Piezoelectric MEMS accelerometer and preparation method thereof

Abstract

The invention provides a piezoelectric MEMS accelerometer and a preparation method thereof. Two ends of a cantilever structure of the piezoelectric MEMS accelerometer are respectively provided with a first piezoelectric sensitive structure and a second piezoelectric sensitive structure. When the piezoelectric MEMS accelerometer is subjected to forward acceleration, the first piezoelectric sensitive structure deforms forward, and the first upper electrode and the first lower electrode generate inductive charges + Q1 and-Q1 respectively; the second piezoelectric sensitive structure deforms reversely, and the second upper electrode and the second lower electrode generate inductive charges-Q2 and + Q2 respectively; the first upper electrode of the first piezoelectric sensitive structure is connected with the second lower electrode of the second piezoelectric sensitive structure, and the first lower electrode of the first piezoelectric sensitive structure is connected with the second upper electrode of the second piezoelectric sensitive structure, so that the overall inductive charges of the first piezoelectric sensitive structure and the second piezoelectric sensitive structure are + (Q1 + Q2) and-(Q1 + Q2); inductive charges are greatly increased, and sensitivity is improved.

Description

Technical Field

[0001] The present application relates to the field of MEMS technology, and in particular to a piezoelectric MEMS accelerometer and a preparation method thereof. Background Art

[0002] Working principle of piezoelectric MEMS accelerometer: When vibrating, the mass block is subjected to the inertial force opposite to the acceleration direction, and the piezoelectric film is subjected to the alternating force from the mass block which is proportional to the acceleration. Correspondingly, induced charge is generated on the electrode, which is converted into a voltage signal through the charge amplifier. When working at a frequency far away from the resonant frequency point, the acceleration of the mass block is proportional to the induced charge of the device, thus achieving detection.

[0003] The piezoelectric MEMS accelerometer mainly includes four parts: a cantilever beam (or a suspended membrane), a frame, a mass block, and a piezoelectric sensitive structure. The cantilever beam can be a single beam or multiple symmetrically distributed beams, and the suspended membrane can be a membrane with central symmetrical distribution. One end of the cantilever beam (or suspended membrane) is connected to the frame, and the other end is connected to the mass block. The connection position between the cantilever beam (or suspended membrane) and the frame is covered with a piezoelectric sensitive structure, which mainly includes a piezoelectric film and upper / lower electrodes. There are also lead wires and PADs for the upper / lower electrodes on the frame.

[0004] Existing piezoelectric MEMS accelerometers fail to fully utilize the deformation of the suspension beam (or suspension membrane), resulting in low sensitivity. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a piezoelectric MEMS accelerometer and a preparation method thereof, so as to solve the problem that the existing piezoelectric MEMS accelerometer fails to fully utilize the deformation of the suspension beam (or suspension membrane), resulting in low sensitivity.

[0006] A method for preparing a piezoelectric MEMS accelerometer provided in an embodiment of the present application includes:

[0007] The upper electrode, the piezoelectric layer and the 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 with the first lower electrode, and to connect the second lower electrode with 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 a cantilever beam structure, a vibration sensitive structure and a frame structure; wherein the first piezoelectric sensitive structure and the second piezoelectric sensitive structure are respectively located at two ends of the cantilever beam structure.

[0010] In the above technical solution, the first piezoelectric sensitive structure and the second piezoelectric sensitive structure are respectively arranged 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 sensitive structure undergoes positive deformation, and the first upper electrode and the first lower electrode generate induced charges +Q1 and -Q1 respectively; the second piezoelectric sensitive 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 sensitive structure is connected to the second lower electrode of the second piezoelectric sensitive structure, and the first lower electrode of the first piezoelectric sensitive structure is connected to the second upper electrode of the second piezoelectric sensitive structure, the overall induced charges of the first piezoelectric sensitive structure and the second piezoelectric sensitive structure are +(Q1+Q2) and -(Q1+Q2), which greatly increases the induced charge and improves the sensitivity.

