LIS design for optimum efficiency

摘要

This paper presents an approach to Laser Illumination System (LIS) efficiency optimization for High Numerical Aperture (NA) Microlithography exposure tools. These advanced tool are immersion systems with NA>1 utilizing many Reticle Enhancement Techniques (RET). In order to provide maximum efficiency, especially for high NA systems, the following conditions have been taken into consideration: endue law for LIS subsystems consisting of sequential optics; proper relations between transverse and longitudinal dimensions of optical path; laser light coherence management by overlap of individual exposure fields generated from different parts of the laser beam; polarization management; flexible illumination partial coherence (PC) management; illumination relay and condenser systems have to be optically matched in order to minimize: pupil ellipticity, field vigneting, and non-telecentricity. Individual importance of listed conditions and their parameters will be explained and discussed as applied to illumination systems with high NA.