Patent ID: 7198873

Claim:
A method of optimizing lithographic processing to achieve substrate uniformity, comprising: deriving correlation information indicative of photoresist behavior, comprising: exposing a pattern onto a plurality of subfields of a plurality of substrates such that, for each of said substrates, said subfields are repeatedly exposed with the pattern at different focal positions of a lithographic exposure apparatus, processing each of said substrates at different target processing conditions, measuring attributes of each of said subfields within each of said processed substrates, determining a characteristic for each of said subfields based on said measured attributes, said characteristic representative of photoresist behavior, and extracting correlation information regarding said subfield characteristics and said different target processing conditions; detecting non-uniformities in a subsequent substrate, comprising: exposing said pattern onto a plurality of subfields of said subsequent substrate such that said subfields are repeatedly exposed with the pattern at different focal positions of said lithographic exposure apparatus, processing said subsequent substrate at a production processing condition, measuring attributes of said subfields within said processed subsequent substrate, determining said characteristic for each of said subfields within said processed subsequent substrate based on said measured attributes, and identifying differences among said subfield characteristics of said processed subsequent substrate; and adjusting said production processing condition based on said correlation information.