IR bolometers made of polycrystalline silicon germanium

Abstract This paper reports the first fabrication of surface-micromachined microbolometers made of polycrystalline silicon-germanium alloy (poly Si 0.7 Ge 0.3 ). The electrical and mechanical properties of this material have been measured and the effects of the deposition conditions and annealing temperature on them have also been investigated. The complete process for the bolometer fabrication is presented and the possibility of reducing the process temperature to 650 °C is demonstrated. The thermal behaviour of the device is fully analysed and it is demonstrated that the use of poly Si 0.7 Ge 0.3 instead of polycrystalline Si (poly Si) decreases the thermal conductance of the device (values lower than 10 −6 W K −1 are obtained). Preliminary measurements give a value of 10 4 V W −1 for the IR responsivity.