MOS Integrated silicon pressure sensor

Abstract

An MOS integrated silicon-diaphragm pressure sensor has been developed. It contains two piezoresistors in a half-bridge circuit, and a new simple signal-conditioning circuit with a single NMOS operational amplifier. The negative temperature coefficient of the pressure sensitivity at the half-bridge is compensated for by a positive coefficient of the variable-gain amplifier with a temperature-sensitive integrated feedback resistor. The sensor was fabricated using the standard IC process, except for the thin diaphragm formation using the N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> . H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O anisotropic etchant. Tile silicon wafer was electrostatically adhered to the glass plate to minimize induced stress. The -1750 ppm/°C temperature coefficient of sensitivity at the half-bridge was compensated for to less than +190 ppm/°C at the amplifier output in the 0- 70°C range. A less than 20-mV thermal-output offset shift was also Obtained after 26-dB amplification in the same temperature range.