A piezoresistive acceleration sensor with a full-bridge micro-beam structure

Abstract

Disclosed is a piezoresistive acceleration sensor having a full-bridge microbeam structure, comprising a frame (1), a cantilever beam (2), microbeams (3) and a mass block (4). The cantilever beam (2) is on the axis of symmetry of the mass block (4), the microbeams (3) are four in number, and are axisymmetrically distributed on an edge of the mass block (4) using the axis on which the cantilever beam (2) is located, and piezoresistive sensing resistors are provided on the four microbeams, the four piezoresistive sensing resistors constituting a Wheatstone full bridge circuit. Amplifying the strain of the cantilever beam increases the sensitivity; the four piezoresistive sensing resistors are all within a chip, and because the effects of resistance drift on the circuit caused by measuring changes in the ambient temperature cancel each other out in a full bridge circuit, the temperature stability is increased; and the four microbeams increase the restriction on the vibration of the mass block, raising the first order resonance frequency.

Description

technical field [0001] The invention relates to the technical field of acceleration sensors, in particular to a piezoresistive acceleration sensor with a full-bridge micro-beam structure. Background technique [0002] Silicon has excellent mechanical properties and electrical properties, and has ready-made technology in microelectronic processing technology, so it is widely used in various MEMS devices. Acceleration measurement sensors with high sensitivity and wide frequency response have important applications in both military and civilian fields. Traditional MEMS acceleration sensors generally use silicon cantilever beams and piezoresistive sensitive elements on the beams as the core components. In this structure, only a small part of the potential energy stored in the cantilever beam due to bending is transmitted to the piezoresistive sensitive elements, resulting in low sensitivity. By changing The parameters of the beam and mass block can improve the sensitivity to a ...

AI Technical Summary

Problems solved by technology

Traditional MEMS acceleration sensors generally use silicon cantilever beams and piezoresistive sensitive elements on the beams as the core components. In this structure, only a small part of the potential energy stored in the cantilever beam due to bending is transmitted to the piezoresistive sensitive elements, resulting in low sensitivity. By changing The parameters of the beam and the mass block can improve the sensitivity to a certain extent, but at the same time, the increase in sensitivity usually leads to a decrease in the resonance frequency, which cannot meet the requirements of high precision, small mechanical measurement, and wide frequency response at the same time

[0003] For example, the Chinese invention patent "Monolithic Integrated CZC Microbeam Structure Piezoresistive Acceleration Sensor and Manufacturing Method" (application number: 02151296.5) precisely designs the positions of two microbeams to make it a CZC microbeam, It requires high manufacturing precision; and only two piezoresistors constitute the Wheatstone half-bridge, and the other two resistances of the Wheatstone bridge are provided by an external circuit. Only two piezoresistors are more sensitive to the temperature of the measurement environment, and their resistance The value drifts significantly with temperature, and the formed Wheatstone bridge is easily affected by temperature and unbalanced, thus affecting the measurement results

The US invention patent "Single-maskFabricationProcessForLinearandAngularPiezoresistiveAccelerometers" ("Single-mask Manufacturing Process for Linear and Angular Piezoresistive Accelerometers" patent number: US7939355B2) also has the above-mentioned defects. The piezoresistor only constitutes the Wheatstone half-bridge and lacks temperature compensation. mechanism, less sensitive

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