JP5788891B2 - Silicon ingot manufacturing container - Google Patents

Description

  The present invention relates to a container for producing a silicon ingot for producing a solar cell grade silicon ingot.

Conventionally, as a method for producing a silicon ingot used for a solar cell or the like, a silicon melt is accommodated in a graphite or quartz container (such as a crucible or a mold), and the silicon melt is solidified from below to obtain a silicon polycrystal. A casting method (casting method) for growing the steel is known.
According to this casting method, the direction of crystal growth is uniform when the silicon melt is solidified, so that it is possible to manufacture a high-quality wafer in which an increase in specific resistance due to grain boundaries is suppressed. Moreover, according to the casting method, mass production of silicon ingots becomes possible.

In general, a release material is formed on the inner surface of a container used in the casting method. When producing a silicon ingot by the casting method, if silicon reacts with the container material when the silicon melt is solidified in the container, the silicon crystals are fixed to the container, making it difficult to take out the ingot. Therefore, a release material is formed on the inner surface of the container so that the silicon crystal does not come into direct contact with the container. As such a release material, silicon nitride (Si ₃ N ₄ ), silicon dioxide (SiO ₂ ), or a mixture thereof is generally used.

By the way, when forming a release material made of Si ₃ N ₄ or the like on the inner surface of the container, an aqueous slurry prepared by mixing a binder such as polyvinyl alcohol with Si ₃ N ₄ powder is applied to the inner surface of the container, and then in an oxygen atmosphere. A technique of firing is used.
This Si ₃ N ₄ has low sinterability (the property of solidifying a solid powder aggregate when heated at a temperature lower than the melting point to form a compact object called a sintered body) and sintering metal impurities In the case where no auxiliary agent is added, the strength is known to be low and fragile. Therefore, the mold release material made of Si ₃ N ₄ sintered body formed on the inner surface of the container may be damaged in the manufacturing process of the silicon ingot (at the time of holding the silicon melt, at the time of crystal growth, and taking out from the container). high.
For example, the density of the silicon melt is 2.5 g / cm ³ , but the solid density is 2.33 g / cm ³ , so that the volume expands by about 7% when the silicon melt is solidified in the container. If excessive stress is generated in the container along with the volume expansion during the solidification of the silicon, the release material is damaged.

When the release material breaks in a series of silicon ingot manufacturing steps, volume expansion stress remains in the grown silicon ingot, and crystal quality such as an increase in dislocation is deteriorated. Even if the silicon ingot is not damaged, the crystal quality is inevitably deteriorated.
In addition, if the release material breaks during crystal growth, the silicon crystal contacts and adheres to the container, so that the take-out property of the silicon ingot is further deteriorated, and the peeled release material is mixed into the silicon ingot and the crystallinity is lowered. Will be invited. Furthermore, since the container cannot be reused as it is, the manufacturing cost increases.

Therefore, there is a demand for a container for producing a silicon ingot that has good mold release properties and can prevent the release material from being damaged in the production process of the silicon ingot.
For example, Patent Documents 1 to ₃ disclose a technique in which Si ₃ N ₄ , SiO ₂ , or a mixture thereof is laminated to form a release material in a multilayer structure. Patent Documents 4 and 5 disclose techniques for mixing a resin into a release material such as Si ₃ N ₄ . Patent Documents 6 and 7 disclose a technique for forming a release material using aluminum nitride (AlN), cerium dioxide (CeO ₂ ), or yttrium oxide (Y ₂ O ₃ ) as a sintering aid. Thus, adding a metal oxide or carbon in the release material forming step is a general method for strengthening the release material.

JP 2003-313023 A Special table 2007-534590 JP 2006-327912 A JP 2006-218537 A JP 2007-191345 A JP 2008-230932 A Japanese Patent Laid-Open No. 7-206419

Journal of Crystal Growth 79 (1986), 583-589

However, when forming a release material containing a metal oxide or carbon, silicon carbide (SiC) is generated in the release material slurry firing step. And the produced | generated SiC mixes with a silicon ingot, precipitates in a crystal grain boundary, and becomes the obstacle at the time of processing a silicon ingot into a wafer not only reducing the quality as an ingot.
Moreover, the metal oxide and carbon contained in the mold release material slurry cause the container to deteriorate. For example, a release material formed on the inner surface of a graphite container is easily peeled into a film by carbonization (SiC conversion), so that the release property is not sufficient and the graphite container is consumed.
In order to improve the strength of the release material, it is common to add silica as a sintering aid in the slurry (for example, Non-Patent Document 1). In the case of a graphite container, Since the silica reacts, the above problems are accelerated.

