Theoretical Study of Ionization of Polymers for EUV Resist

We have investigated the ionization of polymers for extreme ultraviolet (EUV) exposure. Quantum chemical calculation was performed. Upon EUV exposure to the polymer in a resist, the ionization of the polymer occurs and the secondary electrons generate. As the secondary electrons from the polymer cause the reaction of photoacid generator and the photoacid generates, the ionization of the polymer is a key for the sensitivity of resist for EUV. In this paper, the study of polymers was performed. The styrene polymer and acrylate polymer with various substituents and pendant groups were compared. We found that the electron providing substituents assist the ionization of the polymer. Protecting groups of poly(4-hydroxystyrene) decrease the ionization. It was found that the stable condition of radical cation of poly(methacrylic acid) helps the ionization of the polymer.