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15 March 2016 Improvement of unbalanced illumination induced telecentricity within the exposure slit
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Adjustment and control of the illumination pupil asymmetry is relevant for wafer alignment and overlay of lithography tools. Pupil asymmetries can cause a tilt in aerial image (Aerial Image Tilt, or AIT). This AIT, combined with a focus offset, leads to a horizontal image shift. Pupil asymmetries can be related to a shift of the entire illumination pupil (geometrical telecentricity) caused by illuminator misalign. Another type of pupil asymmetry is energetic imbalance (quantified by pupil Center of Gravity, COG). The scanner can show pupil variation across the exposure slit.

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.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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, and Arij Rijke "Improvement of unbalanced illumination induced telecentricity within the exposure slit", Proc. SPIE 9780, Optical Microlithography XXIX, 97800X (15 March 2016);

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