Integrated optical critical dimension metrology with Mueller matrix ellipsometry

Abstract

Mueller matrix ellipsometry (MME) is commonly applied by the standalone instruments in semiconductor manufacturing process for films and nanostructures characterization. However, MME is rarely used in the integrated metrology optical critical dimension (IM OCD) tools due to the difficulty in extracting the parameters under varied azimuth angle conditions, which is induced by the rotation of R-θ wafer stage adapted to the restricted space. When the measurements on a same wafer are achieved under multiple azimuthal angles, the measured nanostructure parameters usually mismatch the baseline values provided by the manufacturer, and therefore lead to the unacceptable accuracy loss. In this paper, we propose an azimuthal sensitivity analysis and ridge regression algorithm (ASA-RR) to enable the MME-based IM OCD. The sensitivity to variability in azimuth angles is calculated by the local sensitivity analysis algorithm, and the result of which is applied as the weight factor for the spectrum input in the ridge regression. Experiments demonstrate that the ASA-RR algorithm provides more accurate results for the IM OCD, which satisfy the requirements in manufacturing.