Accurate measurement of om-product lens fingerprint

摘要

This document relates to a method of determining a lens fingerprint of pattern shifts associated with product features provided by a lithographic apparatus (scanner) to substrates.As overlay specifications become ever lighter, it is now becoming necessary to measure the lens fingerprint on product features positions within a single layer, in addition to the overlay fingerprint (difference in lens fingerprint from each layer). This fingerprint can be used for direct overlay control or to optimize the measurement layout necessary to properly capture and model correction parameters.