Dielectric charging in capacitive RF MEMS switches: The effect of extended durations of electric stress

By focusing on thermally-activated processes, a straight-forward and reliable method is devised to investigate dielectric charging effects in capacitive RF MEMS switches subjected to extended durations of electric stress. A general model of distributed charge and air gap is adopted and further developed for theoretical formulation. Experiments performed over a wide temperature range agree well with the theoretical model. It is shown that for extended stress periods, the algebraic sum of the pull-out voltages is thermally activated, and follows the same temperature trend as the voltage corresponding to the minimum capacitance of the switch. Since pull-out voltages can be measured accurately with little effort, this discovery significantly simplifies the study of thermally-activated processes in these switches. Finally, it is shown that charging increases with time, following a power-law relation.