Development of a Dynamic Imaging Spectroscopic Ellipsometer Equipped with a CCD Image Sensor

采用二维CCD传感器和可变波长光源构成了一台动态成像光谱椭偏仪（DISE）。该椭偏仪已用于CVD氧化膜生长和溶解过程的实时分析，以及不锈钢和碳钢钝化膜厚度和光谱特性的空间变化分析。本研究的主要发现归纳如下：1. DISE设备的开发，使应用于实时光谱椭偏（RTSE）和成像椭偏（IE）测量。RTSE模式可以在100 ms内测量512个波长点的光谱，IE模式可以在5s内获得25 mm分辨率的图像.用RTSE分析了MOCVD沉积的ZrO_2薄膜的生长过程，发现薄膜的生长经历了团簇成核、体层生长和表面粗糙度演化三个连续的阶段。研究还表明，在MOCVD制备的Fe_2O_3-Cr_2O_3薄膜中，Fe_2O_3组分在还原溶解过程中发生选择性溶解，而Cr_2O_3组分在氧化溶解过程中发生选择性溶解.研究了18-8不锈钢在0. 1 M-NaCl溶液中钝化膜厚度和光学常数的空间分布变化。结果表明，在点蚀孕育期内，膜厚存在空间变异性，点蚀倾向于在变异性较大的部位发生。对碳钢（0.12%C）表面钝化膜厚度和光谱的空间分布分析表明，铁素体组织上形成的钝化膜比珠光体组织上形成的钝化膜厚约10%。

A dynamic imaging spectroscopic ellipsometer (DISE) has been constructed using a two-dimensional CCD sensor and a variable wavelength light source. The ellipsometer has been applied to the real-time analysis of growth and dissolution processes of CVD oxide thin films, and also to the analysis of spatial variations in thickness and spectroscopic properties of passive films on stainless steels and crabon steels. The principal findings of this study are summarized as follows :1. The DISE equipment developed enables to be applied to both real-time spectroscopic ellipsometric (RTSE) and imaging ellipsometric (IE) measurements. Spectra with 512 wavelength points could be measured within 100ms by the RTSE mode and images with a 25mm resolution could be obtained within 5s by the IE mode.2. The growth process of ZrO_2 thin films, deposited by MOCVD, was analyzed using RTSE.It was found that the growth of the films proceeds in three consecutive stages ; cluster nucleation, bulk layer growth and surface roughness evolution. It was also demonstrated that the selective dissolution of a Fe_2O_3 component occurs during reductive dissolution of Fe_2O_3-Cr_2O_3 thin films, formed by MOCVD, while that of a Cr_2O_3 component does during oxidative dissolution of the films.3. The changes in spatial distribution of thickness and optical constants of passive films on 18-8 stainless steel were examined in 0.1M-NaCl. It was found that in the incubation period of pitting, the spatial variation in film thickness occurs and the pit tends to initiate at a site where the variation is large. The results of the analysis of spatial distributions of the thickness and optical spectra of passive films on carbon steel (0.12%C) showed that the films formed on a ferrite structure is about 10% thicker than those formed on a pearlite structure.