Electrochemical reduction of copper seed for reducing ECD voids

Abstract

An improved method for forming a copper layer ( 100 ). After the copper seed layer ( 116 ) is formed, any oxidized copper ( 118 ) at the surface is electrochemically reduced back to copper rather than being dissolved. Copper ( 120 ) is then electrochemically deposited (ECD) over the intact seed layer ( 116 ).

In the claims:  
     
         1 . A method of fabricating an integrated circuit, comprising the steps of: 
 forming a copper seed layer over a semiconductor body, wherein copper oxide forms at a surface of said copper seed layer    electrochemically reducing said copper oxide; and    electrochemically depositing a copper layer on said copper seed layer.    
     
     
         2 . The method of  claim 1 , further comprising the step of rinsing said surface of said copper seed layer after said electrochemically reducing step and prior to said electrochemically depositing step.  
     
     
         3 . The method of  claim 1 , wherein said electrochemically reducing step and said electrochemically depositing step occur in the same cluster tool.  
     
     
         4 . The method of  claim 1 , wherein said electrochemically reducing step occurs in a first tool and said electrochemically depositing step occurs in a second, separate, tool.  
     
     
         5 . The method of  claim 1 , further comprising the step of transferring said semiconductor body in an inert atmosphere between said electrochemically reducing step and said electrochemically depositing step.  
     
     
         6 . The method of  claim 1 , wherein said electrochemically reducing step comprises the steps of: 
 immersing said semiconductor body in an electrolyte having a pH greater than or equal to 4;    applying a cathodic current in the copper seed layer during said immersing step to reduce said copper oxide layer;    removing said semiconductor body from said electrolyte;    rinsing said semiconductor body with deionized water; and    transferring said semiconductor body to a plating cell of an electrochemical deposition tool under an inert atmosphere.    
     
     
         7 . The method of  claim 6 , wherein said electrolyte is selected from the group consisting of H 3 BO 3 +(CH 3 ) 4 NOH, H 3 BO 3 +Na 2 B 4 O 7 , (NR 4 )(BF 4 ), or (NR 4 )(PF 6 ), where R stands for alkyl group.  
     
     
         8 . A method of fabricating an integrated circuit, comprising the steps of: 
 forming a copper seed layer over a semiconductor body, wherein copper oxide forms at a surface of said copper seed layer    electrochemically reducing said copper oxide by placing said semiconductor body in an electrolyte having a high pH and applying a current in said seed layer;    rinsing said semiconductor body; and    electrochemically depositing a copper layer on said copper seed layer.    
     
     
         9 . The method of  claim 8 , wherein said electrochemically reducing step and said electrochemically depositing step occur in the same cluster tool.  
     
     
         10 . The method of  claim 8 , wherein said electrochemically reducing step occurs in a first tool and said electrochemically depositing step occurs in a second, separate, tool.  
     
     
         11 . The method of  claim 8 , wherein said electrolyte is selected from the group consisting of H 3 BO 3 +(CH 3 ) 4 NOH, H 3 BO 3 +Na 2 B 4 O 7 , (NR 4 )(BF 4 ), or (NR 4 )(PF 6 ), where R stands for alkyl group.  
     
     
         12 . The method of  claim 8 , further comprising the step of transferring said semiconductor body in an inert atmosphere between said rinsing step and said electrochemically depositing step.  
     
     
         13 . The method of  claim 8 , wherein said current is a cathodic current applied to reduce said copper oxide.