JPWO2018110560A1 - Silicon nitride powder, mold release agent for polycrystalline silicon ingot, and method for producing polycrystalline silicon ingot - Google Patents
Silicon nitride powder, mold release agent for polycrystalline silicon ingot, and method for producing polycrystalline silicon ingot Download PDFInfo
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- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 260
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 259
- 239000000843 powder Substances 0.000 title claims abstract description 240
- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 130
- 239000006082 mold release agent Substances 0.000 title claims abstract description 12
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Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/068—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with silicon
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Silicon Compounds (AREA)
- Mold Materials And Core Materials (AREA)
Abstract
一方向凝固時のシリコンの溶融温度を高くした場合でも、あるいはシリコンの溶融時間を長くした場合でも、多結晶シリコンインゴットの離型性が良好な、多結晶シリコンインゴットの離型剤として好適に使用することができる窒化ケイ素粉末を提供することを目的とする。比表面積が０．４ｍ２／ｇ以上５ｍ２／ｇ以下の窒化ケイ素粉末であって、β型窒化ケイ素の割合が７０質量％以上であり、Ｄ５０が２μｍ以上２０μｍ以下であり、Ｄ９０が８μｍ以上６０μｍ以下であり、Ｆｅの含有割合が１００ｐｐｍ以下であり、Ａｌの含有割合が１００ｐｐｍ以下であり、ＦｅおよびＡｌ以外の金属不純物の含有割合の合計が１００ｐｐｍ以下であり、β型窒化ケイ素の結晶子径をＤＣとしたときに、ＤＣが３００ｎｍ以上であることを特徴とする窒化ケイ素粉末を提供する。Even when the melting temperature of silicon at the time of unidirectional solidification is increased or when the melting time of silicon is extended, it is suitably used as a mold release agent for polycrystalline silicon ingots having good releasability of polycrystalline silicon ingots. It is an object of the present invention to provide a silicon nitride powder that can be Silicon nitride powder with a specific surface area of 0.4 m 2 / g to 5 m 2 / g and a ratio of β-type silicon nitride of 70 mass% or more, D 50 of 2 μm to 20 μm, D 90 of 8 μm to 60 μm The content ratio of Fe is 100 ppm or less, the content ratio of Al is 100 ppm or less, the total content ratio of metal impurities other than Fe and Al is 100 ppm or less, and the crystallite diameter of β-type silicon nitride is Provided is a silicon nitride powder characterized in that DC is 300 nm or more when DC is taken.
Description
本発明は、鋳型への密着性と離型性が良好な離型層を鋳型に形成し得る窒化ケイ素粉末に関し、特に多結晶シリコンインゴットの離型剤として好適な窒化ケイ素粉末に関する。 The present invention relates to a silicon nitride powder capable of forming a mold release layer having good adhesion to a mold and good mold releasability, and in particular to a silicon nitride powder suitable as a mold release agent for polycrystalline silicon ingots.
太陽電池に用いられる多結晶シリコン基板は、通常、縦型ブリッジマン炉を用いて、溶融シリコンを一方向凝固させることにより製造される多結晶シリコンインゴットより採取される。多結晶シリコン基板においては高性能化と低コスト化が要求されており、その要求に応えるには、溶融シリコンの一方向凝固時の多結晶シリコンインゴットへの不純物混入の抑制と、多結晶シリコンインゴットの歩留まりの向上が重要である。縦型ブリッジマン法による溶融シリコンの一方向凝固においては、石英製などの鋳型が用いられるが、多結晶シリコンインゴットの歩留まりを高くするために、鋳型には多結晶シリコンインゴットの離型性が良いことが求められ、窒化ケイ素粉末を含む離型剤が内壁（溶融シリコンと接触する面）に塗布された鋳型が一般的に用いられている。 A polycrystalline silicon substrate used for a solar cell is generally obtained from a polycrystalline silicon ingot manufactured by unidirectionally solidifying molten silicon using a vertical Bridgman furnace. In the polycrystalline silicon substrate, higher performance and lower cost are required, and in order to meet the requirements, suppression of mixing of impurities into the polycrystalline silicon ingot at the time of unidirectional solidification of molten silicon, and polycrystalline silicon ingot are required. It is important to improve the yield of In unidirectional solidification of molten silicon by the vertical Bridgman method, a mold made of quartz or the like is used, but in order to increase the yield of polycrystalline silicon ingot, the mold has good releasability of polycrystalline silicon ingot. In general, a mold in which a release agent containing silicon nitride powder is applied to an inner wall (surface in contact with molten silicon) is generally used.
縦型ブリッジマン炉は、その構造上、鋳型底面より下方に向かって熱が逃げるため、鋳型には上下方向に大きな温度勾配が生じ、鋳型上部の温度が相対的に高くなる。近年太陽電池基板向けの多結晶シリコンインゴットはますます大型化する傾向にあり、鋳型底部のシリコン（融点；１４１４℃）が十分溶融するまで温度を上げると、ブリッジマン炉の構造によっては鋳型上部の温度は１５００℃以上のような高温になることもある。このような場合、温度が高い鋳型上部では、多結晶シリコンインゴットの離型性が悪くなる、また離型層が鋳型から剥がれて多結晶シリコンインゴットに付着する、などの問題が生じることがある。したがって、多結晶シリコンインゴットの離型層には、高い温度、例えば１５００℃以上で一方向凝固を行っても、多結晶シリコンインゴットの離型性や、離型層の鋳型への密着性が良いことが求められる。 In the vertical Bridgman furnace, the heat escapes downward from the bottom of the mold due to its structure, so that a large temperature gradient is generated in the mold in the vertical direction, and the temperature at the top of the mold becomes relatively high. In recent years, polycrystalline silicon ingots for solar cell substrates tend to be larger, and raising the temperature until the silicon (melting point; 1414 ° C) at the bottom of the mold is sufficiently melted, depending on the structure of the Bridgman furnace, the upper part of the mold The temperature may be as high as 1500 ° C. or more. In such a case, problems such as mold releasability of the polycrystalline silicon ingot deteriorating at the upper part of the mold at a high temperature, and the mold releasing layer peeling from the mold and adhering to the polycrystalline silicon ingot may occur. Therefore, even if the mold release layer of the polycrystalline silicon ingot is unidirectionally solidified at a high temperature, for example, 1500 ° C. or more, the releasability of the polycrystalline silicon ingot is good and the adhesion of the mold release layer to the mold is good. Is required.
このような背景から、太陽電池の基板に適用可能な多結晶シリコンインゴットの歩留まりを向上させるために一方向凝固時のシリコンの溶融温度を高くしても、多結晶シリコンインゴットの離型性と、鋳型への密着性が良好な離型層を形成し得る窒化ケイ素粉末の開発が望まれている。また、長尺の多結晶シリコンインゴットを得るために、上下方向に寸法が大きい鋳型を用いると、鋳型上部は特に長時間高温に曝されることになるので、一方向凝固時のシリコンの溶融時間が長くても、多結晶シリコンインゴットの離型性と、鋳型への密着性が良好な離型層を形成し得る窒化ケイ素粉末の開発が望まれている。 From such a background, the releasability of the polycrystalline silicon ingot, even if the melting temperature of silicon at the time of unidirectional solidification is raised to improve the yield of polycrystalline silicon ingot applicable to the substrate of the solar cell, It is desired to develop a silicon nitride powder that can form a release layer with good adhesion to a mold. In addition, if a mold having a large size in the vertical direction is used to obtain a long polycrystalline silicon ingot, the upper part of the mold is exposed to a high temperature particularly for a long time, and therefore the melting time of silicon during unidirectional solidification It is desired to develop a silicon nitride powder capable of forming a release layer having good releasability of polycrystalline silicon ingot and good adhesion to a mold, even though the length of the film is long.
特許文献１には、Ｆｅの濃度とＤ５０を特定の範囲にする窒化ケイ素粉末が、強固な離型層を形成できて、太陽電池の変換効率が高い多結晶シリコンの製造に有用であることは記載されているものの、窒化ケイ素粉末の結晶構造や結晶子径については記載されておらず、シリコンの溶融温度を高くしたり、あるいはシリコンの溶融時間を長くしたりした場合の多結晶シリコンインゴットの離型性や離型層の鋳型への密着性については記載されていない。 In Patent Document 1, it is possible that a silicon nitride powder having a Fe concentration and D50 in a specific range can form a strong release layer and is useful for producing polycrystalline silicon having a high conversion efficiency of a solar cell. Although described, the crystal structure and crystallite diameter of the silicon nitride powder are not described, and the polycrystalline silicon ingot when the melting temperature of silicon is increased or the melting time of silicon is extended. There is no description about the releasability or the adhesion of the releasable layer to the mold.
また特許文献２には、粒度分布とβ相の比率と特定の金属不純物を特定の範囲とする窒化ケイ素粉末が、多結晶シリコンインゴットへの不純物混入量を低減させ、離型剤の剥がれを抑制できることは示されているものの、比較的小さいＤ５０とＤ９０を有する窒化ケイ素粉末や、５０質量％のβ相の比率を有する窒化ケイ素粉末が最も離型剤の剥がれを抑制できることが示されているだけで、窒化ケイ素粉末の結晶子径については記載されておらず、シリコンの溶融温度を高くしたり、シリコンの溶融時間を長くしたりした場合の多結晶シリコンインゴットの離型性や離型層の鋳型への密着性については記載されていない。 Further, according to Patent Document 2, silicon nitride powder whose particle size distribution, the ratio of β phase and specific metal impurities are in a specific range reduces the amount of impurities mixed in the polycrystalline silicon ingot and suppresses peeling of the release agent. Although it has been shown that it can be done, it has only been shown that silicon nitride powder having relatively small D50 and D90 and silicon nitride powder having a proportion of 50% by mass of .beta. Therefore, the crystallite diameter of silicon nitride powder is not described, and the releasability and release layer of polycrystalline silicon ingot when raising the melting temperature of silicon or prolonging the melting time of silicon. The adhesion to the mold is not described.
そこで本発明は、一方向凝固時のシリコンの溶融温度を高くした場合でも、あるいはシリコンの溶融時間を長くした場合でも、多結晶シリコンインゴットの離型性が良好な、多結晶シリコンインゴットの離型剤として好適に使用することができる窒化ケイ素粉末を提供することを目的とする。 Therefore, according to the present invention, even if the melting temperature of silicon in one direction solidification is increased or the melting time of silicon is extended, the mold releasability of the polycrystalline silicon ingot is excellent. It is an object of the present invention to provide a silicon nitride powder that can be suitably used as an agent.
本発明者らは、前記課題を解決するために鋭意研究を重ね、特定の比表面積、特定のβ型窒化ケイ素の割合および特定の粒度分布を有し、特定の金属不純物とそれら以外の金属不純物の含有割合が特定の割合より少なく、結晶子径が特定の値より大きい窒化ケイ素粉末を用いて多結晶シリコンインゴット鋳造用鋳型の離型層を形成すると、一方向凝固時のシリコンの溶融温度を高くしても、多結晶シリコンインゴットの離型性、および離型層の鋳型への密着性が良好であることを見出し、本発明を完成するに至った。すなわち本発明は以下の事項に関する。 The present inventors have intensively studied to solve the above-mentioned problems, and have a specific specific surface area, a specific ratio of β-type silicon nitride and a specific particle size distribution, and specific metal impurities and metal impurities other than them. When the mold release layer of polycrystalline silicon ingot casting mold is formed using silicon nitride powder having a content ratio of less than a specified ratio and a crystallite diameter larger than a specified value, the melting temperature of silicon at the time of unidirectional solidification is It has been found that the releasability of the polycrystalline silicon ingot and the adhesion of the releasable layer to the mold are good even at high temperatures, and the present invention has been completed. That is, the present invention relates to the following matters.
（１） 窒化ケイ素粉末であって、ＢＥＴ法により測定される比表面積が０．４ｍ２／ｇ以上５ｍ２／ｇ以下であり、β型窒化ケイ素の割合が７０質量％以上であり、レーザ回折散乱法により測定される体積基準の５０％粒子径をＤ５０とし、９０％粒子径をＤ９０としたときに、Ｄ５０が２μｍ以上２０μｍ以下であり、Ｄ９０が８μｍ以上６０μｍ以下であり、Ｆｅの含有割合が１００ｐｐｍ以下であり、Ａｌの含有割合が１００ｐｐｍ以下であり、ＦｅおよびＡｌ以外の金属不純物の含有割合の合計が１００ｐｐｍ以下であり、β型窒化ケイ素の粉末Ｘ線回折パターンよりＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式を用いて算出されるβ型窒化ケイ素の結晶子径をＤＣとしたときに、ＤＣが３００ｎｍ以上であることを特徴とする窒化ケイ素粉末。(1) Silicon nitride powder having a specific surface area of 0.4 m 2 / g or more and 5 m 2 / g or less measured by BET method, and having a proportion of β-type silicon nitride of 70 mass% or more; Assuming that the volume-based 50% particle diameter measured by the scattering method is D50 and the 90% particle diameter is D90, D50 is 2 μm or more and 20 μm or less, D90 is 8 μm or more and 60 μm or less, and Fe content ratio Is 100 ppm or less, the content ratio of Al is 100 ppm or less, the total content ratio of metal impurities other than Fe and Al is 100 ppm or less, and the Willison-Hall equation is obtained from the powder X-ray diffraction pattern of β-type silicon nitride the crystallite size of β-type silicon nitride which is calculated using when a D C, silicon nitride powder, characterized in that D C is 300nm or more .
