Patent Publication Number: US-2018030614-A1

Title: Feed system for crystal growing systems

Description:
FIELD 
     The field of the disclosure relates generally to systems for growing single crystal ingots from a melt of semiconductor or solar material, and, more particularly, to feed systems for use with such systems. 
     BACKGROUND 
     In the production of silicon crystals grown by the Czochralski (CZ) method, polycrystalline silicon is first melted within a crucible, such as a quartz crucible, of a crystal growing system to form a silicon melt. A pulling mechanism then lowers a seed crystal into contact with the melt and then slowly raises the seed crystal out of the melt. As the seed crystal is raised from the melt, silicon atoms from the melt align themselves with and attach to the seed crystal to form a single crystal ingot. In a batch CZ method, the silicon melt is depleted as the ingot is grown. When the melt reaches a certain level, or the ingot reaches a desired length, the ingot is separated from the melt and removed from the crystal growing system. 
     In some batch CZ methods, the crystal growing system is cooled, cleaned, and degassed, and the crucible is recharged with polycrystalline silicon in between each successive ingot growth cycle. Performing each of these steps in between each successive ingot growth cycle results in significant down time of the crystal growing system. 
     In other batch CZ methods, silicon feed material is fed into a crucible through an access port of the crystal growing system to enable the crucible to be recharged without cooling the crystal growing system between each successive ingot growth cycle. However, the size of access ports on typical crystal growing systems limits the size of silicon feed material that may be fed through the access ports, and generally requires smaller, more expensive silicon feed material to be used. Modifying at least some conventional crystal growing systems to receive larger, less expensive chunk polycrystalline silicon would require modification of the hot zone configuration of the crystal pulling device and, consequently, would affect the growth environment and conditions (e.g., thermal conditions) within the crystal growing system during growth of a crystal ingot. Moreover, where the crystal growing system has a liquid-cooled housing, modifying the size of the access port would require significant modification. 
     Accordingly, a need exists for a feed system that enables large chunk feed material to be fed into a crystal growing system without significant modification of the hot zone configuration of the crystal growing system. 
     This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     BRIEF SUMMARY 
     In one aspect, a system for growing a crystal ingot from a melt includes a housing and a feed system. The housing defines a growth chamber and an ingot removal chamber positioned above the growth chamber. The feed system includes an enclosure, a feed material reservoir positioned within the enclosure, and a feed channel including an intake end and an outlet end. The intake end is configured to receive feed material from the feed material reservoir. The housing has an opening in communication with the removal chamber and a connector proximate the opening, and the enclosure has an opening and a connector configured to mate with the housing connector. The feed channel is moveable between a retracted position and an extended position in which the feed channel extends through the opening in the housing and the outlet end is positioned within the removal chamber. 
     In another aspect, a feed system for use with a crystal growing system includes a housing defining a growth chamber and a removal chamber positioned above the growth chamber. The feed system includes an enclosure, a feed material reservoir, and a feed channel. The enclosure defines an interior volume and an opening providing communication with the interior volume. The enclosure includes a connector that is proximate the opening and configured to connect the enclosure to the housing. The feed material reservoir is positioned within the interior volume of the enclosure. The feed channel includes an intake end and an outlet end. The intake end is configured to receive feed material from the feed material reservoir. The feed channel is moveable between a retracted position and an extended position in which the feed channel extends through the opening in the enclosure and into the removal chamber of the crystal growing system. 
     In yet another aspect, a method of retrofitting a crystal growing system with a feed system is provided. The feed system includes a feed channel moveable between a retracted position and an extended position. The crystal growing system includes a housing defining a growth chamber and an ingot removal chamber positioned above the growth chamber. The method includes forming a feed port in the housing, the feed port providing communication with the removal chamber of the crystal growing system, and connecting the feed system to the housing such that, when the feed channel is in the extended position, the feed channel extends through the feed port and into the removal′ chamber. 
     Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is cross-section of a crystal growing system including an example feed system; 
         FIG. 2  is a perspective view of the feed system of  FIG. 1 ; 
         FIG. 3  is a cross-section of the feed system of  FIG. 1 ; 
         FIG. 4  is a cross-section of a feed channel of the feed system of  FIG. 1 ; 
         FIG. 5  is a cross-section of a crystal growing system including another embodiment of a feed system mounted on a carriage; and 
         FIG. 6  is a flow chart of an example method of retrofitting a crystal growing system with a feed system. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a crystal growing system is shown schematically and is indicated generally at  100 . The crystal growing system  100  is used to produce single crystal ingots by the Czochralski method. As discussed herein, the system is described in relation to a batch or recharge Czochralski method of producing single crystal ingots. 
     The illustrated crystal growing system  100  generally includes a housing  102  defining a growth chamber  104  and an ingot removal chamber  106  connected to and positioned above the growth chamber  104 . A crucible  108  containing a melt  110  of semiconductor or solar-grade material (e.g., silicon) is positioned within the growth chamber  104 , and one or more heating elements  112  are positioned proximate the crucible  108  for supplying thermal energy to the system  100 . A heat shield  114  is positioned within the growth chamber  104  adjacent the crucible  108 , and is configured to shield a crystal ingot (not shown) being grown from the melt  110  from radiant heat to allow the ingot to solidify. The crystal growing system  100  also includes a feed system  200  removably connected to the housing  102  along the ingot removal chamber  106 , and configured to feed feedstock material, such as chunk polycrystalline silicon (poly-silicon), into the crucible  108 . 
     The housing  102  includes a lower portion  116 , an upper dome  118  connected to the lower portion  116 , and an elongate tubular portion  120  extending generally upward from the upper dome  118 . In the illustrated embodiment, the growth chamber  104  is defined by the lower portion  116  and the upper dome  118 , and the ingot removal chamber  106  is generally defined by the elongate tubular portion  120 . The upper dome  118  includes a central annular opening  122  providing communication between the growth chamber  104  and the removal chamber  106 . The tubular portion  120  includes an access door  124  that provides access to the ingot removal chamber  106 . 
     The housing  102  includes a feed port  126  (broadly, an opening) located along the tubular portion  120  of the housing  102  through which feedstock material from the feed system  200  may be introduced into the removal chamber  106 . In the illustrated embodiment, the feed port  126  is defined along the access door  124 , although the feed port  126  may be located along any suitable location of the housing  102  that enables the feed system  200  to function as described herein. The housing  102  also includes a connector  128  circumscribing the feed port  126 . The connector  128  is configured to sealingly engage a component of the feed system  200  to facilitate maintaining a controlled, sealed environment within the removal chamber  106  and the growth chamber  104 . Suitable connectors include, but are not limited to, vacuum flanges. In some embodiments, the housing  102  may also include a feed port door or seal (not shown) configured to seal the feed port  126  when the feed system  200  is not connected to the housing  102 . 
     The housing  102  may be made of stainless steel or other suitable materials. In some embodiments, one or more of the lower portion  116 , the upper dome  118 , and the tubular portion  120  are constructed from water-cooled stainless steel walls. 
     The crucible  108  is positioned within the growth chamber  104  and beneath the removal chamber  106  such that an ingot grown from the melt  110  can be pulled by a crystal pulling mechanism  130  through the central opening  122  in the upper dome  118  and into the removal chamber  106 . The crucible  108  may be supported within the growth chamber  104  by a susceptor (not shown) and a rotatable shaft (not shown) configured to rotate the crucible  108  during growth of a crystal ingot. 
     The crucible  108  may be constructed from, for example, quartz or any other suitable material that enables the crystal growing system  100  to function as described herein. Further, the crucible  108  may have any suitable size that enables the crystal growing system  100  to function as described herein. In some embodiments, the crucible  108  has a diameter of between about 20 inches and about 32 inches, more suitably between about 20 inches and about 28 inches, and even more suitably between about 20 inches and about 24 inches. 
