JP5079151B1 - Method of absolute liquefaction of silicon melt and high-quality precision casting equipment for silicon crystal using the method - Google Patents

Abstract

Kind Code: A1 A small amount of moisture, oxygen, nitrogen and other outgasses and reaction gases react with a vigorous silicon melt to produce wetness promoting compounds such as silicon dioxide and silicon carbide, and at the same time boron nitride powder, aluminum nitride powder and silicon nitride. It has been extremely difficult to maintain a stable silicon melt for a long period of time in an environment that oxidizes a release material such as powder and lowers the leaching effect of the release material.
In a work space isolated from the atmosphere, a silicon melt holder is surrounded to form an isolation space around the holder, and the work space including the isolation space is evacuated and then evacuated. While preferentially spraying a purified gas composed of a killer gas and a rare gas that removes outgas generated in the work space and the isolation space, into the isolation space or the holder and the silicon melt. Continue to inject.
[Selection] Figure 1

Description

  The present invention relates to a technique for manufacturing a crystal body (hereinafter referred to as a silicon molded body) having a desired shape from a silicon raw material without performing machining such as cutting or cutting.

  Silicon crystals used as materials for solar cells and the like are manufactured as a lump (ingot) of a predetermined size from a melt of silicon raw material. Then, these ingots are subjected to machining such as cutting and cutting so as to have a desired shape necessary for manufacturing a product such as a solar cell substrate (silicon wafer). However, when a desired shape is formed by processing an ingot, the processing takes time and energy, and the waste of the raw material generated by cutting or cutting is difficult to reuse as raw material and must be discarded. There is a problem of causing a great loss of time, energy and resources. In order to reduce these losses, attempts have been made to directly produce thin plate-like silicon (silicon wafer) or pipe-like (tubular) silicon from the melt. The present inventor also produced a shaped crystal manufacturing method and manufacturing apparatus disclosed in JP-A-4-292494 as a method for mass-producing high-quality silicon wafers, and further produced pipe-shaped silicon. As a method for achieving this, a cylindrical silicon crystal manufacturing method disclosed in Japanese Patent No. 469932 has been proposed.

  In the manufacturing method and manufacturing apparatus of the shaped crystal, the raw material of the crystal is heated and melted in a shaping container set in a predetermined atmosphere, and is stored in a shaping jig disposed in the shaping container. It is cooled and crystallized from one end of the shaping jig. Therefore, it becomes possible to manufacture a silicon wafer without cutting or cutting the ingot. In addition, the crystal plane is protected from the outside by the container, so that contamination of the crystal by impurities is reduced, and high-quality crystals can be manufactured. Furthermore, a large number of crystals can be produced in a short time despite the low growth rate by providing a large number of recesses (melt storage portions) in the shaping jig.

Further, in the above cylindrical silicon crystal production method, a melt storage container formed of a material having a smaller thermal expansion coefficient than that of the silicon crystal and a higher melting point, a larger thermal expansion coefficient than that of the silicon crystal, and a melting point of Use cores made of high material. Then, silicon nitride (Si ₃ N ₄ ) is applied to the inner surface of the melt storage container and the outer surface of the core, and the silicon melt is filled into the gap formed by the inner surface of the melt storage container and the outer surface of the core. However, a cylindrical silicon crystal can be manufactured by providing a temperature gradient from the bottom surface side to the upper side of the melt storage container and solidifying the silicon melt while maintaining the liquid-liquid property of the silicon melt.

  However, when the temperature of the electric furnace for holding the silicon melt is increased to a vacuum in an apparatus for manufacturing a silicon molded body such as a shaped crystal or a cylindrical silicon crystal, the surface of a low temperature member such as an inner wall or a heat insulating material is increased. A small amount of outgas (water, oxygen, nitrogen, etc.) is constantly released. On the other hand, in the space inside the electric furnace, there are heaters and heat insulating materials that have reached a high temperature of 1400 ° C. or higher. Therefore, for example, oxygen easily oxidizes silicon to cause oxygen contamination and moisture content. It reacts with the carbon heater to generate carbon monoxide (reactive gas), which causes carbon contamination, and is present as an impurity that degrades the quality of the crystal. For this reason, it is difficult to maintain the quality of the crystal simply by protecting the silicon melt with a container. Therefore, the present inventor has proposed a single crystal growth method disclosed in Japanese Patent Application Laid-Open No. 2009-167073 as a method for removing outgas in the space holding the silicon melt. In this single crystal growth method, an inert gas mixed with 0.01 to 3% monosilane gas or chlorosilane gas (moisture killer gas) is heated and supplied to a crystal growth furnace for crystal growth. The water inside is converted into silicon dioxide, hydrogen and hydrogen chloride, and the water is effectively removed.

