JP2009263174A - Melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a melting furnace in which a base substrate is immersed in a melt so as to stably supply an additional raw material without stopping production of a crystal thin plate to be formed on the surface of the base substrate, and degradation and fluctuation in the quality are decreased, as well as the production yield of the crystal thin plate is improved, and thereby, productivity of the crystal thin plate can be improved. <P>SOLUTION: The melting furnace 1000 is equipped with: a main crucible 1101 for holding a melt 1102; a main crucible heating apparatus 1104 for heating the melt 1102; a sub-crucible 1201 for holding the melt 1202; a sub-crucible heating apparatus 1204 for heating the melt 1202; a solid raw material charging apparatus 1401 for charging a solid raw material 1402; a melt transfer section 1301 for supplying the melt 1202 from the sub-crucible 1201 to the main crucible 1101; and a solid raw material charging control apparatus 1506 which determines whether or not to charge the solid raw material 1402 to the sub-crucible 1201 from the solid raw material charging apparatus 1401. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a melting furnace, in particular, it is possible to perform additional supply of stable raw materials without stopping production of a crystal thin plate formed on the surface of the base substrate by immersing the base substrate in the melt, The present invention also relates to a melting furnace capable of improving the productivity of the crystal thin plate by reducing the quality deterioration and variation and improving the production yield of the crystal thin plate.

  A conventional melting furnace used for manufacturing a crystal thin plate on the surface of a base substrate is provided with a main crucible for holding a melt as a raw material for the crystal thin plate. However, since the amount of the melt in the main crucible decreases as the production of the crystal thin plate proceeds, it is necessary to add the melt to the main crucible.

  In FIG. 6, the structure of the conventional melting furnace used for manufacture of a crystal thin plate is shown typically. The conventional melting furnace 3000 includes a main chamber 3001 in which a thin crystal plate is manufactured, a first sub chamber 3002 disposed adjacent to one side of the main chamber 3001, and the other of the main chamber 3001. And a second sub-chamber 3003 disposed adjacent to the side portion.

  Further, a first crucible 3100 and a base substrate gripping device 3004 for immersing the base substrate 1001 in a melt such as a silicon melt in the first crucible 3100 are provided at the center of the main chamber 3001. In addition, a first crucible preparation chamber 3101, a second crucible preparation chamber 3201, and a third crucible preparation chamber 3301 are installed on the outer periphery of the main chamber 3001.

  The first crucible preparation chamber 3101 is provided with a first solid material supply device 3102 for supplying the solid material 3103 to the first crucible 3100. The second crucible preparation chamber 3201 is provided with a second crucible 3200 and a second solid material supply device 3202 for supplying the solid material 3203 to the second crucible 3200. The third crucible preparation chamber 3301 is provided with a third crucible 3300 and a third solid material supply device 3302 for supplying the solid material 3303 to the third crucible 3300.

  In addition, the first crucible 3100, the second crucible 3200, and the third crucible 3300 each have a side surface protected by a heat insulating material, and an induction heating heating device is installed around each heat insulating material. Yes.

  In the melting furnace 3000 having the above-described configuration, after the base substrate 1001 is transferred from the first sub chamber 3002 to the main chamber 3001, the base substrate 1001 is gripped by the base substrate gripping device 3004, and the first crucible 3100. It is immersed in the melt inside. Then, the melt adheres to the surface of the base substrate 1001, and after the base substrate 1001 is taken out of the melt in the first crucible 3100, it solidifies, so that the crystal thin plate 1002 is formed on the surface of the base substrate 1001. It is formed. Thereafter, the base substrate 1001 on which the crystal thin plate 1002 is formed is carried out from the second sub chamber 3003 to the outside. By repeating the above steps, the crystal thin plate 1002 can be continuously manufactured.

  Also in the conventional melting furnace 3000 having the above configuration, as the production of the crystal thin plate 1002 progresses, the amount of the melt held in the first crucible 3100 decreases, and the height of the liquid level of the melt decreases. .

  Therefore, a solid raw material to be a raw material for the melt is added to the first crucible 3100, and the temperature of the first crucible 3100 is increased by an induction heating type heating device, so that the solid raw material is melted to form a melt. There is a need.

  However, since it is necessary to raise the temperature of the first crucible 3100 to near the melting point of the solid raw material in order to melt the solid raw material, the temperature of the first crucible 3100 is once increased after the solid raw material is charged, After that, the temperature of the first crucible 3100 needs to be lowered and then the production of the crystal thin plate 1002 needs to be resumed.

  Therefore, in the melting furnace 3000 shown in FIG. 6, any one of the crucibles of the first crucible 3100, the second crucible 3200, or the third crucible 3300 is used to improve the production amount of the crystal thin plate 1002. While the crystal thin plate 1002 is manufactured using the solid crucible, a solid raw material is added to the remaining crucible and the temperature of the crucible is increased to melt the solid raw material to form a melt. After forming the melt, The process of lowering the temperature is performed in parallel.

  That is, while the crystal thin plate 1002 is manufactured using the first crucible 3100, the second crucible 3200 is installed in the second crucible preparation chamber 3201, and the third crucible 3300 is also the third crucible 3300. It is installed in the crucible preparation chamber 3301. Then, after the solid raw material 3203 is charged into the second crucible 3200 from the second solid raw material supply apparatus 3202, the temperature of the second crucible 3200 is raised and then lowered to lower the melt in the second crucible 3200. Prepare. On the other hand, after the solid raw material 3303 is charged into the third crucible 3300 from the third solid raw material supply apparatus 3302, the temperature of the third crucible 3300 is increased, and then the temperature of the third crucible 3300 is decreased. The solid raw material is melted to prepare a melt.

  Then, when the amount of the melt in the first crucible 3100 falls below a specified amount, the production of the crystal thin plate 1002 is temporarily stopped, and the first crucible 3100 is moved to the first crucible preparation chamber 3101. Then, the second crucible 3200 or the third crucible 3300 in which the melt is sufficiently produced is installed in the main chamber 3001 instead of the first crucible 3100, and the production of the crystal thin plate 1002 proceeds.

  On the other hand, the solid crucible 3103 is charged into the first crucible 3100 in which the amount of the melt is equal to or less than the specified amount, and the melt is supplied in the same manner as in the second crucible 3200 and the third crucible 3300 described above. Prepare and replenish the melt.

