CN114598286A - Method for forming bulk acoustic wave resonator - Google Patents
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- CN114598286A CN114598286A CN202210101802.6A CN202210101802A CN114598286A CN 114598286 A CN114598286 A CN 114598286A CN 202210101802 A CN202210101802 A CN 202210101802A CN 114598286 A CN114598286 A CN 114598286A
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- 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
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H2003/023—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the membrane type
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
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Abstract
A method of forming a bulk acoustic wave resonator device, comprising: providing a substrate; forming an intermediate layer on a substrate; forming a first opening embedded in the middle layer; forming a sacrificial layer in the first opening, wherein the top surface of the sacrificial layer is flush with the top surface of the intermediate layer; forming a second opening, and embedding the intermediate layer and the sacrificial layer; forming a first electrode layer in the second opening, wherein the top surface of the first electrode layer is flush with the top surface of the intermediate layer; forming a piezoelectric layer on the intermediate layer, the sacrificial layer and the first electrode layer; a second electrode layer is formed on the piezoelectric layer. Since the top surfaces of the intermediate layer, the sacrificial layer and the first electrode layer are flush, the piezoelectric layer is formed without significantly turning grains, thereby contributing to an improvement in the electromechanical coupling coefficient of the resonance device and the Q value of the resonance device. In addition, the bulk acoustic wave resonance device is formed in a layer stacking mode, so that a bonding process is avoided, manufacturing steps are effectively simplified, and manufacturing cost is reduced.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to a method for forming a bulk acoustic wave resonance device.
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 including a duplexer, a low noise amplifier, and the like. The rf filter includes a Surface Acoustic Wave (SAW) filter, a Bulk Acoustic Wave (BAW) filter, a Micro-Electro-Mechanical System (MEMS) filter, an Integrated Passive Devices (IPD) filter, and the like.
The surface acoustic wave resonator and the bulk acoustic wave resonator have high quality factor values (Q values), and radio frequency filters with low insertion loss and high out-of-band rejection, namely the surface acoustic wave filter and the bulk acoustic wave filter, manufactured by the surface acoustic wave resonator and the bulk acoustic wave resonator are mainstream radio frequency filters used by wireless communication equipment such as mobile phones and base stations at present. Where the Q value is the quality factor value of the resonator, defined as the center frequency divided by the 3dB bandwidth of the resonator. The frequency of use of the surface acoustic wave filter is generally 0.4GHz to 2.7GHz, and the frequency of use of the bulk acoustic wave filter is generally 0.7GHz to 7 GHz.
The bulk acoustic wave resonator has better performance than the surface acoustic wave resonator, but the manufacturing cost of the bulk acoustic wave resonator is higher than that of the SAW resonator due to the complicated process steps. However, as wireless communication technology gradually evolves, more and more frequency bands are used, and meanwhile, with the application of frequency band overlapping use technology such as carrier aggregation, mutual interference between wireless frequency bands becomes more and more serious. The high-performance bulk acoustic wave technology can solve the problem of mutual interference between frequency bands. With the advent of the 5G era, higher communication frequency bands are introduced into wireless mobile networks, and currently, only the bulk acoustic wave technology can solve the filtering problem of high frequency bands.
However, the bulk acoustic wave resonator devices formed in the prior art still have many problems.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for forming a bulk acoustic wave resonator, which can enable a piezoelectric layer not to comprise obviously-turned crystal grains, thereby being beneficial to improving the electromechanical coupling coefficient of the resonator and the Q value of the resonator.
In order to solve the above problems, the present invention provides a method of forming a bulk acoustic wave resonator device, including: providing a substrate; forming an intermediate layer on the substrate; forming a first opening embedded in the intermediate layer; forming a sacrificial layer in the first opening, wherein the top surface of the sacrificial layer is flush with the top surface of the intermediate layer; forming a second opening, embedding the intermediate layer and the sacrificial layer; forming a first electrode layer within the second opening, a top surface of the first electrode layer being flush with a top surface of the intermediate layer; forming a piezoelectric layer on the intermediate layer, on the sacrificial layer, and on the first electrode layer; a second electrode layer is formed on the piezoelectric layer.
Optionally, the material of the sacrificial layer is different from the material of the first electrode and the intermediate layer; the material of the sacrificial layer comprises: one or more of polymer, silicon dioxide, doped silicon dioxide, and polysilicon.
