Abstract
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 × 300 × 15μm3 vacuum cavity with 2.0μm thickness diaphragm and 150nm thickness polysilicon piezoresistors. The output sensitivity is 5.48 ± 0.05mV/V/bar and nonlinearity is 0.1% in the range of 0.2 ∼ 1.0bar. The digital output with commercial 14-bit read-out ICs shows 0.44 mbar resolution and good repeatability.
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