CN117614413A - Bulk acoustic wave filter device and method of forming the same - Google Patents

Bulk acoustic wave filter device and method of forming the same Download PDF

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Publication number
CN117614413A
CN117614413A CN202311466981.4A CN202311466981A CN117614413A CN 117614413 A CN117614413 A CN 117614413A CN 202311466981 A CN202311466981 A CN 202311466981A CN 117614413 A CN117614413 A CN 117614413A
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China
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layer
electrode
load
forming
piezoelectric
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金建
黄烜
刘广纯
周琦
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Changzhou Chengxin Semiconductor Co Ltd
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Changzhou Chengxin Semiconductor Co Ltd
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/56—Monolithic crystal filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • 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
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/58—Multiple crystal filters

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

Abstract

A bulk acoustic wave filter device, a method of forming the same, and a bulk acoustic wave filter device, the resonator device including: a piezoelectric layer including a first region and a second region; a first electrode structure and a second electrode structure on a first side of the piezoelectric layer, the second electrode structure having a thickness greater than the thickness of the first electrode structure; a third electrode structure and a fourth electrode structure located on the second side of the piezoelectric layer; the first electrode structure comprises a first electrode layer, the second electrode structure comprises a second electrode layer, a barrier layer and a load layer, and the barrier layer is positioned between the second electrode layer and the load layer; the projection of the load layer on the piezoelectric layer is positioned in the projection of the second electrode layer on the piezoelectric layer, a first interval is arranged between a first load edge of the load layer and a first electrode edge of the corresponding second electrode layer, and a second interval is arranged between a second load edge of the load layer and a second electrode edge of the corresponding second electrode layer. The performance of the bulk acoustic wave filter device is improved.

Description

Bulk acoustic wave filter device and method of forming the same
Technical Field
The present disclosure relates to semiconductor technology, and more particularly, to a bulk acoustic wave filter device and a method for forming the same.
Background
A Radio Frequency (RF) front-end chip of a wireless communication device includes a power amplifier, an antenna switch, a Radio Frequency filter, a multiplexer, a low noise amplifier, and the like. The radio frequency filter includes a piezoelectric surface acoustic wave (Surface Acoustic Wave, SAW for short), a piezoelectric bulk acoustic wave (Bulk Acoustic Wave, BAW for short), a Micro-Electro-Mechanical System (MEMS for short), an integrated passive device (Integrated Passive Devices, IPD for short), and the like.
The BAW filter consists of BAW resonators. A thin film bulk acoustic resonator (Film Bulk Acoustic Wave Resonator, abbreviated as FBAR) is a BAW resonator that can localize acoustic energy within a device, where a cavity exists above the resonating region of the resonator, and below the resonating region, because the acoustic impedance of the vacuum or air differs significantly from that of the metal electrode, the acoustic wave can reflect off the upper surface of the upper metal electrode and the lower surface of the lower metal electrode, forming a standing wave.
The resonant frequency of a BAW resonator depends on the electrode, piezoelectric layer mass and thickness, and when an electrical signal is applied to the FBAR, the electrical signal will be converted into an acoustic signal by the inverse piezoelectric effect of the piezoelectric film.
However, the performance of existing BAW filters remains to be improved.
Disclosure of Invention
The invention provides a bulk acoustic wave filter device and a forming method thereof, which aims to improve the performance of a piezoelectric bulk acoustic wave filter.
In order to solve the above technical problems, the present invention provides a bulk acoustic wave filter device, including: a piezoelectric layer comprising a first region and a second region, the first resonant device being located in the first region and the second resonant device being located in the second region, the piezoelectric layer comprising opposing first and second sides in a direction perpendicular to the piezoelectric layer; a first electrode structure and a second electrode structure on a first side of the piezoelectric layer, the first electrode structure and the second electrode structure being located in a first region and a second region, respectively, the second electrode structure having a thickness greater than a thickness of the first electrode structure; a third electrode structure and a fourth electrode structure located on the second side of the piezoelectric layer, the third electrode structure and the fourth electrode structure being located in the first region and the second region, respectively; wherein the first electrode structure includes a first electrode layer, and the second electrode structure includes: the piezoelectric device comprises a piezoelectric layer, a first electrode layer, a second electrode layer, a barrier layer and a load layer, wherein the barrier layer is positioned between the first electrode layer and the load layer, the first electrode layer is close to the piezoelectric layer, the load layer comprises a first load edge and a second load edge which are opposite, the second electrode layer comprises a first electrode edge and a second electrode edge which are opposite, the first load edge corresponds to the first electrode edge, and the second load edge corresponds to the second electrode edge; the projection of the load layer on the piezoelectric layer is positioned in the projection of the second electrode layer on the piezoelectric layer, a first interval is reserved between a first load edge of the load layer and a corresponding first electrode edge of the second electrode layer, and a second interval is reserved between a second load edge of the load layer and a corresponding second electrode edge of the second electrode layer. Optionally, the first pitch ranges from greater than 4 microns; the second pitch ranges from greater than 4 microns.
