Fast rigorous mask model for extreme ultraviolet lithography.

The calculation of extreme ultraviolet (EUV) mask diffraction spectrum is the key of EUV lithography simulation. In this paper, a fast rigorous EUV mask model is proposed to calculate the diffraction spectrum fast and accurately. Based on the mask structure decomposition method, the relationship among the region diffraction, the boundary diffraction of the absorber, and the direction of incident light is analyzed at first. Then the frequency-domain functions related to angle of incidence and diffraction angle are established to model the geometrical and boundary diffraction of the absorber. The fast rigorous EUV mask model is established by combining the equivalent layer multilayer model based on the Fresnel formula and the accurate absorber model. Simulations and comparisons show the effectiveness of the proposed model. For the 14 nm vertical line-space pattern, the calculation errors of critical dimension (CD) via the proposed model are reduced by 80.6% and 93.9% compared with the structure decomposition method for dense and isolate features.