WO2013128758A1 - Mold for silicon casting, method for silicon casting, silicon material, and method for manufacturing solar cell - Google Patents
Mold for silicon casting, method for silicon casting, silicon material, and method for manufacturing solar cell Download PDFInfo
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- WO2013128758A1 WO2013128758A1 PCT/JP2012/082227 JP2012082227W WO2013128758A1 WO 2013128758 A1 WO2013128758 A1 WO 2013128758A1 JP 2012082227 W JP2012082227 W JP 2012082227W WO 2013128758 A1 WO2013128758 A1 WO 2013128758A1
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 147
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 147
- 239000010703 silicon Substances 0.000 title claims abstract description 147
- 238000005266 casting Methods 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims description 44
- 239000002210 silicon-based material Substances 0.000 title claims description 15
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 239000000654 additive Substances 0.000 claims abstract description 70
- 230000000996 additive effect Effects 0.000 claims abstract description 65
- 239000002245 particle Substances 0.000 claims abstract description 29
- 239000000463 material Substances 0.000 claims description 79
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 19
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 16
- 229910002804 graphite Inorganic materials 0.000 claims description 16
- 239000010439 graphite Substances 0.000 claims description 16
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 11
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 11
- 239000010453 quartz Substances 0.000 claims description 6
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 6
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 6
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 6
- 239000000758 substrate Substances 0.000 claims description 6
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 239000013078 crystal Substances 0.000 description 61
- 239000010410 layer Substances 0.000 description 58
- 210000004027 cell Anatomy 0.000 description 56
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 39
- 230000007547 defect Effects 0.000 description 27
- 239000012535 impurity Substances 0.000 description 18
- 235000012431 wafers Nutrition 0.000 description 18
- 239000002994 raw material Substances 0.000 description 15
- 239000002002 slurry Substances 0.000 description 14
- 230000000694 effects Effects 0.000 description 12
- 239000010408 film Substances 0.000 description 11
- 238000007711 solidification Methods 0.000 description 11
- 230000008023 solidification Effects 0.000 description 11
- 238000010438 heat treatment Methods 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 239000000843 powder Substances 0.000 description 8
- 238000000576 coating method Methods 0.000 description 6
- 238000002844 melting Methods 0.000 description 6
- 230000008018 melting Effects 0.000 description 6
- 230000035882 stress Effects 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 5
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- 230000006872 improvement Effects 0.000 description 5
- 230000006911 nucleation Effects 0.000 description 5
- 238000010899 nucleation Methods 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 description 3
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- 229920002451 polyvinyl alcohol Polymers 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 238000012790 confirmation Methods 0.000 description 2
- 229910021419 crystalline silicon Inorganic materials 0.000 description 2
- 230000003028 elevating effect Effects 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 230000008646 thermal stress Effects 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
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- 230000008901 benefit Effects 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- RPPBZEBXAAZZJH-UHFFFAOYSA-N cadmium telluride Chemical compound [Te]=[Cd] RPPBZEBXAAZZJH-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
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- 210000001787 dendrite Anatomy 0.000 description 1
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- 229910001873 dinitrogen Inorganic materials 0.000 description 1
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- 238000011049 filling Methods 0.000 description 1
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- 238000010348 incorporation Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
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- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
-
- 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 Table
- 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
- 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 a silicon casting mold, a silicon casting method using the same, a silicon material, and a solar cell manufacturing method.
- a polycrystalline silicon wafer which is generally widely used as a substrate for polycrystalline silicon solar cells, is an ingot manufactured by a method called a casting method in which molten silicon is unidirectionally solidified in a mold to obtain a large polycrystalline silicon ingot. It is cut into blocks and made into wafers by slicing.
- the polycrystalline silicon wafer manufactured by the casting method generally has a distribution in the output characteristics of the solar cell as shown in FIG. 3 depending on the position in the height direction in the ingot or block.
- the cause of the characteristic distribution of FIG. 3 is generally described as follows. First, in the region I at the initial stage of unidirectional solidification, the characteristics deteriorate due to the influence of impurities diffused from the mold. In the region II on the upper side, since the incorporation of impurities in the raw material due to segregation and the occurrence of crystal defects are few, the characteristics are the best in the block. Further, in the upper region III, the amount of impurities taken into the crystal gradually increases, the generation of crystal defects increases, and the characteristics are deteriorated as compared with the region II.
- the upper surface portion was formed after the ingot solidified to the end. Impurity reverse diffusion occurs from the high concentration portion of the impurity, and the amount of the impurity further increases, so that the characteristic deterioration becomes more remarkable than in the region III.
- the influence of impurities in the raw material and impurities eluted from the template is considered, but even if there is no such influence, in regions III and IV, crystals that become minority carrier traps toward the top Since defects increase gradually, the characteristics of solar cells tend to deteriorate.
- Patent Document 1 Japanese Patent Application Laid-Open No. 2005-152985
- Patent Document 2 International Publication No. 2005/092791 proposes a method of performing heat flow control during ingot growth with a structure that can change the heat receiving (heat exchange) area.
- Patent Document 3 Japanese Patent Application Laid-Open No. 2005-132671
- Patent Document 4 disclose a dendrite as a crystal nucleus at the bottom of an ingot (at the beginning of solidification) by quenching the bottom of the mold.
- Patent No. 4054873 proposes a method of obtaining a pseudo single crystal by growing crystal pieces (undissolved) left in the melting step of silicon raw material and enlarging crystal grains. ing.
- Patent Document 6 proposes a method of obtaining a pseudo single crystal by heteroepitaxially growing silicon from a seed crystal such as SiC arranged with the crystal orientation aligned on the bottom of the mold. .
- Japanese Unexamined Patent Publication No. 2005-152985 International Publication No. 2005/092791 Japanese Patent No. 4203603
- Japanese Unexamined Patent Publication No. 2005-132671 Japanese Patent No. 4054873
- Patent Document 1 particularly when the heater is located on the side of the mold, the shape of the solid-liquid interface is further deteriorated, and there is a problem that effects such as reduction of crystal defect density and prevention of cracking cannot be obtained.
- Patent Document 2 can improve the controllability of heat removal from the mold side wall, the apparatus configuration is very complicated, there are many high-temperature movable parts, and there is a problem that the cost of the apparatus increases and the failure increases. is there.
- the present invention provides a silicon casting mold, a silicon casting method, a method for producing a silicon material, and a method for producing a solar cell, which can suppress the crystal defect density on the top side of the ingot and enable the production of a solar cell with high cost performance.
- the task is to do.
- the inventors of the present invention have made at least the upper surface of the bottom plate part of the mold when producing a silicon ingot by unidirectionally solidifying the silicon melt from the bottom to the top in the mold.
- the present inventors have found that the above-mentioned problems can be solved by providing a parting material layer containing an additive having a particle size of 0.1 to 3.0 mm in the part, and have reached the present invention.
- a silicon casting mold for solidifying a silicon melt and an additive having an average particle size of 0.1 to 3.0 mm is included on at least the upper surface of the bottom plate portion of the inner wall of the silicon casting mold.
- a silicon casting mold provided with a release material layer is provided.
- a silicon casting method characterized by solidifying a silicon melt in the silicon casting mold, and a silicon material obtained by using silicon cast by the silicon casting method.
- a manufacturing method and a solar cell manufacturing method using the silicon material as a substrate to obtain a solar cell are provided.
- a silicon casting mold, a silicon casting method, a silicon material manufacturing method, and a solar cell manufacturing method capable of suppressing the crystal defect density on the top side of the ingot and manufacturing a solar cell with high cost performance Can be provided.
- the silicon casting mold of the present invention when the release material layer is provided only on the upper surface of the bottom plate portion, when the silicon casting mold is composed of a material mainly composed of graphite or quartz (silica),
- the additive is mainly composed of at least one selected from silicon nitride, silicon carbide, silicon oxide, and graphite
- a release material layer is added to the surface at a surface density of 0.2 to 8.5 pieces / cm 2 . The above-described effect is further exhibited when a product is included.
- the “top of the ingot” means the top of the silicon ingot produced by unidirectionally solidifying the silicon melt in the silicon casting mold from the bottom to the top, that is, the silicon ingot on the side where the solidification process is completed. Means.
- the lower part of the silicon ingot manufactured in the same manner, that is, the silicon ingot on the side where the solidification process starts is called “bottom of the ingot”.
- the “silicon material” means “silicon ingot”, “silicon block” processed from a silicon ingot into a prismatic shape, and “silicon wafer” obtained by slicing the silicon block.
- the “silicon solar battery” means a “silicon solar battery cell” that constitutes a minimum unit and a “solar battery module” in which a plurality of them are electrically connected.
- the silicon casting mold of the present invention is a silicon casting mold for solidifying a silicon melt, and an additive having an average particle size of 0.1 to 3.0 mm is provided on at least the upper surface of the bottom plate portion of the inner wall of the silicon casting mold. A mold release material layer is provided.
- the present inventors have been effective as a method for reducing the crystal defect density on the top side of the ingot. It has been found that there is a completely different method other than the stress reduction by suppressing the temperature distribution which is considered to be common and commonly used. Specifically, the present inventors have developed a polycrystal having a small crystal grain size, which is completely opposite to the techniques described in Patent Documents 3 to 6 in which deterioration of characteristics due to grain boundaries is suppressed by coarsening of crystal grains. It has been found that a silicon ingot is more resistant to stress and less prone to crystal defects than a silicon ingot having a large crystal grain size.
- the density of crystal defects introduced into the inside is large between the grains having a large crystal grain size and the grains having a small crystal grain size even in the portion immediately adjacent to each other in the polycrystalline silicon ingot.
- the crystal grain on the top side of the silicon ingot is reduced by promoting the generation of crystal nuclei at the bottom of the mold and reducing the crystal grain size. Defects can be reduced.
- the crystal defects on the top side of the silicon ingot it has been thought that it is necessary to reduce the thermal stress applied to the ingot, such as flattening of the solid-liquid interface.
- the crystal defects on the top side of the polycrystalline silicon ingot can be reduced only by controlling the crystal grain size to reduce the grain size. By using the template of the present invention, the crystal grain size can be controlled to be small.
- a release material layer containing an additive having an average particle size of 0.1 to 3.0 mm is provided on at least the upper surface of the bottom plate portion of the inner wall of the silicon casting mold.
- the material for the silicon casting mold of the present invention is not particularly limited as long as the effect of the present invention is obtained, and a mold of a conventionally used material can be used.
- the silicon casting mold of the present invention is made of a material mainly composed of graphite or quartz (silica). It is preferable.
- the shape and dimensions of the mold are not particularly limited as long as the effects of the present invention can be obtained.
- the shape and dimensions of the mold may be rectangular or cylindrical, and can hold the silicon melt and the solidified silicon ingot. What is necessary is just to have a dimension shape.
- the mold used in the test example can be mentioned.
- a mold for silicon casting is usually provided with a release material layer for taking out a silicon ingot from the mold after silicon casting.
- the mold release material layer contains an additive having a specific average particle diameter. According to the study by the present inventors, the probability that a position where a specific additive is present in the release material layer becomes a nucleus (crystal nucleus) generation position when the silicon melt is solidified is higher than that of other parts. I found it to be higher. In most cases, a silicon ingot is obtained by unidirectionally solidifying the silicon melt in the mold from the bottom plate portion toward the top.
- the probability of nucleation can be increased by introducing a specific additive into the release material layer on the upper surface portion of the bottom plate portion of the mold where nucleation begins first, and the crystal grain size is reduced. As a result, crystal defects on the top side of the silicon ingot can be suppressed.
- the release material layer of the silicon casting mold of the present invention is preferably provided only on the upper surface of the bottom plate portion of the inner wall of the silicon casting mold. That is, it is preferable that a release material layer containing no additive is provided on the side surface portion of the inner wall of the mold. If a mold release material layer containing a specific additive is also provided on the side surface of the inner wall of the mold, the probability of nucleation at the side surface increases, and the crystal nucleated at the side surface grows away from the side surface. Thus, the crystal grain boundary may be inclined with respect to the vertical direction of the ingot. Such a crystalline silicon ingot does not have a columnar crystal whose peripheral portion is preferable for solar cells.
- the additive is not particularly limited as long as the effects of the present invention can be obtained, but considering the influence of impurities mixed into the silicon melt and silicon ingot from the additive, cost, heat resistance, etc.
- the main component is preferably at least one selected from silicon nitride, silicon carbide, silicon oxide and graphite.
- the average particle size of the additive is 0.1 to 3.0 mm. If the average particle size of the additive is in the above range, an improvement in the output of a silicon solar cell produced using a silicon ingot produced using the silicon casting mold of the present invention can be expected. This means that the crystal state in the silicon ingot is good, and that it is possible to provide a silicon ingot suitable not only for solar cells but also for other applications.
- a more preferable range is 0.3 to 2.8 mm, and a further preferable range is 0.8 to 2.2 mm.
- the average particle size (mm) of specific additives is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, and 3.0.
- the release material layer preferably contains an additive at a surface density of 0.2 to 8.5 pieces / cm 2 on the surface thereof. If the surface density is less than 0.2 / cm 2 , the effect of controlling the crystal grain size of silicon may be reduced. On the other hand, when the areal density exceeds 8.5 / cm 2 , the crystal grain size of silicon becomes too small, and the crystal defect density of the ingot top can be kept low, but the crystal that becomes the recombination center of the electron-hole pair There may be too many grain boundaries.
- Such a silicon ingot is not preferable from the viewpoint of the conversion efficiency of the solar cell, and the range of the surface density of the additive is within the optimum range, and a more preferable range is 2.0 to 6.5 pieces / cm 2 . A more preferable range is 2.5 to 6.0 / cm 2 . Specific areal densities (pieces / cm 2 ) are 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0. .
- the silicon casting mold of the present invention can be produced by a known method, and is not particularly limited.
- it can be produced as follows. That is, the base material of the release material layer and the above additives are dispersed in a solvent to prepare a slurry having a solid concentration of about 1 to 5%, and the obtained slurry is applied to the inner surface of the mold. Is dried and fired to obtain a release material layer.
- the amounts of the main material powder and the additive powder may be appropriately set so that the surface density of the additive on the surface of the release material layer falls within the above range.
- a known release material can be used, and examples thereof include powders of silicon nitride, silicon oxide and mixtures thereof having an average particle size of 0.1 to 60 ⁇ m. Specific average particle diameters ( ⁇ m) are 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5. , 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 15, 20, 25, 30 , 35, 40, 45, 50, 55, 60.
- the solvent is not particularly limited as long as it disappears in the firing step and does not adversely affect the release material layer, and examples thereof include polyvinyl alcohol.
- the coating, drying and firing steps can be performed by appropriately setting conditions by a known method, and the coating and drying steps may be repeated a plurality of times in order to obtain a release material layer having a predetermined film thickness.
- the firing temperature and the time thereof are about 800 to 1100 ° C. and about 1 to 8 hours, although depending on conditions such as the material used and the thickness of the release material layer to be formed.
- Specific firing temperatures (° C.) are 800, 825, 850, 875, 900, 925, 950, 975, 1000, 1025, 1050, 1075, 1100, and specific firing times (hours) are 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8.
- the film thickness of the release material layer is about 150 to 600 ⁇ m.
- the film thickness of the release material layer is thinner than the particle size of the additive, the effect of the present invention can be easily obtained.
- the film thickness of the release material layer is thicker than the particle size of the additive, the additive is embedded inside the release material layer, and the surface shape of the release material layer is not reflected in the shape of the additive, Since the density of the convex portion of the additive serving as a nucleation site is reduced, the effect of the present invention is hardly obtained.
- Specific film thicknesses ( ⁇ m) are 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, and 600.
- only the slurry containing the additive may be applied to form the release material layer having a predetermined thickness.
- a release material layer composed of a plurality of types of layers may be formed by applying a slurry containing an additive after applying a slurry containing only the main material without containing any material.
- the release material layer is preferably provided only on the upper surface of the bottom plate portion of the mold.
- a release material layer containing an additive may be formed only on the upper surface of the bottom plate portion of the mold, and a release material layer not containing the additive may be formed on the side surface of the mold.
- the silicon casting method of the present invention is characterized by solidifying the silicon melt in the silicon casting mold of the present invention. According to this method, a silicon ingot suitable for a solar cell with high cost performance can be manufactured.
