Abstract
One of the critical issues in extreme ultraviolet lithography (EUVL) is flare, which is an integrated light scattering from surface roughness in the EUVL optical system. Flare degrades the control of critical dimension (CD) uniformity across the exposure field. Also, it generates larger CD sensitivity as line and space (L/S) half pitch size decreases. Therefore, we discussed the calculation of accurate flare maps to compensate for flare variation. The influence of three-dimensional (3D) mask topography on flare was investigated with different absorber thicknesses, off-axis illumination angles, and azimuthal angles. Some types of dummy patterns were found to be effective in controlling the flare variation within a L/S patterned target and the average flare of a L/S patterned target. Our studies has definitely made progress in an effective flare variation compensation using a rule-based correction for sub-22 nm L/S half pitch node and beyond.
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