CN112039481B - Bulk acoustic wave resonator and method of manufacturing the same - Google Patents

Bulk acoustic wave resonator and method of manufacturing the same Download PDF

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Publication number
CN112039481B
CN112039481B CN201910735292.6A CN201910735292A CN112039481B CN 112039481 B CN112039481 B CN 112039481B CN 201910735292 A CN201910735292 A CN 201910735292A CN 112039481 B CN112039481 B CN 112039481B
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layer
cavity
substrate
dielectric layer
forming
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CN112039481A (en
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周春宇
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Ningbo Semiconductor International Corp
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Ningbo Semiconductor International Corp
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • 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
    • H03H3/04—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 for obtaining desired frequency or temperature coefficient
    • 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
    • H03H3/04—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 for obtaining desired frequency or temperature coefficient
    • H03H2003/0414—Resonance frequency
    • 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
    • H03H3/04—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 for obtaining desired frequency or temperature coefficient
    • H03H2003/0414—Resonance frequency
    • H03H2003/0421—Modification of the thickness of an element
    • H03H2003/0435—Modification of the thickness of an element of a piezoelectric layer

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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

A bulk acoustic wave resonator and a method of manufacturing the same, the bulk acoustic wave resonator including: a piezoelectric stack; the dielectric layer is positioned on the piezoelectric lamination, and a cavity penetrating through the dielectric layer is arranged in the dielectric layer; the substrate is positioned on the dielectric layer and covers the dielectric layer; the dummy cavity is positioned in the substrate, penetrates through the substrate and extends into the dielectric layer at the periphery of the cavity; the air pressure balance hole is positioned in the dielectric layer and is communicated with the dummy cavity and the cavity; a cavity is arranged in a medium layer between the substrate and the piezoelectric lamination, so that a total reflection interface is formed at the junction of the piezoelectric material of the piezoelectric lamination and the cavity, the cavity is communicated with the pseudo cavity through the air pressure balance hole, the balance between the internal pressure and the external pressure of the cavity between the substrate and the piezoelectric lamination is realized, and the substrate is prevented from being deformed due to the unbalanced internal and external pressure and sinking into the cavity.

Description

Bulk acoustic wave resonator and method of manufacturing the same
Technical Field
The present invention relates to the field of resonator technology, and more particularly, to a bulk acoustic wave resonator and a method of manufacturing the same
Background
Since the development of analog rf communication technology in the beginning of the last 90 th generation, rf front-end modules have gradually become the core components of communication devices. Among all the radio frequency front end modules, the filter has become the most powerful component of growth and development prospect. With the rapid development of wireless communication technology, the 5G communication protocol is mature, and the market also puts forward more strict standards on the performance of the radio frequency filter in all aspects. The performance of the filter is determined by the resonator elements that make up the filter. Among the existing filters, a Film Bulk Acoustic Resonator (FBAR) is one of the most suitable filters for 5G applications due to its small size, low insertion loss, large out-of-band rejection, high quality factor, high operating frequency, large power capacity, and good antistatic impact capability.
In general, a thin film bulk acoustic resonator includes two thin film electrodes, and a piezoelectric thin film layer is disposed between the two thin film electrodes, and the working principle of the thin film bulk acoustic resonator is that the piezoelectric thin film layer is utilized to generate vibration under an alternating electric field, the vibration excites bulk acoustic waves propagating along the thickness direction of the piezoelectric thin film layer, and the acoustic waves are transmitted to the interface between the upper electrode and the lower electrode and air to be reflected back, and then are reflected back and forth inside the thin film to form oscillation. Standing wave oscillation is formed when the acoustic wave propagates in the piezoelectric film layer just an odd multiple of half the wavelength.
However, the quality factor (Q) of the cavity type thin film bulk acoustic resonator manufactured at present cannot be further improved, and thus the requirement of a high-performance radio frequency system cannot be satisfied.
Disclosure of Invention
The invention aims to solve the problem of unbalanced pressure inside and outside a cavity of the traditional bulk acoustic wave resonator, and provides a bulk acoustic wave resonator and a manufacturing method thereof, which ensure that the total reflection of acoustic waves at an electrode material and air interface is ensured, and meanwhile, the balance between the inside of the cavity and the external atmospheric pressure is ensured, so that the stability of the resonator structure is improved.
In order to achieve the above object, the present invention provides a bulk acoustic wave resonator comprising: a substrate; a piezoelectric stack; the dielectric layer is arranged between the substrate and the piezoelectric lamination, and a cavity, a pseudo cavity and a pressure balance hole are arranged in the dielectric layer; the cavity penetrates through the medium layer, the dummy cavity is formed in the medium layer at the periphery of the cavity and penetrates through the substrate, and a space is formed between the cavity and the dummy cavity in the medium layer; the air pressure balance hole is communicated with the cavity and the dummy cavity.
Optionally, the piezoelectric stack includes a first electrode, a piezoelectric layer on the first electrode, and a second electrode on the piezoelectric layer.
Optionally, the air pressure balance hole is located between the dielectric layer and the substrate.
Optionally, the air pressure balance hole is located between the dielectric layer and the piezoelectric stack.
Optionally, the dielectric layer comprises a silicon oxide or silicon nitride material.
Optionally, the width of the cavity is 100 um-400 um, and the width of the dummy cavity is 20 um-50 um.
Optionally, the material of the first electrode and/or the second electrode comprises one of molybdenum, tantalum, an alloy of molybdenum, or an alloy of tantalum.
Optionally, the material of the piezoelectric layer includes one of aluminum nitride, zinc oxide, and scandium aluminum nitride.
Optionally, the semiconductor device further comprises a second insulating layer, wherein the second insulating layer is arranged between the second electrode and the dielectric layer, and the second insulating layer comprises any one or two of silicon oxide and silicon nitride.
