QUARTZ GLASS CRUST

Abstract

Quartz glass crucible (1) comprising: a cylindrical side wall section (10a); a bottom section (10b); a corner section (10c) connecting the side wall section (10a) and the bottom section (10b); a transparent layer (11) of quartz glass, which does not contain bubbles; a bubble layer (12) formed on the outside of the transparent layer (11), which consists of quartz glass and contains a large number of bubbles;and a semi-molten layer (13) formed on the outside of the blister layer (12) and consisting of the raw material silica powder solidified in an incompletely molten state, wherein a ratio of an infrared transmittance of the corner section (10c) at a position of maximum thickness (Pc) of the corner section (10c) to an infrared transmittance of the side wall section (10a) is 0.3 or more and 0.99 or less, an absolute value of a rate of change of the infrared transmittance in a vertical direction along a wall surface of the crucible from a center (Pb) of the bottom section (10b) to an upper end of the side wall section (10a) is 3% / cm or less, and the infrared transmittance is a value measured in a state in which the semi-molten layer (13) is removed.

Description

ARTThe present invention relates to a quartz glass crucible, and more particularly to a quartz glass crucible used for producing a silicon single crystal by the Czochralski (CZ) method.PRIOR ARTA quartz glass crucible is used for producing a silicon single crystal by the CZ method. In the CZ method, a silicon raw material in the quartz glass crucible is heated and melted, a seed crystal is dipped in the silicon melt, and then the seed crystal is gradually pulled up while the crucible is rotated to grow a single crystal. In order to manufacture a high-quality silicon single crystal for a semiconductor device at low cost, it is necessary to increase the rate of crystallization in a single pulling-up step. For this, a crucible capable of stably holding the silicon melt for a long term use is necessary.Regarding the quartz glass crucible, for example, JP 2002-326889 A describes a quartz glass crucible for pulling up a silicon single crystal, which is less likely to be deformed during pulling up a silicon single crystal, does not adversely affect convection of silicon, and can achieve a high crystallization rate. The thickness of this quartz glass crucible is uniform over the entire area, and a transparent layer at a peripheral wall portion is formed thicker than a transparent layer at a corner portion.Moreover, in JP 2010-105880 A, a quartz glass crucible for pulling up a silicon single crystal is proposed, which includes a transparent layer having a bubble content of less than 0.3%, a light transmissive layer having a bubble content of 0.3% to 0.6%, and an opaque layer having a bubble content of more than 0.6% from the inner surface side toward the outer surface side of the crucible, in order to suppress local temperature fluctuations of the molten silicon and produce a homogeneous silicon single crystal even when a large silicon single crystal is pulled up.Moreover, JP H08-301693 A describes a quartz crucible for pulling up a silicon single crystal, which can increase the yield of a single crystal having a high oxygen concentration without impairing the heat retention performance of the crucible. This quartz crucible is characterized in that the inner surface side of a wall body is formed of a transparent glass layer, the outer surface side of the wall body is formed of an opaque glass layer, the thickness of the transparent glass layer at a corner portion connecting a peripheral wall portion and a bottom portion of the crucible is greater than that of the transparent glass layers of other wall body parts by 0.5 mm or more, and the thickness of the opaque glass layer of the corner portion is smaller than that of other parts by 0.5 mm or more.JP 2016-193 809 A describes a quartz glass crucible having a cylindrical straight part, a corner part and a bottom part. An opaque layer is formed on the side of the outer layer. The thickness of the opaque layer at the corner part is 25% or more and 80% or less of the total thickness of the opaque layer and the transparent layer; the thickness of the opaque layer in the straight part and the bottom part is 10% or more and less than 25% of the total thickness of the opaque layer and the transparent layer of the total thickness of the opaque layer and the transparent layer. Here, the thickness of the opaque layer at the corner part is larger than the thickness of the opaque layer in the straight part and the bottom part.US 2010 / 0 107 970 A1 discloses a quartz glass crucible for pulling silicon single crystals. The crucible includes at least a transparent layer, a semi-transparent layer, and an opaque layer disposed from the inner surface side to the outer surface side of the crucible. The content of bubbles in the transparent layer is less than 0.3 percent; the content of bubbles in the semitransparent layer is in a range of 0.3 to 0.6 percent; and the content of bubbles in the opaque layer is greater than 0.6 percent.JP 2004-107 163 A also discloses a quartz glass crucible. This has an opening at one end and a straight part, a small R part and a bottom part extending downward from the opening. The outer peripheral wall surface of at least 25% of the total height from the bottom surface to the end surface of the total height from the bottom surface to the end surface of the opening part from the opening end surface is substantially absent in the raw material powder, and has a surface roughness Ra of 6-14 m and a maximum height Ry of 40-70 m.CN 1 06 868 583 A discloses a quartz glass crucible, characterized in that the crucible wall of the quartz crucible consists of three parts of a crucible bottom wall, a radial transition region and a cylindrical circumferential wall, and a transparent quartz layer and an opaque quartz layer are arranged on the outer surface side from the inner surface side to the outer surface side of the crucible, wherein the bubbling rate of the transparent quartz layer is less than 0.3% and the bubbling rate of the opaque quartz layer is more than 0.6%.LITERATURE ON THE PRIOR ARTPATENT LITERATUREPatent Literature 1: JP 2002-326889 APatent Literature 2: JP 2010-105880 APatent Literature 3: JP H08-301693 APatent Literature 4: JP 2016-193 809 APatent Literature 5: US 2010 / 0 107 970 A1Patent Literature 6: JP 2004-107 163 APatent Literature 7: CN 1 06 868 583 ASUMMARY OF THE INVENTIONPROBLEMS TO BE SOLVED BY THE INVENTIONDuring a silicon single crystal pulling-up step, the inner surface of a quartz glass crucible comes into contact with a silicon melt and is gradually ablated so that the silicon single crystal produced by the CZ method contains oxygen supplied from the quartz glass crucible. In recent years, a silicon single crystal for highly integrated semiconductor devices is required to have a low oxygen concentration of about 9×10 17 to 12×10 17 atoms / cm 3. Moreover, it is desirable that the oxygen concentration in the silicon single crystal is as uniform as possible in both the longitudinal direction (pull-up axis direction) and the radial direction (cross-sectional direction) of the silicon single crystal.However, when a silicon single crystal having a low oxygen concentration is to be pulled up using a quartz glass crucible in the related art, it is difficult to uniformize an oxygen concentration distribution in the longitudinal direction (pulling-up axis direction) of the silicon single crystal. Specifically, as shown in FIG. 10, a certain part (here, a sharp decrease (a decrease of 10% or more) of the oxygen concentration at a position where the crystal length (relative value) is 0.44) in the longitudinal direction of the silicon single crystal becomes a great problem. The oxygen concentration distribution in the longitudinal direction of the silicon single crystal can be adjusted by adjusting the conditions for pulling up the crystal during the crystal pulling up step, but the adjustment range is also limited. Accordingly, improvement is desired.Therefore, an object of the present invention is to provide a quartz glass crucible capable of pulling up a silicon single crystal having a low oxygen concentration and a stable oxygen concentration distribution in a longitudinal direction.MEANS FOR SOLVING THE PROBLEMSIn order to solve the above problems, a quartz glass crucible according to the present invention is a quartz glass crucible including: a cylindrical side wall portion; a bottom portion; a corner portion connecting the side wall portion and the bottom portion; a transparent layer of quartz glass containing no bubbles; and a bubble layer formed on the outer side of the transparent layer and made of quartz glass and containing a large number of bubbles, wherein a ratio of an infrared transmittance of the corner portion at a maximum thickness position of the corner portion to an infrared transmittance of the side wall portion is 0.3 or more and 0.99 or less, and an absolute value of a change rate of the infrared transmittance in a height direction along a wall surface of the crucible from a center of the bottom portion to an upper end of the side wall portion is 3% / cm or less.According to the present invention, by reducing the infrared transmittance of the corner portion of the crucible, the ablation of the crucible due to a temperature rise in the inner surface of the corner portion can be suppressed, and accordingly, the amount of oxygen supplied to the silicon melt from the crucible can be suppressed, whereby a reduction in