A surface micromachined pressure sensor based on polysilicon nanofilm piezoresistors

Abstract

In order to effectively apply the piezoresistive properties of the polysilicon nanofilm and the surface micromachined technology, a surface micromachined pressure sensor based on polysilicon nanofilm piezoresistors and vacuum cavity is presented. The design of the sensor structure is carried out by finite element analysis for improving its performance. Residual stress relaxation in the polysilicon diaphragm and prevention of adhesion in the sensor cavity are carried out in the process of the sensor fabrication. The sensor sample is fabricated according to the structure designed. The sample's measurement results show that a full scale pressure of 2.5MPa, a sensitivity of 2.896×10−2mV/V/kPa at 25°C, an overpressure of 7 times higher than the full scale pressure at 25°C, a thermal zero drift of −0.01%FS/°C and a thermal sensitivity drift of −0.1%FS/°C in a temperature range of −40 to 200°C are achieved. The measurement performance is excellent and agrees with the predictions of the design method.