JP-A-4-292494 Japanese Patent No. 4693932 JP 2009-167073 A

In order to manufacture a silicon molded body, boron nitride (BN) powder, aluminum nitride (AlN) powder, nitridation is used to prevent adhesion between the silicon molded body and a member such as a mold or container that holds the silicon melt. It is indispensable to use a release material such as silicon (Si ₃ N ₄ ) powder and maintain the molten state of the silicon melt. However, in the enclosed space, as described above, there are trace amounts of outgases and reaction gases such as moisture, oxygen, nitrogen, etc., and the process of raising the temperature of the raw silicon contained in the mold to the melting point (1414 ° C.), While holding the silicon melt, the silicon melt is exposed to these outgases and reaction gases. These gases react with a vigorous silicon melt to produce a wet-promoting compound such as silicon dioxide or silicon carbide, and at the same time oxidize release materials such as boron nitride powder, aluminum nitride powder, and silicon nitride powder to release the release material. Reduces the phlegm efficacy. In such an environment, it has been extremely difficult to maintain the silicon melt in a stable molten state for a long time. Therefore, in the prior art, the actual situation is that mass production of high-quality silicon molded bodies including silicon wafers has not been achieved.

  Therefore, as a result of intensive studies on such a situation, the present inventor has found a method for maintaining the silicon melt in an extremely stable liquid-liquid state, that is, a method for absolute liquidation of the silicon melt. In addition, by using this absolute liquefaction method, it is possible to maintain a stable liquefied state of silicon and to mass-produce high-quality silicon molded products including silicon wafers and cylindrical silicon crystals. Has found a precision casting apparatus for high-quality silicon crystals (hereinafter referred to as precision casting apparatus).

  In the present invention, the molten state means that the high-temperature material melt is in a “non-wetting state” on the surface of the substrate or container that supports it. “Wet” refers to the interaction between the liquid and the surface of the solid, and means that the liquid placed on the surface of the solid spreads uniformly over the surface of the solid. Become spherical. The property that water does not get wet is said to be "water repellency", but this term is for liquids near room temperature, whereas "liquid" is "no wettability" in a wider temperature range. It is a universal expression of "state". In addition, the absolute molten state is a space in which oxygen and moisture that completely inhibit the molten liquid of silicon and other inorganic material melts are removed, and the melt remains on the surface of the holder for a long time due to surface tension. It is a perfect and completely liquid-filled state that has a spherical shape (spherical shape that is flattened by gravity when the diameter exceeds 5 mm) and that has a contact angle as close as possible to 180 degrees.

  In the absolute liquefaction method of a silicon melt according to the present invention, a silicon melt holder is surrounded in a work space isolated from the atmosphere to form an isolation space around the holder, including the isolation space After the work space is evacuated, purified gas composed of a killer gas and a rare gas that removes outgas generated in the work space and the isolation space is placed in the isolation space in the holding tool or the holding tool and the It is continuously injected while spraying the silicon melt preferentially.

  A precision casting apparatus according to the present invention comprises a vacuum vessel forming a work space isolated from the atmosphere and an exhaust means for evacuating the vacuum vessel, and a heating heater and a silicon melt are contained in the vacuum vessel. A holding tool is disposed, the holding tool is surrounded by an isolating means for forming an isolation space around the holder, and a purified gas composed of a killer gas and a rare gas for removing outgas generated in the working space and the isolation space, It is continuously injected into the isolation space while being preferentially sprayed on the holder or the holder and the silicon melt.

