Quartz glass crucible

Abstract

Quartz glass crucible, comprising: a cylindrical sidewall portion; a curved floor section; and a corner portion provided between the side wall portion and the bottom portion and having a greater curvature than a curvature of the bottom portion, wherein a first region provided from a crucible inner surface to a center in a thickness direction, a second region provided outside the first region in the thickness direction and having a different stress distribution than the first region, and a third region which is provided outside the second region in the thickness direction and up to a crucible outer surface and has a different stress distribution than the second region, internal residual stresses of the first area and the third area are compressive stresses and an internal residual stress of the second region comprises a tensile stress, characterized in that a surface roughness of the crucible outer surface is 10 µm or more and 50 µm or less in terms of Ra (arithmetic mean roughness) and 80 µm or more and 200 µm or less in terms of Rz (maximum height), each measured according to JIS (Japanese Industrial Standards) B0601-2001.

Description

[Field of expertise]

[0001] The present invention relates to a quartz glass crucible. [State of the art]

[0002] Silicon single crystals are produced by melting a silicon raw material (polycrystalline silicon) placed in a quartz glass crucible, bringing a seed crystal into contact with the molten polycrystalline silicon, and rotating and lifting the polycrystalline silicon (CZ process: Czochralski process). The quartz glass crucible used in this CZ process is manufactured using a rotational molding process.

[0003] That is, a method for manufacturing a quartz glass crucible using the rotational molding method includes a silica powder layer forming step of forming a silica powder layer by depositing silica powders having an average particle diameter of approximately 100 μm to 400 μm on the inside of a rotating carbon mold using a centrifugal force, and an arc melting step of arc melting the silica powder layer while depressurizing the silica powder layer from a mold side to form a quartz glass layer.

[0004] In the arc melting step, a so-called sealing layer is formed by thinly vitrifying an entire outermost surface of the silica powder layer. Then, by removing air bubbles by strongly depressurizing the sealing layer, a quartz glass layer (hereinafter referred to as the "transparent layer") is formed. Then, by gently depressurizing the quartz glass layer, a quartz glass layer containing air bubbles (hereinafter referred to as the "non-transparent layer") in which air bubbles remain is formed. Therefore, for example, a two-layer quartz glass crucible is formed with the transparent layer on an inner surface side and the non-transparent layer on an outer surface side.

[0005] In such an arc melting step, the silica powders are first sintered, volume diffusion occurs, then the temperature rises, grain boundaries disappear, vitrification occurs, and a Si-O-Si network structure is formed. In this process, the sintering rate or vitrification rate changes. Specifically, for example, when the silica powders are small or have a shape with the same volume but a larger surface area, the sintering rate or vitrification rate becomes fast. When the silica powders are small and spaces between adjacent silica powders are also small, the silica powders are sintered or vitrified at a rate faster than the rate of air bubble removal by depressurization, and thus, air bubbles in a manufactured glass crucible become small and the number of them increases.So, the molecular structure of glass, contained air bubbles and the like are changed after arc melting by the sintering rate or the vitrification rate.

[0006] In addition, molten quartz glass is solidified by performing a cooling step after the arc melting step. In this cooling step, depending on the cooling rate or a cooling method such as blowing cooling gas, a bonding manner of silicon and oxygen changes (for example, a six-membered ring or an eight-membered ring), or the size of a void between atoms in the bonding structure of silicon and oxygen changes. For example, as the frequency of a structure with a large number of members in a ring, such as an eight-membered ring, becomes high, the number of voids also increases.Therefore, the bonding state of material atoms changes in a complicated manner depending on a variety of conditions for the melting step, the cooling step, and the like in the manufacture of a crucible, and thus the distribution of internal residual stress after cooling of the quartz glass crucible changes and the strength of the crucible is affected.

[0007] Patent Literature 1 discloses a method for producing a silicon single crystal using a quartz glass crucible, the deformation of which is suppressed even when the quartz glass crucible is used for a long time under high-temperature conditions. The quartz glass crucible used in this method for producing a silicon single crystal includes a transparent layer inside and an air bubble layer outside, and includes a compressive stress layer in which a compressive stress remains on an inner surface side of the transparent layer and a tensile stress layer adjacent to the compressive stress layer with a stress change rate of 0.17 MPa / mm or more and 1.5 MPa / mm or less and in which a tensile stress remains.

[0008] Patent Literature 2 discloses a quartz glass crucible that has high strength at high temperatures and can be easily removed when fully lifted. This quartz glass crucible includes a quartz glass outer layer provided on an outer surface side of the crucible, a quartz glass inner layer provided on an inner surface of the crucible, and a quartz glass intermediate layer provided between the quartz glass outer layer and the quartz glass inner layer.

[0009] Patent Literature 3 discloses a quartz glass crucible that suppresses the expansion of air bubbles present in the quartz glass crucible and can achieve a high single crystal formation rate. In this quartz glass crucible, a compressive stress equal to half the fracture strength of a non-transparent layer is provided in a transparent layer.

