Hysteresis properties of Pb(Zr/sub x/Ti/sub 1-x/)O/sub 3/ thin-film bulk acoustic resonators

Abstract

Applying ferroelectric materials for bulk acoustic resonators, the field dependency of piezoelectric properties has to be considered. In this work, to our knowledge for the first time, the electro-acoustic hysteresis properties of integrated PZT thin-film bulk acoustic resonators are comprehensively investigated. PZT thin film resonators with resonance frequencies around 1.8 GHz and Zr content ranging from 25% to 60% have been fabricated employing multi-target sputtering. The couple coefficient and the impedance characteristics are found to show a hysteresis behaviour particularly dependent on the Zr content. For PZT resonators with low Zr content we observe a distinctive dependence of anti-resonance on the applied field while the series resonance is mostly unaffected. This behaviour changes completely for samples with high Zr content where primarily the series resonance is found to vary dependent on the applied field, a dependence which is supposed to be the consequence of 109/spl deg//71/spl deg/ domain switching in the rhombohedral phase. As potential application making use of this field dependence of acoustic properties a band-width tuneable PZT FBAR based filter will be proposed.