Semiconductor wafer polishing apparatus having magneto-rhelogical elastic pad

Abstract

Disclosed herein is a semiconductor wafer polishing apparatus having a magneto-rheological elastic pad, in which the dielectric layer of the wafer fixed in the wafer holder to contact the abrasive coated on a rotating plate is polished. The semiconductor wafer polishing apparatus comprises a magneto-rheological elastic pad formed by a plurality of segments received to be fixed on the rotating plate; a plurality of electromagnets, having equal or larger diameter than that of wafer to selectively pressurize a part or the entire area of the wafer, which is arranged at the lower portion of the rotating plate in such a way that the central part accords with the central axis of the wafer holder; and a controller for selectively generating the magnetic field at a part or the entire part of the electromagnets.

1 . A semiconductor wafer polishing apparatus having a magneto-rheological elastic pad, in which the dielectric layer of the wafer fixed in the wafer holder to contact the abrasive coated on a rotating plate is polished, the semiconductor wafer polishing apparatus comprising: 
 a) a magneto-rheological elastic pad formed by a plurality of segments received to be fixed on the rotating plate;    b) a plurality of electromagnets each having equal or larger diameter than that of wafer to selectively pressurize a part or the entire area of the wafer, each electromagnet being arranged at the lower portion of the rotating plate in such a way that its central part accords with the central axis of the wafer holder; and    c) a controller for selectively generating the magnetic field at a part or the entire part of the electromagnets.    
     
     
         2 . The apparatus according to  claim 1 , wherein the magneto-rheological elastic pad is formed by the steps of: 
 a) mixing of a magnetic substance with a solvent and a dispersant;    b) stirring and dispersing the above mixture in a powerful mixer to stir the resultant mixture with an elastic substance;    c) stirring the stirred mixture again in a solution of polyurethane polyol using a ball mill for about 10 hours;    d) adding one part of isocyanate to the stirred mixture to harden the resultant mixture for 24 hours at the temperature of 90° C.˜110° C.; and    e) applying magnetic field of about 1 Tesla to the resultant mixture until the hardening is completed.    
     
     
         3 . The apparatus according to  claim 2 , wherein the elastic substance is one selected from the group consisting of natural rubber, EPDM, polybutadien, acrylonitrile rubber, synthetic rubber, polyurethane, silicone rubber, and combinations thereof.  
     
     
         4 . The apparatus according to  claim 2 , wherein the magnetic substance is one selected from the group consisting of iron, alloy iron, iron oxide, iron nitride, iron carbide, nickel, cobalt, chrome dioxide, stainless steel and Fe powder.  
     
     
         5 . The apparatus according to  claim 4 , wherein the iron oxide is one selected from the group consisting of Fe 2 O 3 , Co doped Fe 2 O 3  and Fe 3 O 4 .  
     
     
         6 . The apparatus according to  claim 2 , wherein the magneto-rheological elastic pad has a thickness of 0.1 mm˜50 mm.  
     
     
         7 . The apparatus according to  claim 1 , wherein more than three electromagnets having odd numbers are arranged in a row.