Optionally, the projection range of the barrier layer on the piezoelectric layer is located in the projection of the second electrode layer on the piezoelectric layer; the projection range of the load layer on the piezoelectric layer is positioned in the projection of the barrier layer on the piezoelectric layer.
Optionally, the thickness range of the load layer is smaller than the thickness range of the second electrode layer.
Optionally, the barrier layer has a thickness in a range of less than 100 angstroms.
Optionally, the materials and structures of the second electrode layer and the first electrode layer are the same.
Optionally, an included angle between the side wall surface of the second electrode layer and the bottom surface of the second electrode layer is an acute angle; the included angle ranges from 30 degrees to 70 degrees.
Optionally, the material of the supporting layer is the same as the material of the second electrode layer.
Optionally, the material of the loading layer is different from the material of the second electrode layer.
Optionally, the material of the barrier layer is the same as the material of the piezoelectric layer.
Optionally, the material of the barrier layer is different from the material of the second electrode layer, and the material of the barrier layer is different from the material of the load layer.
Optionally, the material of the barrier layer includes: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
Optionally, the material of the piezoelectric layer includes: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
Optionally, the method further comprises: an intermediate structure on a first side of the piezoelectric layer, and first and second cavities embedded within the intermediate structure, at least a portion of the first electrode structure being located within the first cavity and at least a portion of the second electrode structure being located within the second cavity; and the intermediate structure is positioned between the bearing substrate and the piezoelectric layer, and is contacted with the bearing substrate.
Optionally, the first resonant device is a series resonant device, and the second resonant device is a parallel resonant device.
Correspondingly, the technical scheme of the invention also provides a method for forming the bulk acoustic wave filter device, which comprises the following steps: forming a piezoelectric layer comprising a first region and a second region, the piezoelectric layer comprising opposing first and second sides in a direction perpendicular to the piezoelectric layer; forming a first electrode structure and a second electrode structure on a first side of the piezoelectric layer, wherein the first electrode structure and the second electrode structure are respectively positioned in a first area and a second area, and the thickness of the second electrode structure is larger than that of the first electrode structure; forming a third electrode structure and a fourth electrode structure on the second side of the piezoelectric layer, wherein the third electrode structure and the fourth electrode structure are respectively positioned in the first area and the second area; wherein forming the first electrode structure includes forming a first electrode layer, and forming the second electrode structure includes: forming a second electrode layer, a barrier layer and a load layer, wherein the barrier layer is positioned between the second electrode layer and the load layer, the second electrode layer is close to the piezoelectric layer, the load layer comprises a first load edge and a second load edge which are opposite, the second electrode layer comprises a first electrode edge and a second electrode edge which are opposite, the first load edge corresponds to the first electrode edge, and the second load edge corresponds to the second electrode edge; the projection of the load layer on the piezoelectric layer is positioned in the projection of the second electrode layer on the piezoelectric layer, a first interval is reserved between a first load edge of the load layer and a corresponding first electrode edge of the second electrode layer, and a second interval is reserved between a second load edge of the load layer and a corresponding second electrode edge of the second electrode layer.
Optionally, the projection range of the barrier layer on the piezoelectric layer is within the projection range of the second electrode layer on the piezoelectric layer; the projection range of the load layer on the piezoelectric layer is within the projection range of the barrier layer on the piezoelectric layer.
Optionally, the second electrode layer and the first electrode layer are formed based on the same material layer.
Optionally, the forming method of the first electrode structure and the second electrode structure includes: forming an electrode material layer on a first side of the piezoelectric layer; forming a barrier material layer on the surface of the electrode material layer; forming a loading material layer on the barrier material layer; forming a first mask layer on the load material layer, wherein the first mask layer covers the surface of the load material layer on the second area; removing the load material layer and the blocking material layer outside the second area by taking the first mask layer as a mask, exposing the surface of the electrode material layer, and forming a blocking layer and a load layer on the electrode material layer of the second area; forming a second mask layer on the surface of the electrode material layer and the load layer, wherein the second mask layer covers the surface of the electrode material layer on the first area and the surface of the load layer on the second area; and removing the electrode material layer of the area outside the first area and the second area by taking the second mask layer as a mask, forming a first electrode layer on the first area, and forming a second electrode layer on the second area.
Optionally, an included angle between the side wall surface of the second electrode layer and the bottom surface of the second electrode layer is an acute angle; the included angle ranges from 30 degrees to 70 degrees.