[0010] WO 2017-110762 A1 and WO 2017-110763 A1 disclose, by way of example, quartz crucibles suitable for the CZ process. [List of citations][Patent literature] [Patent Literature 1] Japanese Patent Application Laid-Open No. JP 2017-001951 A [Patent Literature 2] International Publication WO 2011 / 013695 A1 [Patent Literature 3] Japanese Patent Application Laid-Open No. JP H11-278855 A [Summary of the invention][Technical problem]

[0011] The quality of a quartz crucible has a close relationship with the quality of a silicon single crystal (silicon ingot) when lifting a silicon single crystal using a quartz crucible (e.g., a CZ process). For example, fine debris (particles exfoliated from the crucible) in silicon falls into a silicon melt due to the breakage or collapse of particles or air bubbles on the inner surface of the quartz crucible. The ingress of this debris into the silicon ingot leads to warping of the silicon ingot.

[0012] In addition, when placing silicon raw material into a quartz glass crucible, there is a case where the silicon raw material (polycrystalline silicon) will strongly impact the inner surface of the crucible. If the strength of the crucible inner surface is insufficient, there is a risk that the inner surface of the crucible may crack or break during the introduction of the silicon raw material.

[0013] In addition, there is a possibility that some substance may hit a crucible outer surface when transporting the quartz glass crucible, and if the strength of the crucible outer surface is insufficient, there is a case where a crack is generated or breakage is generated in the quartz glass crucible.

[0014] Furthermore, when the surface roughness of the crucible outer surface becomes equal to or smaller than a predetermined value, in a CZ lifting device, a friction force between the quartz glass crucible and a carbon susceptor decreases, and the quartz glass crucible deforms during CZ lifting, which acts as a cause of deteriorating the quality (e.g., single crystal formation rate) of a silicon single crystal.

[0015] An object of the present invention is to provide a quartz glass crucible capable of sufficiently ensuring the strengths of the crucible inner surface and the outer surface. [Means of solving the problems]

[0016] The invention relates to a quartz glass crucible according to claim 1. The quartz glass crucible comprises: a cylindrical side wall portion, a curved bottom portion, and a corner portion provided between the side wall portion and the bottom portion and having a greater curvature than a curvature of the bottom portion, in which a first region provided from a crucible inner surface to a center in a thickness direction, a second region provided outside the first region in the thickness direction and having a different stress distribution than the first region, and a third region provided outside the second region in the thickness direction and up to the crucible outer surface and having a different stress distribution than the second region are provided, internal residual stresses of the first region and the third region are compressive stresses, and an internal residual stress of the second region includes tensile stress.A surface roughness of the crucible outer surface is 10 µm or more and 50 µm or less in terms of Ra (arithmetic mean roughness) and 80 µm or more and 200 µm or less in terms of Rz (maximum height), each measured according to JIS (Japanese Industrial Standards) B0601-2001.

[0017] According to the configuration described above, as the internal residual stresses of the quartz glass crucible, compressive stresses are present on the inner surface side (first region) and on the outer surface side (third region) in the thickness direction, respectively, and tensile stress is present in the central portion (second region), and thus it is possible to sufficiently ensure strengths on the crucible inner surface and on the crucible outer surface, respectively.

[0018] In the quartz glass crucible, the internal residual stress of the second region may not include compressive stress, and the second region may be provided adjacent to each of the first region and the third region. In such a case, a three-layer stress distribution structure with internal residual stresses consisting of compressive stress, tensile stress, and compressive stress is formed in the thickness direction of the quartz glass crucible.

[0019] In the quartz glass crucible, a thickness of the first region in the thickness direction from the crucible inner surface may be 1 mm or more, and preferably 3 mm or more. In such a case, it is possible to ensure sufficient strength even when polycrystalline silicon, which is a material in lifting a silicon single crystal, strikes the crucible inner surface when the polycrystalline silicon is placed in the quartz glass crucible.

[0020] In the quartz glass crucible, a thickness of the third region in the thickness direction from the crucible outer surface may be 1 mm or more, and preferably 5 mm or more. In such a case, it is possible to ensure sufficient strength even when any pressure is applied to the crucible outer surface, such as during transportation of the quartz glass crucible.

[0021] In the quartz glass crucible, when a grain impacts the crucible inner surface with a force of 300 Newtons (N) according to the test method disclosed in WO 2016 / 047694 A1, the diameter of a notch on the crucible inner surface can be 5 mm or less, and preferably 1 mm or less. In such a case, it is possible to ensure sufficient strength even when polycrystalline silicon, which is a material used in lifting a silicon single crystal, impacts the crucible inner surface when the polycrystalline silicon is loaded into the quartz glass crucible.

[0022] In the quartz glass crucible, a surface roughness of the crucible outer surface in terms of Ra (arithmetic mean roughness: JIS (Japanese Industrial Standards) B0601-2001) is 10 µm or more and 50 µm or less. In such a case, it is possible to suppress the generation of a base point of a crack or a fracture attributable to a height difference of unevenness on the crucible outer surface, and it becomes possible to optimize a friction force between the quartz glass crucible and a carbon susceptor by an appropriate degree of unevenness. [Advantageous effects of the invention]