- the silicon melt in the silicon casting mold may be obtained by melting a solid silicon raw material in the mold or by pouring the silicon melt into the mold.
- the form of solidification of the silicon melt is not particularly limited as long as the effects of the present invention can be obtained, and conditions may be set as appropriate depending on the apparatus to be used.
- the silicon casting method of the present invention can be carried out using, for example, a known apparatus as shown in FIG. 4, but the present invention is not limited to this embodiment.
- FIG. 4 is a schematic sectional view showing an example of a casting apparatus to which the silicon casting method of the present invention can be applied.
- This apparatus is generally used for casting a polycrystalline silicon ingot, and has a chamber (sealed container) 7 constituting a resistance heating furnace.
- a mold 1 made of graphite, quartz (SiO 2 ) or the like is disposed inside the chamber 7 so that the atmosphere inside the chamber 7 can be maintained in a sealed state.
- a graphite mold table 3 that supports the mold 1 is disposed in the chamber 7 in which the mold 1 is accommodated.
- the mold table 3 can be moved up and down by the lift drive mechanism 12, and the refrigerant (cooling water) in the cooling tank 11 is circulated therein.
- An outer mold 2 made of graphite or the like is disposed on the upper part of the mold table 3, and the mold 1 is disposed therein.
- a cover made of graphite or the like surrounding the mold 1 may be arranged.
- a resistance heater 10 such as a graphite heater is disposed so as to surround the outer mold 2, and a heat insulating material 8 is disposed so as to cover these from above.
- the resistance heating body 10 can be heated from the periphery of the mold 1 to melt the silicon raw material 4 in the mold 1.
- the resistance heating method is used as the heating element, but an induction heating method may be used.
- thermocouple 5 In order to detect the temperature of the bottom surface of the mold 1, a lower mold thermocouple 5 is disposed near the center of the lower surface of the mold 1, and an outer lower mold thermocouple 6 is disposed near the center of the lower surface of the outer mold. And the heating state by the resistance heater 10 is controlled.
- a thermocouple or a radiation thermometer for detecting the temperature may be disposed, and the thermocouple installation position is not particularly limited.
- the inside of the chamber 7 can be kept in a sealed state so that external oxygen gas, nitrogen gas, etc. do not flow in.
- an inert gas such as argon gas is introduced to maintain an inert atmosphere.
- the apparatus having such a configuration, basically, filling of the silicon raw material 4 into the mold 1, degassing (evacuation) and gas replacement in the chamber 7 by introducing an inert gas, melting of the silicon raw material 4 by heating,
- the polycrystalline silicon ingot is cast by the steps of melting confirmation and holding, temperature control and solidification start by operation of the lifting drive mechanism 12, solidification completion confirmation and annealing, and ingot removal.
- an example of an apparatus of a type that heats and melts a silicon raw material in a mold is given, but other than that, a silicon raw material is heated and melted in a crucible or the like different from a silicon casting mold, and a silicon melt is converted into silicon
- a type of apparatus that pours into a casting mold can also be used.
- the silicon material of the present invention is produced by the silicon casting method of the present invention. That is, the silicon material of the present invention includes, for example, a “polycrystalline silicon ingot” produced by solidifying the silicon melt in the silicon casting mold of the present invention, and a “polycrystalline silicon block” obtained by cutting it into a prismatic shape. And a “polycrystalline silicon wafer” obtained by slicing the same. These silicon materials are suitable for materials for solar cells with high cost performance.
- the “polycrystalline silicon block” can be obtained, for example, by processing the above-mentioned “polycrystalline silicon ingot” into a prismatic shape and a desired size using a known apparatus such as a band saw. In the processing, the surface portion of the polycrystalline silicon ingot where impurities such as a mold material may be diffused may be cut, and the surface of the polycrystalline silicon block may be polished if necessary.
- the “polycrystalline silicon wafer” can be obtained, for example, by slicing the above “polycrystalline silicon block” to a desired thickness using a known apparatus such as a multi-wire saw. At present, a thickness of about 170 to 200 ⁇ m is generally used, but the trend is to reduce the thickness for cost reduction. Further, if necessary, the surface of the polycrystalline silicon wafer may be polished.
- the silicon solar cell of the present invention is manufactured using the silicon material (polycrystalline silicon wafer) of the present invention as a substrate.
- silicon solar cells have various structures, these can be manufactured by a known solar cell process using the silicon wafer of the present invention.
- an n-type impurity for example, phosphorus
- a front electrode and a back electrode To obtain a polycrystalline silicon solar battery cell.
- a p-type impurity for example, boron
- a front electrode and a back surface An electrode is formed to obtain a polycrystalline silicon solar cell.
- MIS type solar cells in which a metal is deposited with a thin insulating layer interposed therebetween, for example, a silicon thin film of an amorphous type having a conductivity type opposite to a silicon wafer is formed.
- p-type and n-type silicon heterojunctions having different structures.
- a polycrystalline silicon solar cell module is obtained by electrically connecting a plurality of them.
- Test Example 1 Examination on average particle diameter of additive contained in release material layer Quartz made by applying a release material layer containing additives of various materials having specific average particle diameter only on the upper surface of the mold bottom plate A polycrystalline silicon ingot is manufactured using the silicon casting mold 1, a polycrystalline silicon wafer is processed from the obtained ingot, a silicon solar cell is manufactured using the obtained wafer, and the obtained solar cell The relationship between the output and the average particle size of the additive was evaluated.
- a silicon nitride powder having a particle diameter of 1 to 60 ⁇ m as a main material of the release material layer and a 3% polyvinyl alcohol aqueous solution are mixed so that the weight ratio is 1: 1, and the additive powder shown in Table 1 is added and dispersed.
- a slurry A was obtained.
- the amount of the additive powder was appropriately set so that the surface density of the additive was about 3.0 / cm 2 as described below.
- a silicon nitride powder and a 3% polyvinyl alcohol aqueous solution were mixed so that the weight ratio was 1: 1 and dispersed to obtain slurry B.
- the side surface portion of the mold was coated with only slurry B and dried at about 50 ° C., and the resulting coating film was baked at 900 ° C. for 2 hours to form a release material layer having a thickness of about 250 ⁇ m on the side surface portion of the mold.
- the release material layer whose coating method is shown as “surface layer” in Table 1 is composed of a lower layer containing no additive and an upper layer containing the additive, and was formed as follows.
- the obtained slurry B is applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C.
- the obtained slurry A is applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C.
- the release material layer whose application method is shown as “mixing” in Table 1 consists of only the layer containing the additive, and was formed as follows.
- the obtained slurry A was applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C., and the obtained coating film was baked at 900 ° C. for 2 hours to obtain an additive surface density of about 3.0 / cm 2.
- a release material layer having a thickness of about 250 ⁇ m was formed.
- application and drying of the slurry were repeated as appropriate.
- said baking was performed simultaneously about the coating film of a mold side surface and a baseplate part upper surface.
- the slurry A containing silicon nitride powder and additive as the main material was used, but slurry containing only the additive can also be used.
- silicon nitride is used as the main material of the release material
- the present invention is not limited to silicon nitride, and other materials or a multiple layer structure of silicon nitride and silicon oxide may be used. It may be within the range where the effects of the invention can be obtained.
- the graphite outer mold 2 (inner dimensions: 900 mm ⁇ 900 mm ⁇ height) 460 mm, bottom plate thickness and side wall thickness 20 mm) were set, and quartz mold 1 (inner dimensions: 830 mm ⁇ 830 mm ⁇ 420 mm, bottom plate thickness and side wall thickness 22 mm) was set therein. Further, thermocouples 5 and 6 for temperature measurement were respectively installed at two locations near the center of the lower surface of the mold 1 and near the center of the lower surface of the outer mold 2.
- Each obtained polycrystalline silicon ingot was processed into 25 polycrystalline silicon blocks (156 mm ⁇ 156 mm ⁇ 200 mm) using a band saw, further sliced using a wire saw, and then a polycrystalline silicon wafer (156 mm ⁇ 156 mm). X thickness 0.18 mm) About 12,000 sheets were obtained.
- the obtained polycrystalline silicon wafer is put into a normal solar cell process to produce about 12,000 solar cells (outer dimensions 156 mm ⁇ 156 mm ⁇ thickness 0.18 mm) per ingot, and its output (W) was measured.
- Table 1 shows the result of calculating and standardizing the average value of the output for each ingot unit. For normalization, the average output of solar cells obtained from an ingot cast from a mold in which a release material layer containing no additive was formed was used, and the average of the outputs calculated in units of each ingot when this was taken as 100. The value was calculated.
- FIG. 1 shows the relationship between the particle size of the additive contained in the release material layer of the mold for casting silicon and the average output of the solar battery cell.
- the average output of the solar battery cell depends on the average particle diameter of the additive regardless of the material of the additive, silicon carbide, silicon oxide, silicon nitride and graphite. I understand that. That is, when the average particle diameter of the additive is in the range of 0.1 to 3.0 mm, the average output is improved as compared with the case of only the release material layer not containing the additive. Particularly when the average particle size of the additive is in the range of 0.3 to 2.8 mm, the improvement rate of the relative average output is 0.5% or more, and the average particle size of the additive is 0.8%. In the range of ⁇ 2.2 mm, the relative average output improvement rate is a preferable result of 1.0% or more.
- the output of the solar battery module manufactured using the solar battery cells with improved average output is improved. Further, when the average particle size of the additive is in the range of 0.1 to 3.0 mm, there is no crack on the bottom side of the silicon block, which is good.
- Test Example 2 Examination of surface density of additives contained in mold release material layer Only the upper surface of the mold bottom plate portion includes a material having an area density of a specific additive and additives of various materials having an average particle diameter of 0.8 mm.
- a polycrystalline silicon ingot was produced in the same manner as in Test Example 1 using a quartz silicon casting mold 1 coated with a mold material layer, and a polycrystalline silicon wafer was processed from the obtained ingot.
- a silicon solar cell was produced using the wafer, and the relationship between the output of the obtained solar cell and the surface density of the additive was evaluated.
- FIG. 2 shows the relationship between the surface density of the additive contained in the release material layer of the silicon casting mold and the average output of the solar cells.
- the average output of the solar cell depends on the surface density of the additive, regardless of the material of the additive and the method of applying the release layer. That is, when the surface density of the additive is in the range of 0.2 to 8.5 pieces / cm 2 , the average output is improved as compared with the case of only the release material layer not containing the additive. In particular, when the surface density of the additive is in the range of 2.0 to 6.5 pieces / cm 2 , the improvement rate of the relative average output is 0.5% or more, and the surface density of the additive is 2%. In the case of the range of 0.5 to 6.0 / cm 2 , the improvement rate of the relative average output is a preferable result of 1.0% or more.
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Abstract
A mold for silicon casting for solidifying a silicon melt, the mold for silicon casting having a mold release layer including an additive having an average particle diameter of 0.1 to 3.0 mm disposed at least on the top surface of the bottom plate of the inner walls of the mold for silicon casting.
Description
本発明は、シリコン鋳造用鋳型、それを用いたシリコン鋳造方法、シリコン材料および太陽電池の製造方法に関する。
The present invention relates to a silicon casting mold, a silicon casting method using the same, a silicon material, and a solar cell manufacturing method.
地球環境に様々な問題を引き起こしている石油などの代替として自然エネルギーの利用が注目されている。その中でも太陽電池は大きな設備を必要とせず、稼働時に騒音などを発生しないことから、日本や欧州などで特に積極的に導入されてきている。
カドミウムテルルなどの化合物半導体を用いた太陽電池も一部で実用化されているが、物質自体の安全性やこれまでの実績、またコストパフォーマンスの面から、結晶シリコン基板を用いた太陽電池が大きなシェアを占め、その中でも多結晶シリコン基板を用いた太陽電池(多結晶シリコン太陽電池)が大きなシェアを占めている。 The use of natural energy is attracting attention as an alternative to oil, which is causing various problems in the global environment. Among them, the solar cell does not require a large facility and does not generate noise during operation, and thus has been particularly actively introduced in Japan and Europe.
Solar cells using compound semiconductors such as cadmium tellurium have also been put into practical use, but solar cells using crystalline silicon substrates are large in terms of the safety of the materials themselves, past achievements, and cost performance. Solar cells using a polycrystalline silicon substrate (polycrystalline silicon solar cells) occupy a large share.
カドミウムテルルなどの化合物半導体を用いた太陽電池も一部で実用化されているが、物質自体の安全性やこれまでの実績、またコストパフォーマンスの面から、結晶シリコン基板を用いた太陽電池が大きなシェアを占め、その中でも多結晶シリコン基板を用いた太陽電池(多結晶シリコン太陽電池)が大きなシェアを占めている。 The use of natural energy is attracting attention as an alternative to oil, which is causing various problems in the global environment. Among them, the solar cell does not require a large facility and does not generate noise during operation, and thus has been particularly actively introduced in Japan and Europe.
Solar cells using compound semiconductors such as cadmium tellurium have also been put into practical use, but solar cells using crystalline silicon substrates are large in terms of the safety of the materials themselves, past achievements, and cost performance. Solar cells using a polycrystalline silicon substrate (polycrystalline silicon solar cells) occupy a large share.
多結晶シリコン太陽電池の基板として一般的に広く用いられている多結晶シリコンウエハは、鋳型内で溶融シリコンを一方向凝固させて大きな多結晶シリコンインゴットを得るキャスト法と呼ばれる方法で製造したインゴットをブロックに切り出し、スライスによりウエハ化したものである。
キャスト法で製造した多結晶シリコンウエハは、インゴットまたはブロック内の高さ方向の位置により、一般的に図3に示すような太陽電池の出力特性に分布を有している。 A polycrystalline silicon wafer, which is generally widely used as a substrate for polycrystalline silicon solar cells, is an ingot manufactured by a method called a casting method in which molten silicon is unidirectionally solidified in a mold to obtain a large polycrystalline silicon ingot. It is cut into blocks and made into wafers by slicing.
The polycrystalline silicon wafer manufactured by the casting method generally has a distribution in the output characteristics of the solar cell as shown in FIG. 3 depending on the position in the height direction in the ingot or block.
キャスト法で製造した多結晶シリコンウエハは、インゴットまたはブロック内の高さ方向の位置により、一般的に図3に示すような太陽電池の出力特性に分布を有している。 A polycrystalline silicon wafer, which is generally widely used as a substrate for polycrystalline silicon solar cells, is an ingot manufactured by a method called a casting method in which molten silicon is unidirectionally solidified in a mold to obtain a large polycrystalline silicon ingot. It is cut into blocks and made into wafers by slicing.
The polycrystalline silicon wafer manufactured by the casting method generally has a distribution in the output characteristics of the solar cell as shown in FIG. 3 depending on the position in the height direction in the ingot or block.
図3の特性分布が生じる原因は一般的に以下のように説明されている。
まず一方向凝固の初期の領域Iでは、鋳型から拡散した不純物の影響により特性低下が起こる。その上部側の領域IIでは、偏析による原料中の不純物の結晶中への取り込みや結晶欠陥の発生が少ないために、ブロック中で最も特性が良好となる。さらに上部側の領域IIIでは、結晶中に取り込まれる不純物量が徐々に増えることに加え、結晶欠陥の発生が増加し、領域IIよりも特性が低下する。さらに上部側の領域IVでは、領域IIIと同様に、結晶中に取り込まれる不純物量や結晶欠陥の発生がさらに増加することに加えて、インゴットが最後まで凝固した後に、最上部表面部分にできた不純物の高濃度部分から不純物の逆拡散が起こり、さらに不純物量が増加するために、領域IIIよりもさらに特性低下が顕著になる。
上記の説明では、原料中の不純物や鋳型から溶出する不純物の影響を考慮しているが、仮にそれらの影響がない場合でも、領域IIIおよびIVでは、上部に向かうにしたがって少数キャリアトラップとなる結晶欠陥が徐々に増加するために、太陽電池の特性は低下する傾向にある。 The cause of the characteristic distribution of FIG. 3 is generally described as follows.
