Molecular Mobility and Interfacial Dynamics in Organic Nano-electromechanical Systems (NEMS)

Abstract

Commercialization of RF MEMS switches and the substitution for conventional gallium arsenide (GaAs) field-effect transistor (FET) and PIN diode switches is hindered by reliability problems and unpredictable switch failures during operation. Such failures are due partly to the fact that as the surface-to-volume ratio increases in MEMS devices, the surface forces become more dominant than the inertial effects, and thus significantly affect the performance and reliability of MEMS devices. Adhesion of the beam to the bottom dielectric surface (sometimes referred to as stiction in the literature) is the primary failure mechanism in MEMS devices in general and capacitive switches [4] in particular. Adhesion forces are mainly attributed to two phenomena; (1) mechanical deterioration of the contact surface with cycling [5], and (2) electrical charge trapping within the dielectric layer which induces electrostatic attraction [6]. One of the main difficulties in capacitive RF MEMS switch research is that these two effects are coupled and occur at the same time, which makes characterization of adhesion behavior of RF MEMS switches more complex, compared to metal switches, for example. Ref. [7] provides an overview of the major interfacial adhesion and tribological issues in MEMS.