Dielectric Modulation of Ionization Energetics in Organotin Extreme Ultraviolet Photoresists

Tin-oxo clusters are promising candidates for extreme ultraviolet (EUV) photoresists owing to their high absorption cross sections and defined molecular structures. However, the influence of solvent environments on their photoionization behavior remains unclear. Here, density functional theory calculations combined with the solvation model based on density (SMD) were performed to systematically investigate solvent-dependent ionization energies of representative organotin clusters across 179 solvents. All solvents were found to reduce the vertical ionization potential (VIP) relative to vacuum, and 24 solvents were identified as particularly favorable. Correlation analysis shows that the dielectric constant exhibits a strong inverse relationship with VIP, whereas the molecular polarity index displays only moderate relevance. A hydrogen-like dielectric cavity model was further developed, yielding an analytical expression of the form VIP = a/ϵ_r + b, which quantitatively describes dielectric stabilization effects. These results provide a physically grounded solvent-selection criterion for enhancing EUV photoresist sensitivity.