Mask diffraction analysis and optimization for EUV masks

This paper employs a direct analysis of the intensity and the phase of the diffracted light by rigorous electromagnetic field (EMF) simulations to investigate mask-induced imaging artifacts in EUV-lithography. Analysis of the diffraction efficiencies and phase differences between the diffraction orders versus mask and illumination parameters is used to explore EUV-specific imaging artifacts such as feature orientation dependent placement errors and feature sizes, shifts of the best focus position, process window asymmetries, and other aberration-like phenomena. The results of these simulations aim to understand the reason for these EUV-specific imaging artifacts and to devise strategies for their compensation. Finally, rigorous EMF models of light scattering from EUV-masks are applied to i dentify ideal mask absorber stacks using global optimization techniques.