WO2013145558A1 - 多結晶シリコンおよびその鋳造方法 - Google Patents
多結晶シリコンおよびその鋳造方法 Download PDFInfo
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- WO2013145558A1 WO2013145558A1 PCT/JP2013/001261 JP2013001261W WO2013145558A1 WO 2013145558 A1 WO2013145558 A1 WO 2013145558A1 JP 2013001261 W JP2013001261 W JP 2013001261W WO 2013145558 A1 WO2013145558 A1 WO 2013145558A1
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- atoms
- concentration
- polycrystalline silicon
- silicon
- carbon
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 43
- 238000005266 casting Methods 0.000 title claims abstract description 40
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 131
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 85
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 77
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 61
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 61
- 239000001301 oxygen Substances 0.000 claims abstract description 61
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 61
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 51
- 239000010703 silicon Substances 0.000 claims abstract description 51
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 50
- 238000001816 cooling Methods 0.000 claims abstract description 30
- 239000002994 raw material Substances 0.000 claims abstract description 27
- 230000006698 induction Effects 0.000 claims abstract description 16
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 10
- 238000010438 heat treatment Methods 0.000 claims abstract description 6
- 230000005674 electromagnetic induction Effects 0.000 claims abstract description 5
- 239000007789 gas Substances 0.000 claims description 39
- 239000000463 material Substances 0.000 claims description 29
- 239000011261 inert gas Substances 0.000 claims description 28
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 19
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 19
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 18
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 17
- 229910001882 dioxygen Inorganic materials 0.000 claims description 17
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 9
- 239000001569 carbon dioxide Substances 0.000 claims description 9
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 9
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 9
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 9
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 229910021419 crystalline silicon Inorganic materials 0.000 claims 2
- 239000000155 melt Substances 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 37
- 238000002844 melting Methods 0.000 abstract description 7
- 230000008018 melting Effects 0.000 abstract description 7
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 abstract description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 18
- 239000013078 crystal Substances 0.000 description 12
- 235000012431 wafers Nutrition 0.000 description 12
- 239000011230 binding agent Substances 0.000 description 11
- 229910052786 argon Inorganic materials 0.000 description 9
- 239000002244 precipitate Substances 0.000 description 7
- 230000008569 process Effects 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 238000002791 soaking Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000009749 continuous casting Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000002019 doping agent Substances 0.000 description 3
- 230000002708 enhancing effect Effects 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000006082 mold release agent Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000006213 oxygenation reaction Methods 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000001004 secondary ion mass spectrometry Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 150000003376 silicon Chemical class 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002463 transducing effect Effects 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Images
Classifications
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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
- C30B28/00—Production of homogeneous polycrystalline material with defined structure
- C30B28/04—Production of homogeneous polycrystalline material with defined structure from liquids
- C30B28/10—Production of homogeneous polycrystalline material with defined structure from liquids by pulling from a melt
-
- 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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/001—Continuous growth
-
- 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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/04—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt
- C30B11/06—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt at least one but not all components of the crystal composition being added
- C30B11/065—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt at least one but not all components of the crystal composition being added before crystallising, e.g. synthesis
-
- 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
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
-
- 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
- C30B30/00—Production of single crystals or homogeneous polycrystalline material with defined structure characterised by the action of electric or magnetic fields, wave energy or other specific physical conditions
- C30B30/04—Production of single crystals or homogeneous polycrystalline material with defined structure characterised by the action of electric or magnetic fields, wave energy or other specific physical conditions using magnetic fields
-
- 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
- H01L31/18—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 System
- H01L31/182—Special manufacturing methods for polycrystalline Si, e.g. Si ribbon, poly Si ingots, thin films of polycrystalline Si
-
- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/546—Polycrystalline silicon PV cells
-
- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/547—Monocrystalline silicon PV cells
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to polycrystalline silicon and a method of casting the same, and more particularly to polycrystalline silicon and a method of casting the same suitable for enhancing the conversion efficiency of a solar cell.
- silicon crystals are mainly used as substrates for solar cells. There are single crystals and poly crystals in this silicon crystal, and a solar cell using a single crystal silicon as a substrate converts incident light energy into electrical energy as compared to a solar cell using polycrystalline silicon as a substrate Conversion efficiency is high.
- single crystal silicon is manufactured, for example, by the Czochralski method as a dislocation-free high quality crystal, but manufacturing of single crystal silicon by this Czochralski method is expensive in production cost and a substrate for solar cells It is not practical to use as Therefore, it is common to manufacture a solar cell using polycrystalline silicon that can be cast from inexpensive materials.
- the electromagnetic casting method is a method of heating and melting the silicon raw material in the crucible by high frequency induction, floating the molten silicon by the action of strong electromagnetic force, and continuously growing the ingot. At that time, high-quality ingots can be cast since molten silicon does not need to be in contact with the crucible.
