Solid-state MOSFET-based micro hydrophone array

Abstract

The fabrication of low-cost, high-sensitivity, and miniaturized hydrophone array is highly desirable for application in sonar technology. However, as hydrophone size decreases, it becomes necessary to provide an amplifier or buffer in close proximity to avoid sensitivity loss due to interconnect capacitance. This suggests the concept of hydrpophone integration with microelectronics in an integrated circuit environment. A proptotype of an integrated transducer was thus realized in which a P(VDF-TrFE) film was bonded to the extended gate of a metal–oxide–semiconductor field-effect transistor (MOSFET) which was fabricated on a silicon wafer using standard NMOS process technology. This technique is compatible with IC fabrication processes and enables the integration of active elements with the transducer element on the same chip. The integrated structure eliminates long leads between the transducer and the amplifier and makes the net transducer–amplifier detectivity superior to the ceramic transducer–amplifier system. The devices are then encapsulated with Rho-C rubber which results in good acoustic impedance to that of water. The acoustic sensing performance was carried out in a pulse tube over a frequency range from 4 to 10 kHz. The experimental results along with the theoretical prediction by Mason equivalent circuit will be presented.