Local critical dimension uniformity (LCDU) for contact holes may be correlated with stochastic defects (missing or merged holes), but metrology noise will bias the LCDU measured by a CD-SEM. In this work, large contact hole data sets will be collected with varying SEM measurement recipes, such as different numbers of frames of averaging. Additionally, multiple measurements of the same after-etch features will be used to quantify the impact of metrology noise on the biasing of measured LCDU. Finally, a recommendation will be made as to an approach that minimizes, or eliminates, bias in LCDU measurements.
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