WO2011104799A1 - Method for continuously casting silicon ingots - Google Patents

Method for continuously casting silicon ingots Download PDF

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Publication number
WO2011104799A1
WO2011104799A1 PCT/JP2010/006841 JP2010006841W WO2011104799A1 WO 2011104799 A1 WO2011104799 A1 WO 2011104799A1 JP 2010006841 W JP2010006841 W JP 2010006841W WO 2011104799 A1 WO2011104799 A1 WO 2011104799A1
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Prior art keywords
cooling crucible
chamber
silicon
crucible
ingot
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PCT/JP2010/006841
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French (fr)
Japanese (ja)
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宣正 内藤
光夫 吉原
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株式会社Sumco
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Publication of WO2011104799A1 publication Critical patent/WO2011104799A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/1213—Accessories for subsequent treating or working cast stock in situ for heating or insulating strands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D23/00—Casting processes not provided for in groups B22D1/00 - B22D21/00
    • B22D23/06—Melting-down metal, e.g. metal particles, in the mould
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C30B11/001—Continuous growth
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon

Definitions

  • the present invention relates to a continuous casting method of a silicon ingot that is a material of a substrate for a solar cell.
  • Photovoltaic power generation is a power generation method in which solar energy is directly converted into electric power using a solar cell, and a polycrystalline silicon wafer is mainly used as a substrate of the solar cell.
  • a polycrystalline silicon wafer for solar cells is manufactured by slicing a unidirectionally solidified silicon ingot. For this reason, in order to promote the spread of solar cells, it is necessary to secure the quality of the silicon wafer and reduce the cost, and it is required to manufacture a high-quality silicon ingot at a low cost in the previous stage.
  • a continuous casting method using electromagnetic induction hereinafter also referred to as “electromagnetic casting method” has been put into practical use.
  • FIG. 1 is a diagram schematically showing a configuration of a conventional typical electromagnetic casting apparatus used in an electromagnetic casting method.
  • the electromagnetic casting apparatus includes a chamber 1.
  • the chamber 1 is a water-cooled container having a double wall structure in which the inside is isolated from the outside air and maintained in an inert gas atmosphere suitable for casting.
  • a raw material supply device (not shown) is connected to the upper wall of the chamber 1 via an openable / closable shutter 2.
  • the chamber 1 is provided with an inert gas inlet 5 on the upper side wall and an exhaust port 6 on the lower side wall.
  • a bottomless cooling crucible 7, an induction coil 8, and an after heater 9 are arranged in the chamber 1.
  • the cooling crucible 7 functions not only as a melting vessel but also as a mold, and is a rectangular tube made of metal (for example, copper) excellent in thermal conductivity and conductivity, and is suspended in the chamber 1.
  • the cooling crucible 7 is divided into a plurality of strip-shaped pieces in the circumferential direction, leaving the upper part, and is forcibly cooled by cooling water flowing through the inside.
  • the induction coil 8 is provided concentrically with the cooling crucible 7 so as to surround the cooling crucible 7 and is connected to a power supply device (not shown).
  • a plurality of after-heaters 9 are concentrically connected to the cooling crucible 7 below the cooling crucible 7 and heat the silicon ingot 3 pulled down from the cooling crucible 7 to provide an appropriate temperature gradient in the axial direction thereof.
  • a raw material introduction pipe 10 is attached below the shutter 2 connected to the raw material supply device. Along with opening and closing of the shutter 2, granular or lump silicon raw material 11 is supplied from the raw material supply device into the raw material introduction pipe 10 and charged into the cooling crucible 7.
  • an outlet 4 for extracting the ingot 3 is provided directly under the after heater 9, and this outlet 4 is sealed with gas.
  • the ingot 3 is pulled down while being supported by a support base 14 that descends through the drawer opening 4.
  • a plasma torch 13 is provided directly above the cooling crucible 7 so as to be movable up and down.
  • the plasma torch 13 is connected to one pole of a plasma power supply device (not shown), and the other pole is connected to the ingot 3 side.
  • the plasma torch 13 is inserted into the cooling crucible 7 while being lowered.
  • the silicon raw material 11 is inserted into the cooling crucible 7, an alternating current is applied to the induction coil 8, and the lowered plasma torch 13 is energized.
  • an eddy current is generated in each piece due to electromagnetic induction by the induction coil 8, and the cooling crucible 7
  • the eddy current on the inner wall side generates a magnetic field in the cooling crucible 7.
  • the silicon raw material 11 in the cooling crucible 7 is melted by electromagnetic induction heating to form molten silicon 12.
  • a plasma arc is generated between the plasma torch 13 and the silicon raw material 11 and further the molten silicon 12, and the silicon raw material 11 is also heated and melted by the Joule heat, thereby reducing the burden of electromagnetic induction heating.
  • the molten silicon 12 is efficiently formed.
  • the molten silicon 12 has a force (pinch force) in the inner normal direction of the surface of the molten silicon 12 due to the interaction between the magnetic field generated with the eddy current on the inner wall of the cooling crucible 7 and the current generated on the surface of the molten silicon 12.
  • the support 14 supporting the molten silicon 12 is gradually lowered while melting the silicon raw material 11 in the cooling crucible 7, the induction magnetic field decreases as the distance from the lower end of the induction coil 8 decreases.
  • the molten silicon 12 is solidified from the outer peripheral portion by cooling from the cooling crucible 7. Then, the silicon raw material 11 is continuously charged as the support base 14 is lowered, and the melting and solidification are continued, whereby the molten silicon 12 is solidified in one direction, and the ingot 3 is continuously cast. it can.
  • the inert gas is sequentially supplied from the inert gas inlet 5 on the upper side wall of the chamber 1 to fill the chamber 1.
  • the inert gas in the chamber 1 is sequentially discharged from the exhaust port 6 on the lower side wall of the chamber 1.
  • SiO silicon oxide
  • the atmospheric temperature in the chamber 1 is high in the central portion where the ingot 3 exists, decreases as the side wall of the chamber 1 is approached, and increases in the same central portion toward the upper portion where the molten silicon 12 exists. Due to this temperature difference, natural convection of atmospheric gas occurs in the chamber 1 as shown by the solid line arrow in FIG. Specifically, it rises between the outer periphery of the ingot 3 and the inner periphery of the after heater 9, passes through the gap between the upper end of the uppermost after heater 9 and the lower end of the cooling crucible 7, further outside the cooling crucible 7. After rising, convection of the atmospheric gas descending near the side wall of the chamber 1 occurs. A part of the atmospheric gas that convects and rises outside the cooling crucible 7 also flows directly above the cooling crucible 7 as indicated by a dotted arrow in FIG.
