Thin films of PZT-based ternary perovskite compounds for MEMS

Stress free heteroepitaxial thin films of PZT-based ternary perovskite, xPb(Mn,Nb)O₃-(1-x)PZT, were fabricated by magnetron sputtering on (001)MgO substrates and evaluated their crystal structure, ferroelectric and piezoelectric properties. The heteroepitaxial thin films showed single c-domain /single crystal structure and exhibit hard ferroelectric behavior with large Pr, Pr=60muC/cm², and high E_c, 2E_c=230kV/cm, at x=0.06. The PZT-based thin films exhibited high piezoelectric coupling factors k_t, k_t=70%, measured at GHz range FBAR structure. High values of mechanical quality factor Q_m, Q_m=185, were observed at 4Ghz range. The observed k_t and Q_m are, to our knowledge, the highest in the reported values. The figure of merit k_t ²Q_m is almost the same to piezoelectric AlN thin films. It is confirmed the PZT-based ternary perovskite thin films have a potential for a fabrication of FBAR and/or wide band filters at GHz range.