A Sc0.2Al0.8N-based 14 GHz Film Bulk Acoustic Resonator with over 8% Coupling Coefficient and over 400 Quality factor for Ku-band applications

It’s challenging to scale down the stack of the acoustic resonator to achieve high frequency like >8 GHz, because of the low crystallinity of the thin piezoelectric film and large parasitics in ultrathin electrode layers. In this work, film bulk acoustic resonator (FBAR) devices based on 90 nm 20% Sc doped AlN (Sc0.2Al0.8N) film have been fabricated and characterized. High-quality thin ScAlN film without obvious interfacial layer and abnormal grains has been achieved. The de-embedded testing results show that the demonstrated resonator has achieved over 14 GHz frequency with a Q factor of over 400 and an effective coupling coefficient of over 8%, which is promising for Ku-band filtering applications.