JP6522963B2 - Casting apparatus and method of manufacturing ingot - Google Patents

Description

  The present invention relates to a casting apparatus and a method of manufacturing an ingot.

  An example of a general casting apparatus for producing an ingot of polycrystalline silicon or the like is shown in FIG. As shown in FIG. 12, the casting apparatus S comprises an upper structure S1 and a lower structure S2.

  In the upper structure S1, a crucible 11 for melting the raw material silicon is disposed, and a heating means 12 is disposed around the crucible 11. Then, the silicon melt 4 is supplied from the crucible 11 to the lower structure S1 disposed therebelow.

  The lower structure S2 has an opening 1c into which the silicon melt 4 is poured, and a mold 1 having a release material layer 2 on the inner wall is disposed. A heat insulating material 3 is provided outside the mold 1. Further, a mold holder 5 and a cooling means 7 are provided below the mold 1. Further, above the mold 1, a mold heating means 6 for heating the melt 4 in the mold 1 to control the solidification thereof is disposed.

  The mold 1 is configured, for example, by combining one bottom member 1 a and four side members 1 b. The release material layer 2 is coated on the inner wall of the mold 1. The heat insulator 3 suppresses heat removal from the mold sidewall.

  The melt 4 is heated by the mold heating means 6 from above the mold 1. Then, by cooling the melt 4 in the mold 1 from the lower side by the cooling means 7, it is possible to form a temperature distribution gradient from the upper side to the lower side in the melt 4 in the mold 1 and the solidified ingot. Thereby, the melt 4 can be directionally solidified from the bottom to the top to obtain an ingot of polycrystalline silicon (see, for example, Patent Document 1 below).

  Further, as a method of cooling the bottom of the mold 1 for one-way solidification, by making the thermal conductivity of the central member and the peripheral member of the mold holder 5 different, the central portion of the bottom member 1a of the mold 1 and the side member 1b There has been proposed a method of adjusting the ratio of heat removal from the portion directly below (see Patent Document 2 below).

  Further, a chill plate (corresponding to the mold holder 5) having a grid-like penetrating portion is brought into contact with the mold 1, and a heat absorbing plate (corresponding to the cooling means 7) is provided below it, using heat radiation and heat conduction. A method for cooling the mold 1 has also been proposed (see Patent Document 3 below).

Unexamined-Japanese-Patent No. 9-263489 gazette JP, 2005-152985, A JP, 2002-103610, A

The melt 4 is cooled and solidified according to the heat removal from the bottom member 1 a and the side member 1 b of the mold 1 and the heat removal / heating from the upper surface of the melt 4. At this time, during solidification and during cooling after solidification, the temperature distribution of the ingot and the solidification rate cause the residual stress in the ingot. And, since the crystal defects in the ingot are generated due to the residual stress, the cracks caused by the crystal defects are generated at the time of cutting the ingot.

  Therefore, one of the objects of the present invention is to make it possible to easily control the amount of heat removal from the bottom of the mold when casting an ingot containing silicon as a main component, and to make it difficult for cracks to occur in the ingot. It is an object of the present invention to provide a casting apparatus and an ingot manufacturing method that can

In order to achieve the above object, a casting apparatus according to one aspect of the present invention has a bottom, and a mold for holding and solidifying a silicon-based melt and a mold disposed under the bottom of the mold ,
Between the cooling means having a cooling surface on the upper surface, the cooling face of the cooling means and the bottom of the mold, the cooling face of the cooling means is disposed in non-contact with the bottom. A plate-like member whose main surface is opposed to the plate-like member, and the plate-like member has through holes at portions facing the bottom of the mold and the cooling surface of the cooling means, respectively. A mold holder which contacts the mold and the cooling means , holds the plate member, and further includes a mold holder having an opening, and the area ratio of the through hole of the plate member to the opening area of the mold holder is 0. It is more than 02 and less than 0.8.

  In the method of manufacturing an ingot according to an aspect of the present invention, after the silicon melt is put into the mold, the melt is adjusted from the bottom of the mold while adjusting the heat removal amount from the mold by the plate member Solidify upward in one direction.

