Reducing polishing pad deformation

Abstract

A polishing system can have a polishing pad with a polishing surface and a bottom surface that includes a recess with a thickness less than the thickness of the polishing pad. An in-situ monitoring module can be positioned in a cavity formed in part by the recess. A vent path is provided with an opening to the cavity.

1 . A polishing pad for use in a chemical mechanical polishing system, the polishing pad comprising: 
 a polishing surface and a non-polishing surface opposed to the polishing surface, the polishing pad having a thickness;    a recess on the non-polishing surface, the recess having a depth less than the thickness of the polishing pad, wherein the recess has no opening to the polishing surface; and    a vent path, the vent path having a first opening to the recess and a second opening to a surface of the polishing pad other than the polishing surface.    
     
     
         2 . The polishing pad of  claim 1  wherein: 
 the polishing pad further comprises a side edge surface;    and the second opening is to the side edge surface.    
     
     
         3 . The polishing pad of  claim 1 , wherein: 
 the vent path is curved and the second opening is located at a radial offset from the first opening.    
     
     
         4 . The polishing pad of  claim 1 , wherein: 
 the vent path has a depth which varies along the length of the vent path.    
     
     
         5 . The polishing pad of  claim 1 , wherein: 
 the second opening is wider than the first opening.    
     
     
         6 . The polishing pad of  claim 5 , wherein: 
 the vent path is notched to form the wider second opening.    
     
     
         7 . The polishing pad of  claim 5 , wherein: 
 a width of the vent path gradually increases to form the wider second opening.    
     
     
         8 . The polishing pad of  claim 5 , wherein: 
 the second opening is about four times wider than the first opening.    
     
     
         9 . The polishing pad of  claim 1 , wherein: 
 the polishing pad includes an outer layer and a backing layer.    
     
     
         10 . The polishing pad of  claim 9 , wherein: 
 the vent path is a groove formed in the backing layer.    
     
     
         11 . The polishing pad of  claim 9 , wherein: 
 the groove has the same thickness as the backing layer.    
     
     
         12 . The polishing pad of  claim 9 , wherein: 
 the vent path is a groove formed in the outer layer.    
     
     
         13 . The polishing pad of  claim 9 , wherein: 
 the vent path is a passage through the backing layer.    
     
     
         14 . The polishing pad of  claim 1 , wherein: 
 the vent path is a groove formed on the non-polishing surface.    
     
     
         15 . The polishing pad of  claim 1 , wherein: 
 the vent path is a passage formed in the polishing pad.    
     
     
         16 . The polishing pad of  claim 1 , wherein: 
 the polishing pad comprises one or more layers and a plug secured to the one or more layers.    
     
     
         17 . The polishing pad of  claim 1 , wherein: 
 the recess is formed in the plug.    
     
     
         18 . The polishing pad of  claim 1 , wherein: 
 the plug is transparent.    
     
     
         19 . A platen for use in a chemical mechanical polishing system, the platen comprising: 
 a surface configured to receive a polishing pad;    a recess formed on the surface, the recess being configured to received an in-situ monitoring module; and    a side edge;    a vent path, the path having a first opening to the recess and a second opening to the side edge.    
     
     
         20 . The platen of  claim 19 , wherein: 
 the vent path is a groove formed on the surface.