Gas doping systems for controlled doping of a melt of semiconductor or solar-grade material

Abstract

A crystal pulling apparatus for producing an ingot is provided. The apparatus includes a furnace and a gas doping system. The furnace includes a crucible for holding a melt. The gas doping system includes a feeding tube, an evaporation receptacle, and a fluid flow restrictor. The feeding tube is positioned within the furnace, and includes at least one feeding tube sidewall, a first end through which a solid dopant is introduced into the feeding tube, and an opening opposite the first end through which a gaseous dopant is introduced into the furnace. The evaporation receptacle is configured to vaporize the dopant therein, and is disposed near the opening of the feeding tube. The fluid flow restrictor is configured to permit the passage of solid dopant therethrough and restrict the flow of gaseous dopant therethrough, and is disposed within the feeding tube between the first end and the evaporation receptacle.

1 . A crystal pulling apparatus for producing a semiconductor or solar-grade ingot, the apparatus comprising:
 a furnace including a crucible for holding a melt of semiconductor or solar-grade material; and   a gas doping system for introducing a dopant into the furnace, the gas doping system including
 a feeding tube positioned within the furnace, the feeding tube including at least one feeding tube sidewall, a first end through which a solid dopant is introduced into the feeding tube, and an opening opposite the first end through which a gaseous dopant is introduced into the furnace; 
 an evaporation receptacle configured to vaporize the dopant therein, the receptacle disposed near the opening of the feeding tube; and 
 a fluid flow restrictor configured to permit the passage of solid dopant therethrough and restrict the flow of gaseous dopant therethrough, the fluid flow restrictor disposed within the feeding tube between the first end and the evaporation receptacle. 
   
     
     
         2 . The crystal pulling apparatus as set forth in  claim 1  wherein the fluid flow restrictor includes a bottom having a second opening therethrough, and a second sidewall extending inwardly from a feeding tube sidewall towards the bottom. 
     
     
         3 . The crystal pulling apparatus as set forth in  claim 2  wherein the fluid flow restrictor is configured to permit the passage of solid dopant through the second opening, and to restrict the flow of gaseous dopant through the second opening. 
     
     
         4 . The crystal pulling apparatus as set forth in  claim 2  wherein the second sidewall includes a conically-shaped portion. 
     
     
         5 . The crystal pulling apparatus as set forth in  claim 1  wherein the evaporation receptacle includes a base extending inwardly from a feeding tube sidewall and a receptacle sidewall adjoining the base and extending upwardly from the base. 
     
     
         6 . The crystal pulling apparatus as set forth in  claim 5  wherein the gas doping system further includes a fluid flow channel at least partially defined by the receptacle sidewall and a feeding tube sidewall. 
     
     
         7 . The crystal pulling apparatus as set forth in  claim 1  wherein the feeding tube is communicatively coupled to a dopant feeding device configured to feed solid dopant into the feeding tube. 
     
     
         8 . The crystal pulling apparatus as set forth in  claim 1  wherein the feeding tube is communicatively coupled to an automated dopant feeding device configured to automatically feed solid dopants into the feeding tube. 
     
     
         9 . The crystal pulling apparatus as set forth in  claim 1  wherein the gas doping system further includes a fluid-distribution plate coupled to the feeding tube at a second end distal from the first end. 
     
     
         10 . The crystal pulling apparatus as set forth in  claim 1  wherein the feeding tube is slidingly coupled to a positioning system configured to raise and lower the feeding tube. 
     
     
         11 . The crystal pulling apparatus as set forth in  claim 1  wherein the opening of the feeding tube is angled at an angle of between about 45 degrees and about 75 degrees with respect to a longitudinal axis of the feeding tube. 
     
     
         12 . The crystal pulling apparatus as set forth in  claim 1  wherein the feeding tube is angled at an angle of between about 45 degrees and about 75 degrees with respect to a surface of the melt. 
     
     
         13 . The crystal pulling apparatus as set forth in  claim 1  wherein the evaporation receptacle is positioned sufficiently near the melt such that radiant heat from the melt is sufficient to vaporize the dopant within the evaporation receptacle. 
     
