High-precision multi-axis sensitive micro acceleration sensor chip and preparation method thereof

Abstract

The invention discloses a high-precision multi-axis sensitive micro acceleration sensor chip and a preparation method thereof, and belongs to the technical field of electric acceleration sensors. According to the multi-axis d33 mode micro piezoelectric acceleration sensor chip disclosed by the invention, the SiO2 layer and the aluminum layer are arranged between the base contact area and the cap-shaped mass block contact area, a silicon dioxide-metal bonding process is realized through metal bonding, and a longitudinal piezoelectric mode is applied to a micro accelerometer; the technical problem that an existing speed sensor chip is difficult to meet the application requirement of a d33 piezoelectric sensor is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of piezoelectric acceleration sensor, and particularly relates to a high-precision multi-axis sensitive miniature acceleration sensor chip and a preparation method thereof. BACKGROUND

[0002] With the rapid development of modern manufacturing industry towards intelligentization, miniaturization and integration, micro-electro-mechanical system (MEMS) technology has been widely applied in industrial automation, consumer electronics, aerospace and other fields due to its advantages such as miniaturization, batch manufacturing, low power consumption and high integration, which are difficult to achieve by traditional mechanical processing technology. As an important branch of MEMS sensor, acceleration sensor chips can be divided into various types according to their working principles, mainly including piezoresistive type based on strain-resistance change effect, piezoelectric type based on strain-charge change effect, capacitive type based on distance change between electrodes, resonant type based on resonant frequency shift, tunneling type based on quantum tunneling effect and thermal conduction type based on heat convection principle, etc.

[0003] Among these numerous types of sensors, piezoelectric acceleration sensor chips exhibit significant advantages due to their unique electromechanical conversion mechanism. This type of sensor directly utilizes the intrinsic characteristics of piezoelectric materials. When subjected to mechanical stress, the lattice structure of the piezoelectric material undergoes asymmetric deformation, resulting in the separation of positive and negative charge centers and the generation of polarization charges. This self-generating characteristic without the need for external power supply makes the sensor have the characteristics of simple structure, fast dynamic response, high signal-to-noise ratio, etc. In particular, its excellent high-frequency response characteristics make it perform excellently in scenarios requiring the capture of rapid dynamic changes such as vibration monitoring and impact measurement.

[0004] Current mainstream piezoelectric acceleration sensor chips generally adopt a transverse piezoelectric effect working mode, utilizing the piezoelectric coefficient d31 (sensitive axis orthogonal to polarization direction), through piezoelectric materials (such as quartz crystal or lead zirconate titanate ceramic) cut in a specific crystal direction. In terms of structure realization, three classic topologies are mainly adopted: cantilever beam-mass block, cross beam-mass block or membrane-mass block. The former causes stress concentration at the root of the beam through the inertial displacement of the concentrated mass block at the end, and the latter relies on the displacement of the mass block caused by the deformation of the thin film to generate strain. These three topologies have the characteristics of mature mechanical model, good process compatibility, etc., and can perfectly match the standard MEMS manufacturing process.

[0005] But for the commonly used thin film piezoelectric material, the longitudinal piezoelectric effect has higher piezoelectric coefficient (d33) and higher quality factor, which can provide more charge signals, and the working mode often has higher resonance frequency. Therefore, the d33 piezoelectric sensor has significant advantages in output voltage, energy conversion efficiency, high-precision application and high-frequency performance, and is especially suitable for application scenarios that require high sensitivity, high power output and high-precision control. However, due to the process and design of the traditional MEMS cross-beam structure sensor chip cannot meet the needs of d33 mode MEMS piezoelectric acceleration sensor, therefore, the d33 mode piezoelectric acceleration sensor chip and its processing method lack relevant exploration. SUMMARY

[0006] The purpose of the present application is to provide a high-precision multi-axis sensitive miniature acceleration sensor chip and its preparation method, to solve the technical problem that the existing acceleration sensor chip cannot meet the application demand of piezoelectric sensor using d33 mode.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: The present application discloses a high-precision multi-axis sensitive miniature acceleration sensor chip, comprising a silicon base and a cap-shaped mass block; the base comprises a base contact area and a base handle; the base contact area is arranged at the center of the base; the base handle is arranged around the base contact area at the outer periphery of the base; the center of the cap-shaped mass block is provided with a cap-shaped mass block contact area; a bottom electrode, a piezoelectric film and a top electrode are sequentially arranged on the base contact area; a SiO2 layer is arranged on the top electrode and the base handle; the cap-shaped mass block contact area and the base contact area are attached by metal bonding, and an aluminum layer is arranged in the attached area.

