Quartz glass crucible and method for producing a silicon monocrystal using the same

Abstract

[Problem] A quartz glass crucible which enables an increase in strength during crystal pulling up by forming a thick crystal layer on an outer surface of the crucible at an appropriate crystallization rate is provided. [Solution] A quartz glass crucible 1 includes a crucible base body 10 made of silica glass and a coating film 13 containing a crystallization accelerator formed on the outer surface 10o of the crucible base body 10. Ten hours after the start of heat treatment performed in an Ar atmosphere at a furnace temperature of 1580°C and a furnace pressure of 20 Torr, the thickness of a crystal layer formed on the outer surface 10o of the crucible base body 10 is 0.21 to 0.5 mm, and the crystallization rate is 21 to 50 μm / h. The crystallization rate of the outer surface 10o is 10 μm / h or less 20 hours after the start of heat treatment.

Description

TECHNICAL AREA

[0001] The present invention relates to a quartz glass crucible used for pulling up a silicon monocrystal by a Czochralski method (CZ method). Furthermore, the present invention relates to a method for producing a silicon monocrystal using such a quartz glass crucible. STATE OF THE ART

[0002] Most silicon monocrystals used as substrate materials for semiconductor devices are produced using the CZ process. In the CZ process, a polycrystalline silicon raw material is melted in a quartz crucible to create a silicon melt. A seed crystal is immersed in the silicon melt, and the seed crystal is gradually pulled upward while rotating the quartz crucible and seed crystal, allowing a large monocrystal to grow at the bottom of the seed crystal. The CZ process can increase the yield of large-diameter silicon monocrystals.

[0003] A quartz crucible (silica crucible) is a container made of silica glass that holds a silicon melt during a silicon monocrystal pull-up step. The inner side portion (inner layer) of the quartz crucible is formed from a transparent glass layer that comes into contact with the silicon melt and therefore contains essentially no bubbles. The outer side portion (outer layer) is formed from a bubble-containing layer containing a number of bubbles to disperse radiant heat from the outside and evenly heat the interior of the crucible.

[0004] Regarding a quartz glass crucible that can appropriately crystallize quartz glass to suppress deformation of the crucible and the occurrence of cracks, for example, Patent Literature 1 describes an opaque quartz glass crucible having a low devitrification tendency, an Al concentration of 55 to 100 ppm by weight, a Ca concentration of 1.2 to 9.5 ppm by weight, and a molar concentration ratio (Al / Ca) of 15 or more.

[0005] Furthermore, Patent Literature 2 describes a quartz glass crucible including an aluminum-rich layer made of quartz glass having a relatively high average aluminum concentration and provided to form an outer surface of the quartz glass crucible, and an aluminum-poor layer made of quartz glass having an average aluminum concentration lower than that of the aluminum-rich layer and provided inside the aluminum-rich layer, wherein the aluminum-poor layer includes an opaque layer made of quartz glass containing a large number of tiny bubbles, the aluminum-rich layer is made of transparent or translucent quartz glass having a reduced bubble content compared to the opaque layer, and the average aluminum concentration in the aluminum-rich layer is 20 ppm or more.In this quartz glass crucible, even if the aluminum-rich layer is crystallized and the crystallization progresses into the interior of the crucible, air bubbles do not accumulate or expand, so the deformation of the crucible can be prevented.

[0006] Patent Literature 3 describes a quartz glass crucible including a crucible base body made of silica glass and a layer containing a crystallization accelerator provided on an outer surface of the crucible base body. The concentration of the crystallization accelerator contained in the layer containing the crystallization accelerator is 1.0 × 10 13 atoms / cm 2 or more and 4.8 × 10 15 atoms / cm 2or less. The crystallization of the outer surface of the crucible is neither too fast nor too slow, and the crystallization has a reasonable time for strength development. Therefore, the crucible can withstand a monocrystal pulling step for a long time, and the gap between the crucible and the carbon susceptor is minimized, and the oxygen concentration and crystal diameter of the silicon monocrystal are stably controlled. The thickness of a crystal layer formed on the outer surface is 200 to 500 μm when heated at temperatures of 1550 °C or higher and 1600 °C or lower for 25 hours.

[0007] The viscosity of a quartz glass crucible depends on temperature profiles such as arc melting temperature and cooling rate, and the fictive temperature of the glass also changes if the temperature profile changes. The fictive temperature correlates with the glass structure. The glass structure, such as the content ratio of polycyclic rings in the glass, can be estimated using a Raman spectral analysis method. Using the Raman spectral analysis method, the content ratio of polycyclic rings in the glass can be measured, and a fictive temperature can be determined from the result (see Non-Patent Literature 1). A method for estimating the fictive temperature of glass using Fourier transform infrared spectroscopy (FT-IR) is also known (see Non-Patent Literature 2). LITERATURE ON THE STATE OF THE ART PATENT LITERATURE Patent Literature 1: Japanese Laid-Open Patent Publication No. 2020-105062 Patent Literature 2: Japanese republication of International Application No. 2018 / 051714 Patent Literature 3: International Publication No. WO2021 / 140729, Publication NON-PATENT LITERATURE Non-patent literature 1: Journal of AE Geissberger and FL Galeener, “Raman studies of vitreous SiO2 versus fictive temperature”, Phys. Rev. B, Vol. 28, pp. 3266-3271 (1983). Non-Patent Literature 2: A. Agarwal, KM Davis and M. Tomozawa, “A simple IR spectroscopic method for determining fictive temperature of silica glasses,” J. Non-Cryst. Solids, Vol. 185, pp. 191-198 (1995). SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] When the crystallization accelerator is applied to the outer surface of the crucible as described above, the strength of the crucible can be improved by crystallizing the outer surface of the crucible. In particular, increasing the coating concentration of the crystallization accelerator accelerates crystallization and allows a thicker crystal layer to be formed.

[0009] However, if the coating concentration of the crystallization accelerator is increased, the crystallization rate of the outer surface of the crucible also increases. If the crystallization rate is too high, foam-induced detachment will occur in the crystal layer of the outer surface of the crucible, resulting in a problem of strength reduction due to crucible deformation. If the crystallization rate of the outer surface of the crucible is too slow, the thickness of the crystal layer of the outer surface of the crucible will decrease, the desired strength cannot be ensured, and problems such as buckling or inward deformation of the crucible may occur.

[0010] Therefore, an object of the present invention is to provide a quartz glass crucible capable of increasing strength during a crystal pulling-up step by forming a thick crystal layer on an outer surface of the crucible at an appropriate crystallization rate, and a method for producing a silicon monocrystal using the quartz glass crucible. MEANS FOR SOLVING THE TASKS

[0011] To achieve the above-described object, a quartz glass crucible according to the present invention includes a crucible base body made of silica glass and a coating film containing a crystallization accelerator formed on an outer surface of the crucible base body, wherein 10 hours after the start of a heat treatment performed in an Ar atmosphere at a furnace temperature of 1580 °C and a furnace pressure of 20 Torr, a thickness of a crystal layer formed on the outer surface of the crucible base body on the outer surface is 0.21 to 0.5 mm and a crystallization rate is 21 to 50 μm / h, and a crystallization rate of the outer surface 20 hours since the start of the heat treatment is 10 μm / h or less.

[0012] According to the present invention, it is possible to form a crystal layer on the outer surface with a sufficient thickness of 200 μm or more on the outer surface of the crucible at a high temperature during the step of pulling up the silicon monocrystal, and since the crystallization of the outer surface proceeds at an appropriate rate that is neither too high nor too low, it is possible to form a crystal layer on the outer surface with a sufficient thickness and at the same time prevent foam-induced peeling of the crystal layer on the outer surface, thereby imparting a desired strength to the crucible.

