A method of forming surface alteration of metal interconnect in integrated circuits for electromigration and adhesion improvement

Abstract

Described is a method and apparatus for altering the top surface of a metal interconnect. In one embodiment of the invention, a metal interconnect and a barrier layer are formed into an interlayer dielectric (ILD) and the metal interconnect and the barrier layer are planarized to the top of the ILD. The top surfaces of the metal interconnect, the barrier layer, and the ILD are altered with a second metal to form an electromigration barrier. In one embodiment of the invention, the second metal is prevented from contaminating the electrical resistivity of the metal interconnect.

What is claimed:  
     
         1 . A method, comprising: 
 forming a metal interconnect in an interlayer dielectric (ILD), the metal interconnect couched in a barrier layer, the top of the metal interconnect and the top of the barrier layer planarized to the top of the ILD, and the metal interconnect comprising a first metal; and    altering the top surfaces of the interconnect, barrier layer and ILD with a second metal to form an electromigration barrier to significantly prevent electromigration at the top surface of the interconnect.    
     
     
         2 . The method of  claim 1 , wherein altering the top surface of the interconnect includes preventing the second metal from significantly increasing the electrical resistivity of the first metal.  
     
     
         3 . The method of  claim 1 , wherein altering the top surfaces of the interconnect, barrier layer, and ILD includes depositing the second metal onto the top surfaces of the interconnect, barrier layer, and ILD.  
     
     
         4 . The method of  claim 1 , wherein altering the top surfaces of the interconnect, barrier layer, and ILD includes ion implanting the second metal into the top surfaces of the interconnect, barrier layer, and ILD.  
     
     
         5 . The method of  claim 1 , wherein altering the top surface of the interconnect includes increasing the activation energy of the top surface of the interconnect.  
     
     
         6 . The method of  claim 5 , wherein altering the top surface of the interconnect includes increasing the activation energy to approximately 1.0 to 1.2 eV.  
     
     
         7 . The method of  claim 1 , wherein the second metal comprises any one of titanium, tantalum, cobalt, chromium, or aluminum.  
     
     
         8 . The method of  claim 1 , wherein the first metal comprises copper.  
     
     
         9 . The method of  claim 1 , further comprising: 
 annealing the second metal in the presence of an oxygen gas at approximately 350° C.-400° C.    
     
     
         10 . A method, comprising: 
 depositing an interlayer dielectric (ILD) over a substrate;    forming an opening in the first ILD;    forming a copper interconnect and barrier layer in the opening; and    implanting a treatment metal species into the top surfaces of the ILD, barrier layer, and interconnect.    
     
     
         11 . The method of  claim 10 , including implanting the treatment metal species at a low energy approximately between 1 keV to 6 keV.  
     
     
         12 . The method of  claim 10 , including implanting the treatment metal species at a dose of approximately 1×10 5  ions/cm 2  to 3×10 16  ions/cm 2 .  
     
     
         13 . The method of  claim 10 , including implanting the treatment metal species approximately between 2 Å to 50 Å deep into the top surfaces of the interconnect, the barrier layer, and the ILD.  
     
     
         14 . The method of  claim 10 , further comprising performing a thermal treatment at approximately 350° C.-400° C.  
     
     
         15 . The method of  claim 10 , wherein the treatment metal species comprises a material that will readily oxidize with the material of the ILD.  
     
     
         16 . The method of  claim 10 , wherein the treatment metal species is any one of titanium, tantalum, cobalt, chromium, or aluminum.  
     
     
         17 . The method of  claim 10 , further comprising preventing the treatment metal species from substantially diffusing into the copper interconnect.  
     
     
         18 . The method of  claim 10 , wherein the treatment metal species comprises a material that will cause an increase in the activation energy of the top of the copper interconnect.  
     
     
         19 . The method of  claim 18 , including increasing the activation energy of the top of the copper interconnect to approximately 1.0 to 1.2 eV.  
     
     
         20 . A method, comprising: 
 depositing an interlayer dielectric (ILD) over a substrate;    forming an opening in the first ILD;    forming a copper interconnect and barrier layer in the opening;    depositing a treatment metal onto the top surfaces of the interconnect, barrier layer, and ILD; and    annealing the treatment metal to cause the treatment metal to adhere to the top surface of the interconnect to form an electromigration barrier.    
     
     
         21 . The method of  claim 20 , including depositing the treatment metal to approximately between 1 to 10 nm in thickness.  
     
     
         22 . The method of  claim 20 , including annealing the treatment metal in the presence of an oxygen gas at approximately 350° C.-400° C.  
     
     
         23 . The method of  claim 20 , including annealing the treatment metal until the treatment metal is sufficiently oxidized to become substantially non-conductive.  
     
     
         24 . The method of  claim 20 , further comprising: 
 planarizing the top of the copper interconnect and barrier layer to the top of the ILD to expose the top surfaces of the ILD, the barrier layer and the copper interconnect before depositing the treatment metal.    
     
     
         25 . An apparatus, comprising: 
 a substrate;    an interlayer dielectric (ILD) overlaying the substrate;    an interconnect of a first metal formed into, and planarized to the top of, the ILD, the interconnect having an altered top to significantly prevent electromigration and the interconnect having an electrical resistivity that is substantially uncontaminated.    
     
     
         26 . The apparatus of  claim 25 , wherein the first metal comprises copper.  
     
     
         27 . The apparatus of  claim 25 , wherein the altered top includes an alloy of the first metal and a second metal, the alloy having an activation energy of electromigration higher than that of the first metal.  
     
     
         28 . The apparatus of  claim 27 , wherein the second metal comprises any one of titanium, tantalum, cobalt, chromium, or aluminum.  
     
     
         29 . The apparatus of  claim 25 , wherein the altered top included a metal-oxide layer comprising any one of titanium oxide, tantalum oxide, cobalt oxide, chromium oxide, or aluminum oxide.  
     
     
         30 . The apparatus of  claim 25 , wherein the altered top of the interconnect has an activation energy of electromigration approximately between 1.0 to 1.2 eV.