BACKGROUND OF THE INVENTION

Related Applications

This application claims priority to U.S. Provisional Application No. 62/608,980 filed December 21, 2017, entitled“CZOCHRALSKI GROWTH APPARATUS CONVERSION ASSEMBLY,” by Keith R. Vaillancourt et ak, the contents of which are hereby incorporated by reference.

Field of the Invention

[0001] The present invention relates to an apparatus conversion assembly useful for the conversion of a Czochralski growth apparatus into a continuous Czochralksi growth apparatus.

Description of the Related Art

[0002] One of the most efficient and economical methods for preparing a single crystal silicon ingot for use in fabricating materials for integrated circuits and photovoltaic solar cells is the Czochralski (CZ) method. In the typical CZ process, a silicon charge is placed in a crucible and melted to its liquid state, typically at a temperature of about l4l6°C. A small crystalline silicon seed of predetermined crystalline orientation is then lowered to contact the surface of the melt and then gradually withdrawn. With proper control of temperatures, the liquid silicon freezes on the crystalline seed with the same orientation as that of the seed. The seed is then slowly raised away from the melt to form a growing crystalline ingot of silicon with an overall cylindrical shape having a final length of a meter or more and a diameter of hundreds of millimeters

[0003] In general, two types of CZ techniques are known, often called the batch

Czochralski method and the continuous Czochralski method. In batch CZ, an amount of charged material required for growing a silicon ingot is melted at the beginning of the process in a heated crucible, and one ingot is drawn to substantially deplete the crucible. The crucible may then be discarded or may be refilled and the process repeated to grow an additional silicon ingot, which is sometimes also referred to as a semi-batch process. Also, a batch recharge process may be used in which growth of an ingot is halted, feedstock is added into the crucible, and growth is then restarted. In both batch cases, no feedstock material is added during the growing of the ingot. Also, the number of ingots and their length is generally restricted by the size of the crucible. By comparison, in continuous Czochralski (CCZ) growth, the charged material is continually or periodically replenished during the growth process and, as a result, multiple ingots can be pulled in a single run from a single crucible that is replenished during growth. In addition, longer and higher quality ingots may be pulled in a single run, as the crucible is replenished during growth. The crucible is only discarded and replaced by a fresh crucible after several ingot cycles. Growth of multiple ingots of longer length in a single run provides economic and procedural advantages but requires a significantly different type of growth apparatus and equipment than is available for batch CZ growth.

SUMMARY OF THE INVENTION

[0004] The present invention relates to a growth apparatus conversion assembly to convert a Czochralski growth apparatus, particularly a batch Czochralski growth apparatus having a growth chamber, into a continuous Czochralski growth apparatus. The growth apparatus conversion assembly includes a feeder assembly that comprises: a feeder connectible to the growth chamber and positioned to feed solid feedstock into the growth chamber, a lower hopper connected to the feeder and positioned to feed solid feedstock to the feeder, at least one upper hopper removably attached above the lower hopper and positioned to feed solid feedstock into the lower hopper, and a feed isolation valve positioned between the upper hopper and the lower hopper. The feed isolation valve is configured to maintain conditions in the lower hopper when the upper hopper is being refilled. In addition, a shut off valve may also be positioned between the upper and lower hoppers. In some embodiments, the growth apparatus conversion assembly further comprises a feed port that is configured to be positioned in a side wall of the growth chamber of the batch Czochralski growth apparatus and to couple to the feeder assembly. In some embodiments, the growth apparatus conversion assembly further comprises a feed spout configured to be fixedly positioned within the growth chamber of the batch Czochralski growth apparatus to direct feed of the solid feedstock from the feed assembly into a crucible in the growth chamber. The feed spout may have a sloping bottom for receiving the solid feedstock from the feeder and for feeding the solid feedstock into the crucible.