[0008] Further, the thickness of the SiO2 layer is 500-1000 nm.

[0009] Further, the bottom electrode and the top electrode are respectively connected with a top electrode circuit for leading out the charge signal.

[0010] Further, the cap-shaped mass block contact area and the base contact area are attached by metal bonding, and a bonding allowance is left.

[0011] Further, the piezoelectric film is a PZT piezoelectric film, a ZnO piezoelectric film, an AlN piezoelectric film, a KNN piezoelectric film or a PMNPT piezoelectric film.

[0012] Further, the material of the bottom electrode and the top electrode is Pt electrode, Ti-Pt electrode, TiW alloy or Cr-Au electrode.

[0013] Further, the material of the cap-shaped mass block is metal.

[0014] The application further discloses a preparation method of the high-precision multi-axis sensitive micro acceleration sensor chip. The piezoelectric film is prepared on the bottom electrode by using a sol-gel method, and the top electrode is sputtered by using a magnetron sputtering method; Then, the SiO2 layer is sputtered on the top electrode and the base handle part, and an aluminum layer is sputtered at the same position; The SiO2 layer and the piezoelectric film are patterned by using a wet etching method, and the bottom electrode is exposed; An aluminum layer is evaporated on the base, front side etching is performed, and then Al masking is obtained by peeling off; An aluminum layer is evaporated on the cap-shaped mass block contact area of the cap-shaped mass block; Finally, the base contact area and the cap-shaped mass block contact area are left with a bonding allowance for metal bonding.

[0015] Further, the sputtering method of the SiO2 layer is plasma enhanced chemical vapor deposition; After the top electrode is sputtered, a top electrode circuit is also sputtered.

[0016] Further, the front side etching further includes front side etching after the front side etching, and the base is released.

[0017] Compared with the prior art, the application has the following beneficial effects: The application discloses a high-precision multi-axis sensitive micro acceleration sensor chip, which is characterized in that a SiO2 layer and an aluminum layer are arranged between a base contact area and a cap-shaped mass block contact area, a silicon dioxide-metal bonding process is realized by metal bonding, a longitudinal piezoelectric mode is applied to a micro accelerometer, better selection is provided for application scenarios that require high sensitivity, high power output and multi-directional measurement, a d33 mode multi-axis piezoelectric MEMS acceleration sensor is designed, a low-cost, high-reliability and small installation space solution is provided for occasions that require multi-vibration direction measurement, the sensitivity of the prepared sensor is influenced by the mass block structure quality, the mass block structure gravity size and the contact surface size, and the flexibility and designability are high, the d33 mode MEMS piezoelectric acceleration sensor chip based on the design has the advantages of high precision, wide frequency response, strong designability and suitability for multi-directional measurement, and the technical problem that existing acceleration sensor chips are difficult to meet the application requirements of piezoelectric sensors using the d33 mode is solved.

