摘要
微/纳电子机械系统(M/NEMS)具有小型化、低功耗、集成度高等优点,可以完成大尺寸机电系统所不能完成的任务,也可嵌入大系统中,把自动化、智能化和可靠性提高到一个新的水平。基于掺杂硅压阻效应的MEMS器件研究已经有几十年的历史,并获得了广泛地应用。但是硅压阻效应存在灵敏度不够高,且电阻率变化对温度的依赖性较大等缺点,限制了其在高精度、高灵敏传感场合的应用。
本论文基于共振隧穿结构(RTS)的介观压阻效应,对GaAs基矢量水声传感器的设计、加工方法和测试等进行了研究。论文主要包括三个方面的工作:RTS的压阻系数标定、GaAs体加工工艺和水声传感器设计与测试。论文采用分子束外延(MBE)技术在半绝缘GaAs衬底上生长了GaAs/AlAs/InGaAs双势垒RTS,并加工出了具有明显微分负阻(NDR)效应的共振隧穿器件。分别采用显微拉曼-探针加压系统、离心机-Agilent4156C半导体特性分析仪测试系统和振动台-电桥解算电路系统对RTS的介观压阻现象进行实验测试,获得了较相近的最大介观压阻系数:10-9Pa-1量级(NDR区);对GaAs基控制孔和腐蚀自停止体加工工艺进行了研究,设计并采用控制孔技术加工出了四梁-方块水声传感器基础结构;最后,在杭州应用声学研究所(715所),对封装后的矢量水声传感器指向性、频响和灵敏度等进行了初步测试。获得了较好的“8”字形矢量指向性和频响曲线,水声传感器的灵敏度在1KHz时达到-184.6dB。
本论文的创新点在于将量子阱共振隧穿材料与M/NEMS相结合,研究纳米尺度的力电耦合现象,并将其应用在矢量水声传感器结构中。优化GaAs基单步工艺,完善了GaAs基成套工艺,加工出介观压阻型M/NEMS器件。
Micro/nano-electro-mechanic System (MEMS) has many merits, such as extreme miniaturization, low power consumption, high integrated level and so on. They can complete tasks that large-dimension electro-mechanic system can not achieve, and raise automatization, intelligentized ability and reliability to a new level by embedding in large system. The study of MEMS devices based on the piezoresistive effect of doped silicon has several ten years history with widely applications. Because of the relative low sensitivity and resistance variety dependency on temperature et al of the piezoresistive effect based on doped silicon, the uses of it are restrained under conditions such as accurate precision and high sensitivity.
Based on the piezo-resistive effect of resonant tunneling structure (RTS), design, process methods and measurement et al of GaAs vector hydrophone are studied in this paper. The works mainly contain three targets: calibration of the piezoresistive coefficient of RTS, GaAs bulk process methods and design, measurements of the hydrophone. By molecular beam epitaxy (MBE) technology, the GaAs/AlAs/InGaAs double barrier RTS is grown on semi-insulating GaAs substrate, and the resonant tunneling devices are fabricated with obvious negative differential resistance (NDR) effect. The meso-piezoresistive phenomena of RTS is measured, either by micro Raman-probe stress system, centrifugal machine-Agilent4156C semiconductor characteristic analyzer system and/or jarring table-Wheatstone bridge solution circuit system, and the consistent largest piezoresistive coefficients: 10-9Pa-1 are discovered (NDR region); The control-hole technology and etch-stop technology of GaAs bulk process methods are studied too, and by control-hole technology, the basic hydrophone structure with four beam-block is designed and fabricated; At last, In Hangzhou Applied Acoustics Research Institute (715 institute), the directivity, frequency response and sensitivity et al of the packaged vector hydrophone are measured primarily. The good“8”cosine vector directivity and frequency response curves are obtained, and the sensor’s sensitivity reaches -184.6dB at 1 KHz.
The innovations of this paper are the combination of quantum well resonant tunneling materials and M/NEMS, the study of the electro-mechanic coupling phenomena in nano-dimension, and its application in vector hydrophone structure. Others contain optimizing GaAs process steps, perfecting series of GaAs fabrication technology, and processing the meso-piezoresistive M/NEMS devices.
引文
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