Illuminating extreme ultraviolet lithography mask defect printability

For the next few years, the extreme ultraviolet lithography (EUVL) community must learn to find mask defects using nonactinic inspection wavelengths. Nonactinic light cannot always determine the exact nature of the defect, whether it is a particle, pattern, or defect in the multilayer. It also cannot predict which defects will induce phase errors and which will induce amplitude errors on wafers. Correlating the signature of the defect as seen by a nonactinic inspection tool and on wafer resist image will inject essential knowledge into the nonactinic defect classification. This paper will explore the correlation between EUVL mask defect signatures detected (and not detected) at both 193 nm and e-beam inspection wavelengths and wafer-printable defects. The defects of interest will be characterized at mask level using atomic force microscopy and critical dimension scanning microscopy. Simulations will be deployed to explain the signatures illuminated by both EUVL and 193 nm exposures. This work addresses the gap between inspection sensitivity at nonactinic wavelengths and EUVL mask defect printability, and provides generalized understanding of how the two views differ.