smooth curved surface extending from the edge of the bottom wall 301 to the upper surface of the substrate 100.
Wherein, the bottom wall 301 and the first sidewall are both surface walls of the substrate 100. And the first side wall is a first smooth curved surface, so that the performance of the resonator cavity can be ensured, and sudden change is avoided.
Referring to fig. 2, in one embodiment, the first smoothly curved surface may include a first curved surface 303 and a second curved surface 304 that are smoothly transitionally connected. The first curved surface 303 and the second curved surface 304 which are connected in a smooth transition manner mean that the joint between the first curved surface 303 and the second curved surface 304 has no abrupt change, and the first curved surface 303 and the second curved surface 304 are also curved surfaces without abrupt changes, so that the performance of the resonator cavity can be ensured. Wherein the substrate 100 is composed of many crystals (e.g. silicon crystals), the absence of abrupt changes means that the gap between the individual crystals at the first rounded surface should not be too large to affect the performance of the resonator.
For example, the vertical section of the first curved surface 303 may be an inverted parabolic shape and is located above the plane of the bottom wall 301; the vertical cross-section of the second curved surface 304 may be parabolic and is located below the plane of the upper surface of the substrate 100. The first curved surface 303 and the second curved surface 304 are smoothly connected. Of course, the first curved surface 303 and the second curved surface 304 may be curved surfaces of other shapes, and the gap between the crystals at the first smooth curved surface may not affect the performance of the resonator.
In one embodiment, the first round curved surface is smooth as a whole, and the curvature of each point of the first round curved surface may be smaller than a first preset value. The first preset value can be set according to actual conditions so as to achieve the purpose that gaps among the crystals at the first smooth curved surface do not affect the performance of the resonator. In order to ensure the mechanical and electrical properties of the multilayer structure, the curvature of the smooth curved surface of the transition region is as small as possible, and under the condition that the thickness of the sacrificial layer is constant, the smallest curvature requires that the length of the transition region is increased, which increases the area of the resonator, so the curvature of the transition region and the length of the transition region are optimized. Preferably, the thickness of the cavity 300 may be 1 μm, and the length of the transition region is controlled to be 3 μm to 5 μm, and the multilayer structure grown in the transition region can satisfy the resonator requirement. The length of the transition zone is the width of the upper surface of the lower cavity half shown in fig. 1.
Referring to fig. 1, in one embodiment, the upper cavity half 302 may be surrounded by the lower side of the multi-layer structure 200, and a portion of the lower side of the multi-layer structure 200 corresponding to the upper cavity half includes a top wall 302 and a second side wall, and the second side wall is a second smooth curved surface extending from an edge of the top wall 302 to the upper surface of the substrate 100.
Wherein the top wall 302 and the second side wall are both lower side walls of the multi-layer structure 200. And the second side wall is a second smooth curved surface, so that the performance of the resonator cavity can be ensured, and sudden change is avoided.
Referring to fig. 1, in one embodiment, the second smoothly curved surface may include a third curved surface 305 and a fourth curved surface 306 that are smoothly transitionally connected. The third curved surface 305 and the fourth curved surface 306 which are connected in a smooth transition manner mean that the joint between the third curved surface 305 and the fourth curved surface 306 has no abrupt change, and the third curved surface 305 and the fourth curved surface 306 are also curved surfaces without abrupt changes, so that the performance of the resonator cavity can be ensured. Wherein, from the crystal perspective, the substrate 100 is composed of many crystals (e.g. silicon crystals), and the absence of abrupt change means that the gap between the respective crystals at the second rounded curved surface should not be too large to affect the performance of the resonator.
For example, the vertical cross-section of the third curved surface 305 may be parabolic and located below the plane of the top wall 302; the vertical cross-section of the fourth curved surface 306 is inverse parabolic and is located above the plane of the upper surface of the substrate 100. Of course, the third curved surface 305 and the fourth curved surface 306 may have other shapes, and the gap between the crystals at the first smooth curved surface may not affect the performance of the resonator.