Optionally, the method further comprises: forming an intermediate structure on a first side of the piezoelectric layer; providing a bearing substrate, and bonding the intermediate structure with the bearing substrate; a first cavity and a second cavity are formed embedded in the intermediate structure, at least a portion of the first electrode structure being located in the first cavity and at least a portion of the second electrode structure being located in the second cavity.
Optionally, the forming method of the intermediate structure and the first cavity and the second cavity in the intermediate structure includes: forming a first sacrificial layer on the first side of the piezoelectric layer and on the first region and a second sacrificial layer on the second region, wherein the first sacrificial layer covers at least part of the first electrode structure, and the second sacrificial layer covers at least part of the second electrode structure; forming an intermediate structure on the first side surface of the piezoelectric layer, the first sacrificial layer sidewall surface and the top surface, and the second sacrificial layer sidewall surface and the top surface; bonding the intermediate structure to the load bearing substrate; removing the first sacrificial layer to form a first cavity in the intermediate structure; and removing the second sacrificial layer to form a second cavity in the intermediate structure.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
according to the technical scheme, the first electrode structure and the second electrode structure with different thicknesses are arranged on the first side of the piezoelectric layer, the first electrode structure is located in the first area, the second electrode structure is located in the second area, the second electrode structure comprises the second electrode layer, the blocking layer and the load layer, the blocking layer is located between the second electrode layer and the load layer, the second electrode layer is close to the piezoelectric layer, and the second electrode structure has different thicknesses by adjusting the thickness of the load layer so as to meet the device frequency requirements on different areas on the filter.
Further, the projection of the load layer on the piezoelectric layer is located in the projection of the second electrode layer on the piezoelectric layer, a first interval is formed between a first load edge of the load layer and a corresponding first electrode edge of the second electrode layer, a second interval is formed between a second load edge of the load layer and a corresponding second electrode edge of the second electrode layer, the first load edge is opposite to the second load edge, the first electrode edge is opposite to the second electrode edge, and a space between the load layer and the second electrode layer can improve the propagation speed of sound waves in a first interval area and a second interval area and excite a piston mode (piston mode), so that a high-order transverse parasitic mode can be restrained, and the Q value of a filter is improved.
Further, an included angle between the side wall surface of the second electrode layer and the bottom surface of the second electrode layer is an acute angle. Therefore, when other film layers are formed on the side wall surface of the second electrode layer in the subsequent process, the film layers are more easily attached to the side wall surface of the second electrode layer, have good binding force, and are not easy to fall off.
Further, the barrier layer is located between the second electrode layer and the load layer, and the barrier layer can protect the second electrode layer and prevent the second electrode layer from being damaged in the process of forming the load layer by etching.
Drawings
FIG. 1 is a schematic diagram of a bulk acoustic wave filter device in an embodiment;
fig. 2 to 6 are schematic structural views of a bulk acoustic wave filter device according to an embodiment of the present invention.
Detailed Description
As described in the background art, the performance of the piezoelectric bulk acoustic wave filter has yet to be improved. The analysis will now be described with reference to specific examples.
Fig. 1 is a schematic structural diagram of a bulk acoustic wave filter device in an embodiment.
Referring to fig. 1, the bulk acoustic wave filter device includes: a piezoelectric layer 100, the piezoelectric layer 100 comprising a first side and a second side; a first electrode layer 101 located on the first side; a second electrode layer 102 located on the second side; an intermediate layer 103 located on the second side, the intermediate layer 103 having a cavity 104 therein, the second electrode layer 102 being located within the cavity 104; a carrier substrate 105, the intermediate layer 103 being bonded to the carrier substrate 105.
The bulk acoustic wave filter device includes one or more bulk acoustic wave filter devices, and in a circuit of the bulk acoustic wave filter device, the plurality of bulk acoustic wave filter devices are connected in series or in parallel. Since the bulk acoustic wave filter devices are formed by the same process, the thicknesses of the film layers of the first electrode layer 101 and the second electrode layer 102 of each bulk acoustic wave filter device are the same, and therefore, the frequencies of each bulk acoustic wave filter device formed on the basis of the same piezoelectric substrate cannot be adjusted by adjusting the thicknesses of the electrode layers. However, in the series circuit and the parallel circuit, a certain difference in the frequency of the bulk acoustic wave filter device is required according to the circuit design, and thus, the individual bulk acoustic wave filter devices having the same frequency cannot meet this requirement.
