Physics-based analysis of variable RF MEMS capacitors

The aim of the paper is to design MEMS variable capacitor using a physics-based simulation approach where DC, stress and high frequency analyses are performed on the same geometric model using a commercial software tool. The design targets a very large capacitor tuning range. This is achieved by using a multi-finger parallel-plate structure that has two electrodes: one stationary and one suspended by a mechanical spring so that it moves by the effect of an applied force. Capacitance, actuation voltage and electrostatic forces as well as tuning range and RF frequency response are determined using a single software interface and coupled multi-physics analyses. As this is a large structure, the effect of deformation with motion could be only captured with the numerical analysis technique used which allows full 3-dimensional simulations without compromising the geometrical details. The resulting final design is submitted for fabrication through CMC and will be tested electrically.