Insight into the mechanism of different substituents on the zinc-oxo cluster in solubility switching

A photoresist based on Zn(MA)_n(TFA)_6-n (n ≤ 6; MA and TFA are methacrylate and trifluoroacetate, respectively) shows excellent performance in extreme ultraviolet lithography (EUVL). The material is a mixture based on the ratio of MA and TFA, which could affect the production and reproducibility of the photoresist. In this paper, the structural characteristics and solubility switch mechanism of diverse compositions based on Zn(MA)_n(TFA)_6-n were systematically investigated using DFT calculations and molecular dynamics (MD) simulations. Our results reveal the relationship between the structure and properties from an atomistic insight into these compounds with different ligand ratios. Diverse organic ligands can generate different free radicals via decarboxylation after ionization. These radicals could determine the energy landscape of the subsequent solubility switch (chain propagation) in EUVL. In addition, the desired compositions in Zn(MA)_n(TFA)_6-n were obtained using different temperatures and solvents, which would offer helpful guidance for synthesis and separation experiments.