High-g-value MEMS acceleration sensor chip based on eight-beam structure

Abstract

The invention relates to a high-g-value MEMS acceleration sensor chip based on an eight-beam structure. The piezoresistive MEMS high-g-value acceleration sensor with the eight-beam structure solves the problem that an existing accelerometer cannot meet the characteristics of high g value, high sensitivity and the like at the same time. The piezoresistive acceleration sensor with the eight-beam structure comprises a silicon-based frame fixed on a glass bottom plate, a cantilever beam and a mass block suspended in the center of the silicon-based frame through the cantilever beam, a piezoresistor forming a Wheatstone bridge is arranged on the cantilever beam, and the thickness of the silicon-based frame, the thickness of the cantilever beam and the thickness of the mass block are equal. The device is reasonable and simple in structure, has the characteristic requirements of good overload resistance and the like, and avoids the problem of failure in a severe impact environment; and an equal-thickness design is adopted, so that the manufacturing process is relatively simple, and the method is suitable for high-range acceleration sensors.

Description

Technical Field

[0001] The present invention relates to a high-g value MEMS acceleration sensor chip based on an eight-beam structure. Specifically, the present invention is applied to accurate acceleration measurement in high acceleration, high impact and high frequency environments, and is widely used in aerospace, automotive safety, industrial monitoring, smart terminals and other fields. Background Art

[0002] With the rapid development of science and technology, micro-electromechanical system (MEMS) accelerometers have been widely used in many fields, including automotive crash detection, vibration monitoring of industrial equipment, sports health tracking, posture control of electronic equipment, etc. Traditional MEMS accelerometers usually use a four-terminal single beam structure. Although these sensors have good performance in a lower acceleration range, they are prone to performance failure or distortion when facing high g values ​​(such as in high-speed collisions, explosions or high-impact environments).

[0003] The current technological development trend is to improve the stability and reliability of MEMS sensors in high-g environments by improving the structure and manufacturing process of the sensors. Some high-g acceleration sensors use a multi-beam structure to increase the durability and sensitivity of the sensors, but these designs still face the problem of balancing sensitivity, linearity and impact resistance. To this end, the present invention proposes a piezoresistive high-g MEMS acceleration sensor based on an eight-beam structure, which can provide accurate acceleration measurement in high-g environments while maintaining high sensitivity and good linearity.

[0004] CN117129711A uses the eight-beam structure of the present invention, but the middle convex point of the substrate layer and the upper surface of the fourth bonding ring around it are in the same plane, and the middle convex point is bonded to the central anchor point of the sensitive structure layer, so that the sensitive structure is rigidly fixed on the substrate layer; a third cavity is formed between the middle convex point of the substrate layer and the fourth bonding ring around it, and the third cavity allows the sensitive structure to move and deform under the action of acceleration. This is because when the sensitive structure is subjected to acceleration, the sensitive structure is subjected to force to cause the deformation of the connecting beam, and the deformation of the connecting beam causes the piezoresistors thereon to produce strain. The piezoresistive high-g value MEMS acceleration sensor of the eight-beam structure of the present application includes a silicon-based frame, and a mass block suspended in the center of the silicon-based frame by a four-end double cantilever beam, and a piezoresistor constituting a Wheatstone bridge is provided on the upper surface of the cantilever beam. When the mass block is subjected to acceleration in the Z-axis direction, the force on the mass block causes the cantilever beam to deform. The deformation of the cantilever beam causes the piezoresistor on the cantilever beam to strain. The lateral and longitudinal stresses on the piezoresistor cause the resistance value to change. The Wheatstone bridge composed of the piezoresistors outputs a signal, which can detect the acceleration in the Z-axis direction. Summary of the invention

[0005] In order to solve the problem that the existing accelerometer cannot simultaneously meet the characteristics of high g value, high sensitivity and the like, the present invention provides a piezoresistive MEMS high g value acceleration sensor with an eight-beam structure.

[0006] The technical solution of the present invention:

[0007] A high-g value MEMS acceleration sensor chip based on an eight-beam structure comprises a silicon-based frame 1, a cantilever beam 2, and a mass block 3 suspended in the center of the silicon-based frame 1 through the cantilever beam 2, a piezoresistor 4 constituting a Wheatstone bridge is arranged on the cantilever beam 2, and the thickness of the silicon-based frame 1, the thickness of the cantilever beam 2 and the thickness of the mass block 3 are equal.

[0008] Furthermore, the silicon-based frame 1 is a square frame, and each side of the mass block 3 is connected to the silicon-based frame 1 via two parallel cantilever beams 2 .