Optionally, the piezoelectric stack further includes a frequency modulation layer, the frequency modulation layer includes a first frequency modulation layer and a second frequency modulation layer, the first frequency modulation layer is disposed on a surface of the first electrode far away from the piezoelectric layer, and the second frequency modulation layer is disposed between the second insulating layer and the second electrode.
Optionally, the material of the first frequency modulation layer and/or the second frequency modulation layer comprises at least one of silicon oxide, silicon nitride, aluminum oxide and aluminum nitride.
Optionally, the method further comprises: a first member connection hole and a second member connection hole located at peripheral regions of the cavity, the air pressure balance hole and the dummy cavity, the first member connection hole penetrating the first frequency modulation layer and exposing a part of the first electrode; the second component connection hole penetrates through the substrate, the dielectric layer, the second insulating layer and the second frequency modulation layer and exposes a part of the second electrode.
Optionally, metal pads are respectively arranged at bottoms of the first component connecting hole and the second component connecting hole.
Optionally, the vertical width of the air pressure balance hole isThe transverse length of the air pressure balance hole is +.>
The invention also provides a manufacturing method of the bulk acoustic wave resonator, which comprises the following steps: providing a substrate, and forming a piezoelectric stack on the substrate; forming a dielectric layer on the piezoelectric stack; forming an air pressure balance hole in the medium layer, wherein the air pressure balance hole is communicated with the cavity; providing a substrate; covering the substrate on the dielectric layer; and forming a dummy cavity penetrating through the substrate in the substrate, wherein the dummy cavity extends into the dielectric layer at the periphery of the cavity, and the dummy cavity is communicated with the cavity through the air pressure balance hole.
Optionally, the air pressure balance hole is positioned between the dielectric layer and the substrate; the method for forming the air pressure balance hole comprises the following steps: forming a cavity penetrating through the dielectric layer and a groove communicated with the cavity in the dielectric layer; providing a substrate; and covering the substrate on the dielectric layer to enable the groove to form a pneumatic balance hole connected with the cavity.
Optionally, forming the piezoelectric stack includes the steps of:
forming a first conductive film layer on the substrate, and patterning the first conductive film layer to form a first electrode;
forming a piezoelectric layer on the first electrode;
and forming a first conductive film layer on the piezoelectric layer, and patterning the first conductive film layer to form a second electrode.
Optionally, before forming the piezoelectric stack on the substrate, the method further includes: a first insulating layer is formed on the substrate.
Optionally, after forming the first insulating layer on the substrate, before forming the piezoelectric stack, the method further includes: forming a first frequency modulation layer on the first insulating layer; and forming a first electrode on the first frequency modulation layer.
Optionally, after forming the piezoelectric stack on the substrate, before forming the dielectric layer over the piezoelectric stack, the method further comprises: a second insulating layer is formed on the second electrode.
Optionally, before forming the second insulating layer on the second electrode, the method further includes: forming a second frequency modulation layer on the second electrode; the second insulating layer is positioned on the second frequency modulation layer.
Optionally, after forming the dummy cavity, the method further includes: and removing the substrate and the first insulating layer to expose the first frequency modulation layer.
Optionally, removing the substrate and the first insulating layer to expose the first frequency modulation layer, and further comprising: forming first component connecting holes penetrating through the first frequency modulation layer and exposing a part of the first electrode in peripheral areas of the cavity, the air pressure balance hole and the dummy cavity; forming second component connecting holes penetrating through the substrate, the dielectric layer, the second insulating layer and the second frequency modulation layer in peripheral areas of the cavity, the air pressure balance hole and the dummy cavity, wherein the second component connecting holes expose parts of the second electrode; metal pads are formed at bottoms of the first and second member connection holes.
The invention has the beneficial effects that: a cavity is provided in the dielectric layer between the substrate and the piezoelectric stack to form a total reflection interface at the interface of the piezoelectric material of the piezoelectric stack and the cavity to confine the acoustic wave within the piezoelectric material of the piezoelectric stack. One side of the cavity is provided with a dummy cavity penetrating through the substrate, the cavity is communicated with the dummy cavity through the air pressure balance hole, the balance between the internal pressure and the external pressure of the cavity between the substrate and the piezoelectric lamination is realized, the substrate is prevented from being deformed to be concave towards the cavity due to unbalanced internal and external pressure, and the stability of the bulk acoustic wave resonator structure is improved.
After forming a piezoelectric lamination layer and a dielectric layer by layer on a substrate and etching a cavity and a groove in the dielectric layer, bonding the substrate on the cavity and the groove, forming an air pressure balance hole in the groove, communicating the air pressure balance hole with a dummy cavity penetrating through a dummy cavity of the substrate, realizing balance between the internal pressure and the external pressure of the cavity between the substrate and the piezoelectric lamination layer, and then turning over the bulk acoustic wave resonator to perform subsequent steps, thereby saving the process steps. The release holes for removing the dielectric layers are not required to be formed in the lower electrode, the piezoelectric layer and the upper electrode, so that the piezoelectric lamination has good continuity, the resonance performance of the bulk acoustic wave resonator is improved, and meanwhile, the process cost is saved.
The device of the present invention has other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.
Drawings
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the invention.
Fig. 1 is a flow chart of a method of manufacturing a bulk acoustic wave resonator according to an embodiment of the present invention.
Fig. 2 (a) to 2 (H) are schematic cross-sectional structures at different stages in the manufacturing process of the bulk acoustic wave resonator according to an embodiment of the present invention.