the amount of oxygen of a silicon single crystal can be achieved. Moreover, by adjusting a smooth change in infrared transmittance from the bottom portion to the side wall portion of the crucible, it is possible to suppress the variations in temperature distribution of the inner surface of the quartz glass crucible, and it is possible to suppress a sudden change in oxygen concentration distribution in a longitudinal direction (crystal growth direction) of the silicon single crystal at a certain part. Therefore, it is possible to pull up a silicon single crystal having a low oxygen concentration and a stable oxygen concentration distribution in the direction of the pulling-up axis.In the present invention, it is preferable that the infrared transmittance of the corner portion at the maximum thickness position is 25% or more and 51% or less. Accordingly, it is possible to reduce the infrared transmittance of the corner portion as compared with the related art and suppress an excessive temperature rise at the inner surface of the corner portion. Therefore, the amount of oxygen supplied from the crucible to the silicon melt can be suppressed, so that a silicon single crystal having a low oxygen concentration can be produced.In the present invention, it is preferable that an absolute value of a change rate of the thickness of the bubble layer in the height direction along the wall surface of the crucible from the center of the bottom portion to the upper end of the side wall portion is 2.5 mm / cm or less. Accordingly, the absolute value of the change rate of the infrared transmittance in the height direction along the wall surface of the crucible can be set to 3% / cm or less. Therefore, it is possible to produce a silicon single crystal having a low oxygen concentration and a stable oxygen concentration distribution in the direction of the pulling-up axis.Moreover, a quartz glass crucible according to the present invention is a quartz glass crucible comprising: a cylindrical side wall portion; a bottom portion; a corner portion connecting the side wall portion and the bottom portion to each other; a transparent layer made of quartz glass containing no bubbles; and a bubble layer made of quartz glass containing a large number of bubbles and formed on the outside of the transparent layer, wherein a ratio of an infrared transmittance of the corner portion at a position of maximum thickness of the corner portion to an infrared transmittance of the side wall portion is 0.3 or more and 0.99 or less, and an absolute value of a change rate of the thickness of the bubble layer in a height direction along a wall surface of the crucible from a center of the bottom portion to an upper end of the side wall portion is 2.5 mm / cm or less.According to the present invention, by reducing the infrared transmittance of the corner portion of the crucible, the ablation of the crucible due to a temperature rise in the inner surface of the corner portion can be suppressed, and accordingly, the amount of oxygen supplied to the silicon melt from the crucible can be suppressed, whereby a reduction in the amount of oxygen of a silicon single crystal can be achieved. Moreover, it is possible to adjust a gradual change in infrared transmittance by adjusting a gradual change in thickness of the bubble layer from the bottom portion to the side wall portion of the crucible, and suppress the variations in temperature distribution of the inner surface of the quartz glass crucible. Therefore, it is possible to suppress sudden change in the oxygen concentration distribution in the longitudinal direction (crystal growth direction) of the silicon single crystal at a certain part, so that it is possible to pull up a silicon single crystal having a low oxygen concentration and a stable oxygen concentration distribution in the direction of the pulling-up axis.In the present invention, it is preferable that an opening of the crucible is 812 mm (32 inches), a maximum thickness of the corner portion is 19 mm or more and 30 mm or less, and a thickness of the bubble layer at the maximum thickness position of the corner portion is 18 mm or more and 29 mm or less. Note that the thickness of each part of the crucible and the thickness of the bubble layer are values obtained by measuring a crucible before use in an environment of room temperature. Accordingly, the infrared transmittance of the corner portion at the maximum thickness position can be set to 25% to 51%, whereby a silicon single crystal having a low oxygen concentration can be produced.In the present invention, it is preferable that a bubble content of the bubble layer at the maximum thickness position of the corner portion is more than 0.1 vol % and 5 vol % or less. Note that the bubble content is a value obtained by measuring a crucible before use in an environment of room temperature. Accordingly, the infrared transmittance of the corner portion at the maximum thickness position can be set to 25% or more and 51% or less, whereby a silicon single crystal having a low oxygen concentration can be manufactured.The quartz glass crucible according to the present invention further includes a semi-molten layer formed on the outside of the bubble layer and made of the raw material silica powder solidified in an incompletely molten state, wherein the infrared transmittance is a value measured in a state in which the semi-molten layer is removed. Accordingly, the infrared transmittance of the crucible can be defined in a state that is as close as possible to an actual pulling-up step.EFFECTS OF THE INVENTIONAccording to the present invention, it is possible to provide a quartz glass crucible capable of pulling up a silicon single crystal having a low oxygen concentration and a stable oxygen concentration distribution in a pulling-up axis direction.BRIEF DESCRIPTION OF THE DRAWINGS[FIG. 1 ] FIG. 1 is a schematic side cross-sectional view illustrating the structure of a quartz glass crucible according to an embodiment of the present invention.[FIG. 2 ] FIG. 2 is a graph showing the relationship between an infrared transmission rate and an average crystal oxygen concentration.[FIG. 3] FIG. 3 is a schematic view illustrating the quartz glass crucible and a state of a silicon melt during a crystal pulling-up step.[FIG. 4] FIG. 4 is a cross-sectional view of a quartz glass crucible in which a semi-molten layer is formed on the outer surface.[FIG. 5 ] FIG. 5 ( a) and ( b) are diagrams for describing the state change of a semi-molten layer of the quartz glass crucible, in which FIG. 5 ( a) illustrates a state before use and FIG. 5 ( b) illustrates a state during use.[FIG. 6 ] FIG. 6 is a flowchart showing a method of measuring infrared transmittance of a quartz glass crucible using a piece of the crucible.[FIG. 7 ] FIG. 7 is a schematic view showing the measurement method of the infrared transmittance of a quartz glass crucible.[FIG. 8] FIG. 8 is a flowchart showing a manufacturing method of a quartz glass crucible including an infrared transmittance evaluation method described above.[FIG. 9] FIG. 9 is a schematic view for describing the manufacturing method of a quartz glass crucible according to a rotation molding method.[FIG. 10 ] FIG. 10 is a diagram showing the oxygen concentration distribution in the longitudinal direction of a silicon single crystal that has been pulled up using a conventional quartz glass crucible.MODE FOR CARRYING OUT THE INVENTIONPreferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.FIG. 1 is a schematic side cross-sectional view illustrating the structure of a quartz glass crucible according to an embodiment of the present invention.As shown in FIG. 1, a quartz glass crucible 1 is a silica glass container for containing a silicon melt, which includes a cylindrical side wall portion 10 a, a bottom portion 10 b, and a corner portion 10 cconnecting the side wall portion 10 aand the bottom portion 10 bto each other. The bottom portion 10 bis preferably a so-called round bottom which is slightly curved, but may also be a so-called flat bottom. The corner portion 10 cis located between the side wall portion 10 aand the bottom portion 10 band is a part having a stronger curvature than the bottom portion 10 b.The opening of the quartz glass crucible 1 is preferably 22 inches (about 560 mm) or more, and more preferably 32 inches (about 800 mm) or more. This is because such a large-opening crucible is used for pulling up a large-sized silicon single crystal ingot having a diameter of 300 mm or more, and the quality of the single crystal is required not to be impaired even when used for a long period of time. In recent years, crystal quality in the direction of the pulling-up axis has become a problem due to the increase in size of crucibles and the elongation of the pulling-up steps caused by an increase in size of silicon single crystals, and stabilization of crystal quality is an extremely important issue in large crucibles. Although the thickness of the crucible slightly varies depending on what part it is, the thickness of the side wall portion 10a of a crucible is 558 mm (22 inches) or more, preferably 7 mm or more, and the thickness of the side wall portion 10a of a crucible is 24 inches (about 600 mm) or more, preferably 8 mm or more. Moreover, the thickness of the large-scale crucible side wall portion 10 ais 812 mm (32 inches) or more, preferably 10 mm or more, and the thickness of the large-scale crucible side wall portion 10 ais 40 inches (about 1000 mm) or more, preferably 13 mm or more.The quartz glass crucible 1 has a two-layer structure and includes a