Synthesis of methacrylate polymers substituted with cholic acid derivatives with polar spacer and their lithographic application

Abstract

New methacrylate based polymers substituted with cholic acid derivatives with polar spacer, poly (TBMSDHC), poly (TBMSHC), and poly (TBMSC), were synthesized. They were synthesized by free radical polymerization initiated by AIBN. The polymers have etch-resistance moiety (cholic acid derivatives), adhesion promotion moiety (polar ester groups in spacer), and solubility change moiety (tert-butoxy group in cholates) in one monomer unit. They are thermally stable up to 250℃ and showed good transmittance at 193 nm and 248 nm DUV. Their dry-etch resistance was much higher than that of conventional 248 nm resist (poly (hydroxystyrene)). Adhesion properties increased according to the number of hydroxyl group and polar ester spacer groups contributed to adhesion enhancement. Poly (TBMSDHC) gave 0.35㎛ pattern profiles and showed good sensitivity and contrast but poly (TBMSHC) and poly (TBMSC) did not give fine patterns because of their poor development properties.