High selectivity and residue free process for metal on thin dielectric gate etch application

A method of etching a substrate, comprising:

• a main etch step comprising exposing the substrate to a plasma from a gas mixture selected from the group consisting of a first mixture including NF3, Cl2, and N2 and a second mixture including NF3, Cl2, and CF4;
• a soft landing step comprising exposing the substrate to a plasma from a gas mixture selected from the group consisting of a third mixture including NF3, Cl2, and N2 and a fourth mixture including Cl2 and O2;
• and an over etch step comprising exposing the substrate to a plasma from a gas mixture selected from the group consisting of a fifth mixture including NF3, Cl2, O2, and Ar and a sixth mixture including Cl2 and O2, wherein the soft landing step is performed with a lower bias power than the main etch step, and the over etch step has a greater etch selectivity than the main etch step and the soft landing step for etching a metal-containing layer of the substrate compared to a dielectric layer of the substrate.

A method of etching a substrate, comprising:

• a main etch step comprising exposing the substrate to a plasma from a gas mixture including NF3, Cl2, and N2;
• and
• a combined soft landing and over etch step comprising exposing the substrate to a second plasma from a second gas mixture including NF3, Cl2, Ar, and O2, wherein the combined soft landing and over etch 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.