Resolution Enhancement for Beyond-22-nm Node Using Extreme Ultraviolet Exposure Tool

EUV1 is a full-field extreme-ultraviolet (EUV) exposure tool that was manufactured by Nikon and is being developed at Selete. Its lithographic performance was evaluated in scanning exposure experiments using line-and-space (L&S) patterns, Selete Standard Resist 4 (SSR4), a numerical aperture (NA) of 0.25, and conventional illumination ($\sigma=0.8$). Results show that 28 nm L&S patterns are resolved and that the critical dimension (CD) uniformity across a shot is 3.7 nm. Simulations predict that the use of dipole illumination will push the resolution limit down to a half pitch of 20 nm for L&S patterns. Moreover, the results of test site exposures using dipole illumination indicate that the EUV1 is suitable for device fabrication beyond the 22 nm node.