  According to the above-described casting apparatus and method for producing an ingot, since the heat removal amount by the cooling means from the bottom of the mold can be easily controlled, control of the temperature distribution and temperature gradient in the ingot during solidification and after solidification is carried out. It will be easier. As a result, residual stress in the ingot can be reduced, and crystal defects such as dislocations are less likely to be generated in the ingot, and cracking due to crystal defects can be reduced.

FIG. 1 is a cross-sectional view showing the configuration of a casting apparatus according to an embodiment of the present invention. Fig. 2 is a view showing a plate-like member constituting the casting apparatus according to the embodiment of the present invention, Fig. 2 (a) is a plan view, and Fig. 2 (b) is an AA of Fig. 2 (a). FIG. Fig. 3 is a view showing a plate-like member constituting the casting apparatus according to the embodiment of the present invention, Fig. 3 (a) is a plan view, and Fig. 3 (b) is an AA of Fig. 3 (a). FIG. Fig. 4 is a view showing a plate-like member constituting the casting apparatus according to the embodiment of the present invention, Fig. 4 (a) is a plan view, and Fig. 4 (b) is an AA of Fig. 4 (a). FIG. Fig. 5 is a view showing a plate-like member constituting the casting apparatus according to the embodiment of the present invention, Fig. 5 (a) is a plan view, and Fig. 5 (b) is an AA of Fig. 5 (a). FIG. Fig. 6 is a view showing a plate-like member constituting the casting apparatus according to the embodiment of the present invention, Fig. 6 (a) is a plan view, and Fig. 6 (b) is an AA of Fig. 6 (a). FIG. FIG. 7 is a view showing a plate-like member constituting the casting apparatus according to an embodiment of the present invention, FIG. 7 (a) is a plan view, and FIG. 7 (b) is an AA of FIG. 7 (a). FIG. Fig. 8 is a view showing a plate-like member constituting the casting apparatus according to the embodiment of the present invention, Fig. 8 (a) is a plan view, and Fig. 8 (b) is an AA of Fig. 8 (a). FIG. FIG. 9 is a cross-sectional view showing a modification of the casting apparatus according to an embodiment of the present invention. FIG. 10 is a cross-sectional view showing a modification of the casting apparatus according to an embodiment of the present invention. FIG. 11 is a cross-sectional view showing a modification of the casting apparatus according to the embodiment of the present invention. FIG. 12 is a cross-sectional view showing an example of a conventional casting apparatus.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings. The drawings are all shown schematically.

  As shown in FIG. 1, the casting apparatus S of this embodiment comprises an upper structure S1 and a lower structure S2. In the upper structure S1, a crucible 11 for melting raw material silicon containing silicon as a main component is disposed. Here, when "A is referred to as a main component", it means that A is contained at 50% by mass or more, and the same applies to the following description. For the crucible 11, a melting crucible 11 a made of, for example, high purity quartz or graphite is held by a holding crucible 11 b. Moreover, the crucible heating means 12 is arrange | positioned around the melting crucible 11a and the holding crucible 11b. For example, the crucible heating means may be divided into a plurality of parts, such as the upper side, the side, and the lower side with respect to the melting crucible 11a and the holding crucible 11b. The silicon raw material placed in the melting furnace 11 a is heated and melted by the crucible heating means 12 composed of a resistance heating heater or an induction heating coil or the like to become a melt 4. Then, the melt 4 is poured into the mold 1 by melt supply means such as a tapping hole provided at the bottom of the melting pot 11a and the holding pot 11b. In the case where the outlet is not provided at the bottom, the lower structure S2 of the casting apparatus S disposed below the melting rod 11a and the holding rod 11b by tilting the melting rod 11a and the holding rod 11b, etc. You may supply four.

  In the lower structure S2, a mold 1 into which the melt 4 is poured is disposed, and a heat insulating material 3 is provided around the outside thereof. A mold holder 5 for holding the mold 1 and the heat insulating material 3 is provided in contact with the bottom of the mold 1 and a cooling means 7 is provided below the mold holder 5. Further, above the mold 1, a mold heating means 6 for controlling the solidification of the melt 4 placed in the mold 1 is disposed. As will be described in detail later, the first mold holder 5a, the plate member 8 and the second mold holder 5b are arranged from the side close to the mold 1. The plate-like member 8 is disposed in non-contact with the bottom of the mold 1, and one main surface is opposed to the cooling surface 7 a of the cooling means 7. The plate member 8 is also disposed in a non-contact state with the cooling surface 7 a of the cooling means 7.

