Quartz glass crucible

Abstract

To provide a quartz glass crucible on which surface layer of an inner layer a generation of a bubble is preferably suppressed over an entire surface.SOLUTION: A quartz glass crucible constructed by a bottom part, a curved part, and a straight trunk part has an outer layer composed of an opaque quartz glass containing a bubble and an inner layer composed of a transparent quartz glass. When an ultraviolet light is irradiated to the quartz glass crucible as an excitation light, a blue fluorescent light is generated in a boundary region between the outer layer and the inner layer, the blue fluorescent light being generated in a whole region of the bottom part, the curved part, and the straight trunk part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a quartz glass crucible.

Background Art

[0002] In the production of a silicon single crystal (silicon single crystal ingot), the so-called Czochralski method (CZ method) is widely used. In this CZ method, a silicon melt is contained in a quartz glass crucible, a seed crystal is brought into contact with the surface of the silicon melt, the quartz glass crucible is rotated, and the seed crystal is rotated in the opposite direction and pulled upward to grow a silicon single crystal at the lower end of the seed crystal.

[0003] This quartz glass crucible is generally manufactured by a method called the arc rotation melting method. First, silicon dioxide powder (silica powder, quartz powder) is supplied as a raw material powder into a rotating mold and molded into a crucible-shaped molded body by centrifugal force. Then, the molded body is heated and melted from the inside by an arc flame to form a semi-transparent quartz glass crucible substrate (outer layer) (substrate forming step). Further, during or after the formation of the crucible substrate, new silicon dioxide powder is supplied into the heating atmosphere inside the crucible substrate to form an inner layer made of transparent quartz glass on the inner surface side of the crucible substrate (inner layer forming step). The method of forming the inner layer made of transparent quartz glass by heating while spraying quartz powder is also called the spraying method.

[0004] Also, the outer layer of the quartz glass crucible is often formed using natural silicon dioxide powder, and the inner layer is often formed using synthesized silicon dioxide powder.

[0005] Incidentally, when pulling up silicon single crystals from silicon molten metal contained in a quartz glass crucible, under conditions such as reduced pressure and high temperature, if there are air bubbles in the inner layer of the quartz glass crucible, they may expand and be released into the silicon molten metal. However, the problem has been that these air bubbles and the detached fragments generated during release can be incorporated into the silicon single crystal, reducing its crystallinity. To address this problem, it is known that the inner layer of a quartz glass crucible is doped with hydrogen during its manufacture. Such hydrogen doping has the effect of suppressing the generation of air bubbles. For example, Patent Document 1 describes a manufacturing method in which a silica powder molded body having a crucible shape is formed by supplying quartz raw material powder into a mold, and this silica powder molded body is heated and melted by arc discharge to obtain a silica glass crucible, wherein hydrogen gas is supplied to the inner surface of the silica powder molded body during heating and melting by arc discharge. Furthermore, Patent Document 2 describes heating and holding a quartz glass crucible manufactured by the arc rotation melting method in a hydrogen or hydrogen-containing atmosphere.

[0006] Furthermore, a method of hydrogen doping quartz glass crucibles is known to be carried out by doping the raw material powder with hydrogen (Patent Documents 3 and 4). Such hydrogen-doped silica powder (often synthetic quartz powder) is used to form the transparent silica glass layer, which is the inner layer of the quartz glass crucible, using the above-described scattering method.

[0007] Furthermore, it is known that water vapor is introduced into the quartz glass crucible during its manufacture (Patent Document 5). Patent Document 5 describes that the expansion of bubbles near the inner surface of the quartz glass crucible can also be suppressed by introducing such water vapor. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2014-65622 [Patent Document 2] Japanese Patent Application Publication No. 05-208838 [Patent Document 3] Japanese Patent Publication No. 2003-335513 [Patent Document 4] Japanese Patent Publication No. 2017-031007 [Patent Document 5] Japanese Patent Publication No. 2001-348240 [Patent Document 6] Japanese Patent Publication No. 2013-014518 [Patent Document 7] Japanese Patent Publication No. 2018-35029 [Patent Document 8] Japanese Patent Publication No. 2006-89301 [Overview of the project] [Problems that the invention aims to solve]

