Research On Measurement System Of Silicon-aluminum Heterostructure Pressure Sensor With Constant Temperature Control And Self-calibration Function

MEMS piezoresistive pressure sensor is an interface of forward channel which has important applications in many fields such as meteorological detection and internet of vehicles.Traditional diffused silicon pressure sensors generally have inherent properties of semiconductor devices such as low sensitivity,temperature drift and time drift.The proposed MEMS pressure sensor utilizing aluminum-silicon hybrid structures and its measurement system with function of thermodynamic control and self-calibration can solve those problems to a certain extent.Firstly,the amplified piezoresistive effect of aluminum-silicon hybrid structure is theoretically analyzed,so the width of the doped silicon piezoresistive strip is optimized to20?m.On the basis of theoretical analysis,a novel MEMS chip-level pressure sensor with two pairs of stress-sensitive and temperature-dependent aluminum-silicon hybrid structures is designed,which are etch on the SOI wafer.Four symmetrical L-shaped raised structures are distributed around the square strained membrane of sensor chip,which enhance the stress of the pair of stress-sensitive aluminum-silicon hybrid structures.In order to prove the reliability of the design of sensor chip,the finite element numerical simulation by using ANSYS software is used to calculate the stress,temperature characteristics,sensitivity and signal-to-noise ratio of MEMS pressure sensor utilizing aluminum-silicon hybrid structures and determine the doping concentration of device layer.The layout of the sensor chip is designed and the sensor is processed and manufactured by using standard MEMS process flow.A package of sensor for thermodynamic control is designed,whose feasibility is verified by thermal steady-state thermal analysis.At an ambient temperature of-20°C,only 1.14W of heating power is required,which is 44.7%of the maximum electric power that the heating actuator of the actual thermodynamic control system can provide,so the thermodynamic control system has good practical reliability.Subsequently,the circuit design and embedded software design of the measurement system of the proposed pressure sensor is completed,which use STM32 microprocessor as the core component.This measurement system mainly has the functions of sensor signal acquisition,thermodynamic control,self-calibration of sensor and data communication.The temperature control algorithm adopts the PID algorithm with the adaptive change of the target temperature.AD5420 adjustable current source is used to simulate the calibrated pressure,so the output characteristic of the proposed sensor can be updated when a certain time drift characteristic occurs.In order to satisfy the intelligent application of the proposed sensor,a software with the functions of real-time transmission and display of the sensor data is designed by using QT on the embedded platform with the Cortex-A8 processor transplanted the Linux kernel.Finally,an experimental platform is built to test and evaluate the proposed sensor.Within the range of testing pressure up to 370k Pa,a single stress-sensitive aluminum-silicon hybrid structure can reach a sensitivity of 0.283m V/V/k Pa cooperated with thermodynamic control system.Combined with the differential output of the temperature-dependent hybrid structure,thermal coefficient of offset(TCO)of proposed sensor can be reduced from-6.92×10^-1%FS/°C to-1.51×10^-3%FS/°C,and the calibrated error is less than±1.49%FS.Simultaneously,the self-calibration operation can achieve good performance when the sensor has a certain time drift,the maximum prediction error of the sensor is reduced from 6.1k Pa to 5k Pa after the output characteristic updates.This thesis effectively improves the sensitivity and compensate the temperature drift of traditional pressure sensor by means of sensor device design and the design of optimized thermodynamic control system,moreover the self-calibration also effectively improve the measurement accuracy of the proposed sensor with time drift,which has certain significance for optimizing the comprehensive performance of the piezoresistive pressure sensor.