High Reproducibility and Reliability of Piezoelectric MEMS Tunable Capacitors for Reconfigurable RF Front-end

A novel RF MEMS tunable capacitor having W-shaped folded beam piezoelectric bimorph actuator using a CMOS compatible surface micromachining process has been proposed. The structure almost completely compensates the curling of the beams due to unbalanced residual stress and thermal expansion mismatch, and assures high reproducibility and negligible temperature dependence. Cyclic and static lifetime tests at as high as 9V had slight effects on the C-V characteristics. The high reproducibility and reliability assure the capacitors are promising as key components in reconfigurable RF systems, such as tunable antennas, tunable filters and tunable impedance networks.