CN113800465B - Process manufacturing method of capacitive micromachined ultrasonic transducer - Google Patents
Process manufacturing method of capacitive micromachined ultrasonic transducer Download PDFInfo
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- CN113800465B CN113800465B CN202110968958.XA CN202110968958A CN113800465B CN 113800465 B CN113800465 B CN 113800465B CN 202110968958 A CN202110968958 A CN 202110968958A CN 113800465 B CN113800465 B CN 113800465B
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- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 239000011248 coating agent Substances 0.000 claims abstract description 62
- 238000000576 coating method Methods 0.000 claims abstract description 62
- 239000000758 substrate Substances 0.000 claims abstract description 24
- 230000000873 masking effect Effects 0.000 claims abstract description 22
- 229910052751 metal Inorganic materials 0.000 claims abstract description 18
- 239000002184 metal Substances 0.000 claims abstract description 18
- 238000007789 sealing Methods 0.000 claims abstract description 16
- 238000000059 patterning Methods 0.000 claims abstract description 15
- 238000001704 evaporation Methods 0.000 claims abstract description 7
- 239000003960 organic solvent Substances 0.000 claims abstract description 3
- 239000003292 glue Substances 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 13
- 229920002120 photoresistant polymer Polymers 0.000 claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims description 11
- 239000010703 silicon Substances 0.000 claims description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 10
- 238000004528 spin coating Methods 0.000 claims description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 5
- 239000003518 caustics Substances 0.000 claims description 5
- 229910052804 chromium Inorganic materials 0.000 claims description 5
- 239000011651 chromium Substances 0.000 claims description 5
- 238000001259 photo etching Methods 0.000 claims description 5
- 230000008020 evaporation Effects 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- 238000002604 ultrasonography Methods 0.000 claims description 3
- VRBFTYUMFJWSJY-UHFFFAOYSA-N 28804-46-8 Chemical compound ClC1CC(C=C2)=CC=C2C(Cl)CC2=CC=C1C=C2 VRBFTYUMFJWSJY-UHFFFAOYSA-N 0.000 claims description 2
- 238000005137 deposition process Methods 0.000 claims description 2
- 229920001486 SU-8 photoresist Polymers 0.000 description 12
- 235000012431 wafers Nutrition 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000000206 photolithography Methods 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000012285 ultrasound imaging Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000001883 metal evaporation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000009281 ultraviolet germicidal irradiation Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
- B81C1/00261—Processes for packaging MEMS devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/03—Microengines and actuators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C2201/00—Manufacture or treatment of microstructural devices or systems
- B81C2201/01—Manufacture or treatment of microstructural devices or systems in or on a substrate
- B81C2201/0101—Shaping material; Structuring the bulk substrate or layers on the substrate; Film patterning
- B81C2201/0156—Lithographic techniques
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Transducers For Ultrasonic Waves (AREA)
- Micromachines (AREA)
Abstract
The invention relates to a capacitive ultrasonic transducer process manufacturing method, which comprises the following steps: coating a sacrificial layer full coating on the upper surface of the substrate; coating a masking layer full-coating on the upper surface of the sacrificial layer full-coating, and patterning to form a masking layer; immersing the substrate in a developer to etch the sacrificial layer full-coating and the masking layer exposed area; immersing the substrate in an organic solvent to remove all masking layers and form a sacrificial layer pattern, wherein the sacrificial layer comprises a cavity positioned in the middle, a cross-shaped cross sacrificial channel and four sacrificial channel holes; coating a vibrating diaphragm layer full coating with insulating property on the upper surface of the sacrificial layer, and patterning to form a vibrating diaphragm layer; coating a stripping layer full-coating on the upper surface of the vibrating diaphragm layer and patterning to form a stripping layer; evaporating the metal layer full coating on the upper surface of the stripping layer; manufacturing an upper electrode; releasing the sacrificial layer to form a cavity; and forming a sealing layer to obtain the complete vibrating element of the capacitive micromachined ultrasonic transducer. The invention also provides the vibrating element prepared by the method.
