Supercritical CO₂ processing for submicron imaging of fluoropolymers

Abstract

To keep pace with the ever-shrinking feature sizes required in the microelectronics industry, suitable developers with high diffusivities, selectivity, and adjustable solvating power are required. Supercritical fluid (SCF) CO2 possesses many of the above unique properties and could serve as an 'environmentally responsible' alternative developer to aqueous base. In this study, the high solubility of fluorinated block copolymers in supercritical CO2 and the selectivity of supercritical CO2 to both polarity changes and the molecular structure of the polymer were utilized to develop an environmentally friendly lithographic process. Polymers with acid-cleavable tetrahydropyranyl groups and supercritical CO2 soluble, fluoro-side-chain-containing methacrylate groups were synthesized with varying volume fractions of the components, and their solubilities in supercritical CO2 were characterized. Chemical amplification was used to effect the polarity change leading to the solubility difference in supercritical CO2, and the lithographic performance was evaluated. Important parameters such as sensitivity, contrast, and resolution were investigated, and 0.2 μm features using supercritical CO2 development were demonstrated.