Quartz glass crucible and method for manufacturing the same, and method for manufacturing silicon single crystal

Abstract

To provide a quartz glass crucible capable of preventing the coating film of a crystallization accelerator from peeling to maintain the in-plane distribution of concentration of the crystallization accelerator as uniformly as possible; a method for manufacturing the same; and a method for manufacturing a silicon single crystal.SOLUTION: A quartz glass crucible 1 includes: a crucible base 10 consisting of silica glass; and a coating film 13 formed on the inner surface 10i of the crucible base 10 and including a crystallization accelerator. The peel strength of the coating film 13 is 0.3 or more kN / m.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a quartz glass crucible and a method for manufacturing the same, and particularly to a quartz glass crucible used for pulling a silicon single crystal by the Czochralski method (CZ method). The present invention also relates to a method for manufacturing a silicon single crystal using such a quartz glass crucible.

Background Art

[0002] Many silicon single crystals are manufactured by the CZ method. The CZ method involves melting a polycrystalline silicon raw material in a quartz glass crucible to generate a silicon melt, immersing a seed crystal in the silicon melt, and gradually pulling up the seed crystal while rotating the quartz glass crucible and the seed crystal, thereby growing a large single crystal at the lower end of the seed crystal. According to the CZ method, it is possible to increase the yield of large-diameter silicon single crystals.

[0003] A quartz glass crucible is a silica glass container that holds a silicon melt during the process of pulling a silicon single crystal. Therefore, the quartz glass crucible is required to have high durability that does not deform at a high temperature above the melting point of silicon and can withstand long-term use. Also, it is required to be of high purity to prevent impurity contamination of the silicon single crystal.

[0004] It is known that brown ring-shaped cristobalite crystals called brown rings grow on the inner surface of a quartz glass crucible that comes into contact with a silicon melt during the pulling of a silicon single crystal. If the brown ring peels off from the surface of the crucible and混入 the silicon melt, it may be carried to the solid-liquid interface by melt convection and incorporated into the single crystal, and the peeling of cristobalite causes dislocation of the silicon single crystal. Therefore, the inner surface of the crucible is actively crystallized with a crystallization promoter to prevent the peeling of crystal flakes.

[0005] Regarding a method for strengthening the inner surface of a crucible by crystallization, for example, Patent Document 1 describes a devitrifying agent for crucibles that is more efficient than conventional ones. This devitrifying agent comprises barium and tantalum, tungsten, germanium, tin, or a combination of two or more thereof, which is dissolved in the crucible during construction, applied to the surface of the final crucible, and / or added to the silicon melt used for crystal pulling.

[0006] Patent Document 2 describes a surface-treated crucible having improved dislocation-free performance. This crucible includes first and second devitrification accelerators distributed on the inner and outer surfaces of the side wall formations of the glassy silica body, respectively. The first devitrification accelerator is distributed such that when the semiconductor material melts in the crucible during crystal growth, a substantially devitrified first layer of silica is formed on the inner surface of the crucible that comes into contact with the molten semiconductor material. The second devitrification accelerator is distributed such that when the semiconductor material melts in the crucible during crystal growth, a substantially devitrified second layer of silica is formed on the outer surface of the crucible.

[0007] Patent Document 3 describes a quartz glass crucible that can withstand very long single-crystal pulling processes such as multi-pulling. This quartz glass crucible comprises a crucible body made of quartz glass and first and second crystallization accelerator-containing coating films formed on the inner and outer surfaces of the crucible body, respectively. The first and second crystallization accelerator-containing coating films contain polymers, and the crystallization accelerator is a water-insoluble barium compound. Due to the action of the crystallization accelerator, a crystalline layer consisting of an aggregate of dome-shaped or columnar crystal grains is formed on the surface layers of the inner and outer surfaces of the crucible body. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 2019-509969 [Patent Document 2] Japanese Patent Application Publication No. 9-110590 [Patent Document 3] Japanese Patent Publication No. 2020-0200236 [Overview of the project] [Problems that the invention aims to solve]

[0009] As described above, applying a crystallization accelerator is effective in uniformly crystallizing the inner surface of the crucible. However, a large amount of polycrystalline silicon chunks are filled into the crucible, and a considerable load is placed on the bottom surface of the crucible. Furthermore, each silicon chunk is finely crushed during the manufacturing process and has sharp edges, so damage to the crystallization accelerator coating becomes a problem. If part of the crystallization accelerator coating peels off between the time the polycrystalline silicon raw material is filled into the crucible and the completion of its melting, it becomes difficult to uniformly crystallize the inner surface of the crucible. Therefore, there is a strong need to form a coating that is resistant to peeling.

[0010] Therefore, an object of the present invention is to provide a quartz glass crucible and a method for manufacturing the same that can prevent the peeling of the crystallization accelerator coating film and maintain the in-plane distribution of the crystallization accelerator concentration as uniformly as possible. Another object of the present invention is to provide a method for manufacturing silicon single crystals using such a quartz glass crucible. [Means for solving the problem]

[0011] To solve the above problems, the quartz glass crucible according to the present invention comprises a crucible substrate made of silica glass and a coating film containing a crystallization accelerator formed on the inner surface of the crucible substrate, characterized in that the peel strength of the coating film is 0.3 kN / m or more.

[0012] According to the present invention, peeling of the crystallization accelerator coating can be prevented. Therefore, the inner surface of the crucible substrate can be uniformly crystallized during the single crystal pulling process, preventing dislocation formation and pinhole generation in the silicon single crystal and improving yield.

[0013] In the present invention, the concentration of the crystallization accelerator is 2.5 × 10 15atoms / cm 2 The following conditions apply, and it is preferable that the peel strength of the coating film is 0.6 kN / m or more. If the peel strength of the coating film is 0.6 kN / m or more, the concentration of the crystallization accelerator is 2.5 × 10 15 atoms / cm 2 Even with the following conditions, the inner surface of the crucible substrate can be uniformly crystallized.

[0014] In the present invention, the concentration of the crystallization accelerator is 2.5 × 10 15 atoms / cm 2 A higher concentration is preferable. 15 atoms / cm 2 If the value is higher than this, even if a portion of the coating film peels off due to its low peel strength, the powerful crystallization accelerator allows crystallization to proceed laterally, enabling crystallization of the peeled portion. Therefore, the inner surface of the crucible substrate can be crystallized uniformly.

[0015] In the present invention, it is preferable that the area of ​​the coating film at the bottom of the crucible substrate is in the range of 0.25 times or more and 1 time the outer diameter of the crucible. By setting the peel strength of the coating film to 0.3 kN / m or more within a range of at least 0.25 times the outer diameter of the crucible in this way, the dislocation formation of the silicon single crystal due to cristobalite peeling and the occurrence rate of pinholes in the silicon single crystal can be reduced.

[0016] In the present invention, it is preferable that the peel strength of the coating film formed within a range of 0.5 times or less the outer diameter of the crucible substrate from the center of the bottom is 0.9 kN / m or more. This makes it possible to reduce the probability of dislocation formation and pinhole occurrence in the silicon single crystal.

[0017] In the present invention, it is preferable that the crystallization accelerator is a water-soluble compound that does not have a carbon atom in the molecule of Group 2a elements (Mg, Ca, Sr, Ba). Thereby, the carbon concentration in the coating film can be reduced, and the carbon contamination of the silicon single crystal can be reduced. Further, since the solubility in water is high and the handling of the aqueous solution is easy, uniform coating of the crystallization accelerator on the crucible surface can be easily realized.

[0018] It is preferable that the thickness of the coating film is 0.1 μm or more and 50 μm or less. Thereby, a uniform coating film can be formed on the inner surface of the crucible substrate.

[0019] It is preferable that the surface roughness (Ra) of the coating film is 0.1 μm or more and 0.25 μm or less. Thereby, peeling of the coating film can be prevented and the inner surface of the crucible substrate can be uniformly crystallized.

[0020] The average carbon concentration in the range of 0 μm or more and 300 μm or less from the inner surface of the coating film and the crucible substrate is 1.0×10 12 atoms / cc or more and 3.0×10 19 atoms / cc or less. In the quartz glass crucible according to the present invention, since the carbon concentration is reduced not only in the vicinity of the inner surface of the crucible substrate but also in the coating film containing the crystallization accelerator, the carbon taken into the silicon single crystal can be reduced.