[0011] In some optional embodiments, patterning the upper electrode on the front side of the substrate includes:

[0012] Forming the design patterns of the first upper electrode and the second upper electrode on the front side of the substrate by photolithography;

[0013] Etching away excess upper electrode metal to form a first upper electrode and a second upper electrode;

[0014] Clean off the 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 optional embodiments, patterning the piezoelectric layer on the front side of the substrate includes:

[0017] After the patterning of the upper electrode is completed, the first piezoelectric layer and the second piezoelectric layer design patterns are formed on the front side of the substrate by photolithography;

[0018] Etching away excess piezoelectric material to form a first piezoelectric layer and a second piezoelectric layer;

[0019] Clean off the 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; the photoresist is removed by organic cleaning or oxygen plasma.

[0021] In some optional embodiments, patterning the lower electrode on the front side of the substrate includes:

[0022] After the patterning of the piezoelectric layer is completed, the design patterns of the first lower electrode and the second lower electrode are formed on the front surface of the substrate by photolithography;

[0023] Etching away excess lower electrode metal to form a first lower electrode and a second lower electrode;

[0024] Clean off the 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; the photoresist is removed by organic cleaning or oxygen plasma.

[0026] In some optional implementations, before forming the metal connection line, the first PAD and the second PAD on the front side of the substrate, the method further includes:

[0027] Depositing a dielectric layer on the front side of the substrate;

[0028] A design pattern of openings is formed on the front side of the substrate by a photolithography method; wherein the first upper electrode, the first lower electrode, the second upper electrode and the second lower electrode are connected to metal connecting wires or PADs through the openings;

[0029] Etching away excess dielectric layer material to form an isolation film layer;

[0030] Clean off the remaining photoresist.

[0031] In the above technical solution, a dielectric layer is deposited on the surface of the substrate by reactive magnetron sputtering or CVD, and the material can be SiO2, Al2O3, SiN, AlN, etc. or a stacked mixed structure of several materials. The design pattern of the opening is formed on the front of the substrate by photolithography; the excess dielectric layer material is etched away by dry etching or wet etching to form an isolation film layer; finally, the photoresist is removed by organic cleaning or oxygen plasma.

[0032] In some optional implementations, forming a metal connection line, a first PAD, and a second PAD on the front side of the substrate includes:

[0033] Forming a design pattern of a metal connection line, a first PAD and a second PAD on the front side of the substrate by a photolithography method;

[0034] depositing a metal layer on the front side of the substrate;

[0035] The photoresist and the metal layer thereon are stripped off to form metal connecting lines, a first PAD and a second PAD.

[0036] In the above technical solution, the design patterns of the metal connection line, the first PAD and the second PAD are formed on the front side of the substrate by photolithography; a metal layer is deposited on the surface of the substrate by electron beam evaporation, and the material can be Ti, Ni, Cr, Al, Ag, Pt, Au, etc. or a laminated mixed structure of several materials. The photoresist and the metal layer thereon are stripped by lift-off stripping method to form the metal connection line, the first PAD and the second PAD.

[0037] In some optional embodiments, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration sensitive structure and a frame structure, including:

[0038] Forming a design pattern of a device layer of the substrate on the front side of the substrate by a photolithography method;

[0039] Etching away excess device layer material to form the shapes of the cantilever beam structure, the vibration sensitive structure and the frame structure on the front side of the substrate;

[0040] Clean off the remaining photoresist.

[0041] In the above technical scheme, a design pattern of the device layer of the substrate is formed on the front side of the substrate by a photolithography method; excess device layer material is etched away by a dry etching or wet etching method 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 optional embodiments, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration sensitive structure and a frame structure, further comprising:

[0043] A front protection structure is provided on the front side of the substrate;

[0044] Forming a design pattern of the mass block on the back side of the substrate by a photolithography method;

[0045] Etching away the excess support layer material on the back of the substrate to form a mass block;

[0046] Clean off the remaining photoresist.

