Low-stress permalloy for magnetic MEMS switches

The residual stress in the electroplated magnetic films is an important factor that limits the functionality of many micromagnetic devices. We have investigated the stress in electroplated Ni-Fe alloy for MEMS as a function of bath concentration, utilizing the wafer-bending method. Our investigation demonstrated that a low-concentration plating solution decreases the residual stress in the electrodeposits, and the stress is further decreased by increasing the saccharin additive content. We obtained the low-stress Permalloy Ni₈₁Fe₁₉ in our experimental conditions. We fabricated a bistable electromagnetic RF MEMS switch with deformation-free cantilever beam using the electroplated Permalloy.