Method for etching a wafer in a plasma etch reactor

Abstract

This invention is a hardware modification which permits greater uniformity of etching to be achieved in a high-density-source plasma reactor (i.e., one which uses a remote source to generate a plasma, and which also uses high-frequency bias power on the wafer chuck). The invention addresses the uniformity problem which arises as the result of nonuniform power coupling between the wafer and the walls of the etch chamber. The solution to greatly mitigate the nonuniformity problem is to increase the impedance between the wafer and the chamber walls. This may be accomplished by placing a cylindrical dielectric wall around the wafer. Quartz is a dielectric material that is ideal for the cylindrical wall if silicon is to be etched selectively with respect to silicon dioxide, as quartz it is virtually inert under such conditions.

1 - 9 . (canceled)  
   
   
       10 . A method for etching a wafer in a plasma etch reactor having a main chamber with a sidewall and a wafer chuck, comprising: 
 disposing a wafer on the wafer chuck, wherein the wafer is surrounded by a dielectric ring that prevents electrical coupling between the wafer and the chamber sidewall;    generating a plasma in a source chamber; and    supplying the plasma to the main chamber.    
   
   
       11 . The method of  claim 10 , wherein the dielectric ring extends above a plane defined by an upper surface of the wafer.  
   
   
       12 . The method of  claim 10 , wherein the plasma is high-density plasma.  
   
   
       13 . The method of  claim 10 , generating the plasma in the source chamber comprises the use of a Mori source, a helicon source, or an ECR source.  
   
   
       14 . The method of  claim 10 , wherein the dielectric ring comprises quartz.  
   
   
       15 . The method of  claim 10 , further comprising establishing a voltage differential between the wafer chuck and the chamber sidewall.