阅读说明：本技术 一种碳化硅振动传感器及其制造方法 (Silicon carbide vibration sensor and manufacturing method thereof ) 是由 赵玉龙 杨玉 赵友 王鲁康 于 2021-07-21 设计创作，主要内容包括：本发明公开了一种碳化硅振动传感器及其制造方法,该传感器采用单桥结构,设计敏感梁的宽度小于敏感梁的厚度,敏感方向平行于质量块平面,与传统敏感方向垂直于质量块平面的振动传感器相比,在不提高加工难度的基础上,提高了输出灵敏度。该传感器敏感梁截面为梯形梁结构,与同截面积矩形梁相比,振动引起的应力更加集中,传感器的输出更大。该传感器两对压敏电阻均布置于敏感梁应力最大值处,利用碳化硅的压阻效应,将振动引起的应力转换为电阻值的变化,采用惠斯通电桥全桥转化成可输出的电压信号,可以及时、准确地完成信号转换,同时保证了传感器的输出灵敏度。(The invention discloses a silicon carbide vibration sensor and a manufacturing method thereof, the sensor adopts a single bridge structure, the width of a designed sensitive beam is smaller than the thickness of the sensitive beam, the sensitive direction is parallel to the plane of a mass block, and compared with the traditional vibration sensor of which the sensitive direction is vertical to the plane of the mass block, the silicon carbide vibration sensor improves the output sensitivity on the basis of not improving the processing difficulty. The cross section of the sensitive beam of the sensor is of a ladder-shaped beam structure, and compared with a rectangular beam with the same cross section, the stress caused by vibration is more concentrated, and the output of the sensor is larger. Two pairs of piezoresistors of the sensor are uniformly distributed at the maximum stress value of the sensitive beam, the stress caused by vibration is converted into the change of the resistance value by utilizing the piezoresistive effect of silicon carbide, the Wheatstone bridge is adopted to convert the stress into an outputvoltage signal in a full-bridge manner, the signal conversion can be timely and accurately completed, and the output sensitivity of the sensor is ensured.)

1. The silicon carbide vibration sensor is characterized by comprising a fixed outer frame (1) and a mass block (3), wherein the fixed outer frame (1) surrounds the mass block (3), and the fixed outer frame (1) and the mass block (3) are spaced by a groove (8);

the fixed outer frame (1) is connected with the mass block (3) through two sensitive beams (2), the two sensitive beams (2) are arranged on a central line in the x direction, and the two sensitive beams (2) are symmetrical relative to the central line in the y direction; the outer end part of each sensitive beam (2) is connected with the fixed outer frame (1), and the inner end part is connected with the mass block (3); grooves (8) are arranged on two sides of each sensitive beam (2);

a pair of piezoresistors (4) is arranged at the outer end part of each sensitive beam (2), two groups of metal bonding pads (5) which are symmetrical relative to the central line of the y direction are arranged on the fixed outer frame (1), and each pair of piezoresistors (4) is communicated with the metal bonding pads (5) at the same side of the piezoresistors through body type leads (6);

the overlapped area of the piezoresistor (4) and the body type lead (6) is an ohmic contact area (7); the piezoresistor (4), the body type lead (6) and the metal bonding pad (5) jointly form a Wheatstone bridge;

the section of the sensitive beam (2) is trapezoidal, and the piezoresistor (4) is arranged on the upper part of the trapezoidal wide surface; the width of the wide surface of the sensitive beam (2) is smaller than the thickness of the whole sensor.

2. A silicon carbide vibration sensor as claimed in claim 1, wherein each pair of piezoresistors (4) comprises a first piezoresistor (401) and a second piezoresistor (402), and the first piezoresistor (401) and the second piezoresistor (402) are arranged along the length of the sensing beam (2).

3. A silicon carbide vibration sensor as claimed in claim 2, characterized in that the first piezo-resistor (401) and the second piezo-resistor (402) of a pair of piezo-resistors (4) are symmetrical with respect to the x-direction centre line.

4. A silicon carbide vibration sensor according to claim 2, wherein the metal pads (5) comprise a first metal pad (501) and two second metal pads (502), the two second metal pads (502) being respectively disposed on both sides of the first metal pad (501), the first metal pad (501) being disposed on the x-direction centerline.

