JP2005127678A - Melting device, and melting method using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a melting device, and a melting method preventing molten silicon leakage occurring before complete melting due to a structure and mechanism of the melting device, reducing scattering of molten silicon when tapping the molten silicon, miniaturizing the device, and capable of efficiently using silicon raw material. <P>SOLUTION: In the melting device, silicon material inputted in a crucible 1 is heated and melted by a heating means 3, and it is tapped from a tap hole 5 provided in a crucible bottom. It is composed by providing a depression part 7 in the crucible bottom, and providing the tap hole in an interior of the depression part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a melting apparatus and a melting method using the same, and more particularly to a melting apparatus suitable for a casting apparatus for casting polycrystalline silicon for solar cells and a melting method using the same.

  A solar cell converts incident light energy into electrical energy. Major solar cells are classified into crystalline, amorphous, and compound types depending on the type of materials used. Of these, most of the crystalline silicon solar cells currently on the market are in the market. This crystalline silicon solar cell is further classified into a single crystal type and a polycrystalline type. A single-crystal silicon solar cell has the advantage that it is easy to increase the efficiency because the quality of the substrate is good, but has the disadvantage that the manufacturing cost of the substrate is high. On the other hand, the polycrystalline silicon solar cell has the advantage that it can be manufactured at a low cost although it has the disadvantage that it is difficult to increase the efficiency because the quality of the substrate is poor. In recent years, conversion efficiency of about 18% has been achieved at the research level due to the improvement of the quality of the polycrystalline silicon substrate and the advancement of cell technology.

  On the other hand, since mass-produced polycrystalline silicon solar cells are low in cost, they have been distributed in the market. However, in recent years, demands are increasing as environmental problems are addressed.

  A polycrystalline silicon substrate used for a polycrystalline silicon solar cell is generally manufactured by a method called a casting method. This casting method is a method of forming a silicon ingot by cooling and solidifying a silicon melt in a mold made of graphite or the like coated with a release material. The ends of the silicon ingot are removed, cut into a desired size, and the cut out ingot is sliced to a desired thickness to obtain a polycrystalline silicon substrate for forming a solar cell.

  Conventionally, for example, a melting apparatus for melting a semiconductor material such as silicon has been known as shown in FIG. 3 (see Patent Document 1). 3 is a conventional melting apparatus for casting silicon or the like described in Patent Document 1. In FIG. 3, 21 is a melting crucible, 22 is a holding crucible, 23 is a pouring gate, and 24 is a silicon that closes the pouring gate 23. The raw material, 25 is a nozzle, 26 is a side heating means, 27 is an upper heating means, 28 is a mold heating means, 29 is a mold, and 30 is a nozzle heating means.

  A melting crucible 21 for melting the raw material silicon is disposed in the upper part of the melting apparatus while being held by a holding crucible 22, and at the bottom of the melting crucible 21 and the holding crucible 22, a hot water outlet 23 for discharging a silicon melt is provided. Nozzle 25 is provided, and nozzle heating means 30 is installed around it. Further, heating means 26 and 27 are respectively disposed on the side and upper portions of the melting crucible 21 and the holding crucible 22, and a mold 29 into which a silicon melt is poured is disposed below the melting crucible 21 and the holding crucible 22, A mold heating means 28 for controlling the solidification of the silicon melt is disposed in the upper part.

  For example, high-purity quartz is used for the melting crucible 21 in consideration of heat resistance and the fact that impurities do not diffuse into the silicon melt. The holding crucible 22 is for holding the melting crucible 21 made of quartz or the like because the melting crucible 21 is softened at a high temperature in the vicinity of the melting point of silicon and cannot retain its shape, and the material is made of graphite or the like. .

  As the heating means 26, 27, 28, a resistance heating type heater, an induction heating type coil, or the like is used. The mold 29 is made of graphite, carbon fiber reinforced material, or the like, and is used by applying a release material mainly composed of silicon nitride or the like on the inside thereof. A mold heat insulating material (not shown) is installed around the mold 29 to suppress heat removal. As the mold heat insulating material, a carbon-based material is generally used in consideration of heat resistance and heat insulating properties. A cooling plate (not shown) may be installed below the mold to cool and solidify the poured silicon melt. These are all arranged in a vacuum vessel (not shown).

