JP2001235287A - Silicon melting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more sharply reduce than a prior art apparatus with respect to melting time of a silicon material. SOLUTION: In a silicon melting apparatus for heating, melting, and holding a solid silicon material 4, a plasma melting section 32 is provided in which a silicon molten solution 7 is obtained by passing the silicon material 4 in plasma 39.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon melting apparatus for melting and heating and holding a solid silicon material, and more particularly to a silicon melting apparatus in which the melting time of a silicon material is significantly reduced as compared with a conventional apparatus.

[0002]

2. Description of the Related Art FIG. 8 is a sectional view showing the structure of a conventional silicon melting apparatus. A guide 5 is provided on a side surface of the container 1, and an electron beam gun 2 is attached to an upper portion of the container 1. A receiving tray 6 is housed inside the container 1, and the inside of the receiving tray 6 is irradiated with the electron beam 3 of the electron beam gun 2. The pulverized solid silicon material 4 is put into the tray 6 along the guide 5 from outside the container 1, and the silicon material 4 inside the tray 6 is irradiated with the electron beam 3. The electron beam gun 2 is rotatably mounted so that the silicon material 4 can be uniformly irradiated with the electron beam 3 so that the electron beam 3 can uniformly irradiate the dotted line range θ. . The silicon material 4 is heated and melted by the electron beam 3 to form a silicon melt 7. Finally, the silicon melt 7 is poured into a mold (not shown) by tilting the tray 6, and a required solid silicon ingot is formed.

[0003] The silicon material 4 in this specification refers to solid silicon alone or a mixture of solid silicon and another material, and its shape is arbitrary such as powdery or massive. Further, the silicon material 4 may have been subjected to a heat treatment or a cold heat treatment. FIG. 9 is a cross-sectional view showing the configuration of a different conventional silicon melting apparatus. A guide 5 is provided on the side surface of the container 1, and a conductive susceptor 9 made of graphite is attached to the upper portion of the container 1 via a support 8. The receiving tray 6 is housed inside the container 1, and a crucible 11 is provided inside the receiving tray 6, and the susceptor 9 is fitted into the crucible 11. Further, a high-frequency coil 10 is wound around the outer periphery of the tray 6, and the high-frequency coil 10 is
Are excited at a high frequency. The crushed solid silicon material 4 is put into the crucible 11 from the outside of the container 1 along the guide 5, and the high-frequency coil 10 is excited at high frequency. Since a high-frequency magnetic field is formed inside the crucible 11 by the high-frequency excitation, an induced current flows through the susceptor 9 itself. Since the susceptor 9 is heated by the eddy current loss due to the induced current, the silicon material 4 is heated and melted by the heat to form a silicon melt. The silicon material 4 becomes conductive when heated to about 600 to 800 ° C. or higher. Therefore, an induced current can be caused to flow in the silicon melt by high-frequency excitation. If a certain amount of silicon melt is formed in the crucible 11,
By raising the support 8, the susceptor 9 moves the
Excluded from That is, even without the susceptor 9, the temperature of the silicon melt itself rises only by the self-eddy current loss, so that the silicon material 4 is heated and melted by the heat. Finally, the silicon melt is poured into a mold (not shown) by tilting the tray 6 together with the crucible 11, and a required solid silicon ingot is formed.

FIG. 10 is a sectional view showing the structure of another conventional silicon melting apparatus. A guide 5 is provided on a side surface of the container 1, and a plasma torch 12 is attached to an upper portion of the container 1. The plasma torch 12
An arc is generated between electrodes provided inside and a high-pressure gas is blown onto the arc to generate a radiation plasma 1.
3 is injected. Further, the receiving tray 6 is housed inside the container 1, and a crucible 11 is provided inside the receiving tray 6. Further, a high-frequency coil 10 is wound around the outer periphery of the receiving tray 6, so that the high-frequency coil 10 is excited at a high frequency by a power source (not shown). The pulverized solid silicon material 4 is put into the crucible 11 from the outside of the container 1 along the guide 5, and the radiated plasma 13 of the plasma torch 12 is injected into the crucible 11. At the same time, the high-frequency coil 10 is excited at a high frequency. The silicon material 4 put into the crucible 11 is heated and melted by the radiation plasma 13 to form a silicon melt 7. Since a high-frequency magnetic field is formed inside the crucible 11 by the high-frequency excitation of the high-frequency coil 10, an induced current flows through the silicon melt 7 having conductivity. Since the silicon melt 7 is heated by the resistance loss due to the eddy current, the silicon material 4 can be heated and dissolved only by the heat generated by the resistance loss. Therefore, if a certain amount of the silicon melt 7 is formed in the crucible 11 with the radiation plasma 13, the radiation plasma 13 of the plasma torch 12 can be extinguished later. That is, even without the radiation plasma 13, the temperature of the silicon melt 7 itself rises due to only the eddy current loss, so that the silicon material 4 is heated and melted by the heat. Finally, crucible 1
By inclining the tray 6 together with 1, the silicon melt 7 is poured into a mold (not shown) to form a required solid silicon ingot.

