Polishing system with platen for substrate edge control

Abstract

A polishing system includes a platen having a top surface to support a main polishing pad. The platen is rotatable about an axis of rotation that passes through approximately the center of the platen. An annular flange projects radially outward from the platen to support an outer polishing pad. The annular flange has an inner edge secured to and rotatable with the platen and vertically fixed relative to the top surface of the platen. The annular flange is vertically deflectable such that an outer edge of the annular flange is vertically moveable relative to the inner edge. An actuator applies pressure to an underside of the annular flange in an angularly limited region, and a carrier head holds a substrate in contact with the polishing pad and is movable to selectively position a portion of the substrate over the outer polishing pad.

What is claimed is: 
     
         1 . A polishing system, comprising:
 a circular platen having a circular top surface to support a circular main polishing pad, the platen rotatable about an axis of rotation that passes through approximately the center of the platen;   an annular flange projecting radially outward from the platen and having an annular top surface to support an annular outer polishing pad, the annular flange having an inner edge secured to and rotatable with the platen and vertically fixed relative to the top surface of the platen, wherein an inner perimeter of the annular top surface of the annular flange is coplanar with the top surface of the platen, and wherein the annular flange is deformable such that an outer edge of the annular flange is vertically movable relative to the inner edge;   an actuator configured to apply pressure to an underside of the annular flange to deflect the flange to move the outer edge of the annular flange vertically relative to the inner edge of the annular flange and the platen; and   a carrier head to hold a substrate in contact with the main polishing pad and movable to selectively position a portion of the substrate on the outer polishing pad.   
     
     
         2 . The polishing system of  claim 1 , wherein in absence of deflection by the actuator the annular top surface of the flange is a planar surface that is coplanar with the circular top surface of the platen. 
     
     
         3 . The polishing system of  claim 1 , wherein the inner edge of the annular flange directly contacts an outer diameter surface of the circular platen such that the annular top surface of the annular flange forms a continuous surface with the circular top surface of the platen. 
     
     
         4 . The polishing system of  claim 1 , wherein the outer edge of the annular flange is free-standing. 
     
     
         5 . The polishing system of  claim 4 , wherein the annular flange comprises a first section contacting to the platen and a second section projecting radially outward from the first section and having a uniform thickness. 
     
     
         6 . The polishing system of  claim 5 , wherein the annular flange has an L-shaped cross-section with a first arm of the L-shaped cross-section providing the first section and a second arm of the L-shaped cross-section extending radially outward to provide the second section and the annular top surface of the annular flange. 
     
     
         7 . The polishing system of  claim 1 , wherein the platen and/or annular flange comprise a conduit having an opening in the top surface of the platen and/or annular flange for polishing residue to drain from a gap between the outer polishing pad and the main polishing pad. 
     
     
         8 . The polishing system of  claim 1 , wherein the actuator includes an arm having a wheel in contact with the underside of the annular flange. 
     
     
         9 . The polishing system of  claim 8 , wherein the wheel is in static contact with the underside of the annular flange. 
     
     
         10 . A polishing system, comprising:
 a platen having an annular top surface to support an annular main polishing pad, the platen having a circular aperture in the top surface of the platen in approximately a center of the platen, the platen rotatable about an axis of rotation that passes through approximately the center of the platen;   an annular flange projecting radially inward from the platen into the circular aperture and having an annular top surface to support an annular inner polishing pad, the annular flange having an outer edge secured to and rotatable with the platen and vertically fixed relative to the top surface of the platen, wherein an outer perimeter of the annular top surface of the annular flange is coplanar with the top surface of the platen, and wherein the annular flange is deformable such that an inner edge of the annular flange is vertically movable relative to the outer edge;   an actuator configured to apply pressure to an underside of the annular flange to deflect the flange to move the inner edge of the annular flange vertically relative to the outer edge of the annular flange and the platen; and   a carrier head to hold a substrate in contact with the main polishing pad and movable to selectively position a portion of the substrate on the inner polishing pad.   
     
     
         11 . The polishing system of  claim 10 , wherein in absence of deflection by the actuator the annular top surface of the flange is a planar surface that is coplanar with the circular top surface of the platen. 
     
     
         12 . The polishing system of  claim 10 , wherein the outer edge of the annular flange directly contacts an inner diameter surface of the circular aperture in the platen such that the annular top surface of the annular flange forms a continuous surface with the annular top surface of the platen. 
     
     
         13 . The polishing system of  claim 10 , wherein the inner edge of the annular flange is free-standing. 
     
     
         14 . The polishing system of  claim 13 , wherein the annular flange comprises a first section contacting to the platen and a second section projecting radially inward from the first section and having a uniform thickness. 
     
     
         15 . The polishing system of  claim 14 , wherein the annular flange has an L-shaped cross-section with a first arm of the L-shaped cross-section providing the first section and a second arm of the L-shaped cross-section extending radially inward to provide the second section and the annular top surface of the annular flange. 
     
     
         16 . The polishing system of  claim 10 , wherein the aperture comprises a recess extending partially but not entirely through the platen. 
     
     
         17 . The polishing system of  claim 16 , comprising a conduit through the platen for liquid polishing residue to drain from the recess. 
     
     
         18 . The polishing system of  claim 10 , comprising:
 a second annular flange projecting radially outward from the platen having an annular top surface to support an annular outer polishing pad, the second annular flange having an inner edge secured to and rotatable with the platen and vertically fixed relative to the top surface of the platen, wherein an inner perimeter of the second annular top surface of the second annular flange is coplanar with the top surface of the platen, and wherein the second annular flange is deformable such that an outer edge of the second annular flange is vertically movable relative to the inner edge of the second annular flange;   a second actuator configured to apply pressure to an underside of the second annular flange to deflect the second annular flange to move the outer edge of the second annular flange vertically relative to the inner edge of the second annular flange and the platen.