Fabrication of a diffusion barrier cap on copper containing conductive elements

Abstract

A method for fabricating a self-aligned diffusion-barrier cap on a Cu-containing conductive element in an integrated-circuit device comprises:—providing a substrate having a Cu-containing conductive element embedded laterally into a dielectric layer and having an exposed surface;—depositing a metal layer on the exposed surface of conductive element;—inducing diffusion of metal from the metal layer into a top section of the conductive element;—removing the remaining metal layer;—letting diffused metal in the top section of the conductive element and particles of a second constituent react with each other so as to build a compound covering the conductive element. The metal of the metal layer and the second constituent are chosen so that the compound forms a diffusion barrier against Cu diffusion. A reduction the dielectric constant of the dielectric material in an interconnect stack of an integrated-circuit device is achieved.