transparent layer 11 made of quartz glass containing no bubbles and a bubble layer 12 (opaque layer) made of quartz glass containing a large number of minute bubbles and provided on the outside of the crucible from the transparent layer 11.The transparent layer 11 is a layer forming an inner surface 10 iof the crucible that is in contact with a silicon melt, and is provided to prevent a decrease in the crystallization rate due to bubbles in the quartz glass. The thickness of the transparent layer 11 is preferably 0.5 to 12 mm and is set to an appropriate thickness for each part of the crucible to prevent the bubble layer 12 from being exposed due to the transparent layer 11 completely disappearing by ablation during a single crystal pulling-up step. Similarly to the bubble layer 12, the transparent layer 11 is preferably provided over the entire crucible from the side wall portion 10 ato the bottom portion 10 bof the crucible. However, in an upper end portion (edge portion) of the crucible that is not in contact with the silicon melt, the formation of the transparent layer 11 may be omitted.The transparent layer 11 is a part on the inside of the quartz crucible having a bubble content of 0.1 vol % or less. The expression "the transparent layer 11 contains no bubbles" means that the bubble content and the bubble size are such that the crystallization rate does not decrease due to the bubbles. Namely, there is a concern that when bubbles exist near the inner surface of the crucible, the bubbles near the inner surface of the crucible cannot be limited to the quartz glass due to the ablation of the inner surface of the crucible; bubbles in the quartz glass may burst due to thermal expansion when the crystals are pulled up, and crucible fragments (pieces of quartz) may delaminate. If crucible fragments released into the melt are carried by convection of the melt to the growth boundary surface of the single crystal and are incorporated into the single crystal, this leads to dislocations of the single crystal. Moreover, if bubbles released into the melt by ablation of the inner surface of the crucible float up to a solid / liquid interface and are incorporated into the single crystal, pinholes will result. The average bubble diameter in the transparent layer 11 is preferably 100 μm or less.The bubble content of the transparent layer 11 and the diameter of the bubbles can be measured non-destructively using an optical detection agent by the method disclosed in Japanese Patent Application Laid-Open JP 2012-116713 A. The optical detection means includes a light receiving device that receives transmitted light or reflected light of the light that irradiates the crucible. Irradiation light emitting means may be incorporated in the light receiving device, or external light emitting means may also be used. In addition, as the optical detection means, one which can be rotated along the inner surface of the crucible is preferably used. As the irradiation light, X-rays, laser light and the like, as well as visible light, ultraviolet light and infrared light can be used. As the light receiving device, a digital camera having an optical lens and an imaging element can be used. Measurement results obtained by the optical detection means are received by an image processing device to calculate the bubble content per unit volume.In order to detect bubbles existing at a certain depth from the surface of the crucible, the focal point of the optical lens may be scanned in the depth direction from the surface. Specifically, an image of the inner surface of the crucible is captured using the digital camera, the inner surface of the crucible is divided into predetermined ranges to obtain a reference range S 1, for each reference range S 1, a range S 2 occupied by bubbles is obtained, and a surface bubble content Ps=(S 2 / S 1)×100(%) is calculated.In the calculation of the bubble content by the volume ratio, a reference volume V1is obtained from the depth at which the image was taken and the reference area S1. Further, a bubble is considered as a spherical shape, and a volume V 2 of the bubble is calculated from the diameter of the bubble. From V1 and V2, a volume bubble content Pv = (V2 / V1) × 100 (%) is calculated. In the present invention, the volume bubble content Pv is defined as "bubble content". An arithmetic mean value resulting from the diameters of the bubbles calculated by regarding the bubble as a sphere is defined as "average diameter of the bubbles".Note that the reference volume is 5 mm×5 mm×thickness 0.45 mm, the minimum bubble diameter to be measured is 5 μm (those having a diameter less than 5 μm are ignored), and resolution may be set so that bubbles having a diameter of 5 μm can be measured. The focal length of the optical lens is shifted in the depth direction of the reference volume V 1, the bubbles contained in the reference volume are detected, and the diameter of the bubbles is measured.The bubble layer 12 is a layer forming an outer surface 100 of the crucible and provided to improve the heat retention performance of the silicon melt in the crucible and heat the silicon melt in the crucible as uniformly as possible by distributing radiant heat from a heating element provided to surround the crucible in a single crystal pulling-up device. Therefore, the bubble layer 12 is provided over the entire crucible from the straight side wall portion 10 ato the bottom portion 10 bof the crucible. The thickness of the bubble layer 12 is a value obtained by subtracting the thickness of the transparent layer 11 from the thickness of the crucible, and varies depending on the part of the crucible. The bubble content of the bubble layer 12 can be obtained, for example, by measuring the specific gravity (Archimedes method) of an opaque silica glass piece cut out from the crucible.The bubble content of the bubble layer 12 is higher than that of the transparent layer 11, preferably more than 0.1 vol % and 5 vol % or less, and more preferably 1 vol % or more and 4 vol % or less. This is because, when the bubble content of the bubble layer 12 is 0.1 vol % or less, the function of the bubble layer 12 cannot manifest itself and the heat retention performance becomes insufficient. Further, in a case where the bubble content of the bubble layer 12 exceeds 5 vol %, there is a concern that the crucible is deformed largely by the expansion of the bubbles and the single crystal yield decreases, resulting in further insufficient heat transfer properties. Particularly when the bubble content of the bubble layer 12 is 1 to 4%, the balance between heat retention property and heat transfer property is good and preferable. A large number of bubbles contained in the bubble layer 12 can be visually recognized.In order to prevent contamination of the silicon melt, it is desirable that the silica glass constituting the transparent layer 11 has high purity. Therefore, the quartz glass crucible 1 according to the present embodiment preferably includes two layers, an inner surface layer of synthetic silica powder (hereinafter referred to as "synthetic layer"), and an outer surface layer of natural silica powder (hereinafter referred to as "natural layer"). The synthetic silica powder can be produced by vapor phase oxidation of silicon tetrachloride (SiCl 4) ( dry synthesis method) or hydrolysis of silicon alkoxide (sol-gel method). The natural silica powder is silica powder prepared by pulverizing a natural mineral containing α-quartz as a main component into particles.As will be described in detail later, the two-layered structure of the synthetic layer and the natural layer can be manufactured by depositing the natural silica powder along the inner surface of a mold for manufacturing a crucible, depositing the synthetic silica powder thereon, and melting the silica powder by Joule heat through arc discharge. In a first stage of arc melting, the transparent layer 11 is formed by removing bubbles from the outside of the deposition layers of the silica powder by highly evacuating. Thereafter, the evacuation is stopped or attenuated, thereby forming the bubble layer 12 on the outside of the transparent layer 11. For this reason, although the interface between the synthetic layer and the natural layer does not always match the interface between the transparent layer 11 and the bubble layer 12, the synthetic layer, like the transparent layer 11, preferably has a thickness which does not completely disappear by ablating the inner surface of the crucible during the crystal pulling-up step.In the quartz glass crucible 1 according to the present embodiment, the infrared transmittance of the corner portion 10 cis lowered to keep the temperature of the inner surface of the corner portion 10 clow, thereby lowering the oxygen concentration in the silicon single crystal. Moreover, the allowable ranges of the change rate of the infrared transmittance from a center Pb of the bottom portion 10 btoward the upper end of the side wall portion 10 aand the change rate of the thickness of the bubble layer 12 are defined such that the temperature distribution of the inner surface of the crucible does not substantially change, and thus a change in the convection of the silicon melt is suppressed, whereby a sudden change in the oxygen concentration in the silicon single crystal can be prevented.In the present embodiment, the infrared transmittance at a maximum thickness position Pc of the corner portion 10 cof the crucible is preferably 25 to 51%. This is because, in a case where the infrared transmittance is higher than 51 %, the amount of the peeled crucible