Enhanced sensitivity with extended linearity in MEMS piezoresistive pressure sensor

Abstract

Focused research efforts on enhancing the sensitivity of piezoresistive MEMS pressure sensors have been made in the past. Most of these techniques applied to enhance sensitivity have depended on manipulating the geometries of the diaphragm, selection of the diaphragm material and improving the piezoresistive properties. Piezoresistors change their resistance linearly proportional to the bending stresses induced in the diaphragm on application of the pressure. Therefore the successful design of a high sensitivity piezoresistive pressure sensor totally depends on the efficiency with which the induced stresses are harvested in the transduction process. Introduced is an innovative way to harvest the maximum stresses. The dual Wheatstone bridge implemented with eight piezoresistors effectively converts the XX and YY plane stresses into electrical voltage to double the sensitivity. The simulation experiment results show that the sensitivity of the 91.72 µV/V/kPa with ensured linearity over 0–14 kPa using a 5 µm-thick diaphragm with a single bridge can now be achieved by employing a 7 µm-thick diaphragm with double Wheatstone bridges but with excellent linearity extended over 0–54 kPa. Almost the same trend is seen between the 3 and the 5 µm-thick diaphragms. Thus, this technique paves the way for achieving large voltage sensitivity bundled with a high level of linearity over a wide pressure range by using thick diaphragms.