阅读说明：本技术 一种高g值、高灵敏度MEMS加速度传感器及其制备方法 (High-g-value and high-sensitivity MEMS acceleration sensor and preparation method thereof ) 是由 张广平 王雪峰 王敏锐 刘杨 于 2021-07-05 设计创作，主要内容包括：本发明公开了一种高g值、高灵敏度MEMS加速度传感器,属于一种MEMS加速度传感器,包括衬底、器件层和盖板,所述衬底和所述盖板分别从所述器件层的两侧键合所述器件层,所述器件层包括外框、质量块和四个支撑梁,所述质量块和四个所述支撑梁位于所述外框的内部；本发明通过采用4个T型结构支撑梁连接质量块的设计方案,创新性的设计了x、y、z三个轴向的止挡结构,传感器采用了盖板-器件层-衬底的三明治封装结构,易于实现批量晶圆级封装；通过支撑梁采用双E型结构设计,极大提高了器件输出灵敏度；优化了器件层与盖板、衬底之间的压膜阻尼,提升了传感器整体动态性能,延长了器件工作寿命。(The invention discloses an MEMS acceleration sensor with high g value and high sensitivity, which belongs to an MEMS acceleration sensor and comprises a substrate, a device layer and a cover plate, wherein the substrate and the cover plate are respectively bonded with the device layer from two sides of the device layer; according to the invention, by adopting a design scheme that 4T-shaped structural support beams are connected with the mass block, three axial stop structures of x, y and z are innovatively designed, and the sensor adopts a sandwich packaging structure of a cover plate, a device layer and a substrate, so that batch wafer level packaging is easy to realize; the supporting beam adopts a double-E type structure design, so that the output sensitivity of the device is greatly improved; the squeeze film damping between the device layer and the cover plate and between the device layer and the substrate is optimized, the overall dynamic performance of the sensor is improved, and the service life of the device is prolonged.)

1. A high g value, high sensitivity MEMS acceleration sensor which characterized in that: including substrate (1), device layer (2) and apron (3), substrate (1) with apron (3) are followed respectively the both sides bonding of device layer (2), device layer (2) are including frame (21), quality piece (22) and four supporting beam (23) are located the inside of frame (21), four supporting beam (23) fixed connection respectively in four sides of quality piece (22), be provided with a plurality of resistance module (4) on supporting beam (23), on the bottom surface of apron (3) with all be provided with Z axle backstop (5) on the bottom surface of quality piece (22), be provided with xy axle spacing post (6) in frame (21), xy axle spacing post (6) pass quality piece (22), just the both ends of xy axle spacing post (6) support respectively substrate (1) with apron (3) The cover plate (3) is provided with 4 bonding pads (7).

2. The high-g-value and high-sensitivity MEMS acceleration sensor according to claim 1, characterized in that a limiting member (8) is disposed at an inner corner of the outer frame (21), an anchor point (9) is formed between two adjacent supporting beams (23), and the anchor point (9) is clamped on the limiting member (8).

3. A high g-value, high sensitivity MEMS acceleration sensor according to claim 1, characterized in that the supporting beam (23) is a T-shaped structure.

4. A high g-value, high sensitivity MEMS acceleration sensor according to claim 3, characterized in that the connection of the support beam (23) and the mass (22) is U-shaped.

5. A high g-value, high sensitivity MEMS acceleration sensor according to claim 3, characterized in that the side of the supporting beam (23) is E-shaped.

6. A high-g-value, high-sensitivity MEMS acceleration sensor according to claim 1, characterized in that the resistive module (4) is a piezo-resistor.

