Impact of developers on roughness of dissolution front in electron-beam resists

Abstract

We describe the impact of various developers on the roughness of dissolution front of electron-beam positive-tone resist ZEP7000. In this study, two types of developers are investigated: single-solvent developer and binary-solvent developer. Atomic force microscope observations of dissolution fronts reveal that, for a homologous series of n-alkyl acetate as a single-solvent developer, there are three categories of dissolution process: molecular-level dissolution, aggregate extraction development, and their intermediate. Small solvent molecules, such as methyl- and ethyl acetate, are very effective for reducing roughness. For good solvents for ZEP resist as single-solvent developer, molecular-level dissolution also occurs and the dissolution front becomes very flat and smooth. However. these developers, though effective for reducing roughness, lead to lower dissolution contrast. We clarified that binary-solvent developers consisting of these effective developers and n-hexane as a poor solvent, especially 1:1 ethyl acetate/n-hexane developer, provide both low roughness and high dissolution contrast.