WO2012102343A1 - シリコン融液接触部材、その製法、および結晶シリコンの製造方法 - Google Patents
シリコン融液接触部材、その製法、および結晶シリコンの製造方法 Download PDFInfo
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- WO2012102343A1 WO2012102343A1 PCT/JP2012/051669 JP2012051669W WO2012102343A1 WO 2012102343 A1 WO2012102343 A1 WO 2012102343A1 JP 2012051669 W JP2012051669 W JP 2012051669W WO 2012102343 A1 WO2012102343 A1 WO 2012102343A1
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- silicon
- sintered body
- silicon melt
- porous sintered
- body layer
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 218
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 217
- 239000010703 silicon Substances 0.000 title claims abstract description 217
- 229910021419 crystalline silicon Inorganic materials 0.000 title claims abstract description 122
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 66
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 50
- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 47
- 239000011148 porous material Substances 0.000 claims abstract description 33
- 239000002245 particle Substances 0.000 claims description 73
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- 239000006185 dispersion Substances 0.000 claims description 24
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- 235000012239 silicon dioxide Nutrition 0.000 claims description 14
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- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 abstract description 9
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 5
- 238000000137 annealing Methods 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
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- 229910052742 iron Inorganic materials 0.000 description 1
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- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
- C04B38/06—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by burning-out added substances by burning natural expanding materials or by sublimating or melting out added substances
- C04B38/0615—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by burning-out added substances by burning natural expanding materials or by sublimating or melting out added substances the burned-out substance being a monolitic element having approximately the same dimensions as the final article, e.g. a porous polyurethane sheet or a prepreg obtained by bonding together resin particles
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- C—CHEMISTRY; METALLURGY
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/002—Crucibles or containers for supporting the melt
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- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/02—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method without using solvents
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B9/00—Single-crystal growth from melt solutions using molten solvents
- C30B9/04—Single-crystal growth from melt solutions using molten solvents by cooling of the solution
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
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- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
- H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
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- H—ELECTRICITY
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
- H01L31/182—Special manufacturing methods for polycrystalline Si, e.g. Si ribbon, poly Si ingots, thin films of polycrystalline Si
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- C—CHEMISTRY; METALLURGY
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Y10T117/1092—Shape defined by a solid member other than seed or product [e.g., Bridgman-Stockbarger]
Definitions
- the present invention relates to a silicon melt contact member useful for producing crystalline silicon used in solar cells and the like, a method for producing the same, and a method for producing crystal silicon using the silicon melt contact member.
- the present invention relates to a silicon melt contact member having on its surface a porous sintered body layer that greatly increases liquid repellency with respect to a molten silicon melt.
- Crystalline silicon (Si) used as a solar cell material is used in products of 85% or more of the entire solar cell. Since this solar cell does not emit a global warming gas, the demand has rapidly increased in recent years as a power generation method friendly to the global environment. However, power generation using solar cells has a higher power generation cost (yen / W) than other power generations such as thermal power generation, and there is a strong demand for reduction thereof.
- crystalline silicon has been produced as a columnar or block-shaped crystal from a silicon melt by a crystal growth method using a chocolate ski method or a floating zone method.
- a manufacturing method of spherical crystalline silicon has been developed. This method is a method of manufacturing spherical crystalline silicon by dropping a certain amount of silicon melt from a high place by utilizing the fact that the melt becomes spherical due to surface tension.
- a solar cell having a structure in which the spherical crystalline silicons are arranged on a plane has been proposed, and the power generation efficiency can be improved by devising a sunlight condensing method.
- the spherical crystalline silicon obtained by the method of dropping from a high place is a fine polycrystal due to a large temperature gradient at the time of manufacture, resulting in poor power generation efficiency and crystal defects.
- the ratio is also large. Therefore, the actual situation is that the spherical silicon obtained by the dropping method is heated again, melted and then cooled to reduce the number of polycrystalline silicon crystal grains forming the spherical crystalline silicon. There is a problem that the process increases and the cost becomes high.
- Patent Document 1 discloses a method of producing spherical crystalline silicon by containing powdered silicon in a hollow of a container such as high-purity ceramics or quartz glass, and melting and heating the powdered silicon, followed by solidification. Are listed. The surface of the container is coated with a silicon melt and a substance that is difficult to wet to form a release layer.
- Patent Document 2 describes a method of manufacturing spherical crystalline silicon by placing a silicon material in a recess on the surface of a base plate, heating and melting it, and then solidifying it. On the concave surface of the base plate, a film of silicon oxide or the like that is difficult to wet with the silicon melt is formed.
- the release layer is applied and formed each time the crystalline silicon is manufactured, the manufacturing process of the crystalline silicon is increased and the manufacturing cost is increased. Furthermore, when a defect or the like occurs in the coating layer having liquid repellency, not only does the spherical shape of the spherical crystalline silicon cause a defect, but the silicon penetrates deeply into the base plate and is fixed. Therefore, there is a possibility that impurities are mixed in the crystalline silicon.
- An object of the present invention is to provide a silicon melt contact member suitable for production of crystalline silicon, which can greatly increase the liquid repellency with respect to a silicon melt and can maintain the liquid repellency permanently. And It is another object of the present invention to provide an efficient method for producing crystalline silicon, particularly highly crystalline spherical crystalline silicon, using the silicon melt contact member.
- the inventors of the present application pay attention to the wettability of the silicon melt and the porosity of the ceramic material, and are eager to determine the size and depth of the pores, the spatial distribution of the pores, and the thickness variation of the porous material. Studied.
- a member made of a specific material and having a surface formed of a porous sintered body layer having a specific pore structure exhibits excellent liquid repellency with respect to the silicon melt, and the silicon melt. It has been found that the characteristics can be maintained over a long period of time even when repeatedly brought into contact with the liquid, and the present invention has been completed.
- a mixture containing organic particles made of thermally decomposable resin particles having an average particle diameter of 1 to 25 ⁇ m and a sinterable powder containing silicon nitride as a main component is formed into a molded body.
- the porous sintered body layer is made of a sintered body obtained by firing the organic particles until the organic particles disappear, and further sintering the sinterable powder, in which pores derived from the shape of the organic particles are formed.
- the porous sintered body layer is formed on a substrate such as a ceramic substrate.
- the surface of the substrate on which the porous sintered body layer is formed is composed of silicon nitride.
- the porous sintered body layer has a thickness of 5 to 500 ⁇ m.
- the porous sintered body layer has an average surface area ratio of 30 to 80% on the surface of the porous sintered body. Holes having a circle-equivalent diameter of 1 to 25 ⁇ m are dispersed and present (5)
- the porous sintered body layer contains silicon dioxide in a proportion of 2% by mass or more and less than 50% by mass. (6) It is preferable that the average depth of the holes existing on the surface of the porous sintered body layer is 5 ⁇ m or more.
- the present invention also provides a method for producing crystalline silicon, characterized in that the silicon melt is cooled and crystallized on the surface of the porous sintered body layer of each of the silicon melt contact members.
- the silicon melt is obtained by melting solid silicon on a porous sintered body layer.
- the crystalline silicon is spherical crystalline silicon, The silicon melt is present in the form of droplets on the surface of the liquid member, cooled in a spheroidized state by the surface tension, and crystallized.
- the crystalline silicon is a plate-like crystalline silicon. It is preferable to perform crystallization by using two silicon melt members and cooling the silicon melt while sandwiching the porous sintered body layer of each member inside.
- a sinterable powder containing silicon nitride powder as a main component on a substrate furthermore, a sinterable powder containing silicon nitride powder as a main component on a substrate, and thermally decomposable resin particles 40 to 400 having an average particle diameter of 1 to 25 ⁇ m with respect to 100 parts by volume of the sinterable powder.
- the organic solvent is removed by drying, and then the thermally decomposable resin particles are thermally decomposed and removed, and further, the sintering is performed.
- a method for producing a silicon melt contact member characterized in that a porous sintered body layer is formed by sintering a functional powder at a temperature of 1100 to 1700 ° C.
- the surface of the substrate on which the porous sintered body layer is formed is composed of silicon nitride.
- the sinterable powder containing silicon nitride powder as a main component contains 2 masses of silicon dioxide. % Or more and less than 50% by mass is preferable.
- the silicon melt contact member of the present invention is composed of a porous sintered body layer having at least the surface as a main component of silicon nitride, and exhibits excellent liquid repellency with respect to the silicon melt. Furthermore, when the porous sintered body layer is formed on a substrate such as a ceramic substrate, deformation or cracking is less likely to occur than in the case where the member is constituted by only the porous sintered body, and the porous Excellent liquid repellency with respect to the silicon melt is exhibited by the sintered material layer. Therefore, by using such a member as a member for producing crystal silicon, spherical crystal silicon or large plate-like crystal silicon can be arbitrarily and efficiently produced on a molding surface having a large area.
- the member for producing crystalline silicon when used as a member for producing crystalline silicon, as described above, since it has excellent liquid repellency with respect to the silicon melt, there are few contact surfaces between the member and the silicon melt, and the obtained crystalline silicon is Also, there is an effect that the mixing of impurities is extremely small. Furthermore, since the surface of the member is a sintered body, it can be used repeatedly for producing crystalline silicon as it is, and has high industrial value.
- This figure is a photograph before and after melting the raw material silicon.
- This figure is a schematic diagram showing an outline of a method for producing spherical crystalline silicon in Example 1.
- FIG. This figure is a schematic view showing an outline of a method for producing spherical crystalline silicon in Example 5.
- This figure is a SEM photograph of the surface of the silicon melt contact member obtained in Example 1 (Sample No. 10).
- This figure is a SEM photograph of the member surface obtained in Comparative Example 1 (Sample No. 2).
- This figure is a stereomicrograph of plate-like crystalline silicon produced using the silicon melt contact member of Example 1.
- This figure is a stereomicrograph of plate-like crystalline silicon produced using the silicon melt contact member of Comparative Example 1.
- This figure is a stereomicrograph of spherical crystalline silicon produced using the member of Comparative Example 1 (Sample No. 2).
- This figure is a stereomicrograph of spherical crystalline silicon produced using the silicon melt contact member of Example 4 (Sample No. 7).
- This figure is a stereomicrograph of spherical crystalline silicon produced using the silicon melt contact member of Example 4 (Sample No. 8).
- This figure is a stereomicrograph of spherical crystalline silicon produced using the silicon melt contact member of Example 4 (Sample No. 9).