  On the other hand, when forming the release material on the inner surface of the quartz container, there is no problem that the release material and the container material deteriorate in the slurry firing process, but the container deteriorates and deforms at a high temperature during crystal growth. After all, it is impossible to effectively prevent the release material and the container from being damaged.

  In the techniques described in Patent Documents 1 to 3, since the release material has a multilayer structure, it takes time and cost to form the release material. In the techniques described in Patent Documents 4 to 7, the strength of the release material is high and it is difficult to break, but there is a possibility that the resin or metal contained in the release material is mixed as impurities into the silicon ingot and the crystal quality is lowered. For example, the mold release material and the metal oxide contained in the container serve as a catalyst for generating SiC in the mold release material forming step. The generated SiC becomes a melt surface floating substance, and hinders single crystallization by crystal pulling such as the Czochralski method or the Cairo porous method.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a container for producing a silicon ingot that can be repeatedly used for producing a silicon ingot and can produce a silicon ingot having a good quality with a high yield. .

The invention according to claim 1 is a container for producing a silicon ingot for solidifying a silicon melt to grow a silicon polycrystal.
A release material made of silicon nitride is formed on the inner surface of a container body made of a porous body of silicon nitride or silicon carbide.

The invention according to claim 2 is the container for manufacturing a silicon ingot according to claim 1,
The open porosity of the porous body is 10% or more and 40% or less.
Here, the open porosity is a ratio of the total volume of pores communicating with the outside to the apparent volume of the porous body.

The invention described in claim 3 is the silicon ingot manufacturing container according to claim 1,
The open porosity of the porous body is 20% or more and 30% or less.

The invention according to claim 4 is the silicon ingot manufacturing container according to any one of claims 1 to 3,
The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) of the container body made of the porous silicon nitride are each 1000 ppm or less. And

The invention according to claim 5 is the silicon ingot production container according to claim 4,
The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) of the container body made of the porous body of silicon carbide are each 10 ppm or less. And

The invention according to claim 6 is the silicon ingot manufacturing container according to any one of claims 1 to 3,
The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) of the container body made of the porous body of silicon carbide are each 100 ppm or less, preferably 10 ppm or less. It is characterized by being.

The invention according to claim 7 is the silicon ingot production container according to claim 6,
The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) of the container body made of the porous body of silicon carbide are each 10 ppm or less. And

The invention according to claim 8 is the silicon ingot manufacturing container according to any one of claims 1 to 7,
The release material has a thickness of 300 to 1000 μm.

The invention according to claim 9 is the silicon ingot manufacturing container according to claim 8,
The release agent has a thickness of 350 to 600 μm.

  According to the present invention, since the release material having a good release property is firmly formed on the inner surface of the container body, it is possible to effectively prevent the release material from being damaged by the stress accompanying the volume expansion during the solidification of silicon. it can. Therefore, the silicon ingot can be repeatedly used for manufacturing a silicon ingot, and a silicon ingot having a good quality can be manufactured with a high yield.

It is sectional drawing of the container for silicon ingot manufacture to which this invention is applied. It is a figure which shows an example of the crystal growth apparatus using the container of embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view of a container for producing a silicon ingot to which the present invention is applied. As shown in FIG. 1, a container (hereinafter referred to as a container) 10 for producing a silicon ingot according to an embodiment includes a container body 11 having heat resistance and a container body 11 for improving the releasability of the grown silicon ingot. And a mold release material 12 formed on the inner surface.

