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An investigation of EUV lithography defectivity

We have used ASML's full field step-and-scan exposure tool for extreme ultraviolet lithography (EUVL), known as an Alpha Demo Tool, to investigate one of the critical issues identified for EUVL, defectivity associated with EUV masks. The main objective for this work was to investigate the infrastructure currently in place to examine defects on a EUV reticle and identify their consequence in exposed resist. Unlike many previous investigations this work looks at naturally occurring defects in a EUV exposed metal layer from a 45 nm node device. The EUV exposure was also integrated into a standard process flow where the other layers were patterned using more conventional 193-nm lithography techniques. This presentation correlates reticle level defectivity to resulting wafer exposures. Defect inspection data from both the 28xx family of KLA-Tencor wafer inspection tool and Terascan reticle inspection tools are presented. Defect populations were characterized with a KLA 5200 Review SEM. Observed defectivity modes were analyzed using both conventional defect inspection methodology as well as advanced techniques in order to gain further insight. We find good correlations between reticle level defects and the resulting wafer exposure defects.