WO2012023165A1

WO2012023165A1 - Electromagnetic casting device for silicon

Info

Publication number: WO2012023165A1
Application number: PCT/JP2010/006744
Authority: WO
Inventors: 大輔海老; 浩小屋; 泰夫竹村
Original assignee: 株式会社Sumco; Ｓｕｍｃｏソーラー株式会社
Priority date: 2010-08-16
Filing date: 2010-11-17
Publication date: 2012-02-23
Also published as: TW201209231A; JP2012041209A

Abstract

Provided is an electromagnetic casting device for silicon which has a non-bottom cooling mold, a heating induction coil, and a heat retention device, which is disposed below the mold and gradually cools silicon concreted, and lowers the silicon melted by electromagnetic induction heating by the induction coil to concrete the silicon. The electromagnetic casting device uses a nonconductive member as a component of an outer frame (16) of the heat retention device (13). The nonconductive member is capable of being used only for a specific surface of the outer frame on which a dissolved loss is particularly significantly caused or only for an upper portion of the entire surface of the outer frame. As the nonconductive member, alumina or silicon carbide is desirable. It is possible to manufacture preferable polycrystalline silicon as a substrate material for a solar cell while preventing the dissolved loss due to heat of the outer frame of the heat retention device provided below the heating induction coil and preventing contamination of the inside of a furnace and an ingot due to metal impurities.

Description

Silicon electromagnetic casting equipment

The present invention relates to an electromagnetic casting apparatus for silicon capable of producing a silicon ingot by applying a continuous casting technique using electromagnetic induction. More particularly, the present invention relates to an electromagnetic casting apparatus for silicon that can efficiently produce polycrystalline silicon used as a substrate material for a solar cell without causing contamination by metal.

If a continuous casting apparatus by electromagnetic induction (hereinafter referred to as “electromagnetic casting apparatus”) to which a bottomless cooling mold divided in the circumferential direction is attached is used, a dissolved substance (here, molten silicon), a mold, Can hardly be in contact with each other, so that an ingot (silicon ingot) free from impurity contamination can be produced. Since there is no contamination from the mold, there is an advantage that it is not necessary to use a high-purity material as the material of the mold, and since it can be continuously cast, the manufacturing cost can be greatly reduced. Therefore, the electromagnetic casting apparatus has been conventionally applied to the production of polycrystalline silicon used as a substrate material for solar cells.

FIG. 2 is a diagram schematically showing a configuration example of an electromagnetic casting apparatus suitable for the production of polycrystalline silicon. As shown in the figure, on the inside of the induction coil 12 for heating, longitudinally long copper plate pieces that can be water-cooled are parallel to the winding axis direction of the induction coil 12 and mutually in the induction coil 12. The space surrounded by the plate-like pieces constitutes a mold (that is, a bottomless cooling mold whose side walls are water-cooled) 11 arranged in an insulated state. As the mold 11, a water-cooled copper mold having a plate-like piece as a copper piece is usually used.

At the lower end position of the induction coil 12 for heating (that is, the position corresponding to the bottom of the mold 11), a support base 4 that can move downward is installed. A heat retention device 13 for heating the solidified ingot (silicon ingot) 19 to prevent rapid cooling is installed below the induction coil 12 for heating. The soaking tube 6 is attached. The silicon ingot 19 is drawn downward by a drawing device (not shown).

Above the cooling mold 11, a raw material charging machine 9 capable of charging the raw material into the mold 11 during melting is installed. Further, in this example, a heating element 10 for heating the raw material silicon is attached above the mold 11 as necessary. It is desirable to arrange a plasma torch as the heating element 10 and to perform ultra-high temperature heating with a plasma arc as necessary.

These devices are installed in the sealed container 1 so that the molten silicon 7 and the high-temperature silicon ingot 19 do not come into direct contact with the atmosphere. Usually, the inside of the container 1 is replaced with an inert gas, It is comprised so that continuous casting can be performed in the pressurized state.

In the production of polycrystalline silicon, when the mold 11 is filled with a silicon raw material and a high-frequency induction current is passed through the heating induction coil 12, the raw material generates heat and melts. The molten silicon 7 in the mold 11 repels the plate-like piece due to the induced current and does not contact the side wall of the mold 11. After the molten silicon 7 is sufficiently uniformed, if the support 4 is moved downward little by little, cooling starts by moving away from the induction coil 12, and unidirectional solidification toward the molten silicon 7 in the mold 11 occurs. As a result, the silicon ingot 19 having a cross section having the same shape as the mold cross section is formed.