increases due to a temperature rise in the inner surface of the corner portion 10 c, which increases the oxygen concentration in the silicon melt, and a decrease in the amount of oxygen of the single crystal cannot be achieved, whereas in a case where the infrared transmittance is lower than 25 %, the amount of heat input to the crucible is too small, and the growth of a single crystal from the silicon melt becomes unstable. The infrared transmittance of the crucible is a ratio of the amount of the emitted infrared light to the amount of the incident infrared light in a case where infrared light from an infrared light source disposed on one surface (outer surface 10 o) of the crucible wall is incident and infrared light emitted from the opposite surface (inner surface 10 i) is received by a laser power meter.In order to set the infrared transmittance of the corner portion 10 cto 25 to 51 %, the maximum thickness of the corner portion 10 cis preferably 19 to 30 mm, and the thickness of the bubble layer 12 at the corner portion 10 cis preferably 18 to 29 mm. Moreover, the bubble content of the bubble layer 12 at the corner portion 10 cis preferably 0.1 to 5 vol %. Note that the thickness and the bubble content of the crucible are values obtained by measuring an unused crucible in an environment of room temperature.The ratio of the infrared transmittance T R(%) of the corner portion 10 cat the maximum thickness position of the corner portion 10 cto the infrared transmittance T W(%) of the side wall portion 10 aof the crucible is preferably 0.3 or more and 0.99 or less (0.30≤T R / T W≤0.9). By reducing the infrared transmittance of the corner portion 10 cof the crucible as compared with that of the side wall portion 10 a, the ablation of the crucible due to a temperature rise in the inner surface of the corner portion 10 cmay be suppressed, and accordingly, the amount of oxygen supplied to the silicon melt from the crucible may be suppressed, whereby a reduction in the amount of oxygen of the silicon single crystal may be achieved.FIG. 2 is a graph showing the relationship between the infrared transmission rate and the average crystal oxygen concentration. As shown in the graph, in a case where the ratio of the infrared transmittance of the corner portion at the maximum thickness position to the infrared transmittance of the side wall portion is less than 0.3, convection of the silicon melt tends to be unstable, and it is difficult to control the oxygen concentration of the crystal. On the other hand, at a ratio of over 0.99, the oxygen concentration in the crystal increases. However, when the ratio of the infrared transmittance is 0.3 or more and 0.99 or less, a decrease in the oxygen amount of the silicon single crystal can be achieved.As described above, by suppressing the infrared transmittance of the corner portion 10 cof the crucible to a lower level than in the related art, the amount of oxygen supplied into the silicon melt can be suppressed and a reduction in the amount of oxygen of the silicon single crystal can be achieved. However, in a case where the infrared transmittance of the corner portion 10 cis extremely lower than that of the side wall portion 10 aand the bottom portion 10 b, there is a concern that a sharp drop in oxygen concentration may occur at a certain part in a pulling-up axis direction of the silicon single crystal. Therefore, in the present embodiment, the above problem is solved by smoothly adjusting changes in the infrared transmittance and thickness of the crucible wall from the bottom portion 10 bof the crucible to the side wall portion 10 a.FIG. 3 is a schematic view illustrating the quartz glass crucible and a state of a silicon melt during a crystal pulling-up step.As shown in FIG. 3, a heater 20 is disposed on the outside of the quartz glass crucible 1 in a crystal pulling-up furnace, and the heat from the heater 20 toward the inside of the crucible (see the solid line arrows) is largely affected by the infrared transmittance and thermal conductivity of the crucible, and reaches the inner surface 10 iof the crucible. By the heating, not only the molten state of the raw material silicon is maintained in the crucible, but also the inner surface 10 iof the crucible is dissolved in the silicon melt. Specifically, the inner surface 10 iof the corner portion 10 cof the quartz glass crucible 1 is a part that tends to have a higher temperature than the inner surfaces 10 iof the side wall portion 10 aand the bottom portion 10 b, and easily dissolves in the silicon melt. Therefore, by decreasing the infrared transmittance at the corner portion 10 c, the temperature of the inner surface 10 iof the corner portion 10 cis lowered, and the resolution of the corner portion 10 cis suppressed. Thereby, the supply of oxygen from the corner portion 10 cof the crucible to the silicon melt is suppressed, so that the oxygen concentration of the silicon single crystal 6 can be reduced.Moreover, in the present embodiment, while decreasing the infrared transmittance at the corner portion 10 cof the quartz glass crucible 1, the rate of change of the infrared transmittance and the rate of change of the thickness of the bubble layer 12 in the height direction along the wall surface of the crucible are gently adjusted, whereby even if the silicon melt 5 in the crucible is consumed and the position of a melting surface 5 ais lowered with the progress of pulling up the silicon single crystal, the effect of a change in the amount of the melt is decreased, whereby a sudden change in the natural convection of the silicon melt 5 is suppressed. By this suppression, it is possible to prevent the oxygen concentration from dropping greatly in a straight body portion of the silicon single crystal 6.Specifically, the absolute value |ΔW| of the rate of change of the infrared transmittance is preferably 3% / cm or less, and the absolute value |ΔT| of the thickness rate of change of the bubble layer 12 is preferably 2.5 mm / cm or less. As described above, by gradually changing the infrared transmittance and the thickness of the bubble layer 12 from the bottom portion 10 bto the side wall portion 10 aof the crucible, a sudden change in the state (mode) of convection of the melt during the crystal pulling-up step can be prevented, thereby suppressing a sudden drop in the oxygen concentration at a certain part in the direction of the pulling-up axis of the silicon single crystal.The change rate ΔW of the infrared transmittance is a value representing the difference in the infrared transmittance between any two points separated by a certain distance (1 cm or more) on a measurement line from the center Pb of the bottom portion 10 bto the upper end of the side wall portion 10 a. Therefore, for example, when the infrared transmittance of the side wall portion 10 aat one measurement position P 1 is W 1(%) and the infrared transmittance at another measurement position P 2, which is separated by a predetermined distance L (cm) along the outer surface 100 of the crucible, is W 2(%) a value obtained by dividing the difference (W 1- W 2) in the infrared transmittance between the two points by the distance L is the change rate of the infrared transmittance: ΔW=(W 1- W 2) / L.Similarly, the change rate ΔT of the thickness of the bubble layer 12 is a value representing the difference in the thickness of the bubble layer 12 between any two points separated by a certain distance (1 cm or more) on the measurement line from the center Pb of the bottom portion 10 bto the upper end of the side wall portion 10 a. Therefore, for example, when the thickness of the bubble layer 12 at the measurement position P 1 of the side wall portion 10 ais given as T 1( mm) and the thickness of the bubble layer 12 at another measurement position P 2, which is separated from P 1 by a predetermined distance L along the outer surface 10 oof the crucible, is given as T 2( mm), a value obtained by dividing the difference (T 1- T 2) of the thickness of the bubble layer 12 between the two points by the distance L is:, the rate of change of thickness of the bubble layer 12: ΔT=(T 1- T 2) / L.The thicknesses of the side wall portion 10 aand the bottom portion 10 bare preferably smaller than the thickness of the corner portion 10 c, and more preferably smaller than the thickness of the corner portion 10 cby 5 mm or more. Note that the thickness of the corner portion 10 cindicates the thickness of the corner portion 10 cat the maximum thickness position Pc. When the thickness of the corner portion 10 cis decreased so that the infrared transmittance of the corner portion 10 cis equal to that of the side wall portion 10 aor the bottom portion 10 b, the thickness of the bubble layer 12 at the corner portion 10 cis also decreased, and the temperature of the inner surface of the corner portion 10 cis increased during use of the crucible, resulting in an increase in the amount of the ablated inner surface of the crucible and an increase in the oxygen concentration in the silicon single crystal. It is not preferable that the thicknesses of the side wall portion 10 aand the bottom portion 10 bare as large as those of the corner portion 10 c. This is because not only insufficient heating of the silicon melt and prolongation of the melting time occur, but also a large amount of raw material is used in the manufacture of the crucible, which is not convenient.The thickness of the side wall portion 10 acompared to the corner portion 10 cis preferably the thickness at an intermediate position Pa (see FIG. 1 ) of the side wall portion 10 ain the height direction. This