In one embodiment, the curvature of each point of the second round curved surface is smaller than a second preset value. The second preset value can be set according to actual conditions so as to achieve the purpose that gaps among the crystals at the second round curved surface do not affect the performance of the resonator.
Further, the top wall 302 also has no abrupt change. The abrupt changes described here are consistent with the aforementioned abrupt changes, and from a crystal standpoint, the multilayer structure 200 is also comprised of many crystals, and the absence of abrupt changes means that the gaps between the individual crystals at the top wall 302 should not be too large to affect the performance of the resonator.
Referring to fig. 1, in one embodiment, the bridge 401 is an unfilled bridge containing air inside, and the vertical cross section of the bridge 401 is in a shuttle shape, that is, the inner side surface of the bridge 401 is a smooth curved surface, so that gaps between crystals inside the bridge 401 do not affect the performance of the resonator, and meanwhile, the arrangement of the bridge 401 avoids adverse effects of lateral propagation modes and high-order harmonic mixing products on the function of the acoustic resonator, and reduces energy loss.
Referring to fig. 2, in an embodiment, a dielectric material is filled in a bridge 401, and a vertical cross section of the bridge 401 is in a shuttle shape, that is, inner side surfaces of the bridge 401 are all smooth curved surfaces, so that gaps between crystals inside the bridge 401 do not affect performance of the resonator, and meanwhile, the arrangement of the bridge 401 avoids adverse effects of lateral propagation modes and high-order harmonic mixing products on functions of the acoustic resonator, and reduces energy loss.
The dielectric material is one of non-etchable silicon borosilicate glass, carbon-doped silicon dioxide glass and silicon carbide.
Referring to fig. 2, in an embodiment, a metal material is filled in a bridge 401, and a vertical cross section of the bridge 401 is in a shuttle shape, that is, inner side surfaces of the bridge 401 are all smooth curved surfaces, so that gaps between crystals inside the bridge 401 do not affect performance of the resonator, and meanwhile, the arrangement of the bridge 401 avoids adverse effects of a lateral propagation mode and a high-order harmonic mixing product on functions of the acoustic resonator, and reduces energy loss.
Wherein the metal material is one of copper, tungsten, molybdenum and iridium.
By selecting specific bridge part filling materials, the firmness of the resonator can be further improved and the service life of the resonator can be prolonged while the function of the resonator is improved.
The bridge portion shown in fig. 1 and 2 has a length of 5-8 μm in a vertical cross-section of a fusiform shape and a maximum width of 2-4 μm.
In the above embodiments, the substrate 100 may be a silicon substrate or a substrate made of other materials, which is not limited to this.
In the resonator in the embodiment of the invention, the series resonance frequency and the parallel resonance frequency are respectively 2.419GHz and 2.506GHz, the series resonance Q value 1524, the parallel resonance Q value 1088 and the electromechanical coupling coefficient is 5.5%.
Above-mentioned resonator, through setting up cavity 300 that has lower half cavity and first half cavity, and lower half cavity whole is located substrate 100 upper surface under, and first half cavity whole is located substrate 100 upper surface on, sets up bridge 401 between lower electrode layer 203 and piezoelectric layer 202 simultaneously, and bridge 401 sets up along the periphery of cavity 300 to form a neotype resonator structure, and have better performance.
The bridge 401 in the above embodiment may be provided in other shapes, so that the gap between the crystals on the inner side surface of the bridge does not affect the performance of the resonator.
Referring to fig. 3, an embodiment of the present invention provides an acoustic resonator including a substrate 100 and a multilayer structure 200. The multilayer structure 200 is formed on the substrate 100, and the multilayer structure 200 sequentially includes a lower electrode layer 203, a piezoelectric layer 202, and an upper electrode layer 201 from bottom to top. Wherein a cavity 300 is formed between the substrate 100 and the multi-layer structure 200, the cavity 300 including a lower half cavity below the upper surface of the substrate 100 and an upper half cavity protruding beyond the upper surface of the substrate 100 and protruding toward the multi-layer structure 200; the edge of the lower electrode layer 203 abuts the planarization layer 204; a first bridge 401 is arranged in the piezoelectric layer 202 adjacent to one side of the lower electrode layer 203, the first bridge is arranged along the periphery of the cavity 300, and the first bridge 401 is partially arranged on the substrate 100 and extends to cross the edge of the cavity 300; a second bridge 402 is provided in the upper electrode layer 201 adjacent to one side of the piezoelectric layer 202, the second bridge 402 being provided along the periphery of the chamber 300, the second bridge 402 being provided partially on the substrate 100 and extending across the edge of the chamber 300.
