In-plane biaxial piezoresistive acceleration sensor chip and preparation method thereof

Abstract

The invention discloses an in-plane biaxial piezoresistive acceleration sensor chip and a preparation method thereof. A chip is made of an SOI silicon wafer, and comprises a chip outer frame. A fixingisland is arranged in the middle of each side of the chip outer frame, a supporting beam is of an L-shaped structure, one end of a long section of the supporting beam is fixed to the chip outer framethrough the fixing islands, the other short section of the supporting beam is sequentially connected with an extending beam and a mass block, and a sensitive piezoresistive micro beam is arranged ina gap between the tail end of the extending beam and the fixing islands. All the eight mass blocks are connected through hinge beams to be square. A piezoresistor on the sensitive piezoresistive microbeam is connected with a bonding pad through a metal lead to form a Wheatstone full-bridge circuit. The extension beam is used as an intermediate structure for connecting the sensitive piezoresistivemicro-beam, the support beam and the mass blocks, and transmits the change of the motion state of the mass blocks to the sensitive piezoresistive micro-beam. According to the piezoresistive acceleration sensor chip, the supporting element and the sensitive element are separated, the dynamic performance and the application range of the piezoresistive acceleration sensor are improved, the preparation method is simple, and the reliability is high.

Description

technical field [0001] The invention belongs to the technical field of measurement of micromechanical electronic sensors, and in particular relates to an in-plane biaxial piezoresistive acceleration sensor chip and a preparation method thereof. Background technique [0002] With the development of Micro Electro Mechanical Systems (MEMS) technology, acceleration sensors based on different principles have been widely used, such as piezoresistive, capacitive, electromagnetic, piezoelectric, resonant, fiber optic and thermocouple type etc. Acceleration sensors with different sensitivity principles have different advantages and disadvantages. For example, although piezoelectric acceleration sensors have been used maturely, they are limited by their sensitivity principles. Piezoelectric sensors cannot measure static acceleration, and the output charge signal needs subsequent assistance. circuit, it is not easy to realize the integrated design of sensitive chips and subsequent cir...

AI Technical Summary

Problems solved by technology

Acceleration sensors with different sensitivity principles have different advantages and disadvantages. For example, although piezoelectric acceleration sensors have been used maturely, they are limited by their sensitivity principles. Piezoelectric sensors cannot measure static acceleration, and the output charge signal needs subsequent assistance. circuit, it is not easy to realize the integrated design of sensitive chips and subsequent circuits; capacitive acceleration sensors have the advantages of high sensitivity, small temperature drift, and low power consumption, but have large input impedance and are easily affected by parasitic capacitance. Sensitive; the piezoresistive acceleration sensor is susceptible to temperature, but it has a wide measurement range, can measure static and dynamic signals, has good dynamic response characteristics, and simple processing circuits, etc.

[0003] The commonly used structures of traditional piezoresistive acceleration sensors include single cantilever beam, double cantilever beam, double-end fixed support beam, four-side four fixed support beam and other structures. Beams and double cantilever beam structures have high sensitivity, but low natural frequency and narrow frequency response range; fixed-supported beam structures such as double-ended fixed-support beams, four-sided four-fixed-support beams, and double-sided four-fixed-support beams have high natural frequencies, but low sensitivity

[0004] With the advancement of technology, the current piezoresistive acceleration sensors have been difficult to meet the requirements of high sensitivity, high natural frequency and low cross-sensitivity in different fields, such as automotive intelligent detection, high-speed precision machine tools, fault diagnosis and monitoring of high-speed moving parts, electronic Component vibration control, etc.

For the traditional piezoresistive acceleration sensor, because the sensitive element is generally made on the surface of the supporting structure, its natural frequency and sensitivity are mutually restricted. This restrictive relationship brings a series of difficulties to the dynamic acceleration measurement, and the measurement is easy to be distorted. Therefore, It is of great significance to study acceleration sensors that can alleviate the contradictory relationship between natural frequency and sensitivity, reduce the influence of cross sensitivity, and solve the problem of high sensitivity and high frequency response measurement of acceleration.

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