JP2007182331A - High frequency induction heating apparatus and high frequency induction melting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency induction heating apparatus and a high frequency induction melting method which can rapidly melt a metal or semiconductor material supplied into a crucible. <P>SOLUTION: The crucible 3 of the high frequency induction heating apparatus 1 for heating and melting silicon in the crucible 3 for example, by generating magnetic field with a high frequency induction coil 4, has a bottom wall part 3a and a side wall part 3b, and is formed so that the wall thickness t1 of a thin side wall part 11 at the lower part of the side wall part 3b is thinner than the wall thickness t2 of a thick side wall part 12 at the upper part of the side wall part 3b. In this melting method using the high frequency induction heating apparatus 1, a part of molten silicon 2 is left in the crucible 3 when discharging the molten silicon 2 from the crucible 3, a solid silicon 2a is supplied into the crucible 3 where the molten silicon 2 remains, and the solid silicon 2a is melted by heat conduction from the crucible 3 and the molten silicon 2 generating heat by the magnetic field generated by the high frequency induction coil 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high frequency induction heating apparatus and a high frequency induction melting method.

  In recent years, various power generation methods such as wind power generation and wave power generation other than thermal power generation using fossil fuels have been attempted in order to reduce the burden on the global environment. Among them, the most noticed and positioned at the forefront of practical use is power generation by solar cells, and polycrystalline silicon is used as a material for the solar cells.

  As a conventional representative technique for producing polycrystalline silicon used in solar cells, high-purity silicon to which a dopant such as phosphorus (P) or boron (B) is added is heated and melted in a crucible in an inert gas atmosphere. There is a casting method in which this melt is poured into a mold and cooled to obtain a polycrystalline ingot (see Patent Document 1).

  The sheet-like silicon used for the solar cell is manufactured by cutting the polycrystalline ingot obtained as described above into small blocks with a band saw or the like, and further slicing with a wire saw or an inner peripheral blade method.

  In addition to the casting process for obtaining a polycrystalline silicon ingot, such a manufacturing method requires a process of cutting into an outer block size of sheet-like silicon and a slicing process of slicing to a sheet thickness requiring high cost, In addition, this slicing step is a major obstacle to reducing the manufacturing cost of solar cells, such as causing material loss that is greater than the thickness of the wire or inner peripheral blade.

  In order to solve this problem, it has been proposed to omit the step of producing and slicing an ingot. For example, a rotating ribbon is immersed in a silicon melt (hereinafter sometimes referred to as molten silicon) in a heating furnace crucible, and a silicon ribbon that is solidified on the surface of the rotating cooling body while rotating the rotating cooling body. A manufacturing method (see Patent Document 2) for continuous drawing, and a sheet shape in which a base plate, which is a plate-like cooling body, is immersed in molten silicon in a heating furnace crucible, and silicon is attached to and grown on the sheet generation surface of the base plate A silicon plate manufacturing method (see Patent Documents 3 and 4) has been proposed.

  In the method of manufacturing the silicon ribbon or the sheet-like silicon plate, the molten silicon in the crucible adheres to the silicon ribbon generation surface or the silicon sheet generation surface of the rotating cooling body or the base plate and is gradually taken out. The amount of molten silicon gradually decreases. Therefore, in the method of manufacturing a ribbon-like or sheet-like silicon thin plate, the production of a silicon thin plate such as a silicon ribbon or a sheet-like silicon plate is temporarily stopped when the molten silicon contained in the crucible is consumed and reduced to some extent. Then, an operation of supplying raw silicon into the crucible is performed.

  However, Patent Documents 2 to 4 do not mention the necessity of replenishing the raw material silicon into the crucible according to the decrease of the molten silicon in the crucible and problems at the time of replenishment.

  As conventional techniques for supplying raw silicon into the crucible, there are methods for supplying granular solid silicon (see, for example, Patent Document 5 and Patent Document 6), and melting means different from the means for melting silicon in the crucible. In addition, there is a method of melting the raw material silicon rod from the tip by another melting means and supplying it to the crucible in the form of a melt (for example, see Patent Document 7).

  However, the techniques disclosed in Patent Document 5 to Patent Document 7 all generate a silicon single crystal by immersing a seed crystal in molten silicon in a crucible and then gradually pulling the seed crystal from the molten silicon. This relates to the Czochralski technology, and does not directly manufacture a silicon thin plate by immersing a cooling body in molten silicon.

  As disclosed in Patent Document 5 to Patent Document 7, the raw material silicon is replenished in the vicinity of the seed crystal pulling portion in the crucible, and the replenished raw material silicon is dissolved or mixed in the original molten silicon in the crucible, Even if it takes some time to equilibrate to the appropriate temperature for single crystal formation, the Czochralski technology has a very slow seed crystal pulling speed, which leads to the quality of the silicon single crystal produced. There is no significant impact.

  On the other hand, for example, the time required to immerse the cooling body in the molten silicon in the crucible and solidify and precipitate the silicon on the sheet generating surface of the cooling body to generate one silicon thin plate is as short as 4 to 5 seconds, for example. It's time. Therefore, when raw material silicon is replenished in the crucible in the vicinity of the position where the cooling body is immersed, the temperature of the molten silicon in the crucible changes and the time required for equilibration to an appropriate temperature for the production of the silicon thin plate Since this is longer than the immersion time for generating the silicon thin plate on the sheet generation surface, the quality of the generated silicon thin plate varies depending on the temperature change of the molten silicon.

  When manufacturing silicon thin plates, if replenishment of raw silicon is performed at the same time and the quality of the produced silicon thin plates is not varied, the position in the crucible is far away from the position where the cooling body is immersed. The raw silicon must be replenished. In order to satisfy this, the opening area of the crucible and its volume must be increased, and the amount of silicon that must be prepared in the crucible becomes unnecessarily large, resulting in wasted silicon and melting power. Therefore, in the manufacture of a silicon thin plate, the crucible is not enlarged unnecessarily, and in general, when the raw material silicon is replenished, the thin plate manufacturing is temporarily stopped.

