Nano edge roughness in polymer resist patterns

Ultrasmall edge roughness in delineated patterns (nano edge roughness) is investigated in nanostructures made of negative-type electron beam polymer resists by atomic force microscope measurements. Very narrow isolated lines 10–20 nm wide are fabricated with a finely focused electron beam provided by a scanning electron microscope. A chemical amplification novolak resin-based resist shows nano edge roughness which cannot be neglected in nanofabrication. To investigate the origin of the roughness, conventional two-component resist systems are microscopically compared. An azide polyvinylphenol-based resist and an azide novolak resin-based resist are used. The novolak resin-based resist exhibits a rougher surface than the polyvinylphenol-based one. This result suggests that the polymer structures of the base resins cause nano edge roughness of a chemical amplification resist in connection with the acid diffusion during the post-exposure bake process.