Interpretation of the roughness at interfaces of photoresists from a perspective molecular aspect*

Developing new materials or process conditions for photoresists, to reduce the roughness in the pattern while maintaining the high resolution and sensitivity upon light exposure, has been considered as a key for the success of high resolution (sub-10 nm) patterning technology. While inherent uncertainties due to the photon shot noise and photochemistry are considered as one of main sources of the roughness, additional factors due to the configurations of polymer chains and its distribution at the interface should be taken into account as the required roughness scales down to the molecule size. Hence beyond the former stochastic modeling, we attempted to introduce molecular simulation/modeling approach to find the inherent limits on the sharpness at the interface focusing on width and fluctuations of the interface between the exposed and unexposed area, and chain configurations during/after development. Coarse-grained polymer chain models allow us to understand the relation between the system conditions and relevant chain configurations near the interfaces.