Abrasive free polishing in copper damascene applications

Abstract

An abrasive free wafer polishing device utilizing an abrasive free chemical solution includes a workpiece fixture ( 11 ), a brush assembly ( 12 ) and a high flow rate fluid dispenser ( 13 ). The fluid dispenser ( 13 ) dispenses an abrasive free chemical solution to an interface at which the workpiece and the brush assembly come into contact with a flow rate of at least 50 ml/min. The abrasive free chemical solution and brush assembly ( 12 ) operate to chemically react with a metal (e.g. copper) on the workpiece and abrade away the reacted copper during a polishing process.

We claim:  
     
         1 . A process for polishing a metal layer of a workpiece, the process comprising: 
 loading a workpiece into a polishing tool;    providing an abrasive free chemical solution to the metal layer of the workpiece at a flow rate of about 50 cc/min to about 500 cc/min; and    polishing the metal layer on the workpiece.    
     
     
         2 . The process of  claim 1  wherein the abrasive free chemical solution is provided to an interface between the workpiece and an abrading surface via through-holes in the abrading surface.  
     
     
         3 . The process of  claim 1  wherein the process is performed at a temperature between about 5 to about 40° C.  
     
     
         4 . The process of  claim 1  wherein the process is performed at a temperature from about 10 to about 30° C.  
     
     
         5 . The process of  claim 1  where the polishing is performed with low thermal weight brushes.  
     
     
         6 . The process of  claim 1  wherein the metal layer comprises copper.  
     
     
         7 . The process of  claim 1  wherein the metal layer comprises silver.  
     
     
         8 . The process of  claim 1  wherein the metal layer comprises tantalum.  
     
     
         9 . The process of  claim 1  performed with the workpiece in a substantially vertical orientation.  
     
     
         10 . The process of  claim 1  further comprising controlling a temperature at which the abrasive free chemical solution reacts with metal of the metal layer.  
     
     
         11 . The process of  claim 1  wherein the abrasive free chemical solution comprises an organic acid, a metallic complex forming agent, and an oxidizer.  
     
     
         12 . The process of  claim 11  wherein the organic acid comprises oxalic acid.  
     
     
         13 . The process of  claim 11  wherein the metallic complex forming agent comprises quinaldic acid.  
     
     
         14 . The process of  claim 11  wherein the oxidizer comprises hydrogen peroxide.  
     
     
         15 . An apparatus for polishing a metal layer formed on a workpiece, the apparatus comprising: 
 means for loading a workpiece into the apparatus;    means for providing an abrasive free chemical solution to the metal layer of the workpiece at a flow rate of about 50 cc/min to about 500 cc/min; and    means for polishing the metal layer on the workpiece.    
     
     
         16 . The apparatus of  claim 15 , wherein the means for polishing includes an abrading surface with through-holes, and wherein the means for providing provides the abrasive free chemical solution to an interface between the abrading surface and the workpiece via the through-holes.  
     
     
         17 . The apparatus of  claim 15 , wherein the means for polishing comprises means for orienting the workpiece in a substantially vertical position.  
     
     
         18 . The apparatus of  claim 15  further comprising means for controlling a temperature at which the abrasive free chemical solution reacts with metal of the metal layer.  
     
     
         19 . The apparatus of  claim 15  wherein the abrasive free chemical solution comprises an organic acid, a metallic complex forming agent, and an oxidizer.  
     
     
         20 . The apparatus of  claim 15  wherein the means for polishing rotates the workpiece through a reservoir of abrasive free chemical solution.  
     
     
         21 . The apparatus of  claim 15  wherein the means for polishing includes a pair of pancake-shaped pads, the workpiece being disposed between the pancake-shaped pads during a polishing operation.  
     
     
         22 . The apparatus of  claim 15  wherein the means for polishing provides an orbital motion and an oscillating motion.  
     
     
         23 . A polishing device for polishing a metal layer formed on a surface of a workpiece, the polishing device comprising: 
 a workpiece fixture;    a brush assembly;    a fluid dispenser configured to store and dispense an abrasive free chemical solution; and    a controller coupled to the workpiece fixture, brush assembly, and fluid dispenser, wherein during a workpiece polishing operation the controller is configured to cause: 
 the fluid dispenser to provide an abrasive free chemical solution to an interface between the brush assembly and a workpiece at a rate of about 50 cc/min to about 500 cc/min,  
 the workpiece to contact the brush assembly, and  
 a polishing motion to be imparted between the workpiece and the brush assembly.  
   
     
     
         24 . The polishing device of  claim 23 , wherein the brush assembly further comprises a platen, the platen having a cooling channel.  
     
     
         25 . The polishing device of  claim 23 , wherein the workpiece fixture comprises a support member.  
     
     
         26 . The polishing device of  claim 25 , wherein the support member is configured to rotatably support a workpiece in a vertical position.  
     
     
         27 . The polishing device of  claim 23 , wherein the workpiece fixture comprises a carrier.  
     
     
         28 . The polishing device of  claim 23  further comprising a platen, the platen having a through-hole extending through the platen.  
     
     
         29 . The polishing device of  claim 23 , wherein the abrasive free chemical solution comprises an organic acid, a metallic complex forming agent, and an oxidizer.  
     
     
         30 . A polishing device for polishing a metal layer formed on a surface of a workpiece, the polishing device comprising: 
 a workpiece fixture;    a brush assembly;    a fluid dispenser configured to store and dispense an abrasive free chemical solution;    a wafer carrier adapted for securely holding at least one semiconductor substrate to expose a frontal surface of the substrate to be polished on an side of the carrier facing a polishing pad on the platen; and    a controller coupled to the workpiece fixture, brush assembly, and fluid dispenser, wherein during a workpiece polishing operation the controller is configured to cause: 
 the fluid dispenser to dispense abrasive free chemical solution to an interface between the brush assembly and a workpiece at a rate of about 50 cc/min to about 500 cc/min,  
 the workpiece to contact the brush assembly, and  
 a polishing motion to be imparted between the workpiece and the brush assembly.  
   
     
     
         31 . The polishing device of  claim 30 , wherein the brush assembly further comprises a platen having a cooling channel configured to conduct a cooling fluid.  
     
     
         32 . The polishing device of  claim 30  further comprising a platen, the platen having a through-hole extending through the platen and configured to conduct abrasive free chemical solution.  
     
     
         33 . The polishing device of  claim 30  further comprising a tank configured to contain abrasive free chemical solution, wherein the brush assembly is configured to rotate the workpiece through the abrasive free chemical solution contained in the tank.  
     
     
         34 . The polishing device of  claim 30  wherein the brush assembly includes a pair of pancake-shaped pads, the workpiece being disposed between the pancake-shaped pads during a polishing operation.