（２） β型窒化ケイ素の粉末Ｘ線回折パターンよりＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式を用いて算出されるβ型窒化ケイ素の結晶歪が０．８×１０−４以下であることを特徴とする上記（１）の窒化ケイ素粉末。(2) The crystal strain of β-type silicon nitride calculated from the powder X-ray diffraction pattern of β-type silicon nitride using the Williamson-Hall equation is 0.8 × 10 −4 or less. ) Silicon nitride powder.
（３） 前記比表面積より算出される比表面積相当径をＤＢＥＴとしたときに、ＤＢＥＴ／ＤＣ（ｎｍ／ｎｍ）が５以下であることを特徴とする上記（１）または（２）の窒化ケイ素粉末に関する。(3) When the specific surface area equivalent diameter calculated from the specific surface area is D BET , D BET / D C (nm / nm) is 5 or less, the above (1) or (2) Silicon nitride powder.
（４） Ｄ５０が３μｍ以上であることを特徴とする上記（１）〜（３）いずれかの窒化ケイ素粉末。 (4) The silicon nitride powder according to any one of the above (1) to (3), wherein D50 is 3 μm or more.
（５） Ｄ９０が５０μｍ以下であることを特徴とする上記（１）〜（４）いずれかの窒化ケイ素粉末。 (5) The silicon nitride powder according to any one of the above (1) to (4), wherein D90 is 50 μm or less.
（６） Ｄ９０が１３μｍ以上であることを特徴とする上記（１）〜（５）いずれかの窒化ケイ素粉末。 (6) The silicon nitride powder according to any one of the above (1) to (5), wherein D90 is 13 μm or more.
（７） β型窒化ケイ素の割合が８０質量％より大きいことを特徴とする上記（１）〜（６）いずれかの窒化ケイ素粉末。 (7) The silicon nitride powder according to any one of the above (1) to (6), wherein the proportion of β-type silicon nitride is greater than 80% by mass.
（８） Ｆｅの含有割合が２０ｐｐｍ以下であり、Ａｌの含有割合が２０ｐｐｍ以下であり、ＦｅおよびＡｌ以外の金属不純物の含有割合の合計が２０ｐｐｍ以下であることを特徴とする上記（１）〜（７）いずれかの窒化ケイ素粉末。 (8) The content of Fe is 20 ppm or less, the content of Al is 20 ppm or less, and the total content of metal impurities other than Fe and Al is 20 ppm or less. (7) Any silicon nitride powder.
（９） レーザ回折散乱法により測定される体積基準の１０％粒子径をＤ１０としたときに、Ｄ１０が０．５μｍ以上８μｍ以下であることを特徴とする上記（１）〜（８）いずれかの窒化ケイ素粉末。 (9) When the volume-based 10% particle diameter measured by the laser diffraction scattering method is D10, D10 is 0.5 μm or more and 8 μm or less, any one of the above (1) to (8) Silicon nitride powder.
（１０） 上記（１）〜（９）いずれかの窒化ケイ素粉末を含む多結晶シリコンインゴット用離型剤。 (10) A mold release agent for polycrystalline silicon ingot containing the silicon nitride powder according to any one of the above (1) to (9).
（１１） 鋳型内に収容された溶融シリコンを凝固させる多結晶シリコンインゴットの製造方法であって、前記鋳型として、前記溶融シリコンとの接触面に上記（１）〜（９）いずれかの窒化ケイ素粉末が塗布された鋳型を用いることを特徴とするシリコンインゴットの製造方法。 (11) A method for producing a polycrystalline silicon ingot for solidifying molten silicon contained in a mold, comprising the silicon nitride according to any one of the above (1) to (9) on the contact surface with the molten silicon as the mold. A manufacturing method of a silicon ingot characterized by using a mold to which powder was applied.
本発明の窒化ケイ素粉末によれば、一方向凝固時のシリコンの溶融温度を高くしても、あるいはシリコンの溶融時間を長くしても、多結晶シリコンインゴットの離型性と、離型層の鋳型への密着性を向上させることができる、多結晶シリコンインゴットの離型剤として好適な窒化ケイ素粉末を提供することができる。 According to the silicon nitride powder of the present invention, the releasability of the polycrystalline silicon ingot and the releasability of the polycrystalline silicon ingot can be obtained even if the melting temperature of silicon at the time of unidirectional solidification is increased or the melting time of silicon is increased. It is possible to provide a silicon nitride powder suitable as a mold release agent for polycrystalline silicon ingots, which can improve adhesion to a mold.
本発明の窒化ケイ素粉末の実施形態について詳しく説明する。 The embodiment of the silicon nitride powder of the present invention will be described in detail.
（窒化ケイ素粉末）
本発明の窒化ケイ素粉末は、ＢＥＴ法により測定される比表面積が０．４ｍ２／ｇ以上５ｍ２／ｇ以下の窒化ケイ素粉末であって、β型窒化ケイ素の割合が７０質量％以上であり、レーザ回折散乱法により測定される体積基準の５０％粒子径をＤ５０とし、９０％粒子径をＤ９０としたときに、Ｄ５０が２μｍ以上２０μｍ以下であり、Ｄ９０が８μｍ以上６０μｍ以下であり、Ｆｅの含有割合が１００ｐｐｍ以下であり、Ａｌの含有割合が１００ｐｐｍ以下であり、ＦｅおよびＡｌ以外の金属不純物の含有割合の合計が１００ｐｐｍ以下であり、β型窒化ケイ素の粉末Ｘ線回折パターンよりＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式を用いて算出されるβ型窒化ケイ素の結晶子径をＤＣとしたときに、ＤＣが３００ｎｍ以上であることを特徴とする。(Silicon nitride powder)
The silicon nitride powder of the present invention is a silicon nitride powder having a specific surface area of 0.4 m 2 / g or more and 5 m 2 / g or less measured by BET method, and the proportion of β-type silicon nitride is 70 mass% or more Assuming that the 50% particle diameter based on volume measured by the laser diffraction scattering method is D50 and the 90% particle diameter is D90, D50 is 2 μm or more and 20 μm or less, D90 is 8 μm or more and 60 μm or less, Fe The content ratio of Al is 100 ppm or less, the content ratio of Al is 100 ppm or less, and the total content of metal impurities other than Fe and Al is 100 ppm or less. According to the powder X-ray diffraction pattern of β-type silicon nitride the crystallite size of β-type silicon nitride which is calculated using the Hall type is taken as D C, to wherein the D C is 300nm or more .
本発明の窒化ケイ素粉末は、ＢＥＴ法により測定される比表面積が０．４ｍ２／ｇ以上５ｍ２／ｇ以下である。比表面積がこの範囲であれば、鋳型への密着性が良好な離型層を形成することができる。窒化ケイ素粉末のＢＥＴ法により測定される比表面積は、４．０ｍ２／ｇ以下、３．０ｍ２／ｇ以下、２．０ｍ２／ｇ以下でもよい。The silicon nitride powder of the present invention has a specific surface area of 0.4 m 2 / g or more and 5 m 2 / g or less measured by BET method. If the specific surface area is in this range, it is possible to form a release layer having good adhesion to the mold. The specific surface area of the silicon nitride powder measured by the BET method may be 4.0 m 2 / g or less, 3.0 m 2 / g or less, or 2.0 m 2 / g or less.
本発明の窒化ケイ素粉末は、β型窒化ケイ素の割合が７０質量％以上である。β型窒化ケイ素の割合がこの範囲であれば、多結晶シリコンインゴットの離型性も、鋳型への密着性も良好な離型層を形成することができる。この観点から、β型窒化ケイ素の割合は８０質量％より大きいことがさらに好ましい。β型窒化ケイ素の割合は８５質量％より大きいこと、９０質量％より大きいこと、９５質量％より大きいことができ、１００質量％であることもできる。 In the silicon nitride powder of the present invention, the proportion of β-type silicon nitride is 70% by mass or more. If the ratio of β-type silicon nitride is in this range, it is possible to form a release layer having good releasability of the polycrystalline silicon ingot and good adhesion to the mold. From this viewpoint, the proportion of β-type silicon nitride is more preferably greater than 80% by mass. The proportion of β-type silicon nitride may be greater than 85% by weight, greater than 90% by weight, greater than 95% by weight, and may be 100% by weight.
窒化ケイ素以外の成分は３質量％未満、さらには１質量％未満、特に０．１質量％未満が好ましい。窒化ケイ素以外の成分が存在すると、本願発明のような一方向凝時のシリコンの溶融温度を高くした場合でも、あるいはシリコンの溶融時間を長くした場合でも、多結晶シリコンインゴットの良好な離型性が得られなくなる恐れがある。 The content of components other than silicon nitride is preferably less than 3% by mass, more preferably less than 1% by mass, and particularly preferably less than 0.1% by mass. If a component other than silicon nitride is present, good releasability of polycrystalline silicon ingot is obtained even when the melting temperature of silicon is increased during unidirectional solidification as in the present invention, or even when the melting time of silicon is increased. There is a risk that you will not get
本発明の窒化ケイ素粉末は、レーザ回折散乱法により測定される体積基準の５０％粒子径をＤ５０としたときに、Ｄ５０が２μｍ以上２０μｍ以下である。Ｄ５０がこの範囲であれば、窒化ケイ素粒子同士の密着性も、窒化ケイ素粒子と鋳型との密着性も良くなりやすく、また緻密な離型層を形成しやすいので、多結晶シリコンインゴットの離型性も、鋳型への密着性も良好な離型層を形成することができる。Ｄ５０は３μｍ以上であることが好ましい。Ｄ５０は、５μｍ以上、１０μｍ以上、１５μｍ以上であってもよい。また、９０％粒子径をＤ９０としたときに、Ｄ９０は８μｍ以上６０μｍ以下である。Ｄ９０がこの範囲であれば、離型層の表面が平滑になりやすく、多結晶シリコンインゴットの離型性が良好な離型層を形成することができる。Ｄ９０は５０μｍ以下であることがさらに好ましく、４０μｍ以下であることが特に好ましい。Ｄ９０は、１３μｍ以上、１４μｍ以上、１５μm以上、１７μm以上、２０μm以上、３０μm以上であってもよい。 The silicon nitride powder of the present invention has a D50 of 2 μm or more and 20 μm or less, where D50 is a 50% particle diameter on a volume basis measured by a laser diffraction scattering method. If D50 is in this range, the adhesion between the silicon nitride particles and the adhesion between the silicon nitride particles and the mold tend to be good, and it is easy to form a fine release layer, so the release of polycrystalline silicon ingot It is possible to form a release layer having good properties as well as adhesion to the mold. It is preferable that D50 is 3 micrometers or more. D50 may be 5 μm or more, 10 μm or more, 15 μm or more. When the 90% particle diameter is D90, D90 is 8 μm or more and 60 μm or less. If D90 is in this range, the surface of the release layer is likely to be smooth, and a release layer having good releasability of the polycrystalline silicon ingot can be formed. D90 is more preferably 50 μm or less, and particularly preferably 40 μm or less. D90 may be 13 μm or more, 14 μm or more, 15 μm or more, 17 μm or more, 20 μm or more, 30 μm or more.
本発明の窒化ケイ素粉末は、レーザ回折散乱法により測定される体積基準の１０％粒子径をＤ１０としたときに、Ｄ１０が０．５μｍ以上８μｍ以下であることが好ましい。D１０は、０．６μm以上、０．７μm以上、１．０μm以上、２．０μm以上、４．０μm以上、６．０μm以上であってもよい。Ｄ１０がこの範囲であれば、離型層がより緻密化しやすくなり、多結晶シリコンインゴットの離型性も、鋳型への密着性もさらに良好な離型層を形成することができる。 The silicon nitride powder of the present invention preferably has a D10 of 0.5 μm or more and 8 μm or less, where D10 is a volume-based 10% particle diameter measured by a laser diffraction scattering method. D10 may be 0.6 μm or more, 0.7 μm or more, 1.0 μm or more, 2.0 μm or more, 4.0 μm or more, 6.0 μm or more. If D10 is in this range, the release layer is more easily densified, and the release layer of the polycrystalline silicon ingot and the adhesion to the mold can be further formed.
本発明の窒化ケイ素粉末は、Ｆｅの含有割合が１００ｐｐｍ以下である。Ｆｅの含有割合がこの範囲であれば、多結晶シリコンインゴットへのＦｅの混入を抑制することができるので、太陽電池用途に適用可能な多結晶シリコンインゴットの歩留まりが高くなる。Ｆｅの含有割合は２０ｐｐｍ以下であることが好ましく、１０ｐｐｍ以下、５ｐｐｍ以下であることが特に好ましい。また、本発明の窒化ケイ素粉末は、Ａｌの含有割合が１００ｐｐｍ以下である。Ａｌの含有割合がこの範囲であれば、多結晶シリコンインゴットへのＡｌの混入を抑制することができるので、太陽電池用途に適用可能な多結晶シリコンインゴットの歩留まりが高くなる。Ａｌの含有割合は２０ｐｐｍ以下であることが好ましく、１０ｐｐｍ以下、５ｐｐｍ以下であることが特に好ましい。また、ＦｅおよびＡｌ以外の金属不純物の含有割合の合計が１００ｐｐｍ以下である。ＦｅおよびＡｌ以外の金属不純物の含有割合がこの範囲であれば、多結晶シリコンインゴットへのＦｅおよびＡｌ以外の金属不純物の混入を抑制することができるので、太陽電池用途に適用可能な多結晶シリコンインゴットの歩留まりが高くなる。ＦｅおよびＡｌ以外の金属不純物の含有割合は２０ｐｐｍ以下であることが好ましく、１０ｐｐｍ以下、５ｐｐｍ以下であることが特に好ましい。 The silicon nitride powder of the present invention has an Fe content of 100 ppm or less. If the content ratio of Fe is in this range, the mixing of Fe into the polycrystalline silicon ingot can be suppressed, so the yield of polycrystalline silicon ingot applicable to solar cell applications is increased. The content ratio of Fe is preferably 20 ppm or less, and particularly preferably 10 ppm or less and 5 ppm or less. Moreover, the silicon nitride powder of this invention is 100 ppm or less in content rate of Al. If the content ratio of Al is in this range, the mixing of Al into the polycrystalline silicon ingot can be suppressed, and the yield of polycrystalline silicon ingots applicable to solar cell applications is increased. The content ratio of Al is preferably 20 ppm or less, and particularly preferably 10 ppm or less and 5 ppm or less. Moreover, the sum total of the content rate of metal impurities other than Fe and Al is 100 ppm or less. If the content ratio of metal impurities other than Fe and Al is in this range, the mixture of metal impurities other than Fe and Al in the polycrystalline silicon ingot can be suppressed, so polycrystalline silicon applicable to solar cell applications The yield of ingots is increased. The content of metal impurities other than Fe and Al is preferably 20 ppm or less, and more preferably 10 ppm or less and 5 ppm or less.
