Operation of clamping retainer for chemical mechanical polishing

Abstract

A method of polishing includes bringing a substrate into contact with a polishing pad and generating relative motion between the substrate and the polishing pad, retaining the substrate on the polishing pad with a retainer, and during polishing of the substrate alternating between reducing a diameter of an inner surface of the retainer to clamp the substrate and increasing the diameter of the inner surface of the retainer to release the substrate from clamping while continuing to retain the substrate.

What is claimed is: 
     
         1 . A method of polishing, comprising:
 bringing a substrate into contact with a polishing pad and generating relative motion between the substrate and the polishing pad;   retaining the substrate on the polishing pad with a retainer; and   during polishing of the substrate, alternating between reducing a diameter of an inner surface of the retainer to clamp the substrate and increasing the diameter of the inner surface of the retainer to release the substrate from clamping while continuing to retain the substrate.   
     
     
         2 . The method of  claim 1 , wherein the substrate precesses relative to the retainer while the substrate is released from clamping by the retainer. 
     
     
         3 . The method of  claim 1 , wherein the substrate has a fixed angular orientation relative to the retainer while the substrate is clamped by the retainer. 
     
     
         4 . The method of  claim 1 , comprising alternating a plurality of times during polishing of the substrate. 
     
     
         5 . The method of  claim 1 , wherein reducing a diameter of the inner surface comprising applying inward pressure to a plurality of arcuate segments of an inner ring. 
     
     
         6 . A polishing system, comprising:
 a support to hold a polishing pad;   a carrier head to hold the substrate against the polishing pad, the carrier head including a retainer having an inner surface to engage an edge of the substrate and wherein the inner surface has an adjustable diameter;   a controller configured to cause an actuator to alternate during polishing of the substrate between reducing a diameter of the inner surface of the retainer to clamp the substrate and increasing the diameter of the inner surface of the retainer to release the substrate from clamping while continuing to retain the substrate.   
     
     
         7 . The system of  claim 6 , wherein the controller is configured to cause the actuator to alternate a plurality of times during polishing of the substrate. 
     
     
         8 . The system of  claim 6 , wherein the retainer includes and inner ring having a plurality of arcuate segments and an outer ring. 
     
     
         9 . The system of  claim 8 , wherein the actuator is positioned between the inner ring and the outer ring. 
     
     
         10 . The system of  claim 9 , wherein the actuator comprises a bladder. 
     
     
         11 . A polishing system, comprising:
 a support to hold a polishing pad;   a carrier head to hold the substrate against the polishing pad, the carrier head including a first chamber to apply a first downward pressure to a center portion of the substrate held by carrier head, a second chamber to apply a second downward pressure to an outer portion of the substrate surrounding the central portion, and a retaining ring having an inner surface to engage an edge of the substrate and wherein the inner surface has an adjustable diameter;   a controller configured to, in response to identifying a polishing non-uniformity, decrease the diameter of the inner surface of the retainer sufficiently that the substrate bows, determine whether the substrate should bow inwardly or outwardly from the carrier head to reduce the polishing non-uniformity, and select whether the first pressure is greater or lower than the second pressure such that the substrate bows in the determined direction.   
     
     
         12 . The polishing system of  claim 11 , wherein the controller is configured to, in response to detecting that a center portion of the substrate is overpolished relative to an edge portion of the substrate, cause the first pressure to be less than the second pressure. 
     
     
         13 . The polishing system of  claim 12 , wherein the controller is configured to decrease the diameter of the inner surface of the retainer sufficiently that the substrate bows to form a convex shape. 
     
     
         14 . The polishing system of  claim 11 , wherein the controller is configured to, in response to detecting that a center portion of the substrate is underpolished relative to an edge portion of the substrate, cause the first pressure to be larger than the second pressure. 
     
     
         15 . The polishing system of  claim 14 , wherein the controller is configured to decrease the diameter of the inner surface of the retainer sufficiently that the substrate bows to form a concave shape. 
     
     
         16 . The polishing system of  claim 11 , wherein the retaining ring includes and inner ring having a plurality of arcuate segments and an outer ring. 
     
     
         17 . The polishing system of  claim 16 , wherein the actuator is positioned between the inner ring and the outer ring. 
     
     
         18 . The polishing system of  claim 17 , wherein the actuator comprises a bladder.