[0018] Further, the chip of the present application proposes a method of applying longitudinal piezoelectric mode to micro-accelerometer, enriches the design means of piezoelectric acceleration sensor using piezoelectric sensitive film; proposes a multi-axis piezoelectric micro-acceleration sensor design method based on d33 mode; meanwhile, under the same sensitive film using area (d33 available area is large, and PZT film d33 is 3-4 times higher than other direction piezoelectric coefficient), the important parameters such as output voltage, energy conversion efficiency, precision application and high frequency performance are improved, and the application ability of piezoelectric sensitive film with high longitudinal piezoelectric coefficient and low transverse piezoelectric coefficient is improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The process flow chart for preparing PZT piezoelectric film of the present application by sol-gel method is shown in the figure. Figure 2 The three-dimensional schematic diagram of the base and the cap-shaped mass of the present application is shown in the figure. Wherein: a - base; b - cap-shaped mass. Figure 3 The overall structure schematic diagram and A-A cross-sectional view of the high-precision multi-axis sensitive micro-acceleration sensor chip of the present application are shown in the figure. Wherein: a - overall structure; b - A-A cross section. Figure 4 The process schematic diagram of the preparation method of the high-precision multi-axis sensitive micro-acceleration sensor chip is shown in the figure. Wherein: a - preparing PZT sensitive film on Pt bottom electrode by sol-gel method; b - magnetron sputtering deposition of top electrode, lead and pad map; c - releasing base structure; d - base and cap-shaped mass bonding map. Figure 5 The working principle diagram of the high-precision multi-axis sensitive micro-acceleration sensor chip is shown in the figure. Wherein: a - longitudinal acceleration measurement working principle diagram; b, c - transverse acceleration measurement working principle diagram. 1 - base; 2 - base contact area; 3 - base handle; 3-1, first base handle; 3-2, second base handle; 3-3, third base handle; 3-4, fourth base handle; 4 - cap mass contact area; 5 - bottom electrode; 5-1, first bottom electrode; 5-2, second bottom electrode; 5-3, third bottom electrode; 5-4, fourth bottom electrode; 6 - piezoelectric thin film; 6-1, first piezoelectric thin film; 6-2, second piezoelectric thin film; 6-3, third piezoelectric thin film; 7 - top electrode; 7-1, first top electrode; 7-2, second top electrode; 7-3, third top electrode; 7-4, fourth top electrode; 8 - SiO2layer; 9 - cap mass; 10 - silicon substrate of base; 11 - top electrode circuit; 12 - opening of cap mass; 12-1, first opening of cap mass; 12-2, second opening of cap mass; 12-3, third opening of cap mass; 12-4, fourth opening of cap mass; 13 - silicon substrate of cap mass. DETAILED DESCRIPTION

[0020] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein are in the ordinary meaning understood by those skilled in the art of the present application, and in the event of a conflict, the definition in the specification shall prevail.

[0021] Theories or mechanisms described and disclosed herein, whether or not correct, should not be considered limiting the scope of the present application, i.e., the present application can be practiced without relying on any particular theory or mechanism.

[0022] Herein, all features defined in the form of numerical ranges or percentage ranges such as values, amounts, contents and concentrations are for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0023] Herein, unless otherwise specified, "comprise", "include", "contain", "have" or similar words encompass the meaning of "consist of" and "consist essentially of", e.g., "A comprises a" encompasses the meaning of "A comprises a and others" and "A comprises only a".

[0024] Herein, for the sake of brevity of the description, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not contradict each other, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present specification.

[0025] like Figures 2-4 As shown, the present invention provides a high-precision multi-axis sensitive micro acceleration sensor chip, which uses two wafers to manufacture a cap-shaped mass block and a base respectively, and the two parts are tightly combined by bonding; specifically, it includes: The base 1 and the metal cap-shaped mass 9 are composed of a base contact area 2 and a base handle 3. A bottom electrode 5 is formed on the base contact area 2 by sputtering. A piezoelectric film 6 is grown on the bottom electrode 5 and formed by sputtering and PECVD. A top electrode 7 and a SiO2 layer 8 are then formed. When an acceleration signal is received, the cap-shaped mass 9 vibrates, causing stress on the piezoelectric film 6 and generating a charge signal. The piezoelectric film 6, acting as a sensitive element, outputs charge when stress is generated. The bottom electrode 5 and the top electrode 7 collect these charge signals and output them through the top electrode circuit 11. In addition to serving as an electrode, the bottom electrode 5 also serves as a guide layer in the sol-gel preparation of the piezoelectric film 6. The base 1 is disposed on a silicon substrate 10.

[0026] After the bottom electrode 5, piezoelectric film 6, and top electrode 7 are fabricated, a 500-1000nm thick SiO2 layer 8 is grown using PECVD as a protective layer. A metal cap-shaped mass 9 is precision-machined to leave a cap-shaped mass contact area 4. A layer of aluminum is sputtered onto both the cap-shaped mass contact area 4 and the base contact area 2 as an intermediate layer. The SiO2 layer 8 is bonded to the aluminum layer to securely connect the cap-shaped mass contact area 4 to the base contact area 2. The cap-shaped mass 9 is then placed on a cap-shaped mass silicon substrate 13.