7. A preparation method of a high-g-value and high-sensitivity MEMS acceleration sensor is characterized by comprising the following steps:

1) etching the back of the device layer (2): selecting a SO wafer with the thickness of 300 mu m for the device layer (2), etching the Z-axis stopper (5) by an RIE dry method, and manufacturing a Z-axis stopper (5) gap, wherein the etching depth is 2-3 mu m;

2) etching the xy-axis limiting column (6) and etching the damping gap: preparing a SiO2 thermal oxygen layer with the thickness of 200nm on the back surface of the device layer (2) by adopting a thermal oxidation process, spraying photoresist, and etching the damping gap between the device layer (2) and the substrate (1) by wet etching, wherein the etching depth is 5 mu m;

3) and (3) gap etching: etching the clearance of the xy-axis limiting column (6) by adopting an RIE dry method, and simultaneously etching the clearance between the mass block (22) and the supporting beam (23) by adopting the RIE dry method;

4) silicon-silicon bonding: the substrate (1) is bonded with the device layer (2) through silicon-silicon;

5) pattern of the piezoresistor: the front surface is doped with concentrated boron by adopting an ion implantation process, and an ICP dry etching process is adopted to etch out the area of the non-resistor strip part on the surface of the supporting beam (23) so as to manufacture the piezoresistor strip; sequentially depositing passivation protective layers with the total thickness of 0.3 micron by adopting a PECVD (plasma enhanced chemical vapor deposition) process, etching the passivation layers at the top of the piezoresistor and in the ohmic contact area of the metal lead by adopting an ICP (inductively coupled plasma) dry etching process, and heavily doping ohmic contact by adopting an ion implantation process; sputtering an Au metal layer by adopting a sputtering process to manufacture a metal lead;

6) etching of the mass (22): the gaps between the xy-axis limiting columns (6) and the mass block (22) and between the mass block (22) and the supporting beams (23) are accurately etched by adopting RIE dry etching, and the mass block (22), the supporting beams (23) and the xy-axis limiting columns (6) are completely released;

7) manufacturing a cover plate (3): shallow slot etching, preparation apron (3), reserve damping clearance between quality piece (22) and apron (3), adopt sputtering technology preparation metal lead:

8) the cover plate (3) is bonded with the device layer (2): eutectic bonding is adopted to realize bonding of the cover plate (3) and the device layer (2);

9) manufacturing a through hole: and manufacturing a lead through hole by adopting an ICP (inductively coupled plasma) process, and manufacturing a through hole metal layer by adopting sputtering and electroplating processes in sequence.

8. The method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor according to claim 7, wherein in the step 2), the thermal oxidation process is high-temperature dry oxygen-wet oxygen-dry oxygen, the time is 60min, the temperature is 1180 ℃, and the temperature of the wet oxygen is 95 ℃.

Technical Field

The invention belongs to an MEMS acceleration sensor, and particularly relates to an MEMS acceleration sensor with a high g value and high sensitivity and a preparation method thereof.

Background

The high-g value acceleration sensor based on the MEMS technology is widely applied to harsh environments such as acceleration signal measurement, vibration measurement, explosion, impact and the like in the fields of automobile industry, military and aerospace, so that the acceleration sensor is required to have excellent impact resistance and a high frequency response range, and effective overload protection and near-critical damping design are required to be realized on the chip level.

The acceleration sensor adopting the cantilever beam structure has low first-order natural frequency, narrow frequency response range and larger transverse sensitivity, although the acceleration sensor adopting the four-side multi-beam structure design has the lowest transverse sensitivity, in addition, the impact response curves of most of the existing piezoresistive acceleration sensors have a burr interference phenomenon, the cause of the burr interference is the natural frequency vibration interference of a supporting beam, the cause of the easy damage phenomenon is the damage phenomenon of a few sensors, and the cause of the damage is the breakage and the damage of a device layer caused by the overlarge vibration amplitude caused by the overlow damping of the sensors.

Disclosure of Invention

The invention aims to: an MEMS acceleration sensor with high g value and high sensitivity and a preparation method thereof are provided.

On one hand, in order to achieve the purpose, the invention adopts the following technical scheme: the utility model provides a high g value, high sensitivity MEMS acceleration sensor, its includes substrate, device layer and apron, the substrate with the apron is followed respectively the both sides bonding on device layer the device layer, the device layer includes frame, quality piece and four supporting beam are located the inside of frame, four supporting beam fixed connection respectively in on four sides of quality piece, be provided with a plurality of resistance module on the supporting beam, on the bottom surface of apron and all be provided with the Z axle backstop on the bottom surface of quality piece, be provided with the spacing post of xy axle in the frame, the spacing post of xy axle passes the quality piece, just the both ends of the spacing post of xy axle support respectively the substrate with the apron, 4 pads have been seted up on the apron.