[0009] As described above, a typical quartz glass crucible consists of an outer layer made of opaque quartz glass containing air bubbles and an inner layer made of transparent quartz glass. However, the transparency of the inner layer (transparent layer) made of transparent quartz glass is not perfect, and it contains a considerable amount of bubbles. Prior art documents such as those exemplified above have been published to suppress these bubbles. In particular, in the "spraying method" performed during melting for the manufacture of quartz glass crucibles, using hydrogen-doped silica powder as described in Patent Documents 3 and 4 results in the formation of a transparent layer with fewer bubbles (a synthetic transparent layer formed from synthetic quartz glass raw material powder). However, in the transparent quartz glass layer (inner layer) formed by the spraying method, hydrogen doping was not sufficiently applied to the intended locations (i.e., there was variation in the state of hydrogen doping depending on the location).

[0010] The present invention was made to solve the above problems, and aims to provide a quartz glass crucible in which the generation of air bubbles on the surface of the inner layer is well suppressed throughout. [Means for solving the problem]

[0011] The present invention has been made to solve the above problems, and provides a quartz glass crucible comprising a bottom, a curved portion and a straight body portion, having an outer layer made of opaque quartz glass containing air bubbles and an inner layer made of transparent quartz glass, characterized in that when ultraviolet light is irradiated onto the quartz glass crucible as excitation light, blue fluorescence is produced in the boundary region between the outer layer and the inner layer of the quartz glass crucible, and the blue fluorescence is produced throughout the bottom, the curved portion and the straight body portion of the quartz glass crucible.

[0012] With such a quartz glass crucible, it is possible to create a quartz glass crucible in which the generation of air bubbles on the surface of the inner layer is well suppressed throughout.

[0013] In this case, the quartz glass crucible of the present invention may have an outer layer containing natural quartz glass, an inner layer containing synthetic quartz glass, and the blue fluorescence may be generated in the region where the natural quartz glass is in contact with the synthetic quartz glass.

[0014] The overall blue fluorescence of the present invention can also be achieved in quartz glass crucibles having a structure in which an outer layer containing natural quartz glass and an inner layer containing synthetic quartz glass are present. The present invention can provide a quartz glass crucible having such a structure in which the generation of air bubbles on the surface of the inner layer is well suppressed throughout the entire surface.

[0015] Furthermore, in the quartz glass crucible of the present invention, the inner layer may include hydrogen-doped quartz glass or water vapor-introduced quartz glass.

[0016] Thus, the overall blue fluorescence of the present invention can be particularly preferably achieved in a quartz glass crucible having an inner layer containing hydrogen-doped quartz glass or steam-introduced quartz glass. Although hydrogen-doped quartz glass and steam-introduced quartz glass are used to suppress the generation of bubbles, as long as it is a quartz glass crucible in which overall blue fluorescence is observed as in the present invention, it can be a quartz glass crucible in which the generation of bubbles on the surface layer of the inner layer is more reliably suppressed overall.

[0017] In addition, in the quartz glass crucible of the present invention, the blue fluorescence can be fluorescence having a peak around a wavelength of 395 nm.

[0018] In addition, in the quartz glass crucible of the present invention, the irradiated ultraviolet light can be ultraviolet light having a peak around a wavelength of 254 nm.

[0019] Thus, the blue fluorescence in the quartz glass crucible of the present invention can be discriminated by detecting the blue fluorescence that occurs as fluorescence having a peak around a wavelength of 395 nm by ultraviolet light having a peak around a wavelength of 254 nm.

Advantages of the Invention

[0020] The quartz glass crucible of the present invention can be a quartz glass crucible in which the generation of bubbles on the surface layer of the inner layer is well suppressed overall because overall blue fluorescence is observed.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic cross-sectional view showing parts of a general quartz glass crucible. [Figure 2] It is a flowchart showing an outline of a method for detecting blue fluorescence of a quartz glass crucible.

