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基于MEMS的阵列式扫描探针显微镜测头理论与技术研究
Theory and Technology Study on Mems Based Probe-array Head of SPM
【作者】 孙凤鸣;
【导师】 傅星;
【作者基本信息】 天津大学 , 仪器科学与技术, 2013, 博士
【摘要】 扫描探针显微镜(SPM)凭借其原子级的分辨力迅速在表面科学、材料科学、生命科学等研究领域中得到广泛的应用,但是随着科学研究和工业应用对成像范围、扫描速度等需求的提高,迫切希望SPM性能也随之提高。本文研究了一种基于微机电系统(MEMS)技术的阵列式SPM测头,借助静电梳齿结构的大行程、高线性度、易集成性和阵列式探针的特点,结合大范围纳米定位平台,搭建了大范围阵列式探针SPM。在提高SPM的扫描效率、扩大测量范围等方面进行了较深入的研究工作。主要工作包括:1.研究了测头的力学等效模型,推导了测头三个维度上的弹性系数计算公式,并结合有限元方法进行仿真,优化测头结构的设计参数。设计了MEMS阵列式探针SPM测头。并合理配置测头整体结构三个维度上的弹性系数,使测头更稳定的工作。2.构建了测头的电学模型,并研究了其电学特性,分析了测头针尖所连接的主梁在受力发生平移和偏转时,给测头电容模型带来的非线性影响。分析测头在加载静电场时的侧向吸合力和悬浮力等。确定了测头的扫描模式、极限扫描行程和极限施加电压。3.提出了阵列式静电梳齿结构测头的三种工作模式:恒高模式、恒力模式和动态模式。分析三种工作模式的特点。并对恒高模式和恒力模式进行了实验研究4.提出了一种利用纳米测量机和超精密电磁天平快速可溯源的探针弹性系数标定方法。保证了测头恒力工作模式的稳定性和测量准确性。5.将测头与大范围精密定位测量平台—纳米测量机结合,设计了阵列式探针SPM。实验标定了测头的灵敏度、迟滞性、重复性、分辨力、低频振动性能等各项参数。在恒力工作模式下,实现了多个探针同时独立地对一维栅格样板、二维栅格样板进行扫描成像,证明了测头的二维扫描成像能力。通过对一维栅格样品600μm行程的线扫描,验证了测头具有一定的大范围扫描能力。
【Abstract】 Almost soon after the invention of the scanning probe microscopy (SPM), itattracted widespread attentions and quickly found its applications invarious scientificdisciplines and industrial fields with its sub-nanometer resolution andmicro-nanoscale manipulation. In spite of their achived successes regardingmeasurement resolution and accuracy, traditional SPMs embody such unsurmountabledisadvantages like relatively low imaging speed and narrow scan range. To improvethe imaging efficiency, novel probe-array SPM head based on MEMS comb structureis developed. Meanwhile, probe-array SPM including probe-array SPM head andNano Measuring Machine is developed to complish multi-probe imaging. Mainachievements of this research work are the following:1. The theoretical model of mechanical structure of a novel MEMS basedprobe-array SPM head is analyzed. Based on material theory, the equation of3Dspring constant is deduced. According to the influence degree of structure andparameters of beam, optimum structure and parameters are chosen. Finite elementsimulated data of optimum structure are compared and validated with the conclusionof theoretical analysis.3D spring constants of the structure are optimum configured toensure the stability of the probe-array SPM head.2. Based on electinics features and electrical model, the nonlinearity influence oftranslation and rotation of the main shaft, which is induced by friction and shear forceapplied on the probe along Y and Z axis in the scanning process, is analyzed. Pull-inand levitation force generated by electrostatic field is analyzed. With above twoanalyses, the scanning routine direction, scanning travel limit and applied voltagelimit is determined.3. As the first time application of this kind of structure, the operating mode of theSPM head is analyzed. According to the traditional AFM operating mode, three kindsof operating mode is proposed as height constant mode, force constant mode anddynamic mode. After comparing three kinds of operating mode, force constant modeis chosen as main operating mode in our experiment. 4. Spring constant along the measurement axis is to be calibrated to keep forceconstant mode stable. A quick and traceable method including Nano MeasuringMachine and ultra-precision balace is proposed and complished.5. Through the combination of probe-array SPM head and Nano MeasuringMachine positioning platform, probe-array SPM is constructed. The measurementdata is traceable though three embedded laser interferometers. Experiments are carriedout to calibrate the sensitivity, hysteresis, repeatability, resolution and dynamiccharacteristics of the SPM probe. A series of standard samples are measured. Theresults demonstrated the system’s nanometer magnitude resolution and lare rangemeasurement capability.
【Key words】 Scanning Probe Microscope; MEMS; probe-array; Nano MeasuringMachine; Force constant mode;