Wherein the planarization layer 204 is also disposed above the substrate 100, the planarization layer 204 may be made of non-etchable borate glass, and the disposition of the planarization layer 204 can improve the growth quality of the subsequent layers and simplify their processing.
Referring to fig. 3, in one embodiment, the lower half cavity is defined by a bottom wall 301 and a first side wall, the bottom wall 301 is entirely parallel to the surface of the substrate 100, and the first side wall is a first smooth curved surface extending from the edge of the bottom wall 301 to the upper surface of the substrate 100.
Wherein, the bottom wall 301 and the first sidewall are both surface walls of the substrate 100. And the first side wall is a first smooth curved surface, so that the performance of the resonator cavity can be ensured, and sudden change is avoided.
Referring to fig. 3, in one embodiment, the first smoothly curved surface may include a first curved surface 303 and a second curved surface 304 that are smoothly transitionally connected. The first curved surface 303 and the second curved surface 304 which are connected in a smooth transition manner mean that the joint between the first curved surface 303 and the second curved surface 304 has no abrupt change, and the first curved surface 303 and the second curved surface 304 are also curved surfaces without abrupt changes, so that the performance of the resonator cavity can be ensured. Wherein the substrate 100 is composed of many crystals (e.g. silicon crystals), the absence of abrupt changes means that the gap between the individual crystals at the first rounded surface should not be too large to affect the performance of the resonator.
For example, the vertical section of the first curved surface 303 may be an inverted parabolic shape and is located above the plane of the bottom wall 301; the vertical cross-section of the second curved surface 304 may be parabolic and is located below the plane of the upper surface of the substrate 100. The first curved surface 303 and the second curved surface 304 are smoothly connected. Of course, the first curved surface 303 and the second curved surface 304 may be curved surfaces of other shapes, and the gap between the crystals at the first smooth curved surface may not affect the performance of the resonator.
In one embodiment, the first round curved surface is smooth as a whole, and the curvature of each point of the first round curved surface may be smaller than a first preset value. The first preset value can be set according to actual conditions so as to achieve the purpose that gaps among the crystals at the first smooth curved surface do not affect the performance of the resonator. In order to ensure the mechanical and electrical properties of the multilayer structure, the curvature of the smooth curved surface of the transition region is as small as possible, and under the condition that the thickness of the sacrificial layer is constant, the smallest curvature requires that the length of the transition region is increased, which increases the area of the resonator, so the curvature of the transition region and the length of the transition region are optimized. Preferably, the thickness of the cavity 300 may be 1 μm, and the length of the transition region is controlled to be 3 μm to 5 μm, and the multilayer structure grown in the transition region can satisfy the resonator requirement. The length of the transition zone is the width of the upper surface of the lower cavity half shown in fig. 4.
Referring to fig. 3, in one embodiment, the upper cavity half may be surrounded by the lower side of the multi-layer structure 200, and a portion of the lower side of the multi-layer structure 200 corresponding to the upper cavity half includes a top wall 302 and a second side wall, and the second side wall is a second smooth curved surface extending from an edge of the top wall 302 to the upper surface of the substrate 100.
Wherein the top wall 302 and the second side wall are both lower side walls of the multi-layer structure 200. And the second side wall is a second smooth curved surface, so that the performance of the resonator cavity can be ensured, and sudden change is avoided.
