Fabrication and Performance of Piezoelectric MEMS Tunable Capacitors Constructed with AlN Bimorph Structure

Fabrication process and electrical performances in a novel piezoelectric tunable capacitor have been studied. The piezoelectric bimorph structure of AlN/Al multilayer was fabricated with CMOS compatible process. The voltage dependence of actuation showed a good agreement with those of theoretical calculation, whereas stress measurements showed that suppression of residual stress in AlN layers was most critical for curling in the beams. Suppression of the distance between capacitor electrodes realized by the folded-beam type design resulted in capacitance tuning ratio of over ten at 3V. High frequency measurements up to 20GHz revealed that the tunable capacitor maintained a capacitive property up to 18GHz