  In this way, in the method of generating the silicon thin plate by immersing the cooling body in the molten silicon in the crucible, the production of the silicon thin plate is stopped while the raw material silicon is being supplied to the crucible. If the time required for this is long, there is a problem that the operation rate of the apparatus decreases and the production efficiency deteriorates. In particular, when solid silicon is replenished as a raw material in the crucible, the time for raising the temperature of the crucible to the temperature necessary for melting the replenished solid silicon and the time for lowering the temperature to the original temperature suitable for solidification precipitation of the silicon thin plate are obtained. , The production stop time is further increased.

  In order to solve this problem, in a silicon thin plate manufacturing apparatus including two melting furnaces, that is, a first melting furnace for generating a silicon thin plate, and a second melting furnace for supplying silicon to the first melting furnace. It is conceivable that raw material silicon previously melted in the second crucible provided in the second melting furnace is supplied to the first crucible provided in the first melting furnace. In this way, the time for raising the temperature of the first crucible to the temperature necessary for melting the raw material silicon and the time for lowering the temperature to a temperature suitable for solidification precipitation of the silicon thin plate become unnecessary.

  In the method of melting silicon for replenishment to the first melting furnace in the second melting furnace, solid silicon equal to or more than the amount of silicon taken out from the first crucible by the silicon thin plate production is specified. There is a problem that the second melting furnace must be melted in time. In order to dissolve solid silicon quickly, there are a method of increasing the output of the second melting furnace, a method of suppressing wasteful heat radiation from the second crucible, and the like.

  However, when the output of the second melting furnace is increased, there is a problem that the cost and power consumption of the second melting furnace increase. On the other hand, as a method for suppressing wasteful heat radiation from the second crucible, for example, it is conceivable to cover the second crucible with a heat insulating material. However, since the second crucible must be charged with solid silicon, the heat insulating material There is a limit to the part that can be covered with, and heat dissipation cannot be significantly suppressed.

  In addition, the solid silicon supplied to the second crucible of the second melting furnace may be in the form of lumps or particles, which slows the melting rate and makes it difficult to melt a predetermined amount of silicon within a specific time. It has become.

  The reason will be described below. In the melting of the solid silicon in the second crucible, the induction current generated by the high frequency induction coil flows through the crucible wall of the second crucible to generate heat, or the heat from the heating element arranged around the second crucible is radiated and / or Alternatively, the second crucible is received by conduction, and the heat is conducted from the second crucible to the solid silicon.

  The heat of the crucible wall of the second crucible is conducted to a solid silicon lump or grain (hereinafter represented by a grain) in contact with the crucible wall of the second crucible. At this time, since the crucible wall of the second crucible and the solid silicon grains are in contact with each other at a point, the contact area is very small, and the heat transfer from the crucible wall to the silicon grains is not performed at a sufficient speed. .

  The heat conduction between the solid silicon grains in the second crucible is sequentially performed as the solid silicon grains that have received heat conduction from the crucible wall conduct heat to the other solid silicon grains in contact with the grains. In this way, heat is conducted between the solid silicon grains that are in contact with each other, but the contact area between the solid silicon grains is also very small, similar to the contact between the crucible wall of the second crucible and the solid silicon grains. Therefore, the heat transfer between the solid silicon grains is not performed at a sufficient speed. As a result, it takes a considerable time to dissolve all of the solid silicon supplied to the second crucible, making it difficult to melt a predetermined amount of silicon within a specific time.

  Further, in the silicon thin plate manufacturing apparatus, when the number of manufactured silicon thin plates per unit time is increased, the amount of silicon taken out from the first crucible increases. Therefore, in the silicon thin plate manufacturing apparatus having a high manufacturing capacity, in particular, in order to keep the apparatus operating rate high by supplying the raw silicon equivalent to the consumed silicon amount from the second crucible to the first crucible in a timely manner. In addition, it is strongly desired that the solid silicon supplied to the second crucible in proportion to the consumption can be rapidly dissolved.

Japanese Unexamined Patent Publication No. 6-64913 Japanese Patent Laid-Open No. 10-29895 JP 2002-175996 A JP 2003-59849 A JP 61-361197 A Japanese Patent Laid-Open No. 5-117077 JP-A-2-279582

  An object of the present invention is to provide a high-frequency induction heating apparatus and a high-frequency induction melting method capable of rapidly melting a solid metal or semiconductor material supplied into a crucible.

The present invention includes a crucible containing a metal or a semiconductor material and a high-frequency induction coil provided around the crucible, and heats and melts the metal or semiconductor material in the crucible by generating a magnetic field with the high-frequency induction coil. A high frequency induction heating device,
Discharging means for discharging the metal or semiconductor material in the crucible;
Supply means for supplying a solid metal or semiconductor material into the crucible,
The crucible has a bottom surface portion and a side wall portion that rises from the periphery of the bottom surface portion, and is formed so that at least a part of the thickness at the lower portion of the side wall portion is thinner than the thickness at the upper portion of the side wall portion. Is a high-frequency induction heating device characterized by

In the present invention, when the resistivity of the crucible material is ρ [μΩ · cm], the relative permeability of the crucible material is μ, and the frequency of the high-frequency current passed through the high-frequency induction coil is f [Hz]
The thickness of the upper part of the side wall is the current penetration depth δ of the high-frequency current generated in the side wall of the crucible by the high-frequency induction coil, and is thicker than the current penetration depth δ given by the following equation:
The thickness of at least a part of the lower portion of the side wall portion is smaller than the current penetration depth δ.
δ = 5.03 × √ {ρ / (μ · f)}

The present invention provides a thin plate manufacturing apparatus for manufacturing a thin plate by immersing a base plate, which is an original plate for manufacturing a thin plate, in a melt of a metal or semiconductor material in a crucible and pulling it up from the melt.
A first high-frequency wave provided with a first crucible containing metal or a semiconductor material and a first high-frequency induction coil provided around the first crucible to generate a magnetic field and melt the metal or semiconductor material in the first crucible. An induction heating device;
A base plate immersing means for holding the base plate, transporting the base plate to be held and immersing it in a melt of a metal or semiconductor material in the first crucible and pulling it up from the melt;
A second high-frequency wave provided with a second crucible containing metal or a semiconductor material and a second high-frequency induction coil provided around the second crucible to generate a magnetic field and melt the metal or semiconductor material in the second crucible An induction heating device including a second high-frequency induction heating device that replenishes the first crucible with a molten metal or semiconductor material in the second crucible,
The second high-frequency induction heating device is the above-described high-frequency induction heating device.

