Methods and apparatus for electropolishing metal interconnections on semiconductor devices

Abstract

A metal layer formed on a surface of a wafer is electropolished using a wafer chuck and a moveable nozzle. The surface on which the metal layer is formed is the same surface on which features of devices are formed. The wafer chuck is configured to rotate the wafer when the wafer is placed on top of the wafer chuck. The moveable nozzle is disposed vertically above the wafer when the wafer is placed on top of the wafer chuck. The moveable nozzle is configured to move from a first position to apply a stream of electrolyte to a first portion of the metal layer to a second position to apply the stream of electrolyte to a second portion of the metal layer when the wafer is rotated by the wafer chuck, where the first and second portions of the metal layer are located at different radial positions on the wafer.

I claim:  
     
         1 . An apparatus for electropolishing a metal layer formed on a surface of a wafer, wherein the surface on which the metal layer is formed is the same surface on which features of devices are formed, the apparatus comprising: 
 a wafer chuck configured to rotate the wafer when the wafer is placed on top of the wafer chuck; and    a moveable nozzle disposed vertically above the wafer when the wafer is placed on top of the wafer chuck,    wherein the moveable nozzle is configured to move from a first position to apply a stream of electrolyte to a first portion of the metal layer to a second position to apply the stream of electrolyte to a second portion of the metal layer when the wafer is rotated by the wafer chuck, and    wherein the first and second portions of the metal layer are located at different radial positions on the wafer.    
     
     
         2 . The apparatus of  claim 1 , wherein the moveable nozzle translates along a radial path parallel to the wafer surface while the wafer chuck rotates the wafer.  
     
     
         3 . The apparatus of  claim 2 , wherein the stream of electrolyte is applied to successive radial portions of the metal layer as the moveable nozzle translates along the radial path while the wafer chuck rotates the wafer.  
     
     
         4 . The apparatus of  claim 3 , wherein the stream of electrolyte is applied in a spiral path.  
     
     
         5 . The apparatus of  claim 1 , wherein the first position is adjacent a peripheral portion of the wafer and the second position is adjacent a center portion of the wafer.  
     
     
         6 . The apparatus of  claim 1 , wherein the first position is adjacent a center portion of the wafer and the second position is adjacent to a peripheral portion of the wafer.  
     
     
         7 . The apparatus of  claim 1 , wherein the wafer is translated at a greater rate when the moveable nozzle is adjacent a center portion than a peripheral portion of the wafer.  
     
     
         8 . The apparatus of  claim 1 , further comprising: 
 a guide bar, wherein the moveable nozzle moves along the guide bar.    
     
     
         9 . The apparatus of  claim 1 , wherein the moveable nozzle includes: 
 a single nozzle configured to emit a single stream of electrolyte; and    a cathode configured to apply a charge to the stream of electrolyte.    
     
     
         10 . The apparatus of  claim 9 , further comprising: 
 at least one power supply connected to the cathode.    
     
     
         11 . The apparatus of  claim 10 , wherein the power supply is configured to apply a current of between about 0.1 amperes per decimeter-squared (A/dm2) and about 40 amperes per decimeter-squared (A/dm2).  
     
     
         12 . The apparatus of  claim 10 , wherein the power supply is configured to operate in direct current (DC) mode.  
     
     
         13 . The apparatus of  claim 10 , wherein the power supply is configured to operate in pulse modes.  
     
     
         14 . The apparatus of  claim 13 , wherein the power supply is configured to operate using a bipolar pulse, a modified sine-wave, unipolar pulse, pulse reverse, or duplex pulse.  
     
     
         15 . The apparatus of  claim 10 , wherein the power supply is configured to operate in a constant current mode or a constant voltage mode.  
     
     
         16 . The apparatus of  claim 1 , wherein the electrolyte includes orthophosphoric acid (H3PO4).  
     
     
         17 . The apparatus of  claim 1 , further comprising: 
 at least one in-situ film thickness uniformity monitor configured to monitor the thickness of the metal layer on the wafer.    
     
     
         18 . The apparatus of  claim 17 , wherein the in-situ film thickness uniformity monitor includes an ultrasonic sensor.  
     
     
         19 . The apparatus of  claim 1  further comprising: 
 a receptacle configured to receive the wafer, wherein the wafer chuck and moveable nozzle are disposed within the receptacle, and wherein the moveable nozzle is moved within the receptacle.  
 