  • the impurity is conveyed to the position just above the cooling crucible 7 along with the flow of the atmosphere gas, falls into the cooling crucible 7 and enters the molten silicon 12. May be mixed.
  • the molten silicon 12 is contaminated with metal impurities, the quality of the ingot 3 cast from the molten silicon 12 is deteriorated.
  • the metal impurities are easily taken into the atmosphere gas in the process in which the atmosphere gas rises along the after heater 9.
  • the present invention has been made in view of the above problems, and when silicon ingots are continuously cast by an electromagnetic casting method, molten silicon is contaminated with metal impurities due to the atmospheric gas that naturally convects in the chamber.
  • An object of the present invention is to provide a continuous casting method of a silicon ingot that can prevent this.
  • the present inventors made extensive studies by paying attention to the flow of atmospheric gas that naturally convects in the chamber during continuous casting, and conducted various tests. As a result, it is possible to prevent impurity contamination of the molten silicon caused by the convection atmosphere gas by controlling the flow of the atmosphere gas so that the atmosphere gas that has once reached the bottom of the cooling crucible does not reach the top of the cooling crucible again. As a result, the present invention was completed.
  • the gist of the present invention resides in the following method for continuously casting a silicon ingot. That is, a silicon raw material is charged into a conductive bottomless cooling crucible disposed in the chamber, and the silicon raw material is melted by electromagnetic induction heating from an induction coil surrounding the bottomless cooling crucible.
  • piping that opens above and below the bottomless cooling crucible is connected to the side wall of the chamber, and the atmosphere above the bottomless cooling crucible is connected through this piping.
  • a continuous casting method of a silicon ingot wherein casting is performed while introducing a gas below the bottomless cooling crucible and blocking a flow of atmospheric gas flowing from the bottom to the bottomless cooling crucible.
  • a partition plate is provided between the upper end of the bottomless cooling crucible and the side wall of the chamber.
  • the atmospheric gas convects below the cooling crucible, and even if the atmospheric gas contains metal impurities, the atmospheric gas flows above the cooling crucible. Therefore, the metal impurities are not transported directly above the cooling crucible and mixed into the molten silicon, and the impurity contamination of the molten silicon caused by the convective atmosphere gas can be prevented.
  • FIG. 1 is a diagram schematically showing a configuration of a typical representative electromagnetic casting apparatus used in the electromagnetic casting method.
  • FIG. 2 is a diagram schematically showing the configuration of an electromagnetic casting apparatus to which the silicon ingot continuous casting method of the present invention can be applied.
  • FIG. 3 is a diagram schematically showing a configuration of an electromagnetic casting apparatus used for comparison.
  • FIG. 4 is a diagram showing the measurement results of the Fe concentration in the silicon ingots in the present invention example and the comparative example.
  • FIG. 2 is a diagram schematically showing the configuration of an electromagnetic casting apparatus to which the silicon ingot continuous casting method of the present invention can be applied.
  • the electromagnetic casting apparatus in the present invention shown in the figure is based on the configuration of the electromagnetic casting apparatus shown in FIG. 1, and the same components as those in FIG.
  • the electromagnetic casting apparatus has a pipe 15 connected to the upper part and the lower part of the side wall of the chamber 1.
  • the upper and lower ends of the pipe 15 are opened at positions corresponding to the upper side of the cooling crucible 7 and positions corresponding to the lower side of the cooling crucible 7, respectively.
  • a partition plate 16 that protrudes horizontally from the upper end of the cooling crucible 7 toward the side wall of the chamber 1 is attached between the upper end of the cooling crucible 7 and the side wall of the chamber 1.
  • the partition plate 16 partitions the space in the chamber 1 up and down with the upper end position of the cooling crucible 7 as a boundary.
  • the internal space of the chamber 1 is partitioned vertically by the partition plate 16 and each end of the pipe 15 is opened in each partitioned space. 2, the atmospheric gas existing above the cooling crucible 7 flows into the pipe 15 from the upper end of the pipe 15 opened here, descends in the pipe 15, and then the cooling crucible 7. It is introduced into the lower part of the chamber 1 corresponding to the lower part.
  • the atmospheric gas introduced into the lower part of the chamber 1 is finally discharged from the exhaust port 6 to the outside of the chamber 1, but most of it is naturally convected in the chamber 1.
  • the atmospheric gas introduced into the lower portion of the chamber 1 through the pipe 15 enters the inside of the after heater 9 through the gap between the upper and lower adjacent after heaters 9 as indicated by solid arrows in FIG.
  • the atmospheric gas that has reached the outside of the cooling crucible 7 is prevented from rising further by the partition plate 16 and descends in the vicinity of the side wall of the chamber 1. Such natural convection of the atmospheric gas occurs.
  • the continuous casting method of the present invention even if the convection atmosphere gas contains metal impurities, the atmosphere gas is blocked from flowing upward from below the cooling crucible 7, so that the metal There is no situation in which impurities are carried directly above the cooling crucible 7 and mixed into the molten silicon 12. As a result, impurity contamination of the molten silicon 12 due to the convection atmosphere gas can be prevented, and the ingot 3 having excellent quality can be manufactured.
  • the ingot produced by continuously casting the silicon ingot using the electromagnetic casting apparatus shown in FIG. 2 has a solidification rate of 0%, 10%, 30%, 50%. Sample wafers were taken from positions corresponding to 70% and 90%, respectively, and a test was performed to measure the Fe concentration in each sample wafer.
  • the solidification rate here represents the ratio of the weight of the solidified ingot to the total weight of the charged silicon raw material, and corresponds to the length from the lower end of the ingot (the first position of continuous casting).
  • a silicon ingot was continuously cast using the electromagnetic casting apparatus shown in FIG. 3 below, and a sample wafer was similarly collected from this ingot to measure the Fe concentration.
  • FIG. 3 is a diagram schematically showing a configuration of an electromagnetic casting apparatus used for comparison.
  • the electromagnetic casting apparatus used in the comparative example shown in the figure has a pipe 15 connected to the upper part and the lower part of the side wall of the chamber 1 as compared with the electromagnetic casting apparatus used in the example of the present invention shown in FIG. Although it is common, it is different in that it does not have a partition plate 16 that partitions the internal space of the chamber 1 up and down.
  • FIG. 4 is a diagram showing the measurement results of the Fe concentration in the silicon ingot in the present invention example and the comparative example. As shown in the figure, when the solidification rate corresponding to the first position of continuous casting is 0%, the Fe concentration of the ingot is the same in the inventive example and the comparative example, but the continuous casting proceeds and the solidification rate. As a result, the Fe concentration in the comparative example significantly increased as compared with the inventive example.
  • the convection atmosphere gas containing metal impurities is cooled in the chamber 1 as in the case of the conventional electromagnetic casting apparatus shown in FIG.