The present invention supplies a solid metal or semiconductor material to a crucible, generates a magnetic field with a high-frequency induction coil provided around the crucible, heats and melts the metal or semiconductor material in the crucible, and the dissolved metal Or a high-frequency induction melting method for discharging a melt of a semiconductor material from a crucible,
When discharging the melt of metal or semiconductor material from the crucible, leaving a part of the melt of metal or semiconductor material in the crucible,
A high frequency induction melting method characterized by supplying a solid metal or semiconductor material into a crucible in which a melt of metal or semiconductor material remains.

In the present invention, the crucible has a bottom surface portion and a side wall portion rising from the periphery of the bottom surface portion, so that at least a part of the thickness at the lower portion of the side wall portion is thinner than the thickness at the upper portion of the side wall portion. Formed,
When discharging the melt of the metal or semiconductor material from the crucible, the thickness of the melt of the metal or semiconductor material remaining in the crucible is at least part of the wall thickness in the lower part of the side wall part. It is characterized in that the melt is left so as to be above a portion formed so as to be thinner.

  According to the present invention, a crucible provided in a high-frequency induction heating apparatus and containing a metal or semiconductor material has a bottom surface portion and a side wall portion rising from a peripheral edge of the bottom surface portion, and at least a part of the lower portion of the side wall portion. The wall thickness is formed to be smaller than the wall thickness at the top of the side wall. As a result, when the molten metal or semiconductor material is left in the lower part of the crucible, the residual melt in the crucible can be heated by causing an induction current to flow through the high-frequency induction coil. The solid metal or semiconductor material fed into the can can be rapidly melted.

  According to the present invention, the thickness of the upper part of the side wall of the crucible is thicker than the current penetration depth δ, and the thickness of at least a part of the lower part of the side wall is thinner than the current penetration depth δ. Solid metal or semiconductor supplied to the residual melt in the crucible. The material can be melted more quickly.

  According to the present invention, the thin plate manufacturing apparatus includes a first plate that deposits a thin plate by immersing a base plate, which is a base plate for manufacturing the thin plate, in a melt of a metal or a semiconductor material in the first crucible and pulling it up from the melt. A second high-frequency induction heating apparatus including a high-frequency induction heating apparatus and a second high-frequency induction heating apparatus that supplies a molten metal or semiconductor material to the first crucible of the first high-frequency induction heating apparatus. The second crucible provided in the second high-frequency induction heating device is formed such that the thickness of at least a part of the lower part of the side wall part is thinner than the thickness of the upper part of the side wall part, preferably the side wall of the crucible The thickness of the upper part of the part is thicker than the current penetration depth δ, and the thickness of at least a part of the lower part of the side wall part is thinner than the current penetration depth δ.

  Thus, in the second high-frequency induction heating device on the side of supplying the raw material for manufacturing the thin plate to the first high-frequency induction heating device, the solid raw material supplied to the second crucible is rapidly melted. Is possible. Therefore, when the melt in the first crucible in the first high-frequency induction heating apparatus is reduced and it is necessary to replenish the raw material for manufacturing the thin plate, the second high-frequency induction heating apparatus quickly supplies the desired amount of solid raw material. Since it can be dissolved and replenished in a short time, when the raw material is replenished from the second high-frequency induction heating apparatus to the first high-frequency induction heating apparatus, the already melted raw material is replaced with the first high-frequency induction heating apparatus. It is only necessary to stop the production of the thin plate for the time required to supply the first crucible of the induction heating device. In this way, the raw material replenishment time, that is, the time during which the production of the thin plate is stopped can be shortened, so that a thin plate production apparatus with a high apparatus operating rate is realized.

  According to the present invention, in the high frequency induction melting method, a solid metal or semiconductor material is supplied to a crucible, and the metal or semiconductor material in the crucible is heated and melted by a high frequency induction coil provided around the crucible. When the molten metal or semiconductor material is discharged from the crucible, the metal or semiconductor material melt is partially left in the crucible, and the solid metal or semiconductor material is left in the crucible where the metal or semiconductor material melt remains. Supply. As a result, heat conduction from the melt of the metal or semiconductor material remaining in the crucible to the solid metal or semiconductor material is efficiently performed, so that the solid metal or semiconductor material supplied into the crucible can be quickly transferred. Can be melted.

  According to the present invention, the crucible has a bottom surface portion and a side wall portion rising from the periphery of the bottom surface portion, and at least a part of the thickness at the lower portion of the side wall portion is thinner than the thickness at the upper portion of the side wall portion. When the melt of the metal or semiconductor material is discharged from the crucible, the liquid level of the melt of the metal or semiconductor material remaining in the crucible is at least part of the wall thickness at the lower part of the side wall. The melt is left so as to be above the portion formed so as to be thinner than the thickness of the upper part of the film. As a result, a magnetic field penetrates into the crucible in the region where the wall thickness is low in the lower part of the side wall of the crucible, and it is possible to heat the melt remaining in the crucible directly by passing an induction current efficiently. When a solid metal or semiconductor material is supplied into a crucible in which the melt remains, it can be rapidly melted by utilizing heat conduction from the efficiently heated melt to the solid metal or semiconductor material. It becomes possible.

  FIG. 1 is a cross-sectional view seen from a side, showing a simplified configuration of a high-frequency induction heating apparatus 1 according to an embodiment of the present invention.

  The high-frequency induction heating apparatus 1 includes a crucible 3 that houses a metal or semiconductor material 2, a high-frequency induction coil 4 provided around the crucible 3, and a discharge means (not shown) that discharges the metal or semiconductor material 2 in the crucible 3. And a supply means 5 for supplying a solid metal or semiconductor material 2 a into the crucible 3. The high frequency induction heating device 1 is used to heat and melt the metal or semiconductor material 2, 2 a in the crucible 3 by generating a magnetic field with the high frequency induction coil 4.

