Development of a micro-electro-mechanical systems (MEMS) vector sensor with mushroom-shaped proof mass and characterization of its properties as a hydrophone

Abstract

Micro-electro-mechanical-systems (MEMS) underwater vector sensors are capable of detecting the distance and the direction of sound signals generated by an underwater target. In this research, a piezoelectric MEMS vector sensor, which has four-clamped beams with a mushroom-shaped proof mass to improve receiving voltage sensitivity (RVS), was designed, fabricated and tested. In the design stage, two different designs were proposed and simulations were carried out using COMSOL Multiphysics® software to optimize the design parameters such as the beam length and the weight of the proof mass, which affect the resonance frequency. Based on the simulation results, the piezoelectric Pb(Zr¬0.52Ti0.48)O3 thin film was deposited by radio frequency (RF) magnetron sputtering and placed between two bottom and top platinum electrodes. The optimized fabrication process involved multiple etching steps and assembly process with mass structure. To investigate its performance as a MEMS vector sensor, its electrical and mechanical properties were characterized and the device showed promising results in resonance frequency and displacement when measured in air, although additional underwater experiments need to be conducted using theoretical algorithms to figure out the directivity in order to evaluate its capability as a hydrophone.