Since the amount of the molten silicon 7 decreases corresponding to the downward movement of the support base 4, the corresponding amount of raw silicon is supplied from the raw material feeder 9, and the upper surface of the molten silicon 7 always maintains the same height level. In this way, the polycrystalline silicon ingot 19 can be continuously produced by continuing the heat melting, drawing, and raw material supply.

The silicon ingot 19 is rapidly cooled as it moves downward from the heating induction coil 12, and due to the difference in shrinkage due to the temperature difference, excessive thermal stress is generated and the ingot 19 is cracked. Generation of cracks can be prevented by heating with the heat retaining device 13 installed under the induction coil 12 for use.

As a heat retaining device, a heating means (electrothermal multistage heater) arranged so as to surround the ingot, a heat insulating material installed on the outside thereof, and a heating means and a heat insulating material are supported on the outer periphery of the heat insulating material. A device to which an outer frame for fixing is attached is generally used. Conventionally, stainless steel such as SUS304 is used for the outer frame of the heat retaining device because it requires high heat resistance and rigidity capable of withstanding thermal deformation.

As a heating means, a heat retaining device using an induction heating type heater is also applied. For example, Patent Document 1 includes a conductor such as graphite, Ta, and Mo, and an induction coil provided around the conductor, and the outer surface of the conductor is covered with a heat insulating material such as a graphite fiber molded body and alumina. A heat retaining device is disclosed.

By the way, in a heat retaining device using an electrothermal heater as a heating means, an induced current is also generated in the outer frame due to the magnetic force from the heating induction coil, and the outer frame itself generates heat and is melted or deformed. To do. When the outer frame of the heat retaining device is melted, metal contaminants are introduced into the atmosphere and the silicon ingot is contaminated. The metal impurity becomes a trap (capture) level of the recombination of carriers generated by light, annihilates the carrier, and the conversion efficiency (the energy that can be extracted by converting the incident light energy into electric energy) In the production of polycrystalline silicon used as a substrate material for solar cells, it is particularly strictly controlled.

In addition, when the outer frame is deformed by heat, the internal heat insulating material is also deformed and damage such as cracks occurs, the internal temperature environment changes, and stable operation cannot be performed, and crystal defects and cracks are induced in the silicon ingot. There is also the problem of being.

On the other hand, in a heat retaining device using an induction heating type heater as a heating means, since an induction coil is provided around the heater, it is not easy to replace the heater. There is also a problem that temperature control in the height direction is difficult.

JP-A-2-30698

The present invention has been made in order to solve the above-mentioned problems, particularly in the case of a heat retaining device using an electrothermal multistage heater as a heating means. This thermal insulation device is targeted for easy temperature control in the height direction, maintaining the internal temperature environment in a stable state, enabling stable operation, and easy replacement when heater replacement is required. This is because there are advantages such as being able to.

The object of the present invention is to perform stable operation by preventing the outer frame of the heat retaining device from being melted or deformed by heat, and to efficiently make polycrystalline silicon suitable as a substrate material for solar cells free from contamination by metal impurities. An object of the present invention is to provide a silicon electromagnetic casting apparatus which can be manufactured well.

In order to solve the above problems, the present inventors have examined in detail the state of the outer frame attached to fix the heat retaining device.

FIGS. 3A and 3B are diagrams showing a schematic structure of the heat retaining device and its surroundings, and a rough melting point in the outer frame. FIG. 3A is a perspective view of the whole, and FIG. It is.

As shown in FIG. 3, the induction coil 12 for heating is attached to the outside of the mold 11, and a heat retaining device 13 for retaining the ingot 19 is installed below the mold 11. The heat retaining device 13 includes a heating means 14 (electric heating type heater) and a heat insulating material 15, and an outer frame 16 is attached so as to cover the outside. The outer frame 16 is made of four (surface) stainless steel plates, and is fastened with metal bolts 17 with an insulating material interposed between each two adjacent frames. The reason why the insulating material is interposed is to prevent welding of the fastening portion. The outer frame 16 is provided with a heater electrode and a thermocouple for measuring the temperature in the heat retaining device 13, but is not shown here.

A heat insulation board 18 made of a heat insulating material is attached between the mold 11 and the heat insulation device 13.