Reference numerals illustrate:
100. a substrate; 110. a piezoelectric stack; 111. a first electrode; 112. a piezoelectric layer; 113. a second electrode; 114. a second member connection hole; 120. a first frequency modulation layer; 121. a second frequency modulation layer; 150. a first insulating layer; 151. a second insulating layer; 152. a silicon oxide layer; 153. a silicon nitride layer; 160. a dielectric layer; 170. a cavity; 171. a dummy cavity; 172. an air pressure balance hole; 173. a groove; 180. a substrate; 190. and a metal pad.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are illustrated in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Example 1
The present invention provides a bulk acoustic wave resonator, as shown in fig. 2 (H), comprising:
a piezoelectric stack 110; a dielectric layer 160 on the piezoelectric stack 110, wherein a cavity 170 penetrating the dielectric layer 160 is provided in the dielectric layer 160; a substrate 180 on the dielectric layer 160, the substrate 180 covering the dielectric layer 160; a dummy cavity 171 in the substrate 180, the dummy cavity 171 penetrating the substrate 180, and the dummy cavity 171 extending into the dielectric layer 160 at the periphery of the cavity 170; and a pressure balance hole 172 in the dielectric layer 160, the pressure balance hole 172 communicating the dummy cavity 171 and the cavity 170.
Alternatively, referring to fig. 2 (H), the piezoelectric stack 110 includes a first electrode 111, a piezoelectric layer 112 on the first electrode 111, and a second electrode 113 on the piezoelectric layer 112.
When power is applied to the first electrode 111 and the second electrode 113, the piezoelectric layer 112 converts the power into a piezoelectric effect having physical vibration, and the piezoelectric stack 110 outputs a radio frequency signal having a resonance frequency corresponding to the vibration of the piezoelectric phenomenon of the piezoelectric layer 112.
The piezoelectric layer in the piezoelectric stack is made of a piezoelectric material, the cavity 170 is located above the second electrode 113 between the piezoelectric stack 110 and the substrate 180, penetrates through the dielectric layer 160, and according to the transmission linearity theory, when the load is zero or infinite, the incident wave will generate total reflection, and because the acoustic impedance of air in the cavity 170 is approximately equal to zero, a good sound wave limiting boundary is formed, so that a sound wave total reflection interface is formed in the cavity 170, the sound wave is completely limited in the piezoelectric material by the cavity 170, and leakage of sound energy is reduced.
Alternatively, referring to fig. 2 (H), the material of the piezoelectric layer 112 includes one of aluminum nitride, zinc oxide, and scandium aluminum nitride. As shown in fig. 2 (H), the piezoelectric stack 110 has an effective area and an ineffective area, and when power is applied to the first electrode 111 and the second electrode 113, the effective area of the piezoelectric stack 110 is a region where the first electrode 111, the piezoelectric layer 112, and the second electrode 113 are stacked on each other in the vertical direction on the cavity 170 by vibration generated in the piezoelectric layer 112 by a piezoelectric phenomenon, and total reflection of sound waves is achieved by impedance mismatch of the cavity 170 and the metal electrode. The ineffective region of the piezoelectric stack 110 is a region where resonance cannot be generated by the piezoelectric phenomenon even if power is applied to the first electrode 111 and the second electrode 113, which corresponds to a region outside the effective region of the piezoelectric stack 110.
As an example, referring to fig. 2 (H), the first electrode 111 is used as an input electrode for receiving a radio frequency signal or an output electrode for outputting a radio frequency signal. For example, when the first electrode 111 is an input electrode, the second electrode 113 is an output electrode; when the first electrode 111 is an output electrode, the second electrode 113 is an input electrode.
Alternatively, the material of the first electrode 111 and/or the second electrode 113 includes one of molybdenum, tantalum, an alloy of molybdenum, or an alloy of tantalum, as shown with reference to fig. 2 (B). In this embodiment, the first electrode 111 and the second electrode 113 may be formed of molybdenum.
As an example, referring to fig. 2 (H), the dielectric layer 160 is disposed between the substrate 180 and the piezoelectric stack 110, the cavity 170 and the air pressure balance hole 172 are located in the dielectric layer 160, and the dummy cavity 171 is partially located in the dielectric layer 160.
As an example, referring to fig. 2 (H), the dielectric layer 160 includes silicon oxide or silicon nitride material, silicon oxide and silicon nitride. The dielectric layer 160 enables the cavity 170, the dummy cavity 171, and the air pressure balance hole 172 to withstand a certain compressive stress.
As an example, the substrate 180 may be made of a P-doped silicon wafer having a resistivity of 8-12 ohm cm, and the substrate 180 is used to prevent acid or glue from entering the cavity 170 during subsequent etching and cleaning processes, thereby damaging the physical structure of the piezoelectric stack 110 within the cavity 170.
As shown in fig. 2 (H), the dummy cavity 171 penetrates through the substrate 180 and is located in the dielectric layer 160 beside the cavity 170, the cavity 170 and the dummy cavity 171 are separated from each other, the dummy cavity 171 is communicated with the cavity 170 through the air pressure balance hole 172, so that the internal pressure of the cavity 170 is communicated with the external air pressure, the pressure balance on the inner and outer sides of the substrate 180 on the cavity 170 is realized, the substrate 180 is prevented from being sunken and the cavity 170 is prevented from being broken, the substrate 180 is prevented from being in direct contact with the piezoelectric material, and the stability of the resonator structure is affected.
As one example, the dielectric layer 160 has a thickness of 10um to 60um. Alternatively, referring to fig. 2 (H), the air pressure balance hole 172 is located between the dielectric layer 160 and the substrate 180.
Alternatively, the air pressure balance hole 172 is located between the dielectric layer 160 and the piezoelectric stack 110.
Alternatively, the air pressure balance holes 172 may also be located within the dielectric layer 160.
As one example, the air pressure balance hole 172 may be located at a middle upper portion, a middle lower portion, or a middle lower portion of the dielectric layer 160 in its depth direction.
Alternatively, the air pressure balance hole 172 has a vertical width ofThe lateral length of the air pressure balance hole 172 is +.>The lateral length of the air pressure balance hole 172 is the length along the plane parallel to the plane of the piezoelectric stack 110; the vertical width of the air pressure balance hole 172 is the width along the plane of the vertical dielectric layer 160.
The air pressure balance hole 172 may be vertically wide between the dielectric layer 160 and the substrate 180, between the dielectric layer 160 and the piezoelectric stack 110, or within the dielectric layer 160The transverse length can be +.>In the present embodiment, the shape of the air pressure balancing hole is rectangular, but in other embodiments of the present invention, the shape of the air pressure balancing hole may be circular, elliptical, or polygonal other than rectangular, such as pentagonal, hexagonal, etc.
