Quartz glass crucible, manufacturing process for it and process for producing a silicon single crystal using a quartz glass crucible

Abstract

Quartz glass crucible (1, 2) used for growing a silicon single crystal by a Czochralski method, comprising: a cylindrical crucible body (10) having a base and made of quartz glass; and a coating film (13A) containing a first crystallization accelerator, which is formed on an inner surface (10a) of the crucible body (10) to bring about the formation of an inner crystal layer (14A) consisting of an aggregate of dome-shaped or columnar crystal grains on a surface layer section of the inner surface (10a) of the crucible body (10) by heating during a step of the pulling up of the silicon single crystal, wherein the coating film (13A) containing the first crystallization accelerator is not heated after application and before pulling up, the coating film (13A) is formed by applying a barium-containing coating solution to the inner surface (10a) of the crucible body (10), The coating solution contains a water-insoluble barium compound and a water-soluble polymer as a thickening agent, and a concentration of barium applied to the inner surface (10a), 3.9×10 16 atoms / cm² 2 up to 1.6×10 17 atoms / cm² 2 amounts.

Description

TECHNICAL AREA

[0001] The present invention relates to a quartz glass crucible and a manufacturing process therefor, and in particular to a quartz glass crucible used for the production of a silicon single crystal by the Czochralski process (CZ process), and a manufacturing process therefor. The present invention further relates to a process for producing a silicon single crystal using a quartz glass crucible. STATE OF THE ART

[0002] A quartz crucible is used to produce a silicon single crystal using the CZ process. In the CZ process, raw silicon material is heated to melting in the quartz crucible, a seed crystal is immersed in the molten silicon, and then the seed crystal is gradually pulled up while the crucible is rotated to grow a single crystal. To produce a high-quality silicon single crystal for a semiconductor device at a low cost, it is necessary to perform a process called multiple pulling. This not only increases the yield of single crystals from a single pulling step but also allows multiple silicon single-crystal blocks to be pulled from a single crucible. For this, a crucible with a stable shape capable of withstanding long-term use is required.

[0003] In a state-of-the-art quartz glass crucible, the viscosity decreases in a thermal environment of 1400 °C or higher during the growth of a silicon single crystal, causing it to lose its shape and leading to crucible deformation such as bulging or inward collapse. Consequently, changes in the height of the liquid surface of the silicon melt, crucible breakage, contact with components in a furnace, and similar events become problematic. Furthermore, the inner surface of the crucible crystallizes upon contact with the silicon melt during single crystal growth, forming cristobalite, also known as the brown ring. If the cristobalite delaminates and is incorporated into the silicon single crystal during growth, this causes dislocation.

[0004] To solve such problems, a method for increasing the strength of a crucible by positively crystallizing the crucible's wall surface is proposed. For example, patent document 1 describes a quartz glass crucible in which a coating film of a crystallization accelerator of elements in group 2a is present on the inner surface of the quartz glass crucible at a depth of 1 mm. When a silicon single crystal is grown using the quartz glass crucible, a crystal layer is formed on the inner surface of the crucible, thus improving its heat resistance properties. For example, even if a silicon single crystal is grown under reduced pressure, the inner surface does not become rough and remains smooth, with the result that growing is possible for a long time with a good crystallization ratio.

[0005] In addition, patent document 2 describes how a devitrification accelerator, such as an aqueous barium hydroxide solution, is applied to the inner surface of a crucible, and the crystallization rate is adjusted by changing the concentration of the devitrification accelerator depending on the section of the crucible, thereby preventing crystal delamination. The crystallization rates of a corner section, a wall section, and a bottom section are set in descending order, and the devitrification growth rate is set to be in the range of 0.1 to 0.6 µm / h for uniform devitrification.

[0006] Patent document 3 describes a method for surface treatment of a quartz glass product such as a quartz glass crucible, wherein the inner surface of a crucible is coated with a reduction coating agent (amines, organosilane halogens or the like) containing a methyl group to accelerate cristobalite formation during drawing, thereby preventing delamination of a devitrification point.

[0007] Patent document 4 describes a quartz glass crucible in which the strength is increased by semi-crystallizing the inner surface. The quartz glass crucible contains a crystallization accelerator in the inner surface of the crucible with a thickness of 1 to 10 µm and a semi-crystal layer with a crystallinity of 80 to 95%. The semi-crystal layer is formed by applying a voltage to a mold during arc melting to move the crystallization accelerator to the inner surface of the quartz glass crucible in a rotational molding process.

[0008] Patent document 5 describes that the outer layer of a crucible's side wall is designed as a doped region containing a first component, such as Ti, which acts as a crosslinking agent in fused silica, and a second component, such as Ba, which acts as a separation point forming agent in the fused silica, and having a thickness of 0.2 mm or more, and when a fused silica crucible is heated in a specific application process for crystal pulling, cristobalite is formed in the doped region to accelerate the crystallization of the fused silica, thereby increasing the strength of the crucible. [Prior technical literature][Patent documents] Patent document 1 Published Japanese patent application JP H08-2932 A Patent document 2: Published Japanese patent application JP 2003-160393 A Patent document 3: Published Japanese patent application JP 2010-537945 A Patent document 4: Published Japanese patent application JP 2006-206342 A Patent document 5: Published Japanese patent application JP 2005-523229 A

[0009] DE 696 09 907 T2 describes quartz crucibles used for the production of silicon single crystals. The crucible has a coating with an alkaline earth metal concentration in the range of 0.1 mmol / 1000 cm². 2 up to 0.6 mmol / 1000 cm 2 on the inner surface and 0.1 mmol / 1000 cm² 2 up to 1.2 mmol / 1000 cm 2 on the exterior surface. Certain areas of the interior surface may be excluded from the coating.

[0010] DE 602 22 073 T2 also describes coatings for quartz crucibles that are applied to the entire or part of the inner and / or outer surface of the crucible. In addition to partial hydrolysates of alkoxysilanes, these coatings contain metal oxides of alkaline earth metals. Barium is explicitly mentioned. The concentration of barium is in the range of 1 × 10 -9 up to 1×10 -6 mol / cm 2 .

[0011] DE 10 2009 013 715 A1 discloses quartz crucibles for the production of silicon single crystals, which have a coating on the inner and outer surfaces of the crucible, wherein the coating contains crystallization promoters in the form of, for example, barium. Furthermore, for the coating of the inner surface of the crucible, the upper area from the rim to the bottom is excluded from the coating.

[0012] US 2013 / 0247818A1 describes quartz crucibles coated on the inner surface with a barium-containing coating.

[0013] However, in the prior art method for increasing the strength of a crucible, as described in patent documents 1 and 2, cases can occur where the thickness of the crystal layer is insufficient and delamination of crystal grains occurs depending on the state of crystallization. That is, if crystals grow in all directions (hereinafter referred to as "random growth"), without regularity in the crystal growth direction within the crystal layer, the crystallization accelerator is trapped at the crystal grain boundary, causing the crystallization rate to decrease over time. As a result, crystal growth in the thickness direction of the crucible is halted at a relatively early stage during a draw-up step.Therefore, in the drawing step, which is carried out over a very long period under high temperature heat stress, such as multiple drawing, the problem is that a thin crystal layer in the inner surface of the crucible is eroded into the silicon melt and disappears completely.

[0014] The prior art method for increasing the strength of a crucible, described in patent document 3, focuses solely on the density of the brown ring on the surface and does not consider crystal growth in the thickness direction of the crucible. If the thickness of the crystal layer is not sufficiently ensured, the crucible's strength cannot be maintained, resulting in deformation or delamination of the brown ring formed on the surface of the quartz glass. Furthermore, since the brown ring does not cover the entire inner surface of the crucible, it does not contribute to increasing the crucible's strength.

[0015] In the prior art method for increasing the strength of a crucible, described in patent documents 4 and 5, the crystallization accelerator, being embedded in a glass matrix, simultaneously generates crystal nuclei, causing the crystal layer to grow randomly. Therefore, the problem arises that the thickness of the crystal layer is insufficient due to a decrease in the crystallization rate. Since there is a possibility that the inner surface of the crucible may be eroded by 1 mm or more during the single-crystal pull-up, there is concern that, in cases where the crystal layer is thin, it may disappear during the second half of the single-crystal pull-up step.

[0016] Consequently, it is necessary to provide a quartz glass crucible capable of withstanding a single-crystal growing step performed over a very long period, such as multiple growing, and a method for its manufacture. In addition, the present invention provides a method for producing a silicon single crystal using a quartz glass crucible.

[0017] The inventors conducted intensive studies on the crystallization mechanism of the surface of a crucible at a high temperature in a crystal-growing step and consequently discovered the structure of a crystal layer and, in particular, the alignment state of crystal grains in the thickness direction of a crucible wall, which enables continuous crystal growth and can prevent the disappearance of the crystal layer due to delamination of the crystal layer and erosion into a silicon melt.

[0018] The present invention is defined in independent claims 1, 10, 14, 18, and 19. The following description is subject to this limitation. Any disclosure beyond the scope of the aforementioned claims is for illustrative and comparative purposes only.

[0019] A quartz glass crucible, according to a first aspect of the present disclosure, is used for growing a silicon single crystal by a Czochralski process and comprises: a cylindrical crucible body having a bottom and made of quartz glass; and a first coating film containing a crystallization accelerator, formed on an inner surface of the crucible body to cause an inner crystal layer, consisting of an aggregate of dome-shaped or columnar crystal grains, to be formed on a surface layer section of the inner surface of the crucible body by heating during a step of growing the silicon single crystal.

[0020] According to the present invention, by ensuring that the crystal structure of the inner crystal layer exhibits an orientation, crystallization is accelerated so that the crystal layer can be formed with a thickness that does not cause deformation of the crucible wall. This makes it possible to prevent crucible deformation that occurs during the very long drawing process, such as multiple drawings. In addition, it is possible to prevent dislocation of the silicon single crystal caused by delamination of crystal grains (cristobalite) from the inner wall surface of the crucible.

[0021] In the present invention, it is preferred that the ratio A / B between a maximum value A of a peak intensity at a diffraction angle 2θ of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the inner surface of the crucible body on which the inner crystal layer is formed by an X-ray diffraction method, is 7 or less. In a case where the analysis result of the X-ray diffraction method satisfies the above conditions, it can be determined that the inner crystal layer has a crystal structure in a dome-like or column-like orientation.It should be noted that “alignment” refers to an aggregate of crystal grains grown in such a way that crystal axes are aligned in a specific direction, and “dome-like alignment” refers to a crystal structure in which, upon evaluation of an aggregate of dome-shaped crystal grains by XRD (X-ray diffraction), crystal grains with random crystal axis directions and crystal grains grown in an alignment coexist, and alignment is confirmed in a part of the aggregate of crystal grains.

[0022] In the present invention, it is preferred that the inner crystal layer comprises a dome-shaped crystal layer, consisting of the aggregate of dome-shaped crystal grains formed on the surface layer section of the inner surface of the crucible body, and a columnar crystal layer, consisting of the aggregate of columnar crystal grains, immediately below the dome-shaped crystal layer. If the inner surface of the crucible undergoes crystal growth in one plane, there is concern that crystal grains that have grown large may delaminate, potentially causing dislocation of the silicon single crystal.However, since the crystal growth of the inner crystal layer changes from a dome-like orientation to a columnar orientation, and the columnar crystal grains grow in the thickness direction, a structure can be achieved in which the crystal grains are less likely to delaminate, even if they grow large, thus preventing dislocation of the silicon single crystal. Additionally, the strength of the crucible can always be increased by allowing further crystal growth.

[0023] In the present invention, it is preferred that the ratio A / B between a maximum value A of a peak intensity at a diffraction angle 2θ of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the inner surface of the crucible body on which the inner crystal layer is formed by an X-ray diffraction method, is less than 0.4. In a case where the analysis result of the X-ray diffraction method satisfies the above conditions, it can be determined that the inner crystal layer exhibits the crystal structure predominantly in a columnar orientation.

