High-Q and Capacitance Ratio Multilayer Metal-on-Piezoelectric RF MEMS Varactors

This letter documents the design and characterization of integrated and continuously tuned, radio frequency multilayer metal noncontact varactors with low-power, large-displacement, thin-film lead zirconate titanate (PZT) actuators. The devices, with capacitances in the 0.019-0.23-pF range, achieved high quality factors at the maximum capacitance state (Q = 100 at 8.7 GHz) and tuning ratios as high as 11.6:1 at 20 V actuation with nW-power consumption. The devices utilize three electroplated copper (Cu) layers ( ~10 μm per layer) directly fabricated on PZT microelectromechanical system actuators.