Removal of copper oxides from integrated interconnects

Abstract

An apparatus and a method for photoreducing copper oxide layers from semiconductor wafers during the processes of forming interconnects in advanced IC manufacturing. The apparatus comprises a reaction chamber with a high intensity UV light source and a wafer holder in the chamber. The UV light source is made of arrays of microdischarge devices fabricated on a semiconductor wafer where each of the microdischarge devices has the structure of a hollow cathode. Multiple arrays of microdischarge devices can be assembled together to make a planar UV lamp so as to provide a sufficient area for the UV illumination. The wafer holder in the chamber is made rotatable for a better uniformity during the photoreduction process. A non-oxidizing gas is flowed into the chamber to prevent instant and subsequent oxidation on the copper surface.

1 . A method of reducing copper oxide in a partially fabricated integrated circuit on a semiconductor substrate, the method comprising: 
 exposing an entire surface of the substrate to UV light having an intensity greater than about 50 W/cm 2 ,    wherein the surface of the substrate comprises copper oxide.    
   
   
       2 . The method of  claim 1 , wherein exposing comprises directing light from an array of microdischarge devices to the entire surface of the substrate.  
   
   
       3 . The method of  claim 2 , wherein the microdischarge devices each comprise a hollow cathode having a diameter between 100 μand 10 μm.  
   
   
       4 . The method of  claim 1 , wherein exposing comprises illuminating a surface area greater than the surface of the substrate.  
   
   
       5 . The method of  claim 1 , wherein the UV light has a wavelength less than 468 nm.  
   
   
       6 . The method of  claim 5 , wherein the UV light has a wavelength from 100 nm to 400 nm.  
   
   
       7 . A method of semiconductor fabrication, comprising: 
 loading a semiconductor wafer into a reaction chamber, a top surface of the semiconductor wafer comprising copper oxide; and    photoreducing, within the chamber, the copper oxide to metallic copper by illuminating the copper oxide with UV light from a planar UV lamp made of at least one array of microdischarge devices.    
   
   
       8 . The method of  claim 7 , wherein the UV light has an intensity exceeding 50 W/cm 2 .  
   
   
       9 . The method of  claim 7 , wherein the UV light has an intensity of 1 W/cm 2  to 100 W/cm 2 .  
   
   
       10 . The method of  claim 7 , wherein the TV light has a wavelength shorter than 468 nm.  
   
   
       11 . The method of  claim 7 , further comprising flowing a non-oxidizing gas into the chamber during photoreducing.  
   
   
       12 . The method of  claim 10 , wherein the non-oxidizing gas is selected from the group consisting of nitrogen, neon, hydrogen and ammonia.  
   
   
       13 . The method of  claim 10 , wherein the non-oxidizing gas has a pressure in the range of 100 Torr to 1000 Torr.  
   
   
       14 . The method of  claim 7 , further comprising subsequently depositing a conductive material to directly contact the metallic copper without exposing the semiconductor wafer to an oxidizing environment.  
   
   
       15 . The method of  claim 7 , wherein the copper oxide is exposed through an opening in an overlying insulating layer.  
   
   
       16 . The method of  claim 15 , further comprising depositing a conductive material in the opening to form a contact to the metallic copper after photoreducing the copper oxide.  
   
   
       17 . The method of  claim 15 , wherein depositing the conductive material in the opening deposits a layer of the conductive material over the insulating layer.  
   
   
       18 . The method of  claim 16 , wherein depositing the conductive material and photoreducing are performed within the reaction chamber.  
   
   
       19 . The method of  claim 7 , further comprising rotating the wafer during photoreducing.  
   
   
       20 . The method of  claim 7 , wherein the reaction chamber is a single wafer reaction chamber.