Piezoelectric MEMS accelerometer and method of manufacture
By setting multiple piezoelectric sensitive structures at both ends of the cantilever structure of the piezoelectric MEMS accelerometer and connecting the electrodes with metal connecting wires, the problem of insufficient sensitivity in the prior art is solved, and the induced charge is significantly increased and the sensitivity is improved.
Patent Information
- Application Number
- CN202510246449.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-04
- Publication Date
- 2025-11-11
- Estimated Expiration
- 2045-03-04
AI Technical Summary
Existing piezoelectric MEMS accelerometers fail to fully utilize the deformation of the suspension beam (or diaphragm), resulting in low sensitivity.
First and second piezoelectric sensitive structures are respectively set at both ends of the cantilever structure of the piezoelectric MEMS accelerometer. The design pattern of upper electrode, piezoelectric layer and lower electrode is formed on the substrate surface by photolithography and etching technology. The electrodes are connected by metal connecting wires to increase the induced charge and improve the sensitivity.
By increasing the number and connection method of piezoelectric sensitive structures, the induced charge is greatly increased, and the sensitivity of the accelerometer is significantly improved.
Smart Images
Figure CN119873737B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of MEMS technology, and more specifically, to a piezoelectric MEMS accelerometer and its fabrication method. Background Technology
[0002] The working principle of a piezoelectric MEMS accelerometer: When vibrating, the mass block is subjected to an inertial force in the opposite direction of acceleration, and the piezoelectric film is subjected to an alternating force from the mass block that is proportional to the acceleration. Correspondingly, induced charges are generated on the electrodes, which are converted into voltage signals by a charge amplifier. When operating at a frequency far from the resonant frequency, the acceleration of the mass block is proportional to the induced charge of the device, thus achieving detection.
[0003] A piezoelectric MEMS accelerometer mainly consists of four parts: a suspended beam (or suspended membrane), a frame, a mass block, and a piezoelectric sensitive structure. The suspended beam can be a single beam or multiple symmetrically distributed beams, and the suspended membrane can be a membrane distributed in a centrally symmetrical manner. One end of the suspended beam (or suspended membrane) is connected to the frame, and the other end is connected to the mass block. The connection position between the suspended beam (or suspended membrane) and the frame is covered with a piezoelectric sensitive structure, which mainly includes a piezoelectric thin film and upper / lower electrodes. The frame also has lead wires for the upper / lower electrodes and PADs.
[0004] Existing piezoelectric MEMS accelerometers fail to fully utilize the deformation of the suspension beam (or diaphragm), resulting in low sensitivity. Summary of the Invention
[0005] The purpose of this application is to provide a piezoelectric MEMS accelerometer and its fabrication method to solve the problem that existing piezoelectric MEMS accelerometers fail to fully utilize the deformation of the suspension beam (or suspension membrane), resulting in low sensitivity.
[0006] This application provides a method for fabricating a piezoelectric MEMS accelerometer, comprising:
[0007] The upper electrode, piezoelectric layer, and lower electrode on the front side of the substrate are patterned to obtain a first piezoelectric sensitive structure and a second piezoelectric sensitive structure; wherein, the first piezoelectric sensitive structure includes a first upper electrode, a first piezoelectric layer, and a first lower electrode, and the second piezoelectric sensitive structure includes a second upper electrode, a second piezoelectric layer, and a second lower electrode;
[0008] On the front side of the substrate, a metal connecting line, a first PAD, and a second PAD are formed; wherein, the metal connecting line is used to connect the second upper electrode to the first lower electrode, and to connect the second lower electrode to the first upper electrode; the first PAD is connected to the first lower electrode, and the second PAD is connected to the first upper electrode;
[0009] The front and back sides of the substrate are patterned to obtain the cantilever structure, the vibration-sensitive structure, and the frame structure; wherein the first piezoelectric sensitive structure and the second piezoelectric sensitive structure are located at the two ends of the cantilever structure, respectively.
