Effects of Fresnel Diffraction on Resolution and Linewidth Control in Synchrotron Radiation Lithography

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Abstract
To investigate the influence of Fresnel diffraction on resolution and linewidth control in synchrotron radiation (SR) lithography, a detailed analysis is performed that takes X-ray phase shift in the absorber into account. The phase shift for 0.65-µm-thick Ta absorber is estimated to be -180°. It becomes clear that the phase shift plays a important role in limiting pattern resolution and linewidth control, especially for replicating fine (<0.3 µm) patterns. The conditions for replicating 0.2-µm lines-and-spaces resist patterns under practical conditions-i.e., with a mask contrast of 7 and a proximity gap of around 30 µm-are described. Designing a Ta absorber that is slightly narrower (<0.05 µm) than 0.2 µm is a great advantage for replicating 0.2-µm patterns because the dose-margin for replicating the patterns faithfully is improved.

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