Optionally, the polymer comprises: one or more of benzocyclobutene, photosensitive epoxy resin photoresist and polyimide.
Optionally, the material of the intermediate layer includes: one or more of a polymer and an insulating dielectric.
Optionally, the polymer comprises: one or more of benzocyclobutene, photosensitive epoxy resin photoresist and polyimide.
Optionally, the insulating dielectric comprises: one or more of aluminum nitride, silicon dioxide, silicon nitride, and titanium oxide.
Optionally, the piezoelectric layer includes a plurality of grains including a first grain and a second grain, wherein the first grain and the second grain are any two grains of the plurality of grains; a first axis along a first direction corresponds to a height of the first die and a second axis along a second direction corresponds to a height of the second die, wherein the first direction and the second direction are the same or opposite.
Optionally, the first crystal grain corresponds to a first coordinate system, where the first coordinate system includes the first coordinate axis and a third coordinate axis along a third direction; the second crystal grain corresponds to a second coordinate system, and the second coordinate system comprises the second coordinate axis and a fourth coordinate axis along a fourth direction.
Optionally, the first coordinate system further includes a fifth coordinate axis along a fifth direction, and the second coordinate system further includes a sixth coordinate axis along a sixth direction.
Optionally, the third direction and the fourth direction are the same or opposite.
Optionally, the material of the piezoelectric layer includes: one or more of aluminum nitride, aluminum nitride alloy, gallium nitride, zinc oxide, lithium tantalate, lithium niobate, lead zirconate titanate, and lead magnesium niobate-lead titanate.
Optionally, before forming the intermediate layer, the method further includes: forming a polycrystalline table on the substrate, the polycrystalline table being located between the substrate and the intermediate layer.
Optionally, the material of the polycrystalline layer includes: a polycrystalline material.
Optionally, the polycrystalline material comprises: one or more of polycrystalline silicon, polycrystalline silicon nitride and polycrystalline silicon carbide.
Optionally, the thickness range of the intermediate layer is: 0.1 to 10 microns.
Optionally, after forming the second electrode layer, the method further includes: and removing the sacrificial layer to form a cavity between the piezoelectric layer and the intermediate layer, wherein one end of the first electrode layer is positioned in the cavity.
Optionally, before forming the sacrificial layer, the method further includes: and forming an etching shielding layer on the side wall and the bottom surface of the first opening.
Optionally, the material of the etching shielding layer includes: one or more of aluminum nitride, silicon carbide, diamond, silicon nitride, silicon dioxide, aluminum oxide, and titanium dioxide.
Optionally, the thickness range of the etching shielding layer is: 0.1 to 3 microns.
Optionally, after forming the second electrode layer, the method further includes: forming an edge structure on the piezoelectric layer, the edge structure being in contact with the piezoelectric layer, the edge structure surrounding the second electrode layer.
Compared with the prior art, the technical scheme of the invention has the following advantages:
in the method for forming a bulk acoustic wave resonator device according to the present invention, the piezoelectric layer is formed on the intermediate layer, the sacrificial layer, and the first electrode layer. Since the top surfaces of the intermediate layer, the sacrificial layer and the first electrode layer are flush, the piezoelectric layer is formed without obviously turning crystal grains, thereby being beneficial to improving the electromechanical coupling coefficient of the resonance device and the Q value of the resonance device. In addition, the bulk acoustic wave resonance device is formed in a layer stacking mode, so that a bonding process is avoided, manufacturing steps are effectively simplified, and manufacturing cost is reduced.
Further, before forming the intermediate layer, the method further includes: forming a polycrystalline table on the substrate, the polycrystalline table being located between the substrate and the intermediate layer. The polycrystalline layer is arranged between the intermediate layer and the substrate, so that the formation of a free electron layer on the surface of the substrate is prevented, and the electric loss caused by the substrate is reduced.
Further, the thickness range of the intermediate layer 202 is: 0.1 to 10 microns. And the acoustic impedance of the intermediate layer is greatly different from that of the piezoelectric layer to form an acoustic reflection structure, so that the sound wave is blocked from leaking into the substrate from the resonance area.
Further, before forming the sacrificial layer, the method further includes: and forming an etching shielding layer on the side wall and the bottom surface of the first opening. When the cavity is formed by removing the sacrificial layer subsequently, the etching shielding layer can play a role in protecting the middle layer. In addition, the etched shielding isolation layer can protect the resonance device from being corroded by water and oxygen.
