EFFECTS OF FRESNEL DIFFRACTION ON RESOLUTION AND LINEWIDTH CONTROL IN SYNCHROTRON RADIATION LITHOGRAPHY

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-mu-m-thick Ta absorber is estimated to be - 180-degrees. It becomes clear that the phase shift plays a important role in limiting pattern resolution and linewidth control, especially for replicating fine (< 0.3-mu-m) patterns. The conditions for replicating 0.2-mu-m lines-and-spaces resist patterns under practical conditions-i.e., with a mask contrast of 7 and a proximity gap of around 30-mu-m-are described. Designing a Ta absorber that is slightly narrower (< 0.05-mu-m) than 0.2-mu-m is a great advantage for replicating 0.2-mu-m patterns because the dose-margin for replicating the patterns faithfully is improved.