WO2015001592A1 - シリコン単結晶引上げ用シリカガラスルツボの製造に好適なシリカ粉の評価方法 - Google Patents
シリコン単結晶引上げ用シリカガラスルツボの製造に好適なシリカ粉の評価方法 Download PDFInfo
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- WO2015001592A1 WO2015001592A1 PCT/JP2013/067947 JP2013067947W WO2015001592A1 WO 2015001592 A1 WO2015001592 A1 WO 2015001592A1 JP 2013067947 W JP2013067947 W JP 2013067947W WO 2015001592 A1 WO2015001592 A1 WO 2015001592A1
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- silica
- silica powder
- powder
- silica glass
- bubble
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 331
- 239000000843 powder Substances 0.000 title claims abstract description 117
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 115
- 238000000034 method Methods 0.000 title claims abstract description 36
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 29
- 239000010703 silicon Substances 0.000 title claims abstract description 29
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 239000013078 crystal Substances 0.000 title claims abstract description 21
- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 238000002844 melting Methods 0.000 claims abstract description 37
- 230000008018 melting Effects 0.000 claims abstract description 37
- 238000001816 cooling Methods 0.000 claims abstract description 4
- 238000011156 evaluation Methods 0.000 claims description 13
- 239000005350 fused silica glass Substances 0.000 claims description 7
- 238000005259 measurement Methods 0.000 claims description 7
- 230000015572 biosynthetic process Effects 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 39
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 8
- 238000010891 electric arc Methods 0.000 description 7
- 230000003287 optical effect Effects 0.000 description 7
- 230000007547 defect Effects 0.000 description 5
- 238000001514 detection method Methods 0.000 description 5
- 239000011800 void material Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 239000002344 surface layer Substances 0.000 description 4
- 235000012431 wafers Nutrition 0.000 description 4
- 239000002131 composite material Substances 0.000 description 3
- 238000011049 filling Methods 0.000 description 3
- 238000010314 arc-melting process Methods 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 230000018199 S phase Effects 0.000 description 1
- 229910003902 SiCl 4 Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- 229920005591 polysilicon Polymers 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000001175 rotational moulding Methods 0.000 description 1
- -1 silicon alkoxide Chemical class 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 229910021489 α-quartz Inorganic materials 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B1/00—Preparing the batches
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/09—Other methods of shaping glass by fusing powdered glass in a shaping mould
- C03B19/095—Other methods of shaping glass by fusing powdered glass in a shaping mould by centrifuging, e.g. arc discharge in rotating mould
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/55—Specular reflectivity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0091—Powders
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/0004—Microscopes specially adapted for specific applications
- G02B21/002—Scanning microscopes
- G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
- G02B21/008—Details of detection or image processing, including general computer control
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/10—Crucibles or containers for supporting the melt
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N2015/0007—Investigating dispersion of gas
- G01N2015/0015—Investigating dispersion of gas in solids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N2015/0096—Investigating consistence of powders, dustability, dustiness
-
- 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
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
Definitions
- the present invention relates to a method for evaluating silica powder suitable for producing a silica glass crucible for pulling a silicon single crystal.
- the silicon single crystal by the Czochralski method is manufactured using a silica glass crucible.
- a silicon single crystal is produced by melting high-purity polysilicon to obtain a silicon melt, bringing the end of the seed crystal into contact with the surface of the silicon melt and pulling it up while rotating.
- the temperature of the silica glass crucible is as high as about 1450 to 1600 ° C. in order to keep the solid-liquid interface at the center of the silicon melt surface where the silicon melt is in contact with the single crystal at around 1420 ° C. which is the melting point of silicon. Yes.
- the amount of deformation of the rim of the silica glass crucible may be 5 cm or more.
- Silica glass crucible sizes include 28 inches (about 71 cm), 32 inches (about 81 cm), 36 inches (about 91 cm), and 40 inches (about 101 cm).