As a further description of the above technical solution:

the inner corner of the outer frame is provided with a limiting part, an anchor point is formed between two adjacent supporting beams, and the anchor point is clamped on the limiting part.

As a further description of the above technical solution:

the supporting beam is of a T-shaped structure.

As a further description of the above technical solution:

the supporting beam and the mass block are connected in a U shape.

As a further description of the above technical solution:

the side of the supporting beam is E-shaped.

As a further description of the above technical solution:

the resistance module is a piezoresistor.

On the other hand, in order to achieve the above object, the present invention employs the steps of: a preparation method of a high-g-value and high-sensitivity MEMS acceleration sensor comprises the following steps:

1) etching the back of the device layer: selecting an SOI wafer with the thickness of 300 microns as a device layer, etching the Z-axis stopper by an RIE dry method, wherein the etching depth is 2-3 microns, and manufacturing a Z-axis stopper gap;

2) etching the xy-axis limiting column and the damping gap: preparing a SiO2 thermal oxygen layer with the thickness of 200nm on the back surface of the device layer by adopting a thermal oxidation process, spraying photoresist, and etching the damping gap between the device layer and the substrate by wet etching, wherein the etching depth is 5 mu m;

3) and (3) gap etching: etching the clearance of the xy-axis limiting column by adopting an RIE dry method, and simultaneously etching the clearance between the mass block and the supporting beam by adopting the RIE dry method;

4) silicon-silicon bonding: the substrate is bonded with the device layer silicon-silicon;

5) pattern of the piezoresistor: adopting an ion implantation process to dope boron on the front surface, adopting an ICP dry etching process to etch the area of the non-resistor strip part on the surface of the supporting beam, and manufacturing the piezoresistor strip; sequentially depositing passivation protective layers with the total thickness of 0.3 micron by adopting a PECVD (plasma enhanced chemical vapor deposition) process, etching the passivation layers at the top of the piezoresistor and in the ohmic contact area of the metal lead by adopting an ICP (inductively coupled plasma) dry etching process, and heavily doping ohmic contact by adopting an ion implantation process; sputtering an Au metal layer by adopting a sputtering process to manufacture a metal lead;

6) etching the mass block: adopting RIE dry etching to accurately etch gaps between the xy-axis limiting column and the mass block and between the mass block and the support beam, and completely releasing the mass block, the support beam and the xy-axis limiting column;

7) manufacturing a cover plate: shallow slot etching, manufacturing a cover plate, reserving a damping gap between a mass block and the cover plate, and manufacturing a metal lead by adopting a sputtering process:

8) and bonding the cover plate with the device layer: eutectic bonding is adopted to realize bonding of the cover plate and the device layer;

9) manufacturing a through hole: and manufacturing a lead through hole by adopting an ICP (inductively coupled plasma) process, and manufacturing a through hole metal layer by adopting sputtering and electroplating processes in sequence.

As a further description of the above technical solution:

in the step 2), the thermal oxidation process is high-temperature dry oxygen-wet oxygen-dry oxygen, the time is 60min, the temperature is 1180 ℃, and the temperature of the wet oxygen is 95 ℃.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. in the invention, a design scheme that 4T-shaped structural support beams are connected with the mass block is adopted, three axial stop structures of x, y and z are innovatively designed, and the sensor adopts a sandwich packaging structure of a cover plate, a device layer and a substrate, so that batch wafer level packaging is easy to realize;

2. in the invention, the support beam adopts a double-E type structure design, thereby greatly improving the output sensitivity of the device; the squeeze film damping between the device layer and the cover plate and between the device layer and the substrate is optimized, the overall dynamic performance of the sensor is improved, and the service life of the device is prolonged.

Drawings

Fig. 1 is a schematic diagram of the overall structure of a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 2 is an exploded view of a high g-value, high sensitivity MEMS acceleration sensor.

