Non-Chemically Amplified EUV Resist Based on PHS

Abstract

Non-chemically amplified negative resist for EUV lithography was designed and the resist property was studied. Photo-induced thiol/ene radical reaction was used to insolubilize the resist based on poly(4-hydroxystyrene) (PHS) derivatives. OH groups of PHS were modified with allyl, norbornen, or methacrylate functions. Dissolution property of the modified-PHS in TMAHaq solution was studied. The degree of the modification of PHS strongly affected the solubility of the modified-PHS in TMAHaq. Resist was formulated as a mixture of modified-PHS, multifunctional thiol compound, and photo-radical generator. Photo-sensitivity of the resist was studied at 254 nm and 13.5 nm. The sensitivity was affected by the concentration of thiol compound added. It was found that the present resist system was highly sensitive (5~6 mJ/cm²) to EUV exposure.