Removal of embedded particles during chemical mechanical polishing

Abstract

A chemical mechanical polishing method and apparatus are introduced that reduce embedded particles during CMP processing. Throughout the CMP process, the wafer-carrier and the polish platen turn or rotate in the same direction. This enables particles to become embedded in the oxide or other film surface. In the disclosed process, during a final polish step, the wafer carrier or polish platen is turned or rotated in the opposite direction. Embedded particles are then pulled out of the oxide or film, creating a much cleaner wafer. This increases manufacturing yield and decreases manufacturing cost while introducing one additional step and a minor modification to conventional equipment.

1 . A chemical mechanical polishing method comprising: 
 loading a semiconductor wafer in a wafer carrier;    rotating the semiconductor wafer in the wafer carrier in a first direction while a polished surface of the semiconductor wafer is maintained against a polishing pad which is rotating in a second direction, the second direction being opposite to the first direction; and    reversing the direction of rotation of one of the wafer carrier and the polishing pad during a final polishing operation to remove embedded particles from the polished surface of the semiconductor wafer.    
   
   
       2 . The method of  claim 1  further comprising: 
 while reversing the direction of rotation, spraying the polishing pad with a liquid to remove the particles from the polishing pad.    
   
   
       3 . The method of  claim 1  further comprising: 
 during a first processing phase, rotating the semiconductor wafer in the wafer carrier in a clockwise direction and rotating the polishing pad in a counter-clockwise direction for a predetermined period of time; and    during a second processing phase, rotating the semiconductor wafer in the wafer carrier in a counter-clockwise direction for a final polish duration.    
   
   
       4 . The method of  claim 1  further comprising: 
 during a first processing phase, rotating the semiconductor wafer in the wafer carrier in a counter-clockwise direction and rotating the polishing pad in a clockwise direction for a predetermined period of time; and    during a second processing phase, rotating the semiconductor wafer in the wafer carrier in a counter-clockwise direction for a final polish duration.    
   
   
       5 . A chemical mechanical wafer polishing system comprising: 
 a wafer carrier configured to retain a semiconductor wafer during a chemical mechanical polishing process;    a first drive system coupled with the wafer carrier to rotate the wafer carrier with the semiconductor wafer in one of a first rotational direction and a second, opposite, rotational direction;    a platen configured for mounting a polishing pad, the polishing pad polishing a surface of the semiconductor wafer when the wafer carrier and the platen are brought into proximity;    a second drive system coupled with the platen to rotate the platen and the polishing pad in one of the first rotational direction and the second rotational direction; and    a control system coupled with the first drive system and the second system to rotate the semiconductor wafer and the polishing pads in opposite directions during a first polishing interval and to reverse rotation of the semiconductor wafer relative to the polishing pad during a second polishing interval to remove embedded particles from the surface of the semiconductor wafer.    
   
   
       6 . The chemical mechanical wafer polishing system of  claim 5  further comprising: 
 a high pressure liquid spray system adjacent the polishing pad and positioned to spray liquid on the polishing pad to remove particles from the polishing pad.    
   
   
       7 . A chemical mechanical wafer polishing (CMP) system comprising: 
 wafer rotation means for rotating a semiconductor wafer in one of a first direction and a second direction in the CMP system;    a polishing pad to polish a surface of the semiconductor wafer;    pad rotation means for rotating the polishing pad relative to the rotation of the semiconductor wafer to produce chemical mechanical polishing of the surface of the semiconductor wafer; and    control means for controlling at least one of the wafer rotation means and the pad rotation means, the control means producing a first relative rotation during a first polishing duration and producing an opposite relative rotation during a second polishing duration.