Thermal and structural deformation and its impact on optical performance of projection optics for extreme ultraviolet lithography

Detailed simulation of thermal and structural deformation and its impact on the optical performance of Nikon's 6-mirror projection optics was performed. The simulation employed the commercial software I-DEAS and CODE V, as well as in-house software. The results show that (a) the maximum temperature increase is 4.09°C in the smallest mirror, (b) the maximum thermal deformation at clear aperture is about 0.251 nm rms, and (c) the maximum nonspherical deformation at clear aperture is about 0.035 nm rms.