     The heat shield  114  is operably connected to the housing  102 , and extends from the housing  102  into a cavity  132  defined by the crucible  108 . The heat shield  114  separates the melt  110  from an upper portion of the growth chamber  104 , and is configured to shield a growing ingot from radiant heat generated by the melt  110  and the heating elements  112  to allow the ingot to solidify. In the example embodiment, the heat shield  114  includes a conical member  134  separating the melt  110  from an upper portion of the growth chamber  104 , and a central opening  136  defined therein to allow an ingot to be pulled therethrough. Further, in the example embodiment, the heat shield  114  is free of holes or openings, other than the central opening  136 . In other embodiments, the heat shield  114  may have any suitable configuration that enables the system  100  to function as described herein. The heat shield  114  may be constructed from any suitable material that enables the system  100  to function as described herein including, for example and without limitation, graphite, silica-coated graphite, high purity molybdenum, and combinations thereof. 
     In the embodiment illustrated in  FIG. 1 , the crystal growing system  100  also includes a guide tube  138  connected to the crystal pulling mechanism  130  and configured to guide feedstock material from the feed system  200  into the crucible  108 . In some embodiments, the guide tube  138  is configured to reduce the velocity of feedstock material fed from the feed system  200  through the guide tube  138  to inhibit splashing of the melt  110  and excessive wear of the crucible  108 . 
     During the crystal growing process, an initial charge of semiconductor or solar material is added to the crucible  108 , and is heated with the heating elements  112  until melted to form the melt  110 . The initial charge of material may be manually fed into the crucible or, as described in more detail herein, fed by the feed system  200 . A desired type and amount of dopant may be added to the melt  110  to modify the base resistivity of ingots grown from the melt. A seed crystal (not shown) is lowered by a crystal pulling mechanism  130  into contact with the melt  110 , and then slowly raised from the melt  110 . As the seed crystal is slowly raised from the melt  110 , atoms from the melt  110  align themselves with and attach to the seed crystal to form an ingot. When the growing ingot reaches a desired length and/or when the level of the melt  110  falls below a certain level, the ingot is separated from the melt  110  and pulled into the ingot removal chamber  106 . A small portion of the initial melt, also referred to as pot scrap, remains in the crucible  108  following removal of the ingot. 
     In conventional batch crystal growing systems, once an ingot is grown from an initial charge, the system is cooled to room temperature to enable the system to be charged with additional melt material. Often, thermal cycling of crystal growing systems results in accelerated consumption of consumable components, such as the crucible. For example, quartz crucibles used in crystal growing systems often crack or fracture when the system is cooled following growth of a crystal ingot. Moreover, thermal cycling of crystal growing systems in between each successive ingot growth cycle results in significant down time. 
     The feed systems described herein are configured to increase the productivity of batch, crystal growing systems by reducing the costs and downtime associated with batch CZ crystal growing processes. For example, the feed systems described herein enable crystal growing systems to be recharged with feedstock material without cooling the system to room temperature. The feed systems described herein thereby enable consumable components, such as quartz crucibles, to be re-used to grow multiple ingots and reduce the down time associated with cooling crystal, growing systems in between ingot growth cycles. Additionally, the feed systems described herein are configured to feed less expensive, large chunk poly-silicon into the crucibles of crystal growing systems, thereby facilitating reducing the costs associated with growing single crystal ingots. The feed systems described herein further facilitate reducing the costs associated with growing single crystal ingots by eliminating the need for every crystal growing system to have a dedicated feeding system. In particular, the feed systems described herein are transportable, and are readily connectable to crystal growing systems to enable one feed system to feed feedstock material into more than one crystal growing system. 
     Referring still to  FIG. 1 , the illustrated feed system  200  generally includes an enclosure  202  defining an interior volume  204 , a feed material reservoir  206  configured to hold feedstock material therein, and a feed channel  208  configured to guide feedstock material from the feed material reservoir  206  into the crucible  108 . In the embodiment illustrated in  FIG. 1 , the feed system  200  is mounted to the housing  102  by mounting brackets  210 . 
