WO2014192163A1 - シリコン単結晶引き上げ用シリカガラスルツボ及びその製造方法 - Google Patents
シリコン単結晶引き上げ用シリカガラスルツボ及びその製造方法 Download PDFInfo
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- WO2014192163A1 WO2014192163A1 PCT/JP2013/065294 JP2013065294W WO2014192163A1 WO 2014192163 A1 WO2014192163 A1 WO 2014192163A1 JP 2013065294 W JP2013065294 W JP 2013065294W WO 2014192163 A1 WO2014192163 A1 WO 2014192163A1
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- silica glass
- glass crucible
- single crystal
- layer
- silica powder
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/10—Crucibles or containers for supporting the melt
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- 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
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- 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
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B35/00—Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
- C30B35/002—Crucibles or containers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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 silica glass crucible used for pulling a silicon single crystal as a semiconductor material.
- a silicon single crystal as a semiconductor material is obtained by heating polysilicon to a temperature of about 1450 to 1600 ° C. using a carbon heater outside in a silica glass crucible, and recently using the Czochralski method (CZ method) by reducing the pressure. Manufactured by pulling up. The price of flash memory and DRAM has been rapidly reduced, and the diameter of silicon single crystals has been shifted from the current mainstream of 300 mm ⁇ to the large size of 400 to 450 mm ⁇ for the purpose of responding to the demand. Accordingly, the diameter of the silica glass crucible is also shifted from about 600 mm to a large diameter of 700 mm or more in order to enable the production of a silicon single crystal having a large diameter.
- the distance from the heater disposed outside the silica glass crucible to the center of the silicon single crystal increases.
- the distance from the heater disposed outside the silica glass crucible to the center of the silicon single crystal increases.
- the distance from the heater to the center of the single crystal is 50 mm or more.
- the amount of silicon melt at about 1420 ° C. increases as the diameter of the silica glass crucible increases.
- a crucible having a diameter of about 1000 mm is a silica glass container having a weight of about 120 kg, and the mass of the silicon melt contained therein is 900 kg or more.
- 900 kg or more of silicon melt at about 1420 ° C. is stored in the crucible.
- Increasing the distance from the heater to the center of the silicon single crystal and increasing the amount of polysilicon melted to a carbon heater temperature of about 1450-1600 ° C increases the temperature of the silica glass crucible and increases the pulling time. I'm imitating. For example, the softening point of silica glass is about 1200 to 1300 ° C., whereas the pulling temperature of silicon single crystal is about 1420 ° C., and the single crystal pulling is performed at a very high temperature exceeding the softening point of silica glass. Is doing.
- the silica glass crucible is held by a carbon susceptor. If there is no carbon susceptor, the silica glass crucible will buckle under its own weight, or it will be deformed to cause inward collapse.
- the lifting time may be more than 2 weeks.
- problems such as deformation of the silica glass crucible occur.
- the silica glass crucible is discarded after one CZ single crystal pulling is completed.
- Patent Document 1 discloses a high-strength quartz glass crucible in which a crystallized glass layer is formed on the inner surface and the outer surface of a crucible to enhance the high heat resistance of the crucible, and deformation does not occur when pulling a silicon single crystal for a long time. Yes.
- Patent Document 2 discloses a silica glass crucible that contains Al as a crystallization accelerator so that the concentration decreases from the outer surface to the inner surface of the crucible, and prevents deformation of the crucible at high temperatures while preventing Al contamination of the single crystal. Is disclosed.
- the present invention has been made in view of such circumstances, and provides a silica glass crucible in which buckling and inward deformation are suppressed even when used under a high temperature condition for a long time, and a method for producing the same. For the purpose.
- the inventors of the present invention have a transparent layer on the inside and a bubble layer on the outside, and the transparent layer is changed from compressive stress to tensile stress from the inside. It has been found that by changing the stress that remains gently on the outside, deformation is suppressed even when a silica glass crucible is used under high temperature conditions for a long time. That is, the present invention includes a substantially cylindrical straight body portion that is open at the top and extends in the vertical direction, a curved bottom portion, and a corner portion that connects the straight body portion and the bottom portion and has a larger curvature than the bottom portion.
- a silica glass crucible comprising a transparent layer on the inside and a bubble layer on the outside, a compressive stress layer in which compressive stress remains on the inner surface side of the transparent layer, and the compressive stress layer,
- a silica glass crucible for pulling a silicon single crystal which is provided with a tensile stress layer in which a tensile stress remains adjacent to each other at a moderate stress change rate.
- the present inventors do not crystallize the silica glass in the process of pulling the silica glass crucible into the CZ single crystal, but change the structure of the synthetic silica powder as a raw material when producing the silica glass crucible to A tempered silica glass crucible that avoids the problems 2 and 2 was studied. As a result, it is clear that compressive stress and tensile stress remain in the transparent layer of the silica glass crucible manufactured using the synthetic silica powder with specified Si—O—Si bond (siloxane bond) and average particle size. It became.
- silica glass crucible When a silica glass crucible is produced by depositing and melting such synthetic silica powder on a rotatable carbon mold (rotary molding method), since the silica powder is melted uniformly, even a large crucible is a transparent layer. The stress distribution becomes uniform, and the strength unevenness does not occur. Therefore, unlike the silica glass crucible described in Patent Document 1, the silica glass crucible according to the present invention is uniformly strengthened. Furthermore, since the silica glass crucible according to the present invention does not use the crystallization accelerator as described in Patent Document 2, contamination of the silicon single crystal by the accelerator can be prevented.
- the present invention provides a process for supplying natural silica powder to a rotating mold for producing a silica glass crucible and forming a layer of the natural silica powder on the inner surface of the rotating mold for producing a silica glass crucible, which is obtained by the Raman measurement method described below.
- a silica glass crucible for pulling up a silicon single crystal comprising a step of depositing a synthetic silica powder satisfying the formula (1) inside a layer of the natural silica powder, and a step of arc discharge to the natural silica powder and the synthetic silica powder. It is a manufacturing method.
- intensity ratio R (I 1 + I 2 ) / I 0
- I 1 the peak intensity of a Raman shift 492cm -1 peak intensities of the bands of the peak intensity
- I 2 Raman shift 606 cm -1 band
- I 0 Raman shift 800 cm -1 band
- the method for producing a silica glass crucible according to the present invention does not require the strengthening treatment after crucible production as in the above-mentioned Patent Document 1, so that the production time and cost can be reduced. Further, as in Patent Document 2, a silica glass crucible that is durable under a high temperature condition for a long time can be produced without using a crystallization accelerator. Thus, by making it within the range of the above-mentioned strength ratio of the synthetic silica powder before melting, it is possible to produce a silica glass crucible in which the compressive stress and tensile stress are adjacent to each other at a moderate stress change rate in the transparent layer. No reports until.
- FIG. 2 is a cross-sectional view of a silica glass crucible and a schematic diagram depicting a strain observation method. It is the electron micrograph of the external appearance and cross section of the synthetic silica powder which concerns on the manufacture example 1 which carried out the plasma processing. It is an electron micrograph of the appearance and section of synthetic silica powder concerning comparative manufacture example 1 which is not plasma-treated. It is a Raman spectrum of the synthetic silica powder concerning the manufacture example 1 which carried out plasma processing, and the synthetic silica powder concerning the comparative manufacture example 1 which has not been plasma-treated.
