27 January 2005 Polarization effects associated with hyper-numerical aperture (NA>1) lithography
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The use of immersion technology will extend the lifetime of 193nm and 157nm lithography by enabling numerical apertures (NA) much greater than 1.0. The ultimate limits of NA are explored by analysis of polarization effects at the reticle and imaging effects at the wafer. The effect of Hertzian or micro-polarization due to the size of the reticle structures is examined through rigorous simulation. For the regime of interest, 20nm to 50nm imaging, it is found that dense features on a Cr binary reticle will polarize the light into the TE component upwards of 15%. Below this regime, the light becomes polarized in the TM direction. The use of polarization in the illuminator for imaging will result in substantial gains in exposure latitude and MEF when the NA~1.3 with 45nm lines at 193nm. The end-of-line pullback for 2-dimensional patterns is reduced by the use of TE polarization in the illuminator. The overall polarization effects increase with decreasing k1. The interaction between the reticle induced polarization and the illumination polarization is shown to be significant when an analysis is done using rigorous mask simulation instead of the more common Kirchhoff approximation.
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Donis G. Flagello, Donis G. Flagello, } "Polarization effects associated with hyper-numerical aperture (NA>1) lithography", Proc. SPIE 5645, Advanced Microlithography Technologies, (27 January 2005); doi: 10.1117/12.582635; https://doi.org/10.1117/12.582635

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