Low-power MEMS Hydrophone Based On The Aluminum Nitride

The hydrophone directly determines the sonar performance as an important component of the sonar.With the continuous development of technology,the demand for miniaturizing and reducing the power consumption of hydrophones has increased.This paper proposes an appropriate path to solve this problem.First,to miniaturize hydrophones,the subject combines MEMS technology with hydrophone design.Second,to reduce the power consumption of hydrophones,a low-power hydrophone preamplifier circuit is designed.However,in the process of reducing the hydrophone size may cause the hydrophone sensitivity to decrease.In order to reduce the size of the hydrophone,the performance of the hydrophone is still the same as that of the conventional hydrophone,so two ways are adopted to compensate the sensitivity of the hydrophone.One is to sensitize the MEMS hydrophone by using the discrete chip electrodes in series.The second way is to choose aluminum nitride as the piezoelectric material for the MEMS chip.Compared with piezoelectric ceramics commonly used in conventional hydrophones,the figure of merit of aluminum nitride is higher,and the sensitivity of the hydrophone made is also greater.In addition,the aluminum nitride material has good compatibility with the MEMS process and is relatively easy to prepare.This is the reason why aluminum nitride is used as the piezoelectric material for the MEMS chips in this project.The MEMS hydrophone package structure,the sensitive chip,and the low-power preamplifier circuit are three important units in a MEMS hydrophone.The watertight package structure ensures that the hydrophone can work in water and that the sound pressure in the water can be transmitted into the hydrophone and received by the sensitive chip.The piezoelectricity of the sensitive chip can convert the sound pressure signal entering the hydrophone into voltage.Finally,the signal is amplified by the low-power preamplifier circuit to realize the function of the hydrophone.In this paper,two different MEMS hydrophones with discrete electrode chip and continuous electrode chip are fabricated by combining theoretical calculation and simulation analysis,introducing the principle,design,fabrication and testing of each part,and giving the specific parameters of each part.After testing,the power consumption of the two hydrophones is about 1.5m W,the sensitivity of the discrete electrode MEMS hydrophone is about-201.5d B and the bandwidth is about 100Hz-1.2k Hz;the sensitivity of the continuous electrode MEMS hydrophone is about-215 d B and the bandwidth is about 100Hz-1.5kHz.