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 copper metal to features of a damascene processed workpiece comprising: 
 providing a workpiece having a barrier layer formed on at least a portion of the features of the damascene processed workpiece, at least a portion of a surface of the barrier layer being exposed;    providing a first electroplating bath including a source of copper metal ions as a principal metal species to be deposited as a seed layer during a first electroplating deposition, wherein the first electroplating bath comprises an alkaline bath;    contacting the at least a portion of a surface of the barrier layer with the first electroplating bath; and    providing electroplating power between the damascene processed workpiece and an anode disposed in electrical contact with the first electroplating bath to electroplate the copper metal species to form a seed layer directly onto the at least a portion of the surface of the barrier layer.    
     
     
         7 . The process of  claim 6 , wherein the copper metal ions are combined with ions of at least one other metal to deposit an alloy.  
     
     
         8 . The process of  claim 6 , further comprising depositing additional copper metal onto the seed layer using a second deposition.  
     
     
         9 . The process of  claim 6 , wherein the workpiece has sub-micron features.  
     
     
         10 . The process of  claim 6 , wherein the workpiece has features comprising contact openings of less than about 0.5 microns.  
     
     
         11 . The process of  claim 9 , further comprising performing a second electroplating deposition using a second electroplating bath to deposit copper onto the copper seed layer to fill the contact openings of the sub-micron features.  
     
     
         12 . The process of  claim 11 , wherein the second electroplating bath comprises an acidic bath.  
     
     
         13 . The process of  claim 6 , wherein the alkaline bath has a pH of at least about 9.0.  
     
     
         14 . The process of  claim 6 , wherein the first electroplating bath further comprises boric acid and a metal ion complexing agent.  
     
     
         15 . The process of  claim 6 , wherein the source of copper metal ions comprises copper sulfate at a level of from about 0.03 to about 0.25 M.  
     
     
         16 . The process of  claim 6 , wherein the source of copper metal ions comprises copper sulfate at a level of from about 0.04 to about 0.1 M.  
     
     
         17 . The process of  claim 6 , wherein the source of copper metal ions comprises copper sulfate at a level of about 0.1 M.  
     
     
         18 . 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.  
     
     
         19 . The process of  claim 11 , wherein metal is deposited in the second deposition process at a higher rate than in the first deposition process.  
     
     
         20 . The process of  claim 14 , wherein the metal ion complexing agent comprises EDTA, ED, polycarboxylic acid, or mixtures thereof.  
     
     
         21 . The process of  claim 14 , wherein the complexing agent comprises ED having a concentration in the first electroplating bath in the range of from about 0.03 to about 1.0 M.  
     
     
         22 . The process of  claim 14 , wherein the complexing agent is citric acid.  
     
     
         23 . The process of  claim 14 , wherein the complexing agent comprises EDTA having a concentration in the first electroplating bath in the range of from about 0.03 to about 1.0 M.  
     
     
         24 . The process of  claim 6 , wherein the source of copper metal ions comprises copper sulfate.  
     
     
         25 . The process of  claim 24 , wherein the complexing agent has a molar ratio relative to copper sulfate of from about 1 to about 4.  
     
     
         26 . The process of  claim 24 , wherein the complexing agent has a molar ratio relative to copper sulfate of about 2.  
     
     
         27 . A process for applying a copper 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 with at least a portion of a surface exposed;    providing a first electroplating bath including a source of metal ions as a principal metal species to be deposited during electroplating, wherein the source of metal ion is copper sulfate at a level of greater than about 0.8 M, and a metal ion complexing agent;    contacting the at least a portion of the surface of the barrier layer of the workpiece with the first electroplating bath; and    providing electroplating power between at least one surface of the workpiece and an anode disposed in electrical contact with the first electroplating bath to electroplate the copper metal species onto the at least a portion of the barrier layer to form a copper metal seed layer directly thereon.    
     
     
         28 . The process of  claim 27 , wherein the workpiece has sub-micron features.  
     
     
         29 . The process of  claim 27 , wherein the workpiece has features comprising contact openings of less than about 0.5 microns.  
     
