9.5 % Scandium Doped ALN PMUT Compatible with Pre-Processed CMOS Substrates

This paper presents an 80 μm squared piezoelectric micromachined ultrasonic transducer (PMUT) using 9.5 % scandium-doped aluminum nitride (AlScN). The improvement in the effective piezoelectric coefficient (e 31,f ) and consequently in the membrane displacement was demonstrating according with the FEM simulation. The proposed device has a high piezoelectric coefficient factor (k t 2 ) in air, 2.76 %, and also in liquid environment, 1.12 %. The output pressure normalized at 1.5 mm in Fluorinert gives 12.57 kPa/V/mm 2 , ~ 9 times higher than 7x7 AlScN array (1.4 kPa/V/mm 2 ). Pulse-echo experiment was validated with a single PMUT considering as reflected surface the air-liquid interface.