IOE OpenIR  > 光电技术研究所博硕士论文
Alternative TitleMeasurements of Semiconductor Wafer Properties by Modulated Free Carrier Absorption
Thesis Advisor李斌成
Degree Grantor中国科学院光电技术研究所
Place of Conferral光电技术研究所
Degree Discipline信号与信息处理
Keyword调制自由载流子吸收 频率扫描曲线 径向位置扫描曲线 多参数拟合 载流子输运特性 载流子有效扩散长度 灵敏度
Abstract半导体的载流子输运特性—载流子扩散系数、少数载流子寿命和前表面复合速度是表征半导体品质及特性的重要参数,是控制微电子器件质量、性能和可靠性的关键参数。精确测量半导体的载流子输运参数也将为半导体产品生产提供可靠数据,以便于制备出性能更为优良的电子产品。所以,对这些参数的准确检测是半导体制造业中的一个重要课题。本文从光激发自由载流子的产生、扩散与复合过程和载流子输运特性的关系出发,结合半导体中的一种重要物理现象—自由载流子吸收,给出了调制自由载流子吸收检测技术的新的理论模型,并采用径向位置扫描方式测量半导体输运参数。具体来说主要分为以下几个方面: 以描述半导体中光激发自由载流子的产生、复合和扩散过程的连续性方程和自由载流子吸收为基础,将传统的调制自由载流子吸收检测技术的一维理论模型推广到三维模型,不仅给出了调制自由载流子吸收检测信号与载流子输运参数的关系式,也给出了检测信号与调制频率以及泵浦-探测光相对距离的关系。 对建立的三维模型进行模拟仿真,详细分析了在不同调制频率、不同探测位置时载流子输运参数对检测信号的影响;通过引入灵敏度系数,分析了调制自由载流子吸收检测技术的三维理论模型对载流子扩散系数、少数载流子寿命和前表面复合速度的灵敏度;通过多参数拟合,仿真分析了均方差对各个参数的灵敏度。 根据建立的三维理论模型,搭建了调制自由载流子吸收检测技术的实验平台,并利用该实验平台测量了半导体单晶硅的调制自由载流子吸收信号的径向位置扫描曲线;通过多参数拟合,从测量结果中获取了测试样品的载流子扩散系数、少数载流子寿命和前表面复合速度值;分析了拟合结果的灵敏度以及测量精度,得到了与仿真一致的结论。 从理论上对调制自由载流子吸收检测技术的频率扫描和径向位置扫描两种测量方式的测量范围进行了分析,发现径向位置扫描测量方式的测量范围比频率扫描方式大,并且测量精度也有大幅度提高。从仿真和实验两个方面对两种测量方式检测结果的相对灵敏度以及拟合结果的可信度进行对比分析,发现在频率扫描拟合过程中载流子输运参数之间以及载流子输运参数和光斑半径之间会相互影响,这大大削弱了频率扫描曲线拟合结果的可信度,而径向位置扫描方式则能使这种影响降低到很小,从而提高了通过多参数拟合得到的载流子输运参数的准确度。
Other AbstractThe electronic transport properties, i.e., the carrier lifetime, the carrier diffusivity and the front surface recombination velocity (FSRV) of semiconductor wafers are crucial parameters controlling the quality, performance and reliability of semiconductor-based micro-electronic devices. Evaluation of these parameters is essential for characterizing semiconductor wafers, for defects and contamination monitoring and for device modeling. The necessity to accurately determine these parameters is continuously driving industrial manufacturers to search for more effective characterization tools. In this thesis a three-dimensional modulated free carrier absorption (MFCA) model based on the continuity equation is proposed, in which amplitude and phase of MFCA signal are measured not only as functions of the electronic transport properties of semiconductor wafers, but also as functions of modulation frequency and pump-probe-beam separation. At different modulation frequencies and two-beam separations the dependences of amplitude and phase on the transport parameters are analyzed indicating that the MFCA signal sensitivities to the transport parameters increase with the increasing two-beam separation. Therefore, a laterally resolved modulated free carrier absorption technique (LR-MFCA), in which amplitude and phase are recorded as functions of two-beam separation at several different modulation frequencies, is presented to determine the electronic transport properties of semiconductor wafers via multi-parameter fitting procedure. The uncertainties of the fitted parameter values are analyzed by investigating the dependences of a mean square variance including both the amplitude and phase on corresponding electronic transport parameters. Simulation results show that the electronic transport parameters can be determined accurately through fitting experimental MFCA data carrying both frequency- and space-domain information of carrier diffusion to a rigorous MFCA model. Experiments were performed with a silicon wafer and the results were in good agreement with the theoretical simulations. The relative accuracy of the transport parameter determination by laterally resolved MFCA and by conventional frequency-scan MFCA (FS-MFCA) is theoretically and experimentally estimated by calculating the dependence of the mean square variance on the individual parameter via multi-parameter estimation process. Simulated and experimental results show that the determination of the electronic transport properties of semiconductors by LR-MFCA is more accurate, compared with that by FS-MFCA.
Document Type学位论文
Recommended Citation
GB/T 7714
张希仁. 基于自由载流子吸收的半导体特性测量方法研究[D]. 光电技术研究所. 中国科学院光电技术研究所,2008.
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