Development of High-Quality FBAR Devices for Wireless Applications Employing Two-Step Annealing Treatments

In this letter, a new two-step annealing technique is presented that can more effectively improve the resonance characteristics of the film bulk acoustic wave resonator (FBAR) devices in terms of return loss,
Q
-factor, and effective electromechanical coupling coefficient (
K
_eff
²
). In the case of the SMR-type FBAR devices, the use of this approach has considerably improved the resonance performance (~8000 of Q-factor value, ~ 2% of
K
_eff
²
) at the operating frequency of ~1.8 GHz, as compared to the conventional annealing techniques.