  As shown in FIG. 3, the outlet 23 provided at the bottom of the melting crucible 21 is closed with the silicon raw material 24, and then the silicon raw material is put into the melting crucible 21. Then, the upper part of the melting crucible 21 and the lower part of the raw material are gradually dissolved by the heating means 27 on the upper part of the melting crucible 21 and the heating means on the side part. At this time, the nozzle heating means 30 is not driven, and the raw material close to the outlet 23 of the nozzle 25 is kept at a low temperature to prevent the silicon melted in the melting crucible 21 from coming out. Thereafter, after all of the silicon raw material in the melting crucible 21 is melted, the nozzle heating means 30 is driven, and the silicon raw material that closes the outlet 23 is finally melted. By doing in this way, since the hot water is started at the moment when the silicon raw material in the melting crucible 21 is completely melted, the hot water after melting the silicon raw material can be efficiently performed. In addition, the nozzle 25 is provided so as to hang from the bottom of the melting crucible 21, thereby preventing the molten silicon melt from splashing.

  FIG. 4 shows another conventional melting apparatus for casting silicon or the like (see Patent Document 2). In FIG. 4, 15 is a heat insulating wall of the crucible 11, and 16 is a reinforcing material of the crucible 11. The raw material charged in the crucible 11 is heated and melted by the heating means 12, a hot water outlet 13 a is provided at the bottom of the crucible 11, and a lid member 18 made of a movable water-cooled metal plate is provided at the hot water outlet 13 a, At this time, the lid member 18 is removed, and the melt in the crucible 11 is discharged. Furthermore, after setting the crucible in the apparatus, it is also possible to use a mechanical plug mechanism to plug the hot water outlet 13a at the bottom of the crucible 11 and withdraw the plug together with the raw material dissolution.

  FIG. 5 shows another conventional melting apparatus for casting silicon or the like (see Patent Document 3). In FIG. 5, 31 is a melting crucible, 32 is a holding crucible, 33 is a tap, 34 is a silicon raw material plug that closes the tap, 35 is a nozzle, 36 is a side heating means, 37 is an upper heating means, and 38 is a mold heating. Means 39 is a mold.

  The basic structure of this melting apparatus is the same as that of the conventional melting apparatus shown in FIGS. 3 and 4, and a melting crucible 31 for melting raw material silicon is held by a holding crucible 32 above the melting apparatus. At the bottom of the melting crucible 31 and the holding crucible 32, a nozzle 35 having a hot water outlet 33 for discharging the silicon melt is provided. Further, heating means 36 and 37 are respectively arranged on the side and upper part of the melting crucible 31 and holding crucible 32, and a mold 39 into which a silicon melt is poured is arranged below the melting crucible 31 and holding crucible 32. A mold heating means 38 for controlling the solidification of the silicon melt is disposed in the upper part.

At this time, in the melting apparatus shown in FIG. 5, the outlet 33 is previously closed with a silicon raw material plug 34 that closes the outlet, and the silicon raw material is put thereon, and the upper heating means 37 and the side heating means of the melting crucible 31 are filled. 36, the silicon raw material at the upper part of the melting crucible 31 is gradually dissolved from the silicon raw material at the lower part, a nozzle 35 having a hot water outlet 33 having a diameter of 2 mm to 10 mm is provided at the bottom of the molten crucible 31, and finally the hot water outlet is closed. The silicon raw material plug 34 is melted and discharged from the nozzle 35. Since the silicon raw material is gradually melted from the upper part of the melting crucible 31 and the hot water starts at the moment when the silicon raw material is completely melted, the hot water after melting the silicon raw material is efficiently performed. And the apparatus can be greatly simplified.
JP 11-43318 A JP 2000-105083 A Japanese Patent Laid-Open No. 2003-247783

  However, in the conventional melting apparatus shown in FIGS. 3 and 4, the nozzle heating means 30 for heating the silicon raw material in the nozzle 25 or the movable water-cooled metal plate is used to melt the silicon raw material and discharge the hot water. The lid member 18 or a driving part such as a mechanical plug mechanism is required, and the melted liquid is melted when the silicon raw material in the crucible 1 is dissolved to discharge the melt, and the mold heating means 28 or the lid There was a problem that the material 18 adhered to the member 18 and was consumed excessively. Further, this melting apparatus requires the nozzle heating means 30 or the lid member 18 made of a movable water-cooled metal plate as an apparatus for discharging the silicon melt, and there is a problem that the apparatus becomes large.