[0005]

However, the conventional silicon melting apparatus as described above has a problem that it takes time to melt the silicon material. That is,
In a conventional silicon melting apparatus, an electron beam, a susceptor, a radiation plasma, or the like is used as a heating source for melting a silicon material. In any case, heating is performed from above the silicon material. Since the silicon material is a crushed solid or powder, the heat conduction between the solid itself and the solid is extremely poor. Therefore, it took much time to heat the silicon material.

There is also a problem that a complicated operation is required to melt the silicon material with the apparatus shown in FIG. That is, when a silicon material is introduced into the silicon melt during induction heating in the crucible, the silicon material accumulates at the boundary (slag line) between the silicon melt and the crucible. FIG. 11 shows a state in which the silicon melt is being induction-heated in the apparatus of FIG.
Is a sectional view, and (B) is a plan view. In a crucible 11 arranged in a container not shown in FIG. 11A, a silicon melt 7 melted by a radiation plasma 13 and a magnetic field formed by a coil 10 is heated and held.
In this state, when the silicon material 4 is additionally charged,
The additionally charged silicon material 4 gathers near the slag line, that is, near the inner wall of the crucible 11. The silicon melt 7 in the crucible 11 flows in the direction of arrow 7A. Therefore, on the surface of the silicon melt 7, the flow direction 7A is radial as shown in FIG. Therefore, the additionally charged silicon material 4 is pushed in the direction of arrow 7A on the surface of the silicon melt 7 and accumulates in the slag line. When the silicon material 4 gathers at the slag line in this way, the dissolution rate of the silicon material 4 is reduced.
To cope with such a phenomenon, various methods have conventionally been used.

FIG. 12 shows a method for increasing the dissolution rate of the silicon material in the apparatus shown in FIG. 10, and (A) and (B) are sectional views showing different methods. FIG.
In (A), the radiated plasma 13 is circulated while facing the inner wall of the crucible 11. Thereby, the silicon material 4 accumulated in the slag line is heated and dissolved. on the other hand,
In FIG. 12B, the crucible 11 receives the pan 6 and the coil 1.
Tilt and shake with 0. Thereby, the silicon material 4 accumulated in the slag line is moved, heated and melted. However, since the operation of the apparatus becomes complicated in any of the methods, the operation is difficult and the automatic operation is also difficult. An object of the present invention is to shorten the preheating time for converting a silicon material into a silicon melt and to simplify the operation of the apparatus.

[0008]

According to the present invention, there is provided a silicon melting apparatus for heating and melting a solid silicon material and holding the same, wherein the silicon material is passed through a plasma. It is preferable to provide a plasma dissolving unit that converts the silicon melt into a silicon melt. As a result, the silicon material can be instantaneously heated by the plasma, so that the preheating time for converting the solid silicon material into a silicon melt is greatly reduced.

In this configuration, the heat melting unit may receive the silicon melt falling from the plasma melting unit at a lower portion. Thereby, the operation mechanism of the device is not required, and the configuration of the device is simplified. Further, in such a configuration, the plasma melting section may form plasma by induction of a high-frequency magnetic field. Thus, a large-diameter plasma can be formed in the plasma melting part, so that a large amount of silicon material can be injected per unit time from the upper part of the plasma melting part.