In the present invention, killer gas refers to oxygen generated from a holder, a container surrounding the holder, or a jig disposed in the enclosed space in a hermetically enclosed space around the holder such as a storage container. It reacts with outgas components such as water and turns into a substance that is inactive to the silicon melt. They are one or more obtained from monosilane (SiH ₄ ), monochlorosilane (SiClH ₃ ), dichlorosilane (SiCl ₂ H ₂ ), trichlorosilane (SiCl ₃ H), tetrachlorosilane (SiCl ₄ ). A mixture of As an example of a killer gas, a chemical reaction formula in which tetrachlorosilane (SiCl ₄ ) reacts with oxygen, moisture, or the like to change into an inactive substance with respect to the silicon melt is shown below.
SiCl ₄ + 2H ₂ O = SiO ₂ + 4HCl (1)
SiCl ₄ + O ₂ = SiO ₂ + 2Cl ₂ (2)

  According to the absolute liquefaction method according to the present invention, a purified gas composed of a killer gas and a rare gas that removes outgas generated in a work space isolated from the atmosphere or in an isolated space provided in the work space is provided. The remaining amount of outgas components such as moisture and oxygen is measured in the vicinity of the silicon melt by continuously injecting it into the isolation space while preferentially spraying the silicon melt holder and the silicon melt. The following PPT order atmosphere can be obtained. In addition, the purified gas after being preferentially blown to the holder and the silicon melt diffuses from the isolation space to the entire work space, and the residual killer gas in the mixed gas reduces the remaining amount of outgas components in the entire work space. . As a result, the outgas component that reacts with the silicon melt is almost completely removed from the vicinity of the silicon melt, and it is possible to stably maintain the absolute molten state. That is, it is possible to maintain a better liquid-salt state (absolute liquid-salt state) than the liquid-salt state aimed at realization in the prior art.

  In the precision casting apparatus according to the present invention, the silicon melt holder is surrounded by an isolating means for forming an isolating space in a vacuum container that forms a working space isolated from the atmosphere. Inside, the purified gas composed of killer gas and noble gas that removes outgas generated in the work space and in the isolation space is continuously sprayed on the holder or the holder and the silicon melt. Since it is injected, the absolute liquefaction method of the present invention can be carried out to mass-produce high-quality silicon molded bodies.

  As described above, even in the prior art, an attempt has been made to remove the outgas component existing in the space including the silicon melt holder with the killer gas. However, the present inventor has found that in the prior art, the outgas component cannot be removed to the extent necessary to stably maintain the molten state of the silicon melt, and the outgas such as moisture and oxygen It has been found that an absolute liquid smoke state appears by setting the residual amount of the component to an atmosphere of a PPT order (one trillionth) below the measurement limit. Furthermore, in the prior art, since the entire space including the holder was intended to be replaced with a gas that does not react with the silicon melt, the atmosphere in the vicinity of the silicon melt changes due to the flow of the replacement gas or killer gas. As a result, it was found that the liquid smoke state cannot be stably maintained. The present invention is based on this new knowledge.

The silicon sphere obtained by carrying out the absolute liquefaction method of the silicon melt according to the present invention is shown, (a) is a drawing substitute photograph of the appearance, (b) is a drawing substitute photograph of the back surface, and (c) is a central cut surface. It is a drawing substitute photograph. The silicon sphere obtained by carrying out the conventional method of injecting the purified gas into the space containing the silicon melt holder is shown, (a) is a drawing substitute photograph of the appearance, and (b) is a drawing substitute photograph of the back surface. (C) is a drawing substitute photograph of the central cut surface. It is sectional drawing which shows typically the structure of the precision casting apparatus which concerns on this invention. It is a cross-sectional view which shows typically the structure of the other Example of the precision casting apparatus which concerns on this invention. It is a longitudinal cross-sectional view which shows typically the structure of the precision casting apparatus for continuously producing a silicon molded object.

With reference to FIGS. 1 to 3, an embodiment of an absolute liquefaction method of a silicon melt according to the present invention and a precision casting apparatus using the method will be described. The precision casting apparatus shown in FIG. 3 includes a vacuum vessel 1 that forms a work space 30 that is isolated from the atmosphere, and a holder 2 on which a silicon raw material is placed is disposed inside the vacuum vessel 1. The holder 2 is made of a quartz plate having a surface coated with silicon nitride (Si ₃ N ₄ ) as a release material. However, the material of the holder 2 is not limited as long as it has heat resistance capable of holding molten silicon without contaminating silicon, and may be formed of silicon carbide ceramics or the like.

  A heat insulating material 3 is disposed around the holder 2, and a heater 4 is disposed between the holder 2 and the heat insulating material 3. Electric power is supplied to the heater 4 from the outside of the vacuum vessel 1 through a lead wire (not shown), and the heat treatment is controlled from the outside of the vacuum vessel 1.