[0013] In the present invention, it is preferable that a fictive temperature of the outer surface of the crucible base body is 50°C or more lower than a fictive temperature of an inner surface of the base body at a depth of 5 mm from the outer surface. If the fictive temperature of the outer surface of the crucible base body is equal to or slightly lower than that of the inner surface of the base body, the probability of diffusion of the crystallization accelerator or substitution of the Si-O bond is lower, and a crystal layer with a sufficient thickness to achieve a desired crucible strength cannot be obtained in the initial heating stage.However, when the fictive temperature of the outer surface of the crucible base body is 50 °C or more lower than that of the inner surface of the base body, the Si-O bond on the outer surface is more likely to be broken than in the inside of the crucible, and diffusion of the crystallization accelerator or substitution of the Si-O bond is likely to occur, which effectively promotes crystallization.

[0014] In the present invention, it is preferable that an Al concentration in a first depth range within 10 mm from the outer surface of the crucible base body is higher than the Fe concentration in the first depth range. Furthermore, it is preferable that an Al concentration in a first depth range within 10 mm from the outer surface of the crucible base body is higher than the Ca concentration in the first depth range. Since the Al concentration within 10 mm from the outer surface of the quartz glass crucible is higher than the Ca or Fe concentration, crystallization in the thickness direction can be relatively promoted compared to the in-plane direction of the crucible, and the outer surface of the crucible can be crystallized at an appropriate crystallization rate to a thickness at which the strength development effect is obtained.

[0015] It is preferable that the crystallization accelerator is Ba, and a Ba concentration in a crystal layer on the outer surface formed on the outer surface of the crucible base body after heat treatment is less than 10 ppm. If the Ba concentration in the crystal layer on the outer surface is 10 ppm or more, the concentration of the crystallization accelerator to be applied to the outer surface of the crucible base body will be high, and crystallization will be excessive during the silicon monocrystal pulling-up step, which may cause foaming-induced detachment of the crystal layer on the outer surface. However, if the Ba concentration in the crystal layer on the outer surface is less than 10 ppm, crystallization of the outer surface can be promoted while suppressing foaming-induced detachment of the crystal layer on the outer surface.

[0016] It is preferable that the coating film containing the crystallization accelerator contains barium carbonate and a thickener, and a Ba concentration in the coating film containing the crystallization accelerator is 1.0 × 10 15 up to 1.0 × 10 18 atoms / cm 2 If the Ba concentration is too low, unevenness in the thickness and area of ​​the crystal layer will occur, and a crystal layer sufficient to improve strength will not be formed. Furthermore, if the Ba concentration is too high, there is a risk that the crystal layer will be broken during the silicon monocrystal pulling-up step due to excessive crystallization progress. However, if the Ba concentration is in the range of 1.0 × 10 15 up to 1.0 × 10 18 atoms / cm 2This problem can be avoided and the crystallization of the outer surface can be promoted while the foam-induced detachment of the crystal layer on the outer surface is suppressed.

[0017] It is preferable that in a second depth range within two-thirds of a wall thickness of the crucible base body from the outer surface of the crucible base body, a B concentration is 0.02 to 0.05 ppm, a Mg concentration is 0.02 to 0.4 ppm, and a Cr concentration is 0.02 to 0.08 ppm. When B, Mg, or Cr is present in the glass, a microstructure around the atom is a regularly arranged crystal structure. When the impurities exist from the outer surface of the crucible base body to a certain depth, the crystallization rate is increased in the depth direction from the outer surface to the inner surface. Therefore, the crystal layer on the outer surface can be made thick to a certain extent, and an attempt can be made to improve the strength of the crucible.

[0018] It is preferable that the concentrations of B, Mg, and Cr in the second depth range within two-thirds of the wall thickness of the crucible base body from the outer surface of the crucible base body are higher than the concentration of B, Mg, and Cr in a third depth range within 2 mm from an inner surface of the crucible base body. By reducing the crystallization rate on the outer surface of the crucible base body, foam-induced detachment of the crystal layer on the outer surface can be prevented, but the crucible is tightly fitted to the carbon susceptor, causing the softened silica glass to penetrate into the gaps between the parts constituting the carbon susceptor. The effect of wrinkles that occurred on the outer surface of the crucible also extends to the inner surface side of the crucible, and unevenness occurs on the inner surface of the crucible.However, by reducing the concentrations of B, Mg and Cr on the inner surface side of the crucible base body, it is possible to prevent a decrease in the viscosity of the silica glass and suppress the deformation of the inner surface side of the crucible.

[0019] Furthermore, the method for producing a silicon monocrystal according to the present invention pulls up a silicon monocrystal using the quartz glass crucible according to the present invention having the above-described features by the CZ method. According to the present invention, the manufacturing yield of a silicon monocrystal can be increased.

[0020] Further, the method for manufacturing a quartz glass crucible according to the present invention includes a step of manufacturing a crucible base body made of quartz glass and a step of forming a coating film containing a crystallization accelerator on an outer surface of the crucible base body, wherein the step of manufacturing the crucible base body includes a step of sequentially filling natural quartz powder and synthetic quartz powder into an inner surface of a rotary mold to form a deposited layer of raw material powder, a step of arc melting the deposited layer of raw material powder from an inner side of the mold, and a step of completing the arc melting and cooling the molten quartz glass, and in the step of cooling the molten quartz glass, the mold is heated to maintain a high-temperature state.This allows a fictive temperature difference between the outer surface of the crucible base body and the inner surface of the base body to be set to 50 °C or more at a depth of 5 mm from the outer surface. Therefore, it is possible to form a crystal layer on the outer surface with a sufficient thickness while simultaneously preventing foam-induced detachment of the crystal layer on the outer surface and imparting the desired strength to the crucible. EFFECTS OF THE INVENTION

[0021] According to the present invention, it is possible to provide a quartz glass crucible capable of increasing the strength during crystal pulling up by forming a thick crystal layer on an outer surface of the crucible with an appropriate crystallization rate, and a method for manufacturing the quartz glass crucible. BRIEF DESCRIPTION OF THE CHARACTERS [ Fig.1] is a schematic perspective view showing a configuration of a quartz glass crucible according to an embodiment of the present invention. [ Fig. 2] is a schematic side sectional view of the Fig. 1 shown quartz glass crucible. [ Fig. 3] is a schematic view for describing an impurity concentration distribution in a depth direction from an outer surface of a crucible base body. [ Fig. 4] is a schematic diagram showing a method of manufacturing a quartz glass crucible according to a rotary molding method. [ Fig. 5] is a diagram for explaining a step of pulling up a monocrystal using the quartz glass crucible according to the present embodiment, and is a schematic sectional view showing a configuration of a monocrystal pulling-up apparatus. [ Fig.6] is a schematic side sectional view showing a crystallization state of the quartz glass crucible by heating. MODE FOR CARRYING OUT THE INVENTION

[0022] Hereinafter, preferred embodiments of the present invention are described in detail with reference to the accompanying figures.

[0023] Fig. 1 is a schematic perspective view showing the configuration of a quartz glass crucible according to an embodiment of the present invention. Fig. 2 a schematic side sectional view of the Fig. 1 shown quartz glass crucible.

[0024] As in Fig. 1 and Fig.As shown in Figure 2, a quartz glass crucible 1 is a silica glass container for holding a silicon melt, which has a cylindrical side wall 10a, a bottom 10b provided below the side wall 10a, and a corner 10c provided between the side wall 10a and the bottom 10b. The bottom 10b is preferably a so-called round bottom that is slightly curved, but may also be a so-called flat bottom. The corner 10c is a portion that has a larger curvature than the bottom 10b. The boundary position between the side wall 10a and the corner 10c and the boundary position between the bottom 10b and the corner 10c are positions where the curvature starts to change from a small curvature to a large curvature.

[0025] The opening (diameter) of the quartz glass crucible 1 also depends on the diameter of the silicon monocrystal ingot pulled up from the silicon melt, but is 18 inches (approximately 450 mm) or more, preferably 22 inches (approximately 560 mm) or more, and more preferably 32 inches (approximately 800 mm) or more. This is because such a large crucible is used to pull up a large silicon monocrystal ingot with a diameter of 300 mm or more, and the quality of the monocrystal must not be deteriorated even after prolonged use.