β型窒化ケイ素の粉末Ｘ線回折パターンよりＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式を用いて算出されるβ型窒化ケイ素の結晶子径をＤＣとしたとき、本発明の窒化ケイ素粉末は、ＤＣが３００ｎｍ以上である。ＤＣがこの範囲であれば、シリコンの溶融温度を高くしたり、溶融時間を長くしたりしても、多結晶シリコンインゴットの離型性も、鋳型への密着性も良好な離型層を形成することができる。ＤＣを３００ｎｍ以上とすることで、例えば１５００℃以上の高温で溶融シリコンと長時間接触しても、本発明の窒化ケイ素粉末は結晶の構造的安定性を維持できるものと推察される。この観点から、ＤＣは６００ｎｍ以上であることが好ましく、１０００ｎｍ以上、１５００ｎｍ以上であることがさらに好ましい。When the crystallite diameter of the β-type silicon nitride which is calculated using the Williamson-Hall type from powder X-ray diffraction pattern of β-type silicon nitride was D C, silicon nitride powder of the present invention is a D C is 300nm or more is there. If D C is in this range, the release layer of the polycrystalline silicon ingot exhibits good releasability and adhesion to the mold even if the melting temperature of silicon is increased or the melting time is increased. It can be formed. By the D C and above 300 nm, even prolonged contact with the molten silicon, for example 1500 ° C. or more high temperature, silicon nitride powder of the present invention is presumed to maintain the structural stability of the crystal. From this viewpoint, it is preferable that D C is 600nm or more, 1000 nm or more, and more preferably 1500nm or more.
本発明の窒化ケイ素粉末は、β型窒化ケイ素の粉末Ｘ線回折パターンよりＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式を用いて算出されるβ型窒化ケイ素の結晶歪が０．８×１０−４以下であることが好ましい。β型窒化ケイ素の結晶歪がこの範囲であれば、シリコンの溶融温度をより高くしても、多結晶シリコンインゴットの離型性も、鋳型への密着性も良好な離型層を形成することができる。前記結晶歪を０．８×１０−４以下とすることで、より高温で溶融シリコンと長時間接触しても、本発明の窒化ケイ素粉末は結晶の構造的安定性を維持できるものと推察される。この観点から、前記結晶歪は０．６×１０−４以下であることがさらに好ましく、０．５×１０−４以下、０．４×１０−４以下、０．３×１０−４以下であることが特に好ましい。The silicon nitride powder of the present invention preferably has a crystal strain of 0.8 × 10 -4 or less of β-type silicon nitride calculated from the powder X-ray diffraction pattern of β-type silicon nitride using the Williamson-Hall equation. . If the crystal strain of β-type silicon nitride is in this range, a release layer is formed which has good releasability of the polycrystalline silicon ingot and adhesion to the mold even if the melting temperature of silicon is higher. Can. By setting the crystal strain to 0.8 × 10 -4 or less, it is surmised that the silicon nitride powder of the present invention can maintain the structural stability of the crystal even if it contacts the molten silicon for a long time at a higher temperature. Ru. From this viewpoint, the crystal strain is more preferably 0.6 × 10 −4 or less, and 0.5 × 10 −4 or less, 0.4 × 10 −4 or less, 0.3 × 10 −4 or less Being particularly preferred.
本発明の窒化ケイ素粉末は、前記比表面積より算出される比表面積相当径をＤＢＥＴとしたときに、ＤＢＥＴ／ＤＣ（ｎｍ／ｎｍ）が５以下であることが好ましい。ＤＢＥＴ／ＤＣ（ｎｍ／ｎｍ）は、４以下、３以下であってもよい。ＤＢＥＴ／ＤＣ（ｎｍ／ｎｍ）がこの範囲であれば、シリコンの溶融温度をより高くしても、多結晶シリコンインゴットの離型性も、鋳型への密着性も良好な離型層を形成することができる。その理由は定かではないが、窒化ケイ素粉末を構成する窒化ケイ素の一粒子中の結晶子の界面の面積が小さい方が、高温で溶融シリコンと長時間接触した場合の、窒化ケイ素の結晶の構造的安定性をより高めると推察される。In the silicon nitride powder of the present invention, it is preferable that D BET / D C (nm / nm) is 5 or less, where D BET is a specific surface area equivalent diameter calculated from the specific surface area. D BET / D C (nm / nm) may be 4 or less and 3 or less. If D BET / D C (nm / nm) is in this range, the release layer has good releasability of polycrystalline silicon ingot and good adhesion to the mold even if the melting temperature of silicon is higher. It can be formed. The reason is not clear, but the smaller the area of the interface of crystallites in one particle of silicon nitride constituting the silicon nitride powder, the structure of the crystal of silicon nitride when it contacts with molten silicon for a long time at high temperature It is surmised that the
（多結晶シリコンインゴット用離型剤）
本発明の多結晶シリコンインゴット用離型剤は、本発明の窒化ケイ素粉末を含む。本発明の多結晶シリコンインゴット用離型剤は、本発明の窒化ケイ素粉末が主成分であれば良く、窒化ケイ素以外の成分を含んでいても良いが、本発明の窒化ケイ素粉末のみからなっていても良い。(Release agent for polycrystalline silicon ingot)
The mold release agent for polycrystalline silicon ingots of the present invention comprises the silicon nitride powder of the present invention. The releasing agent for polycrystalline silicon ingot of the present invention may be any main component of the silicon nitride powder of the present invention, and may contain components other than silicon nitride, but is composed only of the silicon nitride powder of the present invention It is good.
（多結晶シリコンインゴットの製造方法）
本発明の多結晶シリコンインゴットの製造方法を以下に説明する。本発明の多結晶シリコンインゴットの製造方法は、鋳型内に収容された溶融シリコンを凝固（特に一方向凝固）させる多結晶シリコンインゴットの製造方法であって、前記鋳型として、前記溶融シリコンとの接触面に本発明の窒化ケイ素粉末が塗布された鋳型を用いることを特徴とする。(Manufacturing method of polycrystalline silicon ingot)
The method for producing the polycrystalline silicon ingot of the present invention will be described below. The method for producing a polycrystalline silicon ingot according to the present invention is a method for producing a polycrystalline silicon ingot for solidifying (especially directionally solidifying) molten silicon contained in a mold, wherein the mold is in contact with the molten silicon as the mold. It is characterized by using a mold coated with the silicon nitride powder of the present invention on the surface.
（窒化ケイ素粉末の製造方法）
本発明の窒化ケイ素粉末の製造方法の一例を以下に説明する。本発明の窒化ケイ素粉末は、例えば、シリコンの燃焼反応に伴う自己発熱および伝播現象を利用した燃焼合成法により窒化ケイ素を合成する窒化ケイ素の燃焼合成プロセスにおいて、特定の製造条件を用い、具体的には、原料のシリコン粉末に希釈剤として窒化ケイ素粉末を特定の割合で混合し、原料のシリコン粉末と希釈剤として窒化ケイ素粉末の金属不純物の含有割合を少なくし、シリコン粉末と窒化ケイ素粉末との混合物の充填密度を小さくして燃焼反応を行って圧壊強度が小さい燃焼生成物を作製し、得られた圧壊強度が小さい燃焼生成物を、粉砕エネルギーが小さくかつ金属不純物が混入し難い方法を用いて粉砕することによって、金属不純物の含有割合が少なく、β型窒化ケイ素の含有割合が大きく、本発明で特定する比表面積及び粒径分布を有し、結晶子径が大きく結晶歪が小さい等の特徴を有する窒化ケイ素粉末を製造することができる。以下、その製造方法の一例を具体的に説明する。(Method of producing silicon nitride powder)
An example of the method for producing the silicon nitride powder of the present invention will be described below. The silicon nitride powder of the present invention can be produced, for example, by using specific production conditions in the process of synthesis of silicon nitride which synthesizes silicon nitride by a combustion synthesis method utilizing self-heating and propagation phenomena accompanying combustion reaction of silicon. The silicon powder of the raw material is mixed with the silicon powder as a diluent at a specific ratio to reduce the content of metal impurities in the silicon powder of the raw material and the silicon nitride powder as the diluent, and the silicon powder and the silicon nitride powder The packing density of the mixture is reduced and combustion reaction is carried out to produce a combustion product having a small crushing strength, and the obtained combustion product having a small crushing strength is subjected to a method having a small crushing energy and being hard to mix with metal impurities. By using and grinding, the content ratio of metal impurities is small, the content ratio of β-type silicon nitride is large, and the specific surface area specified in the present invention A beauty particle size distribution, it is possible to produce a silicon nitride powder having a characteristic such as large crystal strains crystallite size is smaller. Hereinafter, an example of the manufacturing method will be specifically described.
＜混合原料粉末の調製工程＞
はじめに、シリコン粉末と、希釈剤の窒化ケイ素粉末とを混合して、混合原料粉末を調製する。燃焼合成反応は１８００℃以上の高温となるため、燃焼反応する部分でシリコンの溶融・溶着が起こることがある。これを抑制する目的で、燃焼反応の自己伝播を妨げない範囲で、原料粉末に希釈剤として窒化ケイ素粉末を添加することが好ましい。希釈剤の添加率は、通常、１０〜５０質量％（シリコン：窒化ケイ素の質量比が９０：１０〜５０：５０）、さらには１５〜４０質量％である。また、燃焼合成反応で得られる燃焼生成物のβ型窒化ケイ素の割合を調整する上で、ＮＨ４ＣｌやＮａＣｌなどを添加しても良い。これらの添加物は顕熱、潜熱および吸熱反応により反応温度を下げる効果がある。ここで、得られる混合原料粉末における、Ｆｅの含有割合、Ａｌの含有割合、ＦｅおよびＡｌ以外の金属不純物の含有割合は、それぞれ１００ｐｐｍ以下、さらには５０ｐｐｍ以下、１０ｐｐｍ以下とすることが好ましい。したがって、シリコン粉末にも、希釈剤の窒化ケイ素粉末にも、金属不純物の含有割合が少ない高純度な粉末を用いることが好ましい。また、原料粉末の混合に用いる混合容器の内面と混合メディアなどの、原料粉末と接触する箇所は、ＡｌおよびＦｅなどの含有割合が少ない非金属製の素材であることが好ましい。原料粉末の混合方法は特に制限されないが、例えばボールミル混合を採用する場合は、混合容器の内面は樹脂製であることが好ましく、混合メディアの外面は窒化ケイ素製であることが好ましい。また、混合原料粉末のかさ密度を０．５ｇ／ｃｍ３未満とすることが好ましい。混合原料粉末のかさ密度を０．５ｇ／ｃｍ３未満にするには、かさ密度が０．４５ｇ／ｃｍ３以下のシリコン粉末を原料粉末として用いることが好ましい。混合原料粉末のかさ密度が０．５ｇ／ｃｍ３未満ならば、後述する＜燃焼合成反応工程＞にて得られる塊状の燃焼生成物の圧壊強度を４ＭＰａ以下にすることが容易である。<Preparation process of mixed raw material powder>
First, silicon powder and silicon nitride powder as a diluent are mixed to prepare mixed raw material powder. Since the combustion synthesis reaction has a high temperature of 1,800 ° C. or more, melting and deposition of silicon may occur in the portion where the combustion reaction occurs. For the purpose of suppressing this, it is preferable to add silicon nitride powder as a diluent to the raw material powder, as long as the self propagation of the combustion reaction is not hindered. The addition rate of the diluent is usually 10 to 50% by mass (the mass ratio of silicon: silicon nitride is 90:10 to 50:50), and further 15 to 40% by mass. In addition, NH 4 Cl or NaCl may be added to adjust the ratio of β-type silicon nitride of the combustion product obtained by the combustion synthesis reaction. These additives have the effect of lowering the reaction temperature by sensible heat, latent heat and endothermic reaction. Here, in the mixed raw material powder to be obtained, the content ratio of Fe, the content ratio of Al, and the content ratio of metal impurities other than Fe and Al are preferably 100 ppm or less, more preferably 50 ppm or less, and 10 ppm or less. Therefore, it is preferable to use a high purity powder having a low content of metal impurities, both for silicon powder and silicon nitride powder as a diluent. Moreover, it is preferable that the location which contacts raw material powder, such as the inner surface of a mixing container used for mixing of raw material powder, and mixing media, is a nonmetallic raw material with few content ratios, such as Al and Fe. The mixing method of the raw material powder is not particularly limited, but for example, in the case of employing ball mill mixing, the inner surface of the mixing container is preferably made of resin, and the outer surface of the mixed medium is preferably made of silicon nitride. Moreover, it is preferable to make bulk density of mixed raw material powder less than 0.5 g / cm < 3 >. The bulk density of the mixed raw material powder to be less than 0.5 g / cm 3, it is preferable that the bulk density is used 0.45 g / cm 3 or less of the silicon powder as the raw material powder. If the bulk density of the mixed raw material powder is less than 0.5 g / cm 3 , it is easy to set the crush strength of the massive combustion product obtained in <combustion synthesis reaction step> to 4 MPa or less.
