Enhancement of the two-dimensional corner sharpness in extreme ultraviolet lithography with rigorous imaging analysis

Corner rounding in lithography describes the unintended transformation of designed sharp corners into curved features during pattern transfer. This smoothing effect is primarily driven by light diffraction and is further influenced by factors including mask design, numerical aperture, and process parameters. As a critical two-dimensional effect, inadequate control of corner rounding compromises pattern fidelity directly and ultimately degrades the performance and reliability of microelectronic devices. The adoption of extreme ultraviolet (EUV) lithography, which enables continued scaling of feature sizes and device density, imposes even more stringent requirements on corner rounding control. The reflective optics inherent to EUV systems, combined with the shorter exposure wavelength, introduce additional complexities in preserving corner acuity. This paper presents a comprehensive study of the mechanisms governing corner rounding in EUV lithography, using rigorous imaging simulations to dissect and quantify the individual effects of projection optics, mask diffraction, and resist behavior. By leveraging aerial image simulations and computational modeling, we establish the fundamental limits of corner sharpness and propose mitigation strategies to achieve minimal corner radius in both 0.33 NA and 0.55 NA EUV systems. Our results demonstrate notable improvements in corner sharpness and overall image quality, offering an actionable methodology for enhancing two-dimensional pattern fidelity in advanced semiconductor manufacturing.