As one example, the depth of the dummy cavity 171 in the dielectric layer is less than or equal to the height of the dielectric layer 160.
As an example, referring to fig. 2 (H), the volume of the cavity 170 is greater than the volume of the dummy cavity 171. The space inside the cavity 170 is ensured to have enough space to form an interface where sound waves are totally reflected, and the dummy cavity 171 and the air pressure balance hole 172 are used to make the pressure inside the cavity 170 coincide with the external atmospheric pressure, so the volumes of the dummy cavity 171 and the air pressure balance hole 172 do not need to be too large.
As an example, the depth of the air pressure balance holes is shallow enough to prevent liquid from penetrating into the cavity during the subsequent photoresist stripping process or placement in the acid tank; meanwhile, the length of the air pressure balance hole along the direction parallel to the piezoelectric layer (namely the interval between the dummy cavity and the horizontal direction of the cavity) is not easy to be too large, so that the influence on the bonding contact surface of the dielectric layer and the substrate is reduced, and the bonding firmness is not influenced.
Alternatively, the width of the cavity 170 is 100um to 400um, and the width of the dummy cavity 171 is 20um to 50um.
Alternatively, referring to fig. 2 (H), the bulk acoustic wave resonator further includes a second insulating layer 151 disposed between the second electrode 113 and the dielectric layer 160 at the periphery of the cavity 170, and the second insulating layer 151 includes any one or a combination of silicon oxide and silicon nitride.
As an example, referring to fig. 2 (H), the dummy cavity 171 and the air pressure balance hole 172 are disposed in the dielectric layer 160 above the second insulating layer 151, and the second insulating layer 151 is used to avoid damage to the working area by processes such as photoresist removal, dry etching, and the like, and the working area includes a first electrode, a piezoelectric layer, and a second electrode, whose main materials are molybdenum and aluminum nitride.
The piezoelectric stack 110 region opposite to the lower part of the dummy cavity 171 and the air pressure balance hole 172 is prevented from resonating due to the piezoelectric phenomenon, the second insulating layer 151 is not arranged between the cavity 170 and the second electrode 113, that is, the second insulating layer 151 overlapping the formation region of the cavity 170 is removed, the piezoelectric stack 110 region overlapping the second insulating layer 151 is finally reserved as an ineffective region, and the piezoelectric stack 110 region overlapping the cavity 170 is an effective region.
As an example, referring to fig. 2 (H), the second insulating layer 151 is composed of a silicon oxide layer 152 and a silicon nitride layer 153.
Alternatively, the piezoelectric stack 110 further includes a tuning layer, where the tuning layer includes a first tuning layer 120 and a second tuning layer 121, the first tuning layer 120 is disposed on a surface of the first electrode 111 away from the piezoelectric layer 112, and the second tuning layer 121 is disposed between the second insulating 151 layer and the second electrode 113.
As shown in fig. 2 (H), the resonant frequency of vibration of the piezoelectric stack 110 depends on the piezoelectric induction phenomenon of the piezoelectric layer 112 on the one hand, and on the other hand, the thickness of the piezoelectric layer 112 and the thicknesses of the first and second frequency modulation layers 120 and 121. The first and second fm layers 120 and 121 are used to adjust the frequency of the series or parallel resonators in the filter, while the first and second fm layers 120 and 121 also function to protect the first and second electrodes 111 and 113. As one example, the greater the thicknesses of the first and second tuning layers 120 and 121, the lower the resonant frequency of the bulk acoustic wave resonator; the smaller the thicknesses of the first and second tuning layers 120 and 121, the lower the resonance frequency of the bulk acoustic wave resonator is.
Alternatively, referring to fig. 2 (H), the material of the first and/or second frequency modulation layers 120 and 121 includes at least one of silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride.
Alternatively, as shown with reference to fig. 2 (H), the method further includes: first and second member connection holes (not shown) and 114 located at peripheral regions of the cavity 170, the air pressure balance hole 172 and the dummy cavity 171, the first member connection holes penetrating the first frequency modulation layer 120 and exposing portions of the first electrode 111; the second member connection hole 114 penetrates the substrate 180, the dielectric layer 160, the second insulating layer 151, and the second frequency modulation layer 150 and exposes a portion of the second electrode 113, and the first member connection hole and the second member connection hole 114 enable the first electrode 111 and the second electrode 112 to be electrically connected to the outside, respectively, so that the resonator is electrically connected and then operates.
Alternatively, the bottoms of the first and second member connection holes 114 are provided with metal pads 190, respectively.
As an example, referring to fig. 2 (H), metal pads 190 are provided on surfaces of the first and second electrodes 111 and 113 exposed in the first and second member connection holes 114, respectively, and the metal pads 190 may be formed of a material of gold (Au), gold-tin (Au-Sn) alloy, copper (Cu), copper-tin (Cu-Sn), or the like.
The bulk acoustic wave resonator is characterized in that a cavity is arranged in a dielectric layer between a substrate and a piezoelectric lamination, and a total reflection interface is formed at the junction of a piezoelectric material of the piezoelectric lamination and the cavity, so that acoustic waves are limited in the piezoelectric material of the piezoelectric lamination. One side of the cavity is provided with a dummy cavity penetrating through the substrate, the cavity is communicated with the dummy cavity through the air pressure balance hole, the balance between the inside and outside pressure of the cavity between the substrate and the piezoelectric lamination is realized, the substrate is prevented from being deformed towards the inside of the cavity due to unbalanced internal and external pressure, the cavity is prevented from being broken, and the stability of the structure of the bulk acoustic wave resonator is improved.
Example 2
The embodiment of the invention also provides a method for manufacturing the bulk acoustic wave resonator, and referring to fig. 1, fig. 1 is a flowchart of a method for manufacturing the bulk acoustic wave resonator according to an embodiment of the invention.