- the crucible having a diameter of 101 cm is a huge one weighing about 120 kg, and the mass of the silicon melt accommodated therein is 900 kg or more. In other words, when the silicon single crystal is pulled, 900 kg or more of silicon melt at about 1500 ° C. is stored in the crucible.
- Such a silica glass crucible is suitably used for manufacturing a large single crystal silicon ingot having a diameter of 200 to 450 mm (eg, 200 mm, 300 mm, 450 mm) and a length of 1 m to 5 m or more.
- a single crystal silicon wafer manufactured from such a large ingot is preferably used for manufacturing a flash memory and a DRAM.
- a silicon wafer used for manufacturing a semiconductor is obtained by slicing a silicon single crystal. With the recent increase in the degree of integration of semiconductor devices, reduction of void defects on the surface of silicon wafers is required.
- void defects can be removed by etching the surface layer of the wafer.
- the etching process is time-consuming and expensive, it is desired from the electronics field to produce a silicon single crystal free of void defects.
- Various methods are known for producing silicon single crystals without void defects.
- One of them is a method for reducing bubbles in a transparent layer in a silica glass crucible for pulling a silicon single crystal.
- the silica glass crucible for pulling a silicon single crystal is manufactured using powdered silica.
- the silica glass crucible is manufactured by (1) depositing silica powder on the rotary mold and (2) melting the silica powder by arc discharge. It is considered that the inclusion of bubbles in the silicon single crystal is one cause of void defects. Therefore, for the purpose of avoiding the mixing of bubbles into the silicon single crystal, the transparent layer of the silica glass crucible is formed from a layer without bubbles.
- Patent Document 1 a method for producing a silica glass crucible having a transparent layer, that is, a substantially bubble-free layer.
- Patent Document 2 describes a method for determining the presence or absence of a bubble generation factor in a silica glass raw material.
- Patent Document 1 Even the method of Patent Document 1 may or may not be able to form a bubble-free layer, and it is difficult to stabilize the quality.
- the present invention provides a method for evaluating silica powder that can stably produce a silica glass crucible having a bubble-free layer.
- the present invention provides the following evaluation method. That is, a step of measuring the porosity between silica particles in the silica powder, a step of melting the silica powder, a step of measuring the bubble content of the silica glass block obtained by cooling and curing the fused silica powder, and the silica A silica suitable for forming a bubble-free layer in a silica glass crucible for pulling up a silicon single crystal, the step of determining whether or not the silica powder is a suitable silica powder from the porosity in the powder and the bubble content of the silica glass block This is a method for evaluating powder.
- An evaluation of whether the silica powder is suitable for forming a bubble-free layer of a silica glass crucible can be performed by experimentally producing a silica glass crucible.
- a suitable silica powder is evaluated by measuring the bubble content of a silica block prepared by melting silica powder.
- Patent Document 2 (hereinafter, a conventional evaluation method).
- a conventional evaluation method is to supply silica powder to a heat-resistant container, melt the silica powder in a vacuum atmosphere, and measure the content of bubbles in the silica block in which the silica powder has melted and solidified. It is common.
- the silica powder evaluated as suitable by this method produces silica glass by the Bernoulli method using oxyhydrogen flame melting, but even if it is used for the production of a silica glass crucible by arc melting, it is not always necessary. It does not give good results.
- this method since water vapor, which is a combustion gas from the oxyhydrogen burner, is contained in the silica glass, bubbles are generated when used for pulling a silicon single crystal.
- the inventors of the present invention have been analyzing silica powder from which a silica glass block having a low bubble content can be obtained.
- the average particle diameter of the silica powder was correlated with the bubble content of the silica glass block.
- the silica glass block has a low or high bubble content, resulting in variations in the results.
- the silica powders having variations in the results differed in the porosity of the silica particles before melting. That is, if the particle shape is different, the filling method (filled state) changes even if the average particle diameter is the same.