[0047] In the above technical solution, a front protection structure is set on the front side of the substrate; a design pattern of the mass block is formed on the back side of the substrate by photolithography; excess supporting layer material on the back side of the substrate is etched away by dry etching or wet etching to form a mass block; finally, the photoresist is removed by organic cleaning or oxygen plasma.

[0048] In some optional embodiments, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration sensitive structure and a frame structure, further comprising:

[0049] Forming a design pattern of a support layer of the substrate on the back side of the substrate by a photolithography method;

[0050] Etching away the excess supporting layer material on the back side of the substrate to form the shapes of the cantilever beam structure, the vibration sensitive structure and the frame structure on the back side of the substrate;

[0051] Clean off the remaining photoresist.

[0052] In the above technical scheme, a design pattern of a support layer of a substrate is formed on the back side of the substrate by a photolithography method; excess support layer material on the back side of the substrate is etched away by a dry etching or wet etching method to form the shape of a cantilever structure, a vibration sensitive structure and a frame structure on the back side of the substrate; finally, the photoresist is removed by organic cleaning or oxygen plasma.

[0053] In some optional embodiments, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration sensitive structure and a frame structure, further comprising:

[0054] Etch away the excess buried oxide layer material on the back of the substrate to release the cantilever beam structure;

[0055] Remove the front protection structure.

[0056] In the above technical solution, the excess buried oxide layer material on the back of the substrate is etched away by vapor phase etching, wet etching or dry etching to release the cantilever structure; finally, the front protection structure is removed to complete the preparation of the piezoelectric MEMS accelerometer.

[0057] A piezoelectric MEMS accelerometer provided in an embodiment of the present application 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;

[0058] The lower surface of the first end of the cantilever is fixedly connected to the vibration sensitive structure, and the lower surface of the second end of the cantilever is fixedly connected to the frame structure;

[0059] The upper surface of the first end of the cantilever is fixedly connected to the first piezoelectric sensitive structure, and the upper surface of the second end of the cantilever is fixedly connected to the second piezoelectric sensitive structure;

[0060] 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;

[0061] The first upper electrode and the second lower electrode are connected through a metal connection line, and the first lower electrode and the second upper electrode are connected through a metal connection line; the first lower electrode is connected to the first PAD, and the first upper electrode is connected to the second PAD. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0063] Figure 1 A flowchart of the steps of a method for preparing a piezoelectric MEMS accelerometer provided in an embodiment of the present application;

[0064] Figure 2 A schematic diagram of charge generation by the first piezoelectric sensitive structure and the second piezoelectric sensitive structure provided in an embodiment of the present application;

[0065] Figure 3 A schematic diagram of charge generation for an accelerometer of a piezoelectric sensitive structure corresponding to a cantilever structure;

[0066] Figure 4 A schematic diagram of a four-cantilever beam structure accelerometer provided in this embodiment, in which two piezoelectric sensitive structures are arranged corresponding to each cantilever beam structure;

[0067] Figure 5 Schematic diagram of the substrate after depositing the upper electrode, piezoelectric layer and lower electrode on the SOI substrate;

[0068] Figure 6 A schematic diagram of a substrate after patterning the upper electrode on the front side of the substrate;

[0069] Figure 7 is a schematic diagram of a substrate after the piezoelectric layer on the front side of the substrate is patterned;

[0070] Figure 8 A schematic diagram of a substrate after the lower electrode on the front side of the substrate is patterned;

[0071] Fig. 9 A schematic diagram of a substrate after forming an isolation film layer;

[0072] Fig.10 A schematic cross-sectional view of the substrate after forming metal connecting lines and PAD;

[0073] Fig.11 Another schematic cross-sectional view of the substrate after forming metal connecting lines and PAD;

[0074] Fig.12 is a schematic diagram of a substrate after the device layer is patterned;

[0075] Fig.13 is a schematic diagram of the base after the quality block is graphed;

[0076] Fig.14 is a schematic diagram of a substrate after the support layer is patterned;

[0077] Fig.15 Schematic diagram of the base after removing the front protection structure.

