Mosfet Pressure Sensor Based On Mems Technology Production

Pressure sensor is largely used in the fields such as medical treatment, industry process control, biology and aviation. As far as some literatures concerned, there are many types of pressure sensors, most of them are made from silicon. Silicon diffusion pressure sensor has high sensitivity and could realize miniaturization, integration and so on. So it has made great progress these years. In this paper, the pressure sensor made by MEMS technology has square silicon film with four P type MOSFETs. They make up of Wheatstone bridge. In terms of piezoresistance effect of semiconductor, the sensor has two P type equivalent channel resistances of MOSFET locate at the longitudinal orientation, and the other two locate at the transverse orientation. When the power is supplied and the pressure is applied, two longitudinal P type equivalent channel resistances of MOSFET turn to bigger, the other two become smaller. Then the bridge is out of balance, there is the voltage output, so we can change the pressure signal into the corresponding electric signal.Based on the related research of pressure sensor at home and abroad, this paper describes the structure design, work theory, fabrication process and the simulation of MOSFETs pressure sensor. During the experiment, the I-V characteristic, pressure sensitive characteristic and the temperature characteristic are tested; after that the static characteristic is analyzed. The experiment results indicate that the sensitivity of MOSFETs pressure sensor is 8.9mV/100KPa, the linearity is±1.651%F·S, the lag is±0.529%F·S, the repeatability is±1.550%F·S, the precision is2.326 % F·S, the temperature coefficient of null output is 1.32%/℃, the temperature coefficient of sensitivity is -0.33%/℃. The MOSFETs pressure sensor meets the design demand.The MOSFET pressure sensor this paper designed can easily get the useful information, and it has simple test system. It can get over the difficulties that MOSFET capacitance pressure sensor has, it avoid the complex test circuit and the trouble that tiny signal is hard to test. At the mean time, the MOSFETs pressure sensor use P-MOSFET channel as pressure sensitive resistance instead of using diffusion silicon as pressure sensitive resistance. So the stability of the sensor is enhanced, the disturbance of the sensor is minimized, the test signal is stabilized, the temperature characteristic is better. The process of MOSFETs pressure sensor based on MEMS technology is compatible with IC process, which has expensive application prospect.