CN116981336A - Bonding method and method for forming bulk acoustic wave device - Google Patents
Bonding method and method for forming bulk acoustic wave device Download PDFInfo
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- CN116981336A CN116981336A CN202310944049.1A CN202310944049A CN116981336A CN 116981336 A CN116981336 A CN 116981336A CN 202310944049 A CN202310944049 A CN 202310944049A CN 116981336 A CN116981336 A CN 116981336A
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/072—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by laminating or bonding of piezoelectric or electrostrictive bodies
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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
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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
- H03H3/08—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 resonators or networks using surface acoustic waves
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Abstract
The invention provides a bonding method and a forming method of a bulk acoustic wave device, wherein the bonding method comprises the following steps: providing a first substrate; forming a first bonding layer on a first substrate by adopting a physical vapor deposition process; providing a second substrate; forming a second bonding layer on the second substrate by adopting a thermal oxidation process; bonding the first bonding layer and the second bonding layer; and bonding the first bonding layer formed by using a physical vapor deposition process and the second bonding layer formed by using a thermal oxidation process, so that bonding energy between the first bonding layer and the second bonding layer is improved, stability and reliability between bonding surfaces are improved, and quality of a finally formed bulk acoustic wave device is improved.
Description
Technical Field
The present invention relates to the field of semiconductor technology, and in particular, to a bonding method and a method for forming a bulk acoustic wave 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, a low noise amplifier, and the like. Among other things, radio frequency filters include piezoelectric surface acoustic wave (Surface Acoustic Wave, SAW) filters, piezoelectric bulk acoustic wave (Bulk Acoustic Wave, BAW) filters, microelectromechanical system (Micro-Electro-Mechanical System, MEMS) filters, integrated passive device (Integrated Passive Devices, IPD) filters, and the like.
Compared with the prior generation dielectric filter and piezoelectric surface acoustic wave filter, the film bulk acoustic resonator (Film Bulk Acoustic wave Resonator, FBAR) has the characteristics of small volume, high quality factor (Q), high power capacity and easy integration, and is a core element of the radio frequency front end in modern mobile communication equipment. Generally, in the FBAR, a piezoelectric layer is formed on a wafer, and upper and lower electrodes are formed at upper and lower portions of the piezoelectric layer to apply electricity to the piezoelectric layer to vibrate and further improve resonance.
However, the quality of the currently formed Film Bulk Acoustic Resonator (FBAR) remains to be improved.
Disclosure of Invention
The invention solves the technical problem of providing a bonding method and a forming method of a bulk acoustic wave device, wherein a first bonding layer formed by a physical vapor deposition process and a second bonding layer formed by a thermal oxidation process are bonded, bonding energy between the first bonding layer and the second bonding layer is improved, stability and reliability between bonding surfaces are improved, and quality of the finally formed bulk acoustic wave device is improved.
In order to solve the above problems, the present invention provides a bonding method, comprising: providing a first substrate; forming a first bonding layer on a first substrate by adopting a physical vapor deposition process; providing a second substrate; forming a second bonding layer on the second substrate by adopting a thermal oxidation process; and bonding the first bonding layer and the second bonding layer.
Optionally, parameters of the physical vapor deposition process for forming the first bonding layer include: the process temperature ranges from 45 ℃ to 100 ℃ and the bias power is 115W to 165W.
Optionally, the thickness of the first bonding layer ranges from 1800 angstroms to 2500 angstroms.
Optionally, the thickness of the second bonding layer ranges from 1800 angstroms to 2000 angstroms.
Alternatively, the process temperature of the thermal oxidation process is in the range of 1000 ℃ to 1100 ℃.
Optionally, before forming the first bonding layer, forming a first device layer on the first substrate surface; the first device layer includes a metal.
Optionally, before bonding the first bonding layer and the second bonding layer, the method further includes: and carrying out surface treatment on the first bonding layer to enable the surface of the first bonding layer to have hydrogen bonds.
Optionally, before the surface treatment of the first bonding layer, planarization treatment is further included on the first bonding layer.
Optionally, before bonding the first bonding layer and the second bonding layer, the method further includes: and carrying out surface treatment on the second bonding layer to enable the surface of the second bonding layer to have hydrogen bonds.
Optionally, before the surface treatment of the second bonding layer, planarization treatment is further performed on the second bonding layer.
