Structure with self aligned resist layer on an interconnect surface and method of making same

Abstract

A structure is provided with a self-aligned resist layer on a surface of metal interconnects for use in forming air gaps in an insulator material and method of fabricating the same. The non-lithographic method includes applying a resist on a structure comprising at least one metal interconnect formed in an insulator material. The method further includes blanket-exposing the resist to energy and developing the resist to expose surfaces of the insulator material while protecting the metal interconnects. The method further includes forming air gaps in the insulator material by an etching process, while the metal interconnects remain protected by the resist.

What is claimed is: 
     
         1 . A structure, comprising:
 a dielectric layer having gaps between metal interconnect structures formed in the dielectric layer;   a hard mask layer, including perforations, formed over the gaps between the metal interconnect structures; and   a capping layer formed over the hard mask layer, including over the perforations,   wherein an upper surface of the hard mask layer is substantially coplanar with upper surfaces of the metal interconnect structures.   
     
     
         2 . The structure of  claim 1 , wherein:
 the gaps are air gaps; and   the dielectric material is SiO 2 , low-k SiCOH, or ultralow-k porous SiCOH.   
     
     
         3 . The structure of  claim 2 , wherein:
 the metal interconnect structures are copper;   the copper is lined with TaN or Ta; and   the perforations are smaller than a spacing between adjacent metal interconnect structures.   
     
     
         4 . The structure of  claim 3 , wherein the air gaps are formed below perforations of the perforated hard mask and are completely covered by the perforated hard mask. 
     
     
         5 . The structure of  claim 4 , wherein the capping layer is provided over the upper surfaces of the metal interconnect structures. 
     
     
         6 . The structure of  claim 5 , wherein the capping layer is a SiCNH cap. 
     
     
         7 . The structure of  claim 6 , wherein the air gaps extend from an upper surface of the dielectric layer into, but not completely through, the dielectric layer. 
     
     
         8 . The structure of  claim 7 , wherein at least one of the metal interconnect structures extends completely through the dielectric layer. 
     
     
         9 . The structure of  claim 1 , wherein a poisoning agent is formed on the upper surfaces of the metal interconnect structures. 
     
     
         10 . The structure of  claim 9 , wherein in the poisoning agent is NH 3 , or an amine, or a plasma. 
     
     
         11 . The structure of  claim 1 , wherein capping layer completely covers the perforations in the hard mask layer. 
     
     
         12 . The structure of  claim 11 , wherein a poisoning agent is formed on the upper surfaces of the metal interconnect structures.