Abstract: A method includes (a) creating a plurality of patterns on a plurality of dies, the plurality of dies being formed upon a semiconductor wafer, the plurality of patterns being formed so that each of the dies has a different focus and exposure energy value, (b) selecting at least one known acceptable die from the wafer, wherein acceptability is determined at least in part by a critical dimension value and a defect status, (c) using optical inspection, comparing the at least one known acceptable die to a first subset of the plurality of dies, and (d) classifying each die in the first subset as within established limits or outside of the established limits in response to (c).