Further, after forming the second electrode layer, the method further includes: and forming an edge structure on the piezoelectric layer, wherein the edge structure is in contact with the piezoelectric layer, is annular and is positioned at the edge of the overlapped part of the second electrode layer and the first electrode layer, and the edge structure can be used for limiting transverse wave leakage so as to improve the Q value of the resonance device.
Drawings
FIG. 1 is a schematic diagram of a bulk acoustic wave filter circuit;
FIG. 2 is a schematic diagram of a film bulk acoustic resonator;
fig. 3 to 10 are schematic structural diagrams of steps of a method for forming a bulk acoustic wave resonator according to an embodiment of the present invention;
FIG. 11 is a schematic structural view of a hexagonal crystal grain;
FIG. 12 is a schematic diagram of the structure of different crystal grains.
Detailed Description
As described in the background, the bulk acoustic wave resonator devices formed in the prior art still have problems. The following detailed description will be made in conjunction with the accompanying drawings.
FIG. 1 is a schematic diagram of a bulk acoustic wave filter circuit; fig. 2 is a schematic structural diagram of a film bulk acoustic resonator.
Referring to fig. 1, a bulk acoustic wave filter circuit includes a ladder circuit composed of a plurality of bulk acoustic wave resonators, wherein f1, f2, f3, and f4 respectively represent 4 different frequencies. In each bulk acoustic wave resonator, metal electrodes on two sides of a piezoelectric layer of the resonator generate alternative positive and negative voltages, the piezoelectric layer generates acoustic waves through the alternative positive and negative voltages, and the acoustic waves in the resonator propagate along a direction perpendicular to the piezoelectric layer. In order to form resonance, the acoustic wave needs to generate total reflection on the upper surface of the upper metal electrode and the lower surface of the lower metal electrode to form a standing acoustic wave. The condition for the reflection of the acoustic wave is that the acoustic impedance of the contact area with the upper surface of the upper metal electrode and the lower surface of the lower metal electrode is greatly different from the acoustic impedance of the metal electrode.
A Film Bulk Acoustic Wave Resonator (FBAR) is a Bulk Acoustic Wave Resonator that confines Acoustic energy within the device, with air or vacuum above the resonant region and a cavity below. The difference between the acoustic impedance of the air and the acoustic impedance of the metal electrode is large, and the sound waves can be totally reflected on the upper surface of the upper metal electrode and the lower surface of the lower metal electrode to form standing waves.
Referring to fig. 2, a film bulk acoustic resonator 100 includes: a substrate 101, the upper surface side of the substrate 101 comprising a cavity 103; a first electrode layer 105 disposed on the substrate 101 and the cavity 103; a piezoelectric layer 107 on the substrate 101 covering the first electrode layer 105, the piezoelectric layer 107 including a protrusion 107 a; a second electrode layer 109 on the piezoelectric layer 107, the second electrode layer 109 including a protrusion 109a, the protrusion 109a being on the protrusion 107 a; wherein a resonance region 111 (i.e. the overlapping area of the first electrode layer 105 and the protrusion 109 a) is located on the cavity 103, having an overlapping contact with the substrate 101. The thin film bulk acoustic resonator 100 is formed by stacking layer by layer, i.e., the first electrode layer 105 is formed on the substrate 101, the piezoelectric layer 107 is formed on the first electrode layer 105 and the substrate 101, and then the second electrode layer 109 is formed on the piezoelectric layer 107.
Since the first electrode layer 105 is protruded, the piezoelectric layer 107 is directly formed on the first electrode layer 105 and the substrate 101, which causes a significant turning of some crystal grains in the piezoelectric layer 107 (for example, crystal grains in two side portions 115 of the protruded portion 107 a) and non-parallel with another part of crystal grains (for example, crystal grains in a middle portion 117 of the protruded portion 107 a), thereby reducing the electromechanical coupling coefficient and Q value of the thin film bulk acoustic resonator 100.
