Methods and apparatus for active substrate precession during chemical mechanical polishing

Abstract

In some aspects, a chemical mechanical polishing (CMP) apparatus is provided that includes a polishing head having (a) a rotatable spindle; (b) a membrane coupled to the rotatable spindle and adapted to press a substrate against a polishing pad during polishing of the substrate; and (c) a retaining ring rotatable coupled to the spindle and adapted to surround a substrate being pressed against a polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head. The CMP apparatus also includes a drive mechanism coupled to the retaining ring and adapted to drive the retaining ring at a different rate of rotation than the spindle during polishing. Numerous other aspects are provided.

The invention claims is: 
     
         1 . A chemical mechanical polishing apparatus comprising:
 a polishing head comprising:
 a rotatable spindle; 
 a membrane coupled to the rotatable spindle and adapted to press a substrate against a polishing pad during polishing of the substrate; and 
 a retaining ring rotatable coupled to the spindle and adapted to surround a substrate being pressed against a polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head; and 
   a drive mechanism coupled to the retaining ring and adapted to drive the retaining ring at a different rate of rotation than the spindle during polishing.   
     
     
         2 . The chemical mechanical polishing apparatus of  claim 1  further comprising a controller adapted to cause the drive mechanism to rotate the retaining ring at a different rate of rotation than the spindle during polishing. 
     
     
         3 . The chemical mechanical polishing apparatus of  claim 2  wherein the controller is adapted to cause the drive mechanism to rotate the retaining ring at about twice the rate of rotation of the spindle during polishing. 
     
     
         4 . The chemical mechanical polishing apparatus of  claim 2  wherein the controller is adapted to cause the drive mechanism to rotate the retaining ring at about one-half the rate of rotation of the spindle during polishing. 
     
     
         5 . A method of polishing a substrate comprising:
 pressing the substrate against a polishing pad using a polishing head having:
 a rotatable spindle; 
 a membrane coupled to the rotatable spindle and adapted to press the substrate against the polishing pad during polishing of the substrate; and 
 a retaining ring coupled to the spindle and adapted to surround the substrate being pressed against the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head; 
   rotating the spindle and membrane of the polishing head at a first rotation rate during polishing; and   rotating the retaining ring of the polishing head at a second rotation rate during polishing so as to cause the substrate to rotate relative to the membrane of the polishing head.   
     
     
         6 . The method of  claim 5  wherein the first rate is less than the second rate. 
     
     
         7 . The method of  claim 5  wherein the first rate is greater than the second rate. 
     
     
         8 . A chemical mechanical polishing apparatus comprising:
 a polishing head comprising:
 a rotatable spindle; 
 a membrane coupled to the rotatable spindle and adapted to press a substrate against a polishing pad during polishing of the substrate; 
 a retaining ring rotatable coupled to the spindle and adapted to surround a substrate being pressed against a polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head; and 
 at least one rotation mechanism coupled to the retaining ring, adapted to contact a substrate during polishing and adapted to allow the substrate to rotate at a different rate than the spindle during the during polishing. 
   
     
     
         9 . The chemical mechanical polishing apparatus of  claim 8  wherein the at least one rotation mechanism comprises at least one roller rotatably coupled to a trailing edge of the retaining ring. 
     
     
         10 . The chemical mechanical polishing apparatus of  claim 8  wherein the retaining ring is stationary during polishing. 
     
     
         11 . The chemical mechanical polishing apparatus of  claim 8  wherein the retaining ring comprises multiple retaining ring sections. 
     
     
         12 . The chemical mechanical polishing apparatus of  claim 8  wherein the retaining ring has a different number of slurry grooves along a leading edge of the retaining ring than along a trailing edge of the retaining ring. 
     
     
         13 . The chemical mechanical polishing apparatus of  claim 8  wherein the retaining ring has a different width along a leading edge of the retaining ring than along a trailing edge of the retaining ring. 
     
     
         14 . A method of polishing a substrate comprising:
 pressing the substrate against a polishing pad using a polishing head having:
 a rotatable spindle; 
 a membrane coupled to the rotatable spindle and adapted to press the substrate against the polishing pad during polishing of the substrate; 
 a retaining ring coupled to the spindle and adapted to surround the substrate being pressed against the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head; and 
 at least one rotation mechanism coupled to the retaining ring, adapted to contact the substrate during polishing and adapted to allow the substrate to rotate at a different rate than the spindle during the during polishing; 
   rotating the spindle and membrane of the polishing head at a first rotation rate during polishing; and   rotating the at least one rotation mechanism coupled to the retaining ring of the polishing head at a second rotation rate during polishing so as to cause the substrate to rotate relative to the membrane of the polishing head.   
     
     
         15 . The method of  claim 14  wherein the at least one rotation mechanism comprises at least one roller rotatably coupled to a trailing edge of the retaining ring. 
     
     
         16 . The method of  claim 14  wherein the retaining ring is stationary during polishing. 
     
     
         17 . The method of  claim 14  wherein the retaining ring comprises multiple retaining ring sections. 
     
     
         18 . The method of  claim 14  wherein the retaining ring has a different number of slurry grooves along a leading edge of the retaining ring than along a trailing edge of the retaining ring. 
     
     
         19 . The method of  claim 14  wherein the retaining ring has a different width along a leading edge of the retaining ring than along a trailing edge of the retaining ring. 
     
     
         20 . The method of  claim 14  further comprising applying a different pressure along a leading edge of the retaining ring than along a trailing edge of the retaining ring during polishing.