Embodiments for Carrying Out the Invention

[0022] As mentioned above, conventionally, if the inner layer of a quartz glass crucible is not sufficiently hydrogen-doped, the effect of suppressing bubble expansion may not be sufficiently obtained. In particular, there were cases where the state of hydrogen doping varied depending on the part of the quartz glass crucible. That is, the state of bubbles contained in the inner layer of the quartz glass crucible was not uniform. Furthermore, our research has shown that there are parts where bubbles are more likely to be contained. The evaluation of each part of the quartz glass crucible was carried out by cutting and vacuum heat treatment, based on estimations from past results. For example, using "VBT" described in Patent Document 6, 1650°C, 2 hours, 10 minutes holding, 2 × 10 -2 The evaluation was conducted under conditions below Pa. Until now, it was unknown what factors influenced the bubbles contained within this synthetic transparent layer.

[0023] According to the inventors' research, the "hydrogen" contained in the inner layer (often a synthetic transparent layer) made from hydrogen-doped silica powder diffuses into the outer layer (often a natural foam layer made from natural quartz powder), and by combining with the oxygen abundant in the outer layer, a thin natural layer with slightly fewer bubbles is formed (hereinafter referred to as the "natural transparent layer"). This natural transparent layer has oxygen-deficient defects, and when irradiated with 254 nm ultraviolet light, the natural transparent layer emits blue fluorescence.

[0024] During their research, the inventors noticed that quartz glass crucibles have areas that emit blue fluorescence and areas that do not. They then discovered that when VBT (Vigor-Biotronidation Testing) was performed in these areas, the areas that emitted blue fluorescence exhibited superior bubble suppression on the surface of the synthetic transparent layer.

[0025] According to the inventors' investigation, areas where hydrogen doping is insufficient are thought to occur through the following mechanism. When hydrogen-doped silica powder is scattered as a raw material powder using a scattering method and attached to a quartz glass crucible substrate, there are areas formed by direct attachment of the raw material powder and areas formed by inertia during melting (for example, areas where the raw material powder moved in a glassy state after attachment). It was found that the hydrogen concentration is lower in the areas formed by inertia, and a sufficient foam suppression effect cannot be obtained.

[0026] To solve this problem, the inventors focused on oxygen deficiency defects that occur in the outer layer of a quartz glass crucible when hydrogen-doped silica powder is used as a raw material for manufacturing quartz glass crucibles. By using hydrogen-doped silica powder, hydrogen diffuses from the inner layer (transparent silica glass layer) to the outer layer (opaque silica glass layer) of the quartz glass crucible, and oxygen deficiency defects occur when hydrogen combines with oxygen taken in from the silica and molten atmosphere, which are the main cause of bubbles in the outer layer. The presence of these oxygen deficiency defects causes fluorescence (blue fluorescence) when irradiated with ultraviolet light, allowing the state of oxygen deficiency defects in the outer layer of the quartz glass crucible to be determined, and consequently, the state of hydrogen doping to be determined. Here, the area where blue fluorescence occurs, that is, where oxygen deficiency defects occur, is the shallow part on the outer layer side of the boundary between the inner and outer layers. Blue fluorescence does not necessarily occur throughout the entire thickness of the outer layer. Based on these findings, the inventors came up with the present invention.

[0027] The present invention will be described in more detail below. The quartz glass crucible of the present invention is a quartz glass crucible comprising a bottom portion, a curved portion, and a straight body portion, having an outer layer made of opaque quartz glass containing air bubbles and an inner layer made of transparent quartz glass, and characterized in that when ultraviolet light is irradiated onto the quartz glass crucible as excitation light, blue fluorescence is produced in the boundary region between the outer layer and the inner layer of the quartz glass crucible, and the blue fluorescence is produced throughout the bottom portion, the curved portion, and the straight body portion of the quartz glass crucible.

