High-performance pressure sensors using double silicon-on-insulator structures

A high performance pressure sensor using double silicon-on-insulator (SOI) structures, a (100) Si// (100) Al2O3// (100) Si/ SiO2/ (100) Si substrate, has been developed that is capable of very accurate operation at temperatures as high as 350 °C. A first SOI layer made by bonding two oxidized Si wafers together was employed as an etch-stop layer during KOH selective anisotropic etching and for controlling the thickness of the thin diaphragm. A double-heteroepitaxially grown second SOI layer on the first SOI layer was used as a dielectrically isolated single-element four terminal strain gauge that was placed at the center of a rectangular diaphragm. The dimensions of the diaphragm and its thickness were 360 μm ×1140 μm and 5 μm, respectively. This sensor has high sensitivity (0.04 mV/V⋅mmHg) for 700 mmHg full scale pressure range, with a nonlinearity less than +0.15% full scale. In the temperature range from −20 °C to +350 °C, the shift in sensitivity and offset voltage are less than −0.2% and +0.1%, respectively. Moreover, the implemented sensor is very useful for the miniaturization and integration of the sensor.