EUV resist processing in vacuum

Abstract

In extreme ultraviolet (EUV) lithography, exposures are and can only be performed in vacuum (<1x10^-5 Pa). At present though, conventional resist processing technologies before and after exposure (coating, post application bake, post exposure bake, etc.) are performed in atmospheric pressures. Investigations on the possibility of a EUV-specialized resist processing system; specifically, the development of a 300mm wafer compatible, vacuum-based resist baking and cooling system is presented. Comparative evaluations with conventional atmospheric-based systems were made from the viewpoint of resist lithographic performance (sensitivity, resolution, line width roughness) and resist outgassing rate. As a result, an improvement in LWR was also observed in vacuum post application bake and post exposure bake. However, a difference in resist lithographic performance depending on the type of resist material used was observed between resist processes performed in-atmosphere and in-vacuum. Lastly, the vacuum based bake process was found to have no significant effect on resist outgassing rate released.