[0026] The wall thickness of the crucible varies slightly depending on the part of the crucible, but is preferably 6 to 20 mm. Specifically, it is preferable that the wall thickness of the side wall 10a of the crucible of 18 inches or more be 6 mm or more, the wall thickness of the side wall 10a of the crucible of 22 inches or more be 7 mm or more, and the wall thickness of the side wall 10a of the crucible of 32 inches or more be 10 mm or more. This allows a large amount of silicon melt to be stably maintained at a high temperature. Preferably, the wall thickness of the corner 10c of the crucible is the largest, and the wall thickness of the side wall 10a and the bottom 10b of the crucible is smaller than that of the corner 10c of the crucible.

[0027] As in Fig.As shown in Fig. 2, a quartz glass crucible 1 includes a crucible base body 10 made of silica glass, and a coating film 13 containing a crystallization accelerator formed on an outer surface 10o of the crucible base body 10. The crucible base body 10 has a substantially two-layer structure and includes a transparent layer 11 containing no bubbles (bubble-free layer) and a bubble layer 12 containing a large number of tiny bubbles (opaque layer). The coating film 13 containing the crystallization accelerator is provided outside the bubble layer 12.

[0028] The transparent layer 11 is a glass layer that configures the inner surface 10i of the crucible base body 10 that comes into contact with the silicon melt, and is intended to prevent a decrease in the yield of silicon monocrystals due to bubbles in the silica glass. Since the inner surface 10i of the crucible base body 10 reacts with the silicon melt to melt away, the bubbles near the inner surface of the crucible cannot be confined in the silica glass, and the bubbles burst due to thermal expansion, causing the crucible fragments (silica fragments) to detach. In a case where the crucible fragments released into the silicon melt are transported to a growth interface of the silicon monocrystal by melt convection and incorporated into the silicon monocrystal, they cause dislocations in the silicon monocrystal.In a case where the bubbles released into the silicon melt rise upwards, reach a solid-liquid interface and are incorporated into the monocrystal, they also cause the formation of pinholes in the silicon monocrystal.

[0029] "Bubble-free" in the transparent layer 11 means a bubble content and bubble size such that the monocrystallization rate is not reduced by bubbles. Such a bubble content is, for example, 0.1 vol% or less and the bubble diameter is, for example, 100 µm or less.

[0030] The thickness of the transparent layer 11 is preferably 0.5 to 10 mm and is set to an appropriate thickness for each section of the crucible so that the bubble layer 12 is not exposed due to complete disappearance of the transparent layer 11 due to melting during a crystal pulling-up step. The transparent layer 11 is preferably provided over the entire crucible from the side wall 10a to the bottom 10b of the crucible, but the transparent layer 11 may be omitted from the upper end portion of the crucible that does not come into contact with the silicon melt.

[0031] The air bubble content and diameter in the transparent layer 11 can be measured non-destructively using an optical detection unit. The optical detection unit includes a light-receiving device that receives transmitted light or reflected light from the light irradiated onto the crucible. A digital camera including an optical lens and an imaging element can be used as the light-receiving device. X-rays, laser light, and the like, as well as visible light, ultraviolet light, and infrared light, can be used as the irradiation light. The measurement results obtained by the optical detection unit are received by an image processing device to calculate the bubble diameter and the bubble content per unit volume.

[0032] The bubble layer 12 is a main glass layer of the crucible base body 10. It is located on the outer surface of the transparent layer 11 and is provided to improve the heat retention property of the silicon melt in the crucible and to heat the silicon melt in the crucible as evenly as possible by radiating heat from a heater in a monocrystal pulling-up device. Therefore, the bubble layer 12 is provided over the entire crucible from the side wall 10a to the bottom 10b. The thickness of the bubble layer 12 is substantially equal to a value obtained by subtracting the thickness of the transparent layer 11 from the thickness of the crucible base body 10, and varies depending on the part of the crucible.

[0033] The bubble content of the bubble layer 12 is higher than that of the transparent layer 11, and is preferably more than 0.1 vol% and 5 vol% or less. This is because when the bubble content of the bubble layer 12 is 0.1 vol% or less, the bubble layer 12 cannot exhibit the required heat retention function. Another reason is that when the bubble content of the bubble layer 12 exceeds 5 vol%, the crucible may deform due to thermal expansion of the bubbles, and the yield of the monocrystals may decrease, and further, the heat transfer property is insufficient. From the viewpoint of balancing the heat retention property and the heat transfer property, the bubble content of the bubble layer 12 is particularly preferably 1 to 4 vol%.It should be noted that the bubble content described above is a value obtained by measuring an unused crucible in a room-temperature environment. The bubble content of the bubble layer 12 can be determined, for example, by measuring the density (Archimedes method) of a piece of opaque fused silica cut from the crucible.

[0034] [ Fig. 3] is a schematic view for describing an impurity concentration distribution in a depth direction from an outer surface 10o of a crucible base body 10.

[0035] As in Fig.3, it is preferable that the Al concentration in the first depth range D1 within at least 10 mm from the outer surface 10o of the crucible base body 10 is higher than the concentrations of Fe and Ca in the first depth range D1. In a case where the Al concentration of the outer surface layer portion within 10 mm from the outer surface 10o of the crucible base body 10 is lower than the Ca concentration or the Fe concentration, the crystallization accelerator coated on the outer surface 10o of the crucible base body 10 is less likely to be included in Al, and thus, crystallization in the in-plane direction is promoted compared to crystallization in the depth direction.In order to promote crystallization in the depth direction up to the thickness at which the strength development effect of the crucible is achieved, it is desirable to increase the Al concentration in the mass to the extent that the Al acts as an impurity, which is a starting point for crystallization.

[0036] It is preferable that in a second depth range D2 within two-thirds of a wall thickness of the crucible base body 10 from the outer surface 10o of the crucible base body 10, a B concentration is 0.02 to 0.05 ppm, a Mg concentration is 0.02 to 0.4 ppm, and a Cr concentration is 0.02 to 0.08 ppm. When B, Mg, or Cr is present in the glass, a microstructure around the atom is a regularly arranged crystal structure. In a case where the above-described impurities are present from the outer surface 10o of the crucible base body 10 to a sufficient depth range, crystallization is accelerated in the depth direction from the outer surface 10o, whereby a crystal layer with a certain thickness can be formed on the outer surface 10o of the crucible base body 10, and the strength of the crucible can be improved.

[0037] It is preferable that the concentrations of B, Mg, and Cr in the second depth range D2 within two-thirds of the wall thickness W of the crucible base body 10 from the outer surface 10o of the crucible base body 10 are higher than the concentrations of B, Mg, and Cr in a third depth range D3 within 2 mm from an inner surface 10i of the crucible base body 10. The thickness of the crucible base body 10 here refers to the wall thickness at the measurement position of B, Mg, and Cr. A carbon susceptor that supports a quartz glass crucible during the crystal pulling-up step is configured by combining a plurality of parts, and seams (grooves) between the parts are provided on an inner surface of the divided carbon susceptor. Therefore, the outer surface 10o of the crucible base body 10 may soften at a high temperature before crystallization and penetrate into a gap in the seam of the carbon susceptor.In the event of such penetration, the outer surface 10o of the crucible base body 10 is deformed along the seam, and at the same time, the deformation of the inner surface 10i of the crucible base body 10 is also induced. However, by reducing the concentrations of B, Mg, and Cr on the inner surface 10i side of the crucible base body 10, it is possible to prevent a decrease in the viscosity of the silica glass and suppress the deformation of the inner surface side of the crucible.

[0038] It is preferable that a fictive temperature T1 (°C) of the outer surface 10o of the crucible base body 10 be lower than a fictive temperature T2 (°C) of an inner surface of the base body at a depth of 5 mm from the outer surface 10o by 50°C or more (T1 < T2 - 50). In a case where the fictive temperature T1 of the outer surface 10o of the crucible base body 10 is equal to or slightly lower than the fictive temperature T2 inside the crucible base body 10, diffusion of the crystallization accelerator or substitution of the Si-O bond is unlikely to occur, and a crystal layer on the outer surface with a sufficient thickness to achieve a desired crucible strength cannot be obtained in the initial heating stage.However, when the fictive temperature T1 of the outer surface 10o of the crucible base body 10 is 50 °C or more lower than the fictive temperature T2 inside the crucible base body 10, the Si-O bond in the outer surface 10o is more likely to be broken compared to the inside of the crucible base body 10, diffusion of the crystallization accelerator or substitution of the Si-O bond is likely to occur, and the effect of promoting crystallization occurs.