  Thus, in the melting furnace 3000 shown in FIG. 6, the interruption of the production of the crystal thin plate 1002 accompanied by the addition of the solid raw material to the crucible can be minimized. As described above, by increasing the number of crucibles, the interruption time of the production of the crystal thin plate 1002 can be limited to the movement time of the crucible. Such a melting furnace is disclosed in, for example, International Publication WO 2004/025000 Pamphlet.

  FIG. 7 shows another configuration of a conventional melting furnace used for manufacturing a crystal thin plate. The melting furnace 4000 is a melting furnace in which a melt is directly added to the main crucible 4101. The melting furnace 4000 having such a configuration is disclosed in Japanese Patent Application Laid-Open No. 2007-290914.

  Here, the melting furnace 4000 shown in FIG. 7 includes a main crucible 4101 and a secondary crucible 4201, and a heat insulating material 4103 is provided on a side surface of the main crucible 4101, and a refractory is provided on the bottom surface of the main crucible 4101. A brick 4105 is provided.

  In addition, an induction heating type main crucible heating device 4104 is provided so as to surround a heat insulating material 4103 provided on a side surface of the main crucible 4101. In addition, a heat insulating material 4203 is provided on a side surface of the sub crucible 4201 and a position at a predetermined gap 4207 from the sub crucible 4201. In addition, a secondary crucible heating device 4204 is provided so as to surround the outer periphery of the heat insulating material 4203. A refractory brick 4205 is provided on the bottom surface of the auxiliary crucible 4201, and the refractory brick 4205 is attached on the surface of the crucible receiver 4206.

In the melting furnace 4000 having the above-described configuration, the melt 4102 is held in the main crucible 4101, and the melt 4202 is held inside the auxiliary crucible 4201. When the solid raw material is charged into the melt 4202 in the auxiliary crucible 4201, the melt 4202 overflows from the auxiliary crucible 4201, and is supplied into the main crucible 4101 through the gap 4207. As a result, the melt is supplied from the secondary crucible 4201 to the main crucible 4101, so that the crystal thin plate 1002 can be manufactured without replacing the main crucible 4101.
International Publication WO 2004/025000 Pamphlet JP 2007-290914 A

  In the conventional melting furnace 3000 having the configuration shown in FIG. 6, if the height of the melt level in the crucible is greatly reduced by continuously manufacturing the crystal thin plate 1002 for a certain period, the height of the crucible Alternatively, since it is possible to maintain an arbitrary immersion depth of the base substrate 1001 by adjusting the height of the base substrate 1001, it is considered that the production of the crystal thin plate 1002 can be continued.

  However, in the melting furnace 3000 shown in FIG. 6, when the height of the melt level in the crucible used for the production of the crystal thin plate 1002 is greatly reduced, an induction heating method is used as the crucible heating device. For this reason, the magnetic force that enters the melt surface of the melt in the crucible from the upper part of the side wall of the crucible may change, or the exposure of the inner wall surface of the crucible may increase to increase the radiation loss from the crucible. As a result, the temperature or temperature distribution of the melt in the crucible changes, and the quality of the crystal thin plate 1002 produced at a high position of the melt in the crucible and the quality of the crystal thin plate 1002 produced at a low position ( (Plate thickness, plate thickness distribution) may not be stable, or the manufacturing yield of the crystal thin plate 1002 may be reduced.

  Further, when the melt 4202 is supplied from the auxiliary crucible 4201 to the main crucible 4101 as needed, as in the melting furnace 4000 having the configuration shown in FIG. 7, the production of the crystal thin plate 1002 is not interrupted, and the solid crucible 4202 is solid. Raw materials can be input. However, when a melt 4202 such as a silicon melt is allowed to flow in the gap 4207 on the side surface of the auxiliary crucible 4201, the melt 4202 such as a silicon melt comes into contact with the heat insulating material 4203 on the side surface of the auxiliary crucible 4201, so May deteriorate.

  When the heat insulating material 4203 on the side surface of the auxiliary crucible 4201 is deteriorated, the auxiliary crucible heating device 4204 such as a coil may be heated and damaged by radiation from the molten liquid 4202 such as the auxiliary crucible 4201 or silicon melt. .

  Further, the melt 4202 such as a silicon melt in contact with the heat insulating material 4203 flows into the main crucible 4101 while being contaminated by the heat insulating material 4203, so that the melt 4102 in the main crucible 4101 is also contaminated and the crystal thin plate 1002 is manufactured. Is done. In general, the crystal thin plate 1002 manufactured by such a method is used as a semiconductor material or a solar cell material, and therefore causes deterioration of characteristics when contaminated material is mixed.

  Therefore, in order to stabilize the quality of the crystal thin plate 1002, improve the production yield of the crystal thin plate 1002, and improve the productivity of the crystal thin plate 1002, the melt 4202 supplied from the sub crucible 4201 to the main crucible 4101 is insulated. It is necessary not to contact the material 4203.

  The present invention has been made in view of the above problems, and an object of the present invention is to stop the production of a crystal thin plate formed on the surface of a base substrate by immersing the base substrate in a melt. Provides a melting furnace that can improve the productivity of thin crystal sheets by reducing the quality deterioration and dispersion and improving the production yield of thin crystal sheets. There is to do.

  The present invention provides a main crucible for holding a melt of a substance containing at least one of a metal material and a semiconductor material, a main crucible heating device for heating the melt held in the main crucible, and supplying the main crucible A sub crucible for holding the melt melt, a sub crucible heating device for heating the melt held in the sub crucible, and a solid raw material for charging the sub crucible with a solid raw material as a raw material of the melt It is equipped with a charging device and a melt transfer unit for supplying the melt from the auxiliary crucible to the main crucible. The melt transfer unit is joined to the auxiliary crucible, and the solid material is input from the solid material input device to the auxiliary crucible. This is a melting furnace in which the melt overflowing from the auxiliary crucible is supplied to the main crucible through the melt transport section.

  Here, the melting furnace of the present invention further includes a melt transport unit heating device for heating the melt transport unit, and the melt transport unit is made of a hollow member heated by the melt transport unit heating device. Is preferred.

  The melting furnace of the present invention further includes a base substrate dipping device for forming a crystal thin plate formed by solidifying the melt on the surface of the base substrate by being immersed in the melt held in the main crucible. It is preferable.

