New projection lens system for KrF exposure scanning tool

In this paper we review our newly developed high NA projection lens for KrF scanner (NSR-S205C.) The projection lens has 0.75 NA and small residual aberration. In a designing step, aspherical surfaces are utilized to decrease lens dimensions without degradation of the lens performance. Actual lens performance, which includes wavefront aberration, distortion, image plane flatness and resist profiles, is reviewed.