New analytical model of switching capacitance for MEMS shunt perforated switch

Abstract

A comparative study of modified models for calculating the switch capacitance of electrostatically actuated fixed-fixed beam MEMS shunt switch has been presented considering the effect of beam perforation and dielectric layer simultaneously. Two different capacitance calculation methods using Yang model and Mejis model have been considered in the analysis incorporating fringing field effect due to finite dimension and etching holes on the beam. Using these models capacitances are computed for a range of dimensions and the results are compared with the benchmark FEM solver CoventorWare results. Mejis model is found to be satisfactory for 0.6 μm thick beam in minimum air gap with varying dielectric thickness regime whereas Yang model is good in 1 μm or 4 μm beam thickness with varying air gap and small dielectric thickness range (t d = 0.15 μm). Mejis model outperforms Yang model in μ = 0.5, 0.3 and 0.9 whereas later one shows very close agreement with simulated results (within 1 % error) in μ = 0.7. Therefore for a given range of dimension appropriate model is to be chosen for accurate computation of capacitance.