[0027] The present invention also discloses a method for preparing the high-precision multi-axis sensitive micro acceleration sensor chip, which comprises the following steps: Step 1: preparing a piezoelectric film 6 on the bottom electrode 5 by a sol-gel method; Step 2: Sputter the top electrode 7 and the top electrode circuit 11 using magnetron sputtering, and pattern the metal layer using photolithography; each top electrode 7 is arranged on the base contact area 2; Step 3: using a plasma enhanced chemical vapor deposition (PECVD) method to deposit a dense SiO2 layer 8 on the base 1 including the base contact area 2, and using a sputtering method to sputter a metal aluminum layer at the same position; Step 4: Patterning the SiO2 layer 8 and the piezoelectric film 6 by wet etching to expose the bottom electrode 5; Step 5: Al is evaporated on the base 1, and the front side is overetched. The Al mask is obtained by stripping with acetone, and the front side is etched to release the silicon base 1. The Al is removed by Al etching solution; Step 6: Vapor-depositing an Al layer on the cap-shaped mass block 9 made of metal material after precision machining to leave the cap-shaped mass block contact area 4; Step 7: Leave a bonding margin between the base contact area 2 and the cap-shaped mass contact area 4, and bond the two wafers to complete the processing of the sensor chip; Step 8: Dicing and releasing the sensor structure.

[0028] Preferably, the bottom electrode 5 and the top electrode 7 are made of Pt, Ti-Pt electrode, TiW alloy, Cr-Au electrode, etc.

[0029] Preferably, the piezoelectric film 6 is a PZT piezoelectric film, a ZnO piezoelectric film, an AlN piezoelectric film, a KNN piezoelectric film, a PMNPT piezoelectric film, or the like.

[0030] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0031] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0032] Example 1 like Figure 1 As shown, using Figure 1 The sol-gel method shown in the figure deposits Pb(Zr) with a thickness of about 1 μm on the substrate 1. 0.52 Ti 0.48 )O3 film (piezoelectric film 6); the Pb(Zr 0.52 Ti 0.48 ) The preparation process of O3 film is as follows: An appropriate amount of formamide and acetylacetone was added to the solution to prevent the film from cracking. Each layer was dried at 150 °C and then pyrolyzed in a box furnace at different temperatures from 300 to 500 °C for 10 minutes to fully remove organic matter and sampled for characterization after pyrolysis. The remaining part was returned to the box furnace and annealed at 650 °C for 30 minutes. Annealing was performed after every two layers of pyrolysis, and a total of five annealings were performed to obtain the piezoelectric film 6, as shown in FIG. Figure 4 (a) A first photolithography is performed on the piezoelectric film 6 using a mask to leave the area to be sputtered with a metal film. The silicon wafer after the photolithography is placed in a coating chamber, vacuum is drawn, and a Pt electrode is sputtered by using a magnetron sputtering method. The sample is taken out of the coating chamber, and is stripped with acetone to obtain a patterned electrode, lead and pad. The top electrode 7 covers the entire base contact area to collect all the electric charges generated by the stress on the sensitive material on the base contact surface when the sensor vibrates. A dense SiO2 layer 8 is deposited on the base 1 including the base contact area 2 by using a PECVD method. The SiO2 layer 8 has two functions: protection and bonding material. The SiO2 layer 8 protects the piezoelectric film 6, the top electrode 7 and the top electrode circuit 11 from external pollution and damage in the subsequent process and working state. At the same time, as part of the silicon dioxide-silicon material bonding process, the SiO2 layer 8 combines the base 1 and the cap-shaped mass 9. The PECVD silicon dioxide film and the piezoelectric film 6 of the sol-gel PZT are patterned by using a wet etching method to expose the bottom electrode 5 and the top electrode 7. The bottom electrode 5 and the top electrode 7 are respectively located at the upper and lower electrodes of the PZT piezoelectric film for collecting piezoelectric charges. As shown in Figure 4 (b); the PZT etching solution used in the experiment includes 100 ml BOE (6:1) + 6 ml CH3COOH + 6 ml HNO3 (65%) + 6 ml HCl (35%) + 4 g (NH4Cl) + 2 g C10H18N2O10 (EDTA) + 75 ml deionized water; the silicon dioxide etching solution used in the experiment is BOE (6:1); Sputtering Al on the wafer surface, front side etching, using acetone to peel off the Al mask, dry etching, and then using aluminum etching solution to wash off the remaining Al on the surface of the silicon wafer, releasing the pedestal 1 through front side etching; the Al layer is reserved as an intermediate layer for bonding; the cap-shaped mass 9 is obtained by sputtering a layer of Al on a silicon wafer with an existing structure; the cap-shaped mass 9 is provided with a cap-shaped mass contact area 4 at the center, and the pedestal 1 and the cap-shaped mass 9 are only in contact at the contact area, which is to amplify the stress when vibrating, so that the mechanical energy of vibration is completely collected by the PZT piezoelectric film; the cap-shaped mass 9 is designed to have a height and a horizontal position that are adjusted to be consistent with the pedestal contact area 2 through the cap-shaped mass contact area 4 and the openings 12 of the cap-shaped mass, the openings 12-1 of the first cap-shaped mass, the openings 12-2 of the second cap-shaped mass, the openings 12-3 of the third cap-shaped mass, and the openings 12-4 of the fourth cap-shaped mass correspond to the first pedestal handle 3-1, the second pedestal handle 3-2, the third pedestal handle 3-3, and the fourth pedestal handle 3-4, respectively; the periphery of the cap-shaped mass 9 is higher than the center, and the purpose is to adjust the height distance between the center of gravity of the mass and the contact surface. The pedestal contact area 2 is uniformly provided with four quarter-circle-shaped first piezoelectric films 6-1, second piezoelectric films 6-2, third piezoelectric films 6-3, and fourth piezoelectric films 6-4, and four top electrodes of the same size are arranged on the films and are led out through a circuit, respectively, as a first top electrode 7-1, a second top electrode 7-2, a third top electrode 7-3, and a fourth top electrode 7-4. A first bottom electrode 5-1, a second bottom electrode 5-2, a third bottom electrode 5-3, and a fourth bottom electrode 5-4 are arranged beside the top electrodes 7, respectively.

