Analysis of laser-induced damage effects on lithographic illumination pupil-fill characteristics

Excimer lasers are widely employed in advanced lithography systems. However, the high single-photon energy and the intense peak power of their output can cause damage to optical components in the lithography system during prolonged exposure. To systematically investigate the effects of laser-induced damage on illumination pupil-fill characteristics in deep ultraviolet (DUV) lithography systems, an evaluation model based on the angular spectrum theory and the partially coherent light theory was developed to analyze these effects. Furthermore, simulations were conducted to examine the effects of excimer laser coherence variations and stray light induced by optical component damage on key pupil-fill parameters, including fringe contrast, coherence factor, ellipticity, and pole balance. Finally, an experimental system for measuring pupil-fill characteristic parameters was developed, and the results demonstrate the applicability of the proposed evaluation model for analyzing pupil-fill variations caused by laser-induced damage.