Investigating crosslinking mechanisms in metal oxide photoresists for EUV lithography: a first principles study

Metal oxide photoresists have become attractive candidates for both EUV and high NA lithography due to their high EUV photon absorption, high sensitivity, and resolution. However, to improve selectivity and line edge roughness, it is essential to have a fundamental understanding of the processes involved. In our study, we used first-principles calculations to investigate the interactions between tin oxo cages [(MeSn)₁₂O₁₄(OH)₆](OH)₂ at the atomic level. The interactions between exposed/exposed and exposed/unexposed regions were systematically studied. Our results demonstrated that even with some hydrocarbons remaining, the cages can still bind together. We also highlighted the importance of the local environment in crosslink formation. When there is a sufficient local missing of hydrocarbons, the exposed cage can attach to the unexposed cage, leading to a nonuniform boundary between the two areas. These results provided a clearer picture of how crosslinking occurs in the exposed area and, most importantly, at the boundary between exposed and unexposed regions, which helps us understand the mechanisms behind line edge roughness.