The method comprises the following steps:
step S1, providing a substrate, and forming a piezoelectric lamination layer on the substrate;
s2, forming a dielectric layer on the piezoelectric lamination;
s3, forming air pressure balance holes in the medium layer, wherein the air pressure balance holes are communicated with the cavity;
step S4, providing a substrate;
s5, covering the substrate on the dielectric layer;
and S6, forming a dummy cavity penetrating through the substrate in the substrate, wherein the dummy cavity extends into the dielectric layer at the periphery of the cavity, and the dummy cavity is communicated with the cavity through the air pressure balance hole.
A method of manufacturing a bulk acoustic wave resonator will be described with reference to fig. 1, 2 (a) to 2 (H).
Step S1, providing a substrate 100, and forming a piezoelectric stack 110 on the substrate 100.
As an example, referring to fig. 2 (a), the substrate 100 provided in the present embodiment is made of a P-type doped silicon wafer or an N-type doped silicon wafer.
The resistivity of the substrate 100 may be selected to be 8-10000 ohm.cm, and the resistivity of the substrate 100 of this embodiment is 5000-10000 ohm.cm.
The material of the substrate is at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III/V compound semiconductors, and also include multilayer structures composed of these semiconductors, or are silicon-on-dielectric (SOI), silicon-on-dielectric (SSOI), silicon-germanium-on-dielectric (S-SiGeOI), silicon-germanium-on-dielectric (SiGeOI), germanium-on-dielectric (GeOI), or double-sided polished silicon wafers (Double Side Polished Wafers, DSP), ceramic substrates such as alumina, quartz, or glass substrates, and the like.
The first insulating layer 150 is formed on the <100> crystal direction of the substrate 100, so that the first insulating layer 150 can vertically grow upwards on the <100> crystal direction, and a good insulating effect of the first insulating layer 150 is ensured.
The substrate 100 mainly plays a role of supporting and growing a carrier, and can be formed on the substrate 100 through processes such as chemical vapor deposition or physical vapor deposition, the material property of the substrate 100 and the shape of the surface of the substrate have great influence on the characteristics of deposition substances, because the thickness of the deposition substances is generally between nanometer and micrometer, and the surface of the substrate 100 is required to have ultra-high flatness; the combination of the deposition material and the substrate 100 is also a very important aspect, and if the two are lattice mismatched, a longer transition region is formed during the early stages of deposition material formation.
Referring to fig. 2 (a), before forming the piezoelectric stack 110 on the substrate 100, it further includes: forming a first insulating layer 150 on the substrate 100; a piezoelectric stack 110 is formed on the first insulating layer 150.
As an example, referring to fig. 2 (a), a first insulating layer 150 is formed between the substrate 100 and the piezoelectric stack 110 to electrically isolate the piezoelectric stack 110 from the substrate 100. The first insulating layer 150 may be deposited on the substrate 100 by chemical vapor deposition or physical vapor deposition <100>One of silicon dioxide (SiO 2) and silicon nitride (SiN) is deposited on the crystal direction to form a first insulating layer 150 with a deposition thickness of
Referring to fig. 2 (a), after forming the first insulating layer 150 on the substrate 100, before forming the piezoelectric stack 110, it further includes: forming a first frequency modulation layer 120 on the first insulating layer 150; a piezoelectric stack 110 is formed on the first tuning layer 120.
As an example, referring to fig. 2 (a), the first frequency modulation layer 120 is formed by depositing silicon oxide, silicon nitride, aluminum oxide, or aluminum nitride on the first insulating layer 150.
The first and second fm layers 120 and 121 are used to adjust the frequencies of the series and parallel resonators in the filter, while the first and second fm layers 120 and 121 also function to protect the first and second electrodes 111 and 113. The first fm layer 120 acts as a seed layer for controlling the crystal orientation of the deposited electrode material.
Referring to fig. 2 (a) and 2 (B), forming the piezoelectric stack 110 includes the steps of: forming a first conductive thin film layer on the first insulating layer 150, patterning the first conductive thin film layer to form a first electrode 111; forming a piezoelectric layer 112 on the first electrode 111; a second conductive thin film layer is formed on the piezoelectric layer 112, and the second conductive thin film layer is patterned to form a second electrode 113.
As an example, referring to fig. 2 (B), first, a first conductive film may be formed by a sputtering process using molybdenum as a target by depositing a first conductive film on the first insulating layer 150, and patterning the first conductive film to form the first electrode 111; then, after the first electrode 111 is formed, a piezoelectric layer 112 is formed on the first electrode 111, the piezoelectric layer 112 being formed by depositing aluminum nitride, doped aluminum nitride, zinc oxide, or lead zirconate titanate; finally, a second conductive film is formed on the piezoelectric layer 112 by a sputtering apparatus, and then the second conductive film is patterned to form a second electrode 113, and similarly to the first electrode 111, the second electrode 113 may also be formed of molybdenum. The method of patterning the first conductive film and the second conductive film to form the first electrode 111 and the second electrode 113 uses an etching process, which may be a wet etching process or a dry etching process, wherein the dry etching process includes, but is not limited to, reactive Ion Etching (RIE), ion beam etching, plasma etching, or laser cutting.
In step S2, as shown in fig. 2 (B), a dielectric layer 160 is formed on the piezoelectric stack 110.
Referring to fig. 2 (a), after forming the piezoelectric stack 110 on the substrate 100, it further includes: a second frequency modulation layer 121 and a second insulating layer 151 are formed on the second electrode 113, the second insulating layer 151 being located on the second frequency modulation layer 121.
As an example, referring to fig. 2 (a), a second frequency modulation layer 121 is formed on the second electrode 113 by depositing silicon oxide, silicon nitride, aluminum oxide, or aluminum nitride.
