Method and apparatus for electroplating a semiconductor wafer

Abstract

A method, apparatus and anode for plating copper or other metals onto a barrier or seed layer of a wafer surface is described. A copper layer of uniform thickness is plated on the surface by, for instance, maintaining a constant current density between the anode and wafer surface. Several configurations of anodes are described for obtaining the constant current density.

What is claimed is:  
     
         1 . A method for electroplating a wafer comprising: 
 connecting a first electrode on the periphery of a wafer to provide an electrical path to a surface of the wafer; and    applying a potential with respect to the first electrode to a second electrode disposed adjacent to the surface of the wafer, such that the potential between the second electrode and the surface of the wafer varies across the surface of the wafer.    
     
     
         2 . The method of  claim 1 , wherein the variation results in a substantially uniform current density between the second electrode and the surface of the wafer.  
     
     
         3 . The method of  claim 2 , wherein the second electrode comprises copper.  
     
     
         4 . The method of  claim 3 , including forming a barrier layer or seed layer on the surface of the wafer before connecting the first electrode to the wafer.  
     
     
         5 . A method for electroplating a semiconductor wafer comprising: 
 applying at least one potential to an anode disposed adjacent to a surface of the wafer such that the current flow between the surface of the wafer and the anode is substantially uniform over the surface of the wafer; and    forming a layer of relatively uniform thickness on the surface of the wafer as a result of the uniform current flow.    
     
     
         6 . The method of  claim 5 , including forming a barrier layer on the surface of the wafer prior to the applying of at least one potential to the anode.  
     
     
         7 . The method of  claim 5 , including forming a seed layer on the surface of the wafer prior to the applying of at least one potential to the anode.  
     
     
         8 . The method of  claim 5 , wherein the layer includes copper.  
     
     
         9 . The method of  claim 5 , wherein during the forming of the layer, the voltage drop between the anode and the surface of the wafer is greater at the center of the wafer than it is at distances away from the center.  
     
     
         10 . An apparatus for electroplating a wafer comprising: 
 a conductive clamp for engaging the periphery of a wafer; and    an anode disposed above the wafer, comprising a plurality of conductive elements disposed in an insulative member, the conductive elements being coupled to at least one source of potential.    
     
     
         11 . The apparatus of  claim 10 , wherein the conductive elements comprise a plurality of rods having a uniform density in the insulative member.  
     
     
         12 . The apparatus of  claim 10 , wherein the conductive elements comprise a plurality of rods having a higher density in a center of the anode when compared to a distance away from the center of the anode.  
     
     
         13 . The apparatus of  claim 10 , wherein the conductive elements include a plurality of concentric, annular members.  
     
     
         14 . The apparatus of  claim 10 , wherein a plurality of voltages are applied to the conductive elements with a higher voltage being applied to conductive elements disposed at a center of the anode, when compared to conductive elements disposed at a distance away from the center of the anode.  
     
     
         15 . The apparatus of  claim 10 , wherein the conductive elements comprise copper.  
     
     
         16 . The apparatus of  claim 11 , wherein the conductive elements comprise copper.  
     
     
         17 . The apparatus of  claim 12 , wherein the conductive elements comprise copper.  
     
     
         18 . The apparatus of  claim 13 , wherein the conductive elements comprise copper.  
     
     
         19 . The apparatus of  claim 14 , wherein the conductive elements comprise copper.  
     
     
         20 . An apparatus for electroplating a wafer comprising: 
 a conductive clamp disposed about the periphery of the electrode,    a lenticular shaped anode disposed above a surface of the wafer such that the anode is closer to the wafer at a center of the wafer when compared to the periphery of the wafer.    
     
     
         21 . The apparatus of  claim 20 ,wherein the anode is copper.  
     
     
         22 . An apparatus for electroplating a wafer comprising: 
 an electrode disposed about the periphery of the wafer;    a cell having an inlet and an outlet facing a surface of the wafer, the cell carrying an electroplating fluid and being movable such that the outlet of the cell, sweeps over substantially the entire surface of the wafer;    an anode disposed within the cell; and    a source of potential applied between the electrode and the anode.    
     
     
         23 . The apparatus of  claim 22 , wherein the source of potential is varied as the cell moves.  
     
     
         24 . The apparatus of  claim 23 , wherein the rate at which the cell moves is varied.