Effect of Environmental Humidity on Dielectric Charging Effect in RF MEMS Capacitive Switches Based on $C$ –

A capacitance–voltage ( $C$ – $V$ ) model is developed for RF microelectromechanical systems (MEMS) switches at upstate and downstate. The transient capacitance response of the RF MEMS switches at different switch states was measured for different humidity levels. By using the $C$ – $V$ model as well as the voltage shift dependent of trapped charges, the transient trapped charges at different switch states and humidity levels are obtained. Charging models at different switch states are explored in detail. It is shown that the injected charges increase linearly with humidity levels and the internal polarization increases with increasing humidity at downstate. The speed of charge injection at 80 $%$ relative humidity (RH) is about ten times faster than that at 20 $%$ RH. A measurement of pull-in voltage shifts by $C$ – $V$ sweep cycles at 20 $%$ and 80 $%$ RH gives a reasonable evidence. The present model is useful to understand the pull-in voltage shift of the RF MEMS switch. $\hfill$ [2012-0144]