Referring to fig. 3, in one embodiment, the second smoothly curved surface may include a third curved surface 305 and a fourth curved surface 306 that are smoothly transitionally connected. The third curved surface 305 and the fourth curved surface 306 which are connected in a smooth transition manner mean that the joint between the third curved surface 305 and the fourth curved surface 306 has no abrupt change, and the third curved surface 305 and the fourth curved surface 306 are also curved surfaces without abrupt changes, so that the performance of the resonator cavity can be ensured. Wherein, from the crystal perspective, the substrate 100 is composed of many crystals (e.g. silicon crystals), and the absence of abrupt change means that the gap between the respective crystals at the second rounded curved surface should not be too large to affect the performance of the resonator.
For example, the vertical cross-section of the third curved surface 305 may be parabolic and located below the plane of the top wall 302; the vertical cross-section of the fourth curved surface 306 is inverse parabolic and is located above the plane of the upper surface of the substrate 100. Of course, the third curved surface 305 and the fourth curved surface 306 may have other shapes, and the gap between the crystals at the first smooth curved surface may not affect the performance of the resonator.
In one embodiment, the curvature of each point of the second round curved surface is smaller than a second preset value. The second preset value can be set according to actual conditions so as to achieve the purpose that gaps among the crystals at the second round curved surface do not affect the performance of the resonator.
Further, the top wall 302 also has no abrupt change. The abrupt changes described here are consistent with the aforementioned abrupt changes, and from a crystal standpoint, the multilayer structure 200 is also comprised of many crystals, and the absence of abrupt changes means that the gaps between the individual crystals at the top wall 302 should not be too large to affect the performance of the resonator.
Referring to fig. 3, in an embodiment, cavities containing air are formed inside the first bridge portion 401 and the second bridge portion 402, vertical cross sections of the first bridge portion 401 and the second bridge portion 402 are in a shuttle shape, that is, inner side surfaces of the first bridge portion 401 and the second bridge portion 402 are both smooth curved surfaces, so that gaps between crystals on the inner side surfaces of the first bridge portion 401 and the second bridge portion 402 do not affect the performance of the resonator, and meanwhile, the first bridge portion 401 and the second bridge portion 402 are arranged to avoid adverse effects of a lateral propagation mode and a high-order harmonic mixing product on the function of the acoustic resonator, and reduce energy loss.
Referring to fig. 4, in an embodiment, the first bridge 401 and the second bridge 402 are filled with a filling material having acoustic impedance, the vertical cross-sections of the first bridge 401 and the second bridge 402 are in a shuttle shape, that is, the inner side surfaces of the first bridge 401 and the second bridge 402 are both smooth curved surfaces, so that gaps between crystals on the inner side surfaces of the first bridge 401 and the second bridge 402 do not affect the performance of the resonator, and meanwhile, the first bridge 401 and the second bridge 402 are arranged to avoid adverse effects of side propagation modes and high-order harmonic mixing products on the function of the acoustic resonator, thereby reducing energy loss.
Referring to fig. 5, in one embodiment, the first bridge portion 401 is a cavity containing air; the inside of the second bridge portion 402 is filled with a filling material with acoustic impedance, the vertical cross sections of the first bridge portion 401 and the second bridge portion 402 are in a shuttle shape, that is, the inner side surfaces of the first bridge portion 401 and the second bridge portion are both smooth curved surfaces, so that gaps between crystals on the inner side surfaces of the first bridge portion 401 and the second bridge portion 402 do not affect the performance of the resonator, and meanwhile, the arrangement of the first bridge portion 401 and the second bridge portion 402 avoids adverse effects of a lateral propagation mode and high-order harmonic mixing products on the function of the acoustic resonator, and reduces energy loss.
Referring to fig. 6, in one embodiment, the interior of the first bridge portion 401 is filled with a filling material having acoustic impedance; the second bridge part 402 is internally provided with a cavity containing air, the vertical cross sections of the first bridge part 401 and the second bridge part 402 are in a shuttle shape, namely the inner side surfaces of the first bridge part 401 and the second bridge part 402 are both smooth curved surfaces, so that the performance of the resonator is not influenced by gaps between crystals on the inner side surfaces of the first bridge part 401 and the second bridge part 402, and meanwhile, the first bridge part 401 and the second bridge part 402 are arranged to avoid the adverse effects of a lateral propagation mode and a high-order harmonic mixing product on the functions of the acoustic resonator, and reduce energy loss.
