PIEZOELECTRICALLY ACTUATED RF-MEMS VARIABLE CAPACITORS
G. KLAASSE, L. A. FRANCIS, R. PUERS, H. A. C. TILMANS

Abstract. Piezoelectric actuation is demonstrated in a RF MEMS variable capacitor as an alternative for electrostatic actuation. This potentially avoids typical drawbacks that occur for electrostatic actuation, as charging of the dielectric and limited tuning range due the pull-in effect. A low temperature surface micromachining process, using Aluminum Nitride as the piezoelectric material, is used. Special stress decoupling structures are implemented that eliminate the negative effects of stress and stress gradient at the same time. A capacitance ratio of 5:1 is obtained at an actuation voltage of –19.5 V.