- This figure is a schematic diagram showing an outline of a method for producing plate-like crystalline silicon in Example 1.
- FIG. This figure is a schematic diagram showing an outline of a method for producing plate-like crystalline silicon in Example 5.
- This figure is a SEM photograph of the surface of the silicon melt contact member obtained in Example 5.
- This figure is a SEM photograph of a cross section of the silicon melt contact member obtained in Example 5.
- This figure is a figure which shows the depth synthetic
- FIG. This figure is a photograph of the spherical crystalline silicon obtained in Example 5.
- This figure is a photograph of the plate-like crystalline silicon obtained in Example 5.
- This figure is a SEM photograph of the surface of the silicon melt contact member obtained in Example 6.
- This figure is a SEM photograph of a cross section of the silicon melt contact member obtained in Example 6.
- This figure is a figure which shows the depth synthetic
- FIG. This figure is a photograph of the spherical crystalline silicon obtained in Example 6.
- This figure is a SEM photograph of a cross section of the silicon melt contact member obtained in Example 7.
- the silicon melt contact member of the present invention comprises a molded body of a mixture containing organic particles composed of thermally decomposable resin particles and sinterable powder mainly composed of silicon nitride on at least the surface thereof.
- sinterable powder mainly composed of silicon nitride on at least the surface thereof.
- a porous sintered body layer obtained by firing until it disappears and further sintering the sinterable powder, in which pores derived from the shape of the organic particles are formed.
- Such a porous sintered body is required to have silicon nitride as a main component in order to exhibit excellent liquid repellency with respect to the silicon melt in combination with the pore structure described later.
- the proportion of silicon nitride in the porous sintered body layer is preferably 55% by mass or more, particularly preferably 70% by mass or more.
- the components other than silicon nitride are not particularly limited as long as they can constitute the sintered body, but are formed by suppressing shrinkage during sintering in the manufacturing method described later.
- a component having a function of maintaining the shape of the pores, specifically, silicon dioxide is preferable.
- Such silicon dioxide preferably has a ratio of 2% by mass or more, particularly 10% by mass or more in order to exert a shrinkage suppressing effect. If too much is present, the silicon nitride has a lower liquid repellency with respect to the silicon melt. Therefore, the ratio is preferably less than 50% by mass, particularly 45% by mass or less, more preferably 30% by mass or less. It is preferable that
- the porous sintered body layer of the present invention has pores derived from the shape of the organic particles as described above, and pores having an average equivalent circle diameter of 1 to 25 ⁇ m on the surface at a pore occupation area ratio of 30 to 80%. Are preferably present dispersed.
- the area ratio in which holes exist (hereinafter also referred to as the hole occupation area ratio) is the electronic data of a photograph taken with a scanning electron microscope, image processing by Asahi Kasei Engineering Co., Ltd. It was calculated using the software “A statue-kun”.
- an arbitrary analysis target range was selected and classified into a hole portion and a non-portion portion by binarization processing, and the area of each portion was integrated with the number of pixels included in the area. Then, the area ratio where the holes exist was calculated by dividing the area where the holes exist by the total area (area where the holes exist + area where the holes do not exist). The average equivalent circle diameter was also calculated from the above image.
- the porous sintered body layer of the present invention has liquid repellency (resistance to wetting) to the silicon melt due to the characteristics of the material mainly composed of silicon nitride and the presence of the pores. It becomes possible to repeatedly produce plate-like crystalline silicon.
- the silicon melt contact member of the present invention has a contact angle with respect to the silicon melt of 140 degrees or more, and has very high liquid repellency.
- the porous sintered body layer of the present invention has a large number of pores dispersed on its surface. Each of the holes is circular and exists independently, but there are some holes in which a plurality of holes are connected.
- These pores preferably have an average equivalent circular diameter of 1 to 25 ⁇ m, preferably 2 to 15 ⁇ m when the surface of the porous sintered body layer is viewed from directly above. That is, if the average equivalent circle diameter is less than 1 ⁇ m, it is not preferable because the silicon melt is likely to squeeze into the porous sintered body due to the capillary phenomenon, and the liquid repellency with respect to the silicon melt is reduced. If it exceeds 25 ⁇ m, it is not preferable because the melt easily enters the hole due to its own weight. Further, when the “hole occupied area ratio” of the holes formed on the surface of the porous sintered body layer is less than 30%, the contact area between the surface of the porous sintered body layer and the silicon melt increases.
- the silicon melt contact member of the present invention has a porous sintered body layer on its surface
- other structures are not particularly limited. That is, the whole member may have a structure composed of a porous sintered body layer, or a structure in which a porous sintered body layer is formed on a substrate such as a ceramic substrate.
- Each hole existing in the porous sintered body layer usually forms a communication hole in the depth direction.
- communication holes are formed in the depth direction as shown in FIGS. 15 and 20, and these communication holes are formed from the surface of the porous sintered body layer. It reaches to the ceramic substrate.
- the depth of the communication hole (length in the direction perpendicular to the surface of the sintered body layer) is 5 ⁇ m or more in order to effectively exhibit the liquid repellency of the silicon melt on the surface of the porous sintered body layer.
- the thickness is preferably 20 ⁇ m or more. That is, when the depth of the communication hole is less than 5 ⁇ m, the liquid repellency with respect to the silicon melt tends to be lowered. Therefore, the thickness of the porous sintered body layer may be designed in consideration of the depth of the communication hole, and is preferably 10 ⁇ m or more, and preferably 20 ⁇ m or more. However, even if the thickness of the porous sintered body layer is increased too much, the effect reaches its peak and is not economical. Therefore, the thickness is preferably 500 ⁇ m or less.
- the surface of the porous sintered body layer of the present invention is extremely smooth. In general, the thickness fluctuation width of the surface is about 5 to 7 ⁇ m in absolute value.
- the substrate functions as a support for maintaining the strength of the silicon melt contact member.
- the substrate is not particularly limited as long as it can form a porous sintered body layer, and a ceramic or a carbon material is preferably used.
- a known ceramic material can be used as the ceramic, but alumina or aluminum nitride is generally used because of its high melting point, strength, and availability, but silicon nitride and quartz glass are also preferably used. it can.
- the shape of the substrate is not particularly limited, and may be appropriately determined according to the application. Specifically, it can have any shape such as a plate shape, a crucible shape, or a cylindrical shape.
- the ceramic substrate made of ceramic and having a plate shape will be described in more detail.
- the thickness of the ceramic substrate is not particularly limited, but if it is 0.5 mm or more, preferably 1 mm or more, more preferably 3 mm or more, the ceramic substrate functions sufficiently.
- the surface state of the substrate is not particularly limited, the surface roughness is determined by considering the adhesion to the porous sintered body layer formed thereon and the smoothness of the surface of the porous sintered body layer. It is preferably about 1 to 10 ⁇ m.
- the surface of the substrate on which the porous sintered body layer is formed is preferably composed of silicon nitride. That is, the ceramic substrate and the porous sintered body layer are not necessarily equal in thermal expansion coefficient, and thus may be separated due to the difference in thermal expansion coefficient. In such a case, the problem can be suppressed by configuring the surface of the ceramic substrate with silicon nitride.
- the surface thickness of the silicon nitride is usually selected from the range of 2 to 30 ⁇ m, preferably 5 to 30 ⁇ m.
- the surface of the ceramic substrate is formed of silicon nitride
- an appropriate amount of silicon dioxide is added to the silicon nitride as necessary as a component for promoting sintering and preventing shrinkage during sintering, for example, 2 to Adding 50% by mass is also a preferred embodiment.
- the configuration of the ceramic substrate and the porous sintered body layer can also be applied to substrates of other shapes or other materials.
- the silicon melt contact member of the present invention basically includes a sinterable powder mainly composed of silicon nitride powder, and a thermal decomposability having an average particle diameter of 1 to 25 ⁇ m with respect to 100 parts by volume of the sinterable powder.
- a molded body obtained by molding a mixture for sintered bodies composed of 40 to 400 volume parts of resin particles is fired to eliminate the thermally decomposable resin particles, and the sinterable powder is heated to a temperature of 1100 to 1700 ° C. It can be obtained by sintering.
- holes derived from the shape of the thermally decomposable resin particles are formed.
- the above mixture is dispersed in an organic solvent.
- a later method using a dispersion for ligation is preferred.
- the purity, particle size, particle size distribution, etc. of the silicon nitride powder as the main component of the sinterable powder are not particularly limited, but the object is to produce crystalline silicon for solar cells. Taking this into consideration, the purity is preferably 99.99% or more.
- the average particle diameter is preferably 0.2 to 1 ⁇ m, and commercially available products having such properties can be used as they are.
- the ratio of silicon nitride in the sinterable powder is effective as long as it is the main component, that is, if it exceeds 50% by mass, it is a porous material that exhibits better liquid repellency with respect to the silicon melt. In order to form a quality sintered body layer, it is preferably 55% by mass or more, particularly preferably 70% by mass or more.
- the components other than silicon nitride in the sinterable powder are not particularly limited as long as they are powders having sinterability, but are components that have an action of promoting sintering and suppressing shrinkage during sintering.
- silicon dioxide is preferred. That is, when an attempt is made to form a porous sintered body layer using a mixture or dispersion for a sintered body that does not contain silicon dioxide powder, shrinkage occurs during sintering after removal of the thermally decomposable resin particles described later. However, it is not preferable because the pores cannot be stably formed.
- silicon dioxide at a ratio of 2% by mass or more, particularly 10% by mass or more in order to exhibit the effect of suppressing shrinkage during sintering.
- the proportion is preferably less than 50% by mass, particularly 45% by mass or less, and more preferably 40% by mass or less.
- a ratio is preferred.
- the purity of the silicon dioxide is preferably 99.99% or more.
- the average particle size is 0.05 to 2 ⁇ m, preferably 0.2 to 1 ⁇ m, and commercially available products having such properties can be used as they are.
- the thermally decomposable resin particles are components that serve to generate the predetermined pores through a thermal decomposition and sintering process described later. That is, the particle size of the thermally decomposable resin particles is reflected in the pore diameter in the sintered porous sintered body layer, and the blending amount is reflected in the pore occupation area ratio. Therefore, resin particles having an average particle diameter of 1 to 25 ⁇ m, preferably 3 to 20 ⁇ m are used as the thermally decomposable resin particles, and the total area of the pores per surface reference area with respect to 100 parts by volume of the sinterable powder. It is necessary to blend 40 to 400 parts by volume so that the ratio of the above becomes a predetermined value.