In the above embodiments, the substrate 100 may be a silicon substrate or a substrate made of other materials, which is not limited to this.
The resonator is provided with a cavity 300 with a lower cavity and an upper cavity, wherein the lower cavity is integrally positioned below the upper surface of the substrate 100, the upper cavity is integrally positioned on the upper surface of the substrate 100, a first bridge part 401 is arranged between the lower electrode layer 203 and the piezoelectric layer 202, a second bridge part 402 is arranged between the piezoelectric layer 202 and the upper electrode layer 201, and the first bridge part 401 and the second bridge part 402 are arranged along the periphery of the cavity 300, so that a novel resonator structure is formed and the resonator has better performance.
The spindle-shaped vertical cross-sections of the first and second bridge parts illustrated in fig. 3-6 have a length of 5-8 μm and a maximum width of 2-4 μm.
The first bridge 401 and the second bridge 402 in the above embodiments may be provided in other shapes, so that the gap between the crystals on the inner side surfaces of the first bridge 401 and the second bridge 402 does not affect the performance of the resonator.
An embodiment of the invention discloses a manufacturing method of an acoustic resonator, which comprises the following steps:
step 501, forming a shielding layer on a substrate, wherein the shielding layer covers an area except a preset area on the substrate.
In this step, the process of forming the shielding layer on the substrate may include:
forming a shielding medium on the substrate, wherein the shielding layer is used for shielding the substrate except for a preset region from the preset reaction;
and removing the shielding medium corresponding to the preset area to form the shielding layer.
Wherein the shielding medium acts to make the reaction rate of the portion of the substrate covered with the shielding medium lower than the reaction rate of the portion not covered with the shielding medium. Further, the shielding layer may be used to shield a region of the substrate other than the predetermined region from the predetermined reaction.
Step 502, preprocessing the substrate on which the shielding layer is formed, and controlling a part of the substrate corresponding to the preset region to perform a preset reaction to obtain a sacrificial material part; the sacrificial material portion includes an upper half located above the upper surface of the substrate and a lower half located below the lower surface of the substrate.
Wherein the lower half part is enclosed by a bottom surface and a first side surface; the bottom surface is entirely parallel to the surface of the substrate, and the first side surface is a first smooth curved surface extending from the edge of the bottom wall to the upper surface of the substrate. The upper half part is surrounded by the lower side surface of the multilayer structure, the part of the multilayer structure corresponding to the upper half part comprises a top surface and a second side surface, and the second side surface is a second smooth curved surface extending from the edge of the top surface to the upper surface of the substrate.
Optionally, the first smooth curved surface includes a first curved surface and a second curved surface that are connected in a smooth transition manner. For example, the vertical section of the first curved surface is in an inverted parabolic shape and is located above the plane of the bottom surface; the vertical section of the second curved surface is parabolic and is positioned below the plane of the upper surface of the substrate.
Optionally, the second smooth curved surface includes a third curved surface and a fourth curved surface which are in smooth transition connection; the vertical section of the third curved surface is parabolic and is positioned below the plane of the top surface; the vertical section of the fourth curved surface is in an inverted parabolic shape and is positioned on the plane of the upper surface of the substrate.
In one embodiment, the curvature of the first round curved surface is smaller than a first preset value; and the curvature of the second smooth curved surface is smaller than a second preset value.
As an implementation manner, the implementation process of step 502 may include: and placing the substrate in an oxidizing atmosphere for oxidation treatment, and controlling the part of the substrate corresponding to the preset area to perform oxidation reaction to obtain a sacrificial material part.
