CN104297522B - A kind of MEMS cantilever beam type accelerometers and its manufacturing process - Google Patents

Abstract

A kind of MEMS cantilever beam type accelerometers, including：Measurement body, the upper cover plate and lower cover being connected with the measurement body phase；The measurement body includes framework, the mass in the framework, is connected between the mass and the framework by more cantilever beams；Pilot beam is additionally provided between the mass and the framework, one end of the pilot beam is connected with the mass, and the other end of the pilot beam is connected with the framework.Pilot beam can effectively protect accelerometer, prevent it from being damaged because external force is excessive.

Description

A MEMS cantilever beam accelerometer and its manufacturing process

technical field

The invention relates to the field of sensors, in particular to an accelerometer and a manufacturing process thereof.

Background technique

Today, accelerometers are used in many applications, such as measuring the intensity of earthquakes and collecting data, detecting the impact strength of automobile collisions, and detecting the angle and direction of tilt in mobile phones and game consoles. With the continuous advancement of microelectromechanical systems (MEMS) technology, many small accelerometers at the nanometer scale have been widely used commercially.

A traditional capacitive accelerometer, such as a Chinese patent with the patent number ZL03112312.0 and an announcement date of May 30, 2007, includes a cantilever beam and a mass. When there is acceleration, the mass block of the accelerometer will move towards the acceleration direction, so that the gap distance between the mass block and the electrode will change and lead to a change in capacitance. This kind of accelerometer is made by micromachining technology, and has the characteristics of small size and low cost. However, since only two elastic beams are arranged on both sides of the mass block, the acceleration in the non-sensitive direction will cause crosstalk to the sensitive direction during the detection process, which reduces the detection accuracy. Moreover, each cantilever beam will not produce the same deformation and displacement. This makes the vibration mode shape of the accelerometer less symmetrical. In addition, when the external impact force is large, the cantilever beam will break, and the mass block will collide with the frame. Not only the detection reliability of the accelerometer is greatly reduced, but even the accelerometer cannot work.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the above-mentioned prior art, and provide a MEMS cantilever beam accelerometer that detects acceleration in the vertical direction with less crosstalk and has high stability and reliability.

A MEMS cantilever beam accelerometer provided by the present invention comprises: a measuring body, an upper cover plate connected to the measuring body and a lower cover plate; the measuring body includes a frame, a mass block positioned in the frame , the mass block is connected to the frame through a plurality of cantilever beams; a buffer beam is also arranged between the mass block and the frame, and one end of the buffer beam is connected to the mass block, so The other end of the buffer beam is connected to the frame.

MEMS cantilever beam type accelerometer among the present invention also comprises following accessory feature:

The buffer beam is arranged at an end corner of the mass block.

The cantilever beam is an L-shaped folded beam, which includes a connecting arm of a mass block and a connecting arm of a frame, and the center line of the connecting arm of the mass block corresponds to the center line of the mass block.

The width of the connecting arm of the mass block is greater than the width of the connecting arm of the frame.

Electrodes are arranged on the mass block, the upper cover plate and the lower cover plate.

The measuring body adopts a silicon-on-insulator epitaxial structure including an upper silicon layer and a lower silicon layer, and a buried oxide layer is arranged between each silicon layer.

The measuring body adopts a double-sided epitaxial silicon-on-insulator structure, including an upper silicon layer, a middle silicon layer and a lower silicon layer; a silicon dioxide layer is arranged between every two silicon layers.

An overload protection device is provided between the upper cover plate, the lower cover plate and the mass block, and the overload protection device includes an elastic part and a bump; the bump is arranged on the elastic part, and the The elastic part is arranged on the mass block or the cover plate, and the protruding point limits the movement range of the mass block.

The elastic part is arranged on the mass block, the protruding point is arranged on the cover plate at a position corresponding to the elastic part, the protruding point is in contact with the elastic part, and limits the mass the movement range of the block; or the elastic part is arranged on the cover plate, the protruding point is arranged on the position corresponding to the elastic part on the mass block, and the protruding point is corresponding to the elastic part contact and limit the range of motion of the mass.