  Further, the melting furnace of the present invention includes a melt height detector for detecting the height of the melt level held in the main crucible, and whether or not the solid raw material is charged into the auxiliary crucible from the solid raw material charging device. And a solid raw material charging control device for determining the solid raw material charging control device in the secondary crucible based on the liquid level of the melt held in the main crucible detected by the melt height detector. It is preferable to determine whether or not to input.

  In the melting furnace of the present invention, it is preferable that the solid raw material charging control device also determines the charging amount of the solid raw material charged into the auxiliary crucible.

  The melting furnace of the present invention further includes a base substrate dipping device for forming a crystal thin plate formed by solidifying the melt on the surface of the base substrate by being immersed in the melt held in the main crucible. It is preferable.

  Further, the melting furnace of the present invention includes a crucible lifting / lowering device for moving the main crucible in the vertical direction based on the height of the liquid level of the melt held in the main crucible detected by the melt height detector. Furthermore, it is preferable to adjust the immersion depth of the base substrate in the melt by controlling the height of the main crucible by the crucible lifting device.

  Further, in the melting furnace of the present invention, the base substrate dipping device determines the track height of the base substrate based on the level of the melt held in the main crucible detected by the melt height detector. It is preferable to adjust the immersion depth of the base substrate in the melt by controlling.

  Further, the melting furnace of the present invention includes a melt height detector for detecting the height of the melt level held in the main crucible, and whether or not the solid raw material is charged into the auxiliary crucible from the solid raw material charging device. A solid raw material charging control device to determine, a base substrate dipping device for forming a crystal thin plate formed by solidifying the melt on the surface of the base substrate by dipping in the melt held in the main crucible, and the melt height And a crucible lifting / lowering device for moving the main crucible in the vertical direction based on the height of the melt level held in the main crucible detected by the height detector, and controlled by the crucible lifting / lowering device It is preferable that the solid raw material input control device determines whether or not to supply the solid raw material to the auxiliary crucible based on at least one of the height of the base substrate and the height of the orbit of the base substrate controlled by the base substrate immersion device.

  In the melting furnace of the present invention, the solid raw material charging control device also determines the amount of the solid raw material charged into the auxiliary crucible based on at least one of the height of the main crucible and the height of the orbit of the base substrate. Is preferred.

  Moreover, in the melting furnace of this invention, it is preferable that the immersion depth with respect to the melt of a base substrate is adjusted by controlling the height of the main crucible by a crucible raising / lowering apparatus.

  Moreover, in the melting furnace of this invention, it is preferable that the immersion depth with respect to the melt of a base substrate is adjusted by a base substrate immersion apparatus controlling the height of the track | orbit of a base substrate.

  In the melting furnace of the present invention, the melt height detector detects the height of the melt surface using an electrical signal when the melt held in the main crucible and the base substrate come into contact with each other. It is preferable to do.

  According to the present invention, it is possible to perform additional supply of stable raw materials without suspending the production of a crystal thin plate formed on the surface of the base substrate by immersing the base substrate in the melt, and deterioration in quality. Further, it is possible to provide a melting furnace capable of improving the productivity of the crystal thin plate by reducing the variation and improving the production yield of the crystal thin plate.

  Hereinafter, embodiments of the present invention will be described. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

<Composition of melting furnace>
In FIG. 1, the typical structure of a preferable example of the melting furnace of this invention is shown. Here, the melting furnace 1000 has a main crucible 1101 and an auxiliary crucible 1201. A heat insulating material 1103 is provided on a side surface of the main crucible 1101, and a main crucible heating device 1104 is provided so as to surround the outer periphery of the heat insulating material 1103. A refractory brick 1105 is attached to the bottom surface of the main crucible 1101, and the refractory brick 1105 is installed on the main crucible receiver 1106.

  Further, a heat insulating material 1203 is also provided on the side surface of the sub crucible 1201, and a sub crucible heating device 1204 is provided so as to surround the outer periphery of the heat insulating material 1203. In addition, a refractory brick 1205 is attached to the bottom surface of the auxiliary crucible 1201, and the refractory brick 1205 is installed on the auxiliary crucible receptacle 1206.

  In addition, a melt transfer unit 1301 is connected to the sub crucible 1201, and the melt transfer unit 1301 is provided to transfer the melt 1202 overflowing from the sub crucible 1201 to the main crucible 1101. Further, a heat insulating material 1303 is attached to the outer periphery of the melt conveying unit 1301, and a melt conveying unit heating device 1304 is attached so as to surround the outer periphery of the heat insulating material 1303. Further, a solid material input device 1401 is installed above the sub crucible 1201, and the solid material 1402 is input into the sub crucible 1201 by the solid material input device 1401.

  Both the main crucible receptacle 1106 and the auxiliary crucible receptacle 1206 are installed on the crucible elevating device 1107, and the crucible elevating device 1107 has a function of moving the positions of the main crucible 1101 and the auxiliary crucible 1201 up and down (moving in the vertical direction). have.

  In addition, the melt height detector 1503 is connected to the main crucible 1101 through the electric wiring 1052, and is connected to the base substrate immersion apparatus described later through the electric wiring 1051. Here, the melt height detector 1503 can control the up-and-down movement of the crucible lifting / lowering device 1107 through the path 1504, and the liquid level of the melt 1102 in the main crucible 1101 is transferred to the solid raw material charging control device 1506 through the path 1505. Can transmit height.

  Further, the solid material input control device 1506 can determine whether or not the solid material 1402 of the solid material input device 1401 is input and the input amount through the path 1507.

  Here, the main crucible 1101 and the sub crucible 1201 are filled with a solid raw material in advance, the main crucible heating device 1104 heats the main crucible 1101, and the sub crucible heating device 1204 heats the sub crucible 1201. As a result, the solid material in the main crucible 1101 is melted to become the melt 1102, and the solid material in the auxiliary crucible 1201 is melted to become the melt 1202.

  Then, by feeding the solid material 1402 from the solid material charging device 1401 into the sub crucible 1201, the melt 1202 held in the sub crucible 1201 overflows from the sub crucible 1201 and flows into the melt transport unit 1301. Then, the melt 1202 that has flowed into the melt transport unit 1301 is supplied to the main crucible 1101. Thereby, the amount of the melt 1102 held in the main crucible 1101 can be increased.

