Improved fab CDU with FlexRay and LithoTuner

Abstract

FlexRay programmable illumination and LithoTuner software is combined in several use cases. The first use case is optical proximity error (OPE) minimization. Simulation predicts the rms OPE error is reduced by 39% with LithoTuner and FlexRay, and is confirmed via experiment with a reduction of 33%. For minimizing the OPE error, two types of illumination tuning was performed, sigma tuning and freeform tuning. The sigma tuning is able to reduce the mean-totarget critical dimension (CD) error, but the CD error variance is unaffected. Freeform tuning, however, is able to reduce both the mean-to-target CD and the CD error variance. The second use case is matching two ArF scanners, a XT:1950Hi with FlexRay to a XT:1700Fi with diffractive optical element (DOE) illumination. With LithoTuner and FlexRay, simulation predicts the CD error post-matching is reduced by 51%, and experiment was able to achieve a reduction of 29%.