In order to solve the problems, the technical scheme of the invention provides a bulk acoustic wave filter device and a forming method thereof, and the bulk acoustic wave filter device, wherein a first electrode structure and a second electrode structure with different thicknesses are arranged on a first side of a piezoelectric layer, the first electrode structure is positioned in a first area, the second electrode structure is positioned in a second area, the second electrode structure comprises a second electrode layer, a blocking layer and a load layer, the blocking layer is positioned between the second electrode layer and the load layer, the second electrode layer is close to the piezoelectric layer, and the thickness of the load layer is adjusted to enable the second electrode structure to have different thicknesses so as to meet the device frequency requirements on different areas on the filter; in addition, the projection of the load layer on the piezoelectric layer is positioned in the projection of the second electrode layer on the piezoelectric layer, a first interval is arranged between a first load edge of the load layer and a corresponding first electrode edge of the second electrode layer, a second interval is arranged between a second load edge of the load layer and a corresponding second electrode edge of the second electrode layer, the first load edge is opposite to the second load edge, the first electrode edge is opposite to the second electrode edge, and a distance between the load layer and the second electrode layer can improve the propagation speed of sound waves in a first interval area and a second interval area and excite a piston mode (piston mode), so that a higher-order transverse parasitic mode can be restrained and the Q value of a filter is improved.
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Fig. 2 to 6 are schematic structural views of a bulk acoustic wave filter device according to an embodiment of the present invention.
Referring to fig. 2, a piezoelectric layer 200 is formed, the piezoelectric layer 200 includes a first region I and a second region II, and the piezoelectric layer 200 includes opposite first and second sides along a direction perpendicular to a surface of the piezoelectric layer 200; forming an electrode material layer 201 on a first side of the piezoelectric layer 200; forming a barrier material layer 202 on the surface of the electrode material layer 201; a loading material layer 203 is formed on the surface of the barrier material layer 202.
In the present embodiment, the process of forming the electrode material layer 201 includes a deposition process; the process of forming the barrier material layer 202 includes a deposition process; the process of forming the loading material layer 203 includes a deposition process. The electrode material layer 201, the barrier material layer 202 and the load material layer 203 can be formed by deposition in the same vacuum chamber, so that electrode structures with different thicknesses can be formed later, the process flow is simple, and the quality of the formed electrode material layer 201, barrier material layer 202 and load material layer 203 is good.
In this embodiment, the material of the supporting material layer 203 is the same as the material of the electrode material layer 201. The load material layer 203 is used for forming a load layer subsequently, the electrode material layer 201 is used for forming an electrode layer subsequently, the load layer has a frequency modulation effect, and the material of the load material layer 203 is the same as that of the electrode material layer 201, so that the subsequent frequency modulation is performed through the thickness of the load layer.
In this embodiment, the material of the supporting material layer 203 includes aluminum, copper, titanium, tungsten, molybdenum, thallium, ruthenium, or iridium; the material of the electrode material layer 201 includes aluminum, copper, titanium, tungsten, molybdenum, thallium, ruthenium, or iridium.
In other embodiments, the material of the loading material layer is different from the material of the electrode material layer.
In this embodiment, the material of the blocking material layer 202 is the same as the material of the piezoelectric layer 200; the material of the barrier material layer 202 is different from the material of the electrode material layer 201 and the material of the supporting material layer 203.
The material of the barrier material layer 202 is the same as that of the piezoelectric layer 200, and the formation process of the barrier material layer 202 can follow the formation process of the piezoelectric layer 200, so that the process flow can be saved; the material of the barrier material layer 202 is different from the material of the electrode material layer 201 and the material of the load material layer 203, so that the barrier material layer 202 can play a role of etching stop when the load material layer 203 is etched later, and the barrier layer formed by the barrier material layer 202 has a larger etching selection ratio when the electrode material layer 201 is etched later; in addition, the barrier material layer 202 can function to protect the electrode material layer 201 from damage during etching of a subsequently formed second electrode layer.
In this embodiment, the material of the blocking material layer 202 includes: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
In this embodiment, the materials of the piezoelectric layer 200 include: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
In other embodiments, the material of the barrier material layer and the material of the piezoelectric layer can be different.
Referring to fig. 3, a first mask layer (not shown) is formed on the load material layer 203, and covers the surface of the load material layer 203 on the second region II; the first mask layer is used as a mask, the load material layer 203 and the barrier material layer 202 outside the second region II are removed, the surface of the electrode material layer 201 is exposed, and a barrier layer 204 and a load layer 205 are formed on the electrode material layer 201 in the second region II, and the load layer 205 includes a first load edge and a second load edge which are opposite to each other.
The process of removing the load material layer 203 and the barrier material layer 202 outside the second region II using the first mask layer as a mask includes a dry etching process. The dry etching process can adjust the etching angle to obtain relatively flat side wall surfaces of the barrier layer 204 and the load layer 205, and can accurately control the etching size.