  • the molten silicon is contaminated with metal impurities while flowing into the crucible 7 (see the dotted arrow in FIG. 3). It has become clear that the convection atmosphere gas does not flow directly above the cooling crucible 7 and can prevent impurity contamination of the molten silicon.
  • the Fe concentration increases as the solidification rate increases in both the inventive example and the comparative example. This is due to the segregation phenomenon of the impurity element. This is because impurities are concentrated in the molten silicon as the continuous casting progresses. Further, in the example of the present invention, the result is that Fe is contained in the ingot, but this is because Fe is inevitably contained in the silicon raw material to be charged.
  • the partition plate 16 shown in FIG. 2 may be provided so as to protrude from the side wall of the chamber 1 toward the upper end of the cooling crucible 7.
  • an inert gas is injected from the inner wall of the chamber 1 over the entire horizontal plane of the outer periphery of the cooling crucible 7 instead of the partition plate 16.
  • a partition such as an air curtain can be formed by the injected gas.
  • the continuous casting method of the silicon ingot of the present invention even if the metal gas is contained in the atmospheric gas convection below the cooling crucible, the metal impurity is mixed into the molten silicon in the cooling crucible. In addition, it is possible to prevent the molten silicon from being contaminated with metal impurities due to the convection atmosphere gas. Therefore, the continuous casting method of the present invention is extremely useful in that a silicon ingot for a solar cell excellent in quality can be produced.

Abstract

Provided is a method for continuously casting silicon ingots by introducing a silicon source material to a bottomless cooling crucible disposed in a chamber, melting the silicon source material by means of electromagnetic induction heating using an induction coil, and solidifying the molten silicon while lowering the molten silicon from the cooling crucible. A pipe which opens at the top and the bottom of the cooling crucible is connected to a sidewall of the chamber, a partition board is disposed between the upper end of the cooling crucible and the sidewall of the chamber, and casting is performed while introducing atmospheric gas through the pipe from the top of the cooling crucible to the bottom of the cooling crucible and while blocking, by means of the partition board, the flow of atmospheric gas flowing from the bottom of the cooling crucible to the top of the cooling crucible. Therefore, when continuous casting is carried out, the molten silicon is prevented from being contaminated by metal impurities caused by free convection of the atmospheric gas in the chamber.

Description

シリコンインゴットの連続鋳造方法Silicon ingot continuous casting method
　本発明は、太陽電池用基板の素材であるシリコンインゴットの連続鋳造方法に関する。 The present invention relates to a continuous casting method of a silicon ingot that is a material of a substrate for a solar cell.
　近年、ＣＯ２排出による地球温暖化問題やエネルギー資源の枯渇問題が深刻化しており、それらの問題の対応策の一つとして、無尽蔵に降りそそぐ太陽光エネルギーを活用する太陽光発電が注目されている。太陽光発電は、太陽電池を使用して太陽光エネルギーを直接電力に変換する発電方式であり、太陽電池の基板には、多結晶のシリコンウェーハを用いるのが主流である。 In recent years, the problem of global warming due to CO 2 emissions and the problem of depletion of energy resources have become serious, and solar power generation that uses solar energy that falls indefinitely is attracting attention as one of the countermeasures against these problems. . Photovoltaic power generation is a power generation method in which solar energy is directly converted into electric power using a solar cell, and a polycrystalline silicon wafer is mainly used as a substrate of the solar cell.
　太陽電池用の多結晶シリコンウェーハは、一方向性凝固のシリコンインゴットを素材とし、このインゴットをスライスして製造される。このため、太陽電池の普及を図るには、シリコンウェーハの品質を確保するとともに、コストを低減する必要があり、その前段階で、高品質のシリコンインゴットを安価に製造することが要求される。この要求に対応できる方法として、例えば、特許文献１に開示されるように、電磁誘導を利用した連続鋳造方法（以下、「電磁鋳造法」ともいう）が実用化されている。 A polycrystalline silicon wafer for solar cells is manufactured by slicing a unidirectionally solidified silicon ingot. For this reason, in order to promote the spread of solar cells, it is necessary to secure the quality of the silicon wafer and reduce the cost, and it is required to manufacture a high-quality silicon ingot at a low cost in the previous stage. As a method that can meet this requirement, for example, as disclosed in Patent Document 1, a continuous casting method using electromagnetic induction (hereinafter also referred to as “electromagnetic casting method”) has been put into practical use.
　図１は、電磁鋳造法で用いられる従来の代表的な電磁鋳造装置の構成を模式的に示す図である。同図に示すように、電磁鋳造装置はチャンバー１を備える。チャンバー１は、内部を外気から隔離し鋳造に適した不活性ガス雰囲気に維持する二重壁構造の水冷容器である。チャンバー１の上壁には、開閉可能なシャッター２を介し、図示しない原料供給装置が連結されている。チャンバー１は、上部の側壁に不活性ガス導入口５が設けられ、下部の側壁に排気口６が設けられている。 FIG. 1 is a diagram schematically showing a configuration of a conventional typical electromagnetic casting apparatus used in an electromagnetic casting method. As shown in FIG. 1, the electromagnetic casting apparatus includes a chamber 1. The chamber 1 is a water-cooled container having a double wall structure in which the inside is isolated from the outside air and maintained in an inert gas atmosphere suitable for casting. A raw material supply device (not shown) is connected to the upper wall of the chamber 1 via an openable / closable shutter 2. The chamber 1 is provided with an inert gas inlet 5 on the upper side wall and an exhaust port 6 on the lower side wall.
　チャンバー１内には、無底冷却ルツボ７、誘導コイル８およびアフターヒーター９が配置されている。冷却ルツボ７は、融解容器としてのみならず、鋳型としても機能し、熱伝導性および導電性に優れた金属（例えば、銅）製の角筒体で、チャンバー１内に吊り下げられている。この冷却ルツボ７は、上部を残して周方向で複数の短冊状の素片に分割され、内部を流通する冷却水によって強制冷却される。 In the chamber 1, a bottomless cooling crucible 7, an induction coil 8, and an after heater 9 are arranged. The cooling crucible 7 functions not only as a melting vessel but also as a mold, and is a rectangular tube made of metal (for example, copper) excellent in thermal conductivity and conductivity, and is suspended in the chamber 1. The cooling crucible 7 is divided into a plurality of strip-shaped pieces in the circumferential direction, leaving the upper part, and is forcibly cooled by cooling water flowing through the inside.
