JP4069682B2 - Single crystal manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the structure of a single crystal manufacturing apparatus for growing a single crystal rod by the Czochralski method (CZ method).
[0002]
[Prior art]
An example of a conventional single crystal manufacturing apparatus using the CZ method used for manufacturing a semiconductor single crystal will be described with reference to FIG. Here, silicon is shown as an example of a single crystal. Since a silicon single crystal manufacturing apparatus has high-temperature molten silicon exceeding 1420 ° C. inside, the apparatus components generally have a water-cooled structure. For example, as shown in FIG. 2, the CZ method silicon single crystal manufacturing apparatus 20 includes a water cooling chamber 31, a crucible 32 provided in the water cooling chamber 31, a heater 34 disposed around the crucible 32, and a crucible 32. A crucible shaft 33 that supports and rotates the rotating shaft (not shown), a seed chuck 6 that holds the silicon seed crystal 5, a wire 7 that pulls up the seed chuck 6, and a winding that rotates or winds the wire 7. A take-off mechanism (not shown) is provided. The water cooling chamber 31 has a stainless steel water cooling jacket structure, and cools the chamber wall by passing cooling water through the water cooling chamber wall.
[0003]
The crucible 32 is provided with a quartz crucible 32a for containing molten silicon (hot water) 2 on the inner side, and a graphite crucible 32b on the outer side. The crucible 32 is supported by a crucible shaft 33 which is a stainless steel water-cooled shaft through a carbon pedestal 36.
The heater 34 is provided with a heater electrode 14 for supplying electric power to the heater, and the heater electrode 14 is also water-cooled. A heater heat insulating material 35 is disposed around the outside of the heater 34.
[0004]
Next, a single crystal growth method using the silicon single crystal manufacturing apparatus 20 will be described. First, a high-purity polycrystalline silicon raw material of silicon is heated to a melting point (about 1420 ° C.) or higher in the crucible 32 and melted. Then, by unwinding the wire 7, the tip of the seed crystal 5 is brought into contact with or immersed in the approximate center portion of the molten metal surface 3 of the molten silicon 2. Thereafter, the crucible shaft 33 is rotated in an appropriate direction, and the wire 7 is wound in a direction opposite to the crucible 32 and the seed crystal 5 is pulled up to start growing a single crystal. Thereafter, the single crystal rod 1 having a substantially cylindrical shape can be obtained by appropriately adjusting the pulling speed of the wire 7 and the melt temperature.
[0005]
[Problems to be solved by the invention]
Both the quartz crucible 32a and the graphite crucible 32b in the single crystal pulling apparatus described above have high heat resistance, but are somewhat brittle and have the disadvantage of poor impact resistance. For this reason, when pulling the single crystal, when the polycrystalline raw material is filled in the crucible 32 and heated and melted, the molten polycrystal lump is broken in the crucible 32, and the crucible 32 is broken by the impact and cracks are generated. There is a possibility that the molten silicon 2 leaks from there. In order to increase the efficiency of single crystal growth, a multiple pulling method (multiple pulling method) in which a polycrystalline raw material is recharged without solidifying the residual melt after pulling up to obtain a plurality of single crystal rods from one quartz crucible. CZ Method) is widely used, but the risk of the molten silicon 2 flowing out of the crucible 32 during operation, such as breakage of the crucible 32 during refilling of the polycrystalline material at this time, or scattering of the molten silicon 2, etc. There is sex. In addition, although rarely, when a large shake caused by an earthquake or the like is brought to the pulling device, the molten silicon 2 in the crucible 32 may flow out of the crucible 32 by swinging the pulling machine to the left or right. It is thought. Further, when the crucible 32 gradually deteriorates due to use or the single crystal rod 1 being pulled falls, the crucible 32 is destroyed and almost all the molten silicon 2 contained in the crucible 32 is contained. There is also a risk of leaking.
[0006]
Thus, when high-temperature molten silicon flows out of the crucible and scatters, it reaches the bottom of the chamber 31 from around the crucible, and cools the bottom of the chamber 31, the metal part such as the heater electrode 14 or the crucible shaft 33, or the like. Therefore, the lower cooling water pipes and the like disposed in these inner walls are eroded. In particular, since the molten silicon 2 heated to a high temperature has a strong erosion action on the metal, when the molten silicon 2 leaks and comes into contact with a metal part made of stainless steel or the like, parts such as a water-cooled chamber are melted down due to a lowering of the melting point due to ferrosilicon generation There is also a risk that the cooling water is blown out and vaporized, the water cooling chamber is filled with high-pressure steam, and in the worst case, a steam explosion occurs.