[0010] In the above technical solution, a first piezoelectric sensing structure and a second piezoelectric sensing structure are respectively provided at both ends of the cantilever structure of the piezoelectric MEMS accelerometer. When the piezoelectric MEMS accelerometer is subjected to positive acceleration, the first piezoelectric sensing structure undergoes positive deformation, and the first upper electrode and the first lower electrode generate induced charges +Q1 and -Q1, respectively; the second piezoelectric sensing structure undergoes reverse deformation, and the second upper electrode and the second lower electrode generate induced charges -Q2 and +Q2, respectively. Since the first upper electrode of the first piezoelectric sensing structure is connected to the second lower electrode of the second piezoelectric sensing structure, and the first lower electrode of the first piezoelectric sensing structure is connected to the second upper electrode of the second piezoelectric sensing structure, the overall induced charges of the first and second piezoelectric sensing structures are +(Q1+Q2) and -(Q1+Q2), which greatly increases the induced charge and improves the sensitivity.
[0011] In some alternative implementations, the upper electrode on the front side of the substrate is patterned, including:
[0012] The design patterns of the first and second upper electrodes are formed on the front side of the substrate by photolithography.
[0013] Etch away excess upper electrode metal to form the first upper electrode and the second upper electrode;
[0014] Clean off any remaining photoresist.
[0015] In the above technical solution, the design patterns of the first upper electrode and the second upper electrode are formed on the front side of the substrate by photolithography; the excess upper electrode metal is etched away by dry etching or wet etching to form the first upper electrode and the second upper electrode; finally, the photoresist is removed by organic solvent or oxygen plasma.
[0016] In some alternative implementations, the piezoelectric layer on the front side of the substrate is patterned, including:
[0017] After the top electrode is patterned, the design patterns of the first and second piezoelectric layers are formed on the front side of the substrate using photolithography.
[0018] Excess piezoelectric material is etched away to form a first piezoelectric layer and a second piezoelectric layer.
[0019] Clean off any remaining photoresist.
[0020] In the above technical solution, the design patterns of the first piezoelectric layer and the second piezoelectric layer are formed on the front side of the substrate by photolithography; the excess piezoelectric material is etched away by dry etching or wet etching to form the first piezoelectric layer and the second piezoelectric layer; and the photoresist is removed by organic cleaning or oxygen plasma.
[0021] In some alternative implementations, the lower electrode on the front side of the substrate is patterned, including:
[0022] After the piezoelectric layer is patterned, the design patterns of the first and second lower electrodes are formed on the front side of the substrate using photolithography.
[0023] Etch away excess lower electrode metal to form the first and second lower electrodes;
[0024] Clean off any remaining photoresist.
[0025] In the above technical solution, the design patterns of the first lower electrode and the second lower electrode are formed on the front side of the substrate by photolithography; the excess lower electrode metal is etched away by dry etching or wet etching to form the first lower electrode and the second lower electrode; and the photoresist is removed by organic cleaning or oxygen plasma.
[0026] In some alternative implementations, before forming the metal interconnect, the first PAD, and the second PAD on the front side of the substrate, the following is also included:
[0027] Deposit a medium layer on the front side of the substrate;
[0028] A design pattern of openings is formed on the front side of the substrate using photolithography; wherein, the first upper electrode, the first lower electrode, the second upper electrode, and the second lower electrode are connected to metal interconnects or PADs through the openings;
[0029] Etching away excess dielectric material forms an isolation film layer;
[0030] Clean off any remaining photoresist.
[0031] In the above technical solution, a dielectric layer is deposited on the substrate surface by reactive magnetron sputtering or CVD. The material can be SiO2, Al2O3, SiN, AlN, or a stacked hybrid structure of several materials. A design pattern for openings is formed on the front side of the substrate using photolithography. Excess dielectric material is etched away using dry etching or wet etching to form an isolation film. Finally, the photoresist is removed using organic cleaning or oxygen plasma.
[0032] In some alternative embodiments, a metal interconnect, a first pad, and a second pad are formed on the front side of the substrate, including:
[0033] The design pattern of metal interconnect lines, first PAD and second PAD is formed on the front side of the substrate by photolithography.
[0034] Deposit a metal layer on the front side of the substrate;
[0035] The photoresist and its metal layer are stripped to form metal interconnects, a first pad, and a second pad.