- the polycrystalline silicon wafer obtained from the polycrystalline silicon ingot thus cast has high uniformity of quality in the casting direction, and produces a solar cell having stable characteristics with small variation in conversion efficiency. It has the feature of being able to
- an object of the present invention is to provide polycrystalline silicon and a casting method thereof that are suitable for enhancing the conversion efficiency of a solar cell.
- the inventors diligently studied ways to solve the above problems. As described above, the inventors actually cast polycrystalline silicon with an extremely low carbon concentration and manufactured a solar cell to measure the conversion efficiency.
- the conversion efficiency of the solar cell was investigated by casting polycrystalline silicon having a carbon concentration. As a result, conversion efficiency is adjusted by adding an appropriate amount of carbon and adjusting to a predetermined concentration range while controlling the concentration of oxygen and nitrogen in polycrystalline silicon to an appropriate range rather than excessively reducing the carbon concentration. In the present invention, the present invention has been accomplished.
- the gist configuration of the present invention is as follows.
- Carbon concentration is 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less
- oxygen concentration is 0.3 ⁇ 10 17 atoms / cm 3 or more 5.0 ⁇ 10 17 atoms / cm 3 or less
- the polycrystalline silicon wafer nitrogen concentration is 8.0 ⁇ 10 13 atoms / cm 3 or more 1.0 ⁇ 10 18 atoms / cm 3 or less.
- the adjustment of the carbon concentration is performed by adjusting the partial pressure of the carbon monoxide gas to the inert gas and supplying the carbon monoxide gas into the chamber.
- Method of casting polycrystalline silicon is performed by adjusting the partial pressure of the carbon monoxide gas to the inert gas and supplying the carbon monoxide gas into the chamber.
- the adjustment of the oxygen concentration is performed by adjusting the partial pressure of the oxygen gas to the inert gas and supplying the oxygen gas into the chamber.
- the carbon concentration and the oxygen concentration are adjusted by supplying carbon dioxide gas into the chamber by adjusting the partial pressure of the carbon dioxide gas to the inert gas.
- carbon dioxide gas Of polycrystalline silicon casting method.
- the adjustment of the nitrogen concentration is performed by adjusting the application area of the silicon nitride in the release agent containing nitrogen to the upper surface of the support. Method for casting polycrystalline silicon according to the description.
- the nitrogen concentration is adjusted by adjusting a partial pressure of the nitrogen gas to the inert gas and supplying the nitrogen gas into the chamber.
- the present invention by adjusting the concentrations of carbon, oxygen and nitrogen in a predetermined concentration range, it is possible to improve crystallinity and cast polycrystalline silicon suitable for enhancing the conversion efficiency of a solar cell. be able to.
- the polycrystalline silicon of the present invention has a carbon concentration of 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less and an oxygen concentration of 0.3 ⁇ 10 17 atoms / cm 3 or more. It is important to adjust the concentration to 0 ⁇ 10 17 atoms / cm 3 or less and the nitrogen concentration to 8.0 ⁇ 10 13 atoms / cm 3 or more and 1.0 ⁇ 10 18 atoms / cm 3 or less.
- the carbon concentration of polycrystalline silicon is set to 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less.
- the reason why the concentration is 4.0 ⁇ 10 17 atoms / cm 3 or more is that if the concentration is less than 4.0 ⁇ 10 17 atoms / cm 3 , the carbon concentration is too low to suppress the propagation of dislocations, and the crystallinity It is because it does not improve.
- the reason for setting it as 6.0 * 10 ⁇ 17 > atoms / cm ⁇ 3 > or less is the addition of carbon exceeding 6.0 * 10 ⁇ 17 > atoms / cm ⁇ 3 > and the foreign substance consisting of SiC precipitates in the polycrystalline silicon ingot and the crystal This is because defects increase and conversion efficiency decreases.
- the oxygen concentration is 0.3 ⁇ 10 17 atoms / cm 3 or more and 5.0 ⁇ 10 17 atoms / cm 3 or less.
- the reason why the concentration is 0.3 ⁇ 10 17 atoms / cm 3 or more is that oxygen precipitation does not occur at a concentration of less than 0.3 ⁇ 10 17 atoms / cm 3 .
- the reason for setting the concentration to 5.0 ⁇ 10 17 atoms / cm 3 or less is that when it exceeds 5.0 ⁇ 10 17 atoms / cm 3 , a complex of oxygen and boron is formed to lower the conversion efficiency. It is.
- the nitrogen concentration of polycrystalline silicon is set to 8.0 ⁇ 10 13 atoms / cm 3 or more and 1.0 ⁇ 10 18 atoms / cm 3 or less.