5. The silicon carbide vibration sensor according to claim 4, wherein the outer end portion of the first piezo-resistor (401) and the outer end portion of the second piezo-resistor (402) are connected by a first type lead (601) and a second metal pad (502), respectively;

the inner end part of the first piezoresistor (401) and the inner end part of the second piezoresistor (402) are connected through a second body type lead (602), and the second body type lead (602) is communicated with the first metal pad (501) through a third body type lead (603).

6. The silicon carbide vibration sensor according to claim 5, wherein the two first body type leads (601) do not contact.

7. A silicon carbide vibration sensor as claimed in claim 1, wherein the metal pads (5) and body type leads (6) are each a multi-layer metal combination.

8. The silicon carbide vibration sensor as claimed in claim 7, wherein the plurality of layers of metal are Ni, Ti and Au in order from top to bottom.

9. A silicon carbide vibration sensor according to claim 1, characterized in that the grooves (8) on both sides of the sensing beam (2) are trapezoidal in cross section.

10. A method for manufacturing a silicon carbide vibrator according to claim 1, comprising the steps of:

step 1, selecting an N-type epitaxial doped 4H-SiC wafer, and cleaning;

step 2, spin-coating photoresist on the epitaxial surface of the 4H-SiC wafer, selecting a mask of the piezoresistor (4) and the body type lead (6) for photoetching, carrying out magnetron sputtering by using a nickel target material, sputtering a nickel metal film covering the whole wafer, and stripping to obtain a first process wafer with the piezoresistor (4), the bonding pad (5) and the body type lead (6) which are shielded by metal;

step 3, etching the first process wafer by a plasma dry method, etching off the N-type epitaxial layer which is not protected by the metal masking layer, and forming a second process wafer with a piezoresistor (4), a bonding pad (5) and a body type lead (6);

step 4, depositing SiO on the second process wafer by a plasma enhanced vapor deposition method₂The isolation layer is coated with photoresist in a spinning way, and photoetching is carried out on the isolation layer through an ohmic contact window mask to carry out SiO₂Etching and windowing the isolation layer to obtain a third process wafer with an ohmic contact region (7);

step 5, photoresist is spin-coated on the third process wafer, photoetching is carried out through a metal lead and a laser etching mark mask, a nickel target, a titanium target and a gold target are sequentially used for sputtering, a Ni film, a Ti film and an Au film are sequentially sputtered, and the fourth process wafer with a metal sputtering bonding pad (5) and a body type lead (6) is obtained after stripping;

step 6, annealing the fourth process wafer to obtain a fifth process wafer with an activated ohmic contact region (7);

and 7, etching the fifth process wafer by using femtosecond laser to obtain a sensitive beam (2) and a mass block (3), and preparing the final silicon carbide vibration sensor.

Technical Field

The invention belongs to the technical field of micro electro mechanical systems, and particularly relates to a silicon carbide vibration sensor and a manufacturing method thereof.

Background

The high-temperature vibration monitoring has important application in the fields of petrochemical industry, nuclear power, aerospace and the like. Taking the vibration monitoring of the aircraft engine as an example, abnormal vibration is a significant cause of the failure of the aircraft engine, and the failure rate of the vibration failure in the maintenance of the air route is even more than 90%. The working vibration state of the engine can be obtained by monitoring the vibration of the rotor of the aircraft engine, the service life of the engine is predicted, and the flight cost is greatly reduced. The key structure to be monitored generally works in a high-temperature environment of over 300 ℃, the working temperature of some structures even exceeds 1000 ℃, so that high requirements are provided for the high-temperature performance of the sensor, and the traditional vibration sensor is difficult to meet the requirement of engine monitoring.

The piezoresistive high-temperature vibration sensor has the advantages of small volume, low power consumption and mass production by means of a Micro Electro Mechanical System (MEMS) technology, is high in precision and wide in response frequency band, and can meet the application requirements of high-temperature vibration testing of an aircraft engine on high precision, high frequency response and mass production. Silicon carbide (SiC) is a typical wide band gap semiconductor material, has excellent electrical, thermal and mechanical properties, and attracts extensive attention of researchers at home and abroad. Compared with the traditional Si material, the SiC has better thermoplastic deformation resistance (about 1000 ℃) and high-temperature electric leakage resistance (more than 350 ℃); meanwhile, the SiC material has excellent piezoresistive effect as the Si material, has higher mechanical strength, wear resistance and chemical corrosion resistance than Si material, and is suitable for the application of high-temperature vibration sensors.

