The discharge current through the dielectric film in MEMS capacitive switches

A new method to determine the bulk discharge current in the dielectric film of MEMS capacitive switches is presented. The method is based on the elementary theory of the discharge process in dielectric materials and the physical model of MEMS capacitive switches with non uniform trapped charge and air gap distributions. The shift of the bias for the minimum of the pull-up capacitance allows the calculation of current densities in the order of picoAmpere per unit area. Assessment of switches with silicon nitride dielectric film shows that the discharge current transient obeys the stretched exponential law. Finally the proposed method is applied to assess the discharge of electrical stressed devices.