  Although various materials can be used as the metal or semiconductor material 2, here, silicon used as a raw material for a polycrystalline silicon thin plate that is a member of a solar battery cell will be exemplified. Hereinafter, the metal or semiconductor material 2 is represented by silicon 2.

  The high frequency induction coil 4 is composed of a conductive wire and an insulating material covering the conductive wire, and is wound around the crucible 3. In FIG. 1, the high-frequency induction coil 4 is shown in a cut end view in order to avoid the complexity of illustration. The high frequency induction coil 4 is connected to a high frequency power source (not shown). A magnetic field is generated by flowing a high-frequency current from a high-frequency power source to the high-frequency induction coil 4, and the magnetic field is induced to the silicon melt 2 (molten silicon 2) in the crucible 3 depending on the thickness of the crucible 3 and the crucible 3 ( It generates heat by generating an eddy current.

  The material of the crucible 3 is not particularly limited, but graphite is used in the present embodiment. The crucible 3 is a container-like member that has a bottom surface portion 3a and a side wall portion 3b that rises from the periphery of the bottom surface portion 3a, and has a circular shape when viewed from the plane, that is, a cylindrical member having the bottom surface portion 3a. is there. In this crucible 3, molten silicon 2 and / or solid silicon 2a are accommodated.

  The crucible 3 has a wall thickness t1 from at least a part of the lower portion 11 of the side wall portion 3b, in this embodiment from the periphery of the bottom surface portion 3a to about 30% of the height of the side wall portion 3b. It is formed to be thinner than the wall thickness t2. Here, for the sake of convenience, the thick (t2) portion of the upper portion 12 of the side wall portion 3b is referred to as the thick side wall portion 12, and the thin (t1) portion of the lower portion 11 of the side wall portion 3b is referred to as the thin side wall portion 11. Call. In the present embodiment, the thin-walled side wall portion 11 is realized by cutting the inner wall of the crucible 3 from the inside of the crucible 3 to form a concave groove 13.

  In the crucible 3 of the present embodiment, the thickness t2 of the thick side wall portion 12 is thicker than the current penetration depth δ defined from the principle of high frequency induction heating, and the thickness t1 of the thin side wall portion 11 is equal to the current penetration depth. It is formed to be thinner than δ. The current penetration depth δ defined from the principle of high-frequency induction heating means that the density of the induction current generated in the object to be heated by the magnetic field generated by the high-frequency induction coil is reduced to 0.368 times the surface current density. It means the depth to the position to be.

In general, the current penetration depth δ is defined as the resistivity of the material to be heated is ρ [μΩ · cm], the relative permeability of the material to be heated is μ, and When the frequency is f [Hz], it is given by the following equation (1).
δ = 5.03 × √ {ρ / (μ · f)} (1)

  In this embodiment, since the heating object is the crucible 3 made of graphite, the resistivity ρ is 1000 μΩ · cm, the relative magnetic permeability μ is 1, and the frequency f is 8.5 kHz. δ is 1.7 cm from the equation (1). Therefore, in the crucible 3 of the present embodiment, the thickness t2 of the thick sidewall portion 12 is 2.5 cm (> δ = 1.7 cm), and the thickness t1 of the thin sidewall portion 11 is 1.3 cm (<δ = 1. 7 cm).

  In FIG. 1, there is a gap between the crucible 3 and the high frequency induction coil 4, but actually, the gap is filled with a refractory material or the like, and the crucible 3 and the high frequency induction coil 4 are integrated. For example, it is provided on the stage.

  The discharging means not shown is a tilting means for tilting the crucible 3 and the high frequency induction coil 4 integrally in the direction of the arrow 14 and returning to the original horizontal state. For the tilting means, the crucible 3 and the high frequency induction coil 4 are integrally installed on, for example, a stage, a hydraulic cylinder is mounted on one lower side of the stage, and the piston rod of the hydraulic cylinder is advanced and retracted to tilt the stage. And can be realized by returning to a horizontal position. The molten silicon 2 in the crucible 3 can be discharged by inclining the crucible 3 with the tilting means, and the discharge amount of the molten silicon 2 can be adjusted by adjusting the inclination angle.

  The supply unit 5 includes a storage unit 15, a shutter unit 16, and a conduit unit 17. The reservoir 15 accommodates granular solid silicon 2a prepared for charging into the crucible 3. The storage unit 15 may be charged with a solid silicon 2a that has been weighed in advance so as to have a desired amount by another charging device, or is provided with a device in which the weighing device and the charging device are integrated, A desired amount of solid silicon 2a may be weighed and introduced from the apparatus.

  The shutter portion 16 is provided so as to close the opening formed at the bottom of the storage portion 15 and opens and closes to drop the solid silicon 2a accommodated in the storage portion 15 into the conduit portion 17 through the opening portion. . The conduit portion 17 is a metal tube, and is connected to the opening portion of the storage portion 15 via the shutter portion 16. When the shutter portion 16 is opened, the solid silicon 2a that falls through the opening portion of the storage portion 15 is provided. Is introduced into the crucible 3 and charged.

  Hereinafter, a method of high-frequency induction melting the solid silicon 2a in the high-frequency induction heating apparatus 1 will be described.

  First, when the inside of the crucible 3 is empty, and when the solid silicon 2a is initially charged into the crucible 3 and melted, an amount of solid silicon 2a that can substantially fill the inner volume of the crucible 3 is measured, It is charged into the crucible 3 from the supply means 5.

  When the solid silicon 2a is inserted into the crucible 3, the high frequency induction coil 4 is energized to generate a magnetic field. In the crucible 3 in the magnetic field, an induced current is generated to generate heat, and the heat generated in the crucible 3 is conducted to the solid silicon 2a in contact with the side wall portion 3b of the crucible 3, and further the heat conducted to the solid silicon 2a is Conducted to the other solid silicon 2a that is in contact with the solid silicon 2a, and sequentially conducted between the solid silicon 2a.