[0009] Furthermore, a varistor 4 is arranged on the upper surface of each cantilever beam 2 , and the varistors on the upper surfaces of two adjacent and parallel cantilever beams 2 form two Wheatstone bridges connected in series.

[0010] When the mass block 3 is subjected to the acceleration in the Z-axis direction, the force on the mass block 3 causes the cantilever beam 2 to deform. The deformation of the cantilever beam 2 causes the piezoresistor 4 on the cantilever beam 2 to generate strain. The transverse stress and longitudinal stress on the piezoresistor 4 cause the resistance value to change. The Wheatstone bridge formed by the piezoresistor 4 outputs a signal, which can detect the acceleration in the Z-axis direction.

[0011] The deformation caused by the mass block 3 in the present invention is more direct and obvious, reducing the error and instability caused by the complex structure. It has the following beneficial effects:

[0012] (1) Simple process: The square mass block of the present invention is easy to process and cut, reducing the complexity of geometric design and manufacturing process. However, the return-shaped sensitive structure often requires complex design and fine manufacturing process, which will increase production cost and time.

[0013] (2) Good mechanical properties: The mass distribution of a square mass block is usually more uniform. When subjected to acceleration, the symmetrical structure of the square helps maintain its stability and reduces stress concentration caused by asymmetric shape. This can provide more stable measurement results for high-g acceleration sensors.

[0014] (3) Easy to install and fix: The square mass block has straight edges, which makes it easy to position and install inside the sensor. Through standardized installation methods, it can be more easily fixed in the sensor frame without the need for special support structures or connection methods. Relatively speaking, the circular sensitive structure may require more support structures to ensure its stability during installation.

[0015] (4) Reduce vibration and interference: Square mass blocks are usually more effective in withstanding external vibration or interference. In acceleration sensor applications, the vibration of the accelerometer sensitive structure can lead to measurement errors, and the design of the square mass block can better offset these unnecessary effects and improve the accuracy of the sensor.

[0016] (5) Easy to optimize and debug: Since the square mass block is simple and symmetrical in shape, it is relatively easy to adjust parameters such as mass and size during design and optimization to optimize the performance of the sensor. During the debugging phase, the behavior of the square mass block is easier to predict and control, thereby improving debugging efficiency.

[0017] In addition, the inertial properties of the mass block can make the response during the measurement process more stable, suitable for long-term use and not easily affected by environmental changes or structural fatigue.

[0018] In the present invention, Figure 1 and Figure 3 As shown, an equal thickness design is adopted, and the thickness of the silicon-based frame 1, the thickness of the cantilever beam 2 and the thickness of the mass block 3 are the same. However, as shown in CN117129711A, the sensitive structure layer includes a "U"-shaped sensitive structure, a central anchor point and eight connecting beams, and they do not adopt an equal thickness design.

[0019] The uniform thickness design is not only cost-effective in the manufacturing process, but also brings advantages such as structural stability and thermal expansion consistency. By simplifying the design, improving production efficiency and improving structural performance, the uniform thickness design has a good effect on improving the overall performance, reliability and maintainability of the product.

[0020] In addition, the present invention adopts a four-end double cantilever beam, and through the layout of multiple beams, the force is distributed in multiple directions, thereby effectively reducing the stress concentration of a single beam, especially when subjected to large acceleration, it can avoid overload or failure in local areas. Compared with the four-end single beam structure, the four-end double beam structure can better disperse the external force and increase the overall acceleration resistance of the structure; and the varistor arranged on the cantilever beam to form a Wheatstone bridge is used. When the external acceleration pressure is applied, the resistance value of the resistor changes. The circuit design takes into account the dynamic response performance of high g value, and can maintain stable output in a rapidly changing acceleration environment.

[0021] The invention has a reasonable and simple structure and has good overload resistance and other characteristic requirements, avoiding the problem of failure in a harsh impact environment; and adopts an equal thickness design, the manufacturing process is relatively simple, and is suitable for high-range acceleration sensors.

[0022] Beneficial effects of the present invention:

[0023] (1) Enhanced resistance to high acceleration

[0024] Dispersed stress: Through the layout of multiple beams, the force is distributed in multiple directions, thereby effectively reducing the stress concentration of a single beam, especially when subjected to large acceleration, to avoid overload or failure in local areas. Compared with the circular structure, the circular structure has a complex design process and limited anti-eccentric load capacity. The square mass block used in the middle of the structure of the present invention is more stable and increases the overall anti-acceleration capacity of the structure.