  By repeating the charging of the solid raw material 1402 from the solid raw material charging device 1401 to the auxiliary crucible 1201, the amount of the melt 1202 held in the auxiliary crucible 1201 increases. The melt 1202 flows into the melt transport unit 1301 from the opening provided in the crucible 1201.

  In this way, by providing the melt conveying unit 1301 connected to the sub crucible 1201, the sub crucible receiver 1206 that receives the melt 1202 that leaks when the sub crucible 1201 breaks is installed below the sub crucible 1201. It is possible to effectively prevent the other members constituting the melting furnace 1000 from being damaged.

  In addition, by providing the melt conveying unit 1301 connected to the sub crucible 1201, the sub crucible 1201 can be installed at a position away from the top of the melt 1102 held in the main crucible 1101. Even if the melt 1202 leaks out of the crucible receptacle 1206, it is possible to effectively prevent other members constituting the melting furnace 1000 from being damaged.

  In addition, by providing the melt conveyance unit 1301, deterioration of the heat insulating material 1303 due to the melt 1202 overflowing from the auxiliary crucible 1201 coming into contact with the heat insulating material 1303 and contamination of the melt by the heat insulating material 1303 can be suppressed. it can. Further, by providing the melt transport unit heating device 1304 in the melt transport unit 1301, the temperature drop of the melt transport unit 1301 can be suppressed.

  Further, by using the melt transporting part 1301 as a hollow member, it is possible to reliably prevent the melt 1202 overflowing from the auxiliary crucible 1201 from coming into contact with the heat insulating material 1303. It is possible to suppress solidification of the melt 1202 due to the temperature drop of the transport unit 1301 inside the melt transport unit 1301 and damage to the melt transport unit heating device 1304 due to heat.

  In addition, it is preferable that the main crucible heating device 1104, the sub crucible heating device 1204, and the melt transport unit heating device 1304 are each of an induction heating method. When main crucible heating device 1104, sub crucible heating device 1204, and melt transport unit heating device 1304 are induction heating systems, main crucible 1101, sub crucible 1201 and melt transport unit 1301 are heated by induction heating. Although it is necessary to form with a material, it is preferable to form with a high melting point material which does not contaminate melts, such as a silicon | silicone, for example.

  For example, when the melt 1102 held in the main crucible 1101 and the melt 1202 held in the sub crucible 1201 are silicon melts, respectively, the main crucible 1101, the sub crucible 1201, and the melt transport unit The surface in contact with the silicon melt 1301 is preferably made of graphite, but may be made of a material other than graphite.

  In addition, the main crucible 1101, The durability of the auxiliary crucible 1201 and the melt transfer unit 1301 can also be improved.

  In addition, the solid material charging device 1401 has a handle shape in the present embodiment, but it is needless to say that the shape is not limited to this shape. The solid raw material charging device 1401 is filled with the solid raw material 1402 outside the melting furnace 1000, and then the solid raw material charging device 1401 is moved to above the auxiliary crucible 1201. By rotating in the direction, an arbitrary amount of the solid raw material 1402 can be put into the auxiliary crucible 1201.

  Note that there is no particular limitation on the method of filling the solid raw material charging device 1402 into the solid raw material charging device 1401 outside the melting furnace 1000. Moreover, it is preferable that the solid raw material charging device 1401 is configured such that the amount of the solid raw material 1402 charged into the auxiliary crucible 1201 is controlled by, for example, the solid raw material charging control device 1506. Moreover, it is preferable that the solid raw material charging device 1401 is configured so that the solid raw material 1402 can be charged into the auxiliary crucible 1201 at an arbitrary timing.

<Manufacture of crystal thin plate>
When the crystal thin plate 1002 is manufactured using the melting furnace 1000 having the above-described configuration, first, the melt 1102 is held in the main crucible 1101 and the melt 1202 is held in the auxiliary crucible 1201.

  Here, the melt 1102 and the melt 1202 can each be a melt of a substance containing at least one of a metal material and a semiconductor material, for example, a melt such as silicon, but a metal material other than silicon. Alternatively, at least one melt of a semiconductor material (particularly a semiconductor material having a high melting point) may be used.

  Then, the base substrate 1001 is installed in a base substrate immersion apparatus to be described later, and the base substrate 1001 is immersed in the melt 1102 held in the main crucible 1101 to attach the melt 1102 on the surface of the base substrate 1001. As the adhered melt 1102 solidifies, a crystal thin plate 1002 is formed on the surface of the base substrate 1001.

  In FIG. 2, the typical structure of an example of the base substrate immersion apparatus used for this invention is shown. Here, the base substrate immersion apparatus 2000 includes a horizontal operation shaft 2101 that operates in a horizontal direction by a horizontal operation motor (not shown), and a horizontal operation shaft 2101 that is fixed to the horizontal operation shaft 2101 and moves in the horizontal direction. A horizontal axis pedestal 2102 that moves in the horizontal direction, a lifting operation motor 2103 attached to the horizontal axis pedestal 2102, a suspension column 2104 attached to the elevation operation motor 2103 and extending in the vertical direction, and a suspension column 2104. Are attached to one end of the rotating column 2106, a rotating column 2106 that rotates independently of the suspension column 2104, a rotating column 2106 that is fixed to the rotating mechanism 2105 and rotates along with the rotating unit 2105. Auxiliary column 2107 extending in the vertical direction, rotating column 2106 and auxiliary column 2107 Thus it is supported and a fixed base 2108 for mounting the base substrate 1001.

  Here, the horizontal position of the base substrate 1001 mounted on the fixed base 2108 can be controlled by moving the horizontal operation shaft 2101 in the horizontal direction. Further, the vertical position of the base substrate 1001 can be controlled by raising and lowering the suspension column 2104 in the vertical direction by the elevating operation motor 2103. In addition, by rotating the rotating mechanism 2105 and tilting the rotating support 2106 with respect to the horizontal direction, the tilt of the surface of the base substrate 1001 mounted on the fixed base 2108 with respect to the horizontal direction can be controlled.

  In other words, the base substrate immersion apparatus 2000 is configured such that the horizontal position, the vertical position, and the base position of the base substrate 1001 mounted on the fixed base 2108 by the lifting / lowering motor 2103, the horizontal operation motor (not shown), and the rotation mechanism 2105. The inclination of the surface of the substrate 1001 with respect to the horizontal direction can be controlled independently.

