Metal contact and process

Abstract

Structures and processes are disclosed for reducing electrical contact resistance between two metal layers. Specifically, a resistive aluminum oxide layer forms spontaneously on metal lines including aluminum, within a V-shaped contact via which is opened in an insulating layer through a mask. The mask includes an opening with a width of less than about 0.75 μm. After removing the mask, the via is treated with an RF etch. The resultant contact has a width at the bottom of less than 0.9 μm. A titanium layer of 300 Å to 400 Å is deposited into the via, with about 60 Å to 300 Å reaching the via bottom and reacted with the underlying aluminum. The reaction produces a titanium-aluminum complex (TiAl x ) with a thickness of about 150 Å to 900 Å. Advantageously, this composite layer provides a low resistivity contact between the aluminum-containing layer and a subsequently deposited metal layer.

We claim:  
     
         1 . A process for forming low resistance contacts between conducting lines in an integrated circuit, comprising: 
 forming a first conductive layer over a semiconductor substrate, said conductive layer having an upper surface and comprising a metal;    forming an insulating layer over the upper surface;    forming a patterned mask over said insulating layer, the patterned mask having an opening having a width of less than about 0.75 μm;    forming a contact via in said insulating layer through the opening in said patterned mask to expose a contact region of the upper surface;    removing said patterned mask; and    depositing a titanium layer over said insulating layer and into said contact via, said titanium layer having a thickness over the insulating layer between about 300 Å and 400 Å.    
     
     
         2 . The process of  claim 1 , wherein said first metallic layer comprises an aluminum layer and said upper surface includes an aluminum oxide.  
     
     
         3 . The process of  claim 2 , wherein said aluminum layer comprises copper.  
     
     
         4 . The process of  claim 2 , further comprising reacting said titanium layer with said aluminum layer to form a titanium-aluminum complex.  
     
     
         5 . The process of  claim 4 , wherein the titanium-aluminum complex has a thickness between about 200 Å and 600 Å.  
     
     
         6 . The process of  claim 1 , wherein depositing said titanium layer comprises physical vapor depositing titanium.  
     
     
         7 . The process of  claim 6 , wherein depositing said titanium layer comprises sputter depositing titanium.  
     
     
         8 . The process of  claim 1 , wherein the opening in said patterned mask has a width of less than about 0.65 μm.  
     
     
         9 . The process of  claim 8 , wherein the opening in said patterned mask has a width of less than about 0.55 μm.  
     
     
         10 . The process of  claim 1 , wherein the contact region has a width less than about 0.76 μm.  
     
     
         11 . The process of  claim 10 , wherein the contact region has a width less than about 0.66 μm.  
     
     
         12 . The process of  claim 1 , further comprising depositing a titanium nitride layer over the upper surface prior to forming said insulating layer, wherein forming said contact via comprises etching through said insulating layer and said titanium nitride layer.  
     
     
         13 . The process of  claim 1 , further comprising depositing a conductive layer over the titanium layer and into the contact via.  
     
     
         14 . The process of  claim 1 , wherein said titanium layer has a thickness over the insulating layer between about 325 Å and 375 Å.  
     
     
         15 . The process of  claim 1 , wherein forming said contact via comprises forming sloped sidewalls within said insulating layer.  
     
     
         16 . The process of  claim 1 , further comprising sputter etching after removing said patterned mask and before depositing said titanium layer.  
     
     
         17 . The process of  claim 16 , wherein sputter etching removes between about 200 Å to 500 Å of the insulating layer.  
     
     
         18 . The process of  claim 16 , wherein sputter etching comprises performing an argon plasma etch.