First, in the region I at the initial stage of unidirectional solidification, the characteristics deteriorate due to the influence of impurities diffused from the mold. In the region II on the upper side, since the incorporation of impurities in the raw material due to segregation and the occurrence of crystal defects are few, the characteristics are the best in the block. Further, in the upper region III, the amount of impurities taken into the crystal gradually increases, the generation of crystal defects increases, and the characteristics are deteriorated as compared with the region II. Furthermore, in the upper region IV, similarly to the region III, in addition to further increasing the amount of impurities incorporated into the crystal and the generation of crystal defects, the upper surface portion was formed after the ingot solidified to the end. Impurity reverse diffusion occurs from the high concentration portion of the impurity, and the amount of the impurity further increases, so that the characteristic deterioration becomes more remarkable than in the region III.
In the above explanation, the influence of impurities in the raw material and impurities eluted from the template is considered, but even if there is no such influence, in regions III and IV, crystals that become minority carrier traps toward the top Since defects increase gradually, the characteristics of solar cells tend to deteriorate.
まず一方向凝固の初期の領域Iでは、鋳型から拡散した不純物の影響により特性低下が起こる。その上部側の領域IIでは、偏析による原料中の不純物の結晶中への取り込みや結晶欠陥の発生が少ないために、ブロック中で最も特性が良好となる。さらに上部側の領域IIIでは、結晶中に取り込まれる不純物量が徐々に増えることに加え、結晶欠陥の発生が増加し、領域IIよりも特性が低下する。さらに上部側の領域IVでは、領域IIIと同様に、結晶中に取り込まれる不純物量や結晶欠陥の発生がさらに増加することに加えて、インゴットが最後まで凝固した後に、最上部表面部分にできた不純物の高濃度部分から不純物の逆拡散が起こり、さらに不純物量が増加するために、領域IIIよりもさらに特性低下が顕著になる。
上記の説明では、原料中の不純物や鋳型から溶出する不純物の影響を考慮しているが、仮にそれらの影響がない場合でも、領域IIIおよびIVでは、上部に向かうにしたがって少数キャリアトラップとなる結晶欠陥が徐々に増加するために、太陽電池の特性は低下する傾向にある。 The cause of the characteristic distribution of FIG. 3 is generally described as follows.
First, in the region I at the initial stage of unidirectional solidification, the characteristics deteriorate due to the influence of impurities diffused from the mold. In the region II on the upper side, since the incorporation of impurities in the raw material due to segregation and the occurrence of crystal defects are few, the characteristics are the best in the block. Further, in the upper region III, the amount of impurities taken into the crystal gradually increases, the generation of crystal defects increases, and the characteristics are deteriorated as compared with the region II. Furthermore, in the upper region IV, similarly to the region III, in addition to further increasing the amount of impurities incorporated into the crystal and the generation of crystal defects, the upper surface portion was formed after the ingot solidified to the end. Impurity reverse diffusion occurs from the high concentration portion of the impurity, and the amount of the impurity further increases, so that the characteristic deterioration becomes more remarkable than in the region III.
In the above explanation, the influence of impurities in the raw material and impurities eluted from the template is considered, but even if there is no such influence, in regions III and IV, crystals that become minority carrier traps toward the top Since defects increase gradually, the characteristics of solar cells tend to deteriorate.
結晶欠陥が発生する原因は、インゴット中の温度分布に起因する応力であると考えられ、これを抑制するという観点から、次の2つの方法が提案されている。
第1に、例えば、日本特開2005-152985号公報(特許文献1)には、一方向凝固(キャスト)時に鋳型下部に設置する鋳型ホルダとして、中心部の熱流束が周辺よりも大きいものを使用する方法が提案されている。
第2に、例えば、国際公開第2005/092791(特許文献2)には、受熱(熱交換)面積を可変にできる構造により、インゴット成長の途中で熱流制御を行う方法が提案されている。 The cause of the occurrence of crystal defects is considered to be the stress caused by the temperature distribution in the ingot. From the viewpoint of suppressing this, the following two methods have been proposed.
First, for example, in Japanese Patent Application Laid-Open No. 2005-152985 (Patent Document 1), a mold holder installed at the lower part of a mold at the time of unidirectional solidification (casting) has a larger heat flux at the center than at the periphery. A method to use is proposed.
Secondly, for example, International Publication No. 2005/092791 (Patent Document 2) proposes a method of performing heat flow control during ingot growth with a structure that can change the heat receiving (heat exchange) area.
第1に、例えば、日本特開2005-152985号公報(特許文献1)には、一方向凝固(キャスト)時に鋳型下部に設置する鋳型ホルダとして、中心部の熱流束が周辺よりも大きいものを使用する方法が提案されている。
第2に、例えば、国際公開第2005/092791(特許文献2)には、受熱(熱交換)面積を可変にできる構造により、インゴット成長の途中で熱流制御を行う方法が提案されている。 The cause of the occurrence of crystal defects is considered to be the stress caused by the temperature distribution in the ingot. From the viewpoint of suppressing this, the following two methods have been proposed.
First, for example, in Japanese Patent Application Laid-Open No. 2005-152985 (Patent Document 1), a mold holder installed at the lower part of a mold at the time of unidirectional solidification (casting) has a larger heat flux at the center than at the periphery. A method to use is proposed.
Secondly, for example, International Publication No. 2005/092791 (Patent Document 2) proposes a method of performing heat flow control during ingot growth with a structure that can change the heat receiving (heat exchange) area.
また、上記の方法とは別の多結晶シリコンインゴットの品質向上対策として、大粒径化を目的とした方法が提案されている。
例えば、日本特許第4203603号公報(特許文献3)および日本特開2005-132671号公報(特許文献4)には、鋳型底部を急冷することにより、インゴット底部に(凝固初期に)結晶核としてデンドライト結晶を発生させて、結晶粒を粗大化させる方法が提案されている。
また、日本特許第4054873号公報(特許文献5)には、シリコン原料の融解工程において残存させた結晶片(溶け残り)を成長させ結晶粒を肥大させて、擬似単結晶を得る方法が提案されている。
さらに、日本特許第4569957号公報(特許文献6)には、鋳型底に結晶方位を揃えて配置したSiCなどの種結晶からシリコンをヘテロエピ成長させて、擬似単結晶を得る方法が提案されている。 Further, as a measure for improving the quality of a polycrystalline silicon ingot different from the above method, a method aimed at increasing the particle size has been proposed.
For example, Japanese Patent No. 4203603 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2005-132671 (Patent Document 4) disclose a dendrite as a crystal nucleus at the bottom of an ingot (at the beginning of solidification) by quenching the bottom of the mold. There has been proposed a method of generating crystals and coarsening crystal grains.
Japanese Patent No. 4054873 (Patent Document 5) proposes a method of obtaining a pseudo single crystal by growing crystal pieces (undissolved) left in the melting step of silicon raw material and enlarging crystal grains. ing.
Furthermore, Japanese Patent No. 4569957 (Patent Document 6) proposes a method of obtaining a pseudo single crystal by heteroepitaxially growing silicon from a seed crystal such as SiC arranged with the crystal orientation aligned on the bottom of the mold. .
例えば、日本特許第4203603号公報(特許文献3)および日本特開2005-132671号公報(特許文献4)には、鋳型底部を急冷することにより、インゴット底部に(凝固初期に)結晶核としてデンドライト結晶を発生させて、結晶粒を粗大化させる方法が提案されている。
また、日本特許第4054873号公報(特許文献5)には、シリコン原料の融解工程において残存させた結晶片(溶け残り)を成長させ結晶粒を肥大させて、擬似単結晶を得る方法が提案されている。
さらに、日本特許第4569957号公報(特許文献6)には、鋳型底に結晶方位を揃えて配置したSiCなどの種結晶からシリコンをヘテロエピ成長させて、擬似単結晶を得る方法が提案されている。 Further, as a measure for improving the quality of a polycrystalline silicon ingot different from the above method, a method aimed at increasing the particle size has been proposed.
For example, Japanese Patent No. 4203603 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2005-132671 (Patent Document 4) disclose a dendrite as a crystal nucleus at the bottom of an ingot (at the beginning of solidification) by quenching the bottom of the mold. There has been proposed a method of generating crystals and coarsening crystal grains.
Japanese Patent No. 4054873 (Patent Document 5) proposes a method of obtaining a pseudo single crystal by growing crystal pieces (undissolved) left in the melting step of silicon raw material and enlarging crystal grains. ing.
Furthermore, Japanese Patent No. 4569957 (Patent Document 6) proposes a method of obtaining a pseudo single crystal by heteroepitaxially growing silicon from a seed crystal such as SiC arranged with the crystal orientation aligned on the bottom of the mold. .
特許文献1の方法では、特にヒータが鋳型横にあるような場合、固液界面の形状をより悪化させる結果となり、結晶欠陥密度の低減や割れ防止などの効果が得られないという課題がある。
特許文献2の方法では、鋳型側壁からの抜熱の制御性を向上させることはできるものの、装置構成が大変複雑で、高温の可動部分が多く、装置のコストアップや故障が増加するという課題がある。 In the method ofPatent Document 1, particularly when the heater is located on the side of the mold, the shape of the solid-liquid interface is further deteriorated, and there is a problem that effects such as reduction of crystal defect density and prevention of cracking cannot be obtained.
Although the method ofPatent Document 2 can improve the controllability of heat removal from the mold side wall, the apparatus configuration is very complicated, there are many high-temperature movable parts, and there is a problem that the cost of the apparatus increases and the failure increases. is there.
特許文献2の方法では、鋳型側壁からの抜熱の制御性を向上させることはできるものの、装置構成が大変複雑で、高温の可動部分が多く、装置のコストアップや故障が増加するという課題がある。 In the method of
Although the method of
特許文献3~5の方法では、結晶粒の粗大化により粒界による特性低下を抑制でき、特にインゴットサイズが小さい場合には、温度分布による応力が比較的小さく、インゴットのトップ側で導入される結晶欠陥もある程度抑えられるというメリットがある。しかし、インゴットサイズが大きくなると共にトップ側での結晶欠陥が増加するために、ボトム側での特性向上が見られるものの、やはりトップ側で作製した太陽電池における特性が低下するという課題が残る。
In the methods of Patent Documents 3 to 5, deterioration of characteristics due to grain boundaries can be suppressed by coarsening of crystal grains, and particularly when the ingot size is small, the stress due to temperature distribution is relatively small and is introduced on the top side of the ingot. There is an advantage that crystal defects can be suppressed to some extent. However, as the ingot size increases and crystal defects on the top side increase, the characteristics on the bottom side are improved, but the problem still remains that the characteristics of the solar cell fabricated on the top side deteriorate.
特許文献6の方法では、隣り合うSiCなどの種結晶から成長したシリコン結晶がぶつかりあう境界部分で欠陥が形成され、インゴットは巨視的には単結晶に見えても電気的には多くの欠陥を含むものと考えられる。またトップ側に関しては、インゴットサイズが大きくなると共にトップ側での結晶欠陥密度が高くなり、やはりトップ側で作製した太陽電池における特性が低下するという課題が残る。
In the method of Patent Document 6, defects are formed at a boundary portion where silicon crystals grown from adjacent seed crystals such as SiC collide, and an ingot has many defects electrically even though it looks macroscopically. It is thought to include. On the top side, the ingot size increases and the crystal defect density on the top side increases, and the problem remains that the characteristics of the solar cell fabricated on the top side also deteriorate.
本発明は、インゴットのトップ側の結晶欠陥密度を抑え、コストパフォーマンスの高い太陽電池の製造を可能とする、シリコン鋳造用鋳型、シリコン鋳造方法、シリコン材料の製造方法および太陽電池の製造方法を提供することを課題とする。
The present invention provides a silicon casting mold, a silicon casting method, a method for producing a silicon material, and a method for producing a solar cell, which can suppress the crystal defect density on the top side of the ingot and enable the production of a solar cell with high cost performance. The task is to do.
本発明者らは、上記の課題を解決すべく鋭意研究を重ねた結果、鋳型内でシリコン融液を底部から上部に一方向凝固させてシリコンインゴットを製造する際に、鋳型の少なくとも底板部上面部に粒径0.1~3.0mmの添加物を含む離型材層を設けることにより、上記の課題を解決できることを見出し、本発明に至った。
As a result of intensive studies to solve the above problems, the inventors of the present invention have made at least the upper surface of the bottom plate part of the mold when producing a silicon ingot by unidirectionally solidifying the silicon melt from the bottom to the top in the mold. The present inventors have found that the above-mentioned problems can be solved by providing a parting material layer containing an additive having a particle size of 0.1 to 3.0 mm in the part, and have reached the present invention.
かくして、本発明によれば、シリコン融液を凝固させるシリコン鋳造用鋳型であり、前記シリコン鋳造用鋳型の内壁の少なくとも底板部上面に、平均粒径0.1~3.0mmの添加物を含む離型材層が設けられているシリコン鋳造用鋳型が提供される。
Thus, according to the present invention, there is provided a silicon casting mold for solidifying a silicon melt, and an additive having an average particle size of 0.1 to 3.0 mm is included on at least the upper surface of the bottom plate portion of the inner wall of the silicon casting mold. A silicon casting mold provided with a release material layer is provided.
また、本発明によれば、上記のシリコン鋳造用鋳型内でシリコン融液を凝固させることを特徴とするシリコン鋳造方法、そのシリコン鋳造方法により鋳造されたシリコンを用いてシリコン材料を得るシリコン材料の製造方法およびそのシリコン材料を基板として用いて太陽電池を得る太陽電池の製造方法が提供される。
According to the present invention, a silicon casting method characterized by solidifying a silicon melt in the silicon casting mold, and a silicon material obtained by using silicon cast by the silicon casting method. Provided are a manufacturing method and a solar cell manufacturing method using the silicon material as a substrate to obtain a solar cell.
本発明によれば、インゴットのトップ側の結晶欠陥密度を抑え、コストパフォーマンスの高い太陽電池の製造を可能とする、シリコン鋳造用鋳型、シリコン鋳造方法、シリコン材料の製造方法および太陽電池の製造方法を提供することができる。
According to the present invention, a silicon casting mold, a silicon casting method, a silicon material manufacturing method, and a solar cell manufacturing method capable of suppressing the crystal defect density on the top side of the ingot and manufacturing a solar cell with high cost performance Can be provided.
本発明のシリコン鋳造用鋳型は、離型材層が底板部上面のみに設けられている場合に、シリコン鋳造用鋳型が黒鉛または石英(シリカ)を主成分とする材質で構成されている場合に、添加物が窒化珪素、炭化珪素、酸化珪素および黒鉛から選択される少なくとも1つを主成分とする場合に、離型材層がその表面に面密度0.2~8.5個/cm2で添加物を含む場合に、上記の効果がさらに発揮される。
The silicon casting mold of the present invention, when the release material layer is provided only on the upper surface of the bottom plate portion, when the silicon casting mold is composed of a material mainly composed of graphite or quartz (silica), When the additive is mainly composed of at least one selected from silicon nitride, silicon carbide, silicon oxide, and graphite, a release material layer is added to the surface at a surface density of 0.2 to 8.5 pieces / cm 2 . The above-described effect is further exhibited when a product is included.
本明細書において、「インゴットのトップ」とは、シリコン鋳造用鋳型内のシリコン融液を底部から上部に一方向凝固させて製造されたシリコンインゴットの上部、すなわち凝固工程が完了する側のシリコンインゴットを意味する。他方、同様にして製造されたシリコンインゴットの下部、すなわち凝固工程が開始する側のシリコンインゴットは「インゴットのボトム」と称される。
また、「シリコン材料」とは、「シリコンインゴット」、シリコンインゴットから角柱状に加工した「シリコンブロック」およびシリコンブロックをスライス加工した「シリコンウエハ」を意味する。
さらに、「シリコン太陽電池」とは、最小ユニットを構成する「シリコン太陽電池セル」およびその複数個を電気的に接続した「太陽電池モジュール」を意味する。 In the present specification, the “top of the ingot” means the top of the silicon ingot produced by unidirectionally solidifying the silicon melt in the silicon casting mold from the bottom to the top, that is, the silicon ingot on the side where the solidification process is completed. Means. On the other hand, the lower part of the silicon ingot manufactured in the same manner, that is, the silicon ingot on the side where the solidification process starts is called “bottom of the ingot”.
The “silicon material” means “silicon ingot”, “silicon block” processed from a silicon ingot into a prismatic shape, and “silicon wafer” obtained by slicing the silicon block.
Furthermore, the “silicon solar battery” means a “silicon solar battery cell” that constitutes a minimum unit and a “solar battery module” in which a plurality of them are electrically connected.