But SiC material properties have also limited the development of SiC piezoresistive devices: firstly, SiC is wear-resistant and corrosion-resistant, higher requirements are provided for a processing technology, and the traditional means such as dry etching, wet etching, mechanical processing and the like can not effectively carry out large-depth bulk processing on SiC materials, so that the processing efficiency is seriously influenced; secondly, the Young modulus of SiC is about three times that of Si, and the sensitivity of the sensor with the same structure is only one third of that of Si under the allowable processing conditions, so that the requirement of high sensitivity is difficult to meet; third, the metal-semiconductor electrical connection is unstable at high temperatures, making stable high temperature ohmic contact fabrication of SiC devices difficult.

In order to improve the wider function of the SiC material in the high-temperature vibration field, an efficient manufacturing method of the high-temperature-resistant and high-sensitivity SiC vibration sensor is needed. The Chinese invention patent CN201910009344.1 discloses a high-sensitivity, high-frequency response and overload-resistant silicon carbide high-temperature vibration sensor, and designs a tuning fork composite cantilever beam structure vibration sensor, wherein a single beam is more stressed when being subjected to acceleration, and the composite beam structure also improves the rigidity of the cantilever beam, but the design has the advantages of high processing difficulty, high cost, low yield and difficult mass production; the chinese invention patent CN201911212178.1 discloses a piezoresistive acceleration sensor based on silicon carbide material and a manufacturing method thereof, which adopts a double-cantilever structure, the signal acquisition output circuit is a wheatstone bridge designed as a half-bridge, the signal output change is small, the sensitivity is low, and the natural frequency of the vibration sensor of the double-cantilever structure is low, so that the requirement of high-frequency vibration measurement is difficult to meet.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a silicon carbide vibration sensor and a manufacturing method thereof, so as to solve the problems of low silicon carbide processing efficiency and low sensitivity of the silicon carbide vibration sensor in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a silicon carbide vibration sensor comprises a fixed outer frame and a mass block, wherein the fixed outer frame surrounds the mass block, and the fixed outer frame and the mass block are spaced by a groove;

the fixed outer frame and the mass block are connected through two sensitive beams, the two sensitive beams are arranged on a central line in the x direction, and the two sensitive beams are symmetrical relative to the central line in the y direction; the outer end part of each sensitive beam is connected with the fixed outer frame, and the inner end part of each sensitive beam is connected with the mass block; grooves are formed in the two sides of each sensitive beam;

a pair of piezoresistors is arranged at the outer end part of each sensitive beam, two groups of metal bonding pads which are symmetrical relative to the central line in the y direction are arranged on the fixed outer frame, and each pair of piezoresistors is communicated with the metal bonding pads on the same side of the piezoresistors through body type leads;

the overlapped area of the piezoresistor and the body type lead is an ohmic contact area; the piezoresistor, the body type lead and the metal pad jointly form a Wheatstone bridge;

the cross section of the sensitive beam is trapezoidal, and the piezoresistor is arranged on the upper part of the trapezoidal wide surface; the width of the wide surface of the sensitive beam is smaller than the thickness of the whole sensor.

The invention is further improved in that:

preferably, each pair of piezoresistors comprises a first piezoresistor and a second piezoresistor, and the first piezoresistor and the second piezoresistor are arranged along the length direction of the sensitive beam.

Preferably, the first and second piezoresistors in the pair of piezoresistors are symmetrical with respect to the x-direction center line.

Preferably, the metal pads include a first metal pad and two second metal pads, the two second metal pads are respectively disposed on two sides of the first metal pad, and the first metal pad is disposed on the x-direction central line.

Preferably, the outer end of the first piezoresistor and the outer end of the second piezoresistor are respectively connected through a first integral lead and a second metal pad;

the inner end part of the first piezoresistor and the inner end part of the second piezoresistor are connected through a second body type lead, and the second body type lead is communicated with the first metal pad through a third body type lead.

Preferably, the two first integrated leads do not contact.

Preferably, the metal pad and the body type lead are both a multilayer metal combination.

Preferably, the multilayer metal comprises Ni, Ti and Au in sequence from top to bottom.

Preferably, the cross section of the groove on the two sides of the sensitive beam is trapezoidal.

