A Piezoelectric MEMS Vector Hydrophone Based on Sc 0.2 Al 0.8 N

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This article presents a piezoelectric vector hydrophone based on scandium-doped aluminum nitride (ScAlN) thin films, with its core sensing element being an accelerometer chip fabricated using micro-electromechanical systems (MEMS) technology. The accelerometer features a symmetric design with a central mass and four cantilever beams and a chip size of 2.2 × 2.2 mm. The accelerometer is integrated with a preamplifier, and the components are encapsulated in a cylindrical housing to form a MEMS vector hydrophone. Experimental results indicate that, following amplification by the preamplifier, the accelerometer achieves a voltage sensitivity of 533 mV/g at 100 Hz, with a first-order resonant frequency of 5612 Hz. The sensitivity curve remains stable within 5–2000-Hz frequency range. The output voltage exhibits good linearity across the excitation range from 0.0625 to 8 g. The performance of the MEMS vector hydrophone is evaluated using a comparative calibration method, revealing a bandwidth of 20–1250 Hz, with a sound pressure sensitivity of -195.9 dB at 1000 Hz (ref. 1 V/μPa). The hydrophone also demonstrates a distinct “8”-shaped directional pattern, with a directional depth of 16.72 dB.