[0023] According to the invention, it becomes possible to provide a quartz glass crucible capable of sufficiently ensuring the strengths of the inner surface and the outer surface of the crucible. [Brief description of the drawings] Fig. 1A and Fig. 1B are schematic views illustrating a quartz glass crucible; Fig. 2A and Fig. 2B are views for describing regions in the quartz glass crucible; Fig. 3A to Fig. 3C are views illustrating measurement results of internal residual stress in the quartz glass crucible; Fig. 4 is a view for describing impact positions of an automatic center punch; Fig. 5A and Fig. 5B are views for illustrating impact notches; Fig. 6 is a flowchart schematically showing steps for manufacturing the quartz glass crucible; Fig. 7A and Fig. 7B are schematic views for describing a method of manufacturing the quartz glass crucible; Fig. 8A and Fig. 8B are schematic views for describing the method of manufacturing the quartz glass crucible; Fig. 9 is a schematic view showing an overall configuration of a lifting device which is an apparatus for producing a silicon single crystal; Fig. 10A to Fig. 10C are schematic views for describing a method of manufacturing a silicon single crystal using the quartz glass crucible according to the present embodiment; and Fig. 11 is a schematic view illustrating an ingot of a silicon single crystal. [Description of embodiments]

[0024] An embodiment of the present invention will be described below based on the drawings. In the following description, similar elements are denoted by similar reference numerals, and the description of an element once described will be omitted as appropriate. <quarzglastiegel>

[0025] Fig. 1A and Fig. 1B are schematic views illustrating a quartz glass crucible.

[0026] Fig. 1A shows a perspective view of a quartz glass crucible 11, and Fig. Figure 1B shows a cross-sectional view of the quartz glass crucible 11.

[0027] The quartz glass crucible 11 has a corner portion 11b with a relatively large curvature, a cylindrical side wall portion 11a with an edge portion opening on an upper surface, and a mortar-like bottom portion 11c forming a straight line or a curved line with a relatively small curvature.

[0028] In the present embodiment, the corner portion 11b is a portion connecting the side wall portion 11a and the bottom portion 11c, and denotes a portion from a point where a tangent of the curved line of the corner portion 11b overlaps the side wall portion 11a of the quartz glass crucible 11 to a point where the corner portion has a common tangent with the bottom portion 11c. In other words, a point where the side wall portion 11a of the quartz glass crucible 11 begins to curve is the boundary between the side wall portion 11a and the corner portion 11b. In addition, a portion where the curvature of a bottom of the quartz glass crucible 11 remains substantially constant is the bottom portion 11c, and a point where the curvature starts to change with increasing distance from the center of the bottom of the quartz glass crucible 11 is the boundary between the bottom portion 11c and the corner portion 11b.

[0029] In a thickness direction of the quartz glass crucible 11, a transparent layer 13 is provided on a crucible inner surface (hereinafter also referred to as the "inner surface IS") side, and a non-transparent layer 15 is provided on a crucible outer surface (hereinafter also referred to as the "outer surface OS") side.

[0030] The transparent layer 13 is a layer that essentially contains no air bubbles. "Essentially contains no air bubbles" means that the air bubble content rate and air bubble size are so small that the single crystal formation rate of a silicon single crystal does not decrease due to air bubbles. For example, the air bubble content rate of the transparent layer 13 is 0.1% or less, and the average diameter of air bubbles is 100 μm or less.

[0031] The transparent layer 13 preferably comprises synthetic quartz glass on the inner surface, IS side. Synthetic quartz glass refers, for example, to quartz glass produced by melting a raw material synthesized by hydrolysis of a silicon alkoxide. Generally, synthetic silica has a low metallic impurity concentration and a high OH group concentration compared with natural silica. For example, the content of each metallic impurity contained in synthetic silica is less than 0.05 ppm, and the OH group content is 30 ppm or more.However, synthetic silica to which a metallic impurity such as Al is added is also known. Therefore, whether a particular silica is synthetic silica or not should not be determined based on one element, but rather should be comprehensively determined based on a plurality of elements. Therefore, synthetic quartz glass contains fewer impurities compared to natural silica, and is therefore capable of preventing an increase in impurity leaching from the crucible into a silicon melt and increasing the silicon single crystal formation rate.

[0032] A number of air bubbles are present in the non-transparent layer 15. The non-transparent layer 15 is a layer that appears in a white turbid state due to the air bubbles. The non-transparent layer 15 is preferably made of natural quartz glass. Natural quartz glass refers to quartz glass produced by melting a natural raw material such as natural quartz crystal or silicon dioxide. Generally, compared with synthetic silicon dioxide, natural silicon dioxide has a characteristic of a high concentration of a metallic impurity and a low concentration of an OH group. For example, the content of Al contained in natural silicon dioxide is 1 ppm or more, the contents of alkali metals (Na, K, and Li) are each 0.1 ppm or more, and the content of an OH group is less than 60 ppm.

[0033] Whether a particular silica is natural or not should not be determined based on a single element, but rather should be comprehensively determined based on multiple elements. Compared with synthetic silica, natural silica has a higher viscosity at high temperatures and is therefore capable of increasing the heat resistance strength of the entire crucible. Furthermore, natural raw materials are not as expensive as synthetic silica and are more cost-effective.

[0034] Fig. 2A and Fig. 2B are views for describing regions in the quartz glass crucible.

[0035] Fig. Figure 2A shows an enlarged cross-sectional view of a part as seen from an upper end face, TP, side of the Fig. 1 shown quartz glass crucible 11, and Fig. Figure 2B shows an example of internal residual stress along a line SL in the thickness direction in Fig. 2A.

[0036] As in Fig. 2A, the quartz glass crucible 11 according to the present embodiment has a first region R1 provided from the inner surface IS to a center in the thickness direction, a second region R2 provided outside the first region R1 in the thickness direction, and a third region R3 provided outside the second region R2 in the thickness direction and up to the outer surface OS.