[0033] The upper and lower surfaces of the two wafers are respectively left with a bonding allowance, and metal bonding is carried out at 450 DEG C and 30 MPa; plastic deformation occurs at the Al-Al interface, and bonding is formed through atomic diffusion; a chemical bond Al-O-Si is formed at the Al-SiO2 interface; the upper and lower wafers are only in contact at the cap-shaped mass contact area 4 and each chip frame; the contact in other places except the contact area is to expand the contact area and improve the stability of the bonding process, which is convenient for the subsequent dicing process; the protruding design of the opening 12 of the cap-shaped mass is to adjust the horizontal position of the center of gravity to be consistent with the pedestal contact area 2, and at the same time, it cooperates with the inclined surface of the pedestal as an auxiliary positioning during bonding; The sensor structure is released by a laser dicing machine. In the released sensor chip structure, the cap-shaped mass 9 and the pedestal 1 are only in contact at the cap-shaped mass contact area 4.

[0034] The working principle of the high-precision multi-axis sensitive miniature acceleration sensor chip disclosed by the application is as follows: Referring to Figure 5, according to Newton's second law, when the cap-shaped mass 9 is subjected to a certain direction acceleration, the cap-shaped mass 9 will generate an inertia force proportional to the acceleration in the same direction, so that the cap-shaped mass 9 generates displacement, and its stress 3The size is: (1); Wherein, m is the mass of the mass, a is the vibration acceleration, and s is the contact area.

[0035] And from the first type of piezoelectric equation: (2); Wherein, And The stress and strain of the piezoelectric film 6 in the direction, is the flexibility constant of PZT under the action of a constant electric field, is the electric field in the direction (the corresponding voltage is V), is the dielectric constant of PZT, is the longitudinal piezoelectric coefficient, is the surface polarization intensity; Integrate along the L direction and add the two equations to get: (3); Wherein, the contact area s.