  When the crystal thin plate 1002 is manufactured using the base substrate immersion apparatus 2000 having the above-described configuration, the base substrate 1001 is first fitted on the fixed base 2108, and then the base substrate 1001 is moved in the horizontal direction ( Horizontal movement), vertical movement (vertical movement), and rotational movement to move the liquid 1102 directly above the melt 1102 held in the main crucible 1101, and the surface of the base substrate 1001 is the melt 1102 in the main crucible 1101. Carry to the position facing. Then, after the surface of the base substrate 1001 is immersed in the melt 1102 held in the main crucible 1101, the base substrate 1001 is taken out from the melt 1102.

  Under the control of the base substrate 1001 of the base substrate immersion apparatus 2000 described above, the base substrate 1001 is moved, for example, as indicated by an arrow 2120, and the melt 1102 is solidified on the surface of the base substrate 1001. A thin plate 1002 can be obtained. Thereafter, the base substrate 1001 on which the crystal thin plate 1002 is formed is returned to the original position by horizontally moving, vertically moving, and rotating, and the base substrate 1001 on which the crystal thin plate 1002 is formed is removed from the fixed base 2108. Then, a new base substrate 1001 can be fitted and attached to the fixed base 2108, and the next crystal thin plate 1002 manufacturing process can be started.

  For the operation of the base substrate 1001, for example, a horizontal movement command, a vertical movement command, and a rotation operation command for the base substrate 1001 are programmed by a normal personal computer or the like and transmitted to a controller (not shown). As a result, the base substrate 1001 moves along a trajectory as programmed. In addition, the base substrate immersion apparatus 2000 controls the height of the base substrate 1001 (that is, the vertical position of the base substrate 1001), thereby immersing the base substrate 1001 in the melt 1102 (the base substrate 1001's immersion depth). (The shortest vertical distance between the center of the surface on the immersion side of the base substrate 1001 in the melt 1102 and the liquid surface of the melt 1102 when the center of the surface on the immersion side reaches the lowest point) The crystal thin plate 1002 can be manufactured while adjusting so that is within a certain range (for example, the absolute value of the difference between the maximum value and the minimum value of the immersion depth is within a range of 1 mm). Thus, a thin crystal plate 1002 with little variation can be obtained.

<Detection of melt level>
With reference to FIG. 3, an example of a method for detecting the height of the melt 1102 held in the main crucible 1101 will be described.

  Here, the electrical wiring 1051 is connected to the base substrate immersion apparatus 2000, and the electrical wiring 1052 is connected to the main crucible 1101. The electrical wiring 1052 is connected to the power supply device 1508. The electrical wiring 1051 and the electrical wiring 1052 are connected to a melt height detector 1503 via a relay 1509. Thereby, the base substrate immersion device 2000, the main crucible 1101, the power supply device 1508, the relay 1509, and the melt height detector 1503 are connected.

  The base substrate immersion device 2000 and the main crucible 1101 are electrically insulated, and the base substrate 1001 and the base substrate immersion device 2000 are electrically connected. For example, by forming both the base substrate 1001 and the base substrate immersion device 2000 from graphite, it is possible to electrically connect them.

  In the configuration as described above, first, the base substrate 1001 is mounted on the fixed base 2108 of the base substrate immersion apparatus 2000 shown in FIG. Next, the crucible lifting / lowering device 1107 shown in FIG. 1 is operated to adjust the height of the main crucible 1101 to a specified height.

  Then, the base substrate 1001 is moved by, for example, the path of the arrow 2120 shown in FIG. 2 by the base substrate immersion device 2000, and the base substrate 1001 is immersed in the melt 1102 held in the main crucible 1101.

  At the moment when the base substrate 1001 and the melt 1102 come into contact, the base substrate immersion device 2000 and the main crucible 1101 are electrically connected to each other so that the open circuit is switched to the short circuit state. Become. This is because the base substrate immersion apparatus 2000 and the base substrate 1001 are electrically connected, and the melt 1102 and the main crucible 1101 are electrically connected.

  When the electric circuit shown in FIG. 3 is a closed circuit, the DC power supply device 1508 and the relay 1509 are connected, and therefore the relay is performed by the power supply device 1508 at the moment when the base substrate 1001 and the melt 1102 come into contact with each other. A voltage is applied to 1509, and the relay 1509 operates. As a result, the melt height detector 1503 detects a change in electrical resistance, and can grasp the moment when the base substrate 1001 comes into contact with the liquid surface of the melt 1102. That is, it is possible to detect the height of the liquid level of the melt 1102 in the main crucible 1101 using an electric signal when the melt 1102 held in the main crucible 1101 comes into contact with the base substrate 1001.

  Needless to say, any device capable of measuring voltage, current, and resistance may be used instead of the relay 1509 for measuring electrical resistance.

  Then, the coordinates of the base substrate 1001 at the moment when the base substrate 1001 comes into contact with the melt 1102, that is, the moment when the relay 1509 operates are read. For example, when the base substrate 1001 is operated using a servo motor, the position of the base substrate 1001 in operation can be ascertained at any time by a servo motor controller or a higher-order personal computer. The coordinates of the base substrate 1001 at the moment of contact with the melt 1102 can be recognized. Further, the coordinates of the base substrate 1001 at the moment of contact with the melt 1102 can be recognized by geometric calculation based on the position of the horizontal axis base 2102, the position of the suspension column 2104, the rotation angle of the rotation mechanism 2105, and the like. Is possible.

  Thus, based on the coordinates of the base substrate 1001 at the moment when the base substrate 1001 contacts the melt 1102, the horizontal position and the vertical position of the base substrate 1001 at the moment when the base substrate 1001 contacts the melt 1102 are grasped. In addition, the rotation angle of the base substrate 1001 is also grasped. The height of the liquid surface of the melt 1102 is calculated by calculating, for example, as follows from the horizontal position, vertical position and rotation angle of the base substrate 1001 at the moment when the base substrate 1001 contacts the melt 1102. Detection is possible.

  FIG. 4 schematically illustrates an example of a moment when the base substrate 1001 is immersed in the melt 1102 in the present invention. Hereinafter, an example of a method for calculating the liquid level of the melt 1102 will be described with reference to FIG. In FIG. 4, H21 indicates the relative height of the liquid level of the melt 1102 with respect to the horizontal axis pedestal 2102, and H22 indicates the relative height of the lower end 2104a of the suspension column 2104 with respect to the horizontal axis pedestal 2102. Yes. R2 indicates the shortest distance between the contact point 1001a at the moment when the base substrate 1001 contacts the melt 1102 and the lower end 2104a of the suspension column 2104, and A2 connects the contact point 1001a and the lower end 2104a of the suspension column 2104. The inclination angle with respect to the horizontal direction of the straight line is shown.

