Gradient oxidation and etch of pvd molybdenum for bottom up gap fill

Abstract

A method and apparatus for a gap-fill in semiconductor devices are provided. The method includes forming a metal seed layer on exposed top surface of the substrate, wherein the substrate has features in the form of trenches or vias formed in the top surface of the substrate, the features having sidewalls and a bottom surface extending between the sidewalls. A gradient oxidation process is performed to oxidize exposed portions of the metal seed layer to form a metal oxide, wherein the gradient oxidation process preferentially oxidizes a field region of the substrate over the bottom surface of the features. An etch back process removes the oxidized portion of the seed layer. A second etch process removes portions of the seed layer. A metal gap-fill process fills or partially fills the features with a gap fill material.