[0078] Icons: 1-first piezoelectric sensitive structure, 2-second piezoelectric sensitive structure, 3-first PAD, 4-second PAD. DETAILED DESCRIPTION

[0079] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0080] Please refer to Figure 1 , Figure 1 A flowchart of a method for preparing a piezoelectric MEMS accelerometer provided in an embodiment of the present application includes:

[0081] Step 100: patterning the upper electrode, the piezoelectric layer and the lower electrode on the front side of the substrate to obtain a first piezoelectric sensitive structure 1 and a 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: forming a metal connection line, a first PAD3 and a second PAD4 on the front side of the substrate; wherein the metal connection line is used to connect the second upper electrode with the first lower electrode, and to connect the second lower electrode with 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: Patterning the front and back sides of the substrate to obtain a cantilever beam structure, a vibration sensitive structure and a frame structure; wherein the first piezoelectric sensitive structure 1 and the second piezoelectric sensitive structure 2 are respectively located at two ends of the cantilever beam structure.

[0084] like Figure 2As shown, the first piezoelectric sensitive structure 1 and the second piezoelectric sensitive structure 2 are respectively arranged at both ends of the cantilever structure of the piezoelectric MEMS accelerometer of the embodiment of the present application. When the piezoelectric MEMS accelerometer is subjected to positive acceleration, the first piezoelectric sensitive 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 sensitive 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 sensitive structure 1 is connected to the second lower electrode of the second piezoelectric sensitive structure 2, and the first lower electrode of the first piezoelectric sensitive structure 1 is connected to the second upper electrode of the second piezoelectric sensitive structure 2, the overall induced charges of the first piezoelectric sensitive structure 1 and the second piezoelectric sensitive structure 2 are +(Q1+Q2) and -(Q1+Q2).

[0085] If only one piezoelectric sensitive structure is set corresponding to the cantilever beam structure, such as Figure 3 As shown in the figure, 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 of this embodiment generates induced charges of +(Q1+Q2) and -(Q1+Q2), which greatly increases the induced charges and improves the sensitivity compared to the piezoelectric MEMS accelerometer with only one piezoelectric sensitive structure in the cantilever structure.

[0086] It should be clear that the piezoelectric MEMS accelerometer includes at least one cantilever beam structure, and each cantilever beam structure corresponds to a first piezoelectric sensitive structure 1 and a second piezoelectric sensitive structure 2. Figure 4 The four-cantilever beam structure design shown in the figure is Figure 4 The four-cantilever beam structure accelerometer provided in this embodiment has two piezoelectric sensitive structures corresponding to each cantilever beam structure. The following embodiment is described in detail by taking one cantilever beam structure of the piezoelectric MEMS accelerometer as an example.

[0087] Before step 100, a method for preparing a piezoelectric MEMS accelerometer further includes:

[0088] An SOI substrate of corresponding specifications is selected, and its basic structure includes a device layer, a buried oxide layer and a support layer.

[0089] A 100-1000 nm oxide layer is grown on the surface of the SOI substrate by thermal oxidation as an isolation layer.

[0090] A 20-50 nm seed layer or adhesion layer is deposited on the front side of the substrate by sputtering (or sputtering + oxygen-containing annealing), and may be Ti, TiOx, AlN, ScAlN, etc.

[0091] A lower electrode with a thickness of 50 to 500 nm is deposited on the front side of the substrate by sputtering. The material of the lower electrode may be Pt, Mo or other metals.

[0092] A 50-200 nm buffer layer is deposited on the surface of the substrate by a sputtering method as a buffer.

[0093] A 0.5-5 um piezoelectric layer is deposited on the surface of the substrate by sputtering. The material of the piezoelectric layer can be PZT, AlN, ScAlN or other thin film materials with piezoelectric properties.

[0094] A 50-500 nm upper electrode is deposited on the front side of the substrate by sputtering. The material of the upper electrode layer can be Pt, Mo or other metals.

[0095] After the above steps, the substrate Figure 5 shown.

