Design of High-Sensitivity Piezoelectric Micromachined Ultrasonic Transducer Based on Single-Crystal Lithium Niobate Thin Films

Acoustic technology exhibits unique advantages in underwater applications, with ultrasonic transducers serving as the core sensors for underwater acoustic systems. Due to their high integration, broad bandwidth, and excellent stability, lithium niobate (LiNbO3, LN) piezoelectric micromachined ultrasonic transducers (PMUTs) have attracted significant attention for hydrophone applications. However, the design methodology of lateral-field-receiving (LFR) structured LN PMUTs, along with the key factors influencing sensitivity and corresponding enhancement strategies, remains insufficiently investigated, hindering further development of LN PMUTs. Targeting underwater acoustic detection requirements, this study proposes an optimized design methodology for LN PMUTs based on 128° Y-cut LN on insulator (LNOI) single-crystal films with strong ${e}11$ piezoelectric coupling. Through systematic analysis of electric field distribution and capacitive characteristics, we developed an enhanced electrode configuration. By integrating parylene coating for parasitic capacitance suppression and stress optimization, the single-channel array achieves a fourfold improvement in receiving sensitivity (0.56 mV/kPa) while maintaining an 83% operational bandwidth underwater. To the best of our knowledge, this work reports the first sensitivity enhancement in LN PMUTs while conclusively demonstrating the efficacy of our optimization methodology. The findings provide critical guidance for designing high-sensitivity, wideband PMUT-based receivers.