[0039] The fictive temperature of the silica glass forming the crucible base body 10 can be measured using a Raman spectral analysis method or an FT-IR method. In the Raman spectral analysis method, an area intensity ratio between a peak derived from a 3-membered ring, which is a cyclic structure of Si, and a peak derived from a 4-membered ring is obtained from a Raman spectrum (scattering spectrum) when a sample area to be measured is irradiated with laser light. The obtained result is plotted on a calibration curve obtained from the sample measurement at a known fictive temperature, allowing the fictive temperature of the corresponding sample to be calculated.

[0040] When measuring the fictive temperature using the FT-IR method, a peak wavelength derived from a quartz glass structure is detected from a transmission spectrum when a sample obtained by diluting the glass to be measured is irradiated with laser light. The resulting result is plotted against a calibration curve obtained from the sample measurement at a known fictive temperature, allowing the fictive temperature of the corresponding sample to be calculated.

[0041] A coating film 13 containing a crystallization accelerator is provided on the outer surface 10o of the crucible base body 10. The crystallization accelerator contained in the coating film 13 accelerates the crystallization of the outer surface of the crucible at high temperature during the monocrystal pulling-up step, thus improving the strength of the crucible. In this example, the coating film 13 containing the crystallization accelerator is provided on the outer surface of the crucible for the following reason.First, if the coating film 13 containing the crystallization accelerator is provided on the inner surface side of the crucible, the risk of pinhole formation in the silicon monocrystal and the risk of peeling off the outer layer on the inner surface of the crucible increase, but this risk can be reduced if the coating film 13 containing the crystallization accelerator is provided on the outer surface side of the crucible.In addition, in a case where the coating film 13 containing the crystallization accelerator is provided on the inner surface of the crucible, there is a risk of contamination of the monocrystal due to the contamination of the inner surface of the crucible with impurities, but since the contamination of the outer surface of the crucible with impurities is allowed to a certain extent, the risk of contamination of the monocrystal due to the provision of the coating film 13 containing the crystallization accelerator on the outer surface of the crucible is low.

[0042] In the present embodiment, the coating film 13 containing the crystallization accelerator is provided throughout the crucible from the side wall 10a to the bottom 10b, but the coating film 13 containing the crystallization accelerator may be provided at least in the side wall 10a. This is because the side wall 10a is more easily deformed than the corner 10c and the bottom 10b, and the effect of suppressing deformation of the crucible due to crystallization of the outer surface is strong. It is preferable that the coating film 13 containing the crystallization accelerator be provided not only on the side wall 10a but also on the corner 10c. The coating film 13 containing the crystallization accelerator may or may not be provided on the bottom 10b of the crucible.The reason for this is that the bottom 10b of the crucible absorbs a large amount of weight of the silicon melt and therefore easily adapts to the carbon susceptor, so that a gap is not easily formed between it and the carbon susceptor.

[0043] The upper end portion of the rim, located 1 to 3 cm below the upper edge of the rim, on the outer surface of the side wall 10a of the crucible may be a region where the coating film 13 containing the crystallization accelerator is not formed. This can suppress crystallization at the upper end surface of the rim and prevent dislocation in the silicon monocrystal due to the mixing of the crystal pieces detached from the upper end surface of the rim with the silicon melt.

[0044] The crystallization accelerator contained in the crystallization accelerator-containing coating film 13 is preferably barium (Ba) or strontium (Sr), particularly preferably Ba. This is because Ba has a lower segregation coefficient than silicon, is stable at room temperature, and is easy to handle. Furthermore, Ba has the advantage of not slowing down the crystallization rate of the crucible during crystallization, and it induces orientation growth more strongly than other elements.

[0045] The coating film 13 containing the crystallization accelerator contains barium carbonate and a thickener, and the concentration of Ba in the coating film 13 containing the crystallization accelerator is preferably 1.0 × 10 15 up to 1.0 × 10 18 atoms / cm 2 and particularly preferably 1.0 × 10 16 up to 1.0 × 10 17 atoms / cm2 If the concentration of Ba is less than 1.0 × 10 15 atoms / cm 2 This leads to unevenness in the thickness and crystallization area of ​​the crystal layer on the outer surface, and there is a risk that a crystal layer thick enough to achieve strength improvement will not be formed on the outer surface. Furthermore, if the Ba concentration is higher than 1.0 × 10 18 atoms / cm 2 , the likelihood of cracks in the crystal layer of the outer surface increases due to excessive progress of crystallization of the outer surface. However, if the Ba concentration is within the range described above, this problem can be avoided and the crystallization of the outer surface can be promoted while suppressing foam-induced detachment of the crystal layer on the outer surface.

[0046] The thickness of the coating film 13 containing the crystallization accelerator is not specifically limited, but is preferably 0.1 to 50 μm, and more preferably 1 to 20 μm. This is because if the thickness of the coating film 13 containing the crystallization accelerator is too thin, the peeling strength of the coating film 13 containing the crystallization accelerator is weak, and peeling of the coating film causes uneven crystallization. If the coating film is too thick, the peeling strength is also reduced, and crystallization is uneven.

[0047] When the quartz glass crucible 1 according to the present embodiment is heat-treated in a furnace at 1580°C and 20 Torr in an Ar atmosphere, a crystal growth length (a crystallization length) extending from the outer surface 10o of the crucible base body 10 in the depth direction is 0.21 to 0.5 mm from the start of the heat treatment until 10 hours later. That is, the thickness of the crystal layer formed on the outer surface 10o of the crucible base body 10 on the outer surface after 10 hours is 210 to 500 μm. Moreover, the crystallization rate 10 hours from the start of the heat treatment is 21 to 50 μm / h, but the crystallization rate 20 hours from the start of the heat treatment is 10 μm / h or less. If the crystallization rate of the outer surface is higher than 50 µm / h in the initial phase of crystallization, there is a risk of foam-induced detachment of the crystal layer on the outer surface.Furthermore, if the crystallization rate is below 21 μm / h, the crystallization of the outer surface is insufficient, and the desired strength of the crucible cannot be achieved. However, according to the present invention, it is possible to form a crystal layer on the outer surface with sufficient thickness without foam-induced detachment of the crystal layer on the outer surface, and to develop the desired strength of the crucible.

[0048] In this example, "10 hours later" from the start of heat treatment means a time point at which all the polycrystalline silicon raw materials in the crucible are dissolved, and pressure also begins to act on the wall portion of the crucible. This is because the probability of the crucible being deformed increases if the time point at which the crystal layer on the outer surface has a sufficient thickness is later than this. In addition, the crystallization rate 10 hours after the start of heat treatment is a value obtained by dividing the thickness of the crystal layer on the outer surface 10 hours later by the heat treatment time (10 hours), and is obtained as the average value of the crystallization rate for 10 hours.In addition, the crystallization rate 20 hours since the start of heat treatment is a value obtained by dividing the difference between the thickness of the crystal layer on the outer surface 20 hours later and the thickness of the crystal layer on the outer surface 30 hours later by the heat treatment time (10 hours), and is obtained as the average value of the crystallization rate for 10 hours.

[0049] In addition, as described above, it is preferable that the crystallization rate decreases 15 hours after the start of heat treatment, and the crystallization rate is 10 μm / h or less 20 hours after the start of heat treatment. If the crystallization rate is higher than 10 μm / h 20 hours after the start of heat treatment, the thickness of the crystal layer on the outer surface is too thick, and there is a risk of the crystal layer breaking during crystal pulling. The crystallization rate is reduced after melting the polycrystalline raw material, which not only allows the crucible to develop strength early but also maintains its strength.