＜燃焼合成反応工程＞
次いで、得られた混合原料粉末を窒素含有雰囲気にて燃焼させて、窒化ケイ素からなる塊状の燃焼生成物を作製する。例えば、混合原料粉末を黒鉛製などの容器に着火剤と一緒に収容し、燃焼合成反応装置内で、着火剤に着火し、着火剤の窒化燃焼熱によって混合原料粉末中のシリコンの窒化反応を開始させ、同反応をシリコン全体に自己伝播させて燃焼合成反応を完了させ、窒化ケイ素からなる塊状の燃焼生成物を得る。<Combustion synthesis reaction process>
Next, the mixed raw material powder obtained is burned in a nitrogen-containing atmosphere to produce a massive combustion product of silicon nitride. For example, mixed raw material powder is accommodated together with an ignition agent in a container made of graphite or the like, the ignition agent is ignited in the combustion synthesis reactor, and the nitriding reaction of silicon in the mixed raw material powder is carried out by the nitriding combustion heat of the ignition agent. The reaction is self-propagated throughout the silicon to complete the combustion synthesis reaction to obtain a massive combustion product of silicon nitride.
ここで、得られる燃焼生成物は、その圧壊強度が４ＭＰａ以下であることが好ましい。燃焼生成物の圧壊強度が４ＭＰａ以下ならば、後述する＜燃焼生成物の粉砕・分級工程＞にて、金属不純物の混入が多くなるような、また窒化ケイ素粉末の結晶性が低下するような粉砕エネルギーの大きい粉砕を行わなくても、本発明にて特定する比表面積または粒度分布（Ｄ５０、Ｄ９０またはＤ１０）の窒化ケイ素粉末を得ることが容易になる。 Here, the combustion product obtained preferably has a crushing strength of 4 MPa or less. If the crushing strength of the combustion product is 4 MPa or less, grinding is performed such that the mixing of metal impurities is increased in the <grind and classification step of combustion product> described later, and the crystallinity of the silicon nitride powder is reduced. It becomes easy to obtain the silicon nitride powder having the specific surface area or the particle size distribution (D50, D90 or D10) specified in the present invention even if the pulverization with high energy is not performed.
＜燃焼生成物の粉砕・分級工程＞
次いで、得られた塊状の燃焼生成物を粗粉砕する。粗粉砕の粉砕手段に特に制限はないが、粉砕メディアとして、ＡｌおよびＦｅなどの含有割合が少ない硬質な非金属製の素材を用いることが好ましく、窒化ケイ素製の粉砕メディアを用いることがさらに好ましい。燃焼生成物が塊状であることから、ロールクラッシャーによる粉砕が効率的であり、ロールクラッシャーとしては、窒化ケイ素などのセラミックス製のロールを供えていることが好ましい。<Pulverization and classification process of combustion products>
The resulting massive combustion products are then coarsely crushed. There is no particular limitation on the grinding means of the coarse grinding, but it is preferable to use a hard nonmetallic material having a small content ratio such as Al and Fe as a grinding medium, and it is more preferable to use a grinding medium made of silicon nitride . Since the combustion products are massive, grinding by a roll crusher is efficient, and it is preferable that a roll made of a ceramic such as silicon nitride be provided as the roll crusher.
以上のような粗粉砕によって得られた窒化ケイ素粉末を篩通して、特に粗大な粒子などを除去することで、本発明の窒化ケイ素粉末を得ることができる。篩通しに用いる篩は、ＡｌおよびＦｅなどの含有割合が少ない非金属製であることが好ましく、樹脂製であることが好ましい。 The silicon nitride powder of the present invention can be obtained by sieving the silicon nitride powder obtained by the above-mentioned coarse pulverization to remove particularly coarse particles and the like. The sieve used for the sieving is preferably made of a nonmetal having a small content of Al, Fe and the like, and is preferably made of a resin.
また、所望の比表面積、Ｄ５０またはＤ９０によっては、得られた窒化ケイ素粉末を微粉砕することができる。微粉砕の粉砕手段に特に制限はないが、振動ミルによる粉砕が好ましい。振動ミル用のポットの内面と混合メディアなどの、原料粉末と接触する箇所は、ＡｌおよびＦｅなどの含有割合が少ない非金属製の素材であることが好ましい。ポットの内面は樹脂製であることが好ましく、混合メディアは窒化ケイ素製であることが好ましい。振動ミルの条件（振幅、振動数、粉砕時間）を適宜調節して、所望の比表面積または粒度分布（Ｄ５０、Ｄ９０またはＤ１０）の、本発明の窒化ケイ素粉末を得ることができる。 In addition, depending on the desired specific surface area, D50 or D90, the obtained silicon nitride powder can be pulverized. There is no particular limitation on the pulverizing means of pulverizing, but pulverizing with a vibration mill is preferable. It is preferable that the locations in contact with the raw material powder, such as the inner surface of the pot for the vibration mill and the mixed media, be nonmetallic materials having a small content ratio of Al, Fe and the like. The inner surface of the pot is preferably made of resin, and the mixed medium is preferably made of silicon nitride. The conditions (amplitude, frequency, grinding time) of the vibration mill can be adjusted as appropriate to obtain the silicon nitride powder of the present invention having a desired specific surface area or particle size distribution (D50, D90 or D10).
以上のように、本発明の窒化ケイ素粉末は、シリコン粉末と、希釈剤の窒化ケイ素粉末とを混合し、得られた混合原料粉末を容器に充填して燃焼反応に伴う自己発熱および伝播現象を利用した燃焼合成法により前記シリコン粉末を燃焼させ、得られた燃焼生成物を粉砕する窒化ケイ素粉末の製造方法において、前記混合原料粉末は、Ｆｅの含有割合、Ａｌの含有割合、およびＦｅとＡｌ以外の金属不純物の含有割合が、それぞれ１００ｐｐｍ以下で、かさ密度が０．５ｇ／ｃｍ３未満である窒化ケイ素粉末の製造方法により製造されることが好ましく、さらに、前記燃焼生成物の圧壊強度が４ＭＰａ以下であることが好ましく、特に、前記燃焼生成物の粉砕に窒化ケイ素製の粉砕メディアを用いることが好ましい。As described above, the silicon nitride powder of the present invention is obtained by mixing the silicon powder and the silicon nitride powder as a diluent, filling the obtained mixed raw material powder in a container, and generating self-heating and propagation phenomena associated with the combustion reaction. In the method for producing a silicon nitride powder in which the silicon powder is burned by the combustion synthesis method used and the obtained combustion product is crushed, the mixed raw material powder includes a content ratio of Fe, a content ratio of Al, and Fe and Al It is preferable to manufacture by the manufacturing method of the silicon nitride powder whose content rates of metal impurities other than 100 ppm or less, respectively, and bulk density is less than 0.5 g / cm 3 , and further, crushing strength of the said combustion product is The pressure is preferably 4 MPa or less, and in particular, it is preferable to use a grinding media made of silicon nitride for grinding the combustion product.
以下に具体例を挙げて、本発明をさらに詳しく説明する。本発明の窒化ケイ素粉末、原料粉末として用いたシリコン粉末、原料混合粉末および燃焼生成物の物性測定と、本発明の窒化ケイ素粉末を鋳型の離型剤に適用した場合の多結晶シリコンインゴットの離型性の評価は、以下の方法により行った。 The present invention will be described in more detail by way of specific examples. Physical property measurement of silicon nitride powder of the present invention, silicon powder used as raw material powder, raw material mixed powder and combustion product, and release of polycrystalline silicon ingot when silicon nitride powder of the present invention is applied to mold release agent The evaluation of the moldability was performed by the following method.
（窒化ケイ素粉末の比表面積の測定方法、および比表面積相当径ＤＢＥＴの算出方法）
本発明の窒化ケイ素粉末の比表面積は、Ｍｏｕｎｔｅｃｈ社製Ｍａｃｓｏｒｂを用いて、窒素ガス吸着によるＢＥＴ１点法にて測定して求めた。(Method of measuring specific surface area of silicon nitride powder, and method of calculating specific surface area equivalent diameter D BET )
The specific surface area of the silicon nitride powder of the present invention was determined by measuring with a BET one-point method by nitrogen gas adsorption using Macsorb manufactured by Mountech.
また、比表面積相当径ＤＢＥＴは、粉末を構成する全ての粒子が同一径の球と仮定して、下記の式（１）より求めた。
ＤＢＥＴ＝６／（ρＳ×Ｓ）・・・（１）The specific surface area equivalent diameter D BET was obtained from the following equation (1), assuming that all particles constituting the powder are spheres of the same diameter.
D BET = 6 / (ρ S × S) (1)
ここで、ρＳは窒化ケイ素の真密度（α-Ｓｉ３Ｎ４の真密度３１８６ｋｇ／ｍ３、β-Ｓｉ３Ｎ４の真密度３１９２ｋｇ／ｍ３と、α相とβ相との比により平均真密度を算出し、真密度とした。）、Ｓは比表面積（ｍ２／ｇ）である。Here, [rho S is the true density of silicon nitride (α-Si 3 N 4 of the true density 3186kg / m 3, the true density of 3192kg / m 3 of β-Si 3 N 4, the ratio of the alpha phase and beta phase The average true density was calculated and taken as the true density), S is the specific surface area (m 2 / g).
（窒化ケイ素粉末のβ型窒化ケイ素の割合の測定方法）
本発明の窒化ケイ素粉末のβ型窒化ケイ素粉末の割合は以下のようにして算出した。本発明の窒化ケイ素粉末について、銅の管球からなるターゲットおよびグラファイトモノクロームメーターを使用して、回折角（２θ）１５〜８０°の範囲を０．０２°刻みでＸ線検出器をステップスキャンする定時ステップ走査法にてＸ線回折測定を行った。窒化ケイ素粉末が窒化ケイ素以外の成分を含む場合には、それらの成分のピークをそれらの成分の標準試料の対応するピークと対比することでそれらの成分の割合を求めることができる。以下のすべての実施例及び比較例では、得られた粉末Ｘ線回折パターンより、本発明の窒化ケイ素粉末がα型窒化ケイ素とβ型窒化ケイ素のみから構成されていることを確認した。その上で、本発明の窒化ケイ素粉末のβ型窒化ケイ素の割合は、Ｇ．Ｐ．Ｇａｚｚａｒａ ａｎｄ Ｄ．Ｐ．Ｍｅｓｓｉｅｒ，“Ｄｅｔｅｒｍｉｎａｔｉｏｎ ｏｆ Ｐｈａｓｅ Ｃｏｎｔｅｎｔ ｏｆ Ｓｉ３Ｎ４ ｂｙ Ｘ−ｒａｙ Ｄｉｆｆｒａｃｔｉｏｎ Ａｎａｌｙｓｉｓ”，Ａｍ． Ｃｅｒａｍ．Ｓｏｃ．Ｂｕｌｌ．，５６［９］７７７−８０（１９７７）に記載されたＧａｚｚａｒａ ＆ Ｍｅｓｓｉｅｒの方法により、算出した。(Method of measuring proportion of β-type silicon nitride in silicon nitride powder)
The ratio of β-type silicon nitride powder of the silicon nitride powder of the present invention was calculated as follows. For the silicon nitride powder of the present invention, using a target made of a copper tube and a graphite monochrome meter, step scan the X-ray detector in the range of diffraction angles (2θ) of 15-80 ° in steps of 0.02 ° The X-ray diffraction measurement was performed by the fixed step scanning method. When the silicon nitride powder contains components other than silicon nitride, the ratio of those components can be determined by comparing the peaks of those components with the corresponding peaks of the standard samples of those components. In all of the following examples and comparative examples, it was confirmed from the obtained powder X-ray diffraction patterns that the silicon nitride powder of the present invention was composed only of α-type silicon nitride and β-type silicon nitride. In addition, the proportion of β-type silicon nitride in the silicon nitride powder according to the invention is as described in G.I. P. Gazzara and D. P. Messier, "Determination of Phase Content of Si3N4 by X-ray Diffraction Analysis", Am. Ceram. Soc. Bull. , 56 [9] 777-80 (1977), calculated by the method of Gazzara & Messier.
（窒化ケイ素粉末のＤ１０、Ｄ５０およびＤ９０の測定方法）
本発明の窒化ケイ素粉末、本発明で原料として使用したシリコン粉末の粒度分布は、以下のようにして測定した。前記粉末を、ヘキサメタリン酸ソーダ０．２質量％水溶液中に投入して、直径２６ｍｍのステンレス製センターコーンを取り付けた超音波ホモジナイザーを用いて３００Ｗの出力で６分間分散処理して希薄溶液を調製し、測定試料とした。レーザ回折／散乱式粒子径分布測定装置（日機装株式会社製マイクロトラックＭＴ３０００）を用いて測定試料の粒度分布を測定し、体積基準の粒度分布曲線とそのデータを得た。得られた粒度分布曲線とそのデータより、本発明の窒化ケイ素粉末のＤ５０、Ｄ９０およびＤ１０と、本発明で原料として使用したシリコン粉末のＤ５０を算出した。(Method of measuring D10, D50 and D90 of silicon nitride powder)
The particle size distribution of the silicon nitride powder of the present invention and the silicon powder used as a raw material in the present invention was measured as follows. The above powder is put into a 0.2% by mass aqueous solution of sodium hexametaphosphate, and dispersed for 6 minutes at a power of 300 W using an ultrasonic homogenizer equipped with a stainless steel center cone 26 mm in diameter to prepare a dilute solution. , And the measurement sample. The particle size distribution of the measurement sample was measured using a laser diffraction / scattering type particle size distribution measuring apparatus (Microtrac MT 3000, manufactured by Nikkiso Co., Ltd.), and a volume-based particle size distribution curve and its data were obtained. From the obtained particle size distribution curve and the data thereof, D50, D90 and D10 of the silicon nitride powder of the present invention and D50 of the silicon powder used as a raw material in the present invention were calculated.