  The solid silicon 2a is melted by the heat conducted in this way to become molten silicon 2. When the molten silicon 2 reaches a predetermined temperature, the tilting means is operated to tilt the crucible 3, and the molten silicon 2 in the crucible 3 Is discharged. In this embodiment, the inclination angle of the crucible 3 is adjusted, and the molten silicon 2 having about 1/3 of the crucible internal volume is discharged so as to remain in the crucible 3. In particular, the molten silicon 2 is left so that the liquid level 21 of the molten silicon 2 remaining in the crucible 3 is above the portion 22 that is the upper end in the vertical direction of the thin sidewall 11. . The discharged molten silicon 2 is another crucible for containing molten silicon into which a base plate, which is a base plate for manufacturing a silicon thin plate, is immersed when the high frequency induction heating apparatus 1 is used in a silicon thin plate manufacturing apparatus. To be used for the production of silicon thin plates.

  Next, when the solid silicon 2a is continuously melted in the crucible 3, a desired amount of the solid silicon 2a is supplied into the crucible 3 in which the molten silicon 2 remains. Here, the desired amount supplied into the crucible 3 is the amount of silicon taken out from the other crucible by at least silicon thin plate manufacturing when the high-frequency induction heating apparatus 1 is used in a thin plate manufacturing apparatus described later. The amount of silicon that needs to be replenished to another crucible.

  When the solid silicon 2a is supplied without leaving the molten silicon 2 in the crucible 3, the granular solid silicon 2a comes into contact with the side wall 3b of the crucible 3 as described above, and the solid silicon 2a also has points. Since the contact area is small, the heat transfer efficiency is not sufficient.

  However, if the solid silicon 2a is supplied with the molten silicon 2 remaining in the crucible 3, the liquid molten silicon 2 follows the surface shape of the solid silicon 2a, so the molten silicon in which the solid silicon 2a remains in the crucible 3 is used. 2 can be brought into contact with each other in a surface, and heat conduction from the molten silicon 2 to the solid silicon 2a is efficiently performed.

  Accordingly, the solid silicon 2a supplied into the crucible 3 according to the melting method of the present invention is the heat conducted from the side wall 3b of the crucible 3 (shown by the arrow 23 in FIG. 1) and the molten silicon remaining in the crucible 3. 2 and the heat conducted by 2 (shown by arrow 24 in FIG. 1). As a result, according to the melting method of the present invention, it is possible to melt the solid silicon 2a very quickly as compared with the case where only the solid silicon 2a is supplied in a state where the molten silicon 2 does not remain in the crucible 3. .

  Further, the crucible 3 has a thick side wall portion 12 and a thin side wall portion 11 in the side wall portion 3b, and the thickness t2 = 2.5 cm of the thick side wall portion 12 is the current penetration depth δ = 1. It is thicker than 7 cm, and the thickness t1 = 1.3 cm of the thin side wall 11 is formed to be thinner than the current penetration depth δ.

  Therefore, in the thick side wall portion 12 of the crucible 3, almost all of the induced current induced by the magnetic field 25 (the magnetic field is represented by the arrow 25 in FIG. 1 for convenience) generated by the high frequency induction coil 4 is the side wall portion 3b. It flows inside and is consumed by the heat generation of the side wall 3b. That is, in the thick side wall portion 12 of the crucible 3, the molten silicon 2 and the solid silicon 2a in the crucible 3 are heated by heat conduction from the side wall portion 3b.

  On the other hand, in the thin side wall portion 11 of the crucible 3, the induced current induced by the magnetic field 25 generated by the high frequency induction coil 4 flows into the side wall portion 3b and the molten silicon 2 in the crucible 3 to cause the side wall portion 3b to generate heat. In addition, the heat generation region 26 can be formed in the molten silicon 2 so that the molten silicon 2 can directly generate heat.

  In this way, by forming the thin-walled side wall portion 11 having a thickness smaller than the current penetration depth δ on the side wall portion 3b of the crucible 3, the heat generated in the side wall portion 3b is conducted and the molten silicon 2 is heated. The molten silicon 2 in the crucible 3 is caused to generate heat directly by flowing an induction current, and the molten silicon 2 can be efficiently heated. By realizing efficient heat transfer and efficient heating, it is possible to dissolve the solid silicon 2a in a short time. For example, when manufacturing a silicon thin plate, the production of the silicon thin plate results in unit time per unit time. The amount of solid silicon 2a exceeding the amount of silicon taken out from the crucible for thin plate production can be dissolved by the high-frequency induction heating device 1 within a specific time determined as the replenishment interval of raw material silicon.

  Furthermore, in the present embodiment, thin-walled side wall portion 11 is set to be positioned below the position of liquid level 21 of molten silicon 2 that remains in crucible 3. In other words, the liquid level 21 of the molten silicon 2 that remains in the crucible 3 is set to be higher than the portion 22 that is the upper end in the vertical direction of the thin side wall 11. Although the induced current flows through the molten silicon 2 to generate heat, the solid silicon 2a does not generate heat because the induced resistance does not flow because the electrical resistance is too large. Therefore, by setting the thin-walled side wall portion 11 to be located in the molten silicon 2 as described above, the magnetic field 25 that has entered the crucible 3 is generated in the heat generation of the molten silicon 2. It is used efficiently and can contribute to the improvement of heating efficiency.

  FIG. 2 is a cross-sectional view seen from a side, showing a simplified configuration of a thin plate manufacturing apparatus 30 according to another embodiment of the present invention. In this embodiment, the thin plate manufacturing apparatus 30 is exemplified by an apparatus for manufacturing a polycrystalline silicon thin plate used as a solar cell member. The thin plate manufacturing apparatus 30 manufactures a silicon thin plate by immersing a base plate, which is an original plate for manufacturing a thin plate, in molten silicon in a crucible and pulling it up from the molten silicon.

  In general, the thin plate manufacturing apparatus 30 includes a first high frequency induction heating device 31, a second high frequency induction heating device 32, a base plate dipping means 33, and the devices 31, 32, and 33, which are internal spaces. And a chamber 34 accommodated in the space 35.

The chamber 34 has a substantially rectangular parallelepiped appearance and is a hollow structure. The chamber 34 is provided with a heat-resistant and fire-resistant structure by lining a heat insulating material such as alumina (Al ₂ O ₃ ) although not shown in a steel housing. The chamber 34 is provided with an unillustrated evacuation unit and an inert gas supply unit, and the processing space 35 inside the chamber 34 can be maintained in a vacuum atmosphere or an inert gas non-atmosphere by these.