       FIG. 2  is a perspective view of the feed system  200  of  FIG. 1  connected to the tubular portion  120  of the housing  102 , and  FIG. 3  is an enlarged view of the feed system  200  of  FIG. 1 . With additional reference to  FIGS. 2 and 3 , the enclosure  202  is generally configured to enclose components of the feed system  200 , such as the feed material reservoir  206  and the feed channel  208 , within a sealed environment. The enclosure  202  may be constructed from any suitable material that enables the feed system  200  to function as described herein including, for example and without limitation, stainless steel. 
     The enclosure  202  defines an opening  212  sized to receive the feed channel  208  therein. In some embodiments, the opening  212  is sized to permit relatively large chunk poly-silicon to be fed therethrough. In some embodiments, for example, the opening  212  has a diameter of at least about 150 mm, at least about 200 mm, or even at least about 250 mm. 
     The enclosure  202  includes a connector  214  circumscribing the opening  212 , and configured to sealingly engage the connector  128  on the housing  102  to provide a sealed connection between the interior volume  204  of the enclosure  202  and the removal chamber  106 . Suitable connectors include, but are not limited to, vacuum flanges. 
     In the illustrated embodiment, the enclosure connector  214  is operably connected to the enclosure  202  by an expansion joint  216 . The expansion joint  216  is configured to expand and retract to enable the connector  214  to move relative to the enclosure  202  and facilitate connecting the connectors  128  and  214 . The expansion joint  216  may include any suitable device that enables the feed system  200  to function as described herein including, for example and without limitation, stainless steel bellows. 
     The enclosure  202  also includes a cover  218  moveable between an open position and a closed position to provide access to the feed material reservoir  206  and enable the feed material reservoir  206  to be refilled with feedstock material. The cover  218  is configured to seal the interior volume  204  of the enclosure  202  when the cover  218  is in the closed position (shown in  FIGS. 1-3 ). In the illustrated embodiment, the cover  218  is disposed at the top  220  of the enclosure  202 , although the cover  218  may be positioned at any suitable location along the enclosure  202  that enables the feed system  200  to function as described herein. 
     The feed material reservoir  206  is positioned within the interior volume  204  of the enclosure  202 , and is configured to hold a suitable amount of feedstock material therein. In some embodiments, the feed material reservoir  206  is configured to hold a sufficient amount of feedstock material to enable multiple recharging operations to be carried out without refilling the feed material reservoir  206 . In some embodiments, for example, the feed material reservoir  206  is configured to hold at least about 10 kilograms (kg) of feedstock material, more suitably at least about 50 kg of feedstock material, and yet even more suitably, at least about 150 kg of feedstock material. 
     The feed material reservoir  206  includes an inlet  222  at the top of the feed material reservoir  206 , and an outlet  224  positioned at the bottom of the feed material reservoir  206 . The outlet  224  of the feed material reservoir  206  is suitably sized and shaped to permit chunk feedstock material, such as chunk poly-silicon, to be fed therethrough and into the feed channel  208 . In some embodiments, the outlet  224  is sized and shaped to permit relatively large chunk poly-silicon, such as chunk poly-silicon having a maximum feature size or length of at least about 30 mm, at least about 40 mm, at least about 45 mm, and even up to about 60 mm, to be fed therethrough. The maximum feature size or length of a piece of chunk poly-silicon refers to the largest dimension of the piece of chunk poly-silicon measured along a single direction or axis of the piece of chunk poly-silicon. In some embodiments, for example, the outlet  224  includes an annular opening having a diameter of at least about 100 mm, more suitably at least about 200 mm, and even more suitably, at least about 250 mm. In the embodiment illustrated in  FIGS. 1-3 , the feed material reservoir  206  includes an annular sidewall  226  and a tapered bottom wall  228  extending from the sidewall  226  to the outlet  224  to facilitate guiding feedstock material towards the outlet  224 . 