A kind of manufacturing process of MEMS cantilever beam type accelerometer, described manufacturing process comprises the following steps:

In the first step, a silicon dioxide layer is grown or deposited on the front and back sides of the epitaxial silicon wafer on the insulator;

In the second step, a silicon nitride layer is deposited on the front and back sides of the epitaxial silicon wafer on the insulator;

The third step is to remove part of the silicon nitride layer and silicon dioxide layer on the back side of the epitaxial silicon wafer on insulator by photolithography and etching, and expose the lower silicon layer;

The fourth step is to etch the exposed part of the lower silicon layer to the buried oxide layer;

The fifth step is to remove the exposed buried oxide layer;

The sixth step is to remove the silicon nitride layer and silicon dioxide layer on the back of the epitaxial silicon silicon wafer on insulator;

The seventh step is to carry out back-to-back silicon-silicon bonding of two silicon-on-insulator epitaxial wafers; form a quality block and a frame;

The eighth step is to perform photolithography, etching and deep etching on the front and back of the bonded silicon wafer; etch multiple through holes between the frame and the mass block to form a freely movable cantilever beam;

The ninth step is to remove the silicon nitride layer and silicon dioxide layer on the front and back sides of the bonded silicon wafer to form a complete measuring body;

In the tenth step, bond the key and the silicon wafer with the upper cover and the lower cover to form a complete MEMS cantilever beam accelerometer.

A kind of manufacturing process of MEMS cantilever beam type accelerometer, described manufacturing process comprises the following steps:

The first step is to form a plurality of holes as deep as the middle silicon layer on the upper and lower silicon layers of the epitaxial silicon-on-insulator wafer by photolithography, deep etching and etching respectively;

The second step is to deposit polysilicon in the hole and fill the hole; then grow a silicon dioxide layer on the surface of the upper and lower silicon layers of the epitaxial silicon wafer on the double-sided insulator;

The third step is to form cantilever beams and buffer beams on the upper and lower silicon layers of the epitaxial silicon-on-insulator wafer by photolithography, deep etching and etching; Silicon dioxide is grown on the exposed surface of the beam, or a layer of silicon dioxide is deposited by chemical deposition;

The fourth step is to remove the exposed silicon dioxide on the intermediate silicon layer by photolithography and etching, and deeply etch the intermediate silicon layer to a certain depth;

The fifth step is to etch the intermediate silicon layer between the frame and the mass block to form a free-moving cantilever beam;

The sixth step is to corrode the exposed silicon dioxide;

In the seventh step, the upper cover plate, the processed double-sided silicon-on-insulator epitaxial silicon wafer, and the lower cover plate are bonded at one time to form a complete MEMS cantilever beam accelerometer.

The processing technology for the upper cover plate and the lower cover plate also includes:

A. Forming through holes on the upper cover or the lower cover by photolithography, deep etching and etching;

B. Forming a recessed area on the bonding surface of the upper cover plate and the lower cover plate by photolithography, deep etching and etching respectively;

C. Cleaning the upper cover and the lower cover before bonding with the measuring body;

D. After bonding with the measuring body, deposit metal on the surface of the upper cover plate and the lower cover plate and lead out electrodes, and pass through the through hole on the upper cover plate or the lower cover plate Metal is deposited on the surface of the measuring body, and electrodes are drawn out through the through holes.

The deep etching and the etching method are one or more of the following methods: dry etching or wet etching, and the dry etching includes: deep reactive ion etching of silicon and reactive ion etching.

The etchant used to etch the silicon layer is one or more of the following etchant combinations: potassium hydroxide, tetramethylammonium hydroxide, ethylenediamine phosphoquinone or gaseous xenon difluoride.

The etchant used for etching the silicon dioxide layer is one or a combination of the following etchant: buffered hydrofluoric acid, 49% hydrofluoric acid or gaseous hydrogen fluoride.

