JP2005069532A - Dissolving device, and dissolving method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dissolving device for polycrystalline silicone for solar batteries capable of solving problems wherein fused liquid of silicone is scattered when discharged to adhere to a device to discharge the fused liquid of silicone to cause severe abrasion, need large-sizing of the device, and require long time till sufficiently dissolved, and a dissolving method using that. <P>SOLUTION: Heating means 7 and 6 are provided at an upper part and a side part of crucibles 1 and 2, and silicone material is charged into the crucibles to be dissolved by the heating means to be discharged from a discharge port 3 provided at a bottom part in this dissolving device. The diameter of the discharge port is set to be larger than 10 mm, and smaller than 50 mm. The silicone material is gradually dissolved from the upper part of the crucible to the lower part by the heating means 7 at the upper part of the crucible and the heating means 6 at the side part, so that it is discharged from the discharge port. <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 used in a casting apparatus for casting polycrystalline silicon for solar cells and a melting method using the same.

  2. Description of the Related Art Conventionally, as shown in FIG. 2, a melting apparatus for melting a semiconductor material such as silicon melts a raw material charged in a crucible 1 by heating means 2 and melts a circular tap 13a at the bottom of the crucible 11. The second heating means 14 for heating the raw material in the nozzle 13 is provided, and the melt in the crucible 11 in which the raw material in the nozzle 13 is dissolved by the second heating means 14 is discharged. There existed what was comprised so that it might make (refer patent document 1). In FIG. 2, 15 is a heat insulating wall of the crucible 11, 16 is a reinforcing material for the crucible 11, and 17 is a reinforcing material for the nozzle 13.

  Further, as shown in FIG. 3, the raw material charged in the crucible 11 is heated and melted by the heating means 12, and a hot water outlet 13a is provided at the bottom of the crucible 11, and a movable water-cooled metal plate is provided at the hot water outlet 13a. There is also an apparatus for removing the melt in the crucible 11 by removing the lid member 18 when the lid member 18 is provided (see Patent Document 2). In FIG. 3, 15 is a heat insulating wall of the crucible 11, and 16 is a reinforcing material of the crucible 11.

Further, after setting the crucible in the apparatus, it is 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 melting of the raw material.
JP 11-43318 A JP 2000-105083 A

  However, in these conventional casting apparatuses, in order to melt the silicon raw material and discharge the hot water, the second heating means 14 for heating the silicon raw material in the nozzle 13 or a lid member made of a movable water-cooled metal plate. 18 or a driving part such as a mechanical plug mechanism is required, and the melted liquid melted when the silicon raw material in the crucible 11 is dissolved to discharge the melt adheres to the heating device 16 or the lid member 18. There was a problem that consumption was severe.

  Further, these conventional melting devices require the second heating means 14 or the lid member 18 made of a movable water-cooled metal plate as a device for discharging the silicon melt, and the size of the device is increased. There was also.

  Furthermore, in these conventional casting apparatuses, since it cannot be confirmed that the silicon raw material in the crucible 11 is completely melted, it is sufficient to dissolve the silicon raw material in the crucible 11 so that all the silicon raw material is melted and discharged. There was a problem of having to spend time.

  The present invention has been made in view of such problems of the conventional apparatus, and the silicon melt scattered when the silicon melt is poured out adheres to the apparatus for draining the silicon melt and wears out. It is an object of the present invention to provide a melting apparatus and a melting method using the same, which have solved the problem that the temperature is severe, the problem that the apparatus becomes large, and the problem that it takes a sufficient time for melting.

  The melting apparatus according to the present invention is a melting apparatus in which a silicon raw material charged in a crucible is heated and melted by a heating means and discharged from a circular outlet provided at the bottom, and the diameter of the outlet is larger than 10 mm and larger than 50 mm. It is characterized by a small range.

  In the melting apparatus, it is desirable that a cylindrical nozzle having a diameter that is the same as or larger than the diameter of the pouring spout is provided at the pouring spout.