- the thermally decomposable resin constituting the particles is not particularly limited as long as it is a resin that is thermally decomposed at a predetermined temperature, but remains in the porous sintered body layer after thermal decomposition and sintering, and then manufactured. It is not preferable to contaminate the crystalline silicon. Further, it is preferable that the thermal decomposable resin particles have a specific gravity equal to or smaller than the specific gravity of the sinterable powder because it can surely exist on the surface when the dispersion is applied.
- a hydrocarbon resin such as polyolefin or polystyrene, a benzoguanamine formaldehyde condensate, and an acrylate resin are preferable.
- an acrylate-based resin with little residual resin-derived carbon after sintering is preferable.
- examples of such acrylate resins include spherical polymethyl methacrylate particles (“MBX series” manufactured by Sekisui Plastics Co., Ltd.), and spherical particles of cross-linked polybutyl methacrylate (“BMX series” manufactured by Sekisui Chemicals Co., Ltd.).
- Methacrylic resin particles (“Techpolymer IBM-2” manufactured by Sekisui Plastics Industries Co., Ltd.), true spherical particles of crosslinked polystyrene (“SBX series” manufactured by Sekisui Plastics Industries Co., Ltd.), true of crosslinked polyacrylic ester Spherical particles (“ARX series” manufactured by Sekisui Plastics Industries Co., Ltd.), true spherical particles of crosslinked polymethyl methacrylate (“SSX (monodisperse) series” manufactured by Sekisui Plastics Industries Co., Ltd.), etc. Since those are commercially available, they may be used according to the purpose of the present invention.
- a dispersion for a sintered body in which the above components are dispersed in an organic solvent That is, a sinterable powder containing silicon nitride powder as a main component and 40 to 400 parts by volume of thermally decomposable resin particles having an average particle diameter of 1 to 25 ⁇ m with respect to 100 parts by volume of the sinterable powder in an organic solvent.
- a dispersion for a sintered body dispersed in is prepared. After the dispersion is applied on the ceramic substrate, the organic solvent is removed by drying, and then the thermally decomposable resin particles are thermally decomposed and removed.
- the ceramic substrate a substrate made of the material exemplified above is preferably used.
- the method for forming the surface on which the porous sintered body layer is formed with silicon nitride is to add silicon nitride powder or silicon dioxide powder to the powder and add organic
- An example is a method in which a dispersion liquid dispersed in a solvent is applied onto a ceramic substrate and calcined at 100 to 700 ° C.
- the organic solvent to be used is not particularly limited, in the case of producing crystalline silicon for solar cells, in order to prevent contamination of impurities (atoms), it is composed of carbon, hydrogen, and oxygen atoms as necessary.
- Evaporable organic solvents are preferred.
- hydrocarbon solvents such as toluene and alcohol solvents such as n-octyl alcohol and ethylene glycol are exemplified as suitable solvents.
- the usage-amount of the said organic solvent is not specifically limited, It determines suitably so that the dispersion liquid for sintered compacts may become a viscosity suitable for the coating method mentioned later.
- a sintering aid such as magnesium oxide and yttrium oxide
- a dispersant for the purpose of stabilizing dispersion of the dispersion are added to the mixture for sintered body or the dispersion for sintered body.
- a sintering aid such as magnesium oxide and yttrium oxide
- a dispersant for the purpose of stabilizing dispersion of the dispersion are added to the mixture for sintered body or the dispersion for sintered body.
- blend an agent suitably.
- the mixing order and method of the sinterable powder and the thermally decomposable resin particles as well as additives and organic solvents blended as necessary are not particularly limited.
- the prepared mixture for sintered bodies is formed into a formed body by a method such as press molding.
- the thermally decomposable resin particles are thermally decomposed, and then sintered by sintering at a temperature of 1100 to 1700 ° C. to obtain a porous sintered body.
- the operation of thermally decomposing and disappearing the thermally decomposable resin particles in the molded body may be performed in the process of firing for sintering. However, before sintering, it is preferable to burn the pyrolyzable resin particles by thermal decomposition at a temperature 50 to 300 ° C. higher than the pyrolysis temperature of the pyrolyzable resin particles.
- the atmosphere during the thermal decomposition is not particularly limited as long as the atmosphere in which the thermally decomposable resin particles can be decomposed. In general, in order to effectively remove carbon produced by decomposition, it is usually preferable to carry out in air in the presence of oxygen.
- the molded body having a porous skeleton formed by removing the thermally decomposable resin particles by the above operation is then 1100 to 1700 ° C., preferably 1100 to 1550 ° C., particularly preferably 1400 to 1530 ° C.
- the desired porous sintered body is formed by heating and sintering at. By adopting the firing temperature, the occurrence of deformation and cracks in the obtained porous sintered body can be reduced.
- the atmosphere during sintering is preferably an inert atmosphere, for example, an atmosphere of nitrogen gas or the like.
- the sintering time is 1 hour or longer, preferably 2 hours or longer. If it is carried out for an excessively long time, the holes formed on the surface may be reduced or crushed.
- the dispersion when a dispersion for a sintered body is used to form a porous sintered body layer on a substrate that is a support, the dispersion is used as a ceramic substrate or the like.
- the substrate is applied to a predetermined thickness.
- the coating method is not particularly limited, and methods such as spin coating, dip coating, roll coating, die coating, flow coating, and spraying are adopted. From the viewpoint of appearance quality and film thickness control, spin coating is used. Is preferred.
- a desired thickness can be obtained by repeating the method of coating the dispersion and drying the organic solvent and then coating again. A layer having the same can be formed.
- the organic solvent is removed by drying.
- the drying condition is preferably heating at a temperature equal to or higher than the boiling point of the organic solvent.
- the thermally decomposable resin particles are decomposed and removed, and a layer composed of a porous skeleton derived from the thermally decomposable resin particles is formed.
- the porous sintered body layer is formed on the substrate by firing at the above-described sintering temperature. Removal of the solvent by drying, removal of the thermally decomposable resin particles, and sintering may be performed continuously in the same apparatus by changing the atmospheric gas and temperature, or sequentially performed in separate apparatuses. May be.
- the melt obtained by melting the silicon raw material is cooled and crystallized to produce crystalline silicon.
- a separately melted solution may be placed on the surface of the porous sintered body layer maintained at a temperature equal to or higher than the melting point temperature of silicon, or a predetermined amount may be placed on the surface of the porous sintered body layer.
- the solid silicon After the solid silicon is placed, it may be melted by holding the silicon at a melting point of 1414 ° C. or higher, preferably 1420 to 1480 ° C., with a heating means such as a high frequency coil or a resistance heater.
- the post-melting step and the post-melting cooling crystallization step and the annealing step, etc. are all performed in an inert gas atmosphere in which moisture and oxygen are reduced as much as possible, for example, a high-purity argon gas atmosphere. Etc. are necessary.
- the solid silicon is not particularly limited, and silicon powder, lump, crushed material and the like obtained by an existing manufacturing method such as a crystal growth method or a dropping method can be used. The crystallinity is not questioned. In order to produce crystalline silicon for large-scale batteries according to the present invention, the purity of solid silicon may be 99.9999% or more.
- Cooling crystallization can be performed by appropriately cooling from the melt state under conditions that allow crystallization. In general, it is preferable to cool to approximately 700 ° C. at a cooling rate of 50 to 300 ° C./hour. Crystalline silicon obtained by cooling crystallization is maintained at a predetermined temperature during cooling, or reheated after cooling for the purpose of improving crystallinity by reducing crystal distortion and grain boundary defects. It is preferable to perform an annealing treatment to maintain. The annealing temperature is 900 to 1350 ° C., and the time is suitably 1 to 24 hours. The annealing is particularly effective when the cooling temperature is relatively fast.
- each manufacturing method will be described in detail by dividing into spherical crystalline silicon and plate-like crystalline silicon.
- FIG. 1 shows photographs of the spheroidized state before and after melting of silicon.
- the supply of silicon onto the porous sintered body layer is not limited to the supply in the solid state, but a separately melted silicon melt is heated to the porous sintered body layer, preferably above the melting point of silicon. It is also possible to carry out by dropping it on the surface of the porous sintered body layer.
- the spherical silicon obtained by this method is crystalline silicon with a remarkable metallic luster. The crystal form is often twinned.
- the spherical silicon has a low residual concentration of carbon and oxygen atoms, and further a residual concentration of nitrogen and iron atoms, and can be used as crystalline silicon for solar cells in this state.
- the size of the spherical crystals can be arbitrarily controlled by controlling the amount of solid silicon used and the distance between melts, and spherical crystalline silicon having a particle diameter of 1 to 5 mm can usually be obtained.
- plate-like crystalline silicon solid silicon is sandwiched between the porous sintered body layers of at least two silicon melt contact members held horizontally, and the upper silicon melt contact member is Put a weight on and melt. 12 and 13 schematically show the manufacturing process. Also, plate-like crystalline silicon can be produced by holding it vertically and performing unidirectional solidification. The subsequent steps after crystallization are performed according to the method for producing spherical crystalline silicon. The size and thickness of the plate-like crystalline silicon can be controlled by the size and shape of the silicon melt contact member used, the amount of solid silicon used, the weight of the weight, and the like.
- the silicon melt contact member of the present invention is not limited to the production of the above-described crystalline silicon, but is also useful as a constituent member of a container for handling a silicon melt, such as a crucible for melting silicon and a casting container for producing an ingot. .
- a silicon fusion contact member in which a porous sintered body layer is formed on a ceramic substrate is used, and the container is placed so that the ceramic substrate of the member is a structural material and the porous sintered body layer is an inner surface. It is preferable to configure.
- Example 1 [Manufacture of silicon melt contact members] 30% by mass of silicon nitride powder having a particle size of 0.1-5 ⁇ m, 20% by mass of amorphous silicon dioxide powder having a particle size of 1.8-2 ⁇ m, and thermally decomposable resin particles having an average particle size of 5 ⁇ m (Sekisui Plastics Co., Ltd.) Techpolymer “SSX-105” (cross-linked polymethyl methacrylate) manufactured by Co., Ltd. was weighed to 50% by mass and mixed for 10 minutes in an alumina mortar. The mixed powder was press-molded at 8 kN to obtain a disk-shaped molded body having a diameter of 20 mm and a thickness of 10 mm.
