Polysilicon rod and method for manufacturing polysilicon rod

Abstract

A polysilicon rod wherein in an area whose distance from a center of a cross section of the polysilicon rod is within ⅔ of a radius and that excludes a seed core, average grain boundary characteristics have following features:a coincidence grain boundary ratio exceeds 20%, a grain boundary length exceeds 550 mm/mm2, and a random grain boundary length does not exceed 800 mm/mm2.

What is claimed is: 
     
         1 . A polysilicon rod wherein in an area whose distance from a center of a cross section of the polysilicon rod is within ⅔ of a radius and that excludes a seed core, average grain boundary characteristics have following features:
 a coincidence grain boundary ratio exceeds 20%, a grain boundary length exceeds 550 mm/mm 2 , and a random grain boundary length does not exceed 800 mm/mm 2 . 
 
     
     
         2 . The polysilicon rod according to  claim 1 , wherein the coincidence grain boundary ratio exceeds 25%, the grain boundary length exceeds 650 mm/mm 2 , and the random grain boundary length does not exceed 700 mm/mm 2 . 
     
     
         3 . The polysilicon rod according to  claim 1 , wherein the coincidence grain boundary ratio does not exceed 90%, and the grain boundary length does not exceed 3000 mm/mm 2 . 
     
     
         4 . A polysilicon rod wherein in an area including the entire polysilicon rod but a seed core, average grain boundary characteristics have following features:
 a coincidence grain boundary ratio exceeds 20%, a grain boundary length exceeds 550 mm/mm 2 , and a random grain boundary length does not exceed 800 mm/mm 2 .   
     
     
         5 . The polysilicon rod according to  claim 4 , wherein the coincidence grain boundary ratio exceeds 25%, the grain boundary length exceeds 650 mm/mm 2 , and the random grain boundary length does not exceed 700 mm/mm 2 . 
     
     
         6 . The polysilicon rod according to  claim 4 , wherein the coincidence grain boundary ratio does not exceed 90%, and the grain boundary length does not exceed 3000 mm/mm 2 . 
     
     
         7 . A method for manufacturing a polysilicon rod according to  claim 1 , wherein manufacturing conditions are fed back
 by using a ratio of coincidence grain boundaries to all grain boundaries as an index that expresses a feature of a grain boundary; and   by using a value obtained by dividing a length of a grain boundary that has appeared on a surface when the polysilicon rod is cut at an arbitrary position by a measured area, as an index of a breadth of a grain boundary surface in polysilicon.   
     
     
         8 . The method for manufacturing a polysilicon rod according to  claim 7 , wherein a ratio of Σ3 to 9 coincidence grain boundaries is used as an index that expresses a feature of a grain boundary.