Fig. 3 is a schematic structural diagram of a device layer in a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 4 is a schematic diagram of an internal structure of a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 5 is a schematic view of the processing structure in step 1) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 6 is a schematic view of the processing structure in step 2) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 7 is a schematic view of the processing structure in step 3) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 8 is a schematic view of the processing structure in step 4) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 9 is a schematic view of the processing structure in step 5) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 10 is a schematic view of the processing structure in step 6) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 11 is a schematic view of the processing structure in step 7) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 12 is a schematic view of the processing structure in step 8) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Fig. 13 is a schematic view of the processing structure in step 9) of the method for manufacturing a high-g-value and high-sensitivity MEMS acceleration sensor.

Illustration of the drawings:

1. a substrate; 2. a device layer; 21. an outer frame; 22. a mass block; 23. a support beam; 3. a cover plate; 4. a resistance module; 5. a Z-axis stop; 6. an xy-axis limit post; 7. a pad; 8. a limiting member; 9. and (6) anchoring points.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-4, the present invention provides a technical solution: a high-g-value and high-sensitivity MEMS acceleration sensor comprises a substrate 1, a device layer 2 and a cover plate 3, the substrate 1 and the cover plate 3 are respectively bonded to the device layer 2 from both sides of the device layer 2, the device layer 2 comprises an outer frame 21, a mass block 22 and four supporting beams 23, wherein the mass block 22 and the four supporting beams 23 are located inside the outer frame 21, the four supporting beams 23 are respectively fixedly connected to four sides of the mass block 22, a plurality of resistance modules 4 are arranged on the supporting beam 23, Z-axis stoppers 5 are arranged on the bottom surface of the cover plate 3 and the bottom surface of the mass block 22, an xy-axis limiting column 6 is arranged in the outer frame 21, the xy-axis limiting column 6 penetrates through the mass block 22, two ends of the xy-axis limiting column 6 respectively abut against the substrate 1 and the cover plate 3, and 4 bonding pads 7 are arranged on the cover plate 3;

a limiting part 8 is arranged at the inner corner of the outer frame 21, an anchor point 9 is formed between two adjacent supporting beams 23, and the anchor point 9 is clamped on the limiting part 8;

the supporting beams 23 are of T-shaped structures, the device layer 2 is composed of 4 supporting beams 23 of T-shaped structures and mass blocks 22, the whole body is connected with the outer frame 21 in an anchoring mode through the tail ends of the T-shaped structures, two groups of piezoresistors are manufactured on each supporting beam 23 of the T-shaped structures through ion implantation or diffusion processes, and 16 groups of piezoresistors on the 4 supporting beams 23 jointly form a Wheatstone bridge;

the connection part of the support beam 23 and the mass block 22 is U-shaped, so that the stress concentration condition of the connection part under the condition of maximum displacement of the mass block 22 is improved, and the fracture risk caused by overlarge stress of the connection part is reduced;

the side surface of the supporting beam 23 is E-shaped, the mass blocks 22 on two sides below the supporting beam 23 can be equivalent to a cantilever beam, and the free vibration of the tail end of the cantilever beam in a working state ensures that a piezoresistor area can obtain larger and more concentrated equivalent stress, so that larger variable resistance is obtained;

the resistance module 4 is a voltage dependent resistor.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. in the invention, a design scheme that 4T-shaped structural support beams 23 are connected with the mass block 22 is adopted, three axial stop structures of x, y and z are innovatively designed, and the sensor adopts a sandwich packaging structure of a cover plate 3, a device layer 2 and a substrate 1, so that batch wafer-level packaging is easy to realize;

2. in the invention, the supporting beam 23 adopts a double-E type structure design, thereby greatly improving the output sensitivity of the device; the squeeze film damping between the device layer 2 and the cover plate 3 and between the device layer and the substrate 1 is optimized, the overall dynamic performance of the sensor is improved, and the service life of the device is prolonged.