- FIG. 4 shows a scanning electron micrograph (SEM) of the surface of the porous sintered body layer of the obtained silicon melt contact member. The magnification is 1000 times, and a line segment indicating a length of 10 ⁇ m is displayed on the photograph. It was confirmed that the prepared member had holes with an average equivalent circle diameter of 5 ⁇ m dispersed and present on the surface at a hole occupation area ratio of 60%. It is considered that the presence of the pores improves the liquid repellency with respect to the silicon melt and significantly reduces the penetration of the silicon melt into the silicon melt contact member.
- FIG. 6 shows the state of the obtained plate-like crystalline silicon and the silicon melt contact member used when plate-like crystalline silicon was produced. Almost no soaking of silicon is observed on the surface of the silicon melt contact member.
- the silicon melt contact member of the present invention is such that even if a slight penetration of silicon into the member occurs, the silicon can be removed immediately by rubbing the surface of the member with a paper file, and the penetration depth is very small. it is conceivable that. Therefore, it can be used repeatedly over and over. By changing the production conditions, it was possible to obtain various plate-like crystalline silicon controlled in a 15 mm square and a thickness of 250 to 800 ⁇ m.
- Comparative Example 1 Manufacture of silicon melt contact members. Weighed silicon nitride powder with a particle size of 0.1 to 5 ⁇ m and amorphous silicon dioxide powder with a particle size of 1.8 to 2 ⁇ m to 40% by mass without adding thermally decomposable resin particles. And mixed for 10 minutes in an alumina mortar. The mixed powder was press-molded at 8 kN to obtain a disk-shaped molded body having a diameter of 20 mm and a thickness of 10 mm. This molded body was heated in the atmosphere at 500 ° C. for 3 hours and 1100 ° C. for 6 hours using a muffle furnace to obtain a sintered body member (Table 1 Sample No. 2). In FIG. 5, the scanning electron micrograph (SEM) of the surface of the obtained sintered compact member is shown. Concavities and convexities are observed on the surface of the member, but the presence of pores is not recognized.
- SEM scanning electron micrograph
- Spherical crystalline silicon was produced in the same manner as in Example 1 using the produced sintered body member. Crystalline silicon solidified into a sphere having a diameter of about 2 mm. The contact angle between the silicon melt and the member was about 160 degrees. Although the peelability between the solidified silicon and the member was good, it was inferior to that of Example 1. Silicon penetration into the member surface was observed. Almost the entire silicon surface was covered with impurities, and the metallic luster was hardly seen. A stereomicrograph of the obtained spherical crystalline silicon is shown in FIG.
- FIG. 7 shows the state of the obtained plate-like crystalline silicon and the members used when plate-like crystalline silicon was produced.
- the penetration of silicon into the member surface is severe. From this result, it can be seen that the silicon melt contact member of the present invention has a certain effect in preventing the penetration of silicon.
- the silicon melt penetrated from the member surface to a depth of at least 170 ⁇ m. It was also observed that the soaked silicon melt reacted with the silicon nitride and silicon dioxide components of the member. For this reason, it is very difficult to remove the soaked silicon from the member, and it cannot be reused.
- Comparative Example 2 A sintered body member was produced in the same manner as in Comparative Example 1 except that the raw material blending shown in Sample Nos. 1 and 3 in Table 1 was used without blending the thermally decomposable resin particles. Using each of the obtained sintered body members, spherical crystalline silicon was similarly produced. The results are also shown in Table 1.
- Example 2 Manufacture of silicon melt contact members
- the mixing ratio of the thermally decomposable resin particles was less than that in Example 1. That is, 42% by mass of silicon nitride powder having a particle size of 0.1 to 5 ⁇ m, 28% by mass of amorphous silicon dioxide powder having a particle size of 1.8 to 2 ⁇ m, and 30 thermally decomposable resin particles having an average particle size of 5 microns.
- a silicon melt contact member was produced in the same manner as in Example 1 except that mass% was used (Table 1 sample number 5). It was confirmed that the prepared member had holes with an average equivalent circle diameter of 5 ⁇ m dispersed and present on the surface at a hole occupation area ratio of 30%.
- Spherical crystalline silicon was produced in the same manner as in Example 1 using the produced silicon melt contact member. Crystalline silicon solidified into a sphere having a diameter of about 2 mm. The contact angle between the silicon melt and the member was about 160 degrees. Peeling of the solidified crystalline silicon from the member was very easy, and only a small amount of silicon soaked into the member surface. The crystal silicon surface had slightly more impurities and less metallic luster. From comparison between Example 2 and Example 1, it was found that the amount of the thermally decomposable resin particles to be blended is preferably 50% by mass.
- Example 3 Manufacture of silicon melt contact members
- magnesium oxide (MgO) is added as a sintering aid, 30% by mass of silicon nitride powder having a particle size of 0.1 to 5 ⁇ m, and 20% by mass of amorphous silicon dioxide powder having a particle size of 1.8 to 2 ⁇ m. %, And organic compound spherical particles having a particle size of 5 microns were weighed to 50% by mass, and 3% by mass of magnesium oxide was added thereto and mixed for 10 minutes in an alumina mortar. The mixed powder was press-molded at 8 kN to obtain a disk-shaped molded body having a diameter of 20 mm and a thickness of 10 mm.
- MgO magnesium oxide
- the molded body was heated in the atmosphere at 500 ° C. for 3 hours and 1100 ° C. for 6 hours using a muffle furnace to evaporate and remove the thermally decomposable resin particles, and then at 6400 ° C. in a high purity argon (G2) atmosphere.
- the silicon melt contact member was obtained by baking for a while (Table 1 Sample No. 12). It was confirmed that the prepared member had holes with an average equivalent circle diameter of 4 ⁇ m dispersed on the surface at a hole occupation area ratio of 50%. By blending the sintering aid, the strength of the silicon melt contact member was improved. Further, by performing the main baking at 1400 ° C. or higher, the amount of impurities mixed in the crystalline silicon during the production of the crystalline silicon can be reduced, and the original metallic luster of silicon on the crystalline silicon surface clearly appears.
- Spherical crystalline silicon was produced in the same manner as in Example 1 using the produced silicon melt contact member. Crystalline silicon solidified into a sphere having a diameter of about 2 mm. The contact angle between the silicon melt and the member was about 140 degrees, and a slight decrease in liquid repellency was observed compared to the case where no sintering aid was added. Peeling from the solidified silicon member was easy, and only a small amount of silicon soaked into the member surface. There were few impurities on the silicon surface, and it had a metallic luster.
- Example 4 A silicon melt contact member was produced in the same manner as in Example 1 except that the raw material composition shown in Sample Nos. 4, 6, 7, 8, 9, 11, 13, 14, and 15 in Table 1 was used. It was confirmed that the prepared member had holes having a hole occupied area ratio and an average equivalent circle diameter shown in Table 2 dispersed on the surface. Using each of the obtained silicon melt contact members, spherical crystalline silicon was similarly produced. The results are also shown in Table 1. 9 is a stereomicrograph of spherical crystalline silicon produced using the silicon melt contact member of sample number 7, FIG. 10 is sample number 8, and FIG. 11 is sample number 9.
- Example 5 Manufacture of silicon melt contact members using substrates
- sinterable powder consisting of 70% by mass of silicon nitride powder having an average particle size of 0.5 ⁇ m (manufactured by Ube Industries) and 30% by mass of amorphous silicon dioxide powder having an average particle size of 1.9 ⁇ m
- 100 parts by volume of true spherical heat-decomposable resin particles having an average particle size of 5 ⁇ m (Techpolymer “SSX-105” manufactured by Sekisui Plastics Co., Ltd .; cross-linked polymethyl methacrylate) are added to 100 parts by mass of sinterable powder.
- the silicon nitride substrate on which the dispersion liquid was spin-coated was heated in the atmosphere at 500 ° C. for 3 hours using a muffle furnace (electric furnace), and further in a nitrogen atmosphere at 1100 ° C. for 6 hours to obtain the silicon of the present invention.
- a melt contact member was obtained.
- FIG. 15 shows an SEM photograph of a cross section of the silicon melt contact member. As is clear from FIG. 15, the thickness of the sintered body layer is about 30 ⁇ m, and the pores are connected to each other to form a communication hole, and the communication hole extends from the surface of the sintered body layer to the substrate surface. I understand that.
- FIG. 15 shows an SEM photograph of a cross section of the silicon melt contact member. As is clear from FIG. 15, the thickness of the sintered body layer is about 30 ⁇ m, and the pores are connected to each other to form a communication hole, and the communication hole extends from the surface of the sintered body layer to the substrate surface. I understand that. FIG.
- FIG. 16 shows the result of depth synthesis in which the surface of the porous sintered body layer was analyzed using a CCD microscope apparatus. As seen in FIG. 16, a porous sintered body layer was formed on the aluminum nitride substrate, and the thickness variation of the surface of the sintered body layer was a maximum of 5 ⁇ m. When the contact angle of the silicon melt on the surface of the porous sintered body layer of the obtained silicon contact member was measured, it was 155 degrees.
- FIG. 17 shows a photograph of the obtained spherical crystalline silicon.
- the obtained spherical crystalline silicon has a metallic luster, and has an extremely low impurity content of carbon, oxygen, nitrogen, and iron by analysis using a secondary ion mass spectrometer (SIMS). there were.
- SIMS secondary ion mass spectrometer
- Example 6 Manufacture of silicon melt contact members using substrates
- a silicon melt contact member was produced in the same manner as in Example 5 except that an alumina substrate (40 mm ⁇ 40 mm) was used instead of the aluminum nitride substrate.
- FIG. 19 shows an SEM photograph of the surface of the porous sintered body layer of the silicon melt contact member obtained
- FIG. 20 shows a cross-sectional SEM photograph thereof
- FIG. 21 shows a depth synthesis result.
- Circular holes having an average pore diameter of about 5 ⁇ m were uniformly formed on the surface of the porous sintered body layer, and each hole was connected to form a continuous hole in the depth direction and reached the substrate surface.
- the hole occupation area ratio of the porous sintered body layer was 60%.
- the maximum thickness variation was 6.7 ⁇ m, and a smooth sintered body layer was formed. It was 150 degree
- spherical crystalline silicon was produced in the same manner as in Example 5. On the porous sintered body layer, an interval of about 2 cm is provided, 10 mg of silicon pieces are placed in 9 places, and the manufacturing temperature conditions are maintained at a heating rate of 200 ° C./h and 1480 ° C. for 6 minutes. The same procedure as in Example 5 was performed, except that it was melted and then cooled and crystallized at 150 ° C./h. A photograph of the obtained spherical crystalline silicon is shown in FIG. It was a spherical crystal of about 2 mm and was confirmed to be crystalline silicon with a high metallic luster.
