Selective etch of poly(methyl methacrylate) in block copolymer based on control of ion energy and design of gas chemistry for directed self assembly lithography

The selective etching of poly(methyl methacrylate) (PMMA) in a block copolymer was studied with a focus on the material structures of polystyrene (PS) and PMMA. Based on our predictions, we investigated the effect of ion bombardment and designed a carbon-containing gas plasma to improve selectivity. The etching characteristics of the carbon-containing gas plasma on the polymers were examined. Highly selective etching of PMMA to PS was achieved using the carbon-containing gas plasma. The carbon species in the plasma increased with increasing carbon-containing gas ratio and suppressed the PS etch rate drastically. The CO plasma process was successfully applied to a dry development process for directed-self assembly lithography.