Optionally, the surface treatment process comprises a plasma activation process, the plasma activation process comprises one or more of a reactive ion etching process, an inductive coupling process, a microwave activation process or an external magnetic field-reactive ion etching process, wherein the type of ionized gas used in the plasma activation process comprises nitrogen, argon and oxygen, the activation time ranges from 20 seconds to 30 seconds, and the temperature ranges from 250 ℃ to 500 ℃.
Optionally, the material of the first bonding layer includes one or more of silicon, germanium, silicon dioxide, copper, and tantalum.
Optionally, the material of the second bonding layer includes one or more of silicon, germanium, silicon dioxide, copper, and tantalum.
Optionally, the material of the first substrate is one or more of a low-resistivity silicon material, 30-60 DEG Y-cut lithium tantalate and 110-130 DEG Y-cut lithium niobate, and the resistivity of the low-resistivity silicon material ranges from 0.1 ohm-cm to 100 ohm-cm; the second substrate is a high resistivity material, and the resistivity of the high resistivity material ranges from 3000 ohm-cm to 10000 ohm-cm.
Correspondingly, the invention also provides a method for forming the bulk acoustic wave device, which comprises the following steps: providing a transfer substrate; forming a device layer on a surface of a transfer substrate, the forming the device layer comprising: forming a surface piezoelectric layer on the transfer substrate, forming a first electrode layer on the surface of a part of the piezoelectric layer, forming a protective layer on the surface of the first electrode layer and the surface of the piezoelectric layer, and forming a sacrificial layer on the surface of a part of the protective layer corresponding to the first electrode layer; forming a first bonding layer on the surface of the device layer by adopting a physical vapor deposition process; providing a device substrate; forming a second bonding layer on the surface of the device substrate by adopting a thermal oxidation process; and turning over the transfer substrate, and bonding the first bonding layer and the second bonding layer.
Optionally, parameters of the physical vapor deposition process for forming the first bonding layer include: the process temperature ranges from 45 ℃ to 100 ℃, the bias power is 115W to 165W, and the thickness of the first bonding layer ranges from 1800 angstroms to 2500 angstroms.
Optionally, the process temperature of the thermal oxidation process ranges from 1000 ℃ to 1100 ℃, and the thickness of the second bonding layer ranges from 1800 angstroms to 2000 angstroms.
Optionally, before bonding the first bonding layer and the second bonding layer, the method further includes: flattening the surface of the first bonding layer and the surface of the second bonding layer respectively; after the planarization treatment, the surface of the first bonding layer and the surface of the second bonding layer are subjected to surface treatment, respectively, so that the surface of the first bonding layer and the surface of the second bonding layer have hydrogen bonds.
Optionally, after bonding the first bonding layer and the second bonding layer, the method further includes: removing the transfer substrate; forming a second electrode layer on the surface of a part of the piezoelectric layer, wherein the second electrode layer and the first electrode layer are correspondingly distributed on two sides of the piezoelectric layer; and removing the sacrificial layer to form an air gap.
Compared with the prior art, the technical scheme of the invention has the following advantages:
in the technical scheme of the bonding method, the physical vapor deposition process is adopted to form the first bonding layer on the first substrate, and the process temperature of the physical vapor deposition process is low, so that the performance of a device layer on the first substrate is not damaged, and the bonding process can be applied to a wider range; and simultaneously, bonding the first bonding layer formed by using a physical vapor deposition process and the second bonding layer formed by using a thermal oxidation process, wherein the density of silicon-oxygen covalent bonds generated on the surface of the second bonding layer is increased by using the thermal oxidation process, so that bonding energy between bonding surfaces is improved when the first bonding layer and the second bonding layer are bonded, stability and reliability between the bonding surfaces are improved, and the quality of final bonding is improved.
In the method for forming the bulk acoustic wave device, the physical vapor deposition process is adopted to form the first bonding layer on the surface of the device layer, and the bonding process can be applied to a wider range because the process temperature of the physical vapor deposition process is low and the performance of the device layer is not damaged; and simultaneously, bonding the first bonding layer formed by using a physical vapor deposition process and the second bonding layer formed by using a thermal oxidation process, wherein the density of silicon-oxygen covalent bonds generated on the surface of the second bonding layer is increased by using the thermal oxidation process, so that bonding energy between bonding surfaces is improved when the first bonding layer and the second bonding layer are bonded, stability and reliability between the bonding surfaces are improved, and the quality of final bonding is improved.