Description
Technical Field
The invention relates to a transducer processing method of MEMS technology, in particular to a process manufacturing method of a capacitive micromachined ultrasonic transducer.
Background
Ultrasound imaging is the most widely used medical imaging modality in the world, piezoelectric materials are the dominant materials in the ultrasound transducer industry, and this basic transducer mechanism has been continuously developed nearly a century ago. In ultrasound imaging systems, proper acoustic impedance matching between the transducer and the medium is critical, as such impedance matching has a profound effect on the efficiency of the system. For current piezoelectric systems, there is typically a high acoustic impedance mismatch, and most imaging transducers exhibit limited bandwidth.
Compared with the traditional piezoelectric ultrasonic transducer, the capacitive micromachined ultrasonic transducer is used as an emerging substitute, and has the advantages of wider bandwidth, high sensitivity, low noise, good impedance matching property and the like. The capacitive micromachined ultrasonic transducer has a sealed cavity between a stationary electrode and a suspended metal layer. Manufacturing cost and sensitivity are limiting factors for current capacitive micromachined ultrasonic transducers, depending on the manufacturing equipment, and particularly the materials used. For widespread use of capacitive micromachined ultrasonic transducers, there is a need to use inexpensive materials to maintain or improve existing sensitivity, thereby greatly reducing manufacturing costs. SU8 glue can be inexpensively used to fabricate capacitive micromachined ultrasonic transducers. The natural frequency of a capacitive micromachined ultrasonic transducer is generally determined by the radius of the diaphragm layer, the thickness of the diaphragm layer, the material of the diaphragm layer, and the like. However, changing the radius of the diaphragm layer requires changing the size of the mask, and changing the production flow of the diaphragm layer material is more complicated.
Disclosure of Invention
In view of the defects in the prior art, the invention provides a process manufacturing method of a capacitive micromachined ultrasonic transducer, which changes the natural frequency of the capacitive micromachined ultrasonic transducer by changing the thickness of a vibrating diaphragm layer, uses relatively simple equipment, reduces manufacturing steps, and can possibly increase the use of the capacitive micromachined ultrasonic transducer in the ultrasonic market. The technical proposal is as follows:
a capacitive ultrasound transducer process manufacturing method, comprising:
step S1: selecting a silicon wafer as a bottom electrode and a substrate;
step S2: coating a sacrificial layer full coating on the upper surface of the substrate;
step S3: coating a masking layer full-coating on the upper surface of the sacrificial layer full-coating, and patterning to form a masking layer;
step S4: immersing the substrate processed in the step S3 into a developer to etch the full coating of the sacrificial layer and the exposed area of the masking layer;
step S5: immersing the substrate processed in the step S4 into an organic solvent to remove all masking layers and form a sacrificial layer pattern, wherein the sacrificial layer comprises a cavity positioned in the middle, a cross-shaped cross sacrificial channel and four sacrificial channel holes;
step S6: coating a vibrating diaphragm layer full coating with insulating property on the upper surface of the sacrificial layer, and patterning to form a vibrating diaphragm layer;
step S7: coating a stripping layer full-coating on the upper surface of the vibrating diaphragm layer and patterning to form a stripping layer;
step S8: evaporating a metal layer full coating on the upper surface of the stripping layer;
s9, immersing the substrate processed in the step S8 into a solvent to peel off the vibrating element peeling layer and part of the metal layer full coating to form a metal layer pattern, thereby forming an upper electrode;
step S10: immersing the substrate processed in the step S9 into corrosive agents, wherein the corrosive agents enter the sacrificial channel through the sacrificial channel holes, so that the sacrificial layer is gradually released to form a cavity;
and S11, sealing the sacrificial channel hole after the sacrificial layer is released, and forming a sealing layer to obtain the complete vibrating element of the capacitive micromachined ultrasonic transducer.
