Method and apparatus for refining a molten material

Abstract

A method for the directional solidification of silicon or other materials. A cooled plate is lowered into a silicon melt and an ingot of solid silicon is solidified downwards.

1 . A method of refining a material, which comprises the steps of: forming a melt of the material in a vessel; bringing a temperature controlled contact surface into contact with the surface of the melt said temperature controlled contact surface having no contact with the vessel sidewalls; allowing the molten material to solidify and adhere to the temperature controlled contact surface; and progressively solidifying the molten material downwards to form a solid ingot of the material adhering to the contact surface. 
   
   
       2 . The method of  claim 1 , wherein the temperature controlled contact surface is cooled. 
   
   
       3 . The method of  claim 1 , wherein the walls and bottom of the vessel are heated. 
   
   
       4 . The method of  claim 1 , wherein the melt is maintained in an inert or controlled atmosphere. 
   
   
       5 . The method of  claim 1 , wherein the liquid material remaining after solidification of the ingot contains a higher level of impurities than the starting material and is removed from the vessel. 
   
   
       6 . The method of  claim 1 , wherein the material is silicon. 
   
   
       7 . The method of  claim 1 , wherein the silicon is doped to provide the required resistivity in the final solidified ingot.