Research On Design And Fabrication Technology Of MEMS Piezoelectric Hydrophone Based On AlN

As the core component of the sonar system,hydrophones have been widely used in fields such as underwater acoustic detection,underwater communication,tsunami warning,and submarine detection.Aiming at the disadvantages of traditional hydrophone,such as large volume,high cost and poor consistency,a MEMS piezoelectric hydrophone based on AlN was proposed in this paper.The piezoelectric hydrophone can convert acoustic signals into electrical signals by the directive piezoelectric effect to achieve acoustic-electrical conversion.It has the advantages of simple process flow,batch manufacturing,low cost,small size,and low power consumption.In this paper,the mathematical model of the piezoelectric MEMS hydrophone was established and its finite element simulation analysis,structure optimization,process preparation and performance test were carried out,mainly including the following work contents:(1)The overall structure of the piezoelectric hydrophone was designed and the mathematical model of the piezoelectric hydrophone was established.Based on the mathematical model,some key performance indicators such as the resonance frequency,energy conversion efficiency and the sensitivity of the hydrophone were calculated.The stresses and displacement of the piezoelectric film under uniform sound pressure are analyzed.(2)The finite element simulation of the piezoelectric hydrophone was carried out.The resonant frequency of the hydrophone and the vibration mode under the resonant frequency were simulated,the relationship between the resonant frequency of the hydrophone and its structural parameters was given.The stresses and displacement of the piezoelectric film under uniform sound pressure were calculated,and the simulation results verified the validity of the mathematical model.The structure parameters of the hydrophone were optimized through the established mathematical model and finite element simulation.At the same time,the sensitivity and linearity of the hydrophone were simulated.(3)The fabrication process of piezoelectric hydrophone was designed and the mask layout was drawn.The piezoelectric hydrophone was fabricated using MEMS technology,the principle and precautions of the key technology were introduced in detail,and the specific parameters of the process implementation were given.(4)The morphology of the hydrophone was observed by laser microscope and scanning electron microscope,the AlN piezoelectric film was characterized by XRD and EDS.The resonant frequency and vibration mode of the hydrophone were measured by the Polytec microsystem analyzer.The impedance curve of the hydrophone was measured by the impedance analyzer,and the electromechanical coupling coefficient of the hydrophone was calculated to be 7.5% according to the impedance curve.The sensitivity of the hydrophone was tested,and the sensitivity was between-170.5d B and-202.4d B in the range of 10 Hz to 2KHz.