Apparatus and method for electrolytically depositing copper on a semiconductor workpiece

Abstract

This invention employs a novel approach to the copper metallization of a workpiece, such as a semiconductor workpiece. In accordance with the invention, an alkaline electrolytic copper bath is used to electroplate copper onto a seed layer, electroplate copper directly onto a barrier layer material, or enhance an ultra-thin copper seed layer which has been deposited on the barrier layer using a deposition process such as PVD. The resulting copper layer provides an excellent conformal copper coating that fills trenches, vias, and other microstructures in the workpiece. When used for seed layer enhancement, the resulting copper seed layer provide an excellent conformal copper coating that allows the microstructures to be filled with a copper layer having good uniformity using electrochemical deposition techniques. Further, copper layers that are electroplated in the disclosed manner exhibit low sheet resistance and are readily annealed at low temperatures.

1 - 5 . (canceled)  
     
     
         6 . A method for applying a metal to a microelectronic workpiece having submicron features and a barrier layer on the submicron features, the method comprising: 
 contacting the barrier layer with an alkaline plating solution including a source of metal ions as a principal metal species to be deposited onto the microelectronic workpiece and ethylene diamine as a complexing agent; and    electroplating the metal ions from the plating solution directly onto the barrier layer to form a metal layer over the barrier layer.    
     
     
         7 . The method of  claim 6  wherein the barrier layer comprises tantalum and the metal ions comprise copper.  
     
     
         8 . The method of  claim 6  wherein the plating solution has a pH of approximately 9.0 to approximately 9.5.  
     
     
         9 . The method of  claim 6  wherein the barrier layer comprises tantalum, the metal ions comprise copper, and the plating solution has a pH of approximately 9.0 to approximately 9.5.  
     
     
         10 . The method of  claim 9  wherein electroplating the metal ions comprises applying a plating voltage greater than −1.0 V.  
     
     
         11 . The method of  claim 9  wherein the plating solution further comprises boric acid.  
     
     
         12 . The method of  claim 6 , further comprising removing the workpiece from the alkaline plating solution, contacting the metal layer formed over the barrier layer with an acidic plating solution containing the metal ions as a principal species to be deposited onto the microelectronic workpiece, and electroplating additional metal of the principal metal species onto the metal layer.  
     
     
         13 . A method of applying metal to a microelectronic workpiece having submicron features and a barrier layer on the submicron features, the method comprising: 
 contacting the barrier layer with an alkaline solution including a source of metal ions as a principal species to be deposited onto the microelectronic workpiece;    adhering the metal ions from the plating solution directly to the barrier layer to form a metal layer over the barrier layer; and    annealing the microelectronic workpiece after forming the metal layer over the barrier layer.    
     
     
         14 . The method of  claim 13  wherein the metal ions comprise copper ions and the alkaline plating solution further comprises ethylene diamine as a complexing agent.  
     
     
         15 . The method of  claim 14  wherein the alkaline plating solution has a pH of approximately 9.0 to approximately 9.5.  
     
     
         16 . The method of  claim 14  wherein the barrier layer comprises tantalum and the plating solution has a pH of approximately 9.0 to approximately 9.5.  
     
     
         17 . The method of  claim 14  wherein the alkaline plating solution further comprises boric acid.  
     
     
         18 . The method of  claim 14  wherein adhering the metal ions to the barrier layer comprises electroplating the metal ions onto the barrier layer by applying a voltage greater than −1.0 V.  
     
     
         19 . The method of  claim 14 , further comprising removing the workpiece from the alkaline plating solution, contacting the metal layer formed over the barrier layer with an acidic plating solution, and electroplating additional metal of the principal metal species onto the metal layer.  
     
     
         20 . A method for applying copper to a microelectronic workpiece having submicron features and a barrier layer including tantalum on the submicron features, the method comprising: 
 contacting the barrier layer including tantalum with an alkaline plating solution including copper ions as a principal metal species to be deposited onto the microelectronic workpiece, ethylene diamine as a complexing agent, and boric acid; and    electroplating the copper ions from the alkaline plating solution directly onto the barrier layer including tantalum to form a copper deposit over the barrier layer.    
     
     
         21 . The method of  claim 20  wherein the plating solution has a pH of approximately 9.0 to approximately 9.5.  
     
     
         22 . The method of  claim 21  wherein electroplating the copper ions comprises applying a plating voltage greater than −1.0 V.  
     
     
         23 . The method of  claim 20 , further comprising removing the workpiece from the alkaline plating solution, contacting the copper deposit formed over the barrier layer with an acidic plating solution containing copper ions as the principal species to be deposited onto the microelectronic workpiece, and electroplating additional copper onto the copper deposit.  
     
     
         24 . The method of  claim 23 , further comprising annealing the microelectronic workpiece after electroplating the additional copper onto the copper deposit.  
     
     
         25 . A method of applying copper to a microelectronic workpiece having submicron features and a barrier layer on the submicron features, the method comprising: 
 contacting the barrier layer with an alkaline solution having a pH of approximately 9.0 to approximately 9.5 and including copper ions as a principal species to be deposited onto the microelectronic workpiece and ethylene diamine;    adhering the copper ions directly to the barrier layer to form a copper deposit over the barrier layer; and    removing the workpiece from the alkaline plating solution, contacting the copper deposit formed over the barrier layer with an acidic plating solution containing copper ions as the principal species to be deposited onto the microelectronic workpiece, and electroplating additional copper onto the copper deposit.    
     
     
         26 . The method of  claim 25  wherein the barrier layer comprises tantalum and the plating solution has a pH of approximately 9.0 to approximately 9.5.  
     
     
         27 . The method of  claim 25  wherein the alkaline plating solution further comprises boric acid.  
     
     
         28 . The method of  claim 25  wherein adhering the copper ions to the barrier layer comprises electroplating the copper ions onto the barrier layer by applying a voltage greater than −1.0 V.  
     
     
         29 . The method of  claim 25 , further comprising annealing the microelectronic workpiece after electroplating the additional copper onto the copper deposit.