[0036] From the above analysis, when the sensor chip is subjected to a longitudinal load, the sensor output signal is proportional to the size of the longitudinal acceleration. From the formula, the longitudinal sensitivity can be adjusted, and its size is affected by the structure of the cap-shaped mass 9. The output charge of the MEMS piezoelectric acceleration sensor chip in mode is proportional to the acceleration it receives, realizing the function of converting acceleration into electrical signal output. The stress of the MEMS piezoelectric acceleration sensor chip working in longitudinal piezoelectric mode The size, the weight of the cap-shaped mass 9 and the size of the acceleration.

[0037] When the mechanism is subjected to a transverse acceleration, the sensor cap-shaped mass 9 is subjected to an acceleration load stress. The center of gravity of the cap-shaped mass 9 is away from the joint surface by a height h, and the mass block has a radius r. The bending moment size of the joint surface center from the acceleration load is: (4); Suppose the mass is a rigid body, and the load at a distance x from the center on a certain piece of 1 / 2 circular piezoelectric film is (5); Combined with the bending moment formula (4) (7); Get: (8); Substitute the piezoelectric equation (2) and the charge formula (3) (9); Get (10); From the formula, when the sensor chip is subjected to a lateral load, the sensor output signal is proportional to the acceleration signal size. The lateral sensitivity is adjustable, and its size is affected by the mass of the hat-shaped mass 9, the structural gravity center size of the hat-shaped mass 9, and the size of the base contact area 2.

[0038] Example 2 In this embodiment, the sensor structure and the dielectric layer are the same as in Example 1, and the difference lies in the use of different piezoelectric films to meet the needs of different application scenarios. On this basis, a piezoelectric MEMS acceleration sensor chip is prepared, as follows: The AlN thin film is deposited by reactive magnetron sputtering method. During the process of magnetron sputtering, under the action of electric field, electrons will move rapidly towards the substrate, and in the process, they will collide with inert gas argon atoms, causing argon atoms to ionize, forming Ar + and new electrons, on the one hand, the generated Ar + under the action of electric field and magnetic field, obtains a large kinetic energy and reaches the surface of Al target material, and high-energy bombardment of Al target material surface makes the target material undergo a series of cascade reactions, some Al atoms on the surface obtain enough energy to escape from the target material surface, i.e. sputtering Al atoms, and react with working gas nitrogen to deposit on the substrate, on the other hand, the newly formed secondary electrons change their trajectory due to the action of the magnetic field of the magnetron target, and collide with inert gas Ar atoms again, generating new Ar + and electrons, forming a new round of deposition reaction, thereby preparing an AlN thin film.

[0039] Step 1 is different in that a sputtering gas pressure of 0.3 Pa, a sputtering voltage of 250 W, and a nitrogen content of 50% are used on a Si / SiO 2 / Pt substrate, and sputtering for 45-90 min: nitrogen content 50%, sputtering for 45-90 min to obtain a uniform and dense aluminum nitride thin film with a thickness of 500-1000 nm.

[0040] Step 6 is different in that inductive coupled plasma etching (ICP) is used to etch the AlN epitaxial layer with chlorine gas as the etching gas and metal Cr / Au as the hard mask. Then the silicon wafer is placed in a Cr / Au etching solution to remove the mask. The Cr etching solution is prepared based on high-purity cerium ammonium nitrate, containing a small amount of nitric acid to maintain the acidic environment of the etching solution, and the Au etching solution is usually prepared from potassium iodide and iodine. The AlN thin film prepared by magnetron sputtering can generate high-quality, dense and uniform thin film, has good adhesion and mechanical properties, high purity, uniform film thickness, and by adjusting the sputtering parameters such as target material composition, gas pressure, deposition rate, substrate temperature, etc. The properties of the thin film can be accurately controlled to meet the requirements of different application scenarios for the performance of the thin film. It can be deposited at a relatively low temperature to avoid problems such as substrate damage and thin film defects caused by high-temperature processes, which is particularly important for some temperature-sensitive substrate materials.

[0041] Preferably, the sensitive thin film piezoelectric layer 6 can also be a ZnO piezoelectric thin film, a KNN piezoelectric thin film, and a PMNPT piezoelectric thin film, etc.

