Process for producing high-purity silicon and apparatus

Abstract

When high purity silicon is produced through a gas-phase reaction between silicon tetra-chloride and zinc in a reaction furnace, the produce silicon is obtained as block or molten state. after the reaction in which the silicon is not in contact with air and reaction temperature is maintained at melting point of the silicon or less.

1 . An apparatus for producing silicon for obtaining solid or liquid silicon and gaseous zinc chloride through a gas-phase reaction between silicon tetra-chloride and zinc comprising:
 a reaction furnace section;   a silicon reservoir section placed below the reaction furnace section;   an inlet of reaction gas;   an outlet of produced zinc chloride gas; and   a refractory and electrically conductive trap equipped with a heating mechanism for collecting the solid or liquid silicon produced by the reaction in the reaction furnace,   wherein the trap is heated to silicon melting temperature or more during or after cease of supply of the reaction gas for liquefying the silicon which is then sent to the silicon reservoir section.   
   
   
       2 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that the silicon reservoir section is placed below the reaction furnace section, and the silicon melted in the reaction furnace is sent to the reservoir section by gravity. 
   
   
       3 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that temperature of heating the reaction furnace section is from 910° C. to 1500° C., and a temperature control mechanism which can arbitrary maintain the temperature in the temperature region is provided. 
   
   
       4 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that an inner wall of the reaction furnace is mainly made of quartz glass. 
   
   
       5 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that an inner wall of the reaction furnace is made of tantalum which is concurrently heated with the trap. 
   
   
       6 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that the reaction furnace is a cyclone furnace, and the trap is a mesh positioned inside of the reaction furnace inner wall. 
   
   
       7 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that porous and/or mesh type metal is filled in the reaction furnace. 
   
   
       8 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that the trap is a porous and sintered member for a metal filter placed in the reaction furnace. 
   
   
       9 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that the refractory and electrically conductive trap is made of tantalum and/or molybdenum. 
   
   
       10 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that the refractory and electrically conductive trap is heated by induction heating. 
   
   
       11 . The apparatus for producing the silicon as claimed in  claim 1  characterized in that the refractory and electrically conductive trap is heated by direct electric power current to the trap. 
   
   
       12 . A method of producing silicon for obtaining solid or liquid silicon and gaseous zinc chloride through a gas-phase reaction between silicon tetra-chloride and zinc comprising the steps of
 placing a refractory and electrically conductive trap for collecting the solid or liquid silicon produced by the reaction in the reaction furnace; and   heating the trap to silicon melting temperature or more during or after cease of supply of the reaction gas for liquefying the produced silicon for collection.   
   
   
       13 . The method of producing the silicon as claimed in  claim 12  characterized in that the reaction is performed from 910° C. to 1500° C. 
   
   
       14 . The method of producing the silicon as claimed in  claim 12  characterized in that atmospheric gas is zinc chloride. 
   
   
       15 . The method of producing the silicon as claimed in  claim 12  characterized in that a stoichiometric excess amount of zinc gas is supplied with respect to silicon tetra-chloride. 
   
   
       16 . The method of producing the silicon as claimed in  claim 12  characterized in that the heating temperature of the trap is from 1410° C. to 1500° C. 
   
   
       17 . The method of producing the silicon as claimed in  claim 12  characterized in that the silicon produced in a reservoir section is maintained at 1410° C. or less. 
   
   
       18 . The method of producing the silicon as claimed in  claim 12  characterized in that the reserved silicon in the reservoir section is externally taken out after the silicon is melted and de-gasified. 
   
   
       19 . The method of producing the silicon as claimed in  claim 12  characterized in that the zinc chloride produced in the reaction is taken out from the system and is decomposed into chlorine and zinc through electrolysis, and the chlorine is used for silicon tetra-chloride production, and the zinc is returned to the reaction furnace section as reaction gas for re-circulation. 
   
   
       20 . The method of producing the silicon as claimed in  claim 12  characterized in that the supply gas is supplied to the reaction furnace after preheating.