Silicon wafers and ingots with reduced oxygen content and methods for producing them

Abstract

Silicon nitride coated crucibles for holding melted semiconductor material and for use in preparing multicrystalline silicon ingots by a directional solidification process; methods for coating crucibles; methods for preparing silicon ingots and wafers; compositions for coating crucibles and silicon ingots and wafers with a low oxygen content.

1 . A silicon ingot having a bottom, a top and a height, H 3 , defined between the bottom and top, wherein the oxygen concentration of the ingot at a height about 20% of H 3  is less than about 4.5 ppma. 
     
     
         2 . A multicrystalline silicon ingot as set forth in  claim 1  wherein the oxygen concentration generally decreases from the bottom of the crucible toward the top of the crucible. 
     
     
         3 . A multicrystalline silicon ingot as set forth in  claim 1  wherein the oxygen concentration of the ingot at a height about 20% of H 3  is less than about 4.0 ppm. 
     
     
         4 . A multicrystalline silicon ingot as set forth in  claim 1  wherein the oxygen concentration of the ingot between a height about 20% of H 3  to a height about 80% of H 3  is less than about 3.0 ppma. 
     
     
         5 . A multicrystalline silicon ingot as set forth in  claim 1  wherein the oxygen concentration of the ingot between the bottom and the top is less than about 2.5 ppma. 
     
     
         6 . A multicrystalline silicon ingot as set forth in  claim 1  wherein the ingot is rectangular in shape. 
     
     
         7 . A multicrystalline silicon ingot as set forth in  claim 1  wherein the ingot contains multicrystalline silicon. 
     
     
         8 . A multicrystalline silicon ingot as set forth in  claim 1  wherein the ingot has an average nominal crystal grain size of from about 1 mm to about 15 mm. 
     
     
         9 . A multicrystalline silicon wafer with an oxygen concentration of less than about 2.5 ppma. 
     
     
         10 . A multicrystalline silicon wafer as set forth in  claim 9  wherein the wafer has an oxygen concentration of less than about 2 ppma. 
     
     
         11 . A multicrystalline silicon wafer as set forth in  claim 9  wherein the wafer has an oxygen concentration of from about 1 to about 3 ppma. 
     
     
         12 . A multicrystalline silicon wafer as set forth in  claim 9  wherein the wafer contains multicrystalline silicon. 
     
     
         13 . A multicrystalline silicon wafer as set forth in  claim 9  wherein the wafer has an average nominal crystal size of from about 1 mm to about 15 mm.