Silicon single crystal, and process for producing it

Abstract

A silicon single crystal which, over an ingot length of over 10 percent of the total ingot length, has a uniform defect picture and narrow radial dopant and oxygen variations. The process in accordance with the Czochralski method involves bringing about a temperature distribution in the melt in the region of the solidification interface which deviates from rotational symmetry.

What is claimed is:  
     
         1 . A silicon single crystal 
 which, over an ingot length of over 10 percent of a total ingot length, has a uniform defect picture and narrow radial dopant and oxygen variations.    
     
     
         2 . The silicon single crystal as claimed in  claim 1 , 
 which over an ingot length of over 10 percent of the total ingot length is free of agglomerated intrinsic point defects over at least 60 percent of cross-sectional area.    
     
     
         3 . The silicon single crystal as claimed in  claim 1 , 
 which over an ingot length of over 10 percent of the total ingot length includes only agglomerated vacancies.    
     
     
         4 . The silicon single crystal as claimed in  claim 1 , 
 which over an ingot length of over 10 percent of the total ingot length includes only agglomerated interstitials.    
     
     
         5 . The silicon single crystal as claimed in  claim 1 , 
 which over an ingot length of over 10 percent of the total ingot length has radial dopant variations of less than 10%.    
     
     
         6 . The silicon single crystal as claimed in  claim 1 , 
 which over an ingot length of over 10% of the total ingot length has radial oxygen variations of less than 10%.    
     
     
         7 . The silicon single crystal as claimed in  claim 1 , 
 having a diameter of at least 200 mm.    
     
     
         8 . A silicon semiconductor wafer 
 which is obtained from the silicon single crystal as claimed in  claim 1 .    
     
     
         9 . A process for producing a silicon single crystal comprising 
 pulling the silicon single crystal using Czochralski method from a melt which is held in a rotating crucible; and    producing a temperature distribution which deviates from rotational symmetry in the melt in a region of a solidification interface.    
     
     
         10 . The process as claimed in  claim 9 , 
 wherein asymmetry of the temperature distribution is effected by applying a partially shielded traveling magnetic field.    
     
     
         11 . The process as claimed in  claim 10 , 
 wherein the partially shielded traveling magnetic field is used to control melt flows in order to make an axial temperature gradient more uniform over crystal diameter.    
     
     
         12 . The process as claimed in  claim 10 , 
 wherein the asymmetry of the temperature distribution is influenced by amplitude of the traveling magnetic field.    
     
     
         13 . The process as claimed in  claim 10 , 
 wherein the asymmetry of the temperature distribution is influenced by frequency of the traveling magnetic field.    
     
     
         14 . The process as claimed in  claim 10 , 
 wherein the asymmetry of the temperature distribution is influenced by shape and materials properties of the shield.    
     
     
         15 . The process as claimed in  claim 10 , 
 wherein the asymmetry of the temperature distribution is influenced by rotation of the crucible.    
     
     
         16 . The process as claimed in  claim 10 , 
 wherein the asymmetry of the temperature distribution is effected by extra-axial pulling of the silicon single crystal.    
     
     
         17 . The process as claimed in  claim 16 , 
 wherein the extra-axial pulling of the silicon single crystal makes an axial temperature gradient more uniform over crystal diameter.    
     
     
         18 . The process as claimed in  claim 9 , 
 wherein a curvature of a solidification interface is reduced.    
     
     
         19 . The process as claimed in  claim 9 , 
 wherein an axial temperature gradient is made more uniform at the solidification interface.    
     
     
         20 . A device for pulling a silicon single crystal using the Czochralski method, comprising 
 a crucible with a melt held in the crucible;    a heating device and a magnetic means which generates a traveling magnetic field;    both of these components being arranged around the crucible;    which device has a shield or a plurality of partial shields which eliminate a rotational symmetry of the magnetic field generated by the magnetic means.