[0096] It should be clear that the above-mentioned isolation layer, adhesion layer, seed layer and buffer layer may not be present, or only one or several of them may be present. If there is no isolation layer, adhesion layer, seed layer or buffer layer, the process steps for generating the isolation layer can be removed.

[0097] Please refer to Figure 6 , Figure 6 The schematic diagram of the substrate after the upper electrode on the front side of the substrate is patterned. The patterning of the upper electrode on the front side of the substrate specifically includes: forming the design pattern of the first upper electrode and the second upper electrode on the front side of the substrate by photolithography; etching away the excess upper electrode metal to form the first upper electrode and the second upper electrode; and cleaning away the remaining photoresist.

[0098] In an embodiment of the present application, a design pattern of a first upper electrode and a second upper electrode is formed on the front side of a substrate by a photolithography method; excess upper electrode metal is etched away by a dry etching method or a wet etching method to form a first upper electrode and a second upper electrode; finally, the photoresist is removed by an organic solvent or oxygen plasma.

[0099] Please refer to Figure 7 , Figure 7 The schematic diagram of the substrate after the piezoelectric layer on the front side of the substrate is patterned. The patterning of the piezoelectric layer on the front side of the substrate specifically includes: after the patterning of the upper electrode is completed, the first piezoelectric layer and the second piezoelectric layer design patterns are formed on the front side of the substrate by a photolithography method; the excess piezoelectric material is etched away to form the first piezoelectric layer and the second piezoelectric layer; and the remaining photoresist is cleaned.

[0100] In an embodiment of the present application, a first piezoelectric layer and a second piezoelectric layer design pattern are formed on the front side of the substrate by a photolithography method; excess piezoelectric material is etched away by a dry etching method or a wet etching method to form a first piezoelectric layer and a second piezoelectric layer; and the photoresist is removed by organic cleaning or oxygen plasma.

[0101] Please refer to Figure 8 , Figure 8 The schematic diagram of the substrate after the lower electrode on the front side of the substrate is patterned. The patterning of the lower electrode on the front side of the substrate specifically includes: after the patterning of the piezoelectric layer is completed, the design pattern of the first lower electrode and the second lower electrode is formed on the front side of the substrate by a photolithography method; the excess lower electrode metal is etched away to form the first lower electrode and the second lower electrode; and the remaining photoresist is cleaned away.

[0102] In an embodiment of the present application, a design pattern of a first lower electrode and a second lower electrode is formed on the front side of a substrate by a photolithography method; excess lower electrode metal is etched away by a dry etching method or a wet etching method to form a first lower electrode and a second lower electrode; and the photoresist is removed by organic cleaning or oxygen plasma.

[0103] Please refer to Fig. 9 , Fig. 9 The schematic diagram of the substrate after forming the isolation film layer. Before forming the metal connection line, the first PAD and the second PAD on the front side of the substrate, the method also 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 by photolithography; wherein the first upper electrode, the first lower electrode, the second upper electrode and the second lower electrode are connected to the metal connection line or PAD through the openings; etching away the excess dielectric layer material to form the isolation film layer; and cleaning away the remaining photoresist.

[0104] In the embodiment of the present application, a dielectric layer is deposited on the surface of the substrate by reactive magnetron sputtering or CVD, and the material thereof may be SiO2, Al2O3, SiN, AlN, etc. or a laminated mixed structure of several materials. A design pattern of openings is formed on the front side of the substrate by photolithography; excess dielectric layer material is etched away by dry etching or wet etching to form an isolation film layer; finally, the photoresist is removed by organic cleaning or oxygen plasma.

[0105] Please refer to Fig.10 and Fig.11 , Fig.10 A cross-sectional diagram of the substrate after forming metal connecting lines and PAD. Fig.11 Another cross-sectional schematic diagram of the substrate after forming metal connecting lines and PAD.

[0106] In some optional embodiments, metal connecting lines, a first PAD, and a second PAD are formed on the front side of the substrate, including: forming design patterns of the metal connecting lines, the first PAD, and the second PAD on the front side of the substrate by a photolithography method; depositing a metal layer on the front side of the substrate; and stripping off the photoresist and the metal layer thereon to form metal connecting lines, the first PAD, and the second PAD.

