On the influence of environment gases, relative humidity and gas purification ondielectric charging/discharging processes in electrostatically driven MEMS/NEMSdevices

Abstract

In this paper, we investigate the impact of environment gases and relative humidity ondielectric charging phenomenon in electrostatically actuated micro- and nano-electromechanicalsystems (MEMS and NEMS). The research is based on surface potential measurementsusing Kelvin probe force microscopy (KPFM). Plasma-enhanced chemical vapor deposition(PECVD) silicon nitride films were investigated in view of applications in electrostaticcapacitive RF MEMS switches. Charges were injected through the atomic forcemicroscope (AFM) tip, and the induced surface potential was measured using KPFM.Experiments have been performed in air and in nitrogen environments, both underdifferent relative humidity levels ranging from 0.02% to 40%. The impact of oxygengas and hydrocarbon contaminants has been studied for the first time by usingdifferent gas purifiers in both air and nitrogen lines. Voltage pulses with differentbias amplitudes have been applied during the charge injection step under allinvestigated environmental conditions in order to investigate the effect of biasamplitude. The investigation reveals a deeper understanding of charging anddischarging processes and could further lead to improved operating environmentconditions in order to minimize the dielectric charging. Finally, the nanoscaleKPFM results obtained in this study show a good correlation with the devicelevel measurements for capacitive MEMS switches reported in the literature.