また、「シリコン材料」とは、「シリコンインゴット」、シリコンインゴットから角柱状に加工した「シリコンブロック」およびシリコンブロックをスライス加工した「シリコンウエハ」を意味する。
さらに、「シリコン太陽電池」とは、最小ユニットを構成する「シリコン太陽電池セル」およびその複数個を電気的に接続した「太陽電池モジュール」を意味する。 In the present specification, the “top of the ingot” means the top of the silicon ingot produced by unidirectionally solidifying the silicon melt in the silicon casting mold from the bottom to the top, that is, the silicon ingot on the side where the solidification process is completed. Means. On the other hand, the lower part of the silicon ingot manufactured in the same manner, that is, the silicon ingot on the side where the solidification process starts is called “bottom of the ingot”.
The “silicon material” means “silicon ingot”, “silicon block” processed from a silicon ingot into a prismatic shape, and “silicon wafer” obtained by slicing the silicon block.
Furthermore, the “silicon solar battery” means a “silicon solar battery cell” that constitutes a minimum unit and a “solar battery module” in which a plurality of them are electrically connected.
本発明のシリコン鋳造用鋳型は、シリコン融液を凝固させるシリコン鋳造用鋳型であり、前記シリコン鋳造用鋳型の内壁の少なくとも底板部上面に、平均粒径0.1~3.0mmの添加物を含む離型材層が設けられていることを特徴とする。
The silicon casting mold of the present invention is a silicon casting mold for solidifying a silicon melt, and an additive having an average particle size of 0.1 to 3.0 mm is provided on at least the upper surface of the bottom plate portion of the inner wall of the silicon casting mold. A mold release material layer is provided.
本発明者らは、鋳型内で一方向凝固させたシリコンインゴットの多くについて結晶欠陥の評価、分析および検討を行った結果、インゴットのトップ側の結晶欠陥密度を低減する方法として、従来から有効であると考えられ、そして常用されている温度分布の抑制による応力低減以外に全く別の方法があることを見出した。
具体的には、本発明者らは、結晶粒の粗大化により粒界による特性低下を抑制するという特許文献3~6に記載の技術とは全く逆の発想で、結晶粒径の小さい多結晶シリコンインゴットが、結晶粒径の大きいものと比較して、応力に強く、結晶欠陥が発生し難いことを見出した。 As a result of evaluating, analyzing and examining crystal defects for many of the silicon ingots unidirectionally solidified in the mold, the present inventors have been effective as a method for reducing the crystal defect density on the top side of the ingot. It has been found that there is a completely different method other than the stress reduction by suppressing the temperature distribution which is considered to be common and commonly used.
Specifically, the present inventors have developed a polycrystal having a small crystal grain size, which is completely opposite to the techniques described inPatent Documents 3 to 6 in which deterioration of characteristics due to grain boundaries is suppressed by coarsening of crystal grains. It has been found that a silicon ingot is more resistant to stress and less prone to crystal defects than a silicon ingot having a large crystal grain size.
具体的には、本発明者らは、結晶粒の粗大化により粒界による特性低下を抑制するという特許文献3~6に記載の技術とは全く逆の発想で、結晶粒径の小さい多結晶シリコンインゴットが、結晶粒径の大きいものと比較して、応力に強く、結晶欠陥が発生し難いことを見出した。 As a result of evaluating, analyzing and examining crystal defects for many of the silicon ingots unidirectionally solidified in the mold, the present inventors have been effective as a method for reducing the crystal defect density on the top side of the ingot. It has been found that there is a completely different method other than the stress reduction by suppressing the temperature distribution which is considered to be common and commonly used.
Specifically, the present inventors have developed a polycrystal having a small crystal grain size, which is completely opposite to the techniques described in
本発明者らの知見によれば、(1)多結晶シリコンインゴット内ですぐ隣り合った部分であっても結晶粒径の大きい粒と小さい粒とでは内部に導入されている結晶欠陥密度が大きく異なり、(2)インゴットの結晶粒径とそのトップ側の結晶欠陥密度との間に相関があり、(3)例外はあるものの結晶粒径が小さいほどインゴットのトップ側の結晶欠陥密度が低い。インゴット内の隣り合った部分で、インゴット成長時に受ける熱ストレスに大きな差があるとは考え難いことから、結晶粒径の小さな部分は、粒界部分のすべりなどにより結晶粒内が受けるストレスが緩和され、結果的に結晶粒内への結晶欠陥導入が抑えられるものと考えられる。
According to the knowledge of the present inventors, (1) the density of crystal defects introduced into the inside is large between the grains having a large crystal grain size and the grains having a small crystal grain size even in the portion immediately adjacent to each other in the polycrystalline silicon ingot. Unlikely, (2) there is a correlation between the crystal grain size of the ingot and the crystal defect density on the top side. (3) Although there are exceptions, the smaller the crystal grain size, the lower the crystal defect density on the top side of the ingot. Since it is difficult to think that there is a large difference in thermal stress applied during ingot growth between adjacent parts in the ingot, the stress received in the crystal grains is mitigated due to slipping of the grain boundary part, etc. As a result, it is considered that the introduction of crystal defects into the crystal grains can be suppressed.
したがって、鋳型中のシリコン融液を一方向凝固させてシリコンインゴットを鋳造する際に、鋳型底部での結晶核の発生を促進して結晶粒径を小さくすることで、シリコンインゴットのトップ側の結晶欠陥を低減することができる。
シリコンインゴットのトップ側の結晶欠陥を低減するためには、これまで、固液界面の平坦化など、インゴットにかかる熱ストレスの低減が必要と考えられてきたのに対して、本発明では、結晶粒径を小さくする結晶粒径の制御のみで、多結晶シリコンインゴットのトップ側の結晶欠陥を低減できる。本発明の鋳型を用いることで、結晶粒径を小さく制御することが可能となる。 Therefore, when casting a silicon ingot by unidirectionally solidifying the silicon melt in the mold, the crystal grain on the top side of the silicon ingot is reduced by promoting the generation of crystal nuclei at the bottom of the mold and reducing the crystal grain size. Defects can be reduced.
In order to reduce the crystal defects on the top side of the silicon ingot, it has been thought that it is necessary to reduce the thermal stress applied to the ingot, such as flattening of the solid-liquid interface. The crystal defects on the top side of the polycrystalline silicon ingot can be reduced only by controlling the crystal grain size to reduce the grain size. By using the template of the present invention, the crystal grain size can be controlled to be small.
シリコンインゴットのトップ側の結晶欠陥を低減するためには、これまで、固液界面の平坦化など、インゴットにかかる熱ストレスの低減が必要と考えられてきたのに対して、本発明では、結晶粒径を小さくする結晶粒径の制御のみで、多結晶シリコンインゴットのトップ側の結晶欠陥を低減できる。本発明の鋳型を用いることで、結晶粒径を小さく制御することが可能となる。 Therefore, when casting a silicon ingot by unidirectionally solidifying the silicon melt in the mold, the crystal grain on the top side of the silicon ingot is reduced by promoting the generation of crystal nuclei at the bottom of the mold and reducing the crystal grain size. Defects can be reduced.
In order to reduce the crystal defects on the top side of the silicon ingot, it has been thought that it is necessary to reduce the thermal stress applied to the ingot, such as flattening of the solid-liquid interface. The crystal defects on the top side of the polycrystalline silicon ingot can be reduced only by controlling the crystal grain size to reduce the grain size. By using the template of the present invention, the crystal grain size can be controlled to be small.
(シリコン鋳造用鋳型)
本発明のシリコン鋳造用鋳型は、シリコン鋳造用鋳型の内壁の少なくとも底板部上面に、平均粒径0.1~3.0mmの添加物を含む離型材層が設けられている。 (Silicon casting mold)
In the silicon casting mold of the present invention, a release material layer containing an additive having an average particle size of 0.1 to 3.0 mm is provided on at least the upper surface of the bottom plate portion of the inner wall of the silicon casting mold.
本発明のシリコン鋳造用鋳型は、シリコン鋳造用鋳型の内壁の少なくとも底板部上面に、平均粒径0.1~3.0mmの添加物を含む離型材層が設けられている。 (Silicon casting mold)
In the silicon casting mold of the present invention, a release material layer containing an additive having an average particle size of 0.1 to 3.0 mm is provided on at least the upper surface of the bottom plate portion of the inner wall of the silicon casting mold.
本発明のシリコン鋳造用鋳型は、本発明の効果が得られる範囲であれば、その材質は特に限定されず、従来から用いられている材質の鋳型を用いることができる。
鋳型からシリコン融液およびシリコンインゴットへの混入不純物の影響、コスト、耐熱性などを考慮して、本発明のシリコン鋳造用鋳型は、黒鉛または石英(シリカ)を主成分とする材質で構成されているのが好ましい。
鋳型の形状および寸法は、本発明の効果が得られる範囲であれば、特に限定されず、例えば、矩形、円筒形のいずれであってもよく、シリコン融液および凝固したシリコンインゴットを保持し得る寸法形状を有していればよい。具体的には、試験例で用いた鋳型が挙げられる。 The material for the silicon casting mold of the present invention is not particularly limited as long as the effect of the present invention is obtained, and a mold of a conventionally used material can be used.
In consideration of the influence of impurities mixed into the silicon melt and silicon ingot from the mold, cost, heat resistance, etc., the silicon casting mold of the present invention is made of a material mainly composed of graphite or quartz (silica). It is preferable.
The shape and dimensions of the mold are not particularly limited as long as the effects of the present invention can be obtained. For example, the shape and dimensions of the mold may be rectangular or cylindrical, and can hold the silicon melt and the solidified silicon ingot. What is necessary is just to have a dimension shape. Specifically, the mold used in the test example can be mentioned.
鋳型からシリコン融液およびシリコンインゴットへの混入不純物の影響、コスト、耐熱性などを考慮して、本発明のシリコン鋳造用鋳型は、黒鉛または石英(シリカ)を主成分とする材質で構成されているのが好ましい。
鋳型の形状および寸法は、本発明の効果が得られる範囲であれば、特に限定されず、例えば、矩形、円筒形のいずれであってもよく、シリコン融液および凝固したシリコンインゴットを保持し得る寸法形状を有していればよい。具体的には、試験例で用いた鋳型が挙げられる。 The material for the silicon casting mold of the present invention is not particularly limited as long as the effect of the present invention is obtained, and a mold of a conventionally used material can be used.
In consideration of the influence of impurities mixed into the silicon melt and silicon ingot from the mold, cost, heat resistance, etc., the silicon casting mold of the present invention is made of a material mainly composed of graphite or quartz (silica). It is preferable.
The shape and dimensions of the mold are not particularly limited as long as the effects of the present invention can be obtained. For example, the shape and dimensions of the mold may be rectangular or cylindrical, and can hold the silicon melt and the solidified silicon ingot. What is necessary is just to have a dimension shape. Specifically, the mold used in the test example can be mentioned.
シリコン鋳造用鋳型には、通常、シリコン鋳造後に鋳型からシリコンインゴットを取り出すために離型材層が設けられるが、本発明では、離型材層に特定の平均粒径を有する添加物を含む。
本発明者らの研究によれば、離型材層中に特定の添加物が存在する位置が、シリコン融液が凝固する際に、核(結晶核)発生位置となる確率が他の部分よりも高くなることがわかった。鋳型内のシリコン融液をその底板部から上部に向けて一方向凝固させ、シリコンインゴットを得ることがほとんどである。そのため、少なくとも最初に核発生が始まる鋳型の底板部上面部分の離型材層中に特定の添加物を導入することにより、核発生の確率を上げることができ、結晶粒径を小さくし、またその結果として、シリコンインゴットのトップ側の結晶欠陥を抑制することができる。 A mold for silicon casting is usually provided with a release material layer for taking out a silicon ingot from the mold after silicon casting. In the present invention, the mold release material layer contains an additive having a specific average particle diameter.
According to the study by the present inventors, the probability that a position where a specific additive is present in the release material layer becomes a nucleus (crystal nucleus) generation position when the silicon melt is solidified is higher than that of other parts. I found it to be higher. In most cases, a silicon ingot is obtained by unidirectionally solidifying the silicon melt in the mold from the bottom plate portion toward the top. Therefore, the probability of nucleation can be increased by introducing a specific additive into the release material layer on the upper surface portion of the bottom plate portion of the mold where nucleation begins first, and the crystal grain size is reduced. As a result, crystal defects on the top side of the silicon ingot can be suppressed.
本発明者らの研究によれば、離型材層中に特定の添加物が存在する位置が、シリコン融液が凝固する際に、核(結晶核)発生位置となる確率が他の部分よりも高くなることがわかった。鋳型内のシリコン融液をその底板部から上部に向けて一方向凝固させ、シリコンインゴットを得ることがほとんどである。そのため、少なくとも最初に核発生が始まる鋳型の底板部上面部分の離型材層中に特定の添加物を導入することにより、核発生の確率を上げることができ、結晶粒径を小さくし、またその結果として、シリコンインゴットのトップ側の結晶欠陥を抑制することができる。 A mold for silicon casting is usually provided with a release material layer for taking out a silicon ingot from the mold after silicon casting. In the present invention, the mold release material layer contains an additive having a specific average particle diameter.
According to the study by the present inventors, the probability that a position where a specific additive is present in the release material layer becomes a nucleus (crystal nucleus) generation position when the silicon melt is solidified is higher than that of other parts. I found it to be higher. In most cases, a silicon ingot is obtained by unidirectionally solidifying the silicon melt in the mold from the bottom plate portion toward the top. Therefore, the probability of nucleation can be increased by introducing a specific additive into the release material layer on the upper surface portion of the bottom plate portion of the mold where nucleation begins first, and the crystal grain size is reduced. As a result, crystal defects on the top side of the silicon ingot can be suppressed.
上記の効果を有効に得るためには、本発明のシリコン鋳造用鋳型の離型材層は、シリコン鋳造用鋳型の内壁の底板部上面のみに設けられているのが好ましい。すなわち、鋳型の内壁の側面部には、添加物を含まない離型材層が設けられているのが好ましい。
鋳型の内壁の側面部にも特定の添加物を含む離型材層を設けた場合には、側面部でも核発生する確率が高くなり、側面部で核発生した結晶が側面から離れる方向に成長して、結晶粒界がインゴットの上下方向に対して傾斜することがある。このような結晶状態のシリコンインゴットは、その周辺部が太陽電池用として好ましいコラム状結晶とならない。 In order to effectively obtain the above effect, the release material layer of the silicon casting mold of the present invention is preferably provided only on the upper surface of the bottom plate portion of the inner wall of the silicon casting mold. That is, it is preferable that a release material layer containing no additive is provided on the side surface portion of the inner wall of the mold.
If a mold release material layer containing a specific additive is also provided on the side surface of the inner wall of the mold, the probability of nucleation at the side surface increases, and the crystal nucleated at the side surface grows away from the side surface. Thus, the crystal grain boundary may be inclined with respect to the vertical direction of the ingot. Such a crystalline silicon ingot does not have a columnar crystal whose peripheral portion is preferable for solar cells.
鋳型の内壁の側面部にも特定の添加物を含む離型材層を設けた場合には、側面部でも核発生する確率が高くなり、側面部で核発生した結晶が側面から離れる方向に成長して、結晶粒界がインゴットの上下方向に対して傾斜することがある。このような結晶状態のシリコンインゴットは、その周辺部が太陽電池用として好ましいコラム状結晶とならない。 In order to effectively obtain the above effect, the release material layer of the silicon casting mold of the present invention is preferably provided only on the upper surface of the bottom plate portion of the inner wall of the silicon casting mold. That is, it is preferable that a release material layer containing no additive is provided on the side surface portion of the inner wall of the mold.
If a mold release material layer containing a specific additive is also provided on the side surface of the inner wall of the mold, the probability of nucleation at the side surface increases, and the crystal nucleated at the side surface grows away from the side surface. Thus, the crystal grain boundary may be inclined with respect to the vertical direction of the ingot. Such a crystalline silicon ingot does not have a columnar crystal whose peripheral portion is preferable for solar cells.