     
         30 . The process of  claim 27 , further comprising depositing additional copper metal onto the copper metal seed layer, using a second electroplating bath for a second deposition process.  
     
     
         31 . The process of  claim 30 , wherein the second electroplating bath comprises an acidic bath.  
     
     
         32 . The process of  claim 27 , wherein the first electroplating bath comprises an alkaline bath.  
     
     
         33 . A process for applying a copper seed layer to a damascene processed workpiece comprising: 
 providing a first electroplating bath including a source of copper metal ions as a principal metal species to be deposited during electroplating, wherein the first electroplating bath is at a pH of from about 5.0 to about 13.0;    providing a barrier layer formed on at least a portion of the sub-micron features of the damascene processed workpiece, at least a portion of a surface of the barrier layer being exposed;    contacting the at least a portion of a surface of the barrier layer with the first electroplating bath; and    providing electroplating power between at least one surface of the workpiece and an anode disposed in electrical contact with the first electroplating bath to electroplate the copper seed layer onto the at least a portion of the surface of the barrier layer.    
     
     
         34 . The process of  claim 33 , wherein the first electroplating bath is at a pH of about 9.5.  
     
     
         35 . The process of  claim 33 , further comprising performing a second electroplating deposition using a second electroplating bath to deposit additional copper onto the copper seed layer.  
     
     
         36 . The process of  claim 35 , wherein the second electroplating bath comprises an acidic bath.  
     
     
         37 . A process for electroplating a copper metal onto a barrier layer of a workpiece comprising: 
 providing a workpiece on which one or more microstructures having contact openings of less than about 0.5 microns are formed, the workpiece microstructures having a barrier layer formed in the contact openings with at least a portion of a surface of the barrier layer in the contact openings being exposed;    providing a first electroplating bath including a source of copper metal ions as a principal metal species to be deposited during electroplating and a polycarboxylic acid;    contacting the at least a portion of the surface of the barrier layer to the first electroplating bath; and    providing electroplating power between the at least a portion of the surface of the barrier layer and an anode disposed in electrical contact with the first electroplating bath to electroplate a copper seed layer directly on at least a portion of the surface of the barrier layer.    
     
     
         38 . The process of  claim 37 , wherein the copper metal ions are combined with ions of at least one other metal.  
     
     
         39 . The process of  claim 37 , further comprising depositing additional copper metal onto the copper seed layer using a second deposition process to fill the contact openings of the microstructures.  
     
     
         40 . The process of  claim 39 , wherein the second electroplating process utilizes a second electroplating bath comprising an acidic bath.  
     
     
         41 . The process of  claim 37 , wherein the first electroplating bath comprises an alkaline bath.  
     
     
         42 . The process of  claim 41 , wherein the alkaline bath has a pH of at least about 9.0.  
     
     
         43 . The process of  claim 37 , wherein the first electroplating bath further comprises boric acid and a metal ion complexing agent.  
     
     
         44 . A process for applying a copper metal structure to a workpiece comprising: 
 providing a workpiece having a dielectric layer in which trenches and/or vias are formed and includes a barrier layer formed in the trenches and/or vias;    providing a first electroplating bath including a source of copper metal ions as a principal metal species to be deposited during electroplating and a metal ion complexing agent;    exposing a surface of the barrier layer to the first electroplating bath; and    providing electroplating power between at least one surface of the workpiece and an anode disposed in electrical contact with the first electroplating bath to electroplate the copper metal species onto the surface of the barrier layer in the trenches and/or vias.    
     
     
         45 . The process of  claim 44 , wherein the source of copper metal ions comprises copper sulfate included at a level of from about 0.03 to about 0.25 M.  
     
     
         46 . The process of  claim 44 , wherein the first electroplating bath further comprises boric acid and a metal ion complexing agent.  
     
     
         47 . The process of  claim 44 , wherein the first electroplating bath comprises an alkaline bath.  
     
     
         48 . The process of  claim 47 , 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.  
     
     
         49 . The process of  claim 44 , wherein the metal ion complexing agent comprises EDTA, ED, polycarboxylic acid, or mixtures thereof.  
     
     
         50 . The process of  claim 44 , 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.