US Patent 9494874 Method and apparatus for design of a metrology target

A system to, and a method to, select a metrology target for use on a substrate including performing a lithographic simulation for a plurality of points on a process window region for each proposed target, identifying a catastrophic error for any of the plurality of points for each proposed target, eliminating each target having a catastrophic error at any of the plurality of points, performing a metrology simulation to determine a parameter over the process window for each target not having a catastrophic error at any of the plurality of points, and using the one or more resulting determined simulated parameters to evaluate target quality.