添加物は、本発明の効果が得られる範囲であれば、その材質は特に限定されないが、添加物からシリコン融液およびシリコンインゴットへの混入不純物の影響、コスト、耐熱性などを考慮して、窒化珪素、炭化珪素、酸化珪素および黒鉛から選択される少なくとも1つを主成分とするのが好ましい。
The additive is not particularly limited as long as the effects of the present invention can be obtained, but considering the influence of impurities mixed into the silicon melt and silicon ingot from the additive, cost, heat resistance, etc. The main component is preferably at least one selected from silicon nitride, silicon carbide, silicon oxide and graphite.
添加物の平均粒径は、0.1~3.0mmである。
添加物の平均粒径が上記の範囲であれば、本発明のシリコン鋳造用鋳型を用いて製造されたシリコンインゴットを用いて作製されたシリコン太陽電池の出力向上が期待できる。このことはシリコンインゴット内の結晶の状態が良好であることを意味し、太陽電池のみならず他の用途にも好適なシリコンインゴットを提供できることを意味する。より好ましい範囲は0.3~2.8mmであり、さらに好ましい範囲は0.8~2.2mmである。
具体的な添加物の平均粒径(mm)は、0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9、1.0、1.5、2.0、2.5、3.0である。 The average particle size of the additive is 0.1 to 3.0 mm.
If the average particle size of the additive is in the above range, an improvement in the output of a silicon solar cell produced using a silicon ingot produced using the silicon casting mold of the present invention can be expected. This means that the crystal state in the silicon ingot is good, and that it is possible to provide a silicon ingot suitable not only for solar cells but also for other applications. A more preferable range is 0.3 to 2.8 mm, and a further preferable range is 0.8 to 2.2 mm.
The average particle size (mm) of specific additives is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, and 3.0.
添加物の平均粒径が上記の範囲であれば、本発明のシリコン鋳造用鋳型を用いて製造されたシリコンインゴットを用いて作製されたシリコン太陽電池の出力向上が期待できる。このことはシリコンインゴット内の結晶の状態が良好であることを意味し、太陽電池のみならず他の用途にも好適なシリコンインゴットを提供できることを意味する。より好ましい範囲は0.3~2.8mmであり、さらに好ましい範囲は0.8~2.2mmである。
具体的な添加物の平均粒径(mm)は、0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9、1.0、1.5、2.0、2.5、3.0である。 The average particle size of the additive is 0.1 to 3.0 mm.
If the average particle size of the additive is in the above range, an improvement in the output of a silicon solar cell produced using a silicon ingot produced using the silicon casting mold of the present invention can be expected. This means that the crystal state in the silicon ingot is good, and that it is possible to provide a silicon ingot suitable not only for solar cells but also for other applications. A more preferable range is 0.3 to 2.8 mm, and a further preferable range is 0.8 to 2.2 mm.
The average particle size (mm) of specific additives is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, and 3.0.
離型材層は、その表面に面密度0.2~8.5個/cm2で添加物を含むのが好ましい。
面密度が0.2個/cm2未満では、シリコンの結晶粒径制御の効果が低減することがある。一方、面密度が8.5個/cm2を超えると、シリコンの結晶粒径が小さくなり過ぎ、インゴットトップの結晶欠陥密度は低く抑えられるものの、電子-正孔対の再結合中心となる結晶粒界が多くなり過ぎることがある。このようなシリコンインゴットは、太陽電池の変換効率という観点から好ましくなく、上記添加物の面密度の範囲が最適値の範囲であり、より好ましい範囲は2.0~6.5個/cm2であり、さらに好ましい範囲は2.5~6.0個/cm2である。
具体的な面密度(個/cm2)は、2.0、2.5、3.0、3.5、4.0、4.5、5.0、5.5、6.0である。 The release material layer preferably contains an additive at a surface density of 0.2 to 8.5 pieces / cm 2 on the surface thereof.
If the surface density is less than 0.2 / cm 2 , the effect of controlling the crystal grain size of silicon may be reduced. On the other hand, when the areal density exceeds 8.5 / cm 2 , the crystal grain size of silicon becomes too small, and the crystal defect density of the ingot top can be kept low, but the crystal that becomes the recombination center of the electron-hole pair There may be too many grain boundaries. Such a silicon ingot is not preferable from the viewpoint of the conversion efficiency of the solar cell, and the range of the surface density of the additive is within the optimum range, and a more preferable range is 2.0 to 6.5 pieces / cm 2 . A more preferable range is 2.5 to 6.0 / cm 2 .
Specific areal densities (pieces / cm 2 ) are 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0. .
面密度が0.2個/cm2未満では、シリコンの結晶粒径制御の効果が低減することがある。一方、面密度が8.5個/cm2を超えると、シリコンの結晶粒径が小さくなり過ぎ、インゴットトップの結晶欠陥密度は低く抑えられるものの、電子-正孔対の再結合中心となる結晶粒界が多くなり過ぎることがある。このようなシリコンインゴットは、太陽電池の変換効率という観点から好ましくなく、上記添加物の面密度の範囲が最適値の範囲であり、より好ましい範囲は2.0~6.5個/cm2であり、さらに好ましい範囲は2.5~6.0個/cm2である。
具体的な面密度(個/cm2)は、2.0、2.5、3.0、3.5、4.0、4.5、5.0、5.5、6.0である。 The release material layer preferably contains an additive at a surface density of 0.2 to 8.5 pieces / cm 2 on the surface thereof.
If the surface density is less than 0.2 / cm 2 , the effect of controlling the crystal grain size of silicon may be reduced. On the other hand, when the areal density exceeds 8.5 / cm 2 , the crystal grain size of silicon becomes too small, and the crystal defect density of the ingot top can be kept low, but the crystal that becomes the recombination center of the electron-hole pair There may be too many grain boundaries. Such a silicon ingot is not preferable from the viewpoint of the conversion efficiency of the solar cell, and the range of the surface density of the additive is within the optimum range, and a more preferable range is 2.0 to 6.5 pieces / cm 2 . A more preferable range is 2.5 to 6.0 / cm 2 .
Specific areal densities (pieces / cm 2 ) are 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0. .
本発明のシリコン鋳造用鋳型は、公知の方法により製造することができ、特に限定されないが、例えば次のようにして製造することができる。
すなわち、離型材層の主材と上記の添加物とを溶剤に分散させて固形濃度1~5%程度のスラリーを調製し、得られたスラリーを鋳型の内面に塗布し、得られた塗膜を乾燥・焼成させて、離型材層を得る。
主材の粉末および添加物の粉末の量は、離型材層の表面における添加物の面密度が上記の範囲になるように適宜設定すればよい。 The silicon casting mold of the present invention can be produced by a known method, and is not particularly limited. For example, it can be produced as follows.
That is, the base material of the release material layer and the above additives are dispersed in a solvent to prepare a slurry having a solid concentration of about 1 to 5%, and the obtained slurry is applied to the inner surface of the mold. Is dried and fired to obtain a release material layer.
The amounts of the main material powder and the additive powder may be appropriately set so that the surface density of the additive on the surface of the release material layer falls within the above range.
すなわち、離型材層の主材と上記の添加物とを溶剤に分散させて固形濃度1~5%程度のスラリーを調製し、得られたスラリーを鋳型の内面に塗布し、得られた塗膜を乾燥・焼成させて、離型材層を得る。
主材の粉末および添加物の粉末の量は、離型材層の表面における添加物の面密度が上記の範囲になるように適宜設定すればよい。 The silicon casting mold of the present invention can be produced by a known method, and is not particularly limited. For example, it can be produced as follows.
That is, the base material of the release material layer and the above additives are dispersed in a solvent to prepare a slurry having a solid concentration of about 1 to 5%, and the obtained slurry is applied to the inner surface of the mold. Is dried and fired to obtain a release material layer.
The amounts of the main material powder and the additive powder may be appropriately set so that the surface density of the additive on the surface of the release material layer falls within the above range.
離型材層の主材としては、公知の離型材の材料を用いることができ、例えば、平均粒径0.1~60μmの窒化珪素、酸化珪素およびこれらの混合物の粉末が挙げられる。
具体的な平均粒径(μm)は、0.1、0.5、1.0、1.5、2.0、2.5、3.0、3.5、4.0、4.5、5.0、5.5、6.0、6.5、7.0、7.5、8.0、8.5、9.0、9.5、10、15、20、25、30、35、40、45、50、55、60である。
溶剤としては、焼成工程において消失して、離型材層に悪影響を与えないものであれば特に限定されず、例えば、ポリビニルアルコールが挙げられる。 As the main material of the release material layer, a known release material can be used, and examples thereof include powders of silicon nitride, silicon oxide and mixtures thereof having an average particle size of 0.1 to 60 μm.
Specific average particle diameters (μm) are 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5. , 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 15, 20, 25, 30 , 35, 40, 45, 50, 55, 60.
The solvent is not particularly limited as long as it disappears in the firing step and does not adversely affect the release material layer, and examples thereof include polyvinyl alcohol.
具体的な平均粒径(μm)は、0.1、0.5、1.0、1.5、2.0、2.5、3.0、3.5、4.0、4.5、5.0、5.5、6.0、6.5、7.0、7.5、8.0、8.5、9.0、9.5、10、15、20、25、30、35、40、45、50、55、60である。
溶剤としては、焼成工程において消失して、離型材層に悪影響を与えないものであれば特に限定されず、例えば、ポリビニルアルコールが挙げられる。 As the main material of the release material layer, a known release material can be used, and examples thereof include powders of silicon nitride, silicon oxide and mixtures thereof having an average particle size of 0.1 to 60 μm.
Specific average particle diameters (μm) are 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5. , 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 15, 20, 25, 30 , 35, 40, 45, 50, 55, 60.
The solvent is not particularly limited as long as it disappears in the firing step and does not adversely affect the release material layer, and examples thereof include polyvinyl alcohol.
塗布、乾燥および焼成工程は、公知の方法により条件を適宜設定して実施でき、所定の膜厚の離型材層を得るために、塗布および乾燥工程を複数回繰り返し行ってもよい。
焼成温度およびその時間は、用いる材料や形成する離型材層の膜厚などの条件にも因るが、800~1100℃程度および1~8時間程度である。
具体的な焼成温度(℃)は、800、825、850、875、900、925、950、975、1000、1025、1050、1075、1100であり、具体的な焼成時間(時間)は、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、6.5、7、7.5、8である。 The coating, drying and firing steps can be performed by appropriately setting conditions by a known method, and the coating and drying steps may be repeated a plurality of times in order to obtain a release material layer having a predetermined film thickness.
The firing temperature and the time thereof are about 800 to 1100 ° C. and about 1 to 8 hours, although depending on conditions such as the material used and the thickness of the release material layer to be formed.
Specific firing temperatures (° C.) are 800, 825, 850, 875, 900, 925, 950, 975, 1000, 1025, 1050, 1075, 1100, and specific firing times (hours) are 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8.
焼成温度およびその時間は、用いる材料や形成する離型材層の膜厚などの条件にも因るが、800~1100℃程度および1~8時間程度である。
具体的な焼成温度(℃)は、800、825、850、875、900、925、950、975、1000、1025、1050、1075、1100であり、具体的な焼成時間(時間)は、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、6.5、7、7.5、8である。 The coating, drying and firing steps can be performed by appropriately setting conditions by a known method, and the coating and drying steps may be repeated a plurality of times in order to obtain a release material layer having a predetermined film thickness.
The firing temperature and the time thereof are about 800 to 1100 ° C. and about 1 to 8 hours, although depending on conditions such as the material used and the thickness of the release material layer to be formed.
Specific firing temperatures (° C.) are 800, 825, 850, 875, 900, 925, 950, 975, 1000, 1025, 1050, 1075, 1100, and specific firing times (hours) are 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8.
離型材層の膜厚は、150~600μm程度である。
離型材層の膜厚が添加物の粒径よりも薄い場合には、本発明の効果が顕著に得られ易い。逆に、離型材層の膜厚が添加物の粒径よりも厚い場合には、添加物が離型材層の内部に埋め込まれ、離型材層の表面形状が添加物の形状に反映されず、核発生サイトとなる添加物の凸部の密度が減少するので、本発明の効果が顕著に得られ難い。
具体的な膜厚(μm)は、150、175、200、225、250、275、300、325、350、375、400、425、450、475、500、525、550、575、600である。 The film thickness of the release material layer is about 150 to 600 μm.
When the film thickness of the release material layer is thinner than the particle size of the additive, the effect of the present invention can be easily obtained. Conversely, when the film thickness of the release material layer is thicker than the particle size of the additive, the additive is embedded inside the release material layer, and the surface shape of the release material layer is not reflected in the shape of the additive, Since the density of the convex portion of the additive serving as a nucleation site is reduced, the effect of the present invention is hardly obtained.
Specific film thicknesses (μm) are 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, and 600.
離型材層の膜厚が添加物の粒径よりも薄い場合には、本発明の効果が顕著に得られ易い。逆に、離型材層の膜厚が添加物の粒径よりも厚い場合には、添加物が離型材層の内部に埋め込まれ、離型材層の表面形状が添加物の形状に反映されず、核発生サイトとなる添加物の凸部の密度が減少するので、本発明の効果が顕著に得られ難い。
具体的な膜厚(μm)は、150、175、200、225、250、275、300、325、350、375、400、425、450、475、500、525、550、575、600である。 The film thickness of the release material layer is about 150 to 600 μm.
When the film thickness of the release material layer is thinner than the particle size of the additive, the effect of the present invention can be easily obtained. Conversely, when the film thickness of the release material layer is thicker than the particle size of the additive, the additive is embedded inside the release material layer, and the surface shape of the release material layer is not reflected in the shape of the additive, Since the density of the convex portion of the additive serving as a nucleation site is reduced, the effect of the present invention is hardly obtained.
Specific film thicknesses (μm) are 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, and 600.
したがって、離型材層としての膜厚を確保しつつ本発明の効果を得るためには、添加物を含むスラリーのみを塗布して所定の膜厚の離型材層を形成してもよいが、添加物を含まず主材のみを含むスラリーを塗布した後に、添加物を含むスラリーを塗布することにより複数種の層からなる離型材層を形成してもよい。
Therefore, in order to obtain the effect of the present invention while ensuring the film thickness as the release material layer, only the slurry containing the additive may be applied to form the release material layer having a predetermined thickness. A release material layer composed of a plurality of types of layers may be formed by applying a slurry containing an additive after applying a slurry containing only the main material without containing any material.
上記のように、シリコン太陽電池用のシリコンインゴットでは、鋳型の側面から核発生はその電池特性の面から好ましくないため、離型材層は鋳型の底板部上面のみに設けられているのが好ましい。このような場合には、鋳型の底板部上面のみに添加物を含む離型材層を形成し、鋳型の側面には添加物を含まない離型材層を形成すればよい。
As described above, in a silicon ingot for a silicon solar cell, nucleation from the side surface of the mold is not preferable from the viewpoint of the battery characteristics. Therefore, the release material layer is preferably provided only on the upper surface of the bottom plate portion of the mold. In such a case, a release material layer containing an additive may be formed only on the upper surface of the bottom plate portion of the mold, and a release material layer not containing the additive may be formed on the side surface of the mold.
(シリコン鋳造方法)
本発明のシリコン鋳造方法は、本発明のシリコン鋳造用鋳型内でシリコン融液を凝固させることを特徴とする。この方法によれば、コストパフォーマンスの高い太陽電池に適したシリコンインゴットを製造することができる。
シリコン鋳造用鋳型内のシリコン融液は、鋳型内で固体のシリコン原料を融解させても、あるいは鋳型にシリコン融液を流し込んでもよい。
また、シリコン融液の凝固は、本発明の効果が得られる範囲であれば、その形態は特に限定されず、用いる装置により適宜条件を設定すればよい。
本発明のシリコン鋳造方法は、例えば、図4に示されるような公知の装置を用いて実施することができるが、本発明はこの実施形態に限定されるものではない。 (Silicon casting method)
The silicon casting method of the present invention is characterized by solidifying the silicon melt in the silicon casting mold of the present invention. According to this method, a silicon ingot suitable for a solar cell with high cost performance can be manufactured.
The silicon melt in the silicon casting mold may be obtained by melting a solid silicon raw material in the mold or by pouring the silicon melt into the mold.
The form of solidification of the silicon melt is not particularly limited as long as the effects of the present invention can be obtained, and conditions may be set as appropriate depending on the apparatus to be used.
The silicon casting method of the present invention can be carried out using, for example, a known apparatus as shown in FIG. 4, but the present invention is not limited to this embodiment.