- the present inventors have come to the conclusion that it is not possible to evaluate whether the silica powder is suitable by simply measuring the bubble content in the fused silica glass block. That is, it is a conclusion that it is necessary to consider not only the bubble content of the silica glass block after melting, but also the gap of the silica powder before melting.
- the present inventors have found that silica powder having a bubble content of the silica glass block within the specified range with respect to the porosity between the silica particles is not present in the silica glass crucible for pulling up the silicon single crystal.
- the present invention has been completed by finding that it is suitable for forming a bubble layer. By using the evaluation method according to the present invention, it is possible to identify in advance a silica powder that does not generate bubbles in the transparent layer.
- FIG. 1 is a schematic diagram showing a state where the objective lens 10 scans the surface 11 of the deposited silica powder.
- FIG. 2 is a conceptual diagram of silica powder in a heat-resistant container. A hatched portion indicates silica particles, and a white portion indicates a gap.
- FIG. 3 is a conceptual diagram of a fused silica glass block in a heat resistant container. The hatched portion is silica and the white portion is a gap.
- FIG. 4 is a conceptual diagram of a method for confirming bubbles in a transparent layer in a silica glass crucible created using synthetic silica powder.
- the evaluation method of the embodiment according to the present invention includes a step of measuring a porosity between silica particles in silica powder, a step of melting the silica powder, and a bubble containing silica glass block obtained by cooling and curing the fused silica powder.
- a silica glass crucible for pulling up a silicon single crystal comprising measuring a rate, and determining whether the silica powder is a suitable silica powder from a porosity in the silica powder and a bubble content of the silica glass block
- This is a method for evaluating silica powder suitable for forming a bubble-free layer.
- the silica glass layer that is visually transparent is referred to as a transparent layer.
- the bubble-free layer is a silica glass layer in which the bubble content of bubbles having a diameter of 20 to 100 ⁇ m is 0.1 or less.
- the silica powder in this invention is a synthetic silica powder or a natural silica powder.
- Synthetic silica powder is chemically synthesized silica and has a very low impurity concentration, and is therefore used for the inner surface layer of a silica glass crucible.
- the method for producing the synthetic silica powder is not particularly limited, but gas phase oxidation of silicon tetrachloride (SiCl 4 ) (dry synthesis method) and hydrolysis of silicon alkoxide (Si (OR) 4 ) (sol-gel method) can be used.
- SiCl 4 dry synthesis method
- Si (OR) 4 ) sol-gel method
- Natural silica powder is a powder produced by pulverizing a natural mineral mainly composed of ⁇ -quartz.
- Silica glass crucible is made by supplying natural silica powder to a rotating mold for producing silica glass crucible, supplying synthetic silica powder onto natural silica powder, and melting the silica powder by the heat of arc discharge.
- a silica glass crucible comprising an inner surface layer (synthetic layer) formed from synthetic silica powder and an outer surface layer (natural layer) formed from natural silica powder is produced.
- the silica powder layer is strongly depressurized to remove bubbles to form a transparent silica glass layer (transparent layer), and then the bubble is contained in the bubble-containing silica glass layer by decreasing the depressurization. (Hereinafter referred to as the “bubble-containing layer”).
- Silica powder is supplied to a heat-resistant container by free-falling in the same manner as in the case of manufacturing by a rotary molding method under atmospheric pressure.
- the silica powder that protrudes from the container is worn to flatten the observation surface. By doing so, it becomes the same filling as filling the silica powder by the rotational mold method.
- the heat-resistant container is not particularly limited as long as it is a material that can withstand use at high temperatures. For example, it is a ceramic composite material or a carbon fiber reinforced carbon composite material (C / C composite).
- the size of the heat-resistant container is not particularly limited, but can be, for example, 10 to 50 mm in length, 10 to 50 mm in width, and 10 to 30 mm in height, and specifically, a rectangular parallelepiped of 30 mm in length, 40 mm in width, and 20 mm in height. Can be selected.