- Example 7 Manufacture of silicon melt contact members using substrates
- a ceramic substrate on which the dispersion for a sintered body was spin-coated an aluminum nitride sintered substrate having a surface made of silicon nitride and silicon dioxide formed by the following method was used. Except this, it processed like Example 5 and produced the silicon melt contact member.
- the surface of the sintered body layer of silicon nitride is 270 parts by mass of silicon nitride powder (manufactured by Ube Industries) with an average particle size of 0.5 ⁇ m, 30 parts by mass of amorphous silicon dioxide powder (manufactured by Soekawa Riken), and ethylene glycol.
- FIG. 23 shows an SEM photograph of a cross section of the silicon melt contact member.
- the obtained member was a silicon melt contact member having a structure in which a layer made of silicon nitride and silicon dioxide having a thickness of 15 ⁇ m was laminated on an aluminum nitride sintered substrate, and a porous sintered body layer having a thickness of 15 ⁇ m was further laminated thereon. It was.
- Circular holes having an average pore diameter of about 6 ⁇ m were uniformly formed on the surface of the porous sintered body layer, and each hole was connected to form a continuous hole in the depth direction and reached the substrate surface.
- the pore occupying area ratio of the porous sintered body layer was 60%, the thickness variation was 5 ⁇ m at maximum, and a smooth sintered body layer was formed. It was 150 degree
- the silicon melt contact member showed high durability with very little peeling of the porous sintered body layer in repeated use.
- Example 8 In Example 1, the average particle diameter of the thermally decomposable resin particles to be used (Tech Polymer manufactured by Sekisui Plastics Co., Ltd .; crosslinked polymethyl methacrylate) and the ratio of silicon nitride and silicon dioxide constituting the sinterable powder are as follows.
- a silicon melt contact member was produced in the same manner except that the changes were made as shown in Table 3.
- spherical crystalline silicon was similarly produced. The results are also shown in Table 3.
- the contact angle with the silicon melt showed almost the same value as in Example 1.
- the holes in the porous sintered body layer of the obtained silicon melt contact member were almost circular, and the ratio of the hole occupation area and the average equivalent circle diameter were as shown in Table 4.
- Example 9 A silicon melt contact member having an aluminum nitride substrate as a support was produced in the same manner as in Example 5, except that the average particle size of the thermally decomposable resin particles used was changed as shown in Table 5.
- the pores in the porous sintered body layer of the obtained silicon melt contact member are substantially circular.
- the average equivalent circle diameter, the hole occupation area ratio, and the thickness of the porous sintered body layer are as shown in Table 5. Met. Further, the contact angle of the silicon melt on the surface of the porous sintered body layer of the obtained silicon contact melt member was measured and is shown in Table 5 together.
- the silicon melt contact member showed high durability with very little peeling of the porous sintered body layer in repeated use.
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Abstract
Description
結晶シリコンの切断ロス分をなくし製造コストを低減することを目的に、球状の結晶シリコンの製造方法が開発されている。この方法は、融液が表面張力で球状になることを利用して、一定量のシリコン融液を高所から落下させて球状の結晶シリコンを製造する方法である。この球状の結晶シリコンを平面上に並べた構造の太陽電池も提案されており、太陽光の集光方法を工夫すれば発電効率も向上させることができる。
しかし、高所から落下させる方法(落下法)で得られた球状の結晶シリコンは製造時の大きな温度勾配に起因して微細な多結晶となっていて、発電効率が悪く、また結晶欠陥を有する割合も大きい。このため、落下法で得られた球状シリコンを再度加熱し、融解させた後冷却して、球状結晶シリコンを形成している多結晶シリコンの結晶粒の数を少なくしているのが実情であり、工程が増えてコストが高くなってしまうという問題がある。
また、特許文献2には、台板表面の凹部にシリコン材料を載置して、加熱溶融させた後、凝固させて球状の結晶シリコンを製造する方法が記載されている。台板の凹部表面には、シリコン融液と濡れにくい酸化シリコン等の膜が付着形成されている。
まず、シリコンを溶融・凝固させる容器や台板の表面には、シリコン融液と反応しにくい窒化珪素等の物質(離型材)を塗布する、或いは被膜を形成させて、シリコン融液に対して撥液性を持つようにされているが、これらの撥液性を持つ層が薄く、耐久性の点で問題がある。更に、結晶シリコンの製造のたびに離型層を塗布形成する場合には、結晶シリコンの製造工程が増加して製造コストが上昇してしまう。さらに、撥液性を持つ被膜層に欠損等が発生した場合には、球状の結晶シリコンの球形状に不具合を生じるだけでなく、シリコンが台板に深く染み込んで固着してしまったり、台板から結晶シリコン中に不純物が混入してしまったりするおそれがある。
上記シリコン融液接触部材の発明において、
(1)前記多孔質焼結体層が、セラミック基板等の基体上に形成されていること
(2)前記基体は、多孔質焼結体層が形成されるその表面が窒化ケイ素により構成されていること
(3)前記多孔質焼結体層の厚みが、5~500μmであること
(4)前記多孔質焼結体層は、その表面に、30~80%の孔占有面積割合で、平均円相当直径1~25μmの大きさの孔が分散して存在すること
(5)前記多孔質焼結体層が、二酸化ケイ素を2質量%以上、50質量%未満の割合で含有していること
(6)前記多孔質焼結体層の表面に存在する孔の平均深さが5μm以上であること
が好適である。
上記結晶シリコンの製造方法の発明において、
(1)前記シリコン融液が、固体状シリコンを多孔質焼結体層上にて溶融して得られたものであること
(2)前記結晶シリコンが、球状の結晶シリコンであって、シリコン融液部材の表面にシリコン融液を液滴の状態で存在させ、その表面張力により球状化した状態で冷却して、結晶化を行うこと
(3)前記結晶シリコンが板状の結晶シリコンであって、二枚のシリコン融液部材を用い、各部材の多孔質焼結体層を内側にして挟んだ状態でシリコン融液を冷却して、結晶化を行うこと
が好適である。
上記シリコン融液接触部材の製造方法の発明において、
(1)前記基体が、多孔質焼結体層が形成されるその表面が窒化ケイ素により構成されていること
(2)窒化ケイ素粉末を主成分とする焼結性粉末が、二酸化ケイ素を2質量%以上、50質量%未満の割合で含有していること
が好適である。
更に、セラミック基板等の基体上に上記多孔質焼結体層を形成した場合は、該多孔質焼結体のみにより部材を構成する場合に比べて変形や割れ等が起こり難く、且つ、前記多孔質焼結体層によってシリコン融液に対する優れた撥液性を発揮する。それゆえ、かかる部材を結晶シリコン製造用部材として使用することにより、大面積の成形面において、球状の結晶シリコン或いは大型の板状の結晶シリコンを、任意に且つ効率的に製造することができる。
