Reducing dose sensitivity in high-numerical-aperture extreme ultraviolet lithography using an innovative source optimization method

Errors such as illumination non-uniformity and system drift during scanning can lead to unpredictable dose non-uniformity and degrade the imaging performance across the wafer. This paper proposes a novel, to our knowledge, source optimization (SO) method for high-numerical-aperture extreme ultraviolet lithography (high-NA EUVL) system. This method establishes a dose sensitivity function and integrates it into the cost function of the SO process. It aims at reducing the influence of dose variation on the critical dimension error (CDE) in the EUVL system and increasing the exposure latitude (EL). Simulation results demonstrate that this method significantly improves the stability of imaging performance in case of dose non-uniformity. Additionally, it extends the process window (PW).