[0028] First, the parts of the quartz glass crucible of the present invention will be described with reference to Figure 1. The quartz glass crucible 10 in Figure 1 has an outer layer 21 made of opaque quartz glass containing air bubbles and an inner layer 22 made of transparent quartz glass. Also, as shown in Figure 1, the crucible shape of the quartz glass crucible 10 typically consists of a bottom 12, a curved section 13, and a straight section 14. There is a bottom center 11 at the center of the bottom 12, and the bottom 12 is also called the large radius section, and the curved section 13 is also called the small radius section.

[0029] As described above, the quartz glass crucible 10 of the present invention generates blue fluorescence in the boundary region between the outer layer 21 and the inner layer 22 when irradiated with ultraviolet light as excitation light, and this blue fluorescence is generated throughout the bottom 12, curved portion 13, and straight body portion 14 of the quartz glass crucible 10. Such a quartz glass crucible 10 is one in which the generation of air bubbles on the surface of the inner layer 22 is well suppressed throughout the entire surface.

[0030] The quartz glass crucible 10 of the present invention may have an outer layer 21 containing natural quartz glass and an inner layer 22 containing synthetic quartz glass. A quartz glass crucible having such a structure is particularly common for pulling silicon single crystals. Furthermore, in a quartz glass crucible 10 having such a structure, blue fluorescence generally occurs in the region where the natural quartz glass is in contact with the synthetic quartz glass.

[0031] Furthermore, it is preferable that the quartz glass crucible 10 of the present invention has an inner layer 22 containing hydrogen-doped quartz glass or water vapor-introduced quartz glass. The overall blue fluorescence of the present invention can be particularly favorably achieved in a quartz glass crucible having an inner layer containing hydrogen-doped quartz glass or water vapor-introduced quartz glass. Although hydrogen-doped quartz glass and water vapor-introduced quartz glass are used to suppress bubble generation, a quartz glass crucible in which overall blue fluorescence is observed as in the present invention can be made into a quartz glass crucible in which the generation of bubbles on the surface of the inner layer is more reliably and well suppressed throughout.

[0032] [Method for detecting blue fluorescence] In the quartz glass crucible of the present invention, blue fluorescence is detected, for example, as follows. First, a quartz glass crucible is prepared as shown in step S1 of Figure 2.

[0033] Next, as shown in step S2 of Figure 2, ultraviolet light is irradiated onto the quartz glass crucible as excitation light. Then, as shown in step S3 of Figure 2, blue fluorescence emitted from the irradiated quartz glass crucible is detected. It is preferable to use ultraviolet light with a peak around 254 nm. In that case, the detected blue fluorescence will have a peak around 395 nm. Ultraviolet light with a wavelength of around 254 nm can be easily obtained from a mercury lamp. In this way, in detecting blue fluorescence from a quartz glass crucible, by detecting blue fluorescence that has a peak around 395 nm when exposed to ultraviolet light with a peak around 254 nm, the state of oxygen deficiency defects in the outer layer made of opaque quartz glass can be more easily evaluated. It should be noted that in silica glass, fluorescence with a peak around 395 nm is known to be due to oxygen deficiency defects (B2β). Furthermore, fluorescence around 395 nm often has a peak at wavelengths of 394-396 nm, but this can vary slightly depending on the measuring instrument, and the peak may also be located around 390-400 nm.

[0034] If blue fluorescence is produced during steps S2 and S3, it means that oxygen deficiency defects are present. If blue fluorescence is not produced, it means that oxygen deficiency defects are absent or their density is low.

[0035] This method for detecting blue fluorescence allows for easy, non-destructive evaluation of quartz glass crucibles. As mentioned above, the area where blue fluorescence occurs, i.e., where oxygen deficiency defects occur, is typically the shallow portion of the outer layer 21 at the boundary between the inner layer 22 and the outer layer 21. For example, if natural quartz powder is used as the raw silica powder for the outer layer 21 and synthetic quartz powder is used as the raw silica powder for the inner layer 22, the outer layer 21 becomes a natural quartz glass layer. At this time, the oxygen in the outer layer 21 (natural quartz glass layer) combines with hydrogen introduced by hydrogen doping or the introduction of water vapor, creating a natural transparent layer with few bubbles and oxygen deficiency defects. This natural transparent layer is what generates blue fluorescence. Blue fluorescence does not necessarily occur throughout the entire thickness of the outer layer 21.