[0037] As in Fig. 2B, in the present embodiment, an internal residual stress of the first region R1 is a compressive stress, an internal residual stress of the second region R2 is a tensile stress, and an internal residual stress of the third region R3 is a compressive stress. In Fig. 2B, the horizontal axis indicates positions on the line SL in the thickness direction, with the inner surface being regarded as an origin point "0", and the vertical axis indicates the intensities of stresses, with the (+) side indicating compressive stresses and the (-) side indicating tensile stresses. In the present embodiment, unless specifically described otherwise, a compressive stress and a tensile stress are regarded as internal residual stresses.

[0038] In the Fig. In the example shown in Figure 2, the second region R2 does not include any compressive stress, and the second region R2 is adjacent to the first region R1 and the third region R3, respectively. Therefore, a three-layer structure of the stresses of the first region R1, the second region R2, and the third region R3 is formed in the thickness direction.

[0039] In the quartz glass crucible 11, the first region R1, the second region R2, and the third region R3 are continuous in a circumferential direction. That is, in each of the first region R1, the second region R2, and the third region R3, no significant stress variation is generated at least in the circumferential direction (substantially uniform stress distribution).

[0040] In the quartz glass crucible 11, compressive stress is present in the first region R1, thereby improving the strength of the inner surface IS. For example, in the case of lifting a silicon single crystal using the quartz glass crucible 11, polycrystalline silicon made of one material is introduced into the quartz glass crucible 11. At this time, an impact is likely to be applied to the inner surface IS of the quartz glass crucible 11. Compressive stress is present in the first region R1, thereby obtaining sufficient resistance to impact during the introduction of polycrystalline silicon.

[0041] Furthermore, in the quartz glass crucible 11, compressive stress is present in the third region R3, thereby improving the strength of the outer surface OS. Therefore, it is possible to ensure sufficient strength even when any pressure is applied to the outer surface OS, such as during transportation of the quartz glass crucible 11.

[0042] Fig. 3A to Fig. 3C are views illustrating the measurement results of internal residual stress in the quartz glass crucible.

[0043] Fig. 3A to Fig. 3C shows the results of internal residual stresses measured by a sensitive dye method on samples SP1 to SP3 obtained by cutting out parts of the quartz glass crucible.

[0044] The sensitive color method refers to a method in which two polarizing plates are arranged so that they are perpendicular to each other, and a change in the color of a substance that causes a light path deviation, such as glass with a stress caused when the glass is inserted between the polarizing plates, is observed, thereby observing the presence or absence of internal stress and the direction of the stress (tensile stress / compressive stress). In the sensitive color method, the background color becomes red-violet, and in a case where there is no internal stress in an observation object, the same color as the background color is observed. On the other hand, in a case where there is internal stress in an observation object, a color change to blue or orange is observed depending on the direction of application of a force, such as tensile stress / compressive stress.

[0045] The Fig. Sample SP1 shown in Figure 3A and the sample in Fig. Sample SP2 shown in Fig. 3B are samples cut out from the quartz glass crucible 11 according to the present embodiment, and which are shown in Fig. Sample SP3 shown in Figure 3C is a sample cut from a quartz glass crucible according to a reference example.

[0046] The respective samples SP1 to SP3 are cut out from the corresponding sections (150 mm from the upper end face TP in a height direction) of the respective quartz glass crucibles.

[0047] In the respective drawings, areas where compressive stress is measured are marked with "+" and areas where tensile stress is measured are marked with "-".

[0048] In samples SP1 and SP2, which were Fig. 3A and Fig. 3B, internal residual stresses change in the order of a compressive stress "+", a tensile stress "-", and a compressive stress "+" from the inner surface IS to the outer surface OS in the thickness direction. A region with the compressive stress on the inner surface, IS, side is the first region R1, a region with the tensile stress is the second region R2, and a region with the compressive stress on the outer surface, OS, side is the third region R3.

[0049] In the Fig. 3C, the internal residual stresses change in the order of a compressive stress "+", a tensile stress "-", and a compressive stress "+" and a tensile stress "-" from the inner surface IS to the outer surface OS in the thickness direction.

[0050] A preliminary strength (fracture) test is performed on the quartz glass crucibles from which samples SP1 to SP3 are to be cut. The quartz glass crucibles have a 32-inch outer diameter (approximately 81.2 cm outer diameter). During the strength test, it is observed whether or not a fracture occurs when a blow is applied using an automatic center punch.

[0051] Here, the inspection using the automatic center punch is a method disclosed, for example, in International Publication No. WO2016 / 047694. That is, the automatic center punch includes a shaft made of a rod-shaped metal member having a sharp front end, a hammer portion provided at a rear end portion, a coil spring urging the shaft in a front direction thereof, a coil spring provided at a rear end portion of the hammer portion, and a substantially cylindrical housing accommodating the above-described members. The automatic center punch is capable of briefly applying a large load to an object brought into contact with the front end portion of the shaft.

[0052] Fig. 4 is a view for describing impact positions. That is, as in Fig. As shown in Figure 4, the impact positions are positions on the inner surface of the quartz glass crucible that are at radii ra, rb, and rc from a center (BC) of a bottom portion B when viewed from the upper end surface TP. The load of the automatic center punch used to apply the impact is 300 Newtons (N).

