A method for forming a semiconductor interconnect structure includes forming a dielectric layer on a substrate and patterning the dielectric layer to form an opening therein. A metal layer fills the opening and covers the dielectric layer. The metal layer is planarized so that it is co-planar with a top of the dielectric layer. A treating process is performed on the metal layer to convert a top surface thereof into a metal oxide layer. A copper-containing layer is then formed over the metal oxide layer and the dielectric layer. The copper-containing layer is etched to form interconnect features, wherein the etching stops at the metal oxide layer and does not etch into the underlying metal layer. A radiation exposure process is thereafter performed on the metal oxide layer to convert it into a non-oxidized metal layer.