- a silica glass crucible according to the present invention includes a substantially cylindrical straight body portion that is open at the top and extends in the vertical direction, a curved bottom portion, and a corner portion that connects the straight body portion and the bottom portion and has a larger curvature than the bottom portion.
- the silica glass crucible includes a transparent layer on the inner surface side, a compressive stress layer in which compressive stress remains on the inner surface side of the transparent layer, and a moderate stress change rate with the compressive stress layer. It is a silica glass crucible provided with the tensile stress layer in which the tensile stress remains adjacent to the opposite side.
- Silica powder used for the production of silica glass crucible includes crystalline natural silica powder and amorphous synthetic silica powder produced by chemical synthesis.
- the natural silica powder is a silica powder produced by pulverizing a natural mineral mainly composed of ⁇ -quartz.
- Synthetic silica powder is produced by chemical synthesis techniques such as vapor phase oxidation of silicon tetrachloride (SiCl 4 ) (dry synthesis method) and hydrolysis of silicon alkoxide (Si (OR 4 )) (sol-gel method). be able to.
- Silica glass crucible is made from synthetic silica powder by supplying natural silica powder to a mold for silica glass crucible, supplying synthetic silica powder onto natural silica powder, and melting silica powder by Joule heat of arc discharge.
- a silica glass crucible comprising an inner surface layer (synthetic layer) to be vitrified and an outer surface layer (natural layer) to be vitrified from natural silica powder is produced.
- the silica powder layer is strongly depressurized to remove bubbles to form a transparent silica glass layer (hereinafter referred to as “transparent layer”).
- transparent layer hereinafter referred to as “transparent layer”.
- a remaining bubble-containing silica glass layer hereinafter referred to as “bubble layer”.
- the inner surface layer and the transparent layer formed from the synthetic silica powder do not necessarily coincide with each other.
- the outer surface layer and bubble layer formed from natural silica powder do not necessarily coincide.
- the transparent layer is a layer formed inside the silica glass crucible and substantially does not contain bubbles. “Substantially free of bubbles” means that the bubble content and bubble diameter are such that the single crystallization rate does not decrease due to bubbles.
- the compressive stress layer is a layer in which compressive stress remains on the inner surface side of the transparent layer.
- the tensile stress layer is a layer adjacent to the compressive stress layer and in which tensile stress remains.
- the tensile stress layer is preferably present only in the transparent layer, and the proportion thereof is preferably 90% or more, more preferably 95% or more, and further preferably 100%, and may not be present in the bubble layer. preferable.
- Such a ratio can be calculated, for example, by observing a change in stress from the inner surface of the silica glass crucible in the thickness direction.
- the rate of stress change is preferably 0.17 MPa / mm or more and 1.5 MPa / mm or less, for example, 0.17, 0.2, 0.3, 0.5, 0.00. It is 7, 0.9, 1.1, 1.3, or 1.5 MPa / mm, and may be within the range of any two numerical values exemplified here.
- the rate of stress change is less than 0.17 MPa / mm, the tensile stress may reach the bubble layer. For this reason, in a bubble layer, it becomes easy to produce a fine crack between a bubble, and when the fine crack spreads, it will become a big crack.
- the large-diameter silica glass crucible has a higher degree of deformation risk due to the large degree of deformation of the crucible with respect to external stress and thermal stress applied to the crucible than the small-diameter silica glass crucible.
- the large-diameter silica glass crucible in which the change from compressive stress to tensile stress is gentle can reduce the risk of breakage.
- the silica glass in which stress remains inside exhibits anisotropy at the location where the stress remains and inward tilt occurs.
- the anisotropy of silica glass is observed by slicing a crucible in the vertical direction, placing a sliced crucible piece between two polarizing plates combined in a crossed Nicol state, and allowing white light to pass through. be able to.
- the sliced crucible piece is about 2 mm thick by polishing.
- the crucible piece does not give an optical path difference to the white polarized light, so that the white polarized light that has passed through the crucible piece cannot pass through the orthogonal polarizing plate (analyzer).
- the crucible piece When the crucible piece is distorted, the crucible piece gives an optical path difference with respect to the white polarized light. Therefore, the polarization plane of the white polarized light rotates and a component that can pass through the orthogonal polarizing plate (analyzer) is observed. .
- white polarized light is passed through a crucible piece having strain, an optical path difference corresponding to the strain is generated for each wavelength, and thus the amount of light passing through the polarizing plate is different for each wavelength. As a result, the color of the crucible piece observed through the polarizing plate (analyzer) is observed. It is also possible to evaluate the distortion of the crucible piece from this color.
- the distortion of the crucible piece can be evaluated by using an interference color diagram or a polarization color diagram representing the relationship between chromaticity and birefringence, and the stress can be obtained from the strain. Further, when the sensitive color method is used, it is possible to determine whether the compressive stress or the tensile stress is based on the color, so that the interface between the residual compressive stress and the residual tensile stress can be observed.
- the strain stress can be measured by installing a quarter wave plate between the sample crucible piece and the detector (senalmon method).
- the specific measurement method is as follows. First, an analyzer is installed so as to be in a crossed Nicols state with respect to a polarizing plate (polarizer) installed in front of the light source. At this time, the rotation angle ⁇ of the analyzer is set to 0 degree (degree). Next, the sample is observed from the analyzer side, and the sample is rotated with respect to the analyzer so that the sample portion where the stress measurement is desired is brightest. Further, the analyzer is rotated in the horizontal direction so that the sample portion where stress measurement is desired is darkest. The stress can be obtained by substituting the rotation angle ⁇ from the brightest state to the darkest state into the following formula (2).
- F Stress (MPa) ⁇ : wavelength of light source (nm)
- C Photoelastic constant (nm / cm) / MPa
- L Optical path length (cm)
- the photoelastic constant C of silica glass is 3.5 ⁇ 0.2 (nm / cm) / Mpa.
- ⁇ of the light source a wavelength suitable for the quarter wave plate to be used is selected. You may select the suitable quarter wavelength plate with respect to the wavelength of the light source to be used.
- the optical path length L is the thickness of the sample in the optical axis direction.
- the stress change from compressive stress to tensile stress can be obtained by plotting the stress F at an arbitrary distance in the thickness direction from the inner surface of the crucible. Whether the change from compressive stress to tensile stress on the inner surface side is abrupt or gentle depends on the interface (that is, stress) in the distance-stress graph (X axis: distance from the inner surface, Y axis: stress). This can be determined by obtaining the absolute value of the slope of the tangent to the coordinate (which is 0 MPa) (referred to as the rate of change in stress). For example, when the absolute value of the slope is 0.17 MPa / mm or more and 1.5 MPa / mm or less, it can be determined that the stress change is moderate.