[0053] A testing procedure is as described below. (1) A blow is applied successively to 16 points at the position of radius ra = 200 mm away. (2) In a case where no fracture occurs in (1), a blow is applied successively to 16 points at the position of radius rb = 150 mm away. (3) In a case where no fracture occurs in (2), a blow is applied successively to 16 points at the position of radius rc = 250 mm away.

[0054] As a result of this test, the quartz crucibles from which samples SP1 and SP2 were taken did not fracture. However, the quartz crucible from which sample SP3 was taken did fracture when the impact was applied at a position 200 mm from the center BC of the bottom section B.

[0055] Based on the test results, it was found that sufficient strength can be achieved when compressive stress areas exist on the inner surface (IS) and outer surface (OS) sides of the quartz glass crucible, respectively. Therefore, in order to obtain sufficient strength of the quartz glass crucible, it is important that compressive stress areas exist on the inner surface (IS) and outer surface (OS) sides, as in samples SP1 and SP2.

[0056] The above-described distribution of internal residual stresses in the thickness direction changes depending on the thermal history attributable to arc melting, cooling rate, heating pattern, etc. during the manufacturing of the quartz glass crucible. It is possible to provide compressive stress regions on the inner surface (IS) and outer surface (OS) sides by controlling the thermal history.

[0057] Fig. 5A and Fig. 5B are views illustrating notches made by the automatic center punch.

[0058] Fig. 5A shows an example of a notch, viewed in a direction perpendicular to the inner surface, and Fig. Figure 5B shows an example of a notch viewed in a direction perpendicular to the thickness direction.

[0059] As in Fig. 5A, the size of the notch is approximately 5 mm. The size of a notch created when polycrystalline silicon is introduced into the quartz glass crucible is approximately 1 mm. In addition, as shown in Fig. 5B, the depth of the notch is approximately 3 to 4 mm. The depth of the notch created when polycrystalline silicon is introduced into the quartz glass crucible is approximately 2 mm.

[0060] As described above, the impact force of the 300 N automatic center punch is sufficiently larger than the indentation caused by the insertion of polycrystalline silicon. Therefore, it can be said that the quartz glass crucibles (the present embodiment) from which samples SP1 and SP2 were obtained, which did not break according to the test results described above, can sufficiently ensure the strength of the polycrystalline silicon insertion.

[0061] Based on the test results described above, when the automatic center punch is struck on the inner surface IS with a force of 300 N, the diameter of a notch on the inner surface IS must be 5 mm or smaller, and preferably 1 mm or smaller. Furthermore, in the quartz glass crucible 11 according to the present embodiment, the thickness in the thickness direction of the first region R1 where compressive stress is present must be 1 mm or more from the inner surface IS, preferably 3 mm or more, and more preferably equal to the total thickness of the transparent layer.

[0062] In such a case, when polycrystalline silicon is placed in the quartz glass crucible 11, even in a case where the polycrystalline silicon strikes the crucible inner surface, notches are limited to the first region R1, generation of a crack from the notch as a base point is suppressed, and sufficient strength can be ensured.

[0063] Furthermore, in the quartz glass crucible 11 of the present embodiment, the thickness in the thickness direction of the third region R3 must be 1 mm or more from the outer surface OS, and preferably 5 mm or more. In such a case, even if any pressure is applied to the crucible outer surface, such as during transportation of the quartz glass crucible, and an impact is applied thereto, indentations are limited to the third region R3, the generation of a crack from the indentation as a base point is suppressed, and sufficient strength can be ensured.

[0064] For a large crucible in which the outer diameter of the quartz glass crucible 11 is 32 inches or more, or an ultra-large crucible in which the outer diameter is 40 inches or more, the influence of splitting, breakage, exfoliation, or the like attributable to the distribution of internal residual stress in the thickness direction of the quartz glass crucible 11 is significant. In particular, as the crucible outer diameter is increased, the rate of increase in thickness becomes large compared to the rate of increase in the outer diameter. That is, there is a tendency for the thickness to become relatively thick compared to an increase in the crucible outer diameter. Therefore, as the crucible outer diameter increases, the stress distribution in the thickness direction becomes more complicated, and it is more likely to cause a lack of strength.Providing the first region R1 on the inner surface, IS, side and the third region R3 on the outer surface, OS, side in the thickness direction of the quartz glass crucible 11 with a compressive stress as in the present embodiment is particularly effective for improving the strengths of large or ultra-large crucibles.

[0065] Furthermore, in the quartz glass crucible 11 according to the present embodiment, the surface roughness of the outer surface OS in terms of Ra (arithmetic mean roughness) must be 10 μm or more and 50 μm or less. Furthermore, the surface roughness of the outer surface OS in terms of Rz (maximum height) must be 80 μm or more and 200 μm or less. In the present embodiment, Ra (arithmetic mean roughness) and Rz (maximum height) are values ​​measured based on JIS (Japanese Industrial Standards) B0601-2001. If the unevenness (surface roughness) of the outer surface OS exceeds the above-described upper limit, the unevenness of the outer surface becomes severe, and a base point of cracking or fracture is likely to be generated from a depressed portion due to the difference in the height of the unevenness.Some external force is likely to be applied to the outer surface OS of the quartz glass crucible 11 during transportation of the quartz glass crucible 11 or the like. Therefore, if the surface roughness of the outer surface OS is controlled as described above, it is possible to suppress the generation of a base point of cracking or fracture attributable to the height difference of the unevenness of the outer surface OS.

