Patternable block copolymers with high transparency at 157 nm:: Fluorocarbinol functionalized poly(isoprene-b-cyclohexane)

A three-step polymer modification reaction was developed to prepare polydiene-based patternable block copolymers with high transparency at 157 nm wavelength. In the first step, the ene reaction of poly(isoprene-b-cyclohexadiene) with hexafluoroacetone was carried out to incorporate a pendent hexafluoro-2-hydroxy-2-propyl functional group in the polyisoprene block. Subsequently, the hexafluorocarbinol functionalized block copolymer was hydrogenated to enhance transparency at 157 nm and finally the fluorocarbinol was protected with an ethoxymethyl group to induce a solubility switch after exposure. The final block copolymer exhibited an absorption coefficient of 3.30 mum(-1) stop at 157 nm. Exposure was carried out on a 248 nm stepper and feature sizes down to 0.5 mum were resolved prior to optimization of exposure and formulation conditions.