- the silica glass crucible may fall inward or buckle during the pulling of the silicon single crystal, thereby reducing the yield of the silicon single crystal. In some cases, the pulling of the silicon single crystal is stopped. It is necessary to let In the silica glass crucible according to the present invention, the compressive stress remains on the inner surface side of the transparent layer, thereby strengthening the inner surface of the silica glass crucible and changing the tensile stress toward the outside at a gradual stress change rate. To leave a tensile stress in the transparent layer. If a tensile stress remains in the bubble layer, fine cracks are likely to be generated between the bubbles, and if the fine cracks are spread, they become large cracks that need to be avoided. Therefore, it is preferable to leave a tensile stress in the transparent layer.
- the bubble layer is a layer formed outside the transparent layer.
- the bubble layer has a bubble content of 0.2% to 1% and an average bubble diameter of 20 ⁇ m to 200 ⁇ m.
- the silica glass crucible according to the present invention preferably has a maximum bubble content of 0.10 vol% or less. Furthermore, the silica glass crucible according to the present invention preferably has an average cell diameter of 50 ⁇ m or less. If even a small amount of bubbles are present in the vicinity of the inner surface of the silica glass crucible, bubble expansion occurs in the transparent layer when the silicon single crystal is pulled up. The generated bubbles enter the silicon melt together with the dissolution of the inner surface side of the transparent layer, and the bubbles are taken into the silicon single crystal to be pulled up. The taken-in bubbles cause dislocation (crystal defects) due to crystal transition and lower the single crystallization rate.
- the maximum bubble content of the silica glass crucible is larger than 0.10 vol%, the single crystallization rate is significantly reduced. Further, if the average bubble diameter of the silica glass crucible is more than 50 ⁇ m, the expansion of the bubbles causes deformation of the silica glass crucible.
- Bubbles existing in the vicinity of the inner surface of the silica glass crucible can be detected using, for example, optical detection means.
- the optical detection means includes a light receiving device that receives transmitted light or reflected light of light irradiated on the silica glass crucible.
- the light emitting means for irradiating light may be built-in or may use an external light emitting means.
- the optical detection means one that can be rotated along the inner surface of the silica glass crucible is used. Examples of the irradiation light include visible light, ultraviolet light, infrared light, and laser light, and any light can be applied as long as it can be reflected to detect bubbles.
- the light receiving device is selected according to the type of irradiation light. For example, a digital camera including an optical lens and an image sensor can be used. In order to detect bubbles existing at a certain depth from the surface, the focal point of the objective lens may be scanned in the depth direction from the surface.
- the measurement result by the optical detection means is taken into the image processing apparatus, and the bubble content P (%) is calculated.
- the bubble content can be determined by the volume of bubbles in the unit volume of the crucible, and the bubble content at the highest value among the measured points can be set as the maximum bubble content.
- the maximum bubble content from the inner surface of the crucible toward the outer surface up to a thickness of 0.3 mm is preferably 0.05 vol% or less.
- bubbles having a bubble diameter of 10 ⁇ m or more are measured.
- the single crystallization rate is remarkably reduced.
- the maximum bubble diameter is larger than 100 ⁇ m, since the reduction of the single crystallization rate is remarkable, it is preferably 100 ⁇ m or less.
- the average bubble diameter can be obtained as an average value of the diameters of the spherical bubbles in the measurement range.
- the diameter can be determined by software by acquiring an image of the glass sample.
- the arithmetic average roughness (Ra) of the inner surface of the silica glass crucible is preferably 0.02 ⁇ m or less. When it is larger than 0.02 ⁇ m, the probability that heterogeneous nucleation occurs is increased, and the single crystallization rate is remarkably lowered.
- Ra is extracted from the roughness curve by the reference length in the direction of the average line
- the X-axis is taken in the direction of the average line of the extracted portion
- the Y-axis is taken in the direction of the vertical magnification
- the roughness curve is taken from the center line.
- the integrated value is expressed in micrometers.
- Natural silica powder is supplied to a rotating mold for producing a silica glass crucible, and a layer of natural silica powder is formed on the inner surface of the rotating mold for producing a silica glass crucible.
- Natural silica powder can be produced by pulverizing a natural mineral mainly composed of ⁇ -quartz.
- the measurement conditions of the Raman method can be, for example, a wavelength of 532 nm, an exposure time: 20 seconds, and an integration count of 1: Raman spectrum of the resulting synthetic silica powder from such conditions, Raman shift 492cm -1 characteristic peaks in band and 606 cm -1 band and 800 cm -1 bands were observed, each band, planar four-membered ring (D1 ), The scattering peak of the planar three-membered ring (D2), and the scattering peak due to the fundamental vibration between silicon and oxygen.
- the peak intensity at each scattering peak is the area at each peak.
- the peak area can be calculated by integrating the time change of the peak electrical signal with the line connecting the rising and falling points of the peak as the base.
- a half width method, a triangle approximation method, and a peak clipping method can be taken as examples.
- Strength ratio R is 0.80 or more and 1.0 or less.
- the intensity ratio R is, for example, 0.80, 0.85, 0.90, 0.95, and 1.00, and may be within the range of any two numerical values exemplified here.
- the synthetic silica powder lacks a planar three-membered ring and a planar four-membered ring, which are structures involved in the dense state, and a high dense state is not maintained in the synthetic silica powder.
- Such synthetic silica powder has little change in the glass structure at the time of melting, the glass structure after melting is likely to be uniform, and the stress change between the compressive stress and the tensile stress in the transparent layer is likely to be abrupt.
- a silica glass crucible manufactured using a synthetic silica powder having a strength ratio R of 0.80 or more and 1.0 or less can leave a compressive stress and a tensile stress in the transparent layer at a moderate rate of change in stress.
- produce a crack, an inward fall, and a buckling can be manufactured also under high temperature conditions for a long time.
- the synthetic silica powder preferably has a circularity of 0.73 to 1.0.
- the synthetic silica powder in which the particles are spheroidized has a small gap between the particles, so that the gap is easily closed during melting, and the residual gas component in the silica glass crucible can be prevented.
- the degree of circularity is less than 0.73, the gap between the particles is large, so that the gap is not blocked during melting, gas components remain in the silica glass crucible, and the bubble content may increase.
- the synthetic silica powders used it is not necessary for all the synthetic silica powders used to have a circularity of 0.73 or more and 1.0 or less, and the ratio of such silica particles is preferably 90% or more, more preferably 95% or more, and still more preferably 99%. % Or more.
- the synthetic silica powder preferably has an average particle size of 80 ⁇ m or more and 160 ⁇ m or less.
- the average particle diameter is, for example, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, or 160 ⁇ m, and may be within the range of any two numerical values exemplified here.
- the average particle size is 160 ⁇ m or less, the size of the voids between the particles is small, so that the bubble size in the silica glass crucible formed due to the entrainment of the atmospheric gas can be reduced. As a result, bubbles can be contracted and extinguished during arc melting.
- the average particle size exceeds 160 ⁇ m, the size of the voids between the particles is large, so that the bubble size in the silica glass crucible formed due to the entrainment of the atmospheric gas is large, and the bubbles shrink during arc melting. Progress, but may not lead to the disappearance of bubbles.