The first and second tuning layers 120 and 121 can influence the resonant frequency of the piezoelectric stack 110, the greater the thicknesses of the first and second tuning layers 120 and 121, the lower the resonant frequency of the bulk acoustic wave resonator; the smaller the thicknesses of the first and second tuning layers 120 and 121, the lower the resonance frequency of the bulk acoustic wave resonator is. The thickness of the entire piezoelectric stack 110 can be adjusted by controlling the deposition thicknesses of the first tuning layer 120 and the second tuning layer 121 during the formation of the first tuning layer 120 and the second tuning layer 121, thereby controlling the resonant frequency of the piezoelectric stack 110. Those skilled in the art can preset the filtering frequency according to the specific resonator, and the thickness of the piezoelectric stack 110, the thickness of the first tuning layer 120 and the thickness of the second tuning layer 121 are comprehensively controlled in the manufacturing process to achieve the desired operating frequency of the resonator, which is not described herein.
As one example, the second insulating layer 151 may be manufactured by depositing at least one of silicon oxide and silicon nitride, aluminum oxide and aluminum nitride on the second frequency modulation layer 121 by one of a chemical vapor deposition process, an RF magnetron sputtering process, and evaporation. In this embodiment, as shown in fig. 2 (a), the second insulating layer 151 is composed of a silicon oxide layer 152 and a silicon nitride layer 153.
Referring to fig. 2 (B), a dielectric layer 160 is formed on the second frequency modulation layer 121 by depositing a silicon oxide material by a physical vapor deposition method. In this embodiment, the deposition thickness of the dielectric layer 160 is 10um.
In step S3, referring to fig. 2 (C), a pressure balance hole 172 is formed in the dielectric layer 160, and the pressure balance hole 172 communicates with the cavity 170.
Cavity 170 may be formed by etching dielectric layer 160 through an etching process. The technique of the present invention is not limited thereto. In the present embodiment, the bottom surface of the cavity 170 is rectangular, but in other embodiments of the present invention, the bottom surface of the cavity 170 may be circular, elliptical, or polygonal other than rectangular, such as pentagonal, hexagonal, etc.
As an example, referring to fig. 2 (C), first, a photoresist film is coated on the surface of the dielectric layer 160, and irradiated with ultraviolet light through a mask plate to cause a chemical reaction of the photoresist in the exposed area; then, the photoresist in the exposure area is removed by dissolution through a developing technique, so that the pattern on the mask plate is copied to the photoresist film to form a patterned mask layer, the position of the cavity 170 is defined, and the cavity 170 penetrating the dielectric layer 160 and the second frequency modulation layer 121 and exposing the second electrode 112 is etched by dry etching or wet etching with the patterned mask layer as a mask.
The effective area of the piezoelectric stack 110 is the area where the first electrode 111, the piezoelectric layer 112, and the second electrode 113 are stacked on each other in the vertical direction on the cavity 170, and the total reflection of the acoustic wave is achieved by using the impedance mismatch between the cavity 170 and the metal electrode. The ineffective area of the piezoelectric stack 110 is an area where resonance cannot be generated by the piezoelectric phenomenon even if power is applied to the first electrode 111 and the second electrode 113, which corresponds to an area of the periphery of the effective area of the piezoelectric stack 110.
As an example, referring to fig. 2 (C), a planarization process is performed on a surface of the dielectric layer 160, which is far from the substrate, by Chemical Mechanical Polishing (CMP), to ensure the flatness of the surface of the dielectric layer, and to ensure the bonding firmness of the dielectric layer 160 and the substrate 180.
Alternatively, referring to FIG. 2 (D), the air pressure balance hole 172 may have a depth along the vertical piezoelectric stack 110 ofThe air pressure balance hole 172 is +_ along the length of the parallel piezoelectric stack 110>As an example, referring to fig. 2 (D), the air pressure balance hole 172 is located between the dielectric layer 160 and the substrate 180; the method for forming the air pressure balance hole 172 includes: communication between the cavity 170 and the dielectric layer 160 is formedA groove 173 in which the cavity 170 communicates; providing a substrate 180; the substrate 180 is covered on the dielectric layer 160, so that the groove 173 forms a pressure balance hole 172 connected with the cavity 170. The depth of the air pressure balance holes is shallow enough to prevent liquid from penetrating into the cavity 170 during the subsequent photoresist stripping process or placement in the acid tank; meanwhile, the air pressure balance hole is not easy to be excessively large along the length parallel to the piezoelectric layer, and the bonding contact surface of the dielectric layer 160 and the substrate 180 is increased so as not to influence the bonding firmness.
In another embodiment, the air pressure balance hole 172 is located between the dielectric layer 160 and the piezoelectric stack 110; the method for forming the air pressure balance hole 170 includes: first, a sacrificial layer is formed on a portion of the piezoelectric stack 110. Then, a dielectric layer 160 is formed on the sacrificial layer and the piezoelectric stack 110; finally, a cavity 170 is formed in the dielectric layer 160 through the dielectric layer 160; after the cavity 170 is formed, the sacrificial layer is removed, forming an air pressure balance 172 connected to the cavity 170. The sacrificial material may be carbon or polyimide, and may be formed by physical vapor deposition or chemical vapor deposition, and different removal methods are selected according to the sacrificial material, such as oxygen burning when the sacrificial material is polyimide. The sacrificial layer may be removed after the dummy cavity 171 is formed, so that the sacrificial layer communicates with the air pressure balance hole 172.
In yet another embodiment, the air pressure balance hole 172 is located within the dielectric layer 160. In other embodiments of the present invention, the method for forming the air pressure balance hole 172 includes first etching the dielectric layer 160 beside the cavity 170 to form a deeper trench 173 after etching the cavity 170, wherein the trench 173 is communicated with the cavity 170, the depth of the trench 173 does not exceed the bottom surface of the cavity 170, then filling a layer of sacrificial material in the bottom of the trench 173, then filling silicon oxide or silicon nitride with the same material as the dielectric layer 160 in the upper portion of the sacrificial material, and the top surface of the filled trench 173 is level with the top surface of the dielectric layer 160 (after filling, planarization treatment may be performed), finally removing the dielectric layer 160 in the cavity 170, and removing the sacrificial material from the side wall of the cavity 170 by using an etching material corresponding to the sacrificial material to form the air pressure balance hole 172. The sacrificial material may be carbon or polyimide, and may be formed by physical vapor deposition or chemical vapor deposition, and different removal methods are selected according to the sacrificial material, such as oxygen burning when the sacrificial material is polyimide.