  The mold 1 is made of, for example, graphite, carbon fiber reinforced carbon material, quartz or ceramics (silica, alumina, silicon nitride or the like), and has a bottom member 1a, a side member 1b and an upper opening 1c. The mold 1 may be composed of one member, or may be composed of a split mold or the like which can be divided and assembled by combining one bottom member 1a and a plurality of (usually four) side members 1b. It is also good. In the case of a split mold, the bottom member 1a and the side member 1b are assembled so as to be dividable by fixing them with a bolt (not shown) or the like, or a frame member (in which the bottom member 1a and the side member 1b fit) Can be divided into pieces by fixing them as shown.

Further, on the inner surface of the mold 1, the mold release material layer 2 is applied so that the mold 1 and the ingot are fused and the ingot is not broken when the ingot is taken out from the mold 1. The release material layer 2 is provided on the inner surface of the mold 1 as follows. First, a slurry is prepared. The slurry may be a powder of silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), silicon oxide (SiO ₂ ), etc., or a mixed powder thereof with a suitable binder (eg, polyvinyl alcohol (PVA)) and a solvent (eg, polyvinyl alcohol). For example, it is mixed with water and made. Then, the slurry is coated on the inner surface of the mold 1 by means such as coating or spraying. Specifically, for example, a powder of silicon nitride having an average particle diameter of about 0.4 to 0.6 μm is mixed with a PVA aqueous solution having a concentration of about 5 to 15% by mass to form a slurry, which is made into a spatula. Alternatively, it is applied to the inner surface of the mold 1 using a brush or the like. Then, in this state, it is placed on natural drying or a hot plate, dried and degreased. Thereafter, the melt 4 is poured into the mold 1 or the raw material silicon is put into the mold 1 and heated and melted. In addition, the release material layer 2 may be a mixture of multiple types of powder having different materials or different average particle sizes.

The heat insulating material 3 suppresses heat removal from the side surface of the mold 1 and is made of a material in consideration of heat resistance, heat insulation and the like. The heat insulator 3 is preferably made of a material such as graphite felt, whose main component is carbon. In particular, it is preferable to use a paste whose surface is coated with a paste containing carbon as a main component, since it is difficult to deteriorate.

  The side face of the mold 1 is thermally insulated by the heat insulating material 3, and the upper part of the mold 1 is heated by the mold heating means 6. Then, the cooling means 7 is brought into contact with or approached to the lower part of the mold holder 5 to which the mold 1 is fixed, heat is removed from the lower part of the mold 1 through the mold holder 5, and the melt 4 is unidirectionally directed from the lower part to the upper part. Coagulate.

  As the mold heating means 6, a resistance heating heater or an induction heating coil can be used.

  Further, the cooling means 7 is made of, for example, a material having a good thermal conductivity such as stainless steel, and has a structure such as circulating a refrigerant such as water inside. The cooling means 7 can effectively remove heat from the high temperature melt 4 in the mold 1 through the mold holder 5.

  After solidification of the ingot, the ingot is cooled and the heat insulating material 3 is removed. Finally, by taking out the ingot from the mold 1, a polycrystalline silicon ingot is completed.

  As shown in FIGS. 1 and 9 to 11, the mold holder 5 has at least a first mold holder 5 a, and holds the mold 1 and also holds the plate member 8.

  The first mold holder 5a has an opening, and is in contact with the mold 1 in a region other than the opening, and removes heat from the mold 1 by heat conduction. Further, the plate-like member 8 is disposed below the central portion of the mold 1 in a non-contact state with the mold 1 and has a function of adjusting the heat removal amount by the heat radiation from the mold 1. The plate-like member 8 can adjust the heat removal amount from the bottom of the mold 1 only by replacing it with a plate-like member having another structure as appropriate.

