CORRELATION OF NANO EDGE ROUGHNESS IN RESIST PATTERNS WITH BASE POLYMERS

The origin of ultra small edge roughness in delineated resist patterns (nano edge roughness) is investigated from the viewpoint of molecular structures of the base polymers of the resists. In this article, conventional two-component negative-type electron beam resists are studied to clarify the correlation of the nano edge roughness with base polymers. The base polymers are cresol novolak and polyvinylphenol mixed with the same concentrations of photoactive azide compound. The weight-average molecular weight (M(w)) and polydispersity (M(w)/Mn) of the base resins are controlled. Nanometer feature microscopic surface characteristics obtained with an atomic force microscope (AFM) show that the cresol novolak-based resist exhibits a rougher surface than the polyvinylphenol-based one. Nano edge roughness can be suppressed by using base resins with lower M(w) and M(w)/M(n), suggesting that nano edge roughness reflects the molecular characteristics of the base polymers. There is nanometer level swelling in resist patterns (nano swelling) in polyvinylphenol-based resist. These results suggest that the structures of the base polymers and the interaction with developers affect the nano edge roughness.