Investigation of several materials as buffer layer candidates of EUVL mask

An EUVL mask consists of a multilayer, a capping layer, a buffer layer, and an absorber layer formed on a glass substrate with a low coefficient of thermal expansion. The buffer layer protects the multilayer during the repair of absorber defects. In this study, Ru, Cr, and CrN were investigated as buffer layer candidates, and their etching selectivity with respect to a TaGeN absorber, DUV defect inspection contrast, and film stress were compared. Ru was found to be the most promising material of the three.