[0066] On the other hand, if the surface roughness of the outer surface OS is below the above-described lower limit in a CZ lifting device, the quartz glass crucible 11 is likely to displace the quartz glass crucible 1 in a carbon susceptor, and deformation such as subduction of the sidewall portion 11a is likely to occur when the quartz glass crucible is used at a high temperature. That is, if the surface roughness of the outer surface OS is too low, a frictional force between the outer surface OS and the carbon susceptor decreases, and the quartz glass crucible 11 is likely to deform during CZ lifting. Therefore, Rz (maximum height) of the outer surface OS is set to 80 μm or more, whereby the frictional force between the quartz glass crucible 11 and the carbon susceptor becomes reasonably high due to the appropriate unevenness of the outer surface OS.Therefore, it becomes easy to suppress the deformation of the quartz glass crucible 11 during CZ lifting.

[0067] In the quartz glass crucible 11 according to the present embodiment, an example of the three-layer stress structure in which the second region R2 is adjacent to the first region R1 and the third region R3, respectively, has been described, but the structure is not limited thereto. That is, the first region R1 in which compressive stress exists may be provided on the inner surface (IS) side, the third region R3 in which compressive stress exists may be provided on the outer surface (OS) side of the quartz glass crucible 11, and the second region R2 in which tensile stress exists may be included between the first region R1 and the third region R3. For example, a region with tensile stress and a region with compressive stress may be alternately repeated between the first region R1 and the third region R3.In this case, a tensile stress and a compressive stress are present in a mixed form in the second region R2. <Verfahren zur Herstellung eines Quarzglastiegels>

[0068] Fig. Figure 6 is a flowchart schematically showing steps for manufacturing the quartz glass crucible.

[0069] In addition, Fig. 7A to Fig. 8B are schematic views for describing a method of manufacturing the quartz glass crucible.

[0070] The quartz glass crucible 11 is manufactured using a rotational molding process. As shown in Fig. 6, in the rotational molding process, the quartz glass crucible 11 is manufactured by forming a silica powder layer in a carbon mold (step S101), arc melting and pressure relieving (step S102), cooling (step S103), a polishing treatment (step S104), and an edge cutting and edging treatment (step S105).

[0071] First, in the formation of a silicon dioxide powder layer in a carbon mold shown in step S101, a carbon mold 20 having a cavity corresponding to the outer shape of the quartz glass crucible 11 is prepared as shown in Fig. 7A. Furthermore, a first silica powder 201 is supplied to the carbon mold 20 while rotating, smoothed using a scraper, and formed to a predetermined thickness. Therefore, a silica powder layer is formed along the mold inner surface. The carbon mold 20 rotates at a constant speed, and thus, the supplied first silica powder 201 remains at a certain position in a state of adhesion to the mold inner surface by centrifugal force, and the shape of the silica powder is maintained. The first silica powder 201 becomes a non-transparent layer and is therefore preferably natural silica powder.

[0072] Next, as in Fig. 7B, a second silica powder 202 is supplied to the carbon mold 20 in which the first silica layer 201 is formed, and forms the silica powder layer thicker. The second silica powder 202 is applied to the first silica powder 201 on the mold inner surface to a predetermined thickness. The second silica powder 202 is preferably synthetic silica powder, but may also be natural silica powder.

[0073] Next, in the arc melting and pressure relief shown in step S201, as shown in Fig. As shown in Fig. 8A, arc electrodes 30 are installed in the cavity of the carbon mold 20, an arc discharge is performed from the inside of the carbon mold 20 while rotating the carbon mold 20, and the entire silica powder layer is heated to 1,720°C or higher and melted. At this time, a thin quartz glass sealing layer is formed over the entire circumference. In addition, simultaneously with the heating, pressure is released from the carbon mold 20 side, a gas in the silica is sucked to an outer layer side through vent holes 21 provided in the carbon mold 20, and voids in the silica powder layer are degassed under heating, thereby removing air bubbles in the crucible inner surface. As a result, the transparent layer 13 containing substantially no air bubbles is formed.

[0074] A cooling agent (not shown) is provided in the carbon mold 20. Therefore, vitrification of the silicon dioxide is prevented in a portion serving as the outer surface of the quartz glass crucible 11. The cooling temperature by the cooling agent is a temperature at which the silicon dioxide is not vitrified and remains a sintered body and a powder.

[0075] Thereafter, the pressure relief for degassing is weakened or stopped while heating is continued, and air bubbles are left, thereby forming the non-transparent layer 15 containing a number of fine air bubbles.

[0076] Next, in the cooling shown in step S103, the current supply to the arc electrodes 30 is stopped, and the molten quartz glass is cooled, thereby forming the quartz glass crucible 11. During cooling, a cooling gas is blown onto the quartz glass serving as the inner surface of the quartz glass crucible 11. The internal residual stress distribution of the quartz glass crucible 11 is determined by cooling conditions such as the cooling rate and a method for blowing the cooling gas. Therefore, it is possible to manufacture the quartz glass crucible 11 with a desired stress distribution by adjusting the cooling conditions.

[0077] In addition, the internal residual stresses of the quartz glass crucible 11 also change due to a thermal history during the manufacturing of the crucible. For example, the internal residual stresses change due to a thermal history until the completion of the quartz glass crucible 11, such as the temperature gradient from the crucible inner surface to the outer surface, the stress distribution in the interface between a softened portion and a non-softened portion, or the stress balance when the softened portion is cooled and solidified.

