Modelling, Fabrication and Testing of RF Micro-Electro-Mechanical-Systems Switch

This paper presents an approach to evaluate capacitance developed by perforated membrane of RF MEMS switch with high accuracy. An analytical model is developed for both upstate and downstate of switch by including parasitic and fringing field capacitance in parallel plate capacitance model. The proposed analytical model includes the ligament efficiency term directly in the formula which reduce the efforts to calculate it individually for various perforation sizes. The capacitance analysis has been carried out by varying the physical parameters to optimize the switch dimensions and these analytical results are compared with the simulation results carried out by 3D FEM tool COMSOL multiphysics for validation. The proposed analytical model results are then compared with benchmark models to understand the efficiency of proposed model in estimating the up and downstate capacitances. The proposed analytical model proved to be good with less error percentage of 2.13% at upstate and 2.59% at downstate whereas the other benchmark models gives greater than 5% error. The switch is then fabricated using 4-mask surface micromachining process and experimental evaluation of capacitance at both upstate and downstate is carried out by DC probe station. Experimentally, the upstate capacitance is obtained as 37.4 fF and downstate as 2.43 pF and the analytical models exhibited low error percentage of 3.95% at upstate and 2.05% at downstate condition for µ = 0.5.