During mask or reticle inspection, each region is scanned at least twice, using an overlap between each pair of consecutive frames. System contamination and camera blemishes have approximately constant frame coordinates, while mask defects have constant reticle coordinates, but inconstant scan frame coordinates. True defects are detected at different coordinates in consecutive frames with a known displacement therebetween.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Provisional Application No. 60/489,057 titled "Double inspection on reticle/wafer, filed 21 Jul. 2003.