[0024] One crystallization accelerator contained in the coating film is barium, whose growth, compared to other elements, is most pronounced in one orientation. The concentration of barium on the inner surface of the crucible body is 3.9 × 10⁻⁶.16 atoms / cm² 2 up to 1.6×10 17 atoms / cm² 2 . Accordingly, countless crystal nuclei are generated on the surface of the crucible within a short time, so that crystal growth in a columnar orientation can be accelerated from the earliest possible time.

[0025] It is preferred that the quartz glass crucible according to the present invention further comprises: a coating film containing a second crystallization accelerator, formed on an outer surface of the crucible body to cause an outer crystal layer, consisting of an aggregate of dome-shaped or columnar crystal grains, to form on a surface layer section of the outer surface of the crucible body by heating during the drawing step. With this configuration, crystallization is accelerated by inducing an orientation in the crystal structure of the outer crystal layer, so that the crystal layer can be formed with a thickness that does not cause deformation of the crucible wall. Thus, it is possible to prevent deformation of the crucible that occurs during the drawing step, which is carried out over a very long duration, such as multiple drawings.Since the outer crystal layer can have a corresponding thickness according to the draw-up time, it is also possible to prevent foaming and delamination of the quartz glass interface of the outer crystal layer.

[0026] In the present invention, it is preferred that a region of a predetermined width, extending downwards from an upper edge of the inner surface of the crucible body, is a crystallization accelerator-uncoated region in which the coating film containing the first crystallization accelerator is not formed. Accordingly, the generation of small crystal particles at the upper edge can be suppressed, and a reduction in the yield of the silicon single crystal can be prevented.

[0027] In the present invention, it is preferred that the ratio A / B between a maximum value A of a peak intensity at a diffraction angle 2θ of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the outer surface of the crucible body on which the outer crystal layer is formed by an X-ray diffraction method, is 0.4 or more and 7 or less. In a case where the analysis result of the X-ray diffraction method satisfies the above conditions, it can be determined that the outer crystal layer has the crystal structure in a dome-like orientation.

[0028] A crystallization accelerator contained in the coating film containing the second crystallization accelerator is barium, and the concentration of barium on the outer surface of the crucible body is equal to or greater than 4.9 × 10 15 atoms / cm² 2 and lower than 3.9×1016 atoms / cm² 2 Accordingly, crystal growth can be accelerated in a dome-like orientation.

[0029] In the present invention, it is preferred that a region of a predetermined width, extending downwards from an upper edge of the outer surface of the crucible body, is a crystallization accelerator-uncoated region in which the coating film containing the second crystallization accelerator is not formed. Accordingly, the generation of small crystal particles at the upper edge can be suppressed, and a reduction in the yield of the silicon single crystal can be prevented.

[0030] A quartz glass crucible according to a second aspect of the present invention is used for growing a silicon single crystal by a Czochralski process and comprises: a cylindrical crucible body having a bottom and made of quartz glass; and a coating film containing a crystallization accelerator, formed on an outer surface of the crucible body to cause an outer crystal layer, consisting of an aggregate of dome-shaped or columnar crystal grains, to be formed on a surface layer section of the outer surface of the crucible body by heating during a step of growing the silicon single crystal.

[0031] According to the present invention, by ensuring that the crystal structure of the outer crystal layer has an orientation, crystallization is accelerated so that the crystal layer can be formed with a thickness that does not cause deformation of the crucible wall. This makes it possible to prevent crucible deformation that occurs during the very long drawing process, such as multiple drawings. Since the outer crystal layer can have a thickness appropriate to the drawing time, it is also possible to prevent foaming and delamination of the quartz glass interface of the outer crystal layer.

[0032] A / B ratio between a maximum peak intensity value A at a diffraction angle 2θ of 20° to 25° and a maximum peak intensity value B at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the outer surface of the crucible body on which the outer crystal layer is formed by an X-ray diffraction method, is preferably 7 or less and particularly preferably 0.4 or more and 7 or less. In a case where A / B from the X-ray diffraction analysis is 7 or less, it can be determined that the outer crystal layer has a dome-like or columnar crystal structure, and in a case where A / B is 0.4 or more and 7 or less, it can be determined that it has a dome-like orientation.

[0033] In the present invention, it is preferred that a region of a predetermined width, extending downwards from an upper edge of the outer surface of the crucible body, is a crystallization accelerator-uncoated region in which the coating film containing the crystallization accelerator is not formed. Accordingly, the generation of small crystal particles at the upper edge can be suppressed, and a reduction in the yield of the silicon single crystal can be prevented.

[0034] A manufacturing process of a quartz glass crucible according to a third aspect of the present invention comprises: applying a first crystallization accelerator coating solution containing a thickening agent to an inner surface of the quartz glass crucible to bring about a concentration of a crystallization accelerator in the inner surface of 3.9×10 16 atoms / cm² 2or more. In this case, it is preferred that the first crystallization accelerator coating solution is applied by a spraying process in a state in which an area of ​​a predetermined width, extending downwards from an edge of an upper end in the inner surface of the quartz glass crucible, is masked. Furthermore, it is preferred that the manufacturing process of a quartz glass crucible according to the present invention further comprises: applying a second crystallization accelerator coating solution containing the thickening agent to an outer surface of the quartz glass crucible to bring about a concentration of the crystallization accelerator in the outer surface equal to or greater than 4.9 × 10⁻⁶. 15 atoms / cm² 2 and lower than 3.9×10 16 atoms / cm² 2In this case, it is preferred that the second crystallization accelerator coating solution is applied by spraying in a state where one opening of the quartz glass crucible is closed and an area of ​​predetermined width extending downwards from the upper rim end on the outer surface of the quartz glass crucible is masked. As described above, the inner crystal layer can be formed in a columnar orientation on the inner surface of the crucible, and the outer crystal layer can be formed in a dome-like orientation on the outer surface of the crucible.

[0035] A method for producing a quartz glass crucible according to a fourth aspect of the present invention comprises: applying a crystallization accelerator coating solution to a surface of a quartz glass base material; forming a crystal layer on a surface layer section of the surface of the quartz glass base material by an evaluation heat treatment at 1400 °C or higher; analyzing a crystallization state of the surface of the quartz glass base material by an X-ray diffraction method and adjusting a concentration of a crystallization accelerator in the crystallization accelerator coating solution based on an analysis result; and applying the adjusted crystallization accelerator coating solution to a surface of the quartz glass crucible.

[0036] Crystal grains in a dome-like or columnar orientation can be grown by ensuring that the crystallization accelerator is present at a high density at the interface between the quartz glass and the crystal grains. However, the degree of density achieved by applying the crystallization accelerator coating solution to the surface of the quartz glass crucible is unclear. Nevertheless, by verifying the effect of the crystallization accelerator coating solution using the quartz glass base material beforehand, problems such as deformation of the quartz glass crucible during an actual drawing step can be prevented in advance.

[0037] According to a fifth aspect of the present invention, a method for producing a silicon single crystal by a Czochralski process, in which a silicon single crystal is grown from a silicon melt in a quartz glass crucible, comprises: applying a first crystallization accelerator coating solution to an inner surface of the quartz glass crucible; forming, on a surface layer section of the inner surface of the quartz glass crucible, an inner crystal layer with a laminated structure of a dome-shaped crystal layer consisting of an aggregate of dome-shaped crystal grains and a columnar crystal layer consisting of an aggregate of columnar crystal grains, immediately beneath the dome-shaped crystal layer by heating in a step of growing the silicon single crystal; and growing the silicon single crystal while the inner crystal layer continues to grow.

[0038] According to the present invention, by ensuring that the crystal structure of the inner crystal layer exhibits an orientation, crystallization is accelerated so that the crystal layer can be formed with a thickness that does not cause deformation of the crucible wall. This makes it possible to prevent crucible deformation caused during the very long drawing process, such as multiple drawings. In addition, it is possible to prevent dislocation of the silicon single crystal caused by delamination of crystal grains (cristobalite) from the inner wall surface of the crucible.

[0039] In the present invention, it is preferred that the ratio A / B between a maximum value A of a peak intensity at a diffraction angle 2θ of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the inner surface of the quartz glass crucible on which the inner crystal layer is formed, by an X-ray diffraction method, is less than 0.4. In a case where the analysis result of the X-ray diffraction method satisfies the above conditions, it can be determined that the inner crystal layer exhibits the crystal structure predominantly in a columnar orientation.

[0040] In the present invention, it is preferred that a crystallization accelerator contained in the first crystallization accelerator coating solution is barium and that the concentration of the barium applied to the inner surface is 3.9×10 16 atoms / cm² 2 up to 1.6×1017 atoms / cm² 2 This is the amount. Accordingly, countless crystal nuclei are generated on the surface of the crucible within a short time, so that crystal growth in a columnar orientation can be accelerated from the earliest possible time.

[0041] In the present invention, it is preferred that the first crystallization accelerator coating solution is applied to an area that does not include a region of predetermined width extending downwards from an upper edge end on the inner surface of the quartz glass crucible. Accordingly, the generation of small crystal particles at the upper edge end can be suppressed, and a reduction in the yield of the silicon single crystal can be prevented.

[0042] It is preferred that the method for producing a silicon single crystal according to the present invention further comprises: applying a second crystallization accelerator coating solution to an outer surface of the quartz glass crucible; forming an outer crystal layer, consisting of an aggregate of dome-shaped crystal grains, on a surface layer section of the outer surface of the quartz glass crucible by heating in the step of pulling up the silicon single crystal; and Growing the silicon single crystal without allowing the outer crystal layer to continue growing.

[0043] Accordingly, by ensuring that the crystal structure of the outer crystal layer exhibits an orientation, crystallization is accelerated, allowing the crystal layer to form with a thickness that does not deform the crucible wall. This prevents crucible deformation that occurs during very long drawing processes, such as multiple drawings. Since the outer crystal layer can have a thickness appropriate to the drawing time, it is also possible to prevent foaming and delamination of the quartz glass interface of the outer crystal layer.

[0044] In the present invention, it is preferred that the ratio A / B between a maximum value A of a peak intensity at a diffraction angle 2θ of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the outer surface of the quartz glass crucible on which the outer crystal layer is formed by an X-ray diffraction method, is 0.4 or more and 7 or less. In a case where the analysis result of the X-ray diffraction method satisfies the above conditions, it can be determined that the outer crystal layer has the crystal structure in a dome-like orientation.

[0045] In the present invention, it is preferred that a crystallization accelerator contained in the coating solution containing the second crystallization accelerator is barium and that the concentration of the barium applied to the outer surface is equal to or higher than 4.9×10 15atoms / cm² 2 and lower than 3.9×10 16 atoms / cm² 2 This is the case. Accordingly, crystal growth can be accelerated in a dome-like orientation.

[0046] In the present invention, it is preferred that the second crystallization accelerator coating solution is applied to an area that does not include a region of predetermined width extending downwards from the upper rim end on the outer surface of the quartz glass crucible. Accordingly, the generation of small crystal particles at the upper rim end can be suppressed, and a reduction in the yield of the silicon single crystal can be prevented.

[0047] In the present invention, it is preferred that the first and second crystallization accelerator coating solutions further contain a thickening agent. Accordingly, the viscosity of the coating solution can be increased, thus preventing the coating solution from flowing due to gravity and becoming uneven when applied to the crucible. Additionally, the crystallization accelerator is not held together in the coating solution but diffuses, allowing it to be applied uniformly to the surface of the crucible. Thus, the crystallization accelerator can be fixed uniformly and densely to the wall surface of the crucible at a high concentration, thereby accelerating the growth of crystal grains in a columnar or dome-like orientation.