According to a MEMS cantilever accelerometer provided by the present invention and its manufacturing process, it has the following advantages: First, the MEMS cantilever accelerometer is made by bonding two silicon wafers, or directly using a double-sided insulator epitaxial silicon wafer. To make, the overall quality of the mass block is relatively large, and it has high detection sensitivity. Secondly, the accelerometer calculates the acceleration by detecting the plane capacitance change between the mass block and the upper and lower cover plates. The method for measuring the plate capacitance value has the advantages of high sensitivity and high accuracy. Again, the width of the cantilever beam in this accelerometer is relatively large, which limits the displacement of the mass block in the horizontal direction, and 4 cantilever beams are symmetrically arranged in the horizontal and vertical directions, which further reduces the crosstalk between horizontal acceleration and vertical acceleration and impact. Finally, the accelerometer is provided with overload protection devices in both horizontal and vertical directions. The accelerometer is prevented from being damaged due to excessive external force. It also ensures the detection stability of the accelerometer.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Fig. 2 is a top view of the measuring body in the present invention.

Fig. 3 is a schematic diagram of the first step and the second step of the first manufacturing method in the present invention.

Fig. 4 is a schematic diagram of the third and fourth steps of the first manufacturing method in the present invention.

Fig. 5 is a schematic diagram of the fifth and sixth steps of the first manufacturing method in the present invention.

Fig. 6 is a schematic diagram of the seventh and eighth steps of the first manufacturing method in the present invention.

Fig. 7 is a schematic diagram of the ninth and tenth steps of the first manufacturing method in the present invention.

Fig. 8 is a schematic diagram of the eleventh step of the first manufacturing method in the present invention.

Fig. 9 is a schematic diagram of a second embodiment of the present invention.

Fig. 10 is a schematic diagram of the first step to the third step of the second manufacturing method in the present invention.

Fig. 11 is a schematic diagram of the fourth step to the sixth step of the second manufacturing method in the present invention.

Fig. 12 is a schematic diagram of the seventh step of the second manufacturing method in the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

With reference to Fig. 1, a kind of MEMS cantilever type accelerometer provided according to the present invention comprises: measuring body 1, the upper cover plate 2 that is connected with described measuring body 1 and the lower cover plate 3; Described measuring body 1 adopts comprising The epitaxial silicon-on-insulator structure with the upper silicon layer 4 and the lower silicon layer 5 is called SOI structure for short. A buried oxide layer 6 is respectively arranged between each silicon layer.

Referring to FIG. 2 , the measuring body 1 includes a frame 11 and a mass block 12 located in the frame 11 ; the mass block 12 and the frame 11 are connected by a cantilever beam 13 . A plurality of cantilever beams 13 are arranged in the space between the proof mass 12 and the frame 11 . Preferably, the mass block 12 is a square, and the cantilever beams are symmetrically arranged on both sides of the mass block 12 with the center line of the mass block 12 as an axis. The cantilever beam 13 is an L-bending elastic beam, wherein the cantilever beam 13 includes a mass block connecting arm connected to the mass block 12 and a frame connecting arm connected to the frame 11 . Wherein, the midline of the connecting arm of the mass block corresponds to the midline of the mass block 12 . Therefore, the displacement of the mass block 12 is relatively stable during the detection process. In addition, preferably, the width of the connecting arm of the mass block is relatively large. This limits the displacement of the mass block 12 in the horizontal direction, and also reduces the impact on the mass block 12 caused by torsion or vibration in an insensitive direction.

Referring to FIG. 1 and FIG. 2 , when the measuring body 1 , the upper cover 2 and the lower cover 3 are energized, a capacitance will be formed between the measuring body 1 , the upper cover 2 and the lower cover 3 . In the process of detecting the acceleration, the mass block 12 will be affected by the acceleration and move in the direction of the acceleration. According to the formula C=εA/d, that is, the capacitance between two parallel conductive sheets is equal to the dielectric coefficient multiplied by the facing area divided by the vertical distance. When displacement occurs due to acceleration, the vertical distance between the mass block 12 and the upper cover plate 2 and the lower cover plate 3 will change. resulting in a change in capacitance. The integrated chip can calculate the detected acceleration through the change of capacitance. Preferably, the integrated circuit also includes a feedback control circuit. In the process of detecting the acceleration, the displacement of the mass block 12 deviates very little from the central position, so the inclination of the mass block 12 caused by the displacement is almost negligible, thereby enhancing the detection accuracy of the accelerometer.