[0050] The thickness of the crystal layer formed on the outer surface 10o of the crucible base body 10 on the outer surface 25 hours after the start of the heat treatment at 1580°C is preferably about 210 to 600 μm, and more preferably 210 to 500 μm. If the thickness of the crystal layer on the outer surface 25 hours after the start of the monocrystal pulling-up step is less than 210 μm, the possibility of deformation of the crucible due to insufficient strength increases. Furthermore, if the thickness of the crystal layer on the outer surface is more than 500 μm, the adhesion between the crucible and the carbon susceptor deteriorates, and the thermal conductivity between the carbon susceptor and the quartz glass crucible fluctuates during the monocrystal pulling-up step, thereby impairing the control of the oxygen concentration and the crystal diameter of the silicon monocrystal.Furthermore, if the crystal layer on the outer surface is too thick, it will undergo foam-induced delamination, which will impair the pull-up of the monocrystal. However, if the thickness of the crystal layer is within the range described above, the strength can be developed after adapting the crucible to the carbon susceptor, and the oxygen concentration and crystal diameter of the silicon monocrystal can be stably controlled.

[0051] For a quartz glass crucible with a crystallization accelerator applied to an outer surface, the concentration of the crystallization accelerator is considered to determine the final thickness of the crystal layer on the outer surface. Increasing the concentration of the crystallization accelerator can promote the formation of a thick crystal layer on the outer surface. However, if the concentration of the crystallization accelerator is increased, crystallization of the outer surface is promoted not only in the depth direction but also in the plane direction. Therefore, the crystal layer on the outer surface is likely to undergo foaming or cracking.

[0052] During crystallization of the outer surface of the crucible, point-like crystal nuclei (embryonic nuclei) are initially formed. These nuclei grow with increasing heating time, and during this process, they fuse with another nearby crystal nucleus to form a plate-like crystal layer. Ideally, the plate-like crystal layer should thicken without detaching. However, if the time until the crystal layer reaches the strength development level is too short, foam-induced detachment or cracking may occur. Conversely, if crystallization is too slow, the crucible will deform before strength is developed. To date, the crystallization rate cannot be optimized simply by increasing the concentration of the crystallization accelerator.

[0053] On the other hand, in the quartz glass crucible according to the present embodiment, elements other than the concentration of the crystallization accelerator, that is, the gradient of the fictive temperature in the depth direction from the outer surface or the concentration of metal impurities such as Ca and Fe, are adjusted to promote crystallization in the depth direction of the outer surface, thereby attempting to optimize the crystallization rate. Therefore, it is possible to increase the strength of the crucible by forming a crystal layer on the outer surface with sufficient thickness while preventing the occurrence of foam-related peeling or cracking.

[0054] Next, the method for manufacturing the quartz glass crucible 1 will be described. The quartz glass crucible 1 according to the present embodiment can be manufactured by applying a crystallization accelerator to the outer surface 10o of the crucible base body 10 after manufacturing the crucible base body 10 by a so-called rotary molding method.

[0055] Fig. 4 is a schematic diagram showing a manufacturing process of the quartz glass crucible according to a rotary molding method.

[0056] As in Fig.As shown in Figure 4, in the rotary molding process, a carbon mold 14 having a cavity corresponding to the outer shape of the crucible is prepared, and the natural quartz powder 16a and the synthetic quartz powder 16b are sequentially filled along the inner surface 14i of the rotary carbon mold 14 to form a deposited layer 16 of raw material quartz powders. The raw material quartz powders remain in a fixed position by centrifugal force while adhering to the inner surface 14i of the carbon mold 14, and are held in a crucible shape.

[0057] Subsequently, the carbon arc electrode 15 is installed in the carbon mold 14, and a deposited layer 16 of the raw material quartz powder is melted via an arc from the inside of the carbon mold 14. Specific conditions such as heating time and heating temperature are appropriately determined, taking into account the properties of the raw material quartz powder, the size of the crucible, and the like.

[0058] During arc melting, the amount of bubbles in the quartz glass melt is controlled by evacuating the deposited layer 16 of the raw material quartz powder through a large number of vent holes 14a provided on the inner surface 14i of the carbon mold 14. Specifically, at the beginning of arc melting, the deposited layer 16 of the raw material quartz powder is evacuated to form the transparent layer 11, and after the formation of the transparent layer 11, the evacuation of the raw material quartz powder is stopped or the suction force is reduced to form the bubble layer 12.

[0059] Since arc heat is transferred from the inside to the outside of the deposited layer 16 of the raw quartz powder to melt the raw quartz powder, by changing the decompression conditions at the time the raw quartz powder begins to melt, the transparent layer 11 and the bubble layer 12 can be formed separately. That is, in a case where decompression melting is performed to enhance decompression at the time the raw quartz powder melts, no atmospheric gas is trapped in the glass, and thus the quartz melt becomes silica glass containing no bubbles.In addition, in a case where normal melting (melting under atmospheric pressure) is carried out to weaken the decompression at the time when the raw material quartz powders are melted, atmospheric gas is trapped in the glass and thus the quartz melt becomes silica glass containing a large number of bubbles.

[0060] To make the Al concentration in the first depth region within 10 mm of the outer surface 10o of the crucible base body 10 higher than the Ca and Fe concentrations, it is preferable to use the carbon mold 14 with a high Al impurity concentration on the inner surface and diffuse Al into the region that becomes the outer surface 10o of the crucible base body 10 during arc melting. Alternatively, in a case where the carbon mold 14 is filled with the quartz raw material powders, a raw material with a high Al impurity concentration may be filled outside a region of the outer surface 10o of the crucible base body 10 after arc melting, and Al may diffuse into the region that becomes the outer surface 10o of the crucible base body 10 during arc melting. In addition, the raw material having a high Al impurity concentration may be removed after arc melting.In both methods, the Al concentration can be increased and the Ca and Fe concentrations near the outer surface 10o of the crucible base body 10 can be decreased, thereby promoting crystallization in the thickness direction rather than the in-plane direction.

[0061] The fictive temperature changes depending on the cooling temperature of the glass. If the quartz melt cools quickly, the fictive temperature of the quartz glass increases, and if the quartz melt cools slowly, the fictive temperature of the quartz glass decreases. Since the arc electrode 15, which serves as a heat source in arc melting, is located on the inner surface side of the crucible, cooling of the inner surface of the crucible begins immediately after the arc is terminated. On the other hand, the carbon mold 14 exists on the outer surface side of the crucible, and the carbon mold maintains a high temperature state even after the arc is terminated. In this example, by temporarily stopping the air cooling or water cooling of the carbon mold 14, the cooling rate on the outer surface 10o side of the crucible base body 10 is lower than on the inner surface 10i side.That is, since the outer surface 10o side of the crucible base body 10 cools more slowly than the inner surface 10i side, the fictive temperature of the outer surface 10o is lower than that of the inner side. In the present embodiment, the heat retention property is further improved by heating the carbon mold 14 or the like, and the cooling rate on the outer surface 10o side of the crucible base body 10 is further reduced, thereby increasing the fictive temperature difference between the outer surface 10o of the crucible base body 10 and the inner side of the base body to 50°C or more.

[0062] Subsequently, the arc melting is stopped, and the crucible is cooled. As described above, the crucible base body 10 is completed, with the transparent layer 11 and the bubble layer 12 provided on the crucible wall in this order from the inside to the outside. As described above, the crucible base body 10 according to the present embodiment can be manufactured by filling the rotating carbon mold 14 with the natural quartz powder 16a as the outer layer raw material, filling the carbon mold 14 with the synthetic quartz powder 16b as the inner layer raw material, and melting the deposited layer 16 of the raw material quartz powder with an arc.

[0063] Subsequently, the shape of the crucible base body 10 is adjusted by cutting the edge portion or the like, then cleaned with a cleaning liquid and rinsed with pure water. The cleaning liquid is preferably prepared by diluting semiconductor-grade or higher hydrofluoric acid with pure water with TOC ≤ 2 ppb to adjust it to 10 to 40 wt%.

