Apparatus and method for etching metal nitrides

A method for etching a metal nitride layer disposed on a substrate, the method comprising:

• providing a substrate in a reaction chamber of a semiconductor processing device, the substrate comprising a metal nitride layer, wherein the metal nitride layer comprises at least one of vanadium nitride and molybdenum nitride;
• the method further comprising executing one or more etching cycles, an etching cycle comprising the following steps, in the following order:
• an oxidation step that comprises providing a gaseous oxidizing agent as a gaseous oxidizing agent pulse to the reaction chamber, thereby oxidizing a surface layer of the metal nitride layer, thus forming a metal oxide surface layer overlying an unaffected metal nitride layer;
• and
• an etching step that comprises providing only a gaseous etchant as a gaseous etchant pulse to the reaction chamber and exciting the gaseous etchant with plasma, thereby forming an excited gaseous etchant and selectively etching the metal oxide surface layer with respect to the unaffected metal nitride layer, wherein the gaseous etchant consists of one of HCl, CCl4, BCl4, and Cl2 and optionally a noble gas.