　誘導コイル８は、冷却ルツボ７を囲繞するように、冷却ルツボ７と同芯に周設され、図示しない電源装置に接続されている。アフターヒーター９は、冷却ルツボ７の下方に冷却ルツボ７と同芯に複数連設され、冷却ルツボ７から引き下げられるシリコンインゴット３を加熱して、その軸方向に適切な温度勾配を与える。 The induction coil 8 is provided concentrically with the cooling crucible 7 so as to surround the cooling crucible 7 and is connected to a power supply device (not shown). A plurality of after-heaters 9 are concentrically connected to the cooling crucible 7 below the cooling crucible 7 and heat the silicon ingot 3 pulled down from the cooling crucible 7 to provide an appropriate temperature gradient in the axial direction thereof.
　また、チャンバー１内には、原料供給装置に連結されたシャッター２の下方に原料導入管１０が取り付けられている。シャッター２の開閉に伴って、粒状や塊状のシリコン原料１１が原料供給装置から原料導入管１０内に供給され、冷却ルツボ７内に装入される。 In the chamber 1, a raw material introduction pipe 10 is attached below the shutter 2 connected to the raw material supply device. Along with opening and closing of the shutter 2, granular or lump silicon raw material 11 is supplied from the raw material supply device into the raw material introduction pipe 10 and charged into the cooling crucible 7.
　チャンバー１の底壁には、アフターヒーター９の真下に、インゴット３を抜き出すための引出し口４が設けられ、この引出し口４はガスでシールされている。インゴット３は、引出し口４を貫通して下降する支持台１４によって支えられながら引き下げられる。 In the bottom wall of the chamber 1, an outlet 4 for extracting the ingot 3 is provided directly under the after heater 9, and this outlet 4 is sealed with gas. The ingot 3 is pulled down while being supported by a support base 14 that descends through the drawer opening 4.
　冷却ルツボ７の真上には、プラズマトーチ１３が昇降可能に設けられている。プラズマトーチ１３は、図示しないプラズマ電源装置の一方の極に接続され、他方の極は、インゴット３側に接続されている。このプラズマトーチ１３は、下降させた状態で冷却ルツボ７内に挿入される。 A plasma torch 13 is provided directly above the cooling crucible 7 so as to be movable up and down. The plasma torch 13 is connected to one pole of a plasma power supply device (not shown), and the other pole is connected to the ingot 3 side. The plasma torch 13 is inserted into the cooling crucible 7 while being lowered.
　このような電磁鋳造装置を用いた電磁鋳造法では、冷却ルツボ７にシリコン原料１１を装入し、誘導コイル８に交流電流を印加するとともに、下降させたプラズマトーチ１３に通電を行う。このとき、冷却ルツボ７を構成する短冊状の各素片が互いに電気的に分割されていることから、誘導コイル８による電磁誘導に伴って各素片内で渦電流が発生し、冷却ルツボ７の内壁側の渦電流が冷却ルツボ７内に磁界を発生させる。これにより、冷却ルツボ７内のシリコン原料１１は電磁誘導加熱されて融解し、溶融シリコン１２が形成される。また、プラズマトーチ１３とシリコン原料１１、さらには溶融シリコン１２との間にプラズマアークが発生し、そのジュール熱によっても、シリコン原料１１が加熱されて融解し、電磁誘導加熱の負担を軽減して効率良く溶融シリコン１２が形成される。 In the electromagnetic casting method using such an electromagnetic casting apparatus, the silicon raw material 11 is inserted into the cooling crucible 7, an alternating current is applied to the induction coil 8, and the lowered plasma torch 13 is energized. At this time, since the strip-shaped pieces constituting the cooling crucible 7 are electrically divided from each other, an eddy current is generated in each piece due to electromagnetic induction by the induction coil 8, and the cooling crucible 7 The eddy current on the inner wall side generates a magnetic field in the cooling crucible 7. As a result, the silicon raw material 11 in the cooling crucible 7 is melted by electromagnetic induction heating to form molten silicon 12. In addition, a plasma arc is generated between the plasma torch 13 and the silicon raw material 11 and further the molten silicon 12, and the silicon raw material 11 is also heated and melted by the Joule heat, thereby reducing the burden of electromagnetic induction heating. The molten silicon 12 is efficiently formed.
　溶融シリコン１２は、冷却ルツボ７の内壁の渦電流に伴って生じる磁界と、溶融シリコン１２の表面に発生する電流との相互作用により、溶融シリコン１２の表面の内側法線方向に力（ピンチ力）を受けるため、冷却ルツボ７と非接触の状態に保持される。冷却ルツボ７内でシリコン原料１１を融解させながら、溶融シリコン１２を支える支持台１４を徐々に下降させると、誘導コイル８の下端から遠ざかるにつれて誘導磁界が小さくなることから、発熱量およびピンチ力が減少し、さらに冷却ルツボ７からの冷却により、溶融シリコン１２は外周部から凝固が進行する。そして、支持台１４の下降に伴ってシリコン原料１１を連続的に装入し、融解および凝固を継続することにより、溶融シリコン１２が一方向に凝固し、インゴット３を連続して鋳造することができる。 The molten silicon 12 has a force (pinch force) in the inner normal direction of the surface of the molten silicon 12 due to the interaction between the magnetic field generated with the eddy current on the inner wall of the cooling crucible 7 and the current generated on the surface of the molten silicon 12. ) Is held in a non-contact state with the cooling crucible 7. When the support 14 supporting the molten silicon 12 is gradually lowered while melting the silicon raw material 11 in the cooling crucible 7, the induction magnetic field decreases as the distance from the lower end of the induction coil 8 decreases. Further, the molten silicon 12 is solidified from the outer peripheral portion by cooling from the cooling crucible 7. Then, the silicon raw material 11 is continuously charged as the support base 14 is lowered, and the melting and solidification are continued, whereby the molten silicon 12 is solidified in one direction, and the ingot 3 is continuously cast. it can.
　連続鋳造中は、チャンバー１内を不活性ガス雰囲気に維持するため、チャンバー１の上部側壁の不活性ガス導入口５から不活性ガスが逐次供給され、チャンバー１内に充満する。チャンバー１内の不活性ガスは、チャンバー１の下部側壁の排気口６から逐次排出される。このとき、プラズマトーチ１３からのプラズマアークにより溶融シリコン１２からＳｉＯ（シリコン酸化物）が激しく蒸発しており、このＳｉＯガスは不活性ガスとともに排気口６から排出される。 During the continuous casting, in order to maintain the inside of the chamber 1 in an inert gas atmosphere, the inert gas is sequentially supplied from the inert gas inlet 5 on the upper side wall of the chamber 1 to fill the chamber 1. The inert gas in the chamber 1 is sequentially discharged from the exhaust port 6 on the lower side wall of the chamber 1. At this time, SiO (silicon oxide) is vigorously evaporated from the molten silicon 12 by the plasma arc from the plasma torch 13, and this SiO gas is discharged from the exhaust port 6 together with the inert gas.