is because the thickness of the upper end portion of the side wall portion 10 abends to be slightly smaller than the average thickness, the thickness of the lower end portion tends to be slightly larger than the average thickness, and the intermediate position Pa of the side wall portion 10 ain the height direction is a position at which a value close to the average thickness of the side wall portion 10 acan be obtained. Since a change in infrared transmittance due to the difference in thickness of the side wall portion 10 ais small, the relationship between the infrared transmittance of the corner portion 10 cat the maximum thickness position Pc and the infrared transmittance of the side wall portion 10 ais set at any position of the side wall portion 10 a.Moreover, the thickness of the bottom portion 10 bcompared to the corner portion 10 cis preferably the thickness of the center Pb of the bottom portion 10 b. This is because the thickness of the bottom portion 10 b tends to be smallest at the central position of the bottom portion 10 b, which is a part where the features of the bottom portion 10 bare most clearly visible.The infrared transmittance of each part of the crucible can be adjusted by changing the thickness of the bubble layer 12. The thickness of the bubble layer 12 is a value obtained by subtracting the thickness of the transparent layer 11 from the thickness of the crucible. When the thickness of the transparent layer 11 is constant, the thickness of the bubble layer 12 also increases as the thickness of the crucible increases. Therefore, for example, by increasing the thickness of the corner portion 10 cto increase the thickness of the bubble layer 12, the infrared transmittance of the corner portion 10 cmay be decreased.The infrared transmittance of each part of the crucible can be adjusted by changing the bubble content of the bubble layer 12. For example, the infrared transmittance of the corner portion 10 cmay be decreased by further increasing the bubble content of the bubble layer 12 of the corner portion 10 cwhile keeping the thickness of the bubble layer 12 constant. The bubble content of the bubble layer 12 can be controlled by adjusting the particle size of the raw material silica powder and the arc heating temperature when the quartz glass crucible 1 is manufactured by the so-called rotomolding method.As illustrated in FIG. 4, in a case where a semi-molten layer 13 is formed on the outer surface (surface of the bubble layer 12) of the quartz glass crucible 1, the infrared transmittance of each part of the crucible is preferably measured in a state where the semi-molten layer 13 is removed by polishing or the like. The semi-molten layer 13 is a layer which is solidified by cooling the raw material silica powder in a partially incompletely molten state (semi-molten state), is in a cracked surface state, and therefore, largely scatters and reflects the light incident from the surface. The infrared transmittance of unused crucibles decreases under the action of the semi-molten layer 13, and individual differences among the crucibles also increase. On the other hand, irregularities on the outer surface at high temperature are smoothed during a crystal pulling-up step, and the effect of scattering and reflection decreases, so that the infrared transmittance is increased and the individual differences between the crucibles are cancelled out. Therefore, by evaluating the infrared transmittance in a state where the semi-molten layer 13 is removed, it is possible to evaluate the infrared transmittance of the crucible in a state close to an actual use state.FIGS. 5(a) and (b) are diagrams for describing the state change of the semi-molten layer 13 of the quartz glass crucible 1, in which FIG. 5(a) illustrates a state before use, and FIG. 5(b) illustrates a state during use.As illustrated in FIG. 5( a), there are cases where the semi-molten layer 13 is formed in the quartz glass crucible 1 in a product state before use. As described above, the semi-molten layer 13 is a layer solidified in a state in which the raw material silica powder is partially incompletely melted, and the surface state thereof easily varies for each crucible product due to the difference in the particle size distribution and the melting conditions of the raw material silica powder, and also the infrared transmittance individually varies. Furthermore, differences in the surface state of the crucible also occur in each part of the crucible, such as the side wall portion 10 a, the corner portion 10 c, and the bottom portion 10 b. When such a crucible is incorporated into a carbon susceptor and actually used at a high temperature, the state of the semi-molten layer 13 changes.That is, as illustrated in FIG. 5( b), the quartz glass crucible 1 is softened by a high temperature of 1500° C. or higher during the single crystal pulling-up step, and a liquid pressure that pushes the crucible wall outward is generated by the silicon melt 5 stored in the crucible. On the other hand, since a carbon susceptor 25 [this is not included in the drawings] is provided outside the quartz glass crucible 1 and the outer surface of the crucible is restricted in the radial direction, the irregularities of the semi-molten layer 13 are crushed and smoothed. Therefore, the infrared transmittance of the quartz glass crucible during the single crystal pulling-up step is different from that in a state before the use of the product.Usually, the measurement data of an unused crucible is used to evaluate the quality of the quartz glass crucible. However, as described above, since the irregularities of the outer surface of the crucible are cancelled during use, it is undesirable that the crucible is evaluated based on the infrared transmittance measured in a state in which the irregularities of the outer surface are different for each crucible and each part. For example, in a case where the semi-molten layer 13 is present, even if the infrared transmittance of the crucible is very low, in a case where the infrared transmittance is high, when the semi-molten layer causes it to be present in an actual pulling-up step, heat input from the outside of the crucible cannot be suppressed, and the oxygen concentration in the single crystal cannot be lowered.For the above reasons, in the present invention, the semi-molten layer 13 on the outer surface is intentionally removed to reduce the effect of the irregularities of the outer surface on the infrared transmittance, and then the infrared transmittance of each part of the crucible is measured and evaluated. That is, the present invention simulates the state during use, particularly the state of the semi-molten layer 13 during use of the crucible versus the quartz glass crucible before use, and the infrared transmittance test of the quartz glass crucible in such a state is measured. Note that the infrared transmittance of the quartz glass crucible during the crystal pulling-up step is affected by bubbles thermally expanded at high temperature, but the bubbles before the thermal expansion are also effective as an evaluation index for the infrared transmittance.FIG. 6 is a flow chart showing a method for measuring infrared transmittance of a quartz glass crucible using a piece of a crucible. Moreover, FIG. 7 is a schematic view showing the measurement method of the infrared transmittance of a quartz glass crucible.As shown in FIGS. 6 and 7, in the measurement of the infrared transmittance of the quartz glass crucible, a specimen of the crucible cut out from the quartz glass crucible is first prepared (step S 11). As described above, the quartz glass crucible 1 constituting the measurement object includes the transparent layer 11, the bubble layer 12 formed on the outer side of the transparent layer 11, and the semi-molten layer 13 formed on the outer side of the bubble layer 12.Next, the semi-molten layer 13 is removed from the crucible piece (step S 12). As methods for removing the semi-molten layer 13, a polishing treatment and a blasting treatment are mentioned, but other methods may be used. The semi-molten layer 13 is preferably completely removed, but cannot be completely removed. It is sufficient to process the crucible piece so that the surface roughness of the outer surface of the crucible on which the semi-molten layer 13 is formed becomes small to some extent. In this case, the arithmetic mean roughness Ra of the outer surface of the crucible is preferably 15 μm or less. As described above, by processing the crucible piece so that the surface roughness of the outer surface of the crucible piece becomes small, it is possible to appropriately evaluate the infrared transmittance.Next, the infrared transmittance of the crucible piece is measured (step S 13). As shown in Fig. 7, in measuring the infrared transmittance of a crucible piece 1s, a laser power meter 22 (light receiving device) is disposed below an infrared lamp 21, and the piece of the crucible 1s is disposed on the light receiving portion of the laser power meter 22. The infrared light from the infrared lamp 21 passes through the crucible piece 1s and is received by the laser power meter 22. The infrared transmittance of the crucible piece 1 sis obtained from the ratio of the amount of emitted light to the amount of incident light in a case where infrared light is incident from one surface of the crucible wall and the light emitted from the opposite surface is received.FIG. 8 is a flowchart showing a manufacturing method of a quartz glass crucible 1 including an infrared transmittance evaluation method described above.The