[0007]
In order to prevent this, a carbon hot water leak receiver 15 is generally installed in the lower part of the water cooling chamber 31. However, when the molten silicon 2 scattered on the heater 34 is transmitted from the heater 34 and contacts the heater electrode 14, or when the molten silicon 2 leaking from the crucible 32 reaches the crucible shaft 33 made of stainless steel through the pedestal 36, The molten silicon 2 comes into direct contact with these water-cooled metal parts. Further, if the carbon hot water leak receiver 15 is cracked, the molten silicon 2 comes into direct contact with the inner surface of a metal part such as the water cooling chamber 31.
[0008]
In particular, with the recent increase in the diameter of silicon single crystals, the amount of molten silicon accommodated in the crucible increases and may reach 100 kg or more, or 300 kg or more. Even if such a large amount of molten silicon leaks from the crucible, there has been a demand for a method that can reliably avoid danger.
[0009]
Therefore, the present invention has been made in view of such conventional problems, and in a single crystal manufacturing apparatus, the molten raw material flows out of the crucible due to an accident or the like, and contacts the inner surface of the water cooling chamber. Even so, the main purpose is to make the single crystal production apparatus more safe and to produce the single crystal more stably so that the danger of steam explosion in the water cooling chamber can be prevented.
[0010]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems is an apparatus for producing a single crystal by the Czochralski method, comprising at least a water-cooled chamber, a crucible containing raw material polycrystal, and a heater for melting the raw material polycrystal. The single-crystal manufacturing apparatus is characterized in that the water-cooling chamber is obtained by coating the inner surface of at least a part of the water-cooling chamber located below the crucible with a material that is hardly meltable with respect to the molten raw material. It is .
[0011]
As described above, the single crystal manufacturing apparatus in which the inner surface of at least a part of the water-cooling chamber located at the lower part of the crucible is coated with a material that is hardly meltable with respect to the molten raw material has a molten raw material due to an accident such as breakage of the crucible. Even if it leaks into the lower part of the water cooling chamber and comes into contact with the inner surface of the water cooling chamber, it can prevent the stainless steel parts constituting the water cooling chamber from being melted down. Thus, the production apparatus can be made a safer structure, and a single crystal can be produced more stably.
[0012]
In this case, at least a part of the inner surface to which the coating of the water cooling chamber is applied is such that when all of the molten raw material contained in the crucible leaks into the lower part of the water cooling chamber, the leaked molten raw material enters the lower part of the water cooling chamber. It is preferably the inner surface of the water cooling chamber that will be filled and contacted .
[0013]
Thus, when at least a part of the inner surface to which the coating of the water cooling chamber is applied leaks all the molten raw material contained in the crucible into the lower part of the water cooling chamber, the leaked molten raw material is lower in the lower part of the water cooling chamber. If the inner surface of the water-cooled chamber is filled with, i.e., the amount of the molten raw material in the crucible leaks to the lower part of the water-cooled chamber, for example, at least the portion below the raw material melt surface If it is coated, the risk of the metal surface of the water-cooled chamber coming into direct contact with the molten raw material is greatly reduced, so that the single crystal manufacturing apparatus can be made safer.
[0014]
In this case, the material that is hardly meltable with respect to the melting raw material may be ceramics .
In this way, if a material that is difficult to melt with respect to a molten raw material, such as silicon, is ceramic, the ceramic is less likely to be eroded by molten silicon and has high heat resistance. If it is coated, the safety | security of the manufacturing apparatus of a single crystal can be improved more.
[0015]
Note that, for example, molten silicon is said to dissolve all materials. However, in the present invention, the difficulty of melting with respect to the molten raw material has a sufficiently low reactivity with respect to such an active molten raw material. Say things. That is, for example, even if it is in direct contact with the molten raw material, the surface is only eroded and the whole does not melt, and before that, the molten raw material solidifies and loses its activity. Examples of such a material include the above-mentioned ceramics, particularly oxide ceramics (for example, Y ₂ O ₃ ), SiC, SiN, and the like when the melting raw material is silicon.
[0016]
In this case, it is preferable that the hardly fusible substance with respect to the molten raw material is coated by thermal spraying .
This is because if the coating is performed by thermal spraying, the cost required for coating is low and the coating is difficult to peel off.
[0017]
In this case, it is preferable that the heater electrode for supplying electric power to the heater and / or the crucible shaft for supporting the crucible is coated with a hardly meltable material on the molten raw material .
