Lithographic characterization of the flare in the Berkeley 0.3 numerical aperture extreme ultraviolet microfield optic

Flare remains a crucial issue for extreme ultraviolet (EUV) lithography. Achieving required flare levels demands mid-spatial-frequency surface roughness levels on the order of 1 Å , which is on par with present metrology limits. Lithographic verification of predicted flare levels is thus critical to the validation of current metrology methods. In this work we present the lithographic characterization of flare in the Berkeley EUV microfield exposure tool. Experimental analysis shows good agreement between predicted and measured results. The results also show that it is essential to compensate for proximity and die-to-die effects. In an isolated microfield, flare values of 6.8% and 4.8% in 500 nm and 2 μ m lines, respectively, have been verified.