manufacturing method of the quartz glass crucible 1 according to the present embodiment includes a step (step S 21) of manufacturing a quartz glass crucible (first quartz glass crucible) based on predetermined crucible manufacturing conditions (first manufacturing conditions), a step (step S 22) of removing the semi-molten layer 13 of the quartz glass crucible, a step (step S 23) of measuring the infrared transmittance of the portion of the quartz glass crucible from which the semi-molten layer has been removed, a step (step S 24) of modifying the predetermined crucible manufacturing conditions to cause a measured value of the infrared transmittance to reach a target value, and a step (step S 25) of manufacturing a subsequent quartz glass crucible (second quartz glass crucible) based on new crucible manufacturing conditions (second manufacturing conditions). Note that in the step of removing the semi-molten layer 13, it is not necessary to completely remove the semi-molten layer 13, and it is sufficient to process the outer surface so that the surface roughness becomes small. As described above, by feeding back the evaluation result of the infrared transmittance of the crucible to the crucible production conditions, it is possible to efficiently produce a quartz glass crucible having a desired infrared transmittance for each part.FIG. 9 is a schematic view for describing the manufacturing method of a quartz glass crucible 1 according to a rotation molding method.As illustrated in FIG. 9, the quartz glass crucible 1 according to the present embodiment can be manufactured by a so-called rotomolding method. In the rotomolding process, natural silica powder 16B and synthetic silica powder 16A are sequentially deposited on an inner surface 30 iof a rotary mold 30 to form a deposition layer 16 from the raw material silica powder. It is also possible to use only natural silica powder as the raw material of the crucible. This raw material silica powder remains in a certain position while being adhered to the inner surface 30i of the mold 30 by the centrifugal force and held in the shape of the crucible. By changing the thickness of the deposition layer of the raw material silica powder, the crucible thickness for each part can be adjusted.Next, an arc electrode 31 is installed in the mold 30, and the deposition layer 16 of the raw material silica powder is arc-melted from the inner surface 30 iside of the mold 30. Specific conditions such as heating time and heating temperature must be appropriately determined in consideration of conditions such as raw materials and size of the crucible. In this case, the amount of bubbles in the fused silica glass is controlled by sucking the deposition layer 16 of the raw material silica powder from a large number of vent holes 32 provided on the inner surface 30 iof the mold 30. Specifically, at the start of arc melting, the suction force from the large number of vent holes 32 provided on the inner surface 30 iof the mold 30 is increased to form the transparent layer 11, and after the formation of the transparent layer 11, the suction force is weakened to form the bubble layer 12.Since the arc heat is gradually transferred from the inside to the outside of the deposition layer 16 of the raw material silica powder to melt the raw material silica powder, by changing the decompression conditions at the time when the raw material silica powder starts melting, the transparent layer 11 and the bubble layer 12 can be separately formed. When decompression melting is performed to enhance decompression at the time when the silica powder melts, the arc atmosphere gas is not enclosed in the glass, and quartz glass containing no bubbles is formed. Moreover, when normally melting (melting at atmospheric pressure) with decompression weakened at the time when the raw material silica powder melts, the gas of the arc atmosphere is sealed in the glass, and quartz glass having a large number of bubbles is formed. The thicknesses of the transparent layer 11 and the bubble layer 12 can be adjusted for each part by, for example, changing the arrangement and current of the arc electrode 31 to partially change the amount of melting during decompression melting or normal melting.Thereafter, the arc heating is stopped and the crucible is cooled. Accordingly, the quartz glass crucible 1 is completed in which the transparent layer 11 and the bubble layer 12 are sequentially provided from the inside to the outside of the crucible wall.As described above, in the quartz glass crucible 1 according to the present embodiment, the infrared transmittance of the corner portion 10 cis 25 to 51 %, which is a lower infrared transmittance than that of the corner portion of a conventional crucible. Therefore, an excessive temperature rise in the inner surface of the corner portion 10 cmay be suppressed, and the amount of oxygen supplied to the silicon melt from the crucible may be suppressed, so that a silicon single crystal having a low oxygen concentration may be manufactured. Moreover, the absolute value of the rate of change of the infrared transmittance is 3% / cm or less, the absolute value of the rate of change of the thickness of the bubble layer from the side wall portion 10 ato the corner portion 10 cis 2.5 mm / cm or less, and the changes of the infrared transmittance and the thickness from the side wall portion 10 ato the corner portion 10 care smooth. Therefore, the variations in temperature distribution on the inner surface of the crucible in contact with the silicon melt can be reduced, and a sudden change in the amount of oxygen supplied to the silicon melt due to a sudden change in convection in the silicon melt can be suppressed. Therefore, it is possible to suppress sudden change in the oxygen concentration distribution in the longitudinal direction of the silicon single crystal at a certain part, and it is possible to pull up a silicon single crystal having a stable oxygen concentration distribution in the pull-up axis direction.Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the embodiments and can be variously modified without departing from the scope of the present invention. Accordingly, all such modifications are, of course, included within the scope of the present invention.[Examples]< Over Infrared Transmittance Distribution of Crucible>The effect of the infrared transmittance distribution of the crucible on the oxygen concentration distribution of the silicon single crystal has been discussed. In this discussion, samples A1 to A5 and B1 to B4 were prepared from quartz glass crucibles having an opening of 32 inches (about 800 mm), and the infrared transmittance distribution in the height direction was measured along the inner wall surface of each crucible sample. In the measurement of the infrared transmittance distribution, a measurement line was set from the center of the bottom portion of the crucible toward the upper end of the side wall portion, and the infrared transmittance was obtained at distances of 20 mm from the center of the bottom portion along the measurement line. For measurement of infrared transmittance, a measuring device consisting of a combination of an infrared lamp and a laser power meter was used. As the infrared lamp, a near infrared lamp having a peak near a wavelength of 1000 nm was used. As the laser power meter, one having a measurement range of 1 to 250 W, a wavelength range of 190 nm to 11 μm, and a calibration wavelength of 10.6 μm was used. Note that the infrared transmittance was measured in a direction perpendicular to the inner wall surface of the crucible. Thereafter, the rate of change of the infrared transmittance between two adjacent measurement points was obtained from the measured values of the infrared transmittance.Next, after pulling up a silicon single crystal with each crucible sample, the oxygen concentration in the silicon single crystal was measured by FTIR according to the standard of Old-ASTM_F121 (1979). Subsequently, the presence or absence of sudden changes in the average oxygen concentration and the oxygen concentration distribution in the crystal longitudinal direction of the silicon single crystal was evaluated. Table 1 shows the results. [Table 1] Table 1] [Table 1] Table 1]Example 1(A1)240,32,8Within 90 to 110 %Low LowExample 2(A2)570,82,8Within 90 to 110 %Low LowExample 3(A3)600,993,0Within 90 to 110 %Low LowExample 4(A4)250,82,8Within 95 to 105%Low LowExample 5(A5)510,82,8Within 95 to 105%Low LowComparative Example 1(B1)301,12,8Outside the RegionLow LowComparative Example 2(B2)100,22,8Outside the RegionLow LowComparative Example 3(B3)431,23,5Outside the RegionHigh High LevelComparative Example 4(B4)590,93,3Within 90 to 110 %High High LevelThe infrared transmittance of the corner portion of the crucible sample A 1 according to Example 1 was 24%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.3. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 1 was within a target oxygen concentration of ±10% (within 90% to 110 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The infrared transmittance of the corner portion of the crucible sample A 2 according to Example 2 was 57%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.8, and moreover, the maximum value of the absolute value of the rate of change of the infrared transmittance of this crucible sample A 2 was 2.8% / cm (3% / cm or less) so that there was a smooth change of the infrared transmittance. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 2 was within a target oxygen concentration of ±10% (within 90% to 110 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The infrared transmittance of the corner portion of the crucible sample A 3 according to Example 3 was 60%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.99. Moreover, the maximum value of the absolute value of the rate of change of the infrared transmittance of this crucible sample A 3 was 3.0% / cm (3% / cm or less) so that there was a smooth change of the infrared transmittance. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 3 was within a target oxygen concentration of ±10% (within 90% to 110 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The infrared transmittance of the corner portion of the crucible sample A 4 according to Example 4 was 25%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.8, and moreover, the maximum value of the absolute value of the rate of change of the infrared transmittance of this crucible sample A 4 was 2.8% / cm (3% / cm or less) so that there was a smooth change of the infrared transmittance. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A4 was within a target oxygen concentration of ± 5% (within 95% to 105%), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The infrared transmittance of the corner portion of the crucible sample A 5 according to Example 5 was 51 %, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.8, and moreover, the maximum value of the absolute value of the rate of change of the infrared transmittance of this crucible sample A 5 was 2.8% / cm (3% / cm or less) so that there was a smooth change of the infrared transmittance. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A5 was within a target oxygen concentration of ± 5% (within 95% to 105%), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The infrared transmittance of the corner portion of the crucible sample B 1 according to Comparative Example 1 was 30%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 1.1. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample B 1 became higher than the target oxygen concentration of ±10%. That is, the average oxygen concentration was more than 110% of the target oxygen concentration, and a single crystal having a low oxygen concentration could not be obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The infrared transmittance of the corner portion of the crucible sample B 2 according to Comparative Example 2 was 10%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.2. moreover, the maximum value of the absolute value of the rate of change of the infrared transmittance of this crucible sample B 2 was 2.8% / cm (3% / cm or less) so that there was a smooth change of the infrared transmittance. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample B 2 became lower than the target oxygen concentration of ±10%. Although there was no sudden change in the oxygen concentration in the crystal longitudinal direction, it became difficult to adjust the oxygen concentration because the average oxygen concentration was less than 90% of the target oxygen concentration due to instability of convection of the melt, so that the variations in the oxygen concentration in the crystal axis direction were large.The infrared transmittance of the corner portion of the crucible sample B 3 according to Comparative Example 3 was 43%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 1.2. moreover, the maximum value of the absolute value of the rate of change of the infrared transmittance of this crucible sample B 3 was 3.5% / cm, which is a high rate of change of more than 3% / cm. Further, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample B 3 became higher than the target oxygen concentration ±10%, so that a single crystal having a low oxygen concentration could not be obtained. Further, a sudden change in oxygen concentration in the crystal longitudinal direction was also observed.The infrared transmittance of the corner portion of the crucible sample B 4 according to Comparative Example 4 was 59%, and the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.9. The average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 4 was within a target oxygen concentration of ±10% (within 90% to 110%), so that a single crystal having a low oxygen concentration was obtained. However, a sudden change in oxygen concentration in the crystal longitudinal direction was observed. From the result, it is seen that a sudden change in the infrared transmittance distribution of the crucible results in a sudden change in the oxygen concentration in the crystal longitudinal direction.< Over Thickness Distribution of Bubble Layer of Crucible>Next, the effect of the thickness distribution of the bubble layer of the crucible on the oxygen concentration distribution of the silicon single crystal was discussed. In this discussion, samples A6 to A11 and B5 to B8 were prepared from quartz glass crucibles having an opening of 32 inches (about 800 mm), and the thickness in the height direction along the inner wall surface of each crucible sample and the thickness distribution of the bubble layer were measured together with the infrared transmittance distribution. As in the measurement of the infrared transmittance, also in the measurement of the thickness of the crucible and the thickness distribution of the bubble layer, a measurement line was set from the center of the bottom portion of the crucible toward the upper end of the side wall portion, and the thickness of the crucible and the thickness of the bubble layer were obtained at distances of 20 mm from the center of the bottom portion along the measurement line. For measurement of the crucible thickness and the thickness of the bubble layer, an ultrasonic measurement machine (ultrasonic thickness meter) was used. Note that the thickness of the crucible and the thickness of the bubble layer were measured in a direction perpendicular to the inner wall surface of the crucible. Thereafter, the rate of change of the thickness of the bubble layer between two adjacent measurement points was obtained from the measured values of the thickness of the bubble layer.Next, after pulling up a silicon single crystal with each crucible sample, the oxygen concentration in the silicon single crystal was measured by FTIR according to the standard of Old-ASTM_F121 (1979). Subsequently, the presence or absence of sudden changes in the average oxygen concentration and the oxygen concentration distribution in the crystal longitudinal direction of the silicon single crystal was evaluated. Table 2 shows the results. [Table 2] [Table 2]Example 6(A6)18170,31,5Within 90 to 110 %Low LowExample 7(A7)18170,82,4Within 90 to 110 %Low LowExample 8(A8)31300,992,5Within 90 to 110 %Low LowExample 9(A9)19180,52,4Within 95 to 105%Low LowExample 10(A10)25230,52,4Within 95 to 105%Low LowExample 11(A11)30290,42,4Within 95 to 105%Low LowComparative Example 5(B5)28261,12,3Outside the RegionLow LowComparative Example 6(B6)20170,22,5Outside the RegionLow LowComparative Example 7(B7)18171,02,6Outside the RegionHigh High LevelComparative Example 8(B8)25170,83,0Within 90 to 110 %High High LevelThe thickness of the corner portion of the crucible sample A 6 according to Example 6 was 18 mm, and the thickness of the bubble layer at the corner portion was 17 mm. Note that the thickness of the bubble layer is a value measured at the maximum thickness position of the corner portion. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.3. In addition, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A6 was within the target oxygen concentration of ±10% (within 90 to 110 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The thickness of the corner portion of the crucible sample A 7 according to Example 7 was 18 mm, and the thickness of the bubble layer at the corner portion was 17 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.8, and further, the maximum value of the absolute value of the change rate of the thickness of the bubble layer of this crucible sample A 7 was 2.4 mm / cm (2.5 mm / cm or less), so that a change of the thickness of the bubble layer was smooth. In addition, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 7 was within the target oxygen concentration of ±10% (within 90 to 110 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The thickness of the corner portion of the crucible sample A 8 according to Example 8 was 31 mm, and the thickness of the bubble layer at the corner portion was 30 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.99. Further, the maximum value of the absolute value of the change rate of the thickness of the bubble layer of this crucible sample A 8 was 2.5 mm / cm (2.5 mm / cm or less), so that a change of the thickness of the bubble layer was smooth. In addition, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 8 was within the target oxygen concentration of ±10% (within 90 to 110 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The thickness of the corner portion of the crucible sample A 9 according to Example 9 was 19 mm, and the thickness of the bubble layer at the corner portion was 18 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.5. In addition, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A9 was within the target oxygen concentration of ± 5% (within 95 to 105 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The thickness of the corner portion of the crucible sample A 10 according to Example 10 was 25 mm, and the thickness of the bubble layer at the corner portion was 23 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.5. In addition, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 10 was within the target oxygen