[0018]
As described above, when a molten raw material such as silicon leaks, the molten silicon scattered in the heater contacts the water-cooled heater electrode, or the molten silicon travels through the pedestal and contacts the stainless steel water-cooled crucible shaft. However, these heater electrodes and crucible shafts are also coated with a material that is hardly meltable with respect to the molten raw material, so that a safer structure can be obtained.
[0019]
Hereinafter, the present invention will be described in detail.
Conventionally, in a single crystal manufacturing apparatus, as a countermeasure when a molten raw material leaks from a crucible, by providing a carbon hot water leak receiver as described above, the molten raw material and the water-cooled metal part of the manufacturing apparatus are provided. Techniques to prevent contact were common. However, even if a hot water leak receiver is provided, there still remains a risk that the metal parts and the molten raw material are in direct contact due to damage of the hot water leak receiver.
[0020]
Accordingly, the present inventor has conceived that at least a part of the inner surface of the water-cooled chamber is coated with a material that is hardly meltable on the molten raw material. In the conventional apparatus, even if a hot water leak receiver or the like is provided (for example, see Japanese Patent Publication No. 6-43276), the inner surface of the water cooling chamber has not been coated. In this case, however, in the unlikely event that the hot water leak receiver is damaged, direct contact between the water cooling chamber and the molten raw material is inevitable. Therefore, the present inventors have found that the possibility of steam explosion can be greatly reduced by coating at least a part of the inner surface of the water-cooled chamber that will come into contact with the molten raw material in the event of an accident. .
[0021]
In this case, it is not always necessary to coat the entire inner surface of the water cooling chamber. For example, in determining the portion of the inner surface of the chamber to be coated, at least when the molten raw material contained in the crucible leaks to the lower part of the water cooling chamber, the leaked molten raw material fills the lower part of the water cooling chamber. If the inner surface of the water-cooled chamber that is to be contacted is coated, when the molten raw material leaks, the portion that is in direct contact with the molten raw material is coated, so the inner surface of the water-cooled chamber may be damaged. And the time and cost for coating can be minimized.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is an explanatory view of a main part of a silicon single crystal manufacturing apparatus according to the present invention. Note that components having the same functions as those of the conventional example are denoted by the same reference numerals as those in FIG. For the sake of simplicity, the silicon single crystal rod 1, the seed crystal 5, the seed chuck 6 and the wire 7 in FIG. 2 are omitted.
[0023]
As shown in FIG. 1, the silicon single crystal manufacturing apparatus 10 has a structure that is substantially the same as that of a conventional apparatus. However, this apparatus is characterized in that a part of the inner surface of the water cooling chamber 31 located under the crucible 32 is coated with a coating material 40 which is a material that is hardly meltable with respect to molten silicon. In the example of FIG. 1, the coating material 40 is made of ceramics excellent in heat resistance, more specifically, Y ₂ O ₃ (yttrium oxide) which is an oxide ceramic. However, other ceramics or a material that is hardly meltable with respect to molten silicon other than ceramics may be used for the coating material.
[0024]
In the example of FIG. 1, the covering material 40 is coated by thermal spraying. Thermal spraying is a surface treatment technique in which a thermal spray material is heated by a heat source, sprayed onto a component in a molten state, and solidified by collision to form a coating. By coating by thermal spraying, the cost of coating can be reduced, and the coated coating material has an advantage that it is difficult to peel off. However, coating can also be performed by a method other than thermal spraying such as a CVD method.
[0025]
A broken line 50 in FIG. 1 is a liquid level position when all the amount of molten silicon in the crucible leaks. If at least the inner surface below the liquid level 50 is coated in the water-cooled chamber 31, the portion where the molten silicon 2 directly contacts when the molten silicon 2 leaks is coated. The danger can be greatly reduced. Further, since the liquid level of the leaking silicon may be vibrated, it is desirable that the covering material 40 is coated even slightly above the liquid level 50 of the water cooling chamber.
[0026]
Further, in the example of FIG. 1, the heater electrode 14 and the crucible shaft 33 are also coated with the coating material 40 by thermal spraying, and these metal parts to be water-cooled are in direct contact with the leaked molten silicon 2. Protected. As a result, the device 10 has a safe structure.
[0027]
Moreover, in the apparatus of the present invention, since the coating is directly applied to the inner surface of the water cooling chamber, it is possible to apply the coating to the conventional apparatus as it is without changing the temperature distribution in the furnace. Accordingly, there is an advantage that a silicon single crystal can be produced by the Czochralski method under the same conditions as those of the conventional apparatus. Moreover, in this apparatus 10, even if there is an accident in which all of the molten silicon 2 in the crucible 32 leaks to the lower part of the water cooling chamber 31 due to cracking of the crucible 32, at least the metal part to be water cooled below the liquid level 50 is Since all of the molten silicon 2 is coated with the hardly meltable coating material 40, the possibility of cooling water flowing into the furnace due to melting damage is low, and it is possible to manufacture a silicon single crystal more safely than before. it can.