Drawings
FIGS. 1 to 5 are schematic views of a bonding process according to an embodiment of the present invention;
fig. 6 to 9 are schematic structural views of a bulk acoustic wave device in the process of forming the same according to an embodiment of the present invention.
Detailed Description
As with the background, there are still problems with forming thin Film Bulk Acoustic Resonators (FBARs).
The conventional normal-temperature direct bonding method adopted in the semiconductor process flow is to deposit furnace tube thermal oxide silicon dioxide on the surfaces of two wafers respectively, and then bond the wafers based on the furnace tube thermal oxide silicon dioxide, and the high-temperature process cannot be applied to the manufacture of filter devices because the furnace tube operation temperature is higher than 1000-1100 ℃. The thermal oxidation deposition of silicon dioxide is performed by plating an oxide film on the oxidized material (i.e., silicon wafer) at a high temperature, so that the method is not suitable for a semiconductor process flow including a previous process before bonding, and thus the current direct bonding process has a limited application range.
On the basis, the invention provides a bonding method, wherein a physical vapor deposition process is adopted to form a first bonding layer on a first substrate, the process temperature of the physical vapor deposition process is low, the performance of a device layer on the first substrate is not damaged, and the bonding process can be applied to a wider range; and simultaneously, the first bonding layer formed by using a physical vapor deposition process and the second bonding layer formed by using a thermal oxidation process are bonded, so that the bonding between bonding surfaces can be improved, the stability and the reliability between the bonding surfaces can be improved, and the quality of the final bonding can be improved.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
FIGS. 1 to 5 are schematic views of a bonding process according to an embodiment of the present invention; fig. 6 to 9 are schematic structural views of a bulk acoustic wave device in the process of forming the same according to an embodiment of the present invention.
First, referring to fig. 1, a first substrate 100 is provided.
The material of the first substrate 100 may be a high temperature resistant substrate material, or a non-high temperature resistant substrate material.
In the present embodiment, when the first substrate 100 is a non-high temperature resistant substrate, the material of the first substrate 100 is typically one or more of a low-resistivity silicon material, 30 ° to 60 ° Y-cut lithium tantalate, and 110 ° to 130 ° Y-cut lithium niobate, wherein the low-resistivity silicon material has a resistivity in the range of 0.1 ohm-cm to 100 ohm-cm.
Referring to fig. 2, a physical vapor deposition process is used to form a first bonding layer 101 on a first substrate 100.
In this embodiment, before the first bonding layer 101 is formed on the first substrate 100 by using the physical vapor deposition process, a first device layer (not shown in the drawing) is further formed on the surface of the first substrate 100, where the first device layer may be a bulk acoustic wave device, a memory device, or the like.
In this embodiment, the first device layer includes a metal.
In this embodiment, the first device layer forming process includes a metal deposition process, which results in a thermal oxidation process at a furnace operating temperature of 1000 ℃ to 1100 ℃ not suitable for a semiconductor process flow including a previous process before bonding, and limits the application range of the current direct bonding process.
In this embodiment, the material of the first bonding layer 101 is silicon dioxide.
In other embodiments, the material of the first bonding layer 101 includes semiconductor types such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), gallium phosphide (GaP), indium gallium arsenide phosphide (InGaAsP); the compounds include silicon dioxide (SiO 2 ) Lithium niobate (LiNbO) 3 ) Strontium titanate (SrTiO) 3 ) Yttria stabilized zirconia (ZrO) 2 :Y 2 O 3 ) Polyvinylidene fluoride (BaTiO) 3 ) Yttrium Barium Copper Oxide (YBCO), boron carbide (B) 4 C) Diamond (Diamond), silicon nitride (Si) 3 N 4 ) Barium fluoride (BaF) 2 ) Cerium fluoride (CeF) 3 ) Zinc selenide (ZnSe), metallic bismuth (Bi), copper (Cu), tantalum (Ta).
In this embodiment, parameters of the physical vapor deposition process for forming the first bonding layer 101 include: the process temperature is 45-100 ℃ and the bias power is 115-165W, so that the performance of the first device layer is ensured due to the low temperature of the physical vapor deposition process, and the limit of the application range of the direct bonding process is eliminated.
