US Patent 10014185 Selective etch of metal nitride films

Processing methods comprising oxidizing a metal nitride film to form a metal oxynitride layer and etching the metal oxynitride layer with a metal halide etchant. The metal halide etchant can be, for example, WCl5, WOCl4 or TaCl5. Methods of filling a trench with a seam-free gapfill are also described. A metal nitride film is deposited in the trench to form a seam and pinch-off an opening of the trench. The pinched-off opening is subjected to a directional oxidizing plasma and a metal halide etchant to open the pinched-off top and allow access to the seam.