Distributed dielectric charging and its impact on RF MEMS devices

Abstract

This paper gives a new insight into the problem of RF MEMS irreversible stiction due to dielectric charging. Previous reported works describing the phenomenon only account for a drift of the actuation characteristics as a whole as they consider uniform charge densities. We demonstrate how the spatial charge distribution in the dielectric layer can result in the failure of the devices. We emphasize the role of the variance of the distribution, a parameter neglected in the literature. Our model can account for a shift of the C-V actuation characteristics but also for a change in its profile. In particular, the pull-out window can be narrowed and even made to disappear as a result of the non-zero variance of the charge distribution. We identify the processing, the contact conditions and the distributed charge depths as variance- and thus failure-enhancer parameters.