In the present embodiment, the thickness of the first bonding layer 101 ranges from 1800 to 2500 angstroms; when the thickness of the first bonding layer 101 is less than 1800 angstroms, the thickness of the first bonding layer 101 is thinner, reducing bonding performance; when the thickness of the first bonding layer 101 is greater than 2500 angstroms, the thickness of the first bonding layer 101 is thicker, which is not beneficial to forming a semiconductor device with high integration on the basis of ensuring bonding force.
Referring to fig. 3, a second substrate 200 is provided.
In this embodiment, the material of the second substrate 200 is a high temperature resistant material.
In this embodiment, the second substrate 200 is a high-resistivity material having a resistivity ranging from 3000 ohm-cm to 10000 ohm-cm.
In this embodiment, the high temperature resistance of the second substrate 200 is utilized to ensure that the performance of the second substrate is not damaged in the thermal oxidation process.
Referring to fig. 4, a second bonding layer 201 is formed on a second substrate 200 using a thermal oxidation process.
In this embodiment, the second device layer is not formed on the second substrate 200 before the second bonding layer 201 is formed.
In other embodiments, before forming the second bonding layer 201, the second device layer is formed on the second substrate 200, where the forming process of the second device layer does not include a metal deposition process, so that the thermal oxidation process may be included without damaging the performance of the second device layer, and the application range of the bonding method may be further expanded.
In this embodiment, the thickness of the second bonding layer 201 ranges from 1800 a to 2000 a, and when the thickness of the second bonding layer 201 is less than 1800 a, the thickness of the second bonding layer 201 is thinner, which is not beneficial to bonding; when the thickness of the second bonding layer 201 is greater than 2000 angstroms, the thickness of the second bonding layer 201 is thicker at this time, resulting in waste of material.
In this embodiment, the material of the second bonding layer 201 is silicon dioxide.
In other embodiments, the material of the second bonding layer 201 includes semiconductor species such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), gallium phosphide (GaP), indium gallium arsenide phosphide (InGaAsP); the compounds include silicon dioxide (SiO 2 ) Lithium niobate (LiNbO) 3 ) Strontium titanate (SrTiO) 3 ) Yttria stabilized zirconia (ZrO) 2 :Y 2 O 3 ) Polyvinylidene fluoride (BaTiO) 3 ) Yttrium Barium Copper Oxide (YBCO), boron carbide (B) 4 C) Diamond (Diamond), silicon nitride (Si) 3 N 4 ) Barium fluoride (BaF) 2 ) Cerium fluoride (CeF) 3 ) Zinc selenide (ZnSe), metallic bismuth (Bi), copper (Cu), tantalum (Ta).
In this embodiment, the process temperature of the thermal oxidation process ranges from 1000 ℃ to 1100 ℃.
Referring to fig. 5, the first bonding layer 101 and the second bonding layer 201 are bonded.
Before bonding the first bonding layer 101, performing planarization treatment on the first bonding layer 101; the first bonding layer 101 is subjected to a surface treatment to make the surface of the first bonding layer 101 have hydrogen bonds.
Before bonding the second bonding layer 201, performing planarization treatment on the second bonding layer 201; the second bonding layer 201 is surface-treated to have hydrogen bonds on the surface of the second bonding layer 201.
In the present embodiment, the surfaces of the first bonding layer 101 and the second bonding layer 201 are made very smooth by the planarization process.
In this embodiment, after the planarization process, before the surface treatment, cleaning is further performed on the surfaces of the first bonding layer 101 and the second bonding layer 201, so as to remove impurities such as surface particles, organic matters, and metal ions.
In this embodiment, the surface treatment process includes a plasma activation process, the plasma activation process includes one or more of a reactive ion etching process, an inductive coupling process, a microwave activation process, or an external magnetic field-reactive ion etching process, wherein the plasma activation process employs ionized gas types including nitrogen, argon, and oxygen, the activation time ranges from 20 seconds to 30 seconds, and the temperature ranges from 250 ℃ to 500 ℃.
In this embodiment, the first bonding layer 101 and the second bonding layer 201 are bonded by hydrogen bonding, and hydrogen bonding can be spontaneously bonded directly by attractive force between surfaces without pressurization.
In this embodiment, the physical vapor deposition process is used to form the first bonding layer 101 on the first substrate 100, and the process temperature of the physical vapor deposition process is low, so that the performance of the first device layer on the first substrate 100 is not damaged, and the bonding process can be applied in a wider range; and simultaneously, the first bonding layer 101 formed by using a physical vapor deposition process and the second bonding layer 201 formed by using a thermal oxidation process are bonded, so that the bonding between bonding surfaces can be improved, the stability and the reliability between the bonding surfaces can be improved, and the quality of the final bonding can be improved.
