Investigation of charging mechanisms in RF-MEMS capacitive switches with silicon nitride: The effect of material stoichiometry

The mechanisms responsible for the dielectric charging of RF MEMS capacitive switches with PECVD nitride are systematically investigated. The investigation is based on the shift of the minimum of capacitance-voltage characteristic with maximum bias in pull-down state, temperature and nitride stoichiometry. The contribution of current injection from trap assisted tunneling and Poole-Frenkel effect is investigated. The experimental results indicate that the charging arises from the formation of a defect band where charge transport occurs through a Poole-Frenkel like effect. The calculated activation energy shows direct relation to material stoichiometry hence the nitride band gap. The nitride deposited at a lower temperature is also less prone to dielectric charging.