Patent ID: 7583362

Claim:
A method of lithography, the method comprising: providing a workpiece, the workpiece having a layer of resist disposed thereon, the resist having a resist sensitivity factor; providing an exposure tool, the exposure tool comprising a lens system and being adapted to expose the layer of resist at an exposure dose; measuring an amount of stray light of the lens system of the exposure tool; setting a first threshold level for the stray light measured; determining a stray light dose control factor as a function of at least the amount of stray light; adjusting the exposure dose by the stray light dose control factor; discontinuing using a scanner for lithography for a first type of semiconductor product when the first threshold level is reached or exceeded; using the exposure tool to pattern a second type of semiconductor product after the first threshold level is reached or exceeded, the second type of semiconductor product being different from the first type of semiconductor product, wherein the first type of semiconductor product has a smaller minimum feature size than the second type of semiconductor product; and exposing the layer of resist on the workpiece with the adjusted exposure dose.