Wherein, the placing the substrate in an oxidizing atmosphere for oxidation treatment may include:
introducing high-purity oxygen to the substrate in a process temperature environment within a preset range, so that an oxide layer is generated on the part, corresponding to the preset area, of the substrate;
after the first preset time, stopping introducing high-purity oxygen to the substrate, and enabling the thickness of an oxide layer on the substrate to reach a preset thickness through one or more modes of wet oxygen oxidation, oxyhydrogen synthesis oxidation and high-pressure water vapor oxidation;
and stopping introducing the wet oxygen to the substrate and introducing high-purity oxygen to the substrate, and completing the oxidation treatment of the substrate after a second preset time.
Wherein the preset range can be 1000-1200 ℃; the first preset time may be 20 minutes to 140 minutes; the preset thickness can be 0.4-4 μm; the second preset time may be 20 minutes to 140 minutes; the flow rate of the high-purity oxygen can be 3L/min to 15L/min.
It should be noted that, one or a combination of several means of pure oxygen, wet oxygen, hydrogen-oxygen synthesis and high-pressure water vapor oxidation is adopted, the appearance of the transition region has certain difference; meanwhile, the selection of the type and the structure of the shielding layer has certain marketing effect on the appearance of the transition region, and the oxidation mode and the type and the structure of the shielding layer are reasonably selected according to the thickness of the multilayer structure and the requirement of the piezoelectric layer on curvature change.
Step 503, removing the pretreated substrate shielding layer.
And step 504, forming a multilayer structure on the substrate after the shielding layer is removed, wherein the multilayer structure sequentially comprises a lower electrode layer, a piezoelectric layer and an upper electrode layer from bottom to top.
At step 505, the sacrificial material portion is removed.
Wherein, in the step 504, in the manufacturing method of the bridge part in the multilayer structure, when the bridge part is not filled (i.e. contains air as an acoustic medium), the manufacturing method is the same as that of the cavity; if the bridge portion is filled with the filler material, the filler material is provided, and the filler material is not removed when the sacrificial material is removed, so that the filled bridge portion is obtained.
In this embodiment, the shielding layer may be a SiN material layer or SiO layer2The material layer, the polysilicon material layer, or the multilayer structure formed by mixing the above two or three materials, and the substrate may be a silicon substrate or a substrate made of other materials, which is not limited in this respect.
In one embodiment, the shielding layer may be SiN or may have a multilayer film structure, and SiN is used as the oxidation shielding layer, so that the shielding effect is better, and the reaction rate difference between the shielding region and the non-shielding region is larger. The shielding medium in the area where the resonator needs to be manufactured can be removed by means of etching or corrosion, and the like, the silicon wafer is put in an oxidizing atmosphere for oxidation, and the reaction rate of the part with the shielding medium is larger than that of the part without the shielding medium: the reaction rate of the part without the shielding medium is higher, and the substrate Si reacts with oxygen to form SiO2SiO produced2The thickness is increased continuously, the upper surface of the shielding layer is gradually higher than the surface of the shielding medium part, the Si surface of the shielding medium part is gradually lowered, and the surface of the shielding medium part is lowered relatively. At the edge of the shielding layerAnd a transition region without rate change is formed at the edge, a smooth curved surface can be formed in the transition region by optimizing the oxidation mode and the type and structure of the shielding layer, and a multi-layer structure of the piezoelectric film containing AlN and the like grows on the smooth curved surface, so that the crystal quality of the piezoelectric film can be ensured.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (21)

1. An acoustic resonator, characterized by: the method comprises the following steps:
a substrate;
the multilayer structure is formed on the substrate and sequentially comprises a lower electrode layer, a piezoelectric layer and an upper electrode layer from bottom to top;
a cavity is formed between the substrate and the multilayer structure, and comprises a lower half cavity below the upper surface of the substrate and an upper half cavity which exceeds the upper surface of the substrate and protrudes towards the multilayer structure; an edge of the lower electrode layer abuts the planarization layer; a bridge is disposed in the piezoelectric layer adjacent to one side of the lower electrode layer, the bridge being disposed along a perimeter of the cavity, the bridge being partially disposed on the substrate and extending across an edge of the cavity.