- the reason for setting it to 8.0 ⁇ 10 13 atoms / cm 3 or more is that if it is less than 8.0 ⁇ 10 13 atoms / cm 3 , the nitrogen concentration is too low to suppress the propagation of dislocations, and the crystallinity It is because it does not improve.
- the reason for setting it as 1.0 ⁇ 10 18 atoms / cm 3 or less is that when it exceeds 1.0 ⁇ 10 18 atoms / cm 3 , foreign matter of silicon nitride (Si 3 N 4 ) precipitates and conversion efficiency decreases. It is for.
- FIG. 1 is a schematic view of an example of a continuous casting apparatus used for the polycrystalline silicon casting method of the present invention.
- the continuous casting apparatus 100 includes a chamber 1 which is a dual structure water-cooled vessel that isolates the inside from the outside air and maintains an inert gas atmosphere suitable for casting.
- a bottomless cooling crucible 7 At the center of the chamber 1, a bottomless cooling crucible 7, an induction coil 8, an afterheater 9, and a heat equalizing cylinder 10 are disposed.
- the bottomless cooling crucible 7 is made of a metal material such as copper which not only functions as a melting vessel for melting the charged silicon raw material 12 but also functions as a mold and is excellent in thermal conductivity and electrical conductivity. It is suspended in the chamber 1 by a rectangular cylinder.
- the bottomless cooling crucible 7 is divided into a plurality of strip-shaped pieces in the circumferential direction leaving an upper portion, and is configured to be forcibly cooled by cooling water flowing inside.
- the induction coil 8 is provided concentrically with the bottomless cooling crucible 7 so as to surround the bottomless cooling crucible 7 and is connected to a power supply (not shown).
- a plurality of after-heaters 9 are installed below the bottomless cooling crucible 7 concentrically with the crucible 7 and are configured of a heater (not shown) and a heat insulating material (not shown).
- the after heater 9 heats the ingot 3 drawn down from the bottomless cooling crucible 7 to give a predetermined temperature gradient in the direction of the draw axis of the ingot 3 to prevent the formation of crystal defects in the ingot 3.
- the heat equalizing cylinder 10 holds the ingot 3 at a predetermined temperature for a predetermined time to equalize heat in order to prevent residual stress from being generated by cooling and generation of a crack in the ingot 3.
- a raw material introduction pipe 11 is attached to the upper wall in the chamber 1, and granular or massive silicon raw material 12 is cooled from the raw material supply pipe (not shown) through the raw material supply pipe 11 through the raw material supply pipe 11 via the shutter 2. It is inserted into the crucible 7.
- a plasma torch 14 for melting the silicon source 12 is provided so as to be movable up and down.
- One pole of a plasma power supply (not shown) is connected to the plasma torch 14, and the other pole is connected to the ingot 3 side.
- the plasma torch 14 is lowered and inserted into the bottomless cooling crucible 7.
- a gas inlet 5 for introducing an inert gas, carbon monoxide gas for adjusting oxygen and carbon concentration in the ingot 3, oxygen gas and carbon dioxide gas is provided in the chamber 1.
- the gas introduced into the chamber 1 passes through the reflux piping 17 and circulates in the furnace.
- the gas introduced into the chamber 1 is exhausted from an exhaust port 6 provided below the side wall of the chamber 1.
- an outlet 4 is provided on the bottom wall of the chamber 1, and the ingot 3 placed on the support 16 which has been subjected to the soaking process by the heat equalizing cylinder 10 is configured to be extracted from the outlet 4. It is done.
- a release material is applied to the upper surface of the support 16 (that is, the surface in contact with the ingot 3) in order to prevent fusion of the ingot 3 to the support 16.
- this mold release material there is used a slurry obtained by mixing powder for mold release material such as silicon nitride, silicon carbide, silicon oxide or the like in a solution composed of a binder and a solvent.
- a binder removal process is performed to remove the solvent and the binder, whereby a release material layer is formed on the upper surface of the support 16.
- the binder removal process is a process of removing the binder and the solvent in the mold release material by heat-treating the support table 16 in the atmosphere, for example, at a temperature of 120 ° C. for 1 hour.
- the release material is used not only to prevent the fusion between the ingot 3 and the support 16 mounted on the support shaft 15 as described above, but also to control the nitrogen concentration in the ingot 3.
- a release agent containing nitrogen is used.
- the mold release material layer obtained from this mold release material contacts the molten silicon 13 at the early stage of casting. Therefore, when the mold release agent layer contains nitrogen, nitrogen dissolves into the molten silicon 13 and the ingot 3 It can be added to (ie polycrystalline silicon).
- silicon nitride can be used as the powder for a release agent containing nitrogen.
- polyvinyl alcohol (PVA), an ethyl silicate, etc. can be used as a binder, A pure water and alcohol can be used as a solvent.
