Apparatus and method for electrolytically depositing copper on a semiconductor workpiece

Abstract

A process for applying a metallization interconnect structure to a semiconductor workpiece having a barrier layer deposited on a surface thereof is set forth. The process includes the forming of an ultra-thin metal seed layer on the barrier layer. The ultra-thin seed layer having a thickness of less than or equal to about 500 Angstroms. The ultra-thin seed layer is then enhanced by depositing additional metal thereon to provide an enhanced seed layer. The enhanced seed layer has a thickness at all points on sidewalls of substantially all recessed features distributed within the workpiece that is equal to or greater than about 10% of the nominal seed layer thickness over an exteriorly disposed surface of the workpiece.

1 . A process for applying a metallization interconnect structure to a semiconductor workpiece, the workpiece including a barrier layer deposited on a surface thereof the process comprising the steps of: 
 (a) forming an ultra-thin metal seed layer on the barrier layer, the seed layer having a thickness of less than equal to about 500 Angstroms;    (b) enhancing the ultra-thin seed layer by depositing additional metal to provide an enhanced seed layer, the enhanced seed layer having a thickness at all points on sidewalls of substantially all recessed features distributed within the workpiece that is equal to or greater than about 10% of the nominal seed layer thickness over an exteriorly disposed surface of the workpiece.    
     
     
         2 . The process of  claim 1  wherein the additional metal is copper.  
     
     
         3 . The process of  claim 1  wherein the ultra-thin seed layer is enhanced by a process comprising an electrochemical deposition step.  
     
     
         4 . The process of  claim 3  wherein the electrochemical deposition step occurs in an alkaline bath.  
     
     
         5 . The process of  claim 4  wherein the alkaline bath comprises metal ions and an agent effective in complexing the metal ions.  
     
     
         6 . The process of  claim 1  wherein the ultra-thin metal seed layer formed in step (a) is formed by physical vapor deposition.  
     
     
         7 . The process of  claim 1  wherein the ultra-thin metal seed layer formed in step (a) has a thickness of about 50 to about 500 Angstroms.  
     
     
         8 . The process of  claim 7  wherein the ultra-thin metal layer formed in step (a) has a thickness of about 100 to about 250 Angstroms.  
     
     
         9 . The process of  claim 1  wherein the complexing agent is comprised of one or more complexing agents selected from EDTA, ED, and polycarboxylic acid.  
     
     
         10 . The process of  claim 5  wherein the complexing agent is comprised of EDTA and the EDTA in the bath has a concentration within the range of 0.03 to 1.0 M.  
     
     
         11 . The process of  claim 9  wherein the complexing agent is comprised of ED and wherein the ED in the electrolytic bath has a concentration within the range of 0.03 to 1.0 M.  
     
     
         12 . The process of  claim 10  wherein the complexing agent is comprised of EDTA and the EDTA has a concentration within the range of 0.1 to 0.4 M.  
     
     
         13 . The process of  claim 9  wherein the complexing agent is comprised of citric acid and the citric acid in the bath has a concentration within the range of 0.03 to 1.0 M.  
     
     
         14 . The process of  claim 4  and further comprising the step of subjecting the semiconductor workpiece to a further electrochemical deposition process in an acidic electrolytic solution to complete deposition of the metal to a thickness needed for the formation of the interconnect structure.  
     
     
         15 . The process of  claim 14  and further comprising the step of subjecting the semiconductor workpiece to a rinsing process after electrochemical deposition in the outline bath and prior to the further electrochemical copper deposition procession an acidic electrolytic solution.  
     
     
         16 . In a manufacturing line including a plurality of apparatus for the manufacture of integrated circuits, one or more apparatus of the plurality of apparatus being used for applying a copper metallization interconnect structure to a surface of a semiconductor workpiece used to form the integrated circuits, the one or more apparatus comprising: 
 means for applying a conductive ultra-thin seed layer to a surface of the semiconductor workpiece,    means for electrochemically enhancing the conductive ultra-thin seed layer to render it suitable for subsequent electrochemical application of the copper interconnect metallization to a predetermined thickness representing a bulk portion of the copper interconnect metallization structure.    
     
     
         17 . One or more apparatus as claimed in  claim 16  wherein the means for applying is further defined by means for applying a conductive ultra-thin copper seed layer to a barrier layer surface of the semiconductor workpiece.  
     
     
         18 . One or more apparatus as claimed in  claim 16  wherein the means for applying is further defined by means for applying a conductive ultra-thin copper seed layer to a barrier layer surface of the semiconductor workpiece using a PVD process.  
     
     
         19 . One or more apparatus as claimed in  claim 16  wherein the means for applying is further defined by means for applying a conductive ultra-thin copper seed layer to a barrier layer surface of the semiconductor workpiece using a CVD process.  
     
     
         20 . One or more apparatus as claimed in  claim 17  wherein the means for electrochemically enhancing the conductive ultra-thin seed layer is further defined by means for electrochemically enhancing the conductive ultra-thin seed layer by electrochemically depositing copper using an alkaline copper bath having a complexing agent.  
     
