Conduction and Trapping in RF MEMS capacitive switches with a SiN layer

This paper deals with dielectric charging phenomenon - a key failure mechanism for electrostatically actuated MEMS. Conduction mechanisms and trap properties of silicon nitride are investigated by current-voltage measurements on Metal-Insulator-Metal (MIM) capacitors and RF MEMS capacitive switches. Both structures show a similar behavior with two bulk-controlled conduction mechanisms: space-charge-limited current below 1.5 MV/cm and Poole-Frenkel conduction above 1.5 MV/cm. The number of trapped charges is extracted from the hysteresis of I-V sweeps and used to estimate the corresponding shift of the pull-in voltage on the switches. These results are in agreement with functional tests performed on the switches.