[0036] In the above technical solution, a design pattern of metal interconnects, a first PAD, and a second PAD is formed on the front side of the substrate using photolithography. A metal layer is deposited on the substrate surface using electron beam evaporation; the material can be Ti, Ni, Cr, Al, Ag, Pt, Au, or a stacked or mixed structure of several materials. The photoresist and the metal layer on top are then removed using a lift-off method to form the metal interconnects, the first PAD, and the second PAD.
[0037] In some alternative implementations, the front and back sides of the substrate are patterned to obtain cantilever structures, vibration-sensitive structures, and frame structures, including:
[0038] The design pattern of the device layer of the substrate is formed on the front side of the substrate using photolithography.
[0039] Etching away excess device layer material forms the shape of the cantilever structure, vibration-sensitive structure, and frame structure on the front side of the substrate;
[0040] Clean off any remaining photoresist.
[0041] In the above technical solution, the design pattern of the device layer of the substrate is formed on the front side of the substrate by photolithography; the excess device layer material is etched away by dry etching or wet etching to form the shape of the cantilever structure, vibration-sensitive structure and frame structure on the front side of the substrate; finally, the photoresist is removed by organic cleaning or oxygen plasma.
[0042] In some alternative implementations, the front and back sides of the substrate are patterned to obtain cantilever structures, vibration-sensitive structures, and frame structures, and the following are also included:
[0043] A front protective structure is provided on the front of the substrate;
[0044] The design pattern of the mass block is formed on the back side of the substrate using photolithography.
[0045] Etch away excess support layer material on the back of the substrate to form a mass block;
[0046] Clean off any remaining photoresist.
[0047] In the above technical solution, a front protective structure is set on the front side of the substrate; a design pattern of a mass block is formed on the back side of the substrate by photolithography; excess support layer material on the back side of the substrate is etched away by dry etching or wet etching to form the mass block; finally, the photoresist is removed by organic cleaning or oxygen plasma.
[0048] In some alternative implementations, the front and back sides of the substrate are patterned to obtain cantilever structures, vibration-sensitive structures, and frame structures, and the following are also included:
[0049] The design pattern of the support layer of the substrate is formed on the back side of the substrate using photolithography.
[0050] The excess support layer material on the back of the substrate is etched away to form the shape of the cantilever structure, vibration-sensitive structure and frame structure on the back of the substrate;
[0051] Clean off any remaining photoresist.
[0052] In the above technical solution, the design pattern of the support layer of the substrate is formed on the back side of the substrate by photolithography; the excess support layer material on the back side of the substrate is etched away by dry etching or wet etching to form the shape of the cantilever structure, vibration-sensitive structure and frame structure on the back side of the substrate; finally, the photoresist is removed by organic cleaning or oxygen plasma.
[0053] In some alternative implementations, the front and back sides of the substrate are patterned to obtain cantilever structures, vibration-sensitive structures, and frame structures, and the following are also included:
[0054] Etch away the excess buried oxide layer material on the back of the substrate to release the cantilever structure;
[0055] Remove the front protective structure.
[0056] In the above technical solution, excess buried oxide layer material on the back side of the substrate is etched away by vapor phase etching, wet etching, or dry etching to release the cantilever structure; finally, the front protective structure is removed, thus completing the fabrication of the piezoelectric MEMS accelerometer.
[0057] This application provides a piezoelectric MEMS accelerometer, comprising: a cantilever structure, a vibration-sensitive structure, and a frame structure; the cantilever structure includes a first piezoelectric sensitive structure, a second piezoelectric sensitive structure, and a cantilever.
[0058] A vibration-sensitive structure is fixedly connected to the lower surface of the first end of the cantilever, and a frame structure is fixedly connected to the lower surface of the second end of the cantilever.
[0059] A first piezoelectric sensitive structure is fixedly connected to the upper surface of the first end of the cantilever, and a second piezoelectric sensitive structure is fixedly connected to the upper surface of the second end of the cantilever.
[0060] The first piezoelectric sensing structure includes a first upper electrode, a first piezoelectric layer, and a first lower electrode; the second piezoelectric sensing structure includes a second upper electrode, a second piezoelectric layer, and a second lower electrode.