- the average particle size is less than 80 ⁇ m, melting is rapidly caused by arc melting, so that degassing due to vacuuming becomes insufficient and bubbles remain.
- Average particle size means a particle size (D50) at an integrated value of 50% in the obtained particle size distribution, and in the present specification means a volume average particle size.
- the particle size distribution can be measured by a laser diffraction / scattering measurement method using laser light as a light source.
- Particle size is defined in the column of JIS Z 8901 “Test powder and test particles”.
- the synthetic silica powder preferably has a tap bulk density of 1.35 g / cm 3 ⁇ m or more and 1.44 g / cm 3 or less.
- the tap bulk density is, for example, 1.35, 1.38, 1.39, 1.40, 1.41, 1.42, 1.43, or 1.44 g / cm 3. It may be within the range of two numerical values. If the tap bulk density is less than 1.35 g / cm 3 , the bubble content may increase. This is presumably because gas is included during melting because the interval between the particles is large. When the tap bulk density is more than 1.44 g / cm 3 , degassing due to evacuation is insufficient, and bubbles tend to remain.
- the tap bulk density can be obtained from the density when the sample is dispersed and placed in the container, and then the container is impacted by the tap and the volume of the sample is not changed.
- a measurement container containing a sample is installed in a tap device with an auxiliary cylinder attached, and the tap is performed 600 times. After grinding the sample, the mass is measured. The sample is replenished, and the measurement container with the auxiliary cylinder attached is placed in the tap device, and the tap is performed 100 times. After grinding the sample, the mass is measured, and the operation is repeated until the mass difference from the previous mass is within 0.3%. The mass of the sample is divided by the volume of the measurement container to obtain the tap bulk density. The measurement is performed three times, and an average value can be adopted.
- the synthetic silica powder preferably has a specific surface area of 0.026 m 2 / g or more and 0.045 m 2 / g or less.
- the specific surface area is, for example, 0.026, 0.028, 0.030, 0.032, 0.034, 0.036, 0.038, 0.040, or 0.045 m 2 / g, where It may be within the range of any two given numerical values.
- the specific surface area exceeds 0.045 m 2 / g, the gas present on the surface of the scratches and cracks is taken in at the time of melting and remains as bubbles, thereby increasing the bubble content.
- the specific surface area is less than 0.026 m 2 / g, the gas present at the center of the silica particles can be prevented from escaping from the surface during arc melting. For this reason, it is preferable that the surface has a dent to some extent because the bubble content can be lowered.
- the specific surface area can be determined by a nitrogen adsorption method.
- nitrogen adsorption method (1) nitrogen gas is adsorbed on the synthetic silica powder while gradually increasing the pressure from a high vacuum.
- An adsorption isotherm is created by plotting relative pressure on the X-axis and nitrogen adsorption on the Y-axis.
- This is a method for obtaining the specific surface area by applying such adsorption isotherm data to various adsorption isotherms. Examples of the adsorption isotherm include a Henry adsorption isotherm, a Langmuir adsorption isotherm, and a BET adsorption isotherm.
- the specific surface area of the synthetic silica powder used is 0.026 m 2 / g or more and 0.045 m 2 / g or less, and the ratio of such silica particles is preferably 90% or more, more preferably 95. % Or more, more preferably 99% or more.
- the synthetic silica powder used in the present invention can be produced, for example, by treating a synthetic silica powder raw material at a cooling rate of 10 5 K / min or more after plasma treatment.
- Synthetic silica powder raw materials are produced by chemical synthesis methods such as gas phase oxidation of silicon tetrachloride (SiCl 4 ) (dry synthesis method) and hydrolysis of silicon alkoxide (Si (OR 4 )) (sol-gel method). can do.
- the plasma treatment can be performed using, for example, a plasma reactor (for example, a high-frequency induction thermal plasma generator), and the plasma treatment using such a plasma reactor can easily perform rapid heating and rapid cooling.
- the plasma treatment is preferably a thermal plasma treatment in which a heating-cooling process can be continuously performed.
- the plasma reactor is composed of a plasma torch for generating plasma and a cooling device provided immediately thereafter.
- the plasma torch includes a raw material supply pipe and a gas supply pipe, and a high frequency induction coil on the outer periphery thereof.
- the frequency applied to the high frequency induction coil is, for example, 1 to 15 MHz, specifically 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 15 MHz. It may be within the range of any two numerical values.
- the output is, for example, 90 to 150 kW, specifically 90, 100, 110, 120, 130, 140, or 150 kW, and may be within the range of any two numerical values exemplified here.
- the gas to be supplied for example, argon or oxygen can be selected.
- the gas may be, for example, a mixed gas of oxygen and argon.
- the oxygen partial pressure is, for example, 10 to 30%, specifically, 10, 15, 20, 25, or 30%. Yes, it may be within the range of any two numerical values exemplified here.
- the gas supply amount is, for example, 30 to 150 L / min, specifically, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 L / min.
- Plasma is generated in the plasma torch by energizing the high frequency induction coil while supplying gas.
- a synthetic silica powder raw material is supplied into a plasma torch in which plasma is generated.
- the feed rate of the raw material is, for example, 20 to 50 kg / hr, specifically, 20, 23, 25, 28, 30, 35, 40, 45, or 50 kg / hr. It may be within a range of two numerical values.
- the synthetic silica powder having a desired strength ratio R can be produced by rapidly cooling the synthetic silica powder with a cooling device.
- the cooling rate is preferably 10 5 K / min or more, more preferably 10 6 K / min or more.
- the cooling method is not particularly limited, but is preferably cooling by air cooling, more preferably cooling by water cooling.
- the synthetic silica powder in which the thermal history is reflected can be obtained stably.
- the raw material supply rate and output can be increased, and the plasma-treated synthetic silica powder can be produced in a short time.
- Arc discharge is performed on the laminated natural silica powder and the synthetic silica powder obtained as described above.
- a known method can be adopted for the arc discharge.
- glass melting by arc discharge of a rotary mold method can be employed.
- ⁇ Cooling gas can be introduced into the mold from the tube for vacuuming the mold.
- the outer surface side of the silica glass crucible can be efficiently cooled, the compressive stress can remain on the bubble layer side, and the tensile stress can be prevented from remaining on the bubble layer side.
- the cooling gas can be introduced using a compressor such as a blower with a cleaning function.
- the discharge gas amount of the compressor can be 10 to 50 m 3 / min, specifically, 10, 20, 30, 40, or 50 m 3 / min. , It may be within the range of any two numerical values shown here.
- the amount of discharge gas can be changed according to the size of the silica glass crucible to be produced. When the discharge gas amount is less than 10 m 3 / min, tensile stress remains in the bubble layer due to insufficient cooling. When the discharge gas amount exceeds 50 m 3 / min, the tensile pressure is shifted so as to remain on the inner surface side due to excessive cooling.
- transduces is not specifically limited, For example, helium, argon, nitrogen, or air can be selected.
- the temperature of the cooling gas is not particularly limited, but room temperature can be selected.
- the mold may be provided with an exhaust pipe to discharge the cooling gas in the mold out of the mold.