In the heat retaining device having such a structure, of the four plate members constituting the outer frame 16, a surface located immediately below the support portion of the induction coil 12 (the portion denoted by reference sign “a” in FIG. 3A). In the upper part (this surface is also referred to as “B surface” hereinafter) (parts hatched with a broken line in FIG. 3A), the melting damage is particularly large. Of the metal bolts 17 that respectively fasten the four stainless steel plates, the uppermost bolt 17 (the bolt marked with a circle in FIG. 3A) is particularly damaged. This is because an induced current is also generated in the outer frame 16 itself due to the magnetic force from the induction coil 12, and the current flows concentrated on the uppermost fastening bolt 17.

The problems caused by melting of the outer frame of the heat retaining device and the fastening bolts of the frame are summarized as follows.
(A) It is necessary to replace the outer frame and the bolt which have been melted and deformed accordingly.
(B) The metal contained in the outer frame and the bolt is introduced into the atmosphere as a contaminant by melting damage, and the silicon ingot is exposed to a risk of metal contamination.
(C) As the outer frame is deformed, damage such as deformation or cracking occurs in the internal heat insulating material, so that it is necessary to replace the heat insulating material.
(D) The temperature environment in the heat retaining device changes due to damage to the heat insulating material, making it impossible to perform casting under the same conditions, making stable operation difficult.

Among these problems, if metal contamination occurs in the silicon ingot due to (b), the conversion efficiency of a solar cell composed of this polycrystalline silicon as a substrate material is reduced, so that particularly strict management is required. is there. This problem can be avoided by using a carbon outer frame, but even if the material of the outer frame is changed to carbon, heat is generated by the induced current as in the case of stainless steel, and the carbon It is presumed that the wear of the outer frame is severe and the life of the outer frame is shortened. In addition, the carbon concentration of the silicon ingot increases.

Therefore, the present inventors tried to change the material of the outer frame to ceramics in order to prevent melting of the outer frame of the heat retaining device. This is because ceramics is a non-conductive member, so that it does not generate heat, and a solution to the above problems can be expected.

汎用 A versatile alumina plate was selected as the ceramic, and this was attached to the upper part of the entire outer frame of the heat retaining device for electromagnetic casting. This is because, as described above, the melt damage of the upper part of the outer frame and the uppermost bolt is particularly large. As a result, it was confirmed that the outer frame and bolts could be prevented from being melted.

The present invention has been made on the basis of such knowledge, and the gist thereof is the following silicon electromagnetic casting apparatus.
That is, a conductive bottomless cooling mold in which a part in the axial direction is divided into a plurality in the circumferential direction, an induction coil surrounding the mold, and a heat retaining device that is disposed below the mold and gradually cools solidified silicon. A silicon electromagnetic casting apparatus for lowering and solidifying molten silicon by electromagnetic induction heating by the induction coil, and a non-conductive member is used as a constituent member of the outer frame of the heat retaining apparatus An electromagnetic casting apparatus characterized by the above.

In the silicon electromagnetic casting apparatus of the present invention, an embodiment may be adopted in which the nonconductive member is used only on the entire upper surface of the outer frame of the heat retaining device.

The specific dimensions of the “upper part of the outer frame” vary depending on the size of the mold, the current flowing in the induction coil, etc., but use a bottomless water-cooled copper mold with a cross-sectional dimension of about 350 mm × 500 mm. In the case of casting a silicon ingot, it is a portion from the lower end of the induction coil to 200 mm. It corresponds to a portion up to 60 mm from the upper end of the outer frame.

In the silicon electromagnetic casting apparatus of the present invention, the non-conductive member may be used only on the surface of the outer frame of the heat retaining device located below the support portion of the induction coil.

In the silicon electromagnetic casting apparatus of the present invention, it is desirable to use a member made of alumina or silicon carbide as the non-conductive member.

In the silicon electromagnetic casting apparatus of the present invention, the outer frame of the heat retaining device installed on the lower side of the heating induction coil is made of a non-conductive member. If this device is used, it is suitable as a solar cell substrate material that prevents melting of the outer frame of the heat retaining device due to heat, prevents contamination of the furnace and ingot by metal impurities, and maintains good conversion efficiency. Polycrystalline silicon can be produced. In addition, it is possible to prevent damage to the heat insulating material due to melting or deformation of the outer frame, suppress changes in the temperature environment in the heat retaining device, and perform stable operation.
Furthermore, by reducing the replacement frequency of the outer frame and the heat insulating material, it is possible to contribute to improvement in operation efficiency and cost reduction.