In step S4, as shown in fig. 2 (E), a substrate 180 is provided.
As an example, referring to fig. 2 (E), the substrate 180 is made of a P-type doped carrier wafer or an N-type doped carrier silicon wafer, and the resistivity thereof may be selected to be 8 to 10000ohm.
In another embodiment, the material of the substrate 180 is at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III/V compound semiconductors, and also include multilayer structures composed of these semiconductors, or are silicon-on-dielectric (SOI), silicon-on-dielectric (SSOI), silicon-germanium-on-dielectric (S-SiGeOI), silicon-germanium-on-dielectric (SiGeOI), germanium-on-dielectric (GeOI), or double-sided polished silicon wafers (Double Side Polished Wafers, DSP), ceramic substrates such as alumina, quartz, or glass substrates, and the like.
As an example, referring to fig. 2 (E) and 2 (F), a pair of alignment holes for subsequent alignment with a bonding process of the dielectric layer are formed by dry etching to an edge of one side (i.e., a surface to be connected to the dielectric layer 160) of the substrate 180.
In step S5, as shown in fig. 2 (F), the substrate 180 is covered on the dielectric layer 160.
In this embodiment, the substrate 180 is covered on the dielectric layer 160, so that the trench 173 forms the air pressure balance hole 172 communicating with the cavity 170.
The substrate 180 is bonded to the cavity 170 and the groove 173 in correspondence with the position of the piezoelectric stack 110 by a bonding process, and the other surface of the substrate 180 is laser marked to show the position corresponding to the pressure balance hole 172.
In step S6, referring to fig. 2 (F), a dummy cavity 171 penetrating through the substrate 180 is etched in the substrate 180, the dummy cavity 171 further extends into the dielectric layer 160 at the periphery of the cavity 170, the dummy cavity extends into the dielectric layer at the periphery of the cavity, and the dummy cavity is communicated with the cavity through the air pressure balance hole.
As an example, referring to fig. 2 (F), a dummy cavity 171 is formed by etching a hole into a dielectric layer at a surface of a substrate 180 through a through silicon via (CSV) process, and an etching depth of the dummy cavity 171 is equal to or less than a height of the dielectric layer 160. As one example, the etch depth of dummy cavity 171 is 0.2um to 10um and the etch depth of cavity 170 is 1um to 10.33um.
Alternatively, referring to fig. 2 (G), the width of the cavity 170 is 100 to 400um, and the width of the dummy cavity 171 is 20 to 50um.
After the dummy cavity 171 is etched, the bulk acoustic wave resonator is flipped over to perform the subsequent steps. Referring to fig. 2 (H), after forming the dummy cavity 171, it further includes: the substrate 100 and the first insulating layer 150 are removed, exposing the first fm layer 120.
As an example, the substrate 100 is thinned, and wet etching is performed on the thinned substrate 100 to remove the substrate 100 and the first insulating layer 150, exposing the first frequency modulation layer 120.
Referring to fig. 2 (H), after removing the substrate 100 and the first insulating layer and exposing the first fm layer 120, the method further includes: forming first member connection holes (not shown) penetrating the first fm 120 layer and exposing portions of the first electrode 111 at peripheral areas of the cavity 170, the air pressure balance hole 172, and the dummy cavity 171; forming a second member connection hole 114 penetrating the substrate 180, the dielectric layer 160, the second insulating layer 151, and the second frequency modulation layer 121 in peripheral regions of the cavity 170, the air pressure balance hole 172, and the dummy cavity 171, the second member connection hole 114 exposing a portion of the second electrode 113; metal pads 190 are formed at bottoms of the first and second member connection holes 114.
As an example, referring to fig. 2 (H), first and second member connection holes 114 are formed as deep as the first and second electrodes 111 and 113 by wet etching, and metal pads 190 are formed in the member connection holes 114, exposing the first and second electrodes 111 and 113 through the first and second member connection holes 114, facilitating electrical communication of the piezoelectric stack 110.
As one example, the metal pad 190 is formed of a material such as gold (Au), gold-tin (Au-Sn) alloy, copper (Cu), and/or copper-tin (Cu-Sn), or the like.
According to the manufacturing method of the bulk acoustic wave resonator, the piezoelectric lamination and the dielectric layer are formed layer by layer on the substrate, after the cavity and the groove are etched in the dielectric layer, the substrate is bonded on the cavity and the groove, so that the groove forms the air pressure balance hole and is communicated with the pseudo cavity penetrating through the pseudo cavity of the substrate, the pressure balance between the inside and the outside of the cavity between the substrate and the piezoelectric lamination is realized, then the bulk acoustic wave resonator is turned over to perform subsequent steps, and the process steps are saved. The release holes for removing the dielectric layers are not required to be formed in the lower electrode, the piezoelectric layer and the upper electrode, so that the piezoelectric lamination has good continuity, the resonance performance of the bulk acoustic wave resonator is improved, and meanwhile, the process cost is saved.
It should be noted that, in the present specification, each embodiment is described in a related manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment is mainly described in a different point from other embodiments. In particular, for structural embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and reference is made to the description of method embodiments for relevant points.
The above description is only illustrative of the preferred embodiments of the present invention and is not intended to limit the scope of the present invention, and any alterations and modifications made by those skilled in the art based on the above disclosure shall fall within the scope of the appended claims.