[0005] The present invention further relates to a method in which a batch Czochralski growth apparatus is provided having a growth chamber comprising: a chamber shell having a top wall and at least one side wall, a crucible containing a melt positioned within the chamber shell, and a pull mechanism for retractably supporting a seed for contacting the melt. The method further comprises providing a growth apparatus conversion assembly including a feeder assembly comprising: a feeder connectible to the growth chamber and positioned to feed solid feedstock into the growth chamber, a lower hopper connected to the feeder and positioned to feed solid feedstock to the feeder, at least one upper hopper removably attached above the lower hopper and positioned to feed solid feedstock into the lower hopper, and a feed isolation valve positioned between the upper hopper and the lower hopper. The feed isolation valve is configured to maintain conditions in the lower hopper when the upper hopper is being filled. The method further comprises coupling the feeder assembly of the growth apparatus conversion assembly to the side wall of the growth chamber. In some embodiments, the growth apparatus conversion assembly may further comprise a feed port, and coupling the feeder assembly comprises positioning the feed port in the side wall of the growth chamber of the batch Czochralski growth apparatus and coupling the feeder of the feeder assembly to the feed port. In some embodiments, the growth apparatus conversion assembly further comprises a feed spout and the method further comprises positioning the feed spout within the growth chamber at the feed port. In some embodiments, the growth apparatus conversion assembly further comprises a feed spout, and the method comprises fixedly positioning the feed spout within the growth chamber of the batch Czochralski growth apparatus to direct feed of the solid feedstock from the feed assembly into the crucible in the growth chamber. The feed spout may have a sloping bottom for receiving the solid feedstock from the feeder and for feeding the solid feedstock into the crucible. In this way, the method provides for the conversion of a Czochralski growth apparatus, particularly a batch Czochralski growth apparatus, into a continuous Czochralski growth apparatus.

[0006] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS [0007] The embodiments herein may be better understood by referring to the following description in conjunction with the accompanying drawings in which like reference numerals indicate identically or functionally similar elements, of which:

[0008] FIG. 1 is a view of an embodiment of the growth apparatus conversion assembly of the present invention.

[0009] FIG. 2 is an exploded view of an embodiment of the growth apparatus conversion assembly of the present invention.

[0010] FIG. 3 illustrates an example method for converting a batch Czochralski growth apparatus to a continuous Czochralski growth apparatus, according to embodiments of the present invention.

[0011] It should be understood that the above-referenced drawings are not necessarily to scale and may, in some cases, present a somewhat simplified representation of various preferred features illustrative of the basic principle of the disclosure. The specific design features of the present disclosure, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and use environment.

DETAILED DESCRIPTION OF THE INVENTION

[0014] As noted above, a batch CZ growth apparatus is structurally and operationally very different from a CCZ growth apparatus. As a result, to carry out a continuous growth process in a batch growth apparatus requires significant and, in some cases, prohibitive modification of the equipment. For example, it is necessary to modify the traditional batch Czochralski growth apparatus to include a means for feeding additional charge material to the melt in a continuous or semi-continuous fashion without adversely affecting the properties of the growing ingot. This may also require providing access to the interior of the growth chamber as well, such as through the addition of a port that is typically not present in most batch CZ equipment. Other significant modifications may also be needed to account for both mechanical and thermal changes resulting from relatively colder feedstock entering the system during the ingot growing phase. In addition, in order to reduce the adverse effects of this replenishing activity on simultaneous crystal growth, it may be preferable to replace the quartz crucible traditionally used in batch CZ with a crucible having an outer or annular melt zone into which the added material is delivered along with a separated inner growth zone from which the silicon ingot is pulled, which is more typical for a CCZ growth apparatus. Otherwise, the length and/or number of the ingots that can be grown may be limited by the size of the crucible. Other major structural and procedural modifications may also be required. As a result, an operation desiring to grow silicon by CCZ typically must purchase separate growth apparatuses designed specifically for that purpose, incurring significant cost and requiring additional physical operational space. Currently there are no viable solutions available for effectively and efficiently converting an existing batch CZ growth apparatus into a CCZ growth apparatus.

[0015] The present invention relates to a conversion assembly and method for retrofitting a batch Czochralski growth apparatus and to convert this growth apparatus into a continuous Czochralski growth apparatus. While the assembly and method are most particularly useful for converting from a batch Czochralski apparatus to a continuous apparatus, the techniques described herein may also be used to upgrade various types of continuous Czochralski growth apparatuses as well. Thus, the Czochralski growth apparatus to be retrofitted can be any known in the art and may have a variety of different types of configurations and components as needed to produce an ingot, particularly a silicon ingot. Preferably, the growth apparatus is a batch Czochralski growth apparatus, configured to produce ingots of silicon in a step-wise process in which ingot growth is interrupted in order to replenish the crucible with additional feedstock for the preparation of additional ingots.

