Source optimization for anamorphic magnification high-numerical aperture extreme ultraviolet lithography based on thick mask model

Source optimization (SO) is one of the important resolution enhancement techniques (RETs) in computational lithography. The anamorphic magnification high-numerical aperture (NA) extreme ultraviolet (EUV) lithography can achieve a higher resolution by increasing the NA. However, the increase in NA leads to a significant mask three-dimensional (M3D) effects in the partial direction on the mask, and traditional Kirchhoff model no longer works. In this paper, we propose a SO method for 0.55 NA EUV lithography based on thick mask model. The results demonstrate that thick mask model aware SO can effectively mitigate the M3D effects, achieve high fidelity patterns, and enlarge the process window (PW). The depth of defocus (exposure latitude=10%) of thick mask model aware SO at two types of target patterns is 52nm and 67nm, which is 116.7% and 48.9% larger than that of thin mask model aware SO.