- the gap between the silica particles can be measured in a non-contact manner using an optical detection means provided with a light receiving device that receives reflected light of light irradiated on the silica powder.
- the light emitting means for irradiating light in this optical detecting means may be built-in or may utilize an external light emitting means. Moreover, it is preferable to use what can be scanned along the surface of the silica powder deposited in the heat-resistant container, for example, an optical detection means can be performed using a confocal microscope. A confocal microscope is preferable because an image without blur can be obtained.
- irradiation light in addition to visible light, ultraviolet light, and infrared light, laser light or the like can be used, and any light can be used as long as it can detect a gap between silica particles.
- the light receiving device is selected according to the type of irradiation light.
- an optical camera including a light receiving lens and an image unit can be used.
- a light receiving lens In order to detect the gap between the silica particles, it is preferable to receive only light generated at the condensing point. In order to receive only light generated at the condensing point, it is preferable to provide a pinhole in front of the photodetector included in the light receiving device.
- the focal length is not particularly limited, but is preferably 0.1 to 3 mm deep from the surface, for example, 0.3 to 1.0 mm.
- the objective lens 10 of the optical detection means is disposed in a non-contact manner on the surface 11 of the deposited silica powder in the heat-resistant container 12 and scanned in the scanning direction 13.
- the gap between the silica particles is measured.
- Other scanning methods include a sample scanning method and a laser scanning method.
- the sample scanning method is a method of acquiring a two-dimensional image by driving a stage on which a sample is placed in the XY directions.
- the laser scanning method is a method in which a sample is two-dimensionally scanned by applying a laser in the XY directions. Any scanning method may be adopted.
- the measured porosity may be converted into an arbitrary parameter, for example, area, area ratio, and ratio. If the gap is unclear as a result of the measurement, the focus may be shifted in the direction of the X axis, the Y axis, or the Z axis.
- the porosity between the silica particles before melting is preferably 15% or less, more preferably 10% or less, still more preferably 5% or less, and may be at least 1% or more.
- a heat-resistant container containing silica powder is placed in a furnace, and the temperature in the furnace is raised to a temperature at which the silica powder melts.
- a carbon heater can be selected.
- the heating rate in the furnace is not particularly limited as long as the temperature does not change so rapidly that the gas component in the silica powder expands and bursts.
- the heating rate may be 50 to 300 ° C./min.
- the temperature at which the silica powder is melted is not particularly limited, but is preferably about 1500 to 2600 ° C., which is the temperature at the time of arc melting, for example, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, or 2600, which may be within the range of any two values exemplified here. By setting the temperature within this temperature range, it is possible to reproduce temperature conditions close to arc melting.
- the heating time is preferably 20 to 60 hours, more preferably 30 to 50 hours after reaching the melting temperature.
- the melting of the silica powder may be performed under atmospheric pressure. By melting under atmospheric pressure, the properties of the target silica powder can be analyzed in more detail. When performed under vacuum, it may be, for example, between 1.0 ⁇ 10 4 Pa and 1.0 ⁇ 10 5 Pa, preferably 2.0 ⁇ 10 4 Pa.
- the fused silica powder is cooled and the bubble content of the vitrified silica glass block is measured. What is necessary is just to cool a fused silica powder with completion
- the focal length is not particularly limited, but is preferably 0.1 mm to 3 mm deep from the surface, for example, 0.3 to 1.0 mm deep.
- the method for evaluating whether or not the silica powder is optimal is not particularly limited, but the bubble content of the silica glass block after melting relative to the porosity between the silica particles before melting (hereinafter referred to as the shrinkage index before and after melting) However, it can be evaluated as an excellent silica powder when it is preferably 0.5 or more, more preferably 0.7 or more, and still more preferably 0.8 or more. By defining the numerical value, it is possible to evaluate high-quality silica powder in advance, and no such method has existed so far.
