Improving lens performance through the most recent lens manufacturing process

A continuous demand for finer and finer exposed patterns is pushing the k1 factor down to 0.4 or below, which is very close to its theoretical limit. The low-k1 lithography requires high NA and small residual aberration of a deep ultra-violet (DUV) projection lens system. The amount of aberration of current projection lens is less than design residual value of the lens in a decade ago. A lot of designers’ efforts are put into optical design and opt-mechanical design of the projection lens to meet lithography requirements. However, technological innovations in manufacturing process are also needed for the realization of a state of the art projection lens. In some cases, manufacturing process is rather essential for the final lens performance improvement. This paper shows the most recent lens manufacturing process in Nikon. In addition to the manufacturing process itself, some supporting technologies in the manufacturing process are also reviewed.