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

• Applicant: Professor Dr. Wolfgang Osten
• Subject Area: Measurement Systems
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 367363335

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.

• DFG Programme: Research Grants