The container body 11 is composed of a porous body (porous material) of Si ₃ N ₄ or SiC. The thickness of the container body 11 is such that warpage does not occur during molding, for example, 5 mm or more.
The container body 11 is produced, for example, by sintering and molding Si ₃ N ₄ or SiC powder, and the open porosity is 10% or more and 40% or less. When the open porosity of the porous body constituting the container main body 11 is less than 10%, bubbles remain in the release material 12, so that the release material 12 becomes brittle and easily breaks. In addition, when the open porosity is more than 40%, the possibility of melt leakage increases. Therefore, the open porosity of the porous body constituting the container main body 11 is desirably 10% or more and 40% or less.

The container main body 11 made of a porous molded body of Si ₃ N ₄ or SiC is superior in heat resistance as compared with a quartz container, and does not deteriorate or deform when the silicon ingot is manufactured at a high temperature. Therefore, when the silicon ingot is manufactured, it is possible to effectively prevent the release material 12 from being damaged due to deterioration and deformation of the container body 11. In addition, when the container main body 11 consists of a porous molded body of Si ₃ N ₄ , it contains metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr). Is 1000 ppm or less, desirably 10 ppm or less. When the container body 11 is made of a porous porous body of SiC, the metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) are each 100 ppm or less, Desirably, it is 10 ppm or less.
By reducing the metal oxide contained in the mold release material and the container, the generation amount of SiO gas is reduced during the Si crystal growth, and the generation of SiC foreign matter by the reaction between the carbon contained in the mold release material and the container and the above SiO gas. It becomes possible to suppress. As a result, SiC foreign matter does not float on the melt surface, and single crystallization by a crystal pulling operation such as the Czochralski method or the Cairo porous method is facilitated. Further, when Si polycrystal is produced by a casting method or the like, it is possible to prevent the SiC melt surface suspended matter from being mixed into the crystal, and as a result, the Si crystal quality is improved.

The release material 12 is composed of a sintered body of Si ₃ N ₄ . The mold release material 12 is prepared by, for example, applying an aqueous slurry prepared by mixing a binder such as polyvinyl alcohol to Si ₃ N ₄ powder on the inner surface of the container body 11 with a brush or spray, and inactive in an oxygen atmosphere or argon. It is formed by baking at 700 to 1550 ° C. in a gas atmosphere. The thickness of the release material 12 is 300 to 1000 μm. When it is thinner than 300 μm, the volume expansion stress relaxation of Si is insufficient, and the crystal is cracked. On the other hand, when it is thicker than 1000 μm, the release material breaks during crystal growth and becomes a float on the melt surface, and single crystallization from the melt surface tends to be hindered. Considering the labor for forming the release material, the desirable thickness of the release material is 300 to 600 μm.
The slurry applied to the container body 11 penetrates into the pores of the container body 11 because the container body 11 is composed of a porous body. In addition, bubbles in the slurry are degassed by the container body 11 made of a porous material. Since the firing is performed in this state, the release material 12 is firmly formed on the inner surface of the container body 11. Therefore, it is possible to effectively prevent the release material 12 from being damaged when the silicon ingot is manufactured.

  If bubbles remain in the release material 12, the release material 12 tends to be damaged during the production of the silicon ingot according to the number and size of the remaining bubbles. When forming, defoaming treatment such as reduced pressure was performed. On the other hand, in the case of the container 10 of the present embodiment, it is not necessary to perform a defoaming process when forming the release material 12, and the release material 12 can be easily formed.

Further, since the release material 12 is firmly formed on the inner surface of the container body 11, it is not necessary to have a multilayer structure as in the prior art. Therefore, the labor and cost for producing the container 10 do not increase, and it is easy to increase the film thickness of the release material 12. Furthermore, since it is not necessary to use a sintering aid such as silica or a metal oxide when forming the release material 12, it is possible to prevent the impurity concentration in the silicon ingot from increasing and the crystallinity from being lowered. That is, during the Si crystal growth, the amount of generated SiO gas due to the thermal decomposition of SiO ₂ containing the metal oxide is reduced, and it is possible to prevent the generation of SiC foreign substances that deteriorate the crystal quality. Based on the same principle, it is possible to suppress the generation of SiO gas which is a thermally decomposable product of SiO ₂ by not using a conventional quartz container.

