Interstitial type absorber for extreme ultraviolet mask

A method, comprising:

• forming a reflective multilayer stack over a substrate;
• depositing a capping layer over the reflective multilayer stack;
• and
• forming an absorber layer over the capping layer, wherein the absorber layer is a single layer consisting of a matrix metal exhibiting a cubic lattice structure or a hexagonal lattice structure and an interstitial element occupying octahedral interstitial sites of the lattice structure of the matrix metal, wherein the matrix metal is selected from the group consisting of chromium (Cr), titanium (Ti), tungsten (W), zirconium (Zr), iridium (Ir), nickel (Ni), cobalt (Co), vanadium (V), yttrium (Y) and hafnium (Hf);
• forming a patterned hard mask layer over the absorber layer;
• etching the absorber layer using the patterned hard mask layer as an etch mask to form a patterned absorber layer, the patterned absorber layer comprising a pattern of first openings exposing portions of the capping layer;
• and
• removing the patterned hard mask layer.

An extreme ultraviolet (EUV) mask, comprising:

• a substrate;
• a reflective multilayer stack over the substrate;
• and
• a patterned absorber layer over the reflective multilayer stack, the patterned absorber layer being the topmost layer of the EUV mask, wherein the patterned absorber layer is a single layer consisting of a matrix metal exhibiting a cubic lattice structure or a hexagonal lattice structure and an interstitial element occupying octahedral interstitial sites of the matrix metal, wherein the matrix metal is selected from the group consisting of zirconium (Zr), iridium (Ir), nickel (Ni), cobalt (Co), vanadium (V), yttrium (Y) and hafnium (Hf), and the interstitial element is selected from the group consisting of boron (B), carbon (C), nitrogen (N), silicon (Si) and phosphorus (P).