Correspondingly, the invention also provides a method for forming the bulk acoustic wave device, please refer to fig. 6, and a transfer substrate 301 is provided.
In this embodiment, the material of the transfer substrate 301 is a high temperature resistant substrate material.
In other embodiments, the material of transfer substrate 301 is a non-refractory substrate material.
In this embodiment, the material of the transfer substrate 301 is a normal silicon material, and the resistivity ranges from 0.1 ohm-cm to 100 ohm-cm.
In other embodiments, transfer substrate 301 may also employ one or more of other low resistivity silicon materials, 30-60Y cut lithium tantalate, and 110-130Y cut lithium niobate.
With continued reference to fig. 6, forming a device layer on the surface of the transfer substrate 301 includes forming a piezoelectric layer 302 on the surface of the transfer substrate 301, forming a first electrode layer 304 on the surface of a portion of the piezoelectric layer 302, forming a protective layer 303 on the surface of the first electrode layer 304 and the surface of the piezoelectric layer 302, and forming a sacrificial layer 305 on the surface of a portion of the protective layer 303 corresponding to the first electrode layer 304.
In this embodiment, the material of the first electrode layer 304 is metal.
In this embodiment, the material of the sacrificial layer 305 is polysilicon.
In other embodiments, the material of the sacrificial layer 305 includes one or more of polysilicon, silicon oxide, a polymer, or a metal alloy.
With continued reference to fig. 6, a physical vapor deposition process is used to form a first bonding layer 306 on the surface of the device layer.
Parameters of the physical vapor deposition process for forming the first bonding layer 306 include: the process temperature ranges from 45 ℃ to 100 ℃, the bias power is 115W to 165W, and the thickness of the first bonding layer 306 ranges from 1800 angstroms to 2500 angstroms.
In the embodiment, the temperature of the physical vapor deposition process is low, so that the performance of the device layer is not damaged, the performance of the device layer is ensured, and the limitation of the application range of the direct bonding process is eliminated.
In this embodiment, a first bonding layer 306 is formed on the surface of the protective layer 303, and the first bonding layer 306 covers the sacrificial layer 305.
In the present embodiment, the thickness of the first bonding layer 306 ranges from 1800 to 2500; when the thickness of the first bonding layer 101 is less than 1800 angstroms, the thickness of the first bonding layer 306 is thinner, reducing bonding performance; when the thickness of the first bonding layer 306 is greater than 2500 angstroms, the thickness of the first bonding layer 101 is thicker, which is not beneficial to forming a semiconductor device with high integration on the basis of ensuring bonding force.
In this embodiment, the material of the first bonding layer 306 is silicon dioxide.
In other embodiments, the material of the first bonding layer 306 includes semiconductor species such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), gallium phosphide (GaP), indium gallium arsenide phosphide (InGaAsP); the compounds include silicon dioxide (SiO 2 ) Lithium niobate (LiNbO) 3 ) Strontium titanate (SrTiO) 3 ) Yttria stabilized zirconia (ZrO) 2 :Y 2 O 3 ) Polyvinylidene fluoride (BaTiO) 3 ) Yttrium Barium Copper Oxide (YBCO), boron carbide (B) 4 C) Diamond (Diamond), silicon nitride (Si) 3 N 4 ) Barium fluoride (BaF) 2 ) Cerium fluoride (CeF) 3 ) Zinc selenide (ZnSe), metallic bismuth (Bi), copper (Cu), tantalum (Ta).
Referring to fig. 7, a device substrate 307 is provided, and a thermal oxidation process is used to form a second bonding layer 309 on the surface of the device substrate 307.
In this embodiment, the material of the device substrate 307 is a high temperature resistant material, the device substrate is a high resistivity material, and the resistivity of the high resistivity material ranges from 3000 ohm-cm to 10000 ohm-cm.
In this embodiment, forming the second bonding layer 309 on the device substrate 307 further includes forming a capture layer 308 on a surface of the device substrate 307.
In this embodiment, the material of the trapping layer 308 (e.g., carrier trap layer, i.e., trap-rich layer) is polysilicon, which can trap charges generated between the device substrate 307 and the bonding layer, and reduce the electrical loss of the device, thereby improving the device performance.
