Structure and method for capping cobalt contacts

Abstract

A process for forming a conductive structure includes the formation of a self-aligned silicide cap over a cobalt-based contact. The silicide cap is formed in situ by the deposition of a thin silicon layer over exposed portions of a cobalt contact, followed by heat treatment to react the deposited silicon with the cobalt and form cobalt silicide, which is an effective barrier to cobalt migration and oxidation.

What is claimed is: 
     
         1 . A semiconductor structure comprising:
 a dielectric layer disposed over a semiconductor substrate;   a conductive contact extending through the dielectric layer, wherein the conductive contact comprises cobalt; and   a cobalt silicide capping layer disposed directly over the conductive contact.   
     
     
         2 . The semiconductor structure of  claim 1 , wherein the cobalt silicide capping layer thickness is 2 to 10 nm. 
     
     
         3 . The semiconductor structure of  claim 1 , wherein a top surface of the cobalt silicide capping layer is co-planar with a top surface of the dielectric layer. 
     
     
         4 . The semiconductor structure of  claim 1 , further comprising an interlayer dielectric disposed over the cobalt silicide capping layer and over the dielectric layer. 
     
     
         5 . The semiconductor structure of  claim 4 , wherein an interface between the interlayer dielectric layer and the dielectric layer is substantially free of cobalt.