Further, the sacrificial layer full coating, the masking layer full coating, the vibrating membrane layer full coating and the stripping layer full coating all adopt spin coating, so that the thicknesses of the sacrificial layer cavity, the cross-shaped cross sacrificial channels and the four sacrificial channel holes are consistent.
Further, the sacrificial layer cavity is a round cavity, and the sacrificial layer sacrificial channel hole is triangular.
Further, the masking layer adopts a photoetching process, and positive photoresist S1813 is exposed and developed to form a pattern;
further, the stripping layer is subjected to photoetching technology, and the positive photoresist AZP4620 is subjected to exposure and development to form a pattern.
Further, the diaphragm layer adopts a photoetching process, and a pattern is formed after exposure and development of negative photoresist SU 8; the stripping layer adopts stripping process, and the metal layer on the upper surface of the stripping layer is stripped together with the stripping layer.
And when the metal layer full coating is evaporated on the upper surface of the stripping layer, adopting an evaporation directional deposition process.
The invention also provides a capacitive micromachined ultrasonic transducer vibrating element manufactured by the method, which is characterized by comprising a silicon wafer substrate serving as a bottom electrode, a cavity positioned in the middle, a sacrificial channel hole, a vibrating diaphragm layer, an upper electrode, a sealing layer and a film supporting wall; the cavity is communicated with the sacrifice channel, the sacrifice channel is in a cross shape extending outwards from the cavity, and each end part of the sacrifice channel is provided with a sacrifice channel hole; the vibrating diaphragm layer is simultaneously used as an insulating layer; the cavity is positioned between the silicon wafer substrate and the vibrating diaphragm layer; the supporting wall surrounds the periphery of the cavity; a sealing layer is filled in each sacrificial passage hole; the upper electrode is positioned between the upper surface of the vibrating diaphragm layer and the sealing layer.
Further, the sacrificial layer cavity is a round cavity, and the sacrificial layer sacrificial channel hole is triangular.
Further, the vibrating diaphragm layer is made of SU8 glue.
Compared with the traditional process of manufacturing the capacitive micromachined ultrasonic transducer by adopting the sacrificial layer release method, the invention only changes the thickness of the vibrating diaphragm layer on the basis of not changing the radius of the vibrating diaphragm layer and the material of the vibrating diaphragm layer, thereby changing the natural frequency of the capacitive micromachined ultrasonic transducer. The thickness of the vibrating diaphragm layer has a larger influence on the natural frequency of the capacitive micromachined ultrasonic transducer, and the natural frequency of the capacitive micromachined ultrasonic transducer is improved by increasing the thickness of the vibrating diaphragm layer. The size of the mask plate is not required to be changed without changing the radius of the diaphragm layer, and the cost is reduced by using SU8 glue without changing the material of the diaphragm layer.
Drawings
In order to more clearly illustrate the manufacturing flow of the present invention, the drawings of the embodiments of the present invention will be correspondingly described.
FIG. 1 is a schematic flow chart of a manufacturing method according to an embodiment of the invention;
FIG. 2 is a schematic cross-sectional view of step S1 of the present invention.
FIG. 3 is a schematic cross-sectional structure of step S2 of the present invention.
Fig. 4 is a schematic cross-sectional structure of step S3 of the present invention.
FIG. 5 is a schematic diagram of the structure of the photolithography mask in step S3 of the present invention.
FIG. 6 is a schematic cross-sectional view of step S4 of the present invention.
FIG. 7 is a schematic cross-sectional view of step S5 of the present invention.
FIG. 8 is a schematic cross-sectional view of step S6 of the present invention.
FIG. 9 is a schematic diagram of the structure of the photolithography mask in step S6 of the present invention.
FIG. 10 is a schematic sectional view of the step S7 of the present invention.
