Apparatus and method for chemical mechanical polishing with improved uniformity

Abstract

A chemical mechanical polishing (CMP) apparatus includes a workpiece carrier configured for retaining a workpiece thereupon, a polishing platen configured for retaining a polishing pad thereupon, and an electromagnetic coil surrounding a periphery of the workpiece carrier. The electromagnetic coil is configured to provide a magnetic field of alternating polarity to cause the rotation of ferromagnetic slurry particles disposed on the workpiece to facilitate polishing of the workpiece.

1 . A chemical mechanical polishing (CMP) apparatus, comprising:
 a workpiece carrier configured for retaining a workpiece thereupon;   a polishing platen configured for retaining a polishing pad thereupon; and   an electromagnetic coil surrounding a periphery of the workpiece carrier, said electromagnetic coil configured to provide a magnetic field of alternating polarity to ferromagnetic slurry particles disposed on the workpiece.   
   
   
       2 . The CMP apparatus of  claim 1 , wherein a longitudinal axis of the electromagnetic coil is perpendicular to a plane defined by the surface of contact between the polishing platen and the workpiece carrier. 
   
   
       3 . The CMP apparatus of  claim 2 , wherein at least one of the polishing platen and the workpiece carrier has a shaft connected to the center thereof and is configured for rotational motion around the shaft. 
   
   
       4 . The CMP apparatus of  claim 3 , wherein the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are coaxial. 
   
   
       5 . The CMP apparatus of  claim 3 , wherein the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are not coaxial and the diameter of the polishing platen is larger than the diameter of the workpiece carrier. 
   
   
       6 . The CMP apparatus of  claim 2 , further comprising a housing containing the electromagnetic coil, wherein the housing comprises a non-rotating part of the polishing platen. 
   
   
       7 . The CMP apparatus of  claim 6 , wherein at least one of the polishing platen and the workpiece carrier has a shaft connected to the center thereof and is configured for rotational motion around the shaft. 
   
   
       8 . The CMP apparatus of  claim 7 , wherein the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are coaxial. 
   
   
       9 . The CMP apparatus of  claim 7 , wherein the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are not coaxial and the diameter of the polishing platen is larger than the diameter of the workpiece camer. 
   
   
       10 . The CMP apparatus of  claim 2 , further comprising a housing containing the electromagnetic coil, wherein the housing comprises a non-rotating part of the workpiece carrier. 
   
   
       11 . The CMP apparatus of  claim 10 , wherein at least one of the polishing platen and the workpiece carrier has a shaft connected to the center thereof and is configured for rotational motion around the shaft. 
   
   
       12 . The CMP apparatus of  claim 11 , wherein the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are coaxial. 
   
   
       13 . The CMP apparatus of  claim 11 , where the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are not coaxial and the diameter of the polishing platen is larger than the diameter of the workpiece carrier. 
   
   
       14 . The CMP apparatus of  claim 1 , wherein a longitudinal axis of the electromagnetic coil is within a plane defined by a surface of contact between the polishing platen and the workpiece carrier. 
   
   
       15 . The CMP apparatus of  claim 14 , wherein the electromagnetic coil is within a housing enclosing the polishing platen and the workpiece carrier. 
   
   
       16 . The CMP apparatus of  claim 14 , wherein at least one of the polishing platen and the workpiece carrier has a shaft connected to the center thereof and is configured for rotational motion around the shaft. 
   
   
       17 . The CMP apparatus of  claim 16 , where the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are coaxial. 
   
   
       18 . The CMP apparatus of  claim 16 , where the shaft of rotation for the polishing platen and the shaft of rotation for the workpiece carrier are not coaxial and the diameter of the polishing platen is larger than the diameter of the workpiece carrier. 
   
   
       19 . A method for planarizing a workpiece, the method comprising:
 disposing a plurality of ferromagnetic slurry particles upon the polishing platen;   affixing the workpiece upon a workpiece carrier;   placing the workpiece carrier upon the polishing platen such that the ferromagnetic slurry particles contact both the polishing platen on one side and the workpiece on the other side; and,   subjecting the ferromagnetic slurry particles to a magnetic field of alternating polarity so as to cause the rotation of the ferromagnetic slurry particles.