[0016] In general, the Czochralski growth apparatus to be retrofitted comprises a growth chamber in which an ingot, such as a silicon ingot, may be prepared. In particular, the growth chamber comprises a chamber shell having a top wall and one or more side walls forming a heatable space in which a crucible containing feedstock is provided. For example, the crucible may contain a pre-charge comprising silicon, which is subsequently melted in the crucible within the growth chamber. The crucible, which can be supported from below by one or more pedestals and rotated if desired, can be any known in the art for use in crystal growing that is capable of containing both solid and liquid material, particularly solid and liquid silicon. For example, the crucible can be a quartz crucible or can be a graphite crucible containing a quartz inner liner. The crucible can also have any cross-sectional shape depending, for example, on the geometry of the crystal growth system, but typically has a circular cross-sectional shape.

[0017] In some embodiments, the crucible comprises at least two zones, each separated by a wall or other separating means having at least one opening, such as a notch, hole, or pipe, that provides restricted fluid communication between the zones. For example, the crucible can comprise a wall that divides it into two zones - an inner zone, referred to herein as the inner growth zone, and an outer zone, referred to herein as the outer feed zone. These zones are in fluid communication with each other. The inner zone is where growth of the ingot is initiated and from where the ingot is grown (e.g., pulled) while the outer zone feeds additional material to the inner zone as the ingot is grown. Thus, as material is removed from the inner growth zone by the crystallization process, fresh material can enter from the outer feed zone. Preferably, the inner growth zone and/or the outer feed zone contain a solid pre-charge to be melted therein comprising silicon and may further comprise at least one dopant material, including, for example, phosphorus, boron, gallium, indium, aluminum, arsenic, or antimony.

[0018] The Czochralski growth apparatus to be retrofitted and converted further comprises at least one system from which growth of the crystalline ingot can be initiated. For example, the apparatus can further comprise a pull mechanism including a retractable cable on which a small crystalline seed, such as a silicon crystal, is supported. Using this mechanism, the seed, having a predetermined crystalline orientation, can be lowered into contact with molten material (e.g., feedstock) contained within the crucible and then gradually withdrawn. With proper control of temperatures, the liquid material freezes on the crystalline seed with the same orientation as that of the seed, thereby initiating growth of the crystalline ingot. The seed is then slowly raised away from the melt to form a growing crystalline ingot having a desired final length and diameter. One or more load cells supporting the pull mechanism can also be used, along with a control means responsive to the load cells for activating the supply of feedstock into the growth apparatus from the solid feedstock delivery system.

[0019] As discussed above, a feedstock pre-charge is typically provided to the crucible in the growth chamber and melted, and growth is then initiated from the melt. In some embodiments, the Czochralski growth apparatus to be retrofitted (e.g, the batch CZ growth apparatus) may further include a system for delivering feedstock into the crucible to provide the pre-charge when no growth is occurring. Any pre-charge delivery system may be used capable of providing feedstock such as silicon, including metallurgical grade silicon or solar grade silicon, which may further comprise at least one dopant material, such as phosphorus, boron, gallium, indium, aluminum, arsenic, or antimony, prior to or during growth or after growth is complete. For example, solid feedstock as a pre-charge may be provided via gravity feed from a hopper through a feed tube that enables transport of the feedstock from the hopper into the crucible in the growth chamber. A feed port in the chamber shell, such as in the top wall, may provide access through which the feeder delivers the pre-charge. The feed port may provide a seal so that conditions within the growth chamber can be maintained while the pre-charge is being supplied to the crucible.

[0020] The Czochralski growth apparatus to be retrofitted may further comprise a thermally-insulated shield positioned over the crucible. The shield is configured to protect the growing ingot from being excessively heated as a molten charge is maintained in the crucible and therefore is made of or comprises material possessing low thermal conductivity that is capable of withstanding the high temperatures and conditions within the growth apparatus. A variety of types of thermally-insulated shields are known in the art, and any of these can be used in the growth apparatus. The size and shape will depend on the geometry of the growth apparatus. For example, for a crucible having a circular cross-sectional shape, and used to form a silicon ingot having a generally circular cross-sectional shape, the thermally-insulated shield preferably also has a circular cross-sectional shape and is generally cylindrical or conical in geometry. In particular, the thermally-insulated shield may have an inverse conical shape, being larger in cross-sectional area at the top of the shield than at the bottom and having a diameter at the bottom that is large enough for the growing ingot to pass through.

