Metal removal with reduced surface roughness

A method of etching a metal layer on a semiconductor substrate, the method comprising:

• contacting the semiconductor substrate with a pre-treatment plasma, wherein the pre-treatment plasma is formed from a hydrogen-containing precursor;
• treating the metal layer with the pre-treatment plasma to form a pre-treated metal layer, wherein the treating of the metal layer includes:
• (i) reducing metal oxide formed on the metal layer to additional metal, and
• (ii) bombarding the metal layer to disorder crystalline regions on the metal layer;
• reacting the pre-treated metal layer with a halogen-containing precursor, wherein the halogen-containing precursor reacts with the pre-treated metal layer to form a halogenated metal layer comprising a halogenated etch product;
• removing the halogen-containing precursor from the semiconductor substrate;
• reacting the halogenated etch product on the halogenated metal layer with a carbon-and-nitrogen-containing precursor to form one or more volatile etch products;
• and
• removing the carbon-and-nitrogen-containing precursor and the volatile etch products from the semiconductor substrate, wherein the removal of the volatile etch products leaves behind the etched metal layer on the semiconductor substrate.