A method for manufacturing an interconnect structure includes providing a substrate structure including a substrate, a first metal layer on the substrate, a dielectric layer on the substrate and covering the first metal layer, and an opening extending to the first metal layer; forming a first barrier layer on a bottom and sidewalls of the opening with a first substrate bias; forming a second barrier layer on the first barrier layer with a second substrate bias, the second substrate bias being greater than the first substrate bias, the first and second barrier layers forming collectively a barrier layer; removing a portion of the barrier layer on the bottom and on the sidewalls of the opening by bombarding the barrier layer with a plasma with a vertical substrate bias; and forming a second metal layer filling the opening.