[0021] According to embodiments of the present invention, a growth apparatus conversion assembly is provided to convert a batch Czochralski growth apparatus to a continuous Czochralski growth apparatus. The growth apparatus conversion assembly includes a feeder assembly for providing solid feedstock while a silicon ingot is being grown and may further include additional components, described in more detail below. The feeder assembly is configured to be attached or otherwise coupled to the growth chamber of the batch Czochralski growth apparatus to enable continuous feed of feedstock while ingots are grown. Preferably, the feeder assembly is configured to be connected to a side wall of the chamber shell of the growth apparatus, at a position in which the addition of feedstock during growth would have minimal impact on the ingot growth process or on the properties of the resulting grown ingot.

[0022] In particular, the feeder assembly of the growth apparatus conversion assembly of the present invention comprises a feeder, a lower hopper, and at least one upper hopper. In some embodiments, the feeder assembly is connectible to the growth chamber of the batch Czochralski apparatus at the feeder, which is configured to deliver solid feedstock into the growth chamber, as described in more detail below. The lower hopper is connected to the feeder and is positioned to feed solid feedstock into the feeder, preferably from above (i.e., gravity fed). Other means of feeding solid feedstock into the lower hopper may also be used, such as a conveyor or feed system from a remote upper hopper. Furthermore, the upper hopper is attached to the lower hopper and positioned to feed solid feedstock into the lower hopper, also preferably by gravity feed from above. In this way, solid feedstock contained in the upper hopper may be fed into the lower hopper, which may then pass into the feeder for transport into the growth chamber of Czochralski growth apparatus.

[0023] The upper hopper(s) and lower hopper are containers for holding solid feedstock and may have any shape or configuration known in the art. Preferably, the hoppers have a cylindrical upper section and a funnel-shaped conical lower section with an opening (e.g., a spout) through which solid feedstock may pass. A lid or cover may also be included in order to prevent dust or other contaminants from entering the solid feedstock. In addition, the upper hopper and the lower hopper may be the same or different and their capacities may vary depending, for example, on cost, available space, and the size and number of ingots to be prepared. In some embodiments, the upper hopper may be smaller than the lower hopper. In this way, a high capacity may be provided in the lower hopper that is sufficient for growing the desired ingots while a lower capacity may be used for the upper hopper for ease of removal, discussed below. Also, the lower hopper should be capable of withstanding conditions, such as vacuum and/or heat, as needed to provide solid feedstock properly conditioned into the feeder and then into growth chamber of the batch Czochralksi growth apparatus.

[0024] Furthermore, in embodiments of the present invention, the upper hopper is capable of being removed from the lower hopper, such as during feeding of solid feedstock into the growth chamber from the feeder. In particular, the feeder assembly of the growth apparatus conversion assembly may comprise an upper hopper that may be configured to be detached from the lower hopper for transport or movement away from its position providing feedstock to the lower hopper. For example, the upper hopper may be physically detached from the lower hopper and carried or otherwise transported to a location where it can be refilled or for maintenance/repair of the hopper components. Alternatively, or in addition, the upper hopper, in some embodiments, may be laterally maneuvered (e.g., moved along a track) or pivoted (e.g., rotated around a pivoting axis) away from the lower hopper to a position in which solid feedstock could no longer be delivered into the lower hopper, or to a position to refill a different lower hopper, depending on relative sizes (i.e., refilling multiple feeders with on large hopper). In this second position, refilling of the upper hopper or other operations may occur. If the feeder assembly comprises multiple upper hoppers, detachment of one upper hopper may occur with subsequent or simultaneous replacement with a different upper hopper (e.g., by a carousel or other means).

[0025] In order to maintain conditions in the lower hopper when a connected upper hopper is removed, the feeder assembly further comprises a feed isolation valve between the connected upper hopper and the lower hopper. In this way, if the upper hopper is to be removed, the feed isolation valve may be closed and/or sealed, maintaining the conditions provided within the lower hopper. When the removed upper hopper is reattached or replaced, the valve may be reopened, reestablishing conditions in the feed assembly, including in both hoppers. Thus, after the upper and lower hoppers are attached and conditions for feeding solid feedstock to the feeder and into the growth chamber are established within the feed assembly, the upper hopper may be removed by first closing the feed isolation valve in order to isolate the upper hopper and maintain those conditions in the lower hopper and feeder. In this way, feed of solid feedstock may continue into the growth chamber uninterrupted while the detached upper hopper is filled or repaired and, when reattached, establishing conditions in the upper hopper can occur without significant impact to the conditions below it.