Referring to Figure 1 and Figure 2, in addition, the accelerometer is also provided with an overload protection device. The overload protection device includes a bumper beam 14 protected in the horizontal direction and a raised point 15 and an elastic portion 16 protected in the vertical direction. Wherein, the buffer beam 14 is an elastic beam. And it is arranged at two end corners of the mass block 12 symmetrically with the center line of the mass block 12 as an axis. When the external force is too large, the mass block 12 will produce a displacement beyond the detection range. At this time, the buffer beam 14 in the moving direction of the mass block 12 will be compressed, and the buffer beam 14 in the opposite direction to the moving direction of the mass block 12 will be stretched. The buffer beam 14 will absorb part of the external force and limit the mass block 12 within the displacement range. The mass 12 and the frame 11 are thereby protected. In the vertical direction, the protruding point 15 and the elastic portion 16 can be integrally arranged on the mass block 12, the upper cover plate 2 or the lower cover plate 3, or respectively arranged on the mass block 12, the upper cover plate 2 or the lower cover plate 3 in positions corresponding to each other. When the external force in the vertical direction is too large, the convex point 15 will contact the elastic part 16 first, and force the elastic part 16 to produce a certain deformation, thereby slowing down the further movement of the mass block 12 in the moving direction and reducing the external impact force on the mass block. 12 shocks and effects. The overload protection device in this accelerometer is optional. Designers can choose according to the working environment and cost of the accelerometer after considering many aspects. In addition, the number of buffer beams 14 and the number of overload protection devices in the vertical direction are not limited to the numbers given in this embodiment.

Next, describe in detail the manufacturing process for manufacturing the MEMS cantilever beam accelerometer in the present invention according to Fig. 3 to Fig. 8, this manufacturing process comprises the following steps:

The first step is to perform high-temperature oxidation treatment on the front and back of the SOI silicon wafer to form a silicon dioxide layer 7 on the surface; or deposit a silicon dioxide layer 7 by chemical vapor deposition (CVD).

In the second step, a layer of silicon nitride 8 is deposited on the front and back of the SOI silicon wafer by chemical vapor deposition (CVD).

In the third step, a photoresist is coated on the back surface of the SOI silicon wafer. Afterwards, the backside of the SOI silicon wafer is exposed according to a specific pattern, and developed with a developer. This way the exposed pattern will appear. Reactive ion dry etching or buffered hydrofluoric acid is then used to etch the exposed parts of the silicon dioxide layer 7 and the silicon nitride layer 8 until the lower silicon layer 5 is exposed.

The fourth step is to etch the exposed lower silicon layer 5 to the buried oxide layer 6 by using potassium hydroxide, or tetramethylammonium hydroxide, or ethylenediaminephosphoquinone;

Step 5, using buffered hydrofluoric acid to remove the exposed buried oxide layer 6 of the SOI silicon wafer;

The sixth step is to remove the silicon dioxide layer 7 and silicon nitride layer 8 on the back of the SOI silicon wafer by dry reactive ion etching or buffered hydrofluoric acid;

The seventh step is to carry out back-to-back silicon-silicon bonding of two SOI silicon wafers; form a mass 12 and a frame 11;

In the eighth step, photoresist is coated on the front and back of the bonded silicon wafers. Afterwards, the front and back sides of the bonded silicon wafer are exposed according to a specific pattern, and developed with a developer. This way the exposed pattern will appear. Reactive ion dry etching or buffered hydrofluoric acid are used to etch the exposed parts of the silicon dioxide layer 7 and silicon nitride layer 8 on the front and back sides of the bonded silicon wafer to etch a plurality of deep To expose the hole of the upper silicon layer 4.

In the ninth step, deep etching is used to etch through the exposed upper silicon layer 4 to form freely movable cantilever beams 13 and buffer beams 14 .

In the tenth step, the silicon nitride layer 8 and the silicon dioxide layer 7 on the bonded surface of the silicon wafer are removed by reactive ion dry etching or buffered hydrofluoric acid to form a complete measuring body 1 .

In the eleventh step, bonding the bonded silicon chip with the upper cover 2 and the lower cover 3 to form a complete MEMS cantilever beam accelerometer.

Referring to Fig. 9, the measuring body 1 in the MEMS cantilever beam accelerometer in the present invention can also be made of a double-sided SOI silicon wafer, and the double-sided SOI silicon wafer includes an upper silicon layer 4, a middle silicon layer 9 and a lower silicon layer 5 A buried oxide layer 6 is provided between every two silicon layers, that is, between the upper silicon layer 4 and the middle silicon layer 9 and between the middle silicon layer 9 and the lower silicon layer 5 .

