Temperature sensitivity in silicon piezoresistive pressure transducers

The various mechanisms responsible for temperature sensitivity in silicon piezoresistive pressure sensors are described. As a representative transducer, a full-bridge device having a 1-mm-square 23-µm-thick diaphragm is used. The 200 Ω/square, 2K-Ω bridge resistors produce a pressure sensitivity of 13.3 µV/V.mmHg with a temperature coefficient of -1300 ppm/°C. Variability in this sensitivity is most strongly influenced by the diaphragm thickness and the absolute resistor tolerance. A new technique-the electrochemical EDP etch-stop-is found to offer significant advantages over alternative schemes for diaphragm formation. Temperature sensitivity in electrostatically-bonded, vacuum-sealed devices is dominated by resistor match, with oxide stress and junction leakage current playing relatively minor roles over the -40 to + 180°C temperature range. While individual pressure trims for offset and sensitivity will continue to be required, individual temperature trims may be eliminated in these devices for many applications as increasingly precise resistor processes are used.