- ethyl silicate is used as a binder, hydrochloric acid can be used as an additive in order to accelerate hydrolysis.
- Control of the nitrogen concentration in the ingot 3 can be performed by adjusting the application area of the mold release material.
- 100 g of silicon nitride powder, 100 ml of ethyl silicate as a binder, 400 ml of pure water as a solvent, and 0.5 ml of hydrochloric acid as an additive are mixed to form a slurry, and a support for the obtained release material is obtained.
- the nitrogen concentration in the ingot 3 can be changed by 1.6 ⁇ 10 17 atoms / cm 3 by changing the application area to the top surface 16 by 200 cm 2 .
- the nitrogen concentration in the ingot 3 when the release material is not applied varies depending on the ingot 3 depending on the purity of the silicon raw material 12, etc., but the application area of the release material is adjusted according to the nitrogen concentration when the release material is not applied. Control the nitrogen concentration within the range defined above. For example, the nitrogen concentration in the ingot 3 in the case of not applying a release material 7.0 ⁇ 10 13 atoms / cm 3 , when the nitrogen concentration is 17 mass% in the release material, to the application area and 1 cm 2 or more 1300 cm 2 or less Thus, the nitrogen concentration can be controlled to 8.0 ⁇ 10 13 atoms / cm 3 or more and 1.0 ⁇ 10 18 atoms / cm 3 or less.
- the nitrogen concentration in the ingot 3 can be measured, for example, by secondary ion mass spectrometry (SIMS).
- SIMS secondary ion mass spectrometry
- a silicon raw material 12 such as polycrystalline silicon is charged into the crucible 7 from a raw material supply device (not shown) through the raw material introduction pipe 11.
- a plasma arc is generated between the plasma torch 14 and the silicon source 12 and the molten silicon 13, and the silicon source 12 is also heated and melted by its Joule heat, The burden of electromagnetic induction heating can be reduced and the molten silicon 13 can be melted efficiently.
- the bottomless cooling crucible 7 is produced by the interaction of the magnetic field generated with the eddy current on the inner wall of the crucible 7 and the current generated on the surface of the molten silicon 13.
- the force acts in the direction of the molten silicon from the bottom, and is held in a noncontact state with the bottomless cooling crucible 7.
- an inert gas such as argon is introduced into the chamber 1 from the gas inlet 5.
- an inert gas such as argon is introduced into the chamber 1 from the gas inlet 5.
- the oxygen concentration is 0.3 ⁇ 10 17 atoms / cm 3 Control to 5.0 ⁇ 10 17 atoms / cm 3 or less and adding an appropriate amount of carbon to control carbon concentration to 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less
- the oxygen concentration is 0.3 ⁇ 10 17 atoms / cm 3 Control to 5.0 ⁇ 10 17 atoms / cm 3 or less and adding an appropriate amount of carbon to control carbon concentration to 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less
- the inventors have found that the partial pressure of oxygen gas and carbon monoxide gas relative to the inert gas affects the oxygen concentration and carbon concentration in the ingot 3 respectively. did. Moreover, in order to raise the carbon concentration in the ingot 3 by 1.0 ⁇ 10 17 atoms / cm 3 , for example, in the case of using argon gas as an inert gas, argon flow rate 200 l / min and furnace internal pressure 0.03 kg / cm 2 It has become clear that the partial pressure to argon gas should be 1.2 ⁇ 10 -4 times that of carbon monoxide gas.
- the carbon concentration and the oxygen concentration in the ingot 3 in the case where carbon monoxide gas and oxygen gas are not introduced into the inert gas differ from one ingot 3 to another. Therefore, by adjusting the partial pressure of carbon monoxide gas and oxygen gas to the inert gas according to the carbon concentration and oxygen concentration in the ingot 3 when carbon monoxide gas and oxygen gas are not introduced into the inert gas, It can be adjusted to the range of carbon concentration and oxygen concentration defined above.
- the carbon concentration in the ingot 3 was 2.0 ⁇ 10 17 atoms / cm 3 and the oxygen concentration was 0.1 ⁇ 10 17 atoms / cm 3 when carbon monoxide gas and oxygen gas were not introduced into the inert gas.
- the partial pressure of carbon monoxide gas with respect to the inert gas is 2.5 ⁇ 10 ⁇ 4 or more and 5.0 ⁇ 10 ⁇ 4 or less, and the partial pressure of oxygen gas is 1.2 ⁇ 10 ⁇ 5 or more.
- the oxygen concentration in the ingot 3 is 0.3 ⁇ 10 17 atoms / cm 3 or more and 5.0 ⁇ 10 17 atoms / cm 3 or less, and the carbon concentration is 4.0 ⁇
- the concentration can be adjusted to 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less.
