Silica crucible with inner layer crystallizer and method

Abstract

A silica glass crucible is disclosed comprising a barium-doped inner wall layer. The crucible is made by introducing into a rotating crucible mold bulk silica grain to form a bulky wall. After heating the interior of the mold to fuse the bulk silica grains, an inner silica grain, doped with barium, is introduced. The heat at least partially melts the inner silica grain, allowing it to fuse to the wall to form an inner layer. The inner layer of the crucible crystallizes when used in a CZ process, extending the operating life of the crucible.

1 . A crucible comprising: 
 a wall having a side portion and a bottom portion thereby defining an interior cavity, said wall comprising: 
 a bulk layer; and  
 an inner layer doped with barium.  
   
     
     
         2 . The crucible of  claim 1 , wherein the inner layer is in the range of 0.2-1.2 mm deep.  
     
     
         3 . The crucible of  claim 1 , wherein the inner layer is doped with barium in the range of about 5-150 ppm.  
     
     
         4 . The crucible of  claim 3 , wherein the inner layer is doped with barium in the range of about 15-75 ppm.  
     
     
         5 . The crucible of  claim 1 , the wall further comprising a metal-doped outer layer formed on an outer portion of said wall.  
     
     
         6 . The crucible of  claim 5 , wherein the outer layer is substantially an outer layer of the side portion.  
     
     
         7 . The crucible of  claim 5 , wherein the outer layer is substantially 0.5-2.5 mm deep.  
     
     
         8 . The crucible of  claim 5 , wherein the outer layer is doped with aluminum in the range of about 100-500 ppm.  
     
     
         9 . The crucible of  claim 1 , wherein said inner layer is at least partially crystallized.  
     
     
         10 . The crucible of  claim 1 , wherein said inner layer is adapted to substantially completely crystallize prior to full melt-down of a silicon charge in a Czochralski process.  
     
     
         11 . A method for making a silica glass crucible, comprising: 
 forming a bulk grain layer on an interior surface of a rotating crucible mold, said bulk grain layer having a bottom portion, a side portion and a bulk grain layer interior surface;    generating a region of heat in the interior of the mold, wherein the region of heat at least partially fuses said bulk grain layer to form a bulk layer; and    depositing a barium-containing inner layer on the bulk grain layer interior surface.    
     
     
         12 . The method of  claim 11 , wherein forming a bulk grain layer comprises introducing into the rotating crucible mold bulk silica grain.  
     
     
         13 . The method of  claim 12 , wherein bulk silica grain consists essentially of quartz grain.  
     
     
         14 . The method of  claim 11 , wherein a selected thickness of the inner layer is in the range of 0.2-1.0 mm.  
     
     
         15 . The method of  claim 11 , wherein depositing a barium-containing inner layer comprises introducing into said mold inner silica grain doped with barium, wherein the region of heat at least partially melts said inner silica grain and fuses said at least partially molten inner silica grain to the bulk layer.  
     
     
         16 . The method of  claim 15 , wherein the inner silica grain is doped with barium in the range of 5-150 ppm.  
     
     
         17 . The method of  claim 15 , wherein the inner silica grain is doped with barium in the range of 15-75 ppm.  
     
     
         18 . The method of  claim 11 , wherein depositing a barium-containing inner layer comprises introducing into said mold inner silica grain and barium, and wherein the region of heat at least partially melts said inner silica grain and fuses said at least partially molten inner silica grain to the bulk layer.  
     
     
         19 . The method of  claim 18 , wherein the inner silica grain consists essentially of natural silica grain.  
     
     
         20 . The method of  claim 18 , wherein the inner silica grain consists essentially of synthetic silica grain.  
     
     
         21 . The method of  claim 18 , wherein the barium is a solid compound admixed with the inner silica grain.  
     
     
         22 . The method of  claim 21 , wherein the solid barium compound is admixed with the inner silica grain prior to introducing into said mold inner silica grain and barium.  
     
     
         23 . The method of  claim 11 , further comprising, prior to forming a bulk grain layer: 
 forming an outer grain layer on an interior surface of a rotating crucible mold, wherein the region of heat at least partially fuses said outer grain layer to form an outer layer.    
     
     
         24 . The method of  claim 23 , wherein the outer layer is formed substantially on the side portion.  
     
     
         25 . The method of  claim 23 , wherein forming an outer grain layer comprises introducing into the rotating crucible mold outer silica grain.  
     
     
         26 . The method of  claim 25 , wherein the outer silica grain is doped with aluminum in the range of 100-500 ppm.  
     
     
         27 . A crucible comprising: 
 a wall having a side portion and a bottom portion thereby defining an interior cavity, said wall comprising: 
 a bulk layer;  
 an inner layer formed, said inner layer being doped with barium; and  
 a transition layer formed between the inner layer and the bulk layer.  
   
     
     
         28  The crucible of  claim 27 , wherein the inner layer is in the range of 0.2-1.2 mm deep.  
     
     
         29 . The crucible of  claim 27 , wherein the inner layer is doped with barium in the range of about 5-150 ppm.  
     