[0061] The first upper electrode and the second lower electrode are connected by a metal connecting wire; the first lower electrode is connected to the first PAD, and the first upper electrode is connected to the second PAD. Attached Figure Description
[0062] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0063] Figure 1 A flowchart illustrating the fabrication steps of a piezoelectric MEMS accelerometer provided in this application embodiment;
[0064] Figure 2 A schematic diagram illustrating the charge generation of the first and second piezoelectric sensitive structures provided in the embodiments of this application;
[0065] Figure 3 A schematic diagram showing the charge generation of an accelerometer with a piezoelectric sensitive structure corresponding to a cantilever beam structure;
[0066] Figure 4 This embodiment provides a schematic diagram of a four-beam accelerometer with two piezoelectric sensitive structures for each cantilever structure.
[0067] Figure 5 A schematic diagram of the substrate after depositing the top electrode, piezoelectric layer and bottom electrode on an SOI substrate;
[0068] Figure 6 This is a schematic diagram of the substrate after the top electrode on the front side of the substrate has been patterned.
[0069] Figure 7 This is a schematic diagram of the substrate after the piezoelectric layer on the front side of the substrate has been patterned.
[0070] Figure 8 This is a schematic diagram of the substrate after the lower electrode on the front side of the substrate has been patterned.
[0071] Figure 9 A schematic diagram of the substrate after the isolation membrane layer has been formed;
[0072] Figure 10 A schematic cross-section of the substrate after the metal connecting lines and PADs are formed;
[0073] Figure 11 Another cross-sectional view of the substrate after the metal connecting lines and PADs are formed;
[0074] Figure 12 This is a schematic diagram of the substrate after the device layer has been patterned;
[0075] Figure 13 This is a schematic diagram of the base after the mass block has been graphically represented;
[0076] Figure 14 This is a schematic diagram of the base after the support layer has been graphically represented;
[0077] Figure 15 This is a schematic diagram of the base after the front protective structure has been removed.
[0078] Icons: 1-First piezoelectric sensitive structure, 2-Second piezoelectric sensitive structure, 3-First PAD, 4-Second PAD. Detailed Implementation
[0079] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.
[0080] Please refer to Figure 1 , Figure 1 A flowchart illustrating the fabrication method of a piezoelectric MEMS accelerometer provided in this application embodiment includes:
[0081] Step 100: Pattern the upper electrode, piezoelectric layer and lower electrode on the front side of the substrate to obtain the first piezoelectric sensitive structure 1 and the second piezoelectric sensitive structure 2; wherein, the first piezoelectric sensitive structure 1 includes a first upper electrode, a first piezoelectric layer and a first lower electrode, and the second piezoelectric sensitive structure 2 includes a second upper electrode, a second piezoelectric layer and a second lower electrode.
[0082] Step 200: On the front side of the substrate, a metal connecting line, a first PAD3, and a second PAD4 are formed; wherein, the metal connecting line is used to connect the second upper electrode to the first lower electrode, and to connect the second lower electrode to the first upper electrode; the first PAD3 is connected to the first lower electrode, and the second PAD4 is connected to the first upper electrode.
[0083] Step 300: Graphicalize the front and back sides of the substrate to obtain the cantilever structure, vibration-sensitive structure and frame structure; wherein, the first piezoelectric sensitive structure 1 and the second piezoelectric sensitive structure 2 are located at the two ends of the cantilever structure, respectively.
[0084] like Figure 2As shown, the piezoelectric MEMS accelerometer of this embodiment has a first piezoelectric sensing structure 1 and a second piezoelectric sensing structure 2 respectively disposed at both ends of the cantilever structure. When the piezoelectric MEMS accelerometer is subjected to a positive acceleration, the first piezoelectric sensing structure 1 undergoes positive deformation, and the first upper electrode and the first lower electrode generate induced charges +Q1 and -Q1 respectively; the second piezoelectric sensing structure 2 undergoes reverse deformation, and the second upper electrode and the second lower electrode generate induced charges -Q2 and +Q2 respectively; since the first upper electrode of the first piezoelectric sensing structure 1 is connected to the second lower electrode of the second piezoelectric sensing structure 2, and the first lower electrode of the first piezoelectric sensing structure 1 is connected to the second upper electrode of the second piezoelectric sensing structure 2, the overall induced charges of the first piezoelectric sensing structure 1 and the second piezoelectric sensing structure 2 are +(Q1+Q2) and -(Q1+Q2).
