Ecmp polishing sequence to improve planarity and defect performance

Abstract

A method for processing a substrate having a conductive layer disposed thereon is provided. The substrate is coupled with a planarizing head. The planarizing head is moved to a position above a polishing pad assembly. The planarizing pad is positioned relative to the polishing pad assembly without applying a voltage to the substrate. A first voltage is applied to the substrate for a first time period. A second voltage is applied to the substrate for a second time period in order to remove a portion of the conductive layer, wherein the second voltage is greater than the first voltage. In certain embodiments, applying a first voltage to the substrate further comprises forming a uniform passivation layer on the conductive layer.

1 . A method for electro polishing a substrate having a conductive layer disposed thereon, comprising:
 coupling the substrate with a planarizing head;   moving the planarizing head to a position above a polishing pad assembly;   positioning the planarizing head relative to the polishing pad assembly without applying voltage to the substrate;   applying a first voltage to the substrate for a first time period; and   applying a second voltage to the substrate for a second time period in order to remove a portion of the conductive layer, wherein the second voltage is greater than the first voltage.   
   
   
       2 . The method of  claim 1 , wherein the positioning the planarizing head relative to the polishing pad assembly comprises pressing the planarizing head against the polishing pad assembly. 
   
   
       3 . The method of  claim 1 , further comprising sweeping the planarizing head across a surface of the polishing pad assembly after positioning the planarizing head relative to the polishing pad assembly. 
   
   
       4 . The method of  claim 3 , further comprising rotating the planarizing head at an RPM range between about 5 RPM and about 80 RPM while sweeping the planarizing head across a surface of the polishing pad assembly. 
   
   
       5 . The method of  claim 1 , wherein the first voltage comprises a ramp-up voltage between about 1.5 volts and about 3 volts. 
   
   
       6 . The method of  claim 5 , wherein the second voltage comprises a voltage between about 2.4 volts and about 3.5 volts. 
   
   
       7 . The method of  claim 1 , wherein applying a first voltage to the substrate further comprises forming a uniform passivation layer on the conductive layer. 
   
   
       8 . A method for electro polishing a substrate having a conductive layer disposed thereon, comprising:
 coupling the substrate with a planarizing head;   adjusting the planarizing head so the substrate contacts a surface of a polishing pad assembly at a first processing position without the application of voltage to the substrate;   forming a passivation layer on the conductive layer of the substrate;   sweeping the planarizing head from the first processing position to a second processing position;   applying a first voltage to the substrate to increase the uniformity of the passivation layer; and   applying a second voltage to the substrate to remove a portion of the conductive layer, wherein the second voltage is greater than the first voltage.   
   
   
       9 . The method of  claim 8 , wherein sweeping the polishing head and applying a first voltage to the substrate occur simultaneously. 
   
   
       10 . The method of  claim 8 , wherein applying a first voltage to the substrate and forming a passivation layer on the conductive layer occur simultaneously. 
   
   
       11 . The method of  claim 8 , wherein sweeping the planarizing head further comprises rotating the polishing head relative to the polishing pad. 
   
   
       12 . The method of  claim 8 , wherein sweeping the polishing head comprises moving the polishing head in a linear direction while maintaining contact with the surface of the polishing pad. 
   
   
       13 . The method of  claim 8 , wherein sweeping the polishing head further comprises returning the substrate to the first processing position. 
   
   
       14 . The method of  claim 8 , wherein the sweeping the polishing head begins prior to applying a first voltage to the substrate. 
   
   
       15 . The method of  claim 14 , wherein the sweeping the polishing head continues while applying a first voltage to the substrate. 
   
   
       16 . A method for electro polishing a substrate having a conductive layer disposed thereon, comprising:
 loading a substrate onto a planarizing head;   mechanically stabilizing the planarizing head without the application of voltage to the substrate;   applying a first voltage to the substrate for a first time period to form a uniform passivation layer on the conductive layer; and   applying a second voltage to the substrate for a second time period in order to remove a portion of the conductive layer, wherein the second voltage is greater than the first voltage.   
   
   
       17 . The method of  claim 16 , wherein loading the substrate further comprises contacting the substrate with the planarizing head. 
   
   
       18 . The method of  claim 16 , wherein mechanically stabilizing the polishing head comprises moving the polishing head to a first position prior to applying a first voltage to the substrate for a first time period. 
   
   
       19 . The method of  claim 18 , further comprising moving the polishing head from the first position to a second position while applying a first voltage to the substrate for a first time period. 
   
   
       20 . The method of  claim 19 , wherein applying a first voltage to the substrate for a first time period comprises applying a ramp-up voltage.