[0064] The crystallization accelerator is then applied to the outer surface 10o of the crucible base body 10. A brush is preferably used to apply the coating liquid. To distribute the crystallization accelerator evenly over the outer surface 10o, a coating liquid in which the crystallization accelerator is dissolved in pure water (15°C to 25°C, 17.2 MΩ or more, and TOC ≤ 2 ppb) is preferably used. To increase the solubility of the crystallization accelerator, the coating liquid is preferably stirred with a stirrer.

[0065] For example, if the crystallization accelerator is barium, a solution containing a barium compound such as barium carbonate can be used. The coating liquid containing a barium compound can be a coating liquid consisting of a barium compound and water, or a coating liquid containing absolute ethanol and a barium compound without water. Barium carbonate is preferable as the barium compound, but other barium compounds such as barium chloride, barium acetate, barium nitrate, barium hydroxide, barium oxalate, and barium sulfate can also be used. It should be noted that at the same area concentration (atoms / cm 2) of the barium element, the effect of crystallization acceleration is the same regardless of whether it is insoluble or water-soluble, but the water-insoluble barium is harder to absorb into the human body and is therefore very safe and advantageous in handling.

[0066] The coating liquid containing the barium compound preferably further contains a high-viscosity water-soluble polymer (thickener) such as carboxyvinyl polymer. If a coating liquid without a thickener is used, the fixation of the barium to the crucible wall surface is unstable, so heat treatment is required to fix the barium. When such heat treatment is performed, barium diffuses and penetrates into the interior of the quartz glass, which is a factor that promotes random growth of crystals. In this example, random growth refers to growth that has no regularity in the crystal growth direction in the crystal layer and in which the crystals grow in all directions. In random growth, crystallization stops in the initial stage of heating, so a sufficient thickness of the crystal layer cannot be ensured.

[0067] However, when using a coating liquid containing a thickener together with the barium compound, the viscosity of the coating liquid increases, so that uneven flow of the coating liquid due to gravity or the like can be prevented when the coating liquid is applied to the crucible. Furthermore, if the coating liquid of a barium compound such as barium carbonate contains a water-soluble polymer, the barium compound is dispersed in the coating liquid without aggregating, allowing the barium compound to be evenly coated on the crucible surface. Therefore, high-concentration barium can be uniformly and densely fixed on the crucible wall surface, and the growth of columnar-oriented or dome-oriented crystal grains can be promoted.

[0068] A columnar orientation refers to a crystal layer composed of an aggregate of columnar crystal grains. A dome orientation refers to a crystal layer composed of an aggregate of dome-shaped crystal grains. A columnar orientation or dome orientation can promote crystal growth, thus forming a crystal layer with sufficient thickness.

[0069] Examples of thickeners may include water-soluble polymers with few metal impurities, such as polyvinyl alcohol, cellulose-based thickeners, high-purity glucomannan, acrylic polymers, carboxyvinyl polymers, and polyethylene glycol fatty acid esters. In addition, an acrylic acid-alkyl methacrylate copolymer, polyacrylate, polyvinylcarboxylic acid amide, vinylcarboxylic acid amide, or the like may be used as a thickener. The viscosity of the barium-containing coating liquid is preferably in the range of 100 to 10,000 mPa s, and the boiling point of the solvent is preferably in the range of 50°C to 100°C.

[0070] For example, a coating liquid with crystallization accelerator for coating the outer surface of a 32-inch crucible contains 0.0012 g / ml barium carbonate and 0.0008 g / ml carboxyvinyl polymer and can be prepared by adjusting the ratio of ethanol and pure water and mixing and stirring them.

[0071] [ Fig. 5] is a diagram for explaining a step of pulling up a monocrystal using the quartz glass crucible 1 according to the present embodiment, and is a schematic sectional view showing the configuration of a monocrystal pulling-up apparatus.

[0072] As in Fig.As shown in Figure 5, a monocrystal pulling-up apparatus 20 is used for the silicon monocrystal pulling-up step by the CZ method. The monocrystal pulling-up apparatus 20 includes a water-cooled chamber 21, a quartz glass crucible 1 holding a silicon melt in the chamber 21, a carbon susceptor 22 holding the quartz glass crucible 1, a rotary shaft 23 supporting the carbon susceptor 22 so that it can be rotated and lifted, a shaft drive mechanism 24 driving the rotation and lift of the rotary shaft 23, a heater 25 arranged around the carbon susceptor 22, a monocrystal pulling-up wire 28 arranged above the quartz glass crucible 1 and on the same axis as the rotary shaft 23, and a wire winding mechanism 29 arranged above the chamber 21.

[0073] The chamber 21 is configured by a main chamber 21a and a narrow cylindrical pulling chamber 21b connected to an upper opening of the main chamber 21a. The quartz glass crucible 1, the carbon susceptor 22, and the heater 25 are provided in the main chamber 21a. A gas inlet 21c for introducing an inert gas (purge gas) such as argon gas or a doping gas into the main chamber 21a is provided in the upper portion of the pulling chamber 21b, and a gas outlet 21d for discharging the atmospheric gas within the main chamber 21a is provided in the lower portion of the main chamber 21a.

[0074] The carbon susceptor 22 is used to maintain the shape of the quartz glass crucible 1, which is softened at high temperature, and holds the quartz glass crucible 1 in a manner that envelops it. The quartz glass crucible 1 and the carbon susceptor 22 configure a dual-structured crucible that supports the silicon melt in the chamber 21.

[0075] The carbon susceptor 22 is fixed to the upper end of the rotating shaft 23, and the lower end of the rotating shaft 23 passes through the bottom of the chamber 21 and is connected to a shaft drive mechanism 24 provided outside the chamber 21.

[0076] The heater 25 serves to melt the polycrystalline silicon raw material filled into the quartz glass crucible 1 to produce the silicon melt 3 and to maintain the silicon melt 3 in a molten state. The heater 25 is a resistance heating type carbon heater and is provided surrounding the quartz glass crucible 1 in the carbon susceptor 22.

[0077] The wire winding mechanism 29 is arranged above the pulling chamber 21b. The wire 28 extends downward from the wire winding mechanism 29 and passes through the interior of the pulling chamber 21b. A distal end of the wire 28 reaches the interior of the main chamber 21a. This figure shows a state in which the silicon monocrystal 2 is suspended from the wire 28 in the middle of growth.

[0078] As the silicon monocrystal 2 is pulled up, the wire 28 is gradually pulled up while the quartz glass crucible 1 and the silicon monocrystal 2 are individually rotated to grow the silicon monocrystal 2. Although the amount of silicon melt in the quartz glass crucible 1 decreases with the growth of a silicon monocrystal 2, the quartz glass crucible 1 is raised so that the height of the melting surface remains constant. In this way, an attempt can be made to stabilize the crystal quality in the crystal growth direction.

[0079] Fig. 6 is a schematic side sectional view showing a crystallization state of the quartz glass crucible by heating.

[0080] As in Fig.As shown in Fig. 6, a crystal layer 31 on the outer surface 10o of the quartz glass crucible 1 is formed during the crystal pulling-up step. The Ba concentration in the crystal layer 31 on the outer surface formed on the outer surface 10o of the crucible base body 10 by heating during the crystal pulling-up step or an equivalent heat treatment is preferably less than 10 ppm. In a case where the Ba concentration in the crystal layer 31 on the outer surface is 10 ppm or more, since the concentration of the crystallization accelerator applied to the outer surface 10o of the crucible base body 10 is high, the crystallization of the outer surface 10o is excessively promoted, and the crystal layer 31 on the outer surface is likely to undergo foaming peeling.However, when the Ba concentration in the crystal layer 31 on the outer surface is less than 10 ppm, the crystallization of the outer surface can be promoted and at the same time, the foam-induced detachment of the crystal layer 31 on the outer surface can be suppressed.