  Further, in the method shown in FIG. 3, when the size of silicon that closes the tap is large, a gap is formed in the nozzle 25, and the tap cannot be completely suppressed. There was a problem that the melt leaked and solidified, resulting in a decrease in yield. On the other hand, if it is too small, the outlet 23 may not be blocked and the raw material may fall into the mold 29 as it is. Further, since it takes time to process the silicon raw material in the nozzle 25, there is a problem that it is difficult to reduce the cost.

  In the method shown in FIG. 5, if the silicon material plug 34 that plugs the outlet 33 of the melting crucible 31 is distorted, the melt slightly leaks out and solidifies before the silicon material is completely melted. There was a problem of dropping the yield. Further, when the silicon raw material is introduced, if the silicon raw material plug 34 moves from the position where it was originally placed, it may cause the silicon melt to leak. It was necessary to pay attention. Furthermore, in these conventional melting apparatuses, it was not possible to confirm that the silicon raw material in the crucible was completely melted and discharged, and the silicon raw material was likely to remain inside the crucible.

  The present invention has been made in view of such problems of the conventional apparatus, and an object thereof is to solve the problem that silicon melt leaks before complete melting due to the structure and mechanism of the melting apparatus. And It is another object of the present invention to provide a melting apparatus and a melting method that can reduce the scattering of the silicon melt when discharging the silicon melt, reduce the size of the apparatus, and efficiently use the silicon raw material.

  A melting apparatus according to claim 1 of the present invention is a melting apparatus that heats and melts a silicon raw material charged in a crucible with a heating means, and discharges the hot water from a hot water outlet provided at the bottom of the crucible. A recess is provided, and a hot water outlet is provided inside the recess.

  A melting apparatus according to a second aspect of the present invention is the melting apparatus according to the first aspect, wherein at least a part of the bottom of the recess is a flat surface, and a tap is provided on the bottom flat surface.

  Furthermore, the melting apparatus according to claim 3 of the present invention is the melting apparatus according to claim 2, wherein a minimum dimension of the bottom plane is 40 mm or more and 100 mm or less, and a diameter of the tap is 2 mm or more and 20 mm or less. .

  A melting apparatus according to a fourth aspect of the present invention is the melting apparatus according to any one of the first to third aspects, wherein the diameter is the same as or larger than the diameter of the hot water outlet outside the hot water outlet of the crucible. A cylindrical nozzle is provided to hang down.

  In the melting method according to claim 5 of the present invention, heating means are provided at the upper and side portions of the crucible, and silicon raw material is charged into the crucible, heated and melted by the heating means, and discharged from a tap outlet provided at the bottom. A melting portion is provided at the bottom of the crucible, a hot water outlet is provided inside the hollow portion, and a predetermined amount of silicon raw material is charged into the crucible so as to close the hot water outlet, The silicon raw material at the upper part of the crucible is gradually dissolved from the silicon raw material at the upper part of the crucible by the heating means at the upper part of the crucible and the heating means at the side part, and the hot water is discharged from the outlet.

  Further, the melting method according to claim 6 of the present invention is the melting method according to claim 5, wherein after the pouring gate is closed with a plug of silicon raw material having a size capable of covering the pouring gate, another silicon raw material is used. Is put into a crucible so as to be a predetermined amount.

  Furthermore, the melting method according to claim 7 of the present invention is the melting method according to claim 6, wherein the plug of the silicon raw material is planarized in advance, and the pouring gate is closed by the planarized surface.

  According to the melting apparatus of the first aspect of the present invention, there is provided a melting apparatus that heats and melts the silicon raw material charged in the crucible with a heating means, and discharges the hot water from a hot water outlet provided at the bottom of the crucible. Since the bottom is provided with a recess, and a pouring gate is provided inside the recess, when the silicon material is charged into the crucible, the silicon source is well placed in the recess, and external force is applied. It is hard to move by. For this reason, for example, when a silicon raw material stopper is placed at the outlet provided in the depression, it is difficult to move due to the introduction of the raw material, etc. The effect of being difficult to cause is obtained. As a result, deterioration of crystal quality can be prevented, and yield can be improved. Furthermore, it is possible to control the hot water without adding a device such as a heating means for discharging the melt near the nozzle. Can be solved. Moreover, since an apparatus for controlling the hot water is not added near the nozzle, the apparatus can be greatly simplified.