[0021] The average carbon concentration in the coating film is preferably 3.0×10 18 atoms / cc or less. Thereby, the carbon taken into the silicon single crystal can be further reduced. The average carbon concentration in the coating film can be measured by SIMS.

[0022] Furthermore, the method for manufacturing a quartz glass crucible according to the present invention comprises the steps of: preparing a crucible substrate made of silica glass; and forming a coating film of a crystallization accelerator on the inner surface of the crucible substrate by spraying a coating solution containing a crystallization accelerator, wherein the step of spraying the coating solution is characterized by using a two-fluid nozzle that mixes gas and liquid at the spray tip and sprays the liquid with an average droplet diameter of 5 μm or more and 1000 μm or less.

[0023] According to the present invention, dripping of the coating liquid on the crucible surface can be prevented, and the crystallization accelerator can be applied uniformly. Therefore, a uniform coating film can be formed on the inner surface of the crucible substrate, and the peel strength of the coating film can be increased.

[0024] In the present invention, the step of forming the coating film preferably involves setting the maximum thickness of the coating film formed in a single application to 0.5 μm or less, and then repeating the drying and reapplication of the coating film alternately to create a multilayer coating film. This makes it possible to form a dense and uniform coating film and to increase the peel strength of the coating film.

[0025] In the present invention, it is preferable that the spray volume of the coating solution is 300 mL / min or less. By limiting the spray volume of the coating solution to 300 mL / min or less, a dense coating film can be uniformly formed.

[0026] The crystallization accelerator is preferably a water-soluble compound of a group 2a element (Mg, Ca, Sr, Ba) that does not contain carbon atoms in its molecule. This reduces the carbon concentration in the coating film and reduces carbon contamination of the silicon single crystal. Furthermore, because it has high solubility in water and the aqueous solution is easy to handle, uniform application of the crystallization accelerator to the crucible surface can be easily achieved.

[0027] In the step of forming the coating film, it is preferable to spray the coating liquid while heating the crucible substrate at a temperature of 60°C to 500°C, and it is particularly preferable to heat it at a temperature of 100°C to 180°C. In this case, it is preferable to spray the coating liquid while heating the crucible substrate so that the temperature difference between the boiling point of the solvent in the coating liquid and the crucible substrate is between -40.0°C and 100°C, and it is even more preferable to heat the crucible substrate to a temperature between the boiling point of the solvent and 80°C. This makes it possible to suppress the generation of carbonates and reduce the carbon concentration in the coating film.

[0028] The step of spraying the coating liquid is 1 × 10 2 Pa or more 1×10 5 It is preferable to carry out the process under a low vacuum of Pa or less. By spraying the coating solution onto the heated crucible substrate under a low vacuum in this way, the solvent can be instantly evaporated, allowing the crystallization accelerator to be uniformly fixed, and preventing variations in the coating film due to dripping of the coating solution on the crucible surface. In addition, since the heating time can be shortened by evaporating the solvent in a short time, it is possible to suppress the generation of carbonates.

[0029] Furthermore, the method for producing a silicon single crystal according to the present invention is characterized by pulling the silicon single crystal by the CZ method using the quartz glass crucible according to the present invention. According to the present invention, it is possible to prevent a decrease in yield due to dislocation formation in the silicon single crystal. [Effects of the Invention]

[0030] According to the present invention, it is possible to provide a quartz glass crucible in which the coating film of the crystallization accelerator is less likely to peel off, and a method for manufacturing the same. Furthermore, according to the present invention, it is possible to provide a method for manufacturing silicon single crystals using such a quartz glass crucible. [Brief explanation of the drawing]

[0031] [Figure 1] Figure 1 is a schematic perspective view showing the configuration of a quartz glass crucible according to an embodiment of the present invention. [Figure 2] Figure 2 is a schematic side cross-sectional view and a partially enlarged view of the quartz glass crucible shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram illustrating a method for measuring the peel strength of a coated film. [Figure 4] Figure 4 is a schematic plan view showing the measurement locations for carbon concentration at the bottom of the crucible. [Figure 5] Figure 5 is a schematic diagram illustrating the manufacturing method of a quartz glass crucible using the rotary molding method. [Figure 6] Figure 6 is a schematic diagram showing a method for applying a crystallization accelerator to the inner surface of a crucible substrate. [Figure 7] Figure 7 is a diagram illustrating the single crystal pulling process using a quartz glass crucible according to this embodiment, and is a schematic cross-sectional view showing the configuration of the single crystal pulling apparatus. [Modes for carrying out the invention]

[0032] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0033] Figure 1 is a schematic perspective view showing the configuration of a quartz glass crucible according to an embodiment of the present invention. Figure 2 is a schematic side cross-sectional view and a partially enlarged view of the quartz glass crucible shown in Figure 1.

[0034] As shown in Figures 1 and 2, the quartz glass crucible 1 is a silica glass container for holding a silicon melt, and has a cylindrical side wall portion 10a, a bottom portion 10b provided below the side wall portion 10a, and a corner portion 10c provided between the side wall portion 10a and the bottom portion 10b. The bottom portion 10b is preferably a gently curved so-called round bottom, but it may also be a so-called flat bottom. The corner portion 10c is a portion having a greater curvature than the bottom portion 10b.

[0035] The diameter of the quartz glass crucible 1 varies depending on the diameter of the silicon single crystal ingot pulled from the silicon melt, but it is 18 inches (approximately 450 mm) or larger, preferably 22 inches (approximately 560 mm), and particularly preferably 32 inches (approximately 800 mm) or larger. Such large crucibles are used for pulling large silicon single crystal ingots with a diameter of 300 mm or more, and it is required that the quality of the single crystal is not affected even after prolonged use.

[0036] The wall thickness of the crucible varies slightly depending on the location, but it is preferable that the wall thickness of the side wall portion 10a of a crucible 18 inches or larger is 6 mm or more, the wall thickness of the side wall portion 10a of a crucible 22 inches or larger is 7 mm or more, and the wall thickness of the side wall portion 10a of a crucible 32 inches or larger is 10 mm or more. This allows a large amount of molten silicon to be stably held at high temperatures.

[0037] As shown in Figure 2, the quartz glass crucible 1 comprises a crucible substrate 10 made of silica glass and a coating film 13 of a crystallization accelerator formed on the inner surface 10i of the crucible substrate 10. The crucible substrate 10 mainly has a two-layer structure, having a transparent layer 11 (bubble-free layer) that does not contain air bubbles and a bubble layer 12 (opaque layer) that contains many minute air bubbles, and the coating film 13 is provided inside the transparent layer 11.

[0038] The transparent layer 11 is a layer that constitutes the inner surface 10i of the crucible substrate 10 that comes into contact with the silicon melt, and is provided to prevent a decrease in the yield of silicon single crystals due to air bubbles in the silica glass. Since the inner surface 10i of the crucible reacts with the silicon melt and melts away, air bubbles near the inner surface of the crucible cannot be contained within the silica glass, and there is a risk that the bubbles will burst due to thermal expansion and crucible fragments (silica fragments) will peel off. If crucible fragments released into the silicon melt are carried by melt convection to the growth interface of the silicon single crystal and incorporated into the silicon single crystal, it can cause dislocations in the single crystal. Also, if air bubbles released into the silicon melt float to the solid-liquid interface and are incorporated into the single crystal, it can cause the formation of pinholes in the silicon single crystal.

[0039] The statement that the transparent layer 11 is bubble-free means that it has a bubble content and bubble size such that the single crystallization rate does not decrease due to bubbles. Such a bubble content is, for example, 0.1 vol% or less, and the bubble diameter is, for example, 100 μm or less.

[0040] The thickness of the transparent layer 11 is preferably 0.5 to 10 mm, and is set to an appropriate thickness for each part of the crucible so that it does not completely disappear due to melting during the crystal pulling process and expose the bubble layer 12. The transparent layer 11 is preferably provided throughout the crucible from the side wall portion 10a to the bottom portion 10b, but it is also possible to omit the transparent layer 11 at the upper end of the crucible where it does not come into contact with the silicon melt.