  Here, the height H21 of the liquid level of the melt 1102 held in the main crucible 1101 can be calculated by the following equation (1).

H21 = R2 × sin (A2) + H22 (1)
Further, when the surface of the base substrate 1001 becomes horizontal in the melt 1102 (when the center of the surface on the immersion side of the base substrate 1001 reaches the lowest point), the lower end of the suspension column 2104 with respect to the horizontal axis pedestal 2102 When the relative height of 2104a is H23 and the distance from the lower end 2104a of the suspension column 2104 to the surface center of the base substrate 1001 is R23, the surface of the base substrate 1001 is immersed from the liquid level of the melt 1102. If the depth is the immersion depth D, the immersion depth D can be calculated by the following equation (2).

D = R23 + H23−H21 (2)
When the immersion depth D is different from the target immersion depth D, for example, the height of the base substrate 1001 in the vertical direction by the difference until the base substrate 1001 is immersed in the next production of the crystal thin plate 1002 and // The height in the vertical direction of the main crucible 1101 is adjusted. By continuing this, it becomes possible to control the immersion depth D of the base substrate 1001 in the melt 1102 to be within a specified range.

  Note that, when the deviation of the immersion depth D is adjusted by the height of the main crucible 1101 in the vertical direction, it is preferable to suppress a rapid change in the trajectory of the base substrate 1001. In addition, it is preferable to take appropriate safety measures in case the correct liquid level of the melt 1102 cannot be detected.

<Inputting solid raw materials>
In general, when manufacturing the crystal thin plate 1002, it is preferable that the temperature of the main crucible 1101 is set to a temperature close to the melting point of the melt 1102 suitable for manufacturing the crystal thin plate 1002. On the other hand, the temperature of the melt 1202 held in the auxiliary crucible 1201 is usually adjusted to a temperature higher than the melting point of the melt 1102 in order to melt the solid material 1402 charged from the solid material charging device 1401. . Therefore, when the amount of the melt 1202 supplied from the auxiliary crucible 1201 to the main crucible 1101 is large, the temperature of the main crucible 1101 increases. In addition, when a large amount of melt is supplied after the amount of the melt 1102 in the main crucible 1101 is significantly reduced, the temperature and temperature distribution of the melt 1102 in the main crucible 1101 change.

  Accordingly, the supply of the melt from the sub crucible 1201 to the main crucible 1101 is preferably performed in small portions so that the level of the melt 1102 in the main crucible 1101 does not change as much as possible.

  For this purpose, rather than inclining the auxiliary crucible 1201 and supplying the melt 1202 to the main crucible 1101 at a time, the melt 1202 overflowed by the amount of the solid raw material 1402 supplied to the auxiliary crucible 1201 as in the present invention. It is preferable to supply the melt to the main crucible 1101 in small portions by using a method of supplying the melt to the main crucible 1101 through the melt transfer unit 1301.

  However, when the amount of the melt 1202 supplied from the sub crucible 1201 is larger than the production amount of the crystal thin plate 1002, the melt 1102 in the main crucible 1101 overflows. Conversely, when the amount of the melt 1202 supplied from the auxiliary crucible 1201 is smaller than the production amount of the crystal thin plate 1002, the amount of the melt 1102 in the main crucible 1101 decreases.

  Therefore, in order to reduce the variation in the quality of the crystal thin plate 1002, simply supplying a certain amount of the solid raw material 1402 at a certain timing may eventually lead to insufficient supply or excessive supply. There is a need to.

  Hereinafter, an example of a method for determining whether or not the solid raw material 1402 is charged and how much solid raw material 1402 is charged in the present invention will be described.

  First, the case where the immersion depth is adjusted by raising and lowering the crucible will be described. In this case, it is assumed that the base substrate passes through a certain trajectory.

  The height of the liquid level of the melt 1102 in the main crucible 1101 (the distance from the bottom surface of the main crucible 1101 to the liquid level of the melt 1102) is adjusted as follows.

  First, an appropriate immersion depth is maintained by adjusting the height of the main crucible 1101 in the vertical direction (hereinafter referred to as “crucible height”) so that the immersion depth of the base substrate 1001 is close to a specified value. can do.

  At this time, when the height of the crucible is in the vicinity of the specified value, it can be determined that the height of the melt 1102 of the main crucible 1101 is close to the specified value. If the crucible height is lower than the specified value, it can be determined that the amount of the melt 1102 in the main crucible 1101 is larger than the specified value. When the crucible height is higher than the specified value, it can be determined that the amount of the melt 1102 in the main crucible 1101 is smaller than the specified value. By utilizing this, the level of the melt 1102 in the main crucible 1101 can be determined, and whether or not the solid raw material 1402 is charged and the amount of the solid raw material 1402 charged can be determined.

  Accordingly, as a method for determining whether or not solid raw material 1402 is charged and how much solid raw material 1402 is charged, the liquid level of melt 1102 in main crucible 1101 is determined based on the crucible height. The method is effective.

  That is, when the crucible height becomes equal to or less than the specified value, it is determined that the amount of the melt 1102 in the main crucible 1101 is too large, and the charging of the fixed raw material 1402 is stopped. On the other hand, when the crucible height is equal to or higher than the specified value, it is determined that the amount of the melt 1102 in the main crucible 1101 is too small, and the solid raw material 1402 is continuously charged.

  According to such a method, the solid raw material 1402 can be charged at an appropriate timing while adjusting the crucible height while manufacturing the crystal thin plate 1002. Further, since it is not necessary to adjust the height of the melt 1102 in the main crucible 1101 by interrupting the manufacture of the crystal thin plate 1002, the productivity of manufacturing the crystal thin plate 1002 can be improved.

  Further, as a more desirable method, the height of the melt 1102 in the main crucible 1101 is determined from the height of the crucible, and the shortage of the melt 1102 in the main crucible 1101 is calculated to be insufficient. This is a method of adding the solid raw material 1402 by the amount.