[0107] In the embodiment of the present application, the design patterns of the metal connecting wire, the first PAD and the second PAD are formed on the front side of the substrate by photolithography; a metal layer is deposited on the surface of the substrate by electron beam evaporation, and the material thereof can be Ti, Ni, Cr, Al, Ag, Pt, Au, etc. or a laminated mixed structure of several materials. The photoresist and the metal layer thereon are stripped by lift-off stripping method to form the metal connecting wire, the first PAD and the second PAD.

[0108] Please refer to Fig.12 , Fig.12 Schematic diagram of the substrate after the device layer is patterned.

[0109] In some optional embodiments, 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 a device layer of the substrate on the front side of the substrate by a photolithography method; etching away excess device layer material to form the shape of the cantilever structure, the vibration-sensitive structure and the frame structure on the front side of the substrate; and cleaning off remaining photoresist.

[0110] In an embodiment of the present application, a design pattern of a device layer of a substrate is formed on the front side of the substrate by a photolithography method; excess device layer material is etched away by a dry etching or wet etching method to form the shape of a cantilever structure, a vibration sensitive structure and a frame structure on the front side of the substrate; finally, the photoresist is removed by organic cleaning or oxygen plasma.

[0111] Please refer to Fig.13 , Fig.13 Schematic diagram of the substrate after the quality block is graphed.

[0112] In some optional embodiments, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration-sensitive structure and a frame structure, and also include: setting a front protection structure on the front side of the substrate; forming a design pattern of a mass block on the back side of the substrate by a photolithography method; etching away excess supporting layer material on the back side of the substrate to form a mass block; and cleaning away remaining photoresist.

[0113] In an embodiment of the present application, a front protection 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 by a photolithography method; excess supporting layer material on the back side of the substrate is etched away by a dry etching or wet etching method to form a mass block; finally, the photoresist is removed by organic cleaning or oxygen plasma.

[0114] Please refer to Fig.14 , Fig.14 Schematic diagram of the substrate after the support layer is patterned.

[0115] In some optional embodiments, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration-sensitive structure and a frame structure, and the method also includes: forming a design pattern of a supporting layer of the substrate on the back side of the substrate by a photolithography method; etching away excess supporting layer material on the back side of the substrate to form the shape of the cantilever structure, the vibration-sensitive structure and the frame structure on the back side of the substrate; and cleaning off remaining photoresist.

[0116] In an embodiment of the present application, a design pattern of a support layer of a substrate is formed on the back side of the substrate by a photolithography method; excess support layer material on the back side of the substrate is etched away by a dry etching or wet etching method to form the shape of a cantilever structure, a vibration sensitive structure and a frame structure on the back side of the substrate; finally, the photoresist is removed by organic cleaning or oxygen plasma.

[0117] Please refer to Fig.15 , Fig.15 Schematic diagram of the base after removing the front protection structure.

[0118] In some optional embodiments, the front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration sensitive structure and a frame structure, and also include: etching away excess buried oxide layer material on the back side of the substrate to release the cantilever structure; and removing the front protective structure.

[0119] In the embodiment of the present application, the 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 protection structure is removed to complete the preparation of the piezoelectric MEMS accelerometer.

[0120] A piezoelectric MEMS accelerometer provided in an embodiment of the present application 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 lower surface of the first end of the cantilever is fixedly connected to the vibration sensitive structure, and the lower surface of the second end of the cantilever is fixedly connected to the frame structure; the upper surface of the first end of the cantilever is fixedly connected to the first piezoelectric sensitive structure, and the upper surface of the second end of the cantilever is fixedly connected to the second piezoelectric sensitive structure; 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 the second PAD.