In this configuration, the plasma melting section may generate plasma in a plasma generating tube made of a water-cooled metal having a slit. Thereby, the plasma generating tube is not broken by heat. Further, in this configuration, the heating and melting unit may be configured to magnetically levitate the silicon melt by inducing a high-frequency magnetic field. Thus, the silicon material can be heated and melted and held without causing any contamination of the silicon material. In this configuration, an opening may be formed at a lower portion of the heating and melting unit, and a silicon ingot may be cast while continuously dropping the silicon melt from the opening. This allows for continuous casting.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. FIG. 1 is a sectional view showing a configuration of a silicon melting apparatus according to an embodiment of the present invention. A silicon dissolving device includes a plasma dissolving unit 32 for dissolving the silicon material 4 into the droplet 7A, and a heat dissolving unit 28 disposed below the plasma dissolving unit 27 for heating and holding the silicon melt 7
It is composed of The plasma melting section 32 has a negative electrode 38 at the center, an inner nozzle 34 around the electrode 38, and an outer nozzle 35 around the outer nozzle 35.
Covered with. The inner nozzle 34 also serves as a positive electrode, and the electrode 38 and the inner nozzle 34 are connected to a DC power supply 33. On the other hand, the heating and melting unit 28 includes a crucible 11 housed inside the pan 6, a high-frequency coil 10 wound around the outer periphery of the pan 6, and the high-frequency coil 1
And a high-frequency power supply 22 for exciting 0.

In FIG. 1, a seed gas 37 is supplied between the electrode 38 and the inner nozzle 34, and an assist gas 36 is supplied between the inner nozzle 34 and the outer nozzle 35. The seed gas 37 becomes a plasma 39 between the electrode 38 and the inner nozzle 34 by applying a voltage from the DC power supply 33. The plasma 39 is supplied to the inner nozzle 34 by the flow of the seed gas 37 and the assist gas 36.
Of the outer nozzle 35 and the opening 34A of the outer nozzle 35. In this state, when the silicon material 4 is injected from the upper portion between the electrode 38 and the inner nozzle 34,
The silicon material 4 passes through the plasma 39. Plasma 3
Reference numeral 9 denotes a high temperature of about 10,000 K. When the silicon material 4 comes into contact with the plasma 39, the temperature rises and dissolves instantaneously, forming a droplet 7A and falling into the crucible 11 of the heating and dissolving part 28, and the silicon melt 7 become. Since the silicon melt 7 is conductive, an annular induced current flows through the silicon melt 7 itself due to induction of a high-frequency magnetic field generated from the high-frequency coil 10, and the silicon melt 7 is heated and held by the eddy current loss. You.
The silicon melt 7 is poured into a mold (not shown) to form a required solid silicon ingot.

The apparatus shown in FIG. 1 does not heat the silicon material 4 from above as in the conventional apparatus shown in FIGS. Since the heating is performed, the preheating time for forming the silicon melt 7 is significantly reduced as compared with the related art. Therefore, the silicon melt 7 can be efficiently generated. Further, since the silicon material 4 is simply introduced from above, the operation mechanism of the device is not required, and the manufacturing cost of the device is reduced.

FIG. 2 is a sectional view showing the structure of a silicon melting apparatus according to another embodiment of the present invention. The plasma melting section 27 includes a plasma generating tube 15 made of quartz glass or the like, a high-frequency coil 17 wound around the outer periphery of the plasma generating tube 15, a high-frequency power supply 16 for exciting the high-frequency coil 17, and an argon gas or the like. A gas cylinder 21 for supplying the seed gas to the plasma generating tube 15 through a gas pipe 20 and a valve 19 in which a seed gas is sealed is provided. The guide 5 is provided above the plasma melting section 27 and the funnel 14 is provided.
Along the guide 5 and the funnel 14
It is to be thrown in. The rest of FIG. 2 is the same as the configuration of FIG.

In FIG. 2, first, the valve 19 is opened, and the seed gas from the gas cylinder 21 is supplied into the plasma generating tube 15. Next, the high-frequency coil 17 is excited by the high-frequency power supply 16 to form a high-frequency electromagnetic field in the plasma generating tube 15. Most of the molecules of the seed gas are initially neutral, but minute initial electrons contained in the seed gas vibrate by a high-frequency electromagnetic field. As a result, the initial electrons collide with the neutral molecules and are ionized, and the multiplication of ions and electrons causes the seed gas to be in a plasma state, thereby forming a plasma 18 as shown in FIG. Next, when the silicon material 4 is put into the plasma generating tube 15 via the guide 5 and the funnel 14, the silicon material 4 comes into contact with the plasma 18 and is instantaneously melted and drops downward as a droplet 7A. Thereafter, as in the case of FIG. 1, the silicon melt 7 is heated and held by the heating / dissolving portion 28.

