Numerical Simulations of Novel Constant-Charge Biasing Method for Capacitive RF MEMS SW
J. Lee and C. Goldsmith
University of Texas at Dallas, US
Keywords: RF MEMS, Switch, dielectric charging, constant charge
In the capacitive RF MEMS SW, it has been shown that every 5V of increased actuation voltage decreases the lifetime by an order of magnitude. In this paper, a novel method for automatically controlling the voltage across the dielectric of the capacitive RF MEMS SW is proposed and numerical simulation results are reported. A novel approach for biasing RF MEMS SWs can be achieved by applying a constant charge instead of a constant voltage. Because the total charge remains constant, as the SW capacitance increases the resulting voltage decreases. Electromechanical 1-D nonlinear model that takes into account variable damping of the medium and contact forces of the surface of the dielectric was used for numerical simulations. Simulations of CC and CV methods for doubly-clamped capacitive RF MEMS SW have been carried out using Mathematica. It was found that the higher initial voltage of the CC biasing scheme results in 35% faster switching times. In addition, the maximum electric field across the dielectric with CC biasing is almost nine times less than CV biasing. Such a small electric field (0.17 MV/cm) of CC biasing is considerably less prone to dielectric charging resulting in significant improvement in reliability.
NSTI Nanotech 2003 Conference Technical Program Abstract