Creating air gap in multi-level metal interconnects using electron beam to remove sacrificial material

Abstract

An embodiment of the present invention includes a method to form an air gap in a multi-layer structure. A dual damascene structure is formed on a substrate. The dual damascene structure has a metallization layer, a barrier layer, a sacrificial layer, and a hard mask layer. The sacrificial layer is made of a first sacrificial material having substantial thermal stability and decomposable by an electron beam. The sacrificial layer is removed by the electron beam to create the air gap between the barrier layer and the hard mask layer.

1 - 21 . (canceled)  
   
   
       22 . A device comprising: 
 a barrier layer on a substrate;    a hard mask layer;    an air gap between the barrier layer and the hard mask layer, the air gap being formed by removing a sacrificial layer using an electron beam, the sacrificial sacrifical layer being made of a sacrificial material having substantial thermal stability and decomposable by the electron beam; and    a metallization layer through the barrier layer, the air gap, and the hard mask layer, the metallization layer being formed by a dual damascene process.    
   
   
       23 . The device of  claim 22  wherein the sacrificial material is one of a low-k dielectric and an electron beam photo resist material.  
   
   
       24 . The device of  claim 23  wherein the electron beam photo resist material is produced from a cross-linked aromatic polymer incorporated with a positive tone electron beam photo resist, the electron beam photo resist being based on one of acrylate, styrene, and butene.  
   
   
       25 . The device of  claim 22  wherein the barrier layer is one of an etch stop and a diffusion layer.  
   
   
       26 . The device of  claim 25  wherein the diffusion layer is silicon oxide or silicon nitride.  
   
   
       27 . The device of  claim 22  wherein the hard mask layer is porous and non-porous.  
   
   
       28 . The device of  claim 22  wherein the hard mask layer is made by one of silicon oxide, silicon nitride, carbon-doped silicon nitride, silicon oxy-nitride, sputtered silicon, amorphous silicon, and amorphous carbon.  
   
   
       29 . The device of  claim 22  wherein the hard mask layer is a porous interlevel dielectric (ILD).