[0042] In summary, the application proposes a method of applying longitudinal piezoelectric mode to a three-axis micro-accelerometer, enriching the design means of piezoelectric acceleration sensor using piezoelectric sensitive thin film; a method of designing sensitivity by adjusting the weight of the mass, the height of the center of gravity and the area of the contact surface is proposed; under the same use area of the sensitive thin film, the important parameters such as output voltage, energy conversion efficiency, precision application and high frequency performance are improved; the application ability of part of the piezoelectric sensitive thin film with high longitudinal piezoelectric coefficient and low transverse piezoelectric coefficient is improved.

[0043] The above content only illustrates the technical idea of the application, and cannot limit the protection scope of the application. Any modification made according to the technical idea of the application on the basis of the technical scheme falls within the protection scope of the claims of the application.

Claims

1. A high-precision multi-axis sensitive micro acceleration sensor chip, characterized in that: The invention comprises a silicon base (1) and a cap-shaped mass block (9); the base (1) comprises a base contact area (2) and a base handle (3); the base contact area (2) is arranged at the center of the base (1); the base handle (3) is arranged at the periphery of the base (1) around the base contact area (2); a cap-shaped mass block contact area (4) is arranged at the center of the cap-shaped mass block (9); a bottom electrode (5), a piezoelectric film (6), and a top electrode (7) are arranged on the base contact area (2) in sequence; a SiO2 layer (8) is arranged on the top electrode (7) and the base handle (3); the cap-shaped mass block contact area (4) and the base contact area (2) are bonded together by metal bonding, and an aluminum layer is provided in the bonded area.

2. A high-precision multi-axis sensitive micro acceleration sensor chip according to claim 1, characterized in that: The thickness of the SiO2 layer (8) is 500-1000 nm.

3. The high-precision multi-axis sensitive micro acceleration sensor chip according to claim 1, characterized in that: The bottom electrode (5) and the top electrode (7) are respectively connected to a top electrode circuit (11) for deriving a charge signal.

4. The high-precision multi-axis sensitive micro acceleration sensor chip according to claim 1, characterized in that: The cap-shaped mass block contact area (4) and the base contact area (2) are bonded together by metal bonding, leaving a bonding margin.

5. The high-precision multi-axis sensitive micro acceleration sensor chip according to claim 1, characterized in that: The piezoelectric film (6) is a PZT piezoelectric film, a ZnO piezoelectric film, an AlN piezoelectric film, a KNN piezoelectric film or a PMNPT piezoelectric film.

6. The high-precision multi-axis sensitive micro acceleration sensor chip according to claim 1, characterized in that: The bottom electrode (5) and the top electrode (7) are made of Pt electrode, Ti-Pt electrode, TiW alloy or Cr-Au electrode.

7. The high-precision multi-axis sensitive micro acceleration sensor chip according to claim 1, characterized in that: The material of the cap-shaped mass block (9) is metal.

8. The method for preparing a high-precision multi-axis sensitive micro acceleration sensor chip according to any one of claims 1 to 7, characterized in that: The following steps are involved: A piezoelectric film (6) is prepared on the bottom electrode (5) by a sol-gel method, and a top electrode (7) is sputtered by a magnetron sputtering method; Subsequently, a SiO2 layer (8) is sputtered on the top electrode (7) and the base handle (3), and an aluminum layer is sputtered at the same position by the sputtering method; The SiO2 layer (8) and the piezoelectric film (6) are patterned by wet etching to expose the bottom electrode (5); An aluminum layer is evaporated on the base (1), and a front surface overlay is performed, followed by peeling to obtain an Al mask; Vapor-depositing an aluminum layer on a cap-shaped mass block contact area (4) on the cap-shaped mass block (9); Finally, the base contact area (2) and the cap-shaped mass block contact area (4) are metal-bonded with a bonding margin.

9. The method for preparing a high-precision multi-axis sensitive micro acceleration sensor chip according to claim 8, characterized in that: The sputtering method of the SiO2 layer (8) is plasma enhanced chemical vapor deposition; After the top electrode (7) is sputtered, a top electrode circuit (11) is also sputtered.

10. The method for preparing a high-precision multi-axis sensitive micro acceleration sensor chip according to claim 8, characterized in that: After the front overlay, the method further includes front etching to release the base (1).

Images