Claims (20)

1. A bulk acoustic wave resonator, comprising:
a piezoelectric stack;
the dielectric layer is positioned on the piezoelectric lamination, and a cavity penetrating through the dielectric layer is arranged in the dielectric layer;
the substrate is positioned on the dielectric layer and covers the dielectric layer;
the dummy cavity is positioned in the substrate, penetrates through the substrate and extends into the dielectric layer at the periphery of the cavity;
and the air pressure balance hole is positioned in the medium layer and is communicated with the dummy cavity and the cavity.
2. The bulk acoustic wave resonator of claim 1, wherein the piezoelectric stack comprises a first electrode, a piezoelectric layer on the first electrode, and a second electrode on the piezoelectric layer.
3. The bulk acoustic resonator of claim 1, wherein the air pressure balance layer is located between the dielectric layer and the substrate.
4. The bulk acoustic wave resonator of claim 1, wherein the air pressure balance layer is located between the dielectric layer and the piezoelectric stack.
5. The bulk acoustic resonator of claim 1, wherein the cavity has a width of 100um to 400um and the dummy cavity has a width of 20um to 50um.
6. The bulk acoustic wave resonator according to claim 2, further comprising a second insulating layer disposed between the second electrode and the dielectric layer except for a region where the cavity is located, the second insulating layer comprising any one or a combination of two of silicon oxide and silicon nitride.
7. The bulk acoustic resonator of claim 6, wherein the piezoelectric stack further comprises a tuning layer comprising a first tuning layer and a second tuning layer, the first tuning layer disposed on a surface of the first electrode that is distal from the piezoelectric layer, the second tuning layer disposed between the second insulating layer and the second electrode;
the material of the first frequency modulation layer and/or the second frequency modulation layer comprises at least one of silicon oxide, silicon nitride, aluminum oxide and aluminum nitride.
8. The bulk acoustic wave resonator of claim 7, further comprising: a first member connection hole and a second member connection hole located at peripheral regions of the cavity, the air pressure balance hole and the dummy cavity, the first member connection hole penetrating the first frequency modulation layer and exposing a part of the first electrode; the second component connection hole penetrates through the substrate, the dielectric layer, the second insulating layer and the second frequency modulation layer and exposes a part of the second electrode.
9. The bulk acoustic wave resonator according to claim 8, characterized in that the first member connection hole and the second member connection hole bottom are respectively provided with a metal pad.
10. The bulk acoustic wave resonator according to claim 1, characterized in that,
the vertical width of the air pressure balance hole is 200-5000A, and the transverse length of the air pressure balance hole is 1-5K A.
11. A method of manufacturing a bulk acoustic wave resonator, comprising:
providing a substrate, and forming a piezoelectric stack on the substrate;
forming a dielectric layer on the piezoelectric stack;
forming a cavity penetrating through the dielectric layer in the dielectric layer;
forming an air pressure balance hole in the medium layer, wherein the air pressure balance hole is communicated with the cavity;
providing a substrate;
covering the substrate on the dielectric layer;
and forming a dummy cavity penetrating through the substrate in the substrate, wherein the dummy cavity extends into the dielectric layer at the periphery of the cavity, and the dummy cavity is communicated with the cavity through the air pressure balance hole.
12. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that,
the air pressure balance hole is positioned between the dielectric layer and the substrate; the method for forming the air pressure balance hole comprises the following steps: forming a cavity penetrating through the dielectric layer and a groove communicated with the cavity in the dielectric layer; providing a substrate; and covering the substrate on the dielectric layer to enable the groove to form a pneumatic balance hole connected with the cavity.
13. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that,
the air pressure balance hole is positioned between the dielectric layer and the piezoelectric lamination; the method for forming the air pressure balance hole comprises the following steps: forming a sacrificial layer over a portion of the piezoelectric stack; a dielectric layer on the sacrificial layer and the piezoelectric stack; forming a cavity penetrating through the dielectric layer in the dielectric layer; and after the cavity is formed, removing the sacrificial layer to form an air pressure balance hole connected with the cavity.
14. The method for manufacturing a bulk acoustic wave resonator according to any one of claims 11 to 13, characterized in that,
forming the piezoelectric stack comprises the steps of:
forming a first conductive film layer on the substrate, and patterning the first conductive film layer to form a first electrode;
forming a piezoelectric layer on the first electrode;
and forming a second conductive film layer on the piezoelectric layer, and patterning the second conductive film layer to form a second electrode.
15. The method of manufacturing a bulk acoustic wave resonator according to claim 14, further comprising, prior to forming a piezoelectric stack on the substrate: a first insulating layer is formed on the substrate.
16. The method of manufacturing a bulk acoustic wave resonator according to claim 15, characterized in that after forming the first insulating layer on the substrate, before forming the piezoelectric stack, further comprising: forming a first frequency modulation layer on the first insulating layer; and forming a first electrode on the first frequency modulation layer.
17. The method of manufacturing a bulk acoustic wave resonator according to claim 16, characterized in that after forming a piezoelectric stack on the substrate, before forming a dielectric layer over the piezoelectric stack, further comprising: a second insulating layer is formed on the second electrode.
18. The method of manufacturing a bulk acoustic wave resonator according to claim 17, characterized in that before forming a second insulating layer on the second electrode, it further comprises: forming a second frequency modulation layer on the second electrode; the second insulating layer is positioned on the second frequency modulation layer.
19. The method of manufacturing a bulk acoustic wave resonator according to claim 18, further comprising, after forming the dummy cavity: and removing the substrate and the first insulating layer to expose the first frequency modulation layer.
20. The method of manufacturing a bulk acoustic wave resonator according to claim 19, characterized in that after removing the substrate and the first insulating layer and exposing the first tuning layer, further comprising: forming first component connecting holes penetrating through the first frequency modulation layer and exposing a part of the first electrode in peripheral areas of the cavity, the air pressure balance hole and the dummy cavity; forming second component connecting holes penetrating through the substrate, the dielectric layer, the second insulating layer and the second frequency modulation layer in peripheral areas of the cavity, the air pressure balance hole and the dummy cavity, wherein the second component connecting holes expose parts of the second electrode; metal pads are formed at bottoms of the first and second member connection holes.
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