[0041] The bubble layer 12 is the main layer of the crucible substrate 10, located outside the transparent layer 11. It is provided to improve the heat retention of the silicon melt inside the crucible and to disperse the radiant heat from the heater of the single crystal pulling apparatus to heat the silicon melt inside the crucible as uniformly as possible. For this reason, the bubble layer 12 is provided throughout the entire crucible, from the side wall portion 10a to the bottom portion 10b.

[0042] The bubble content of the bubble layer 12 is preferably higher than that of the transparent layer 11, greater than 0.1 vol%, and 5 vol% or less. This is because if the bubble content of the bubble layer 12 is 0.1 vol% or less, it cannot perform the heat retention function required of the bubble layer 12. Furthermore, if the bubble content of the bubble layer 12 exceeds 5 vol%, the crucible may deform due to the thermal expansion of the bubbles, which may reduce the single crystal yield and result in insufficient heat transfer. From the viewpoint of balancing heat retention and heat transfer, the bubble content of the bubble layer 12 is particularly preferably 1 to 4 vol%. The bubble content mentioned above is the value measured in a crucible at room temperature before use.

[0043] To prevent contamination of the silicon melt, it is desirable that the silica glass constituting the transparent layer 11 be of high purity. Therefore, it is preferable that the crucible substrate 10 has a two-layer structure consisting of a synthetic silica glass layer (synthetic layer) formed from synthetic quartz powder and a natural silica glass layer (natural layer) formed from natural quartz powder. Synthetic quartz powder can be produced by gas-phase oxidation of silicon tetrachloride (SiCl4) (dry synthesis method) or hydrolysis of silicon alkoxide (sol-gel method). Natural quartz powder is produced by crushing natural minerals mainly composed of α-quartz into granules.

[0044] The two-layer structure of synthetic silica glass and natural silica glass can be manufactured by depositing natural quartz powder along the inner surface of a crucible manufacturing mold, depositing synthetic quartz powder on top of it, and melting these raw quartz powders by Joule heating due to arc discharge. In the arc melting process, bubbles are removed by strongly evacuating from the outside of the deposited layer of raw quartz powder to form a transparent layer 11, and a bubble layer 12 is formed by stopping or weakening the vacuum. Therefore, the interface between the synthetic silica glass layer and the natural silica glass layer does not necessarily coincide with the interface between the transparent layer 11 and the bubble layer 12, but it is preferable that the synthetic silica glass layer, like the transparent layer 11, has a thickness such that it does not completely disappear due to erosion of the inner surface of the crucible during the single crystal pulling process.

[0045] The quartz glass crucible 1 according to this embodiment has a structure in which the inner surface 10i of the crucible substrate 10 is covered with a coating film 13 of a crystallization accelerator. The crystallization accelerator is a compound of a group 2a element (Mg, Ca, Sr, Ba) and plays a role in promoting the crystallization of the inner surface 10i of the crucible substrate 10 during the single crystal pulling process. In this embodiment, the crystallization accelerator is preferably a hydroxide or oxide that does not have carbon atoms in its molecule, and hydroxides are particularly preferred because they have high solubility in water and are easy to handle. Barium (Ba) is particularly preferred as the group 2a element for the crystallization accelerator. This is because barium has a smaller segregation coefficient than silicon, is stable at room temperature, and is easy to handle. In addition, barium has advantages such as the crystallization rate not decreasing with crystallization and causing stronger oriented growth than other elements.

[0046] The crystallization accelerator coating film 13 is formed in a range of 0.25 times to 1 time the outer diameter of the crucible. In this embodiment, it is preferable that the crystallization accelerator coating film 13 is formed on the entire inner surface 10i of the crucible substrate 10, excluding the area near the upper end of the rim. The reason for excluding the area near the upper end of the rim is that the area near the upper end of the rim does not come into contact with the silicon melt and does not necessarily need to crystallize there, and also because when crystallization occurs near the upper end of the rim, the crystal fragments mixed into the silicon melt can cause dislocations in the silicon single crystal.

[0047] The thickness of the coating film 13 is not particularly limited, but is preferably 0.1 to 50 μm, and particularly preferably 1 to 20 μm. If the thickness of the coating film 13 is too thin, the peel strength of the coating film will be weak, and the peeling of the coating film 13 will result in uneven crystallization. If the coating film 13 is too thick, the peel strength will also decrease, and the crystallization will be uneven.

[0048] It is desirable that the coating film 13 does not peel off, and for this purpose, a peel strength of 0.3 kN / m or more is required. The coating film 13 must satisfy such a peel strength in at least the central bottom region of the crucible substrate 10, and it is preferable that such a peel strength is satisfied throughout the entire region where the coating film 13 is formed. Here, the central bottom region of the crucible substrate 10 refers to the region within a range of 0.5r (where r is the outer diameter (radius) of the crucible) from the center of the bottom of the crucible substrate 10.

[0049] Figure 3 is a schematic diagram showing a method for measuring the peel strength of the coated film 13.

[0050] As shown in Figure 3, the peel strength of the coating film 13 can be measured using SAICAS (Surface And Interfacial Cutting Analysis System) 30. SAICAS 30 measures the vertical load F when the diamond blade 31 is cutting the coating at an angle. Z (Vertical force) and horizontal load F YThe deemed shear strength can be determined from the (horizontal force), and the horizontal load F when the diamond blade 31 is cutting parallel to the interface between the coating and the substrate. Y The peel strength can be determined from the horizontal force. The peel strength of the coating film 13 is determined by the horizontal load F when a sample 1s of a crucible piece on which the coating film 13 is formed is placed on a stage and the interface between the coating film 13 and the crucible substrate 10 (the inner surface 10i of the crucible substrate 10) is cut with a diamond blade 31. Y It can be calculated from this.

[0051] The concentration of the crystallization accelerator contained in the coated film 13 is 2.5 × 10⁻⁶. 15 atoms / cm 2 The above is preferable. In this way, when the concentration of the crystallization accelerator is relatively high, even if some of the crystallization accelerator peels off, crystallization can be promoted in the surface direction, and uniform crystallization of the inner surface 10i of the crucible substrate 10 can be achieved.

[0052] On the other hand, when the concentration of the crystallization accelerator on the crucible surface is high, the crystallization rate on the crucible surface is fast, and crystallization also proceeds in the lateral direction (surface direction), so the requirement for peel strength is relaxed compared to when the concentration is low. Therefore, when the concentration of the crystallization accelerator on the crucible surface is 2.6 × 10⁻⁶ 15 atoms / cm 2 If the value is higher than that, the peel strength of the crystallization accelerator should be 0.3 kN / m or higher.

[0053] The concentration of the crystallization accelerator is 2.5 × 10⁻⁶. 15 atoms / cm 2 The following conditions may also apply, in which case the peel strength of the coating film 13 is preferably 0.6 kN / m or higher. When the peel strength of the coating film is high, the inner surface 10i of the crucible substrate 10 can be reliably crystallized without using a high concentration of crystallization accelerator.

[0054] The concentration of the crystallization accelerator on the crucible surface is 2.6 × 10 15 atoms / cm 2At concentrations below the specified level, if the crystallization accelerator peels off, it becomes impossible to uniformly form Brown ring crystal nuclei; therefore, the peeling strength of the crystallization accelerator must be 0.6 kN / m or higher.

[0055] In the central region at the bottom of the crucible substrate 10, it is particularly preferable that the peel strength of the coating film 13 be 0.9 kN / m or more. As described above, a large amount of polycrystalline silicon raw material is filled into the quartz glass crucible 1, and a very large load is applied to the bottom of the crucible, making the coating film 13 prone to peeling. However, if the peel strength of the coating film 13 at the bottom of the crucible substrate 10 is 0.9 kN / m or more, peeling can be prevented even when such a large load is applied.

[0056] The surface roughness (Ra) of the coated film 13 is preferably 0.1 μm or more and 0.25 μm or less. This is because if the surface roughness (Ra) of the coated film is greater than 0.25 μm, the coated film is prone to peeling, and it is difficult to reduce the surface roughness (Ra) of the coated film to less than 0.1 μm from a manufacturing standpoint.

