Design and fabrication of reliable MEMS switch for power applications

Abstract

Electro-magnetic relays (EMR``s) and Solid-state relays (SSR``s) have been widely used in various applications and kept up their market share separately according to strength and weakness of both. In the meantime, the emergence and growth of MEMS technology could generate the new switching device, micromechanical relay. This MEMS switch has been actively studied because it is able to not only combine fine attributes but also overcome the disadvantages of both EMR``s and SSR``s. In spite of these many merits, high power handling and reliability issues are most critical bottlenecks in MEMS relays. Most of these essential issues are closely related to the metal-to-metal contact (friction, wear, contamination, welding, etc) and it is currently the subject of intensive research efforts. So, in order to achieve both reliable performance and high current carrying capacity, low contact resistance is needed to reduce joule heating as a fundamental approach because low contact resistance should mitigate the switching failure mechanism, both contact resistance degradation and stiction by generating less heat originally. Additionally, it is more preferred feature in power applications from the viewpoint of power efficiency. In general, it is known that contact force and hardness of contact material are the key parameters in determining the contact resistance. In this research, new method using window frame shaped drain electrode (for high contact force) and soft dielectric layer under the contact material (for low hardness) is proposed to achieve low contact resistance. First, conventional cantilever switches are actuated by gate electrode somewhat apart from the drain electrode, but this smart drain structure transforms the electrostatic force effectively to the contact force because where electrostatic force is generated is near by the position real contacts are occurred in . Second, soft BCB under the contact layer is able to lower the contact resistance due to the fa...