     Components of the feed material reservoir  206  may include an inert or non-reactive coating or cover to inhibit contamination of feedstock material. In some embodiments, for example, at least the interior surfaces of the annular sidewall  226 , the tapered bottom wall  228 , and the outlet  224  are covered with quartz. In other embodiments, one or more of the annular sidewall  226 , the tapered bottom wall  228 , and the outlet  224  is coated with silicon. 
     The feed channel  208  includes an intake end  230  positioned proximate the outlet  224  of the feed material reservoir  206 , and an outlet end  232  distal from the intake end  230 . The feed channel  208  includes a back plate  234  at the intake end  230  to inhibit feedstock material from falling out of the intake end  230  and into the enclosure  202 . The feed channel  208  is configured to receive feedstock material from the outlet  224  of the feed material reservoir  206  at the intake end  230 , and guide the feedstock material towards the outlet end  232  and into the crucible  108  of the crystal growing system  100 . 
       FIG. 4  is a cross-section of the feed channel  208  shown in  FIGS. 1 and 3 . As shown in  FIG. 4 , the feed channel  208  includes a base  402  and a pair of sidewalls  404  extending from opposite side edges of the base  402 . In the embodiment illustrated in  FIG. 4 , each sidewall  404  extends from the base  402  at an oblique angle  406  thereto. The sidewalls  404  may extend from the base  402  at any suitable angle that enables the feed system  200  to function as described herein, such as between about 30° and about 90°. In some embodiments, the sidewalls  404  may be oriented substantially perpendicular to the base  402 . 
     Components of the feed channel  208  may include an inert or non-reactive coating or cover to inhibit contamination of feedstock material. In some embodiments, for example, at least the interior surfaces of the sidewalls  404  and the base  402  of the feed channel  208  are covered with a quartz sleeve. In other embodiments, the sidewalls  404  and the base  402  of the feed channel  208  are coated with silicon. 
     The feed channel  208  is suitably sized and shaped to feed feedstock material from the feed material reservoir  206  through the opening  212  in the enclosure  202  and the housing feed port  126 . In some embodiments, the feed channel  208  is configured to feed chunk poly-silicon having a maximum feature size or length of at least about 30 mm, more suitably, at least about 40 mm, yet even more suitably, at least about 45 mm, and even up to about 60 mm. In some embodiments, for example, a minimum width  406  of the feed channel  208  as measured between the sidewalls  404  is at least about 10 cm, more suitably at least about 12 cm, and yet even more suitably, at least about 15 cm. 
     Referring again to  FIGS. 1-3 , the feed channel  208  is configured to move between a first, retracted position (not shown), and a second, extended position (shown in  FIGS. 1 and 3 ). When the feed channel  208  is in the extended position (shown in  FIGS. 1 and 3 ), the feed channel  208  extends through the opening  212  in the enclosure  202  and the feed port  126  in the housing  102 , and the outlet end  232  is positioned within the removal chamber  106 . When the feed channel  208  is in the retracted position (not shown), the outlet end  232  of the feed channel  208  is recessed within the connector  214  of the feed system  200 . 
     The feed system  200  may include any suitable device configured to move the feed channel  208  between the extended position and the retracted position. In the embodiment illustrated in  FIGS. 1-3 , the feed system  200  includes a linear slide mechanism  236  configured to move the feed channel  208  between the extended position and the retracted position along a generally horizontal direction, indicated by arrow  238  in  FIG. 3 . The feed system  200  is operably connected to a base plate  240  of the linear slide mechanism  236 , which is supported by a plurality of roller bearings (not shown) that enable the base plate  240  to slide along the horizontal direction  238 . The linear slide mechanism  236  may include one or more drive mechanisms (not shown) configured move the feed channel  208  and/or the base plate  240  in the horizontal direction  238 . Suitable drive mechanisms include, but are not limited to, electric motors, pneumatic cylinders, servomechanisms, and combinations thereof. 