[0048] In the process for producing a silicon single crystal according to the present invention, it is preferred that the crystallization state of the inner crystal layer, formed by heating in the growing step, is analyzed and, based on the analysis result, the concentration of the crystallization accelerator in the first crystallization accelerator coating solution, which is applied to an inner surface of a new quartz glass crucible used in a subsequent growing step of a silicon single crystal, is adjusted. Accordingly, the crystallization state of the inner surface of the crucible used can be evaluated and used as feedback for the quality of a subsequent quartz glass crucible, thereby increasing the crucible's durability and reliability.

[0049] In the process for producing a silicon single crystal according to the present invention, it is preferred that the crystallization state of the outer crystal layer, formed by heating in the growing step, is analyzed and, based on the analysis result, the concentration of the crystallization accelerator in the second crystallization accelerator coating solution, which is applied to an outer surface of a new quartz glass crucible used in a subsequent growing step of a silicon single crystal, is adjusted. Accordingly, the crystallization state of the crucible's outer surface can be evaluated and used as feedback for the quality of a subsequent quartz glass crucible, thereby increasing the crucible's durability and reliability. [Effects of the invention]

[0050] According to the present invention, it is possible to provide a quartz glass crucible capable of withstanding a single crystal growth step carried out over a very long period of time, such as multiple growth, and a manufacturing method for this. According to the present invention, it is possible to provide a method for producing a silicon single crystal using the quartz glass crucible. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig. Figure 1 is a schematic cross-sectional view illustrating the structure of a quartz glass crucible according to a first embodiment of the present invention. [ Fig. 2] Fig. Figure 2 is a schematic cross-sectional view illustrating the structure of the quartz glass crucible in a state where the surface has crystallized by heating. [ Fig. 3] Fig.Figures 3(a) to (c) are schematic views to illustrate a crystallization mechanism of the surface layer section of the crucible by a crystallization accelerator. [ Fig. 4] Fig. Figure 4 shows diagrams that show measurement results of the surface layer section of the crucible by a surface X-ray diffraction method, wherein Fig. 4 (a), Fig. 4 (b) and Fig. 4 (c) Show crystal layers in a random orientation, in a dome-like orientation or in a column-like orientation. [ Fig. 5] Fig. Figure 5 is a table showing the corresponding crystal structures of an inner crystal layer 14A and an outer crystal layer 14B for each part. [ Fig. 6] Fig. Figure 6 is a flowchart to explain a process for producing a silicon single crystal using the quartz glass crucible 1 according to the embodiment. [ Fig. 7] Fig. 7 (a) is an image showing SEM observation results, and Fig. 7 (b) is a diagram showing the relationship between the heating time of a quartz glass plate and the thickness of a crystal layer formed on the surface layer section of the quartz glass plate. [ Fig. 8] Fig. Figure 8 shows evaluation results of crystallization states and deformation using a quartz glass crucible onto which a barium-containing coating solution is applied, in an actual crystal-pulling step and shows SEM images and an X-ray diffraction spectrum diagram of the crystal layer of each of the crucible samples No. 1 to 3. [ Fig. 9] Fig. Figure 9 is a schematic view to illustrate one step of the growing of a silicon single crystal by the CZ process. [ Fig. 10] Fig.Figure 10 is a schematic cross-sectional view illustrating the structure of a quartz glass crucible according to a second embodiment of the present invention. [ Fig. 11] Fig. Figure 11 is a schematic view illustrating a method for forming a coating film 13B containing a crystallization accelerator on the outer surface of the in Fig. 10 illustrated quartz glass crucibles 2. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0051] Preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0052] Fig. Figure 1 is a schematic cross-sectional view illustrating the structure of a quartz glass crucible 1 according to a first embodiment of the present invention.

[0053] As in Fig.As illustrated in Figure 1, a quartz glass crucible 1 is a cylindrical container with a bottom for receiving a silicon melt, and comprises a straight main part 1a with a cylindrical shape, a lower part 1b which is slightly curved, and a corner part 1c which has a greater curvature than the lower part 1b and connects the straight main part 1a to the lower part 1b.

[0054] The diameter D (opening) of the quartz glass crucible 1 is 24 inches (about 600 mm) or more, and preferably 32 inches (about 800 mm) or more. This is because such a crucible, which has a large opening, is used for drawing up a large-format silicon single-crystal block with a diameter of 300 mm or more, and it is necessary that it be less likely to deform, even when used for extended periods. In recent years, with the increasing size of crucibles due to the increasing size of silicon single crystals and the increasing time required for a single drawing step, the thermal environment of the crucible is becoming harsher, and improving the durability of a large crucible is a crucial consideration.Although the thickness of the crucible varies somewhat depending on the crucible part, the thickness of the straight main part 1a of a crucible of 24 inch or more is preferably 8 mm or more, the thickness of the straight main part 1a of a large crucible of 32 inch or more is preferably 10 mm or more, and the thickness of the straight main part 1a of a large crucible of 40 inch (about 1000 mm) or more is preferably 13 mm or more.

[0055] The quartz glass crucible 1 has a two-layer structure and includes an opaque layer 11 (bubble layer) made of quartz glass and containing a high number of tiny bubbles, and a transparent layer 12 (bubble-free layer) made of quartz glass and containing essentially no bubbles.

[0056] The opaque layer 11 is provided to heat the silicon melt in the crucible as uniformly as possible without radiant heat from a heating element of a single-crystal puller being transferred through the crucible wall. Therefore, the opaque layer 11 is provided throughout the crucible and extends from the straight body section 1a to the bottom section 1b of the crucible. The thickness of the opaque layer 11 is a value obtained by subtracting the thickness of the transparent layer 12 from the thickness of the crucible wall and varies depending on the part of the crucible.

[0057] The bubble content rate in the quartz glass forming the opaque layer 11 is 0.8% or more, and preferably 1 to 5%. The bubble content rate of the opaque layer 11 can be obtained by measuring the relative density (Archimedes' method). If an opaque quartz glass sample of one unit volume (1 cm³) 3) is cut from a crucible and its mass is designated as A, and the relative density of the quartz glass containing no bubbles (pure density of the quartz glass) is B = 2.2 g / cm³ 3 The bubble content rate P (%) is denoted as: P = (B - A) / B × 100.

[0058] The transparent layer 12 is a layer forming the inner surface of the crucible wall, which is in contact with the silicon melt. It must be highly pure to prevent contamination of the silicon melt and is provided to prevent the dislocation of a single crystal due to crucible fragments or the like when bubbles burst. The thickness of the transparent layer 12 is preferably 0.5 to 10 mm and is determined accordingly for each part of the crucible to prevent the opaque layer 11 from being exposed due to the complete removal of the transparent layer 12 by erosion during a single-crystal pulling step. Similar to the opaque layer 11, it is preferably that the transparent layer 12 extends over the entire crucible from the straight body section 1a to the bottom section 1b of the crucible.However, in the upper end section (edge ​​section) of the crucible, which is not in contact with the silicon melt, it is also possible to omit the formation of the transparent layer 12.

[0059] "Essentially free of bubbles" with respect to the transparent layer 12 means a bubble content rate at which the single-crystal integrity is not reduced by crucible fragments when bubbles burst, and means that the bubble content rate is 0.8% or less and the mean diameter of the bubbles is 100 µm or less. A change in the bubble content rate at the boundary between the opaque layer 11 and the transparent layer 12 is abrupt, and the boundary between the two is visible to the naked eye.

[0060] The bubble content of the transparent layer 12 can be measured non-destructively using optical detection means. The optical detection means include a light-receiving device that captures the reflected light from the light irradiating the inner surface of a crucible under inspection. A light-emitting device for irradiation can be integrated or an external light-emitting device can also be used. Additionally, the optical detection means is preferably one that can be rotated along the inner surface of the quartz glass crucible. X-rays, laser light, and the like, as well as visible light, ultraviolet light, and infrared light, can be used as irradiation light, provided that the light can be reflected for bubble detection.The light-receiving device is selected according to the type of irradiated light and, for example, an optical camera which includes a light-receiving lens and an image-generating unit can be used.

[0061] Measurement results from the optical detection means are received by an image processing device to calculate the bubble content rate. Specifically, an image of the crucible's inner surface is captured using the optical camera. The inner surface of the crucible is divided into predetermined areas as reference areas S1. An area S2 occupied by bubbles is obtained for each reference area S1, and the bubble content rate P (%) is calculated as P = (S2 / S1) × 100. To detect bubbles located at a constant depth from the surface of the quartz glass, the focal point of a light-gathering lens can be scanned in a depth direction from the surface. Multiple images are captured in this way, and the bubble content rate in a given area can be determined based on the bubble content rate of each image.

[0062] The quartz glass crucible 1 according to the embodiment comprises a crucible body 10 made of quartz glass and coating films 13A and 13B containing first and second crystallization accelerators, respectively, which are formed on an inner surface 10a and an outer surface 10b of the crucible body 10. Such coating films play a role in accelerating the crystallization of the surface layer section of the crucible body 10 by heating in a step of growing a silicon single crystal. Typically, the inner surface 10a of the crucible body 10 serves as the surface of the transparent layer 12, the outer surface 10b serves as the surface of the opaque layer 11, and the coating film 13A containing the first crystallization accelerator and the coating film 13B containing the second crystallization accelerator are formed on the transparent layer 12 and the opaque layer 11, respectively.The coating films 13A and 13B containing crystallization accelerators contain a water-soluble polymer that acts as a thickening agent, forming a hard film on the surface of the crucible body 10.

[0063] The thickness of the coating films 13A and 13B containing crystallization accelerators is preferably 0.3 to 100 µm. Accordingly, the concentration of barium applied thereto is controlled by changing the thickness of the coating films 13A and 13B containing the crystallization accelerators. It should be noted that elements that can act as crystallization accelerators are not intentionally added to the crucible body 10 made of quartz glass, and, for example, in a case where the crucible body 10 is formed from natural quartz powder, it is preferred that the concentration of barium be less than 0.10 ppm, the concentration of magnesium be less than 0.10 ppm, and the concentration of calcium be less than 2.0 ppm.In the case of using synthetic quartz powder as the constituent raw material of the inner surface of the crucible body 10, it is preferred that the concentrations of both magnesium and calcium contained in the crucible body 10 are less than 0.02 ppm.

[0064] The crystallization accelerator contained in the coating films 13A and 13B is barium. Barium is particularly preferred because it has a low segregation coefficient on silicon, does not weaken the crystallization rate during crystallization, and, compared to other elements, induces the strongest alignment growth. The coating films 13A and 13B containing the crystallization accelerator can be formed by applying a barium-containing coating solution to the wall surface of the crucible.

[0065] The barium-containing coating solution can be a coating solution containing a barium compound and water, or a coating solution containing anhydrous ethanol and a barium compound instead of water. Examples of barium compounds include barium carbonate, barium chloride, barium acetate, barium nitrate, barium hydroxide, barium oxalate, and barium sulfate. It should be noted that if the surface concentration (atoms / cm²) 2 The crystallization-accelerating effect of barium is the same regardless of whether it is insoluble or water-soluble. However, since water-insoluble barium is less likely to be absorbed into the human body, it is highly safe and advantageous in terms of handling.

[0066] The barium-containing coating solution also contains a highly viscous, water-soluble polymer (thickener), such as a carboxyvinyl polymer. If a coating solution lacking a thickener is used, the barium's fixation to the wall surface is unstable, necessitating heat treatment. When such heat treatment is performed, barium diffuses and penetrates the quartz glass, accelerating random crystal growth, as described later. However, the viscosity of the coating solution increases when a solution containing a thickener is used along with the barium, preventing the solution from flowing unevenly due to gravity when applied to the crucible.Regarding barium compounds such as barium carbonate, in cases where the coating solution contains the water-soluble polymer, the barium compound is not held together in the coating solution but diffuses, allowing it to be applied uniformly to the surface of the crucible. This enables barium to be fixed uniformly and densely to the crucible wall at a high concentration, thereby accelerating the growth of crystal grains in a columnar or dome-like orientation.

