Effective SAW excitation on non-piezoelectric substrate using AlScN piezoelectric thin film BAW/SAW hybrid transducer

Acoustic delay lines based on Al _0.85 Sc _0.15 N thin film hybrid transducers were investigated by finite element modeling. It was found that an acoustic impedance matching between transducer and non-piezoelectric substrate material plays a crucial role to efficiently excite a traveling surface acoustic wave (SAW) through the BAW piston motion. Test devices based on the 2.5 um thick Al _0.85 Sc _0.15 N piezoelectric film on the silicon substrate were fabricated and characterized.