Method and apparatus for etching a metal layer disposed on a substrate, such as a photolithographic reticle, are provided. In one aspect, a method is provided for processing a substrate including positioning a substrate having a metal layer disposed on an optically transparent material in a processing chamber, introducing a processing gas processing gas comprising an oxygen containing gas, a chlorine containing gas, and a chlorine-free halogen containing gas, and optionally, an inert gas, into the processing chamber, generating a plasma of the processing gas in the processing chamber, and etching exposed portions of the metal layer disposed on the substrate.