[0067] Examples of thickening agents include water-soluble polymers containing a small amount of metallic impurities, such as polyvinyl alcohol, a cellulose thickener, high-purity glucomannan, an acrylic polymer, a carboxyvinyl polymer, and a polyethylene glycol fatty acid ester. Additionally, an acrylic acid-alkyl methacrylate copolymer, polyacrylate, polyvinyl carboxylamide, vinyl carboxylamide, or the like may also be used as thickening agents. The viscosity of the barium-containing coating solution is preferably in the range of 100 to 10,000 mPa·s, and the boiling point of the solvent is preferably 50 to 100 °C.

[0068] For example, a crystallization accelerator coating solution for coating the outer surface of a 32-inch crucible contains 0.0012 g / ml barium carbonate and 0.0008 g / ml of a carboxyvinyl polymer and can be prepared by adjusting the ratio between ethanol and pure water and mixing and stirring the mixture therein.

[0069] The crystallization accelerator coating solution can be applied to the crucible surface using a brush or sprayer. After application, water and other substances evaporate, and the thickening agent forms a hard film. It should be noted that in a prior art process, after applying water or alcohols containing barium carbonate, the crucible is heated to 200–300 °C to suppress delamination. Due to the heating, barium diffuses inwards across the surface, simultaneously generating crystal nuclei and resulting in random crystal growth. Therefore, the coating film should not be heated after application before being drawn up.

[0070] Fig.Figure 2 is a schematic cross-sectional view illustrating the structure of the quartz glass crucible 1 in a state in which the surface has crystallized by heating.

[0071] As in Fig.As illustrated in Figure 2, the surface of the quartz glass crucible, onto which the crystallization accelerator is applied, is heated during the step of growing a silicon single crystal, thus accelerating the crystallization of the quartz glass. This results in the formation of an inner crystal layer 14A and an outer crystal layer 14B on the inner surface 10a and outer surface 10b, respectively, of the crucible body 10. Heating during the step of growing a silicon single crystal is also carried out for several tens of hours or longer at a temperature close to the melting point of silicon (approximately 1400 °C) or higher.However, the formation of the crystal layer on the surface layer section of the crucible body 10 can also be evaluated by actually carrying out the step of growing a silicon single crystal by performing a heat treatment at a temperature equal to or higher than 1400 °C and equal to or lower than the softening point of silica for 1.5 hours or longer.

[0072] It is preferred that the crystallization state of the inner crystal layer 14A comprises a single layer of a dome-shaped crystal layer or a two-layer structure of a dome-shaped crystal layer and a columnar crystal layer (hereinafter referred to as the dome-shaped / columnar crystal layer). Specifically, in a case where the crucible's service life is very long, the inner crystal layer 14A is preferably a dome-shaped / columnar crystal layer, and in a case where the crucible's service life is relatively short, the inner crystal layer 14A may have a single-layer structure consisting solely of a dome-shaped crystal layer.Here, the dome-shaped crystal layer refers to a crystal layer consisting of an aggregate of dome-shaped crystal grains, and the columnar crystal layer refers to a crystal layer consisting of an aggregate of columnar crystal grains.

[0073] The thickness of the inner crystal layer 14A, capable of suppressing crucible deformation, is 200 µm or more, and specifically 400 µm or more. The inner crystal layer 14A, which is in contact with the silicon melt during the pulling of a single crystal, is gradually eroded. However, since the columnar crystal layer grows gradually, it is also possible to maintain the thickness of the inner crystal layer 14A at 400 µm or more. Furthermore, the degree of thickness of the inner crystal layer 14A at which crucible deformation can be suppressed can be easily evaluated by a so-called beam bending test using a quartz glass crucible section with a crystal layer formed within it.

[0074] The crystallization state of the outer crystal layer 14B preferably exhibits a single-layer structure of the dome-shaped crystal layer. Although described in detail later, this is because crystal growth continues in the dome-shaped / columnar crystal layer, thus increasing the thickness of the outer crystal layer 14B, and deformation and delamination are likely to occur at the interface between the crystal layer and the quartz glass layer. However, in a case where the crucible's service life is relatively short and the outer crystal layer does not become excessively thick, the outer crystal layer 14B may exhibit a structure consisting of the dome-shaped / columnar crystal layer.

[0075] As described above, since the inner surface of the crucible is covered with the crystal layer, erosion of the crucible can be suppressed and dislocation of the silicon single crystal due to crystal grain delamination is prevented. Furthermore, since the outer surface of the crucible is crystallized, the crucible's strength can be increased and deformation of the crucible, such as bulging or inward collapse, can be suppressed.

[0076] Fig. Figures 3 (a) to (c) are schematic views to illustrate a crystallization mechanism of the surface layer section of the crucible by the crystallization accelerator.

[0077] As in Fig. 3(a) illustrates a case in which barium (Ba) is present as a crystallization accelerator on the surface of the crucible (quartz glass interface) and the concentration of Ba ions (Ba 2+) from ionized barium lower than the concentration of Si ions (Si 4+ The number of crystal nuclei initially formed on the crucible surface is small, resulting in random crystal growth on these nuclei. Here, the Ba ions are trapped at the crystal grain boundaries, thus reducing the amount of Ba ions present at the interface between the quartz glass and the crystal grains, and therefore contributing to crystal growth in the thickness direction of the crucible. Consequently, crystal growth gradually weakens and soon ceases.

[0078] However, as in Fig.Figure 3(b) illustrates that in a case where the concentration of Ba ions is higher than the concentration of Si ions, a large number of crystal nuclei are produced on the surface of the crucible, and crystals grow competitively on these nuclei as origins, forming crystal grains in a dome-like orientation. As crystallization progresses, only crystals in a vertical orientation survive the competition. However, the Ba ions are trapped at the crystal grain boundaries, so the amount of Ba ions present at the interface between the quartz glass and the crystal grains decreases. Consequently, crystal growth gradually weakens and soon ceases. However, if the crystal layer is in a dome-like orientation, it is possible to form a crystal layer that is sufficiently thick than a crystal layer in a random orientation.

[0079] Additionally, in a prior art structure where Ba ions are present in a glass matrix, Ba ions simultaneously generate crystal nuclei. However, the crystals grow randomly, and the amount of Ba ions contributing to crystal growth in the thickness direction decreases. Therefore, the crystal layer cannot be produced thickly. In contrast, as in Fig. As illustrated in Figure 3(b), in a model in which crystal nuclei begin to grow uniformly in the depth direction from the glass surface, there is no compensation by crystals in a vertical orientation, so that a thick crystal layer can be formed.

[0080] Furthermore, as in Fig.As illustrated in Figure 3(c), in a case where the concentration of Ba ions is very high, specifically 50 times or more than the concentration of Si ions on the surface of the quartz glass, countless crystal grains are generated on the surface of the crucible within a short time, and selective crystal growth in a vertical direction occurs rapidly, resulting in the formation of crystal grains in a columnar orientation. As the crystal grains grow, it becomes less likely that Ba ions will be trapped at the crystal grain boundaries, and a decrease in the amount of Ba ions is suppressed, thus preventing a decrease in the crystallization rate.As described above, by allowing Ba ions to be present in high concentrations on the outermost surface of the quartz glass, while simultaneously promoting crystallization towards the interior of the glass, the crystal structure can be changed from a dome-like to a columnar orientation. With the crystal layer in a columnar orientation, crystal growth of the surface layer of the crucible can continue, allowing a crystal layer to form that is thicker than the crystal layer in a dome-like orientation.

[0081] Since the crystal layer on the inner surface of the crucible melts due to the reaction with the molten silicon, it disappears during random growth, where crystallization of the quartz glass ends in an initial heating stage. This is not practical for long-term use. Furthermore, because the thickness of the crystal layer on the outer surface of the crucible also decreases due to the reaction with a carbon susceptor, there are concerns that the outer crystal layer will disappear during random growth, where crystallization ends in an initial heating stage. However, the crystal growth time can be increased in the case of dome-shaped growth, and the thickness of the crystal layer can be adequately ensured.In addition, the crystal growth time can be further increased in the case of columnar growth, and continuous crystal growth can be achieved.

[0082] The crystallization state of the surface layer section of the crucible can be observed using a SEM (scanning electron microscope), but can also be evaluated by a surface X-ray diffraction method.

[0083] Fig. Figure 4 shows diagrams that show measurement results of the surface layer section of the crucible by the surface X-ray diffraction method, wherein Fig. 4 (a), Fig. 4 (b) and Fig. 4 (c) Show crystal layers in a random orientation, in a dome-like orientation or in a column-like orientation.

[0084] In a case where the crystal layer is in a random orientation, as in Fig.As illustrated in Figure 4(a), the maximum value A of the peak intensity (Counts) at a diffraction angle 2θ of 20° to 25°, caused by a crystal orientation (100), is very high, and the maximum value B of the peak intensity at a diffraction angle 2θ of 33° to 40°, caused by a crystal orientation (200), is very low, and the peak intensity ratio A / B becomes greater than 7.

[0085] In contrast, in a case where the crystal layer is in a dome-like orientation, as in Fig. Figure 4(b) illustrates the difference between the maximum value A of the peak intensity at a diffraction angle 2θ of 20° to 25° and the maximum value B of the peak intensity at a diffraction angle 2θ of 33° to 40°, and the peak intensity ratio A / B becomes 0.4 or more and 7 or less.

[0086] Furthermore, in a case where the crystal layer is in a columnar orientation, as in Fig.Figure 4(c) illustrates that the maximum value A of the peak intensity at a diffraction angle 2θ of 20° to 25° is very low and the maximum value B of the peak intensity at a diffraction angle 2θ of 33° to 40° is very high, and the peak intensity ratio A / B becomes less than 0.4.

[0087] Fig. Figure 5 is a table showing the corresponding crystal structures of the inner crystal layer 14A and the outer crystal layer 14B for each part, where a preferred crystal structure for each part is indicated by “B” and an even more preferred crystal structure is indicated by “A”.

[0088] As in Fig.As shown in Figure 5, it can be ensured that the entire inner surface 10a of the crucible body 10, from the straight body section (W section) 1a to the bottom section (B section) 1b, exhibits a dome-shaped / columnar crystal layer (A / B is less than 0.4). Additionally, it can be ensured that only the corner section (R section) 1c and the bottom section 1b exhibit a dome-shaped / columnar crystal layer, while the inner surface of the straight body section 1a also exhibits a dome-shaped crystal layer (A / B is equal to or greater than 0.3 and less than 7). This is because the inner surface of the straight body section 1a has a shorter contact time with the silicon melt than that of the corner section 1c or the bottom section 1b, and this contact time is sufficient to form a dome-shaped crystal layer.In a case where the crystal growth time is relatively short, it is also preferred to assume the condition that the inner surface of the straight body section 1a of the crucible body 10 becomes a dome-shaped crystal layer. The thickness of the coating film 13A containing the crystallization accelerator in the straight body section 1a can be reduced, thus reducing the incorporation of impurities contained in the coating film into the silicon melt.

[0089] Regarding the outer surface 10b of the crucible body 10, the entire outer surface from the straight body section 1a to the bottom section 1b can have a dome-shaped / columnar crystal layer or a dome-shaped crystal layer, regardless of the part of the crucible, but a dome-shaped crystal layer is particularly preferred. This is because, although the strength of the crucible can be increased by allowing the outer crystal layer 14B to have a certain thickness, as the thickness of the outer crystal layer 14B increases, bubbles in a bubble layer of the crystallized quartz glass adhere to one another and expand, resulting in easy deformation of the crucible or delamination of the crystal layer. Delamination of the outer crystal layer 14B occurs particularly easily when the thickness of the outer crystal layer 14B becomes 1.5 mm or more.Therefore, it is preferred that the crystal growth rate of the outer crystal layer 14B decreases as its crystal growth progresses, and it is preferred that the thickness of the outer crystal layer 14B is suppressed to be less than 1.5 mm.

