Wafer Holder And Method Of Holding A Wafer

Abstract

A wafer holder including a wafer stage and a wafer stage outer-ring surrounding the wafer stage wherein the wafer stage has a diameter smaller than the diameter of a wafer loaded on the wafer stage, the wafer stage outer-ring has an inner diameter at the upper side of the outer-ring which is larger than the diameter of the wafer loaded on the wafer stage, and the upper surface of the outer-ring lies above the upper surface of the wafer loaded on the wafer stage.

1 . A wafer holder, comprising: 
 a wafer stage having an upper surface for supporting a wafer; and    a wafer stage outer-ring surrounding said wafer stage;    said wafer stage has an outer diameter;    said wafer stage outer-ring has a first inner diameter at an upper portion of said outer-ring and a second inner diameter at a lower portion of the wafer stage outer ring, the first inner diameter being larger than the second inner diameter;    the wafer stage outer diameter being smaller than the wafer stage outer-ring second inner diameter;    an upper surface of the wafer stage outer-ring lies above the upper surface of the wafer stage, and all of the lower portion of the wafer stage outer ring lies below the upper surface of the wafer stage, such that a wafer on the wafer stage lies adjacent the upper portion of the wafer stage outer ring between the upper surface of the wafer stage outer ring and the lower portion of the wafer stage outer ring.    
   
   
       2 . The wafer holder claimed in  claim 1 , wherein the second inner diameter of the wafer stage outer ring is smaller than a diameter of the wafer but larger than the outer diameter of said wafer stage.  
   
   
       3 . The wafer holder claimed in  claim 1 , wherein: 
 said wafer stage outer-ring has a horizontal plane between the wafer stage outer ring upper portion and the wafer stage outer ring lower portion; and    said horizontal plane lies below the upper surface of the wafer stage.    
   
   
       4 . The wafer holder claimed in  claim 1 , wherein said wafer stage is made of two or more separate pieces for adjusting the height of said wafer stage thereby adjusting the space between the upper surface of said wafer stage and the upper surface of said wafer stage outer-ring.  
   
   
       5 . The wafer holder claimed in  claim 2 , wherein said wafer stage is made of two or more separate pieces for adjusting the height of said wafer stage thereby adjusting the space between the upper surface of said wafer stage and the upper surface of said wafer stage outer-ring.  
   
   
       6 . The wafer holder claimed in  claim 3 , wherein said wafer stage is made of two or more separate pieces for adjusting the height of said wafer stage thereby adjusting the space between the upper surface of said wafer stage and the upper surface of said wafer stage outer-ring.  
   
   
       7 . A method of holding a wafer, the method comprising: 
 providing a wafer stage having an upper surface for supporting a wafer and a wafer stage outer-ring surrounding said wafer stage;    putting a wafer on the upper surface of a wafer stage, wherein an outer diameter of the wafer is larger than an outer diameter of the wafer stage; and    said wafer stage outer-ring has a first inner diameter at an upper portion of said wafer stage outer-ring and a second inner diameter at a lower portion of the wafer stage outer ring, the first inner diameter being larger than the second inner diameter and being larger than the outer diameter of the wafer;    the wafer stage outer diameter being smaller than the wafer stage outer-ring second inner diameter;    the second inner diameter of the wafer stage outer ring being smaller than the outer diameter of the wafer; and    an upper surface of the wafer stage outer-ring lies above the upper surface of the wafer stage, and all of the lower portion of the wafer stage outer ring lies below the upper surface of the wafer stage, such that the wafer on the wafer stage lies adjacent the upper portion of the wafer stage outer ring between the upper surface of the wafer stage outer ring and the lower portion of the wafer stage outer ring.    
   
   
       8 . The method of  claim 7 , wherein: 
 said wafer stage outer-ring has a horizontal plane between the wafer stage outer ring upper portion and the wafer stage outer ring lower portion; and    said horizontal plane lies below the upper surface of the wafer stage.    
   
   
       9 . The method of  claim 7 , wherein said wafer stage is made of two or more separate pieces for adjusting the height of said wafer stage thereby adjusting the space between the upper surface of said wafer stage and the upper surface of said wafer stage outer-ring.