  Further, in the melting method of the present invention, heating means are provided at the upper and side portions of the crucible, a silicon raw material is charged into the crucible, and is melted by heating with the heating means and discharged from a circular outlet provided at the bottom. In the method, the diameter of the outlet is larger than 10 mm and smaller than 50 mm, and the upper crucible heating means and the side heating means gradually dissolve the silicon raw material from the upper crucible into the lower silicon raw material. The hot water is discharged from the hot water outlet.

  As described above, according to the melting apparatus according to the present invention, the diameter of the circular tap for pouring the melted silicon is larger than 10 mm and smaller than 50 mm, thereby adversely affecting the block quality, cutting and slicing. The rapid solidification layer on the bottom of the casting mold can be re-dissolved only by supplying the high-temperature melt from the crucible, and the time and power cost due to the driving of the mold heating means can be reduced, and the casting apparatus by installing a new heating means The problem of enlargement can be solved.

  Further, according to the melting method of the present invention, the hot water is started when the silicon raw material in the crucible is completely changed to the melt, and the silicon raw material in the crucible is gradually dissolved from above by controlling the heating means. As a result, leakage of the melt during melting can be prevented, so that the melting time can be shortened and the melting can be performed with the minimum necessary power.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an embodiment of a melting apparatus according to the present invention, wherein 1, 2 are crucibles, 3 is a circular outlet provided at the bottom of the crucible, 4 is a silicon raw material for closing the outlet, Reference numeral 5 denotes a nozzle provided at the bottom of the crucible, 6, 7 and 8 are heating means, and 9 is a mold.

  The crucibles 1 and 2 are for melting the silicon raw material by heating and pouring the melt into the mold 9 and comprising a quartz crucible 1 provided on the inside and a graphite crucible 2 provided on the outside. The silicon material melted in the quartz crucible 1, poured into the mold 9 and solidified is used as a polycrystalline silicon substrate material for solar cells. The quartz crucible 1 dissolves the silicon raw material that has been charged, and quartz or the like is used in consideration of fire resistance and the fact that impurities do not diffuse into the semiconductor material. The quartz crucible 1 is softened at a high temperature and cannot keep its shape, so the quartz crucible 1 is held by the graphite crucible 2.

  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, etc. at a temperature higher than the melting temperature of the silicon raw material, and does not deteriorate the solar cell characteristics. Quartz and graphite are used.

  At the beginning of the hot water, the melt passing through the hot water outlet 3 is pushed out by the pressure depending on the water level. However, since the pressure due to the water level almost disappears in the late stage of the hot water, the melt flows out of the hot water outlet 3 due to falling by its own weight. Therefore, the bottoms of the crucibles 1 and 2 need to have a certain slope or more in order to discharge hot water without waste.

  The dimensions of the crucibles 1 and 2 are required to include silicon raw materials according to the amount dissolved at a time. The amount of silicon raw material dissolved is in the range of approximately 1 kg to 150 kg.

  A heating means 7 is provided on the upper parts of the crucibles 1 and 2, and a heating means 6 is provided on the sides of the crucibles 1 and 2. The heating means 6 and 7 are formed of a resistance heating type heater, an induction heating type coil, or the like.

  A hot water outlet 3 is provided at the bottom of the quartz crucible 1. The hot water outlet 3 has a diameter larger than 10 mm and smaller than 50 mm. When the diameter of the tap 3 is 10 mm or less, when the silicon melt is poured from the tap 3 into the mold 9 disposed under the crucible 1, a rapidly solidified layer is formed at the bottom of the mold, and the silicon for solar cells In addition to reducing the quality of the wafer, it is also undesirable because it adversely affects block cutting and slicing.

  Further, when the diameter of the tap 3 is 50 mm or more, a gap is formed between the tap 3 and the silicon that closes the tap, and the melt slightly leaks out in the middle of melting, thereby reducing the yield. Therefore, it is not desirable.

  For the above reasons, the diameter of the tap 3 is set to a range larger than 10 mm and smaller than 50 mm.

  Moreover, since the raw material which blocks the hot water outlet 3 is melted lastly, the hot water is started at the moment when the raw material is completely melted, so that the hot water after melting can be efficiently performed.