[0090] It is preferred that the coating solution used to form the coating films 13A and 13B containing crystallization accelerators is used in an actual quartz glass crucible after a crystallization state test has been performed beforehand on a base material such as a quartz glass plate. In the crystallization state test, after a coating solution containing crystallization accelerators has been applied to the surface of the quartz glass base material at a predetermined concentration, an evaluation heat treatment at 1400 °C or higher is carried out to form a crystalline layer on a surface layer section of the surface of the quartz glass base material.Next, the crystallization state of the surface of the quartz glass base material is analyzed using X-ray diffraction, and the concentration of the crystallization accelerator in the crystallization accelerator coating solution is adjusted based on the analysis result. Then, after adjusting the concentration, the crystallization accelerator coating solution is applied to the surface of the quartz glass crucible (the crucible body 10), thus completing the quartz glass crucible 1. As described above, a desired crystallization state can be reliably reproduced regardless of minor variations in conditions such as the concentration, composition, coating conditions, and the like of the crystallization accelerator coating solution, enabling the production of a quartz glass crucible with high reliability.

[0091] Fig.Figure 6 is a flowchart to explain a process for producing a silicon single crystal using the quartz glass crucible 1 according to the embodiment.

[0092] As in Fig. As illustrated in Figure 6, the production of a silicon single crystal according to the embodiment uses a quartz glass crucible in which the coating films 13A and 13B containing the first and second crystallization accelerators are formed. Thus, a quartz glass crucible (crucible body 10) is produced onto which the crystallization accelerator is not applied (uncoated), and barium compound coating solutions with appropriate concentrations are applied to its inner surface and outer surface, respectively (step S11).

[0093] Next, a step of growing a silicon single crystal is carried out using the quartz glass crucible 1 in which the coating films 13A and 13B containing the first and second crystallization accelerators are formed (step S12). The growing step can be multiple growing, in which a plurality of silicon single crystals are grown from the same crucible, or single growing, in which only a single silicon single crystal is grown.

[0094] Fig. Figure 9 is a schematic view to illustrate the step of growing a silicon single crystal using the CZ process.

[0095] As in Fig.Figure 9 illustrates that a single-crystal growing device 20 is used in the step of growing a silicon single crystal by the CZ process.The single-crystal growing device 20 comprises a water-cooled chamber 21, a quartz crucible 1 holding a silicon melt 4 in the chamber 21, a carbon susceptor 22 holding the quartz crucible 1, a rotating shaft 23 supporting the carbon susceptor 22, a shaft drive mechanism 24 rotating and raising / lowering the rotating shaft 23, a heating element 25 located in the vicinity of the carbon susceptor 22, a thermal insulation material 26 located outside the heating element 25 along the inner surface of the chamber 21, a heat shield body 27 located above the quartz crucible 1, a crystal growing wire 28 located above the quartz crucible 1 coaxially with the rotating shaft 23, and a wire winding mechanism 29 located in the upper section of the chamber 21.

[0096] Chamber 21 consists of a main chamber 21a and an elongated cylindrical drawing chamber 21b, which is connected to an upper opening of the main chamber 21a. The quartz glass crucible 1, the carbon susceptor 22, the heating element 25, and the heat shield body 27 are provided in the main chamber 21a. A gas inlet channel 21c for introducing inert gas (purge gas), such as argon or doping gas, into chamber 21 is provided in the upper section of the drawing chamber 21b, and a gas outlet channel 21d for venting atmospheric gas from chamber 21 is provided in the lower section of the main chamber 21a. Additionally, a viewing window 21e is provided at the upper section of the main chamber 21a to allow observation of the growth of a silicon single crystal 3.

[0097] The carbon susceptor 22 is used to maintain the shape of the quartz glass crucible 1, which is softened by heating, and holds and surrounds the quartz glass crucible 1 by coming into close contact with its outer surface. The quartz glass crucible 1 and the carbon susceptor 22 form a double-structure quartz glass crucible that carries the silicon melt 4 in chamber 21.

[0098] The carbon susceptor 22 is fixed to the upper end section of the rotating shaft 23, and the lower end section of the rotating shaft 23 passes through the bottom section of the chamber 21 and is connected to the shaft drive mechanism 24, which is located outside the chamber 21. The rotating shaft 23 and the shaft drive mechanism 24 constitute a rotation mechanism and a lifting / lowering mechanism for the quartz glass crucible 1 and the carbon susceptor 22.

[0099] The heating element 25 is used to generate the silicon melt 4 by melting a silicon raw material with which the quartz glass crucible 1 is filled, and to maintain the molten state of the silicon melt 4. The heating element 25 is a carbon heating element of a resistance heating type and is positioned to surround the quartz glass crucible 1 within the carbon susceptor 22. Furthermore, the thermal insulation material 26 is positioned outside the heating element 25 to surround it, thereby improving the thermal insulation within the chamber 21.

[0100] The heat shield 27 is provided to form a suitable hot zone in the vicinity of the crystal growth interface by suppressing temperature fluctuations of the silicon melt 4 and to prevent the silicon single crystal 3 from being heated by radiant heat from the heating element 25 and the quartz glass crucible 1. The heat shield 27 is a graphite element that covers the area above the silicon melt 4, excluding the pull-up path of the silicon single crystal 3, and has, for example, the shape of an inverted truncated cone with an opening that increases in size from the bottom to the top.

[0101] The diameter of an opening 27a at the lower end of the heat shield body 27 is larger than the diameter of the silicon single crystal 3, thus ensuring sufficient clearance for the silicon single crystal 3 to be pulled upwards. The diameter of the opening 27a of the heat shield body 27 is smaller than the opening of the quartz glass crucible 1, and the lower end section of the heat shield body 27 is positioned inside the quartz glass crucible 1. Therefore, the heat shield body 27 does not interfere with the quartz glass crucible 1, even if the upper rim of the quartz glass crucible 1 is raised above the lower end of the heat shield body 27.

[0102] As the amount of melt in the quartz glass crucible 1 decreases with the growth of the silicon single crystal 3, temperature fluctuations in the silicon melt 4 are suppressed by raising the quartz glass crucible 1 to create a gap between the melt surface and the lower end of the heat shield body 27. The amount of dopants evaporating from the silicon melt 4 can be controlled by maintaining a constant flow rate of gas flowing in the vicinity of the melt surface. Thus, the stability of the distribution of crystal defects, the oxygen concentration distribution, the resistivity distribution, and the like can be improved along the pull-up axis of the silicon single crystal 3.

[0103] Above the quartz glass crucible 1, the wire 28, serving as the draw-up axis for the silicon single crystal 3, and the wire winding mechanism 29 for winding the wire 28 are provided. The wire winding mechanism 29 rotates the silicon single crystal 3 together with the wire 28. The wire winding mechanism 29 is attached to the upper section of the draw chamber 21b. The wire 28 extends downwards from the wire winding mechanism 29 through the draw chamber 21b, and the tip end of the wire 28 extends into the interior of the main chamber 21a. Fig. Figure 9 illustrates a state in which the silicon single crystal 3 is suspended on the wire 28 during growth. During the growth of the silicon single crystal 3, the silicon single crystal 3 is grown by gradually pulling up the wire 28 while both the quartz glass crucible 1 and the silicon single crystal 3 are rotated.

[0104] A CCD camera 30 is positioned outside the viewing window 21e. During the single-crystal pull-up process, the CCD camera 30 photographs the boundary between the silicon single crystal 3 and the silicon melt 4, which is viewed obliquely from above through the opening 27a of the heat shield body 27 from the viewing window 21e. The image captured by the CCD camera 30 is processed by an image processing unit 31, and the processing result is used by a controller 32 to control pull-up conditions.

[0105] Although the inner surface of the quartz glass crucible 1 is eroded by the reaction with the silicon melt 4 during the pull-up of a silicon single crystal step, as crystallization of the inner and outer surfaces progresses due to the action of the crystallization accelerator applied to the inner and outer surfaces of the crucible, the crystal layer on the inner surface does not disappear and its thickness can be maintained to a certain extent, thus preserving the crucible's strength and suppressing deformation. This prevents the crucible from deforming and coming into contact with elements in the furnace, such as the heat shield 27, and also prevents variations in the position of the liquid surface of the silicon melt 4 due to changes in the crucible's internal volume.

[0106] If a crystal fragment delaminated from the inner surface of the quartz glass crucible 1 is carried along by the convection current of the silicon melt 4 and reaches a solid-liquid interface, the crystal fragment is incorporated into the silicon single crystal 3, raising concerns about dislocation. However, according to the embodiment, delamination of the crystal fragment from the inner surface of the crucible can be prevented, thus preventing dislocation of a single crystal.

[0107] Next, the surface of the crucible used is analyzed by X-ray diffraction after the completion of the drawing step, and the crystallization state of the crystal layer is evaluated (step S13). As described above, a peak intensity ratio A / B greater than 7 can be evaluated as a crystal layer in random orientation, a peak intensity ratio A / B of 0.4 or greater and 7 or less can be evaluated as a crystal layer in dome-like orientation, and a peak intensity ratio A / B of less than 0.4 can be evaluated as a crystal layer in a column-like orientation.

[0108] Next, the analysis and evaluation results are fed back to adjust the concentration of the barium compound coating solution (step S14). For example, if the outer crystal layer 14B has a columnar orientation and the crystal layer becomes excessively thick, the barium concentration in the barium compound coating solution can be reduced. Conversely, if the inner crystal layer 14A has a dome-like orientation but a columnar orientation is desired, the barium concentration in the barium compound coating solution can be increased.

[0109] The analysis and evaluation results can include the degree of crystal alignment (evaluation results by X-ray diffraction: peak ratio), the thickness of a crystal layer, the thickness gradient, the thickness distribution, the grain size of crystals, the presence or absence of foaming and delamination of the crystal layer, and the like. Additionally, adjustment elements can include the concentration (of each component), the thickness of the coating film (of each component), the formulation of the thickening agent, the particle size of barium carbonate, and the like.As a method for adjusting the elements, due to the fact that the thermal stress varies depending on the part of the crucible and the crystal growing conditions, the growing process is initially carried out by applying barium in a uniform barium concentration regardless of the part of the crucible, the thickness distribution and the like of the crystal layer of the crucible used are analyzed and the above-mentioned elements can be adjusted for each part so that the crystal layer becomes uniform.

[0110] Subsequently, a new uncoated quartz glass crucible is produced, the barium compound coating solution, the concentration of which has been adjusted, is applied to its surface (step S15), and the step of growing a silicon single crystal is carried out again using the quartz glass crucible (step S16). In the growing step carried out as described above, the crystal layer on the surface of the quartz glass crucible 1 is in the optimal crystallization state for each part, so that a crystal layer that is uniform in one plane can be formed without delamination of crystal grains on the inner surface 10a of the crucible body 10, and columnar crystals can be continuously grown, which in turn maintains the strength at all times.In addition, disturbances such as deformation and delamination can be prevented on the outer surface 10b of the crucible body 10, while maintaining a certain strength.

[0111] As described above, in the quartz glass crucible 1 according to the embodiment, the inner crystal layer 14A can have a sufficient thickness because the inner crystal layer 14A, which is formed from the dome-shaped / columnar crystal layer or the dome-shaped crystal layer, is formed on the inner surface 10a of the crucible body 10 by heating during the drawing step. Thus, deformation of this layer can be prevented by increasing the strength of the crucible. In addition, it can be prevented that the inner crystal layer 14A disappears completely due to the erosion of the inner surface of the crucible.