On the basis, the invention provides a method for forming a bulk acoustic wave resonance device, wherein a piezoelectric layer is formed and is positioned on the middle layer, the sacrificial layer and the first electrode layer. Since the top surfaces of the intermediate layer, the sacrificial layer and the first electrode layer are flush, the piezoelectric layer is formed without obviously turning crystal grains, thereby being beneficial to improving the electromechanical coupling coefficient of the resonance device and the Q value of the resonance device. In addition, the bulk acoustic wave resonance device is formed in a layer stacking mode, so that a bonding process is avoided, manufacturing steps are effectively simplified, and manufacturing cost is reduced.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Fig. 3 to 10 are schematic structural diagrams of steps of a method for forming a bulk acoustic wave resonator according to an embodiment of the present invention; FIG. 11 is a schematic structural view of a hexagonal crystal grain; FIG. 12 is a schematic diagram of the structure of different crystal grains.
Referring to fig. 3, a substrate 200 is provided.
In this embodiment, the substrate 200 is made of high-resistance silicon.
With continued reference to fig. 3, a polycrystalline table 201 is formed on the substrate 200.
In the present embodiment, the material of the polycrystalline table 201 includes, but is not limited to: a polycrystalline thin film.
In this embodiment, the material of the polycrystalline thin film includes, but is not limited to, at least one of the following: polycrystalline silicon, polycrystalline silicon nitride, polycrystalline silicon carbide. It should be noted that the polycrystalline layer 201 is formed between the substrate 200 and the subsequently formed intermediate layers, which helps to prevent the formation of a free electron layer on the surface of the substrate 200, thereby reducing the electrical loss caused by the substrate.
Referring to fig. 4, an intermediate layer 202 is formed on the substrate 200.
In the present embodiment, the intermediate layer 202 is in contact with the polycrystalline layer 202.
With continued reference to fig. 4, a first opening 203 is formed to be embedded in the middle layer 202.
In this embodiment, the method for forming the first opening 203 includes: forming a first patterned layer (not shown) on the intermediate layer 202, the first patterned layer exposing a portion of a top surface of the intermediate layer 202; etching the intermediate layer 202 by using the first patterning layer as a mask to form the first opening 203; after the first opening 203 is formed, the first patterning layer is removed.
In this embodiment, the material of the intermediate layer 202 includes, but is not limited to, at least one of the following: polymer, insulating dielectric.
In this embodiment, the polymer includes, but is not limited to, at least one of: benzocyclobutene (i.e., BCB), photosensitive epoxy photoresist (e.g., SU-8), polyimide.
In this embodiment, the insulating dielectric includes, but is not limited to, at least one of: silicon dioxide, silicon nitride, titanium oxide.
Referring to fig. 5, a sacrificial layer 204 is formed within the first opening 203, wherein a top surface of the sacrificial layer 204 is flush with a top surface of the intermediate layer 202.
In this embodiment, the method for forming the sacrificial layer 204 includes: forming a sacrificial material layer (not shown) within the first opening 203 and on the intermediate layer 202; the sacrificial material layer is planarized until the top surface of the intermediate layer 202 is exposed, forming the sacrificial layer 204.
In this embodiment, the process of planarizing the sacrificial material layer includes, but is not limited to: and (5) carrying out a chemical mechanical polishing process.
In this embodiment, the material of the sacrificial layer 204 includes, but is not limited to, at least one of the following: polymer, silicon dioxide, doped silicon dioxide, polysilicon.
In this embodiment, the polymer includes, but is not limited to, at least one of: benzocyclobutene (i.e., BCB), photosensitive epoxy photoresist (e.g., SU-8), polyimide. The doped silica is silica doped with other elements.
With reference to fig. 5, in the present embodiment, before forming the sacrificial layer 204, the method further includes: an etching mask layer 205 is formed on the sidewall and bottom surface of the first opening 203.
In this embodiment, the material of the etching mask layer 205 includes, but is not limited to, at least one of the following: aluminum nitride, silicon carbide, diamond, silicon nitride, silicon dioxide, aluminum oxide, titanium dioxide.
In this embodiment, the thicknesses of the etching mask layer 205 include, but are not limited to: 0.1 to 3 microns.
Referring to fig. 6, a second opening 206 is formed to be embedded in the intermediate layer 202 and the sacrificial layer 204.
In this embodiment, the method for forming the second opening 206 includes: forming a second patterned layer (not shown) on the intermediate layer 202 and the sacrificial layer 204, the second patterned layer exposing a portion of the top surface of the intermediate layer 202 and the sacrificial layer 204; etching the intermediate layer 202 and the sacrificial layer 204 by using the second patterning layer as a mask to form the second opening 206; after forming the second opening 206, the second patterned layer is removed.
