Clear evidence of mechanical deformation in RF-MEMS switches during prolonged actuation

Dielectric charging is normally considered one of the most important problems when dealing with RF-MEMS switch reliability, especially for applications which require long-term operation. Other important effects are therefore often neglected. In this paper we demonstrate that, for the case of long-term actuation in dielectric-less switches, the most important issue for switch reliability is not dielectric charging but viscoelastic deformation and creep of the mobile membrane. The measurements and the analysis are performed both for a cantilever and for a clamped–clamped switch configuration, evidencing that in the first case the mechanical deformations are more pronounced, and that they can justify almost completely the variation of actuation and release voltage experimentally measured. Mechanical deformation is also detected in a clamped–clamped switch, but it is less evident than that in the previous case. Nonetheless, even in this case they are responsible for most of the actuation and de-actuation voltage change experimentally detected.