[0112] In a case where the inner crystal layer 14A is the dome-shaped / columnar crystal layer, even if the dome-shaped crystal layer is removed, delamination of the columnar crystal grains can be prevented because the orientation direction of the columnar crystal layer is the thickness direction of the crucible wall. Additionally, by inducing the inner crystal layer 14A to adopt the columnar orientation, crystal growth can be concentrated in the thickness direction of the crucible wall, thus increasing the crystal growth rate.

[0113] In addition, according to the embodiment, the outer crystal layer 14B in the quartz glass crucible 1 can have a sufficient thickness because the outer crystal layer 14B, which is formed from the dome-shaped crystal layer, is formed on the outer surface 10b of the crucible body 10 by heating during the drawing step. Thus, deformation of this layer can be prevented by increasing the strength of the crucible. Furthermore, by forming the dome-shaped crystal layer on the outer surface 10b of the crucible body 10, the crystal grain boundaries can be compacted, thereby preventing cracks caused by impacts and the like from propagating from the outer surface of the crucible to the interior of the crucible.

[0114] In addition, by ensuring that the outer crystal layer 14B exhibits a dome-shaped crystal structure instead of a columnar one, crystal growth is not sustained, thus preventing the outer crystal layer 14B from becoming excessively thick. Therefore, delamination of the crystal layer due to bubble expansion at the interface between a thick crystal layer and quartz glass can be prevented, and furthermore, the formation of cracks propagating from the bubbles along the columnar crystal grain boundaries can be prevented.

[0115] Furthermore, according to the embodiment, the crystallization states of the crystal layers on the surfaces (the inner and outer surfaces) of the crucible can be easily evaluated by X-ray diffraction. Therefore, the coating conditions of the crystallization accelerator can be selected based on the evaluation results, and the quartz glass crucible 1, which has a crystallization state corresponding to the growing conditions of the silicon single crystal and the portion of the crucible, can be produced.

[0116] Fig. Figure 10 is a schematic cross-sectional view illustrating the structure of a quartz glass crucible according to a second embodiment of the present invention.

[0117] As in Fig.Figure 10 illustrates a quartz glass crucible 2 according to the embodiment, in which the coating films 13A and 13B containing crystallization accelerators, which are formed on the inner surface 10a and the outer surface 10b of the crucible body 10 respectively, are not formed in such a way that they reach the upper edge end of the crucible body 10.That is, a band-like region with a predetermined width extending downwards from the upper edge of the inner surface 10a of the crucible body 10 is a crystallization accelerator-uncoated region 15A (hereinafter simply referred to as "uncoated region 15A") in which the crystallization accelerator-containing coating film 13A is not formed, and a band-like region with a predetermined width extending downwards from the upper edge of the outer surface 10b is a crystallization accelerator-uncoated region 15B (hereinafter simply referred to as "uncoated region 15B") in which the crystallization accelerator-containing coating film 13B is not formed.

[0118] In the case where the coating films 13A and 13B containing crystallization accelerators are each configured to reach the upper edge of the inner surface 10a or the outer surface 10b of the crucible body 10, the upper edge section (the inner surface 10a and the outer surface 10b in the vicinity of the upper edge and the surface of the upper edge) crystallizes, and there is concern that particles of small crystal fragments generated from the crystallized area will be incorporated into the silicon melt, leading to a reduction in the silicon single crystal yield. However, in a case where the uncoated areas 15A and 15B are provided, crystallization of the upper edge section can be suppressed, and a reduction in the silicon single crystal yield due to the generation of particles of small crystal fragments at the upper edge section can be prevented.

[0119] It is preferred that the uncoated areas 15A and 15B extend downwards from the upper edge end section in a span of 2 mm or more and 40 mm or less. This is because, in a case where the width of the uncoated areas 15A and 15B is less than 2 mm, the effect of providing these uncoated areas is insufficient. Furthermore, in a case where the width of the uncoated areas 15A and 15B is greater than 40 mm, the boundary between the coating film containing the crystallization accelerator and the uncoated area may be located in the silicon melt. If the boundary between the crystal layer and the glass layer is immersed in the silicon melt, there is a greater likelihood that stress concentration at the boundary will induce cracks and generate particles of small crystal fragments.

[0120] As in Fig. As illustrated in Figure 9, the quartz glass crucible 1 is housed within the carbon susceptor 22 during the crystal-pulling step. The upper rim section of the quartz glass crucible 1 projects upwards from the upper end of the carbon susceptor 22 and is therefore always in a self-supporting state, without being held by the carbon susceptor 22. It is preferred that the uncoated areas 15A and 15B are provided in a region projecting upwards from the upper end of the carbon susceptor 22. As described above, by ensuring that the upper rim section of the quartz glass crucible 1, which is not in contact with the carbon susceptor 22, is the uncoated region, the yield of the silicon single crystal can be improved, and crucible deformation due to foaming and crystal layer delamination can be prevented.

[0121] It is preferred that the width of the uncoated areas 15A and 15B ranges from 0.02 to 0.1 times the length of the straight body section 1a of the crucible. This is because, if the width of the uncoated areas 15A and 15B is less than 0.02 times the length of the straight body section 1a of the crucible, the effect of providing the uncoated areas 15A and 15B is insufficient. In addition, in a case where the width of the uncoated areas 15A and 15B is greater than 0.1 times the length of the straight body section 1a of the crucible, the uncoated area is designed to reach the area held by the carbon susceptor 22, taking into account concerns about deformation of the crucible due to foaming and delamination of the crystal layer or deterioration of the yield of the silicon single crystal.

[0122] Fig.Figure 11 is a schematic view illustrating an example of a method for forming the uncoated region 15B together with the coating film 13B containing the crystallization accelerator on the outer surface of the in Fig. 10 illustrated quartz glass crucibles 2.

[0123] As in Fig. As illustrated in Figure 11, in one case of forming the coating film 13B containing the crystallization accelerator on the outer surface 10b of the crucible body 10, the coating film 13B containing the crystallization accelerator can be formed by a spraying process. In this case, where the uncoated area 15B is provided at the upper edge end section, a polyethylene film (PE film) 41 is first applied to an opening 10d of the crucible body 10 to cover the opening 10d. The PE film 41 at the entrance of the opening 10d is fixed by a polypropylene band (PP band) 42 to close the opening 10d.

[0124] As illustrated, the opening 10d of the crucible body 10 is then placed on a rotating platform 40 in a downward-facing state, and in a state in which an end section 41e of the PE film 41, which extends outwards from the fixing position of the PP band 42, is fixed to the surface of the outer circumference of the rotating platform 40 by a rubber band 43.

[0125] After masking the area with a predetermined width (2 to 40 mm) extending downwards from the upper edge of the outer surface 10b of the crucible body 10 with the PE film 41 and the PP tape 42, a coating solution containing a crystallization accelerator is applied to the entire outer surface 10b of the crucible body 10 using a spray device 45, whereby the coating film 13B containing the crystallization accelerator and the uncoated area 15B in the vicinity of the upper edge of the outer surface 10b of the crucible body 10 can be formed.

[0126] The above description is an example of the method for forming the uncoated area 15B together with the coating film 13B containing the crystallization accelerator on the outer surface of the quartz glass crucible 2, and the same can also be applied in a case where the uncoated area 15A together with the coating film 13A containing the crystallization accelerator is formed on the inner surface of the quartz glass crucible 2. That is, the crystallization accelerator coating solution can be applied by spraying in a state where an area of ​​a predetermined width, extending downwards from the upper edge of the inner surface 10a of the quartz glass crucible 10, is masked.

[0127] As described above, due to the fact that the quartz glass crucible 2 according to the embodiment is provided with the crystallization accelerator-uncoated areas 15A and 15B on the inner surface 10a and the outer surface 10b of the upper edge end section of the crucible body 10, in addition to the effect of the invention by the first embodiment, it is possible to prevent a reduction in the yield of the silicon single crystal due to the generation of particles of small crystal parts at the upper edge end section.

[0128] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can be modified in various ways without deviating from the scope of protection of the present invention. Accordingly, all such modifications are included in the present invention.

[0129] For example, the coating films 13A and 13B containing crystallization accelerators do not necessarily have to be formed on both the inner surface 10a and the outer surface 10b of the crucible body 10, but can be formed only on the inner surface 10a or only on the outer surface 10b. However, since the inner surface 10a of the crucible is in contact with the silicon melt and has a large degree of erosion, the effect of its crystallization is greater than that of the outer surface 10b of the crucible, and it is more important to form a crystal layer on the inner surface than on the outer surface of the crucible.

[0130] In addition, in the embodiment the inner crystal layer 14A can have a single-layer structure of a dome-shaped crystal layer and the outer crystal layer 14B can have a random crystal layer or a dome-shaped crystal layer.

[0131] In addition, the embodiment provides an example of a case in which the crystallization state of the crucible used in the current crystal growth step is fed back to the crucible used in the subsequent growth step. However, the present invention is not limited to such a case. Thus, for example, the conditions of a simulation test with a quartz piece can be determined based on predetermined crystal growth conditions, evaluation of the quartz piece can be carried out under these conditions, and coating conditions can be determined based on the evaluation results.This means that the crystallization state of the crystal layer formed on the surface layer of the quartz piece by heating during the simulation test replicating the crystal growing step can be analyzed, and based on the analysis results, the concentration of the crystallization accelerator in the crystallization accelerator coating solution applied to the inner surface of the quartz glass crucible used in an actual silicon single crystal growing step can be adjusted.

[0132] In addition, as a method for applying the crystallization accelerator coating solution to the surface of the crucible, in addition to a method using a brush, a spray type, dip type, curtain coating or the like can also be used. [Example]

[0133] The effect of the barium compound coating solution concentration on the crystallization state of the crystal layer was evaluated. In this evaluation test, an aqueous solution with a reference concentration of 50 g / L polyvinyl alcohol (thickener) dissolved in barium acetate (0.02 M metal ions) was first prepared. Six types of coating solutions were then prepared in which the concentration of barium acetate in the aqueous solution was adjusted to 0.01, 0.031, 0.063, 0.125, 0.5, and 2 times the reference concentration. Next, 12 quartz glass plates were prepared, and a set of two plates was immersed in each of the six coating solutions after adjusting the concentration.

[0134] Next, the barium concentration on the surface of the quartz glass plate was determined. To calculate the barium concentration, the number of moles of barium was obtained from the weight of the aqueous barium acetate solution, which was reduced by immersing the quartz glass plate. The number of atoms of barium was calculated from the number of moles of barium and Avogadro's constant. Finally, the barium concentration was obtained from the number of atoms of barium and the surface area of ​​the quartz glass plate onto which the aqueous barium acetate solution was applied.

[0135] Next, the 12 quartz glass plates were heated to 1450 °C in a test oven. The heating time was set to 30 minutes for one of the two quartz glass plates, onto which the same aqueous solution was applied, and to 90 minutes for the other.

[0136] Next, the crystallization state of the surface layer section of the 12 quartz glass plates was observed after heat treatment using a SEM (scanning electron microscope). Furthermore, the surfaces of the 12 quartz glass plates that had undergone heat treatment with coating solutions at concentrations of 0.031, 0.125, 0.5, and 2 times the standard concentration for 90 minutes were analyzed using X-ray diffraction, and the peak intensity ratio A / B was determined. The evaluation of the quartz glass plates by the X-ray diffraction method was carried out using an X-ray diffractometer RINT 2500, manufactured by Rigaku Corporation, with the following parameters: Cu (λ = 1.5418 nm), scan axis: 2θ, measurement method: continuous, 2θ angle scan range: 10° to 70°, light-receiving slit: 0.15 mm, divergence slit: 1°, scattering slit: 1°, scanning width: 0.02°, and scan speed: 10° / min.The depth (detection depth) of the surface evaluated using X-rays varied depending on the angle of incidence of the X-rays and was set to several nanometers to several tens of micrometers.

