WO2013141471A1 - Silicon ingot growing apparatus provided with feed unit - Google Patents

Description

Silicon Ingot Growth Apparatus With Feed Unit

The present invention relates to a silicon ingot growth apparatus, and more particularly, to a silicon ingot growth apparatus for supplying a feedstock through a feed unit.

Single crystal materials such as silicon have important industrial applications in the semiconductor and photovoltaic industries. For example, in semiconductor applications where microprocessors operate at quantum sizes, the presence of grain boundaries can have a significant impact on the functionality of field effect transistors by changing local electrical properties. Similarly, when using materials such as silicon for solar cells, monocrystalline silicon solar cells generally exhibit high efficiency compared to polycrystalline silicon solar cells. In general, since grain boundaries show more impurities and defects, solar cells made of monocrystalline silicon can increase performance compared to solar cells made of polycrystalline silicon.

Silicon solar cells are manufactured from silicon ingots, and commercially available technologies for producing silicon ingots include Czochralski method and unidirectional solidification method. It is possible to produce polycrystalline silicon ingot through unidirectional solidification method, and the low production cost is an advantage compared to Czochralski method. In unidirectional coagulation, the crucible containing the feedstock can be located above the heat exchanger block. The feedstock is melted at about 1412 degrees or more through a heater installed around the crucible, and gradually cools to a temperature below the melting point through a stabilization time, thereby unidirectionally solidifying. In the unidirectional solidification process, either induction heating or resistance heating can be used. Unlike Czochralski growth, coagulation in unidirectional coagulation proceeds from the bottom of the crucible to the top, and the solid-liquid interface undergoes nuclear growth and crystal growth. At this time, impurities are suspended to the upper side by the mass distribution coefficient.

As such, after melting the feedstock, which is polycrystalline silicon, a polycrystalline silicon ingot can be produced through unidirectional solidification from the bottom to the top. The cost of producing polycrystalline silicon ingots is cheaper than the cost of monocrystalline silicon ingots produced by the Czochralski method.

An object of the present invention to provide a silicon ingot growth apparatus that can be used to fill the feedstock in the crucible using a feed unit.

Another object of the present invention to provide a silicon ingot growth apparatus that can increase the productivity compared to the existing by growing a bulky ingot.

Still other objects of the present invention will become more apparent from the following detailed description and drawings.

According to one embodiment of the present invention, a silicon ingot growth apparatus includes a furnace having a supply port through which a feedstock is supplied from the outside; A crucible installed inside the furnace and having a feedstock filled with a single crystal seed and an upper portion of the single crystal seed; A heater for heating the crucible to melt the single crystal seed and the feedstock; And a feed unit connected to the supply port to supply the feedstock to the crucible, wherein the feed unit is filled with the feedstock therein and discharges the feedstock through a discharge port formed at a lower portion thereof. ; And a fixing tube having a supply tube having an inlet open toward the discharge port and a discharge tube inclined downward toward the inside of the furnace.

The feed unit may be further provided on the discharge tube is movable along the discharge tube, the moving tube for discharging the feedstock in the crucible through the discharge port formed at the bottom.

The feed unit may further include a vibration feeder connected to the moving tube to apply vibration to the moving tube at a predetermined frequency.

The feed unit may be arranged in parallel with the moving direction of the moving tube, the moving rod is formed on the outer circumferential surface; And it may be further provided with a connecting bracket fixed to the moving tube, screwed to the moving rod through a screw thread formed on the inner peripheral surface to move along the moving rod as the moving rod rotates.

The moving tube may include: a first supply position at which the discharge port is disposed adjacent to the sidewall of the crucible spaced apart from the supply port to supply the feedstock; And the discharge port is arranged adjacent to the side wall of the crucible at least spaced from the supply port can be switched to the second supply position for supplying the feedstock.

The moving tube is located between the first and second supply positions and is switchable to a third supply position for supplying the feedstock.

The moving tube may be sequentially moved from the first supply position to the second supply position by a predetermined distance.