  In addition, the mold holder 5 may further include a second mold holder 5b that removes heat by heat conduction. The second mold holder 5 b has an opening, contacts the cooling means 7 in the area other than the opening, and removes heat by heat conduction. In this case, as shown in FIG. 10, for example, if the first mold holder 5a and the second mold holder 5b are integrally configured, the mold holder 5 can be easily assembled. Furthermore, it is preferable that the heat conduction from the high temperature mold 1 to the lower temperature mold holder 5 and further to the low temperature cooling means 7 is insusceptible to the assembly accuracy of the mold holder 5 and the change over time with use. . Further, for example, as shown in FIG. 11, the mold holder 5 is in contact with the first mold holder 5a and the second mold holder 5b as separate bodies so that the heat conduction can be made good and it is easy to manufacture. You may configure it.

  The material of the mold holder 5 may be any stable material which does not have a large deformation in its shape in the operating temperature range and does not generate a substance which adversely affects the characteristics of the ingot to be produced. For example, ceramics, quartz, metal or graphite (graphite) can be used as the mold holder 5. The first mold holder 5a and the second mold holder 5b may be the same material. In particular, the mold holder 5 is, for example, an isotropic graphite having a thermal conductivity of 80 to 150 W / (m · K), a carbon fiber reinforced carbon material having a thermal conductivity of 4 to 60 W / (m · K), a thermal conductivity A graphite felt having a degree of 0.1 to 0.5 W / (m · K) can be used.

  The plate-like member 8 is a plate-like member in which through holes 8a for adjusting the amount of heat radiation and the like can be adjusted, in portions facing the bottom of the mold 1 and the cooling surface 7a of the cooling means 7, respectively. For example, the plate member 8 may be drilled only to a plate having a thickness of about 2 mm to 30 mm. For this reason, it is cheap compared with the case where the mold holder 5 whole is processed and the amount of heat removal etc. is adjusted, and replacement | exchange and attachment work also become easy. Moreover, there is no restriction | limiting in particular in the external appearance shape of the plate-shaped member 8, For example, circular view etc. may be carried out in planar view.

  The plate-like member 8 may be made of the same material as the mold holder 5 for the same reason as the mold holder 5. For example, the plate-like member 8 has a thermal conductivity higher than that of the first mold holder 5a and the second mold holder 5b. It may be a small material. Thus, of the heat transfer from the bottom of the mold 1 to the cooling means 7, heat conduction is mainly controlled by the first mold holder 5a and the second mold holder 5b, and heat radiation from the mold 1 is mainly controlled by the plate member 8. can do. The first mold holder 5a and the second mold holder 5b are made of a carbon fiber reinforced carbon material or a felt made of graphite, and the plate member 8 is made of an isotropic graphite material, whereby the plate member 8 is The thermal conductivity can be smaller than that of the first mold holder 5a and the second mold holder 5b. Thus, the heat removal can be easily controlled by using the mold holder 5 and the plate-like member 8 having different thermal conductivities.

  The adjustment of the heat removal amount (heat radiation amount) by the plate member 8 is based on the opening area Sa of the first mold holder 5a and the opening area Sc of the second mold holder 5b with respect to the area outside the bottom of the mold (Sa in this embodiment) = Sc), ratio of total area Sb of through holes (openings) formed in the plate member 8 (through hole area ratio) R1 = Sb / Sa, R2 = Sb / Sc (in the embodiment, R1 = R2 It can be adjusted with). Here, the through hole area ratios R1 and R2 can be adjusted between 0 and 1, respectively. In the present embodiment, the reason that R1 = R2 is set as Sa = Sc is because the mold holder 5 distinguishes the heat-removing area from the heat-removing area and the heat-removing area from the heat-removing area. To facilitate control of the

  As shown in FIG. 2, only one circular through hole 8a may be provided on the plate member 8 in a plan view, or a plurality of through holes 8a may be provided as shown in FIGS. It is also good. Moreover, as shown to FIGS. 3-8, it is possible to adjust the shape, area, number, position, etc. of each through-hole. Further, for example, as shown in FIGS. 3 to 5, the arrangement of the through holes 8 a is at the central portion (when the plate-like member 8 is viewed in plan, the area of the similar shape having the same outer shape and center is 1/4 or less of the outer surface area The area may be designed appropriately, for example, by changing the area of (1) and the end (in a planar view of the plate member 8, the area of a similar shape having the same shape and center as the area larger than 1⁄4 of the area). It is possible. Thereby, the distribution of heat removal amount (heat radiation amount) from the bottom surface of the mold 1 is adjusted, and the ingot shape (bottom area and height of the ingot), individual difference of the casting apparatus, change over time (for example, furnace It is also possible to obtain a heat dissipation distribution suitable for the number of times the heat insulating material is used, and the like.