In the case of FIG. 2 as well, since the silicon material 4 is instantaneously heated by the high-temperature plasma 18, the preheating time for forming the silicon melt 7 is greatly reduced as compared with the prior art. Therefore, the silicon melt 7 can be efficiently generated. Further, since the silicon material 4 is simply introduced from above, the operation mechanism of the device is not required, and the manufacturing cost of the device is reduced. Further, since the plasma dissolving unit 27 can form the plasma 18 having a larger diameter than that of the apparatus of FIG. 1, a large amount of the silicon material 4 can be supplied per unit time from the upper portion of the plasma dissolving unit 27. . Thereby, the production efficiency of the silicon melt 7 is further improved. Also, since the plasma melting part 27 has no electrodes,
The silicon melt 7 is not contaminated by the electrodes,
A high-quality silicon melt 7 can be generated.

FIG. 3 is a sectional view showing the structure of a silicon melting apparatus according to a further different embodiment of the present invention. The heating and melting unit 40 stores the silicon melt 7 in the skull furnace 41. High frequency coil 1
0 is wound, and the high-frequency coil 10
It is connected to the. A cooling path 42 is embedded in the skull furnace 41, and the skull furnace 4
1 is constantly cooled. The silicon melt 7 is poured into a mold (not shown) to form a required solid silicon ingot. The rest of FIG. 3 is the same as the configuration of FIG.

In FIG. 3, the droplet 7A from the plasma melting part 27 falls into the skull furnace 41. A current is generated in the silicon melt 7 in the skull furnace 41 by induction of a high-frequency magnetic field generated from the high-frequency coil 10, and the silicon melt 7 is heated or kept warm by the current. Skull furnace 41
Is cooled by the refrigerant in the cooling passage 42, so that the silicon melt 7 near the contact portion with the inner wall of the skull furnace 41
B solidifies. Therefore, the silicon melt 7 is heated and held in a molten state without being contaminated by the material of the skull furnace 41 itself, so that a high-quality silicon ingot can be produced.

FIG. 4 is a sectional view showing the structure of a silicon melting apparatus according to a further different embodiment of the present invention. The heating and melting unit 43 arranges a plurality of conductive metal segments (not shown) through slits, and stores the silicon melt 7 in a water-cooled crucible 45 in which a cooling path 44 is embedded in each metal segment. I have. This water-cooled crucible 45
The high-frequency coils 10A and 10B are wound around the outer periphery of the high-frequency coils 10A and 10B.
A and 22B are connected. The silicon melt 7 is transferred from the water-cooled crucible 29 to the mold (not shown) through the lower opening 45A, and then cooled to form an alloy. FIG.
Others are the same as the conventional configuration of FIG.

In FIG. 4, a current is generated in the silicon melt 7 by induction of a high-frequency magnetic field generated from the high-frequency coils 10A and 10B. Surface. Therefore, even if the silicon melt 7 is heated and melted, the silicon melt 7 is heated and held in a molten state without being contaminated by the material of the water-cooled crucible 45 itself, so that a silicon ingot of excellent quality can be produced. .

The heating and melting section in the embodiment shown in FIGS. 1 to 4 may be a device for heating the silicon melt 7 by a heating lamp or a heating resistor. FIG. 5 is a cross-sectional view showing a configuration of a silicon melting apparatus according to another embodiment of the present invention. An opening 31 is formed in the lower part of the crucible 23 of the heating and melting part 29, and the high frequency coil 1
0 is wound. The rest of FIG. 5 is the same as the configuration of FIG. The silicon melt 7 is cooled down toward the lower part of the crucible 23, and the solidified silicon melt 7 is continuously dropped from the opening 31 to cast the silicon ingot 24. Thereby, continuous casting of the silicon ingot 24 becomes possible, and the production efficiency of the silicon ingot 24 is improved.