Referring to fig. 7, a first electrode layer 207 is formed within the second opening 206, and a top surface of the first electrode layer 207 is flush with a top surface of the intermediate layer 202.
In this embodiment, the method for forming the first electrode layer 207 in the second opening 206 includes: forming a first electrode material layer (not shown) in the second opening 206 and on the surfaces of the intermediate layer 202 and the sacrificial layer 204; the first electrode material layer is planarized until the top surfaces of the intermediate layer 202 and the sacrificial layer 204 are exposed, forming the first electrode layer 207.
In this embodiment, the process of performing the planarization process on the first electrode material layer includes, but is not limited to: and (5) carrying out a chemical mechanical polishing process.
In this embodiment, the material of the first electrode layer 207 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum.
Referring to fig. 8, a piezoelectric layer 208 is formed on the intermediate layer 202, the sacrificial layer 204, and the first electrode layer 207.
It should be noted that, since the top surfaces of the intermediate layer 202, the sacrificial layer 204 and the first electrode layer 207 are flush, the piezoelectric layer 208 is formed without including grains with obvious turning directions, thereby contributing to the improvement of the electromechanical coupling coefficient of the resonant device and the Q value of the resonant device.
In this embodiment, the material of the piezoelectric layer 208 includes, but is not limited to, at least one of: aluminum nitride, aluminum nitride alloy, gallium nitride, zinc oxide, lithium tantalate, lithium niobate, lead zirconate titanate, lead magnesium niobate-lead titanate.
In the present embodiment, the piezoelectric layer 208 includes a plurality of grains including a first grain and a second grain, wherein the first grain and the second grain are any two grains of the plurality of grains. Those skilled in the art know that the crystal orientation, crystal plane, etc. of the crystal grain can be expressed based on a coordinate system. As shown in fig. 11, the hexagonal crystal grains, for example, aluminum nitride crystal grains, are represented by an ac three-dimensional coordinate system (including a-axis and c-axis). As shown in fig. 12, crystal grains in fig. 12 such as (i) orthorhombic system (a ≠ b ≠ c), (ii) tetragonal system (a ≠ b ≠ c), and (iii) cubic system (a ═ b ═ c), where a is the width of the crystal system, b is the height of the crystal system, and c is the length of the crystal system, are expressed by xyz cubic coordinate system (including x-axis, y-axis, and z-axis). In addition to the above two examples, the die may also be represented based on other coordinate systems known to those skilled in the art, and thus the present invention is not limited by the above two examples.
In this embodiment, the first die may be represented based on a first stereo coordinate system, and the second die may be represented based on a second stereo coordinate system, where the first stereo coordinate system at least includes a first coordinate axis along a first direction and a third coordinate axis along a third direction, and the second stereo coordinate system at least includes a second coordinate axis along a second direction and a fourth coordinate axis along a fourth direction, where the first coordinate axis corresponds to a height of the first die, and the second coordinate axis corresponds to a height of the second die.
In this embodiment, the first direction and the second direction are the same or opposite. It should be noted that the first direction and the second direction are the same: the included angle range of the vector along the first direction and the vector along the second direction comprises 0 degree to 5 degrees; the first direction and the second direction are opposite to each other: an included angle range of a vector along the first direction and a vector along the second direction includes 175 degrees to 180 degrees.
In other embodiments, the first stereo coordinate system is an ac stereo coordinate system, wherein the first coordinate axis is a first c-axis, and the third coordinate axis is a first a-axis; the second three-dimensional coordinate system is an ac three-dimensional coordinate system, the second coordinate axis is a second c-axis, the fourth coordinate axis is a second a-axis, and the first c-axis and the second c-axis are directed in the same direction or in opposite directions.
In other embodiments, the first stereoscopic coordinate system further includes a fifth coordinate axis along a fifth direction, and the second stereoscopic coordinate system further includes a sixth coordinate axis along a sixth direction. In other embodiments, the first direction and the second direction are the same or opposite, and the third direction and the fourth direction are the same or opposite. It should be noted that the third direction and the fourth direction are the same: the included angle range of the vector along the third direction and the vector along the fourth direction comprises 0 degree to 5 degrees; the third direction and the fourth direction are opposite to each other: an included angle range of a vector along the third direction and a vector along the fourth direction includes 175 degrees to 180 degrees.