Next, the manufacturing process for manufacturing the MEMS cantilever beam accelerometer in the present invention is described in detail with reference to FIGS. 10 to 12, and the manufacturing process includes the following steps:

In the first step, photoresists are respectively coated on the upper silicon layer 4 and the lower silicon layer 5 of the double-sided SOI silicon wafer. Afterwards, the upper silicon layer 4 and the lower silicon layer 5 are exposed according to a specific pattern, and developed with a developer. This way the exposed pattern will appear. The exposed parts of the upper silicon layer 4 and the lower silicon layer 5 are deeply etched to the buried oxide layer 6 by deep reactive ion etching of silicon. Then reactive ion dry etching or buffered hydrofluoric acid etch the exposed buried oxide layer 6 . A plurality of holes are thus formed as deep as the intermediate silicon layer 9 . The photoresist layer is then removed.

The second step is to deposit polysilicon in the hole to the middle silicon layer 9 and fill the hole to form an electrical path; then grow on the surface of the upper silicon layer 4 and the lower silicon layer 5 of the double-sided SOI silicon wafer Silicon dioxide layer 7. The surfaces of the upper silicon layer 4 and the lower silicon layer 5 are polished by chemical and mechanical polishing methods to achieve smooth surfaces.

The third step is to coat photoresist on the upper silicon layer 4 and the lower silicon layer 5 of the double-sided SOI silicon wafer respectively. Afterwards, the upper silicon layer 4 and the lower silicon layer 5 are exposed according to a specific pattern, and developed with a developer. This way the exposed pattern will appear. Firstly, the exposed part on the grown silicon dioxide layer is etched by reactive ion dry etching or buffered hydrofluoric acid. The upper silicon layer 4 and the lower silicon layer 5 are deeply etched to the buried oxide layer 6 by using deep reactive ion etching of silicon. Finally, the exposed buried oxide layer 6 is etched by reactive ion dry etching or buffered hydrofluoric acid. Thereby, a plurality of cantilever beams 13 and buffer beams 14 are formed. And after photoresist is removed, utilize high temperature to grow a layer of silicon dioxide layer 7 on the surface of described cantilever beam 13 and buffer beam 14, or use chemical deposition (CVD) method on the surface of described cantilever beam 13 A silicon dioxide layer 7 is deposited.

The fourth step is to remove the exposed silicon dioxide in the silicon dioxide layer 7 by dry etching. And the middle silicon layer 6 is deeply etched to a certain depth by deep reactive ion etching of silicon or gaseous xenon difluoride again.

The fifth step is to use potassium hydroxide, or tetramethyl ammonium hydroxide, or ethylenediamine phosphoquinone, or gaseous xenon difluoride to etch the middle silicon layer 9 etched to a certain depth horizontally and vertically . And the etching time is controlled according to the size of the area to be etched in the middle silicon layer 9 . After the middle silicon layer 9 is etched, a plurality of cantilever beams 13 and buffer beams 14 that move freely on the upper and lower layers are formed.

The sixth step is to etch the silicon dioxide 7 exposed on the surface of the SOI silicon wafer with buffered hydrofluoric acid, or 49% hydrofluoric acid, or gaseous hydrogen fluoride.

In the seventh step, the upper cover plate, the processed double-sided SOI silicon wafer, and the lower cover plate are bonded at one time to form a complete accelerometer.

The processing technology of the upper cover plate 2 and the lower cover plate 3 also includes:

A. Before bonding with the measuring body 1 , coat a photoresist on the surface of the upper cover 2 or the lower cover 3 . It is then exposed in a specific pattern and developed with a developer. This way the exposed pattern will appear. Then use deep reactive ion etching, or potassium hydroxide, or tetramethyl ammonium hydroxide, or ethylenediamine phosphoquinone to etch the exposed part of the upper cover plate 2 or the lower cover plate 3 to form a plurality of channels. hole. and remove the photoresist.