  FIG. 2 is a diagram illustrating an example of a crystal growth apparatus using the container of the embodiment. The crystal growth apparatus 1 shown in FIG. 2 is used when manufacturing a silicon ingot. In the crystal growth apparatus 1, the container 10 is supported by a susceptor 13 made of graphite, and a heater 14 is disposed on the outer periphery of the susceptor 13.

When a silicon ingot is manufactured by the casting method using the crystal growth apparatus 1, first, a predetermined amount of silicon raw material (for example, silicon melt) 15 is put into the container 10. Then, by gradually lowering the temperature, the silicon melt is solidified from the melt surface of the container 10 to grow the silicon polycrystal 15a, and a silicon ingot is manufactured.
When the open porosity of the container material is small, the release material is easily peeled off and becomes a floating surface on the melt surface during crystal growth, which prevents single crystallization from the Si melt surface. On the other hand, when the open porosity of the container material is too large, the thickness of the release material becomes 300 μm or less, the volume expansion stress relaxation by the release material becomes insufficient, and cracks are recognized in the ingot. Table 1 shows the results of the test using the Si ₃ N ₄ crucible.

[Example 1]
When the open porosity was 10%, bubbles when the slurry was brushed remained and a large dent was formed on the surface, and after firing, many cracks originated from the dent were generated. Although it was possible to take out the ingot from the container, there was a tendency for cracks to be large in the R part (curved part of the boundary between the bottom wall and the side wall) at the bottom of the container, and the bottom of the Si ingot solidified from the melt surface Was cracked.

[Examples 2 and 3]
When the open porosity was 20% and 30%, no bubbles remained after applying the slurry brush, and no crack was observed even when the film thickness was increased to 600 μm. An ingot produced by solidifying from the Si melt surface in a container in which such a release material was formed had a smooth form without surface irregularities and cracks, and could be easily taken out from the container.

[Example 4]
When the open porosity was 40%, the penetration of the release material slurry was large, and it was difficult to increase the thickness of the release material. When the thickness of the mold release material was smaller than 300 μm, there was a tendency for unevenness to occur on the bottom surface of the ingot. Although the ingot could be removed from the container, cracks were observed in the ingot at the R portion at the bottom of the container.

[Comparative Example 1]
When the open porosity exceeded 40%, it was difficult to increase the film thickness although no cracks were observed in the release material. When solidified from the surface of the Si melt in the vessel, melt leakage occurred from the bottom. It is considered that the melt below the crystal was compressed and the melt penetrated into the pores.

[Comparative Example 2]
When the open porosity is less than 10%, the release agent slurry is difficult to wet on the container material, and the grooves after slurry brush coating tend to remain, and the entire surface becomes uneven due to foaming from the slurry, and cracks occur after firing. There has occurred. It was difficult to increase the film thickness to 400 μm or more because the air bubbles were so severe that the release material became brittle. When Si was solidified from the melt surface in such a container, the container and Si partially adhered and the ingot was broken.
As described above, the open porosity of the container material is related to the thickness of the release material and the presence or absence of cracks. The releasable range of the Si ingot is 10 to 40%, preferably 20 to 30%, of the open porosity.

[Example 5]
In the crystal growth apparatus 1 shown in FIG. 1, the top inner diameter is 68.2 mm, the bottom inner diameter is 36 mm, the depth is 48 mm, and the thickness is 2 mm. All metal impurities (Na, Ca, Al, Cr, Cu, Fe, A container 10 is used in which a release material 12 having a thickness of 350 to 600 μm is formed on the inner surface of a SiC container main body (open porosity: 20%) 11 in which Ni, Ti, W, V, Zn, and Zr are each 10 ppm or less. After melting, Si was solidified from the melt surface.
Specifically, 100 g of silicon raw material was accommodated in the container 10 and heated to 1550 ° C. under an argon atmosphere of 1 atm to melt silicon. Thereafter, the heater was cooled at 10 ° C./min.

[Examples 6 and 7]
In Example 6, after forming the release material on the inner surface of the SiC container having the same specifications as in Example 5, baking was performed at 1550 ° C. for 12 hours under 1 atm of argon, and then the silicon was melted and solidified by the same method as in Example 5. went.
In Example 7, the top inner diameter: 84.4 mm, the bottom inner diameter: 48 mm, the depth: 48 mm, the thickness: 10 mm, and metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, After forming a release material on the inner surface of the Si ₃ N ₄ container having W, V, Zn, and Zr) of 10 to 1000 ppm, silicon was melted and solidified in the same manner as in Example 5. These results are shown in Table 2.