　このような電磁鋳造法によれば、溶融シリコン１２と冷却ルツボ７との接触が軽減されるため、その接触に伴う冷却ルツボ７からの不純物汚染が防止され、高品質のインゴット３を得ることができる。しかも、連続鋳造であることから、安価にインゴット３を製造することが可能になる。 According to such an electromagnetic casting method, since contact between the molten silicon 12 and the cooling crucible 7 is reduced, impurity contamination from the cooling crucible 7 due to the contact is prevented, and a high quality ingot 3 can be obtained. it can. And since it is continuous casting, it becomes possible to manufacture the ingot 3 at low cost.
国際公開ＷＯ０２／０５３４９６号パンフレットInternational Publication WO02 / 053496 Pamphlet
　上述した電磁鋳造法では、チャンバー１内の雰囲気温度は、インゴット３が存在する中心部で高く、チャンバー１の側壁に近づくほど低くなり、同じ中心部でも溶融シリコン１２が存在する上方ほど高くなる。この温度差に起因し、チャンバー１内には、図１中の実線矢印で示すように、雰囲気ガスの自然対流が発生する。具体的には、インゴット３の外周とアフターヒーター９の内周との間を上昇し、最上段のアフターヒーター９の上端と冷却ルツボ７の下端との隙間を抜けて冷却ルツボ７の外側をさらに上昇した後、チャンバー１の側壁近傍を下降する雰囲気ガスの対流が発生する。このように対流して冷却ルツボ７の外側を上昇する雰囲気ガスの一部は、図１中の点線矢印で示すように、冷却ルツボ７の真上にも流入する。 In the electromagnetic casting method described above, the atmospheric temperature in the chamber 1 is high in the central portion where the ingot 3 exists, decreases as the side wall of the chamber 1 is approached, and increases in the same central portion toward the upper portion where the molten silicon 12 exists. Due to this temperature difference, natural convection of atmospheric gas occurs in the chamber 1 as shown by the solid line arrow in FIG. Specifically, it rises between the outer periphery of the ingot 3 and the inner periphery of the after heater 9, passes through the gap between the upper end of the uppermost after heater 9 and the lower end of the cooling crucible 7, further outside the cooling crucible 7. After rising, convection of the atmospheric gas descending near the side wall of the chamber 1 occurs. A part of the atmospheric gas that convects and rises outside the cooling crucible 7 also flows directly above the cooling crucible 7 as indicated by a dotted arrow in FIG.
　すると、対流する雰囲気ガス中に金属不純物が含まれていた場合、その不純物が雰囲気ガスの流れに伴って冷却ルツボ７の真上まで運ばれ、冷却ルツボ７内に落下して溶融シリコン１２中に混入することがある。この場合、溶融シリコン１２が金属不純物で汚染されることから、この溶融シリコン１２から鋳造されたインゴット３は品質が低下する。金属不純物は、例えば、アフターヒーター９の構成部材にＦｅやＣｒを含有する耐熱合金を採用する場合に、雰囲気ガスがアフターヒーター９に沿って上昇する過程で雰囲気ガス中に取り込まれ易い。 Then, when a metal impurity is contained in the convection atmosphere gas, the impurity is conveyed to the position just above the cooling crucible 7 along with the flow of the atmosphere gas, falls into the cooling crucible 7 and enters the molten silicon 12. May be mixed. In this case, since the molten silicon 12 is contaminated with metal impurities, the quality of the ingot 3 cast from the molten silicon 12 is deteriorated. For example, when a heat-resistant alloy containing Fe or Cr is used as a constituent member of the after heater 9, the metal impurities are easily taken into the atmosphere gas in the process in which the atmosphere gas rises along the after heater 9.
　本発明は、上記の問題に鑑みてなされたものであり、電磁鋳造法によりシリコンインゴットを連続鋳造する際に、チャンバー内で自然対流する雰囲気ガスに起因して、溶融シリコンが金属不純物で汚染されることを防止できるシリコンインゴットの連続鋳造方法を提供することを目的とする。 The present invention has been made in view of the above problems, and when silicon ingots are continuously cast by an electromagnetic casting method, molten silicon is contaminated with metal impurities due to the atmospheric gas that naturally convects in the chamber. An object of the present invention is to provide a continuous casting method of a silicon ingot that can prevent this.
　本発明者らは、上記目的を達成するため、連続鋳造時にチャンバー内で自然対流する雰囲気ガスの流れに着目して鋭意検討を重ね、種々の試験を行った。その結果、一旦冷却ルツボの下方に達した雰囲気ガスが再び冷却ルツボの上方に達しないように、雰囲気ガスの流れを制御することにより、対流する雰囲気ガスに起因した溶融シリコンの不純物汚染を防止できることを知見し、本発明を完成させた。 In order to achieve the above-mentioned object, the present inventors made extensive studies by paying attention to the flow of atmospheric gas that naturally convects in the chamber during continuous casting, and conducted various tests. As a result, it is possible to prevent impurity contamination of the molten silicon caused by the convection atmosphere gas by controlling the flow of the atmosphere gas so that the atmosphere gas that has once reached the bottom of the cooling crucible does not reach the top of the cooling crucible again. As a result, the present invention was completed.
　本発明の要旨は、以下に示すシリコンインゴットの連続鋳造方法にある。すなわち、チャンバー内に配置した導電性を有する無底冷却ルツボにシリコン原料を装入し、無底冷却ルツボを囲繞する誘導コイルからの電磁誘導加熱によりシリコン原料を融解させ、この溶融シリコンを無底冷却ルツボから引き下げながら凝固させてシリコンインゴットを連続鋳造する方法において、チャンバーの側壁に無底冷却ルツボの上方と下方で開口する配管が連結されており、この配管を通じて無底冷却ルツボの上方の雰囲気ガスを無底冷却ルツボの下方に導入しつつ、無底冷却ルツボの下方から上方に流入する雰囲気ガスの流れを遮断しながら鋳造を行うことを特徴とするシリコンインゴットの連続鋳造方法である。 The gist of the present invention resides in the following method for continuously casting a silicon ingot. That is, a silicon raw material is charged into a conductive bottomless cooling crucible disposed in the chamber, and the silicon raw material is melted by electromagnetic induction heating from an induction coil surrounding the bottomless cooling crucible. In the method of continuously casting a silicon ingot by solidifying while being pulled down from a cooling crucible, piping that opens above and below the bottomless cooling crucible is connected to the side wall of the chamber, and the atmosphere above the bottomless cooling crucible is connected through this piping. A continuous casting method of a silicon ingot, wherein casting is performed while introducing a gas below the bottomless cooling crucible and blocking a flow of atmospheric gas flowing from the bottom to the bottomless cooling crucible.