[0026] In addition, a feed shut off valve (also sometimes referred to as a dump or discharge valve) may be included between the upper and lower hoppers in order to provide a flow of solid feedstock that can be regulated and adjusted. For example, with the feed isolation valve open, the feed shut off valve may be opened to vary the flow rate of solid feedstock into the lower hopper. If the upper hopper is to be removed, the feed may first be stopped by closing the feed shut-off valve, and then the feed isolation valve can be closed to maintain conditions in the lower hopper. The feed shut-off valve may also prevent solid feedstock from interfering with the operation of the isolation valve.

[0027] As discussed above, the feeder assembly of the growth apparatus conversion assembly comprises a feeder for conveying solid feedstock into the growth chamber, and, more particularly, into the crucible of the batch Czochralski growth apparatus that is to be converted into a continuous Czochralski growth apparatus. For example, the feeder may be a trough system, through which a controlled amount of solid silicon feedstock is provided to the crucible. The feeder can comprise at least one delivery point that overhangs the crucible. When the crucible comprises an inner growth zone and an outer feed zone, preferably the feeder provides material to the outer feed zone of the crucible in order to minimize disturbance of the molten silicon from which the crystalline ingot is grown or pulled.

[0028] In more detail, the feeder of the growth apparatus conversion assembly delivers solid feedstock into the growth chamber, and a variety of different types of feeders may be used. For example, the feeder may comprise a feeder pan that is both insertable into the growth chamber and also removable from the growth chamber back into the feed assembly. In one embodiment, the feeder pan may be movable for insertion into the growth chamber while the feeder itself is stationary. In other embodiments, the feeder pan is stationary relative to the feeder while the feeder (and, as a result, the corresponding feeder assembly) may be movably positioned along a feeder track. In this way, the feeder assembly and feeder may be properly positioned to be coupled to the growth chamber of the batch Czochralksi growth apparatus and to provide feed of solid feedstock into the growth chamber.

[0029] The feeder pan may be formed of any material known in the art that is capable of withstanding the temperatures and conditions in a high temperature crystal growth furnace, including, for example, a high modulus, non-contaminating material such as silicon carbide. Preferably, the feeder pan comprises a receiving section in which feedstock is received from the lower hopper along with an injector section connected to the receiving section that can be inserted into the growth chamber, such as through a feed port and/or isolation valve described below. The spout of the lower hopper can be positioned within sidewalls of the receiving section. In some embodiments, the cross section of the injector section is smaller than that of the receiving section. Furthermore, the injector section can have a bottom that is concave in cross-sectional shape, including, for example, a V shape with walls that are oppositely included from the vertical. The slope of the concave bottom can vary depending on, for example, the amount of feedstock being fed into the growth chamber. For example, the walls of the injector section can have a slope of between about 30° and about 60°. Furthermore, the receiving section of the feeder pan can be supported by a vibrator which aids in the delivery of the feedstock. For example, the vibrator can be supported on the hopper of the container, and the hopper can be supported in the feed chamber by at least one load cell, which is capable of measuring the amount of material present. Thus, the feeder pan may be a vibrating feeder, with solid feedstock movement caused by vibration along the feeder pan. Alternatively, the feeder pan may be a rotating feeder tube configured to move solid feedstock along an axis of rotation.

[0030] When the feeder assembly and feeder are movable along the feeder track relative to the growth chamber, the feeder may further comprise one or more bellows to provide expansion and contraction as the feeder is moved. In this way, the feeder can be retracted or moved towards the growth chamber by displacement of the bellows, without disconnecting the feeder from the growth chamber. In addition, for a vibrating feeder pan, the bellows may also provide damping properties to prevent transfer of vibrational energy to the growth chamber, which may cause defects in the growing ingot. Furthermore, if needed, a shielding system can also be used, interposed between the feeder pan and the bellows, to protect the bellows from any potential loose solid feedstock.