  Further, according to the melting apparatus according to claim 2 of the present invention, since at least a part of the bottom portion of the hollow portion is a flat surface and a pouring gate is provided on the bottom flat surface, the pouring gate is made of silicon raw material. It becomes easy to close the gap. In addition, when a silicon raw material plug is used, if the silicon raw material plug is processed into a shape corresponding to the bottom plane, that is, a flat shape, the tap can be easily closed.

  Furthermore, according to the melting device according to claim 3 of the present invention, the minimum dimension for passing the bottom plane is 40 mm or more and 100 mm or less, and the diameter of the tap is 2 mm or more and 20 mm or less. As a result, the gap is optimally closed when the gap is closed, and it becomes difficult for the silicon melt to leak.

  Further, according to the melting device of the fourth aspect of the present invention, a cylindrical nozzle having a diameter equal to or larger than the diameter of the pouring tap is provided outside the crucible pouring tap. As a result, the rectified silicon melt can be poured into the mold with a single line without being scattered around.

  In the melting method according to claim 5 of the present invention, heating means are provided at the upper and side portions of the crucible, and silicon raw material is charged into the crucible, heated and melted by the heating means, and discharged from a tap outlet provided at the bottom. A melting portion is provided at the bottom of the crucible, a hot water outlet is provided inside the hollow portion, and a predetermined amount of silicon raw material is charged into the crucible so as to close the hot water outlet, The crucible upper heating means and the side heating means are gradually dissolved from the silicon raw material at the upper part of the crucible into the lower silicon raw material and discharged from the hot water outlet, so that the silicon raw material in the crucible is completely When the melt is changed to the melt, the hot water is started, and the silicon raw material in the crucible is gradually dissolved from above by controlling the heating means to prevent the melt from leaking during melting. To shorten Kill. In addition, since the silicon raw material is stably contained in the recess, an effect of hardly causing the silicon melt to leak can be obtained. As a result, deterioration of crystal quality can be prevented, and yield can be improved.

  According to the melting method of the sixth aspect of the present invention, after the pouring gate is closed with a silicon raw material plug having a size capable of covering the pouring gate, the other silicon raw material is charged in a predetermined amount. Therefore, when a silicon raw material stopper is placed at the tap provided in the recess, it is difficult to move due to the raw material being charged. The effect of hardly causing leakage of the silicon melt can be obtained. As a result, deterioration of crystal quality can be prevented, and yield can be improved.

  Furthermore, according to the melting method according to claim 7 of the present invention, since the plug of the silicon raw material is planarized in advance and the pouring gate is blocked by the plane processed surface, It is possible to easily close the hot water outlet only by performing a simple plane processing, and the effects of the present invention can be achieved extremely easily and at low cost.

  Hereinafter, a melting device according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a structural view showing an embodiment of a melting apparatus according to the present invention, wherein 1 (1a, 1b) is a crucible, 2 is an upper heating means, 3 is a lower heating means, and 4 (4a, 4b) is heat insulation. Walls 5 are outlets, 6 are nozzles provided at the bottom of the crucible, 7 are recesses provided at the bottom of the crucible, 8 is a mold heating means, 9 is a mold, and 10 is silicon for closing the outlet. It is a raw material stopper.

  The crucible 1 heats and melts a silicon raw material and pours a melt into a solidification mold 9 and includes a quartz crucible 1a provided inside and a graphite crucible 1b provided outside. The silicon ingot melted in the quartz crucible 1a, poured into the solidification mold 9 and cooled and solidified is used as a polycrystalline silicon substrate material for solar cells. The quartz crucible 1a is used for melting the charged silicon raw material, and is made of quartz or the like in consideration of fire resistance and preventing impurities from diffusing into the semiconductor material. Since the quartz crucible 1a is softened and cannot keep its shape at a high temperature, the quartz crucible 1a is held by the graphite crucible 1b.

