Charge accumulation in composite dielectric layers in capacitive RF MEMS switches

In this paper, our work is focusing on investigating the mechanisms of the charge accumulation in dielectric layer of RF MEMS capacitive switches. In our experiments, silicon-nitride and silicon-oxide composite films, e.g., SiO2+Si3N4 and SiO2+Si3N4+SiO2 films are chosen as the dielectric layers for study. The composite films were prepared by thermal oxidation and PECVD process. The Metal-Insulator-Semiconductor (MIS) structure was produced by using the composite films as the dielectric layer. The capacitance versus voltage (C-V) measurement is employed to study the space charge injection and relaxation process in the composite films. The results show that the charge accumulation can be reduced by using the composite films structure.