Lithographic apparatus and method

摘要

A device manufacturing method includes conditioning a beam of radiation using an illumination system. The conditioning includes controlling an array of individually controllable mirror elements (33a-33e) of the illumination system to convert the radiation beam into a desired illumination mode, the controlling including allocating different individually controllable mirror elements (33a-33e) to different parts of the illumination mode in accordance with an allocation scheme, the allocation scheme selected to provide the desired illumination mode, radiation beam or both, taking into account a variation in reflectivity of the individually controllable mirror elements. The method also includes patterning the radiation beam with a pattern in its cross-section to form a patterned beam of radiation, and projecting the patterned radiation beam onto a target portion of a substrate.