Design and Implementation of 6 × 6 Array Piezoelectric AlN Hydrophone With High Sensitivity
Tingting Yang, Qiang Wang, Zengxing Zhang, Zhiwei Liao, Yunlong Zhao, Yu Li, Junbin Zang, Rui Gao, Danfeng Cui, Chenyang Xue
Abstract
This paper presents the design, fabrication and characterization of a MEMS piezoelectric hydrophone based on Silicon-On-Insulator (SOI), using Aluminum Nitride (AlN) as the functional piezoelectrical material. The hydrophone has a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${6}\times {6}$ </tex-math></inline-formula> array and a sandwich structure composed of Molybdenum-Aluminum-Molybdenum (Mo-AlN-Mo) films. The three-layered films adhere back cavities that have a radius of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~ \boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> and a pitch of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400~ \boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> . The hydrophone shows proximal resonance frequencies of 479 kHz and 476 kHz under Impedance and Doppler tests, respectively. The initial deformation of the diaphragm is avoided by using a hollow PCB in the packaging to keep the hydrophone in a pressure-equalizing environment. The hydrophone is characterized in both water and air platforms. In water, the hydrophone has a sensitivity of −172.6 dB in the range of 100-2000 Hz, and a linearity of 99% at 1000 Hz, whereas in air it has a linearity of 98% at 1000 Hz. These results demonstrate the potential of high performance miniaturized hydrophone systems for wide-band and low-frequency applications.