- the carbon concentration and the oxygen concentration in the ingot 3 can be measured, for example, by Fourier transform infrared spectroscopy (FT-IR), and the oxygen concentration is defined based on ASTM F121-1979.
- the carbon concentration is a concentration defined based on ASTM F123-1981 (ASTM (American Society for Testing and Materials)).
- adjustment of carbon concentration can also be performed by adding a carbon powder to the silicon raw material 12 instead of performing by introduce
- the carbon concentration in the ingot 3 is 2.0 ⁇ 10 17 atoms / cm 3 when the carbon powder is not added to the ingot 3
- the total weight of the raw material not including the carbon powder is 1.7 ⁇ 10 10
- the above carbon concentration requirement can be satisfied by adding -3 to 3.4 ⁇ 10 -3 carbon powder.
- the carbon powder graphite powder is preferably used because it is easily dissolved in molten silicon.
- carbon dioxide gas can be introduced to simultaneously control oxygen and carbon concentrations.
- the partial pressure of the carbon dioxide gas with respect to the inert gas affects the oxygen concentration and the carbon concentration in the ingot 3 respectively.
- the oxygen concentration is 0.3 ⁇ 10 17 atoms / cm 3 or more by controlling the partial pressure of carbon dioxide to the inert gas to be 2.5 ⁇ 10 ⁇ 4 or more and 5.0 ⁇ 10 ⁇ 4 or less.
- the carbon concentration can be controlled to 0 ⁇ 10 17 atoms / cm 3 or less and the carbon concentration to 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less.
- the molten silicon 13 whose carbon, oxygen and nitrogen concentrations are adjusted solidifies the molten silicon 13 by gradually lowering the support shaft 15 supporting the molten silicon 13. That is, the molten silicon 13 in the crucible 7 is separated from the lower end of the induction coil 8 by the descent of the support shaft 15, the induction magnetic field becomes smaller, the calorific value and the pinch force decrease, and the cooled bottomless crucible 7 cools it.
- the molten silicon 13 solidifies from the outer peripheral side.
- the polycrystalline silicon material 12 is continuously and additionally charged to the bottomless cooling crucible 7 through the raw material introduction pipe 11 with the lowering of the support shaft 15 to continuously melt and solidify the silicon raw material 12 to obtain polycrystals. Continuous casting of silicon is possible.
- the ingot 3 obtained by the solidification of the molten silicon 13 is cooled to room temperature over a long time using the after heater 9 and the heat equalizing cylinder 10.
- the after heater 9 By heating the ingot 3 by the after heater 9 and providing an appropriate temperature gradient in the direction of the pull-down axis, generation of crystal defects in the ingot 3 during cooling is prevented.
- the heater (not shown) of the heat equalizing cylinder 10 holds the ingot 3 at a predetermined temperature for a predetermined time to perform soaking Apply.
- the temperature at which the ingot 3 is held at the time of the soaking is preferably at about 1100 ° C. because the growth speed of dislocation defects in the crystal is high and the crystal defects are easily generated if the temperature exceeds 1200 ° C.
- the output of the heater (not shown) of the heat equalizing cylinder 10 is reduced to cool the ingot 3 to room temperature.
- the oxygen concentration is 0.3 ⁇ 10 17 atoms / cm 3 or more and 5.0 ⁇ 10 17 atoms / cm 3 or less
- the carbon concentration is 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3
- the polycrystalline silicon ingot 3 can be cast under the adjustment of cm 3 or less and nitrogen concentration of 8.0 ⁇ 10 13 atoms / cm 3 or more and 1.0 ⁇ 10 18 atoms / cm 3 or less.
- the adjustment of the nitrogen concentration in the ingot 3 is performed by adjusting the application area of the nitrogen-containing release material on the upper surface of the support 16, but instead, the carbon concentration and the oxygen concentration As in the case of the adjustment, it can also be carried out by introducing nitrogen gas into the inert gas. Also in this case, the partial pressure of nitrogen gas to the inert gas affects the nitrogen concentration in the ingot 3.
- the partial pressure of nitrogen gas to the inert gas is 7.2 ⁇ 10 ⁇
- the nitrogen concentration can be controlled to 8.0 ⁇ 10 13 atoms / cm 3 or more and 1.0 ⁇ 10 18 atoms / cm 3 or less by controlling 7 times or more and 1.0 ⁇ 10 ⁇ 2 times or less.
- the adjustment of the nitrogen concentration is performed by the introduction of nitrogen gas, as the release material, one not containing nitrogen is used.
- the conductivity of polycrystalline silicon can be controlled by inserting a silicon source 12 to which a dopant is added. That is, when casting p-type polycrystalline silicon, boron, gallium, aluminum or the like may be used as a dopant. On the other hand, when casting n-type polycrystalline silicon, phosphorus, arsenic, antimony or the like may be used as a dopant.
