Polishing head of a chemical and mechanical polishing apparatus for polishing a wafer

Abstract

Disclosed is a polishing head of a chemical and mechanical polishing apparatus uniformly polishing a wafer. The polishing head has a body defining at least one air passage therein through which air is introduced into and exhausted from the polishing head. The body is movable upward and downward. An air pressure distributing member is mounted to a lower portion of the body for distributing a pressure of the air supplied through the air passage. A membrane is mounted to enclose a lower surface of the air pressure distributing member so as to be expanded and shrunk by the pressure of the air supplied through the air pressure distributing member. A surface of the air pressure distributing member makes contact with a back surface of a wafer. An air pressure compensating member makes uniformly the pressure that is applied to central and edge portions of the wafer which makes contact with the membrane. Since the air pressure compensating member applies to the edge portion of the wafer, the air pressure is compensated so that the uniform air pressure is applied to the wafer. Thus, the wafer is uniformly polished.

What is claimed is:  
     
         1 . A polishing head of a chemical and mechanical polishing apparatus for polishing a wafer, said polishing head comprising: 
 a body having at least one air passage therein, through which air is introduced into the body and exhausted from the body;    an air pressure distributing unit mounted to a lower portion of the body for distributing air pressure supplied through the air passage;    a membrane for enclosing a lower surface of the air pressure distributing unit, the membrane having a lower surface for making contact with a back surface of the wafer, the membrane being expanded and shrunk by the pressure of the air supplied through the air pressure distributing unit; and    an air pressure compensating unit for distributing pressure to selected portions of the surface of the wafer contacting the membrane.    
     
     
         2 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 1 , wherein the selected portions of the surface of the wafer contacting membrane include a center portion and an edge portion of the wafer.  
     
     
         3 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 1 , wherein the air pressure compensating unit is disposed between the air pressure distributing unit and the membrane and an upper surface and a lower surface of the air pressure compensating unit are respectively fixed to edge of the lower surface of the air pressure distributing unit and edge of an upper surface of the membrane.  
     
     
         4 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 3 , wherein the air pressure compensating unit has a ring shape, which is adhered to edges of the air pressure distributing unit and the membrane.  
     
     
         5 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 4 , wherein the air pressure compensating unit has a cross-sectional shape of which an upper side and a lower side are parallel with each other, an inner side is inclined and an outer side is vertical to the upper and lower sides.  
     
     
         6 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 5 , wherein the inner side of the air pressure compensating unit is inclined in a direction to a center of the membrane so as to compensate a space between the membrane and an edge of the wafer when the membrane is expanded by the air pressure.  
     
     
         7 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 5 , wherein the air pressure compensating unit has a thickness enough to compensate an expanding difference between the edge portion and the center portion of the membrane when the membrane is expanded by the air pressure.  
     
     
         8 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 1 , wherein the air pressure compensating unit has a ring shape, disposing under the membrane and an edge of the membrane.  
     
     
         9 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 8 , wherein the air pressure compensating unit is inclined in a direction to a center of the membrane.  
     
     
         10 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 1 , wherein the air pressure compensating unit is comprised of resilient material.  
     
     
         11 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 10 , wherein the resilient material is a rubber or a silicon resin.  
     
     
         12 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 1 , wherein the air pressure distributing unit is formed as a disc shape having a predetermined diameter, in which a plurality of thru-holes are formed at portions within a range of a predetermined radius from a center of the disc shape.  
     
     
         13 . A polishing head of a chemical and mechanical polishing apparatus for polishing a wafer, said polishing head comprising: 
 a body having a plurality of air passages therein, through which air is introduced into and exhausted from the polishing head, and a retainer ring for securing the wafer, said body being movable upwardly and downwardly;    an air pressure distributing plate mounted to a lower portion of the body for distributing air pressure supplied through the air passages;    an air cushion connected with an end portion of one of the air passages so as to close the end portion and make contact with an edge portion of an upper surface of the air pressure distributing plate, the air cushion being resiliently expanded and shrunk during introducing and venting of the air through the air passages for applying pressure to the edge portion of the upper surface of the air pressure distributing plate;    a membrane mounted to enclose a lower surface of the air pressure distributing unit for being expanded and shrunk by the pressure of the air supplied through the air pressure distributing plate, a lower surface of the membrane making contact with a back side of the wafer; and    an air pressure compensating member for uniformly distributing the pressure that is applied at central and edge portions of the wafer which makes contact with the membrane.    
     
     
         14 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 13 , wherein the air pressure compensating member is disposed between the air pressure distributing plate and the membrane so that an upper surface and a lower surface of the air pressure compensating member are respectively fixed to an edge on the lower surface of the air pressure distributing plate and an edge of an upper surface of the membrane.  
     
     
         15 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 13 , wherein the air pressure compensating member has a ring shape, which is adhered to edges of the air pressure distributing plate and the membrane.  
     
     
         16 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 15 , wherein the air pressure compensating member has a cross-sectional shape in which an upper side and a lower side are in parallel with each other, an inner side is inclined and an outer side is vertical to the upper and lower sides.  
     
     
         17 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 16 , wherein the inner side of the air pressure compensating member is inclined in a direction to a center of the polishing he ad so as to compensate a space between the membrane and an edge of the wafer when the membrane is expanded by the air pressure.  
     
     
         18 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 16 , wherein the air pressure compensating member has a thickness enough to compensate an expanding difference between the edge portion and the center portion of the membrane when the membrane is expanded by the air pressure.  
     
     
         19 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 13 , wherein the air pressure compensating member has a ring shape, disposing under the membrane and an edge of the membrane.  
     
     
         20 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 19 , wherein the air pressure compensating member is inclined in a direction to a center of the membrane.  
     
     
         21 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 13 , wherein the air pressure compensating member is comprised of resilient material.  
     
     
         22 . The polishing heads of a chemical and mechanical polishing apparatus as claimed in  claim 21 , wherein the resilient material is a rubber or a silicon resin.  
     
     
         23 . The polishing head of a chemical and mechanical polishing apparatus as claimed in  claim 13 , further comprising a dividing plate between the body and the air pressure distributing member for reducing a space between the body and the air pressure distributing plate.