CMOS integrated silicon pressure sensor

The sensor described includes a four-arm piezoresistance bridge circuit, an amplifier, and a bridge excitation circuit. This circuit is used to stabilize changes in sensitivity due to variations in temperature and supply voltage. The sensor was fabricated using a self-aligned double-poly Si gate p-well CMOS process combined with an electrochemical etch-stop technique using N/SUB 2/H/SUB 4/-H/SUB 2/O anisotropic etchant for the thin-square diaphragm formation. The silicon wafer was electrostatically adhered to a glass plate to minimize thermally induced stress. Less than a ±0.5% sensitivity shift and less than a ±5-mV offset shift were obtained in the 0-70°C range, with a 1-V/kg/cm/SUP 2/ pressure sensitivity. By using a novel excitation technique, a sensitivity change of less than ±1.5% under a ±10% supply voltage variation was also achieved.