- the crystallinity is improved by containing an appropriate amount of carbon in the crystal and adjusting the carbon concentration to an appropriate range while adjusting the oxygen and nitrogen concentrations to an appropriate range, and thus the conversion efficiency is high.
- Polycrystalline silicon suitable for solar cells can be cast.
- Polycrystalline silicon ingots were cast by the method of the present invention. That is, first, 100 g of silicon nitride as a powder for mold release material, 100 ml of ethyl silicate as a binder, 400 ml of pure water as a solvent, and 0.5 ml of hydrochloric acid as an additive are prepared to prepare a mold release material. , And was applied to the upper surface of the support 16.
- the nitrogen concentration in the ingot 3 is adjusted by the area of the mold release material applied on the upper surface of the support 16, and the nitrogen concentration is 8 ⁇ 10 13 atoms / cm 3 , 1 ⁇ 10 15 atoms / cm 3 , 1 ⁇ as the 10 18 atoms / cm 3, and adjusting the area of the release agent applied to the upper surface of the supporting table 16, and respectively 1cm 2, 50cm 2, 1300cm 2 .
- the support stand 16 was heat-processed as a binder removal process, it hold
- the shutter 2 was opened and 20 kg of polycrystalline silicon as the silicon source 12 was charged into the bottomless cooling crucible 7 from the source introduction pipe 11.
- the silicon raw material 12 in the crucible 7 was heated to 1420 degrees and melted by the induction coil 8 and the plasma torch 14 to obtain a molten silicon 13.
- the polycrystalline silicon ingot 3 having a total length of 7000 mm was cast by pulling down the support base 16.
- oxygen gas and carbon monoxide gas are supplied together with argon gas from the gas inlet 5 into the chamber 1, and the carbon concentration in the ingot 3 is 4.0 ⁇ 10 17 atoms / cm 3 , 5.
- the carbon concentration in the polycrystal on the assumption that carbon monoxide gas is not doped is 2.0 ⁇ 10 17 atoms / cm 3 .
- the oxygen concentration relative to argon gas is set to 3.0 ⁇ 10 16 atoms / cm 3 , 2.0 ⁇ 10 17 atoms / cm 3 , and 5.0 ⁇ 10 17 atoms / cm 3.
- the pressure was 1.2 ⁇ 10 ⁇ 5 times, 6.2 ⁇ 10 ⁇ 5 times and 1.9 ⁇ 10 ⁇ 4 times, respectively.
- the oxygen concentration in the polycrystal on the assumption that oxygen gas is not doped is 1.0 ⁇ 10 16 atoms / cm 3 .
- the oxygen concentration in the polycrystal on the assumption that oxygen gas is not doped is 1.0 ⁇ 10 16 atoms / cm 3 .
- the nitrogen concentration of 7.0 ⁇ 10 13 atoms / cm 3 so that a 2.0 ⁇ 10 18 atoms / cm 3 , the area of the release agent to be applied to the upper surface of the support table 16 was 0 cm 2, 1700 cm 2 .
- the other conditions are all the same as in Invention Example 1.
- the nitrogen concentration is fixed at 1 ⁇ 10 15 atoms / cm 3 and the oxygen concentration and the carbon concentration are changed
- FIG. 2 is when the oxygen concentration is fixed at 2 ⁇ 10 17 atoms / cm 3 .
- the results are for the case where the carbon concentration and the nitrogen concentration are changed.
- the conversion efficiency on the vertical axis is an average value of 10 sheets.
- the conversion efficiency is given as the value (E2 / E1) ⁇ 100 (%) of the converted electric energy E2 extracted from per unit area of the cell relative to the light energy E1 irradiated per unit area of the solar battery cell .
- the carbon concentration is 4.0 ⁇ 10 17 atoms / cm 3 or more and 6.0 ⁇ 10 17 atoms / cm 3 or less
- the oxygen concentration is 0.3 ⁇ 10 17 atoms / cm 3 or more
- the crystallinity is improved by containing an appropriate amount of carbon in the crystal and adjusting the carbon concentration to the appropriate range while adjusting the oxygen and nitrogen concentrations to the appropriate range, so that the conversion efficiency is high.