[0137] Table 1 is a list of evaluation test results of the quartz glass plates. [Table 1] Quartz glass plate sample Coating solution concentration ratio Surface concentration (atoms / cm²) 2 ) Crystal alignment Crystal growth rate 30 → 90 min X-ray diffraction peak intensity ratio A1 ×0,01 7,8E14 Randomly A2 ×0,031 2,4E15 Randomly 0 µm / h 8 A3 ×0,063 4,9E15 dome-shaped A4 ×0,125 9,7E15 dome-shaped 150 µm / h 0,64 A5 ×0,5 3,9E16 Column-like 450 µm / h 0,16 A6 ×2 1,6E17 Column-like 450 µm / h

[0138] As shown in Table 1, the barium concentration on the surface (surface barium concentration) of a quartz glass plate sample A1, onto which the aqueous barium acetate solution was applied at a concentration ratio of 0.01 times the reference concentration, was 7.8×10 14 atoms / cm² 2 , and the barium concentration on the surface of a quartz glass plate sample A2, onto which the aqueous barium acetate solution was applied at a 0.031-fold concentration ratio, was 2.4×10 15 atoms / cm² 2, so that both exhibited cristobalite crystal growth in a random orientation.

[0139] The barium concentration on the surface of a quartz glass plate sample A3, onto which the aqueous barium acetate solution was applied at a concentration ratio of 0.063 times, was 4.9×10 15 atoms / cm² 2 , and the barium concentration on the surface of a quartz glass plate sample A4, onto which the aqueous barium acetate solution was applied at a concentration ratio of 0.125, was 9.7×10 15 atoms / cm² 2 , so that both exhibited crystal growth of cristobalite in a dome-like orientation.

[0140] In addition, the barium concentration on the surface of a quartz glass plate sample A5, onto which the aqueous barium acetate solution was applied at a concentration ratio of 0.5, was 3.9 × 10 16 atoms / cm² 2, and the barium concentration on the surface of a quartz glass plate sample A6, onto which the aqueous barium acetate solution was applied at a concentration ratio of 2, was 1.6×10 17 atoms / cm² 2 , so that both exhibited crystal growth of cristobalite in a columnar orientation.

[0141] Fig. Figure 7(a) is an image showing the observation results of the crystal layers by SEM. In addition, Fig. 7(b) a diagram showing the relationship between the heating time of the quartz glass plate and the thickness of the crystal layer formed on the surface layer section of the quartz glass plate, where the horizontal axis represents the heating time and the vertical axis represents the thickness of the crystal layer.

[0142] As in Fig.As shown in Figure 7(b), in a case where the aqueous barium acetate solution, diluted to 0.031 times the reference concentration, was applied to the quartz glass plate, the thickness of the crystal layer after 30 minutes from the start of heating was approximately 200 µm and was also approximately 200 µm after 90 minutes, meaning that the crystal layer hardly grew after 30 minutes from the start of heating. That is, the crystal growth rate after 30 minutes from the start of heating was approximately 0 µm / h. In addition, as shown in Fig. As shown in Figure 7(a), the crystal layer from the SEM image exhibited crystal growth of cristobalite in a random orientation. Furthermore, the crystal structure of the crystal layer was analyzed by X-ray diffraction and showed a peak pattern as shown in Figure 7(a). Fig. 4(a) shown, and the peak intensity ratio A / B mentioned above was 8.

[0143] In one case where aqueous barium acetate solution, diluted to 0.125 times the reference concentration, was applied to a quartz glass plate, the thickness of the crystal layer after 30 minutes was approximately 250 µm and after 90 minutes approximately 400 µm, meaning that the crystal growth rate after 30 minutes from the start of heating was approximately 150 µm / h. Additionally, as in Fig. As shown in Figure 7(a), the crystal layer from the SEM image exhibited cristobalite crystal growth in a dome-like orientation. Both the width and length of the dome-shaped crystal grains were approximately 5 to 30 µm. Furthermore, the crystal structure of the crystal layer was analyzed by X-ray diffraction and showed a peak pattern as shown in Figure 7(a). Fig. 4(b) shown, and the peak intensity ratio A / B mentioned above was 0.64.

[0144] In one case where the aqueous barium acetate solution, diluted to 0.5 times the reference concentration, was applied to the quartz glass plate, the thickness of the crystal layer after 30 minutes was approximately 190 µm, but after 90 minutes it was approximately 600 µm, meaning that the crystal growth rate after 30 minutes from the start of heating was approximately 450 µm / h. Additionally, as in Fig. As shown in Figure 7(a), the crystal layer in the SEM image changed from a dome-shaped orientation to a columnar orientation. The width of the columnar crystal grains was approximately 10 to 50 µm, and their length was 50 µm or more, mostly about 50 to 100 µm. Furthermore, the crystal structure of the crystal layer was analyzed by X-ray diffraction and showed a peak pattern as shown in Figure 7(a). Fig. 4 (c) shown, and the peak intensity ratio A / B mentioned above was 0.16.

[0145] In one case, where the aqueous barium acetate solution, adjusted to twice the reference concentration, was applied to the quartz glass plate, the same results were obtained as when using an aqueous barium acetate solution adjusted to 0.5 times the reference concentration. In addition, as in Fig. As shown in Figure 7(a), it was found that despite the change in the crystal layer from the SEM image from dome-shaped to column-shaped crystal growth, the dome-shaped crystal growth period was very short and the crystal layer changed from the dome-shaped to the column-shaped orientation at a very early stage.

[0146] From the above results, it was found that the crystallization state of the crystal layer changed from random orientation to dome-shaped and columnar orientation by increasing the concentration of the aqueous barium acetate solution, and that the crystal layer reliably changed from dome-shaped to columnar growth when the concentration was four times or more than the concentration during dome-shaped growth. It can be seen from this that when the crystal layer is in a columnar orientation, the barium concentration on the surface is 3.9 × 10⁻⁶. 16 atoms / cm² 2 or more. It should be noted that the barium concentration on the surface can also be obtained by analysis using fluorescent X-rays or similar methods.

[0147] Next, an evaluation test of the crystallization state and deformation of the crucible surface was performed when the quartz crucible, onto which the barium-containing coating solution had been applied, was used in an actual crystal-growing step. In the crystal-growing step, a silicon single-crystal block approximately 300 mm in diameter was grown using a 32-inch quartz crucible. A barium carbonate coating solution was used as the coating solution applied to the quartz crucible. This solution contained 0.0012 g / ml barium carbonate and 0.0008 g / ml carboxyvinyl polymer, with the ratio of ethanol to pure water adjusted. Application to the crucible surface was performed using a brush.

[0148] In this evaluation test, three types of crucible samples were prepared. Sample No. 1 was obtained by applying the coating solution once to the outer surface of the crucible, Sample No. 2 was obtained by applying the coating solution six times to the inner surface of the crucible, and Sample No. 3 was obtained by applying the coating solution five times to the inner surface of the crucible. After application, water evaporated in approximately 10 minutes and ethanol evaporated in approximately 30 minutes, resulting in the formation of a hard film due to the thickening agent. The barium concentration on the surface of the crucible was determined from the amount of coating solution used.

[0149] Subsequently, silicon single-crystal blocks were pulled up using samples 1 to 3 of the quartz glass crucible by the CZ method. After completion of the pulling step, the shapes of the crucible samples 1 to 3 were optically inspected, and no deformation was observed. The crystallization state of the crucible was evaluated from SEM images of the sections of the crucible samples 1 to 3, and the crystal structure of the crystal layer was further analyzed by X-ray diffraction.

[0150] Table 2 is a table showing the evaluation test results of the quartz glass crucibles. [Table 2] crucible test Coating conditions Surface concentration (atoms / cm²) 2 ) Crystal alignment Crystal layer thickness X-ray diffraction peak intensity ratio Crucible deformation Nr. 1 Exterior surface: once 1,1E16 dome-shaped 360 µm 1,7 No Nr. 2 Inner surface: six times 6,6E16 Column-like 380 µm 0,14 No Nr. 3 Inner surface: five times 5,5E16 Column-like 350 µm 0,23 No

[0151] Fig. Figure 8 is a SEM image and an X-ray diffraction spectrum diagram of the crystal layer of each of the crucible samples No. 1 to No. 3.

[0152] The barium concentration on the outer surface of sample no. 1 of the quartz glass crucible, where the coating solution was applied once to the outer surface of the crucible, was 1.1×10 16 atoms / cm² 2 Crystal growth of cristobalite in a dome-like orientation was confirmed from the SEM image shown in (a). Additionally, the thickness of the outer crystal layer was approximately 360 µm. Furthermore, the X-ray diffraction spectrum of the outer crystal layer exhibited a peak pattern in which the peak intensity B (the right peak at 20° from 33° to 40°) was lower than the peak intensity A (the left peak at 20° from 20° to 25°), as shown in (b), and the aforementioned peak intensity ratio A / B was 1.7.

[0153] In addition, the barium concentration on the inner surface of crucible sample No. 2, where the coating solution was applied six times to the inner surface of the crucible, was 6.6×10 16 atoms / cm² 2The crystal growth of cristobalite in a columnar orientation was confirmed from the SEM image shown in (c). Additionally, the thickness of the inner crystal layer was approximately 380 µm. Furthermore, the X-ray diffraction spectrum of the inner crystal layer exhibited a peak pattern in which the peak intensity B was higher than the peak intensity A, as shown in (d), and the aforementioned peak intensity ratio A / B was 0.14.

[0154] In addition, the barium concentration on the inner surface of crucible sample No. 3, where the coating solution was applied five times to the inner surface of the crucible, was 5.5×10 16 atoms / cm² 2The crystal growth of cristobalite in a columnar orientation was confirmed from the SEM image shown in (e). Additionally, the thickness of the inner crystal layer was approximately 350 µm. Furthermore, the X-ray diffraction spectrum of the inner crystal layer exhibited a peak pattern in which the peak intensity B was higher than the peak intensity A, as shown in (f), and the aforementioned peak intensity ratio A / B was 0.23. [Description of reference symbols] 1, 2 quartz glass crucibles 1a straight body section of the quartz glass crucible 1b Bottom section of the quartz glass crucible 1c Corner section of the quartz glass crucible 3 Silicon single crystal 4 Silicon melt 10 crucible bodies 10a Inner surface of the crucible body 10b Outer surface of the crucible body 10d Opening of the crucible body 11 opaque layers 12 transparent layers 13A first crystallization accelerator containing coating film 13B second crystallization accelerator containing coating film 14A inner crystal layer 14B outer crystal layer 15A Crystallization accelerator - uncoated area 15B Crystallization accelerator - uncoated area 20 single crystal puller 21st Chamber 21a Main Chamber 21b Draw chamber 21c Gas intake channel 21d Gas outlet channel 21e Viewing window 22 Carbon susceptor 23 Rotational shaft 24 Shaft drive mechanism 25 heating element 26 Thermal insulation material 27 heat shield bodies 27a Opening of the heat shield body 28 Crystal drawing wire 29 Wire winding mechanism 30 CCD camera 31 Image processing unit 32 Control 40 rotating platforms 41 polyethylene film (PE film) 41e End section of the polyethylene film 42 Polypropylene tape (PP tape) 43 rubber band 45 Spray device

Claims

[1] Quartz glass crucible (1, 2) used for growing a silicon single crystal by a Czochralski process, comprising: a cylindrical crucible body (10) having a base and made of quartz glass; and a coating film (13A) containing a first crystallization accelerator, which is formed on an inner surface (10a) of the crucible body (10) to bring about the formation of an inner crystal layer (14A) consisting of an aggregate of dome-shaped or column-like crystal grains on a surface layer section of the inner surface (10a) of the crucible body (10) by heating during a step of the pulling up of the silicon single crystal, wherein the coating film (13A) containing the first crystallization accelerator is not heated after application and before pulling up, the coating film (13A) is formed by applying a barium-containing coating solution to the inner surface (10a) of the crucible body (10), The coating solution contains a water-insoluble barium compound and a water-soluble polymer as a thickening agent, and a concentration of barium applied to the inner surface (10a), 3.9×10 16 atoms / cm² 2 up to 1.6×10 17 atoms / cm² 2 amounts. [2] Quartz glass crucible (1, 2) according to claim 1, wherein a ratio A / B between a maximum value A of a peak intensity at a diffraction angle 20 of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the inner surface (10a) of the crucible body (10) on which the inner crystal layer (14A) is formed, by an X-ray diffraction method at a wavelength of 1.5418 nm, 7 or less. [3] Quartz glass crucible (1, 2) according to claim 1, wherein the inner crystal layer (14A) comprises a dome-shaped crystal layer consisting of the aggregate of dome-shaped crystal grains formed on the surface layer section of the inner surface (10a) of the crucible body (10), and a columnar crystal layer consisting of the aggregate of columnar crystal grains immediately below the dome-shaped crystal layer. [4] Quartz glass crucible (1, 2) according to claim 3, wherein a ratio A / B between a maximum value A of a peak intensity at a diffraction angle 20 of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the inner surface (10a) of the crucible body (10) on which the inner crystal layer (14A) is formed, by an X-ray diffraction method at a wavelength of 1.5418 nm, is less than 0.