A method for manufacturing the silicon carbide vibrator comprises the following steps:

step 1, selecting an N-type epitaxial doped 4H-SiC wafer, and cleaning;

step 2, spin-coating photoresist on the epitaxial surface of the 4H-SiC wafer, selecting a mask of the piezoresistor and the body type lead for photoetching, carrying out magnetron sputtering by using a nickel target material, sputtering a nickel metal film covering the whole wafer, and obtaining a first process wafer with the piezoresistor, the bonding pad and the body type lead which are shielded by metal after stripping;

step 3, etching the first process wafer by a plasma dry method, etching off the N-type epitaxial layer which is not protected by the metal masking layer, and forming a second process wafer with a piezoresistor, a bonding pad and a body type lead;

step 4, depositing SiO on the second process wafer by a plasma enhanced vapor deposition method₂The isolation layer is coated with photoresist in a spinning way, and photoetching is carried out on the isolation layer through an ohmic contact window mask to carry out SiO₂Etching the isolation layer to form a window, and obtaining a third process wafer with an ohmic contact region;

step 5, spin-coating photoresist on the third process wafer, photoetching through a metal lead and a laser etching mark mask, sputtering by using a nickel target material, a titanium target material and a gold target material in sequence, sputtering a Ni film, a Ti film and an Au film in sequence, and stripping to obtain a fourth process wafer with a bonding pad and a body type lead of sputtered metal;

step 6, annealing the fourth process wafer to obtain a fifth process wafer with an activated ohmic contact region;

and 7, etching the fifth process wafer by using femtosecond laser to obtain a sensitive beam and a mass block, and obtaining the final silicon carbide vibration sensor.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a silicon carbide vibration sensor, which adopts a single bridge structure, the width of a designed sensitive beam is smaller than the thickness of the sensitive beam, the sensitive direction is parallel to the plane of a mass block, and compared with the traditional vibration sensor with the sensitive direction vertical to the plane of the mass block, the silicon carbide vibration sensor improves the output sensitivity on the basis of not improving the processing difficulty. The cross section of the sensitive beam of the sensor is of a ladder-shaped beam structure, and compared with a rectangular beam with the same cross section, the stress caused by vibration is more concentrated, and the output of the sensor is larger. Two pairs of piezoresistors of the sensor are uniformly distributed at the maximum stress value of the sensitive beam, the stress caused by vibration is converted into the change of the resistance value by utilizing the piezoresistive effect of silicon carbide, the Wheatstone bridge is adopted to convert the stress into an outputvoltage signal in a full-bridge manner, the signal conversion can be timely and accurately completed, and the output sensitivity of the sensor is ensured. The sensor utilizes the body type lead to replace a metal circuit, the body type lead and the bonding pad are electrically connected with the piezoresistor through ohmic contact, the lead and the resistor are on the same plane, the high-temperature stability of the electrical connection of the sensor circuit is effectively improved, and a homogeneous contact surface is provided for the further lead.

Furthermore, the metal bonding pad and the body type lead are made of multilayer metal, so that the metal bonding pad and the body type lead can form a high-temperature-resistant ohmic contact region with 4H-SiC, meanwhile, the ohmic contact region is isolated and protected, and the metal bonding pad and the body type lead can be interconnected with a gold wire.

The invention also discloses a preparation method of the vibration sensor, which combines the traditional MEMS technology with the femtosecond laser processing technology, adopts the traditional MEMS technology to manufacture the sensitive resistor and the body type lead wire, releases the cantilever beam and the mass block by the femtosecond laser etching method, has the advantages of processing precision and efficiency, reasonable process and easy batch production. In the preparation method, the metal lead and the laser alignment mark are manufactured on the same mask plate, so that the processing steps are reduced, the alignment precision is improved, and the processing cost is reduced.

Drawings

FIG. 1 is a front view of a high sensitivity, high temperature resistant silicon carbide vibration sensor and a partial enlargement thereof;

FIG. 2 is a three-dimensional schematic diagram of the overall structure of a high sensitivity, high temperature resistant silicon carbide vibration sensor;

FIG. 3 is a schematic diagram of a piezoresistor on a cross-section and a face of a sensitive beam of a high-sensitivity, high-temperature resistant silicon carbide vibration sensor;

