Design and optimization of collectors for extreme ultraviolet lithography

The design and optimization of nested grazing incidence collectors for extreme ultra-violet lithography is discussed taking into account the boundary conditions set by optical, mechanical, thermal, and manufacturing requirements. The trend of the collection efficiency as a function of numerical the aperture at the intermediate focus, the source-optics distance and the focal length is presented. The effect of the thickness of the mirrors on the optical performance and stability under thermal load is also discussed as a specific example involving optical, thermal and manufacturing issues. As an introduction to the discussion of the design and optimization of the collector, a theoretical maximum limit for the collection efficiency is studied as a function of collected solid angle and system etendue.