Center flex single side polishing head

Abstract

A polishing head assembly for single side polishing of silicon wafers includes a polishing head and a cap. The polishing head includes a top surface and a bottom surface and defines a longitudinal axis extending therethrough. The cap is positioned coaxially with the polishing head and includes an upper surface and a lower surface. The upper surface is spaced from the bottom surface of the polishing head to form a chamber that allows the cap to deflect toward the polishing head.

What is claimed is: 
     
         1 . A polishing head assembly for single side polishing of silicon wafers, the polishing head assembly comprising:
 a polishing head having a top surface and a bottom surface and defining a longitudinal axis extending therethrough; and   a cap positioned coaxially with the polishing head, the cap having an upper surface and a lower surface, the upper surface being spaced from the bottom surface of the polishing head to form a chamber therebetween to allow the cap to deflect toward the polishing head.   
     
     
         2 . The polishing head assembly of  claim 1 , further comprising a source of pressurized fluid connected with the chamber to increase a pressure within the chamber and to deflect the cap. 
     
     
         3 . The polishing head assembly of  claim 1 , further comprising a controller connected with the source of pressurized fluid to control the pressure within the chamber. 
     
     
         4 . The polishing head assembly of  claim 1 , further comprising a liquid on the lower surface of the cap to retain a wafer by surface tension. 
     
     
         5 . The polishing head assembly of  claim 4 , further comprising a wafer connected with the cap, the wafer being retained against the lower surface of the cap by surface tension. 
     
     
         6 . The polishing head assembly of  claim 1 , wherein the polishing head assembly is configured to cause movement of the polishing head along the longitudinal axis to increase and decrease a polishing pressure. 
     
     
         7 . The polishing head assembly of  claim 1 , further comprising a first stopper located within the chamber, between the polishing head and cap to limit deflection of the cap at a first location, the first stopper having a first height. 
     
     
         8 . The polishing head assembly of  claim 7 , further comprising a second stopper located within the chamber, between the polishing head and cap to limit deflection of the cap at a first location, the first stopper having a second height. 
     
     
         9 . The polishing head assembly of  claim 8 , wherein the second stopper is a ring coaxially located about the first stopper. 
     
     
         10 . The polishing head assembly of  claim 8 , wherein the first height is one of less than and greater than the second height. 
     
     
         11 . The polishing head assembly of  claim 8 , wherein the chamber has a chamber height, the chamber height is greater than at least one of the first height and the second height. 
     
     
         12 . A single side polishing apparatus for single side polishing of silicon wafers, the single side polishing apparatus comprising:
 a polishing pad;   a polishing head for forcing the wafer toward the polishing pad, the polishing head having a polishing side facing a location of the wafer;   a cap mounted in spaced relation from the polishing side of the polishing head, the cap being capable of deflecting toward the polishing head under a polishing pressure and away from the polishing head by an increase of pressure in the chamber.   a movable stopper located between the polishing head and the cap to limit deflection of the cap along a direction that is perpendicular to the polishing side of the polishing head.   
     
     
         13 . The single side polishing apparatus of  claim 12 , further comprising a source of pressurized fluid connected with the chamber to increase pressure within the chamber and to deform the cap. 
     
     
         14 . The single side polishing apparatus of  claim 12 , further comprising a second stopper located between the polishing head and the cap at a position radially outward from the movable stopper to limit deflection of the cap. 
     
     
         15 . The single side polishing apparatus of  claim 12 , wherein the cap is attached to the polishing head with an adhesive. 
     
     
         16 . The single side polishing apparatus of  claim 14 , wherein the floor is flat in an undeflected state. 
     
     
         17 . The single side polishing apparatus of  claim 12 , further comprising a movable stopper located between the polishing head and the cap to limit deflection of the cap along a direction that is perpendicular to the polishing side of the polishing head. 
     
     
         18 . The single side polishing apparatus of  claim 17 , further comprising a source of pressurized fluid connected with the stopper to adjust pressure within the stopper and to regulate a height of the stopper. 
     
     
         19 . A method for polishing of silicon wafers; the method comprising:
 providing a polishing apparatus including a polishing pad, a wafer carrier for retaining a wafer placed therein, and a polishing head assembly having a polishing head and a cap attached to a polishing side of the polishing head;   forcing the polishing head toward the polishing pad to cause the wafer to contact the polishing pad at a polishing pressure;   polishing a surface of the wafer by causing rotational movement of the polishing pad with respect to the wafer;   deflecting the cap with respect to the polishing head; and   adjusting the polishing pressure to regulate the deflection of the cap for improving flatness of the polished surface.   
     
     
         20 . The method of  claim 19 , further comprising adjusting an internal pressure within a chamber formed between the polishing head and the cap to deflect the cap for improving flatness of the polished surface. 
     
     
         21 . The method of  claim 19 , further comprising placing the wafer adjacent to the cap and retaining the wafer with surface tension to the cap. 
     
     
         22 . The method of  claim 19 , wherein the polishing head includes a stopper to limit the deflection of the cap. 
     
     
         23 . The method of  claim 22 , further comprising adjusting the height of the stopper to regulate the deflection of the cap. 
     
     
         24 . The method of  claim 23 , wherein adjusting the height of the stopper includes the step of adjusting pressure within the stopper.