Method of fabricating an semiconductor interconnect structure

A method for forming a semiconductor interconnect structure, comprising:

• forming a dielectric layer on a substrate;
• patterning the dielectric layer to form an opening in the dielectric layer;
• filling the opening and covering the dielectric layer with a metal layer;
• planarizing the metal layer so that the metal layer is co-planar with a top of the dielectric layer;
• performing a treating process on the metal layer to convert a top surface thereof into a metal oxide layer, the metal oxide layer having a predetermined thickness;
• forming a copper-containing layer over the metal oxide layer and the dielectric layer;
• etching the copper-containing layer to form interconnect features, wherein the etching stops at the metal oxide layer and does not etch into the underlying metal layer;
• and
• performing a radiation exposure process on the metal oxide layer to convert the metal oxide layer into a non-oxidized metal layer.