  In this manner, the crystal thin plate 1002 can be manufactured by determining whether or not the solid raw material 1402 has been charged, the amount to be charged, or both, based on the height of the liquid level of the melt 1102 held in the main crucible 1101. The crucible height can be adjusted without interruption, and the solid material 1402 can be charged at an appropriate timing while maintaining an appropriate substrate height.

  Next, the case where the immersion depth is adjusted according to the height of the base substrate will be described. In this case, it is assumed that the height of the crucible is always fixed at a constant height.

  The height of the liquid level of the melt 1102 in the main crucible 1101 (the distance from the bottom surface of the main crucible 1101 to the liquid level of the melt 1102) is adjusted as follows.

  First, the height of the trajectory in the vertical direction of the base substrate 1001 (hereinafter referred to as “substrate height”) so that the immersion depth of the base substrate 1001 is close to a specified value. The base substrate 1001 depends on the position of the liquid surface of the melt 1102. It is possible to maintain an appropriate immersion depth by adjusting whether to move deeply or shallowly.

  At this time, if the substrate height is in the vicinity of the specified value, it can be determined that the height of the liquid surface of the melt 1102 of the main crucible 1101 is close to the specified value. Further, when the substrate height is higher than the specified value, it can be determined that the amount of the melt 1102 in the main crucible 1101 is larger than the specified value. When the substrate height is lower than the specified value, it can be determined that the amount of the melt 1102 held in the main crucible 1101 is less than the specified value. By utilizing this, the level of the melt 1102 in the main crucible 1101 can be determined, and whether or not the solid raw material 1402 is charged and the amount of the solid raw material 1402 charged can be determined.

  Therefore, as a method of determining whether or not solid raw material 1402 is charged and how much solid raw material 1402 is charged, the liquid level of melt 1102 in main crucible 1101 is determined based on the substrate height. The method is effective.

  That is, when the substrate height is equal to or higher than the specified value, it is determined that the amount of the melt 1102 in the main crucible 1101 is too large, and the charging of the fixed raw material 1402 is stopped. On the contrary, when the substrate height is equal to or less than the specified value, it is determined that the amount of the melt 1102 in the main crucible 1101 is too small, and the charging of the solid material 1402 is continued.

  According to such a method, the solid material 1402 can be introduced at an appropriate timing while adjusting the substrate height while manufacturing the crystal thin plate 1002. Further, since it is not necessary to adjust the height of the melt 1102 in the main crucible 1101 by interrupting the manufacture of the crystal thin plate 1002, the productivity of manufacturing the crystal thin plate 1002 can be improved.

  Further, as a more desirable method, the height of the melt 1102 in the main crucible 1101 is determined from the height of the substrate, and the shortage of the melt 1102 in the main crucible 1101 is calculated to be insufficient. This is a method of adding the solid raw material 1402 by the amount.

  In this manner, the crystal thin plate 1002 can be manufactured by determining whether or not the solid raw material 1402 has been charged, the amount to be charged, or both, based on the height of the liquid level of the melt 1102 held in the main crucible 1101. The crucible height and / or substrate height can be adjusted without interruption, and the solid material 1402 can be charged at an appropriate timing while maintaining the appropriate substrate height.

  In this embodiment mode, the method of determining the height of the liquid level of the melt 1102 in the main crucible 1101 from the resistance change due to electrical contact when the base substrate 1001 contacts the melt 1102 has been described. A method may be used. For example, a method of directly contacting the confirmation member with the liquid level of the melt 1102 in the main crucible 1101 or a method of detecting the height by applying a laser beam to the liquid level of the melt 1102 can be used. However, it is preferable to use a method of detecting the height of the melt 1102 in the main crucible 1101 without interrupting the production of the crystal thin plate 1002.

  In this embodiment mode, the case where the crystal thin plate 1002 is manufactured on the surface of the base substrate 1001 has been described. However, the present invention is applicable to any method for producing and taking out a solid from the melt 1102 of the main crucible 1101. Can do. For example, the present invention can also be applied to a method for producing a solid from a high melting point melt such as a silicon melt, such as a method of pulling up a single crystal ingot in the vertical direction or a method of pulling up a polycrystalline thin plate in the vertical direction. Further, the main crucible 1101 is supplied by supplying the melt 1202 from the auxiliary crucible 1201 while controlling the height of the melt 1102 so that the liquid level of the melt 1102 of the main crucible 1101 is constant. It is possible to produce a solid continuously without greatly changing the temperature of the melt 1102.

  A silicon crystal thin plate 1002 was manufactured on the surface of a base substrate 1001 made of graphite using the melting furnace 1000 having the configuration shown in FIG. 1 and the base substrate immersion apparatus 2000 shown in FIG. Here, graphite was used as the material of the main crucible 1101, and a method of using an electric circuit shown in FIG. 3 was adopted as a method of determining the height of the melt 1102 in the main crucible 1101.

  In this example, while the silicon crystal thin plate 1002 is manufactured 100 times by the method described in the above embodiment, the contact timing between the base substrate 1001 and the melt 1102 is measured every time the crystal thin plate 1002 is manufactured. The immersion depth D was measured by the above equation (2). The difference between the immersion depth D and the specified value was calculated, and the crucible height was always adjusted by the crucible lifting device 1107 so that the immersion depth D approached the specified value. Further, the additional amount of the solid raw material 1402 is 500 g per time, and when the crucible height is equal to or higher than the reference value (0 mm), it is not added.

  Further, in this embodiment, the silicon crystal thin plate 1002 was manufactured in a fully automated manner by using automatic determination by the melt height detector 1503 and the solid material input control device 1506. FIG. 5 shows the relationship between the amount of deviation from the prescribed value of the immersion depth D and the amount of deviation from the reference value of the crucible height when the silicon crystal thin plate 1002 is manufactured in this example.

  As shown in FIG. 5, the immersion depth D was able to be suppressed to approximately the specified value ± 0.5 mm. Also, the height of the crucible was generally within the standard value ± 0.5 mm, and it was confirmed that continuous production of the silicon crystal thin plate 1002 could be performed without causing excessive supply or insufficient supply of the solid raw material 1402.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the present invention, it is possible to perform additional supply of stable raw materials without suspending the production of a crystal thin plate formed on the surface of the base substrate by immersing the base substrate in the melt, and deterioration in quality. Further, it is possible to provide a melting furnace capable of improving the productivity of the crystal thin plate by reducing the variation and improving the production yield of the crystal thin plate.

