Patent ID: 7486814

Claim:
A method of inspecting target patterns formed on a surface of a reticle, which method comprises: imaging the target patterns to produce a plurality of target data elements representative of the target patterns, each target data element associated with a respective location on the surface; receiving a plurality of reference data elements corresponding to substantially the same respective location on the surface as the target data elements; comparing the target data elements with the reference data elements to obtain differences between the target data elements and the corresponding reference data elements; calculating the sum of the largest negative magnitude of all the difference values and largest positive magnitude of all the difference values to produce a peak-to-peak difference value; comparing the peak-to-peak difference value with a threshold peak-to-peak difference value; and generating a graphical display map of substantially all the differences as a function of the locations on the surface associated with the target and the reference data elements from which each respective difference was obtained.