　この連続鋳造方法では、前記無底冷却ルツボの上端と前記チャンバーの側壁との間に仕切り板を設ける構成とすることが好ましい。 In this continuous casting method, it is preferable that a partition plate is provided between the upper end of the bottomless cooling crucible and the side wall of the chamber.
　本発明のシリコンインゴットの連続鋳造方法によれば、冷却ルツボの下方で雰囲気ガスが対流し、この雰囲気ガスに金属不純物が含まれる場合であっても、その雰囲気ガスが冷却ルツボの上方に流入するのを遮断されるため、金属不純物が冷却ルツボの真上に運ばれて溶融シリコン中に混入することはなく、対流する雰囲気ガスに起因した溶融シリコンの不純物汚染を防止することができる。 According to the silicon ingot continuous casting method of the present invention, the atmospheric gas convects below the cooling crucible, and even if the atmospheric gas contains metal impurities, the atmospheric gas flows above the cooling crucible. Therefore, the metal impurities are not transported directly above the cooling crucible and mixed into the molten silicon, and the impurity contamination of the molten silicon caused by the convective atmosphere gas can be prevented.
図１は、電磁鋳造法で用いられる従来の代表的な電磁鋳造装置の構成を模式的に示す図である。FIG. 1 is a diagram schematically showing a configuration of a typical representative electromagnetic casting apparatus used in the electromagnetic casting method. 図２は、本発明のシリコンインゴットの連続鋳造方法を適用できる電磁鋳造装置の構成を模式的に示す図である。FIG. 2 is a diagram schematically showing the configuration of an electromagnetic casting apparatus to which the silicon ingot continuous casting method of the present invention can be applied. 図３は、比較のために用いた電磁鋳造装置の構成を模式的に示す図である。FIG. 3 is a diagram schematically showing a configuration of an electromagnetic casting apparatus used for comparison. 図４は、本発明例および比較例でのシリコンインゴットにおけるＦｅ濃度の測定結果を示す図である。FIG. 4 is a diagram showing the measurement results of the Fe concentration in the silicon ingots in the present invention example and the comparative example.
　以下に、本発明のシリコンインゴットの連続鋳造方法について、その実施形態を詳述する。 Hereinafter, embodiments of the silicon ingot continuous casting method of the present invention will be described in detail.
　図２は、本発明のシリコンインゴットの連続鋳造方法を適用できる電磁鋳造装置の構成を模式的に示す図である。同図に示す本発明における電磁鋳造装置は、前記図１に示す電磁鋳造装置の構成を基本とし、それと同じ構成には同一の符号を付し、重複する説明は適宜省略する。 FIG. 2 is a diagram schematically showing the configuration of an electromagnetic casting apparatus to which the silicon ingot continuous casting method of the present invention can be applied. The electromagnetic casting apparatus in the present invention shown in the figure is based on the configuration of the electromagnetic casting apparatus shown in FIG. 1, and the same components as those in FIG.
　図２に示すように、本発明における電磁鋳造装置は、チャンバー１の側壁の上部と下部に連結された配管１５を有する。この配管１５の上下の各端は、冷却ルツボ７の上方に相当する位置と、冷却ルツボ７の下方に相当する位置にそれぞれ開口している。 As shown in FIG. 2, the electromagnetic casting apparatus according to the present invention has a pipe 15 connected to the upper part and the lower part of the side wall of the chamber 1. The upper and lower ends of the pipe 15 are opened at positions corresponding to the upper side of the cooling crucible 7 and positions corresponding to the lower side of the cooling crucible 7, respectively.
　チャンバー１内には、冷却ルツボ７の上端とチャンバー１の側壁との間に、冷却ルツボ７の上端からチャンバー１の側壁に向けて水平に突出する仕切り板１６が取り付けられている。この仕切り板１６は、冷却ルツボ７の上端位置を境にして、チャンバー１内の空間を上下に仕切る。 In the chamber 1, a partition plate 16 that protrudes horizontally from the upper end of the cooling crucible 7 toward the side wall of the chamber 1 is attached between the upper end of the cooling crucible 7 and the side wall of the chamber 1. The partition plate 16 partitions the space in the chamber 1 up and down with the upper end position of the cooling crucible 7 as a boundary.
　このような構成の電磁鋳造装置を用いた連続鋳造では、チャンバー１の内部空間が仕切り板１６により上下に仕切られ、仕切られたそれぞれの空間に配管１５の各端が開口しているため、図２中の実線矢印で示すように、冷却ルツボ７の上方に存在する雰囲気ガスは、ここに開口する配管１５の上端から配管１５内に流出し、配管１５内を下降した後、冷却ルツボ７の下方に相当するチャンバー１の下部内に導入される。 In continuous casting using the electromagnetic casting apparatus having such a configuration, the internal space of the chamber 1 is partitioned vertically by the partition plate 16 and each end of the pipe 15 is opened in each partitioned space. 2, the atmospheric gas existing above the cooling crucible 7 flows into the pipe 15 from the upper end of the pipe 15 opened here, descends in the pipe 15, and then the cooling crucible 7. It is introduced into the lower part of the chamber 1 corresponding to the lower part.
　チャンバー１の下部内に導入された雰囲気ガスは、最終的には排気口６からチャンバー１の外部に排出されるが、大半はチャンバー１内で自然対流する。すなわち、配管１５を通じてチャンバー１の下部内に導入された雰囲気ガスは、図２中の実線矢印で示すように、上下に隣接するアフターヒーター９同士の隙間を抜けてアフターヒーター９の内側に進入し、そのままインゴット３の外周とアフターヒーター９の内周との間を上昇した後、最上段のアフターヒーター９の上端と冷却ルツボ７の下端との隙間を抜けて冷却ルツボ７の外側に到達する。そして、冷却ルツボ７の外側に到達した雰囲気ガスは、仕切り板１６によってそれ以上の上昇を阻止され、チャンバー１の側壁近傍を下降する。このような雰囲気ガスの自然対流が発生する。 The atmospheric gas introduced into the lower part of the chamber 1 is finally discharged from the exhaust port 6 to the outside of the chamber 1, but most of it is naturally convected in the chamber 1. In other words, the atmospheric gas introduced into the lower portion of the chamber 1 through the pipe 15 enters the inside of the after heater 9 through the gap between the upper and lower adjacent after heaters 9 as indicated by solid arrows in FIG. Then, after ascending between the outer periphery of the ingot 3 and the inner periphery of the after-heater 9, it passes through the gap between the upper end of the uppermost after-heater 9 and the lower end of the cooling crucible 7 and reaches the outside of the cooling crucible 7. The atmospheric gas that has reached the outside of the cooling crucible 7 is prevented from rising further by the partition plate 16 and descends in the vicinity of the side wall of the chamber 1. Such natural convection of the atmospheric gas occurs.