[0085] If the cantilever structure only corresponds to one piezoelectric sensitive structure, such as Figure 3 As shown, when the piezoelectric MEMS accelerometer is subjected to positive acceleration, the piezoelectric sensitive structure undergoes positive deformation, and the upper electrode and the first lower electrode generate induced charges +Q and -Q, respectively. However, the piezoelectric MEMS accelerometer in this embodiment generates induced charges of +(Q1+Q2) and -(Q1+Q2), which significantly increases the induced charge and improves sensitivity compared to the piezoelectric MEMS accelerometer with only one piezoelectric sensitive structure in a cantilever structure.
[0086] It should be clarified that the piezoelectric MEMS accelerometer includes at least one cantilever structure, and each cantilever structure corresponds to a first piezoelectric sensing structure 1 and a second piezoelectric sensing structure 2, such as... Figure 4 The four-cantilever structure design shown is as follows: Figure 4 This embodiment provides a four-beam accelerometer with two piezoelectric sensing structures for each cantilever structure. The following embodiment uses one of the cantilever structures of a piezoelectric MEMS accelerometer as an example for detailed description.
[0087] Prior to step 100, a method for fabricating a piezoelectric MEMS accelerometer further includes:
[0088] Select an SOI substrate of appropriate specifications. Its basic structure includes a device layer, a buried oxide layer, and a support layer.
[0089] An oxide layer of 100–1000 nm is grown on the surface of an SOI substrate by thermal oxidation, serving as an isolation layer.
[0090] A seed layer or adhesion layer of 20–50 nm is deposited on the front side of the substrate by sputtering (or sputtering + oxygen annealing), which can be Ti, TiOx, AlN, ScAlN, etc.
[0091] A lower electrode of 50–500 nm is deposited on the front side of the substrate by sputtering. The material of the lower electrode can be Pt, Mo, or other metals.
[0092] A 50–200 nm buffer layer is deposited on the substrate surface using a sputtering method to serve as a buffer.
[0093] A 0.5–5 μm piezoelectric layer is deposited on the substrate surface by sputtering. The piezoelectric layer material can be PZT, AlN, ScAlN, or other thin film materials with piezoelectric properties.
[0094] A top electrode of 50–500 nm is deposited on the front side of the substrate by sputtering. The material of the top electrode layer can be Pt, Mo, or other metals.
[0095] The substrate after the above steps is as follows Figure 5 As shown.
[0096] It should be clarified that the aforementioned isolation layer, adhesive layer, seed layer, and buffer layer may be absent, or only one or a few of them may be present. If there is no isolation layer, adhesive layer, seed layer, or buffer layer, the process step of generating the isolation layer can be removed.
[0097] Please refer to Figure 6 , Figure 6 This is a schematic diagram of the substrate after patterning the top electrode on the front side. Patterning the top electrode on the front side of the substrate specifically includes: forming the design patterns of the first and second top electrodes on the front side of the substrate using photolithography; etching away excess top electrode metal to form the first and second top electrodes; and cleaning away any remaining photoresist.
[0098] In this embodiment, the design patterns of the first upper electrode and the second upper electrode are formed on the front side of the substrate by photolithography; the excess upper electrode metal is etched away by dry etching or wet etching to form the first upper electrode and the second upper electrode; finally, the photoresist is removed by organic solvent or oxygen plasma.
[0099] Please refer to Figure 7 , Figure 7 This is a schematic diagram of the substrate after patterning the piezoelectric layer on the front side. Patterning the piezoelectric layer on the front side of the substrate specifically includes: after the top electrode is patterned, forming the design patterns of the first and second piezoelectric layers on the front side of the substrate using photolithography; etching away excess piezoelectric material to form the first and second piezoelectric layers; and cleaning away any remaining photoresist.
[0100] In this embodiment, a first piezoelectric layer and a second piezoelectric layer design pattern are formed on the front side of the substrate by photolithography; excess piezoelectric material is etched away by dry etching or wet etching to form the first piezoelectric layer and the second piezoelectric layer; and photoresist is removed by organic cleaning or oxygen plasma.