[0057] It is desirable that the carbon concentration in the silicon single crystal grown by the CZ method be as low as possible. To achieve this, it is necessary to minimize the amount of carbon supplied from the quartz glass crucible 1, and particular attention must be paid not only to the carbon concentration in the crucible substrate 10 but also in the carbon concentration in the coated film 13. Therefore, in the quartz glass crucible 1 according to this embodiment, the average carbon concentration in the range from a depth of 0 μm to 300 μm from the inner surface 10i of the coated film 13 and the crucible substrate 10 (i.e., the surface layer of the crucible substrate 10) is 1.0 × 10⁻¹⁰. 12 atoms / cc or more 3.0×10 19 The carbon content is less than or equal to atoms / cc. This reduces the amount of carbon that dissolves from the quartz glass crucible 1 into the silicon melt, making it possible to produce silicon single crystals with a low carbon concentration.

[0058] The average carbon concentration in the coated film 13 is 3.0 × 10⁻⁶. 18 It is preferable that the oxygen concentration in the coated film is 3.0 × 10¹⁶ atoms / cc or less. 18If the amount is less than or equal to atoms / cc, the amount of carbon supplied from the coated film into the silicon melt can be reduced.

[0059] The average carbon concentration in the coated film 13 and the average carbon concentration in the crucible substrate 10 within a depth of 0 μm to 300 μm from the inner surface are both 1.3 × 10⁻¹⁰. 16 It is preferable that the concentration is less than or equal to atoms / cc. Furthermore, the average carbon concentration within a depth of 300 μm to 2000 μm from the inner surface of the crucible substrate 10 is 1.1 × 10⁻¹⁰. 19 It is preferable that the carbon concentration is less than or equal to atoms / cc. This makes it possible to manufacture silicon single crystals with a sufficiently low carbon concentration.

[0060] Average carbon in the range of 300 μm to 2000 μm depth from the inner surface of the crucible substrate 10 concentration This refers to the average carbon in the surface layer, which is in the range of 0 μm to 300 μm. concentration It can be higher, but 1.1 × 10 19 It is preferable that the concentration is less than or equal to atoms / cc.

[0061] Variations in the in-plane distribution of carbon concentration on the inner surface of the crucible lead to variations in the thickness of the cristobalite layer formed on the inner surface, which causes the cristobalite crystal to peel off. In particular, if the crystal layer is non-uniform at the bottom of the crucible, it can cause pinhole formation in the silicon single crystal. Therefore, it is desirable that the variation in the in-plane distribution of carbon concentration be small at the bottom of the crucible.

[0062] Specifically, it is preferable that the coefficient of variation when measuring the carbon concentration at five points P1 to P5 at the bottom of the crucible is 1.1 or less. Here, as shown in Figure 4, the five points at the bottom of the crucible are the center P1 of the bottom and four points P2 to P5 that are equally far apart in four directions from the center P1. It is preferable that the other four points P2 to P5, other than the center P1 of the bottom, are set at positions 0.08r to 0.7r radially away from the center P1 (first measurement point) of the bottom of the crucible substrate 10 (where r is the radius of the outer diameter of the crucible substrate 10). The third to fifth measurement points P3 to P5 are the positions obtained by rotating the second to fourth measurement points P2 to P4 by 90° clockwise in the circumferential direction.

[0063] The quartz glass crucible 1 according to this embodiment is formed by rotating the crucible base 10 in a so-called rotary mold. law After being manufactured by [method], it can be manufactured by applying a crystallization accelerator to the inner surface of the crucible substrate 10.

[0064] Figure 5 is a schematic diagram illustrating the manufacturing method of a quartz glass crucible using the rotary molding method.

[0065] As shown in Figure 5, in the rotary molding method, a mold 14 having a cavity that matches the outer shape of the crucible is prepared, and natural quartz powder 16a and synthetic quartz powder 16b are sequentially filled along the inner surface 14i of the rotating mold 14 to form a deposit layer 16 of raw quartz powder. The raw quartz powder adheres to the inner surface 14i of the mold 14 by centrifugal force and remains in a fixed position, maintaining the crucible shape.

[0066] In the manufacture of quartz glass crucible 1, crystalline or amorphous silica powder with a carbon content of less than 6 ppm is prepared, and this silica powder is used as the raw material near the inner surface to manufacture the quartz glass crucible 1. By using silica powder with a very low carbon content as the raw material near the inner surface of the quartz glass crucible, the carbon concentration near the inner surface of the crucible can be reduced.

[0067] Next, an arc electrode 15 is placed inside the mold 14, and the deposited layer 16 of raw quartz powder is arc-melted from the inside of the mold 14. Specific conditions such as heating time and heating temperature are determined as appropriate, taking into consideration the characteristics of the raw quartz powder and the size of the crucible.

[0068] To reduce the carbon concentration on the inner surface 10i of the crucible substrate 10, it is preferable to use a carbon electrode 15 with a bulk density of 1.50 g / cc to 1.75 g / cc and a resistivity of 330 μΩcm to 600 μΩcm. During arc melting, CO2 gas is generated as the carbon electrode is oxidized and consumed from the surface. If the density or resistivity of the electrode falls below the above range, the electrode will be consumed rapidly, generating a large amount of CO2 gas and negatively affecting the shape of the crucible. On the other hand, if the density or resistivity of the carbon electrode exceeds the above range, carbon particles may scatter from the electrode surface and be taken into the crucible before they burn out due to the arc heat. However, in this embodiment, a carbon electrode with density and resistivity within the above range is used, so the increase in CO2 gas and the scattering of carbon particles can be suppressed. Therefore, the carbon concentration near the inner surface of the crucible substrate 10 can be reduced.

[0069] During arc melting, the amount of bubbles in the molten silica glass is controlled by evacuating the deposited layer 16 of raw quartz powder through numerous ventilation holes 14a provided on the inner surface 14i of the mold 14. Specifically, the raw quartz powder is evacuated at the start of arc melting to form a transparent layer 11, and after the formation of the transparent layer 11, the evacuation of the raw quartz powder is stopped to form a bubble layer 12.

[0070] The arc heat gradually propagates from the inside to the outside of the deposited layer 16 of raw quartz powder, melting the raw quartz powder. By changing the reduced pressure conditions at the moment the raw quartz powder begins to melt, it is possible to create either a transparent layer 11 or a bubble layer 12. In other words, if reduced pressure melting is performed by increasing the reduced pressure at the moment the raw quartz powder melts, the arc atmosphere gas is not trapped in the glass, and the molten quartz becomes silica glass without bubbles. On the other hand, if normal melting (atmospheric pressure melting) is performed by decreasing the reduced pressure at the moment the raw quartz powder melts, the arc atmosphere gas is trapped in the glass, and the molten silica becomes silica glass containing many bubbles.

[0071] Afterward, the arc melting is terminated and the crucible is cooled. This completes the crucible base 10, in which the transparent layer 11 and the bubble layer 12 are sequentially formed from the inside to the outside of the crucible wall.

[0072] Next, the molded crucible base 10 is shaped into a predetermined form by cutting the rim portion, and then washed with a cleaning solution, followed by rinsing with pure water. The cleaning solution is preferably prepared by diluting semiconductor-grade or higher hydrofluoric acid with pure water with a TOC of ≤ 2 ppb to a concentration of 10-40 w%.

[0073] Next, a crystallization accelerator is applied to the inner surface of the crucible substrate 10. To uniformly disperse the crystallization accelerator on the inner surface 10i, a coating solution is prepared by dissolving the crystallization accelerator in pure water (15°C to 25°C, 17.2 MΩ or higher, TOC ≤ 2 ppb) or a high-purity organic solvent. At this time, stirring is performed using a stirrer to increase the solubility of the crystallization accelerator particles and to make the concentration of the solution uniform.