The silicon ingot growth apparatus may include: a driving motor connected to the moving rod to drive the moving rod; And a controller connected to the heater and the drive motor, wherein the controller is capable of resupplying the feedstock into the crucible by switching the moving tube to the first and second supply positions through the drive motor. have.

The silicon ingot growth apparatus further comprises a temperature sensor for sensing the temperature of the feedstock melted in the crucible, the controller is the temperature in the crucible when the temperature detected by the temperature sensor is within a predetermined range Feedstock can be resupplyed.

The silicon ingot growth apparatus may further include a valve for opening and closing any one of the discharge port and the supply tube.

The silicon ingot growth apparatus may further include a cooling plate installed under the crucible to absorb heat from the crucible.

The silicon ingot growth apparatus may further include a cooling rod disposed at a position corresponding to the single crystal seed, in thermal contact with the cooling plate, and having a refrigerant flowing therein.

The crucible has a mounting groove recessed from the bottom surface, and the silicon ingot growth apparatus may further include a fixing chuck to fix the single crystal seed and to be inserted into the mounting groove.

According to an embodiment of the present invention, the feedstock may be filled into the crucible through the feed unit, and the bulky ingot may be grown by filling the feedstock secondly after the primary filling and melting.

1 is a view schematically showing an ingot growth apparatus according to an embodiment of the present invention.

2 is a view schematically showing a feed unit shown in FIG.

3 is a view showing a state in which the feedstock is primarily filled in the crucible shown in FIG.

4 is a block diagram illustrating a state in which a driving motor and a heater are operated through a controller.

5 is a view schematically showing the operation of the temperature sensor shown in FIG.

6 to 8 are views showing the secondary charging of the feedstock in the crucible shown in FIG.

9 is a view showing a state in which the single crystal seed shown in FIG. 1 is fixed by using a fixed chuck.

Hereinafter, embodiments of the present invention will be described in more detail with reference to FIGS. 1 to 9. The embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. These embodiments are provided to explain in detail the present invention to those skilled in the art. Accordingly, the shape of each element shown in the drawings may be exaggerated to emphasize a more clear description.

On the other hand, the "connection" used below is interpreted to include not only the case of directly connecting 'A' to 'B', but also the case of connecting 'A' to 'B' through 'C'. In addition, the following "connection" is used not only to connect the 'A' and 'B' mechanically, but also to spatially connect the 'A' and 'B' to move a material from 'A' to 'B'. It is interpreted to include the case where possible. In addition, the ingot growth apparatus described below is described as growing a polycrystalline ingot of a single crystal tendency, but the scope of the present invention is not limited thereto, and the polycrystalline ingot may be grown in a state where the single crystal seed is removed.

1 is a view schematically showing an ingot growth apparatus according to an embodiment of the present invention, Figure 2 is an enlarged view of the feed unit shown in FIG. As shown in FIG. 1, the ingot growth apparatus includes a furnace 1, and crystal growth through unidirectional solidification, which will be described later, takes place inside the furnace 10.

The crucible 10 is installed inside the furnace 1, and the single crystal seed 20 is located in the crucible 10. The crucible 10 may be made of quartz or silica, and may be cylindrical or rectangular. The crucible 10 has an open top shape, and the feedstock 23 described later is filled in the crucible 10 through the top. The single crystal seed 20 has a flat plate shape and is in close contact with the bottom surface of the crucible 10. In the process of filling the feedstock 23 into the crucible 10, the single crystal seed 20 is placed on the single crystal seed 20 by using a bulk of the bulky feedstock 23. It may be in close contact with the bottom surface of the single crystal seed 20 is separated from the bottom surface of the crucible 10 can be prevented from being completely melted like the feedstock (23). The heater 14 is disposed on both sides of the crucible 10 and heats the crucible 10 to melt the seed 20 and the feedstock 23.

The crucible 10 is placed on top of the cooling plate 16. The cooling plate 10 has a flat plate shape and has a receiving groove 17 recessed from the lower surface. One or more cooling rods 18 are installed in the receiving grooves 17 and the cooling rods 18 are in thermal contact with the receiving grooves 17. The cooling rod 18 is connected to the refrigerant supply line 19, and the refrigerant is supplied to the cooling rod 18 through the refrigerant supply line 19. The coolant supply line 19 is opened and closed through the valve 19a.

