Effect of creep in RF MEMS static and dynamic behavior

This paper presents the experimental characterization of the creep effect in electrostatically actuated gold microstructures. The tested specimens follow the typical configuration of the microbridge based radio frequency microelectromechanical systems switches and varactors. Initially, the plastic creep strain accumulation with time is measured for the specimens with different geometric dimensions and at different actuation voltages and temperatures. To avoid the size and cumulative heating effects, three specimens with the same geometric dimensions, actuation voltages and constant temperatures are tested. The test results allowed decoupling the permanent plastic strains due to the creep effect and reversible anelastic strains due to the viscoelastic behavior. The pull-in voltage and natural frequency values measured before and after the creep tests are compared, revealing the mechanical stiffness decrease caused by creep.