US Patent 9613856 Method of forming metal interconnection

A method of fabricating a semiconductor device is disclosed. The method includes forming a first conductive feature over a substrate, forming a dielectric layer over the first conductive feature, forming a trench in the dielectric layer, forming a first barrier layer in the trench, applying a thermal treatment to convert a first portion of the barrier layer to a second barrier layer, exposing the first conductive feature in the trench while a portion of the second barrier layer is disposed over the dielectric layer and forming a second conductive feature in the trench.