Patent attributes
An illumination optical unit for EUV projection lithography serves to illuminate an object field with illumination light. A transmission optical unit images field facets in a manner superposed on one another into the object field via illumination channels, which each have assigned to them one of the field facets and one pupil facet of a pupil facet mirror. The superposition optical unit has at least two mirrors for grazing incidence, downstream of the pupil facet mirror. The mirrors for grazing incidence produce an illumination angle bandwidth of an illumination light overall beam, composed of the illumination channels, in the object field. The bandwith is smaller for a plane of incidence parallel to the object displacement direction than for a plane perpendicular thereto. The result can be an illumination optical unit, by which a projection optical unit can be adapted to a configuration of an EUV light source for the illumination light.