FIG. 11 is a schematic diagram of the structure of the photolithography mask in step S7 of the present invention.
FIG. 12 is a schematic cross-sectional view of step S8 of the present invention.
Fig. 13 is a schematic cross-sectional structure of step S9 of the present invention.
Fig. 14 is a schematic cross-sectional structure of step S10 of the present invention.
Fig. 15 is a schematic cross-sectional structure of step S11 of the present invention.
Reference numerals illustrate:
21-silicon wafer substrate 31-sacrificial layer full coating
32-sacrificial layer 33-masking layer
41-sacrificial passage holes 42-sacrificial passages
43-cavity 51-diaphragm layer
61-release layer 71-electrode connecting wire
72 electrode pattern 81-full coating of metal layer
82-upper electrode 91-sealing layer
Detailed Description
The present invention will be further described in detail below with reference to the accompanying drawings in order to make the objects, technical solutions and advantages of the present invention more apparent.
The capacitive micromachined ultrasonic transducer provided by the invention is manufactured by adopting the SU8 glue, and the SU8 glue is manufactured into the vibrating diaphragm layer, so that the capacitive micromachined ultrasonic transducer can be used as a structural material for application due to unique dielectric and thermal properties, low density, photoinduced patternability, optical transparency and mechanical flexibility of the SU8 glue. The common methods for raising the natural frequency of the capacitive micromachined ultrasonic transducer include methods of reducing the radius of the diaphragm layer, increasing the thickness of the diaphragm layer, changing the material of the diaphragm layer, and the like. However, reducing the radius of the diaphragm layer, changing the diaphragm layer material adds additional manufacturing costs. Under the condition of not changing the size of the mask plate, the natural frequency of the capacitive micromachined ultrasonic transducer can be improved by properly increasing the thickness of the vibrating diaphragm.
FIG. 1 is a schematic diagram of a process flow for manufacturing a capacitive micromachined ultrasonic transducer, with specific manufacturing steps as shown below.
Step S1: a clean silicon wafer is selected as a bottom electrode and a substrate 21;
silicon wafers were fabricated prior to production using highly doped and clean silicon wafers (silicon purity 99.999%). The schematic cross-sectional structure is shown in fig. 2.
Step S2: spin-coating a sacrificial layer full-coating 31 on the upper surface of the substrate 21;
we spin-coated the concentrated version of the glue onto the substrate 21 and heated at 150 ℃ for 3 minutes to obtain the full coat 31 of sacrificial layer. The schematic cross-sectional structure is shown in fig. 3.
The sacrificial layer full-coat 31 uses Omnicoat glue that increases the adhesion of the diaphragm layer 51 to the substrate 21.
Step S3: spin-coating and patterning a masking layer full-coating on the upper surface of the sacrificial layer full-coating 31 to form a masking layer 33;
preparation of a layer of positive photoresist the pattern is prepared using ultraviolet light to create a pattern of masking layer 33 for selectively removing the underlying sacrificial layer full coating 31. The schematic cross-sectional structure is shown in fig. 4.
The positive photoresist is formed by exposing and developing the shading parts by using S1813 photoresist, and then forming a circular cavity 43, a cross-shaped cross sacrificial channel 42 and four triangular sacrificial channel holes 41 after patterning. A schematic of the structure of the lithographic reticle is shown in fig. 5.
Step S4: immersing the vibrating element in a developer to etch exposed areas of the sacrificial layer full-coating 31 and the masking layer 33;
immersed in an alkaline MF319 developer while etching the exposed areas of masking layer 33 and sacrificial layer full-coating 31; etching was stopped by rinsing the sample in deionized water solution. The schematic cross-sectional structure is shown in fig. 6.
Step S5: removing all masking layers 33 of the vibrating element in acetone to form a sacrificial layer 32 pattern, wherein the sacrificial layer 32 comprises a circular cavity 43, a crisscross sacrificial channel 42 and four triangular sacrificial channel holes 41; the schematic cross-sectional structure is shown in fig. 7.
