ZnO thin film piezoelectric micromachined vector hydrophone

A silicon micromachined vector hydrophone based on ZnO thin film has been first developed. The key elements of MEMS piezoelectric vector hydrophone are piezoelectric accelerometers with cantilever beam structures fabricated by microelectromechanical systems (MEMS) technology. The approximate theory and finite element method were adopted in MEMS piezoelectric accelerometer structure analysis, and the influence of materials and structural parameters on accelerometer's sensitivity and resonance frequency were obtained. The MEMS piezoelectric accelerometers were fabricated using silicon micromachining process, and MEMS piezoelectric vector hydrophone was assembled successfully. The measured results show that the sensitivity of MEMS piezoelectric accelerometer is flat from 20 Hz to 1200 Hz, and equal to about 0.83 mV/(m/s²). The equivalent pressure sensitivity at 1 kHz of MEMS piezoelectric vector hydrophone is -229.5 dB (ref. 1 V/μPa), which is 17 dB higher than that of the same type MEMS piezoresistive vector hydrophone.