Method and apparatus for minimizing thickness-to-planarity and dishing in CMP

Abstract

The present technique is directed toward the fabrication of integrated circuits and provides for the hardening (modification) of a metal layer surface of a semiconductor wafer to reduce the amount of material removed during chemical mechanical planarization (CMP) of the metal layer. This hardening may be accomplished, for example, by oxidizing the metal surface and/or coating the metal surface with a polymer. In one implementation, a relatively thick and dense oxide layer is formed on the wafer metal surface prior to CMP, by injecting, for example, an oxidant, such as oxygen or ozone, near the end of an annealing cycle. Such hardening of the surface beneficially protects recessed regions from CMP chemical attack and CMP pad deformation, and thus reduces the thickness-to-planarity, dishing, and waste generation realized during CMP.

1 . A process comprising the acts of: 
 hardening a metal layer of a semiconductor wafer prior to chemical mechanical planarization (CMP); and    performing CMP on the semiconductor wafer.    
     
     
         2 . The process, as set forth in  claim 1 , wherein hardening of the metal layer comprises making the metal layer more resistant to abrasion.  
     
     
         3 . The process, as set forth in  claim 1 , wherein hardening of the metal layer comprises making the metal layer more resistant to chemical attack.  
     
     
         4 . The process, as set forth in  claim 1 , wherein hardening of the metal layer comprises oxidizing the metal layer.  
     
     
         5 . The process, as set forth in  claim 4 , wherein a thickness of an oxide layer formed on a surface of the metal layer is in the range of 300-600 angstroms.  
     
     
         6 . The process, as set forth in  claim 4 , wherein the metal layer comprises copper.  
     
     
         7 . The process, as set forth in  claim 4 , wherein copper oxide is formed on the metal layer.  
     
     
         8 . The process, as set forth in  claim 4 , wherein the metal layer comprises tungsten.  
     
     
         9 . The process, as set forth in  claim 8 , wherein tungsten oxide is formed on the metal layer.  
     
     
         10 . The process, as set forth in  claim 1 , wherein hardening of the metal layer comprises coating a surface of the metal layer with polymer.  
     
     
         11 . A process comprising the acts of: 
 oxidizing a metal layer of a semiconductor wafer prior to chemical mechanical planarization (CMP) of the metal layer; and    performing CMP on the metal layer.    
     
     
         12 . The process, as set forth in  claim 11 , wherein the semiconductor wafer has one or more metal contact plugs.  
     
     
         13 . The process, as set forth in  claim 11 , wherein during oxidation of the metal layer, the temperature surrounding the semiconductor wafer is elevated to a predetermined temperature for a predetermined period of time.  
     
     
         14 . The process, as set forth in  claim 13 , wherein the predetermined temperature is in the range of 150-250° C.  
     
     
         15 . The process, as set forth in  claim 13 , wherein the predetermined period of time is in the range of 1-2 minutes.  
     
     
         16 . The process, as set forth in  claim 11 , wherein the metal layer is oxidized in an annealing process.  
     
     
         17 . The process, as set forth in  claim 16 , wherein the metal layer is oxidized with oxygen.  
     
     
         18 . The process, as set forth in  claim 16 , wherein the metal layer is oxidized with ozone.  
     
     
         19 . A method comprising the acts of: 
 plating a semiconductor wafer with a metal layer;    annealing the wafer;    introducing an oxidant near the end of an annealing cycle;    oxidizing a surface of the metal layer prior to chemical mechanical planarization (CMP) of the wafer; and    applying CMP to the wafer.    
     
     
         20 . The method, as set forth in  claim 19 , wherein the oxidant comprises oxygen (O2).  
     
     
         21 . The method, as set forth in  claim 19 , wherein the oxidant comprises ozone (O3).  
     
     
         22 . The method, as set forth in  claim 19 , wherein the metal layer comprises copper and the CMP comprises copper CMP.  
     
     
         23 . The method, as set forth in  claim 19 , wherein the metal layer comprises tungsten and the CMP comprises tungsten CMP.