B. Coating photoresist on the bonding surface of the upper cover plate 2 and the lower cover plate 3, then exposing it according to a specific pattern, and developing it with a developer. This way the exposed pattern will appear. Then use deep reactive ion etching, or potassium hydroxide, or tetramethyl ammonium hydroxide, or ethylenediamine phosphoquinone to etch the exposed parts of the upper cover plate 2 and the lower cover plate 3 to a certain depth. Location. Thus, a recessed area is formed on the bonding surfaces of the upper cover 2 and the lower cover 3 respectively, and the photoresist is removed.

C. Before bonding with the measuring body 1, the upper cover plate 2 and the lower cover plate 3 are cleaned;

D. After bonding with the measuring body 1, deposit metal on the surface of the upper cover plate 2 and the lower cover plate 3 and lead out electrodes, through the upper cover plate 2 or the lower cover plate 3 Metal is deposited on the surface of the measuring body 1 through the through hole, and electrodes are drawn out through the through hole.

Wherein, the silicon nitride layer 8 and the silicon dioxide layer 7 in the above-mentioned processing technology in the present invention protect the silicon layer covered by them from being etched or corroded.

The deep etching and the etching method described in the present invention are one or more methods in the following methods: dry etching or wet etching, and the dry etching includes: deep reaction of silicon Ion etching and reactive ion etching.

Since the accelerometer calculates the vertical acceleration through the plane capacitance change between the detection mass 12 and the upper and lower cover plates 2, 3, this detection method has high detection sensitivity and accuracy. Moreover, the mass block 12 in the accelerometer is relatively large, which further increases the detection sensitivity. In addition, because the cantilever beam 13 is wider, the displacement of the mass block 12 in the horizontal direction is limited. At the same time, four cantilever beams are symmetrically arranged in this structure to reduce the crosstalk and influence between the horizontal direction and the vertical acceleration. Adding a buffer beam 14 between the mass block 12 and the frame 11 can effectively protect the accelerometer from being damaged due to excessive external force.

Claims (12)