（窒化ケイ素粉末、シリコン粉末および原料混合粉末のＦｅ、Ａｌ、およびＦｅとＡｌ以外の金属不純物の含有割合の測定方法）
本発明の窒化ケイ素粉末、本発明で原料として使用したシリコン粉末、および原料混合粉末のＦｅおよびＡｌ、ＦｅおよびＡｌ以外の金属不純物の含有割合は、以下のようにして測定した。フッ酸と硝酸とを混合した液を収容した容器に、上記粉末を投入し密栓して、同容器にマイクロ波を照射して加熱し、窒化ケイ素またはシリコンを完全に分解し、得られた分解液を超純水で定容して検液とした。エスアイアイ・ナノテクノロジー社製ＩＣＰ−ＡＥＳ（ＳＰＳ５１００型）を用いて、検出された波長とその発光強度から検液中のＦｅ、Ａｌ、およびＦｅとＡｌ以外の金属不純物を定量し、Ｆｅ、Ａｌ、およびＦｅとＡｌ以外の金属不純物の含有割合を算出した。(Method of measuring the content ratio of Fe, Al, and metallic impurities other than Fe and Al of silicon nitride powder, silicon powder and raw material mixed powder)
The content ratios of the silicon nitride powder of the present invention, the silicon powder used as a raw material in the present invention, and Fe and Al, Fe, and metal impurities other than Al in the raw material mixed powder were measured as follows. The above powder is charged into a container containing a mixture of hydrofluoric acid and nitric acid and sealed up, and the container is irradiated with microwaves and heated to completely decompose silicon nitride or silicon, and the obtained decomposition is obtained. The solution was adjusted to volume with ultrapure water to prepare a test solution. Fe, Al, and metallic impurities other than Fe and Al in the test solution are quantified from the detected wavelength and its emission intensity using ICP-AES (SPS 5100 type) manufactured by SII Nano Technology Inc., Fe, Al The content ratio of metal impurities other than Fe and Al was calculated.
（β型窒化ケイ素の結晶子径ＤＣおよび結晶歪の測定方法）
本発明の窒化ケイ素粉末のβ型窒化ケイ素の結晶子径ＤＣおよび結晶歪は、次のようにして測定した。本発明の窒化ケイ素粉末について、銅の管球からなるターゲットおよびグラファイトモノクロームメーターを使用して、回折角（２θ）１５〜８０°の範囲を０．０２°刻みでＸ線検出器をステップスキャンする定時ステップ走査法にてＸ線回折測定を行った。得られた本発明の窒化ケイ素粉末のＸ線回折パターンより、β型窒化ケイ素の（１０１）、（１１０）、（２００）、（２０１）および（２１０）面のそれぞれの積分幅を算出し、前記積分幅を下記の式（２）のＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式に代入した。下記の式（２）における「２ｓｉｎθ／λ」をｘ軸、「βｃｏｓθ／λ」をｙ軸としてプロットし、最小二乗法を用いて、このＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式より得られる直線の切片および傾きを求めた。そして、前記切片よりβ型窒化ケイ素の結晶子径Ｄｃを、また、前記傾きよりβ型窒化ケイ素の結晶歪を算出した。
βｃｏｓθ／λ＝η×（２ｓｉｎθ／λ）＋（１／Ｄｃ）・・・（２）
（β；積分幅（ｒａｄ）、θ；ブラッグ角（ｒａｄ）、η；結晶歪、λ；Ｘ線源の波長（ｎｍ）、Ｄｃ；結晶子径（ｎｍ））(Method of measuring crystallite diameter D C and crystal strain of β-type silicon nitride)
Crystallite diameter D C and crystal distortion β-type silicon nitride of the silicon nitride powder of the present invention was measured as follows. For the silicon nitride powder of the present invention, using a target made of a copper tube and a graphite monochrome meter, step scan the X-ray detector in the range of diffraction angles (2θ) of 15-80 ° in steps of 0.02 ° The X-ray diffraction measurement was performed by the fixed step scanning method. From the X-ray diffraction pattern of the obtained silicon nitride powder of the present invention, the respective integral widths of (101), (110), (200), (201) and (210) planes of β-type silicon nitride are calculated, The integration width was substituted into the Williamson-Hall equation of the following equation (2). Plot “2 sin θ / λ” in the following equation (2) with x axis and “β cos θ / λ” as y axis, and use the least squares method to find the intercept and slope of the straight line obtained from this Williamson-Hall equation The Then, the crystallite diameter Dc of β-type silicon nitride was calculated from the section, and the crystal strain of β-type silicon nitride was calculated from the inclination.
β cos θ / λ = η × (2 sin θ / λ) + (1 / Dc) (2)
(Β; integral width (rad), θ; Bragg angle (rad), η; crystal strain, λ; wavelength of X-ray source (nm), Dc: crystallite diameter (nm))
（混合原料粉末のかさ密度の測定方法）
本発明で得られる混合原料粉末のかさ密度は、ＪＩＳ Ｒ１６２８「ファインセラミックス粉末のかさ密度測定方法」に準拠した方法により求めた。(Method of measuring bulk density of mixed raw material powder)
The bulk density of the mixed raw material powder obtained in the present invention was determined by a method in accordance with JIS R1628 "Method for measuring bulk density of fine ceramic powder".
（燃焼生成物の圧壊強度の測定方法）
本発明で得られる燃焼生成物の圧壊強度は、以下のようにして測定した。燃焼生成物より、一辺が１０ｍｍの立方体を５個切り出して測定試料とした。手動式圧壊強度測定装置（アイコーエンジニアリング株式会社製、ＭＯＤＥＬ-１３３４型）を用いて前記測定試料の圧壊強度を測定した。台座に載置した測定試料に荷重を印加して圧縮試験を行い、測定された最大荷重より圧壊強度を算出した。本発明で得られる燃焼生成物の圧壊強度は、５個の測定試料の圧壊強度の平均値とした。(Method of measuring crushing strength of combustion products)
The crushing strength of the combustion product obtained in the present invention was measured as follows. From the combustion product, five cubes each having a side of 10 mm were cut out and used as measurement samples. The crushing strength of the measurement sample was measured using a manual crushing strength measuring device (Model 1334 manufactured by Aiko Engineering Co., Ltd.). A load was applied to the measurement sample placed on the pedestal to perform a compression test, and the crushing strength was calculated from the measured maximum load. The crushing strength of the combustion product obtained in the present invention was taken as an average value of crushing strengths of five measurement samples.
（多結晶シリコンインゴットの離型性の評価方法）
本発明においては、本発明の窒化ケイ素粉末を離型剤として塗布して作製した鋳型を用いて多結晶シリコンインゴットの一方向凝固実験を行い、多結晶シリコンインゴットを鋳型から離型して、以下のようにして本発明の窒化ケイ素粉末を評価した。多結晶シリコンインゴットが鋳型から離型でき、多結晶シリコンインゴットに離型層の付着が確認されない場合を○、多結晶シリコンインゴットが鋳型から離型できるものの、多結晶シリコンインゴットに離型層の付着が確認される場合を△、多結晶シリコンインゴットが鋳型から離型できないか、離型できても多結晶シリコンインゴットに割れまたは欠けが生じる場合を×とした。(Evaluation method of releasability of polycrystalline silicon ingot)
In the present invention, a unidirectional solidification experiment of a polycrystalline silicon ingot is conducted using a mold produced by applying the silicon nitride powder of the present invention as a mold release agent, and the polycrystalline silicon ingot is released from the mold. The silicon nitride powder of the present invention was evaluated as follows. When the polycrystalline silicon ingot can be released from the mold and adhesion of the release layer is not confirmed in the polycrystalline silicon ingot, ○, although the polycrystalline silicon ingot can be released from the mold, adhesion of the release layer to the polycrystalline silicon ingot In the case where is confirmed, the case in which the polycrystalline silicon ingot can not be released from the mold, or in the case where it can be released, cracking or chipping in the polycrystalline silicon ingot is regarded as ×.
（多結晶シリコンインゴットに含まれる金属不純物の測定方法）
一方向凝固実験にて得られた多結晶シリコンインゴットに含まれるＦｅ、Ａｌ、およびＦｅとＡｌ以外の金属不純物を、以下のようにして測定した。得られた多結晶シリコンインゴットを、切断面が凝固方向に対して平行になるように二分割し、その切断面の中心軸上で、底から１ｃｍ上の位置を測定位置として、飛行時間型二次イオン質量分析法（アルバック・ファイ社製（ＴＲＩＦＴ Ｖ ｎａｎｏ ＴＯＦ型））にて表面分析を行った。Ｆｅ、Ａｌ、およびＦｅとＡｌ以外の金属不純物の二次質量スペクトルの規格化二次イオン強度が１×１０−４以上の場合を検出、１×１０−４未満の場合を未検出とした。ここで、規格化二次イオン強度とは、各スペクトルの二次イオン強度を、検出された全スペクトルの二次イオン強度で除したものである。(Method of measuring metal impurities contained in polycrystalline silicon ingot)
Fe, Al, and metal impurities other than Fe and Al contained in the polycrystalline silicon ingot obtained in the directional solidification experiment were measured as follows. The obtained polycrystalline silicon ingot is divided into two so that the cut surface is parallel to the solidification direction, and a position 1 cm from the bottom on the central axis of the cut surface is taken as a measurement position. Surface analysis was performed by next ion mass spectrometry (manufactured by ULVAC-PHI, Inc. (TRIFT V nano TOF type)). The case where the secondary ion intensity of secondary mass spectra of Fe, Al, and metal impurities other than Fe and Al was 1 × 10 −4 or more was detected, and the case of less than 1 × 10 4 was not detected. Here, the normalized secondary ion intensity is obtained by dividing the secondary ion intensity of each spectrum by the secondary ion intensity of all detected spectra.
（実施例１−１）
Ｄ５０が４．０μｍ、かさ密度が０．４０ｇ／ｃｍ３で、Ｆｅの含有割合が３ｐｐｍ、Ａｌの含有割合が４ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が３ｐｐｍのシリコン粉末に、希釈剤として、窒化ケイ素粉末（宇部興産株式会社製、製品名「ＳＮ−Ｅ１０」（Ｆｅの含有割合；９ｐｐｍ、Ａｌの含有割合；２ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合；４ｐｐｍ））を、窒化ケイ素の添加率が２０質量％（シリコン：窒化ケイ素の質量比が８０：２０）になるように添加して原料粉末とした。前記原料粉末を、窒化ケイ素製ボールが充填された、内壁面がウレタンでライニングされたナイロン製のポットに収容して、バッチ式振動ミルを用いて、振動数１２００ｃｐｍ、振幅８ｍｍで０．５時間混合し、混合原料粉末を得た。Example 1-1
Diluent to silicon powder with D50 of 4.0 μm, bulk density of 0.40 g / cm 3 , Fe content rate of 3 ppm, Al content rate of 4 ppm, and Fe and other metal impurities content rate of 3 ppm As a silicon nitride powder (manufactured by Ube Industries, Ltd., product name "SN-E10" (content ratio of Fe: 9 ppm, content ratio of Al; 2 ppm, content ratio of metal impurities other than Fe and Al; 4 ppm)), It was added as the raw material powder so that the addition rate of silicon nitride might be 20 mass% (the mass ratio of silicon: silicon nitride is 80:20). The raw material powder is accommodated in a nylon pot filled with silicon nitride balls and whose inner wall is urethane-lined, and a batch type vibration mill is used for 0.5 hours with a frequency of 1200 cpm and an amplitude of 8 mm. It mixed and obtained mixed raw material powder.