- the silica glass crucible for pulling a silicon single crystal according to the present invention can be used, for example, as follows. Polycrystalline silicon (polysilicon) is put into a silica glass crucible and heated by a heater to melt the polycrystalline silicon. A silicon single crystal is manufactured by pulling up while rotating the seed crystal in a state where the end of the silicon seed crystal is immersed in a silicon melt.
- the shape of the silicon single crystal is a cylindrical silicon seed crystal from the top, a conical silicon single crystal below (top portion), a cylindrical silicon single crystal having the same diameter as the bottom of the upper cone (straight barrel portion), It is a conical silicon single crystal (tail part) whose apex is downward.
- the silica glass crucible for pulling a silicon single crystal according to the present invention has a maximum bubble content, an average open cell number density, an average brown ring number density, and an average brown ring diameter of the transparent layer of the silica glass crucible after pulling the silicon single crystal. It can be remarkably lowered and the single crystallization rate can be improved.
- the single crystallization rate is defined as the weight ratio of the single crystal to the silicon raw material. However, not all the silicon melt in the crucible is used, and only the straight body portion excluding the top portion and the tail portion of the silicon single crystal ingot is subject to calculation of the single crystallization rate. Therefore, even if a sufficient silicon single crystal is pulled, the single crystallization rate is 100% or less, 80% or more is preferable, and 90% or more is more preferable.
- the maximum bubble content of the silica glass crucible after pulling up the silicon single crystal is preferably 0.1 Vol% or less. Under these conditions, mixing of bubbles into the silicon single crystal can be reduced, and a good single crystallization rate can be realized.
- the maximum bubble content can be determined in the same manner as the maximum bubble content before use of the silica glass crucible.
- the average open cell number density of the silica glass crucible after pulling the silicon single crystal is preferably 7 (number / cm 2 ) or less. Under these conditions, mixing of bubbles into the silicon single crystal can be reduced, and a good single crystallization rate can be realized.
- An open bubble is a recess derived from bubbles that appears on the inner surface of the silica glass crucible due to melting of the inner surface of the silica glass crucible when the silicon single crystal is pulled up.
- the open cell number density can be calculated by counting the number of open cells per unit area formed on the inner surface of the silica glass crucible after pulling up the silicon single crystal by microscopic observation.
- the average open cell number density can be calculated from the average open cell number density of the straight body part, bottom part and corner part of the silica glass crucible.
- the average brown ring number density of the silica glass crucible after pulling the silicon single crystal is preferably 7 (number / cm 2 ) or less.
- the brown ring is brown cristobalite generated on the inner surface of a silica glass crucible when it is in contact with a high-temperature silicon melt for a long time.
- cristobalite grows on the inner surface of the silica glass crucible or in a direction perpendicular to the inner surface to form ring-shaped spots.
- the formed brown ring is easy to peel off. When the peeled brown ring falls and mixes in the silicon melt, it is carried to the silicon single crystal.
- the pulled silicon ingot is polycrystallized and the single crystallization rate is lowered.
- the average brown ring number density of the silica glass crucible is low, the ratio of brown rings falling into and mixing in the silicon melt is reduced, and the decrease in single crystallization rate can be suppressed, and a good single crystallization rate can be achieved. realizable.
- the brown ring number density can be calculated by counting the number of brown rings per unit area formed on the inner surface of the silica glass crucible after pulling up the silicon single crystal by microscopic observation.
- the average brown ring number density can be calculated from the average value of the brown ring number density of the straight body part, bottom part and corner part of the silica glass crucible.
- the average brown ring diameter of the silica glass crucible after pulling the silicon single crystal is preferably 4 mm or less. Under this condition, the growth of the brown ring is suppressed, the rate at which the brown ring falls and mixes into the silicon melt is reduced, and the decrease in the single crystallization rate can be suppressed, and a good single crystallization rate is achieved. realizable.
- the brown ring diameter is the diameter of the brown ring formed on the inner surface of the silica glass crucible after the silicon single crystal is pulled.
- the average brown ring diameter can be calculated from an average value obtained by measuring the diameters of 100 brown rings from the straight body part, bottom part, and corner part from the straight body part to the bottom part of the silica glass crucible.
- the synthetic silica powder plasma-treated using a plasma reactor equipped with a water-cooled cooling device was rapidly cooled at a cooling rate of 10 6 K / min or more.
- the synthetic silica powder was recovered, and the synthetic silica powder was washed by ultrasonic cleaning using ultrapure water. The washing was performed until there were no fine particles adhering to the synthetic silica powder.
- the synthetic silica powder after washing was classified to obtain a synthetic silica powder according to Production Example 1.
- the strength ratio R, average particle diameter, specific surface area, tap bulk density and circularity of the synthetic silica powder were measured as follows, and the results are shown in Table 1.
- Intensity ratio R A distributed micro Raman apparatus was used. The measurement conditions were laser wavelength: 532 nm (5 mw), exposure time: 20 seconds, and integration count: once. And the peak intensity I 1 of Raman shift 492cm -1 band, Raman shift 606 cm -1 peak intensity of band I 2, by integrating the time variation of Raman shift 800 cm -1 band peak of the electric signal and the peak intensity I 0 of The intensity ratio R was calculated from the formula (I 1 + I 2 ) / I 0 .
- the Raman spectra of Production Example 1 and Comparative Production Example 1 are shown in FIG.
- Average particle size The particle size distribution was determined by a laser diffraction / scattering measurement method using laser light as a light source, and the particle size (D50) at an integrated value of 50% in the obtained particle size distribution was defined as the average particle size.
- Tap bulk density The measurement container containing the sample (silica powder) was placed on the tap device with the auxiliary cylinder attached, and tapping was performed 600 times. After the sample was ground, the mass was measured. The sample was replenished again, the measurement container with the auxiliary cylinder attached was placed in the tap device, and the tap was performed 100 times. After the sample was ground, the mass was measured, and the operation was repeated until the mass difference from the previous mass was within 0.3%. The mass of the sample was divided by the volume of the measurement container to obtain the tap bulk density. The measurement was performed 3 times, and the average value was defined as the tap bulk density.
- FIG. 2 is an electron micrograph of the appearance and cross section of the synthetic silica powder according to Production Example 1.
- Production Examples 2 to 6 Synthetic silica powders according to Production Examples 2 to 6 were obtained in the same manner as in Production Example 1 except that classified synthetic silica powder classified after Production Example 1 was used. Similar to Production Example 1, the strength ratio R, average particle diameter, specific surface area, tap bulk density and circularity of the synthetic silica powder were measured, and the results are shown in Table 1.
- Comparative Production Examples 1 to 3 Comparative production examples 1 to 3 were carried out in the same manner as in production example 1 except that the thermal plasma treatment was not performed and classified synthetic silica powder different from production example 1 was used in the synthetic silica powder classified after washing. Such synthetic silica powder was obtained. Similar to Production Example 1, the strength ratio R, average particle diameter, specific surface area, tap bulk density and circularity of the synthetic silica powder were measured, and the results are shown in Table 1.
- FIG. 3 is an electron micrograph of the appearance and cross section of the synthetic silica powder according to Comparative Production Example 1.