  Further, as shown in FIGS. 7 and 8, the plurality of through holes 8 a of the plate-like member 8 may extend toward the side where the cooling means 7 is located. Thereby, the heat radiation from each through hole 8a can be diffused and reach the cooling means 7, so that heat removal can be performed efficiently.

  In the present embodiment, if the through hole area ratio R1 (= R2) is 0.02 to 0.80, more preferably 0.04 to 0.5, it is preferable because the stress and crack generated in the ingot can be reduced. .

  The first mold holder 5a and the second mold holder 5b are required to have mechanical strength for mechanically supporting or holding silicon in the mold 1 and the mold 1. Therefore, for example, the first mold holder 5a and the second mold holder 5b may be made of a carbon fiber reinforced carbon material. Further, in this case, the plate-like member 8 may be made of isotropic graphite material, graphite felt, ceramics, high melting point metal or the like. Thus, the mold holder 5 and the plate-like member 8 may be used in combination of materials whose mechanical or physical properties are different from each other.

When the mold holder 5 is brought into contact with the mold 1 and the cooling means 7 and heat removal is carried out by heat conduction, the contact situation changes due to changes in dimensions and the like of each member (in particular, temporal change in flatness of contact surface) As a result, adjustment of the heat removal amount tends to be unstable. In the casting apparatus S according to the present embodiment, since the plate-like member 8 for adjusting the heat removal amount is not in contact with at least the mold 1, the heat removal amount can be adjusted by heat radiation. For this reason, the influence of the temporal change of the mold holder 5 and the plate-like member 8 is small, and it is possible to obtain a stable heat removal amount by the cooling means 7.

  The cooling means 7 is in contact with the mold holder 5 at the upper cooling surface. Then, with the cooling means 7 not in contact with the plate member 8, the cooling means 7 is in contact with the first mold holder 5a or the second mold holder 5b. Thereby, on the cooling surface 7a of the cooling means 7, a region for heat removal by heat conduction via the first mold holder 5a and the second mold holder 5b, and a region for heat radiation by heat radiation via the plate-like member 8 And can be formed. In this case, the mold holder 5 and the plate-like member are configured such that the area contributing to the heat conduction control increases the contact area and the area contributing to the heat radiation control reduces reflection of heat radiation (increases heat absorption). For example, it is preferable to apply a process such as a concavo-convex shape to the surface of No. 8 because efficient heat removal can be performed.

  The heat removal amount by the cooling means 7 can be measured by monitoring the flow rate of the refrigerant (water or the like) supplied to the cooling means 7 and the temperature difference between the supply time and discharge time of the refrigerant. By exchanging the plate-like member 8 of the present embodiment, the heat removal amount can be made in the optimum range. This makes it possible to optimize the temperature gradient and temperature distribution of the ingot during solidification and cooling after solidification.

  In the mold holder 5, as shown in FIGS. 10 and 11, the peripheral part of the mold 1 removes heat from the mold 1 by heat transfer through the first mold holder 5a and the second mold holder 5b, and the central part at the bottom of the mold 1 is a plate The mold 1 may be removed by heat radiation through the bar-like member 8. Thereby, the desired heat removal amount and the heat removal desired for each of the casting initial stage (heat removal by heat radiation is dominant) and the middle stage of casting (heat removal by heat transfer is dominant) at which the bottom of the mold 1 is close to the melting point of silicon. A heat extraction distribution can be obtained.

