High Sensitivity Surface Micromachined Absolute Pressure Sensor

In this paper, a high sensitivity surface micromachined absolute pressure sensor with an internal substrate reference cavity was developed. The substrate internal vacuum cavity is formed by direct etching of substrate under the sensing diaphragm and sealing the etching holes. It is much smaller than that of previously bulk micromachined pressure sensors and its fabrication process has full CMOS compatibility. Also thin sensing diaphragm and nanofilm piezoresistor, which is fabricated by using CMOS process, improves the sensor performances. The fabricated pressure sensor has a 300 x 300 x 15 mu m(3) vacuum cavity with 2.0 mu m thickness diaphragm and 150 nm thickness polysilicon piezoresistors. The output sensitivity is 5.48 +/- 0.05 mV/V/bar and nonlinearity is 0.1 % in the range of 0.2 similar to 1.0 bar. The digital output with commercial 14-bit read-out ICs shows 0.44 mbar resolution and good repeatability. (C) 2016 The Authors. Published by Elsevier Ltd.