Abstract
Description
そこで、本発明の目的は、太陽電池の変換効率を高めるのに好適な、多結晶シリコンおよびその鋳造方法を提供することにある。
(1)炭素濃度が4.0×1017atoms/cm3以上6.0×1017atoms/cm3以下かつ酸素濃度が0.3×1017atoms/cm3以上5.0×1017atoms/cm3以下かつ窒素濃度が8.0×1013atoms/cm3以上1.0×1018atoms/cm3以下である多結晶シリコンウェーハ。
本発明の多結晶シリコンは、炭素濃度を4.0×1017atoms/cm3以上6.0×1017atoms/cm3以下かつ酸素濃度を0.3×1017atoms/cm3以上5.0×1017atoms/cm3以下かつ窒素濃度を8.0×1013atoms/cm3以上1.0×1018atoms/cm3以下に調整することが肝要である。
アフターヒータ9は、無底冷却ルツボ7の下方にルツボ7と同心に複数設置されており、ヒータ(図示せず)や保温材(図示せず)から構成されている。このアフターヒータ9は、無底冷却ルツボ7から引き下げられるインゴット3を加熱して、インゴット3の引き下げ軸方向に所定の温度勾配を与え、インゴット3に結晶欠陥が形成されるのを防止する。
均熱筒10は、冷却により残留応力が生じインゴット3にクラックが発生するのを防止するために、インゴット3を所定の温度で所定時間保持して均熱する。
ここで、窒素濃度の調整を窒素ガスの導入により行う場合には、離型材としては、窒素を含まないものを用いる。
以下、本発明の実施例について説明する。
本発明の方法により、多結晶シリコンインゴットを鋳造した。すなわち、まず、離型材用粉末としての窒化珪素を100g、バインダーとしての珪酸エチルを100ml、溶媒としての純水を400ml、添加剤としての塩酸を0.5mlを混合させてなる離型材を用意し、支持台16の上面に塗布した。インゴット3における窒素濃度の調整は、支持台16の上面に塗布された離型材の面積で調整し、窒素濃度が、8×1013atoms/cm3、1×1015atoms/cm3、1×1018atoms/cm3となるように、支持台16の上面に塗布する離型材の面積を調整し、それぞれ1cm2、50cm2、1300cm2とした。その後、脱バインダー処理として、支持台16を加熱処理し、120℃で1時間保持し、その後室温まで冷却して支持台16上面に離型材層を形成した。
次いで、図1に示すように、シャッタ2を開いて原料導入管11から、シリコン原料12として多結晶シリコンを20kg無底冷却ルツボ7内に装入した。
続いて、誘導コイル8およびプラズマトーチ14により、ルツボ7内のシリコン原料12を1420度まで加熱して溶融させ、溶融シリコン13を得た。さらにシリコン原料12を追加して該シリコン原料12を溶融させつつ、支持台16を引き下げることにより、全長7000mmの多結晶シリコンインゴット3を鋳造した。
その際、ガス導入口5から、チャンバ1内には、アルゴンガスとともに、酸素ガスと一酸化炭素ガスを供給し、インゴット3における炭素濃度は、4.0×1017atoms/cm3、5.0×1017atoms/cm3、6.0×1017atoms/cm3となるように、2.5×10-4倍、3.7×10-4倍、5.0×10-4倍とした。ただし、一酸化炭素ガスをドープしていないと仮定した場合の多結晶中の炭素濃度は、2.0×1017atoms/cm3である。また、酸素濃度は、3.0×1016atoms/cm3、2.0×1017atoms/cm3、5.0×1017atoms/cm3となるように、アルゴンガスに対する酸素ガスの分圧をそれぞれ1.2×10-5倍、6.2×10-5倍、1.9×10-4倍とした。ただし、酸素ガスをドープしていないと仮定した場合の多結晶中の酸素濃度は、1.0×1016atoms/cm3である。
こうして得られた345mm×510mmサイズのインゴットを6分割し、インゴット長手方向の中心(インゴット終端から2000mm)位置から一辺の長さ:156mmの正方形形状、厚み:180μmのウェーハを、発明例1~4の多結晶シリコンインゴットの各々から1000枚ずつ切り出した。そのうちの10枚に対して、模擬の酸テクスチャー処理(HF:HNO3:H2=1:4:5、室温、5分)を施したあと、気相成長法(CVD法)によりウェーハ上に窒化膜を形成させた。
発明例と同様に、多結晶シリコンを鋳造した。ただし、インゴット3における炭素濃度が3×1017atoms/cm3、7×1017atoms/cm3となるように、アルゴンガスに対する一酸化炭素の分圧をそれぞれ1.9×10-4倍、8.7×10-4倍とした。ただし、一酸化炭素ガスをドープしていないと仮定した場合の多結晶中の炭素濃度は2.0×1017atoms/cm3である。また、酸素濃度が6.0×1017atoms/cm3となるように、アルゴンガスに対する酸素の分圧を2.5×10-4倍とした。ただし、酸素ガスドープしていないと仮定した場合の多結晶中の酸素濃度は1.0×1016atoms/cm3である。さらに窒素濃度が7.0×1013atoms/cm3、2.0×1018atoms/cm3となるように、支持台16の上面に塗布する離型材の面積を0cm2、1700cm2とした。その他の条件は、発明例1と全て同じである。