Referring to fig. 4, a second mask layer (not shown) is formed on the surface of the electrode material layer 201 and the load layer 205, and covers the surface of the electrode material layer 201 on the first region I and the surface of the load layer 205 on the second region II; with the second mask layer as a mask, the electrode material layer 201 in the area outside the first area I and the second area II is removed, a first electrode layer 207 is formed on the first area I, a second electrode layer 206 is formed on the second area II, the barrier layer 204 is located between the second electrode layer 206 and the load layer 205, the second electrode layer 206 is close to the piezoelectric layer 200, the second electrode layer 206 includes a first electrode edge and a second electrode edge which are opposite, the first load edge corresponds to the first electrode edge, and the second load edge corresponds to the second electrode edge.
The process of removing the electrode material layer 201 outside the first region I and the second region II using the second mask layer as a mask includes a dry etching process. The dry etching process can adjust the etching angle to obtain relatively flat side wall surfaces of the first electrode layer 207 and the second electrode layer 206, and can accurately control the etching size.
The first electrode layer 207 and the second electrode layer 206 are formed based on the electrode material layer 201, the first electrode layer 207 constituting a first electrode structure located on the first region I, and the second electrode layer 206, the barrier layer 204 and the load layer 205 constituting a second electrode structure located on the second region II, the second electrode structure having a thickness greater than that of the first electrode structure.
In this embodiment, the projection range of the load layer 205 on the piezoelectric layer 200 is within the projection range of the second electrode layer 206 on the piezoelectric layer 200, a first spacing S is provided between a first load edge of the load layer 205 and a corresponding first electrode edge of the second electrode layer 206, and a second spacing (not labeled) is provided between a second load edge of the load layer 205 and a corresponding second electrode edge of the second electrode layer 206.
In this embodiment, the first spacing S is in a range of greater than 4 microns; the second pitch ranges from greater than 4 microns. The space between the load layer 205 and the second electrode layer 206 can increase the propagation speed of the acoustic wave in the first space region and the second space region, and excite the piston mode (piston mode), so that the high-order transverse parasitic mode can be restrained, and the Q value of the filter can be increased.
In this embodiment, the barrier layer 204 is formed in the etching process after the formation of the load layer 205, and the second electrode layer 206 is formed in the etching process after the formation of the barrier layer 204, since the first load edge of the load layer 205 has the first spacing S between the corresponding first electrode edge of the second electrode layer 206, the second load edge of the load layer 205 has the second spacing between the corresponding second electrode edge of the second electrode layer 206, and the projection range of the barrier layer 204 on the piezoelectric layer 200 is within the projection range of the second electrode layer 206 on the piezoelectric layer 200 based on the smoothness of the process; the projection range of the load layer 205 on the piezoelectric layer 200 is within the projection range of the barrier layer 204 on the piezoelectric layer 200.
In this embodiment, the included angle α between the sidewall surface of the second electrode layer 206 and the bottom surface of the second electrode layer 206 is an acute angle; the sidewall surface of the first electrode layer 207 forms an acute angle with the bottom surface of the first electrode layer 207.
In this embodiment, the included angle α ranges from 30 degrees to 70 degrees.
In this embodiment, the thickness range of the load layer 205 is smaller than the thickness range of the second electrode layer 206. The load layer 205 acts as a frequency modulation layer, and the frequency fluctuation should be small, so the thickness of the load layer 205 is also small.
In this embodiment, the thickness of the barrier layer 206 is in the range of less than 100 angstroms.
Referring to fig. 5, an intermediate structure 210 is formed on a first side of the piezoelectric layer 200; providing a bearing substrate 211, and bonding the intermediate structure 210 with the bearing substrate 211; a first cavity 209 and a second cavity 208 are formed embedded within the intermediate structure 210, at least part of the first electrode structure being located within the first cavity 209 and at least part of the second electrode structure being located within the second cavity 208.
The method for forming the intermediate structure 210 and the first cavity 209 and the second cavity 208 located in the intermediate structure 210 includes: forming a first sacrificial layer (not shown) on the first region and a second sacrificial layer (not shown) on the second region on the first side of the piezoelectric layer 200, the first sacrificial layer covering at least a portion of the first electrode structure and the second sacrificial layer covering at least a portion of the second electrode structure; forming an intermediate structure 210 on the first side surface of the piezoelectric layer 200, the first sacrificial layer sidewall surface and the top surface, and the second sacrificial layer sidewall surface and the top surface; bonding the intermediate structure 210 to the carrier substrate 211; after bonding the intermediate structure 210 and the carrier substrate 211, removing the first sacrificial layer to form a first cavity 209 in the intermediate structure 210; the second sacrificial layer is removed and a second cavity 208 is formed within the intermediate structure 210.
In this embodiment, the materials of the first and second sacrificial layers include an organic material including amorphous carbon.