  As described above, according to the mold apparatus S of the present embodiment, the apparatus is disposed between the cooling surface 7 a of the cooling means 7 and the bottom of the mold 1 in a non-contact state with the bottom of the mold 1. The plate-like member 8 whose main surface is opposed to the cooling surface 7 a of the cooling means 7 is provided. Thereby, the heat removal amount by the cooling means 7 from the bottom surface of the mold 1 can be easily controlled, and the control of the temperature distribution and temperature gradient in the ingot during solidification and cooling after solidification can be facilitated. Then, residual stress in the ingot can be reduced, and crystal defects such as dislocations are less likely to be generated in the ingot, and crack generation due to crystal defects can be reduced.

  The present invention is not limited to the embodiment described above. For example, it is also possible to apply to an apparatus for a mold for producing a single crystal or a pseudo single crystal as an ingot. Alternatively, a solid silicon raw material arranged in advance in the mold 1 may be heated and melted in the mold 1 to obtain the melt 4, and then the melt 4 is unidirectionally solidified from the bottom to the top of the mold 1 You may

  Hereinafter, examples of the present invention will be described.

  As members of the mold 1, four side members 1 b of 2 mm in thickness made of high purity graphite and one bottom member 1 a of 5 mm in thickness were prepared. A silicon nitride powder having an average particle diameter of 0.5 μm and a silicon dioxide powder having an average particle diameter of 20 μm were weighed and stirred and mixed with a 10% by mass polyvinyl alcohol aqueous solution to form a slurry and obtain a mold release material. The release material was applied to the surfaces of the side member 1b and the bottom member 1a using a brush. Then, this was placed on a hot plate and dried to obtain a release material layer 2. Then, the side member 1b and the bottom member 1a were combined so that the mold release material layer 2 was inside, and a mold 1 having an inner size of 500 mm × 500 mm and a depth of 200 mm was produced.

  A heat insulating material 3 made of graphite having a shape shown in FIG. 1 was disposed so as to cover the outer periphery of the mold 1. In addition, the thickness of the heat insulating material 3 was 30 mm.

  Furthermore, a mold holder 5 for holding the mold 1 and the heat insulating material 3 was disposed below the mold 1. Further, the first mold holder 5a and the second mold holder 5b are made of isotropic graphite having a thickness of 25 mm, and provided with openings of the same shape at the same position when viewed from above. The plate-like member 8 used was a plate-like member made of a carbon fiber reinforced carbon material having a thickness of 5 mm and provided with a circular through hole 8 a in a plan view. As shown in Table 1, a plurality of through holes 8a of the plate-like member 8 were prepared with different area ratios (size and number) and different arrangement, and the ingot was repeatedly manufactured while replacing the plate-like member 8 .

  Here, condition No. of the example. 2 to 7 used one in which one circular through hole 8a was formed as shown in FIG. 2 and the area was gradually increased. Moreover, condition No. As compared with the case where the plurality of circular through holes 8a are formed and the through holes 8a are formed uniformly (refer to FIG. 4), the condition No. 8 and 9 have the same condition No. In No. 8, the number (density) of through holes on the end side is reduced (see FIG. 5). In No. 9, the number (density) of through holes in the central portion was reduced (see FIG. 3). Moreover, the plate-shaped member 8 which has not formed the through-hole for comparison was also used (condition No. 1).

The mold 1, the heat insulator 3 and the mold holder 5 were set at predetermined positions on the cooling means 7 of the casting apparatus S. The cooling means 7 is made of stainless steel, has a plate-like portion with an area of 1600 cm ^{2 at} the top, and has water circulated inside. Moreover, the cooling means 7 measured the water flow rate and the water temperature at the time of discharge | emission at the time of supply, and measured the heat removal amount. Table 1 shows the heat removal amount for 3 hours after the start of solidification of the ingot. In addition, a graphite heater was disposed at a predetermined position as the mold heating means 6.

Thereafter, solid raw material silicon is filled in the crucible 11, and the inside of the casting apparatus S is 11 kPa.
The atmosphere was reduced to argon. Then, the raw material silicon was heated to the melting point (1414 ° C.) or more using the crucible heating means 12 composed of a graphite heater to prepare a melt. Furthermore, a melt of 11 to 85 kg was poured into the interior of the mold 1 heated to 1000 ° C. using the mold heating means 6 consisting of a graphite heater.