また、結晶シリコン製造用部材として用いた場合は、上記のように、シリコン融液に対して優れた撥液性を有するため、部材とシリコン融液との接触面が少なく、得られる結晶シリコンは、不純物の混入が極めて少ないという効果をも有する。更に、当該部材はその表面が焼結体であるため、そのままの状態で繰返し結晶シリコンの製造に使用でき、工業的価値が高い。
本発明のシリコン融液接触部材は、少なくともその表面に、熱分解性樹脂粒子からなる有機粒子と、窒化ケイ素を主成分とする焼結性粉末とを含む混合物の成形体を、前記有機粒子が消失するまで焼成し、更に、前記焼結性粉末を焼結することにより得られ、前記有機粒子の形状に由来する孔が形成された多孔質焼結体層が存在することを特徴とする。かかる多孔質焼結体層は、窒化ケイ素を主成分とすることが、後述する孔の構造と相まって、シリコン融液に対する優れた撥液性を発揮するために必要である。多孔質焼結体層における窒化ケイ素の割合は、55質量%以上、特に、70質量%以上であることが好ましい。
前記多孔質焼結体層において、窒化ケイ素以外の成分は、焼結体を構成し得るものであれば特に制限されないが、後述の製造方法において、焼結時の収縮を抑制して形成される孔の形状を維持する機能を有する成分、具体的には、二酸化ケイ素が好適である。かかる二酸化ケイ素は、収縮抑制効果を発揮するために、2質量%以上、特に、10質量%以上の割合であることが好ましい。あまり多く存在すると、前記窒化ケイ素の、シリコン融液に対する撥液性を低下させるため、50質量%未満の割合であることが好ましく、特に、45質量%以下、更には、30質量%以下の割合であることが好ましい。
尚、上記多孔質焼結体層の表面において、孔の存在する面積割合(以下、孔占有面積割合ともいう)は、走査型電子顕微鏡で撮影した写真の電子データーを、旭化成エンジニアリング社製画像処理ソフト「A像君」を用いて算出した。算出方法は、任意の解析対象範囲を選択して、ニ値化処理により孔の部分とそうでない部分に分類し、それぞれの部分の面積を当該面積中に含まれる画素数を積算した。そして、孔の存在する面積を総面積(孔の存在する面積+孔の存在しない面積)で除することで孔の存在する面積割合を算出した。また、平均円相当直径も、上記画像より平均値を算出した。
本発明の多孔質焼結体層は図4、図14に示す如く、その表面に多数の孔が分散して存在している。各孔は、円形状で独立して存在しているが、一部孔が複数連結しているものも存在する。
この孔は、多孔質焼結体層の表面を真上から見た場合の平均円相当径が、平均1~25μm、好ましくは2~15μmであることが好ましい。即ち、上記平均円相当径が1μm未満では、毛細管現象によりシリコン融液が多孔質焼結体内部に沁み込み易くなり、シリコン融液に対する撥液性が減少するので好ましくない。25μmを超えると、シリコン融液の自重で孔内部に融液が入りやすくなるので好ましくない。
また、前記多孔質焼結体層の表面に形成される孔の「孔占有面積割合」は、30%未満の場合、多孔質焼結体層の表面とシリコン融液との接触面積が増大して十分な撥液性を発揮することが困難となる。80%を超える場合、シリコン融液と接触して支える面積が低減し、孔内にシリコン融液が進入し易くなる。また、多孔質焼結体層の強度が著しく低減する傾向がある。
多孔質焼結体層に存在する各孔は、通常、深さ方向に連通孔を形成している。例えば、セラミック基板上に多孔質焼結体層を形成した場合、図15、図20に示す如く、深さ方向に連通孔を形成し、この連通孔は、多孔質焼結体層の表面からセラミック基板まで達する。この連通孔の深さ(焼結体層の表面に対し垂直方向の長さ)は、多孔質焼結体層表面におけるシリコン融液の撥液性を効果的に発揮させるために、5μm以上、特に、20μm以上とすることが好ましい。即ち、かかる連通孔の深さが5μm未満である場合、シリコン融液に対する撥液性が低下する傾向にある。
従って、多孔質焼結体層の厚みは、この連通孔の深さを勘案して設計すればよく、10μm以上、好ましくは、20μm以上が好適である。但し、多孔質焼結体層の厚みをあまり厚くしても効果は頭打ちとなり、経済的でないため、その厚みは、500μm以下とすることが好ましい。
本発明の多孔質焼結体層の表面は極めて平滑であり、一般に、その表面の厚み変動幅は絶対値で5~7μm程度である。
また、上記基体の形状は特に制限されず、用途に応じて適宜決定すればよい。具体的には、板状、るつぼ状、筒状など、任意の形状とすることができる。
上記セラミック基板と多孔質焼結体層との構成は、他の形状、あるいは、他の材質の基体に対しても適用することができる。
本発明のシリコン融液接触部材は、基本的には、窒化ケイ素粉末を主成分とする焼結性粉末、及び該焼結性粉末100容量部に対して平均粒子径1~25μmの熱分解性樹脂粒子40~400容量部からなる焼結体用混合物を成形して得た成形体を焼成して前記熱分解性樹脂粒子を消失せしめ、更に、前記焼結性粉末を1100~1700℃の温度で焼結せしめることにより得られる。得られた焼結体には、該熱分解性樹脂粒子の形状に由来する孔が形成される。
尚、支持体である基体上に多孔質焼結体層を形成する場合は、多孔質焼結体層の厚みの制御、製法の容易性の観点から、上記混合物を有機溶媒に分散させた焼結体用分散液を使用する後出の方法が好適である。
また、焼結性粉末中の窒化ケイ素の割合は、主成分である限り、即ち、50質量%を超えれば効果を発揮するが、シリコン融液に対してより優れた撥液性を発揮する多孔質焼結体層を形成するためには、55質量%以上、特に、70質量%以上であることが好ましい。
従って、かかる二酸化ケイ素は、焼結時の収縮抑制効果を発揮するために、2質量%以上、特に、10質量%以上の割合で使用することが好ましい。しかし、あまり多く存在すると、前記窒化ケイ素によるシリコン融液に対する撥液性を低下させるため、50質量%未満の割合であることが好ましく、特に、45質量%以下、更には、40質量%以下の割合であることが好ましい。
上記二酸化ケイ素の純度は、99.99%以上であることが好ましい。平均粒径は、0.05~2μm、好ましくは0.2~1μmが良く、かかる性状を有する市販品をそのまま使用できる。
前記粒子を構成する熱分解性樹脂としては、所定の温度で熱分解する樹脂であれば特に制限はないが、熱分解および焼結後に多孔質焼結体層に残存して、その後、製造する結晶シリコン中に混入して汚染することは好ましくない。また、熱分解性樹脂粒子は、比重が、焼結性粉末の比重と同等かそれより小さいことが、前記分散液を塗布した際にその表面に確実に存在せしめることができ好ましい。
このようなアクリレート系樹脂としては、架橋ポリメタクリル酸メチルの真球状粒子(積水化成製品工業社製「MBXシリーズ」)、架橋ポリメタクリル酸ブチルの真球状粒子(積水化成製品工業社製「BMXシリーズ」)、メタクリル系樹脂の粒子(積水化成製品工業社製「テクポリマーIBM-2」)、架橋ポリスチレンの真球状粒子(積水化成製品工業社製「SBXシリーズ」)、架橋ポリアクリル酸エステルの真球状粒子(積水化成製品工業社製「ARXシリーズ」)、架橋ポリメタクリル酸メチルの真球状粒子(積水化成製品工業社製「SSX(単分散)シリーズ」)等、様々な粒径や粒度分布のものが市販されているので、本発明の目的に応じて使用すればよい。
即ち、予め窒化ケイ素粉末を主成分とする焼結性粉末、及び該焼結性粉末100容量部に対して平均粒子径1~25μmの熱分解性樹脂粒子40~400容量部を、有機溶媒中に分散させた焼結体用分散液を調製する。該分散液をセラミック基板上に塗布した後、有機溶媒を乾燥により除去し、次いで、上記熱分解性樹脂粒子を熱分解せしめて除去する。その後、焼結せしめて多孔質焼結体層を形成する。
上記製造方法において、セラミック基板としては、先に例示した材質の基板が好適に使用される。セラミック基板が窒化ケイ素以外のセラミックよりなる場合に、多孔質焼結体層が形成される表面を窒化ケイ素により構成する方法としては、窒化ケイ素粉末、または該粉末に二酸化ケイ素粉末を添加して有機溶媒に分散した分散液を、セラミック基板上に塗布し、100~700℃で仮焼する方法が挙げられる。
上記有機溶媒の使用量は特に限定されず、焼結体用分散液が後出の塗布方法に適した粘度となるように適宜決定される。
焼結性粉末及び熱分解性樹脂粒子、更には必要に応じて配合される添加剤や有機溶媒の混合順序やその方法は特に限定されない。
成形体中の熱分解性樹脂粒子を熱分解して消失せしめる操作は、焼結のための焼成の過程において行ってもよい。しかし、焼結を行う前に、熱分解性樹脂粒子の熱分解温度より50~300℃高い温度で焼成して熱分解性樹脂粒子を熱分解して消失せしめることが好ましい。熱分解時における雰囲気は、熱分解性樹脂粒子が分解可能な雰囲気が特に制限無く実施される。一般には、分解によって生成したカーボンを効果的に除去するため、酸素の存在下、通常は、空気中で実施することが好ましい。
前記操作により、熱分解性樹脂粒子が除去されて形成された、多孔質体の骨格を有する成形体は、次いで、1100~1700℃、好ましくは1100~1550℃、特に好ましくは、1400~1530℃で加熱して焼結せしめることにより、目的とする多孔質焼結体が形成される。当該焼成温度を採用することにより、得られる多孔質焼結体における変形や割れの発生を減少することができる。焼結時の雰囲気は、不活性雰囲気下、例えば、窒素ガス等の雰囲気下で行うことが好ましい。焼結時間は、1時間以上、好ましくは、2時間以上行う。余り長時間行うと、表面に形成された孔が小さくなったり潰れたりする虞があるため、30時間以下とすることが好ましい。
次いで、熱分解性樹脂粒子の分解温度以上の温度で加熱することにより熱分解性樹脂粒子が分解除去され、上記熱分解性樹脂粒子に由来する多孔質体の骨格からなる層が形成される。更に、前出の焼結温度で焼成して、基板上に多孔質焼結体層が形成される。
前記溶媒の乾燥による除去と上記熱分解性樹脂粒子の除去、更に、焼結は、同一の装置内で、雰囲気ガスや温度を変えて連続的に行ってもよいし、別々の装置において逐次行ってもよい。
前記本発明のシリコン融液接触部材の多孔質焼結体層の表面において、シリコン原料を融解した融液を冷却して結晶化を行って結晶シリコンを製造する。
シリコン融液としては、別途融解した融液をシリコンの融点温度以上の温度に保持した多孔質焼結体層の表面に載置してもよいし、多孔質焼結体層の表面に所定量の固体状シリコンを載置した後、高周波コイルや抵抗加熱式ヒーター等の加熱手段で、シリコンの融点1414℃以上の温度、好ましくは1420~1480℃に保持して融解してもよい。上記した融解工程並びに融解後の冷却結晶化工程や、アニール処理工程などの後工程は、いずれにおいても、水分及び酸素が可及的に低減された不活性ガス雰囲気、例えば、高純度アルゴンガス雰囲気等で行うことが必要である。
固体状シリコンとしては、特に限定されず結晶成長法或いは落下法などの既存の製造方法で得られたシリコンの粉末、塊状物、破砕物などが使用できる。その結晶性も問わない。本発明によって大量電池用結晶シリコンを製造するためには、固体状シリコンの純度は、99.9999%以上あればよい。
以下、球状の結晶シリコンと板状の結晶シリコンとに分けて、各々の製造方法を詳述する。
また、多孔質焼結体層上へのシリコンの供給は、前記固体状での供給に限らず、別途融解したシリコン融液を多孔質焼結体層、好ましくは、シリコンの融点以上に加熱された多孔質焼結体層の表面に滴下することにより行うことも可能である。