In this embodiment, the material of the intermediate structure 210 includes silicon oxide. In this embodiment, the included angle between the sidewall surface of the second electrode layer 206 and the bottom surface of the second electrode layer 206 is an acute angle, the included angle α between the sidewall surface of the first electrode layer 207 and the bottom surface of the first electrode layer 207 is an acute angle, when the sidewall and the top surface of the first electrode structure form the first sacrificial layer, when the sidewall and the top surface of the second electrode structure form the second sacrificial layer, the first sacrificial layer is easier to attach to the sidewall surface of the first electrode structure, the second sacrificial layer is easier to attach to the sidewall surface of the second electrode structure, so that the second sacrificial layer has good bonding force, is not easy to fall off the film, and is convenient for the formation of the subsequent intermediate structure 210.
By arranging the first electrode structure and the second electrode structure with different thicknesses in the first region I and the second region II, the second electrode structure comprises a second electrode layer 206, a barrier layer 204 and a load layer 205, and the barrier layer 204 is positioned between the second electrode layer 206 and the load layer 205, and the thickness of the load layer 205 is adjusted to enable the second electrode structure to have different thicknesses under the condition of not adding additional process flows so as to meet the device frequency requirements in different regions.
Referring to fig. 6, a third electrode structure 212 and a fourth electrode structure 213 are formed on the second side of the piezoelectric layer, and the third electrode structure 212 and the fourth electrode structure 213 are respectively located in the first region I and the second region II.
The third electrode structure 212 is identical to the first electrode structure or the second electrode structure, and the fourth electrode structure 213 is identical to the first electrode structure or the second electrode structure.
The third electrode structure 212 shown in the figure is identical to the first electrode structure, and the fourth electrode structure 213 is identical to the first electrode structure.
Accordingly, an embodiment of the present invention further provides a bulk acoustic wave filter device, including at least one first resonant device and at least one second resonant device, please continue to refer to fig. 6, including:
a piezoelectric layer 200, the piezoelectric layer 200 comprising a first region I and a second region II, the first resonant device being located in the first region I and the second resonant device being located in the second region II, the piezoelectric layer 200 comprising opposite first and second sides in a direction perpendicular to the piezoelectric layer 200;
a first electrode structure and a second electrode structure located on a first side of the piezoelectric layer 200, the first electrode structure and the second electrode structure being located in a first region I and a second region II, respectively, the second electrode structure having a thickness greater than a thickness of the first electrode structure;
a third electrode structure and a fourth electrode structure located on the second side of the piezoelectric layer 200, the third electrode structure and the fourth electrode structure being located in the first region I and the second region II, respectively;
wherein the first electrode structure comprises a first electrode layer 207 and the second electrode structure comprises: a second electrode layer 206, a barrier layer 204, and a load layer 205, the barrier layer 204 being located between the second electrode layer 206 and the load layer 205, the second electrode layer 206 being proximate to the piezoelectric layer 200, the load layer 205 comprising opposing first and second load edges, the second electrode layer 206 comprising opposing first and second electrode edges, the first load edge corresponding to the first electrode edge and the second load edge corresponding to the second electrode edge;
wherein the projection of the load layer 205 on the piezoelectric layer 200 is located within the projection of the second electrode layer 206 on the piezoelectric layer 200, a first spacing S is provided between a first load edge of the load layer 205 and a corresponding first electrode edge of the second electrode layer 206, and a second spacing is provided between a second load edge of the load layer 205 and a corresponding second electrode edge of the second electrode layer 206.
In this embodiment, the first spacing S is in a range of greater than 4 microns; the second pitch ranges from greater than 4 microns.
In this embodiment, the projection of the barrier layer 204 onto the piezoelectric layer 200 is located within the projection of the second electrode layer 206 onto the piezoelectric layer 200; the projection of the loading layer 205 onto the piezoelectric layer 200 is located within the projection of the barrier layer 204 onto the piezoelectric layer 200.
In this embodiment, the thickness of the load layer 205 is smaller than the thickness of the second electrode layer 206.
In this embodiment, the thickness of the barrier layer 206 is less than 100 angstroms.
In this embodiment, the second electrode layer 206 and the first electrode layer 207 are the same in material and structure.
In this embodiment, the included angle between the sidewall surface of the second electrode layer 206 and the bottom surface of the second electrode layer 206 is an acute angle; the included angle ranges from 30 degrees to 70 degrees.
In this embodiment, the material of the supporting layer 205 is the same as the material of the second electrode layer 206.
In other embodiments, the material of the support layer is different from the material of the second electrode layer.
In this embodiment, the material of the barrier layer 204 is the same as the material of the piezoelectric layer 200.
In this embodiment, the material of the barrier layer 204 is different from the material of the second electrode layer 206, and the material of the barrier layer 204 is different from the material of the load layer 205.
