Wet chemical treatment to form a thin oxide for high k gate dielectrics

Abstract

Described herein are methods of forming a thin silicon dioxide layer having a thickness of less than eight angstroms on a semiconductor substrate to form the bottom layer of a gate dielectric. A silicon dioxide layer having a thickness of less than eight angstroms may be formed by two different methods. In one method, a sulfuric acid solution is applied to a semiconductor substrate to grow a silicon dioxide layer of less than eight angstroms. The growth of the silicon dioxide layer by the sulfuric acid solution is self-limiting. In another method, a hydrogen peroxide containing solution is applied to a semiconductor substrate for a time sufficient to grow a silicon dioxide layer having a thickness of greater than eight angstroms and then applying an etching solution to etch the silicon dioxide layer down to a thickness of less than eight angstroms.

1 . A device, comprising: 
 a semiconductor substrate;    a pair of source and drain regions formed within the semiconductor substrate;    a composite gate dielectric layer formed above the semiconductor substrate and the pair of source and drain regions, comprising a silicon dioxide layer having a thickness of less than approximately 8 angstroms and a high dielectric constant material; and    a gate electrode formed above the composite gate dielectric layer.    
   
   
       2 . The device of  claim 1 , wherein the silicon dioxide layer has a thickness in the approximate range of 2 angstroms and 4 angstroms.  
   
   
       3 . The device of  claim 1 , wherein the silicon dioxide layer is a monolayer.  
   
   
       4 . The device of  claim 1 , wherein the silicon dioxide layer is terminated with ammonium groups.  
   
   
       5 . The device of  claim 1 , wherein 1%-10% of silicon atoms at a surface of the silicon dioxide layer are terminated with ammonium groups.  
   
   
       6 . The device of  claim 1 , wherein the high dielectric constant material is halfnium oxide.