　したがって、本発明の連続鋳造方法によれば、対流する雰囲気ガスに金属不純物が含まれる場合であっても、その雰囲気ガスが冷却ルツボ７の下方から上方に流入するのを遮断されるため、金属不純物が冷却ルツボ７の真上に運ばれて溶融シリコン１２中に混入する状況は起こらない。その結果、対流する雰囲気ガスに起因した溶融シリコン１２の不純物汚染を防止することができ、品質に優れたインゴット３を製造することができる。 Therefore, according to the continuous casting method of the present invention, even if the convection atmosphere gas contains metal impurities, the atmosphere gas is blocked from flowing upward from below the cooling crucible 7, so that the metal There is no situation in which impurities are carried directly above the cooling crucible 7 and mixed into the molten silicon 12. As a result, impurity contamination of the molten silicon 12 due to the convection atmosphere gas can be prevented, and the ingot 3 having excellent quality can be manufactured.
　本発明の連続鋳造方法による効果を確認するため、前記図２に示す電磁鋳造装置を用いてシリコンインゴットを連続鋳造し、製造したインゴットにおいて、固化率が０％、１０％、３０％、５０％、７０％および９０％のときに対応する位置からそれぞれサンプルウェーハを採取し、各サンプルウェーハ中のＦｅ濃度を測定する試験を行った。ここでいう固化率とは、装入したシリコン原料の総重量に対する固化したインゴットの重量の比率を表わし、インゴットの下端（連続鋳造の最初の位置）からの長さに対応する。また、比較のために、下記の図３に示す電磁鋳造装置を用いてシリコンインゴットを連続鋳造し、このインゴットからも同様にサンプルウェーハを採取してＦｅ濃度を測定した。 In order to confirm the effect of the continuous casting method of the present invention, the ingot produced by continuously casting the silicon ingot using the electromagnetic casting apparatus shown in FIG. 2 has a solidification rate of 0%, 10%, 30%, 50%. Sample wafers were taken from positions corresponding to 70% and 90%, respectively, and a test was performed to measure the Fe concentration in each sample wafer. The solidification rate here represents the ratio of the weight of the solidified ingot to the total weight of the charged silicon raw material, and corresponds to the length from the lower end of the ingot (the first position of continuous casting). For comparison, a silicon ingot was continuously cast using the electromagnetic casting apparatus shown in FIG. 3 below, and a sample wafer was similarly collected from this ingot to measure the Fe concentration.
　図３は、比較のために用いた電磁鋳造装置の構成を模式的に示す図である。同図に示す比較例で用いた電磁鋳造装置は、前記図２に示す本発明例で用いた電磁鋳造装置と比較し、チャンバー１の側壁の上部と下部に連結された配管１５を有する点で共通するが、チャンバー１の内部空間を上下に仕切る仕切り板１６を有しない点で相違する。 FIG. 3 is a diagram schematically showing a configuration of an electromagnetic casting apparatus used for comparison. The electromagnetic casting apparatus used in the comparative example shown in the figure has a pipe 15 connected to the upper part and the lower part of the side wall of the chamber 1 as compared with the electromagnetic casting apparatus used in the example of the present invention shown in FIG. Although it is common, it is different in that it does not have a partition plate 16 that partitions the internal space of the chamber 1 up and down.
　図４は、本発明例および比較例でのシリコンインゴットにおけるＦｅ濃度の測定結果を示す図である。同図に示すように、連続鋳造の最初の位置に対応する固化率が０％のときは、本発明例と比較例とでインゴットのＦｅ濃度が同等であるが、連続鋳造が進行し固化率が高くなるのに伴って、比較例でのＦｅ濃度が本発明例に比べ著しく増加する結果となった。 FIG. 4 is a diagram showing the measurement results of the Fe concentration in the silicon ingot in the present invention example and the comparative example. As shown in the figure, when the solidification rate corresponding to the first position of continuous casting is 0%, the Fe concentration of the ingot is the same in the inventive example and the comparative example, but the continuous casting proceeds and the solidification rate. As a result, the Fe concentration in the comparative example significantly increased as compared with the inventive example.
　この結果から、前記図３に示す電磁鋳造装置を用いた比較例では、前記図１に示す従来の電磁鋳造装置の場合と同様に、チャンバー１内で金属不純物を含んで対流する雰囲気ガスが冷却ルツボ７の真上に流入し（前記図３中の点線矢印参照）、溶融シリコンが金属不純物で汚染され、一方、前記図２に示す電磁鋳造装置を用いた本発明例では、金属不純物を含んで対流する雰囲気ガスが冷却ルツボ７の真上に流入することはなく、溶融シリコンの不純物汚染を防止できることが明らかになった。 From this result, in the comparative example using the electromagnetic casting apparatus shown in FIG. 3, the convection atmosphere gas containing metal impurities is cooled in the chamber 1 as in the case of the conventional electromagnetic casting apparatus shown in FIG. In the example of the present invention using the electromagnetic casting apparatus shown in FIG. 2, the molten silicon is contaminated with metal impurities while flowing into the crucible 7 (see the dotted arrow in FIG. 3). It has become clear that the convection atmosphere gas does not flow directly above the cooling crucible 7 and can prevent impurity contamination of the molten silicon.
　なお、図４に示す結果では、本発明例および比較例のいずれの場合も、固化率が高くなるのに伴ってＦｅ濃度が上昇しているが、これは、不純物元素の偏析現象に起因し、連続鋳造の進行に伴って不純物が溶融シリコン中に濃化することによる。また、本発明例でもインゴット中にＦｅを含有する結果となっているが、これは、装入されるシリコン原料中に不可避的にＦｅが含まれていることによる。 In the results shown in FIG. 4, the Fe concentration increases as the solidification rate increases in both the inventive example and the comparative example. This is due to the segregation phenomenon of the impurity element. This is because impurities are concentrated in the molten silicon as the continuous casting progresses. Further, in the example of the present invention, the result is that Fe is contained in the ingot, but this is because Fe is inevitably contained in the silicon raw material to be charged.
　その他本発明は上記の実施形態に限定されず、本発明の趣旨を逸脱しない範囲で、種々の変更が可能である。例えば、前記図２に示す仕切り板１６をチャンバー１の側壁から冷却ルツボ７の上端に向けて突出するように設けても構わない。また、冷却ルツボ７の下方から上方に流入する雰囲気ガスの流れを遮断できる限り、仕切り板１６に代え、例えば、チャンバー１の内壁から冷却ルツボ７の外周の水平面内全域にわたり不活性ガスを噴射し、噴射したガスによってエアーカーテンのような仕切りを形成する構成とすることもできる。 Others The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the partition plate 16 shown in FIG. 2 may be provided so as to protrude from the side wall of the chamber 1 toward the upper end of the cooling crucible 7. Further, as long as the flow of the atmospheric gas flowing from the lower side of the cooling crucible 7 to the upper side can be interrupted, for example, an inert gas is injected from the inner wall of the chamber 1 over the entire horizontal plane of the outer periphery of the cooling crucible 7 instead of the partition plate 16. A partition such as an air curtain can be formed by the injected gas.