The feedstock 23 may be directly filled by an operator or automatically charged through a feed unit, and the feedstock 23 may be polycrystalline silicon. As shown in FIG. 2, the feed unit includes a hopper 201, fixed tubes 208 and 209, and a moving tube 232. Hopper 201 contains feedstocks 23. The feedstocks 23 may be in the form of powder, granules, chips, or waste silicon, such as broken wafers. The upper portion of the hopper 201 is cylindrical and the lower portion of the hopper 201 is funnel-shaped, the cross-sectional area of which decreases downward. The hopper 201 has a discharge port 204 formed at the bottom, and the feedstocks 23 filled in the hopper 201 may be discharged through the discharge port 204.

The fixed pipes 208 and 209 are fixed to the feed cylinder 228 and have a supply tube 208 and an outlet tube 209. The feed tube 208 is arranged in the vertical direction, the feed tube 208 has an inlet open toward the discharge port (204). The discharge tube 209 is disposed to be inclined downward toward the inside of the furnace 1, and is connected to the supply tube 208. The feedstocks 23 discharged through the discharge port 204 move through the inlet of the supply tube 208 into the discharge tube 209 and are discharged through the open lower portion of the discharge tube 209.

The on-off valve 229 is installed at the lower end of the discharge port 204 to open and close the discharge port 204, the discharge of the feedstock 23 may be limited through the on-off valve 229. The operation of the on-off valve 229 can be controlled through the controller 40 to be described later, the operator can adjust the discharge of the feedstock (23) through the controller 40. Unlike the present embodiment, the on-off valve 229 may be installed on the supply tube (208).

The moving tube 232 is connected to the discharge tube 209, the moving tube 232 is disposed substantially parallel to the discharge tube (209). The moving tube 232 has an inner diameter larger than the outer diameter of the discharge tube 209, the discharge tube 209 is inserted into the moving tube 232. The feedstocks 23 discharged through the discharge tube 209 move into the inside of the moving tube 232, and are supplied into the crucible 10 through the open lower portion of the moving tube 232. The moving tube 232 has a slot 232a, and when the moving tube 232 moves, the supply tube 208 moves along the slot 232a.

The vibration feeder 206 is connected to the moving tube 232 to apply a vibration to the moving tube 232 at a predetermined frequency. As described above, the feedstocks 23 may be in the form of granules or chips, and the feedstocks 23 moving through the moving tube 232 may be caught inside the moving tube 232 to limit movement. Thus, by applying a constant vibration through the vibration feeder 206 it is possible to facilitate the movement of the feedstock (23).

On the other hand, as shown in Figure 2, the feed unit further includes a housing 210, the housing 210 has an internal space blocked from the outside. The hopper 201 may be installed in the inner space of the housing 210. The inner space of the housing 210 communicates with the inside of the feed cylinder 228 which will be described later, and the inner space of the housing 210 may form a vacuum state through an exhaust pump (not shown) connected to the feed cylinder 228. have. The housing 210 has an open top, and the cover 203 opens and closes the open top of the housing 210. When filling the hopper 201 with the feedstocks 23, the cover 203 of the housing 210 may be opened and the feedstock 23 may be charged within the hopper 201. The housing 210 has a connection port 222 formed at the bottom, and the connection port 222 is connected to the cylinder inlet 226 of the feed cylinder 228 which will be described later.

The feed unit further includes a feed cylinder 228 and a moving rod 234. The feed cylinder 228 has a cylinder outlet 228b, and the cylinder outlet 228b is connected to the supply port 130. The interior of the feed cylinder 228 is in communication with the interior of the supply port 130 (or the furnace 1).