- the shrinkage index before and after melting is less than 0.5, a bubble-free transparent layer may not be produced stably.
- the evaluation may be an area of a gap or a bubble. Further, even when the gaps and bubbles are quantified other than in the area, the result of conversion into the area or calculation of the area using other means may be within the above-described range.
- silica glass crucible is (1) while rotating a mold having a bowl-shaped inner surface that defines the outer shape of the silica glass crucible, natural silica powder is placed on the bottom and side surfaces of the silica glass crucible. A silica powder layer is formed by depositing to a thickness and then a synthetic silica powder is deposited to a predetermined thickness, and (2) the silica powder layer is melted by arc discharge and then cooled. Can do.
- the silica powder is preferably melted so that the maximum temperature reached on the inner surface of the rotary mold is 2000 to 2600 ° C.
- Arc melting is performed, for example, by arc discharge of alternating current three phases (R phase, S phase, T phase). Therefore, in the case of AC three-phase, the silica powder layer is melted by generating arc discharge using three carbon electrodes. Arc melting starts arc discharge at the point where the tip of the carbon electrode is located above the mold opening. Thereby, the silica powder layer in the mold opening vicinity is preferentially melted. Thereafter, the carbon electrode is lowered to melt the silica powder layer in the mold body part, the corner part, and the bottom part.
- Example 1 Measurement of gap (Example 1)
- the synthetic silica powder of Example 1 was supplied to a rectangular parallelepiped carbon container 30 mm long ⁇ 40 mm wide ⁇ 20 mm high in a heat resistant container, and the porosity was measured with a confocal microscope. The focal length was 0.3 mm from the surface. The porosity was calculated based on an arithmetic average value of the gap area at three measurement positions (focal length is the same). The porosity at this time was 7.2%. After measuring the porosity, a heat-resistant container containing synthetic silica powder was placed in the furnace.
- the temperature in the furnace was raised using a carbon heater, the furnace temperature was about 2200 ° C., and the synthetic silica powder of Example 1 in the heat-resistant container was melted. After melting at 2200 ° C. for 40 hours, it was left to reach room temperature without opening the furnace. When the temperature reached room temperature, the silica glass block was taken out and the bubble content was measured by the same method as before melting and found to be 4.2%.
- the silica powder of Example 1 had a shrinkage index before and after melting ((bubble content of silica glass block) / (porosity of silica particles)) of 0.58.
- Example 6 A synthetic silica powder (Example 6) of a production lot different from that in Example 1 was supplied to a heat-resistant container into a rectangular carbon container 30 mm long ⁇ 40 mm wide ⁇ 20 mm high, and the porosity was measured with a confocal microscope. . The measurement method is the same as in Example 1. The porosity at this time was 10.2%. After measuring the porosity, a heat-resistant container containing synthetic silica powder was placed in the furnace.
- the temperature in the furnace was increased using a carbon heater, and the temperature in the furnace was increased to about 2200 ° C. to melt the synthetic silica powder of Example 2 in a heat-resistant container. After melting at 2200 ° C. for 40 hours, it was left to reach room temperature without opening the furnace. When the temperature reached room temperature, the silica glass block was taken out and the bubble content was measured by the same method as before melting and found to be 4.0%.
- the silica powder of Example 6 had a shrinkage index ((porosity of silica glass block) / (bubble content of silica particles)) before and after melting of 0.39.
- Example 1 shows the porosity before melting, the bubble content of the silica glass block, and the shrinkage index before and after melting for Examples 1 to 10.
- Silica glass crucibles were produced by the rotational molding method using the synthetic silica powders of Examples 1 to 10.
- the diameter of the mold was 32 inches (81.3 cm)
- the average thickness of the silica powder layer deposited on the inner surface of the mold was 15 mm
- arc discharge was performed with three electrodes of three-phase alternating current.
