CD Metrology for Avoiding Shrinkage of ArF Resist Patterns in 100nm ArF Lithography

摘要

ArF (193 nm) lithography process has still challengers, which are low etching resistance, pattern collapse, line edge roughness (LER), pattern shrinkage and so on. Recently, most of them look to be nearly matured except pattern shrinkage. Pattern shrinkage is caused by some reasons, but we want to focus on the CD measurement in this paper. Pattern shrinkage deteriorates CD measurement confidence. We investigated the pattern shrinkage effect as a function of CD SEM measurement conditions and ArF resist pattern size. Also we observed the etched pattern profile to evaluate whether the shrunk resist pattern affects the sub-layer etch profile. As the results, pattern shrinkage was not improved by optimizing CD measurement conditions and other process treatments. More advanced CD SEM or more robust ArF resist against electron beam should be developed to mitigate pattern shrinkage. But it is hard to overcome that kind of problem in a short time. Therefore, we suggest off-site focusing CD measurement technique, which improves the CD measurement confidence. This paper will describe how to do and it's results for 100nm ArF resist patterns.