FIG. 1 is a longitudinal sectional view showing a schematic configuration example of a heat retaining device having an outer frame in which a nonconductive member is used as a constituent member, which is installed in an electromagnetic casting apparatus of the present invention. FIG. 2 is a diagram schematically illustrating a configuration example of an electromagnetic casting apparatus suitable for manufacturing polycrystalline silicon. FIG. 3 is a view showing a schematic structure of the heat retaining device and its surroundings, and a rough melting point in the outer frame. FIG. 3 (a) is a perspective view of the whole, and FIG. 3 (b) is an I of FIG. 3 (a). It is -I arrow sectional drawing. FIG. 4 is a diagram showing the results of the example, and the results of investigating the amount of metal contamination in the silicon ingot. FIG. 5 is a diagram showing the influence of the use of the alumina member on the upper part of the outer frame of the heat retaining device on the lifetime.

An electromagnetic casting apparatus for silicon according to the present invention includes a conductive bottomless cooling mold in which a part of the axial direction is divided into a plurality of parts in the circumferential direction, an induction coil surrounding the mold, and a lower part of the mold. It is assumed that the electromagnetic casting apparatus has a heat retaining device for slowly cooling the silicon.

The premise of such an electromagnetic casting apparatus is that, when producing polycrystalline silicon used as a substrate material for a solar cell, casting is performed in a mold with almost no contact between the molten silicon and the mold. This is because it is possible to manufacture a silicon ingot that is free from metal contamination and can maintain good conversion efficiency. It is not necessary to use a high-purity material as the mold material, and since it can be continuously cast, the manufacturing cost can be significantly reduced.

A feature of the electromagnetic casting apparatus of the present invention is that a non-conductive member is used as a constituent member of the outer frame of the heat retaining device.
This heat retaining device is a device that gradually cools by applying moderate heat to prevent rapid cooling of the silicon ingot that has been solidified by lowering the molten silicon downward, and as described above, surrounds the ingot. The heating means (electric heating type multi-stage heater) arranged, a heat insulating material installed on the outside thereof, and an outer frame attached to the outer periphery of the heat insulating material.

The non-conductive member is used as a component of the outer frame because the outer frame itself is heated and melted when it is made of stainless steel as in the conventional case, and metal contaminants are generated due to it. This is to prevent contamination of the silicon ingot. Heat generation of the outer frame itself is due to the fact that the material constituting the outer frame is conductive, and an induced current flows through the outer frame due to the magnetic force from the heating induction coil. By using a conductive member, it is possible to eliminate the generation of induced current in the outer frame.

The non-conductive member is a so-called insulator having a sufficiently low electric conductivity. As the non-conductive member, various ceramics can be used in consideration of application as a constituent member of the outer frame.

Ceramics is defined as a non-metallic inorganic solid material obtained through processes such as molding and firing. In addition to various refractories and industrial ceramics, glass that has conventionally been added to the category of ceramic products, Cement, brick, etc. are also included. In addition to conventional ceramic products that use natural oxide-based minerals based on silicic acid as the raw material, chemically synthesized high-purity oxides (alumina, zirconia, etc.) and non-oxides ( Also included are products called fine ceramics, which use special materials such as carbides and nitrides, and perform special molding and firing.

There is no particular limitation on what is selected as the non-conductive member. The outer frame is a member used to form the outer shell of the heat retaining device by placing the outer frame on the outer periphery of the heating means of the ingot and the heat insulating material installed on the outside thereof, supporting and fixing the heating means and the heat insulating material. Yes, any one having a material function necessary for it can be applied. The necessary material function includes having a strength capable of holding a heating means, etc., having high heat resistance, and having a material and a shape that does not deform due to heat (or has high strength even if it is slightly deformed). is there.

In the electromagnetic casting apparatus of the present invention, it is desirable that the non-conductive member used as a constituent member of the outer frame of the heat retaining device is an alumina member or a silicon carbide member.

Alumina (Al ₂ O ₃ ) is a representative oxide-based ceramic, and has excellent heat resistance, thermal shock resistance, corrosion resistance, wear resistance, and electrical insulation, is hard, has high mechanical strength, and is relatively inexpensive. There are many excellent properties. Although there is a drawback of “brittleness” common to ceramics, by taking measures such as increasing the thickness, adding a reinforcing material, or changing to a shape that is difficult to break as necessary, It can be sufficiently applied as a constituent member of the outer frame of the heat retaining device.

Recently, for the purpose of improving the toughness of alumina, research and development of composite materials such as Al ₂ O ₃ —TiC and Al ₂ O ₃ —ZrO ₂ has been conducted. “Is not limited to alumina (Al ₂ O ₃ ), but also includes composite materials containing Al ₂ O ₃ as a main component.