[0074] Next, the crucible substrate 10 is heated in a halogen heater or clean oven installed in a clean room to a temperature of 60°C to 500°C, and then the coating solution is sprayed onto it using a spray nozzle. When the coating solution comes into contact with the high-temperature crucible, the solvent evaporates instantly, and the components of the crystallization accelerator are fixed to the crucible. As described above, the crystallization accelerator is a compound of group 2a elements (Mg, Ca, Sr, Ba), and hydroxides with particularly high hydrophilicity are ideal for improving adhesion to the crucible.

[0075] Hydroxides of group 2a elements react with carbon dioxide in the atmosphere to form carbonates (for example, in the case of barium hydroxide, 2.5% becomes barium carbonate). Carbon on the inner surface of the quartz glass crucible is directly incorporated into the silicon melt when the polysilicon melts. Furthermore, the carbon elements incorporated into the silicon single crystal promote oxygen deposition and affect device performance such as current leakage. Therefore, to reduce the formation of carbonates, it is important to keep the surface temperature of the crucible below 500°C, preferably below 200°C. In addition, to accelerate the evaporation of the solvent, it is preferable to heat the crucible substrate 10 so that the temperature difference between the boiling point of the solvent and the crucible is between -40.0°C and 100°C.

[0076] To reduce carbonate formation by evaporating the solvent in a short time, it is even more preferable to heat the crucible substrate 10 to a temperature between the boiling point of the solvent and 80°C. If the temperature of the crucible substrate 10 is lower than the boiling point of the solvent, the evaporation time of the solvent will be longer, resulting in uneven thickness of the coating film and concentration distribution of the crystallization accelerator, which reduces the peel strength of the coating film. Furthermore, if the evaporation time of the solvent is long, condensation of the coating liquid may occur on the surface of the crucible, which may result in a high and uneven carbon concentration. If the temperature of the crucible substrate 10 is 80°C or lower, the generation of carbonate can be sufficiently suppressed and the carbon concentration in the coating film can be reduced.

[0077] When spraying the coating solution, it is preferable to use a two-fluid nozzle that mixes gas and liquid at the spray nozzle and sprays them, and it is preferable to adjust the average droplet diameter to 5 μm to 1000 μm. This is because if the droplet diameter is too large, the adhesion of the coating solution will be uneven, reducing the uniformity of the coating film and decreasing the peel strength, and if the droplet diameter is too small, it will be difficult to spray the coating solution. It is particularly preferable that the average droplet diameter be 200 μm or less.

[0078] A spray rate of 300 mL / min or less is preferable. If the spray rate of the coating solution exceeds 300 mL / min, dripping is likely to occur on the coated surface, making it difficult to uniformly fix the crystallization accelerator.

[0079] The coating liquid is sprayed in 1 x 10 2 Pa~1×10 5 It is preferable to carry out the process under low vacuum at Pa. Under low pressure (vacuum), the evaporation of the solvent is accelerated, allowing the crystallization accelerator to be uniformly fixed and a coating film with high peel strength to be formed. In addition, since the solvent is evaporated in a short time, the heating time is also shortened, which helps to suppress the generation of carbonates.

[0080] In forming the coated film, it is preferable to apply the crystallization accelerator in multiple layers until the desired concentration is achieved, with a maximum thickness of approximately 0.5 μm per application. This allows for a stronger coated film.

[0081] Simply heating the crucible when spraying the coating solution will result in a patchy coating film. It is easy to become Forming a dense and uniform coating film is difficult. However, by controlling the coating conditions as described above, a dense and uniform coating film can be formed, and the peel strength of the coating film can be improved.

[0082] Figure 6 is a schematic diagram showing a method for applying a crystallization accelerator to the inner surface 10i of the crucible substrate 10.

[0083] As shown in Figure 6, when applying the crystallization accelerator, the crucible substrate 10 is placed on the rotating support 17A with its opening facing upward, and the coating liquid 6 is sprayed from a spray nozzle 19 attached to the tip of a robot arm 18 placed inside the crucible substrate 10. At this time, in order to prevent dripping of the coating liquid 6, it is preferable to install a heater 17B on the outside of the crucible substrate 10 and apply the coating while heating the crucible substrate 10 to 60°C to 500°C, with 100°C to 180°C being particularly preferable. If the surface temperature of the crucible substrate 10 is 60°C or higher, the solvent evaporates instantly on the surface of the crucible substrate 10, so the crystallization accelerator can be uniformly fixed to the inner surface 10i of the crucible substrate 10.

[0084] When the crystallization accelerator is a metal hydroxide, it reacts with carbon dioxide in the atmosphere to form a carbonate. For example, in an atmospheric, normal pressure environment, 2.5% of barium hydroxide becomes barium carbonate. The carbonate in the coated film 13 increases the carbon concentration of the silicon single crystal. To suppress the formation of such carbonates, it is preferable to keep the surface temperature of the crucible when applying the crystallization accelerator below 500°C, and particularly preferable to keep it above the boiling point of the solvent but below 80°C. This makes it possible to keep the weight ratio of carbonate to the total weight of the coated film below 20.0 w%.

[0085] Figure 7 is a diagram illustrating the single crystal pulling process using the quartz glass crucible 1 according to this embodiment, and is a schematic cross-sectional view showing the configuration of the single crystal pulling apparatus.

[0086] As shown in Figure 7, a single crystal pulling apparatus 20 is used in the silicon single crystal pulling process by the CZ method. The single crystal pulling apparatus 20 comprises a water-cooled chamber 21, a quartz glass crucible 1 that holds the silicon melt inside the chamber 21, a carbon susceptor 22 that holds the quartz glass crucible 1, a rotating shaft 23 that supports the carbon susceptor 22 so that it can rotate and move up and down, a shaft drive mechanism 24 that drives the rotating shaft 23 to rotate and move up and down, and a heater 25 arranged around the carbon susceptor 22. Above Quartz Glass Crucible 1 The apparatus includes a single crystal pulling wire 28 arranged coaxially with the rotating shaft 23, and a wire winding mechanism 29 located above the chamber 21.

[0087] Chamber 21 consists of a main chamber 21a and an elongated cylindrical pull chamber 21b connected to the upper opening of the main chamber 21a. The quartz glass crucible 1, carbon susceptor 22, and heater 25 are located inside the main chamber 21a. A gas inlet 21c is provided at the top of the pull chamber 21b for introducing an inert gas (purge gas) such as argon gas or a dopant gas into the main chamber 21a, and a gas outlet 21d is provided at the bottom of the main chamber 21a for discharging the atmospheric gas inside the main chamber 21a.

[0088] The carbon susceptor 22 is used to maintain the shape of the quartz glass crucible 1, which has softened at high temperatures, and holds the quartz glass crucible 1 by enclosing it. The quartz glass crucible 1 and the carbon susceptor 22 constitute a double-layered crucible that supports the silicon melt within the chamber 21.

[0089] 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 located on the outside of the chamber 21.

[0090] The heater 25 is used to melt the polycrystalline silicon raw material packed inside the quartz glass crucible 1 to produce a silicon melt 3, and to maintain the molten state of the silicon melt 3. The heater 25 is a resistance heating type carbon heater and is positioned to surround the quartz glass crucible 1 inside the carbon susceptor 22.

[0091] As the silicon single crystal 2 grows, the amount of molten silicon in the quartz glass crucible 1 decreases, but the quartz glass crucible 1 is raised so that the height of the molten surface remains constant.

[0092] The wire winding mechanism 29 is positioned above the pull chamber 21b, and the wire 28 extends downward from the wire winding mechanism 29 through the pull chamber 21b, with the tip of the wire 28 reaching the internal space of the main chamber 21a. This figure shows a silicon single crystal 2 in the process of growth suspended from the wire 28. When pulling up the silicon single crystal 2, the wire 28 is gradually pulled up while the quartz glass crucible 1 and the silicon single crystal 2 are rotated, thereby growing the silicon single crystal 2.

[0093] During the single crystal pulling process, the inner surface of the crucible crystallizes, but the crystallization accelerator ensures that the crystallization of the inner surface of the crucible proceeds uniformly, thus preventing the formation of dislocations in the silicon single crystal due to the peeling off of Brown's rings. In addition, although the quartz glass crucible 1 softens, the uniform crystallization of the inner surface of the crucible ensures the strength of the crucible and suppresses deformation. Therefore, it is possible to prevent the crucible from deforming and coming into contact with the furnace components, and to prevent the liquid level of the silicon molten liquid 3 from fluctuating due to changes in the volume inside the crucible.