FIG. 4 is a flow chart of a high sensitivity, high temperature resistant silicon carbide vibration sensor fabrication;

wherein (a) is a structural diagram of step 1; (b) FIG. 2 is a block diagram; (c) FIG. 3 is a view showing the structure of step 3; (d) FIGS. 4 to (f) are views showing the structure of step 4; (g) the figures are the structure diagrams of the steps 5-6; (h) FIG. 7 is a block diagram;

FIG. 5 is a schematic diagram of the placement of piezoresistors on a sensitive beam of a high-sensitivity, high-temperature resistant silicon carbide vibration sensor;

FIG. 6 is a schematic diagram of a Wheatstone bridge connection of a high-sensitivity, high-temperature resistant silicon carbide vibration sensor;

FIG. 7 is a schematic diagram of a mask for making piezo-resistive strips and body leads for a high sensitivity, high temperature resistant silicon carbide vibration sensor;

FIG. 8 is a schematic diagram of a reticle for making an ohmic contact window of a high sensitivity, high temperature resistant silicon carbide vibration sensor;

FIG. 9 is a schematic diagram of a reticle for fabricating high sensitivity, high temperature resistant silicon carbide vibration sensor metal leads and laser etched marks;

wherein, 1-fixing the outer frame; 2-sensitive beam; 3-a mass block; 4-a voltage dependent resistor; 401-a first varistor; 402-a second varistor; 5-a metal pad; 501-a first metal pad; 502-a second metal pad; 6-body type leads; 601-a first integral lead; 602-a second bulk lead; 603-third body type leads; a 7-ohmic contact region; 8-a trench; 801-a first trench; 802-a second trench; 803-third trench.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

in the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention; the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; furthermore, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly and encompass, for example, both fixed and removable connections; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 1 and 2, the invention discloses a high-sensitivity and high-temperature-resistant silicon carbide vibration sensor, the chip material of which is 4H-SiC, the thickness of the chip is about 350 μm, and the sensor structurally comprises a square fixed outer frame 1, a double sensitive beam 2 and a mass block 3; two edges of the whole chip are set to be located in the x direction, and two edges are located in the y direction, specifically, the double sensitive beams 2 are symmetrical relative to the central line of the y direction, and the reference is made to the two edges, so that the details are not repeated.

The mass block 3 is surrounded by the square fixed outer frame 1, the two mass blocks are isolated by the grooves 8, the grooves 8 include two first grooves 801 in the x direction and four second grooves 802 in the y direction, the two first grooves 801 are symmetrically arranged relative to the center line of the x direction of the chip, the four second grooves 802 in the y direction are symmetrically arranged relative to the center line of the y direction of the chip, two second grooves 802 are arranged on each side of the center line of the y direction, a third groove 803 is connected to the end part of each second groove 802 close to the center line of the x direction, the third groove 803 is perpendicular to the second grooves 802, therefore, two sides of each end of the center line of the x direction are respectively provided with one third groove 803, the four third grooves 803 are symmetrical in pairs relative to the center line of the x direction, and the two third grooves 803 on one side of the center line of the x direction are not contacted. The mass block 3 forms an I-shaped structure through the grooves 8.

Two sensitive beams 2 are symmetrical relative to a y-direction central line, one end of each sensitive beam 2 is integrally connected with the mass block 3, the other end of each sensitive beam 2 is integrally connected with the outer frame 1, a third groove 803 is respectively arranged on each of two sides of each sensitive beam 2, a pair of piezoresistors 4 are arranged at the ends, close to the fixed outer frame 1, of each sensitive beam 2, metal bonding pads 5 are arranged on the corresponding fixed outer frame 1, and the piezoresistors 4 are connected with the metal bonding pads 5 through body type leads 6.

Specifically, each pair of piezoresistors 4 comprises a first piezoresistor 401 and a second piezoresistor 402 which are identical in shape, and the first piezoresistor 401 and the second piezoresistor 402 are arranged in parallel and along the length (i.e. x direction) direction of the sensitive beam 2 and are symmetrical about the x direction center line of the chip. The two sides of the y-direction central line of the chip are respectively provided with one metal pad 5, the metal pads 5 are all arranged on the fixed outer frame 1, each metal pad 5 comprises a first metal pad 501 and two second metal pads 502, the two second metal pads 502 are respectively arranged on the two sides of the first metal pad 501, every two second metal pads 502 are symmetrical relative to the y-direction central line, and each first metal pad 501 is arranged on the y-direction central line.

