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26 June 2003 MEF revisited: low k1 effects versus mask topography effects
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At 4X magnification and k1 approaching 0.25, primary mask features, that will ultimately print on the wafer, can be on the order of the wavelength for conventional exposure tool. For immersion lithography, the primary mask feature sizes could even fall below the wavelength. At the same time, the aspect ratio of the features defined on the mask increases since the absorber thickness did not scale with the technology nodes. For alternating phase-shifting masks, the etch depth into the quartz required to create a 180 degree phase-shift has not scaled with technology nodes since it is proportional to the wavelength of exposure and the wavelength of exposure has not scaled with technology nodes. Near wavelength and high aspect ratio mask features increase the importance of mask topography effects. Simulations can be used as a mean to de-correlate the contributions of low k1 effects versus mask topography effects. The “thin-mask” approximation results can be compared to the “thick-mask” simulation results. The effect of the feature aspect ratio can be investigated by changing the magnification factor. The results indicated in this paper show that mask topography effects can represent a significant part of the MEEF even for binary masks.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Christophe Pierrat and Alfred K. K. Wong "MEF revisited: low k1 effects versus mask topography effects", Proc. SPIE 5040, Optical Microlithography XVI, (26 June 2003);

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