[0081] As described above, the quartz glass crucible 1 according to the present embodiment includes the crucible base body 10 made of silica glass and the coating film 13 containing the crystallization accelerator and formed on the outer surface 10o of the crucible base body 10, wherein 10 hours after the start of a heat treatment, the length of crystal growth extending from the outer surface 10o of the crucible base body 10 in the depth direction is 0.21 to 0.5 mm and the crystallization rate is 21 to 50 μm / h, and the crystallization rate of the outer surface 10o after 20 hours from the start of the heat treatment is 10 μm / h or less, wherein the heat treatment is carried out in the furnace at a furnace temperature of 1580 °C and a furnace pressure of 20 Torr and in an Ar atmosphere.Therefore, it is possible to form the crystal layer 31 on the outer surface with a sufficient thickness of 200 μm or more on the outer surface of the crucible at a high temperature during the silicon monocrystal pulling-up step, and it is possible to allow the crystallization of the outer surface 10o to proceed at an appropriate rate that is neither too high nor too low. Therefore, it is possible to form a crystal layer 31 on the outer surface with a sufficient thickness while preventing foam-induced peeling of the crystal layer 31 on the outer surface and imparting a desired strength to the crucible.

[0082] Furthermore, in the quartz glass crucible 1 according to the present embodiment, since the fictive temperature of the outer surface 10o of the crucible base body 10 is 50°C lower than the fictive temperature of the inner surface at a depth position of 5 mm from the outer surface 10o, the crystallization of the outer surface of the crucible can be promoted, and the crystallization of the outer surface of the crucible does not occur too quickly or too slowly, and has an appropriate strength development time. Therefore, it is possible not only to withstand a long-duration monocrystal pulling step, but also to minimize the gap between the crucible and the carbon susceptor, thus stably controlling the oxygen concentration and the crystal diameter of the silicon monocrystal.

[0083] Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications may be added without departing from the scope of the present invention, and such modifications are of course covered by the scope of the present invention. [Examples]

[0084] Four crucible bases with different concentrations of metal impurities on an outer surface were prepared. A portion of the outer surface of the crucible base was coated with a barium carbonate solution using a brush, and then the crucible was crushed and fragmented. Of a plurality of crucible pieces obtained from the same crucible base, those not coated with barium carbonate were used to conduct metal impurity analysis in the depth direction from the outer surface of the crucible base. In the metal impurity analysis, fused silica was dissolved at a certain depth from the outer surface of the crucible by wet etching, the etchant was recovered, and the amount of metal impurities dissolved in the etchant was measured by inductively coupled plasma-mass spectrometry (ICP-MS).

[0085] When measuring Al, Ca, and Fe among the metal impurities, a depth range from the outer surface of the crucible base body to 5 mm was set as the measurement range for the first measurement, a depth range from 5 to 10 mm from the inner surface of the crucible base body was set as the measurement range for the second measurement, and a depth range from 10 to 15 mm from the inner surface of the crucible base body was set as the measurement range for the third measurement. The measurement results are shown in Tables 1 and 2. [Table 1] Outer surface up to 5 mm 5 to 10 mm 10 to 15 mm Fe concentration (ppm) Al concentration (ppm) Fe concentration (ppm) Al concentration (ppm) Fe concentration (ppm) Al concentration (ppm) Comparison example 1 1 0,5 1 0,5 1 0,5 Comparison example 2 1 10 1 0,5 1 0,5 Example 1 1 10 1 10 1 0,5 Example 2 1 10 1 10 1 10

[0086] As shown in Table 1, in the Fe and Al concentration profiles of the crucible base body of Comparative Example 1, the Fe concentration was higher in the entire range from the outer surface to 15 mm in the depth direction, and a relationship of Fe concentration > Al concentration was established. Moreover, in the Fe and Al concentration profiles of the crucible base body of Comparative Example 2, a relationship of Fe concentration < Al concentration was established in a depth range from the outer surface to 5 mm, and a relationship of Fe concentration > Al concentration was established in a depth range from 5 to 15 mm. On the other hand, in the Fe and Al concentration profiles of the crucible base body of Example 1, a relationship of Fe concentration < Al concentration was established in a depth range from the outer surface to 10 mm, and a relationship of Fe concentration > Al concentration was established in a depth range from 10 to 15 mm.In addition, in the crucible base body of Example 2, a relationship of Fe concentration < Al concentration was established in the entire range of the depth direction from the outer surface to 15 mm. [Table 2] Outer surface up to 5 mm 5 to 10 mm 10 to 15 mm Ca concentration (ppm) Al concentration (ppm) Ca concentration (ppm) Al concentration (ppm) Ca concentration (ppm) Al concentration (ppm) Comparison example 1 1 0,5 1 0,5 1 0,5 Comparison example 2 1 10 1 0,5 1 0,5 Example 1 1 10 1 10 1 0,5 Example 2 1 10 1 10 1 10

[0087] As shown in Table 2, the Ca concentration profile showed the same tendency as the Fe concentration profile. That is, in the Ca and Al concentration profiles of the crucible base body of Comparative Example 1, the Ca concentration was higher throughout the range from the outer surface to 15 mm in the depth direction, and the relationship of Ca concentration > Al concentration was established. Furthermore, in the Ca and Al concentration profiles of the crucible base body of Comparative Example 2, a relationship of Ca concentration < Al concentration was established in a depth range from an outer surface to 5 mm, and a relationship of Ca concentration > Al concentration was established in a depth range from 5 to 15 mm.On the other hand, in the Ca and Al concentration profiles of the crucible base body of Example 1, a relationship of Ca concentration < Al concentration was established in a depth range from the outer surface to 10 mm, and a relationship of Ca concentration > Al concentration was established in a depth range from 10 to 15 mm. Furthermore, in the crucible base body of Example 2, a relationship of Ca concentration < Al concentration was established in the entire depth direction from the outer surface to 15 mm.

[0088] As described above, in the crucible samples of Comparative Examples 1 and 2, the Fe concentration and the Ca concentration were higher than the Al concentration in the depth range from the outer surface to 10 mm, whereas in the crucible samples of Examples 1 and 2, the Al concentration was lower than the Fe concentration and the Ca concentration in the depth range from the outer surface to 10 mm.

[0089] For the measurement of B, Mg, and Cr among the metal impurities, a depth range from the outer surface to two-thirds of the wall thickness of the crucible was set as the measurement range. The silica glass was dissolved by wet etching, the etchant was recovered, and the amount of metal impurities dissolved in the etchant was measured by ICP-MS. The measurement results are shown in Table 3. [Table 3] B concentration (ppm) Mg concentration (ppm) Cr concentration (ppm) Comparison example 1 0,1 0,5 0,1 Comparison example 2 0,01 0,01 0,01 Example 1 0,02 0,02 0,02 Example 2 0,05 0,4 0,08

[0090] As shown in Table 3, the B concentration of the crucible base body of Comparative Example 1 was 0.1 ppm. The B concentration of the crucible base body of Comparative Example 2 was 0.01 ppm. On the other hand, the B concentration profile of the crucible base body of Example 1 was 0.02 ppm, and the B concentration of the crucible base body of Example 2 was 0.05 ppm.

[0091] Furthermore, as shown in Table 3, the Mg concentration of the crucible base body of Comparative Example 1 was 0.5 ppm. The Mg concentration of the crucible base body of Comparative Example 2 was 0.01 ppm. On the other hand, the Mg concentration profile of the crucible base body of Example 1 was 0.02 ppm, and the Mg concentration of the crucible base body of Example 2 was 0.4 ppm.

[0092] Furthermore, as shown in Table 3, the Cr concentration of the crucible base body of Comparative Example 1 was 0.1 ppm. The Mg concentration of the crucible base body of Comparative Example 2 was 0.01 ppm. On the other hand, the Cr concentration of the crucible base body of Example 1 was 0.02 ppm, and the Cr concentration of the crucible base body of Example 2 was 0.08 ppm.