  In the melting apparatus according to the present invention, it is desirable to provide the nozzle 5 so as to hang from the bottom of the crucible 1.

  A nozzle 5 protrudes from the bottom of the quartz crucible 1. The entire nozzle 5 is formed in a cylindrical shape. The nozzle 5 is also made of quartz or the like, and is usually formed integrally with the quartz crucible 1. The quartz crucible 1 may be formed separately and attached to the bottom of the quartz crucible 1. The nozzle 5 is for suppressing splashing of the molten silicon melt, and the shape of the nozzle 5 is preferably a shape that does not hinder the direction of dropping of the molten silicon discharged from the hot water outlet 3.

  Next, a method for controlling the molten silicon melt will be described. First, a silicon raw material is supplied into the quartz crucible 1. When the quartz crucible 1 is new and the pouring gate 3 is not clogged with the silicon raw material, it is plugged with the silicon raw material so as to close the pouring gate 3. Next, the heater is energized to drive the heating means 7 so that the raw material in the quartz crucible 1 is heated to a predetermined temperature and gradually melted from above. When a part of the upper silicon material in the quartz crucible 1 becomes a melt, the heating means 6 is driven to promote dissolution of the silicon material. By driving the side heating means 6 after the upper heating means 7 is driven, the silicon raw material close to the tap 3 of the nozzle 5 is kept at a low temperature until the hot water, and the silicon raw material in the quartz crucible 1 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 tap 3. Thus, the silicon melt in the quartz crucible 1 is held in the quartz crucible 1 so that it does not easily flow out of the quartz crucible 1 until the silicon raw material is completely changed to the melt.

  The silicon raw material in the quartz crucible 1 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 tap 3 into the mold 9 disposed below. At this time, since the melt at the beginning of the hot water is low in temperature and high in viscosity, it rapidly solidifies at the bottom of the mold 9 to form a rapidly solidified layer having poor quality and adversely affecting cutting and cutting properties. When the diameter is in the range of 10 mm to 50 mm, the supply amount of the high-temperature melt from the crucible 1 per unit time increases, so that the rapidly solidified layer is redissolved without using heating means, and the silicon melt is formed on the bottom of the mold 9. Solidification can be performed from a uniformly wet state.

  Further, in the melting method according to the present invention, the silicon melt flows down from the upper part to the lower part in the crucible 1, but at the initial stage of melting, the temperature of the bottom of the crucible 1 reaches 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 3 at the bottom of the crucible 1.

  Further, since the nozzle 5 is provided so as to hang down from the bottom of the quartz crucible 1, the silicon melt dissolved in the quartz crucible 1 always remains regardless of the remaining amount of silicon melt in the quartz crucible 1. It falls to the same position just below the quartz crucible 1.

It is a figure which shows one Embodiment of the melt | dissolution apparatus which concerns on this invention. It is a figure which shows the conventional melt | dissolution apparatus. It is a figure which shows the other conventional melt | dissolution apparatus.

Explanation of symbols

1, 2, crucible 3, outlet 4, silicon raw material 5 that closes the outlet 5, nozzles 6, 7, 8, heating means 9, mold

Claims (3)

In a melting apparatus in which a silicon raw material charged in a crucible is heated and melted by a heating means and discharged from a circular hot water outlet provided at the bottom, the diameter of the hot water outlet is set to a range larger than 10 mm and smaller than 50 mm. A melting device. The melting apparatus according to claim 1, wherein a cylindrical nozzle having a diameter equal to or larger than the diameter of the hot water outlet is provided at the hot water outlet. In a melting method in which heating means are provided at the top and sides of a crucible, silicon raw material is charged into the crucible, heated and melted by the heating means, and discharged from a circular outlet provided at the bottom, the diameter of the outlet is determined. The range is larger than 10 mm and smaller than 50 mm, and gradually melts from the silicon raw material at the upper part of the crucible into the silicon raw material at the lower part by the heating means at the upper part of the crucible and the heating means at the side part. A dissolution method characterized by the above.

Images