Enhanced n-type silicon material for epitaxial wafer substrate and method of making same

Abstract

An enhanced n + silicon material for epitaxial substrates and a method for producing it are described. The enhanced material leads to improved gettering characteristics of n/n + epitaxial wafers based on these substrates. The method for preparing such n + silicon material includes applying a co-doping of carbon to the usual n dopant in the silicon melt, before growing respective CZ crystals. This improves yield of enhanced n + silicon material in crystal growing and ultimately leads to device yield stabilization or improvement when such n/n + epitaxial wafers are applied in device manufacturing.

1 . An enhanced n +  silicon crystal material for epitaxial substances having: 
 a dopant of n-type material at a concentration of at least 10 18  atoms cm −3 ; and  
 a co-dopant of carbon at a concentration of at least 10 16  atoms cm −3 .  
 
     
     
         2 . An enhanced n +  silicon crystal material for epitaxial substances as defined in  claim 1  wherein said dopant of n-type material is arsenic at a concentration of at least 10 19  atoms cm −3 .  
     
     
         3 . An enhanced n +  silicon crystal material for epitaxial substances as defined in  claim 1  wherein said dopant of n-type material is antimony.  
     
     
         4 . An enhanced n +  silicon crystal material for epitaxial substances as defined in  claim 1  wherein said dopant on n-type material is phosphorus at a concentration of at least 10 19  atoms cm −3 .  
     
     
         5 . An enhanced n +  silicon crystal material for epitaxial substances as defined in  claim 1  in which the co-dopant of carbon is present in a concentration of at least 1.9×10 16  atoms cm −3 .  
     
     
         6 . An enhanced n +  silicon crystal material for epitaxial substances as defined in  claim 1  in which the co-dopant of carbon is present in a concentration sufficient in the presence of said n +  doping concentration to produce oxygen-precipitation-related bulk defects in the material of at least 10 9  defects cm −3 .  
     
     
         7 . A wafer of an enhanced n +  silicon crystal material according to  claim 1 , including: 
 an epitaxial layer on a major surface of the substrate wafer, thereby providing an active device layer for active device layer formation decoupled from defects in the substrate wafer,  
 the epitaxial layer having an n-type dopant concentration at least 3 orders of magnitude less than the n +  doping concentration.  
 
     
     
         8 . A method for preparing n +  silicon material comprising the steps of: 
 applying a dopant of phosphorus to silicon melt in an amount sufficient to produce an n +  doping concentration of at least 10 18  atoms cm −3 ;  
 applying a co-dopant of carbon to the silicon melt in an amount effective to promote oxygen precipitation in the silicon material in the presence of said n +  doping concentration; and  
 applying a seed crystal to said melt and growing a crystal therefrom by withdrawing the seed in the Czochralski technique, wherein said co-dopant of carbon is at a concentration of at least 10 16  atoms cm −3 .  
 
     
     
         9 . A method for preparing n +  silicon material as defined in  claim 1  wherein said dopant of phosphorus produces an n-type doping concentration of at least 10 19  atoms cm −3 .  
     
     
         10 . A method for preparing n +  silicon material as defined in  claim 1  wherein said co-dopant of carbon is at a concentration of at least 10 16  atoms cm −3 .  
     
     
         11 . A method for preparing n +  silicon material comprising the steps of: 
 applying a dopant of phosphorus to silicon melt in an amount sufficient to produce an n +  doping concentration of at least 10 19  atoms cm −3 ;  
 applying a co-dopant of carbon to the silicon melt; and  
 applying a seed crystal to said melt and growing a crystal therefrom by withdrawing the seed in the Czochralski technique;  
 the co-dopant of carbon being applied in an amount sufficient to produce a carbon concentration of at least 1.9×10 16  atoms cm −3 .  
 
     
     
         12 . A method for preparing n +  silicon material comprising the steps of: 
 applying a dopant of phosphorus to silicon melt in an amount sufficient to produce an n +  doping concentration of at least 10 19  atoms cm −3 ;  
 applying a co-dopant of carbon to the silicon melt; and  
 applying a seed crystal to said melt and growing a crystal therefrom by withdrawing the seed in the Czochralski technique;  
 the co-dopant of carbon being applied in a concentration sufficient in the presence of said n +  doping concentration to produce oxygen-precipitation-related bulk defects in the material of at least 10 9  defects cm −3 .  
 
     
     
         13 . A method for preparing n +  silicon material comprising the steps of: 
 applying a dopant of phosphorus to silicon melt in an amount sufficient to produce an n +  doping concentration of at least 10 19  atoms cm −3 ;  
 applying a co-dopant of carbon to the silicon melt in an amount sufficient to produce a carbon concentration in the n +  silicon material of at least 1.9×10 6  atoms cm −3 ; and  
 applying a seed crystal to said melt and growing a crystal therefrom by withdrawing the seed in the Czochralski technique;  
 slicing the crystal into wafers and manufacturing substrate wafers therefrom; and  
 forming an epitaxial layer on a major surface of the substrate wafers, thereby providing an active device layer for active device layer formation decoupled from defects in the substrate wafer,  
 the epitaxial layer having an n-type dopant concentration at least 3 orders of magnitude less than the n +  doping concentration.