Patent ID: 7262127

Claim:
A method for forming a void-free copper damascene structure from a composite comprising a substrate having a conductive structure, a first dielectric layer on said substrate, a diffusion barrier layer on said first dielectric layer, and a second dielectric layer on said barrier layer, said method comprising: forming a via opening by etching said second dielectric layer, said diffusion barrier layer and said first dielectric layer, said etching comprising exposing said conductive structure by developing said photoresist through a first hard mask which defines a via opening, and said first hard mask is situated over an underlying second dielectric layer; filling at least the via opening with a gap fill material to form a gap fill layer; etching said gap fill layer and second dielectric layer to about a first depth by developing said photoresist through a second hard mask which defines a trench opening; laterally etching the first hard mask such that it is eroded to a greater extent from a sidewall of the trench opening than the underlying second dielectric layer; removing remaining gap fill layer and diffusion barrier layer within the via opening to expose the conductive structure; plating the via and trench openings with a barrier metal and a copper seed layer to obtain copper features that fill the openings and to form a copper damascene structure.