[0078] As described above, the heating state differs from the crucible inner surface side to the outer surface side due to the heat history. Therefore, it is assumed that there is a difference in the distribution of a force for suppressing deformation of a heated area and a difference in the state of compressive and tensile stress layers distributed in a layered manner from the crucible inner surface side to the outer surface side. Therefore, it is possible to obtain a desired stress distribution of the quartz glass crucible 11 by controlling the heat history.

[0079] Next, as the polishing treatment shown in step S104, a sandblasting treatment is performed on the outer surface OS of the quartz glass crucible 11, and the outer surface is finished to a predetermined surface roughness. In the present embodiment, the surface roughness of the outer surface OS is brought to 50 μm or less in terms of Ra (arithmetic mean roughness) and 80 μm or more and 200 μm or less in terms of Rz (maximum height) by this polishing treatment.

[0080] In addition, in the edge cutting and edge treatment shown in step S105, as shown in Fig. 8B, a part of the upper end side of the side wall portion 11a of the quartz glass crucible 11 removed from the carbon mold 20 is cut off, thereby adjusting the height of the quartz glass crucible 11. Subsequently, chamfering is performed on the inner peripheral edge and the outer peripheral edge, which are edges of the upper end surface TP, thereby forming chamfered portions C. After the edge cutting, washing is performed, thereby completing the quartz glass crucible 11. <hebevorrichtung>

[0081] Fig. 9 is a schematic view showing the overall configuration of a lifting device which is an apparatus for producing a silicon single crystal.

[0082] In a chamber 510 resembling a hoist 500, the quartz glass crucible 11 containing a silicon melt 23 is provided, and a carbon susceptor 520 is provided to cover the outside of the quartz glass crucible 11. The carbon susceptor 520 is fixed to the upper end of a supporting shaft 530 parallel to the vertical direction. The quartz glass crucible 11, fitted into the carbon susceptor 520, is rotated by the supporting shaft 530 in a predetermined direction together with the carbon susceptor 520 and is movable in the vertical direction to control the liquid surface of the silicon melt at a constant height relative to a heating element 540 in a furnace (so that the temperature gradient becomes constant).

[0083] The outer peripheral surfaces of the quartz glass crucible 11 and the carbon susceptor 520 are surrounded by the heating element 540. The heating element 540 is further surrounded by a heat-insulating tube 550. In a raw material melting process for growing a silicon single crystal, a high-purity polycrystalline silicon raw material introduced into the quartz glass crucible 11 is heated and melted by heating by the heating element 540, and turns into the silicon melt 23.

[0084] A lifting means 560 is provided in the upper end portion of the chamber 510 of the lifting device 500. A wire cable 561, which is lowered toward the rotation center of the quartz glass crucible 11, is attached to the lifting means 560, and a lifting motor (not shown) that winds or unwinds the wire cable 561 is arranged. A seed crystal 24 is attached to the lower end of the wire cable 561. During the lifting, the seed crystal 24 rotates and grows, and at the same time, a silicon single crystal 25 (block) also rotates.

[0085] A cylindrical heat shield member 570 is provided between the silicon single crystal 25 and the heat insulation tube 550 to surround the silicon single crystal 25 in the middle of growth. The heat shield member 570 has a cone portion 571 and a flange portion 572. The heat shield member 570 is arranged at a predetermined position (hot zone) by attaching the flange portion 572 to the heat insulation tube 550. The silicon single crystal 25 can be manufactured using the lifting device 500 described above. <Verfahren zur Herstellung eines Silicium-Einkristalls>

[0086] Fig. 10A to Fig. 10C are schematic views for describing a method of manufacturing a silicon single crystal using the quartz glass crucible according to the present embodiment.

[0087] The silicon single crystal 25 is manufactured by inserting the quartz glass crucible 11 according to the present embodiment into the above-described lifting device 500 and lifting the quartz glass crucible.

[0088] First, as in Fig. 10A, polycrystalline silicon is introduced into the quartz glass crucible 11, and in this state, the polycrystalline silicon is heated and melted using a heating element arranged around the quartz glass crucible 11. Thus, the silicon melt 23 is obtained. Meanwhile, the use of the quartz glass crucible 11 according to the present embodiment can prevent the crucible from breaking during the introduction.

[0089] Next, the front end of the seed crystal 24 attached to the wire cable 561 is lowered and brought into contact with the silicon melt 23. In addition, the wire cable 561 is slowly raised while being rotated. Therefore, as shown in Fig. 10B, causes the silicon single crystal 25 to grow below the seed crystal 24. By continuously lifting the wire cable and simultaneously controlling the lifting speed, the silicon single crystal 25 is caused to grow into a block, as shown in Fig. 10C shown.

[0090] In the quartz glass crucible 11 according to the present embodiment, breakage or chipping of the inner surface IS or the outer surface OS is suppressed, and thus, it is possible to suppress the introduction of a foreign substance during lifting. Furthermore, due to the appropriate surface roughness of the outer surface OS, the friction force between the quartz glass crucible 11 and the carbon susceptor in the CZ lifting device increases, the deformation of the quartz glass crucible 11 during CZ lifting is suppressed, and it becomes possible to produce a silicon single crystal with excellent quality (e.g., single crystal formation rate). <Block aus Silicium-Einkristall]

[0091] Fig. 11 is a schematic view illustrating an ingot of the silicon single crystal.

