Induced charging phenomena on SiNx dielectric films used in RF MEMS capacitive switches

Contact-less charging process has been found to constitute a compensation mechanism to dielectric charging of MEMS capacitive switches. The present paper aims to provide a better knowledge of induced charging mechanisms that appear in HF PECVD silicon nitride films. The characteristics of this process as well as the degree of compensation are investigated for different stressing field intensities of both polarities in MEMS capacitive switches. The experimental results indicate that the degree of compensation in HF PECVD SiNx films seems to increase with the intensity of the applied electric field and it is also affected by the polarity of the stressing bias. A new theoretical model that describes the build-up of induced charging is also proposed. Taking into account that the electric field during contact-less charging is quite low, the model assumes that induced charging arises from charge displacement inside the film through hopping conduction processes. © 2015 Elsevier Ltd