- Average bubble diameter It calculated
- Maximum bubble content It calculated
- the bubble content at the highest value among the measured points was taken as the maximum bubble content.
- Stress change rate The residual stress in the silica glass crucible was measured by the Senarmon method. The measurement was performed at intervals of 0.5 to 1.0 mm in the thickness direction from the inner surface, and a stress-distance graph was created. From the stress-distance graph, the slope of the tangential line (stress change rate) with respect to the position where the stress becomes 0 MPa (that is, the interface) was obtained. For the silica glass crucibles according to Example 1 and Comparative Example 1, a stress-distance graph is shown in FIG.
- Comparative Example 13 A silica glass crucible according to Comparative Example 13 was obtained in the same manner as in Example 1 except that the amount of gas discharged by the blower with the cleaning function was changed to 5 m 3 / min. The stress change rate was measured in the same manner as in Example 1, and the results are shown in Table 3.
- Comparative Example 14 A silica glass crucible according to Comparative Example 14 was obtained in the same manner as in Example 2 except that the amount of gas discharged by the blower with the cleaning function was changed to 5 m 3 / min. The stress change rate was measured in the same manner as in Example 1, and the results are shown in Table 3.
- Comparative Example 15 A silica glass crucible according to Comparative Example 15 was obtained in the same manner as in Example 3 except that the amount of gas discharged by the blower with the cleaning function was changed to 5 m 3 / min. The stress change rate was measured in the same manner as in Example 1, and the results are shown in Table 3.
- Comparative Example 16 A silica glass crucible according to Comparative Example 16 was obtained in the same manner as in Example 4 except that the amount of gas discharged by the blower with the cleaning function was changed to 5 m 3 / min. The stress change rate was measured in the same manner as in Example 1, and the results are shown in Table 3.
- Comparative Example 17 A silica glass crucible according to Comparative Example 17 was obtained in the same manner as in Example 5 except that the amount of gas discharged by the blower with the cleaning function was changed to 5 m 3 / min. The rate of change in stress was obtained in the same manner as in Example 1. The results are shown in Table 3.
- Comparative Example 18 A silica glass crucible according to Comparative Example 18 was obtained in the same manner as in Example 6 except that the amount of gas discharged by the blower with the cleaning function was changed to 5 m 3 / min. The stress change rate was measured in the same manner as in Example 1, and the results are shown in Table 3.
- FIG. 5 is a graph plotting the X-axis as each part of the silica glass crucible and the Y-axis as the bubble content (Vol%).
- the silica glass crucible according to Comparative Example 1 the bubble content increases from the corner portion to the wall portion, whereas the silica glass crucible according to Example 1 shows a bubble content rate of 0.01 Vol% or less only in the wall portion. It was. Therefore, it turns out that the silica glass crucible which concerns on Example 1 is a glass crucible which does not contain a bubble substantially.
- FIG. 8 is a polarization photograph of a cross-sectional sample in the silica glass crucible according to Comparative Example 1.
- a clear interface was observed between the compressive stress and the tensile stress.
- FIG. 9 is a polarized photograph of a cross-sectional sample in the silica glass crucible according to Example 1.
- silica glass crucible according to Example 1 there was no clear interface between the compressive stress and the tensile stress. That is, the compressive stress and the tensile stress changed gently.
- FIG. 6 shows a laser confocal microscope photograph of the inner surface of the silica glass crucible according to Example 1
- FIG. 7 shows a laser confocal microscope photograph of the inner surface of the silica glass crucible according to Comparative Example 1.
- Maximum bubble content It calculated
- the bubble content at the highest value among the measured points was taken as the maximum bubble content.
- Average open cell number density The open cell number density was calculated by counting the number of open cells per unit area formed on the inner surface of the silica glass crucible after pulling up the silicon single crystal by microscopic observation.
- Average brown ring number density Calculation was performed by counting the number of brown rings per unit area formed on the inner surface of the silica glass crucible after the silicon single crystal was pulled.
- Average brown ring diameter 100 diameters of brown rings were measured from the straight body part, bottom part, and corner part from the straight body part to the bottom part of the silica glass crucible, and calculated from the average value.
- Single crystallization rate It calculated
- the silica glass crucibles according to Examples 1 to 6 having an intensity ratio R of 0.8 ⁇ R ⁇ 1.0 were used, the single crystallization rate was good.
- the average particle size is 87 to 160 ⁇ m
- the specific surface area is 0.026 to 0.045 (m 2 / g)
- the tap bulk density is 1.35 to 1.44 (g / cm 3 )
- the circularity is 0.73.
- the silica glass crucibles according to Examples 1 to 3 produced using the synthetic silica powders of Production Examples 1 to 3 having a value of ⁇ 0.91 had a single crystallization rate exceeding 90%.
- the silica glass crucibles according to Examples 1 to 6 after pulling the silicon single crystal were compared with the silica glass crucibles according to Comparative Examples 1 to 12, with an average open cell number density, an average brown ring number density, and an average brown ring.
- the crucibles according to Examples 1 to 3 having a small diameter have an average open cell number density of 4.0 to 4.5 (number / cm 2 ) and an average brown ring number density of 2.6 to 3.1 (number). / Cm 2 ), and the average brown ring diameter was 2.3 to 2.5 (mm), which was extremely low.
- the silica glass crucibles according to Examples 1 to 6 have low generation of bubbles and brown rings during pulling of the silicon single crystal, and have a good single crystallization rate.
- Examples 1 to 3 have a single crystallization rate. Was significantly better.