[0092] An ingot 600 of the silicon single crystal is manufactured by inserting the quartz glass crucible 11 according to the present embodiment into the lifting device 500 and lifting the quartz glass crucible using the method for manufacturing a silicon single crystal.

[0093] The block 600 has a shoulder portion 610 on a seed crystal 24 side, a straight trunk portion 620 extending from the shoulder portion 610, and an end portion 630 extending from the straight trunk portion 620. There is also a case where the seed crystal 24 is removed from the block 600. The diameter of the shoulder portion 610 gradually increases from the seed crystal 24 side to the straight trunk portion 620. The diameter of the straight trunk portion 620 is almost constant. The diameter of the end portion 630 gradually decreases as the portion becomes further away from the straight trunk portion 620.

[0094] The quality of the ingot 600 has a close relationship with the quality of the quartz glass crucible 11 being lifted. For example, the introduction of an impurity (e.g., a metallic impurity element in the glass) or a foreign substance into the quartz glass crucible 11 causes warping of the silicon single crystal in the ingot 600. Furthermore, depending on the smoothness (unevenness noticeable in appearance) of the inner surface of the quartz glass crucible 11 and the amount or size of air bubbles near the surface, when fine debris (particles exfoliated from the crucible inner surface, or the like) generated by chipping of the crucible surface and the breakage or collapse of air bubbles falls into the silicon melt, the fine debris is introduced into the ingot, causing warping of the single crystal.

[0095] In addition, in a case where a small crack remains on the outer surface of the crucible, if the silicon raw material is introduced into the crucible and a force is applied, there is a risk that the crack may propagate. If this crack causes the crucible to break, there is a possibility that the molten silicon raw material may leak out.

[0096] In the quartz glass crucible 11 according to the present embodiment, the breakage or chipping of the inner surface IS or the outer surface OS is suppressed, and thus the generation of a crystal defect in the block 600 lifted by the quartz glass crucible 11 is suppressed.

[0097] As described above, according to the present embodiment, it becomes possible to provide the quartz glass crucible 11 capable of sufficiently ensuring the strengths of the inner surface IS and the outer surface OS of the quartz glass crucible 11, and to provide a method for producing a high-quality silicon single crystal. In particular, the quartz glass crucible 11 that is preferable in producing a silicon single crystal for a semiconductor using the CZ method is provided.

[0098] The present embodiment has been described above, but the present invention is not limited to these examples. For example, the respective embodiments described above, in which a person skilled in the art appropriately makes the addition, omission, and design change of a configuration element, or an appropriate combination of the features of the respective embodiments, are also included in the scope of the present invention as long as they conform to the gist of the present invention. [List of reference symbols] 11 quartz glass crucibles 11a Side wall section 11b Corner section 11c floor section 13 transparent layer 15 non-transparent layer 20 Carbon form 21 Ventilation hole 23 Silicon melt 23a Liquid surface 24 Seed crystal 25 silicon single crystal 30 arc electrode 201 first silicon dioxide powder 202 second silicon dioxide powder 500 lifting device 510 Chamber 520 Carbon susceptor 530 supporting shaft 540 heating element 550 heat insulation pipe 560 lifting equipment 561 wire cable 570 heat shielding element 571 conical section 572 flange section 600 blocks 610 shoulder section 620 Straight trunk section 630 final section B floor section C bevelled section IS inner surface OS outer surface R1 first area R2 second area R3 third area SP1 sample SP2 sample SP3 sample TP upper end face ra radius rb radius rc radius< / hebevorrichtung> < / quarzglastiegel>

Claims

[1] Quartz glass crucible, comprising: a cylindrical sidewall portion; a curved floor section; and a corner portion provided between the side wall portion and the bottom portion and having a greater curvature than a curvature of the bottom portion, wherein a first region provided from a crucible inner surface to a center in a thickness direction, a second region provided outside the first region in the thickness direction and having a different stress distribution than the first region, and a third region which is provided outside the second region in the thickness direction and up to a crucible outer surface and has a different stress distribution than the second region, internal residual stresses of the first area and the third area are compressive stresses and an internal residual stress of the second region comprises a tensile stress, characterized by that a surface roughness of the crucible outer surface is 10 µm or more and 50 µm or less in terms of Ra (arithmetic mean roughness) and 80 µm or more and 200 µm or less in terms of Rz (maximum height), each measured according to JIS (Japanese Industrial Standards) B0601-2001. [2] The quartz glass crucible according to claim 1, wherein the internal residual stress of the second region does not include compressive stress and the second region is adjacent to each of the first region and the third region. [3] The quartz glass crucible according to claim 1 or 2, wherein a thickness of the first region in the thickness direction from the crucible inner surface is 1 mm or more, and preferably 3 mm or more. [4] A quartz glass crucible according to any one of claims 1 to 3, wherein a thickness of the third region in the thickness direction from the crucible outer surface is 1 mm or more, and preferably 5 mm or more. [5] Quartz glass crucible according to one of claims 1 to 4, wherein when a grain is struck against the crucible inner surface with a force of 300 Newton (N) according to the test method disclosed in WO 2016 / 047694, a diameter of a notch on the crucible inner surface is 5 mm or less, and preferably 1 mm or less.

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