Step S6: spin-coating and patterning the whole coating of the diaphragm layer on the upper surface of the sacrificial layer 32 to form a diaphragm layer 51;
a layer of SU8 glue was spun on the vibrating element at 2000RPM to obtain a full coating of the diaphragm layer. A short pre-bake was performed at 95 ℃ for 3 minutes prior to uv irradiation. The capacitive micromachined ultrasonic transducer was patterned under ultraviolet light and the sample was post-exposure baked and developed. The SU8 glue also has the function of an insulating layer, so that an additional insulating layer is not needed. The diaphragm layer 51 acts as a mechanical support and insulating layer for the top electrode to avoid any shorting due to the high dielectric strength of SU8 glue. A schematic cross-sectional structure is shown in fig. 8.
SU8 photoresist is a negative photoresist and mask process fabrication is opposite to positive photoresist. The non-shading parts are exposed and developed to leave patterns, and four triangular sacrificial channel holes 41 are formed after patterning. A schematic diagram of the structure of the photolithographic reticle is shown in fig. 9.
Step S7: spin-coating and patterning a release layer full-coating on the upper surface of the diaphragm layer 51 to form a release layer 61;
the release layer 61 uses AZP4620 positive photoresist, and a schematic cross-sectional structure is shown in fig. 10.
The AZP4620 positive photoresist shading part is exposed and developed to leave a pattern, the pattern is a circle 72 and a cross electrode connecting line 71, and the structural schematic diagram of the photoetching mask is shown in fig. 11.
Step S8: evaporating a metal layer full-coating 81 on the upper surface of the peeling layer 61;
the metal layer full coating 81 is selected for chromium because it has excellent adhesion to SU8 glue and low resistance, while the evaporation process is used, metal evaporation is superior to sputtering because it is directionally deposited, simplifying the lift-off process. A schematic cross-sectional structure is shown in fig. 12.
Step S9, immersing the vibrating element into a solvent to peel off the vibrating element peeling layer 61 and part of the metal layer full-coating 81 to form a metal layer pattern, thereby forming an upper electrode 82;
after the release layer 61 is developed by exposure, the release layer 61 is coated in all areas except the upper electrode area. After the metal layer full-coat 81 is evaporated, chromium in the area of the upper electrode 82 directly contacts SU8 glue and chromium in the other areas is evaporated on the release layer 61. After immersing in the MIF developer, the peeling layer 61 is peeled off together with the evaporated chromium on the peeling layer 61. A schematic cross-sectional structure is shown in fig. 13.
Step S10: immersing the vibrating element in an etchant, wherein the etchant enters the sacrificial channel 42 through the sacrificial channel hole 41, so that the sacrificial layer 32 is gradually released to form a circular cavity 43;
immersing the vibrating element in corrosive agent. The etchant penetrates the sacrificial via 42 and gradually removes the sacrificial layer 32. After the sacrificial layer 32 is completely removed, the vibrating element is immersed in deionized water to replace the etchant trapped in the circular cavity 43. Finally, the sample was immersed in isopropanol instead of water. A schematic cross-sectional structure is shown in fig. 14.
And S11, sealing the sacrificial channel hole 41 after the sacrificial layer 32 is released, and forming a sealing layer 91 to obtain the complete vibrating element of the capacitive micromachined ultrasonic transducer.
The sealing layer 91 uses a Parylene-C material having biocompatibility, optical transparency, low young's modulus, and a water absorption coefficient close to zero. In order to make the vibrating element waterproof, the vibrating element is sealed in a low-pressure chamber, and a sealed vacuum cavity is formed in the vibrating element, so that excellent electric insulation is provided. A schematic cross-sectional structure is shown in fig. 15.
In view of the foregoing, it will be appreciated that various modifications, adaptations and the like can be made by those skilled in the art in view of the foregoing description, and that these modifications, adaptations and the like are intended to be comprehended within the scope of the present invention as set forth in the following claims.