The moving tube 232 is connected to the moving rod 234 through the connecting bracket 233. The connection bracket 233 has a fastening hole formed with a screw thread on the inner circumferential surface, and the fastening hole is screwed with the screw thread formed on the outer circumferential surface of the moving rod 234. Accordingly, the connecting bracket 233 may move along the moving rod 234 according to the rotation direction of the moving rod 234, and the moving tube 232 may move together with the connecting bracket 233. The moving rod 234 is connected to the driven pulley 234a, and the driven pulley 234a is connected to the drive pulley 236a connected to the drive motor 236 through a belt.

FIG. 3 is a view illustrating a state in which a feedstock is primarily charged in the crucible shown in FIG. 1, and FIG. 4 is a block diagram illustrating a state in which a driving motor and a heater are operated through a controller. Hereinafter, referring to FIGS. 3 and 4, a method of melting and charging the feedstock in the crucible will be described.

First, the single crystal seed 20 is in close contact with the bottom surface of the crucible 10, the feedstock 23 is loaded on the top of the single crystal seed 20 and filled in the crucible 10. As described above, the feedstocks 23 may be in the form of powder, granules, chips, or waste silicon, such as broken wafers.

As shown in FIG. 3, when the feedstock 23 is sufficiently filled in the crucible 10, the controller 40 starts the heater 14 to start the melting process. Melting proceeds with the seed 20 and feedstock 23 together, while the feedstock 23 is completely melted while the seed 20 is partially (about 2/3) melted while avoiding complete melting. In this case, the seed 20 may be completely melted by using the cooling plate 16 and the cooling rod 18.

Since the silicon melts at 1412 ° C., the temperature of the crucible 10 is maintained between about 1415 ° C. and 1550 ° C. Since the heater 14 is installed at both sides of the crucible 10, the feedstock 23 is heated through the side wall of the crucible 10, the temperature distribution is formed with a higher edge than the center of the crucible 10.

5 is a view schematically showing the operation of the temperature sensor shown in FIG. When the heater 14 is operated for a predetermined time, the feedstock 23 melts to form the melt 25, and the controller 40 senses the temperature of the melt 25 through the temperature sensor 37. The temperature sensor 37 is installed on the upper part of the furnace 1 and senses the surface temperature of the melt 25 through the see-through window 35 of the furnace 1. The temperature sensor 37 may be a pyrometer, which measures the temperature of the surface of the object based on the surface brightness from which the irradiated laser is reflected by the object.

When the temperature sensed by the temperature sensor 37 is close to the melting temperature of silicon (about 1412 ° C.), it may be determined that the feedstock 23 is melted at a predetermined level or more. As described above, since the temperature distribution inside the crucible 10 has a higher edge than the center, the temperature sensor 37 preferably measures the temperature of the melt 25 located at the center of the crucible 10. When the melt 25 located at the center of the crucible 10 approaches the melting temperature of silicon, it may be determined that the feedstock 23 is almost melted.

Thereafter, the controller 40 further supplies the feedstock 23 to the crucible 10. As described above, since the feedstock 23 is in the form of granules or chips, the packing density is low and the volume of the feedstock 23 that can be filled in the crucible 10 is limited. . In particular, the volume limitation of the feedstock 23 directly affects the production yield and throughput of the ingot and directly limits the size of the ingot. Therefore, it is necessary to supply the feedstock 23 after supplying the feedstock 23 and improving the filling density through melting. That is, as shown in FIG. 3, even when a sufficient amount of the feedstock 23 is filled in the crucible 10, as shown in FIG. 5, the feedstock 23 melts the melt 25 by melting. When formed, the space occupied by the feedstock 23 is greatly reduced.

6 to 8 are views showing the secondary charging of the feedstock in the crucible shown in FIG.

First, as described above, a constant amount of feedstock 23 is filled in hopper 201. In this case, when the filling is completed, a vacuum state may be formed in the furnace 1 through the exhaust pump, and the exhaust pump may be controlled through the controller 40.

