Understanding the efficacy of linewidth roughness post-processing

摘要

Lack of progress in reducing linewidth roughness of lithographic features has led to investigations of the use of post-lithography process smoothing techniques. But it remains unclear whether such postprocessing will sufficiently reduce the detrimental effects of feature roughness. Thus, there is a need to understand the efficacy of post-processing on not just roughness reduction, but on the negative device impacts of roughness. This work derives model equations of how roughness impacts lithographic performance, and incorporates smoothing using post-processing. These models clearly show that post-process smoothing works best by increasing the correlation length. Increasing the correlation length is very effective at reducing high-frequency roughness that impacts within-feature variations, but is not very effective at reducing low-frequency roughness that impacts feature-to-feature variations. It seems that post-process smoothing is not a substitute for reducing the initial roughness of resist features.