In Examples 5, 6, and 7 using the container material having an open porosity of 20%, no release material was peeled off. The obtained silicon ingot was not fixed to the container 10 and could be easily taken out only by turning the container 10 upside down.
When the surface of the silicon ingot and the inner surface of the manufactured container 10 were observed, the surface of the silicon ingot was extremely smooth, and there was no evidence that the release material 12 was damaged on the inner surface of the container 10. Since no bubbles were generated when the release agent slurry was applied to the surface of the porous container, it is considered that a uniform and high density extremely strong release material was formed. As a result, the silicon ingot expanded in volume so as to slide along the release material 12 and almost no friction was generated at the interface between the release material 12 and the silicon ingot. Therefore, the stress accompanying the volume expansion during the solidification of the silicon was effective. It is thought that it was relaxed.
Moreover, since the mold release material 12 and the container main body 11 were not damaged, the container 10 could be reused, and it could be used repeatedly for producing silicon ingots 10 times or more.

[Comparative Example 3]
In Comparative Example 3, a silicon ingot was manufactured under the same manufacturing conditions as in Example, using a container in which a release material similar to that in Example was formed on the inner surface of a quartz container body.
The resulting silicon ingot was severely uneven as compared to the silicon ingot obtained in the examples, and particularly, the ingot was cracked in the ingot due to severe deformation at the top and side surfaces of the ingot. Since the release material peeled off on the surface having the irregularities of the silicon ingot taken out, the release material was damaged due to the volume expansion at the time of solidification of silicon and the thermal deformation of the container due to high temperature, and part of the silicon ingot was It is thought that the ingot was cracked because it was fixed to the container. Further, SiC, which is a floating material on the melt surface, is generated during crystal growth, and is mixed into the silicon ingot together with the release material that has been peeled off during growth, and it is considered that the crystal quality of the silicon ingot has deteriorated.

[Comparative Example 4]
In Comparative Example 4, a mold release material was formed on the inner surface of a Si ₃ N ₄ container having a top inner diameter of 84.4 mm, a bottom inner diameter of 48 mm, a depth of 48 mm, and a thickness of 10 mm, and then baked at 1550 ° C. for 12 hours under 1 atm of argon. Then, melt solidification was performed in the same manner as in Example 5.
When the furnace was opened and the container was taken out, it was found that the Si melt leaked from the bottom of the container. Si was distributed by spreading the mold release material, but there was no leakage from the side. Since Si was solidified from the melt surface, it is considered that the melt compressed at the bottom of the container permeated the porous material.

In the case of the SiC containers of Examples 5 and 6, the melt surface float was not generated during crystal growth, but in the case of Si ₃ N ₄ of Example 7, a large amount of SiC float was generated. When a large amount of SiC suspended matter was generated, a large amount of SiO adhered to the furnace wall. It is considered that SiO reacted with carbon remaining in the release material to generate SiC.
Table 3 below shows the result of comparison of the metal impurity concentration in the Si crystal.

As in Examples 5 and 6, when a Si ingot is produced in a low metal impurity SiC (made by POCO) container produced by using the conversion method instead of the sintering method, it is produced by the sintering method as in Example 7. Compared with the case where the Si ingot was produced with the Si ₃ N ₄ container, the metal impurities remaining in the Si could be reduced. By baking the container on which the release material has been formed before the crystal growth step, it was possible to reduce metal impurities such as Fe, Al, Ca, Cu, and Cr. In addition, it was confirmed that in the case of a SiC container having a lower metal impurity concentration, SiC that is a float on the melt surface is not generated.

