Copper anode for semiconductor interconnects

Abstract

A copper anode is described for use in electroplating semiconductor interconnects, where said anode has a preferred grain size or crystallographic orientation and a preferred chemical composition. The microstructure of the anode may be of two types (1) grains smaller than 100 microns in any dimension or (2) large columnar grains aligned perpendicularly to the anode corroding surface. Copper cathodes of not less than 99.99 weight percent of copper are alloyed to achieve an anode with a phosphor content of 0.045 to 0.060 weight percent.

What is claimed is:  
     
         1 . A copper anode for the electroplating of a substrate wherein the copper grain size in the anode is less than 100 microns in any dimension.  
     
     
         2 . The copper anode of  claim 1 , wherein the substrate is a silicon wafer.  
     
     
         3 . The copper anode of  claim 1 , wherein the anode is formed from a copper billet using a series of cold working and annealing steps.  
     
     
         4 . The copper anode of  claim 1 , wherein the anode is manufactured from a copper cathode having a purity of at least 99.99% and wherein the anode has a phosphor content of between 0.045 and 0.060 weight percent.  
     
     
         5 . A copper anode for the electroplating of a substrate wherein the copper grains in the anode are parallel and columnar shaped and oriented so as to be aligned perpendicular to a corroding surface of the anode.  
     
     
         6 . The copper anode of  claim 5 , wherein the substrate is a silicon wafer.  
     
     
         7 . The copper anode of  claim 5 , wherein the anode is formed using a continuous casting process.  
     
     
         8 . The copper anode of  claim 5 , wherein the anode is manufactured from a copper cathode having a purity of at least 99.99% and wherein the anode has a phosphor content of between 0.045 and 0.060 weight percent.  
     
     
         9 . A copper anode for the electroplating of semiconductor interconnects wherein the anode is manufactured from a copper cathode having a purity of at least 99.99% and wherein the final anode has a phosphor content of between 0.045 and 0.060 weight percent.  
     
     
         10 . A copper anode according to  claim 9 , wherein the anode is either continuously cast or cold worked and annealed.  
     
     
         11 . A method for electroplating copper on a substrate using a copper anode, wherein at least one of the following conditions are satisfied: 
 a) the anode has a copper grain size of less than 100 microns;    b) the copper grains in the anode are oriented so as to be aligned perpendicular to a corroding surface of the anode; and    c) the anode has a phosphor content of between 0.045 and 0.060 weight percent and is formed from a copper cathode comprising at least 99.99% copper.    
     
     
         12 . The method of  claim 11 , wherein said electroplating is conducted in a electroplating chamber including an electrolyte plating solution.  
     
     
         13 . The method of  claim 11 , wherein said substrate is a silicon wafer.  
     
     
         14 . The method of  claim 12 , wherein said substrate functions as a cathode and further wherein a current is applied across the chamber from the anode to the cathode.  
     
     
         15 . The method of  claim 14 , wherein Cu 2+  ions are formed at the anode and deposited on the substrate.  
     
     
         16 . A method for the electroplating of semiconductor interconnects on a silicon substrate including the steps of: 
 immersing the silicon substrate in an electroplating chamber containing an electrolyte solution;    positioning a copper anode and a cathode in the electroplating chamber;    mounting the silicon substrate on the cathode; and    providing a current between the anode and cathode to effect the transfer of Cu 2+  ions from the anode to a surface of the silicon substrate; wherein at least one of the following conditions are satisfied: 
 a) the anode has a copper grain size of less than 100 microns; and  
 b) the copper grains in the anode are oriented so as to be aligned perpendicular to a corroding surface of the anode.  
   
     
     
         17 . A method according to  claim 16 , wherein the anode has a phosphor content of between 0.045 and 0.060 weight percent and is formed from a copper cathode comprising at least 99.99% copper.