IR BOLOMETERS MADE OF POLYCRYSTALLINE SILICON-GERMANIUM

This paper reports the first fabrication of surface-micromachined micr obolometers made of polycrystalline silicon-germanium alloy (poly Si0. 7Ge0.3). The electrical and mechanical properties of this material hav e been measured and the effects of the deposition conditions and annea ling temperature on them have also been investigated. The complete pro cess for the bolometer fabrication is presented and the possibility of reducing the process temperature to 650 degrees C is demonstrated. Th e thermal behaviour of the device is fully analysed and it is demonstr ated that the use of poly Si0.7Ge0.3 instead of polycrystalline Si (po ly Si) decreases the thermal conductance of the device (values lower t han 10(-6) W K-1 are obtained). Preliminary measurements give a value of 10(4) V W-1 for the IR responsivity. (C) 1998 Published by Elsevier Science S.A. All rights reserved.