In this study, mask simulations were performed at the extreme ultraviolet wavelength of 13.5nm to determine criteria for the uniformity of the reflectivity of mask blanks and the printability of clear- and opaque-type absorber defects in order to obtain satisfactory lithographic performance. The simulations were performed on typical 70-nm line-and-space patterns for different flares and numerical apertures (NA) of the illumination. The simulation results for a numerical aperture of 0.1 and 18% flare showed that local variations in the reflectivity of multilayer mask blanks must be kept below 1% for practical lithography. It was also found that clear flank defects are even less printable than opaque ones. The results indicate that there is a large enough process margin for the repair of opaque flank defects, though the possibility still exists that the reflectivity of multilayer may drop during repair.

Date Published: 5 September 2001
PDF: 7 pages
Proc. SPIE 4409, Photomask and Next-Generation Lithography Mask Technology VIII, (5 September 2001); doi: 10.1117/12.438371

Published in SPIE Proceedings Vol. 4409:
Photomask and Next-Generation Lithography Mask Technology VIII
Hiroichi Kawahira, Editor(s)