Multi-scale Simulation Development and Microscopic Contact Physics in Ohmic RF Microelectromechanical Systems (MEMS) Switches

Radio frequency microelectromechanical system (RF-MEMS) switches hold great potential market demand in many RF systems, especially smart phones, because of their exceptional advantages over traditional devices. These advantages include excellent performance, low fabrication cost, almost zero power consumption and wide operational frequency band. However, despite the efforts of many researchers, contact degradation problems are still a major threat against the reliability of RF-MEMS as well as its commercialization.;Understanding the failure mechanisms of RF-MEMS is challenging, as many variables such as contact wear and stiction, joule heating, contact surface contamination, and oxidation could be involved. The microscopic evolution of these mechanisms are difficult to be directly investigated via experimental approaches, especially considering the high temperature caused by joule heating at contact surface. In order to provide useful feedback for experiments, high-throughput computing simulations are performed at atomic scale to reveal and study microscopic details of different switch contacts. Traditional RF-MEMS switches use gold as contact material due to its good electrical conductivity and corrosion resistance, however gold contacts also suffer from low strength, low melting point and hydrocarbon contamination. Experimental improvements of gold contacts include alloying gold with other metal elements and surface coating, and we performed single asperity indentation simulations on three different systems: 1) two-phase AuNi polycrystal binary alloy, 2) SAM/hydrocarbon coated Au, and 3) surface oxidized two-phase AuNi polycrystal binary alloy.;This dissertation is a combination work of software development and computational materials research. While no existing software can perfect fulfill the demand of our research topics, there are always programmingchallenges before studying different systems. Performing simulations on RF-MEMS contacts require handling millions of atoms system as well as joule-heating and thermal dissipation in metal, which requires performance improvement of existing multi-scale software. Simulations of SAM/hydrocarbon coating and oxidation also requires adding or even implementing new force fields. Finally, a parallelMonte Carlo code for embedded atom potential is developed to study the segregation problem of two-phase AuNi polycrystal binary alloy.;Based on our simulation results, the degradation of gold and gold alloy contact at below melting point high temperature includes plastic deformation via FCC slip system and grain rotation. Our unique dynamic structure analysis method reveals that degradation of polycrystal binary alloy is restricted to surface grains. Our work also contributes to future computational materials research via the development of simulation software.With efficient finite difference calculation as well as incorporation of new force fields for atomistic simulation, it is possible to study systems at much larger size and longer time scale than before.