The vacuum container 1 communicates with the two gas cylinders 8 and 9 through the exhaust gas pipe 5 and the exhaust gas device 6 through the purified gas supply pipe 7. The exhaust device 6 corresponds to the exhaust means of the present invention and employs a known vacuum pump. Of the two gas cylinders 8 and 9, one gas cylinder 8 is filled with argon gas, and the other gas cylinder 9 is filled with tetrachlorosilane (SiCl ₄ ). The mixing ratio of the argon gas and the tetrachlorosilane gas can be adjusted via adjusting valves 10 and 11 provided at the junction of the discharge pipes from the gas cylinders 8 and 9 and the purified gas supply pipe 7.

  A dome-shaped isolation introduction portion 12 is provided in the opening inside the vacuum vessel 1 of the purified gas supply pipe 7. The isolation introducing portion 12 corresponds to the isolation means of the present invention, and an isolation space 31 is formed around the holder 2. The purified gas supplied through the purified gas supply pipe 7 is preferentially sprayed to the holder 2 and the silicon melt 13 thereon without diffusing in all directions of the work space 30. It has become. In addition, in FIG. 3, the arrow drawn inside the introducing | transducing part 12 has shown the flow of purified gas notionally.

  In carrying out the method of absolute liquefaction of silicon melt with this precision casting apparatus, a solid silicon raw material is first placed on the holder 2. Next, the exhaust device 6 is operated, and the inside of the vacuum vessel 1 is brought into a vacuum state (about 0.01 Pa). When the heater 4 is heated to about 800 ° C. in a vacuum state, the exhaust system valve is closed, the adjustment valves 10 and 11 are opened, and injection of the purified gas into the isolation space 31 in the vacuum container 1 is started. At this time, the ratio of tetrachlorosilane in the purified gas is 0.1 to 1%. When the purified gas starts to be injected, the heater 4 is subsequently operated to heat the silicon raw material and raise the temperature to the melting point. At this time, the purified gas composed of a killer gas and a rare gas that removes the outgas generated from the heat insulating material 3 and the heater 4 is preferentially sprayed on the holder 2 and the silicon raw material or silicon melt 13 while inside the isolation space 31. By continuously injecting, the vicinity of the silicon melt 13 can be made into an atmosphere of the PPT order in which the remaining amount of outgas components such as moisture and oxygen is below the measurement limit. Further, the purified gas after being blown onto the holder 2 and the silicon melt 13 diffuses throughout the work space 30 inside the vacuum vessel 1, and the residual killer gas in the purified gas is the remaining amount of outgas components in the entire vacuum vessel 1. Reduce. As a result, the outgas component that reacts with the silicon melt 13 is almost completely removed from the vicinity of the silicon melt 13, and the absolute molten state can be stably maintained. Therefore, by stopping the heater 4 and removing the silicon melt 13 in this state, a high-quality silicon molded body can be manufactured.

Silicon spheres were created using the precision casting apparatus shown in FIG. The conditions for creation are as follows.
Internal pressure of vacuum vessel: 1 atm (100 KPa)
Noble gas species and purity: Argon gas, 99.9999%
Purified gas composition: argon gas 99-99.9%, tetrachlorosilane gas 0.1-1%
Purified gas injection amount: 300 cm ³ / min Further, as a comparative example, the separation introducing portion 12 was not provided, and purified gas was injected into the vacuum vessel 1 by a conventional method, and silicon spheres were created under the same conditions as described above. FIG. 1 shows a silicon sphere obtained by solidification from the absolute liquid-cooled state when the isolation introducing portion 12 is provided. Further, FIG. 2 shows a silicon sphere obtained by solidifying from a conventional liquid-salt state when the isolation introducing portion 12 is not provided.