球状化後は、前述の方法によって、冷却結晶化、アニール処理、並びに冷却を行って球状の結晶シリコンを得る。図2および図3に、その製造過程を模式的に示す。この方法によって得られた球状のシリコンは、金属光沢が顕著な結晶シリコンである。また、その結晶形態は、双晶になっていることが多い。
上記球状シリコンは、炭素や酸素原子の残存濃度、更には窒素や鉄原子の残存濃度が低く、このままの状態で太陽電池用結晶シリコンとして利用できる。球状の結晶の大きさは、固体状シリコンの使用量や融液同士の間隔などを制御することにより任意にコントロールでき、通常1~5mmの粒径の球状の結晶シリコンを得ることができる。
〔シリコン融液接触部材の製造〕
粒径0.1~5μmの窒化ケイ素粉末を30質量%、粒径1.8~2μmの非晶質二酸化ケイ素粉末を20質量%、平均粒子径5μmの熱分解性樹脂粒子(積水化成品工業株式会社製 テクポリマー「SSX-105」;架橋ポリメタクリル酸メチル)を50質量%となるように評量し、アルミナ乳鉢で10分間混合した。混合した粉末を8kNでプレス成形し、直径20mm、厚さ10mmの円板状成形体とした。この成形体をマッフル炉(電気炉)を用いて大気中において500で3時間、1100℃で6時間加熱し、有機化合物球状粒子を蒸発除去し、シリコン融液接触部材を得た(表1 試料番号10)。
図4に、得られたシリコン融液接触部材の多孔質焼結体層表面の走査電子顕微鏡写真(SEM)を示す。倍率は1000倍であり、写真上に10μmの長さを示す線分が表示されている。作製された部材は、その表面に、60%の孔占有面積割合で、平均円相当直径5μmの大きさの孔が分散して存在していることが確認された。この空孔の存在が、シリコン融液に対する撥液性を向上させ、シリコン融液接触部材に対するシリコン融液の染み込みを大幅に減少させているものと考えられる。
作製したシリコン融液接触部材上にシリコンウェハ10mgを乗せ、管状電気炉を用いてシリコンウェハの融解を行った。雰囲気には高純度アルゴンガス(G2)を用い、純化装置によって水分・酸素の除去を行った。シリコンウェハの融解は1480℃で6分間保時することで行い、冷却速度は150℃/時間とした。シリコンは直径約2mmの球状に固化した。シリコン融液と部材との接触角は約160度であった。固化した結晶シリコンと部材との剥離は非常に容易であった。部材表面へのシリコンの染み込みは見られなかった。シリコン表面の不純物は少なく、金属光沢を帯びていた。
図6に、板状結晶シリコンを製造した場合の、得られた板状結晶シリコンと用いたシリコン融液接触部材の状態を示した。シリコン融液接触部材の表面にはシリコンの染み込みがほとんど認められない。本発明のシリコン融液接触部材は、部材へのシリコンの染み込みが僅かに生じたとしても、紙ヤスリで部材の表面をこするとシリコンがすぐにとれる程度であり、染み込んでいる深さもごく小さいものと考えられる。したがって、何度も繰り返して使用することができる。
製造条件を変えることにより、15mm角で、厚み250~800μmの間で制御した各種板状結晶シリコンを得ることができた。
〔シリコン融液接触部材の製造〕
熱分解性樹脂粒子を加えること無く、粒径0.1~5μmの窒化ケイ素粉末を60質量%、粒径1.8~2μmの非晶質二酸化ケイ素粉末を40質量%となるように評量し、アルミナ乳鉢で10分間混合した。混合した粉末を8kNでプレス成形し、直径20mm、厚さ10mmの円板状成形体とした。この成形体をマッフル炉を用いて大気中において500℃で3時間、1100℃で6時間加熱し、焼結体部材を得た(表1 試料番号2)。図5に、得られた焼結体部材の表面の走査電子顕微鏡写真(SEM)を示す。部材表面には、凹凸が見られるが、空孔の存在は認められない。
作製した焼結体部材を用いて、実施例1と同様にして球状の結晶シリコンを製造した。結晶シリコンは直径約2mmの球状に固化した。シリコン融液と部材との接触角は約160度であった。固化したシリコンと部材との剥離性は良いが、実施例1に比べると劣っていた。部材表面へのシリコンの染み込みが見られた。シリコン表面のほぼ全体が不純物によって覆われており、金属光沢がほとんど見られなかった。得られた球状結晶シリコンの実体顕微鏡写真を図8に示す。
図7に、板状結晶シリコンを製造した場合の、得られた板状結晶シリコンと用いた部材の状態を示した。この部材を用いても板状結晶シリコンは作製できるが、部材表面へのシリコンの染み込みが激しい。この結果から、本発明のシリコン融液接触部材はシリコンの染み込み防止に確かな効果があることが分かる。染み込んだ部材の破断面を観察した結果、シリコン融液が部材表面から少なくとも170μmの深さまで浸透していることが分かった。さらに、染み込んだシリコン融液が部材の窒化ケイ素および二酸化ケイ素成分と反応していることも観察された。このため、染み込んだシリコンを部材から除去することは極めて困難であり、再利用することができなかった。
熱分解性樹脂粒子を配合せずに、表1の試料番号1、3に示す原料配合にした以外は、比較例1と同様にして焼結体部材を製造した。
得られた各焼結体部材を用いて、同様に球状の結晶シリコンを製造した。その結果を、併せて表1に示す。
〔シリコン融液接触部材の製造〕
熱分解性樹脂粒子の混合割合を実施例1よりも少なくした。即ち、粒径0.1~5μmの窒化ケイ素粉末を42質量%、粒径1.8~2μmの非晶質二酸化ケイ素粉末を28質量%、平均粒子径5ミクロンの熱分解性樹脂粒子を30質量%を用いた以外は、実施例1と同様にして、シリコン融液接触部材を製造した(表1 試料番号5)。作製された部材は、その表面に、30%の孔占有面積割合で、平均円相当直径5μmの大きさの孔が分散して存在していることが確認された。
〔球状の結晶シリコンの製造〕
作製したシリコン融液接触部材を用いて、実施例1と同様にして、球状結晶シリコンを製造した。結晶シリコンは直径約2mmの球状に固化した。シリコン融液と部材との接触角は約160度であった。固化した結晶シリコンの部材からの剥離は非常に容易であり、部材表面へのシリコンの染み込みは少ししか見られなかった。結晶シリコン表面の不純物はやや多く、金属光沢が少なかった。この実施例2と実施例1との比較から、配合する熱分解性樹脂粒子の量は50質量%の方が望ましいことが分かった。
〔シリコン融液接触部材の製造〕
焼結助剤として酸化マグネシウム(MgO)を添加した例であり、粒径0.1~5μmの窒化ケイ素粉末を30質量%、粒径1.8~2μmの非晶質二酸化ケイ素粉末を20質量%、粒径5ミクロンの有機化合物球状粒子を50質量%となるように評量し、ここに全体の3質量%分の酸化マグネシウムを加えアルミナ乳鉢で10分間混合した。混合した粉末を8kNでプレス成形し、直径20mm、厚さ10mmの円板状成形体とした。この成形体をマッフル炉を用いて大気中において500℃で3時間、1100℃で6時間加熱して熱分解性樹脂粒子を蒸発除去した後、高純度アルゴン(G2)雰囲気下において1400℃で6時間焼成し、シリコン融液接触部材を得た(表1 試料番号12)。作製された部材は、その表面に、50%の孔占有面積割合で、平均円相当直径4μmの大きさの孔が分散して存在していることが確認された。
焼結助剤を配合することにより、シリコン融液接触部材の強度が向上した。また、1400℃以上での本焼成を行うことにより、結晶シリコン製造時に、結晶シリコンに混入する不純物量を減少させることができ、結晶シリコン表面のシリコン本来の金属光沢がはっきりと表れた。
作製したシリコン融液接触部材を用いて、実施例1と同様にして球状の結晶シリコンを製造した。結晶シリコンは直径約2mmの球状に固化した。シリコン融液と部材との接触角は約140度であり、焼結助剤を添加しない場合に比べてやや撥液性の低下が認められた。固化したシリコンの部材からの剥離は容易であり、部材表面へのシリコンの染み込みは少ししか見られなかった。シリコン表面の不純物は少なく、金属光沢を帯びていた。
表1の試料番号4,6,7,8,9,11,13,14,15に示す原料配合にした以外は、実施例1と同様にしてシリコン融液接触部材を製造した。作製された部材は、その表面に、表2に示す孔占有面積割合、平均円相当直径の大きさの孔が分散して存在していることが確認された。得られた各シリコン融液接触部材を用いて、同様に球状の結晶シリコンを製造した。その結果を、併せて表1に示す。
図9は試料番号7の、図10は試料番号8の、図11は試料番号9のシリコン融液接触部材を用いて製造した球状の結晶シリコンの実体顕微鏡写真である。熱分解性樹脂粒子を用いて作製した本発明のシリコン融液接触部材を使用した場合は、結晶シリコン表面の不純物が少なく金属光沢がはっきりと認められる。さらに、焼成温度を高くしたシリコン融液接触部材(試料番号9)の方が、金属光沢は顕著で不純物量がより減少していることが分かる。
試料番号8,9の部材を用いて球状の結晶シリコンを製造した場合、シリコンの部材表面への染み込みは認められたものの、試料番号1,2,3に比べて、小さいものであった。
〔基板を使用したシリコン融液接触部材の製造〕
平均粒径0.5μmの窒化ケイ素粉末(宇部興産社製)70質量%、及び平均粒径1.9μmの非晶質二酸化ケイ素粉末30質量%よりなる焼結性粉末100容量部に対して、平均粒子径5μmの真球状の熱分解性樹脂粒子(積水化成品工業株式会社製 テクポリマー「SSX-105」;架橋ポリメタクリル酸メチル)を100容量部、更に、焼結性粉末100質量部に対して、エチレングリコールグリコール600質量部および分散剤としてDisperbyk-164(BYK社製)0.05質量部を加えて混合攪拌した。攪拌時に随時分散液の粘度を測定し、粘度が最小になった時点での分散液を焼結体用分散液として、以下のスピンコートに使用した。
窒化アルミニウム基板(42×42mm、厚み2mm)を、スピンコート装置(トキワ真空資材社製「リンサードライヤー SPDY-1」)の保持台に載せて基板表面に上記分散液をスピンコートした。この分散液がスピンコートされた窒化アルミニウム基板を、マッフル炉(電気炉)を用いて大気中において500℃で3時間、更に、窒素雰囲気下、1100℃で6時間加熱して、本発明のシリコン融液接触部材を得た。
図15に、シリコン融液接触部材の断面のSEM写真を示す。図15より明らかなように、焼結体層の厚みは約30μmであり、空孔は互いに連結して連通孔を形成し、該連通孔が焼結体層の表面から基板表面にまで達していることが分かる。
多孔質焼結体層の表面を、CCD顕微鏡装置を使用して解析した深度合成結果を図16に示す。図16に見られるように、窒化アルミニウム基板上に多孔質焼結体層が形成され、該焼結体層の表面の厚み変動は最大5μmであった。
得られたシリコン接触部材の多孔質焼結体層の表面におけるシリコン融液の接触角を測定したところ、155度であった。
水平に保持したシリコン融液接触部材の多孔質焼結体層上に、間隔を約2cm開けて、四箇所に、一箇所当たりシリコン片10mgを載せた。管状電気炉を用いてシリコン片の融解を行った。雰囲気は、予め純化装置によって水分・酸素の除去を行った高純度アルゴンガス(G2)雰囲気として。シリコン片の融解は1480℃で6分間保時して行い、冷却速度は150/時間とした。シリコンは直径約2mmの球状に結晶固化した。図17に、得られた球状の結晶シリコンの写真を示す。
得られた球状の結晶シリコンは、金属光沢を帯びており、二次イオン質量分析装置(SIMS)を用いた分析により、炭素、酸素、窒素、および鉄元素の不純物の含有量が極めて低いものであった。
二枚のシリコン融液接触部材(42mm×42mm)の多孔質焼結体層間に、シリコン片3gを挟み、実施例1と同様に、融解、冷却操作を行い板状の結晶シリコンを得た。