concentration of ± 5% (within 95 to 105 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The thickness of the corner portion of the crucible sample A 11 according to Example 11 was 30 mm, and the thickness of the bubble layer at the corner portion was 29 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.4. In addition, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 11 was within the target oxygen concentration of ± 5% (within 95 to 105 %), and a single crystal having a low oxygen concentration was obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The thickness of the corner portion of the crucible sample B 5 according to Comparative Example 5 was 28 mm, and the thickness of the bubble layer at the corner portion was 26 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 1.1. Further, the maximum value of the absolute value of the change rate of the thickness of the bubble layer of this crucible sample B 5 was 2.3 mm / cm (2.5 mm / cm or less), so that a change of the thickness of the bubble layer was smooth. However, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample B 5 was higher than the target oxygen concentration of ±10%. That is, the average oxygen concentration was more than 110% of the target oxygen concentration, and a single crystal having a low oxygen concentration could not be obtained. There was no sudden change in oxygen concentration in the crystal longitudinal direction.The thickness of the corner portion of the crucible sample B 6 according to Comparative Example 6 was 20 mm, and the thickness of the bubble layer at the corner portion was 17 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.2, and further, the maximum value of the absolute value of the change rate of the thickness of the bubble layer of this crucible sample B 6 was 2.5 mm / cm (2.5 mm / cm or less), so that a change of the thickness of the bubble layer was smooth. However, the average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample B 6 was lower than the target oxygen concentration of ±10%. Although there was no sudden change in the oxygen concentration in the crystal longitudinal direction, it became difficult to adjust the oxygen concentration because the average oxygen concentration was less than 90% of the target oxygen concentration due to instability of convection of the melt, so that the variations in the oxygen concentration in the crystal axis direction were large.The thickness of the corner portion of the crucible sample B 7 according to Comparative Example 7 was 18 mm, and the thickness of the bubble layer at the corner portion was 17 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 1.0. Further, the maximum value of the absolute value of the change rate of the thickness of the bubble layer of this crucible sample B 7 was 2.6 mm / cm, which is a high change rate of more than 2.5 mm / cm. The average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample B 7 became higher than the target oxygen concentration ±10%, so that a single crystal having a low oxygen concentration could not be obtained. Further, a sudden change in oxygen concentration in the crystal longitudinal direction was also observed.The thickness of the corner portion of the crucible sample B 8 according to Comparative Example 8 was 25 mm, and the thickness of the bubble layer at the corner portion was 17 mm. Moreover, the ratio of the infrared transmittance of the corner portion to that of the side wall portion was 0.8, and further, the maximum value of the absolute value of the change rate of the thickness of the bubble layer of this crucible sample B 8 was 3.0 mm / cm, which is a high change rate of more than 2.5 mm / cm. The average oxygen concentration in the longitudinal direction of a silicon single crystal pulled up using this crucible sample A 8 was within a target oxygen concentration of ±10% (within 90% to 110%), so that a single crystal having a low oxygen concentration was obtained. However, a sudden change in oxygen concentration in the crystal longitudinal direction was observed.[List of Reference Numerals]1 Quartz glass crucible 5 Silicon melt 5 a Schmelz surface of silicon melt 6 Silicon single crystal 10 a Seitenwand wall portion 10 b Bodenabschnitt portion 10 c Eck portion 10 i Innenfläche surface of the crucible 10 o Außenfläche surface of the crucible 11 Transparent layer 12 Bubble layer 16 Abscheidungs layer of raw material silica powder 16A Synthetic silica powder 16B Natural silica powder 20 Heater 21 Infrared lamp 22 Laser power meter 25 Carbon susceptor 30 Mold 30 i Innenfläche surface of the mold 31 Arc electrode 32 Vent hole

Claims

A quartz glass crucible (1) comprising: a cylindrical side wall portion (10a); a bottom portion (10b); a corner portion (10c) connecting the side wall portion (10a) and the bottom portion (10b) to each other; a transparent layer (11) made of quartz glass containing no bubbles; a bubble layer (12) formed on the outside of the transparent layer (11) and made of quartz glass and containing a large number of bubbles; and a semi-molten layer (13) formed on the outside of the bubble layer (12) and made of the raw material silica powder solidified in an incompletely molten state, wherein a ratio of an infrared transmittance of the corner portion (10c) at a maximum thickness position (Pc) of the corner portion (10c) to an infrared transmittance of the side wall portion (10a) is 0.3 or more and 0.99 or less, an absolute value of a change rate of the infrared transmittance in a height direction along a wall surface of the crucible from a center (Pb) of the bottom portion (10b) to an upper end of the side wall portion (10a) is 3% / cm or less, and the infrared transmittance is a value measured in a state in which the semi-molten layer (13) is removed.The quartz glass crucible (1) according to claim 1, wherein the infrared transmittance of the corner portion (10c) at the maximum thickness position (Pc) is 25% or more and 51% or less.The quartz glass crucible (1) according to claim 1 or 2, wherein an absolute value of a change rate of the thickness of the bubble layer (12) in the height direction along the wall surface of the crucible from the center (Pb) of the bottom portion (10b) to the upper end of the side wall portion (10a) is 2.5 mm / cm or less.The quartz glass crucible (1) according to any one of claims 1 to 3, wherein an opening of the crucible is 812 mm (32 inches), a maximum thickness of the corner portion (10c) is 19 mm or more and 30 mm or less, and a thickness of the bubble layer (12) at the maximum thickness position (Pc) of the corner portion (10c) is 18 mm or more and 29 mm or less.The quartz glass crucible (1) according to any one of claims 1 to 4, wherein a bubble content of the bubble layer (12) at the maximum thickness position (Pc) of the corner portion (10c) is more than 0.1 vol% and 5 vol% or less.The quartz glass crucible (1) according to any one of claims 1 to 5, wherein a thickness of the bubble layer (12) of the side wall portion (10a) is greater than a thickness of the transparent layer (11) of the side wall portion (10a), and a thickness of the bubble layer (12) of the corner portion (10c) is greater than the thickness of the transparent layer (11) of the side wall portion (10a).A quartz glass crucible (1) comprising: a cylindrical side wall portion (10a); a bottom portion (10b); a corner portion (10c) connecting the side wall portion (10a) and the bottom portion (10b) to each other; a transparent layer (11) made of quartz glass containing no bubbles; a bubble layer (12) made of quartz glass containing a large number of bubbles and formed on the outside of the transparent layer (11); and a semi-molten layer formed on the outside of the bubble layer and made of the raw material silica powder solidified in an incompletely molten state, wherein a ratio of an infrared transmittance of the corner portion (10c) at a maximum thickness position (Pc) of the corner portion (10c) to an infrared transmittance of the side wall portion (10a) is 0.3 or more and 0.99 or less, and an absolute value of a change rate of the thickness of the bubble layer ( 12) in a height direction along a wall surface of the crucible from a center (Pb) of the bottom portion ( 10 b) to an upper end of the side wall portion ( 10 a) is 2.5 mm / cm or less, and the infrared transmittance is a value measured in a state where the semi-molten layer ( 13) is removed.The quartz glass crucible (1) according to claim 7, wherein an opening of the crucible is 812 mm (32 inches), a maximum thickness of the corner portion (10c) is 19 mm or more and 30 mm or less, and a thickness of the bubble layer (12) at the maximum thickness position (Pc) of the corner portion (10c) is 18 mm or more and 29 mm or less.The quartz glass crucible (1) according to claim 7 or 8, wherein a bubble content of the bubble layer (12) at the maximum thickness position (Pc) of the corner portion (10c) is more than 0.1 vol% and 5 vol% or less.The quartz glass crucible (1) according to any one of claims 7 to 9, wherein the infrared transmittance of the corner portion (10c) at the maximum thickness position (Pc) is 25% or more and 51% or less.The quartz glass crucible (1) according to any one of claims 7 to 10, wherein a thickness of the bubble layer (12) of the side wall portion (10a) is greater than a thickness of the transparent layer (11) of the side wall portion (10a), and a thickness of the bubble layer (12) of the corner portion (10c) is greater than the thickness of the transparent layer (11) of the side wall portion (10a).

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