Method and apparatus for conformable polishing

Abstract

Methods and apparatus provide for a conformable polishing head for uniformly polishing a workpiece. The polishing head includes an elastic polishing pad mounted on an elastic membrane that seals a cavity in the polishing head. The cavity is pressurized to expand the membrane and press the polishing pad down on the top surface of the workpiece, such that the polishing pad conforms to the surface and applies a substantially uniform pressure distribution across the workpiece and thereby uniformly removes material across high and low spots on the workpiece.

1 - 12 . (canceled) 
     
     
         13 . A method for uniformly removing material from a surface of a workpiece, comprising the steps of:
 mounting the workpiece to a table;   pressing a flexible annular polishing pad against the surface of the workpiece with substantially uniform pressure distribution;   rotating the annular polishing pad, while translating the annular polishing pad across the surface of the workpiece, thereby removing a substantially uniform thickness of material from the surface of the workpiece.   
     
     
         14 . A method according to  claim 13 , wherein the step of translating the annular polishing pad across the surface of the workpiece comprises oscillating one of the polishing pad and the table. 
     
     
         15 . A method according to  claim 13 , wherein the step of translating the annular polishing pad across the surface of the workpiece comprises conveying a plurality of workpieces on the table and past the annular polishing pad one workpiece at a time in continuous process. 
     
     
         16 . A method according to  claim 13 , wherein the step of pressing the flexible annular polishing pad against the surface of the workpiece with substantially uniform pressure comprises providing an inflatable elastic membrane behind the annular polishing pad, inflating the elastic membrane, and thereby conformably pressing the annular polishing pad against the surface of the workpiece with a substantially uniform pressure. 
     
     
         17 . A method according to  claim 13 , further comprising the step of supplying polishing slurry through a center of the elastic membrane and a center of the polishing pad to the surface of the workpiece. 
     
     
         18 . A method according to  claim 13 , wherein:
 the workpiece has an undulating surface and a layer of material on the undulating surface, the layer of material having a thickness that is less than a height of undulations on the surface; and   the steps of pressing a flexible annular polishing pad against the surface of the workpiece with substantially uniform pressure distribution, rotating the annular polishing pad, and translating the annular polishing pad across the surface of the workpiece, remove a substantially uniform thickness of material from the layer of material without entirely removing the layer of material at a top of any undulations on the surface of the workpiece.   
     
     
         19 . A method according to  claim 18 , wherein the layer of material is thinner than the height of the undulations. 
     
     
         20 . A method according to  claim 19 , wherein the workpiece is a flat rectangular workpiece. 
     
     
         21 . A method according to  claim 13 , wherein the workpiece is a flat rectangular workpiece. 
     
     
         22 . (canceled)