More specifically, the outer ends of the first piezoresistor 401 and the second piezoresistor 402 close to the fixed outer frame 1 are respectively connected with the upper bonding pad 502 of the fixed outer frame 1 through a first body type lead 601, the inner ends close to the mass block 3 are connected through a second body type lead 602, and the second body type lead 602 is connected to the first metal bonding pad 501 of the fixed outer frame 1 through a third body type lead 603. The first body type lead 601 is arranged on the fixed frame 1, the second body type lead 603 is arranged on the mass block 3, and the third body type lead 601 is partially arranged on the fixed frame 1 and partially arranged on the mass block 3. The first body type lead 601 is longer than the third body type lead 603, and the third body type lead 603 is longer than the second body type lead 602.

The piezoresistor 4 and the body type lead 6 are connected and overlapped in an ohmic contact region 7, and the piezoresistor 4, the body type lead 6 and the bonding pad 5 jointly form a Wheatstone bridge.

Referring to fig. 3, the cross section of the sensitive beam 2 is trapezoidal, the width of the sensitive beam is gradually reduced from the wide surface to the narrow surface, the width of the wide surface of the sensitive beam 2 is about 200 μm, the width of the narrow surface is about 100 μm, and the widths are both smaller than the thickness of a chip 350 μm, and the piezoresistor 4 is arranged on the wide surface of the sensitive beam 2. Correspondingly, the third trench 803 has a trapezoidal structure, and the narrow surface of the third trench 3 is on the top and the wide surface is on the bottom, which is opposite to the trend of the sensitive beam 2.

In fig. 1 and 2, the metal pad 5 and the body type lead 6 are both a multilayer metal combination, and from top to bottom: ni, Ti and Au, the thicknesses of Ni, Ti and Au are respectively 100nm, 50nm and 100 nm.

The invention discloses a manufacturing method of a silicon carbide vibration sensor, which specifically comprises the following steps of:

step 1, cleaning and preparing a wafer, selecting an N-type doped epitaxial 4H-SiC wafer with the doping concentration of about 1.5 multiplied by 10¹⁹cm^-3The doping thickness is about 2 μm; the wafer was first immersed in NH at a temperature of 78 ℃ in a ratio of 1:1:5₄OH、H₂O₂,、H₂Rinsing with deionized water and drying in O solution for 15min to remove organic pollutants on the surface; then immersing in HF and H at room temperature in a ratio of 1:50₂O solution is used for 1min, and the surface oxide is removed by rinsing and drying with deionized water; finally, the wafer is immersed in HCl and H with the temperature of 75-80 ℃ and the ratio of 1:1:6₂O₂、H₂Rinsing with deionized water and drying to remove surface ionic contaminants in O solution for 15min to obtain a wafer as shown in FIG. 4 (a);

step 2, referring to fig. 7, spin-coating photoresist on the 4H-SiC epitaxial surface, selecting a mask of a piezoresistor strip and a body type lead for photoetching, and performing magnetron sputtering by using a nickel target material with a vacuum degree of 3.3 × 10^-6Pa, sputtering a nickel metal film with the thickness of about 130nm and covering the whole wafer; stripping nickel metal with acetone to obtain a first process wafer with metal-masked piezoresistors 4, bonding pads 5 and body type leads 6, and the graph is shown in fig. 4 (b);

step 3, CF at 30sccm₄And 10sccm O₂In the atmosphere environment, etching the first process wafer obtained in the step 2 by a plasma dry etching method, wherein the ICP power is 800W, the RF power is 100W, the chamber pressure is 10mTorr, and after etching for 20min, etching off an N-type epitaxial layer which is not protected by a metal masking layer to form the piezoresistor 4, the bonding pad 5 and the body type lead 6, and using 36% HCl: 68% HNO₃3: 1, corroding the residual metal masking layer by using the solution to obtain a corroded 4H-SiC substrate and obtain a second process wafer, wherein the second process wafer is shown in a figure 4 (c);

step 4, depositing a layer of SiO with the thickness of 300nm on the surface of the second process wafer obtained in the step 3 by a plasma enhanced vapor deposition method₂As a barrier layerSpin-coating photoresist, and performing photolithography through an ohmic contact window mask, as shown in fig. 8; with 49% HF: 40% NH₄F is 1:6 (BOE solution) etching and windowing the SiO2 isolation layer; and removing the photoresist by using acetone and absolute ethyl alcohol to obtain the 4H-SiC substrate with the ohmic contact region 7 windowing oxidation isolation layer, which is a third process wafer. As shown in FIGS. 4(d) (e) (f);

