Performances of resists for 157-nm lithography based on monocyclic fluoropolymers

Fluoropolymers are key materials for the single-layer resists used in 157-nm lithography. We have been studying fluoropolymers to determine their potential for use as the base resin and have developed a monocyclic fluorinated polymer with a blocking group of Cyclohexylcyclohexyloxymethyl (CCOM) that has high transmittance (an absorption coefficient of 0.64 μm-1) at a 157-nm exposure wavelength and high dry-etching resistance (a dry-etching rate of 1.75 times that of KrF resist) under organic bottom anti-reflective coating/hard mark dry-etching conditions. A resist based on our monocyclic fluoropolymer had high sensitivity. Using it, we were able to resolve a 60-nm line-and-space pattern using a 157-nm laser microstepper (numerical aperture = 0.85) with a resolution enhanced technology of an alternating phase-shifting mask. This polymer was demonstrated to simultaneously enable high transparency, high dry-etching resistance, and good imaging performance.