Thermal modelling and characterisation of micropower chemoresistive silicon sensors

There is considerable interest in the development of low-cost, low-power resistive sensors for possible application in hand-held gas monitors. In this paper we describe the fabrication of a high-temperature, resistive sensor using silicon microtechnology which lies on a sub-micron thick membrane with an embedded platinum resistance heater. A thermal model of this micro-hotplate is constructed and compared with its observed behaviour. The microsensor can be operated at temperatures of up to 600 degrees C and has a low d.c. power consumption per sensor of 40 mW at 300 degrees C. As the thermal time-constant of the microsensor is only about 5 ms, its average power consumption can be reduced by a factor of at least ten through an a.c. mode of operation, thus making a single device or even an array device suitable for battery-powered instruments. (C) 1997 Elsevier Science S.A.