  One side wall 34a of the chamber 34 is an original plate for producing a silicon thin plate between a transfer device (not shown) outside the chamber 34 and a base plate dipping means 33 provided in the processing space 35. A base plate carry-in port (not shown) for delivering the base plate 45 made of carbon is formed. An opening / closing door (not shown) is provided at the base plate carry-in port, and a sub chamber (not shown) is further provided outside the door. This subchamber chamber is configured such that the atmosphere can be adjusted in the same manner as the chamber 34, and an openable / closable door is provided on the side opposite to the base plate carry-in port. Therefore, the base plate 45 transported to the chamber 34 by the transport device is first transported into the sub chamber chamber opened to the atmosphere, and after the atmosphere in the sub chamber chamber is adjusted, the base plate 45 is further lowered by the transport means provided in the sub chamber chamber. It passes to the base plate dipping means 33 through the main plate carry-in port.

  On the other side wall 34b facing the one side wall 34a of the chamber 34, a base plate 45 for transporting the base plate 45 having the silicon thin plate 50 formed at a position facing the base plate carry-in port to the outside of the chamber 34. A carry-out port (not shown) is formed. A sub chamber chamber is provided also on the base plate carry-out side in the same manner as the base plate carry-in side, and the base plate 45 on which the silicon thin plate 50 is formed is delivered to another transfer means through the sub chamber chamber. The

  The first high-frequency induction heating device 31 is provided around the first crucible 42 containing the silicon 41 and the first high-frequency induction heat generating the magnetic field by melting the silicon 41 in the first crucible 42. An induction coil 43.

  The first crucible 42 is made of, for example, graphite and is a bottomed rectangular tube container. In the present embodiment, the first crucible 42 is formed in a square shape when viewed from the plane. This is because the silicon thin plate 50 manufactured in the thin plate manufacturing apparatus 30 is formed in a rectangular shape like the base plate 45 so that the planar shape is solidified and deposited on the surface of the base plate 45 having a rectangular shape. The first crucible 42 in which the base plate 45 is immersed also has a sufficiently large area of the silicon melt surface in which the base plate 45 is immersed, and without waste, so that the base plate 45 can be easily immersed and pulled up. A planar shape is formed in a square. The first crucible 42 is provided in the processing space 35 such that the bottom surface portion 42 a is placed on a base 44 provided on the bottom surface of the chamber 34. The first crucible 42 contains a melt of silicon 41 (molten silicon 41) that is a raw material for thin plate production.

  The first high-frequency induction coil 43 is composed of a conductive wire and an insulating material that covers the conductive wire, and is wound around the first crucible 42. In FIG. 2, the first high-frequency induction coil 43 is shown in a cut end view in order to avoid the complexity of illustration. In addition, the space between the first crucible 42 and the first high-frequency induction coil 43 is represented by a gap in FIG. 2, but in reality, this is filled with a heat-insulating and insulating refractory material, and the first crucible 42. And the first high-frequency induction coil 43 are integrally provided on the base 44. The first high-frequency induction coil 43 is connected to a high-frequency power source (not shown), a high-frequency current flows from the high-frequency power source to generate a magnetic field, an induced current is generated in the first crucible 42 to generate heat, and the first crucible 42 is Then, the silicon in the first crucible 42 is melted to form molten silicon 41, and the molten silicon 41 is maintained at a desired temperature.

  The base plate immersion means 33 includes a holding head 46 that holds the base plate 45, a vertical arm 47 that is provided with the holding head 46 and extends in the vertical direction, and a holding head that is attached to the vertical arm 47 and the vertical arm 47. 46 is configured to include a drive unit 48 that moves the drive unit 46 in the horizontal direction and the vertical direction, and a track member 49 that serves as a track in which the drive unit 48 travels in the horizontal direction.

  The track member 49 is an elongated member made of, for example, metal, and is attached to the side wall connected to both the one side wall 34 a and the other side wall 34 b or the top plate of the chamber 34 in the processing space 35. The upper space is provided so as to extend from the base plate carry-in port toward the base plate carry-out port. The drive unit 48 is guided by, for example, a track on a groove formed in the track member 49, and moves the vertical arm 47 and the holding head 46 so as to advance and retract in the horizontal direction. Further, the drive unit 48 moves the vertical arm 47 and the holding head 46 attached to the vertical arm 47 so as to freely advance and retract in the vertical direction.

  The holding head 46 includes a handling mechanism, and can hold and release the base plate 45 by the operation of the handling mechanism.

  The base plate dipping means 33 configured as described above can perform the following operations. The base plate dipping means 33 moves the vertical arm 47 and the holding head 46 to the vicinity of the base plate carry-in entrance by the operation of the drive unit 48, receives the base plate 45 through the base plate carry-in port, and holds it by the hold head 46. Then, by the operation of the driving unit 48 again, the base plate is moved from the base plate entrance to above the first crucible 42. Further, the base plate dipping means 33 moves the vertical arm 47 downward, that is, moves downward by the operation of the drive unit 48, so that the base plate 45 held by the holding head 46 is moved to the first crucible 42. It is immersed in the molten silicon 41 inside, and silicon is solidified and deposited on the surface of the base plate 45.

  After the silicon is solidified and deposited on the surface of the base plate 45 to form the silicon thin plate 50, the base plate immersion means 33 operates the drive unit 48 to move the vertical arm 47 upward (moves so as to rise). Then, the base plate 45 held by the holding head 46 and the silicon thin plate 50 generated on the surface thereof are pulled up from the molten silicon 41.

  Next, the base plate dipping means 33 operates the drive unit 48 to horizontally move the base plate 45 and the silicon thin plate 50 held by the holding head 46 from the position above the first crucible 42 to the vicinity of the base plate carry-out port. Then, it is transferred to other transfer means outside the chamber 34 through the sub chamber.

  As described above, when the silicon thin plate 50 is continuously generated by the first high-frequency induction heating device 31 and the base plate dipping means 33, the molten silicon 41 in the first crucible 42 is solidified on the surface of the base plate 45. Since it is taken out by precipitation, it is consumed and reduced.

