Enhancement of process latitude by reducing resist thickness for KrF excimer laser lithography

摘要

Abstract: Reducing resist thickness easily and simultaneously decreases the k1 factor and increases the k2 factor in conventional Rayleigh equations, without changing the wavelength of the illumination light and NA of the optics. In this work, we investigated the effect of reduced resist thickness on process latitude and optical proximity effect (OPE) at the sub-quarter micron level. The experiment exposures were performed by a 0.6 NA KrF excimer step and scan system with an in-house chemically amplified positive resist in the thickness range of 0.6 $mu@m to 0.25 $mu@m. The results showed remarkable improvements in process latitude of both 0.175 $mu@m L&S and 0.225 $mu@m contact hole, as well as OPE such as a CD variation between different pitches and a feature deformation at isolation by reducing resist thickness.!10