  The material of the crucible 1 is not particularly limited as long as it has a purity that does not cause melting, evaporation, softening, deformation, decomposition, and the like, and does not deteriorate the solar cell characteristics at a temperature equal to or higher than the melting temperature of the silicon raw material. High purity quartz or graphite is used.

  The size of the crucible 1 (1a, 1b) needs to be a size that can enclose a silicon raw material in accordance with the amount dissolved at a time. The amount of silicon raw material dissolved is in the range of approximately 1 kg to 150 kg.

  An upper heating means 2 is provided above the crucible 1 (1a, 1b), and a side heating means 3 is provided on the side of the crucible 1. The upper heating means 2 and the side heating means 3 are composed of a resistance heating type heater, an induction heating type coil, or the like.

  According to the present invention, the recess 7 is provided at the bottom of the crucible 1, and the tap 5 is provided in the recess 7. For this reason, when the silicon raw material is charged into the crucible 1, the silicon raw material is well contained in the recess 7 and is placed in a state where it is difficult to move. Here, if the silicon raw material stopper 10 is arranged so as to close the tap 5 provided in the recess 7, the silicon raw material stopper 10 is difficult to move even if the silicon raw material is added later. Therefore, the plug 10 of silicon raw material is disposed in the recess 7 and is held in the original state where the tap hole 5 is closed, and it is difficult for the silicon melt to leak.

  Moreover, it is desirable to make the bottom part of the hollow part 7 into a plane, and to provide the tap 5 in the part made into this plane. As a result, when the tap 5 is closed with the silicon raw material plug 10, the gap between the bottom surface of the recess 7 and the silicon raw material plug 10 is reduced and can be easily closed. This is because there are fewer.

  Further, in the case of using the silicon raw material stopper 10, if the one surface of the silicon raw material stopper 10 is processed into a flat shape so as to correspond to the flat surface of the bottom portion, the tap 5 can be easily closed. When the hot water outlet 5 is closed with the silicon material plug 10, the effect of reducing the gap between the bottom surface of the recess 7 and the silicon material plug 10 can be enhanced.

  In addition, the bottom part of the hollow part 7 does not necessarily need to be the whole flat, and if the location including the peripheral part of the tap 5 is flat, the effect of this invention is fully show | played. Here, the peripheral edge of the tap 5 indicates the surface side of the bottom of the recess 7 around the tap 5. FIG. 2 is an enlarged view for explaining the present invention. Here, FIG. 2 (a) shows the hollow portion 7, and FIGS. 2 (b) and 2 (c) are portions A in FIG. 2 (a), that is, the tap 5 provided at the bottom of the hollow portion 7. 2C, FIG. 2C and FIG. 2D are enlarged views of the B portion of FIG. In FIG. 2B and FIG. 2C, a location x indicated by an arrow is a region around the hot water outlet 5 and corresponding to the bottom surface of the recessed portion 7, and corresponds to the peripheral edge of the hot water outlet 5. In the present invention, as shown in FIG. 2C, it is desirable to chamfer the C surface or the R surface. This is because the silicon melt can be discharged from the inside of the crucible 1 without waste. Further, the outer shape of the bottom plane of the recess 7 is drawn gently from the peripheral end z of the recess 7 of the quartz crucible 1a to the peripheral end y of the bottom plane as shown in FIG. Or may have a reverse taper shape extending from the peripheral end y of the bottom plane toward the peripheral end z of the recess 7 of the quartz crucible 1a as shown in FIG. good. As described above, if the inclined portion 7 of the hollow portion 7 of the quartz crucible 1a is inclined from the peripheral end portion y of the bottom plane, the silicon melt can be discharged from the inside of the crucible 1 more efficiently.

  The bottom plane of the recess 7 provided at the bottom of the quartz crucible 1a has a minimum dimension of 40 mm or more and 100 mm or less, and the tap 5 provided inside the recess 7 has a diameter of 2 mm. It is desirable to set it as 20 mm or less above. If the minimum dimension of the bottom plane of the recess 7 is 40 mm or less, it is not desirable because it limits the size of the silicon raw material that can be used as the stopper 10. If the minimum dimension of the depression 7 is 100 mm or more, it is not desirable. This is undesirable because the rest can occur. In addition, when the diameter of the tap 5 is 2 mm or less, the tap 5 may be blocked when the crucible 1 is deformed by heat, and it may not be discharged. When the diameter of the tap 5 is 20 mm or more, It is necessary to limit the silicon raw material plug 10 for closing the hot water outlet 5 to a raw material having a size of 20 mm or more and capable of being closed without a gap.

