A defect-to-yield correlation study for marginally printing reticle defects in the manufacture of a 16Mb flash memory device

This paper presents a defect-to-yield correlation for marginally printing defects in a gate and a contact 4X DUV reticle by describing their respective impact on the lithography manufacturing process window of a 16Mb flash memory device. The study includes site-dependent sort yield signature analysis within the exposure field, followed by electrical bitmap and wafer strip back for the lower yielding defective sites. These defects are verified using both reticle inspection techniques and review of printed resist test wafers. Focus/exposure process windows for defect-free feature and defective feature are measured using both in-line SEM CD data and defect printability simulation software. These process window models are then compared against wafer sort yield data for correlation. A method for characterizing the lithography manufacturing process window is proposed which is robust to both marginally printing reticle defects and sources of process variability outside the lithography module.