step 5, spin-coating photoresist on the surface of the third process wafer obtained in the step 4, photoetching through a metal lead and a laser etching mark mask plate, and sputtering by using a nickel target material, a titanium target material and a gold target material in sequence with the vacuum degree of 3.3 multiplied by 10 as shown in figure 9^-6Pa, power of 100W, sputtering Ni, Ti and Au films with thickness of 100nm, 50nm and 100nm respectively, stripping the nickel, titanium and gold metal films by acetone to obtain a 4H-SiC substrate of a pad 5 and a body type lead 6 of sputtered metal, which is a fourth process wafer, as shown in FIG. 4 (g);

step 6, at N of 2L/min₂Carrying out rapid thermal annealing treatment on the fourth process wafer under air flow, wherein the heating rate is 100K/min, the temperature is kept for 2min at 500 ℃, the temperature is kept for 3min after the temperature is raised to 1000 ℃, and then the fourth process wafer is taken out when the temperature is reduced to be close to the room temperature, so that the substrate with the activated ohmic contact region 7 is obtained and is the fifth process wafer;

and 7, etching the 4H-SiC substrate by using femtosecond laser according to the laser etching mark on the fifth process wafer obtained in the step 6, wherein the SiC is a transparent material, the laser etching mark obtained by processing in the steps 5 and 6 can be observed on a non-epitaxial surface, and the laser alignment mark is used as a reference, and the laser parameters are set as follows: laser wavelength 535nm, power 4W, repetition frequency 100kHz, scanning speed 300mm/min, laser scanning mode line scanning in a word-back mode, scanning line interval 10um and repetition times 300 times; and (3) releasing the sensitive beam 2 and the mass block 3 by utilizing laser etching, cleaning the etched substrate to obtain a completely processed SiC substrate as shown in figure 4(h), and scribing by utilizing laser to obtain a single sensor chip.

The invention provides a silicon carbide vibration sensor, as shown in figures 1, 2 and 3, four groups of piezoresistors of the vibration sensor are uniformly distributed at the maximum stress value of a sensitive beam 2, the stress caused by vibration is converted into the change of the resistance value by utilizing the piezoresistive effect of silicon carbide, and the change of the resistance value is converted into an outputable voltage signal by adopting a Wheatstone bridge full bridge, so that the signal conversion can be timely and accurately finished, and the output sensitivity of the sensor is ensured.

The sensor sensitive resistor and the connection mode are shown in fig. 5 and 6, the resistances of the piezoresistors are equal to each other, and R is₁＝R₂＝R₃＝R₄When the sensor receives an upward acceleration parallel to the mass block 3, the sensitive beam 2 deforms under the action of inertia force, and the resistor R on the sensitive beam 2₁、R₃Tensile stress, resistance value of the resistor is increased by delta R; r₂、R₄To R₁、R₃With equal compressive stress, the resistance of the resistor decreases by Δ R, the upward arrow indicates that the resistor becomes larger, the downward arrow indicates that the resistor decreases, and a Wheatstone bridge rear circuit is formed, as shown in FIG. 6, U_sRepresenting the supply voltage, U_oRepresenting the output voltage. Then under the acceleration corresponding to fig. 5, the output voltage of the sensor is:the bridge combination mode maximally utilizes the differential output capacity of the Wheatstone bridge, and ensures the sensitivity of the sensor.

R when the sensor is subjected to an acceleration perpendicular to the mass 3₁、R₂、R₃、R₄The tensile stress or the compressive stress is uniform, the resistance changes are the same, the output voltage of the corresponding Wheatstone bridge is zero, namely the resistance arrangement mode can avoid the influence of the acceleration vertical to the mass block 3; when the sensor is subjected to an acceleration parallel to the sensitive beam 2, R₁、R₂Same stress, same corresponding resistance change, R₃、R₄The stress is the same, the corresponding resistance change is also the same, and the output voltage of the corresponding Wheatstone bridge is zero, i.e. the resistance arrangement mode can avoid the influence of the acceleration parallel to the sensitive beam 2. The invention provides a high-sensitivity and high-temperature-resistant silicon carbide vibration sensor, which reduces cross connection through reasonable resistor arrangement and bridge combinationFork sensitivity.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.