It is a typical block diagram of an example of the melting furnace of this invention. It is a typical block diagram of an example of the base substrate immersion apparatus used for this invention. It is a figure which shows the electric circuit used for an example of the method of detecting the height of the liquid level of a melt in this invention. It is a schematic diagram illustrating an example of the moment when the base substrate is immersed in the melt in the present invention. It is a figure which shows the relationship between the deviation | shift amount from the regulation value of immersion depth D at the time of manufacture of the silicon crystal thin plate in the Example of this invention, and the deviation | shift amount from the reference value of crucible height. It is a typical block diagram of an example of the conventional melting furnace. It is a typical block diagram of other examples of the conventional melting furnace.

Explanation of symbols

  1000, 3000, 4000 Melting furnace, 1001 Base substrate, 1001a Contact point, 1002 Crystal thin plate, 1051, 1052 Electrical wiring, 1102, 1202, 4102, 4202 Melt, 1103, 1203, 1303, 4103, 4203 Thermal insulation, 1104 4104 Main crucible heating device, 1105, 1205, 4105 Refractory brick, 1106 Main crucible receiver, 1107 Crucible lifting device, 1201, 4201 Sub crucible, 1204, 4204 Sub crucible heating device, 1206 Sub crucible receiver, 1301 Melt conveying unit, 1304 Melt conveying unit heating device, 1401 Solid raw material charging device, 1402 Solid raw material, 1503 Melt height detector, 1504, 1505, 1507 path, 1506 Solid raw material charging control device, 1508 Power supply device, 1509 Relay, 2000 Substrate dipping device, 2101 horizontal operation axis, 2102 horizontal axis pedestal, 2103 lifting operation motor, 2104 suspension column, 2104a lower end, 2105 rotation mechanism, 2106 rotation column, 2107 auxiliary column, 2108 fixed platform, 2120 arrow, 3001 main room, 3002 1st subchamber, 3003 2nd subchamber, 3004 Base substrate gripping device, 3100 1st crucible, 3101 1st crucible preparation chamber, 3102 1st solid material supply device, 3103, 3203, 3303 Solid material 3200, second crucible, 3201, second crucible preparation chamber, 3202 second solid raw material supply device, 3300 third crucible, 3301, third crucible preparation chamber, 3302 third solid raw material supply device, 1101, 4101 Main crucible, 4205 refractory brick, 4206 crucible receptacle, 4207 gap.

Claims (13)

A main crucible for holding a melt of a substance containing at least one of a metal material and a semiconductor material;
A main crucible heating device for heating the melt held in the main crucible;
An auxiliary crucible for holding the melt supplied to the main crucible;
An auxiliary crucible heating device for heating the melt held in the auxiliary crucible;
A solid raw material charging device for charging a solid raw material as a raw material of the melt into the auxiliary crucible;
A melt conveying section for supplying the melt from the sub-crucible to the main crucible,
The melt conveying part is joined to the sub-crucible,
The melt that has overflowed from the auxiliary crucible by supplying the solid raw material to the auxiliary crucible from the solid raw material input device is supplied to the main crucible through the melt conveying unit, Melting furnace. It further comprises a melt transport unit heating device for heating the melt transport unit,
The melting furnace according to claim 1, wherein the melt transport unit is formed of a hollow member that is heated by the melt transport unit heating device.   It further comprises a base substrate dipping device for forming a crystal thin plate formed by solidifying the melt on the surface of the base substrate by being immersed in the melt held in the main crucible, The melting furnace according to claim 1 or 2. A melt height detector for detecting the height of the liquid level of the melt held in the main crucible;
A solid raw material charging control device that determines whether or not the solid raw material is charged into the auxiliary crucible from the solid raw material charging device;
Whether or not the solid raw material input control device supplies the solid raw material to the auxiliary crucible based on the liquid level height of the melt held in the main crucible detected by the melt height detector. The melting furnace according to claim 1, wherein the melting furnace is determined.   The melting furnace according to claim 4, wherein the solid raw material charging control device also determines an input amount of the solid raw material charged into the auxiliary crucible.   It further comprises a base substrate dipping device for forming a crystal thin plate formed by solidifying the melt on the surface of the base substrate by being immersed in the melt held in the main crucible, The melting furnace according to claim 4 or 5. A crucible lifting device for moving the main crucible in a vertical direction based on the height of the liquid level of the melt held in the main crucible detected by the melt height detector;
The melting furnace according to claim 6, wherein an immersion depth of the base substrate in the melt is adjusted by controlling a height of the main crucible by the crucible lifting device.   By controlling the height of the orbit of the base substrate based on the height of the liquid level of the melt held in the main crucible detected by the melt height detector, The melting furnace according to claim 6 or 7, wherein the immersion depth of the base substrate in the melt is adjusted. A melt height detector for detecting the height of the liquid level of the melt held in the main crucible;
A solid raw material charging control device that determines whether or not the solid raw material is charged into the auxiliary crucible from the solid raw material charging device;
A base substrate dipping apparatus for forming a crystal thin plate formed by solidifying the melt on the surface of the base substrate by immersing in the melt held in the main crucible;
A crucible lifting and lowering device for moving the main crucible in a vertical direction based on the height of the liquid level of the melt held in the main crucible detected by the melt height detector;
Based on at least one of the height of the main crucible controlled by the crucible lifting device and the height of the trajectory of the base substrate controlled by the base substrate dipping device, the solid material input controller controls the sub crucible to the sub crucible. The melting furnace according to claim 1, wherein it is determined whether or not a solid raw material is charged.   The solid raw material charging control device also determines the amount of the solid raw material charged into the sub crucible based on at least one of the height of the main crucible and the height of the orbit of the base substrate, The melting furnace according to claim 9.   The melting furnace according to claim 9 or 10, wherein the immersion depth of the base substrate in the melt is adjusted by controlling the height of the main crucible by the crucible lifting device.   The said base substrate immersion apparatus adjusts the immersion depth with respect to the said melt of the said base substrate by controlling the height of the track | orbit of the said base substrate, The any one of Claims 9-11 characterized by the above-mentioned. Melting furnace.   The melt height detector detects the height of the melt surface using an electrical signal when the melt held in the main crucible and the base substrate come into contact with each other. The melting furnace according to any one of claims 4 to 12.

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