Claims (2)
1. A capacitive ultrasound transducer process manufacturing method, comprising:
step S1: selecting a silicon wafer as a bottom electrode and a substrate;
step S2: coating a sacrificial layer full coating on the upper surface of the substrate; the Omnicoat glue is used for the full coating of the sacrificial layer;
step S3: coating a masking layer full-coating on the upper surface of the sacrificial layer full-coating and patterning to form a masking layer, wherein the method comprises the following steps: preparing a layer of positive photoresist by using S1813 glue, preparing a pattern by using ultraviolet light to create a masking layer pattern for selectively removing the full coating of the sacrificial layer, and forming a circular cavity of the sacrificial layer, a cross-shaped cross sacrificial channel and four triangular sacrificial channel holes after patterning;
step S4: immersing the substrate processed in the step S3 into a developer to etch the full coating of the sacrificial layer and the exposed area of the masking layer;
step S5: immersing the substrate processed in the step S4 into an organic solvent to remove all masking layers and form a sacrificial layer pattern, wherein the sacrificial layer comprises a sacrificial layer circular cavity positioned in the middle, a cross-shaped cross sacrificial channel and four sacrificial channel holes;
step S6: coating a vibrating diaphragm layer full coating with insulating property on the upper surface of the sacrificial layer, and patterning to form a vibrating diaphragm layer; the diaphragm layer adopts a photoetching process, and a pattern is formed after exposure and development of negative photoresist SU 8;
step S7: coating a stripping layer full-coating on the upper surface of the vibrating diaphragm layer, and patterning to form a stripping layer, wherein the stripping layer uses AZP4620 positive photoresist;
step S8: evaporating a full coating of a metal layer on the upper surface of the stripping layer, wherein the full coating of the metal layer adopts chromium;
step S9: immersing the substrate processed in the step S8 into a solvent to peel off the vibrating element peeling layer and part of the metal layer full coating to form a metal layer pattern, thereby forming an upper electrode;
step S10: immersing the substrate processed in the step S9 into corrosive agents, wherein the corrosive agents enter the sacrificial channel through the sacrificial channel holes, so that the sacrificial layer is gradually released to form a sacrificial layer circular cavity;
step S11: sealing the sacrificial channel hole after the sacrificial layer is released, forming a sealing layer to obtain a complete vibrating element of the capacitive micromachined ultrasonic transducer, wherein the sealing layer is made of a Parylene-C material;
the sacrificial layer full coating, the masking layer full coating, the vibrating diaphragm layer full coating and the stripping layer full coating all adopt spin coating, so that the thicknesses of the circular cavity, the crisscross sacrificial channels and the four sacrificial channel holes of the sacrificial layer are consistent;
the prepared capacitive micromachined ultrasonic transducer vibrating element comprises a silicon wafer substrate serving as a bottom electrode, a sacrificial layer round cavity positioned in the middle, a sacrificial channel hole, a vibrating diaphragm layer, an upper electrode, a sealing layer and a film supporting wall; the sacrificial layer circular cavity is communicated with the sacrificial channel, the sacrificial channel is cross-shaped and extends outwards from the sacrificial layer circular cavity, and each end part of the sacrificial channel is provided with a sacrificial channel hole; the vibrating diaphragm layer is simultaneously used as an insulating layer; the sacrificial layer round cavity is positioned between the silicon wafer substrate and the vibrating diaphragm layer; the film supporting wall surrounds the round cavity of the sacrificial layer; a sealing layer is filled in each sacrificial passage hole; the upper electrode is positioned between the upper surface of the vibrating diaphragm layer and the sealing layer; the vibrating diaphragm layer is made of SU8 glue.
2. The process of claim 1 wherein the evaporation directional deposition process is used to evaporate the full coating of the metal layer on the top surface of the release layer.
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