[0025] Avoid stress concentration: A single cantilever beam design is prone to stress concentration in a high-g environment, leading to structural damage. Through the four-end double-beam structure, the force is evenly distributed, reducing local excessive stress, thereby improving the working stability and durability of the accelerometer in a high-g environment.

[0026] (2) Improve sensitivity and linearity

[0027] Improved mechanical response: The eight-beam structure provides a more stable and linear response. Due to the joint action of multiple beams, the displacement response of the accelerometer is more uniform, providing accurate measurement over a wider acceleration range. This is especially important for high-g applications, because in these cases, the linear response of the sensor is critical for accurate measurement.

[0028] Reduce nonlinear effects: Compared with the circular structure, the mass block structure in the middle of this structure can effectively reduce the nonlinear effects caused by uneven force or local deformation, and improve the measurement accuracy of the accelerometer.

[0029] (3) Enhance the stability and rigidity of the structure

[0030] Improved rigidity: The eight-beam structure provides multiple support points and contact points, and the overall rigidity is significantly enhanced, which can better withstand external shock or vibration. The increase in rigidity reduces structural deformation under large acceleration or shock, ensuring the stability of the accelerometer and the reliability of long-term use.

[0031] Reduce elastic deformation: By properly arranging the eight beams, the overall structure of the sensor is more robust, which can effectively reduce the elastic deformation caused by large acceleration or mechanical stress, which helps to improve the accuracy of the accelerometer in high-speed or intense motion environments.

[0032] (4) Improve fatigue resistance and impact resistance

[0033] Fatigue resistance: Since multiple beams share the load, eight-beam MEMS accelerometers are generally more resistant to fatigue than traditional single-beam designs. In high-g and frequent vibration environments, the eight-beam structure can avoid local fatigue failure and improve the long-term stability of the sensor.

[0034] Strong shock resistance: The eight-beam structure can better cope with sudden acceleration changes by evenly distributing external impact forces, reducing the damage caused by impact forces to the structure. This makes the accelerometer more resilient in high-g shocks or rapid vibrations.

[0035] (5) Improve robustness to temperature and environmental changes

[0036] Better temperature compensation: Because the eight-beam design can disperse thermal stress and material expansion effects, the response of the MEMS accelerometer when the temperature changes will be more stable. The eight-beam structure is easier to achieve uniform temperature distribution than the traditional structure, reducing the measurement error caused by thermal effects.

[0037] Improved resistance to environmental interference: The multi-beam structure helps to improve the robustness of the accelerometer under various environmental conditions and can better cope with performance degradation caused by environmental factors (such as temperature changes, humidity changes, pressure fluctuations, etc.).

[0038] (6) Enhance the adjustability and flexibility of the structure

[0039] Flexible design options: Based on the eight-beam structure, designers can flexibly adjust the length, width, support point location and other parameters of the beam according to the needs of different applications, thereby optimizing the sensitivity and response characteristics of the accelerometer while ensuring structural stability.

[0040] Adapt to different application scenarios: This flexibility enables the eight-beam MEMS accelerometer to perform better in a variety of application scenarios, such as the automotive industry, aerospace, military, consumer electronics and other fields, and can adapt to complex working environments.

[0041] (7) Improve signal output quality

[0042] Reduce noise and nonlinear distortion: Since the eight-beam structure and equal thickness design can provide more uniform stress distribution, it can reduce the noise and distortion caused by uneven force or local deformation. Therefore, the signal output is more stable and accurate, reducing the error caused by nonlinearity or stress concentration during the measurement process.

[0043] Optimizing electrical performance: Through proper arrangement and design, the eight-beam structure not only improves the mechanical performance, but also improves the electrical performance of the sensor, such as signal strength and signal-to-noise ratio, thereby improving the performance of the overall accelerometer.

[0044] (8) Improve the fault tolerance of the manufacturing process

[0045] Strong fault tolerance: The equal thickness design has a higher tolerance for minor errors during the manufacturing process. Compared with the return structure, it has less performance deviation caused by errors during the production process. Due to the equal thickness design of the cantilever beam, even if some beams have minor manufacturing defects, the overall performance can still remain stable.

