Electro-Thermo-Mechanical Modeling of Metal to Metal Contact RF MEMS Switches

Abstract

SHANTHRAJ, PRATHEEK. Electro-Thermo-Mechanical Modeling of Metal to Metal Contact RF MEMS Switches (Under the supervision of Professor Mohammed A. Zikry.) Three-dimensional fractal representations of surface roughness are incorporated into a finite-element framework to obtain the electro-thermo-mechanical behavior of asperities, and to relate them to the behavior of metal to metal contact RF MEMS switches. Fractal surfaces are generated from the Weierstrass-Mandelbrot function that is representative of AFM surface roughness in RF MEMS devices. A specialized finite element scheme is developed, which couples the thermo-mechanical asperity deformation with the electro-mechanical contact characteristics to obtain accurate predictions of contact evolution as a function of time and loading. Using this approach, simulations are then used to investigate how surface roughness, different material choices, initial residual strains, applied voltages, and operating temperatures affect contact parameters. Based on these detailed predictions, tribological design guidelines are obtained for predictions that can be used to significantly increase the lifetime of low contact resistance RF MEMS switches by limiting stiction, friction, and adhesion.