Substrate precession mechanism for cmp polishing head

Abstract

A substrate precession apparatus for a carrier head is provided. The apparatus enables substrate precession, which is the rotational movement of the substrate relative to the carrier head during polishing of the substrate. The carrier head and a retaining ring assembly may be de-coupled and move independently of one another to promote substrate precession during a CMP process.

1 . An apparatus for polishing a substrate, comprising:
 a head assembly;   a retaining ring assembly comprising:
 an internal gear; and 
 a bearing disposed between the head assembly and the retaining ring assembly, wherein the bearing is adapted to decouple the retaining ring assembly from the head assembly; and 
   a drive assembly adapted to rotate the retaining ring assembly relative to the head assembly.   
     
     
         2 . The apparatus of  claim 1 , wherein the head assembly further comprises:
 a housing;   a carrier body; and   a flexible membrane.   
     
     
         3 . The apparatus of  claim 1 , wherein the head assembly further comprises a cover plate coupled to the drive assembly. 
     
     
         4 . The apparatus of  claim 1 , further comprising:
 a transmission comprising:
 a first gear; 
 a second gear; 
 a shaft encoder; and 
 a drive shaft. 
   
     
     
         5 . The apparatus of  claim 4 , wherein the first gear is rotatably coupled to the drive assembly. 
     
     
         6 . The apparatus of  claim 4 , wherein the second gear is rotatably coupled to the internal gear. 
     
     
         7 . The apparatus of  claim 4 , wherein the first gear and the second gear are coupled to the drive shaft. 
     
     
         8 . The apparatus of  claim 1 , wherein the drive assembly comprises:
 an actuator;   a spindle coupled to the actuator; and   a worm drive coupled to the spindle.   
     
     
         9 . The apparatus of  claim 8 , wherein the actuator is an air motor. 
     
     
         10 . The apparatus of  claim 1 , wherein the internal gear comprises a plurality of teeth. 
     
     
         11 . The apparatus of  claim 1 , wherein an inner diameter of the retaining ring assembly is between about 11.830 in and about 11.870 in. 
     
     
         12 . The apparatus of  claim 1 , wherein an inner diameter of the retaining ring assembly is between about 11.890 in and about 11.950 in. 
     
     
         13 . A retaining ring assembly for a polishing head, comprising:
 a retaining ring having an upper annular portion and a lower annular portion;   a carrier ring coupled to the upper annular portion;   a bearing clamp coupled to the carrier ring, the bearing clamp adapted to receive a bearing; and   an internal gear coupled to the bearing clamp.   
     
     
         14 . The apparatus of  claim 13 , wherein the bearing decouples the retaining ring assembly from a polishing head assembly. 
     
     
         15 . A method of operating a polishing apparatus, comprising:
 providing a polishing head assembly and a retaining ring assembly, wherein the retaining ring assembly is decoupled from the polishing head assembly;   rotating the polishing head at a first speed; and   rotating the retaining ring assembly at a second speed greater than the first speed.   
     
     
         16 . The method of  claim 15 , wherein the first speed is between about 60 rpm and about 120 rpm. 
     
     
         17 . The method of  claim 15 , wherein the polishing head assembly and the retaining ring assembly are rotated in the same direction. 
     
     
         18 . The method of  claim 15 , wherein the polishing head assembly and retaining ring assembly are rotated in opposite directions. 
     
     
         19 . The method of  claim 15 , wherein a rotation direction of the polishing head assembly and a rotation direction of a polishing pad are the same. 
     
     
         20 . The method of  claim 15 , wherein the rotation direction of the polishing head assembly and a rotation direction of a polishing pad are opposite.