Method and Apparatus Of Eddy Current Monitoring For Chemical Mechanical Polishing

Abstract

A polishing system can have a rotatable platen, a polishing pad secured to the platen, a carrier head to hold a substrate against the polishing pad, and an eddy current monitoring system including a coil or ferromagnetic body that extends at least partially through the polishing pad. A polishing pad can have a polishing layer and a coil or ferromagnetic body secured to the polishing layer. Recesses can be formed in a transparent window in the polishing pad.

1 . A carrier head for a polishing system, comprising: 
 a substrate receiving surface; and    a ferromagnetic body in the carrier head on a side opposite the substrate receiving surface.    
   
   
       2 . A polishing pad, comprising: 
 a polishing layer; and    an induction coil secured to the polishing layer.    
   
   
       3 . The polishing pad of  claim 2 , wherein the induction coil is embedded in the polishing pad.  
   
   
       4 . The polishing pad of  claim 2 , wherein the polishing layer includes a recess formed in a bottom surface thereof, and the coil is positioned into the recess.  
   
   
       5 . The polishing pad of  claim 2 , wherein the coil is positioned with a primary axis perpendicular to a surface of the polishing layer.  
   
   
       6 . The polishing pad of  claim 2 , wherein the coil is positioned with a primary axis at an angle greater than 0 and less than 90 degrees to a surface of the polishing layer.  
   
   
       7 . The polishing pad of  claim 2 , wherein further comprising electrical contacts on a bottom surface of the polishing pad, wherein the induction coil is electrically connected to the contacts.  
   
   
       8 . The polishing pad of  claim 2 , further comprising a transparent window through the polishing layer, and wherein the induction coil is embedded in the transparent window.  
   
   
       9 . The polishing pad of  claim 2 , further comprising a backing layer.  
   
   
       10 . The polishing pad of  claim 2 , wherein the polishing layer includes polyurethane.  
   
   
       11 . A method of polishing, comprising: 
 bringing a substrate into contact with a polishing surface of a polishing pad;    positioning an induction coil on a side of the polishing surface opposite the substrate so that the induction coil extends at least partially through the polishing pad;    causing relative motion between the substrate and the polishing pad; and    monitoring a magnetic field using the induction coil.    
   
   
       12 . The method of  claim 11 , wherein the induction coil is secured to the polishing pad.  
   
   
       13 . The method of  claim 12 , wherein the induction coil is embedded in the polishing pad.  
   
   
       14 . The method of  claim 13 , wherein the polishing pad includes a polishing layer, and the induction coil is embedded in the polishing layer.  
   
   
       15 . The method of  claim 12 , wherein a recess is formed in a bottom surface of the polishing pad, and the induction coil extends into the recess.