Methods and Apparatus for Manufacturing Monocrystalline Cast Silicon and Monocrystalline Cast Silicon Bodies for Photovoltaics

Abstract

Methods and apparatuses are provided for casting silicon for photovoltaic cells and other applications. With such methods and apparatuses, a cast body of monocrystalline silicon may be formed that is free of, or substantially free of, radially-distributed impurities and defects and having at least two dimensions that are each at least about 35 cm is provided.

What is claimed is: 
     
         1 . A method of manufacturing cast silicon, comprising:
 placing molten silicon in contact with at least one silicon seed crystal in a vessel having one or more side walls heated to at least the melting temperature of silicon and at least one wall for cooling;   melting a desired portion of the at least one seed crystal by measuring the extent of melting; and   forming a solid body comprising near-monocrystalline silicon by cooling the molten silicon to control crystallization, wherein the forming includes forming a solid-liquid interface at an edge of the molten silicon that at least initially parallels the at least one wall for cooling, the interface being controlled during the cooling so as to move in a direction that increases a distance between the molten silicon and the at least one wall for cooling.   
     
     
         2 . The method according to  claim 1 , wherein the placing further includes placing the at least one silicon seed crystal in a bottom of a crucible, and further wherein the cooling moves the solid-liquid interface in a direction away from the bottom of the crucible while maintaining the edge that parallels the at least one wall for cooling. 
     
     
         3 . The method according to  claim 2 , further comprising arranging the at least one seed crystal so that a specific pole direction is perpendicular to a bottom of the crucible. 
     
     
         4 . The method according to  claim 2 , wherein the placing molten silicon further includes melting silicon feedstock in a melt container separate from the crucible, heating the crucible and the silicon to the melting temperature of silicon, controlling the heating so that the at least one seed crystal in the crucible does not melt completely, and transferring the molten silicon from the melt container into the crucible. 
     
     
         5 . The method according to  claim 2 , further including forming a portion of the body to include the at least one seed crystal.