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

基于模型的散射测量法是光刻加工纳米结构的最先进的光学检测方法。然而，大参数空间结构的定量表征往往由于灵敏度不足和相互关系高而失败。为了改进重建过程，需要对尽可能多的光场信息通道进行测量和评估，从而增加不相关数据集的数量。在此背景下，该方案的主要目标是将传统的傅立叶散射测量与穆勒矩阵偏振测量和白光干涉测量相结合，使相关信息通道同时可访问。信息含量的显著增加使得具有大参数空间的（亚波长）光栅结构的快速和高精度表征成为可能。所提出的评估策略包括复折射率的空间分辨重建，这是特别重要的，因为经常使用的恒定值假设通常会导致很大的误差。此外，几何光栅参数的小散射体积，如侧壁角或线边缘粗糙度，是表征。总而言之，该提案旨在证明显著降低测量不确定度（不超过标称值的1%），并提高类似结构类型的可判别性。

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.