[0101] Please refer to Figure 8 , Figure 8 This is a schematic diagram of the substrate after patterning the lower electrode on the front side. Patterning the lower electrode on the front side of the substrate specifically includes: after the piezoelectric layer is patterned, the design patterns of the first and second lower electrodes are formed on the front side of the substrate using photolithography; excess lower electrode metal is etched away to form the first and second lower electrodes; and the remaining photoresist is cleaned away.
[0102] In this embodiment, the design patterns of the first lower electrode and the second lower electrode are formed on the front side of the substrate by photolithography; the excess lower electrode metal is etched away by dry etching or wet etching to form the first lower electrode and the second lower electrode; and the photoresist is removed by organic cleaning or oxygen plasma.
[0103] Please refer to Figure 9 , Figure 9 This is a schematic diagram of the substrate after the isolation film layer has been formed. Before forming the metal interconnects, the first PAD, and the second PAD on the front side of the substrate, the process includes: depositing a dielectric layer on the front side of the substrate; forming a design pattern of openings on the front side of the substrate using photolithography; wherein the first upper electrode, the first lower electrode, the second upper electrode, and the second lower electrode are connected to the metal interconnects or PADs through the openings; etching away excess dielectric layer material to form the isolation film layer; and cleaning away any remaining photoresist.
[0104] In this embodiment, a dielectric layer is deposited on the substrate surface by reactive magnetron sputtering or CVD. The material can be SiO2, Al2O3, SiN, AlN, or a hybrid structure of several materials. A design pattern for openings is formed on the front side of the substrate using photolithography. Excess dielectric layer material is etched away using dry etching or wet etching to form an isolation film. Finally, the photoresist is removed using organic cleaning or oxygen plasma.
[0105] Please refer to Figure 10 and Figure 11 , Figure 10 A schematic cross-sectional view of the substrate after the metal connecting lines and PADs are formed. Figure 11 Another cross-sectional view of the substrate after the metal connecting lines and PADs are formed.
[0106] In some alternative embodiments, metal interconnects, a first PAD, and a second PAD are formed on the front side of the substrate, including: forming a design pattern of the metal interconnects, the first PAD, and the second PAD on the front side of the substrate by photolithography; depositing a metal layer on the front side of the substrate; and stripping the photoresist and the metal layer thereon to form the metal interconnects, the first PAD, and the second PAD.
[0107] In this embodiment, a design pattern of metal interconnects, a first PAD, and a second PAD is formed on the front side of the substrate using photolithography. A metal layer is deposited on the substrate surface using electron beam evaporation; the material can be Ti, Ni, Cr, Al, Ag, Pt, Au, or a composite structure of several materials. The photoresist and the metal layer on top are then removed using a lift-off method to form the metal interconnects, the first PAD, and the second PAD.
[0108] Please refer to Figure 12 , Figure 12 This is a schematic diagram of the substrate after the device layer has been patterned.
[0109] In some alternative implementations, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration-sensitive structure, and a frame structure, including: forming a design pattern of the device layer of the substrate on the front side of the substrate using a photolithography method; etching away excess device layer material to form the shape of the cantilever structure, vibration-sensitive structure, and frame structure on the front side of the substrate; and cleaning away the remaining photoresist.
[0110] In this embodiment, the design pattern of the device layer of the substrate is formed on the front side of the substrate by photolithography; the excess device layer material is etched away by dry etching or wet etching to form the shape of the cantilever structure, vibration-sensitive structure and frame structure on the front side of the substrate; finally, the photoresist is removed by organic cleaning or oxygen plasma.
[0111] Please refer to Figure 13 , Figure 13 This is a schematic diagram of the base after the mass block has been graphically represented.
[0112] In some alternative implementations, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration-sensitive structure, and a frame structure. The implementation also includes: setting a front protective structure on the front side of the substrate; forming a design pattern of a mass block on the back side of the substrate using photolithography; etching away excess support layer material on the back side of the substrate to form a mass block; and cleaning away any remaining photoresist.
[0113] In this embodiment, a front protective structure is provided on the front side of the substrate; a design pattern of a mass block is formed on the back side of the substrate using photolithography; excess support layer material on the back side of the substrate is etched away using dry etching or wet etching methods to form the mass block; finally, the photoresist is removed by organic cleaning or oxygen plasma.
