Structure Design And Processing Of Thin Films Piezoelectric Hydrophone Based On AlN Films

Hydrophone is based on the principle of underwater acoustics,which can measure the sound field in the fluid.With the continuous in-depth study of deep-sea environment and the development of marine military science and technology,the frequency of the signals needed to be detected in the fluid environment is constantly decreasing,and the acoustic signal detection standard is becoming higher and higher.The traditional hydrophone has been unable to meet the higher and higher requirements of acoustic signal detection.The development of MEMS Hydrophones Based on new materials and new structures has become the focus of research in the field of underwater acoustic detection in various countries.Miniaturization,low-frequency detection,high integration,high sensitivity and consistency have become an important direction of the development of MEMS hydrophones.The piezoelectric hydrophone based on AlN films,which combines the new piezoelectric material AlN films,piezoelectric effect and MEMS technology,is expected to solve the problems of large volume,high energy consumption and low sensitivity of traditional hydrophone.The third generation of AlN films have good piezoelectric properties,excellent physical properties and stable chemical properties,such as high temperature and high pressure resistance and acid alkali corrosion resistance.Through the MEMS processing technology of SOI substrate,Mo-AlN-Al is used as the structure design of piezoelectric layer to realize the advantages of high sensitivity,low frequency,miniaturization and consistency of underwater acoustic sensor.In this paper,the piezoelectric effect of AlN piezoelectric films material and the theoretical analysis of piezoelectric underwater acoustic sensor are analyzed,and the feasibility of the device development is demonstrated.Based on the characteristics of AlN thin films and the theoretical research of underwater acoustic sensor,the vibration elements of piezoelectric layer and suspended cavity of sandwich structure are designed.The natural frequency,sensitivity and stress of the structure are simulated and analyzed by COMSOL simulation software.According to the simulation results,the structure and size parameters of AlN films piezoelectric hydrophone are designed,and the corresponding processing flow is designed.In the first round of the process,the yield of the process is low because of the over etching of the bottom electrode and the oxidation of the aluminum electrode which leads to the decrease of the adhesion of the lead bonding.On the basis of the first round of structural design and technological processing,the second round of structural design and technological processing are improved.In the second round,the yield of the chip is greatly improved,and the structure and size of the processed chip are measured,and the measurement results are consistent with the design parameters.