MODELLING AND SIMULATION OF MEMS BEAM-TYPE SWITCHES WITH DIELECTRIC INTERFACES AND GEOMETRICAL VARIATIONS

Abstract

Low power consumption, great isolation, and fast switching capability of microelectromechanical systems beam-type capacitive switches have made them interesting components in various radio frequency and microwave applications. The modelling, simulation, and analysis of MEMS cantilever beam capacitive switches including dielectric interfaces is presented in this thesis in its whole. The aim of this work is to investigate the effects on the electromechanical performance of switches of geometric parameters, dielectric layers, and electrode layouts. Considering beam dimensions, electrode area, air gap, and the presence of a dielectric layer, an analytical model for pull-in voltage was developed offering a theoretical foundation for design optimisation. Four different cases varying beam length, width, dielectric presence, and electrode size were investigated tip displacement, pull-in voltage, electric field distribution, and stress concentration using COMSOL Multiphysics by means of detailed finite element simulations. Larger beams with dielectric layers show reduced pull-in voltages due to modified electric field distribution and effective gap reduction; smaller beams show increased pull-in voltages and higher von Mises stress, so indicating greater mechanical constraints. The electric field study shows enhanced field localisation at dielectric interfaces, so influencing device dependability. Under less than 6% error, comparison of simulation results with analytical predictions reveals good agreement, so verifying the modelling technique. This work illustrated important trade-offs of device miniaturization, operating voltage and mechanical reliability that provided a rich framework to think about designing and fabricating MEMS switches. These findings create a path for bettering MEMS technology to use for safe, low-power RF switching for real-world usage and the techniques we have developed could provide a strong methodology to improve devices in the oscillators and near-ideal RF CA filter space.