本発明のシリコン鋳造方法は、本発明のシリコン鋳造用鋳型内でシリコン融液を凝固させることを特徴とする。この方法によれば、コストパフォーマンスの高い太陽電池に適したシリコンインゴットを製造することができる。
シリコン鋳造用鋳型内のシリコン融液は、鋳型内で固体のシリコン原料を融解させても、あるいは鋳型にシリコン融液を流し込んでもよい。
また、シリコン融液の凝固は、本発明の効果が得られる範囲であれば、その形態は特に限定されず、用いる装置により適宜条件を設定すればよい。
本発明のシリコン鋳造方法は、例えば、図4に示されるような公知の装置を用いて実施することができるが、本発明はこの実施形態に限定されるものではない。 (Silicon casting method)
The silicon casting method of the present invention is characterized by solidifying the silicon melt in the silicon casting mold of the present invention. According to this method, a silicon ingot suitable for a solar cell with high cost performance can be manufactured.
The silicon melt in the silicon casting mold may be obtained by melting a solid silicon raw material in the mold or by pouring the silicon melt into the mold.
The form of solidification of the silicon melt is not particularly limited as long as the effects of the present invention can be obtained, and conditions may be set as appropriate depending on the apparatus to be used.
The silicon casting method of the present invention can be carried out using, for example, a known apparatus as shown in FIG. 4, but the present invention is not limited to this embodiment.
図4は、本発明のシリコン鋳造方法が適用可能な鋳造装置の一例を示す概略断面図である。
この装置は、一般に多結晶シリコンインゴットを鋳造するために使用され、抵抗加熱炉を構成するチャンバー(密閉容器)7を有している。
チャンバー7の内部には、黒鉛製、石英(SiO2)製などの鋳型1が配置され、チャンバー7の内部の雰囲気を密閉状態で保持できるようになっている。
鋳型1が収容されるチャンバー7内には、鋳型1を支持する、黒鉛製の鋳型台3が配置されている。鋳型台3は、昇降駆動機構12により昇降が可能であり、その内部には冷却槽11内の冷媒(冷却水)が循環されるようになっている。
鋳型台3の上部には、黒鉛製などの外鋳型2が配置され、その中に鋳型1が配置されている。外鋳型2の代わりに、鋳型1を取り囲むような黒鉛製などのカバーが配置されていてもよい。 FIG. 4 is a schematic sectional view showing an example of a casting apparatus to which the silicon casting method of the present invention can be applied.
This apparatus is generally used for casting a polycrystalline silicon ingot, and has a chamber (sealed container) 7 constituting a resistance heating furnace.
Amold 1 made of graphite, quartz (SiO 2 ) or the like is disposed inside the chamber 7 so that the atmosphere inside the chamber 7 can be maintained in a sealed state.
In thechamber 7 in which the mold 1 is accommodated, a graphite mold table 3 that supports the mold 1 is disposed. The mold table 3 can be moved up and down by the lift drive mechanism 12, and the refrigerant (cooling water) in the cooling tank 11 is circulated therein.
Anouter mold 2 made of graphite or the like is disposed on the upper part of the mold table 3, and the mold 1 is disposed therein. Instead of the outer mold 2, a cover made of graphite or the like surrounding the mold 1 may be arranged.
この装置は、一般に多結晶シリコンインゴットを鋳造するために使用され、抵抗加熱炉を構成するチャンバー(密閉容器)7を有している。
チャンバー7の内部には、黒鉛製、石英(SiO2)製などの鋳型1が配置され、チャンバー7の内部の雰囲気を密閉状態で保持できるようになっている。
鋳型1が収容されるチャンバー7内には、鋳型1を支持する、黒鉛製の鋳型台3が配置されている。鋳型台3は、昇降駆動機構12により昇降が可能であり、その内部には冷却槽11内の冷媒(冷却水)が循環されるようになっている。
鋳型台3の上部には、黒鉛製などの外鋳型2が配置され、その中に鋳型1が配置されている。外鋳型2の代わりに、鋳型1を取り囲むような黒鉛製などのカバーが配置されていてもよい。 FIG. 4 is a schematic sectional view showing an example of a casting apparatus to which the silicon casting method of the present invention can be applied.
This apparatus is generally used for casting a polycrystalline silicon ingot, and has a chamber (sealed container) 7 constituting a resistance heating furnace.
A
In the
An
外鋳型2を取り囲むように、黒鉛ヒータのような抵抗加熱体10が配置され、さらにこれらを上方から覆うように、断熱材8が配置されている。
抵抗加熱体10は、鋳型1の周囲から加熱して、鋳型1内のシリコン原料4を融解させることができる。ここでは、発熱体として、抵抗加熱方式を挙げたが、誘導加熱方式であってもよい。 Aresistance heater 10 such as a graphite heater is disposed so as to surround the outer mold 2, and a heat insulating material 8 is disposed so as to cover these from above.
Theresistance heating body 10 can be heated from the periphery of the mold 1 to melt the silicon raw material 4 in the mold 1. Here, the resistance heating method is used as the heating element, but an induction heating method may be used.
抵抗加熱体10は、鋳型1の周囲から加熱して、鋳型1内のシリコン原料4を融解させることができる。ここでは、発熱体として、抵抗加熱方式を挙げたが、誘導加熱方式であってもよい。 A
The
鋳型1の底面の温度を検出するために、鋳型1下面中央近傍に鋳型下熱電対5が、外鋳型下面の中央近傍に外鋳型下熱電対6がそれぞれ配置され、これらの出力を制御装置9に入力し、抵抗加熱体10による加熱状態を制御する。上記の熱電対以外にも温度を検出するための熱電対や放射温度計が配置されていてもよく、また上記熱電対設置位置も特に限定されない。
In order to detect the temperature of the bottom surface of the mold 1, a lower mold thermocouple 5 is disposed near the center of the lower surface of the mold 1, and an outer lower mold thermocouple 6 is disposed near the center of the lower surface of the outer mold. And the heating state by the resistance heater 10 is controlled. In addition to the thermocouple described above, a thermocouple or a radiation thermometer for detecting the temperature may be disposed, and the thermocouple installation position is not particularly limited.
チャンバー7は、外部の酸素ガス、窒素ガスなどが流入しないように、その内部を密閉状態に保持でき、通常、多結晶シリコンなどのシリコン原料を投入した後でその溶融前に、チャンバー7内を真空にし、その後アルゴンガスなどの不活性ガスを導入して、不活性な雰囲気に保持する。
The inside of the chamber 7 can be kept in a sealed state so that external oxygen gas, nitrogen gas, etc. do not flow in. Normally, after the silicon raw material such as polycrystalline silicon is charged and before the melting, A vacuum is applied, and then an inert gas such as argon gas is introduced to maintain an inert atmosphere.
このような構成の装置により、基本的に、鋳型1へのシリコン原料4の充填、脱気(真空化)および不活性ガスの導入によるチャンバー7内のガス置換、加熱によるシリコン原料4の溶融、溶融確認とその保持、温度制御および昇降駆動機構12の動作による凝固開始、固化完了確認およびアニールならびにインゴット取り出しの工程により、多結晶シリコンインゴットを鋳造する。なお、ここではシリコン原料を鋳型内で加熱、溶融するタイプの装置の例を挙げたが、その他にもシリコン鋳造用鋳型とは別の坩堝等でシリコン原料を加熱溶融し、シリコン融液をシリコン鋳造用鋳型に注湯するタイプの装置なども利用できる。
By the apparatus having such a configuration, basically, filling of the silicon raw material 4 into the mold 1, degassing (evacuation) and gas replacement in the chamber 7 by introducing an inert gas, melting of the silicon raw material 4 by heating, The polycrystalline silicon ingot is cast by the steps of melting confirmation and holding, temperature control and solidification start by operation of the lifting drive mechanism 12, solidification completion confirmation and annealing, and ingot removal. Here, an example of an apparatus of a type that heats and melts a silicon raw material in a mold is given, but other than that, a silicon raw material is heated and melted in a crucible or the like different from a silicon casting mold, and a silicon melt is converted into silicon A type of apparatus that pours into a casting mold can also be used.
(シリコン材料)
本発明のシリコン材料は、本発明のシリコン鋳造方法により製造される。
すなわち、本発明のシリコン材料は、例えば、本発明のシリコン鋳造用鋳型内のシリコン融液を凝固させることによって製造された「多結晶シリコンインゴット」、それを角柱状に切り出した「多結晶シリコンブロック」およびそれをスライス加工した「多結晶シリコンウエハ」を意味する。これらのシリコン材料は、コストパフォーマンスの高い太陽電池の材料に適する。 (Silicon material)
The silicon material of the present invention is produced by the silicon casting method of the present invention.
That is, the silicon material of the present invention includes, for example, a “polycrystalline silicon ingot” produced by solidifying the silicon melt in the silicon casting mold of the present invention, and a “polycrystalline silicon block” obtained by cutting it into a prismatic shape. And a “polycrystalline silicon wafer” obtained by slicing the same. These silicon materials are suitable for materials for solar cells with high cost performance.
本発明のシリコン材料は、本発明のシリコン鋳造方法により製造される。
すなわち、本発明のシリコン材料は、例えば、本発明のシリコン鋳造用鋳型内のシリコン融液を凝固させることによって製造された「多結晶シリコンインゴット」、それを角柱状に切り出した「多結晶シリコンブロック」およびそれをスライス加工した「多結晶シリコンウエハ」を意味する。これらのシリコン材料は、コストパフォーマンスの高い太陽電池の材料に適する。 (Silicon material)
The silicon material of the present invention is produced by the silicon casting method of the present invention.
That is, the silicon material of the present invention includes, for example, a “polycrystalline silicon ingot” produced by solidifying the silicon melt in the silicon casting mold of the present invention, and a “polycrystalline silicon block” obtained by cutting it into a prismatic shape. And a “polycrystalline silicon wafer” obtained by slicing the same. These silicon materials are suitable for materials for solar cells with high cost performance.
「多結晶シリコンブロック」は、例えば、バンドソーなどの公知の装置を用いて、上記の「多結晶シリコンインゴット」を角柱状、所望のサイズに加工することにより得ることができる。
加工において、鋳型材料などの不純物が拡散されているおそれのある、多結晶シリコンインゴットの表面部分を切断してもよく、必要に応じて、多結晶シリコンブロックの表面を研磨加工してもよい。 The “polycrystalline silicon block” can be obtained, for example, by processing the above-mentioned “polycrystalline silicon ingot” into a prismatic shape and a desired size using a known apparatus such as a band saw.
In the processing, the surface portion of the polycrystalline silicon ingot where impurities such as a mold material may be diffused may be cut, and the surface of the polycrystalline silicon block may be polished if necessary.
加工において、鋳型材料などの不純物が拡散されているおそれのある、多結晶シリコンインゴットの表面部分を切断してもよく、必要に応じて、多結晶シリコンブロックの表面を研磨加工してもよい。 The “polycrystalline silicon block” can be obtained, for example, by processing the above-mentioned “polycrystalline silicon ingot” into a prismatic shape and a desired size using a known apparatus such as a band saw.
In the processing, the surface portion of the polycrystalline silicon ingot where impurities such as a mold material may be diffused may be cut, and the surface of the polycrystalline silicon block may be polished if necessary.
「多結晶シリコンウエハ」は、例えば、マルチワイヤーソーなどの公知の装置を用いて、上記の「多結晶シリコンブロック」を所望の厚さにスライス加工することにより得ることができる。
現状では、厚さ170~200μm程度が一般的であるが、傾向としてはコスト削減のため、薄型化の傾向にある。また、必要に応じて、多結晶シリコンウエハの表面を研磨加工してもよい。 The “polycrystalline silicon wafer” can be obtained, for example, by slicing the above “polycrystalline silicon block” to a desired thickness using a known apparatus such as a multi-wire saw.
At present, a thickness of about 170 to 200 μm is generally used, but the trend is to reduce the thickness for cost reduction. Further, if necessary, the surface of the polycrystalline silicon wafer may be polished.
現状では、厚さ170~200μm程度が一般的であるが、傾向としてはコスト削減のため、薄型化の傾向にある。また、必要に応じて、多結晶シリコンウエハの表面を研磨加工してもよい。 The “polycrystalline silicon wafer” can be obtained, for example, by slicing the above “polycrystalline silicon block” to a desired thickness using a known apparatus such as a multi-wire saw.
At present, a thickness of about 170 to 200 μm is generally used, but the trend is to reduce the thickness for cost reduction. Further, if necessary, the surface of the polycrystalline silicon wafer may be polished.
(シリコン太陽電池)
本発明のシリコン太陽電池は、本発明のシリコン材料(多結晶シリコンウエハ)を基板として用いて製造される。
シリコン太陽電池には、様々な構造のものが存在するが、これらは、本発明のシリコンウエハを用いて、公知の太陽電池プロセスにより製造することができる。例えば、p型の不純物がドープされたシリコンウエハの場合、n型の不純物(例えばリン)を表面から拡散(ドープ)させてn型層を形成してpn接合を形成し、表面電極および裏面電極を形成して多結晶シリコン太陽電池セルを得る。同様に、n型の不純物がドープされたシリコンウエハの場合、p型の不純物(例えばボロン)を表面から拡散(ドープ)させてp型層を形成してpn接合を形成し、表面電極および裏面電極を形成して多結晶シリコン太陽電池セルを得る。あるいは、これらシリコン同士のpn接合を利用したものの他にも、薄い絶縁層を挟んで金属を蒸着するなどしたMIS型太陽電池、例えばシリコンウエハと反対の導電型のアモルファスなどのシリコン薄膜を製膜し、異なる構造のp型、n型シリコンヘテロ接合を利用したものなどがある。また、その複数個を電気的に接続することで、多結晶シリコン太陽電池モジュールを得る。 (Silicon solar cell)
The silicon solar cell of the present invention is manufactured using the silicon material (polycrystalline silicon wafer) of the present invention as a substrate.
Although silicon solar cells have various structures, these can be manufactured by a known solar cell process using the silicon wafer of the present invention. For example, in the case of a silicon wafer doped with a p-type impurity, an n-type impurity (for example, phosphorus) is diffused (doped) from the surface to form an n-type layer to form a pn junction, and a front electrode and a back electrode To obtain a polycrystalline silicon solar battery cell. Similarly, in the case of a silicon wafer doped with an n-type impurity, a p-type impurity (for example, boron) is diffused (doped) from the surface to form a p-type layer to form a pn junction, and a front electrode and a back surface An electrode is formed to obtain a polycrystalline silicon solar cell. Alternatively, in addition to those using pn junctions between silicon, MIS type solar cells in which a metal is deposited with a thin insulating layer interposed therebetween, for example, a silicon thin film of an amorphous type having a conductivity type opposite to a silicon wafer is formed. However, there are those using p-type and n-type silicon heterojunctions having different structures. In addition, a polycrystalline silicon solar cell module is obtained by electrically connecting a plurality of them.
本発明のシリコン太陽電池は、本発明のシリコン材料(多結晶シリコンウエハ)を基板として用いて製造される。
シリコン太陽電池には、様々な構造のものが存在するが、これらは、本発明のシリコンウエハを用いて、公知の太陽電池プロセスにより製造することができる。例えば、p型の不純物がドープされたシリコンウエハの場合、n型の不純物(例えばリン)を表面から拡散(ドープ)させてn型層を形成してpn接合を形成し、表面電極および裏面電極を形成して多結晶シリコン太陽電池セルを得る。同様に、n型の不純物がドープされたシリコンウエハの場合、p型の不純物(例えばボロン)を表面から拡散(ドープ)させてp型層を形成してpn接合を形成し、表面電極および裏面電極を形成して多結晶シリコン太陽電池セルを得る。あるいは、これらシリコン同士のpn接合を利用したものの他にも、薄い絶縁層を挟んで金属を蒸着するなどしたMIS型太陽電池、例えばシリコンウエハと反対の導電型のアモルファスなどのシリコン薄膜を製膜し、異なる構造のp型、n型シリコンヘテロ接合を利用したものなどがある。また、その複数個を電気的に接続することで、多結晶シリコン太陽電池モジュールを得る。 (Silicon solar cell)
The silicon solar cell of the present invention is manufactured using the silicon material (polycrystalline silicon wafer) of the present invention as a substrate.