[0094] As described above, the quartz glass crucible 1 according to this embodiment comprises a crucible substrate 10 made of silica glass and a crystallization accelerator coating film 13 formed on the inner surface 10i of the crucible substrate 10. Since the peel strength of the coating film 13 is 0.3 kN / m or more, it is possible to reduce surface roughness on the inner surface of the crucible, the occurrence of pinholes, and the formation of dislocations in single crystals due to the peeling of the coating film 13.

[0095] Furthermore, in the method for manufacturing a quartz glass crucible according to this embodiment, when spraying the crystallization accelerator coating solution onto the inner surface 10i of the crucible substrate 10, a two-fluid nozzle is used that mixes gas and liquid at the spray tip and sprays it, so that the average droplet diameter of the coating solution is 5 μm or more and 1000 μm or less. As a result, the droplet diameter is reduced and a dense coating film can be formed, thereby increasing the peel strength of the coating film.

[0096] Furthermore, in the method for manufacturing a quartz glass crucible according to this embodiment, when forming a coating film of the crystallization accelerator by spraying a coating solution containing the crystallization accelerator onto the inner surface of the crucible substrate 10, the maximum thickness of the coating film formed in a single application is set to 0.5 μm or less, and the drying and reapplication of the coating film are repeated alternately until the desired carbon concentration is reached, thereby creating a multilayer coating film 13, which makes it possible to form a coating film with high peel strength.

[0097] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention, and these modifications are also included within the scope of the present invention.

[0098] For example, in the above embodiment, the inner surface 10i of the crucible substrate 10 is covered with a coating film 13 of the crystallization accelerator, and the outer surface 10o is not covered with the coating film. However, both the inner surface 10i and the outer surface 10o may be covered with a coating film of the crystallization accelerator. That is, the coating film of the crystallization accelerator only needs to cover at least the inner surface 10i of the crucible substrate 10. Furthermore, the coating film 13 does not necessarily need to be formed on the entire inner surface except for the vicinity of the upper end of the rim of the crucible substrate, and the coating film on the inner surface of the side wall portion 10a may be omitted. That is, the coating film 13 only needs to be provided on the inner surface of at least the central bottom region of the crucible substrate 10 (within a range of 0.5r from the bottom center).

[0099] Furthermore, in the above embodiment, the crucible substrate 10 was positioned upward when spraying the coating liquid onto its inner surface. However, it is also possible to apply the coating liquid with the crucible substrate 10 inverted downwards. Moreover, the heating of the crucible substrate 10 may be performed while applying the crystallization accelerator, or the coating may be performed after preheating the crucible substrate 10. Furthermore, when applying the crystallization accelerator after preheating the crucible substrate 10, it is possible to continue heating the crucible using a different heating means than that used for preheating while applying the crystallization accelerator to prevent a rapid drop in the temperature of the crucible substrate 10 during the coating process. [Examples]

[0100] <Evaluation of peel strength of coating film with crystallization accelerator (1)> A crucible substrate constituting a 32-inch quartz glass crucible was fabricated using a rotary molding method. Example A 1~ A 4. Comparative Examples A 1~ A The crucible substrates according to 4 were fabricated using the same type of polycrystalline silicon raw material under the same conditions.

[0101] During arc melting of quartz powder, carbon electrodes with a bulk density of 1.50 g / cc to 1.75 g / cc and resistivity of 330 μΩcm to 600 μΩcm were used. For the crucible substrate, a transparent layer was formed by vacuuming the raw material powder from the outside of the rotating mold supporting the raw material powder during melting of the inner surface. Subsequently, the vacuuming was stopped or the suction force was weakened to form a bubble layer.

[0102] Next, the crucible substrate was washed with a cleaning solution and rinsed with pure water, after which a crystallization accelerator was applied to the inner surface of the crucible. The cleaning solution used was semiconductor-grade hydrofluoric acid diluted with pure water (TOC ≤ 2 ppb, 17.2 MΩ or higher, 15-25°C) to a concentration of 10-40 w%. An aqueous barium hydroxide solution was used as the crystallization accelerator and was applied uniformly by spraying. During the application of the crystallization accelerator, the crucible substrate was heated with a halogen heater, and the surface temperature of the crucible was measured while applying the agent.

[0103] A two-fluid nozzle was used to spray the crystallization accelerator, and the spraying conditions were adjusted so that the average droplet diameter was approximately 200 μm. A laser diffraction particle size distribution analyzer (AEROTRAC II, manufactured by Microtrac-Bell Co., Ltd.) was used to confirm the droplet diameter. The thickness of the crystallization accelerator coating film formed in a single application was set to approximately 0.5 μm, and the coating was repeated in multiple applications until the desired concentration was achieved. In this way, as shown in Table 1, a quartz glass crucible with a crystallization accelerator coating film formed on the inner surface of the crucible substrate was completed.

[0104] In the formation of a crystallization accelerator coating, the concentration of the crystallization accelerator at the bottom of the crucible (within 0.5 times the outer diameter of the crucible, from the center of the bottom of the crucible) is 2.6 × 10⁻⁶. 15 atoms / cm 2 The coating conditions were adjusted as follows. Furthermore, the coating conditions were adjusted so that the concentration of the crystallization accelerator differed between the bottom and other areas. Thus, the comparative example was created. A 1~ A 4. Examples A 1~ A I completed the quartz glass crucible using method 4.

[0105] Next, the peel strength of the crystallization accelerator coating in each quartz glass crucible was measured using SAICAS. The peel strength was measured at the bottom of the crucible and at other points. The peel strength at the bottom of the crucible was measured at a single point in the center of the bottom. The peel strength at other points was measured at any point within a range of 0.55 to 0.6 times the outer diameter of the crucible from the center of the bottom.

[0106] Next, silicon single crystals were pulled using other crucible samples with the same characteristics as the quartz glass crucibles produced in Comparative Examples A1-A4 and Examples A1-A4, under the same conditions. The degree of peeling and roughness of the inner surface of the crucibles after use was evaluated. The yield (dislocation-free rate) of silicon single crystals was also evaluated. The yield of single crystals is the weight ratio of single crystals to polycrystalline raw material. The results are shown in Table 1. In Table 1, "low" peeling means that the area of ​​the peeled portion is less than 0.1% of the coated area, "medium" means 0.1% or more and less than 0.5%, and "high" means 0.5% or more. The evaluation of inner surface roughness was based on the area occupancy rate of the part where the brown ring has peeled off, exposing the silica glass and creating an uneven surface. "High" means 50% or more, "medium" means 20% or more and less than 50%, and "low" means less than 20%.

[0107] [Table 1]

[0108] As shown in Table 1, the concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Comparative Example A1 was 2.6 × 10⁻⁶ at the bottom. 14 atoms / cm 2 , 3.1 × 10 in all areas except the bottom 14 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.2 kN / m at the bottom and 0.3 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of peeling of cristobalite (Brown ring) formed on the inner surface of the used crucible was It was most prevalent at the bottom of the crucible, but moderate elsewhere. Furthermore, the inner surface of the used crucibles was often rough. The yield of silicon single crystals pulled using these quartz glass crucibles was 61.5%, which is below 80%.

[0109] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Comparative Example A2 was 2.4 × 10⁻⁶ at the bottom. 14 atoms / cm 2 , 2.1 × 10 in all areas except the bottom. 15 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.2 kN / m at the bottom and 0.5 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of peeling of cristobalite (brown ring) formed on the inner surface of the used crucible was greater at the bottom of the crucible, but moderate elsewhere. Furthermore, the surface roughness of the inner surface of the used crucible was There were many The yield of silicon single crystals pulled using the quartz glass crucible was 62.2%, which is below 80%.

[0110] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Comparative Example A3 was 2.6 × 10⁻⁶ at the bottom. 15 atoms / cm 2 , 2.5 × 10 in all areas except the bottom 15atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.5 kN / m at the bottom and 0.6 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was moderate at the bottom of the crucible, but less elsewhere. The surface roughness of the inner surface of the used crucible was also moderate. The yield of silicon single crystals pulled using this quartz glass crucible was 69.1%, which is below 80%.