　本発明のシリコンインゴットの連続鋳造方法によれば、冷却ルツボの下方で対流する雰囲気ガスに金属不純物が含まれる場合であっても、その金属不純物が冷却ルツボ内の溶融シリコン中に混入することはなく、対流する雰囲気ガスに起因して溶融シリコンが金属不純物で汚染されるのを防止することができる。したがって、本発明の連続鋳造方法は、品質に優れた太陽電池用のシリコンインゴットを製造することができる点で極めて有用である。 According to the continuous casting method of the silicon ingot of the present invention, even if the metal gas is contained in the atmospheric gas convection below the cooling crucible, the metal impurity is mixed into the molten silicon in the cooling crucible. In addition, it is possible to prevent the molten silicon from being contaminated with metal impurities due to the convection atmosphere gas. Therefore, the continuous casting method of the present invention is extremely useful in that a silicon ingot for a solar cell excellent in quality can be produced.
１：チャンバー、　２：シャッター、　３：シリコンインゴット、
４：引出し口、　５：不活性ガス導入口、　６：排気口、
７：無底冷却ルツボ、　８：誘導コイル、　９：アフターヒーター、
１０：原料導入管、　１１：シリコン原料、　１２：溶融シリコン、
１３：プラズマトーチ、　１４：支持台、　１５：配管、
１６：仕切り板
  1: chamber, 2: shutter, 3: silicon ingot,
4: Drawer port, 5: Inert gas inlet port, 6: Exhaust port,
7: bottomless cooling crucible, 8: induction coil, 9: after heater,
10: raw material introduction pipe, 11: silicon raw material, 12: molten silicon,
13: Plasma torch, 14: Support base, 15: Piping,
16: Partition plate

Claims (2)

  1. 　チャンバー内に配置した導電性を有する無底冷却ルツボにシリコン原料を装入し、無底冷却ルツボを囲繞する誘導コイルからの電磁誘導加熱によりシリコン原料を融解させ、この溶融シリコンを無底冷却ルツボから引き下げながら凝固させてシリコンインゴットを連続鋳造する方法において、
    　チャンバーの側壁に無底冷却ルツボの上方と下方で開口する配管が連結されており、この配管を通じて無底冷却ルツボの上方の雰囲気ガスを無底冷却ルツボの下方に導入しつつ、無底冷却ルツボの下方から上方に流入する雰囲気ガスの流れを遮断しながら鋳造を行うことを特徴とするシリコンインゴットの連続鋳造方法。     A silicon raw material is charged into a conductive bottomless cooling crucible disposed in the chamber, and the silicon raw material is melted by electromagnetic induction heating from an induction coil surrounding the bottomless cooling crucible. In the method of continuously casting a silicon ingot by solidifying while pulling down,
    Piping that opens above and below the bottomless cooling crucible is connected to the side wall of the chamber. Through this piping, the atmosphere gas above the bottomless cooling crucible is introduced below the bottomless cooling crucible, A continuous casting method for a silicon ingot, wherein the casting is performed while the flow of the atmospheric gas flowing upward from below is blocked.
  2. 　チャンバー内に配置した導電性を有する無底冷却ルツボにシリコン原料を装入し、無底冷却ルツボを囲繞する誘導コイルからの電磁誘導加熱によりシリコン原料を融解させ、この溶融シリコンを無底冷却ルツボから引き下げながら凝固させてシリコンインゴットを連続鋳造する方法において、
    　チャンバーの側壁に無底冷却ルツボの上方と下方で開口する配管が連結され、前記無底冷却ルツボの上端と前記チャンバーの側壁との間に仕切り板が設けられており、前記配管を通じて無底冷却ルツボの上方の雰囲気ガスを無底冷却ルツボの下方に導入しつつ、無底冷却ルツボの下方から上方に流入する雰囲気ガスの流れを前記仕切り板によって遮断しながら鋳造を行うことを特徴とするシリコンインゴットの連続鋳造方法。
          A silicon raw material is charged into a conductive bottomless cooling crucible disposed in the chamber, and the silicon raw material is melted by electromagnetic induction heating from an induction coil surrounding the bottomless cooling crucible. In the method of continuously casting a silicon ingot by solidifying while pulling down,
    Piping that opens above and below the bottomless cooling crucible is connected to the side wall of the chamber, and a partition plate is provided between the upper end of the bottomless cooling crucible and the side wall of the chamber, and bottomless cooling is performed through the piping. Casting while introducing the atmospheric gas above the crucible below the bottomless cooling crucible and performing the casting while blocking the flow of the atmospheric gas flowing from below the bottomless cooling crucible by the partition plate Ingot continuous casting method.
PCT/JP2010/006841 2010-02-25 2010-11-24 Method for continuously casting silicon ingots WO2011104799A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01264920A (en) * 1988-04-15 1989-10-23 Osaka Titanium Co Ltd Silicon casting device
JPH0251493A (en) * 1988-08-11 1990-02-21 Osaka Titanium Co Ltd Silicone casting device
JPH04342496A (en) * 1991-05-16 1992-11-27 Osaka Titanium Co Ltd Production of polycrystal silicon cast mass for solar cell
WO2007020706A1 (en) * 2005-08-19 2007-02-22 Sumco Solar Corporation Silicon electromagnetic casting apparatus and method for operating said apparatus
JP2008156166A (en) * 2006-12-25 2008-07-10 Sumco Solar Corp Method for casting and cutting silicon ingot
JP2009046339A (en) * 2007-08-17 2009-03-05 Sumco Solar Corp Silicon casting device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01264920A (en) * 1988-04-15 1989-10-23 Osaka Titanium Co Ltd Silicon casting device
JPH0251493A (en) * 1988-08-11 1990-02-21 Osaka Titanium Co Ltd Silicone casting device
JPH04342496A (en) * 1991-05-16 1992-11-27 Osaka Titanium Co Ltd Production of polycrystal silicon cast mass for solar cell
WO2007020706A1 (en) * 2005-08-19 2007-02-22 Sumco Solar Corporation Silicon electromagnetic casting apparatus and method for operating said apparatus
JP2008156166A (en) * 2006-12-25 2008-07-10 Sumco Solar Corp Method for casting and cutting silicon ingot
JP2009046339A (en) * 2007-08-17 2009-03-05 Sumco Solar Corp Silicon casting device

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