Method of photolithographic exposure dose control as a function of resist sensitivity
AssigneeInternational Business Machines Corporation
InventorsKeith J. Machia, Matthew C. Nicholls, Charles J. Parrish, Craig E. Schneider, Charles A. Whiting
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Abstract
A predictive method is used to compensate for intermediate batch sensitivities which inevitably occur during resist batch changeover. The compensation is applied to historical dose levels to arrive at a new dose level estimating an optimum dose. When the system discovers that a new batch of resist is loaded to a tool, historical data is used to calculate a reference dose for each tool. A batch factor is continuously calculated and using historical data along with the batch factor, a dose adjustment is made to maintain proper image size.
Claims7
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.
Dependencies are inferred from the claim text.