  Here, the minimum dimension for passing the bottom plane of the recess 7 is a straight line passing through the center of gravity of the outline of the bottom plane and included in the bottom plane, and is cut out by the outline of the bottom plane. The minimum length of the line segments that can be created. FIG. 6 illustrates the outline shape of the bottom plane. In the figure, G is a center of gravity, and l is a line segment corresponding to the minimum dimension for passing. For example, as shown in FIG. 6A, when the outline shape of the bottom plane is a circle, the center of gravity G coincides with the center of the circle, and the length of the line segment l, that is, the minimum dimension of the passing is the bottom portion. It matches the diameter of the plane circle. In addition, as shown in FIG. 6B, when the outline shape of the bottom plane is a rectangle, the length of the line segment l, that is, the minimum dimension for passing is the same as the length of the short side of the rectangle. Further, as shown in FIG. 6C, even when the contour shape of the bottom plane is irregular, the center-of-gravity point G of the contour shape is obtained, and among the straight lines on the bottom plane passing through this point, If the following line segment l is obtained, the minimum dimension for passing can be known.

  Moreover, it is preferable to arrange | position so that the center-of-gravity point of the outline shape of a bottom part plane may be located inside the peripheral part of the tap 5 in a bottom part plane, and if it does in this way, silicon melt from inside the crucible 1 The hot water can be discharged more efficiently.

  When the diameter of the tap 5 is 10 mm or less, the silicon melt passing through the tap 5 at the end of the pouring does not drop due to its own surface tension and closes the tap 5, so that it acts as an effective plug at the next use. This is particularly effective when the crucible 1 is used repeatedly. However, in order to shorten the hot water discharge time, the diameter of the hot water outlet 5 is more preferably in the range of 10 mm to 15 mm. For example, when the hot water outlet 5 is changed from 10 mm to 15 mm, the hot water time is approximately halved. If the tap is small, it takes time to pour out, and the melt poured into the mold at the beginning may solidify, resulting in poor crystallinity and contributing to the characteristics.

  Further, it is desirable that a cylindrical nozzle 6 having a diameter equal to or larger than the diameter of the hot water outlet 5 is provided outside the hot water outlet 5 of the crucible 1. In the embodiment shown in FIG. 1, the nozzle 6 is provided so as to protrude from the bottom of the quartz crucible 1a. The entire nozzle 6 is formed in a cylindrical shape, and the nozzle 6 is also made of quartz or the like and is formed integrally with the quartz crucible 1a. The quartz crucible 1a may be formed separately and attached to the bottom of the quartz crucible 1a. The nozzle 6 is for suppressing splashing of the molten silicon melt, and the shape of the nozzle 6 is preferably a shape that does not hinder the direction of dropping of the silicon melt discharged from the hot water outlet 5. A cylindrical nozzle 6 having a diameter that is the same as or larger than the diameter of the gate 5 may be provided. If it does in this way, the silicon melt melt | dissolved in the quartz crucible 1a will always fall to the same position directly under the quartz crucible 1a, without scattering.

  Around the crucible 1, the upper heating means 2, and the side heating means 3, heat insulating walls 4a and 4b made of graphite or the like are provided for heat insulation and heat insulation. The heat insulating wall 4b above the heating means 2 is formed to open and close in order to supply the silicon raw material into the crucible 1.

  In addition, a mold 9 for pouring a silicon melt dissolved in the quartz crucible 1 a is disposed at the lower part of the crucible 1, and a mold heating means 8 is provided between the mold 9 and the crucible 1. . The mold heating means 8 is composed of, for example, a carbon heater, and the silicon melt is gradually heated upward from the lower part of the mold 9 by appropriately heating the surface of the silicon melt discharged from the mold 9. Has the function of solidifying in one direction. As the mold 9, for example, a graphite plate-like body is assembled so as to be separable, and a release material layer containing silicon nitride, silicon oxide or the like is provided on the inner surface thereof, and a cooled and solidified silicon ingot is formed. It is easy to demold. Although not shown in the drawing, a heat insulating material is provided around the mold 9 to prevent heat removal from the circumferential direction, or a cooling plate is provided below the mold 9 to remove heat from the lower part. As a result, the effect of unidirectionally solidifying the silicon melt inside the mold 9 from the lower part to the upper part is further promoted.