     
         21 . One or more apparatus as claimed in  claim 20  wherein the electrochemical enhancement of the ultra-thin seed layer takes place at a plating voltage having a magnitude that is at least about or greater than 1.1 volts.  
     
     
         22 . One or more apparatus as claimed in  claim 20  wherein the alkaline bath has a pH> or equal to about 9.0.  
     
     
         23 . One or more apparatus as claimed in  claim 20  wherein the complexing agent is comprised of EDTA.  
     
     
         24 . One or more apparatus as claimed in  claim 20  wherein the complexing agent is comprised of ED.  
     
     
         25 . One or more apparatus as claimed in  claim 20  wherein the complexing agent is a comprised of a carboxylic acid or salt thereof.  
     
     
         26 . One or more apparatus as claimed in claims  25  wherein the complexing agent is citric acid or salt thereof.  
     
     
         27 . One or more apparatus as claimed in  claim 20  and further comprising means for electrochemically adding a further layer of copper over the conductive ultra-thin seed layer by electrochemically depositing copper using an acidic copper bath.  
     
     
         28 . One or more apparatus as claimed in  claim 27  wherein the electrochemical enhancement of the ultra-thin seed layer takes place at a plating voltage having a magnitude that is greater than the magnitude of the plating voltage in the acidic copper bath.  
     
     
         29 . One or more apparatus as claimed in  claim 28  and further comprising means for rinsing the semiconductor workpiece prior to its introduction to the means for electrochemically adding a further layer of copper.  
     
     
         30 . A process for applying a metallization interconnect structure to a a semiconductor workpiece, the workpiece including a barrier layer deposited on a surface thereof, the process comprising the steps of: 
 (a) forming an ultra-thin metal seed layer on the barrier layer, the seed layer having a thickness of less than or equal to about 500 Angstroms;    (b) subjecting the semiconductor workpiece to an electrochemical copper deposition process in an alkaline electrolytic bath having copper ions complexed with a complexing agent such that additional copper is deposited on the ultra-thin copper seed layer to thereby enhance the seed layer.    
     
     
         31 . The process of  claim 30  wherein the ultra-thin metal seed layer formed in step (a) is formed by physical vapor deposition.  
     
     
         32 . The process of  claim 30  wherein the ultra-than seed layer formed in step (a) has a thickness of about 50 to about 500 Angstroms.  
     
     
         33 . The process of  claim 32  wherein the ultra-thin seed layer formed in step (a) has a thickness of about 100 to about 250 Angstroms.  
     
     
         34 . The process of  claim 33  wherein the ultra-thin seed layer formed in step (a) has a thickness of about 200 Angstroms.  
     
     
         35 . The process of  claim 30  wherein the alkaline electrolytic bath has a pH of at least 9.0.  
     
     
         36 . The process of  claim 30  wherein the copper ions in the electrolytic bath are provided by copper sulfate.  
     
     
         37 . The process of  claim 36  wherein the copper sulfate in the electrolytic bath has a concentration within the range of 0.03 to 0.25 M.  
     
     
         38 . The process of  claim 36  wherein the concentration of copper sulfate is about 0.1 M.  
     
     
         39 . The process of  claim 30  wherein the copper complexing agent is comprised of a copper complexing agent selected from EDTA, ED, and citric acid.  
     
     
         40 . The process of  claim 39  wherein the complexing agent is comprised of EDTA and the EDTA in the electrolytic bath has a concentration within the range of 0.03 to 1.0 M  
     
     
         41 . The process of  claim 39  wherein the complexing agent is comprised of ED and the ED in the electrolytic bath has a concentration within the range of 0.03 to 1.0 M.  
     
     
         42 . The process of  claim 39  wherein the complexing agent is comprised of EDTA and the EDTA has a concentration within the range of 0.1 to 0.4 M.  
     
     
         43 . The process of  claim 39  wherein the complexing agent is comprised of citric acid and the citric acid in the electrolytic bath has a concentration within the range 0.03 to 1.0 M.  
     
     
         44 . The process of  claim 43  wherein the citric acid has a concentration within the range of 0.1 to 0.4 M  
     
     
         45 . The process of  claim 30  and further comprising the step of subjecting the semiconductor workpiece to a further electrochemical copper deposition process in an acidic electrolytic solution to complete deposition of the copper to a thickness needed for the formation of the copper interconnect structure.  
     
     
         46 . The process of  claim 45  and further comprising the step of subjecting the semiconductor workpiece to a rinsing process after step (b) and prior to the further electrochemical copper deposition process in an acidic electrolytic solution.  
     
     
         47 . A semiconductor workpiece comprising: 
 a plurality of the recessed structures distributed in a face of the semiconductor workpiece;    an enhanced seed layer having a thickness at all points on sidewalls of substantially all recessed features distributed within the workpiece that is equal to or greater than about 10% of the nominal seed layer thickness over an exteriorly disposed surface of the workpiece.    
     
     
         48 . A semiconductor workpiece as claimed in  claim 48  wherein the thickness of the sidewalls of substantially all recessed features is equal to or greater than about 20%.