FIG. 6 is a sectional view showing a configuration of a plasma melting section of a silicon melting apparatus according to still another embodiment of the present invention, and FIG. 7 is a sectional view taken along line AA of FIG. As shown in FIG. 6, the plasma melting section 30 has a vessel 25 interposed between a plasma generating tube 26 for generating plasma 18 and a high-frequency coil 17 connected to the high-frequency power supply 16. Slit 26B as shown in FIG.
Of water-cooled metal 26C formed with That is, a cooling hole 26A is formed in the metal 26C, and a cooling liquid is passed through the cooling hole 26A. The heating melting part shown in FIGS. 1 and 4 is arranged below the plasma melting part 30 in FIG. Since the plasma generating tube 26 is made of a metal 26C which is constantly cooled, the plasma generating tube 26 is not broken by heat as in the case of quartz glass, and its durability is improved.

[0023]

According to the present invention, as described above, a preheating time for converting a silicon material into a silicon melt is provided by providing a plasma melting portion for converting a silicon material into a plasma by passing the silicon material into the plasma. Is greatly shortened, and the production efficiency of the silicon melt is improved.

In such a configuration, the heating and melting unit receives the silicon melt falling from the plasma melting unit at the lower part, thereby simplifying the structure of the device and reducing the manufacturing cost of the device. Further, in such a configuration, a large amount of silicon material can be injected per unit time from the upper portion of the plasma melting section by forming the plasma by the induction of the high-frequency magnetic field by the plasma melting section. Production efficiency is further improved.

Further, in such a configuration, the plasma melting portion is configured to generate plasma in the plasma generating tube made of a water-cooled metal having a slit, so that the plasma generating tube is not broken by heat. The durability of the plasma generating tube is improved. Further, in this configuration, the heating and melting unit is configured to magnetically levitate the silicon melt by induction of a high-frequency magnetic field, so that the silicon material can be heated and melted and held without causing any contamination of the silicon material. An excellent silicon ingot can be produced.

In this configuration, an opening may be formed at a lower portion of the heating and melting unit, and a silicon ingot may be cast while continuously dropping the silicon melt from the opening. Thereby, continuous casting becomes possible, and the production efficiency of the silicon ingot is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a silicon melting apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a silicon melting apparatus according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a silicon melting apparatus according to still another embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a silicon melting apparatus according to still another embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration of a silicon melting apparatus according to still another embodiment of the present invention.

FIG. 6 is a sectional view showing a configuration of a plasma unit of a silicon melting apparatus according to still another embodiment of the present invention.

FIG. 7 is a sectional view taken along line AA of FIG. 6;

FIG. 8 is a sectional view showing the configuration of a conventional silicon melting apparatus.

FIG. 9 is a cross-sectional view showing the configuration of a different conventional silicon melting apparatus.

FIG. 10 is a cross-sectional view showing the configuration of another conventional silicon melting apparatus.

11 shows a state in which the silicon melt is being induction-heated in the apparatus of FIG. 10, (A) is a sectional view,
(B) is a plan view

12 shows a method for increasing the dissolution rate of a silicon material in the apparatus of FIG. 10, and (A) and (B) are cross-sectional views showing different methods.

[Explanation of symbols]

4: Silicon material, 7: Silicon melt, 18, 39: Plasma, 24: Silicon ingot, 26: Plasma generating tube, 27, 28, 30, 32: Plasma melting part, 28,
29, 40, 43: heating melting part, 31: opening

Claims (6)

[Claims] 1. A silicon melting apparatus for heating and melting a solid silicon material and holding the same, comprising a plasma melting unit for converting the silicon material into a plasma by passing the silicon material through a plasma. Silicon dissolving equipment. 2. The silicon dissolving apparatus according to claim 1, wherein the heat dissolving section receives silicon melt dropped from the plasma dissolving section at a lower portion. 3. The silicon melting apparatus according to claim 1, wherein said plasma melting section forms plasma by induction of a high-frequency magnetic field. 4. The silicon dissolving apparatus according to claim 3, wherein said plasma dissolving portion generates plasma in a plasma generating tube made of a water-cooled metal having a slit formed therein. 5. The alloy melting apparatus according to claim 3, wherein the heat melting section magnetically levitates the silicon melt by induction of a high-frequency magnetic field. 6. The silicon melting apparatus according to claim 1, wherein an opening is formed in a lower portion of said heat melting section, and a silicon ingot is cast while continuously dropping a silicon melt from said opening. A silicon dissolving apparatus characterized in that it is made.