In this embodiment, the materials of the piezoelectric layer 200 include: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
In this embodiment, the material of the blocking layer 204 includes: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
In this embodiment, further comprising: an intermediate structure 210 on a first side of the piezoelectric layer 200 and a first cavity 209 and a second cavity 208 embedded within the intermediate structure 210, at least part of the first electrode structure being located within the first cavity 209 and at least part of the second electrode structure being located within the second cavity 208; a carrier substrate 211, the intermediate structure 210 is located between the carrier substrate 211 and the piezoelectric layer 200, and the intermediate structure 210 is in contact with the carrier substrate 211.
In this embodiment, the first resonant device is a series resonant device, and the second resonant device is a parallel resonant device.
Accordingly, the embodiment of the present invention further provides a bulk acoustic wave filter device, where the bulk acoustic wave filter device includes one or more bulk acoustic wave filter devices, and structures, processes, materials and performances of the bulk acoustic wave filter device are formed by the forming methods shown in fig. 2 to 6, which are not described herein again.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims (22)

1. A bulk acoustic wave filter device comprising at least one first resonant device and at least one second resonant device, comprising:
a piezoelectric layer comprising a first region and a second region, the first resonant device being located in the first region and the second resonant device being located in the second region, the piezoelectric layer comprising opposing first and second sides in a direction perpendicular to a surface of the piezoelectric layer;
a first electrode structure and a second electrode structure on a first side of the piezoelectric layer, the first electrode structure and the second electrode structure being located in a first region and a second region, respectively, the second electrode structure having a thickness greater than a thickness of the first electrode structure;
a third electrode structure and a fourth electrode structure located on the second side of the piezoelectric layer, the third electrode structure and the fourth electrode structure being located in the first region and the second region, respectively;
wherein the first electrode structure includes a first electrode layer, and the second electrode structure includes: the piezoelectric device comprises a piezoelectric layer, a first electrode layer, a second electrode layer, a barrier layer and a load layer, wherein the barrier layer is positioned between the first electrode layer and the load layer, the first electrode layer is close to the piezoelectric layer, the load layer comprises a first load edge and a second load edge which are opposite, the second electrode layer comprises a first electrode edge and a second electrode edge which are opposite, the first load edge corresponds to the first electrode edge, and the second load edge corresponds to the second electrode edge;
the projection of the load layer on the piezoelectric layer is positioned in the projection of the second electrode layer on the piezoelectric layer, a first interval is reserved between a first load edge of the load layer and a corresponding first electrode edge of the second electrode layer, and a second interval is reserved between a second load edge of the load layer and a corresponding second electrode edge of the second electrode layer.
2. The bulk acoustic wave filter device of claim 1, wherein the first pitch ranges from greater than 4 microns; the second pitch ranges from greater than 4 microns.
3. The bulk acoustic wave filter device of claim 1, wherein the projection of the barrier layer onto the piezoelectric layer is within the projection of the second electrode layer onto the piezoelectric layer; the projection of the load layer onto the piezoelectric layer is located within the projection of the barrier layer onto the piezoelectric layer.
4. The bulk acoustic wave filter device of claim 1, wherein the thickness of the loading layer is less than the thickness of the second electrode layer.
5. The bulk acoustic wave filter device of claim 1, wherein the barrier layer has a thickness of less than 100 angstroms.
6. The bulk acoustic wave filter device of claim 1, wherein the second electrode layer and the first electrode layer are the same material and structure.
7. The bulk acoustic wave filter device of claim 6, wherein a sidewall surface of the second electrode layer forms an acute angle with a bottom surface of the second electrode layer; the included angle ranges from 30 degrees to 70 degrees.
8. The bulk acoustic wave filter device of claim 1, wherein the material of the loading layer is the same as the material of the second electrode layer.
9. The bulk acoustic wave filter device of claim 1, wherein the material of the loading layer is different from the material of the second electrode layer.
10. The bulk acoustic wave filter device of claim 1, wherein the material of the barrier layer is the same as the material of the piezoelectric layer.
11. The bulk acoustic wave filter device of claim 1, wherein a material of the barrier layer is different from a material of the second electrode layer, and wherein a material of the barrier layer is different from a material of the load layer.
12. The bulk acoustic wave filter device of claim 1, wherein the material of the barrier layer comprises: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
13. The bulk acoustic wave filter device of claim 1, wherein the material of the piezoelectric layer comprises: zinc oxide, gallium nitride, lithium tantalate, lithium niobate, lead zirconate titanate, aluminum nitride, or aluminum nitride alloys.
