Design,Fabrication And Testing Of MEMS Hydrophone Based On AlN Piezoelectric Film

With the increasing attention paid to the exploration and exploitation of Marine resources,the development of hydrophone has been paid more and more attention by the country.Due to the requirements of low power consumption,low cost,miniaturization and array of hydrophones in ocean information acquisition,MEMS hydrophones have become one of the important research focuses.In this thesis,a kind of MEMS hydrophone based on Al N piezoelectric thin film is designed and manufactured,and its sensitivity,equivalent noise sound pressure spectrum level are calibrated.Moreover,its application in the fields of ocean rainfall noise measurement,pipeline damage and leakage monitoring,interception network monitoring are also been studied.Firstly,the piezoelectric materials are selected according to theoretical analysis of the basic principle,influence factors of sensitivity and equivalent noise spectrum density of the MEMS hydrophone chip.The hydrophone chip is designed by simulating the transmitting and receiving performance of piezoelectric sensing units of different sizes in low frequency.Furthermore,experiments are designed to extract the mechanical and electrical characteristics of a hydrophone chip.The resonant frequency in the air is measured to be about 984 k Hz,and the chip shows good reception performance in the frequency band of 0-20 k Hz.Then,the signal processing circuit and waterproof matching layer are designed and manufactured.The test gain of the signal processing circuit is about 40 d B,the bandwidth is about 30-900 Hz,and the voltage spectrum density of the simulated equivalent input noise is only 15.8n V/?Hz.The calculated transmittance of the waterproof matching layer can reach 52%,and the sound attenuation is only 0.015 d B.Finally,the Al N piezoelectric film MEMS hydrophone performance parameters calibration and preliminary application exploration are carried out.The results show that at the frequency of 100Hz-1600 Hz,the sensitivity of the MEMS hydrophone designed is-179.58 d B ± 2.42 d B(Ref.1V/?Pa),and the equivalent noise pressure spectrum level is 52.6 d B@100Hz(Ref.1?Pa/?Hz),the lowest equivalent noise pressure spectrum level of MEMS hydrophone and better than most traditional bulky hydrophones.Moreover,the MEMS hydrophone shows great potential in applications of ocean rainfall noise measurement,pipeline damage and leakage monitoring,interception network impact monitoring and so on.