Cold development of positive-tone resist ZEP520A (Nippon Zean) in electron-beam lithography needs quantitative analysis for further improvement in resolution. Contrast curves and groove widths in cold development of ZEP520A were analyzed using models, and resolution enhancement was confirmed experimentally. Although the contrast improved at the expense of sensitivity in cold development, the improvement of contrast became smaller when the development temperature became colder. The dependence of contrast curve on developing temperature can be explained assuming resist dissolution rates that have an activation energy. For resolution evaluation, circumferentially aligned line-and-space patterns were exposed using an electron-beam recorder with a rotary stage. The resolved groove widths were explained by using the resist dissolution model and an incident electron distribution that consists of three Gaussians. Using these models, groove widths after development can be easily calculated at arbitrary development and exposure conditions. The resolution improved in lower temperature, and dense line-and-space patterns of 35 nm pitch were resolved in 10°C.

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