[0036] Furthermore, blue fluorescence can be observed visually. Specifically, by irradiating a quartz glass crucible with ultraviolet light in a dark room, the generation of blue fluorescence can be confirmed. The distribution of blue fluorescence on the outer layer of the quartz glass crucible can also be observed visually.

[0037] Furthermore, in the detection of blue fluorescence, it is also possible to define the detection of blue fluorescence quantitatively based on numerical values. Specifically, this is done as follows: The peak intensity (peak height) of the blue fluorescence generated when ultraviolet light is irradiated as excitation light is measured as peak intensity A. In addition, the peak intensity (peak height) of the Rayleigh scattered light produced as a result of ultraviolet irradiation is measured as peak intensity B. Here, if A and B satisfy the following equation (1), it can be defined that blue fluorescence has been detected. (A / B)×1000≧20...Equation (1)

[0038] In this way, blue fluorescence can be detected without relying on visual inspection. The reason for using equation (1) above is as follows.

[0039] Patent documents 7 and 8 describe measuring red fluorescence to detect excess oxygen defects in quartz glass crucibles. In the case of red fluorescence, a 514 nm wavelength Ar laser is used as the excitation light to measure Raman scattered light and fluorescence.

[0040] In the case of blue fluorescence, 254 nm ultraviolet light is used as excitation light, and the fluorescence wavelength is 395 nm, so the same measurement method as for red fluorescence cannot be used. Since the fluorescence intensity depends on the excitation light intensity, it is preferable to normalize using the ratio of these two. In order to normalize, it is necessary to know the excitation light intensity, but the excitation light intensity is not constant as it varies depending on the equipment and is subject to degradation over time. Therefore, Rayleigh scattered light, which has the same wavelength as the excitation light, is adopted as the standard. In principle, Rayleigh scattered light has the same wavelength as the incident light, but it varies slightly depending on the measurement equipment, and there is often a peak around 253 nm to 256 nm.

[0041] However, as mentioned above, even when Rayleigh scattered light is used as the reference, specularly reflected excitation light, which is unnecessary for measurement, may be mixed into the light-receiving section. Therefore, it is preferable to set the irradiation angle of ultraviolet light to an angle shifted from the direction perpendicular to the inner surface of the quartz glass crucible, and to perform the detection of blue fluorescence at an angle shifted from the specularly reflected ultraviolet light. For example, the irradiation surface of the quartz glass crucible can be tilted so that the incident angle of the excitation light is 60 degrees, and the measurement can be performed with a spectrofluorescence intensity meter.

[0042] The relationship between the detection of blue fluorescence and bubble density in this invention will be explained with illustrative experimental examples.

[0043] [Experimental Examples 1-1 to 1-8] A standard quartz glass crucible 10, as shown in Figure 1, was manufactured using hydrogen-doped synthetic quartz powder (hydrogen-doped synthetic quartz powder described in Patent Document 3) as the raw material powder for the inner layer 22. Samples were cut from multiple parts of this manufactured quartz glass crucible 10 (Experimental Examples 1-1 to 1-8).

[0044] (Measurement of blue fluorescence) Each sample was irradiated with ultraviolet light having a peak at a wavelength of approximately 254 nm, and blue fluorescence with a peak at approximately 395 nm was detected. As a result, samples in which blue fluorescence was detected were designated as Experimental Examples 1-1 to 1-4, and samples in which it was not detected were designated as Experimental Examples 1-5 to 1-8.

[0045] (Measurement of bubble density) After measuring the blue fluorescence as described above, the bubble density after VBT was measured for each sample in the quartz glass crucible 10 of Experimental Examples 1-1 to 1-8, based on the evaluation method in Patent Document 6. For each sample, a vacuum of 2 × 10⁻¹⁰ was applied. -2 Bubbles were generated by keeping the temperature below Pa and holding it at 1650°C for 2 hours and 10 minutes. The density of bubbles exposed on the surface of each sample was then visually inspected.