  The silicon sphere shown in FIG. 1 has a spherical shape whose shape is flattened by gravity, and has a specular gloss on its surface as shown in FIG. This indicates that there is no impurity contamination. Further, on the back surface, no adhesion of the silicon nitride powder of the release material was observed at the portion indicated by the solid arrow line in FIG. 1 (b), and further, as indicated by the broken arrow line in FIG. 1 (b). The outline of the contact portion with the release material is unclear. Furthermore, as shown in FIG. 1 (c), since there is no interaction with the release material, the contact angle θ is 174 degrees which is as close as possible to 180 degrees. On the other hand, the surface of the silicon sphere shown in FIG. 2 is cloudy as shown in FIG. This is because it is covered with silicon carbide and indicates that there is impurity contamination. In addition, on the back surface, adhesion of the silicon nitride powder of the release material is observed in the portion indicated by the solid arrow in FIG. 2B, and further, the release material indicated by the broken arrow in FIG. The outline of the contact part with the is clearly shown. Furthermore, as shown in FIG. 2C, the contact angle θ is 156 degrees smaller than 180 degrees due to the interaction with the release material. As a result, it was confirmed that according to the present invention, a silicon molded body with higher quality than before can be produced.

  In the precision casting apparatus shown in FIG. 3, silicon spheres are manufactured, but a silicon wafer or a cylindrical silicon crystal can be manufactured by changing the shape of the holder 2. Further, in the precision casting apparatus shown in FIG. 3, for convenience of explanation, only one product is manufactured in one batch. However, the vacuum vessel 1 and the isolating introduction part 12 are formed in a tunnel shape, and a large number of holders 2 are provided. It is also possible to mass-produce by supplying continuously. An embodiment of a precision casting apparatus suitable for mass production of silicon wafers will be described with reference to FIGS. 4 and 5, parts that are substantially the same as those of the precision casting apparatus shown in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted or simplified.

  The holder 20 of the precision casting apparatus shown in FIG. 4 includes a hollow box 21 and a core 22 that is slidably disposed inside the box 21. The core 22 has a comb-like shape in which a plurality of parallel slits are provided in a columnar body, and a silicon wafer can be manufactured by the following procedure. First, a solid silicon raw material is placed inside the box 21 and the entire holder 20 containing the silicon raw material is heated with the core 22 fitted therein. When the silicon raw material becomes a silicon melt, the core 22 is moved downward to allow the silicon melt to flow into the slit. And if it cools slowly in that state, a silicon wafer can be manufactured. Note that a rod body 23 extends from the upper surface of the core 22, and the core 22 can be moved downward by pushing down the rod body 23 with a handle 24 extending to the outside of the vacuum vessel 1. It is possible.

  As shown in FIG. 5, the vacuum vessel 1 of this precision casting apparatus has a tunnel shape extending in the horizontal direction, and the isolation introducing portion 12 is also formed in a tunnel shape extending in the horizontal direction. In FIG. 5, the position of the discharge pipe 5 does not coincide with the position shown in FIG. 4 for convenience of illustration. Also, the relationship between the sizes of the parts is not accurate for the convenience of illustration.

  A conveyor 14 that moves in the horizontal direction indicated by a white arrow in FIG. 5 is installed inside the vacuum vessel 1. The supply section S <b> 1 and the heating section are sequentially arranged from the upstream side (right side in FIG. 5) of the conveyor 14. S2, a pushing section S3, and a slow cooling section S4. The supply section S1 is an area for supplying the holding tool 20 including the silicon raw material with the core 22 on the upper side to the precision casting apparatus. The holding tool 20 is mounted on the conveyor 14 by an interlock mechanism (not shown). It is good also as partitioning with the field to set. The heating section S2 is a region in which the holder 20 is heated and the silicon raw material is used as a silicon melt, and the holder 20 placed on the conveyor 14 in the supply section S1 is first transported to the heating section S2. become. The pushing section S3 is an area for pushing the core 22 downward by the handle 24 and allowing the silicon melt to flow into the slit of the core 22, and the holder 20 heated in the heating section S2 is inserted into the pushing section S3. Will be transported. The slow cooling section S4 is a region where the silicon melt is slowly cooled. At the end of the slow cooling section S4, the silicon melt flowing into the slit of the core 22 is solidified, and a plate body having the same shape as the slit, It becomes a silicon wafer.

  In this precision casting apparatus, the isolation introducing portion 12 has a tunnel shape, and the purified gas injected from the insertion hole of the handle 24 flows in the direction indicated by the arrow in FIG. The atmosphere necessary for absolute liquefaction can be maintained. Therefore, a large number of silicon wafers can be continuously manufactured using a large number of holders 20.