  When the amount of the molten silicon 41 accommodated in the first crucible 42 is reduced by the production of the silicon thin plate 50 and the production of the silicon thin plate 50 becomes difficult to continue, On the other hand, it is provided to replenish silicon 2 in a molten state.

  What should be noted in the thin plate manufacturing apparatus 30 of the present invention is that the second high-frequency induction heating device 32 is constituted by the high-frequency heating device 1 shown in FIG. Therefore, the second high frequency induction heating device 32 is hereinafter referred to as the high frequency induction heating device 1, the second crucible provided in the second high frequency induction heating device 32 is referred to as the crucible 3, and the second high frequency induction coil is referred to as the high frequency induction coil 4. Call it. Since the configuration and operation of the high-frequency induction heating device 1 have already been described, description thereof is omitted in the present embodiment.

  When the molten silicon 41 in the first crucible 42 is consumed and reduced by the first high-frequency induction heating device 31 and it becomes difficult to continue the production of the silicon thin plate 50, the production of the silicon thin plate 50 is temporarily stopped and the high-frequency induction is stopped. The crucible 3 of the heating device 1 is tilted in the direction of the arrow 14 by the discharging means (not shown), and the molten silicon 2 in the crucible 3 is supplied into the first crucible 42. At this time, the inclination angle of the crucible 3 is adjusted, and an appropriate amount of the molten silicon 2 is left in the crucible 3 as described above. Therefore, when the crucible 3 provided in the high frequency induction heating apparatus 1, particularly the high frequency induction heating apparatus 1 is inclined in the direction of the arrow 14, the molten silicon 2 accommodated in the crucible 3 is supplied into the first crucible 42. The installation position is determined as follows.

  In the first high-frequency induction heating device 31, the amount of the molten silicon 41 in the first crucible 42 that becomes the production limit of the silicon thin plate 50 can be detected, for example, as follows. When a weight sensor for measuring the total weight of the first crucible 42 and the molten silicon 41 accommodated therein is provided, and when the molten silicon 41 in the first crucible 42 is consumed and the measured weight falls below a predetermined limit value It can be determined that the generation of the silicon thin plate 50 is difficult to continue. Further, a liquid level sensor for detecting the liquid level of the molten silicon 41 in the first crucible 42 is provided so that the molten silicon 41 in the first crucible 42 is consumed and the liquid level becomes below a predetermined limit value. It can be determined that the generation of the silicon thin plate 50 is difficult to continue.

  The high frequency induction heating device 1 supplies the molten silicon 2 to the first crucible 42 of the first high frequency induction heating device 31, and the amount of the molten silicon 41 accommodated in the first crucible 42 generates the silicon thin plate 50. When the amount returns to a sufficient amount, the generation operation of the silicon thin plate 50 by the first high-frequency induction heating device 31 and the base plate immersion means 33 is resumed.

  Further, in the high frequency induction heating apparatus 1, the solid silicon 2 a is supplied from the supply means 5 into the crucible 3 in which the molten silicon 2 remains, and the solid silicon 2 a is melted for the next replenishment to generate the silicon thin plate 50. Maintained at a suitable temperature.

  An example of the melting capacity in the high-frequency induction heating apparatus 1 of the thin plate manufacturing apparatus 30 of the present invention, in other words, the replenishment capacity, is as follows.

In the first high-frequency induction heating device 31 of the thin plate manufacturing apparatus 30, when the silicon thin plate 50 having a size of 200 mm × 200 mm × 0.5 mm is produced at a speed of 10 seconds / sheet, the silicon crucible 42 is generated from the first crucible 42. The amount of silicon taken out is 4.66 g / sec. When the molten silicon 2 is added from the crucible 3 of the high frequency induction heating device 1 to the first crucible 42 at a cycle of once every 10 minutes, the high frequency induction heating device 1 is given by the equation (2). The ability to dissolve about 2.8 kg of silicon in 10 minutes is required.
4.66 g / sec × 600 sec = 2796 g≈2.8 kg (2)

  The size of the crucible 3 of the high frequency induction heating apparatus 1 is such that the inner diameter of the crucible is 200 mm, the depth is 200 mm, the thickness t2 of the thick wall portion 12 is 2.5 cm, and the thickness t1 of the thin wall portion 11 is 1.3 cm. When the molten silicon 2 is discharged from the crucible, the molten silicon 2 is left in the crucible 3 by about 30% of the crucible internal volume, the solid silicon 2a is supplied onto the remaining molten silicon 2, and the inverter output of the high frequency power source is 100 kW. When melted, 2.8 kg of supplied solid silicon 2a could be dissolved in about 8 minutes.

  As described above, according to the apparatus and method of the present invention, the first high frequency induction heating apparatus 31 has a shorter time (about 8 minutes) than the time interval (10 minutes) at which the molten silicon 2 must be replenished. The amount of solid silicon 2a necessary for replenishment can be dissolved, in other words, the amount of silicon exceeding the amount taken out from the first crucible 42 can be dissolved in 10 minutes, which is the time interval for replenishment. can do.

  Therefore, when the molten silicon 41 in the first crucible 42 in the first high-frequency induction heating device 31 decreases and the raw material supply for manufacturing the silicon thin plate becomes necessary, the high-frequency induction heating device 1 uses the desired amount of solid silicon 2a. Can be dissolved quickly and ready to be replenished in a short time. Thus, when silicon is replenished from the high frequency induction heating device 1 to the first high frequency induction heating device 31, silicon that has already melted is replenished to the first crucible 42 of the first high frequency induction heating device 31. It is only necessary to stop the production of the silicon thin plate 50 for the time required for (injection). As described above, since the time during which the production of the silicon thin plate 50 is stopped is shortened, a thin plate manufacturing apparatus having a high apparatus operation rate with respect to the silicon thin plate production is realized.

  On the other hand, the size of the crucible provided in the high frequency induction heating device for supplying molten silicon is such that the crucible has an inner diameter of 200 mm, a depth of 200 mm, and a uniform side wall thickness of 2.5 cm. All the molten silicon was discharged without leaving it inside, solid silicon was supplied into an empty crucible, and the inverter output of the high-frequency power source was melted at 100 kW. It took 20 minutes to dissolve 2.8 kg of solid silicon. did.