[0121] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0122] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0123] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0124] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0125] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a piezoelectric MEMS accelerometer, characterized in that: include: The upper electrode, the piezoelectric layer and the 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 with the first lower electrode, and to connect the second lower electrode with 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 beam structure, a vibration sensitive structure and a frame structure; wherein the first piezoelectric sensitive structure and the second piezoelectric sensitive structure are respectively located at two ends of the cantilever beam structure.

2. The method according to claim 1, characterized in that Patterning the upper electrode on the front side of the substrate includes: Forming the design patterns of the first upper electrode and the second upper electrode on the front side of the substrate by photolithography; Etching away excess upper electrode metal to form the first upper electrode and the second upper electrode; Clean off the remaining photoresist.

3. The method according to claim 2, characterized in that Patterning the piezoelectric layer on the front side of the substrate includes: After the patterning of the upper electrode is completed, the first piezoelectric layer and the second piezoelectric layer design patterns are formed on the front surface of the substrate by photolithography; Etching away excess piezoelectric material to form the first piezoelectric layer and the second piezoelectric layer; Clean off the remaining photoresist.

4. The method according to 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 lower electrode and the second lower electrode are formed on the front surface of the substrate by photolithography; Etching away excess lower electrode metal to form the first lower electrode and the second lower electrode; Clean off the remaining photoresist.

5. The method according to claim 1, characterized in that Before forming the metal connection line, the first PAD and the second PAD on the front side of the substrate, the method further includes: Depositing a dielectric layer on the front side of the substrate; A design pattern of openings is formed on the front side of the substrate by photolithography; wherein the first upper electrode, the first lower electrode, the second upper electrode and the second lower electrode are connected to metal connecting wires or PADs through the openings; Etching away excess dielectric layer material to form an isolation film layer; Clean off the remaining photoresist.

6. The method according to claim 5, characterized in that The method of forming a metal connection line, a first PAD and a second PAD on the front side of the substrate comprises: Forming the design patterns of the metal connection line, the first PAD and the second PAD on the front side of the substrate by a photolithography method; depositing a metal layer on the front side of the substrate; The photoresist and the metal layer thereon are stripped off to form the metal connecting line, the first PAD and the second PAD.

7. The method according to claim 1, characterized in that 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 a device layer of the substrate on the front side of the substrate by a photolithography method; Etching away excess device layer material to form the shapes of the cantilever beam structure, the vibration sensitive structure and the frame structure on the front side of the substrate; Clean off the remaining photoresist.

8. The method according to claim 7, characterized in that The front and back sides of the substrate are patterned to obtain a cantilever beam structure, a vibration sensitive structure and a frame structure, and further includes: A front protection structure is provided on the front side of the substrate; Forming a design pattern of the mass block on the back side of the substrate by a photolithography method; Etching away excess supporting layer material on the back side of the substrate to form the mass block; Clean off the remaining photoresist.

9. The method according to claim 8, characterized in that The front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration sensitive structure and a frame structure, and further include: Forming a design pattern of a support layer of the substrate on the back side of the substrate by a photolithography method; Etching away the excess supporting layer material on the back side of the substrate to form the shapes of the cantilever beam structure, the vibration sensitive structure and the frame structure on the back side of the substrate; Clean off the remaining photoresist.

10. The method according to claim 9, characterized in that The front and back sides of the substrate are patterned to obtain a cantilever structure, a vibration sensitive structure and a frame structure, and further include: Etching away the excess buried oxide layer material on the back side of the substrate to release the cantilever beam structure; The front protection structure is removed.

11. A piezoelectric MEMS accelerometer, characterized in that: include: 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 lower surface of the first end of the cantilever is fixedly connected to the vibration sensitive structure, and the lower surface of the second end of the cantilever is fixedly connected to the frame structure; The upper surface of the first end of the cantilever is fixedly connected to the first piezoelectric sensitive structure, and the upper surface of the second end of the cantilever is fixedly connected to the second piezoelectric sensitive structure; 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 through a metal connection line, and the first lower electrode and the second upper electrode are connected through a metal connection line; the first lower electrode is connected to a first PAD, and the first upper electrode is connected to a second PAD.

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