[0093] Subsequently, a Raman spectral analysis method was used to measure a fictive temperature of the outer surface of the crucible base body and a fictive temperature of the inner surface of the base body at a depth of 5 mm from the outer surface. The measurement range for the fictive temperature of the outer surface was set to a depth of 0 mm to 0.5 mm from the outer surface. Furthermore, the measurement range for the fictive temperature of the inner surface of the base body was set to a depth of 5.0 mm to 5.5 mm from the outer surface. Table 4 shows the difference in the fictive temperature between the outer surface and the inner surface of the crucible base body. [Table 4] Difference in fictitious temperature between outer surface and inside (°C) Crystallization rate (µm / h) Strength development effect deformation replacement Comparison example 1 +10 °C 0,5 unavailable unavailable available Comparison example 2 0 1 unavailable available unavailable Example 1 ▲50 °C 21 available unavailable unavailable Example 2 ▲100 °C 50 available unavailable unavailable

[0094] A heating test was then carried out using the barium carbonate-coated crucible piece. In the heating test, a crucible piece with a side of 10 to 20 cm and an area of ​​200 cm 2 or more and an aspect ratio of preferably 1. As heating conditions, the furnace temperature was raised from room temperature to 1580 °C in an Ar atmosphere within 2.5 hours and then held at 1580 °C for 10 hours. The pressure in the furnace maintained at 1580 °C was set to 20 Torr.

[0095] Subsequently, the crystallization state of the outer surface of the crucible piece was evaluated. Specifically, the thickness of the crystal layer on the outer surface of the crucible piece was obtained, and the relationship between the thickness of the crystal layer on the outer surface and the high-temperature holding time (10 h) at 1580 °C was obtained as the crystallization rate. Furthermore, it was determined that the crucible piece with a crystal layer thickness of 200 μm or more on the outer surface exhibited the strength development effect, while the crucible piece with a thickness of less than 200 μm did not exhibit any strength development effect.

[0096] Therefore, as shown in Table 4, for the crucible samples of Comparative Examples 1 and 2, the fictive temperature difference was 10 °C or less, the crystallization rate was 1 μm / h or less, and the strength development effect was not obtained. On the other hand, for the crucible samples of Examples 1 and 2, the fictive temperature difference was 50 °C or more, the crystallization rate was 21 μm / h or more, and the strength development effect was obtained. From the above results, it was found that when the fictive temperature difference was 50 °C or more, a crystal layer with a thickness of 200 μm or more could be formed on the outer surface of the crucible, and the strength development effect could be obtained.

[0097] The silicon monocrystals were actually pulled up using another crucible manufactured under the same conditions as in Examples 1 and 2 and Comparative Examples 1 and 2, and the state of deformation and detachment of the crucible was visually confirmed. Table 4 also shows the results of the deformation and detachment of the crucible. In this example, "deformation" is a result of judgment by visual observation of whether or not deformation, such as inward deformation of the opening portion, buckling of the corner of the side wall, and unevenness of the surface caused by fitting to the carbon susceptor, occurred with respect to the crucible before use.In addition, the “peeling” is a result of judging by visual observation whether a part of the crystal layer formed on the outer surface of the crucible is detached by foam, deformation or the like, and an uncrystallized glass surface is exposed.

[0098] As shown in Table 4, detachment of the crystal layer was observed in the quartz glass crucible of Comparative Example 1. Furthermore, deformation was observed in the quartz glass crucible of Comparative Example 2. However, neither deformation nor detachment occurred in the quartz glass crucibles of Examples 1 and 2. DESCRIPTION OF REFERENCE SYMBOLS 1 quartz glass crucible 2 silicon monocrystal 3 Silicon melt 10 crucible base bodies 10a side wall 10b Floor 10c corner 10i inner surface 10o exterior surface 11 Transparent layer 12 bubble layer 13 Coating film containing a crystallization accelerator 14 Carbon form 14a Ventilation holes 14i Inner surface of the carbon mold 15 Arc electrode 16 Deposited layer of raw material quartz powders 16a Natural quartz powder 16b Synthetic quartz powder 20 Device for pulling a monocrystal 21 Chamber 21a Main Chamber 21b Drawing chamber 21c Gas inlet 21d Gas outlet 22 Carbon susceptor 23 Rotating shaft 24 Shaft drive mechanism 25 Heating device 28 wire 29 Wire winding mechanism 31 crystal layer on the outer surface D1 First depth range D2 Second depth range D3 Third depth range QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-105062

[0007] JP 2018 / 051714

[0007] WO 2021 / 140729

[0007] Cited non-patent literature

[0000] Journal of AE Geissberger and FL Galeener, “Raman studies of vitreous SiO2 versus fictive temperature,” Phys. Rev. B, Vol. 28, pp. 3266-3271 (1983

[0007] A. Agarwal, KM Davis and M. Tomozawa, “A simple IR spectroscopic method for determining fictive temperature of silica glasses,” J. Non-Cryst. Solids, Vol. 185, pp. 191-198 (1995

[0007]

Claims

[1] Quartz glass crucible, comprising: a crucible base body made of silica glass; and a coating film containing a crystallization accelerator formed on an outer surface of the crucible base body, wherein 10 hours after the start of a heat treatment carried out in an Ar atmosphere at a furnace temperature of 1580 °C and a furnace pressure of 20 Torr, a thickness of a crystal layer formed on the outer surface of the crucible base body is 0.21 to 0.5 mm and a crystallization rate is 21 to 50 µm / h, and a crystallization rate of the outer surface is 10 µm / h or less 20 hours since the start of heat treatment. [2] The quartz glass crucible according to claim 1, wherein a fictive temperature of the outer surface of the crucible base body is lower by 50 °C or more than a fictive temperature of an inner side of the base body at a depth of 5 mm from the outer surface. [3] The quartz glass crucible according to claim 1, wherein an Al concentration in a first depth range within 10 mm from the outer surface of the crucible base body is higher than an Fe concentration in the first depth range. [4] The quartz glass crucible according to claim 1, wherein an Al concentration in a first depth range within 10 mm from the outer surface of the crucible base body is higher than a Ca concentration in the first depth range. [5] The quartz glass crucible according to claim 1, wherein the crystallization accelerator is Ba, and a Ba concentration in a crystal layer formed on the outer surface of the crucible base body after the heat treatment is less than 10 ppm. [6] The quartz glass crucible according to claim 1, wherein the coating film containing the crystallization accelerator contains barium carbonate and a thickener, and a Ba concentration in the coating film containing the crystallization accelerator is 1.0 × 10 15 up to 1.0 × 10 18 atoms / cm 2 amounts. [7] The quartz glass crucible according to claim 1, wherein a B concentration in a second depth range within two-thirds of a wall thickness of the crucible base body from the outer surface of the crucible base body is 0.02 to 0.05 ppm. [8] A quartz glass crucible according to claim 1, wherein a Mg concentration in a second depth range within two-thirds of a wall thickness of the crucible base body from the outer surface of the crucible base body is 0.02 to 0.4 ppm. [9] A quartz glass crucible according to claim 1, wherein a Cr concentration in a second depth range within two-thirds of a wall thickness of the crucible base body from the outer surface of the crucible base body is 0.02 to 0.08 ppm. [10] A quartz glass crucible according to claim 7, wherein the B concentration in the second depth range within two-thirds of the wall thickness of the crucible base body from the outer surface of the crucible base body is higher than a B concentration in a third depth range within 2 mm from an inner surface of the crucible base body. [11] A quartz glass crucible according to claim 8, wherein the Mg concentration in the second depth range within two-thirds of the wall thickness of the crucible base body from the outer surface of the crucible base body is higher than a Mg concentration in a third depth range within 2 mm from an inner surface of the crucible base body. [12] A quartz glass crucible according to claim 9, wherein the Cr concentration in the second depth range within two-thirds of the wall thickness of the crucible base body from the outer surface of the crucible base body is higher than a Cr concentration in a third depth range within 2 mm from an inner surface of the crucible base body. [13] Quartz glass crucible, comprising: a crucible base body made of silica glass; and a coating film containing a crystallization accelerator formed on an outer surface of the crucible base body, wherein a fictitious temperature of the outer surface of the crucible base body is 50 °C or more lower than a fictitious temperature of an inner side of the base body at a depth of 5 mm from the outer surface. [14] A method of manufacturing a silicon monocrystal, comprising: Pulling up a silicon monocrystal by a CZ method using the quartz glass crucible according to claim 1.

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