[0031] In some embodiments, the growth apparatus conversion assembly of the present invention further comprises a chamber isolation valve, which is configured to maintain conditions within the growth chamber when the feeder assembly is detached. In this way, process conditions present on one side of the valve (e.g., ingot growth conditions) may be isolated from different process conditions on the other side (e.g., feedstock maintenance conditions). A variety of different types of valves may be used, such as a slide valve, a gate valve, a pancake valve, or the like, as would be understood by one skilled in the art. For example, the chamber isolation valve may be attached to a feed port in the growth chamber, which is discussed in more detail below or may be attached to the feeder of the feeder assembly. In a preferred embodiment, the feeder assembly comprises the chamber isolation valve, which is connected to the feeder, thereby isolating conditions present within the feeder assembly. For this example, the feeder assembly may be vacuum sealed to the growth chamber at the chamber isolation valve, and the feeder is thereby insertable into the growth chamber and also removable from the growth chamber back into the feeder assembly through the chamber isolation valve. The valve can be any known in the art but is preferably a gate valve with an expandable water-cooled gate, such as those described in U.S. Patent Application Publication Nos. 2011/0006235, 2011/0006236, and 2011/0006240, which are fully incorporated by reference herein. While the use of an isolation valve may be advantageous in some embodiments, the use of the valve is optional and, in another embodiment of the present invention, the growth system does not comprise any isolation valve.

[0032] In some embodiments, the growth apparatus conversion assembly further comprises a feed port which is configured to be positioned in the chamber shell of the growth chamber and through which feedstock, such as silicon, is delivered as a silicon ingot is grown. While the feed port can be disposed anywhere along the chamber shell, including in at least one of the side walls or the top wall, depending for example, of the configuration of the batch Czochralski growth apparatus, preferably the feed port is disposed in a side wall of the chamber shell of the growth chamber for ease of delivery of feedstock. Furthermore, it is particularly preferred that the feed port be positioned in the side wall of the growth chamber at a height such that feedstock is delivered into the crucible without significant impact to a melt formed therein. For example, preferably the feed port is positioned so that feedstock enters the growth chamber from the feeder of the feeder assembly at a height substantially similar to the height of the crucible. In addition, it is also preferred that the feed port is positioned so that feedstock enters the crucible substantially horizontally. For example, the feed port is preferably at a height such that the center of the port forms an overall path of delivery having an angle that is between 0° (i.e., horizontal) and about 45°, more preferably between about 0° and about 30°, and even more preferably between about 0° and about 20°. As such, a slight slope is preferred so that feedstock slowly and consistently enters the crucible without binding or clogging, but does not enter the crucible with a high enough velocity to cause splashing or rebound. In addition, the height and/or angle of the feed path can be adjustable within these parameters, including during the delivery of feedstock. By positioning the feed port so that feedstock is delivered from the side of the growth chamber at a low height and entry angle, ingots having improved overall properties can be produced from a batch Czochralski growth apparatus converted into a continuous Czochralksi growth process using the growth apparatus conversion assembly of the present invention.

[0033] In some embodiments, the growth apparatus conversion assembly further comprises a feed spout fixed in position inside the growth chamber of the batch Czochralksi growth apparatus. The feed spout is configured to receive the solid feedstock from the feeder of the feeder assembly and to direct the feedstock into the crucible in the growth chamber. For example, the feed spout can have a sloping bottom and a spout positioned over the crucible so that feedstock provided from the feeder assembly can enter the feed spout and is added to the crucible without considerable splashing. The slope of the bottom of the feed spout can vary depending on, for example, the height of the feed spout above the crucible and the desired rate of feedstock addition. For example, the sloping bottom can be inclined at an angle of between about 30° and about 60°. For a crucible having inner and outer zones, preferably the spout of the feed spout is disposed over the outer feed zone. The feed spout box can comprise any material known in the art that is capable of withstanding the temperatures and conditions in a high temperature crystal growth furnace, including, for example, a high modulus, non-contaminating material such as silicon carbide.

[0034] Specific embodiments and components of the growth apparatus conversion assembly of the present invention are shown in FIGS. 1-3 and discussed below. However, it should be apparent to those skilled in the art that these are merely illustrative in nature and not limiting, being presented by way of example only. Numerous modifications and other embodiments are within the scope of one of ordinary skill in the art and are contemplated as falling within the scope of the present invention. In addition, those skilled in the art should appreciate that the specific configurations are exemplary and that actual configurations will depend on the specific system. Those skilled in the art will also be able to recognize and identify equivalents to the specific elements shown, using no more than routine experimentation.