Thereafter, when the temperature sensed by the temperature sensor 37 is within a predetermined range, as shown in FIG. 6, the driving motor 236 is operated to move the moving tube 232 to the initial supply position. The drive motor 236 is connected to the controller 40 and can operate the drive motor 236 through the controller 40. When the driving motor 236 is operated, the moving rod 234 rotates in one direction (for example, clockwise), and the moving tube 232 moves forward together with the connecting bracket 233 by the rotation of the moving rod 234. can do. As shown in FIG. 6, when the moving tube 232 is in the initial supply position, the discharge port of the moving tube 232 is disposed adjacent to the side wall of the crucible 10 spaced apart from the supply port 130 at the maximum. Thereafter, the on / off valve 229 is operated through the controller 40 to open the discharge port 204, and the feedstocks 23 are inside the crucible 10 through the discharge tube 209 and the moving tube 232. Is charged.

On the other hand, as shown in Figure 6, the feedstock 23 discharged through the discharge port of the moving tube 232 is concentrated in a position close to the discharge port to form a hill, it is not evenly loaded in the crucible 10. In this case, it is not possible to charge a large amount of the feedstocks 23 in the crucible 10, and in the future, when the feedstocks 23 are melted through the heater 14, the melting rate decreases due to the decrease in efficiency. Can be. Therefore, it is necessary to move the moving tube 232 to a supply position different from the initial supply position.

After the moving tube 232 discharges the feedstocks 23 for a preset supply time from the initial supply position, the controller 40 operates the drive motor 236 to move the moving rod 234 in a direction different from one direction (eg, For example, it rotates in a counterclockwise direction, and by the rotation of the moving rod 234, the moving tube 232 can be reversed together with the connecting bracket 233. As shown in FIG. 7, the moving tube 232 moves to the intermediate supply position, and when the moving tube 232 is in the intermediate supply position, the discharge port of the moving tube 232 may be located at the center of the crucible 10. .

Similarly, after the moving tube 232 discharges the feedstocks 23 for a predetermined supply time from the intermediate supply position, as shown in FIG. 8, the moving tube 232 moves to the last supply position, and the moving tube 232 ) Is in the last supply position, the discharge port of the moving tube 232 is disposed adjacent to the side wall of the crucible 10 that is at least (or closest) to the supply port 130.

When a certain amount of feedstock 23 is charged in the crucible 10, the controller 40 operates the on / off valve 229 to close the discharge port 204, and the feedstock 23 is no longer a crucible 10. ) Is not charged. On the other hand, since the amount of the feedstock 23 charged in the crucible 10 increases while discharging the feedstock 23 at each position from the first feed position to the last feed position, the feedstock 23 at each position. The feed time for releasing the gas can be reduced gradually.

Through the above method, the moving pipe 232 may discharge the feedstocks 23 while moving from the initial supply position to the intermediate supply position and the last supply position, and the feedstocks 23 are concentrated at a predetermined position. The state of loading can be improved.

In addition, through the above method, it is possible to improve the filling density of the feedstock 23, and to secure a large amount of the melt 25 to improve the size of the ingot generated through the crystal growth 25 to 35% compared to the existing Can be. In the present embodiment, the feedstock 23 has been described as being charged two times, but the filling of the feedstock 23 may be performed through three or more processes, and the melt 25 is formed at the top of the crucible 10. It can be done until it is reached.

Thereafter, when the feedstock 23 is sufficiently filled in the crucible 10, the controller 40 starts the melting process by starting the heater 14. Melting proceeds with the seed 20 and feedstock 23 together, while the feedstock 23 is completely melted while the seed 20 is partially melted while avoiding complete melting. In this case, the seed 20 may be completely melted by using the cooling plate 16 and the cooling rod 18.

After the feedstock 23 is melted and the seed 20 is partially melted, the crucible 10 is cooled to unidirectionally solidify the molten feedstock 23, and crystal growth is initiated to produce an ingot. . The cooling rod 18 can be used to start the initial solidification of the melt 25 by lowering the bottom temperature of the crucible 10 below the melting point of silicon.

