In general the COG at the edge of the slit is often worse than in the center part of the slit. Recently, ASML has released the NXT:1980Di that is equipped with an enhanced illuminator to improve pupil COG variation across the slit. In this paper we explore the performance of this scanner system and show that the AIT variation across the slit is also reduced significantly.
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Jonghoon Jang, ByeongSoo Lee, Young Seog Kang, Chansam Chang, Jeong-Heung Kong, Young Ha Kim, Wim Bouman, Roelof de Graaf, Stefan Weichselbaum, Richard Droste, Wim P. de Boeij, Bart van Bussel, Patrick Neefs, Arij Rijke, "Improvement of unbalanced illumination induced telecentricity within the exposure slit," Proc. SPIE 9780, Optical Microlithography XXIX, 97800X (15 March 2016);