Although silicon solar cells have various structures, these can be manufactured by a known solar cell process using the silicon wafer of the present invention. For example, in the case of a silicon wafer doped with a p-type impurity, an n-type impurity (for example, phosphorus) is diffused (doped) from the surface to form an n-type layer to form a pn junction, and a front electrode and a back electrode To obtain a polycrystalline silicon solar battery cell. Similarly, in the case of a silicon wafer doped with an n-type impurity, a p-type impurity (for example, boron) is diffused (doped) from the surface to form a p-type layer to form a pn junction, and a front electrode and a back surface An electrode is formed to obtain a polycrystalline silicon solar cell. Alternatively, in addition to those using pn junctions between silicon, MIS type solar cells in which a metal is deposited with a thin insulating layer interposed therebetween, for example, a silicon thin film of an amorphous type having a conductivity type opposite to a silicon wafer is formed. However, there are those using p-type and n-type silicon heterojunctions having different structures. In addition, a polycrystalline silicon solar cell module is obtained by electrically connecting a plurality of them.
上記のように、本明細書においては、「太陽電池セル」と「太陽電池モジュール」とを含む概念として、単に「太陽電池」と称する。したがって、例えば、「多結晶シリコン太陽電池」と記載されたものがあれば、それは「多結晶シリコン太陽電池セル」および「多結晶シリコン太陽電池モジュール」を含む意味となる。
As described above, in this specification, the concept including “solar battery cell” and “solar battery module” is simply referred to as “solar battery”. Therefore, for example, what is described as “polycrystalline silicon solar cell” is meant to include “polycrystalline silicon solar cell” and “polycrystalline silicon solar cell module”.
以下に試験例により本発明を具体的に説明するが、これらの試験例により本発明が限定されるものではない。
Hereinafter, the present invention will be described in detail by test examples, but the present invention is not limited by these test examples.
(試験例1)離型材層に含まれる添加物の平均粒径に関する検討
鋳型底板部上面のみに、特定の平均粒径を有する各種材質の添加物を含む離型材層を塗布形成した石英製のシリコン鋳造用鋳型1を用いて、多結晶シリコンインゴットを製造し、得られたインゴットから多結晶シリコンウエハを加工し、得られたウエハを用いてシリコン太陽電池を作製し、得られた太陽電池の出力と添加物の平均粒径との関係を評価した。 (Test Example 1) Examination on average particle diameter of additive contained in release material layer Quartz made by applying a release material layer containing additives of various materials having specific average particle diameter only on the upper surface of the mold bottom plate A polycrystalline silicon ingot is manufactured using thesilicon casting mold 1, a polycrystalline silicon wafer is processed from the obtained ingot, a silicon solar cell is manufactured using the obtained wafer, and the obtained solar cell The relationship between the output and the average particle size of the additive was evaluated.
鋳型底板部上面のみに、特定の平均粒径を有する各種材質の添加物を含む離型材層を塗布形成した石英製のシリコン鋳造用鋳型1を用いて、多結晶シリコンインゴットを製造し、得られたインゴットから多結晶シリコンウエハを加工し、得られたウエハを用いてシリコン太陽電池を作製し、得られた太陽電池の出力と添加物の平均粒径との関係を評価した。 (Test Example 1) Examination on average particle diameter of additive contained in release material layer Quartz made by applying a release material layer containing additives of various materials having specific average particle diameter only on the upper surface of the mold bottom plate A polycrystalline silicon ingot is manufactured using the
離型材層の主材としての粒径1~60μmの窒化珪素粉末と3%ポリビニルアルコール水溶液を重量比が1:1となるように混合し、表1に示す添加物の粉末を加え分散させてスラリーAを得た。
なお、添加物の粉末の量は、下記のように添加物の面密度が約3.0個/cm2になるように適宜設定した。
同様に、窒化珪素粉末と3%ポリビニルアルコール水溶液を重量比が1:1となるように混合し、分散させてスラリーBを得た。
鋳型の側面部はスラリーBのみを塗布し約50℃で乾燥させ、得られた塗膜を900℃で2時間焼成して、鋳型の側面部に膜厚約250μmの離型材層を形成した。 A silicon nitride powder having a particle diameter of 1 to 60 μm as a main material of the release material layer and a 3% polyvinyl alcohol aqueous solution are mixed so that the weight ratio is 1: 1, and the additive powder shown in Table 1 is added and dispersed. A slurry A was obtained.
The amount of the additive powder was appropriately set so that the surface density of the additive was about 3.0 / cm 2 as described below.
Similarly, a silicon nitride powder and a 3% polyvinyl alcohol aqueous solution were mixed so that the weight ratio was 1: 1 and dispersed to obtain slurry B.
The side surface portion of the mold was coated with only slurry B and dried at about 50 ° C., and the resulting coating film was baked at 900 ° C. for 2 hours to form a release material layer having a thickness of about 250 μm on the side surface portion of the mold.
なお、添加物の粉末の量は、下記のように添加物の面密度が約3.0個/cm2になるように適宜設定した。
同様に、窒化珪素粉末と3%ポリビニルアルコール水溶液を重量比が1:1となるように混合し、分散させてスラリーBを得た。
鋳型の側面部はスラリーBのみを塗布し約50℃で乾燥させ、得られた塗膜を900℃で2時間焼成して、鋳型の側面部に膜厚約250μmの離型材層を形成した。 A silicon nitride powder having a particle diameter of 1 to 60 μm as a main material of the release material layer and a 3% polyvinyl alcohol aqueous solution are mixed so that the weight ratio is 1: 1, and the additive powder shown in Table 1 is added and dispersed. A slurry A was obtained.
The amount of the additive powder was appropriately set so that the surface density of the additive was about 3.0 / cm 2 as described below.
Similarly, a silicon nitride powder and a 3% polyvinyl alcohol aqueous solution were mixed so that the weight ratio was 1: 1 and dispersed to obtain slurry B.
The side surface portion of the mold was coated with only slurry B and dried at about 50 ° C., and the resulting coating film was baked at 900 ° C. for 2 hours to form a release material layer having a thickness of about 250 μm on the side surface portion of the mold.
表1に塗布方法を「表層」として示す離型材層は、添加物を含まない下層と添加物を含む上層からなり、次のようにして形成した。
得られたスラリーBを鋳型の底板部上面のみに塗布し約50℃で乾燥させ、次いで得られたスラリーAを鋳型の底板部上面のみに塗布し約50℃で乾燥させ、得られた塗膜を900℃で2時間焼成して、添加物の面密度約3.0個/cm2、膜厚約250μmの離型材層を形成した。 The release material layer whose coating method is shown as “surface layer” in Table 1 is composed of a lower layer containing no additive and an upper layer containing the additive, and was formed as follows.
The obtained slurry B is applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C., and then the obtained slurry A is applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C. Was fired at 900 ° C. for 2 hours to form a release material layer with an additive surface density of about 3.0 / cm 2 and a film thickness of about 250 μm.
得られたスラリーBを鋳型の底板部上面のみに塗布し約50℃で乾燥させ、次いで得られたスラリーAを鋳型の底板部上面のみに塗布し約50℃で乾燥させ、得られた塗膜を900℃で2時間焼成して、添加物の面密度約3.0個/cm2、膜厚約250μmの離型材層を形成した。 The release material layer whose coating method is shown as “surface layer” in Table 1 is composed of a lower layer containing no additive and an upper layer containing the additive, and was formed as follows.
The obtained slurry B is applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C., and then the obtained slurry A is applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C. Was fired at 900 ° C. for 2 hours to form a release material layer with an additive surface density of about 3.0 / cm 2 and a film thickness of about 250 μm.
一方、表1に塗布方法を「混合」として示す離型材層は、添加物を含む層のみからなり、次のようにして形成した。
得られたスラリーAを鋳型の底板部上面のみに塗布し約50℃で乾燥させ、得られた塗膜を900℃で2時間焼成して、添加物の面密度約3.0個/cm2、膜厚約250μmの離型材層を形成した。
なお、所定の膜厚を得るために、適宜スラリーの塗布と乾燥を繰り返した。
また、上記の焼成は、鋳型側面および底板部上面の塗膜について同時に行った。
また本試験例では、主材としての窒化珪素粉末と添加物を含むスラリーAを用いたが、添加物のみを含むスラリーも同様に用いることができる。
また、ここでは離型材の主材として窒化珪素を用いた例を示したが、本発明は窒化珪素に限定されず、他の材料あるいは、窒化珪素と酸化珪素の複数の層構造などでも、本発明の効果が得られる範囲内であればよい。 On the other hand, the release material layer whose application method is shown as “mixing” in Table 1 consists of only the layer containing the additive, and was formed as follows.
The obtained slurry A was applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C., and the obtained coating film was baked at 900 ° C. for 2 hours to obtain an additive surface density of about 3.0 / cm 2. A release material layer having a thickness of about 250 μm was formed.
In order to obtain a predetermined film thickness, application and drying of the slurry were repeated as appropriate.
Moreover, said baking was performed simultaneously about the coating film of a mold side surface and a baseplate part upper surface.
Further, in this test example, the slurry A containing silicon nitride powder and additive as the main material was used, but slurry containing only the additive can also be used.
In addition, although an example in which silicon nitride is used as the main material of the release material is shown here, the present invention is not limited to silicon nitride, and other materials or a multiple layer structure of silicon nitride and silicon oxide may be used. It may be within the range where the effects of the invention can be obtained.
得られたスラリーAを鋳型の底板部上面のみに塗布し約50℃で乾燥させ、得られた塗膜を900℃で2時間焼成して、添加物の面密度約3.0個/cm2、膜厚約250μmの離型材層を形成した。
なお、所定の膜厚を得るために、適宜スラリーの塗布と乾燥を繰り返した。
また、上記の焼成は、鋳型側面および底板部上面の塗膜について同時に行った。
また本試験例では、主材としての窒化珪素粉末と添加物を含むスラリーAを用いたが、添加物のみを含むスラリーも同様に用いることができる。
また、ここでは離型材の主材として窒化珪素を用いた例を示したが、本発明は窒化珪素に限定されず、他の材料あるいは、窒化珪素と酸化珪素の複数の層構造などでも、本発明の効果が得られる範囲内であればよい。 On the other hand, the release material layer whose application method is shown as “mixing” in Table 1 consists of only the layer containing the additive, and was formed as follows.
The obtained slurry A was applied only to the upper surface of the bottom plate portion of the mold and dried at about 50 ° C., and the obtained coating film was baked at 900 ° C. for 2 hours to obtain an additive surface density of about 3.0 / cm 2. A release material layer having a thickness of about 250 μm was formed.
In order to obtain a predetermined film thickness, application and drying of the slurry were repeated as appropriate.
Moreover, said baking was performed simultaneously about the coating film of a mold side surface and a baseplate part upper surface.
Further, in this test example, the slurry A containing silicon nitride powder and additive as the main material was used, but slurry containing only the additive can also be used.
In addition, although an example in which silicon nitride is used as the main material of the release material is shown here, the present invention is not limited to silicon nitride, and other materials or a multiple layer structure of silicon nitride and silicon oxide may be used. It may be within the range where the effects of the invention can be obtained.
図4に示される鋳造装置内の断熱材8で囲われた黒鉛製の鋳型台3(880mm×880mm×厚さ200mm)上に、黒鉛製の外鋳型2(内寸:900mm×900mm×高さ460mm、底板肉厚および側面肉厚20mm)を設置し、その中に石英製の鋳型1(内寸:830mm×830mm×420mm、底板肉厚および側面肉厚22mm)を設置した。また、温度測定用の熱電対5および6を、それぞれ鋳型1下面中央近傍および外鋳型2下面中央近傍の2ヵ所に設置した。
On the graphite mold base 3 (880 mm × 880 mm × thickness 200 mm) surrounded by the heat insulating material 8 in the casting apparatus shown in FIG. 4, the graphite outer mold 2 (inner dimensions: 900 mm × 900 mm × height) 460 mm, bottom plate thickness and side wall thickness 20 mm) were set, and quartz mold 1 (inner dimensions: 830 mm × 830 mm × 420 mm, bottom plate thickness and side wall thickness 22 mm) was set therein. Further, thermocouples 5 and 6 for temperature measurement were respectively installed at two locations near the center of the lower surface of the mold 1 and near the center of the lower surface of the outer mold 2.
次いで、インゴットの比抵抗が約1.4Ωcmになるようにボロンの濃度を調整したシリコン原料4の420kgを鋳型1にチャージした後、装置のチャンバー7内を真空引きし、アルゴンガスで置換した。その後、装置の加熱手段として鋳型横に配置された抵抗加熱体(黒鉛ヒータ)10および制御装置9を用いてシリコン原料4を融解し、全原料の融解を確認した後、制御装置9および冷却槽11を備えた昇降駆動機構12を用いて、所定の条件(凝固速度約8mm/時間)でシリコンを一方向凝固させた。
Next, after 420 kg of silicon raw material 4 whose boron concentration was adjusted so that the specific resistance of the ingot was about 1.4 Ωcm was charged to the mold 1, the inside of the chamber 7 of the apparatus was evacuated and replaced with argon gas. Thereafter, the silicon raw material 4 is melted by using a resistance heating element (graphite heater) 10 and a control device 9 arranged next to the mold as heating means of the device, and after confirming the melting of all the raw materials, the control device 9 and the cooling bath Silicon was unidirectionally solidified under a predetermined condition (solidification rate of about 8 mm / hour) by using an elevating drive mechanism 12 having 11.
得られたそれぞれの多結晶シリコンインゴットを、バンドソーを用いて多結晶シリコンブロック(156mm×156mm×200mm)25本に加工し、さらにワイヤーソーを用いてスライスして、多結晶シリコンウエハ(156mm×156mm×厚さ0.18mm)約12,000枚を得た。
Each obtained polycrystalline silicon ingot was processed into 25 polycrystalline silicon blocks (156 mm × 156 mm × 200 mm) using a band saw, further sliced using a wire saw, and then a polycrystalline silicon wafer (156 mm × 156 mm). X thickness 0.18 mm) About 12,000 sheets were obtained.
得られた多結晶シリコンウエハを通常の太陽電池セルプロセスに投入して、1つのインゴット当たり約12,000個の太陽電池セル(外形156mm×156mm×厚さ0.18mm)を作製し、その出力(W)を測定した。各インゴット単位で出力の平均値を算出し、規格化した結果を表1に示す。
規格化には、添加物を含まない離型材層を形成した鋳型で鋳造したインゴットから得られた太陽電池セルの平均出力を用い、これを100としたときの各インゴット単位で算出した出力の平均値を算出した。 The obtained polycrystalline silicon wafer is put into a normal solar cell process to produce about 12,000 solar cells (outer dimensions 156 mm × 156 mm × thickness 0.18 mm) per ingot, and its output (W) was measured. Table 1 shows the result of calculating and standardizing the average value of the output for each ingot unit.
For normalization, the average output of solar cells obtained from an ingot cast from a mold in which a release material layer containing no additive was formed was used, and the average of the outputs calculated in units of each ingot when this was taken as 100. The value was calculated.
規格化には、添加物を含まない離型材層を形成した鋳型で鋳造したインゴットから得られた太陽電池セルの平均出力を用い、これを100としたときの各インゴット単位で算出した出力の平均値を算出した。 The obtained polycrystalline silicon wafer is put into a normal solar cell process to produce about 12,000 solar cells (outer dimensions 156 mm × 156 mm × thickness 0.18 mm) per ingot, and its output (W) was measured. Table 1 shows the result of calculating and standardizing the average value of the output for each ingot unit.
For normalization, the average output of solar cells obtained from an ingot cast from a mold in which a release material layer containing no additive was formed was used, and the average of the outputs calculated in units of each ingot when this was taken as 100. The value was calculated.
1つのインゴット内で太陽電池の出力が低下する原因の大部分は、シリコン原料が太陽電池用として十分に高純度である場合には、インゴットのトップ側での結晶欠陥、およびインゴットのボトム側での鋳型および離型材からの不純物拡散のいずれかであると考えられる。したがって、所定の条件で一方向凝固したインゴットでは、凝固時間がほぼ一定であるため、インゴットのボトム側の不純物拡散に大きな差はなく、各インゴットから得られた太陽電池セルの出力平均を比較することでインゴットトップ側での結晶欠陥を評価できる。
Most of the causes of the decrease in the output of the solar cell in one ingot are that when the silicon raw material is sufficiently high purity for the solar cell, the crystal defect on the top side of the ingot and the bottom side of the ingot This is considered to be one of impurity diffusion from the mold and mold release material. Therefore, ingots solidified in one direction under a predetermined condition have a substantially constant solidification time, so there is no significant difference in impurity diffusion on the bottom side of the ingot, and the average output of solar cells obtained from each ingot is compared. Thus, the crystal defects on the ingot top side can be evaluated.