- the energization time was 90 minutes
- the output was 2500 kVA
- the silica powder layer was evacuated for 10 minutes from the start of energization.
- the silica glass crucibles using the synthetic silica powders of Examples 1 to 5 were all confirmed to be a bubble-free transparent layer, and a silica glass crucible having a bubble-free layer can be stably produced. It was. On the other hand, in the silica glass crucibles using the synthetic silica powders of Examples 6 to 10, it was confirmed that the location where the bubble content was more than 0.1% was present in all five silica glass crucibles. A silica glass crucible having such a layer could not be stably produced.
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Abstract
Description
本発明におけるシリカ粉は、合成シリカ粉又は天然シリカ粉である。合成シリカ粉は、化学合成されたシリカであり、不純物濃度が非常に低いため、シリカガラスルツボの内面層に使用される。合成シリカ粉の製造方法は、特に限定されないが、四塩化珪素(SiCl4)の気相酸化(乾式合成法)や、シリコンアルコキシド(Si(OR)4)の加水分解(ゾル・ゲル法)が挙げられる。天然シリカ粉は、α―石英を主成分とする天然鉱物を粉砕して粉状にすることによって製造される粉末である。
シリカガラスルツボは、シリカガラスルツボ製造用回転モールドに、天然シリカ粉を供給し、更に合成シリカ粉を天然シリカ粉上に供給し、アーク放電の熱によりシリカ粉を熔融することで、合成シリカ粉から形成される内面層(合成層)と天然シリカ粉から形成される外面層(天然層)からなるシリカガラスルツボが製造される。アーク熔融工程の初期にはシリカ粉層を強く減圧することによって気泡を除去して透明シリカガラス層(透明層)を形成し、その後、減圧を弱くすることによって気泡が残留した気泡含有シリカガラス層(以下、「気泡含有層」と称する。)が形成される。
耐熱性容器に大気圧下で、回転モールド法で製造するときと同様にシリカ粉を自由落下させて供給する。容器からはみ出たシリカ粉はすり切って観察面を平らにする。こうすることで回転モールド法によりシリカ粉を充填するのと同様の充填となる。耐熱性容器は、高温での使用に耐えられる素材であれば特に限定されないが、例えば、セラミック系複合材料や炭素繊維強化炭素複合材(C/Cコンポジット)である。耐熱性容器のサイズは特に限定されないが、例えば、縦10から50mm、横10から50mm、高さ10から30mmとすることができ、具体的には、縦30mm×横40mm×高さ20mmの直方体の容器を選択することができる。
間隙率:n=((S―Sp)/S)×100
また、間隙の合計面積をSnとすると、以下の式で求めることができる。
間隙率:n=(Sn/S)×100
シリカガラスルツボは、(1)シリカガラスルツボの外形を規定する碗状の内表面を有するモールドを回転させながら、その内部の底部及び側面上に天然シリカ粉を所定の厚さに堆積させ、その後、合成シリカ粉を所定厚さに堆積させることによってシリカ粉層を形成し、(2)このシリカ粉層をアーク放電によって熔融させた後に冷却することによって、製造することができる。
(実施例1)
耐熱性容器に実施例1の合成シリカ粉を縦30mm×横40mm×高さ20mmの直方体のカーボン製容器に供給し、共焦点顕微鏡で間隙率を測定した。焦点距離は、表面から0.3mmの位置とした。間隙率は、3箇所の測定位置(焦点距離は同じ)における間隙面積の相加平均値に基づいて算出した。この時の間隙率は、7.2%であった。間隙率を測定の後、合成シリカ粉入りの耐熱性容器を炉内に設置した。
耐熱性容器に実施例1とは異なる製造ロットの合成シリカ粉(実施例6)を縦30mm×横40mm×高さ20mmの直方体のカーボン製容器に供給し、共焦点顕微鏡で間隙率を測定した。測定方法は、実施例1と同じである。この時の間隙率は、10.2%であった。間隙率の測定後、合成シリカ粉入りの耐熱性容器を炉内に設置した。
