Exploring the limits of high contrast contact imaging using split pupil exposures in high-NA EUV lithography

The lithographic imaging performance of contact holes is limited by the efficient use of light and contrast fading caused by 3D mask effects. "Split pupil"exposures have been proposed to mitigate contrast fading for line-space-patterns. We present a simulation study investigating the extendibility of split pupil exposures to dense arrays of contacts on dark field and light field masks using different mask absorber options. Our simulations indicate that the combination of split pupil exposures and low-n/low-k absorbers can offer comfortable imaging performance for arrays of 10 nm square contacts with a pitch of 20 nm on a dark field mask. These results indicate the potential of combining low-n absorbers and split pupil exposure strategies to enable high-NA EUV lithography to reach its ultimate optical resolution limits.