[0114] Please refer to Figure 14 , Figure 14 This is a schematic diagram of the base after the support layer has been graphically represented.
[0115] In some optional implementations, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration-sensitive structure, and a frame structure. This also includes: forming a design pattern of the support layer of the substrate on the back side of the substrate using a photolithography method; etching away excess support layer material on the back side of the substrate to form the shape of the cantilever structure, vibration-sensitive structure, and frame structure on the back side of the substrate; and cleaning away the remaining photoresist.
[0116] In this embodiment, the design pattern of the support layer of the substrate is formed on the back side of the substrate by photolithography; the excess support layer material on the back side of the substrate is etched away by dry etching or wet etching to form the shape of the cantilever structure, vibration-sensitive structure and frame structure on the back side of the substrate; finally, the photoresist is removed by organic cleaning or oxygen plasma.
[0117] Please refer to Figure 15 , Figure 15 This is a schematic diagram of the base after the front protective structure has been removed.
[0118] In some alternative implementations, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration-sensitive structure, and a frame structure. This also includes: etching away excess buried oxide layer material on the back side of the substrate to release the cantilever structure; and removing the protective structure on the front side.
[0119] In this embodiment, excess buried oxide layer material on the back side of the substrate is etched away by vapor phase etching, wet etching, or dry etching to release the cantilever structure; finally, the front protective structure is removed, thus completing the fabrication of the piezoelectric MEMS accelerometer.
[0120] This application provides a piezoelectric MEMS accelerometer, comprising: a cantilever structure, a vibration-sensitive structure, and a frame structure; the cantilever structure includes a first piezoelectric sensitive structure, a second piezoelectric sensitive structure, and a cantilever; the vibration-sensitive structure is fixedly connected to the lower surface of the first end of the cantilever, and the frame structure is fixedly connected to the lower surface of the second end of the cantilever; the first piezoelectric sensitive structure is fixedly connected to the upper surface of the first end of the cantilever, and the second piezoelectric sensitive structure is fixedly connected to the upper surface of the second end of the cantilever; the first piezoelectric sensitive structure includes a first upper electrode, a first piezoelectric layer, and a first lower electrode; the second piezoelectric sensitive structure includes a second upper electrode, a second piezoelectric layer, and a second lower electrode; the first upper electrode and the second lower electrode are connected by a metal connecting wire, and the first lower electrode and the second upper electrode are connected by a metal connecting wire; the first lower electrode is connected to a first PAD, and the first upper electrode is connected to a second PAD.
[0121] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.
[0122] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.
[0123] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.
[0124] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.
[0125] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. A method for fabricating a piezoelectric MEMS accelerometer, characterized in that, include: The upper electrode, piezoelectric layer, and lower electrode on the front side of the substrate are patterned to obtain a first piezoelectric sensitive structure and a second piezoelectric sensitive structure; wherein, the first piezoelectric sensitive structure includes a first upper electrode, a first piezoelectric layer, and a first lower electrode, and the second piezoelectric sensitive structure includes a second upper electrode, a second piezoelectric layer, and a second lower electrode; On the front side of the substrate, a metal connecting line, a first PAD, and a second PAD are formed; wherein, the metal connecting line is used to connect the second upper electrode to the first lower electrode, and to connect the second lower electrode to the first upper electrode; the first PAD is connected to the first lower electrode, and the second PAD is connected to the first upper electrode; The front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration-sensitive structure, and a frame structure; wherein the first piezoelectric sensitive structure and the second piezoelectric sensitive structure are located at the two ends of the cantilever structure, respectively.
2. The method as described in claim 1, characterized in that, Patterning the top electrode on the front side of the substrate includes: The design patterns of the first and second upper electrodes are formed on the front side of the substrate using photolithography. Etch away excess upper electrode metal to form the first upper electrode and the second upper electrode; Clean off any remaining photoresist.
3. The method as described in claim 2, characterized in that, Patterning the piezoelectric layer on the front side of the substrate includes: After the top electrode is patterned, the design patterns of the first piezoelectric layer and the second piezoelectric layer are formed on the front side of the substrate using photolithography. Excess piezoelectric material is etched away to form the first piezoelectric layer and the second piezoelectric layer. Clean off any remaining photoresist.