  Furthermore, the holder 20 is composed of a melt storage container having a cylindrical recess and a cylindrical core, and a silicon melt is filled into a gap formed by the outer surface of the core and the inner surface of the melt storage container. If it does, cylindrical silicon crystal can be manufactured continuously. And the cylindrical silicon crystal obtained in that case has higher surface purity than the conventional silicon crystal, and surface treatment such as cutting becomes unnecessary. In order to easily take out the solidified silicon crystal, the melt storage container is made of a material having a lower thermal expansion coefficient and a higher melting point than that of the silicon crystal, and the core is more thermally expanded than the silicon crystal. It is made of a material having a large coefficient and a high melting point. Further, a release material such as silicon nitride powder is applied to the outer surface of the core and the inner surface of the melt storage container.

  In the precision casting apparatus shown in FIG. 3 or FIG. 4 and FIG. 5, the composition of the purified gas supplied from the gas cylinder 7 is argon and tetrachlorosilane, but the composition of the purified gas depends on the situation inside the vacuum vessel 1. It can be selected as appropriate. For example, as the killer gas, monosilane, monochlorosilane, dichlorosilane, or trichlorosilane may be used instead of tetrachlorosilane, or a mixture of two or more of these killer gases may be used.

  Needless to say, the precision casting apparatus shown in FIGS. 4 and 5 can be applied to a conventional batch or continuous silicon ingot manufacturing method to produce high-quality single crystals and polycrystals. In this case, when the silicon melt holders 2 and 20 are for polycrystalline silicon, they are containers having a square cross section, and for the single crystal silicon, the seed crystal is placed on the bottom of the container.

DESCRIPTION OF SYMBOLS 1 Vacuum container 2, 20 Holder 3 Heat insulating material 4 Heater 5 Exhaust pipe 6 Exhaust device 7 Purified gas supply pipe 8, 9 Gas cylinder 10, 11 Control valve 12 Isolation introduction part 13 Silicon melt 14 Conveyor 21 Box 22 Core 23 Rod 24 Handle 30 Work space 31 Isolation space S1 Supply section S2 Heating section S3 Push section S4 Slow cooling section

Claims (5)

In a work space isolated from the atmosphere, a silicon melt holder is surrounded to form an isolation space around the holder, and the work space and the isolation are evacuated together with the isolation space. Purified gas composed of a killer gas and a rare gas that reacts with an outgas component generated in the space to remove the outgas by changing the material into an inactive substance with respect to the silicon melt , in the isolation space, the holder or An absolute liquefaction method of a silicon melt, wherein the silicon melt is continuously injected while being preferentially sprayed onto the holder and the silicon melt. The killer gas may be one or two types obtained from monosilane (SiH ₄ ), monochlorosilane (SiClH ₃ ), dichlorosilane (SiCl ₂ H ₂ ), trichlorosilane (SiCl ₃ H), and tetrachlorosilane (SiCl ₄ ). The method for absolute liquefaction of a silicon melt according to claim 1, which is a mixture of the above. A vacuum vessel that forms a work space isolated from the atmosphere; and an evacuation unit that evacuates the vacuum vessel, wherein a heater for heating and a holder for silicon melt are disposed in the vacuum vessel, and the holder Is surrounded by an isolating means for forming an isolating space around it, and reacts with an outgas component generated in the working space and the isolating space to remove the outgas by changing to an inactive substance with respect to the silicon melt. Purified gas composed of a rare gas and a rare gas is continuously injected into the isolation space while being preferentially sprayed onto the holder or the holder and the silicon melt. Precision casting equipment for silicon crystals.   The holder is composed of a hollow box and a core having a tooth shape provided with a plurality of parallel slits in a columnar body, and the core is movably disposed inside the box, The precision casting apparatus for high-quality silicon crystals according to claim 3, wherein the precision casting apparatus is capable of moving from a state in which a space for storing the silicon melt is formed on a bottom side of the box to a state in which the space is closed.   The holder is formed of a material having a smaller thermal expansion coefficient and a higher melting point than that of the silicon crystal and having a cylindrical recess, and a material having a higher thermal expansion coefficient and a higher melting point than that of the silicon crystal. The high quality silicon | silicone of Claim 3 comprised by the cylindrical core formed by this, and the space | gap which fills the said silicon melt with the outer surface of the said core and the inner surface of the said melt storage container is formed. Precision casting equipment for crystals.