Silicon nitride damage-free dry etch method for tungsten removal in middle of line bottom-up tungsten integration

Abstract

A method of filling a feature in a semiconductor structure with metal includes depositing a metal cap layer on a bottom surface of a feature formed within a dielectric layer and top surfaces of the dielectric layer, partially filling the feature from the bottom surface with a flowable polymer layer, performing a metal pullback process to remove the metal cap layer on the top surfaces of the dielectric layer selectively to the dielectric layer, wherein the metal pullback process includes a first etch process including a chemical etch process using molybdenum hexafluoride (MoF) to remove the metal cap layer selectively to the dielectric layer, and a second etch process to remove residues on etched surfaces of the dielectric layer, removing the flowable polymer layer, pre-cleaning a surface of the metal cap layer, and filling the feature from the surface of the metal cap layer with metal fill material.