Eddy current monitoring of metal residue or metal pillars

Abstract

A method of chemical mechanical polishing a substrate includes polishing a metal layer on the substrate at a polishing station, monitoring thickness of the metal layer during polishing at the polishing station with an eddy current monitoring system, and halting polishing when the eddy current monitoring system indicates that residue of the metal layer is removed from an underlying layer and a top surface of the underlying layer is exposed.

1 . A method of chemical mechanical polishing a substrate, comprising:
 polishing a metal layer on the substrate at a polishing station;   monitoring thickness of the metal layer during polishing at the polishing station with an eddy current monitoring system; and   halting polishing when the eddy current monitoring system indicates that residue of the metal layer is removed from an underlying layer and a top surface of the underlying layer is exposed.   
     
     
         2 . The method of  claim 1 , wherein the underlying layer is a barrier layer. 
     
     
         3 . The method of  claim 1 , wherein the underlying layer is a dielectric layer. 
     
     
         4 . The method of  claim 1 , wherein the eddy current monitoring system has a resonant frequency greater than 12 MHz. 
     
     
         5 . The method of  claim 3 , wherein the eddy current monitoring system has a resonant frequency between about 14 and 16 MHz. 
     
     
         6 . The method of  claim 1 , wherein metal of the metal layer has a resistivity less than 700 ohm-Angstroms. 
     
     
         7 . The method of  claim 5 , wherein the metal is copper, aluminum or tungsten. 
     
     
         8 . The method of  claim 1 , further comprising monitoring polishing of the metal layer without an optical monitoring system. 
     
     
         9 . The method of  claim 5 , further comprising determining that residue of the metal layer is removed by detecting a change in the rate of change in magnitude of a signal from the eddy current monitoring system. 
     
     
         10 . A method of chemical mechanical polishing a substrate, comprising:
 polishing a plurality of metal pillars on the substrate, the pillars projecting upwardly from a generally planar surface;   monitoring thickness of the pillars during polishing at the polishing station with an eddy current monitoring system; and   halting polishing when the eddy current monitoring system indicates that the pillars are substantially co-planar with the planar surface.   
     
     
         11 . The method of  claim 10 , wherein the generally planar surface is a dielectric layer 
     
     
         12 . The method of  claim 10 , wherein the eddy current monitoring system has a resonant frequency greater than 12 MHz. 
     
     
         13 . The method of  claim 12 , wherein the eddy current monitoring system has a resonant frequency between about 14 and 16 MHz. 
     
     
         14 . The method of  claim 10 , wherein metal of the metal layer has a resistivity less than 700 ohm-Angstroms. 
     
     
         15 . The method of  claim 14 , wherein the pillars are copper. 
     
     
         16 . The method of  claim 10 , further comprising determining that the metal pillars are co-planar with the planar surface by detecting a change in the rate of change in magnitude of a signal from the eddy current monitoring system.