製品ロットが異なる合成シリカ粉を用いて同様に溶融前後の収縮指数を測定した。表1は、実施例1~10に関する、溶融前の間隙率、シリカガラスブロックの気泡含有率及び溶融前後の収縮指数である。
実施例1~10の合成シリカ粉を用いて、回転モールド法により、シリカガラスルツボを製造した。モールド口径は、32インチ(81.3cm)、モールド内表面に堆積したシリカ粉層の平均厚さは15mm、3相交流電流3本電極によりアーク放電を行った。アーク熔融工程の通電時間は90分、出力2500kVA、通電開始から10分間はシリカ粉層の真空引きを行った。
特許文献2(特開2009-007211)の実施例に記載の方法に基づいて、気泡発生要因が無いと判断した合成シリカ粉を用いた以外は、上記と同様にしてシリカガラスルツボを作成し、気泡を共焦点顕微鏡を用いて測定した。結果を表2に示す。
11 表面
12 耐熱容器
13 捜査方向
21 直銅部
22 コーナー部
23 底部
24 気泡層
25 透明層
26 スライス片
Claims (5)
- シリカ粉におけるシリカ粒子間の間隙率を測定する工程と、
前記シリカ粉を熔融する工程と、
熔融シリカ粉を冷却し硬化させたシリカガラスブロックの気泡含有率を測定する工程と、
前記シリカ粉における間隙率と前記シリカガラスブロックの気泡含有率から好適なシリカ粉であるか否かを判定する工程と、を有する、シリコン単結晶引上げ用シリカガラスルツボにおける無気泡層の形成に好適なシリカ粉の評価方法。 - 間隙率及び気泡含有率の測定が、共焦点顕微鏡を用いて行われる、請求項1に記載の評価方法。
- 前記シリカ粉を熔融する温度が、約1500から2600℃である、請求項1に記載の評価方法。
- 前記好適なシリカ粉は、(前記シリカガラスブロックの気泡含有率)/(前記シリカ粒子の間隙率)が、0.5以上の場合である、請求項1に記載の評価方法。
- 請求項1ないし4いずれかに記載のシリカ粉の評価方法を用いてシリカ粉の無気泡層の形成に好適なシリカ粉を選び、前記好適なシリカ粉を用いてアーク溶融法によりシリカガラスルツボを製造することを特徴とするシリカガラスルツボ製造方法。
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JP2015524913A JP6150309B2 (ja) | 2013-06-30 | 2013-06-30 | シリコン単結晶引上げ用シリカガラスルツボの製造に好適なシリカ粉の評価方法 |
EP13888555.3A EP3018468B1 (en) | 2013-06-30 | 2013-06-30 | Method for evaluating suitability of silica powder for manufacturing of silica-glass crucible for pulling silicon single crystal |
KR1020167001690A KR101771615B1 (ko) | 2013-06-30 | 2013-06-30 | 실리콘 단결정 인상용 실리카 유리 도가니의 제조에 적합한 실리카 분말의 평가 방법 |
PCT/JP2013/067947 WO2015001592A1 (ja) | 2013-06-30 | 2013-06-30 | シリコン単結晶引上げ用シリカガラスルツボの製造に好適なシリカ粉の評価方法 |
US14/901,034 US9637405B2 (en) | 2013-06-30 | 2013-06-30 | Evaluation method of suitable silica powder in manufacturing vitreous silica crucible for pulling of silicon single crystal |
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JP5774400B2 (ja) | 2010-08-12 | 2015-09-09 | 株式会社Sumco | シリカ粉の評価方法、シリカガラスルツボ、シリカガラスルツボの製造方法 |
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EP3018468A1 (en) | 2016-05-11 |
JP6150309B2 (ja) | 2017-06-21 |
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