[0035] FIG. 1 is a side view of a growth apparatus conversion assembly 100, according to a specific embodiment of the present invention. As shown, the assembly comprises feeder assembly 110, feed port 160, and feed spout 170. FIG. 2 is an exploded perspective view of the growth apparatus conversion assembly 100, without the feed port. As shown, feeder assembly 110 comprises upper hopper 120 positioned above and removably connected to lower hopper 130, which, as shown, is positioned above and connected to feeder 140. In this way, solid feedstock is gravity fed from the upper hopper to the lower hopper and to the feeder. In this specific embodiment, upper hopper 120 has a smaller capacity than lower hopper 130, and both have an overall cylindrical shape with a generally conical, funnel-shaped spout. Upper hopper 120 includes lid 122 at the top and also includes coupler 124 which enables attachment to and detachment from the lower hopper. Feed isolation valve 150 is positioned between upper hopper 120 and lower hopper 130, which, when opened, allows the two hoppers and the feeder to be under similar feed conditions (temperature, vacuum, etc.) and, when closed, isolates the lower hopper and feeder from the upper hopper, allowing the upper hopper to be removed without changing feed conditions. In addition, feed shut off valve 152 is also positioned between the hoppers, allowing the flow of solid feedstock from upper hopper 120 to lower hopper 130 to be interrupted or adjusted as needed.

[0036] In the specific embodiment shown in FIG. 1 and FIG. 2, feeder 140 of feeder assembly 110 is connectible to chamber shell 190 of a batch Czochralski growth apparatus to be retrofitted and converted into a continuous Czochralski growth apparatus. In particular, the feeder assembly further comprises tracks 145, upon which feeder 140 is positioned, so that the feeder assembly may be moved along the track into a position adjacent to the chamber shell. Feeder assembly 110 may optionally rest on pedestal 156 for support and to position the feeder assembly at the proper height for the target Czochralski growth apparatus. The height of the pedestal may be static or adjustable.

[0037] Feeder 140 comprises feeder pan 142 which receives solid feedstock from lower hopper 130 and conveys the feedstock into the growth chamber of the batch Czochralski growth apparatus. While, in some embodiments, the feeder pan is movable into position to deliver solid feedstock into the growth chamber, in the specific embodiment shown in FIG. 1 and FIG. 2, the feeder pan is stationary relative to the feed assembly, and the feed assembly is movable into position along tracks 145. Feeder 140 further comprises bellows 144, which expand and contract as the feeder assembly is moved along tracks 145 and also provides vibrational damping when the feeder pan operates by vibrational feed.

[0038] As shown in FIG. 1, growth apparatus conversion assembly 100 further comprises feed port 160 which is positioned in side wall of chamber shell 190 at a height essentially horizontal with the top of the crucible within the growth chamber. As shown in both FIG 1 and FIG. 2, feeder 140 further comprises chamber isolation valve 148 which is connectible to feed port 160 and, when closed, maintains the conditions in the growth chamber when the feeder assembly is detached. Bellows 144, by expansion and contraction, allow movement of feeder assembly 110 relative to the attached chamber isolation valve 148 as feeder 140 moves along tracks 145. In this way, feeder pan 142 is inserted into the growth chamber through feed port 160. Note that, in some embodiments, the feed port may be an optional component of the growth apparatus conversion assembly. For example, if the Czochralski growth apparatus to be retrofitted and converted already includes a port positioned in the side wall of the growth chamber, feed port 160 may not be needed.

[0039] Also as shown in FIG. 1 and FIG. 2, growth apparatus conversion assembly

100 further comprises feed spout 170, which is fixedly positioned within the growth chamber of the Czochralksi growth apparatus to overhang crucible 199. As shown, feed spout 170 is positioned at a height to provide a substantially horizontal flow path from feeder 140. Solid feedstock from the feeder passing through feed port 160 then flows through feed spout 170 to be directed into the crucible of the Czochralski growth apparatus. Feed spout 170 comprises sloping bottom 172 for receiving the solid feedstock from the feeder and down which the solid feedstock can flow into crucible 199.