  Next, a method for controlling the molten silicon melt will be described.

  In the present invention, when the silicon raw material is supplied into the quartz crucible 1a, the plug 10 is plugged with the silicon raw material so as to close the tap 5 provided inside the recess 7. Due to the presence of the dent 7, the silicon raw material is well accommodated and hardly moved by an external force or the like. Therefore, for example, when the silicon raw material stopper 10 is disposed at the tap 5 provided in the recess 7, the silicon raw material is kept in its original state because it is difficult to move due to the introduction of the raw material. It is hard to cause leakage. In addition, it is desirable that the silicon raw material used for the stopper 10 is flattened on the entire surface in accordance with the shape of the bottom surface of the recess 7 of the quartz crucible 1a.

  The shape of the silicon raw material plug 10 is not limited to the shape shown in the figure, and any shape can be used as long as it can close the hot water outlet 5 and stop the hot water of the silicon melt. As long as it has a size larger than the tap 5 so that the tap 5 can be closed, and if the surface that closes the tap 5 is a flat surface, the effect of blocking the tap 5 is sufficiently exhibited. .

  Note that the silicon raw material plug 10 is not necessarily required, and when the diameter of the tap 5 is small and the quartz crucible 1a is reused, the remainder of the previously treated silicon melt is caused by the surface tension. 5 may be solidified as it is. In such a case, this can be used as a substitute for the plug 10 of silicon raw material. However, when the tap 5 is not clogged with solidified silicon, for example, when the silicon crucible 1a is newly used or when all the silicon melt has been drained even when reused (for example, For example, when the diameter of the tap 5 is large), it is desirable to close the tap 5 with the plug 10 of silicon raw material.

  After the silicon raw material is put into the quartz crucible 1a as described above, the heater 2 is energized to drive the heating means 2, and the raw material in the quartz crucible 1a is heated to a predetermined temperature and gradually melted from above. To do. When a part of the upper silicon material in the quartz crucible 1a becomes a melt, the heating means 3 is driven to promote the dissolution of the silicon material. By driving the side heating means 3 after driving the upper heating means 2, the silicon raw material close to the tap 5 of the nozzle 6 is kept at a low temperature until the hot water, and the silicon raw material in the quartz crucible 1a is completely melted. The melt that has flowed down through the gaps of the silicon raw material that has not yet melted is solidified around the outlet 5. Thus, the silicon melt in the quartz crucible 1a is held in the quartz crucible 1a so that it does not easily flow down from the quartz crucible 1a until the silicon raw material is completely changed to the melt.

  The silicon raw material in the quartz crucible 1a is changed to a melt, and the silicon raw material closing the nozzle becomes a melt, so that the silicon melt flows out from the hot water outlet 5.

  When the silicon melt in the quartz crucible 1a finishes flowing, the silicon raw material solidified by closing the pouring gate 5 with the surface tension of the remaining silicon melt can be used as a plug of the pouring gate 5, so that the quartz crucible 1a can be reused. A plug of silicon raw material that functions to block the tap 5 during use can be formed.

  In the melting method according to the present invention, the silicon melt flows down from the upper part of the crucible 1 to the lower part. However, at the initial stage of melting, the temperature of the bottom of the crucible 1 has reached a temperature sufficient to dissolve silicon. Therefore, the silicon melt that has flowed down from the upper part is deprived of its latent heat by the surrounding silicon raw material and solidifies, so that it is not discharged from the hot water outlet 5 at the bottom of the crucible 1.

  In addition, this invention is not limited to the said embodiment, Many corrections and changes can be added within the scope of the present invention.