     
         30 . The crucible of  claim 29 , wherein the inner layer is doped with barium in the range of about 15-75 ppm.  
     
     
         31 . The crucible of  claim 27 , wherein the transition layer is free of barium doping.  
     
     
         32 . The crucible of  claim 31 , wherein the transition layer consists essentially of pure natural silica glass.  
     
     
         33 . The crucible of  claim 31 , wherein the transition layer consists essentially of pure synthetic silica glass.  
     
     
         34 . The crucible of  claim 27 , wherein the transition layer is doped with a metal.  
     
     
         35 . The crucible of  claim 34 , wherein the metal is aluminum.  
     
     
         36 . The crucible of  claim 27 , further comprising an aluminum-doped outer layer formed on an exterior aspect of the wall.  
     
     
         37 . The crucible of  claim 36 , wherein the aluminum-doped outer layer is substantially an outer layer of the side portion of the wall.  
     
     
         38 . The crucible of  claim 36 , wherein the outer layer is no more than substantially 0.5-2.5 mm deep.  
     
     
         39 . The crucible of  claim 36 , wherein the outer layer is doped with aluminum in the range of about 100-500 ppm.  
     
     
         40 . The crucible of  claim 27 , wherein said inner layer is at least partially crystallized.  
     
     
         41 . The crucible of  claim 27 , wherein said inner layer is adapted to substantially completely crystallize prior to full melt-down of a silicon charge in a Czochralski process.  
     
     
         42 . A method for making a silica glass crucible, comprising: 
 forming a bulk grain layer on an interior surface of a rotating crucible mold;    generating a region of heat in the interior of the mold, wherein the region of heat at least partially fuses said bulk grain layer to form a bulk layer;    depositing a transition layer on the bulk grain layer; and    depositing a barium-containing inner layer on the transition layer.    
     
     
         43 . The method of  claim 33 , wherein a selected thickness of the inner layer is in the range of 0.2-1.0 mm.  
     
     
         44 . The method of  claim 42 , wherein forming a bulk grain layer comprises introducing into a rotating crucible mold bulk silica grain.  
     
     
         45 . The method of  claim 44 , wherein the bulk silica grain consists essentially of quartz grain.  
     
     
         46 . The method of  claim 42 , wherein depositing a transition layer comprises introducing into a rotating crucible mold transition silica grain, wherein the region of heat at least partially melts said transition silica grain and fuses said at least partially molten transition silica grain to the bulk layer to form a transition layer.  
     
     
         47 . The method of  claim 46 , wherein the transition silica grain consists essentially of pure natural silica grain.  
     
     
         48 . The method of  claim 46 , wherein the transition silica grain consists essentially of pure synthetic silica grain.  
     
     
         49 . The method of  claim 46 , wherein the transition silica grain is doped with a metal.  
     
     
         50 . The method of  claim 49 , wherein the metal is aluminum.  
     
     
         51 . The method of  claim 42 , wherein a selected thickness of the inner layer is in the range of 0.2-1.0 mm.  
     
     
         52 . The method of  claim 42 , wherein depositing a barium-containing inner layer comprises introducing into said mold inner silica grain doped with barium, wherein the region of heat at least partially melts said inner silica grain and fuses said at least partially molten inner silica grain to the bulk layer.  
     
     
         53 . The method of  claim 52 , wherein the inner silica grain is doped with barium in the range of 5-150 ppm.  
     
     
         54 . The method of  claim 52 , wherein the inner silica grain is doped with barium in the range of 15-75 ppm.  
     
     
         55 . The method of  claim 42 , wherein depositing a barium-containing inner layer comprises introducing into said mold inner silica grain and barium, and wherein the region of heat at least partially melts said inner silica grain and fuses said at least partially molten inner silica grain to the bulk layer.  
     
     
         56 . The method of  claim 55 , wherein the inner silica grain consists essentially of natural silica grain.  
     
     
         57 . The method of  claim 55 , wherein the inner silica grain consists essentially of synthetic silica grain.  
     
     
         58 . The method of  claim 55 , wherein the barium is a solid compound admixed with the inner silica grain.  
     
     
         59 . The method of  claim 58 , wherein the solid barium compound is admixed with the inner silica grain prior to introducing into said mold inner silica grain and barium.  
     
     
         60 . The method of  claim 42 , further comprising, prior to forming a bulk grain layer: 
 forming an outer grain layer on an interior surface of a rotating crucible mold, wherein the region of heat at least partially fuses said outer grain layer to form an outer layer.    
     
     
         61 . The method of  claim 60 , wherein the outer layer is formed substantially on the side portion.  
     
     
         62 . The method of  claim 60 , wherein forming an outer grain layer comprises introducing into the rotating crucible mold outer silica grain.  
     
     
         63 . The method of  claim 62 , wherein the outer silica grain is doped with aluminum in the range of 100-500 ppm.