Method of making large surface area filaments for the production of polysilicon in a cvd reactor

Abstract

The bulk polysilicon deposition rate of a Siemens method CVD reactor system having a power supply configured for deposition on a solid rod silicon filament of a specified diameter and length is increased by installing a high surface area silicon filament in the CVD reactor in lieu of the specified solid rod filament, the high surface area filament being dimensionally configured such that it can be used in place of the solid rod filament without reconfiguring or replacing the reactor power supply. The high surface area filament can be tubular, flat, or shaped with radial fins. Existing reactors thereby require only adaptation or replacement of filament supports to be adapted for use of the high surface area filament. The high surface area filament can be grown from silicon melt using the EFG method, so as to maintain a cross-sectional shape within a tolerance of +/−10%.

What is claimed is: 
     
         1 . A CVD reactor for bulk production of polysilicon comprising:
 a base plate system configured with filament supports;   an enclosure attachable to said base plate system so as to form a deposition chamber;   a power supply adjusted and configured for use with a solid rod silicon filament having a specified solid rod diameter, a specified solid rod length, and a specified solid rod surface area;   at least one high surface area silicon filament disposed within said chamber on said filament supports, said high surface area silicon filament having a length substantially equal to the solid rod length and a surface area greater than the solid rod surface area, while also being usable in the CVD reactor without reconfiguring or replacing the power supply of the CVD reactor;   electrical feedthroughs in said base plate system, said electrical feedthroughs being adapted for connection of the power supply to both ends of said high surface area silicon filament;   a gas inlet in said base plate system connectable to a source of silicon-containing gas; and   a gas outlet in said base plate system whereby gas may be released from said chamber.   
     
     
         2 . The CVD reactor of  claim 1 , wherein the cross sectional shape of the high surface area silicon filament includes outwardly projecting fins. 
     
     
         3 . The CVD reactor of  claim 1 , wherein the high surface area silicon filament is tubular. 
     
     
         4 . The CVD reactor of  claim 1 , wherein the high surface area silicon filament comprises two vertical filament segments electrically connected by a bridge segment. 
     
     
         5 . The CVD reactor of  claim 4 , wherein the bridge segment is tubular. 
     
     
         6 . The CVD reactor of  claim 1 , wherein the high surface area silicon filament includes an annular tube section having an outer diameter of at least 20 mm and a ratio of tube wall thickness to outer diameter of not greater than 1:4. 
     
     
         7 . The method of  claim 1 , wherein a wall thickness of the high surface area silicon filament is constant along the length of the high surface area silicon filament to within a tolerance of 10%. 
     
     
         8 . A CVD reaction system for bulk production of polysilicon comprising:
 a CVD reactor having:
 a base plate system configured with filament supports; 
 an enclosure attachable to said base plate system so as to form a deposition chamber; 
 a power supply adjusted and configured for use with the solid rod silicon filament; 
 electrical feedthroughs in said base plate system, said electrical feedthroughs being adapted for connection of the power supply to said solid rod silicon filament; 
 a gas inlet in said base plate system connectable to a source of silicon-containing gas; and 
 a gas outlet in said base plate system whereby gas may be released from said chamber; 
   a solid rod silicon filament having a solid rod surface area; and   a high surface area silicon filament having a surface area greater than the solid rod surface area,   said solid rod silicon filament and said high surface area filament being usable interchangeably in the CVD reactor without reconfiguration or replacement of the power supply of the CVD reactor.   
     
     
         9 . The CVD reaction system of  claim 8 , wherein the cross sectional shape of the high surface area silicon filament includes outwardly projecting fins. 
     
     
         10 . The CVD reaction system of  claim 8 , wherein the high surface area silicon filament is tubular. 
     
     
         11 . The CVD reaction system of  claim 8 , wherein the high surface area silicon filament comprises two vertical filament segments electrically connected by a bridge segment. 
     
     
         12 . The CVD reaction system of  claim 11 , wherein the bridge segment is tubular. 
     
     
         13 . The CVD reaction system of  claim 8 , wherein the high surface area silicon filament includes an annular tube section having an outer diameter of at least 20 mm and a ratio of tube wall thickness to outer diameter of not greater than ¼. 
     
     
         14 . The CVD reaction system of  claim 8 , wherein a wall thickness of the high surface area silicon filament is constant along the length of the high surface area silicon filament to within a tolerance of 10%. 
     
     
         15 . A method of modifying a CVD reactor system so as to increase its rate of bulk polysilicon production, the CVD reactor system including a reactor having:
 a base plate system configured with filament supports;   an enclosure attachable to said base plate system so as to form a deposition chamber;   a power supply adjusted and configured for use with a solid rod silicon filament having a specified solid rod diameter, a specified solid rod length, and a specified solid rod surface area;   electrical feedthroughs in said base plate system, said electrical feedthroughs being adapted for connection of the power supply to both ends of said solid rod silicon filament;   a gas inlet in said base plate system connectable to a source of silicon-containing gas; and   a gas outlet in said base plate system whereby gas may be released from said chamber,   the method comprising:   providing a high surface area silicon filament having a length substantially equal to the solid rod length and a surface area greater than the solid rod surface area, said high surface area filament having dimensions that cause the high surface area filament to be usable in the CVD reactor without reconfiguring or replacing the power supply of the CVD reactor;   installing the high surface area filament in the CVD reactor;   introducing a silicon-containing gas into the deposition chamber through the gas inlet; and   causing the power supply of the CVD reactor to apply electrical energy to the high surface area filament without adjusting, reconfiguring, or replacing the power supply, thereby initiating heating of the high surface area filament and causing silicon to be deposited from the silicon-containing gas onto the high surface area filament.   
     
     
         16 . The method of  claim 15 , wherein:
 the method further comprises, before installing the high surface area filament in the CVD reactor:
 installing a solid rod silicon filament in the CVD reactor, said solid rod silicon filament having a length substantially equal to said specified solid rod length, a diameter substantially equal to the specified solid rod diameter, and a surface area substantially equal to the solid rod surface area; 
 attaching said enclosure to said base plate system so as to form said deposition chamber; 
 introducing a silicon-containing gas into the deposition chamber through the gas inlet; and 
 causing the power supply of the CVD reactor to apply electrical energy to the solid rod silicon filament without adjusting, reconfiguring, or replacing the power supply, thereby initiating heating of the solid rod silicon filament and causing silicon to be deposited from the silicon-containing gas onto the solid rod silicon filament; 
   and wherein installing the high surface area filament in the CVD reactor includes removing the solid rod silicon filament from the CVD reactor and installing the high surface area filament in its place without reconfiguring or replacing the power supply of the CVD reactor.   
     
     
         17 . The method of  claim 15 , wherein the cross sectional shape of the high surface area silicon filament includes outwardly projecting fins. 
     
     
         18 . The method of  claim 15 , wherein the high surface area silicon filament is tubular. 
     
     
         19 . The method of  claim 15 , wherein the high surface area silicon filament comprises two vertical filament segments electrically connected by a bridge segment. 
     
     
         20 . The method of  claim 19 , wherein the bridge segment is tubular. 
     
     
         21 . The method of  claim 15 , wherein the high surface area silicon filament includes an annular tube section having an outer diameter of at least 20 mm and a ratio of tube wall thickness to outer diameter of not greater than 1:4. 
     
     
         22 . The method of  claim 15 , wherein a wall thickness of the high surface area silicon filament is constant along the length of the high surface area silicon filament to within a tolerance of 10%.