Source optimization method employing dynamic polarization aberration model for high-NA EUVL

Scanning technology is widely used in current lithography. During scanning, any point on the wafer scanning through the field of view (FOV) is successively affected by varying levels of polarization aberrations (PAs) that depend on the position within the FOV. However, current computational lithography studies for extreme ultraviolet lithography (EUVL) neglect this effect of the "dynamic PA" caused by scanning. Consequently, the optimization results cannot meet the actual imaging requirements, leading to a decline in image quality for the lithographic projection objective, particularly in high numerical aperture (NA) EUVL systems. This paper establishes a dynamic PA model for NA0.55 EUVL and proposes a source optimization method employing this model to increase image quality. The model samples the FOV points in the scanning direction at equal intervals based on the characteristics of the EUVL pulsed lasers. Then, it calculated the images at different sampling points and the iterative exposure of the resist, considering the impact of PA from each sampling point. The optimization strategy of source parameters based on this model is realized. Experimental results demonstrate that this SO method effectively reduces pattern errors by 15.5%-28.2%, and the process window is expanded by 15.0%-22.2%.