     
         14 . The crystal pulling apparatus as set forth in  claim 1  wherein the evaporation receptacle is positioned between about 1 centimeter and about 15 centimeters above a surface of the melt. 
     
     
         15 . The crystal pulling apparatus as set forth in  claim 1  wherein the feeding tube is communicatively coupled to an inert gas supply. 
     
     
         16 . A method of using the crystal pulling apparatus as set forth in  claim 15 , the method comprising the steps of
 introducing a dopant through the first end of the feeding tube;   vaporizing the dopant within the evaporation receptacle; and   flowing an inert gas through the feeding tube at a flow rate of less than about 10 normal-liters per minute.   
     
     
         17 . A crystal pulling apparatus for producing a semiconductor or solar-grade ingot, the apparatus comprising:
 a furnace including a crucible for holding a melt of semiconductor or solar-grade material;   a gas doping system for introducing a dopant into the furnace, the gas doping system including:
 a feeding tube positioned within the furnace, the feeding tube including at least one feeding tube sidewall, a first end through which a solid dopant is introduced into the feeding tube, and an opening opposite the first end through which a gaseous dopant is introduced into the furnace; 
 an evaporation receptacle configured to vaporize the dopant therein, the receptacle disposed near the opening of the feeding tube, and including:
 a base extending inwardly from a feeding tube sidewall; and 
 a receptacle sidewall adjoining the base and extending upwardly from the base; and 
 
 a fluid flow channel at least partially defined by the receptacle sidewall and a feeding tube sidewall. 
   
     
     
         18 . The crystal pulling apparatus as set forth in  claim 17  wherein the gas doping system further includes a fluid flow restrictor configured to permit the passage of solid dopant therethrough and restrict the flow of gaseous dopant therethrough, the fluid flow restrictor disposed within the feeding tube between the first end and the evaporation receptacle. 
     
     
         19 . The crystal pulling apparatus as set forth in  claim 18  wherein the fluid flow restrictor includes a bottom having a second opening therethrough, and a second sidewall extending inwardly from a feeding tube sidewall towards the bottom. 
     
     
         20 . The crystal pulling apparatus as set forth in  claim 19  wherein the fluid flow restrictor is configured to permit the passage of solid dopant through the second opening, and restrict the flow of gaseous dopant through the second opening. 
     
     
         21 . The crystal pulling apparatus as set forth in  claim 19  wherein the second sidewall includes a conically-shaped portion. 
     
     
         22 . The crystal pulling apparatus as set forth in  claim 17  wherein the feeding tube is communicatively coupled to a dopant feeding device configured to feed solid dopant into the feeding tube. 
     
     
         23 . The crystal pulling apparatus as set forth in  claim 17  wherein the feeding tube is communicatively coupled to an automated dopant feeding device configured to automatically feed solid dopants into the feeding tube. 
     
     
         24 . The crystal pulling apparatus as set forth in  claim 17  wherein the gas doping system further includes a fluid-distribution plate coupled to the feeding tube at a second end distal from the first end. 
     
     
         25 . The crystal pulling apparatus as set forth in  claim 17  wherein the feeding tube is slidingly coupled to a positioning system configured to raise and lower the feeding tube. 
     
     
         26 . The crystal pulling apparatus as set forth in  claim 17  wherein the opening of the feeding tube is angled at an angle of between about 45 degrees and about 75 degrees with respect to a longitudinal axis of the feeding tube. 
     
     
         27 . The crystal pulling apparatus as set forth in  claim 17  wherein the feeding tube is angled at an angle of between about 45 degrees and about 75 degrees with respect to a surface of the melt. 
     
     
         28 . The crystal pulling apparatus as set forth in  claim 17  wherein the evaporation receptacle is positioned sufficiently near the melt such that radiant heat from the melt is sufficient to vaporize the dopant within the evaporation receptacle. 
     
     
         29 . The crystal pulling apparatus as set forth in  claim 17  wherein the evaporation receptacle is positioned between about 1 centimeter and about 15 centimeters above a surface of the melt.