[0028]
(Experiment)
A test was conducted in which a stainless steel (SUS 316L) of the same material as the water-cooled chamber was coated with ceramic and immersed in molten silicon. First, a φ20 mm × 200 mm stainless steel rod was prepared. As shown in FIG. 3, the stainless steel rod 60 is configured such that cooling water circulates through the inside of the rod except for a portion up to 50 mm from the tip, so that the upper portion of the stainless steel rod is cooled from the inside. It has become. Next, coating was performed by spraying a coating material 61 made of Y ₂ O ₃ on the stainless rod 60 (coating thickness of about 0.5 mm). Next, a granular silicon polycrystalline raw material was charged into a quartz crucible of a single crystal pulling apparatus that was separately prepared, and then melted by heating with a heater. And after immersing the tip 30mm of the stainless rod 60 which performed the said coating in the molten silicon in a crucible for 30 minutes, it pulled up from the molten silicon and observed the presence or absence of melt | dissolution.
[0029]
As a result of observation, the coated stainless steel rod 60 showed no melting damage even after 30 minutes. Further, by cutting the immersed portion of the stainless steel rod 60, observation of the cross section, change the inner portion of the stainless steel Y ₂ O ₃ coated was not observed to prevent erosion by a coating I found that I was able to. Usually, the leaked molten silicon is solidified and loses its activity for about 10 minutes. Therefore, if such a coating is applied to the water-cooled chamber, it is possible to sufficiently prevent the molten silicon from being melted.
For comparison, as shown in FIG. 4, the tip 30 mm of the uncoated stainless rod 70 was similarly immersed in molten silicon for 10 minutes and then pulled up from the molten silicon. The stainless steel rod 70 that was not coated had all the immersed parts dissolved in the molten silicon in a few minutes.
[0030]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably prevent the trouble of melting failure of the water-cooled chamber at the time of occurrence of leakage of the molten raw material, particularly the danger of steam explosion, for example, when using a large volume of molten raw material. However, it is possible to produce a single crystal safely and stably.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a silicon single crystal manufacturing apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing a conventional silicon single crystal manufacturing apparatus.
FIG. 3 is a schematic view showing a coated stainless steel rod used in the experiment.
FIG. 4 is a schematic view showing an uncoated stainless steel rod used in the experiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon single crystal rod, 2 ... Molten silicon (hot water), 3 ... Hot water surface, 5 ... Seed crystal, 6 ... Seed chuck, 7 ... Wire,
10, 20 ... Silicon single crystal manufacturing equipment,
14 ... heater electrode 15 ... hot water leak receiver,
31 ... Water-cooled chamber, 32 ... Crucible, 32a ... Quartz crucible,
32b ... graphite crucible, 33 ... crucible shaft, 34 ... heater,
35 ... heater insulation, 36 ... pedestal,
40 ... covering material,
50: Liquid level when all of the molten silicon in the crucible leaks.
60, 70 ... stainless steel bar, 61 ... coating material.

Claims (4)

An apparatus for producing a single crystal by the Czochralski method, comprising at least a water cooling chamber, a crucible containing raw material polycrystals, and a heater for melting the raw material polycrystals, wherein the water cooling chamber is a lower part of the crucible A single crystal characterized in that at least a part of the inner surface of the water-cooled chamber located in the substrate is coated with one of Y ₂ O ₃ , SiC, and SiN, which are ceramics that are hardly fusible to the melting raw material Manufacturing equipment.   At least a part of the inner surface to which the coating of the water cooling chamber is applied is such that when all of the molten raw material contained in the crucible leaks to the lower part of the water cooling chamber, the leaked molten raw material is filled in the lower part of the water cooling chamber. The single crystal manufacturing apparatus according to claim 1, wherein the single crystal manufacturing apparatus is an inner surface of a water-cooled chamber to be contacted. The molten material Y _{2 O} 3 is hardly meltable ceramic respect, _SiC, single crystal manufacturing apparatus according to claim 1 or claim 2, wherein the SiN are those coated by spraying . Further, a heater electrode for supplying electric power to the heater and / or a crucible shaft for supporting the crucible is coated with one of Y ₂ O ₃ , SiC, and SiN which is a hardly fusible ceramic with respect to the melting raw material. The apparatus for producing a single crystal according to any one of claims 1 to 3 , wherein the apparatus is a single crystal.

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