Overlay target with orthogonal lower layer dummy fill

摘要

The present disclosure is directed to designing and using overlay targets having orthogonal lower layer dummy fills. The overlay target includes one or more segmented overlay pattern elements that form at least one overlay target structure. The overlay target further includes one or more inert pattern elements that form at least one dummy fill target structure. Each of the one or more inert pattern elements includes a dummy fill segmented along an axis orthogonal to the segmentation axis of at least one proximally disposed overlay pattern element. Each of the target structures or layers can be formed from separate process layers disposed sequentially on a substrate, such as a silicon wafer. The overlay and dummy fill target structure can be two or four-fold symmetric.