Hybrid BAW/SAW AlN and AlScN thin film resonator

A novel type of hybrid resonator based on BAW transformation into SAW in a ridged layered structure was fabricated and characterized. Bulk waves are excited by micromachined piezoelectric AlScN pillars located on the non-piezoelectric Si and sapphire substrates. The effect of film thickness and etching depth on the electromechanical coupling and velocity dispersion were calculated by finite element simulation. Resonators of various geometries were fabricated. Maximum effective coupling coefficient of 3.8% was achieved with a 3 um thick Al
0.85
Sc
0.15
N film on a sapphire substrate.