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Abstract
Description
式(1)中、強度比R=(I1+I2)/I0
I1=ラマンシフト492cm-1バンドのピーク強度
I2=ラマンシフト606cm-1バンドのピーク強度
I0=ラマンシフト800cm-1バンドのピーク強度
本発明に係るシリカガラスルツボは、上端が開口し鉛直方向に延びる略円筒形の直胴部、湾曲した底部、及び直胴部と底部とを連結し且つ底部よりも曲率が大きいコーナー部を備える。シリカガラスルツボは、内表面側に透明層を備え、前記透明層の内表面側に圧縮応力が残留する圧縮応力層と、前記圧縮応力層と緩やかな応力変化率で、前記内表面側とは反対側に隣接している、引張応力が残留する引張応力層とを備えるシリカガラスルツボである。以下、各構成要素について詳細に説明する。
λ:光源の波長(nm)
C:光弾性定数(nm/cm)/MPa
L:光路長(cm)
シリカガラスの光弾性定数Cは、3.5±0.2(nm/cm)/Mpaである。光源の波長λは、使用する1/4波長板に適する波長を選択する。使用する光源の波長に対して、適する1/4波長板を選択してもよい。光路長Lは、サンプルにおける、光軸方向の厚さである。
次に、本発明に係るシリコン単結晶引き上げ用シリカガラスルツボの製造方法について説明する。
0.8≦R≦1.0 ・・・(1)
式(1)中、強度比R=(I1+I2)/I0
I1=ラマンシフト492cm-1バンドのピーク強度
I2=ラマンシフト606cm-1バンドのピーク強度
I0=ラマンシフト800cm-1バンドのピーク強度
円形度=4πS/L2 ・・・(3)
S:撮影した記録画像の粒子投影図における面積
L:粒子投影図の周囲長
本発明に係るシリコン単結晶引き上げ用シリカガラスルツボは、例えば、次のように用いることができる。シリカガラスルツボに多結晶シリコン(ポリシリコン)を投入し、ヒーターにより加熱して多結晶シリコンを熔融させる。シリコン単結晶は、シリコン種結晶の端部をシリコン融液に中に浸けた状態で種結晶を回転させながら引き上げることで製造される。シリコン単結晶の形状は、上側から円柱状のシリコン種結晶、その下に円錐状のシリコン単結晶(トップ部)、上部円錐底面と同じ径を持つ円柱状のシリコン単結晶(直胴部)、頂点が下向きである円錐状のシリコン単結晶(テール部)である。
(製造例1)
アルコキシシランの加水分解により得られた合成シリカ粉低真空条件下にて焼成し、焼成された合成シリカ粉原料を得た。得られた合成シリカ粉原料を冷却装置付き高周波誘導熱プラズマ発生装置に投入した。プラズマ発生装置の条件は、以下の通り行った;周波数:7~10MHz、出力:100~110kW、ガス:アルゴン-酸素混合ガス(酸素分圧20%)、ガス供給量:90~110L/min、原料供給速度:25~35kg/hr。プラズマ処理した後、水冷冷却装置付きのプラズマ反応器を用いてプラズマ処理された合成シリカ粉を106K/min以上の冷却速度で急冷させた。熱プラズマ処理後、合成シリカ粉を回収し、超純水を用いた超音波洗浄により合成シリカ粉を洗浄した。洗浄は、合成シリカ粉に付着する微粒子がなくなるまで行った。洗浄後の合成シリカ粉を分級して、製造例1に係る合成シリカ粉を得た。合成シリカ粉の強度比R、平均粒径、比表面積、タップ嵩密度及び円形度を以下のように測定し、結果を表1に示す。
分散型顕微ラマン装置を使用した。測定条件は、レーザー波長:532nm(5mw)、露光時間:20秒、積算回数:1回とした。ラマンシフト492cm-1バンドのピーク強度I1と、ラマンシフト606cm-1バンドのピーク強度I2と、ラマンシフト800cm-1バンドのピーク強度I0をピークの電気信号の時間変化を積分することで算出し、式(I1+I2)/I0から強度比Rを求めた。製造例1および比較製造例1のラマンスペクトルを図4に示す。
粒度分布をレーザー光を光源としたレーザー回折・散乱式測定法で求め、得られた粒度分布における積算値50%での粒径(D50)を平均粒径とした。
BETの吸着等温式を用いたガス吸着法で求めた。
試料(シリカ粉)の入った測定容器を補助円筒を付けたままタップ装置に設置して、タップを600回実施した。試料のすり切りを行った後、質量を測定した。再度試料を補充し、補助円筒を付けたままの測定容器をタップ装置に設置し、タップを100回実施した。試料のすり切りを行った後、質量を測定し、先の質量との質量差が0.3%以内になるまで操作を繰り返した。試料の質量を測定容器の容積で除してタップ嵩密度とした。測定は3回行い、平均値をタップ嵩密度とした。
得られた合成シリカ粉末を液体に分散させて、この液体を平面伸長流動セルへ流した。平面伸長流動セル内に移動する粉末粒子200個を、対物レンズに画像として記録し、この記録画像から円形度を下記式(3)により算出した。測定は2回行い、その平均値を粉末の円形度とした。なお、粒子が真円の時、円形度は1となる。
円形度=4πS/L2 ・・・(3)
S:撮影した記録画像の粒子投影図における面積
L:粒子投影図の周囲長
洗浄後に分級された合成シリカ粉において、製造例1と異なる分級合成シリカ粉を用いた以外は製造例1と同様にして、製造例2~6に係る合成シリカ粉を得た。製造例1と同様に、合成シリカ粉の強度比R、平均粒径、比表面積、タップ嵩密度及び円形度を測定し、結果を表1に示す。
熱プラズマ処理を行わなかったこと、および洗浄後に分級された合成シリカ粉において、製造例1と異なる分級合成シリカ粉を用いた以外は、製造例1と同様にして、比較製造例1~3に係る合成シリカ粉を得た。製造例1と同様に、合成シリカ粉の強度比R、平均粒径、比表面積、タップ嵩密度及び円形度を測定し、結果を表1に示す。
冷却装置付き高周波誘導熱プラズマ発生装置の代わりに冷却装置を除いた高周波誘導熱プラズマ発生装置により熱プラズマ処理を行ったこと、および洗浄後に分級された合成シリカ粉において、製造例1と異なる分級合成シリカ粉を用いた以外は、製造例1と同様にして、比較製造例4~12に係る合成シリカ粉を得た。製造例1と同様に、合成シリカ粉の強度比R、平均粒径、比表面積、タップ嵩密度及び円形度を測定し、結果を表1に示す。
(実施例1~6,比較例1~12)
合成シリカ粉として、製造例1~6および比較製造例1~12を用い、回転モールド法に基づいて、それぞれ実施例1~6および比較例1~12に係る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25mmとし、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。アーク熔融後、清浄化機能付き送風機を用いて、20~30m3/minの吐出ガス量で空気をモールド内部へ送った。得られた実施例1~6および比較例1~12に係るシリカルツボについて、平均気泡径、最大気泡含有率、および表面粗さ(Ra)を以下のように測定し、結果を表2に示す。
測定範囲の中で球状の気泡の直径の平均値として求めた。直径は、ガラスサンプルの画像を取得し、ソフトウェアによって求めた。
ルツボの単位体積に占める気泡の体積で求めた。測定した点のうち最も値が高い点の気泡含有率を最大気泡含有率とした。
シリカガラスルツボの内表面を切り出してレーザー共焦点顕微鏡を用いて内表面の粗さを非接触で測定し、座標点を求め、内表面の高低差をソフトウェアを用いて表面粗さを求めた。図6は、実施例1に係るシリカガラスルツボの表面写真であり、図7は比較例1に係るシリカガラスルツボの表面写真である。
シリカガラスルツボにおける残留応力をセナルモン法により測定した。測定は、内表面から肉厚方向に0.5~1.0mm間隔で測定し、応力-距離グラフを作成した。応力-距離グラフから、応力が0MPaとなる位置(即ち界面)に対する接線の傾き(応力変化率)を求めた。実施例1および比較例1に係るシリカガラスルツボについては、応力-距離グラフを図10に示す。