     In some embodiments, the feed system  200  includes a feed transport mechanism  244  configured to facilitate transporting feedstock material from the intake end  230  of the feed channel  208  towards the outlet end  232  of the feed channel  208 . The feed transport mechanism  244  may include any suitable device or devices that enable the feed transport mechanism  244  to transport feedstock material from the intake end  230  of the feed channel  208  towards the outlet end  232 . In some embodiments, for example, the feed transport mechanism  244  includes a mechanical oscillator configured to impart oscillatory motion to the feed channel  208  to facilitate the flow of granular or chunk feedstock material from the intake end  230  of the feed channel  208  towards the outlet end  232  of the feed channel  208 . 
     In some embodiments, the feed system  200  may be transportable such that the feed system  200  can be used to charge more than one crystal growing system  100  with feedstock material. In some embodiments, for example, the enclosure  202  is mounted on a moveable carriage (see, e.g.,  FIG. 5 ) that enables the feed system  200  to be transported to another crystal growing system (not shown) such that the feed system  200  can be used to charge multiple crystal growing systems with feedstock material. 
     In use, a desired amount of feedstock material is loaded into the feed material reservoir  206  through the inlet  222  of the feed material reservoir  206 . The feedstock material is funneled downwardly by gravity through the outlet  224  and into the intake end  230  of the feed channel  208 . In some embodiments, the feed system  200  is, loaded with relatively large chunk poly-silicon, such as chunk poly-silicon having a maximum feature size or length of at least about 30 mm, at least about 40 mm, at least about 45 mm, and even up to about 60 mm. 
     To charge a crucible with feedstock material, the enclosure connector  214  is connected to the housing connector.  128  to provide a sealed connection between the interior volume  204  of the enclosure  202  and the growth chamber  104  and the removal chamber  106 . The feed channel  208  is moved in the horizontal direction  238  via the linear slide mechanism  236  from the retracted position (not shown) to the extended position (shown in  FIGS. 1 and 3 ), such that, the outlet end  232  of the feed channel  208  is positioned within the removal chamber  106  of the housing  102 . When the feed channel  208  is positioned in the extended position, feedstock material is fed along the feed channel  208  from the intake end  230  to the outlet end  232 , and down through the removal chamber  106 , through the opening  122  in the upper dome  118 , and into the crucible  108 . In embodiments including a guide tube  138  ( FIG. 1 ), feedstock material is fed into the guide tube  138  from the outlet end  232  of the feed channel  208 , and down through the guide tube  138  into the crucible  108 . In some embodiments, a feed transport mechanism, such as a mechanical oscillator, is used to facilitate transporting feedstock material from the intake end  230  of the feed channel  208  towards the outlet end  232  of the feed channel  208 . The feed system  200  may be used to provide an initial charge of feedstock material to a crucible, or to recharge a crucible following the growth of one or more crystal ingots. 
     In some embodiments, the feed system  200  is used to charge multiple crystal growing systems with feedstock material. In some embodiments, for example, after the crucible of a first crystal growing system is charged with feedstock material using the feed system  200 , the feed system  200  is disconnected from the first crystal growing system, for example, by disconnecting the enclosure connector  214  of the feed system  200  from the housing connector  128 . The feed system  200  is then transported to a second crystal growing system remote from the first crystal growing system, and connected to the second crystal growing system, for example, by connecting the enclosure connector  214  of the feed system  200  to a connector of the housing of the second crystal growing system. Feedstock material is then fed into a crucible of the second crystal growing system in the same manner as described above. Because the feed system  200  can be used to charge multiple crystal growing systems with feedstock material, the feed system  200  eliminates the need for every crystal growing system to have a dedicated feeding system, and thereby facilitates reducing the costs associated with growing single crystal ingots. 