[0046] The results of experimental examples 1-1 to 1-8 are shown in Table 1.

[0047] [Table 1]

[0048] As can be seen from Table 1, differences were observed in the density of exposed bubbles on the inner surface depending on the degree of fluorescence. In other words, in the areas where blue fluorescence was detected, the bubble density after VBT was significantly suppressed.

[0049] Furthermore, repeated melting experiments suggested that it was crucial for the scattered hydrogen-doped silica powder to be directly supplied to that specific area. In other words, it can be explained by assuming that the hydrogen effect disappears in the synthetic transparent layer formed when the scattered hydrogen-doped silica powder does not directly adhere but flows downward due to gravity or circumferentially due to centrifugal force, and that the natural transparent layer below it does not emit fluorescence. Based on this hypothesis, during the melting of the quartz glass crucible, the raw material supply port for supplying hydrogen-doped silica powder was moved from the bottom towards the straight section, and hydrogen-doped silica powder was supplied. As a result, hydrogen-doped silica powder could be directly attached to the entire inner surface region and hydrogen could be supplied, resulting in a quartz glass crucible that emitted blue fluorescence in the natural transparent thin layer across the entire surface. When the synthetic transparent layer in each part of the quartz glass crucible obtained in this way was evaluated, it was found to have excellent bubble suppression. When the same quartz glass crucible was used for pulling silicon single crystals, the silicon single crystal pulling performance (DF ratio) improved. By repeatedly conducting melting experiments in this manner, we succeeded in melting and producing a quartz glass crucible that exhibited blue fluorescence across its entire surface. This will be explained by referring to Experimental Examples 2-1 to 2-8.

[0050] [Experimental Example 2-1] Using the same method as in Experimental Examples 1-1 to 1-8, but with modified manufacturing conditions, a standard quartz glass crucible 10, as shown in Figure 1, was manufactured using hydrogen-doped synthetic quartz powder as the raw material for the inner layer 22 (Experimental Example 2-1).

[0051] (Sample preparation) For each of the quartz glass crucibles 10 that were prepared, samples of approximately 4 cm x 8 cm were cut out at 100 mm intervals from the bottom center 11 to the straight body section 14. Of these, the portion at a distance of 0 mm from the bottom center 11 (bottom center) includes the bottom center 11. The portions at distances of 100 mm, 200 mm, and 300 mm from the bottom center 11 are located in the bottom section 12 (i.e., the large radius section). The portion at a distance of 400 mm from the bottom center 11 is located in the curved section 13 (i.e., the small radius section). The portions at distances of 500 mm, 600 mm, and 700 mm from the bottom center 11 are located in the straight body section 14. Of these, the portion at a distance of 500 mm from the bottom center 11 is located near the bottom of the straight body section 14.

[0052] (Measurement of blue fluorescence) Each sample was irradiated with ultraviolet light having a peak at a wavelength of approximately 254 nm, and the presence or absence of blue fluorescence with a peak at a wavelength of approximately 395 nm was visually confirmed.

[0053] (Measurement of bubble density) After measuring the blue fluorescence as described above, the bubble density after VBT was measured for each sample in the quartz glass crucible 10 of Experimental Example 2-1, based on the evaluation method in Patent Document 6. For each sample, a vacuum of 2 × 10⁻⁶ was applied. -2 Bubbles were generated by keeping the temperature below Pa and holding it at 1650°C for 2 hours and 10 minutes. The density of bubbles exposed on the surface of each sample was then visually inspected.

[0054] [Experimental Examples 2-2 to 2-8] Using the same methods as in Experimental Examples 1-1 to 1-8 and Experimental Example 2-1, but with modified manufacturing conditions, a standard quartz glass crucible 10, as shown in Figure 1, was prepared using hydrogen-doped synthetic quartz powder as the raw material for the inner layer 22 (Experimental Examples 2-2 to 2-8).