     
     
         20 . The apparatus of  claim 19 , wherein the receptacle holds a volume of electrolyte, and wherein the wafer is immersed in the volume of electrolyte while the moveable nozzle applies the stream of electrolyte to the wafer.  
     
     
         21 . An apparatus for electropolishing a metal layer formed on a surface of a wafer, wherein the surface on which the metal layer is formed is the same surface on which features of devices are formed, the apparatus comprising: 
 a wafer chuck configured to rotate the wafer when the wafer is placed on top of the wafer chuck; and    a moveable nozzle disposed vertically above the wafer when the wafer is placed on top of the wafer chuck,    wherein the moveable nozzle is configured to move from a first radial position to a second radial position on the wafer while the wafer is rotated by the wafer chuck, and    wherein the moveable nozzle applies electrolyte vertically to successive portions of the metal layer as the moveable nozzle is moved from the first radial position to the second radial position on the wafer and the wafer is rotated by the wafer chuck.    
     
     
         22 . The apparatus of  claim 21 , wherein the moveable nozzle translates along a radial path parallel to the wafer surface while the wafer chuck rotates the wafer.  
     
     
         23 . The apparatus of  claim 21 , wherein the wafer is translated at a greater rate when the moveable nozzle is adjacent a center portion than a peripheral portion of the wafer.  
     
     
         24 . The apparatus of  claim 23 , wherein the first radial position is adjacent the peripheral portion of the wafer and the second radial position is adjacent the center portion of the wafer.  
     
     
         25 . The apparatus of  claim 23 , wherein the first radial position is adjacent the center portion of the wafer and the second radial position is adjacent to the peripheral portion of the wafer.  
     
     
         26 . The apparatus of  claim 21 , wherein the moveable nozzle includes: 
 a single nozzle configured to emit a single stream of electrolyte; and    at least one power supply configured to apply a charge to the stream of electrolyte.    
     
     
         27 . The apparatus of  claim 26  further comprising: 
 at least one in-situ film thickness uniformity monitor configured to monitor the thickness of the metal layer on the wafer.  
 
     
     
         28 . The apparatus of  claim 27  further comprising: 
 a receptacle configured to receive the wafer, wherein the wafer chuck and moveable nozzle are disposed within the receptacle, and wherein the moveable nozzle is translated within the receptacle.  
 
     
     
         29 . A method of electropolishing a metal layer formed on a surface of a wafer, wherein the surface on which the metal layer is formed is the same surface on which features of devices are formed, the method comprising: 
 placing the wafer on a wafer chuck;    rotating the wafer on the wafer chuck;    applying a stream of electrolyte to a first portion of the metal layer through a moveable nozzle disposed vertically above the wafer in a first position while the wafer is rotated on the wafer chuck; and    moving the moveable nozzle from the first position to a second position while the wafer is rotated on the wafer chuck to apply the stream of electrolyte to a second portion of the metal layer, wherein the first and second portions of the metal layer are located at different radial positions on the wafer.    
     
     
         30 . The method of  claim 29 , wherein moving the moveable nozzle comprises: 
 translating the moveable nozzle along a radial path parallel to the wafer surface while the wafer chuck rotates the wafer.    
     
     
         31 . The method of  claim 30 , wherein the stream of electrolyte is applied to successive radial portions of the metal layer as the moveable nozzle translates along the radial path while the wafer chuck rotates the wafer.  
     
     
         32 . The method of  claim 29 , wherein the metal layer adjacent to a center portion of the wafer is first exposed to the stream of electrolyte, then the wafer is translated toward a peripheral portion of the wafer.  
     
     
         33 . The method of  claim 29 , wherein the metal layer adjacent to a peripheral portion of the wafer is first exposed to the stream of electrolyte, then the wafer is translated toward a center portion of the wafer.  
     
     
         34 . The method of  claim 29 , wherein the wafer is translated at a greater rate when the moveable nozzle is adjacent a center portion than a peripheral portion of the wafer.  
     
     
         35 . The method of  claim 29 , further comprising: 
 applying a charge to the stream of electrolyte using a power supply.    
     
     
         36 . The method of  claim 29 , further comprising: 
 monitoring the thickness of the metal layer using at least one in-situ film thickness uniformity monitor.