作製した1000枚のウェーハのうちのウェーハ10枚を用いて評価用の太陽電池セルを作製し、変換効率を測定した。インゴット3における炭素濃度と変換効率との関係を図2および3に示す。ここで、図2は、窒素濃度を1×1015atoms/cm3に固定し、酸素濃度および炭素濃度を変化させた場合、図3は、酸素濃度が2×1017atoms/cm3に固定し、炭素濃度および窒素濃度を変化させた場合についての結果である。また、縦軸の変換効率は、10枚の平均値である。また、変換効率は、太陽電池セルの単位面積当たりに照射した光エネルギーE1に対する、セルの単位面積当たりから取り出される変換後の電気エネルギーE2の値(E2/E1)×100(%)として与えられる。図2および3から明らかなように、炭素濃度が4.0×1017atoms/cm3以上6.0×1017atoms/cm3以下、酸素濃度が0.3×1017atoms/cm3以上5.0×1017atoms/cm3以下かつ窒素濃度が8.0×1013atoms/cm3以上1.0×1018atoms/cm3以下に調整されている場合には、16%を超える高い変換効率が得られていることも分かる。
2 シャッタ
3 インゴット
4 引き出し口
5 ガス導入口
6 排気口
7 無底冷却ルツボ
8 誘導コイル
9 アフターヒータ
10 均熱筒
11 原料導入管
12 シリコン原料
13 溶融シリコン
14 プラズマトーチ
15 支持シャフト
16 支持台
17 還流配管
Claims (9)
- 炭素濃度が4.0×1017atoms/cm3以上6.0×1017atoms/cm3以下かつ酸素濃度が0.3×1017atoms/cm3以上5.0×1017atoms/cm3以下かつ窒素濃度が8.0×1013atoms/cm3以上1.0×1018atoms/cm3以下である多結晶シリコンウェーハ。
- 不活性ガスが導入されたチャンバの誘導コイル内に、軸方向の少なくとも一部が周方向で複数に分割され、内表面に窒素を含む離型材が塗布された無底冷却ルツボを配置し、前記誘導コイルによる電磁誘導加熱により、前記無底冷却ルツボ内に装入した多結晶シリコンの原料を溶融し、溶融シリコンを順次冷却して凝固させつつ下方へ引き抜く、多結晶シリコンの鋳造方法であって、前記溶融シリコンにおける、炭素濃度を4.0×1017atoms/cm3以上6.0×1017atoms/cm3以下、酸素濃度を0.3×1017atoms/cm3以上5.0×1017atoms/cm3以下および窒素濃度を8.0×1013atoms/cm3以上1.0×1018atoms/cm3以下に調整することを特徴とする多結晶シリコンの鋳造方法。
- 前記炭素濃度の調整は、一酸化炭素ガスを、該一酸化炭素ガスの前記不活性ガスに対する分圧を調整して前記チャンバ内に供給することにより行う、請求項2に記載の多結晶シリコンの鋳造方法。
- 前記炭素濃度の調整は、前記多結晶シリコンの原料に炭素粉を添加することにより行う、請求項2に記載の多結晶シリコンの鋳造方法。
- 前記酸素濃度の調整は、酸素ガスを、該酸素ガスの前記不活性ガスに対する分圧を調整して前記チャンバ内に供給することにより行う、請求項2~4のいずれか一項に記載の多結晶シリコンの鋳造方法。
- 前記炭素濃度および酸素濃度の調整は、二酸化炭素ガスを、該二酸化炭素ガスの前記不活性ガスに対する分圧を調整して前記チャンバ内に供給することにより行う、請求項2に記載の多結晶シリコンの鋳造方法。
- 前記窒素濃度の調整は、前記窒素を含む離型材における窒化珪素の前記支持台の上面への塗布面積を調整することにより行う、請求項2~6のいずれか一項に記載の多結晶シリコンの鋳造方法。
- 前記窒素濃度の調整は、窒素ガスを、該窒素ガスの前記不活性ガスに対する分圧を調整して前記チャンバ内に供給することにより行う、請求項2~6のいずれか一項に記載の多結晶シリコンの鋳造方法。
- 前記窒素を含む離型材は窒化珪素、珪酸エチル、純水および塩酸からなる、請求項2~8のいずれか一項に記載の多結晶シリコンの鋳造方法。
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US9546436B2 (en) | 2017-01-17 |
US20150082833A1 (en) | 2015-03-26 |
CN104169475A (zh) | 2014-11-26 |
TW201341602A (zh) | 2013-10-16 |
CN104169475B (zh) | 2018-01-12 |
JPWO2013145558A1 (ja) | 2015-12-10 |
JP5861770B2 (ja) | 2016-02-16 |
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