Fabrication of thermal microbridge actuators and characterization of their electrical and mechanical responses

This study presents thermal silicon microbridge actuators which have been made by a novel fabrication process utilizing dry processes for all critical steps. The fabrication process results in microbridges which are fully oxide covered, with excellent surface quality and dimensional control. The microbridges are made in the device layer of a silicon-on-insulator (SOI) wafer which ensures uniform doping profile and accurate thickness control. The electrical and mechanical responses of the bridges were measured upon rapid heating up to near the melting point of silicon. Up to 12 μm mechanical deflection due to thermal expansion was detected by white light interferometry (WLI) which allowed accurate measurement. Mechanical deflection has previously not been measured for silicon microlamps. Thermal conduction in the air gap between the actuator and the neighbouring solid silicon parts was analysed and shown to be more important than convection or radiation, even at very high operation temperatures.