4. [5] Quartz glass crucible (1, 2) according to claim 3 or 4, where barium carbonate is used as the barium compound. [6] Quartz glass crucible (2) according to any one of claims 1 to 5, wherein a region (15A) of a predetermined width extending downwards from an edge of an upper end of an inner surface (10a) of the crucible body (10) is a crystallization accelerator-uncoated region in which the first crystallization accelerator-containing coating film (13A) is not formed. [7] Quartz glass crucible (1, 2) according to any one of claims 1 to 6, further comprising: a coating film (13B) containing a second crystallization accelerator, which is formed on an outer surface (10b) of the crucible body (10) to cause an outer crystal layer (14B) consisting of an aggregate of dome-shaped or column-shaped crystal grains to be formed on a surface layer section of the outer surface (10b) of the crucible body (10) by heating during the drawing-up step, wherein the coating film (13B) containing the second crystallization accelerator is not heated after application and before being pulled up, the coating film (13B) is formed by applying a barium-containing coating solution to the outer surface (10b) of the crucible body (10), The coating solution contains a water-insoluble barium compound and a water-soluble polymer as a thickening agent, and a concentration of barium in the outer surface (10b) of the crucible body (10) equal to or higher than 4.9×10 15 atoms / cm² 2 and lower than 3.9×10 16 atoms / cm² 2 is. [8] Quartz glass crucible (1, 2) according to claim 7, wherein a ratio A / B between a maximum value A of a peak intensity at a diffraction angle 20 of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the outer surface (10b) of the crucible body (10) on which the outer crystal layer (14B) is formed, by an X-ray diffraction method at a wavelength of 1.5418 nm, 0.4 or more and 7 or less. [9] Quartz glass crucible (2) according to claim 7 or 8, wherein a region (15B) of a predetermined width extending downwards from an edge of the upper end of the outer surface (10b) of the crucible body (10) is a crystallization accelerator-uncoated region in which the second crystallization accelerator-containing coating film (13B) is not formed. [10] Quartz glass crucible (1, 2) used for growing a silicon single crystal by a Czochralski process, comprising: a cylindrical crucible body (10) having a base and made of quartz glass; and a coating film (13B) containing a crystallization accelerator, which is formed on an outer surface (10b) of the crucible body (10) to bring about the formation of an outer crystal layer (14B) consisting of an aggregate of dome-shaped or columnar crystal grains on a surface layer section of the outer surface (10b) of the crucible body (10) by heating during a step of the pulling up of the silicon single crystal, wherein the coating film (13B) containing the crystallization accelerator is not heated after application and before pulling up, the coating film (13B) is formed by applying a barium-containing coating solution to the outer surface (10b) of the crucible body (10), The coating solution contains a water-insoluble barium compound and a water-soluble polymer as a thickening agent, and a concentration of barium in the outer surface (10b) of the crucible body (10) equal to or higher than 4.9×10 15 atoms / cm² 2 and lower than 3.9×10 16 atoms / cm² 2 is. [11] Quartz glass crucible (1, 2) according to claim 10, wherein a ratio A / B between a maximum value A of a peak intensity at a diffraction angle 20 of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the outer surface (10b) of the crucible body (10) on which the outer crystal layer (14B) is formed, by an X-ray diffraction method at a wavelength of 1.5418 nm, 7 or less. [12] Quartz glass crucible (1, 2) according to claim 11, wherein the ratio A / B between the maximum value A of the peak intensity at a diffraction angle 20 of 20° to 25° and the maximum value B of the peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the outer surface (10b) of the crucible body (10) on which the outer crystal layer (14B) is formed, by the X-ray diffraction method at a wavelength of 1.5418 nm, is 0.4 or more and 7 or less. [13] Quartz glass crucible (2) according to any one of claims 10 to 12, wherein a region (15B) of a predetermined width extending downwards from an edge of the upper end of the outer surface (10b) of the crucible body (10) is a crystallization accelerator-uncoated region in which the crystallization accelerator-containing coating film (13B) is not formed. [14] Method for producing a quartz glass crucible (1, 2), comprising: Preparation of an initial crystallization accelerator coating solution containing a water-insoluble barium compound as a crystallization accelerator and a water-soluble polymer with a viscosity of 100 to 10000 mPas as a thickening agent, and Applying the first crystallization accelerator coating solution containing the thickening agent, on an inner surface (10a) of the quartz glass crucible (1, 2) to bring about a concentration of the crystallization accelerator in the inner surface (10a) of 3.9×10 16 atoms / cm² 2 up to 1.6×10 17 atoms / cm² 2 amounts. [15] Method for producing a quartz glass crucible (1, 2) according to claim 14, wherein the first crystallization accelerator coating solution is applied by a spraying process in a state in which an area (15A) of a predetermined width extending downwards from an edge of an upper end in the inner surface (10a) of the quartz glass crucible (1, 2) is masked. [16] Method for producing a quartz glass crucible (1, 2) according to claim 14 or 15, further comprising: Preparation of a second crystallization accelerator coating solution containing a water-insoluble barium compound as a crystallization accelerator and a water-soluble polymer with a viscosity of 100 to 10000 mPas as a thickening agent, and Applying the second crystallization accelerator coating solution containing the thickening agent to an outer surface (10b) of the quartz glass crucible (1, 2) to bring about a concentration of the crystallization accelerator in the outer surface (10b) equal to or greater than 4.9×10 15 atoms / cm² 2 and lower than 3.9×10 16 atoms / cm² 2 is. [17] Method for producing a quartz glass crucible (1, 2) according to claim 16, wherein the second crystallization accelerator coating solution is applied by a spraying process in a state in which an opening of the quartz glass crucible (1, 2) is closed and an area (15B) of a predetermined width extending downwards from the edge of the upper end in the outer surface (10b) of the quartz glass crucible (1, 2) is masked. [18] Method for producing a quartz glass crucible (1, 2), comprising: Preparation of a crystallization accelerator coating solution containing a water-insoluble barium compound as a crystallization accelerator and a water-soluble polymer with a viscosity of 100 to 10000 mPas as a thickening agent, Application of the crystallization accelerator coating solution to a surface of a quartz glass base material; Formation of a crystal layer on a surface layer section of the surface of the quartz glass base material by an evaluation heat treatment at 1400 °C or higher; Analyzing the crystallization state of the surface of the quartz glass base material using an X-ray diffraction method and adjusting the concentration of the crystallization accelerator in the crystallization accelerator coating solution based on the analysis result; and Applying the adjusted crystallization accelerator coating solution to a surface of the quartz glass crucible (1, 2). [19] Method for producing a silicon single crystal by a Czochralski method in which a silicon single crystal is grown from a silicon melt in a quartz glass crucible (1, 2), the production method comprising: Preparation of an initial crystallization accelerator coating solution containing a water-insoluble barium compound as a crystallization accelerator and a water-soluble polymer with a viscosity of 100 to 10000 mPas as a thickening agent, Applying the first crystallization accelerator coating solution to an inner surface (10a) of the quartz glass crucible (10) such that the concentration of barium applied to the inner surface (10a) is 3.9×10 16 atoms / cm² 2 up to 1.6×10 17 atoms / cm² 2 amounts; Forming, on a surface layer section of the inner surface (10a) of the quartz glass crucible (1, 2), an inner crystal layer (14A) with a laminated structure of a dome-shaped crystal layer consisting of an aggregate of dome-shaped crystal grains and a columnar crystal layer consisting of an aggregate of columnar crystal grains, immediately below the dome-shaped crystal layer by heating in one step of growing the silicon single crystal; and Pulling up the silicon single crystal while the inner crystal layer (14A) continues to grow. [20] Method for producing a silicon single crystal according to claim 19, wherein the ratio A / B between a maximum value A of a peak intensity at a diffraction angle 2θ of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the inner surface (10a) of the quartz glass crucible (1, 2) on which the inner crystal layer (14A) is formed, by an X-ray diffraction method at a wavelength of 1.5418 nm, is less than 0.

4. [21] Method for producing a silicon single crystal according to one of claims 19 to 20, wherein the first crystallization accelerator coating solution is applied to an area which does not include a region (15A) of a predetermined width extending downwards from an edge of the upper end in the inner surface (10a) of the quartz glass crucible (1, 2). [22] Method for producing a silicon single crystal according to any one of claims 19 to 21, further comprising: Preparation of a second crystallization accelerator coating solution containing a water-insoluble barium compound as a crystallization accelerator and a water-soluble polymer with a viscosity of 100 to 10000 mPas as a thickening agent; application of the second crystallization accelerator coating solution to an outer surface (10b) of the quartz glass crucible (1, 2) such that the concentration of barium applied to the outer surface (10b) is equal to or greater than 4.9 × 10 15 atoms / cm² 2 and lower than 3.9×10 16 atoms / cm² 2 is; Forming an outer crystal layer (14B) consisting of an aggregate of dome-shaped crystal grains on a surface layer section of the outer surface (10b) of the quartz glass crucible (1, 2) by heating in the step of drawing up the silicon single crystal; and Pulling up the silicon single crystal without allowing the outer crystal layer (14B) to continue growing. [23] Method for producing a silicon single crystal according to claim 22, wherein a ratio A / B between a maximum value A of a peak intensity at a diffraction angle 2θ of 20° to 25° and a maximum value B of a peak intensity at a diffraction angle 2θ of 33° to 40°, obtained by analyzing the outer surface (10b) of the quartz glass crucible (1, 2) on which the outer crystal layer (14B) is formed, by an X-ray diffraction method at a wavelength of 1.5418 nm, 0.4 or more and 7 or less. [24] Method for producing a silicon single crystal according to claim 22 or 23, wherein the second crystallization accelerator coating solution is applied to an area which does not include a region (15B) of a predetermined width extending downwards from the edge of the upper end in the outer surface (10b) of the quartz glass crucible (1, 2). [25] Method for producing a silicon single crystal according to claim 19, wherein a crystallization state of the inner crystal layer (14A) formed by heating in the pull-up step is analyzed and, based on an analysis result, a concentration of the crystallization accelerator in the first crystallization accelerator coating solution applied to an inner surface (10a) of a new quartz glass crucible (1, 2) used in a subsequent pull-up step of a silicon single crystal is adjusted. [26] Method for producing a silicon single crystal according to claim 22, wherein a crystallization state of the outer crystal layer (14B) formed by heating in the pull-up step is analyzed and, based on an analysis result, a concentration of the crystallization accelerator in the second crystallization accelerator coating solution applied to an outer surface (10b) of a new quartz glass crucible (1, 2) used in a subsequent pull-up step of a silicon single crystal is adjusted.

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