Stress-induced failure modes in high-tuning range RF MEMS varactors

In this paper we focus on electromechanical modeling of high-tuning range MEMS varactors with a focus on failures caused by residual compressive stress. In particular, we quantitatively evaluate for the first time a high-tuning range parallel-plate MEMS varactor in the presence of residual compressive stress. A 3D model generated in ANSYS agrees very favorably with the measured data and explains non-ideal discontinuities in the varactor's C - V curve. It is interesting to note that, although the failures considered in this paper are not encountered in RF MEMS switches, they become particularly important in analog MEMS varactors since they directly impact their effective tuning range.