Silicon carbide (SiC) is a carbonized ceramic, and is characterized by excellent high-temperature strength, high hardness, and corrosion resistance, and is often used as a heat-resistant, corrosion-resistant, wear-resistant part or abrasive. Although it is expensive and difficult to use, it is functionally suitable as a component of the outer frame of the heat retaining device in the electromagnetic casting apparatus of the present invention, and as described later, it can also be applied to a part of the outer frame. Conceivable.

FIG. 1 is a longitudinal sectional view showing a schematic configuration example of a heat retention device having an outer frame in which a non-conductive member is used as a constituent member, which is installed in the electromagnetic casting apparatus of the present invention. As shown in FIG. 1, an induction coil 12 for heating is attached to the outside of the mold 11, and a heat retaining device 13 for retaining the ingot 19 is installed below the mold 11.

The heat retaining device 13 has a heating means 14 (electric heating heater) and a heat insulating material 15, and an outer frame 16 made of alumina is attached so as to cover the outside. As shown in FIG. 3, the external appearance of the heat retaining device 13 is usually rectangular according to the shape of the mold 11, and four alumina plates are attached. The outer frame 16 is provided with a heater electrode and a thermocouple for measuring the temperature in the heat retaining device 13, but is not shown here.

In the example shown in FIG. 1, the heater has three stages, and a plurality of heaters are arranged in each stage. Each heater can be independently controlled in temperature, and is configured to control the temperature in the height direction in the heat retaining device 13 with high accuracy.

In the silicon electromagnetic casting apparatus of the present invention, an embodiment in which a non-conductive member is used only on the entire upper surface of the outer frame of the heat retaining device may be adopted.

When a stainless steel outer frame is used, of the upper part of the surface (B surface) located directly below the support portion of the induction coil 12 and the metal bolts that fasten the stainless steel plate This is because the melting damage of the uppermost bolt is particularly large, and if the melting damage in this portion can be prevented, most of the melting damage in the outer frame of the heat retaining device and the fastening bolt can be prevented.

In this case, since the range of replacement by the non-conductive member is limited to a part of the outer frame, the application of expensive silicon carbide (SiC) is sufficiently conceivable.

In the silicon electromagnetic casting apparatus of the present invention, an embodiment in which the non-conductive member is used only on the surface (B surface) located below the induction coil support portion of the outer frame of the heat retaining device is employed. It is good as well. Thereby, the especially big melting loss which arises in the upper part of B surface can be prevented.

As described above, if the electromagnetic casting apparatus of the present invention provided with a heat retaining device having an outer frame in which a non-conductive member is used as a constituent member, the outer frame of the heat retaining device is deformed by melting or heat, Furthermore, damage to the heat insulating material can be prevented, stable operation can be performed, and there can be efficiently produced polycrystalline silicon suitable as a substrate material for a solar cell that is free from contamination by metal impurities and can maintain good conversion efficiency. .

Example 1
1 has the configuration illustrated in FIG. 1 and uses an alumina member only on the upper part of the entire outer frame (the portion from the lower end of the induction coil to 200 mm), and the other is a heat insulating material having an outer frame made of stainless steel (SUS304). A silicon ingot (length 4 m) was manufactured using the electromagnetic casting apparatus of the present invention (cross-sectional dimension of a water-cooled copper mold: 345 mm × 345 mm) in which the apparatus was installed, and the amount of metal contamination of the ingot was investigated. As the alumina member, an Al ₂ O ₃ 98% (thickness 15 mm) member was used, and after necessary processing, it was continuously provided with a stainless steel member using a jig.

For comparison, the same investigation was performed when an electromagnetic casting apparatus provided with a heat retaining device having an outer frame made of stainless steel (SUS304) was used. The number of ingots investigated was 5 (comparative examples: A to E, examples of the invention: F to J), and the average value at 5 locations in the longitudinal direction of each ingot was taken.

The amount of metal contamination is measured by collecting samples from the outer periphery and the center in the longitudinal direction of each ingot and dissolving them, and then ICP-MS (Inductively Coupled Plasma-Mass Spectroscopy; inductively coupled high-frequency plasma spectroscopy analysis) ) Was used to analyze Fe, Cr and Ni, and the total amount thereof was obtained.

FIG. 4 is a diagram showing the investigation results of the amount of metal contamination in the silicon ingot. In FIG. 4, the amount of metal contamination on the vertical axis is expressed as a ratio relative to the amount of contamination in the ingot A of the comparative example being 1.

