Lithographic apparatus and device manufacturing method

摘要

In an illumination system using mirrors, the facets of a field facet mirror focus plural source images on respective facets of a pupil facet mirror to perform the function of an integrator. A facet mask is constructed and arranged to selectively block facets of the filed or pupil facet mirrors. The facet mask has a grid selectively interposable in the projection beam to provide intermediate illumination settings. The grid has a spacing smaller than the source images but larger than the wavelength of the projection beam so that there is no diffraction.