The ingot grows from the seed 20 in a single crystal state, and the resulting ingot may be polycrystalline silicon having a single crystal region. This can be defined as polycrystalline silicon with a single crystal orientation. While the photoelectric conversion efficiency of single crystal-oriented polycrystalline silicon is similar to that of single crystal silicon, the production cost is lower than that of Czochralski method for producing single crystal ingot and is similar to polycrystalline silicon.

The thickness of the seed 20 before melting is 25-30 mm (excluding the inserts), and in part it is desired to make polycrystalline ingots of single crystal tendency to initiate crystal growth when the seed thickness of the seed 20 is about 13-17 mm. Can be.

11 is a view showing a state in which the seed shown in FIG. 1 is fixed by using a fixing chuck. The ingot growth apparatus may further include a fixed chuck 27. The crucible 10 has a mounting groove 12 recessed in the bottom surface, and the fixing chuck 27 is inserted onto the mounting groove 12 in a state where the projection of the seed 20 is inserted and fixed to the fixing chuck 27. Can be fixed. This is to prevent damage of the seed 20 and the crucible 10 and to prevent the seed 20 from being separated from the crucible 10 during crystal growth. In addition, to prevent the melt 25 from flowing into the crucible 10 through the fixing chuck 27. The fixed chuck 27 may be made of silicon, and like the seed 20, may be single crystal silicon.

Although the present invention has been described in detail by way of examples, other types of embodiments are possible. Therefore, the spirit and scope of the claims set forth below are not limited to the embodiments.

The present invention can be applied to various ingot growth apparatuses including silicon.

Claims (12)

Furnace (furnace) having a supply port for supplying the feedstock from the outside; A crucible installed inside the furnace and having a feedstock filled with a single crystal seed and an upper portion of the single crystal seed; A heater for heating the crucible to melt the single crystal seed and the feedstock; And A feed unit connected to the supply port to supply the feedstock to the crucible, The feed unit, A hopper filled with the feedstock and discharging the feedstock through a discharge port formed at a lower portion thereof; And And a fixed tube having a supply tube having an inlet open toward the discharge port and a discharge tube inclined downward toward the inside of the furnace. The method of claim 1, The feed unit, And a moving tube installed on the discharge tube and movable along the discharge tube and discharging the feedstock into the crucible through a discharge hole formed at a lower end thereof. The method of claim 2, And the feed unit further comprises a vibration feeder connected to the moving tube to apply vibration to the moving tube at a predetermined frequency. The method of claim 2, The feed unit, A moving rod disposed in parallel with a moving direction of the moving tube and having a thread formed on an outer circumferential surface thereof; And And a connection bracket fixed to the moving tube and screwed to the moving rod through a screw thread formed on an inner circumferential surface thereof to move along the moving rod as the moving rod rotates. The method of claim 4, wherein The moving tube, A first supply position at which the discharge port is disposed adjacent to a side wall of the crucible spaced apart from the supply port to supply the feedstock; And And the discharge port is disposed adjacent to the sidewall of the crucible at least spaced from the supply port and is switched to a second supply position for supplying the feedstock. The method of claim 5, And the moving tube is located between the first and second supply positions and is switchable to a third supply position for supplying the feedstock. The method of claim 5, And the moving tube sequentially moves from the first supply position to the second supply position by a predetermined distance. The method of claim 5, The silicon ingot growth apparatus, A driving motor connected to the moving rod to drive the moving rod; And Further comprising a controller connected to the heater and the drive motor, The controller, And the moving tube is switched to the first and second supply positions through the drive motor to resupply the feedstock into the crucible. The method of claim 1, The ingot growth apparatus further comprises a valve for opening and closing any one of the discharge port and the supply tube. The method of claim 1, The ingot growth apparatus further comprises a cooling plate installed in the lower portion of the crucible to absorb heat from the crucible. The method of claim 10, The ingot growth apparatus further comprises a cooling rod disposed in a position corresponding to the single crystal seed and in thermal contact with the cooling plate and flowing with a refrigerant therein. The method of claim 1, The crucible has a mounting groove recessed from the bottom surface, The ingot growth apparatus further comprises a fixed chuck to fix the single crystal seed and is inserted into the mounting groove.

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