As is clear from FIG. 4, the effect of improving metal contamination on the ingot by using the electromagnetic casting apparatus of the present invention is extremely remarkable, and the amount of contamination is reduced to several tenths or less on average. This is because the use of an alumina member at the upper part of the outer frame of the heat retaining device eliminates melting damage of the outer frame and bolts for fastening the outer frame, and suppresses the introduction of metal into the atmosphere. Conceivable.

(Example 2)
1 has the configuration illustrated in FIG. 1 and uses an alumina member only on the upper part of the entire outer frame (the portion from the lower end of the induction coil to 200 mm), and the other is a heat insulating material having an outer frame made of stainless steel (SUS304). A silicon ingot (length 4 m) is manufactured using the electromagnetic casting apparatus of the present invention (cross-sectional dimension of a water-cooled copper mold: 345 mm × 345 mm) in which the apparatus is installed, and the lifetime of the silicon substrate cut out from the obtained ingot Was measured. As the alumina member, Al ₂ O ₃ 98% (thickness 15 mm) was used, and after necessary processing, it was continuously provided with a stainless steel member using a jig. For comparison, the same investigation was performed when an electromagnetic casting apparatus provided with a heat retaining device having an outer frame made of stainless steel (SUS304) was used.

The reason why the lifetime is measured is that the crystallinity of the silicon substrate can be electrically evaluated by the lifetime, and the conversion efficiency when a solar cell is configured using the silicon substrate can be evaluated to some extent. That the lifetime is long (improves) means that the conversion efficiency as a solar cell is high. The lifetime was measured by the μ-PCD method in which the reflection microwave was used to measure by optical propagation attenuation. The lifetime measured here is a lifetime when a p-type semiconductor having a resistivity of 1 to 2 Ω · cm is used.

FIG. 5 is a diagram showing the influence of the use of an alumina member on the upper part of the outer frame of the heat retaining device on the lifetime. In FIG. 5, the lifetime is the ratio of the lifetime of the silicon substrate cut out from the silicon ingot manufactured by the electromagnetic casting apparatus of the comparative example using stainless steel as the outer frame of the heat retaining device to the reference (1.0). Displayed.

As can be seen from FIG. 5, the lifetime of the silicon ingot manufactured by the electromagnetic casting apparatus of the present invention using the alumina member on the entire upper surface of the outer frame is improved by 1.2 times compared to before implementation. Was confirmed. That is, according to the electromagnetic casting apparatus of the present invention, polycrystalline silicon suitable for a solar cell substrate material having high conversion efficiency can be produced.

According to the electromagnetic casting apparatus for silicon according to the present invention, the outer frame of the heat retaining device installed under the induction coil for heating is prevented from being melted by heat, thereby preventing contamination of the furnace and ingot with metal impurities. Thus, it is possible to produce polycrystalline silicon suitable as a substrate material for a solar cell that can maintain good conversion efficiency. In addition, it is possible to prevent damage to the heat insulating material due to melting or deformation of the outer frame, suppress changes in the temperature environment in the heat retaining device, and perform stable operation.
Therefore, the present invention can be effectively used in the manufacturing field of solar cells, and can greatly contribute to the progress of natural energy utilization technology.

1: closed container,
4: support stand, 6: soaking tube,
7: Molten silicon,
9: Raw material charging machine, 10: Heating element, 11: Mold,
12: induction coil for heating, 13: heat retention device, 14: heating means,
15: heat insulating material, 16: outer frame, 17: bolt,
18: Thermal insulation board, 19: Ingot

Claims

A conductive bottomless cooling mold having a part in the axial direction divided into a plurality of parts in the circumferential direction, an induction coil surrounding the mold, and a heat retaining device that is disposed below the mold and gradually cools the solidified silicon. And a silicon electromagnetic casting apparatus for lowering and solidifying the molten silicon by electromagnetic induction heating by the induction coil,
A silicon electromagnetic casting apparatus, wherein a non-conductive member is used as a constituent member of the outer frame of the heat retaining device.
2. The silicon electromagnetic casting apparatus according to claim 1, wherein the non-conductive member is used only on the entire upper surface of the outer frame of the heat retaining device.
2. The silicon electromagnetic casting apparatus according to claim 1, wherein the non-conductive member is used only on a surface of the outer frame of the heat retaining device positioned below the support portion of the induction coil. 3.
4. The silicon electromagnetic casting apparatus according to claim 1, wherein the non-conductive member is a member made of alumina or silicon carbide.