Surfactant-aided supercritical carbon dioxide drying for photoresists to prevent pattern collapse

Several CO₂-soluble surfactants with different molecular architectures were investigated as possible agents to remove rinse water from aqueous-based photoresists utilizing supercritical carbon dioxide (scCO₂) drying process. Hydrocarbon and fluorocarbon surfactants having a short chain length and polymeric surfactants based on block or random copolymers were selected for this study. A hybrid type KrF photoresist having 130-140 nm (line-space), with an aspect ratio of 3.8 was used as a model. Though some of the surfactants were not compatible with the resists, others were found to be highly efficient in removing the rinse water from the resist. Scanning electron microscopic (SEM) images confirmed that the positive resist patterns were preserved without any deformation or damage by rinsing with de-ionized water followed by surfactants-aided scCO₂ drying.