14. The bulk acoustic wave filter device of claim 1, further comprising: an intermediate structure on a first side of the piezoelectric layer, and first and second cavities embedded within the intermediate structure, at least a portion of the first electrode structure being located within the first cavity and at least a portion of the second electrode structure being located within the second cavity; and the intermediate structure is positioned between the bearing substrate and the piezoelectric layer, and is contacted with the bearing substrate.
15. The bulk acoustic wave filter device of claim 1, wherein the first resonant device is a series resonant device and the second resonant device is a parallel resonant device.
16. A method of forming a bulk acoustic wave filter device, comprising:
forming a piezoelectric layer comprising a first region and a second region, the piezoelectric layer comprising opposing first and second sides in a direction perpendicular to a surface of the piezoelectric layer;
forming a first electrode structure and a second electrode structure on a first side of the piezoelectric layer, wherein the first electrode structure and the second electrode structure are respectively positioned in a first area and a second area, and the thickness of the second electrode structure is larger than that of the first electrode structure;
forming a third electrode structure and a fourth electrode structure on the second side of the piezoelectric layer, wherein the third electrode structure and the fourth electrode structure are respectively positioned in the first area and the second area;
wherein forming the first electrode structure includes forming a first electrode layer, and forming the second electrode structure includes: forming a second electrode layer, a barrier layer and a load layer, wherein the barrier layer is positioned between the second electrode layer and the load layer, the second electrode layer is close to the piezoelectric layer, the load layer comprises a first load edge and a second load edge which are opposite, the second electrode layer comprises a first electrode edge and a second electrode edge which are opposite, the first load edge corresponds to the first electrode edge, and the second load edge corresponds to the second electrode edge;
the projection of the load layer on the piezoelectric layer is positioned in the projection of the second electrode layer on the piezoelectric layer, a first interval is reserved between a first load edge of the load layer and a corresponding first electrode edge of the second electrode layer, and a second interval is reserved between a second load edge of the load layer and a corresponding second electrode edge of the second electrode layer.
17. The method of forming a bulk acoustic wave filter device according to claim 16, wherein a projection range of the barrier layer on the piezoelectric layer is within a projection range of the second electrode layer on the piezoelectric layer; the projection range of the load layer on the piezoelectric layer is within the projection range of the barrier layer on the piezoelectric layer.
18. The method of forming a bulk acoustic wave filter device of claim 16, wherein the second electrode layer and the first electrode layer are formed based on the same material layer.
19. The method of forming a bulk acoustic wave filter device of claim 18, wherein the method of forming the first electrode structure and the second electrode structure comprises: forming an electrode material layer on a first side of the piezoelectric layer; forming a barrier material layer on the surface of the electrode material layer; forming a load material layer on the surface of the barrier material layer; forming a first mask layer on the load material layer, wherein the first mask layer covers the surface of the load material layer on the second area; removing the load material layer and the blocking material layer outside the second area by taking the first mask layer as a mask, exposing the surface of the electrode material layer, and forming a blocking layer and a load layer on the electrode material layer of the second area; forming a second mask layer on the surface of the electrode material layer and the load layer, wherein the second mask layer covers the surface of the electrode material layer on the first area and the surface of the load layer on the second area; and removing the electrode material layer of the area outside the first area and the second area by taking the second mask layer as a mask, forming a first electrode layer on the first area, and forming a second electrode layer on the second area.
20. The method of forming a bulk acoustic wave filter device of claim 16, wherein a sidewall surface of the second electrode layer forms an acute angle with a bottom surface of the second electrode layer; the included angle ranges from 30 degrees to 70 degrees.
21. The method of forming a bulk acoustic wave filter device of claim 16, further comprising:
forming an intermediate structure on a first side of the piezoelectric layer; providing a bearing substrate, and bonding the intermediate structure with the bearing substrate; a first cavity and a second cavity are formed embedded in the intermediate structure, at least a portion of the first electrode structure being located in the first cavity and at least a portion of the second electrode structure being located in the second cavity.
22. The method of forming a bulk acoustic wave filter device as recited in claim 21, wherein the method of forming the intermediate structure and the first and second cavities within the intermediate structure comprises: forming a first sacrificial layer on the first side of the piezoelectric layer and on the first region and a second sacrificial layer on the second region, wherein the first sacrificial layer covers at least part of the first electrode structure, and the second sacrificial layer covers at least part of the second electrode structure; forming an intermediate structure on the first side surface of the piezoelectric layer, the first sacrificial layer sidewall surface and the top surface, and the second sacrificial layer sidewall surface and the top surface; bonding the intermediate structure to the load bearing substrate; removing the first sacrificial layer to form a first cavity in the intermediate structure; and removing the second sacrificial layer to form a second cavity in the intermediate structure.
CN202311466981.4A 2023-11-06 2023-11-06 Bulk acoustic wave filter device and method of forming the same Pending CN117614413A (en)

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