[0055] Sample preparation, blue fluorescence measurement, and bubble density measurement were performed on 10 quartz glass crucibles prepared in Experimental Examples 2-2 to 2-8 in the same manner as in Experimental Example 2-1.

[0056] In Experimental Examples 2-2 and 2-3, blue fluorescence was observed in all samples, similar to Experimental Example 2-1, and fluorescence was detected across the entire surface. Furthermore, in the post-VBT bubble formation test, bubble formation was suppressed in all samples.

[0057] On the other hand, in experimental examples 2-4 to 2-8, blue fluorescence was detected only in some cases, and not in others.

[0058] The results of experimental examples 2-1 to 2-8 are shown in Table 2.

[0059] [Table 2]

[0060] This is per unit area (1cm²) 2 When converted to the density of bubbles exposed on the inner surface after VBT, the results are as shown in Table 3.

[0061] [Table 3]

[0062] As can be seen from Tables 2 and 3, under certain manufacturing conditions, blue fluorescence can be detected across the entire surface of the quartz glass crucible 10. Such manufacturing conditions can be easily determined by repeatedly conducting melting experiments and verifying the detection of blue fluorescence. Examples of such manufacturing conditions include changing the gas circulation position in the melting atmosphere or changing the supply position of the raw quartz powder. [Examples]

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0064] [Comparative Example] In a study of quartz glass crucibles from a period before the relationship between blue fluorescence and the transparent layer was discovered, it was found that quartz glass crucibles exhibiting blue fluorescence throughout the entire crucible (bottom, curved section, and straight section) accounted for 0% of the production rate.

[0065] [Examples] During the dispersal method, while adjusting the airflow generated by the arc discharge, hydrogen-doped silica powder was supplied at a rate of 200 g / min or more from the bottom to the straight section of the quartz glass crucible using a synthetic quartz raw material powder supply tube with an inner diameter of 16 mm or less, and melted so that a synthetic transparent layer of 1 mm or more was formed on the entire inner surface of the quartz glass crucible. The blue fluorescence emission state of the quartz glass crucible was checked, and the position of the raw material powder supply tube was adjusted so that the hydrogen-doped silica powder adhered to areas where there was no emission or the emission was weak, and then melting was performed. This melting experiment and condition adjustment were repeated until blue fluorescence could be observed across the entire surface of the quartz glass crucible, and the manufacturing conditions for quartz glass crucibles with full-surface blue fluorescence were established. As a result of manufacturing quartz glass crucibles under these manufacturing conditions, the production rate of quartz glass crucibles that emit full-surface blue fluorescence increased to 93.8% (61 out of 65), enabling a stable supply.

[0066] [Table 4]

[0067] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any configuration that has substantially the same technical idea as described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0068] 10...Quartz glass crucible, 11...Center of the base, 12...Bottom, 13...Curved section, 14...Straight section 21...Outer layer, 22...Inner layer.

Claims

1. A quartz glass crucible consisting of a bottom, a curved section, and a straight section, It has an outer layer made of opaque quartz glass containing air bubbles and an inner layer made of transparent quartz glass. When ultraviolet light is irradiated onto the quartz glass crucible as excitation light, blue fluorescence is produced in the shallow portion of the outer layer side of the boundary region between the outer and inner layers of the quartz glass crucible. A quartz glass crucible characterized in that the blue fluorescence occurs throughout the bottom, curved portion, and straight portion of the quartz glass crucible.

2. The outer layer contains natural quartz glass, The inner layer contains synthetic quartz glass, The quartz glass crucible according to claim 1, characterized in that the blue fluorescence is generated in the region where the natural quartz glass is in contact with the synthetic quartz glass.

3. The quartz glass crucible according to claim 1 or 2, characterized in that the inner layer includes hydrogen-doped quartz glass or water vapor-introduced quartz glass.

4. The quartz glass crucible according to any one of claims 1 to 3, characterized in that the blue fluorescence has a peak around a wavelength of 395 nm.

5. The quartz glass crucible according to any one of claims 1 to 4, characterized in that the ultraviolet light irradiated is ultraviolet light having a peak around a wavelength of 254 nm.

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