[0111] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Comparative Example A4 was 2.3 × 10⁻⁶ at the bottom. 15 atoms / cm 2 , 2.8 × 10 in all areas except the bottom 14 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.4 kN / m at the bottom and 0.2 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was moderate at the bottom of the crucible, but high elsewhere. The surface roughness of the inner surface of the used crucible was also moderate. The yield of silicon single crystals pulled using this quartz glass crucible was 65.2%, which is below 80%.

[0112] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible according to Example A1 was at the bottom. 2.5 ×10 14 atoms / cm 2 , 2.4 × 10 in all areas except the bottom 14 atoms / cm 2The peel strength of the crystallization accelerator coating was 0.6 kN / m at the bottom and 0.6 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was low both at the bottom and elsewhere. Furthermore, the surface roughness of the inner surface of the used crucible was also low. The yield of silicon single crystals pulled using this quartz glass crucible was 81.2%, which is a good result exceeding 80%.

[0113] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible according to Example A2 was at the bottom. 2.6 ×10 14 atoms / cm 2 , 2.4 × 10 in all areas except the bottom 15 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.7 kN / m at the bottom and 1.2 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was low both at the bottom and elsewhere. Furthermore, the surface roughness of the inner surface of the used crucible was also low. The yield of silicon single crystals pulled using this quartz glass crucible was 83.6%, which is a good result exceeding 80%.

[0114] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible according to Example A3 was at the bottom. 2.0 ×10 15 atoms / cm 2 , 2.6 × 10 in all areas except the bottom 15 atoms / cm 2The peel strength of the crystallization accelerator coating was 1.0 kN / m at the bottom and 1.1 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was low both at the bottom and elsewhere. Furthermore, the surface roughness of the inner surface of the used crucible was also low. The yield of silicon single crystals pulled using this quartz glass crucible was 85.3%, which is a good result exceeding 80%.

[0115] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible according to Example A4 was at the bottom. 2.6 ×10 15 atoms / cm 2 , except at the bottom 2.2×10 14 atoms / cm 2 The peel strength of the coating film with the crystallization accelerator was at the bottom. 0.9 kN / m, even outside the bottom 0.7 The value was kN / m. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of flaking of cristobalite (brown ring) formed on the inner surface of the used crucible was small both at the bottom and outside the crucible. In addition, the surface roughness of the inner surface of the used crucible was also small. The yield of silicon single crystals pulled using this quartz glass crucible was 83.1 The result was a good one, exceeding 80%.

[0116] <Evaluation of peel strength of coating film with crystallization accelerator (2)> The concentration of the crystallization accelerator at the bottom of the crucible is 2.6 × 10⁻⁶. 15 atoms / cm 2 The comparison was made in the same way as in "Evaluation of Peel Strength (1)," except that the application conditions were adjusted to be higher than the above. B 1~ B 3 and Examples B 1~ BA quartz glass crucible was completed using method 3. Subsequently, an evaluation similar to that in "Evaluation of Peel Strength (1)" was performed. The results are shown in Table 2.

[0117] [Table 2]

[0118] As shown in Table 2, the concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Comparative Example B1 was 5.2 × 10⁻¹⁰ in both the bottom and other areas. 15 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.2 kN / m at both the bottom and other areas. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was high at both the bottom and other areas. In addition, the inner surface of the used crucible was also rougher. The yield of silicon single crystals pulled using this quartz glass crucible was 70.2%, which is below 80%.

[0119] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Comparative Example B2 was 5.2 × 10⁻⁶ at the bottom. 15 atoms / cm 2 , 2.8 × 10 in all areas except the bottom 16 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.1 kN / m at the bottom and 0.4 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was greater at the bottom of the crucible, but moderate elsewhere. The surface roughness of the inner surface of the used crucible was also moderate. The yield of silicon single crystals pulled using this quartz glass crucible was 72.3%, which is below 80%.

[0120] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Comparative Example B3 was 4.9 × 10⁻⁶ at the bottom. 17 atoms / cm 2 , 2.4 × 10 in all areas except the bottom 15 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.2 kN / m at the bottom and 0.3 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of cristobalite (brown ring) peeling formed on the inner surface of the used crucible was greater at the bottom of the crucible, but moderate elsewhere. The surface roughness of the inner surface of the used crucible was also moderate. The yield of silicon single crystals pulled using this quartz glass crucible was 71.5%, which is below 80%.

[0121] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible in Example B1 was 5.2 × 10⁻¹⁰ in both the bottom and other areas. 15 atoms / cm 2 The peel strength of the crystallization accelerator coating was 0.3 kN / m at the bottom and 0.4 kN / m elsewhere. When silicon single crystals were pulled using another crucible sample with the same properties manufactured under the same conditions as this crucible sample, the degree of crustalite (brown ring) peeling formed on the inner surface of the used crucible was moderate both at the bottom and elsewhere. The inner surface of the used crucible showed little roughness. The yield of silicon single crystals pulled using this quartz glass crucible was 80.2%, which is a good result exceeding 80%.

[0122] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible according to Example B2 was at the bottom. 2.8 ×10 16 atoms / cm 2 , 5.2 × 10 in all areas except the bottom 15 atoms / cm 2It was so. The peel strength of the coating film of the crystallization accelerator was 1.0 kN / m at the bottom and 0.3 kN / m outside the bottom. When pulling up a silicon single crystal using another crucible sample of the same characteristics manufactured under the same conditions as this crucible sample, the degree of peeling of cristobalite (brown ring) formed on the inner surface of the used crucible was small at the bottom of the crucible and moderate outside the bottom. Also, the roughening of the inner surface of the used crucible was small. The yield of the silicon single crystal pulled up using this quartz glass crucible was 87.6%, resulting in a good result exceeding 80%.

[0123] The concentration of the crystallization accelerator on the inner surface of the quartz glass crucible according to Example B3 was 2.6×10 16 atoms / cm 2 at the bottom and 4.9×10 17 atoms / cm 2 outside the bottom. The peel strength of the coating film of the crystallization accelerator was 1.3 kN / m at the bottom and also 1.1 kN / m outside the bottom. When pulling up a silicon single crystal using another crucible sample of the same characteristics manufactured under the same conditions as this crucible sample, the degree of peeling of cristobalite (brown ring) formed on the inner surface of the used crucible was small both at the bottom and outside the bottom of the crucible. Also, the roughening of the inner surface of the used crucible was small. The yield of the silicon single crystal pulled up using this quartz glass crucible was 87.8%, resulting in a good result exceeding 80%.

[0124] <Evaluation of the Thickness of the Coating Film of the Crystallization Accelerator> The correlation between the thickness of the coating film of the crystallization accelerator formed on the inner surface of the quartz glass crucible and the yield of the silicon single crystal was evaluated. The results are shown in Table 3.

[0125]

Table 3

[0126] As shown in Comparative Examples C1 to C4 in Table 3, the thickness of the crystallization accelerator coating film is 54.3 When the thickness was greater than μm, it was not possible to achieve a yield of 80% or more for silicon single crystals. In contrast, as shown in Examples C1 to C4, when the thickness of the crystallization accelerator coating film was 50 μm or less, it was possible to achieve a yield of 80% or more for silicon single crystals.

[0127] <Evaluation of surface roughness of coating film with crystallization accelerator> The correlation between the surface roughness (Ra) of the crystallization accelerator coating film formed on the inner surface of a quartz glass crucible and the yield of silicon single crystals was evaluated. The results are shown in Table 4.

