30 July 2002 High-NA lithographic imagery at Brewster's angle
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Abstract
Recent advances have enabled exposure tool manufacturers to ship tools with Numerical Aperture (NA) equals 0.8, and to envision optics with even larger NA. Thus the lithography community must grapple with images formed by oblique waves close to Brewster's angle. (For a typical chemically amplified resist with index of refraction n equals 1.7, Brewster's angle is 59 degree(s), corresponding to NA equals 0.86.) This paper will consider some of the surprising phenomena that occur at such high NA. Both vector diffraction simulation results and experimental results from the IBM interferometric lithography apparatus will be discussed. One of the most interesting modeling predictions is that, near Brewster's angle, the swing curve for TM polarization is much smaller than normal, while the swing curve for TE polarization is much larger than normal, and experimental measurements verify this prediction. Special image cross sections using the Flagello decoration method will also demonstrate the loss of TM image contrast due to vector imaging effects.
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Timothy A. Brunner, Nakgeuon Seong, William D. Hinsberg, John A. Hoffnagle, Frances A. Houle, Martha I. Sanchez, "High-NA lithographic imagery at Brewster's angle", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); doi: 10.1117/12.474473; https://doi.org/10.1117/12.474473
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