[0046] Summary: The eight-beam structure and equal-thickness design bring multiple advantages to MEMS high-g accelerometers, including enhanced high-acceleration resistance, improved sensitivity and linearity, enhanced structural stability and stiffness, and improved fatigue and shock resistance. These advantages make the eight-beam structure very suitable for applications in high-g environments, such as automotive airbags, aerospace, military equipment, and industrial measurements. By reasonably designing the eight-beam structure, not only can the performance of the accelerometer be improved, but also its long-term stability and reliability in complex and extreme working environments can be ensured. Description of the Drawings

[0047] Figure 1 It is a schematic structural diagram of the present invention.

[0048] Figure 2 It is a schematic circuit diagram of the Wheatstone bridge formed by the piezoresistors of the present invention.

[0049] Figure 3 It is a three-dimensional schematic structural diagram of the present invention.

[0050] In the figure: 1 is a silicon-based frame; 2 is a cantilever beam; 3 is a mass block; 4 is a piezoresistor; 2-1 is the first cantilever beam; 2-2 is the second cantilever beam; 4-1 is the first piezoresistor; 4-2 is the second piezoresistor. Detailed Embodiments

[0051] The following further describes the detailed embodiments of the present invention in conjunction with the drawings and technical solutions.

[0052] The piezoresistive high-g MEMS accelerometer with an eight-beam structure includes a silicon-based frame 1, a cantilever beam 2, and a mass block 3 suspended in the center of the silicon-based frame 1 through the cantilever beam 2. A piezoresistor 4 forming a Wheatstone bridge is provided on the upper part of the cantilever beam 2. The thickness of the silicon-based frame 1, the thickness of the cantilever beam 2, and the thickness of the mass block 3 are equal. The silicon-based frame 1 is a square frame, and each side of the mass block 3 is connected to the silicon-based frame 1 by two parallel cantilever beams 2. A piezoresistor 4 is arranged on the upper surface of each cantilever beam 2, and the piezoresistors on the upper surfaces of two adjacent and parallel cantilever beams 2 form two Wheatstone bridges connected in series.

[0053] During specific implementation, such as Figure 1As shown, a first varistor 4-1 is arranged on the upper surface of the first cantilever beam 2-1, and a second varistor 4-2 is arranged on the upper surface of the second cantilever beam 2-2. The first varistor 4-1 and the second varistor 4-2 respectively form two Wheatstone bridges connected in series. As shown in the figure, in a clockwise direction, the varistors 4 arranged on the eight cantilever beams 2 are numbered as follows: R1, R5, R2, R6, R3, R7, R4, R8. The varistors R1, R2, R3 and R4 form a Wheatstone bridge, and the other four varistors R5, R6, R7 and R8 form another Wheatstone bridge. Connecting the two bridges in series can increase the output signal and further improve the output sensitivity of the structure. Figure 2 As shown in the figure, this is a double Wheatstone bridge measurement circuit. Two symmetrical power supplies Vin are located on both sides of the bridge. When the bridge is balanced, the output voltage Vout is 0. In addition, the symmetry of the power supply can reduce the offset of the signal, greatly reduce the measurement error, and improve the measurement accuracy.

Claims

1. A high g-value MEMS acceleration sensor chip based on an eight-beam structure, characterized in that: The invention comprises a silicon-based frame (1), a cantilever beam (2), and a mass block (3) suspended in the center of the silicon-based frame (1) via the cantilever beam (2); a varistor (4) constituting a Wheatstone bridge is arranged on the cantilever beam (2); and the thickness of the silicon-based frame (1), the thickness of the cantilever beam (2) and the thickness of the mass block (3) are equal.

2. The high g-value MEMS acceleration sensor chip based on the eight-beam structure according to claim 1, characterized in that: The silicon-based frame (1) is a square frame, and each side of the mass block (3) is connected to the silicon-based frame (1) via two parallel cantilever beams (2).

3. The high g-value MEMS acceleration sensor chip based on an eight-beam structure according to claim 1, characterized in that: A varistor (4) is arranged on the upper surface of each cantilever beam (2), and the varistor on the upper surfaces of two adjacent and parallel cantilever beams (2) form two Wheatstone bridges connected in series.

4. The high g-value MEMS acceleration sensor chip based on an eight-beam structure according to claim 1, characterized in that: When the mass block (3) is subjected to acceleration in the Z-axis direction, the force exerted on the mass block (3) causes the cantilever beam (2) to deform, and the deformation of the cantilever beam (2) causes the piezoresistor (4) on the cantilever beam (2) to generate strain. The transverse stress and longitudinal stress exerted on the piezoresistor (4) cause the resistance value to change, and the Wheatstone bridge composed of the piezoresistor (4) outputs a signal, which can detect the acceleration in the Z-axis direction.

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