Gas-phase tungsten etch

Abstract

Methods of evenly etching tungsten liners from high aspect ratio trenches are described. The methods include a remote plasma etch using plasma effluents formed from a fluorine-containing precursor and a high flow of helium. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with tungsten coating a patterned substrate having high aspect ratio trenches. The plasmas effluents react with exposed surfaces and evenly remove tungsten from outside the trenches and on the sidewalls of the trenches. The plasma effluents pass through an ion suppression element positioned between the remote plasma and the substrate processing region. Optionally, the methods may include concurrent ion bombardment of the patterned substrate to help remove potentially thicker horizontal tungsten regions, e.g., at the bottom of the trenches or between trenches.