Enhanced extreme ultraviolet lithography mask inspection contrast using fabry-perot type antireflective coating

In this paper, we describe two strategies for solving the low-contrast problem during extreme ultraviolet lithography (EUVL) mask inspection processes. One is the use of single-layer antireflective coating (ARC), and the other is the use of Fabry-Perot-type ARC. The materials of ARC are the same as those of buffer layers, such as SiO₂ and Si₃N₄ which are easy to fabricate. Contrast can be increased up to >95% by adding ARC. For both absorbers, Single-layer Si₃N₄ ARC and Si ₃N₄-based Fabry-Perot-type ARC show better performances than SiO₂ ARC. Both types of ARC maintain a high contrast at 40% with a large thickness variation even until ±40%. Moreover, the top absorber in Fabry-Perot-type ARC has good conductivity that can eliminate electrical distortion, which is caused by electron charging during e-beam direct writing. The Fabry-Perot-type ARC structure has better contrast and thickness variation tolerance than the single-layer ARC structure. The film materials in Fabry-Perot structure can also be used for various absorber and dielectric materials.