図１に、本実施例にてシリコンの燃焼合成反応に用いる燃焼合成反応装置１を示す。前記原料粉末を混合して得られた混合原料粉末２を、底面が２００×４００ｍｍで、深さが３０ｍｍで、厚みが１０ｍｍの角サヤ状の黒鉛製容器３に収容した。このとき混合原料粉末のかさ密度は０．４５ｇ／ｃｍ３であった。チタン粉末とカーボン粉末とをチタン：カーボンが４：１の質量比で混合し成形して、燃焼合成反応に用いる着火剤４を調製し、着火剤４を混合原料粉末２の上に載置した。次いで、混合原料粉末２および着火剤４が収容された黒鉛製容器３を、着火剤加熱用のカーボンヒータ５を備えた耐圧性容器６内に、着火剤４の直上にカーボンヒータ５が位置するように収容した。FIG. 1 shows a combustion synthesis reaction apparatus 1 used for the combustion synthesis reaction of silicon in the present embodiment. The mixed raw material powder 2 obtained by mixing the above raw material powder was accommodated in a square-sheared graphite container 3 having a bottom surface of 200 × 400 mm, a depth of 30 mm and a thickness of 10 mm. At this time, the bulk density of the mixed raw material powder was 0.45 g / cm 3 . A mixture of titanium powder and carbon powder in a mass ratio of titanium to carbon of 4: 1 was formed to prepare an
耐圧性容器６内を、真空ポンプ７を用いて脱気した後、前記反応容器内に窒素ボンベ８より窒素ガスを導入して雰囲気圧力を０．６ＭＰａとした。次に、カーボンヒータ５に通電して着火剤４を加熱し、前記混合原料粉末を着火させ、燃焼合成反応を開始させた。燃焼合成反応中、耐圧性容器６の窒素雰囲気圧力は０．６ＭＰａでほぼ一定であった。覗き窓９から耐圧性容器６の内部を観察したところ、燃焼合成反応は、約２０分継続した後、終了した。反応終了後、耐圧性容器６から黒鉛製容器３を取り出し、塊状の燃焼生成物を回収した。
After degassing the inside of the pressure
得られた燃焼生成物から着火剤近傍部分を除去し、残りの部分を、内面がウレタンコーティングされ、窒化ケイ素製ロールを備えたロールクラッシャーで粗粉砕して、目開きが１００μｍのナイロン製篩で篩通しし、篩下の粉末を回収して、実施例１−１の窒化ケイ素粉末を得た。 A portion near the ignition agent is removed from the obtained combustion product, and the remaining portion is roughly crushed with a roll crusher having a urethane-coated inner surface and equipped with a silicon nitride roll, and a nylon sieve with an opening of 100 μm. The powder was sieved and the powder under the sieve was collected to obtain a silicon nitride powder of Example 1-1.
実施例１−１における、原料粉末に用いたシリコン粉末および希釈剤の物性値と、混合原料粉末の物性値と、燃焼生成物の圧壊強度を表１に、また、窒化ケイ素粉末の物性値を表２に示す。 Physical properties of silicon powder and diluent used for raw material powder, physical properties of mixed raw material powder, crushing strength of combustion product, and physical properties of silicon nitride powder in Example 1-1 It shows in Table 2.
実施例１−１の窒化ケイ素粉末の多結晶シリコンインゴット鋳造用鋳型の離型剤としての評価は、以下のように実施した。 The evaluation of the silicon nitride powder of Example 1-1 as a mold release agent for a mold for casting a polycrystalline silicon ingot was carried out as follows.
実施例１−１の窒化ケイ素粉末を、密栓できるポリエチレン製容器に収容し、水を添加することで窒化ケイ素粉末の混合比が２０質量％となるように調製した。窒化ケイ素粉末と水を収納した容器に、窒化ケイ素製ボールを投入して密栓し、バッチ式振動ミルを用いて、振幅５ｍｍ、振動数１７８０ｃｐｍで５分間混合し、窒化ケイ素スラリーを得た。 The silicon nitride powder of Example 1-1 was accommodated in a pluggable polyethylene container, and water was added to adjust the mixing ratio of the silicon nitride powder to be 20% by mass. A silicon nitride ball was charged into a container containing silicon nitride powder and water, and sealed up, and mixed for 5 minutes with an amplitude of 5 mm and a frequency of 1780 cpm using a batch-type vibration mill to obtain a silicon nitride slurry.
得られた実施例１−１の窒化ケイ素スラリーを、予め９０℃に加温した、気孔率１６％で、底面が１００ｍｍの正方形で、深さ１００ｍｍの石英製坩堝の内面にスプレー塗布し、次いで９０℃で１５時間乾燥した。このときの離型層の厚みは約０．２ｍｍであった。さらに、大気雰囲気炉を用いて、空気中１１００℃で３時間保持して加熱処理し、実施例１−１の窒化ケイ素粉末を離型層に適用した多結晶シリコンインゴット鋳造用鋳型を得た。 The obtained silicon nitride slurry of Example 1-1 was spray-coated on the inner surface of a quartz crucible having a porosity of 16%, a bottom of 100 mm and a depth of 100 mm, which had been heated to 90 ° C. in advance, and then It dried at 90 degreeC for 15 hours. The thickness of the release layer at this time was about 0.2 mm. Furthermore, it heat-processed by hold | maintaining in the air for 3 hours at 1100 degreeC using air atmosphere furnace, and the mold for polycrystalline silicon ingot casting which applied the silicon nitride powder of Example 1-1 to the mold release layer was obtained.
前記鋳型に、純度が７Ｎで、大きさが２〜５ｍｍのシリコン顆粒を３００ｇ充填し、ブリッジマン炉に収容した。大気圧のアルゴン流通下で１５００℃まで５時間かけて炉内を昇温してシリコン顆粒を溶融させた。１５００℃で２４時間保持した後、５０ｍｍ／ｈの引き下げ速度で前記鋳型を引き下げることで、溶融シリコンを一方向凝固させ、さらに室温まで冷却した。また、実施例１−１の多結晶シリコンインゴット鋳造用鋳型をもう一つ作製し、その鋳型を用いて、保持温度を１５５０℃に変更したこと以外は、前記一方向凝固実験と同様の方法で一方向凝固実験を行った。 The mold was filled with 300 g of silicon granules having a purity of 7 N and a size of 2 to 5 mm, and was housed in a Bridgman furnace. The temperature in the furnace was raised to 1500 ° C. under argon flow at atmospheric pressure for 5 hours to melt the silicon granules. After holding at 1500 ° C. for 24 hours, the molten silicon was unidirectionally solidified by pulling down the mold at a pulling rate of 50 mm / h and further cooled to room temperature. Also, another polycrystalline silicon ingot casting mold of Example 1-1 was produced, and the same method as the unidirectional solidification experiment was used except that the holding temperature was changed to 1550 ° C. using the mold. One-way coagulation experiments were performed.
取り出した前記鋳型から多結晶シリコンインゴットを離型し、「多結晶シリコンインゴット鋳造用鋳型の評価方法」で説明した方法で、実施例１−１の多結晶シリコンインゴット鋳造用鋳型および多結晶シリコンインゴットを評価した。その結果を表３に示す。 The polycrystalline silicon ingot is released from the mold taken out, and the mold for polycrystalline silicon ingot casting of Example 1-1 and the polycrystalline silicon ingot according to the method described in "Method for evaluating mold for polycrystalline silicon ingot". Was evaluated. The results are shown in Table 3.
（実施例１−２）
粗粉砕後の篩通しを、目開き１２０μｍの篩を用いて行ったこと以外は実施例１−１と同様にして、実施例１−２の窒化ケイ素粉末を作製した。そして、実施例１−２の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。１５００℃および１５２５℃の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-2)
A silicon nitride powder of Example 1-2 was produced in the same manner as in Example 1-1 except that sieving after coarse grinding was performed using a sieve with 120 μm openings. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-2. Two-way solidification experiments at two furnace temperatures of 1500 ° C. and 1525 ° C. are conducted using these molds in the same manner as in Example 1-1, and polycrystalline in the same manner as in Example 1-1. The silicon ingot casting mold was evaluated.
（実施例１−３）
粗粉砕後の篩通しを、目開き８０μｍの篩を用いて行ったこと以外は実施例１−１と同様にして、実施例１−３の窒化ケイ素粉末を作製した。そして、実施例１−３の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-3)
A silicon nitride powder of Example 1-3 was produced in the same manner as in Example 1-1 except that sieving after coarse grinding was performed using a sieve with an aperture of 80 μm. Then, using the silicon nitride powder of Example 1-3, two polycrystalline silicon casting molds were produced in the same manner as in Example 1-1. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−４）
粗粉砕後の篩通しを、目開き１２５μｍの篩を用いて行ったこと以外は実施例１−１と同様にして、実施例１−４の窒化ケイ素粉末を作製した。そして、実施例１−４の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を３個作製した。１５００℃、１５２５℃および１５５０℃の三通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-4)
The silicon nitride powder of Example 1-4 was produced in the same manner as in Example 1-1 except that sieving after coarse grinding was performed using a sieve with an opening of 125 μm. And three casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-4. Three-way solidification experiments at three furnace temperatures of 1500 ° C., 1525 ° C. and 1550 ° C. were carried out using these molds in the same manner as in Example 1-1, and in the same manner as Example 1-1. The mold for casting of polycrystalline silicon ingot was evaluated.
（実施例１−５）
粗粉砕し篩通しして得られた窒化ケイ素粉末を、窒化ケイ素製ボールが充填された内壁面がウレタンでライニングされたナイロン製のポットに収容し、バッチ式振動ミルを用いて、振動数１７８０ｃｐｍ、振幅５ｍｍ、で２０分微粉砕したこと以外は実施例１−１と同様にして、実施例１−５の窒化ケイ素粉末を作製した。なお、バッチ式振動ミルでの粉砕の際には、粉砕助剤として燃焼生成物に対して１質量％のエタノールを添加した。そして、実施例１−５の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-5)
The silicon nitride powder obtained by coarse crushing and sieving is housed in a nylon pot lined with a urethane nitride on the inner wall surface filled with silicon nitride balls, and using a batch type vibration mill, the frequency 1780 cpm The silicon nitride powder of Example 1-5 was produced in the same manner as Example 1-1 except that the fine grinding was performed for 20 minutes with an amplitude of 5 mm. In addition, in the case of grinding | pulverization with a batch type vibration mill, 1 mass% of ethanol was added with respect to the combustion product as a grinding | pulverization auxiliary agent. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-5. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−６）
微粉砕の時間を４０分にしたこと以外は実施例１−５と同様にして、実施例１−６の窒化ケイ素粉末を作製した。そして、実施例１−６の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-6)
The silicon nitride powder of Example 1-6 was produced in the same manner as in Example 1-5 except that the pulverizing time was 40 minutes. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-6. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−７）
微粉砕の時間を５０分にしたこと以外は実施例１−５と同様にして、実施例１−７の窒化ケイ素粉末を作製した。そして、実施例１−７の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-7)
A silicon nitride powder of Example 1-7 was produced in the same manner as in Example 1-5 except that the time for pulverization was set to 50 minutes. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-7. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−８）
粗粉砕後の篩通しを、目開き２０μｍの篩を用いて行ったこと以外は実施例１−７と同様にして、実施例１−８の窒化ケイ素粉末を作製した。そして、実施例１−８の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−２と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−２と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-8)
The silicon nitride powder of Example 1-8 was produced in the same manner as in Example 1-7 except that sieving after coarse grinding was performed using a sieve with an aperture of 20 μm. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-8. The same two-way solidification experiments at the same furnace temperature as in Example 1-2 are carried out using those molds in the same manner as in Example 1-2, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−９）
粗粉砕して得られた窒化ケイ素粉末を、接吻部に窒化ケイ素製のライナーを備えた気流式粉砕機（日清エンジリング株式会社製ＳＪ−１５００型）を使用して、必要空気量３．０ｍ３／分、原料供給速度２５０ｇ／分程度の条件で粉砕し、実施例１−９の窒化ケイ素粉末を作製した。そして、実施例１−９の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-9)
The silicon nitride powder obtained by the coarse grinding is used with an air flow crusher (SJ-1500 manufactured by Nisshin Engineering Co., Ltd.) equipped with a silicon nitride liner at the kiss part, and the required air amount is 3. The silicon nitride powder of Example 1-9 was produced by grinding under the conditions of 0 m 3 / min and a raw material feed rate of about 250 g / min. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-9. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−１０）
原料粉末に、添加剤として、塩化アンモニウム（和光純薬製、純度９９．９％）を、６．９質量％（シリコンと窒化ケイ素の混合粉末と塩化アンモニウムの質量比が９３．１：６．９になるように）さらに添加したこと以外は実施例１−６と同様にして、実施例１−１０の窒化ケイ素粉末を作製した。そして、実施例１−１０の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-10)
In the raw material powder, ammonium chloride (manufactured by Wako Pure Chemical Industries, purity 99.9%) as an additive, 6.9% by mass (mixed powder of silicon and silicon nitride and ammonium chloride in a mass ratio of 93.1: 6. The silicon nitride powder of Example 1-10 was produced in the same manner as in Example 1-6 except that 9) was further added. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-10. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−１１）
添加剤の塩化アンモニウムの添加割合を、９．２質量％（シリコンと窒化ケイ素の混合粉末と塩化アンモニウムとの質量比が９０．８：９．２となるように）としたこと以外は実施例１−１０と同様にして、実施例１−１１の窒化ケイ素粉末を作製した。そして、実施例１−１１の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を３個作製した。実施例１−４と同様の三通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-11)
Example except that the addition ratio of ammonium chloride of the additive was 9.2 mass% (the mass ratio of the mixed powder of silicon and silicon nitride and ammonium chloride is 90.8: 9.2) The silicon nitride powder of Example 1-11 was produced in the same manner as in 1-10. And three casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-11. The same three-way solidification experiments at the same furnace temperature as in Example 1-4 are carried out using those molds in the same manner as in Example 1-1, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−１２）
原料粉末のシリコン粉末を、Ｄ５０が３．３μｍ、かさ密度が０．３６ｇ／ｃｍ３で、Ｆｅの含有割合が３ｐｐｍのシリコン粉末にし、Ａｌの含有割合が３ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が３ｐｐｍ、希釈剤を、ＳＫＷ社製窒化ケイ素粉末（Ｆｅの含有割合；３１０ｐｐｍ、Ａｌの含有割合；１４５ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合；４２ｐｐｍ）にしたこと以外は実施例１−１と同様にして、実施例１−１２の窒化ケイ素粉末を作製した。そして、実施例１−１２の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-12)
The silicon powder of the raw material powder is converted to a silicon powder having a D50 of 3.3 μm, a bulk density of 0.36 g / cm 3 and a Fe content of 3 ppm, an Al content of 3 ppm, Fe and metallic impurities other than Al Example except that the content ratio was 3 ppm, and the diluent was made to silicon nitride powder (content ratio of Fe: 310 ppm, content ratio of Al: 145 ppm, content ratio of metallic impurities other than Fe and Al; 42 ppm) manufactured by SKW. The silicon nitride powder of Example 1-12 was produced in the same manner as 1-1. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-12. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（実施例１−１３）
原料粉末のシリコン粉末を、Ｄ５０が３．３μｍ、かさ密度が０．３６ｇ／ｃｍ３で、Ｆｅの含有割合が３ｐｐｍ、Ａｌの含有割合が３ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が３ｐｐｍのシリコン粉末にし、希釈剤を、ＶＥＳＴＡ Ｓｉ社製製窒化ケイ素粉末（Ｆｅの含有割合；２２４ｐｐｍ、Ａｌの含有割合；５００ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合；１７４ｐｐｍ）にしたこと以外は実施例１−７と同様にして、実施例１−１３の窒化ケイ素粉末を作製した。そして、実施例１−１３の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を２個作製した。実施例１−１と同様の二通りの炉内温度での一方向凝固実験を、それらの鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Example 1-13)
The silicon powder of the raw material powder has a D50 of 3.3 μm, a bulk density of 0.36 g / cm 3 , an Fe content of 3 ppm, an Al content of 3 ppm, and a content of metal impurities other than Fe and Al 3 ppm Silicon powder, and the diluent used was silicon nitride powder (Fe content: 224 ppm, Al content: 500 ppm, Fe and metal impurities other than Al: 174 ppm) manufactured by VESTA Si The silicon nitride powder of Example 1-13 was produced in the same manner as in Example 1-7. And two casting molds for polycrystalline silicon casting were produced by the method similar to Example 1-1 using the silicon nitride powder of Example 1-13. The same two-way solidification experiments at the same furnace temperature as in Example 1-1 are carried out in the same manner as in Example 1-1 using these molds, and in the same manner as in Example 1-1. The polycrystalline silicon ingot casting mold was evaluated.