清浄化機能付き送風機による吐出ガス量を5m3/minに変化させた以外は実施例1と同様にして比較例13に係るシリカガラスルツボを得た。実施例1と同様に応力変化率を測定し、結果を表3に示す。
清浄化機能付き送風機による吐出ガス量を5m3/minに変化させた以外は実施例2と同様にして比較例14に係るシリカガラスルツボを得た。実施例1と同様に応力変化率を測定し、結果を表3に示す。
清浄化機能付き送風機による吐出ガス量を5m3/minに変化させた以外は実施例3と同様にして比較例15に係るシリカガラスルツボを得た。実施例1と同様に応力変化率を測定し、結果を表3に示す。
清浄化機能付き送風機による吐出ガス量を5m3/minに変化させた以外は実施例4と同様にして比較例16に係るシリカガラスルツボを得た。実施例1と同様に応力変化率を測定し、結果を表3に示す。
(清浄化機能付き送風機による吐出ガス量を5m3/minに変化させた以外は実施例5と同様にして比較例17に係るシリカガラスルツボを得た。実施例1と同様に応力変化率を測定し、結果を表3に示す。
清浄化機能付き送風機による吐出ガス量を5m3/minに変化させた以外は実施例6と同様にして比較例18に係るシリカガラスルツボを得た。実施例1と同様に応力変化率を測定し、結果を表3に示す。
実施例1及び比較例1に係るシリカガラスルツボの透明層において、ルツボの底部からコーナー部を通って直胴部(壁部)までの気泡含有率を測定した。図5は、X軸をシリカガラスルツボの各パーツとし、Y軸を気泡含有率(Vol%)としてプロットしたグラフである。比較例1に係るシリカガラスルツボは、コーナー部から壁部にかけて気泡含有率が上昇するのに対し、実施例1に係るシリカガラスルツボは壁部のみに0.01Vol%以下の気泡含有率を示した。従って、実施例1に係るシリカガラスルツボは、実質的に気泡を含まないガラスルツボであることが分かる。
実施例1と比較例1に係るシリカガラスルツボの中心軸とその底部の交点から内表面に沿ってリム方向600mmの位置において、シリカガラスルツボを垂直方向に切断し、スライス片を約2mm厚になるまで研磨した。研磨した断面サンプル(スライス片)を用いて、鋭敏色により圧縮応力か引張応力かを調べた。その結果、いずれのサンプルも内表面側は、圧縮応力が残留しており、圧縮応力に隣接するように引張応力が残留していた(図示せず)。
実施例1に係るシリカガラスルツボの内表面のレーザー共焦点顕微鏡写真を図6に、比較例1に係るシリカガラスルツボの内表面のレーザー共焦点顕微鏡写真を図7に示す。
実施例1~6および比較例1~12に係るシリカガラスルツボを用いて、シリコン単結晶の引き上げを行い、最大気泡含有率(Vol%)、平均開気泡数密度(個数/cm2)、平均ブラウンリング数密度(個数/cm2)、平均ブラウンリング径(mm)、および単結晶化率(%)の評価を以下のように行った。これらの結果を表4に記載する。
ルツボの単位体積に占める気泡の体積で求めた。測定した点のうち最も値が高い点の気泡含有率を最大気泡含有率とした。
シリコン単結晶引き上げをおこなった後のシリカガラスルツボ内表面に形成されている単位面積当たりの開気泡の個数を顕微鏡観察により計数することで開気泡数密度を算出した。
シリコン単結晶引き上げをおこなった後のシリカガラスルツボ内表面に形成されている単位面積当たりのブラウンリングの個数を顕微鏡観察により計数することで算出した。
シリカガラスルツボの直胴部、底部及び直胴部から底部に至るコーナー部からそれぞれから100個ずつブラウンリングの直径を測定し、その平均値から算出した。
シリコン原料に対する単結晶の重量比として求めた。
実施例1~3、比較例1~3、および比較例13~18に係るシリカガラスルツボを用いて、シリコン単結晶の引き上げを行い、引き上げ後のルツボを観察した。結果を表5に示す。実施例1~3に係るシリカガラスルツボは、内倒れや座屈等が見当たらず良好な形状を保っていた。比較例13~15については、ルツボ全体の形状に内倒れが生じたり座屈が生じたりした。また、比較例16~18については、リムにクラックや内倒れが生じていた。従って、圧縮応力から引張応力への応力の変化が急であったり、緩やかすぎたりする場合は、シリカガラスルツボにクラックや内倒れ及び座屈が生じることが分かる。
Claims (6)
- 上端が開口し鉛直方向に延びる略円筒形の直胴部、湾曲した底部、及び前記直胴部と前記底部とを連結し且つ前記底部よりも曲率が大きいコーナー部を備えるシリカガラスルツボであって、
前記シリカガラスルツボは、内側に透明層、及びその外側に気泡層を備え、
前記透明層の内表面側に圧縮応力が残留する圧縮応力層と、
前記圧縮応力層と緩やかな応力変化率で隣接している、引張応力が残留する引張応力層と、
を備えることを特徴とするシリコン単結晶引き上げ用シリカガラスルツボ。 - 前記応力変化率が0.17MPa/mm以上、1.5MPa/mm以下である請求項1記載のシリコン単結晶引き上げ用シリカガラスルツボ。
- 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、前記シリカガラスルツボ製造用回転モールドの内面に前記天然シリカ粉の層を形成する工程、
ラマン測定法で求められる下記式(1)を満たす合成シリカ粉を前記天然シリカ粉の層の内側に堆積する工程、及び
前記天然シリカ粉および前記合成シリカ粉にアーク放電する工程を備えることを特徴とする請求項1記載のシリコン単結晶引き上げ用シリカガラスルツボの製造方法。
0.8≦R≦1.0 ・・・(1)
式(1)中、強度比R=(I1+I2)/I0
I1=ラマンシフト492cm-1バンドのピーク強度
I2=ラマンシフト606cm-1バンドのピーク強度
I0=ラマンシフト800cm-1バンドのピーク強度 - 前記アーク放電後、前記モールドの内部に冷却ガスを導入する工程を更に備える請求項3記載のシリコン単結晶引き上げ用シリカガラスルツボの製造方法。
- 前記合成シリカ粉の円形度が0.73以上1.0以下である請求項3または4記載のシリコン単結晶引き上げ用シリカガラスルツボの製造方法。
- 前記合成シリカ粉は、平均粒径が80μm以上、160μm以下、タップ嵩密度が1.35g/cm3以上、1.44g/cm3以下、及び比表面積が0.026m2/g以上、0.045m2/g以下である請求項3ないし5いずれか記載のシリコン単結晶引き上げ用シリカガラスルツボの製造方法。
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JP2018030774A (ja) * | 2016-07-29 | 2018-03-01 | 友達晶材股▲ふん▼有限公司AUO Crystal Corporation | シリコンインゴット作製用の容器およびその製造方法、ならびに結晶シリコンインゴットを製造するための方法 |
JP2019172515A (ja) * | 2018-03-28 | 2019-10-10 | 三菱ケミカル株式会社 | 合成シリカガラス粉 |
WO2024062783A1 (ja) * | 2022-09-20 | 2024-03-28 | 株式会社Sumco | 石英ガラスルツボ及びその製造方法及び石英ガラスルツボ用石英粉 |
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JP2019151494A (ja) * | 2018-02-28 | 2019-09-12 | 株式会社Sumco | シリカガラスルツボ |
CN108579834A (zh) * | 2018-03-29 | 2018-09-28 | 连云港格航工业设计有限公司 | 一种大小可调节的石英坩埚 |
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