In the present embodiment, the process temperature of the thermal oxidation process ranges from 1000 ℃ to 1100 ℃, and the thickness of the second bonding layer 309 ranges from 1800 angstroms to 2000 angstroms.
In the present embodiment, the thickness of the second bonding layer 309 ranges from 1800 a to 2000 a, and when the thickness of the second bonding layer 309 is less than 1800 a, the thickness of the second bonding layer 309 is thinner, which is not beneficial to bonding; when the thickness of the second bonding layer 309 is greater than 2000 angstroms, the thickness of the second bonding layer 309 is thicker at this time, resulting in waste of material.
In this embodiment, the material of the second bonding layer 309 is silicon dioxide.
In other embodiments, the material of the second bonding layer 309 includes semiconductor species such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), gallium phosphide (GaP), indium gallium arsenide phosphide (InGaAsP); the compounds include silicon dioxide (SiO 2 ) Lithium niobate (LiNbO) 3 ) Strontium titanate (SrTiO) 3 ) Yttria stabilized zirconia (ZrO) 2 :Y 2 O 3 ) Polyvinylidene fluoride (BaTiO) 3 ) Yttrium Barium Copper Oxide (YBCO), boron carbide (B) 4 C) Diamond (Diamond), silicon nitride (Si) 3 N 4 ) Barium fluoride (BaF) 2 ) Cerium fluoride (CeF) 3 ) Zinc selenide (ZnSe), metallic bismuth (Bi), copper (Cu), tantalum (Ta).
Referring to fig. 8, the transfer substrate 301 is flipped and the first bonding layer 306 and the second bonding layer 309 are bonded.
In this embodiment, before bonding the first bonding layer 306 and the second bonding layer 309, the planarization process is further performed on the surface of the first bonding layer 306 and the surface of the second bonding layer 309, respectively; after the planarization treatment, the surface of the first bonding layer 306 and the surface of the second bonding layer 309 are subjected to surface treatment, respectively, so that the surface of the first bonding layer 306 and the surface of the second bonding layer 309 have hydrogen bonds.
In this embodiment, the first bonding layer 306 is formed on the surface of the device layer by adopting a physical vapor deposition process, and the performance of the device layer is not damaged due to the low process temperature of the physical vapor deposition process, so that the bonding process can be applied to a wider range; and meanwhile, the first bonding layer 306 formed by the physical vapor deposition process and the second bonding layer 309 formed by the thermal oxidation process are bonded, so that bonding energy between the first bonding layer 306 and the second bonding layer 309 is improved, stability and reliability between the first bonding layer 306 and the second bonding layer 309 are improved, and quality of a final bulk acoustic wave device is improved.
In this embodiment, the surfaces of the first bonding layer 306 and the second bonding layer 309 are made very smooth by the planarization process.
In this embodiment, after the planarization process, before the surface treatment, cleaning is further performed on the surfaces of the first bonding layer 306 and the second bonding layer 309, so as to remove impurities such as surface particles, organic matters, and metal ions.
In this embodiment, the surface treatment process includes a plasma activation process including one or more of a reactive ion etching process, an inductive coupling process, a microwave activation process, or an external magnetic field-reactive ion etching process, wherein the type of ionized gas employed in the plasma activation process includes N 2 Ar and O 2 The activation time ranges from 20 seconds to 30 seconds and the temperature ranges from 250 ℃ to 500 ℃.
Referring to fig. 9, after bonding the first bonding layer 306 and the second bonding layer 309, removing the transfer substrate 301 is further included; forming a second electrode layer 311 on the surface of a part of the piezoelectric layer 302, wherein the second electrode layer 311 and the first electrode layer 304 are correspondingly distributed on two sides of the piezoelectric layer 302; the sacrificial layer 305 is removed to form an air gap 310.
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 (19)
1. A bonding method, comprising:
providing a first substrate;
forming a first bonding layer on the first substrate by adopting a physical vapor deposition process;
providing a second substrate;
forming a second bonding layer on the second substrate by adopting a thermal oxidation process;
and bonding the first bonding layer and the second bonding layer.
2. The bonding method of claim 1, wherein the parameters of the physical vapor deposition process forming the first bonding layer comprise: the process temperature ranges from 45 ℃ to 100 ℃ and the bias power is 115W to 165W.
3. The bonding method of claim 1, wherein the first bonding layer has a thickness in the range of 1800 angstroms to 2500 angstroms.