2. The resonator of claim 1, wherein: the lower half cavity is enclosed by a bottom wall and a first side wall, the whole bottom wall is parallel to the surface of the substrate, and the first side wall is a first smooth curved surface extending from the edge of the bottom wall to the upper surface of the substrate.
3. The resonator of claim 2, wherein: the first smooth curved surface comprises a first curved surface and a second curved surface which are in smooth transition connection.
4. The resonator of claim 1, wherein: the upper half cavity is formed by surrounding the lower side surface of the multilayer structure, the part of the multilayer structure corresponding to the upper half cavity comprises a top wall and a second side wall, and the second side wall is a second smooth curved surface which is formed by extending the edge of the top wall to the upper surface of the substrate.
5. The resonator of claim 4, wherein: the second smooth curved surface comprises a third curved surface and a fourth curved surface which are in smooth transition connection.
6. The resonator of claim 1, wherein: the bridge part is an unfilled bridge part containing air therein.
7. The resonator of claim 1, wherein: the bridge portion is filled with a dielectric material.
8. The resonator of claim 7, wherein: the dielectric material is one of non-etchable silicon borosilicate glass, carbon-doped silica glass and silicon carbide.
9. The resonator of claim 1, wherein: the bridge part is a filling bridge part filled with a metal material.
10. The resonator of claim 9, wherein: the metal material is one of copper, tungsten, molybdenum and iridium.
11. The resonator of claim 1, wherein: the vertical section of the bridge part is in a shuttle shape.
12. An acoustic resonator, characterized by: the method comprises the following steps:
a substrate;
the multilayer structure is formed on the substrate and sequentially comprises a lower electrode layer, a piezoelectric layer and an upper electrode layer from bottom to top;
a cavity is formed between the substrate and the multilayer structure, and comprises a lower half cavity below the upper surface of the substrate and an upper half cavity which exceeds the upper surface of the substrate and protrudes towards the multilayer structure; an edge of the lower electrode layer abuts the planarization layer; a first bridge part is arranged in the piezoelectric layer adjacent to one side of the lower electrode layer, the first bridge part is arranged along the periphery of the cavity, and the first bridge part is partially arranged on the substrate and extends to cross the edge of the cavity; a second bridge is disposed in the upper electrode layer adjacent one side of the piezoelectric layer, the second bridge being disposed along a perimeter of the cavity, the second bridge being partially disposed on the substrate and extending across an edge of the cavity.
13. The resonator of claim 12, wherein: the lower half cavity is enclosed by a bottom wall and a first side wall, the whole bottom wall is parallel to the surface of the substrate, and the first side wall is a first smooth curved surface extending from the edge of the bottom wall to the upper surface of the substrate.
14. The resonator of claim 13, wherein: the first smooth curved surface comprises a first curved surface and a second curved surface which are in smooth transition connection.
15. The resonator of claim 12, wherein: the upper half cavity is formed by surrounding the lower side surface of the multilayer structure, the part of the multilayer structure corresponding to the upper half cavity comprises a top wall and a second side wall, and the second side wall is a second smooth curved surface which is formed by extending the edge of the top wall to the upper surface of the substrate.
16. The resonator of claim 15, wherein: the second smooth curved surface comprises a third curved surface and a fourth curved surface which are in smooth transition connection.
17. The resonator of claim 12, wherein: the first bridge part and the second bridge part are internally provided with cavities containing air.
18. The resonator of claim 12, wherein: the inside of the first bridge portion and the second bridge portion is filled with a filling material having an acoustic impedance.
19. The resonator of claim 12, wherein: the first bridge part is internally provided with a cavity containing air; the inside of the second bridge portion is filled with a filling material having an acoustic impedance.
20. The resonator of claim 12, wherein: the inside of the first bridge part is filled with a filling material having acoustic impedance; the second bridge part is internally provided with a cavity containing air.
21. The resonator of claim 12, wherein: the vertical cross sections of the first bridge part and the second bridge part are in a shuttle shape.
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