Multiscale simulations for exploring photo-chemical processes to mitigate the critical dimension variability of contact holes in EUV lithography

In extreme ultraviolet lithography (EUVL), the non-uniformity of patterned surface roughness of contact holes results in pattern failures such as bridging or missing holes, which affects production yield. In this study, we propose a multiscale model for reproducing 10-35 nm contact hole patterns based on the photo-chemical reactions in a photoresist (PR). To determine the heterogeneous spatial distribution of the resist components at the mesoscopic level, we employed a coarse-graining (CG) strategy for the PR. Additionally, we constructed a statistical model to obtain the novel acid/base distributions using existing MD data. The chemical reaction kinetics were reproduced via the finite difference method (FDM). We predicted resulting hole-patterned surfaces according to the target hole size. The variability in interfacial surface roughness among the holes, which is quantified by local critical dimension uniformity (LCDU), increased with decreasing target hole size, which is consistent with experimental reports. By investigating the photochemistry in the PR at the molecular level, we confirmed that the decrease in the chemical gradient due to the increase in relative acid diffusivity to hole size caused the LCDU and hole-failure probability trends. The diffusivity control enhanced this interpretation further, resulting in mitigation of CD variability in the 10 nm contact holes.