4 April 2016 Aerial imaging study of the mask-induced line-width roughness of EUV lithography masks
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Abstract
EUV lithography uses reflective photomasks to print features on a wafer through the formation of an aerial image. The aerial image is influenced by the mask’s substrate and pattern roughness and by photon shot noise, which collectively affect the line-width on wafer prints, with an impact on local critical dimension uniformity (LCDU). We have used SHARP, an actinic mask-imaging microscope, to study line-width roughness (LWR) in aerial images at sub-nanometer resolution. We studied the impact of photon density and the illumination partial coherence on recorded images, and found that at low coherence settings, the line-width roughness is dominated by photon noise, while at high coherence setting, the effect of speckle becomes more prominent, dominating photon noise for exposure levels of 4 photons/nm2 at threshold on the mask size.
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Antoine Wojdyla, Alexander Donoghue, Markus P. Benk, Patrick P. Naulleau, Kenneth A. Goldberg, "Aerial imaging study of the mask-induced line-width roughness of EUV lithography masks", Proc. SPIE 9776, Extreme Ultraviolet (EUV) Lithography VII, 97760H (4 April 2016); doi: 10.1117/12.2219513; https://doi.org/10.1117/12.2219513
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