Modeling of dielectric charging in electrostatic MEMS switches

The most important failure mechanism for electrostatic MEMS switches is dielectric charging, which contributes to a significant reduction of the device lifetime. In this study the correlation between the dielectric properties and the switch lifetime is evaluated. The conduction mechanism and trapping kinetics for two types of PECVD SiNx are determined by I–V sweeps and constant-current injections from Metal–Insulator–Metal (MIM) capacitors. This type of procedure is used as a basis for modeling the charge build-up in a switch. Despite significant differences between the dielectrics, in terms of leakage current and trapping properties, the numerical model of charge build-up fits well with experimental data. We conclude that the switch lifetime can be correlated with the trapping properties of the dielectric itself.