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题名	表面等离子体共振椭偏技术高精度表征超薄膜层光学常数
作者	单尧
文献子类	硕士
导师	胡国行
关键词	椭偏技术 Ellipsometry 表面等离子体共振 Surface plasmon resonance (SPR) 光学常数 Optical constants 超薄薄膜 Ultrathin films
其他题名	High-precision measurement of optical constants of ultrathin layers using surface plasmon resonance ellipsometry
英文摘要	超薄薄膜已经被广泛应用于各种微纳器件，它的厚度和光学常数将直接决定器件的性能，精确表征超薄薄膜的厚度和光学常数对于研究其力学、光学、电学、磁学等性质尤为重要。为了提升超薄薄膜的表征精度，本文研究了结合表面等离子体共振（SPR）效应的椭偏技术，椭偏法可以提取偏振光的振幅和相位差信息，而SPR对于表面特性非常敏感。本课题结合了椭偏法和SPR法两种技术优点，获得由SPR诱导的振幅和相位变化信息，由此反演出超薄薄膜的厚度、折射率、消光系数。这种技术可实现对厚度小于10 nm的超薄薄膜的精确表征。 本文具体开展了下列工作： 结合SPR和成像椭偏技术，在宽光束（~13 mm）成像椭偏光路中嵌入Otto–Bliokh结构，构建了一种表面等离子体共振成像椭偏技术。光在Otto–Bliokh结构中不同空气隙厚度处被SPR吸收的强度不同，成像时形成椭圆形的SPR吸收环。研究了图像处理模块，分析不同起偏角和检偏角状态的SPR吸收环，建立椭偏参数Ψ、Δ随空气隙厚度的变化关系。研究了数据分析模块，Otto–Bliokh结构中椭偏参数的理论值通过多层膜的特性矩阵理论计算得到，椭偏参数的理论值与实验测量值之间通过Levenberg-Marquardt算法进行拟合，提取超薄薄膜的厚度和光学常数。实验中，基于该方法测量了多组超薄金膜和银膜，测量结果与XRR的测量结果一致。该技术具有在线、实时、非接触测量的优点，可直观地观察不同偏振态的SPR吸收图像。 结合Otto–Bliokh结构和微米尺寸细光束光谱椭偏仪，构建了一种表面等离子体共振光谱椭偏技术。模拟结果显示，光谱椭偏技术结合SPR之后，椭偏参数在特定的入射角和入射波长处随着光学常数改变有着更显著的变化，这是由于SPR效应对偏振光的振幅比和相位差产生放大。实验表征分析了多组超薄金属膜和金属膜上的超薄介质膜，得到金属薄膜的厚度和从可见光到近红外范围内的光学常数，厚度测量值与TEM和XRR测量结果一致。这种技术可以获得固定空气隙处的光学常数色散曲线，具有测量速度快、易与商用光谱椭偏仪结合的特点。理论分析和实验结果均表明，这种技术对于金属膜和金属膜上的介质膜具有高灵敏度和精度。 将Otto结构中的空气隙替换为低折射率的介质层，并匹配各层材料找到最佳共振效应，构建了一种改进型的Otto结构，实现对Otto结构中棱镜与金属膜之间间距的纳米级精确控制，由此发展了改进型SPR光谱型椭偏仪。仿真结果表明这种改进型的Otto结构与Otto–Bliokh结构具有类似的共振行为和共振强度。实验结果表明，振幅和相位对于角度的变化均非常敏感。随着入射角度的增大，共振中心向短波漂移，且薄膜厚度越大，共振角越大。实验得到的薄膜折射率与参考数据吻合良好，厚度测量结果与TEM和AFM的测量结果一致。这种改进型的Otto结构相比在先结构具有结构简单、拟合参数少的优点，可实现薄膜表面光学常数均匀性测量，这种测量方法对于进一步提高超薄薄膜的测量精度具有很大的潜力。; Ultrathin films have been widely used in various micro-nano devices. Their thickness and optical constants directly determine the performance of a device. Precise characterization of the thicknesses and optical constants of ultrathin films is particularly important. To improve the characterization precision of ultrathin films, the ellipsometry combined with surface plasmon resonance (SPR) was studied. In this research, the sensitivity of SPR was combined with an ellipsometry, and the amplitude ratio and phase difference of polarized light induced by SPR were obtained. The thickness, refractive index, and extinction coefficient of ultrathin films were therefore obtained by fitting the ellipsometric parameters. This technique enables the precise characterization of ultrathin films with a thickness of less than 10 nm. The details of our work are described as following: The SPR-based imaging ellipsometry, consisted of an Otto–Bliokh configuration and a wide-beam imaging ellipsometry was self-built. The images of SPR elliptical fringes, which corresponding to different absorption values at different air gap thicknesses, were captured to obtain the ellipsometric parameters varied with the air gap thickness. The theoretical values of ellipsometric parameters were calculated by stratified medium theory, and they were fitted with the measured values by Levenberg-Marquardt algorithm to extract the optical constants of ultrathin films. The measured thicknesses of gold and silver films are in good agreement with the results of XRR measurements. This technology is an on-line, real-time, and non-contact measurement, which enables observation of SPR images at different polarization states. The SPR-based spectroscopic ellipsometry, consisted of an Otto–Bliokh configuration and a micro-scale beam spectroscopic ellipsometry was developed. The simulation results showed that the ellipsometric parameters obtained by SPR-based spectroscopic ellipsometry, are more sensitive to the optical constants, compared with the spectroscopic ellipsometry. Several ultrathin metal films and ultrathin dielectric films on metal layer were experimentally studied, the thicknesses and optical constants of metal films were obtained, the measured thicknesses are in agreement with the results of XRR and TEM measurements. This method enables the acquisition of the dispersion of optical constants at a fixed air gap, it has the advantages of fast measurement and easy integration with commercial spectroscopic ellipsometry. Both theoretical analysis and experimental results show that this technique has high sensitivity and precision for optical constants of ultrathin metal films and dielectric films. A modified Otto configuration was developed by replacing the air gap in the Otto configuration with a low refractive index dielectric layer, the accuracy of the gap between the prism and the metal layer reaches nanometer scale and is easily controlled. The liquid under the metal layer and a prism with high refractive index were applied to match the conditions of SPR and increase the resonance intensity. The simulation results showed SPR-ellipsometry based on the modified Otto configuration has similar resonance behavior and resonance intensity compared with that based on an Otto–Bliokh configuration. The measured optical constants were found to be in good agreement with the reference data, and the measured film thicknesses were found to be in good agreement with TEM and AFM measurements. The modified Otto configuration has the advantages of simple structure and less fitting parameters compared with the previous configurations, it shows a great potential for characterizing the surface uniformity of ultrathin layer.
学科主题	材料学
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31096]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	单尧. 表面等离子体共振椭偏技术高精度表征超薄膜层光学常数[D].

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