（比較例１−１）
粗粉砕後の篩通しを行わなかったこと以外は実施例１−１と同様にして、比較例１−１の窒化ケイ素粉末を作製した。比較例１−１で得られた窒化ケイ素粉末は、表２に見られるように、比表面積が０．２５ｍ２/ｇと小さく、Ｄ１０，Ｄ５０，Ｄ９０はそれぞれ１５．５０μｍ、２６．３４μｍ、６２．３４μｍといずれも大きかった。そして、比較例１−１の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。１５００℃の炉内温度での一方向凝固実験のみを、その鋳型を用いて実施例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative Example 1-1)
A silicon nitride powder of Comparative Example 1-1 was produced in the same manner as Example 1-1 except that sieving after coarse grinding was not performed. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-1 has a small specific surface area of 0.25 m 2 / g, and D10, D50, D90 are 15.50 μm, 26.34 μm, 62 respectively. Both were as large as .34 μm. And one mold for polycrystalline silicon casting was produced by the method similar to Example 1-1 using the silicon nitride powder of comparative example 1-1. A unidirectional solidification experiment at a furnace temperature of 1500 ° C. is performed using the mold in the same manner as in Example 1-1, and a mold for casting polycrystalline silicon ingots in the same manner as in Example 1-1. evaluated.
（比較例１−２）
微粉砕の時間を６０分にしたこと以外は実施例１−５と同様の方法で、比較例１−２の窒化ケイ素粉末を作製した。比較例１−２で得られた窒化ケイ素粉末は、表２に見られるように、比表面積が５．７０ｍ２/ｇ、Ｄ９０が５．６９μｍであり、粒径が小さい粉末であった。そして、比較例１−２の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative example 1-2)
The silicon nitride powder of Comparative Example 1-2 was produced in the same manner as in Example 1-5 except that the time for pulverization was set to 60 minutes. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-2 had a specific surface area of 5.70 m 2 / g, D90 of 5.69 μm, and was a powder with a small particle size. Then, using the silicon nitride powder of Comparative Example 1-2, one polycrystalline silicon casting mold was produced in the same manner as in Example 1-1. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−３）
原料粉末に、添加剤として塩化アンモニウム（和光純薬製、純度９９．９％）を、１２．３質量％（シリコンと窒化ケイ素の混合粉末と塩化アンモニウムとの質量比が８７．７：１２．３となるように）さらに添加したこと以外は実施例１−７と同様にして、比較例１−３の窒化ケイ素粉末を作製した。比較例１−３で得られた窒化ケイ素粉末は、表２に見られるように、β型窒化ケイ素の割合が６４％で少ない粉末であった。そして、比較例１−３の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative example 1-3)
In the raw material powder, ammonium chloride (manufactured by Wako Pure Chemical Industries, purity 99.9%) as an additive, 12.3 mass% (mixed powder of silicon and silicon nitride and mass ratio of ammonium chloride to ammonium chloride) is 87.7: 12. The silicon nitride powder of Comparative Example 1-3 was produced in the same manner as in Example 1-7 except that it was 3). As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-3 was a powder in which the proportion of β-type silicon nitride was as low as 64%. Then, using the silicon nitride powder of Comparative Example 1-3, one polycrystalline silicon casting mold was produced in the same manner as in Example 1-1. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−４）
原料粉末に、Ｄ５０が６．０μｍ、かさ密度が０．６０ｇ／ｃｍ３で、Ｆｅの含有割合が４ｐｐｍ、Ａｌの含有割合が４ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が４ｐｐｍのシリコン粉末を用いたこと以外は実施例１−７と同様にして、比較例１−４の窒化ケイ素粉末を作製した。比較例１−４で得られた窒化ケイ素粉末は、表２に見られるように、結晶子径Ｄｃが２９０ｎｍと小さく、結晶歪が０．９２×１０−４と大きい粉末であった。そして、比較例１−４の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative Example 1-4)
Silicon powder with D50 of 6.0 μm, bulk density of 0.60 g / cm 3 , Fe content of 4 ppm, Al content of 4 ppm, Fe and metal impurities other than Al content of 4 ppm in raw material powder A silicon nitride powder of Comparative Example 1-4 was produced in the same manner as in Example 1-7 except for using. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-4 was a powder with a small crystallite diameter D c of 290 nm and a large crystal strain of 0.92 × 10 −4 . And one mold for polycrystalline silicon casting was produced by the method similar to Example 1-1 using the silicon nitride powder of Comparative Example 1-4. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−５）
微粉砕の時間を１００分にしたこと以外は比較例１−４と同様にして、比較例１−５の窒化ケイ素粉末を作製した。比較例１−５で得られた窒化ケイ素粉末は、表２に見られるように、結晶子径Ｄｃが１８２ｎｍと小さく、結晶歪が１．２５×１０−４と大きい粉末であった。そして、比較例１−５の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative Example 1-5)
A silicon nitride powder of Comparative Example 1-5 was produced in the same manner as in Comparative Example 1-4 except that the pulverizing time was changed to 100 minutes. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-5 was a powder having a small crystallite diameter D c of 182 nm and a large crystal strain of 1.25 × 10 −4 . And one mold for polycrystalline silicon casting was produced by the method similar to Example 1-1 using the silicon nitride powder of Comparative Example 1-5. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−６）
原料粉末に、Ｄ５０が５．０μｍ、かさ密度が０．５０ｇ／ｃｍ３で、Ｆｅの含有割合が２０５ｐｐｍ、Ａｌの含有割合が２２０ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が５０３ｐｐｍのシリコン粉末を用いたこと以外は比較例１−４と同様にして、比較例１−６の窒化ケイ素粉末を作製した。比較例１−６で得られた窒化ケイ素粉末は、表２に見られるように、Ｆｅの含有割合が１０９ｐｐｍ、Ａｌの含有割合が１２７ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が２７１ｐｐｍと、金属不純物の含有割合が多い粉末であった。そして、比較例１−６の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative example 1-6)
Silicon powder having a D50 of 5.0 μm, a bulk density of 0.50 g / cm 3 , an Fe content of 205 ppm, an Al content of 220 ppm, and a content of metal impurities other than Fe and Al of 503 ppm in the raw material powder A silicon nitride powder of Comparative Example 1-6 was produced in the same manner as in Comparative Example 1-4 except for using. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-6 had a content of Fe of 109 ppm, a content of Al of 127 ppm, and a content of metal impurities other than Fe and Al of 271 ppm, It was a powder having a high content of metal impurities. Then, using the silicon nitride powder of Comparative Example 1-6, one polycrystalline silicon casting mold was produced in the same manner as in Example 1-1. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−７）
原料粉末に、Ｄ５０が８．５μｍ、かさ密度が０．７０ｇ／ｃｍ３で、Ｆｅの含有割合が２ｐｐｍ、Ａｌの含有割合が１ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が２ｐｐｍのシリコン粉末を用いたことと、原料粉末を、アルミナ製ボールが充填されたナイロン製のポットに収容してエタノールを溶媒として用いて２４時間ボールミル混合したことと、燃焼生成物の粗粉砕を、アルミナ製ロールを備えたロールクラッシャーを用いて行ったことと、粗粉砕後の篩通しを、ステンレス製の目開き１５０μｍの篩を用いて行ったこと以外は実施例１−１と同様にして、比較例１−７の窒化ケイ素粉末を作製した。比較例１−７で得られた窒化ケイ素粉末は、表２に見られるように、Ａｌの含有割合が８４６ｐｐｍと、金属不純物の含有割合が多く、比表面積が０．２１ｍ２/ｇと小さく、Ｄ１０，Ｄ５０，Ｄ９０はそれぞれ１５．４３μｍ、２６．５０μｍ、６２．４４μｍといずれも大きい粉末であった。そして、比較例１−７の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative Example 1-7)
Raw material powder: Silicon powder with D50 of 8.5 μm, bulk density of 0.70 g / cm 3 , Fe content of 2 ppm, Al content of 1 ppm, Fe and metal impurities other than Al content ratio of 2 ppm The raw material powder was placed in a nylon pot filled with alumina balls and ball mill mixed for 24 hours using ethanol as a solvent, and the coarse grinding of the combustion product was carried out using an alumina roll. Comparative Example 1 was carried out in the same manner as Example 1-1 except that the process was carried out using a roll crusher equipped with the above, and the coarse-crushed sieve was carried out using a stainless steel sieve with a 150 .mu.m opening. A silicon nitride powder of -7 was produced. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-7 has a high content of Al at 846 ppm, a high content of metal impurities, and a low specific surface area of 0.21 m 2 / g, Each of D10, D50 and D90 was a large powder of 15.43 μm, 26.50 μm and 62.44 μm, respectively. Then, using the silicon nitride powder of Comparative Example 1-7, one polycrystalline silicon casting mold was produced in the same manner as in Example 1-1. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−８）
原料粉末に、Ｄ５０が５．０μｍ、かさ密度が０．５０ｇ／ｃｍ３で、Ｆｅの含有割合が２０５ｐｐｍ、Ａｌの含有割合が２２０ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が５０３ｐｐｍのシリコン粉末を用いたことと、原料粉末を、アルミナ製ボールが充填された遊星ボールミルにて１時間混合したこと以外は実施例１−６と同様にして、比較例１−８の窒化ケイ素粉末を作製した。比較例１−８で得られた窒化ケイ素粉末は、表２に見られるように、Ｆｅの含有割合が１０９ｐｐｍ、Ａｌの含有割合が４２０ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が３１２ｐｐｍと、金属不純物の含有割合が多く、結晶子径Ｄｃ２９０ｎｍと小さい粉末であった。そして、比較例１−８の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative Example 1-8)
Silicon powder having a D50 of 5.0 μm, a bulk density of 0.50 g / cm 3 , an Fe content of 205 ppm, an Al content of 220 ppm, and a content of metal impurities other than Fe and Al of 503 ppm in the raw material powder A silicon nitride powder of Comparative Example 1-8 was produced in the same manner as in Example 1-6 except that the raw material powder was mixed for 1 hour in a planetary ball mill filled with alumina balls. . As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-8 had a content of Fe of 109 ppm, a content of Al of 420 ppm, and a content of metal impurities other than Fe and Al of 312 ppm, The powder contained a large amount of metal impurities and a small crystallite diameter D c of 290 nm. Then, using the silicon nitride powder of Comparative Example 1-8, one polycrystalline silicon casting mold was produced in the same manner as in Example 1-1. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−９）
Ｄ５０が２．５μｍ、かさ密度が０．２６ｇ／ｃｍ３、Ｆｅの含有割合が２ｐｐｍ、Ａｌの含有割合が３ｐｐｍ、ＦｅおよびＡｌ以外の金属不純物の含有割合が３ｐｐｍのシリコン粉末を、内径３０ｍｍの金型に充填し、１５００ｋｇ／ｃｍ２の圧力で一軸成型し、シリコン粉末の一軸成型体を得た。前記成型体を黒鉛製容器に充填し、それをバッチ式窒化炉に収容して、炉内を窒素雰囲気に置換した後、窒素雰囲気下で、１４５０℃まで昇温し、３時間保持させた。室温まで冷却させた後に、窒化生成物を取り出した。得られた窒化生成物を、内面がウレタンコーティングされた、窒化ケイ素製ロールを備えたロールクラッシャーで粗粉砕して、目開きが１００μｍのナイロン製篩で篩通しし、篩下の粉末を回収した。次に、前記粉末を、窒化ケイ素製ボールが充填され、内面がウレタンでライニングされたアルミナ製のポットに収容して、バッチ式振動ミルで振動数１７８０ｃｐｍ、振幅５ｍｍで、３０分間微粉砕することで、比較例１−９の窒化ケイ素粉末を作製した。燃焼合成でない直接窒化法である比較例１−９で得られた窒化ケイ素粉末は、表２に見られるように、比表面積が６．１０ｍ２/ｇと大きく、β型窒化ケイ素の割合が５０％と少なく、Ｄ１０、Ｄ５０はそれぞれ０．４０μｍ、１．６０μｍといずれも小さく、結晶子径Ｄｃが５５ｎｍと小さく、結晶歪が３．０１×１０−４と大きく、ＤＢＥＴ/Ｄｃが５．６と大きい粉末であった。そして、比較例１−９の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative Example 1-9)
Silicon powder with a D50 of 2.5 μm, a bulk density of 0.26 g / cm 3 , an Fe content of 2 ppm, an Al content of 3 ppm, and a content of metallic impurities other than Fe and Al of 3 ppm, inner diameter 30 mm The mold was filled and uniaxially molded at a pressure of 1,500 kg / cm 2 to obtain a uniaxially molded silicon powder. The molded body was filled in a container made of graphite, housed in a batch type nitriding furnace, and the inside of the furnace was replaced with a nitrogen atmosphere, and then the temperature was raised to 1450 ° C. under a nitrogen atmosphere and held for 3 hours. After cooling to room temperature, the nitrided product was removed. The obtained nitrided product was roughly crushed with a roll crusher equipped with a silicon nitride roll whose inner surface was urethane coated, and sieved through a nylon screen with a 100 μm mesh to recover the powder under the sieve. . Next, the powder is contained in a pot made of alumina which is filled with silicon nitride balls and whose inner surface is lined with urethane, and finely ground for 30 minutes with a frequency of 1780 cpm and an amplitude of 5 mm with a batch type vibration mill. The silicon nitride powder of Comparative Example 1-9 was produced. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-9, which is a direct nitriding method that is not combustion synthesis, has a large specific surface area of 6.10 m 2 / g and a ratio of β-type silicon nitride of 50. %, D10 and D50 are as small as 0.40 μm and 1.60 μm, respectively, the crystallite diameter D c is as small as 55 nm, the crystal strain is as large as 3.01 × 10 −4, and D BET / D c is as small as It was a large powder of 5.6. Then, using the silicon nitride powder of Comparative Example 1-9, one polycrystalline silicon casting mold was produced in the same manner as in Example 1-1. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
（比較例１−１０）
微粉砕の時間を１０分にしたこと以外は比較例１−９と同様にして比較例１−１０の窒化ケイ素粉末を作製した。燃焼合成でない直接窒化法である比較例１−１０で得られた窒化ケイ素粉末は、表２に見られるように、β型窒化ケイ素の割合が５８％と少なく、Ｄ１５，Ｄ９０はそれぞれ１．６０μｍ、５．９０μｍといずれも小さく、結晶子径Ｄｃが８８ｎｍと小さく、結晶歪が１．９０×１０−４と大きく、ＤＢＥＴ/Ｄｃが６．７と大きい粉末であった。そして、比較例１−１０の窒化ケイ素粉末を用いて実施例１−１と同様の方法で多結晶シリコン鋳造用鋳型を１個作製した。比較例１−１と同様の炉内温度での一方向凝固実験を、その鋳型を用いて比較例１−１と同様の方法で行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型を評価した。(Comparative Example 1-10)
A silicon nitride powder of Comparative Example 1-10 was produced in the same manner as in Comparative Example 1-9 except that the milling time was 10 minutes. As shown in Table 2, the silicon nitride powder obtained in Comparative Example 1-10, which is a direct nitriding method that is not combustion synthesis, has a low proportion of β-type silicon nitride of 58%, and D15 and D90 are each 1.60 μm. The powder was as small as 5.90 μm, the crystallite diameter Dc was as small as 88 nm, the crystal strain was as large as 1.90 × 10 −4, and the D BET / D c was as large as 6.7. Then, using the silicon nitride powder of Comparative Example 1-10, one polycrystalline silicon casting mold was produced in the same manner as in Example 1-1. The same direction solidification experiment in the same furnace temperature as Comparative Example 1-1 is conducted by the same method as Comparative Example 1-1 using its mold, and a polycrystalline silicon ingot is produced by the same method as Example 1-1. The casting molds were evaluated.
