Illumination optical unit

摘要

An illumination optical unit for an EUV projection exposure apparatus has a diaphragm comprising a radiation-transmissive region having a discrete symmetry group. The form of the diaphragm is adapted to the form of the facets of a pupil facet mirror or to the form of the radiation source. The diaphragm is preferably arranged in the region of an intermediate focal plane.

主权项

1. An illumination optical unit, comprising:
a pupil facet mirror comprising a multiplicity of facets having a form; and a diaphragm comprising first and second regions, wherein:
the illumination optical unit is configured to illuminate an object field imageable via an imaging optical unit with radiation from an EUV radiation source;the first region is transmissive to the EUV radiation;the second region is opaque to the EUV radiation;the first and second regions define a diaphragm plane;at least one region selected from the group consisting of the first region and the second region has a discrete symmetry group in the diaphragm plane;the diaphragm is in a region of an intermediate focal plane of the illumination optical unit; andthe at least one region has a rectangular form with an aspect ratio corresponding exactly to an aspect ratio of the facets of the pupil facet mirror.