In other embodiments, the first stereo coordinate system is an xyz stereo coordinate system, where the first coordinate axis is a first z axis, the third coordinate axis is a first y axis, and the fifth coordinate axis is a first x axis; the second three-dimensional coordinate system is an xyz three-dimensional coordinate system, the second coordinate axis is a second z axis, the fourth coordinate axis is a second y axis, and the sixth coordinate axis is a second x axis. In other embodiments, the first and second z-axes are oriented identically, and the first and second y-axes are oriented identically. In other embodiments, the first and second z-axes are oppositely directed and the first and second y-axes are oppositely directed. In other embodiments, the first and second z-axes are pointing in the same direction, and the first and second y-axes are pointing in opposite directions. In other embodiments, the first and second z-axes are oppositely directed, and the first and second y-axes are identically directed.
In this embodiment, the piezoelectric layer includes a plurality of crystal grains, and a half-width of a rocking curve of a crystal composed of the plurality of crystal grains is less than 2.5 degrees. It should be noted that a Rocking curve (Rocking curve) describes the angular divergence size of a specific crystal plane (a crystal plane determined by a diffraction angle) in a sample, and is represented by a planar coordinate system, wherein an abscissa is an included angle between the crystal plane and the sample plane, an ordinate represents the diffraction intensity of the crystal plane at a certain included angle, the Rocking curve is used for representing the crystal quality, and the smaller the half-peak width angle is, the better the crystal quality is. Further, the Full Width at Half Maximum (FWHM) refers to the distance between two points in one peak of the function, the front and rear function values of which are equal to Half of the peak value.
In this embodiment, the thickness range of the intermediate layer 202 is: 0.1 to 10 microns. The acoustic impedance of the intermediate layer 202 is significantly different from the acoustic impedance of the piezoelectric layer 208 so as to block the leakage of acoustic waves from the resonance region into the substrate 200.
Referring to fig. 9, a second electrode layer 209 is formed on the piezoelectric layer 208.
In this embodiment, the material of the second electrode layer 209 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum.
With reference to fig. 9, in the present embodiment, after forming the second electrode layer 209, the method further includes: an edge structure 210 is formed on the piezoelectric layer 208, the edge structure 210 is in contact with the piezoelectric layer 208, and the edge structure 210 is in a ring shape and is located at an edge of a superposition portion of the second electrode layer 209 and the first electrode layer 207. The edge structure 210 can be used to limit lateral wave leakage so that the Q value of the resonant device can be increased.
Referring to fig. 10, after the second electrode layer 209 is formed, the sacrificial layer 207 is removed, a cavity 211 is formed between the piezoelectric layer 208 and the intermediate layer 202, and one end of the first electrode layer 207 is located in the cavity 211.
In the embodiment, the bulk acoustic wave resonator is formed by stacking layers, so that a bonding process is avoided, manufacturing steps are effectively simplified, and manufacturing cost is reduced.
In this embodiment, the method for removing the sacrificial layer 204 includes, but is not limited to, at least one of the following: oxygen ion etching, hydrofluoric acid etching and xenon difluoride etching.
In this embodiment, the material of the sacrificial layer 204 is different from the material of the intermediate layer 202 and the first electrode layer 207. The purpose of this is to reduce the etching damage to the intermediate layer 202 and the first electrode layer 207 during the process of removing the sacrificial layer 204.
In this embodiment, when the sacrificial layer 204 is removed by etching to form a cavity, the etching shielding layer 205 may serve to protect the intermediate layer 202. In addition, the etched shielding layer 205 may also serve to protect the resonator device from water and oxygen.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (20)
1. A method of forming a bulk acoustic wave resonator device, comprising:
providing a substrate;
forming an intermediate layer on the substrate;
forming a first opening embedded in the intermediate layer;
forming a sacrificial layer in the first opening, wherein the top surface of the sacrificial layer is flush with the top surface of the intermediate layer;
forming a second opening, embedding the intermediate layer and the sacrificial layer;
forming a first electrode layer within the second opening, a top surface of the first electrode layer being flush with a top surface of the intermediate layer;
forming a piezoelectric layer on the intermediate layer, on the sacrificial layer, and on the first electrode layer;
a second electrode layer is formed on the piezoelectric layer.
