Theoretical study on relationship between exposure pattern width and chemical gradient of 16 nm half-pitch line-and-space patterns in electron beam lithography used for photomask and nanoimprint mold production

Abstract

Line edge roughness (LER) is a significant concern for electron beam (EB) lithography used for the production of photomasks and nanoimprint molds owing to the trade-off relationships between resolution, LER, and sensitivity. In this study, the relationship between exposure pattern width and chemical gradient (an indicator of LER) was investigated, assuming the use of a chemically amplified resist consisting of a partially protected polymer, an acid generator, and a photodecomposable quencher. The formation of line-and-space patterns with 16 nm half-pitch was calculated on the basis of the sensitization and reaction mechanisms of chemically amplified EB resists. The effects of exposure pattern width on the chemical gradient were clarified in terms of sensitivity, the concentration of sensitizers, and the diffusion constant of photodecomposable quenchers. The exposure pattern width should be set by taking into account these factors to maximize the chemical gradient for the suppression of LER.