  That is, in the apparatus and method other than the present invention, a time exceeding the interval time (10 minutes) for supplying molten silicon is required to dissolve a desired amount of solid silicon in the high-frequency induction heating apparatus for supply. In addition to the time required for replenishing (injecting) molten silicon into the first crucible of the first high-frequency induction heating device, silicon is used until the dissolution of solid silicon is completed by the high-frequency induction heating device for replenishment. The production of the sheet had to be stopped.

  As described above, in the present embodiment, the raw material of the melt is exemplified by silicon, but is not limited thereto, germanium, gallium, arsenic, indium, phosphorus, boron, antimony, zinc, It may be a semiconductor material such as tin, aluminum, nickel, or a metal.

  Further, when the molten silicon 2 is discharged from the crucible 3 of the high-frequency induction heating apparatus 1, the amount of the molten silicon 2 remaining in the crucible 3 is set to approximately 1/3 of the internal volume of the crucible 3, but this is not limitative. Instead, it may be 1/2 of the inner volume of the crucible 3, or may be 1/4 or 1/8, whichever is smaller. The amount of the molten silicon 2 remaining in the crucible 3 is appropriately selected because there is an appropriate amount depending on the shape of the crucible 3 and the amount of solid silicon 2a to be additionally charged.

  Moreover, although the thickness t2 of the thick side wall part 12 in the crucible 3 of the high frequency induction heating apparatus 1 is set to 2.5 cm and the thickness t1 of the thin side wall part 11 is set to 1.3 cm, it is limited to this. Instead, the thickness may be determined by the strength of the crucible, the volume of the crucible, the frequency of the current passed through the high-frequency induction coil, the target heating temperature of the metal or semiconductor material, and the like. Therefore, for example, due to factors such as strength, the thickness t1 of the thin side wall portion may be thicker than the current penetration depth δ, but even in such a case, a slight magnetic field penetrates into the molten silicon inside the crucible. By doing so, it is possible to obtain the heating efficiency improvement effect by direct heating of the molten silicon.

It is sectional drawing seen from the side surface which simplifies and shows the structure of the high frequency induction heating apparatus 1 which is one Embodiment of this invention. It is sectional drawing seen from the side which shows simply the structure of the thin plate manufacturing apparatus 30 which is another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,32 High frequency induction heating apparatus 2,41 Silicon 3 Crucible 4 High frequency induction coil 5 Supply means 11 Thin side wall part 12 Thick side wall part 30 Thin plate manufacturing apparatus 31 1st high frequency induction heating apparatus 33 Base plate immersion means 34 Chamber 45 Bottom Ground plate 50 Silicon thin plate

Claims (5)

A high-frequency induction heating apparatus comprising a crucible for storing a metal or semiconductor material and a high-frequency induction coil provided around the crucible, and heating and melting the metal or semiconductor material in the crucible by generating a magnetic field with the high-frequency induction coil Because
Discharging means for discharging the metal or semiconductor material in the crucible;
Supply means for supplying a solid metal or semiconductor material into the crucible,
The crucible has a bottom surface portion and a side wall portion that rises from the periphery of the bottom surface portion, and is formed so that at least a part of the thickness at the lower portion of the side wall portion is thinner than the thickness at the upper portion of the side wall portion. High frequency induction heating device characterized by When the resistivity of the crucible material is ρ [μΩ · cm], the relative permeability of the crucible material is μ, and the frequency of the high-frequency current flowing in the high-frequency induction coil is f [Hz],
The thickness of the upper portion of the side wall is the current penetration depth δ of the induced current generated in the side wall portion of the crucible by the high frequency induction coil, and is thicker than the current penetration depth δ given by the following equation:
2. The high frequency induction heating device according to claim 1, wherein a thickness of at least a part of the lower portion of the side wall portion is thinner than the current penetration depth δ.
δ = 5.03 × √ {ρ / (μ · f)} In a thin plate manufacturing apparatus for manufacturing a thin plate by immersing a base plate, which is a base plate for manufacturing a thin plate, in a melt of a metal or semiconductor material in a crucible and pulling it up from the melt,
A first high-frequency wave provided with a first crucible containing metal or a semiconductor material and a first high-frequency induction coil provided around the first crucible to generate a magnetic field and melt the metal or semiconductor material in the first crucible. An induction heating device;
A base plate immersing means for holding the base plate, transporting the base plate to be held and immersing it in a melt of a metal or semiconductor material in the first crucible and pulling it up from the melt;
A second high-frequency wave provided with a second crucible containing metal or a semiconductor material and a second high-frequency induction coil provided around the second crucible to generate a magnetic field and melt the metal or semiconductor material in the second crucible An induction heating device including a second high-frequency induction heating device that replenishes the first crucible with a molten metal or semiconductor material in the second crucible,
A thin plate manufacturing apparatus, wherein the second high-frequency induction heating apparatus is the high-frequency induction heating apparatus according to claim 1 or 2. A solid metal or semiconductor material is supplied to the crucible, and a magnetic field is generated by a high-frequency induction coil provided around the crucible to heat and melt the metal or semiconductor material in the crucible. A high frequency induction melting method for discharging a melt from a crucible,
When discharging the melt of metal or semiconductor material from the crucible, leaving a part of the melt of metal or semiconductor material in the crucible,
A high-frequency induction melting method characterized by supplying a solid metal or semiconductor material into a crucible in which a melt of metal or semiconductor material remains. The crucible has a bottom surface portion and a side wall portion rising from the periphery of the bottom surface portion, and is formed such that at least a part of the thickness at the lower portion of the side wall portion is thinner than the thickness of the upper portion of the side wall portion,
When discharging the melt of the metal or semiconductor material from the crucible, the thickness of the melt of the metal or semiconductor material remaining in the crucible is at least part of the wall thickness in the lower part of the side wall part. 5. The high frequency induction melting method according to claim 4, wherein the melt is left so as to be above a portion formed so as to be thinner.

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