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 process for applying a metal structure to a workpiece comprising: 
 providing a workpiece on which one or more microelectronic devices are to be formed, the workpiece having a barrier layer wherein at least a portion of a surface of the barrier layer is uncovered;    providing a first electroplating bath including a source of copper ions as a principal species to be deposited, the first electroplating bath comprising an alkaline bath;    exposing at least a portion of the surface of the barrier layer to the first electroplating bath; and    applying electroplating power between at least one surface of the workpiece and an electrode disposed in electrical contact with the first electroplating bath to electroplate a copper seed layer directly onto at least a portion of the surface of the barrier layer in a first electrolytic deposition process, wherein power is applied during at least a portion of the first deposition process for a workpiece surface current density of between about 1.0 mA/cm 2  and about 5.0 mA/cm 2 .    
     
     
         7 . The process of  claim 6 , wherein power is applied during at least a portion of the first deposition process at a workpiece surface current density of about 2.0 mA/cm 2 .  
     
     
         8 . The process of  claim 6 , wherein power is applied at a workpiece surface current density of between 1.0 mA/cm 2  and 5.0 mA/cm 2  over a time period of between 1.0 and 5.0 minutes.  
     
     
         9 . The process of  claim 6 , wherein power is applied in periodic pulses during deposition.  
     
     
         10 . The process of  claim 9 , wherein power is applied in forward pulses having a period of about 2 msec at a 50% duty cycle.  
     
     
         11 . The process of  claim 6 , further comprising depositing additional copper onto the copper seed layer deposited in the first deposition process using a second deposition process that is different than the first electrolytic deposition process.  
     
     
         12 . The process of  claim 6 , wherein the copper seed layer comprises a copper alloy.  
     
     
         13 . The process of  claim 11 , wherein the second deposition process occurs in an acidic electrolytic bath.  
     
     
         14 . The process of  claim 11 , wherein metal is deposited in the second deposition process at a higher rate than in the first deposition process.  
     
     
         15 . The process of  claim 6 , wherein the source of copper ions comprises copper sulfate included at a level of from about 0.03 to about 0.25 M.  
     
     
         16 . The process of  claim 6 , wherein the first electroplating bath further comprises boric acid and a metal ion complexing agent.  
     
     
         17 . The process of  claim 6 , wherein the alkaline bath has a pH of at least about 9.0.  
     
     
         18 . The process of  claim 6 , further comprising performing a second electroplating deposition using a second electroplating bath having a different composition than the first electroplating bath, to deposit additional copper onto the copper seed layer.  
     
     
         19 . The process of  claim 6 , wherein the alkaline bath is pH adjusted with an alkaline agent comprising potassium hydroxide, tetramethylammonium hydroxide, sodium hydroxide, ammonium hydroxide, an organic hydroxide, or mixtures thereof.  
     
     
         20 . The process of  claim 16 , wherein the metal ion complexing agent comprises EDTA, ED, polycarboxylic acid, or mixtures thereof.  
     
     
         21 . The process of  claim 19 , wherein the complexing agent comprises ED and wherein the ED in the electrolytic bath has a concentration within the range of from about 0.03 to about 1.0 M.  
     
     
         22 . The process of  claim 16 , wherein the complexing agent is citric acid.  
     
     
         23 . The process of  claim 6 , wherein the source of metal ions comprises copper sulfate and the complexing agent comprises ED.  
     
     
         24 . The process of  claim 22 , further comprising tetramethylammonium hydroxide in an amount sufficient to adjust the pH of the first electroplating bath to at least about 9.0.  
     
     
         25 . A process for applying a metal structure to a workpiece comprising: 
 providing a workpiece on which one or more microelectronic devices are to be formed, the workpiece having a barrier layer wherein at least a portion of a surface of the barrier layer is uncovered;    providing a first electroplating bath including a source of copper ions to be deposited, a metal ion complexing agent and an alkaline agent in an amount sufficient to adjust the pH of the bath to at least about 9.0;    exposing at least a portion of the surface of the barrier layer to the first electroplating bath; and    applying electroplating power between at least one surface of the workpiece and an electrode disposed in electrical contact with the first electroplating bath to electroplate a copper seed layer directly onto at least a portion of the surface of the barrier layer in a first electrolytic deposition process, wherein power is applied during at least a portion of the first deposition process for a workpiece surface current density of between about 1.0 mA/cm 2  and about 5.0 mA/cm 2 .    
     
     
         26 . A process for applying a metal structure to a workpiece comprising: 
 providing a first electroplating bath including a source of copper ions to be deposited as a seed layer during subsequent electroplating, boric acid, and a metal ion complexing agent;    providing a workpiece having a barrier layer, wherein at least a portion of a surface of the barrier layer is exposed;    exposing at least a portion of the surface of the barrier layer to the first electroplating bath; and    applying electroplating power between at least one surface of the workpiece and an electrode disposed in electrical contact with the first electroplating bath to electroplate a copper seed layer directly onto at least a portion of the surface of the barrier layer in an electrolytic first deposition process, wherein power is applied during at least a portion of the first deposition process in periodic pulses.    
     
     
         27 . The process of  claim 26 , wherein the electroplating power is applied during at least a portion of the first deposition process for a workpiece surface current density of between about 1.0 mA/cm 2  and about 5.0 mA/cm 2 .  
     
     
         28 . The process of  claim 26 , wherein power is applied in forward pulses having a period of about 2 msec at a 50% duty cycle.  
     
     
         29 . The process of  claim 26 , wherein pulsed power is applied for a period of from about 1.0 to about 5.0 minutes.  
     
     
         30 . The process of  claim 26 , further comprising depositing additional copper metal onto the copper seed layer using a second deposition process that is different from the first deposition process.