Stray light (flare) in optical microlithography causes critical dimension (CD) variation. We present a method to correct the CD variation by equalization of the stray-light distribution. This is achieved by doing a second "correction" exposure with the mask that has the reverse tone compared to the mask of the first exposure. A small exposure dose and large defocus are required for the correction exposure to mimic stray light. This correction method has been confirmed by experiments for 100 nm features with standard ArF (193 nm) lithographic processes. (c) 2006 American Vacuum Society.