A characterization of the thermal parameters of thermally driven polysilicon microbridge actuators using electrical impedance analysis

Abstract

We have fabricated microrelays with a thermally driven polysilicon microbridge actuator to characterize their thermal parameters. An electrically equivalent circuit for the thermal microactuator has been modeled in functions of experimental parameters. The thermal conductance and the thermal capacitance of the thermal microactuator have been derived at the same time from the model and the frequency response analysis results. For the thermal microactuator having a bridge length of 500 mu m, a width of 40 mu m and a thickness of 3 mu m, the thermal conductance and the thermal capacitance were 3.3 x 10(-4) W/degrees C and 4.3 x 10(-7) J/degrees C at 16 mTorr, respectively. A radiation source, which is needed to oscillate the temperature of thermal sensors in other measurement method, is not necessary in this work because signal voltage supplied by a FRA (Frequency Response Analyzer) heats the thermal microactuator. The method also eliminates the error from the ambient temperature variation because it considers the change of de resistance affected by the ambient temperature variation. (C) 1999 Elsevier Science S.A. All rights reserved.