Spatial convergence analysis on model-based optical critical dimension metrology of high-aspect ratio holes

We investigated the error caused by the rasterization of the model region in 3D rigorous coupled-wave analysis (RCWA) simulations of high-aspect ratio holes compared to an analytical Fourier series expansion. We found that the best approach is to calculate an effective medium approximation for each sampling cell, and that there is an optimal spatial resolution and number of subcells for the different truncation orders.