また、離型材層に含まれる添加物の粒径が大きい場合には、多結晶シリコンインゴットのブロック加工の際に、ボトム側で応力に起因すると考えられる割れが発生した。この割れの有無についても表1に示す。
さらに、図1には、シリコン鋳造用鋳型の離型材層に含まれる添加物の粒径と、太陽電池セルの平均出力の関係を示す。 Moreover, when the particle size of the additive contained in the release material layer was large, cracks that were thought to be caused by stress occurred on the bottom side during the block processing of the polycrystalline silicon ingot. The presence or absence of this crack is also shown in Table 1.
Furthermore, FIG. 1 shows the relationship between the particle size of the additive contained in the release material layer of the mold for casting silicon and the average output of the solar battery cell.
さらに、図1には、シリコン鋳造用鋳型の離型材層に含まれる添加物の粒径と、太陽電池セルの平均出力の関係を示す。 Moreover, when the particle size of the additive contained in the release material layer was large, cracks that were thought to be caused by stress occurred on the bottom side during the block processing of the polycrystalline silicon ingot. The presence or absence of this crack is also shown in Table 1.
Furthermore, FIG. 1 shows the relationship between the particle size of the additive contained in the release material layer of the mold for casting silicon and the average output of the solar battery cell.
表1および図1の結果から明らかなように、太陽電池セルの平均出力は、添加物の材質が炭化珪素、酸化珪素、窒化珪素および黒鉛に因らず、添加物の平均粒径に依存することがわかる。すなわち、添加物の平均粒径が0.1~3.0mmの範囲である場合は、添加物を含まない離型材層のみの場合よりも平均出力が向上している。特に添加物の平均粒径が0.3~2.8mmの範囲である場合には、相対的な平均出力の向上率が0.5%以上であり、添加物の平均粒径が0.8~2.2mmの範囲である場合には、相対的な平均出力の向上率が1.0%以上という好ましい結果になっている。したがって、このように平均出力が向上した太陽電池セルを用いて作製した太陽電池モジュールの出力が向上することは明らかである。
また、添加物の平均粒径が0.1~3.0mmの範囲である場合には、シリコンブロックのボトム側での割れがなく、良好である。 As is apparent from the results of Table 1 and FIG. 1, the average output of the solar battery cell depends on the average particle diameter of the additive regardless of the material of the additive, silicon carbide, silicon oxide, silicon nitride and graphite. I understand that. That is, when the average particle diameter of the additive is in the range of 0.1 to 3.0 mm, the average output is improved as compared with the case of only the release material layer not containing the additive. Particularly when the average particle size of the additive is in the range of 0.3 to 2.8 mm, the improvement rate of the relative average output is 0.5% or more, and the average particle size of the additive is 0.8%. In the range of ˜2.2 mm, the relative average output improvement rate is a preferable result of 1.0% or more. Therefore, it is clear that the output of the solar battery module manufactured using the solar battery cells with improved average output is improved.
Further, when the average particle size of the additive is in the range of 0.1 to 3.0 mm, there is no crack on the bottom side of the silicon block, which is good.
また、添加物の平均粒径が0.1~3.0mmの範囲である場合には、シリコンブロックのボトム側での割れがなく、良好である。 As is apparent from the results of Table 1 and FIG. 1, the average output of the solar battery cell depends on the average particle diameter of the additive regardless of the material of the additive, silicon carbide, silicon oxide, silicon nitride and graphite. I understand that. That is, when the average particle diameter of the additive is in the range of 0.1 to 3.0 mm, the average output is improved as compared with the case of only the release material layer not containing the additive. Particularly when the average particle size of the additive is in the range of 0.3 to 2.8 mm, the improvement rate of the relative average output is 0.5% or more, and the average particle size of the additive is 0.8%. In the range of ˜2.2 mm, the relative average output improvement rate is a preferable result of 1.0% or more. Therefore, it is clear that the output of the solar battery module manufactured using the solar battery cells with improved average output is improved.
Further, when the average particle size of the additive is in the range of 0.1 to 3.0 mm, there is no crack on the bottom side of the silicon block, which is good.
(試験例2)離型材層に含まれる添加物の面密度に関する検討
鋳型底板部上面のみに、特定の添加物の面密度を有する、平均粒径0.8mmの各種材質の添加物を含む離型材層を塗布形成した石英製のシリコン鋳造用鋳型1を用いて、試験例1と同様にして、多結晶シリコンインゴットを製造し、得られたインゴットから多結晶シリコンウエハを加工し、得られたウエハを用いてシリコン太陽電池を作製し、得られた太陽電池の出力と添加物の面密度との関係を評価した。 (Test Example 2) Examination of surface density of additives contained in mold release material layer Only the upper surface of the mold bottom plate portion includes a material having an area density of a specific additive and additives of various materials having an average particle diameter of 0.8 mm. A polycrystalline silicon ingot was produced in the same manner as in Test Example 1 using a quartzsilicon casting mold 1 coated with a mold material layer, and a polycrystalline silicon wafer was processed from the obtained ingot. A silicon solar cell was produced using the wafer, and the relationship between the output of the obtained solar cell and the surface density of the additive was evaluated.
鋳型底板部上面のみに、特定の添加物の面密度を有する、平均粒径0.8mmの各種材質の添加物を含む離型材層を塗布形成した石英製のシリコン鋳造用鋳型1を用いて、試験例1と同様にして、多結晶シリコンインゴットを製造し、得られたインゴットから多結晶シリコンウエハを加工し、得られたウエハを用いてシリコン太陽電池を作製し、得られた太陽電池の出力と添加物の面密度との関係を評価した。 (Test Example 2) Examination of surface density of additives contained in mold release material layer Only the upper surface of the mold bottom plate portion includes a material having an area density of a specific additive and additives of various materials having an average particle diameter of 0.8 mm. A polycrystalline silicon ingot was produced in the same manner as in Test Example 1 using a quartz
得られた結果を表2および図2に示す。図2には、シリコン鋳造用鋳型の離型材層に含まれる添加物の面密度と、太陽電池セルの平均出力の関係を示す。
The obtained results are shown in Table 2 and FIG. FIG. 2 shows the relationship between the surface density of the additive contained in the release material layer of the silicon casting mold and the average output of the solar cells.
表2および図2の結果から明らかなように、太陽電池セルの平均出力は、添加物の材質および離型材層の塗布方法に因らず、添加物の面密度に依存することがわかる。すなわち、添加物の面密度が0.2~8.5個/cm2の範囲である場合は、添加物を含まない離型材層のみの場合よりも平均出力が向上している。特に添加物の面密度が2.0~6.5個/cm2の範囲である場合には、相対的な平均出力の向上率が0.5%以上であり、添加物の面密度が2.5~6.0個/cm2の範囲である場合には、相対的な平均出力の向上率が1.0%以上という好ましい結果になっている。したがって、このように平均出力が向上した太陽電池セルを用いて作製した太陽電池モジュールの出力が向上することは明らかである。
なお、試験例2では、平均粒径0.8mmの比較的細かい添加物を用いたため、シリコンブロックのボトム側での割れはなく、良好であった。 As is apparent from the results of Table 2 and FIG. 2, it can be seen that the average output of the solar cell depends on the surface density of the additive, regardless of the material of the additive and the method of applying the release layer. That is, when the surface density of the additive is in the range of 0.2 to 8.5 pieces / cm 2 , the average output is improved as compared with the case of only the release material layer not containing the additive. In particular, when the surface density of the additive is in the range of 2.0 to 6.5 pieces / cm 2 , the improvement rate of the relative average output is 0.5% or more, and the surface density of the additive is 2%. In the case of the range of 0.5 to 6.0 / cm 2 , the improvement rate of the relative average output is a preferable result of 1.0% or more. Therefore, it is clear that the output of the solar battery module manufactured using the solar battery cells with improved average output is improved.
In Test Example 2, since a relatively fine additive having an average particle diameter of 0.8 mm was used, there was no crack on the bottom side of the silicon block, which was good.
なお、試験例2では、平均粒径0.8mmの比較的細かい添加物を用いたため、シリコンブロックのボトム側での割れはなく、良好であった。 As is apparent from the results of Table 2 and FIG. 2, it can be seen that the average output of the solar cell depends on the surface density of the additive, regardless of the material of the additive and the method of applying the release layer. That is, when the surface density of the additive is in the range of 0.2 to 8.5 pieces / cm 2 , the average output is improved as compared with the case of only the release material layer not containing the additive. In particular, when the surface density of the additive is in the range of 2.0 to 6.5 pieces / cm 2 , the improvement rate of the relative average output is 0.5% or more, and the surface density of the additive is 2%. In the case of the range of 0.5 to 6.0 / cm 2 , the improvement rate of the relative average output is a preferable result of 1.0% or more. Therefore, it is clear that the output of the solar battery module manufactured using the solar battery cells with improved average output is improved.
In Test Example 2, since a relatively fine additive having an average particle diameter of 0.8 mm was used, there was no crack on the bottom side of the silicon block, which was good.
1 鋳型
2 外鋳型
3 鋳型台
4 シリコン原料
5 鋳型下熱電対
6 外鋳型下熱電対
7 チャンバー
8 断熱材
9 制御装置
10 抵抗加熱体(黒鉛ヒータ)
11 冷却槽
12 昇降駆動機構 DESCRIPTION OFSYMBOLS 1 Mold 2 Outer mold 3 Mold stand 4 Silicon raw material 5 Mold lower thermocouple 6 Outer mold lower thermocouple 7 Chamber 8 Heat insulating material 9 Control device 10 Resistance heating body (graphite heater)
11Cooling tank 12 Elevating drive mechanism
2 外鋳型
3 鋳型台
4 シリコン原料
5 鋳型下熱電対
6 外鋳型下熱電対
7 チャンバー
8 断熱材
9 制御装置
10 抵抗加熱体(黒鉛ヒータ)
11 冷却槽
12 昇降駆動機構 DESCRIPTION OF
11
Claims (8)
- シリコン融液を凝固させるシリコン鋳造用鋳型であり、前記シリコン鋳造用鋳型の内壁の少なくとも底板部上面に、平均粒径0.1~3.0mmの添加物を含む離型材層が設けられているシリコン鋳造用鋳型。 A casting mold for solidifying silicon melt, and a release material layer containing an additive having an average particle diameter of 0.1 to 3.0 mm is provided on at least the upper surface of the bottom plate portion of the inner wall of the casting mold. Silicon casting mold.
- 前記離型材層が、前記底板部上面のみに設けられている請求項1記載のシリコン鋳造用鋳型。 The mold for silicon casting according to claim 1, wherein the release material layer is provided only on the upper surface of the bottom plate portion.
- 前記シリコン鋳造用鋳型が、黒鉛または石英(シリカ)を主成分とする材質で構成されている請求項1に記載のシリコン鋳造用鋳型。 The silicon casting mold according to claim 1, wherein the silicon casting mold is made of a material mainly composed of graphite or quartz (silica).
- 前記添加物が、窒化珪素、炭化珪素、酸化珪素および黒鉛から選択される少なくとも1つを主成分とする請求項1に記載のシリコン鋳造用鋳型。 The silicon casting mold according to claim 1, wherein the additive is mainly composed of at least one selected from silicon nitride, silicon carbide, silicon oxide, and graphite.
- 前記離型材層が、その表面に面密度0.2~8.5個/cm2で前記添加物を含む請求項1に記載のシリコン鋳造用鋳型。 The silicon casting mold according to claim 1, wherein the release material layer includes the additive at a surface density of 0.2 to 8.5 pieces / cm 2 on the surface thereof.
- 請求項1に記載のシリコン鋳造用鋳型内でシリコン融液を凝固させるシリコン鋳造方法。 A silicon casting method for solidifying a silicon melt in the silicon casting mold according to claim 1.
- 請求項6に記載のシリコン鋳造方法により鋳造されたシリコンを用いてシリコン材料を得るシリコン材料の製造方法。 A method for producing a silicon material, wherein a silicon material is obtained using silicon cast by the silicon casting method according to claim 6.
- 請求項7記載の製造方法により製造されたシリコン材料を基板として用いて太陽電池を得る太陽電池の製造方法。 A method for producing a solar cell, wherein a solar cell is obtained using the silicon material produced by the production method according to claim 7 as a substrate.
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JPH06144824A (en) * | 1992-09-16 | 1994-05-24 | Kawasaki Steel Corp | Production of polycrystalline silicon |
JPH11244988A (en) * | 1998-02-27 | 1999-09-14 | Mitsubishi Materials Corp | Mold for casting silicon ingot and manufacture therefor |
JPH11248363A (en) * | 1998-02-26 | 1999-09-14 | Mitsubishi Materials Corp | Laminate crucible for producing silicon ingot and manufacture thereof |
JP2005152985A (en) * | 2003-11-27 | 2005-06-16 | Kyocera Corp | Apparatus for casting silicon |
WO2005092791A1 (en) * | 2004-03-29 | 2005-10-06 | Kyocera Corporation | Silicon casting device and multicrystal silicon ingot producing method |
JP2006151708A (en) * | 2004-11-25 | 2006-06-15 | Kyocera Corp | Method for casting polycrystalline silicon, polycrystalline silicon ingot obtained by using the same, polycrystalline silicon substrate, and solar battery element |
JP2007191343A (en) * | 2006-01-18 | 2007-08-02 | Nippon Steel Materials Co Ltd | Mold for solidifying silicon and its manufacturing method |
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DE69912668T2 (en) * | 1998-02-26 | 2004-09-30 | Mitsubishi Materials Corp. | Mold and process for the production of silicon rods |
EP2543751A3 (en) * | 2009-07-16 | 2013-06-26 | MEMC Singapore Pte. Ltd. | Coated crucibles and methods for preparing and use thereof |
CN102858687A (en) * | 2010-03-31 | 2013-01-02 | 三菱综合材料株式会社 | Multilayer crucible for casting silicon ingot and method for manufacturing the crucible |
-
2012
- 2012-02-28 JP JP2012042116A patent/JP6014336B2/en not_active Expired - Fee Related
- 2012-12-12 WO PCT/JP2012/082227 patent/WO2013128758A1/en active Application Filing
- 2012-12-12 CN CN201280070752.4A patent/CN104159847B/en not_active Expired - Fee Related
- 2012-12-19 TW TW101148492A patent/TWI458863B/en not_active IP Right Cessation
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JPH06144824A (en) * | 1992-09-16 | 1994-05-24 | Kawasaki Steel Corp | Production of polycrystalline silicon |
JPH11248363A (en) * | 1998-02-26 | 1999-09-14 | Mitsubishi Materials Corp | Laminate crucible for producing silicon ingot and manufacture thereof |
JPH11244988A (en) * | 1998-02-27 | 1999-09-14 | Mitsubishi Materials Corp | Mold for casting silicon ingot and manufacture therefor |
JP2005152985A (en) * | 2003-11-27 | 2005-06-16 | Kyocera Corp | Apparatus for casting silicon |
WO2005092791A1 (en) * | 2004-03-29 | 2005-10-06 | Kyocera Corporation | Silicon casting device and multicrystal silicon ingot producing method |
JP2006151708A (en) * | 2004-11-25 | 2006-06-15 | Kyocera Corp | Method for casting polycrystalline silicon, polycrystalline silicon ingot obtained by using the same, polycrystalline silicon substrate, and solar battery element |
JP2007191343A (en) * | 2006-01-18 | 2007-08-02 | Nippon Steel Materials Co Ltd | Mold for solidifying silicon and its manufacturing method |
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Also Published As
Publication number | Publication date |
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TWI458863B (en) | 2014-11-01 |
TW201335443A (en) | 2013-09-01 |
CN104159847B (en) | 2016-10-19 |
JP6014336B2 (en) | 2016-10-25 |
CN104159847A (en) | 2014-11-19 |
JP2013177274A (en) | 2013-09-09 |
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