In Comparative Example 4, it was found from the difference in the weight of the container including the release material before and after baking and the baking time, the container weight reduction rate was 0.2 wt% / h. After baking, a large amount of SiO adhered to the furnace. In the case of the SiC container with low metal impurities after baking under the same conditions (Example 6), weight reduction and large amount of SiO generation during crystal growth were not observed. Therefore, there is a possibility that the Si ₃ N ₄ container main body containing a large amount of SiO ₂ and metal oxide and the adjacent Si ₃ N ₄ release material were thermally decomposed as SiO. That is, it is considered that melt leakage occurred in Comparative Example 4 because the sinterability of the release material Si ₃ N ₄ particles covered with SiO ₂ decreased during baking.

As described above, in the container 10 of the embodiment, the release material 12 made of Si ₃ N ₄ is formed on the inner surface of the container body 11 made of a porous body of Si ₃ N ₄ or SiC. The open porosity of the porous body constituting the container body 11 is 10% or more and 40% or less, preferably 20% or more and less than 40%.
In this container 10, since the release material 12 having good releasability is firmly formed on the inner surface of the container body 11, it is effective for the release material 12 to be damaged due to the stress accompanying the volume expansion at the time of silicon solidification. Can be prevented.
Also, by using porous SiC with low metal impurities produced by the conversion method as the container material, much less metal impurities can be obtained than when using a Si ₃ N ₄ container produced by the conventional sintering method. Si ingot containing could be manufactured. Furthermore, when the SiC container is used, it was possible to perform baking at a temperature higher than that of the Si ₃ N ₄ container to reduce metal impurities in the Si ingot. By using the low metal impurity container as a container for producing an Si ingot, it was possible to suppress contamination of SiC foreign matter into the melt.
Therefore, the silicon ingot can be repeatedly used for the production of the silicon ingot and the silicon ingot having a good quality can be produced.

As mentioned above, although the invention made by this inventor was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.
The container 10 according to the embodiment can be used not only in the casting method but also in any method for producing a silicon ingot that holds and solidifies the Si melt in the container. For example, the present invention can be used in a chiloporous method in which a seed crystal is brought into contact with the surface of a silicon melt and the silicon crystal is solidified from the surface while the seed crystal is pulled up to grow a silicon single crystal. The problem that the release material breaks down due to the stress associated with the volume expansion at the time of silicon solidification is prevented on the porous container material with low metal impurities is to suppress the occurrence of floating surface of the melt that hinders the single crystallization from the seed crystal. It is because it can solve by forming a mold release material firmly.
Further, the container main body 11, not the Si ₃ N ₄ or SiC only those formed in the crucible shape, assembled type as a template by combining a plurality of plate-like member formed of Si ₃ N ₄ or SiC in a plate shape Can be applied.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. 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.

DESCRIPTION OF SYMBOLS 1 Crystal growth apparatus 10 Silicon ingot manufacturing container 11 Container main body 12 Release material 13 Susceptor 14 Heater 15 Silicon raw material (silicon melt)
15a Polycrystalline silicon

Claims (9)

A container for producing a silicon ingot for solidifying a silicon melt and growing a silicon polycrystal,
A container for producing a silicon ingot, wherein a release material made of silicon nitride is formed on the inner surface of a container body made of a porous body of silicon nitride or silicon carbide.   The container for producing a silicon ingot according to claim 1, wherein the porous body has an open porosity of 10% or more and 40% or less.   The container for producing a silicon ingot according to claim 1, wherein an open porosity of the porous body is 20% or more and 30% or less.   The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) of the container body made of the porous silicon nitride are each 1000 ppm or less. A container for producing a silicon ingot according to any one of claims 1 to 3.   The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, and Zr) of the container body made of the porous silicon nitride are each 10 ppm or less. The container for manufacturing a silicon ingot according to claim 4.   The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) of the container body made of the porous body of silicon carbide are each 100 ppm or less. A container for producing a silicon ingot according to any one of claims 1 to 3.   The metal impurities (Fe, Al, Mn, Mg, Ca, Cu, Ti, Cr, Ni, W, V, Zn, Zr) of the container body made of the porous body of silicon carbide are each 10 ppm or less. The container for manufacturing a silicon ingot according to claim 6.   The container for producing a silicon ingot according to any one of claims 1 to 7, wherein the release agent has a thickness of 300 to 1000 µm.   The container for manufacturing a silicon ingot according to claim 8, wherein the release agent has a thickness of 350 to 600 μm.

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