Viscoelastic modeling and simulation of electrostatically actuated RF MEMS switches.

摘要

The linear viscoelastic behavior of RF MEMS switches is investigated using the Finite Element Method in this study. Relaxation measurements and temperature dependence of thin gold films is the foundation for implementing the viscoelastic material data in the simulations. Due to the operation of the specific MEMS device of interest, charging occurs in the dielectric material, when the switch is electrostatically actuated. These electrostatic forces need to be overcome by mechanical restoring forces for the MEMS switch to open and operate again. Thus, it is important to understand and investigate restoring forces for this class of devices.;A variety of RF MEMS switches, with different geometries, were investigated in this study. Linear viscoelasticity of Gold (Au) has been implemented to observe the relaxation behavior of restoring forces. The effect of geometry on the restoring forces is also investigated. The important effect of temperature dependency and its effect on the restoring forces are demonstrated. Residual stresses, which occur during device fabrication, were included in the simulation models. The role that residual stresses play in controlling the switch restoring forces is examined in detail. Simple hand calculations are included in this study to verify and better understand the FEA results.;Additionally, finite element simulation results are utilized to match analytical modeling of restoring forces. Restoring forces are separated into three components to compare results obtained using different boundary conditions. A good match was obtained between analytical modeling and FEA models, helping to validate the more complex viscoelastic behavior of actual RF MEMS switches. The final models for actual RF MEMS switches currently in operation, included realistic boundary conditions to better mimic the exact operation of these devices.