得られた結晶シリコンは、30mm×44mmの大きさで、厚みは0.908~1.012mmのほぼ均一な板状の結晶シリコンであり、結晶性は多結晶であった。図18に、得られた板状の結晶シリコンの写真を示す。
上記製造に使用したシリコン融液接触部材を二回、三回と再使用して板状の結晶シリコンを製造したところ、何れも、同じ形状の板状の結晶シリコンが得られ、該部材はシリコン融液に対する撥液性に優れ、且つ、持続性があることが示された。
〔基板を使用したシリコン融液接触部材の製造〕
窒化アルミニウム基板に代えて、アルミナ基板(40mm×40mm)を使用した以外は実施例5と同様にして、シリコン融液接触部材を作製した。
図19に得られたシリコン融液接触部材の多孔質焼結体層の表面のSEM写真を、図20にその断面SEM写真を、図21に深度合成結果を示す。多孔質焼結体層の表面には、平均孔径5μm程度の円形状の孔が均質に形成され、各孔は連結して深さ方向に連通孔となって基板表面まで達していた。多孔質焼結体層の孔占有面積割合は60%であった。厚み変動は最大6.7μmであり、平滑な焼結体層が形成されていた。得られたシリコン融液接触部材の多孔質焼結体層の表面におけるシリコン融液の接触角を測定したところ、150度であった。
水平に保持した上記シリコン融液接触部材を用いて、実施例5と同様にして球状の結晶シリコンを製造した。
孔質焼結体層上に、間隔を約2cm開けて、9箇所に、一箇所当たりシリコン片10mgを載せ、製造温度条件を、加熱速度を200℃/h、1480℃で6分保持して溶融、その後150℃/hで冷却結晶化した以外は、実施例5と同様に行った。
得られた球状の結晶シリコンの写真を図22に示す。約2mmの球状の結晶であり、金属光沢の高い結晶シリコンであることが確認された。
〔基板を使用したシリコン融液接触部材の製造〕
焼結体用分散液をスピンコートするセラミック基板として、以下の方法により表面に窒化ケイ素と二酸化ケイ素からなる層を形成せしめた窒化アルミニウム焼結体基板を使用した。これ以外は、実施例5と同様に処理して、シリコン融液接触部材を作製した。
窒化ケイ素の焼結体層表面は、平均粒径0.5μmの窒化ケイ素粉末(宇部興産社製)270質量部、非晶質二酸化ケイ素粉末(添川理科学社製)30質量部、およびエチレングリコールグリコール700質量部を混合攪拌して調製した分散液を、窒化アルミニウム基板上にスピンコートしたのち焼成して形成した。その後は、実施例5と同様に行った。
図23に、シリコン融液接触部材の断面のSEM写真を示す。得られた部材は、窒化アルミニウム焼結体基板上に厚み15μmの窒化ケイ素と二酸化ケイ素からなる層、更にその上に15μmの多孔質焼結体層が積層した構造のシリコン融液接触部材であった。
多孔質焼結体層の表面には、平均孔径6μm程度の円形状の孔が均質に形成され、各孔は連結して深さ方向に連通孔となって基板表面まで達していた。多孔質焼結体層の孔占有面積割合は60%であり、厚み変動は最大5μmであり、平滑な焼結体層が形成されていた。得られたシリコン接触融液部材の多孔質焼結体層の表面におけるシリコン融液の接触角を測定したところ、150度であった。
上記シリコン融液接触部材は、繰り返し使用において、多孔質焼結体層の剥離が極めて少なく、高い耐久性を示した。
実施例1において、使用する熱分解性樹脂粒子(積水化成品工業株式会社製 テクポリマー;架橋ポリメタクリル酸メチル)の平均粒子径、並びに焼結性粉末を構成する窒化ケイ素と二酸化ケイ素の割合を、表3に示すように変更した以外は、同様にして、シリコン融液接触部材を製造した。
得られた各シリコン融液接触部材を用いて、同様に球状の結晶シリコンを製造した。その結果を、併せて表3に示す。各部材において、シリコン融液との接触角は実施例1とほぼ同様な値を示した。得られたシリコン融液接触部材の多孔質焼結体層における孔は、ほぼ円形であり、その孔占有面積割合、平均円相当直径は、表4に示す通りであった。
実施例5において、使用する熱分解性樹脂粒子の平均粒子径を、表5に示すように変えた以外は、同様にして、窒化アルミニウム基板を支持体とするシリコン融液接触部材を製造した。
得られたシリコン融液接触部材の多孔質焼結体層における孔は、ほぼ円形であり、その平均円相当直径、孔占有面積割合、多孔質焼結体層の厚みは、表5に示す通りであった。また、得られたシリコン接触融液部材の多孔質焼結体層の表面におけるシリコン融液の接触角を測定し、併せて表5に示した。
上記シリコン融液接触部材は、繰り返し使用において、多孔質焼結体層の剥離が極めて少なく、高い耐久性を示した。
2 セラミック基板
3 多孔質焼結体層
4 固体状シリコン片
5 重り
6 シリコン融液
7 球状の結晶シリコン
8 板状の結晶シリコン
Claims (14)
- 熱分解性樹脂粒子からなる平均粒子径1~25μmの有機粒子と、窒化ケイ素を主成分とする焼結性粉末とを含む混合物を成形して成形体とし、該成形体を前記有機粒子が消失するまで焼成し、更に、前記焼結性粉末を焼結して得られる焼結体よりなり、前記有機粒子の形状に由来する孔が形成された多孔質焼結体層が表面に存在することを特徴とするシリコン融液接触部材。
- 前記多孔質焼結体層が、基体上に形成されていることを特徴とする請求項1に記載のシリコン融液接触部材。
- 前記基体は、多孔質焼結体層が形成されるその表面が窒化ケイ素により構成されていることを特徴とする請求項1または2に記載のシリコン融液接触部材。
- 前記多孔質焼結体層の厚みが、5~500μmであることを特徴とする請求項2または3に記載のシリコン融液接触部材。
- 前記多孔質焼結体層は、その表面に、30~80%の孔占有面積割合で、平均円相当直径1~25μmの大きさの孔が分散して存在することを特徴とする請求項1~4の何れか一項に記載のシリコン融液接触部材。
- 前記多孔質焼結体層が、二酸化ケイ素を2質量%以上、50質量%未満の割合で含有していることを特徴とする請求項1~5の何れか一項に記載のシリコン融液接触部材。
- 前記多孔質焼結体層の表面に存在する孔の平均深さが、5μm以上であることを特徴とする請求項1~6の何れか一項に記載のシリコン融液接触部材。
- 請求項1~7の何れか一項に記載のシリコン融液接触部材の多孔質焼結体層の表面においてシリコン融液を冷却し、結晶化を行うことを特徴とする結晶シリコンの製造方法。
- 前記シリコン融液が、固体状シリコンを多孔質焼結体層上にて溶融して得られたものであることを特徴とする請求項8に記載の結晶シリコンの製造方法。
- 前記結晶シリコンが、球状の結晶シリコンであることを特徴とする請求項8または9に記載の結晶シリコンの製造方法。
- 前記結晶シリコンが板状の結晶シリコンであって、二枚のシリコン融液接触部材を用い、各部材の多孔質焼結体層を内側にしてシリコン融液を挟んだ状態で、該シリコン融液を冷却して、結晶化を行うことを特徴とする請求項8に記載の結晶シリコンの製造方法。
- 基体上に、窒化ケイ素粉末を主成分とする焼結性粉末、及び該焼結性粉末100容量部に対して平均粒子径1~25μmの熱分解性樹脂粒子40~400容量部を有機溶媒中に含有させた焼結体用分散液を塗布した後、該有機溶媒を乾燥により除去し、次いで、上記熱分解性樹脂粒子を熱分解せしめて除去し、更に、前記焼結性粉末を1100~1700℃の温度で焼結せしめて多孔質焼結体層を形成することを特徴とするシリコン融液接触部材の製造方法。
- 前記基体が、多孔質焼結体層が形成されるその表面が窒化ケイ素により構成されていることを特徴とする請求項12に記載のシリコン融液接触部材の製造方法。
- 窒化ケイ素粉末を主成分とする焼結性粉末が、二酸化ケイ素を2質量%以上、50質量%未満の割合で含有していることを特徴とする請求項12または13に記載のシリコン融液接触部材の製造方法。
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EP12739533.3A EP2669411B1 (en) | 2011-01-26 | 2012-01-26 | Silicon melt contacting member and process for production thereof, and process for production of crystalline silicon |
JP2012554839A JP5875529B2 (ja) | 2011-01-26 | 2012-01-26 | シリコン融液接触部材、その製法、および結晶シリコンの製造方法 |
ES12739533.3T ES2600652T3 (es) | 2011-01-26 | 2012-01-26 | Elemento de contacto de silicio fundido y proceso para producir el mismo, y proceso para producir silicio cristalino |
US13/997,498 US20130298822A1 (en) | 2011-01-26 | 2012-01-26 | Silicon melt contact member, process for production thereof, and process for production of crystalline silicon |
KR1020137007465A KR20140004067A (ko) | 2011-01-26 | 2012-01-26 | 실리콘 융액 접촉 부재, 그의 제조 방법 및 결정 실리콘의 제조 방법 |
CA2825772A CA2825772A1 (en) | 2011-01-26 | 2012-01-26 | Silicon melt contact member, process for production thereof, and process for production of crystalline silicon |
CN201280003251.4A CN103154332B (zh) | 2011-01-26 | 2012-01-26 | 硅熔体接触构件及其制法、以及晶体硅的制造方法 |
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JP2018098272A (ja) * | 2016-12-08 | 2018-06-21 | 住友ベークライト株式会社 | ペースト状接着剤組成物および電子装置 |
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EP2669411A1 (en) | 2013-12-04 |
CA2825772A1 (en) | 2012-08-02 |
CN103154332A (zh) | 2013-06-12 |
JP5875529B2 (ja) | 2016-03-02 |
KR20140004067A (ko) | 2014-01-10 |
EP2669411B1 (en) | 2016-10-12 |
US20130298822A1 (en) | 2013-11-14 |
TW201235390A (en) | 2012-09-01 |
TWI554561B (zh) | 2016-10-21 |
JPWO2012102343A1 (ja) | 2014-06-30 |
ES2600652T3 (es) | 2017-02-10 |
CN103154332B (zh) | 2016-04-13 |
EP2669411A4 (en) | 2014-10-01 |
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