Characterization of nanostructures with large parameter spaces by fast white light Mueller matrix scatterometry

基于模型的散射测量是用于光刻加工的纳米结构的最先进的光学检测方法。然而，大参数空间的结构的定量表征往往失败，由于灵敏度不足和高的互相关。为了改善重建过程，必须测量和评估尽可能多的光场信息通道，从而增加不相关数据集的数量。在此背景下，该提案的主要目标是将传统的傅里叶散射测量与Mueller矩阵偏振测量和白色光干涉测量相结合，从而使相关的信息渠道同时可用。显著增加的信息内容使得能够快速且高度精确地表征具有大参数空间的（亚波长）光栅结构。建议的评估策略包括空间分辨重建的复杂折射率，这是特别重要的，因为经常使用的恒定值的假设通常会导致很大的误差。此外，具有小散射体积的几何光栅参数，例如侧壁角或线边缘粗糙度，将被表征。总而言之，该提案旨在证明显著降低的测量不确定性（不超过标称值的1%）和改进的相似结构类型的可辨别性。

Model-based scatterometry is the state-of-the-art optical inspection method for lithographically processed nanostructures. However, the quantitative characterization of structures with large parameter spaces often fails due to insufficient sensitivities and high cross-correlations. In order to improve the reconstruction process, it is essential to measure and evaluate as many information channels of the light field as possible, thus increasing the number of uncorrelated data sets. Against this background, the main objective of the proposal consists of combining conventional Fourier scatterometry with Mueller matrix polarimetry and white light interferometry, which makes relevant information channels simultaneously accessible. The significantly increased information content enables the fast and highly precise characterization of (sub-wavelength) grating structures with large parameter spaces. The proposed evaluation strategy includes the spatially-resolved reconstruction of the complex indices of refraction, which is particularly important since the frequently used assumption of constant values typically causes large errors. Furthermore, geometrical grating parameters with small scattering volumes, such as sidewall angles or line edge roughness, are to be characterized. All in all, the proposal aims at a demonstration of significantly reduced measurement uncertainties (not exceeding 1% of the nominal value) and an improved discriminability of similar structure types.