The working principle is as follows:

when an acceleration signal is applied to a sensitive direction (z direction), the supporting beams 23 can generate periodic tensile and compressive deformation along with the mass block 22, the resistance modules 4 on each supporting beam 23 generate opposite deformation to Ri1, Ri2, Ri3 and Ri4(i is 1, 2, 3 and 4) due to an E-shaped structure corresponding to the supporting beam 23, Ri2 generates opposite tensile deformation when the areas of the Ri1 are compressed and deformed, and vice versa, therefore, due to symmetry, when Ri1 and Ri4 are reduced, Ri2 and Ri3 are correspondingly increased, in terms of a Wheatstone bridge loop, the total resistance change is increased by 4 times, the output sensitivity of the device is greatly improved, the T-shaped supporting beam 23 design improves the overall compactness of the device, the in-plane size of the device is greatly reduced, the U-shaped design is adopted for the connection between the supporting beam 23 and the mass block 22, the stress concentration condition at the connection position under the maximum displacement condition of the mass block 22 is improved, the fracture risk caused by overlarge stress at the joint is reduced, the supporting beam 23 adopts a double-E type design, the mass blocks 22 at two sides below the supporting beam 23 can be equivalent to a cantilever beam, and the free vibration of the tail end of the cantilever beam in a working state ensures that a piezoresistor area can obtain larger and more concentrated equivalent stress, so that larger variable resistance is obtained; the xy-axis limiting column 6, the substrate 1 and the limiting column on the cover plate 3 jointly realize the limiting function in a plane through silicon-silicon bonding, the transverse sensitivity of a device is reduced to the maximum extent, the Z-axis stop 5 is arranged on the lower sides of the mass block 22 and the cover plate 3, the overload protection of the Z axis (the sensitive direction) is jointly realized, and for the high-g-value acceleration sensor, the stop structure can realize the overload protection of not less than 2 times of the range.

Referring to fig. 5-13, the present invention provides a method: a preparation method of a high-g-value and high-sensitivity MEMS acceleration sensor comprises the following steps:

1) etching the back of the device layer 2: selecting an SOI wafer with the thickness of 300 microns for the device layer 2, etching the Z-axis stopper 5 by an RIE dry method, and manufacturing a Z-axis stopper 5 gap, wherein the etching depth is 2-3 microns;

2) etching the xy-axis limiting column 6 and etching the damping gap: preparing a SiO2 thermal oxygen layer with the thickness of 200nm on the back surface of the device layer 2 by adopting a thermal oxidation process, wherein the thermal oxidation process is high-temperature dry oxygen-wet oxygen-dry oxygen, the time is 60min, the temperature is 1180 ℃, the temperature of wet oxygen and water is 95 ℃, photoresist is sprayed, and a damping gap between the device layer 2 and the substrate 1 is etched by wet corrosion, and the etching depth is 5 microns;

3) and (3) gap etching: etching the clearance of the xy-axis limiting column 6 by adopting an RIE dry method, and simultaneously etching the clearance between the mass block 22 and the supporting beam 23 by adopting the RIE dry method;

4) silicon-silicon bonding: the substrate 1 is bonded with the device layer 2 through silicon-silicon;

5) pattern of the piezoresistor: the front surface is doped with concentrated boron by adopting an ion implantation process, and the area of the non-resistor strip part on the surface of the supporting beam 23 is etched by adopting an ICP (inductively coupled plasma) dry etching process to manufacture a piezoresistor strip; sequentially depositing passivation protective layers with the total thickness of 0.3 micron by adopting a PECVD (plasma enhanced chemical vapor deposition) process, etching the passivation layers at the top of the piezoresistor and in the ohmic contact area of the metal lead by adopting an ICP (inductively coupled plasma) dry etching process, and heavily doping ohmic contact by adopting an ion implantation process; sputtering an Au metal layer by adopting a sputtering process to manufacture a metal lead;

6) proof mass 22 etch: the gaps between the xy-axis limiting columns 6 and the mass block 22 and between the mass block 22 and the supporting beams 23 are accurately etched by adopting RIE dry etching, and the mass block 22, the supporting beams 23 and the xy-axis limiting columns 6 are completely released;

7) and (3) manufacturing a cover plate: shallow slot etching, preparation apron 3, reserve the damping clearance between quality piece 22 and apron 3, adopt sputtering technology preparation metal lead:

8) the cover plate 3 is bonded to the device layer 2: eutectic bonding is adopted to realize the bonding of the cover plate 3 and the device layer 2;

9) manufacturing a through hole: and manufacturing a lead through hole by adopting an ICP (inductively coupled plasma) process, and manufacturing a through hole metal layer by adopting sputtering and electroplating processes in sequence.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.