4. The bonding method according to claim 1, wherein the thickness of the second bonding layer ranges from 1800 angstroms to 2000 angstroms.
5. The bonding method according to claim 1, wherein the thermal oxidation process has a process temperature ranging from 1000 ℃ to 1100 ℃.
6. The bonding method of claim 1, wherein a first device layer is formed on the first substrate surface prior to forming the first bonding layer; the first device layer includes a metal.
7. The bonding method according to claim 1, further comprising, before bonding the first bonding layer and the second bonding layer: and carrying out surface treatment on the first bonding layer to enable the surface of the first bonding layer to have hydrogen bonds.
8. The bonding method according to claim 7, further comprising planarizing the first bonding layer before the surface treatment of the first bonding layer.
9. The bonding method according to claim 7, further comprising, before bonding the first bonding layer and the second bonding layer: and carrying out surface treatment on the second bonding layer to enable the surface of the second bonding layer to have hydrogen bonds.
10. The bonding method according to claim 9, further comprising planarizing the second bonding layer before the surface treatment of the second bonding layer.
11. The bonding method of claim 10, wherein the surface treatment process comprises a plasma activation process comprising one or more of a reactive ion etching process, an inductive coupling process, a microwave activation process, or an external magnetic field-reactive ion etching process, wherein the plasma activation process employs ionized gas types comprising nitrogen, argon, and oxygen for an activation time ranging from 20 seconds to 30 seconds and a temperature ranging from 250 ℃ to 500 ℃.
12. The bonding method of claim 1, wherein the material of the first bonding layer comprises one or more of silicon, germanium, silicon dioxide, copper, and tantalum.
13. The bonding method of claim 1, wherein the material of the second bonding layer comprises one or more of silicon, germanium, silicon dioxide, copper, and tantalum.
14. The bonding method according to claim 1, wherein the material of the first substrate is one or more of a low-resistivity silicon material, 30 ° to 60 ° Y-cut lithium tantalate, and 110 ° to 130 ° Y-cut lithium niobate, the low-resistivity silicon material having a resistivity in the range of 0.1 ohm-cm to 100 ohm-cm; the second substrate is made of a high-resistivity material, and the resistivity of the high-resistivity material ranges from 3000 ohm-cm to 10000 ohm-cm.
15. A method of forming a bulk acoustic wave device, comprising:
providing a transfer substrate;
forming a device layer on the surface of the transfer substrate, the forming the device layer comprising:
forming a surface piezoelectric layer positioned on the transfer substrate, forming a first electrode layer positioned on the surface of part of the piezoelectric layer, forming a protective layer on the surface of the first electrode layer and the surface of the piezoelectric layer, and forming a sacrificial layer positioned on the surface of part of the protective layer corresponding to the first electrode layer;
forming a first bonding layer on the surface of the device layer by adopting a physical vapor deposition process;
providing a device substrate;
forming a second bonding layer on the surface of the device substrate by adopting a thermal oxidation process;
and turning over the transfer substrate, and bonding the first bonding layer and the second bonding layer.
16. The method of forming a bulk acoustic wave device of claim 15, wherein the parameters of the physical vapor deposition process for forming the first bonding layer comprise: the process temperature ranges from 45 ℃ to 100 ℃, the bias power is 115W to 165W, and the thickness of the first bonding layer ranges from 1800 angstroms to 2500 angstroms.
17. The method of forming a bulk acoustic wave device according to claim 15, wherein a process temperature of the thermal oxidation process ranges from 1000 ℃ to 1100 ℃, and a thickness of the second bonding layer ranges from 1800 angstroms to 2000 angstroms.
18. The method of forming a bulk acoustic wave device of claim 15, further comprising, prior to bonding the first bonding layer and the second bonding layer:
flattening the surface of the first bonding layer and the surface of the second bonding layer respectively; after the planarization treatment, the surface of the first bonding layer and the surface of the second bonding layer are subjected to surface treatment respectively, so that the surfaces of the first bonding layer and the second bonding layer have hydrogen bonds.
19. The method of forming a bulk acoustic wave device of claim 15, further comprising, after bonding the first bonding layer and the second bonding layer: removing the transfer substrate; forming a second electrode layer on the surface of part of the piezoelectric layer, wherein the second electrode layer and the first electrode layer are correspondingly distributed on two sides of the piezoelectric layer; and removing the sacrificial layer to form an air gap.
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