LiNbO3 Film Bulk Acoustic Resonator

As layer transfer techniques have been notably improved these passed years, lithium niobate (LiNbO₃) appears as a candidate for the next generation of ultra wide band Radio Frequency (RF) filters. Depending on the crystalline orientation, LiNbO₃ can achieve electromechanical coupling factors Kt² more than 6 times larger than those of sputtered aluminium nitride films. In this paper, a process based on direct bonding, grinding, polishing and Deep Reactive Ion Etching (DRIE) is proposed to fabricate a single crystal LiNbO₃ Film Bulk Acoustic Resonator (FBAR). From the fabricated test vehicles Kt² of 45% is measured confirming the values predicted by theoretical computations.