Patent ID: 6674516
Filing Date: 2004-01-06
Classification: G03B,G03F

Abstract:
A method for controlling exposure dose in a lithographic system comprising a photoresist apply tool supplying photoresist material to said system and a reticle for developing images on semiconductor wafers, wherein said photoresist apply tool is subject to photoresist material batch changeover, said method for controlling exposure doses after said resist batch changeover comprising:a) calculating a reference dose Doseref for said reticle as a function of previous optimum exposure doses and batch factors obtained from process runs from a time before said resist batch changeover; b) calculating a most recent batch factor, BFm-1, for a reticle for each lot run implementing resist subsequent to said resist batch changeover said BFm-1 being a function of an optimum dose for a most recent lot of product already run and said Doseref; and, c) adjusting said exposure dose based on said calculated most recent batch factor, said exposure dose being adjusted according to resist sensitivity changes so that proper image size is maintained for each new lot run subsequent to said resist batch changeover.