1. a kind of MEMS cantilever beam type accelerometer, comprise: measuring body, upper cover plate and lower cover plate that are connected with described measuring body; Described measuring body comprises frame, is positioned at the mass block in described frame, described The mass block is connected to the frame through a plurality of cantilever beams; it is characterized in that a buffer beam is also arranged between the mass block and the frame, and one end of the buffer beam is connected to the mass block, The other end of the buffer beam is connected to the frame; the cantilever beam is an L-shaped folded beam, which includes a connecting arm of a mass block and a connecting arm of a frame, and the center line of the connecting arm of the mass block is parallel to the center line of the mass block. Corresponding; an overload protection device is provided between the upper cover plate, the lower cover plate and the mass block, the overload protection device includes an elastic part and a bump; the bump is arranged on the elastic part, The elastic part is arranged on the mass block or the cover plate, and the bumps limit the movement range of the mass block; The buffer beams are arranged at the two end corners of the mass block and symmetrically arranged along the center line of the mass block. 2. MEMS cantilever beam type accelerometer as claimed in claim 1, is characterized in that, the width of described mass block connecting arm is greater than the width of described frame connecting arm. 3. The MEMS cantilever beam accelerometer according to claim 1, wherein electrodes are arranged on the mass block, the upper cover plate and the lower cover plate. 4. MEMS cantilever beam type accelerometer as claimed in claim 1, is characterized in that, described measurement body adopts the epitaxial silicon structure on the insulator that comprises upper silicon layer and lower silicon layer, is respectively provided with between every layer of silicon layers buried oxide layer. 5. MEMS cantilever beam type accelerometer as claimed in claim 4, is characterized in that, described measuring body adopts epitaxial silicon structure on double-sided insulator, comprises upper silicon layer, middle silicon layer and lower silicon layer; Silicon dioxide layers are respectively arranged between the layers. 6. MEMS cantilever beam type accelerometer as claimed in claim 1, is characterized in that, described elastic part is arranged on the described mass block, and described protruding point is arranged on described cover plate and is corresponding to described elastic part position, the protruding point is in contact with the elastic part, and limits the movement range of the mass block; or the elastic part is set on the cover plate, and the protruding point is set on the mass block and At the position corresponding to the elastic part, the convex point is in contact with the elastic part, and limits the movement range of the mass block. 7. a manufacturing process of MEMS cantilever beam accelerometer according to claim 4, is characterized in that, described manufacturing process comprises the following steps: The first step is to grow or deposit a silicon dioxide layer on the front and back of the epitaxial silicon wafer on the insulator; The second step is to deposit a layer of silicon nitride on the front and back of the epitaxial silicon wafer on the insulator; The third step is to remove part of the silicon nitride layer and silicon dioxide layer on the back side of the epitaxial silicon wafer on insulator by photolithography and etching, and expose the lower silicon layer; The fourth step is to etch the exposed part of the lower silicon layer to the buried oxide layer; The fifth step is to remove the exposed buried oxide layer; The sixth step is to remove the silicon nitride layer and silicon dioxide layer on the back of the epitaxial silicon silicon wafer on insulator; The seventh step is to carry out back-to-back silicon-silicon bonding of two silicon-on-insulator epitaxial silicon wafers; form a quality block and a frame; The eighth step is to perform photolithography, etching and deep etching on the front and back of the bonded silicon wafer; etch multiple through holes between the frame and the mass block to form a freely movable cantilever beam; The ninth step is to remove the silicon nitride layer and silicon dioxide layer on the front and back sides of the bonded silicon wafer to form a complete measuring body; In the tenth step, the bonded silicon chip is bonded to the upper cover and the lower cover to form a complete MEMS cantilever beam accelerometer. 8. a manufacturing process of MEMS cantilever beam accelerometer according to claim 5, is characterized in that, described manufacturing process comprises the following steps: The first step is to form a plurality of holes as deep as the middle silicon layer on the upper and lower silicon layers of the epitaxial silicon-on-insulator wafer by photolithography, deep etching and etching respectively; The second step is to deposit polysilicon in the hole and fill the hole; then grow a silicon dioxide layer on the surface of the upper and lower silicon layers of the epitaxial silicon wafer on the double-sided insulator; The third step is to form cantilever beams and buffer beams on the upper and lower silicon layers of the epitaxial silicon-on-insulator wafer by photolithography, deep etching and etching; Silicon dioxide is grown on the exposed surface of the beam, or a layer of silicon dioxide is deposited by chemical deposition; The fourth step is to remove the exposed silicon dioxide on the intermediate silicon layer by photolithography and etching, and deeply etch the intermediate silicon layer; The fifth step is to etch the intermediate silicon layer between the frame and the mass block to form a free-moving cantilever beam; The sixth step is to corrode the exposed silicon dioxide; In the seventh step, the upper cover plate, the processed double-sided silicon-on-insulator epitaxial silicon wafer, and the lower cover plate are bonded at one time to form a complete MEMS cantilever beam accelerometer. 9. the manufacturing process of MEMS cantilever beam type accelerometer as claimed in claim 7 or 8, is characterized in that, the processing technology to described upper cover plate and lower cover plate also comprises: A. Forming through holes on the upper cover or the lower cover by photolithography, deep etching and etching; B. Forming a recessed area on the bonding surface of the upper cover plate and the lower cover plate by photolithography, deep etching and etching respectively; C. Cleaning the upper cover and the lower cover before bonding with the measuring body; D. After bonding with the measuring body, deposit metal on the surface of the upper cover plate and the lower cover plate and lead out electrodes, and pass through the through hole on the upper cover plate or the lower cover plate Metal is deposited on the surface of the measuring body, and electrodes are drawn out through the through holes. 10. according to the manufacturing process of the MEMS cantilever beam type accelerometer described in claim 7 or 8, it is characterized in that, the method for described deep etching and described etching is one or more methods in the following methods: etching or wet etching, the dry etching includes: deep reactive ion etching and reactive ion etching of silicon. 11. according to the manufacturing process of the MEMS cantilever beam type accelerometer described in claim 7 or 8, it is characterized in that, the etchant used to corrode silicon layer is the combination of one or more in the following etchant: potassium hydroxide, four Methyl ammonium hydroxide, ethylenediamine phosphoquinone, or gaseous xenon difluoride. 12. The manufacturing process of the MEMS cantilever beam accelerometer according to claim 7 or 8, wherein the etchant used to corrode the silicon dioxide layer is a combination of one or more of the following etchant: buffered hydrogen fluorine acid, 49% hydrofluoric acid, or gaseous hydrogen fluoride.