       FIG. 5  is a cross-section of a crystal growing system  500  including another suitable embodiment of a feed system  502  mounted on a moveable carriage  504 . The crystal growing system  500  and the feed system  502  may have substantially the same configuration as the crystal growing system  100  and the feed system  200  described above with reference to  FIGS. 1-4 , except the feed system  502  of  FIG. 5  includes the moveable carriage  504 . 
     The carriage  504  enables the feed system  502  to be transported to multiple crystal growing system (not shown) such that the feed system  502  can be used to charge multiple crystal growing systems with feedstock material. In particular, the carriage  504  includes a plurality of wheels  506  that enable the carriage  504  and the feed system  502  to be transported to another crystal growing system (not shown). The carriage  504  also includes an elevator platform  508  configured to move the feed system  502  up and down in a vertical direction, indicated by arrow  510  in  FIG. 5 , to facilitate connecting the feed system  502  to the removal chamber of the crystal growing system  500 . 
     In some embodiments, the feed systems described herein are retrofitted onto commercial crystal growing systems to enable large chunk feedstock material, such as chunk poly-silicon, to be fed into the crystal growing systems. The feed systems described herein are particularly suited for retrofitting crystal growing systems without modifying the hot zone configuration of such systems. As used herein, the term “hot zone configuration” generally refers to the arrangement of components within the growth chamber of a crystal growing system including, but not limited to, the crucible, the heat shield, and the heating elements. 
       FIG. 6  is a flow chart of an example method  600  of retrofitting a crystal growing system with a feed system, such as the feed system  200  shown in  FIGS. 1-3 . The crystal growing system may have the same configuration as the crystal growing system  100  shown in  FIG. 1 , and include a housing defining a growth chamber and an ingot removal chamber positioned above the growth chamber. The method generally includes forming  610  a feed port in the housing such that the feed port provides communication with the removal chamber of the crystal growing system, and connecting  620  the feed system to the housing such that, when the feed channel is in an extended position, the feed channel extends through the feed port and into the removal chamber. In some embodiments, forming  610  a feed port in the housing includes forming a feed port having a diameter of at least about 150 mm, more suitably at least about 200 mm, and yet even more suitably, at least about 250 mm. In some embodiments, connecting  620  the feed system to the housing includes sealingly connecting the feed system to the housing. In some embodiments, the method  600  further includes connecting a connector to the housing, such as a vacuum flange, to facilitate sealingly connecting the feed system to the housing. In such embodiments, connecting  620  the feed system to the housing may include connecting the vacuum flange to a connector of the feed system. 
     The feed systems described herein are configured to increase the productivity of batch crystal growing systems by reducing the costs and downtime associated with batch crystal growing processes. For example, the feed systems described herein enable crystal growing systems to be recharged with feedstock material without cooling the system in between successive crystal growth cycles. The feed systems described herein thereby enable consumable components, such as quartz crucibles, to be re-used to grow multiple ingots, and reduce the down time associated with cooling crystal growing systems in between ingot growth cycles. Additionally, the feed systems described herein are configured to feed less expensive, large chunk poly-silicon into the crucibles of crystal growing systems, thereby facilitating reducing the costs associated with growing single crystal ingots. 
     The feed systems described herein further facilitate reducing the costs associated with growing single crystal ingots by, for example, eliminating the need to provide a feed system on every crystal growing system. Embodiments, of the feed systems described herein are transportable to different crystal growing systems, and are connectable to crystal growing systems to enable one feed system to provide feedstock material into more than one crystal growing system. 
     Additionally, the feed systems described herein enable commercial batch CZ crystal growing systems to be retrofitted with feed systems capable of recharging the crucibles of such systems without modifying the hot zone configuration of such systems. For example, the feed systems described herein are configured to feed or provide feedstock material through a feed port in the removal chamber of a crystal growing system. The feed systems do not require modification of the hot zone configuration of the crystal growing system. Further, the feed systems described herein can be used with different types of CZ crystal growing systems with little to no modification of the crystal growing systems. 
     When introducing elements of the present invention or the embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.