Modeling and analysis of capacitance in consideration of the deformation in RF MEMS shunt switch

This paper deals with the modeling of capacitance in an actuated RF MEMS switch where the beam layer forms tilted contact at the edges and touches completely with the dielectric layer at the center. The tilted and overlapping sections of the beam are modeled separately and combined with the effect of etched holes to estimate the overall capacitance formed between the beam and central part of coplanar waveguide. Effects of beam width, dielectric thickness, and the air gap between beam and dielectric layer on total capacitance of the switch are analyzed. RF analysis and beam length optimization has also been done to ensure an efficient grounding of signal in the transmission line. Model and simulated values using Coventorware MEMS plus 4.0 are compared in different configurations and percentage of errors are also estimated. For beam height variation of 1-2.25 μm, the error is within ±8%, while for varying dielectric thickness of the layer from 0.15 to 0.3 μm and beam width variation of 40-70 μm shows an accuracy within ±6%.