RF-MEMS Switched Capacitor using Ta/Ta2O5 Electrodes

This paper presents the fabrication and measurements of RF-MEMS, zero-level packaged switched capacitors. Crystallized Ta/Ta2O5 electrodes are used for electrostatic actuation. The electrode formation is conducted in a single deposition step, providing a very good metal (Ta) to dielectric (Ta2O5) interface. The 60×50 µm MEMS capacitor can be switched from 50 fF to 350 fF, by applying a 15 V unipolar bias voltage. 8-hours hold-down testing have shown the absence of charging. The high permittivity of Ta2O5 also increases 5 times the capacitance value compared to SiN-based switched MEMS capacitors with the same surface.