Temperature Acceleration of Dielectric Charging in RF MEMS Capacitive Switches

Temperature acceleration of dielectric-charging effects in state-of-the-art RF MEMS capacitive switches was characterized and modeled. From the measured charging and discharging transient currents at different temperatures, densities and time constants of traps in the dielectric were extracted. It was found that, while charging and discharging time constants are relatively independent of temperature, steady-state charge densities increase with temperature. A charging model was constructed to predict the amount of charge injected into the dielectric and the corresponding shift in actuation voltage under different temperatures. Agreement was obtained between the model prediction and experimental data.

I. Introduction

Despitetheir nearly-ideal high-frequency characteristics, lifetime of electrostatically actuated RF MEMS capacitive switches is limited by dielectric-charging effects [1]. To date, dielectric-charging effects in RF MEMS devices have been studied by different research groups [2]–[4]. We have proposed an approach to characterize the switch dielectric and extracted a charging model to predict charge injection and actuation-voltage shift at room temperature [2]. However, for switch applications in harsh environment (e. g., over the military temperature range of −55 to 125°C), temperature effects on charging also need to be modeled and characterized. In this paper, we present the results on temperature acceleration of the dielectric-charging effects in state-of-the-art RF MEMS capacitive switches. By using the methodology proposed in [2], a temperature-dependent charging model was extracted to predict the actuation-voltage shift under different temperatures and found to be in agreement with the experimental data.