Patent ID: 6933243

Claim:
A method of etching a substrate, comprising: a main etch step comprising exposing the substrate to a plasma from a first gas mixture wherein the main etch step removes a portion of a metal layer from the substrate; a soft landing step comprising exposing the substrate to a plasma from a second gas mixture wherein the soft landing step removes an additional portion of the metal layer to expose a metal nitride layer of the substrate; and an over etch step comprising exposing the substrate to a plasma from a third gas mixture, wherein the over etch step removes a portion of the metal nitride layer to expose a dielectric layer of the substrate, the soft landing step has a greater etch selectivity than the main etch step for etching a metal-containing layer of the substrate compared to a dielectric layer of the substrate, and the over etch step has a greater etch selectivity than the soft landing step for etching the metal-containing layer of the substrate compared to the dielectric layer of the substrate.