Patent ID: 7376260

Claim:
A method for performing post-optical proximity correction (OPC) multi layer overlay quality inspection, comprising: generating a virtual target mask for a first mask and a second mask overlay using design rules at least partially defining the relationship between the first mask and the second mask; creating a composite aerial image representing a first mask image formed from the first mask and a second mask image formed by the second mask by performing imaging of the first mask and the second mask and overlaying the second mask image onto the first mask image; generating an overlay image map of the composite aerial image using the design rules at least partially defining the relationship between the first mask and the second mask; and comparing the overlay image map area and the virtual target mask area, wherein the step of comparing the overlay image map area and the virtual target mask area comprises: calculating the area of the overlay image map; calculating the area of the virtual target mask; and determining if the area calculated for the overlay image map matches the area calculated for the virtual target mask within the predetermined tolerance.