基于巨压阻效应的MEMS三维矢量水声传感器基础研究

MEMS tri-axial vector hydrophone based on giant piezoresistance effect is proposed to realize the high-precision requirement on underwater detection platform for the 3D orientation of the remote acoustic target. In order to increase the receiving sensitivity, the silicon nanowires are applied as sensitive unite due to its giant piezoresistance effect, which are fabricated by spacer patterning technology, showing good compatibility with semiconductor technique. The Giant Piezoresistance effect is investigated through theoretic analysis and experiment to verify its mathematical modal based on the surface depletion mechanism, which provides the broad prospection on increasing the detection sensitivity. The vibration pickup mechanism of MEMS tri-axial vector hydrophone is investigated, to overcome the space limitation of 2D orientation. The equilibrium of tri-axial sensitivity is realized by appropriate structure parameters, which could be validated though theoretic calculation and simulation result. Furthermore, the reliable fabrication process is developed to manufacture MEMS tri-axial vector hydrophone with the high performance. The sensitivity is estimated to be increased by 20dB(@1KHz , 0dB=1V/μPa, working frequency 20~1000Hz), corresponding to almost 10 times farther detection range. Meanwhile, the tri-axial sensitivity asymmetry is expected below 3dB. These results would lay a foundation for the further development of space detection of remote acoustic target.

本项目针对远距离声目标三维空间定位对小体积水下装置平台的高精度需求，提出基于巨压阻效应的MEMS三维矢量水声传感器。为提高探测灵敏度，本项目利用与半导体工艺兼容的侧墙掩模法制备硅纳米线，理论和实验上探究其巨压阻效应，建立及验证基于表面耗尽机制的巨压阻模型，为突破远距离探测的灵敏度瓶颈开拓研究思路；针对目前MEMS水声传感器二维探测的局限，本项目揭示三维矢量水声拾振机理，理论和仿真分析设计结构参数，实现三轴灵敏度平衡，为三维空间定位应用奠定基础；开发可靠的一体化制备工艺流程，研制高性能的MEMS三维矢量水声传感器，实现灵敏度提高20dB（0dB=1V/μPa，参考频率1KHz，工作频带 20~1000Hz），探测距离提高10倍，三轴灵敏度不一致性小于3dB，为海洋远距离声目标空间探测提供技术支持。

本项目开展了基于硅纳米结构的高灵敏MEMS矢量水听器的研究工作，探究了MEMS水听器三维拾振机理，优化与建立了微纳一体化加工工艺，研制出了高灵敏度高一致性的水听器。. 通过理论分析、仿真优化，设计基于硅纤毛/硅纳米膜MEMS二维矢量水听器结构，并完成了工艺加工，实现硅纳米线、二氧化硅微米梁和硅纤毛的一体化集成。纳米膜厚度100nm，纳米线宽度70-120nm可控，二氧化硅梁厚2μm，硅纤毛高度大于500μm。. 通过增加支撑块面积实现检测三维空间声波，增加支撑块厚度使得水听器受到振动时敏感纤毛和支撑块对梁的弯矩相互抵消，降低振动引起的矢量水听器信号输出。抑制面内振动MEMS三维矢量水听器X、Y和Z三个通道灵敏度分别为-182dB、-184dB和-160dB @400Hz (0dB=1V/μPa)，X、Y轴灵敏度不一致性小于3dB，对比传统MEMS水听器灵敏度-204dB@400Hz，提高了20dB以上；水听器具有良好的“8”字指向性，三个通道凹点深度分别为34dB、35dB和33dB，水听器受到面内振动噪声实验结果表明，设计的水听器和以前的传统结构相比，振动灵敏度降低了92%，可以有效地提高水听器的信噪比。本项目的研究为小体积水下平台高灵敏三维矢量水声探测提供理论基础和技术支持。