Defectivity Performance of Full Field Immersion Photolithography Tool

In this paper, we report results of comprehensive studies of defects originating in immersion photolithography clusters comprising immersion volume production tool (S609B, NA=1.07) and engineering evaluation tool (EET NA = 0.85). Defectivity S609B was very low, 0.013 cm² it attained dry exposure level successfully. Defectivity results using EET were also very promising in all three major resist processes including solvent soluble topcoat, developer soluble topcoat and topcoat-less resist. Defectivity did not show any scan speed dependency and target size dependency, showing the extendibility of our immersion technology in future mass production phase. In particular, we found that for 50 ml water droplets, weeding angle larger than about 70 degree provides immersion process free of immersion-specific defects. We successfully demonstrated very effective defect analysis technique named DSA (defect source analysis) to show what defects are immersion-specific. We also revealed the defect generation mechanism of each defect types. Deep understanding of defectivity behavior leads to a conclusion that immersion lithography is viable for IC manufacture at 45 nm node