High-NA Benefit Assessment through ZEISS AIMS EUV for Tip-to-Tip Patterning by EUVL

Abstract

High-NA EUV lithography is being prepared for the next stage of volume production of state-of-the-art integrated devices. First wafer exposures on ASML's EXE5000 are expected early in 2024. Beyond assessment of the benefit of high-NA by simulation, ZEISS AIMS EUV offers the potential to compare the imaging benefit of 0.55NA to the established 0.33NA, through aerial image analysis of dedicated mask patterns. The recently available capability of high-NA imaging on AIMS (R) EUV was applied to compare options for imec's logic patterning roadmap, specifically for tip-to-tip structures (T2T). Beyond direct comparison of 0.33 and 0.55 NA, low-n absorber was compared to conventional Ta-based absorber. Moreover, in view of anamorphic imaging at high-NA, T2T pattern orientation was compared, i.e., either along the 4X exposure slit direction or along the 8X scan direction. Lastly pattern tonality, i.e., darkfield versus lightfield, were evaluated side by side. The comparisons were made for selected, yet not optimized, dipole-like sources. Beyond normalized intensity log-slope (NILS) for the line-space part, the through-focus analysis comprised ILS and required bias for shrinking T2T size. The results show that 0.55NA provides clear advantages, but their variation among absorber type, T2T pattern orientation and tonality highlight the potential of preferred combinations. Such are suggested as starting points for further optimization.