4. The method as described in claim 3, characterized in that, Patterning the lower electrode on the front side of the substrate includes: After the piezoelectric layer is patterned, the design patterns of the first and second lower electrodes are formed on the front side of the substrate using photolithography. Etch away excess lower electrode metal to form the first lower electrode and the second lower electrode; Clean off any remaining photoresist.
5. The method as described in claim 1, characterized in that, Before forming the metal interconnect, the first pad, and the second pad on the front side of the substrate, the method further includes: Deposit a medium layer on the front side of the substrate; A design pattern of openings is formed on the front side of the substrate using photolithography; wherein the first upper electrode, the first lower electrode, the second upper electrode, and the second lower electrode are connected to metal interconnects or PADs through the openings; Etching away excess dielectric material forms an isolation film layer; Clean off any remaining photoresist.
6. The method as described in claim 5, characterized in that, The metal connecting line, the first PAD, and the second PAD are formed on the front side of the substrate, including: The design patterns of the metal connection lines, the first PAD, and the second PAD are formed on the front side of the substrate using photolithography. Deposit a metal layer on the front side of the substrate; The photoresist and the metal layer thereon are stripped to form the metal interconnect, the first PAD, and the second PAD.
7. The method as described in claim 1, characterized in that, The process of patterning the front and back sides of the substrate yields cantilever structures, vibration-sensitive structures, and frame structures, including: The design pattern of the device layer of the substrate is formed on the front side of the substrate using photolithography. Etching away excess device layer material forms the shape of the cantilever structure, vibration-sensitive structure, and frame structure on the front side of the substrate; Clean off any remaining photoresist.
8. The method as described in claim 7, characterized in that, The process of graphically representing the front and back sides of the substrate to obtain the cantilever structure, vibration-sensitive structure, and frame structure also includes: A front protective structure is provided on the front of the substrate; The design pattern of the mass block is formed on the back side of the substrate using photolithography. The excess support layer material on the back of the substrate is etched away to form the mass block; Clean off any remaining photoresist.
9. The method as described in claim 8, characterized in that, The process of graphically representing the front and back sides of the substrate to obtain the cantilever structure, vibration-sensitive structure, and frame structure also includes: The design pattern of the support layer of the substrate is formed on the back side of the substrate using photolithography. The excess support layer material on the back of the substrate is etched away to form the shape of the cantilever structure, vibration-sensitive structure and frame structure on the back of the substrate; Clean off any remaining photoresist.
10. The method as described in claim 9, characterized in that, The process of graphically representing the front and back sides of the substrate to obtain the cantilever structure, vibration-sensitive structure, and frame structure also includes: The excess buried oxide layer material on the back of the substrate is etched away to release the cantilever structure; Remove the aforementioned front protective structure.
11. A piezoelectric MEMS accelerometer, characterized in that, It is prepared by the fabrication method of a piezoelectric MEMS accelerometer as described in any one of claims 1-10; The piezoelectric MEMS accelerometer includes: a cantilever structure, a vibration-sensitive structure, and a frame structure; the cantilever structure includes a first piezoelectric sensitive structure, a second piezoelectric sensitive structure, and a cantilever. The vibration-sensitive structure is fixedly connected to the lower surface of the first end of the cantilever, and the frame structure is fixedly connected to the lower surface of the second end of the cantilever. The first piezoelectric sensitive structure is fixedly connected to the upper surface of the first end of the cantilever, and the second piezoelectric sensitive structure is fixedly connected to the upper surface of the second end of the cantilever. The first piezoelectric sensing structure includes a first upper electrode, a first piezoelectric layer, and a first lower electrode; the second piezoelectric sensing structure includes a second upper electrode, a second piezoelectric layer, and a second lower electrode. The first upper electrode and the second lower electrode are connected by a metal connecting wire; the first lower electrode is connected to the first PAD, and the first upper electrode is connected to the second PAD.
Citation Information
Patent Citations
Piezoelectric MEMS accelerometer integrated with temperature detection and preparation method thereof
CN118992970A