[0128] [Table 4]

[0129] As shown in Comparative Examples D1 to D4 of Table 4, when the surface roughness (Ra) of the crystallization accelerator coating film was 0.27 μm or higher, the yield of silicon single crystals could not be increased to 80% or higher. In contrast, as shown in Examples D1 to D4, when the surface roughness (Ra) of the crystallization accelerator coating film was 0.25 μm or lower, the yield of silicon single crystals could be increased to 80% or higher. [Explanation of symbols]

[0130] 1 Quartz glass crucible 1s Crucible Sample 2. Silicon single crystal 3. Silicon melt 6. Coating solution 10 Crucible substrate 10a Side wall part 10b bottom 10c Corner section 10i Inner surface of crucible substrate 10° outer surface of crucible substrate 11 Transparent layer 12. Bubble layer 13. Coating film of crystallization accelerator 14 molds 14a Ventilation holes 14i mold interior 15 Arc electrode 16. Quartz powder deposits 16a natural quartz powder 16b Synthetic quartz powder 17A Rotating support 17B Heater 18 Robot Arm 19 Spray nozzle 20 Single crystal pulling apparatus 21 Chambers 21a Main Chamber 21b Pull Chamber 21c Gas inlet 21d Gas outlet 22 Carbon Susceptors 23 Rotating shaft 24 Shaft drive mechanism 25 Heater 28 Single crystal pulling wire 29 Wire winding mechanism 30 SAICAS 31 Diamond blades

Claims

1. A crucible substrate made of silica glass has a cylindrical side wall portion, a bottom portion provided below the side wall portion, and a corner portion provided between the side wall portion and the bottom portion. The crucible substrate comprises a coating film containing a crystallization accelerator formed on at least the inner surface of the bottom portion of the crucible substrate, The peel strength of the coating film at least at the bottom of the crucible substrate is 0.6 kN / m or more. The concentration of the crystallization accelerator at the bottom is 2.5 × 10 １４ atoms / cm ２ The above 2.5 x 10 １５ atoms / cm ２ The following: The crystallization accelerator is a water-soluble compound of a group 2a element (Mg, Ca, Sr, Ba) that does not contain carbon atoms in its molecule. A quartz glass crucible characterized in that the thickness of the coating film is 0.1 μm or more and 50 μm or less.

2. The quartz glass crucible according to claim 1, wherein the area of ​​the coating film at the bottom of the crucible substrate is a circular region in plan view within a certain range from the center of the bottom, and the radius of the circular region is 0.25 times or more and 1 time or less of the radius r of the crucible substrate.

3. The quartz glass crucible according to claim 2, wherein the peel strength of the coating film formed in a circular central region of the bottom within a radius of 0.5r from the center of the bottom is 0.9 kN / m or more.

4. The average carbon concentration within a depth of 0 μm to 300 μm from the inner surface of the coating film and the crucible substrate is 1.0 × 10⁻¹⁴. １２ atoms / cc or more 3.0×10 １９ A quartz glass crucible according to any one of claims 1 to 3, wherein the atom / cc is less than or equal to atoms / cc.

5. The average carbon concentration in the aforementioned coating film is 3.0 × 10 １８ A quartz glass crucible according to any one of claims 1 to 4, wherein the atom / cc is less than or equal to atoms / cc.

6. A crucible substrate made of silica glass has a cylindrical side wall portion, a bottom portion provided below the side wall portion, and a corner portion provided between the side wall portion and the bottom portion. The crucible substrate comprises a coating film containing a crystallization accelerator formed on at least the inner surface of the bottom portion of the crucible substrate, The peel strength of the coating film at least at the bottom of the crucible substrate is 0.3 kN / m or more. The area of ​​the coating film at the bottom of the crucible substrate is a circular region in plan view within a certain range from the center of the bottom, and the radius of the circular region is 0.25 times or more and 1 time or less of the radius r of the crucible substrate. The peel strength of the coating film formed in the circular central region of the bottom within a radius of 0.5r from the center of the bottom is 0.9 kN / m or more. The concentration of the crystallization accelerator at the bottom is higher than 2.5×10 １５ atoms / cm ２ and The crystallization accelerator is a water-soluble compound of a group 2a element (Mg, Ca, Sr, Ba) that does not contain carbon atoms in its molecule. A quartz glass crucible characterized in that the thickness of the coating film is 0.1 μm or more and 50 μm or less.

7. The average carbon concentration within a depth of 0 μm to 300 μm from the inner surface of the coating film and the crucible substrate is 1.0 × 10⁻¹⁴. １２ atoms / cc or more 3.0×10 １９ A quartz glass crucible according to claim 6, wherein the atom / cc is less than or equal to atoms / cc.

8. The average carbon concentration in the aforementioned coating film is 3.0 × 10 １８ A quartz glass crucible according to claim 6 or 7, wherein the atom / cc is less than or equal to the atom / cc value.

9. A crucible substrate made of silica glass has a cylindrical side wall portion, a bottom portion provided below the side wall portion, and a corner portion provided between the side wall portion and the bottom portion. The crucible substrate comprises a coating film containing a crystallization accelerator formed on at least the inner surface of the bottom portion of the crucible substrate, The peel strength of the coating film at least at the bottom of the crucible substrate is 0.3 kN / m or more. The concentration of the crystallization accelerator at the bottom is 5.2 × 10 １５ atoms / cm ２ That's all. The crystallization accelerator is a water-soluble compound of a group 2a element (Mg, Ca, Sr, Ba) that does not contain carbon atoms in its molecule. A quartz glass crucible characterized in that the thickness of the coating film is 0.1 μm or more and 50 μm or less.

10. The quartz glass crucible according to claim 9, wherein the area of ​​the coating film at the bottom of the crucible substrate is a circular region in plan view within a certain range from the center of the bottom, and the radius of the circular region is 0.25 times or more and 1 time or less of the radius r of the crucible.

11. A process for producing a crucible substrate made of silica glass, having a cylindrical side wall portion, a bottom portion provided below the side wall portion, and a corner portion provided between the side wall portion and the bottom portion, The process includes a step of spraying a coating solution containing a crystallization accelerator to form a coating film of the crystallization accelerator on at least the inner surface of the bottom of the crucible substrate, the film having a thickness of 0.1 μm or more and 50 μm or less, and a peel strength of 0.3 kN / m or more. The area of ​​the coating film at the bottom of the crucible substrate is a circular region in plan view within a certain range from the center of the bottom, and the radius of the circular region is 0.25 times or more and 1 time or less of the radius r of the crucible substrate. The peel strength of the coating film formed in the circular central region of the bottom within a radius of 0.5r from the center of the bottom is 0.9 kN / m or more. The crystallization accelerator is a water-soluble compound of a group 2a element (Mg, Ca, Sr, Ba) that does not contain carbon atoms in its molecule. The concentration of the crystallization accelerator in the coating film at the bottom is 2.5 × 10 １５ atoms / cm ２ Higher, The weight ratio of carbonate to the total weight of the coating film is 20 wt% or less. The method for manufacturing a quartz glass crucible is characterized in that the step of spraying the coating liquid is performed using a two-fluid nozzle that mixes gas and liquid at the spray tip and sprays the coating liquid so that the average droplet diameter is 5 μm or more and 1000 μm or less.

12. A method for manufacturing a quartz glass crucible according to claim 11, wherein the maximum thickness of the coating film formed in a single application is 0.5 μm or less, and the coating film is multilayered by alternately repeating drying and reapplication of the coating film.

13. The method for producing a quartz glass crucible according to claim 11 or 12, wherein the amount of the coating solution sprayed is 300 mL / min or less.

14. A method for producing a quartz glass crucible according to any one of claims 11 to 13, wherein the coating liquid is sprayed onto the crucible substrate while it is heated at a temperature of 60°C to 500°C.

15. A method for producing a quartz glass crucible according to any one of claims 11 to 14, wherein the crucible substrate is heated while the coating liquid is sprayed on, so that the temperature difference between the boiling point of the solvent in the coating liquid and the crucible substrate is between -40.0°C and 100°C.

16. A method for producing a quartz glass crucible according to any one of claims 11 to 15, wherein the coating liquid is sprayed onto the crucible substrate while it is heated at a temperature of 100°C to 180°C.

17. 1 x 10 ２ Pa or more 1×10 ５ A method for manufacturing a quartz glass crucible according to any one of claims 11 to 16, wherein the coating liquid is sprayed onto the crucible substrate while heating it under a low vacuum of Pa or less.

18. A method for producing a silicon single crystal, characterized by pulling up a silicon single crystal by the CZ method using a quartz glass crucible as described in any one of claims 1 to 10.

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