Abstract

We discuss the performance requirements for reflective imaging systems which will be needed to obtain ~0.1-μn resolution via projection lithography in the extreme-ultraviolet (XUV) wavelength region ≤100 nm. Designs are considered that use centered, non-tilted, annular optical elements. The inter-relationships between the illumination system, degree of spatial coherence, and the reduction system are evaluated, and the tradeoffs in performance for the total system between using an optimized annular illumination system and full illumination are analyzed. It will be shown that for our designs, annular illumination with XUV wavelengths does not significantly improve system performance. This result simplifies the illumination system design.

© 1991 Optical Society of America