US Patent 11988953 EUV masks to prevent carbon contamination

A method includes forming a multi-layered reflective layer over a substrate; depositing a metal capping layer over the multi-layered reflective layer; depositing a first metal oxide layer over the metal capping layer; depositing a metal nitride layer over the first metal oxide layer; depositing a second metal oxide layer over the metal nitride layer; forming a plurality of features on the second metal oxide layer and the metal nitride layer.