Resist materials providing small line-edge roughness

Our research focuses on the line-edge roughness of resist patterns and how to reduce it in order to establish nanolithography as a practical tool. Commercially available e-beam resists exhibit a line-edge roughness of 3 nm (sigma) or more. It is caused mainly by polymer aggregates in the resist. During development, they are extracted through dissolution of the surrounding polymer matrix. That is, the aggregates themselves dissolve more slowly than the surrounding matrix; and those that remain embedded in the resist produce line-edge roughness. To reduce the roughness, the effect of the aggregates must be suppressed. One way of doing this is to use a resist containing small aggregates. A good candidate is hydrogen silsesquioxane, which has a three-dimensional framework. Another way is to use a resist in which the aggregates are linked together, which makes them difficult to extract during development. A good example is an acrylate-type resist with a cross-linker mixed in.