2. The method of forming a bulk acoustic wave resonator device according to claim 1, wherein a material of the sacrifice layer is different from a material of the first electrode and the intermediate layer; the material of the sacrificial layer comprises: one or more of polymer, silicon dioxide, doped silicon dioxide, and polysilicon.
3. The method of forming a bulk acoustic wave resonator device according to claim 2, wherein the polymer comprises: one or more of benzocyclobutene, photosensitive epoxy resin photoresist and polyimide.
4. The method of forming a bulk acoustic wave resonator device according to claim 1, wherein the material of the intermediate layer includes: one or more of a polymer and an insulating dielectric.
5. The method of forming a bulk acoustic wave resonator device, according to claim 4, wherein the polymer comprises: one or more of benzocyclobutene, photosensitive epoxy resin photoresist and polyimide.
6. The method of forming a bulk acoustic wave resonator device according to claim 4, wherein the insulating dielectric comprises: one or more of aluminum nitride, silicon dioxide, silicon nitride, and titanium oxide.
7. The method of forming a bulk acoustic wave resonator device according to claim 1, wherein the piezoelectric layer includes a plurality of crystal grains including a first crystal grain and a second crystal grain, wherein the first crystal grain and the second crystal grain are any two crystal grains of the plurality of crystal grains; a first axis along a first direction corresponds to a height of the first die and a second axis along a second direction corresponds to a height of the second die, wherein the first direction and the second direction are the same or opposite.
8. The method of forming a bulk acoustic wave resonator device according to claim 7, wherein the first crystal grain corresponds to a first coordinate system, the first coordinate system including the first coordinate axis and a third coordinate axis along a third direction; the second crystal grain corresponds to a second coordinate system, and the second coordinate system comprises the second coordinate axis and a fourth coordinate axis along a fourth direction.
9. The method of forming a bulk acoustic wave resonator device according to claim 8, wherein the first coordinate system further includes a fifth coordinate axis in a fifth direction, and the second coordinate system further includes a sixth coordinate axis in a sixth direction.
10. The method of forming a bulk acoustic wave resonator device according to claim 9, wherein the third direction and the fourth direction are the same or opposite.
11. The method of forming a bulk acoustic wave resonator device according to claim 1, wherein the material of the piezoelectric layer comprises: one or more of aluminum nitride, aluminum nitride alloy, gallium nitride, zinc oxide, lithium tantalate, lithium niobate, lead zirconate titanate, and lead magnesium niobate-lead titanate.
12. The method of forming a bulk acoustic wave resonator device according to claim 1, further comprising, before forming the intermediate layer: forming a polycrystalline table on the substrate, the polycrystalline table being located between the substrate and the intermediate layer.
13. The method of forming a bulk acoustic wave resonator device according to claim 12, wherein the material of the polycrystalline layer comprises: a polycrystalline material.
14. The method of forming a bulk acoustic wave resonator device, according to claim 13, wherein the polycrystalline material comprises: one or more of polycrystalline silicon, polycrystalline silicon nitride and polycrystalline silicon carbide.
15. The method of forming a bulk acoustic wave resonator device according to claim 1, wherein the intermediate layer has a thickness in a range of: 0.1 to 10 microns.
16. The method of forming a bulk acoustic wave resonator device according to claim 1, further comprising, after forming the second electrode layer: and removing the sacrificial layer to form a cavity between the piezoelectric layer and the intermediate layer, wherein one end of the first electrode layer is positioned in the cavity.
17. The method of forming a bulk acoustic wave resonator device according to claim 1, further comprising, before forming the sacrifice layer: and forming an etching shielding layer on the side wall and the bottom surface of the first opening.
18. The method of forming a bulk acoustic wave resonator device according to claim 17, wherein the material of the etching shield layer comprises: one or more of aluminum nitride, silicon carbide, diamond, silicon nitride, silicon dioxide, aluminum oxide, and titanium dioxide.
19. The method of forming a bulk acoustic wave resonator device according to claim 17, wherein the etch shield layer has a thickness in a range of: 0.1 to 3 microns.
20. The method of forming a bulk acoustic wave resonator device according to claim 1, further comprising, after forming the second electrode layer: and forming an edge structure on the piezoelectric layer, wherein the edge structure is in contact with the piezoelectric layer and is annular and is positioned at the edge of the overlapped part of the second electrode layer and the first electrode layer.
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