[0040] As discussed above, the present invention further relates to a method of converting a Czochralski growth apparatus, particularly a batch CZ growth apparatus, to a continuous Czochralski growth apparatus. FIG. 3 illustrates an example simplified procedure for this method. For example, procedure 300 may begin at step 305 and continue to step 310, where, as described in greater detail above, a batch Czochralski growth apparatus is provided having a growth chamber. While the batch Czochralski growth apparatus may vary in specific configuration and components, in some embodiments, the growth chamber comprises a chamber shell having a top wall and at least one side wall, a crucible containing a melt positioned within the chamber shell, and a pull mechanism for retractably supporting a seed for contacting the melt.

[0041] At step 315, the method further comprises providing a growth apparatus conversion assembly including a feeder assembly, as described in greater detail above. Any of the assemblies described above may be used in the present method. In some embodiments, the growth apparatus conversion assembly comprises a feeder assembly, a feed port to be positioned in the side wall of the chamber shell (which may be optional in some embodiments), and a feed spout, which is fixedly positioned within the growth chamber to direct solid feedstock flow into the crucible. The feeder assembly comprises a feeder connectible to the growth chamber and positioned to feed solid feedstock into the growth chamber. The feeder assembly further comprises a lower hopper connected to the feeder and positioned to feed solid feedstock to the feeder and at least one upper hopper removably attached above the lower hopper and positioned to feed solid feedstock into the lower hopper. Furthermore, the feeder assembly also comprises a feed isolation valve positioned between the upper hopper and the lower hopper configured to maintain conditions in the lower hopper when the upper hopper is being filled.

[0042] At step 320, the method further comprises coupling the feeder assembly of the growth apparatus conversion assembly to the side wall of the growth chamber, as described in greater detail above. In embodiments in which the growth apparatus conversion assembly includes a feed port, coupling the feeder assembly comprises positioning the feed port in the side wall of the growth chamber of the batch Czochralski growth apparatus and coupling the feeder of the feeder assembly to the feed port. Coupling may also comprise moving the feeder assembly along a track to a position adjacent to the chamber shell of the batch Czochralski growth apparatus. Bellows of the feeder may be adjusted by expansion and/or contraction as needed to couple the feeder assembly to the growth chamber. An optional pedestal may also be used to adjust the height of the feeder assembly for ease of coupling. Procedure 300 then ends at step 325.

[0043] It should be noted that while certain steps within procedure 300 may be optional as described above, the steps shown in FIG. 3 are merely examples for illustration, and certain other steps may be included or excluded as desired. Further, while a particular order of the steps is shown, this ordering is merely illustrative, and any suitable arrangement of the steps may be utilized without departing from the scope of the embodiments herein.

[0044] Use of the growth apparatus conversion assembly in a method of converting a batch Czochralski growth apparatus to a continuous Czochralski growth apparatus provides significant advantages. For example, a user of the batch process, desiring to grown a silicon ingot by a continuous process, can do so without purchasing an entirely new growth apparatus. Retrofitting the existing batch equipment can be done without significant modification to the existing growth chamber and its components. Furthermore, once coupled to the growth chamber, the growth apparatus conversion assembly of the present invention allows for uninterrupted processing of silicon ingots. In particular, since the feeder assembly comprises two solid feedstock hoppers separated by an isolation valve, solid silicon can be fed from the upper hopper to the lower hopper through the feeder and into the crucible of the growth apparatus. While growing a silicon ingot, the upper hopper, when emptied, can be removed by closing the feed isolation valve, allowing growth of the same or additional ingots to continue while the upper hopper is being refilled. Once filled, the upper hopper can be reattached, the feed isolation valve can be opened, and feed from the upper hopper into the lower hopper can continue. This can be repeated multiple times, all without interrupting the silicon ingot growth process. In essence, an ingot of nearly infinite length may be grown as feedstock is provided continually replenished during growth by refilling a removable and isolatable upper hopper. This is not possible in a batch Czochralski process, in which ingot length is limited by crucible size, and also cannot generally be achieved in a standard continuous Czochralski process, in which ingot length is limited by the size of the hopper refilling the crucible. Other advantages will be known to one of ordinary skill in the art, given the benefit of the present disclosure.

[0045] The foregoing description of preferred embodiments of the present invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings, or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.