実施例１−２〜１−１３および比較例１−１〜１−１０における、原料粉末に用いたシリコン粉末および希釈剤の物性値と、混合原料粉末の物性値と、燃焼生成物の圧壊強度を表１に、また、窒化ケイ素粉末の物性値を表２に示す。また、実施例１−２〜１−１３および比較例１−１〜１−１０の多結晶シリコンインゴット鋳造用鋳型および多結晶シリコンインゴットの評価結果を表３に示す。 Physical property values of silicon powder and diluent used for raw material powder, physical property values of mixed raw material powder, and crushing strength of combustion products in Examples 1-2 to 1-13 and Comparative examples 1-1 to 1-10 Table 1 shows the physical properties of the silicon nitride powder and Table 2 shows the physical properties of the silicon nitride powder. The evaluation results of the mold for casting polycrystalline silicon ingots and the polycrystalline silicon ingots of Examples 1-2 to 1-13 and Comparative Examples 1-1 to 1-10 are shown in Table 3.
（実施例２−１）
以下に述べる手法で、実施例１−１の窒化ケイ素粉末を含む離型層を具えた多結晶シリコンインゴット鋳造用鋳型を作製し、多結晶シリコンインゴット鋳造用鋳型、およびシリコンインゴットの評価を実施した。(Example 2-1)
A mold for casting a polycrystalline silicon ingot having a release layer containing the silicon nitride powder of Example 1-1 was produced by the method described below, and the mold for casting a polycrystalline silicon ingot and the evaluation of the silicon ingot were carried out. .
実施例１−１の窒化ケイ素粉末を、密閉できるポリエチレン製容器に収容し、シリカ濃度２０質量％のシリカゾル（扶桑化学社製、製品名「ＰＬ−３」）と水を添加した。このとき、質量比で窒化ケイ素：シリカゾル：水が２０：８：７２となるように混合した。次に、窒化ケイ素粉末とシリカゾルと水を収容した容器に、窒化ケイ素製ボールを投入して密閉し、バッチ式振動ミルを用いて、振幅５ｍｍ、振動数１７８０ｒｐｍの振動ミルで５分間混合し、窒化ケイ素スラリーを得た。 The silicon nitride powder of Example 1-1 was housed in a sealable polyethylene container, and a silica sol having a silica concentration of 20% by mass (manufactured by Sakai Chemical Co., Ltd., product name "PL-3") and water were added. At this time, they were mixed so that the mass ratio of silicon nitride: silica sol: water was 20: 8: 72. Next, a silicon nitride ball is charged into a container containing silicon nitride powder, silica sol and water, and sealed, and mixed for 5 minutes with a vibration mill with an amplitude of 5 mm and a frequency of 1780 rpm using a batch vibration mill. A silicon nitride slurry was obtained.
得られた実施例２−１の窒化ケイ素スラリーを、予め９０℃に加温した、気孔率１６％で、底面が１００ｍｍの正方形で、深さ１００ｍｍの石英製坩堝の内壁面にスプレー塗布し、９０℃で１５時間乾燥し、実施例２−１の窒化ケイ素粉末を含む離型層を具えた多結晶シリコンインゴット鋳造用鋳型を得た。このときの離型層の厚みは約０．２ｍｍであった。 The resulting silicon nitride slurry of Example 2-1 was spray-applied to the inner wall surface of a quartz crucible having a porosity of 16%, a bottom of 100 mm square, and a depth of 100 mm, which had been preheated to 90 ° C., It was dried at 90 ° C. for 15 hours to obtain a polycrystalline silicon ingot casting mold provided with a release layer containing the silicon nitride powder of Example 2-1. The thickness of the release layer at this time was about 0.2 mm.
得られた実施例２−１の多結晶シリコン鋳造用鋳型を用いて実施例１−１と同様にして一方向凝固実験を行い、実施例１−１と同様の方法で実施例２−１の多結晶シリコン鋳造用鋳型および多結晶シリコンインゴットを評価した。その結果を表４に示す。 A unidirectional solidification experiment is carried out in the same manner as in Example 1-1 using the obtained mold for casting of polycrystalline silicon in Example 2-1, and the same procedure as in Example 1-1 is carried out in the same manner as in Example 1-1. Polycrystalline silicon casting molds and polycrystalline silicon ingots were evaluated. The results are shown in Table 4.
（実施例２−２〜２−１３、比較例２−１〜２−１０）
表４に示す窒化ケイ素粉末を用いたこと以外は実施例２−１と同様にして、窒化ケイ素スラリーを作製し、多結晶シリコン鋳造用鋳型を製造した。得られた各実施例および各比較例の多結晶シリコン鋳造用鋳型を用いて、実施例１−１と同様にして一方向凝固実験を行い、実施例１−１と同様の方法で多結晶シリコンインゴット鋳造用鋳型およびシリコンインゴットを評価した。その結果を表４に示す。(Examples 2-2 to 2-13, comparative examples 2-1 to 2-10)
A silicon nitride slurry was produced in the same manner as in Example 2-1 except that the silicon nitride powder shown in Table 4 was used, to produce a polycrystalline silicon casting mold. A unidirectional solidification experiment is conducted in the same manner as in Example 1-1 using the mold for casting polycrystalline silicon in each of the obtained Examples and Comparative Examples, and polycrystalline silicon is obtained in the same manner as in Example 1-1. Ingot casting molds and silicon ingots were evaluated. The results are shown in Table 4.
以上の通り、本発明の窒化ケイ素粉末は、鋳型に塗布した後に高温で熱処理することで、実質的にそれ単独で密着性と離型性が良好な離型層を鋳型に形成し得ること、また、シリカゾルと混合して鋳型に塗布することで、高温の熱処理を行わなくても密着性と離型性が良好な離型層を鋳型に形成し得ることがわかった。 As described above, the silicon nitride powder of the present invention can form a release layer having excellent adhesion and releasability on its mold by heat treatment at high temperature after being applied to the mold. Moreover, it turned out that a mold release layer with favorable adhesiveness and releasability can be formed in a casting_mold | template by mix | blending with a silica sol and apply | coating to a casting_mold | template without heat-processing at high temperature.
本発明の窒化ケイ素粉末は、鋳型への密着性と離型性が良好な離型層を鋳型に形成し得る離型剤として有用であり、特に、太陽電池用の高品質なシリコン基板を高い歩留まりで採取し得る多結晶シリコンインゴットの離型剤として有用である。また、本発明の窒化ケイ素粉末は、緻密な離型層を形成し得ること、結晶性が高いことから、高温で高強度を発現する窒化ケイ素焼結体の原料としても有用である。 The silicon nitride powder of the present invention is useful as a mold release agent capable of forming a mold release layer having good adhesion to the mold and good mold release property to the mold, and in particular, high quality silicon substrates for solar cells. It is useful as a mold release agent for polycrystalline silicon ingots that can be collected at a yield. The silicon nitride powder of the present invention is also useful as a raw material of a silicon nitride sintered body that exhibits high strength at high temperature because it can form a compact release layer and has high crystallinity.
１ 燃焼合成反応装置
２ 混合原料粉末
３ 黒鉛製容器
４ 着火剤
５ カーボンヒータ
６ 耐圧性容器
７ 真空ポンプ
８ 窒素ボンベ
９ 覗き窓Reference Signs List 1 combustion synthesis reactor 2 mixed raw material powder 3 container made of
Claims (11)
ＢＥＴ法により測定される比表面積が０．４ｍ２／ｇ以上５ｍ２／ｇ以下であり、
β型窒化ケイ素の割合が７０質量％以上であり、
レーザ回折散乱法により測定される体積基準の５０％粒子径をＤ５０とし、９０％粒子径をＤ９０としたときに、Ｄ５０が２μｍ以上２０μｍ以下であり、Ｄ９０が８μｍ以上６０μｍ以下であり、
Ｆｅの含有割合が１００ｐｐｍ以下であり、
Ａｌの含有割合が１００ｐｐｍ以下であり、
ＦｅおよびＡｌ以外の金属不純物の含有割合の合計が１００ｐｐｍ以下であり、
β型窒化ケイ素の粉末Ｘ線回折パターンよりＷｉｌｌｉａｍｓｏｎ−Ｈａｌｌ式を用いて算出されるβ型窒化ケイ素の結晶子径をＤＣとしたときに、ＤＣが３００ｎｍ以上であることを特徴とする窒化ケイ素粉末。Silicon nitride powder,
The specific surface area measured by the BET method is 0.4 m 2 / g or more and 5 m 2 / g or less,
The proportion of β-type silicon nitride is 70% by mass or more,
Assuming that the 50% particle diameter based on volume measured by the laser diffraction scattering method is D50 and the 90% particle diameter is D90, D50 is 2 μm to 20 μm, and D90 is 8 μm to 60 μm,
The content of Fe is 100 ppm or less,
The content ratio of Al is 100 ppm or less,
The total content of metal impurities other than Fe and Al is 100 ppm or less,
The crystallite size of β-type silicon nitride which is calculated using the Williamson-Hall type from powder X-ray diffraction pattern of β-type silicon nitride is taken as D C, nitriding, characterized in that D C is 300nm or more Silicon powder.
Ａｌの含有割合が２０ｐｐｍ以下であり、
Ｆｅ及びＡｌ以外の金属不純物の含有割合の合計が２０ｐｐｍ以下であることを特徴とする請求項１〜７いずれか一項に記載の窒化ケイ素粉末。The content of Fe is 20 ppm or less,
The content ratio of Al is 20 ppm or less,
The silicon nitride powder according to any one of claims 1 to 7, wherein the total content of metal impurities other than Fe and Al is 20 ppm or less.
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