There is provided an illumination system for light having wavelengths ≦193 nm. The system includes (a) a first raster element for receiving a first diverging portion of the light and directing a first beam of the light, (b) a second raster element for receiving a second diverging portion of the light...http://www.google.fr/patents/US6859515?utm_source=gb-gplus-shareBrevet US6859515 - Illumination system, particularly for EUV lithography
Illumination system, particularly for EUV lithography