  Next, while the upper surface of the melt 4 was heated by the mold heating means 6, the cooling means 7 was brought into contact with the mold holder 5 to solidify the melt 4 in one direction, and an ingot of polycrystalline silicon was produced. Then, the solidified ingot was cooled and taken out of the mold 1. The ingot was cut using a band saw, and the occurrence of cracks on the cut surface of the ingot was examined.

  The results are shown in Table 1. In the evaluation results of Table 1, the solidification time and the occurrence of cracks in the ingot are indicated by symbols. The meaning of each symbol is as follows.

<Coagulation time>
Good: The solidification time is sufficiently short (the solidification time when the area ratio of the through holes is 1 is 125% or less, assuming 100%), and the productivity is good.
Δ: The solidification time is short (the solidification time when the area ratio of the through holes is 1 is 100%, is longer than 125% and is 150% or less), and the productivity is not a problem.
X: The solidification time is long (the solidification time when the area ratio of the through holes is 1 is 100% and 150% or more), and the productivity is reduced.

<Crack status>
○: no cracks were observed at all.
Δ: Crack slightly observed but acceptable range without affecting the yield (can be used as an ingot).
X: Cracks affecting yield (cannot be used as ingots) were observed.

  As apparent from Table 1, by using the mold holder 5 of the present embodiment for the mold apparatus S, it has been confirmed that an ingot with reduced cracks can be manufactured with high productivity. In particular, when the through hole area ratio R1 or R2 was 0.02 to 0.80, the solidification time and the condition of the crack were within the allowable range (see Condition Nos. 2 to 6). Furthermore, when the through hole area ratio R1 or R2 was 0.04 to 0.5 (see conditions No. 3 to 5), no generation of cracks was observed. In the arrangement of the through holes, the through holes are arranged more at the end than at the central portion of the plate-like member 8 (the hole area in the plan view of the through holes is increased to increase the heat removal amount), The effect of reducing the occurrence of cracks was high (see conditions No. 8 and 9). In addition, it was confirmed that there is an optimum value (42 to 58 kWh in 3 hours after solidification) in the heat extraction amount of the cooling means. In the case where it is smaller than 42 kWh or larger than 58 kWh in 3 hours after solidification of the melt 4, it was confirmed that the stress of the ingot becomes large and the crack is easily generated. Furthermore, even when the shape of the through hole 8a of the plate-like member 8 is various shapes such as a square other than circular in plan view, the same effect as the circular can be confirmed.

1: mold 1a: bottom member 1b: side member 1c: upper opening 2: release material layer 3: heat insulating material 4: melt 5: mold holder 5a: first mold holder 5b: second mold holder 6: mold heating means 7: Cooling means 8: Plate-like member 8a: through hole S: device for casting

Claims (5)

A mold which has a bottom and holds and solidifies a silicon-based melt;
Cooling means disposed below the bottom of the mold and having a cooling surface on the top surface;
Between the cooling surface of the cooling means and the bottom of the mold, the main surface is disposed in non-contact with the bottom and facing the cooling surface of the cooling means And a plate-like member
The plate-like member has through holes at portions facing the bottom of the mold and the cooling surface of the cooling means, respectively.
The mold holder further comprises a mold holder which contacts the mold and the cooling means , holds the plate-like member, and has an opening.
The apparatus for casting whose area ratio of the through-hole of the said plate-shaped member with respect to the opening part area of the said mold holder is 0.02 or more and 0.8 or less.   The casting apparatus according to claim 1, wherein the plate-like member is disposed in non-contact with the cooling surface of the cooling means.   The casting apparatus according to claim 1, wherein the plate-like member is made of a material having a thermal conductivity smaller than that of the mold holder.   The casting apparatus according to any one of claims 1 to 3, wherein the through hole of the plate-like member extends toward the side where the cooling means is located.   The melt for silicon is put into the mold using the casting apparatus according to any one of claims 1 to 4, and then the melt is adjusted while adjusting the heat removal amount from the mold by the plate-like member. The manufacturing method of the ingot made to solidify in one direction upward from the bottom part of the said casting_mold | template.

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