  You may have the heating prevention means which prevents the plug 10 of raw material silicon | silicone from being heated. For example, if a heat insulating plate such as graphite is disposed under the side heating means 3 to inhibit the heating of the raw silicon plug 10, the raw silicon plug 10 is influenced by the side heating means 3 and the upper heating means 2. Therefore, in order to melt the silicon raw material in the crucible 1 in a short time, the upper and side heating means 2 and 3 can be effectively operated simultaneously. .

  And you may have a heating means to heat the plug 10 of raw material silicon. By doing so, it becomes possible to dissolve the plug 10 of the raw material silicon without considering the influence of other parts, and it becomes possible to dissolve the plug 10 of the raw material silicon in a short time. In addition, it is possible to arbitrarily set the timing of the hot water of the silicon melt in the crucible 1.

  Further, as a method of dissolving the raw material silicon plug 10, the silicon raw material charged into the crucible 1 is gradually dissolved from above using the upper heating means 2 and the side heating means 3, and finally the raw material silicon plug 10. During the melting of the silicon raw material in the crucible 1, for example, a heat insulating plate (heating prevention means) such as graphite is disposed under the side heating means 6, and the raw silicon plug It is also possible to inhibit the heating of 10 and dissolve the silicon plug 10 by heating the raw silicon plug 10 by moving the heat insulating plate after it is completely dissolved.

1 is a structural diagram of a melting apparatus according to the present invention. (A)-(e) is the elements on larger scale for demonstrating the structure of the melt | dissolution apparatus concerning this invention. It is a structural diagram of a conventional melting apparatus. It is a structural diagram of another conventional melting apparatus. It is a structural diagram of another conventional melting apparatus. (A)-(c) is a figure for showing the outline shape of the bottom part plane of the present invention, and explaining the minimum dimension of passing.

Explanation of symbols

1: crucible 1a: quartz crucible 1b: graphite crucible 2: upper heating means 3: side heating means 4, 4a, 4b: heat insulating wall 5: tap outlet 6: nozzle 7: recess 8: mold heating means 9: mold 10 : Silicon material plug 11: Crucible 12: Heating means 13 a: Outlet 18: Lid member 21: Melting crucible 22: Holding crucible 23: Outlet 24: Silicon raw material 25: Nozzle 26: Side heating means 27: Upper heating means 28: Mold heating means 29: Mold 30: Nozzle heating means 31: Melting crucible 32: Holding crucible 33: Outlet 34: Silicon material plug 35: Nozzle 36: Side heating means 37: Upper heating means 38: Mold heating means 39: Mold x: Peripheral edge y of tap hole: Peripheral end z of bottom plane G: Peripheral end G of recessed part G: Center of gravity l: Line segment corresponding to minimum dimension of passing

Claims (7)

A melting apparatus that heats and melts silicon raw material charged in a crucible with a heating means, and discharges hot water from a hot water outlet provided at the bottom of the crucible, wherein a hollow portion is provided at the crucible bottom, and A melting apparatus. The melting device according to claim 1, wherein at least a part of the bottom of the hollow portion is a flat surface, and a hot water outlet is provided on the bottom flat surface. The melting apparatus according to claim 2, wherein a minimum dimension of the bottom plane is 40 mm or more and 100 mm or less, and a diameter of the tap is 2 mm or more and 20 mm or less. The melting apparatus according to any one of claims 1 to 3, wherein a cylindrical nozzle having a diameter equal to or larger than the diameter of the hot water outlet is provided outside the hot water outlet of the crucible. Heating means are provided at the top and sides of the crucible, a silicon raw material is charged into the crucible, heated and melted by the heating means, and discharged from a hot water outlet provided at the bottom, comprising a melting method at the bottom of the crucible A hollow portion is provided, and a hot water outlet is provided inside the hollow portion, and after a predetermined amount of silicon raw material is charged into the crucible so as to close the hot water outlet, heating means on the upper part of the crucible and heating means on the side part thereof In the melting method, the silicon raw material at the upper part of the crucible is gradually dissolved from the silicon raw material at the lower part and discharged from the hot water outlet. 6. The melting method according to claim 5, wherein after the pouring gate is closed by a silicon raw material plug having a size capable of covering the pouring gate, another silicon raw material is charged into the crucible so that a predetermined amount is obtained. The melting method according to claim 6, wherein the silicon raw material stopper is flattened in advance and the pouring gate is closed with the flattened surface.

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