Quartz glass crucible

Abstract

The invention relates to a crucible capable of sufficiently ensuring the strength of the inner surface and the outer surface of the crucible. One embodiment of the present invention is a quartz glass crucible provided with a cylindrical side wall section, a curved bottom section, and a corner section provided between the side wall section and the bottom section and having a curvature higher than that of the bottom section, the quartz glass crucible being provided with: a first region provided midway from the inner surface of the crucible in the thickness direction; a second region provided on the outside of the first region in the thickness direction and having a strain distribution different from that of the first region; and a third region which is provided to the outer surface of the crucible at a position further outward than the second region in the thickness direction and has a strain distribution different from that of the second region, the internal residual stress of the first region and the third region being compressive stress, and the internal residual stress of the second region including tensile stress.

Description

Technical Field

[0001] This invention relates to a quartz glass crucible. Background Technology

[0002] Monocrystalline silicon is manufactured by pulling a molten silicon raw material (polycrystalline silicon) into a quartz glass crucible while simultaneously contacting and rotating a seed crystal with the molten polycrystalline silicon (CZ method: Czeklaussky method). The quartz glass crucible used in this CZ method is manufactured using a rotary mold process.

[0003] That is, the manufacturing method of quartz glass crucible based on the rotary mold method includes: a quartz powder layer forming process, in which quartz powder with an average particle size of about 100μm to 400μm is deposited on the inner side of a rotating carbon mold by using centrifugal force to form a quartz powder layer; and an electric arc melting process, in which the quartz powder layer is melted by electric arc while the pressure is reduced from the mold side to form a quartz glass layer.

[0004] In the arc melting process, a so-called sealing layer is formed by thinly vitrifying the outermost surface of the quartz powder layer. Then, air bubbles are removed by rapidly reducing pressure to form a transparent quartz glass layer (hereinafter also referred to as the "transparent layer"). Then, a bubble-containing quartz glass layer (hereinafter also referred to as the "non-transparent layer") is formed due to the weakening of pressure reduction. Thus, a quartz glass crucible with a double-layer structure, such as having a transparent layer on the inner surface and a non-transparent layer on the outer surface, is formed.

[0005] In this arc melting process, quartz powder is initially sintered. After volume diffusion, the temperature rises further, causing grain boundaries to disappear, thus forming a vitrified and Si-O-Si network structure. At this point, the sintering rate or vitrification rate gradually changes. Specifically, for example, if the quartz powder is fine, or even if the volume is the same but the surface area is large, the sintering rate or vitrification rate increases. If the quartz powder is fine, the space between adjacent quartz powder particles also becomes smaller, and sintering and vitrification occur faster than the rate of removing bubbles by depressurization. Therefore, the resulting glass crucible contains smaller and more numerous bubbles. Thus, the molecular structure of the glass after arc melting changes due to the sintering rate or vitrification rate.

[0006] Furthermore, the molten quartz glass is solidified through a cooling process following the arc melting process. During this cooling process, the bonding mode between silicon and oxygen (e.g., 6-membered rings, 8-membered rings) or the size of the interatomic gaps in the silicon-oxygen bonding structure are altered by cooling methods such as cooling rate or the blowing of cooling gas. For example, if the proportion of structures with larger rings, such as 8-membered rings, increases, the number of gaps also increases. Thus, depending on the conditions of the melting or cooling processes during crucible manufacturing, the bonding state of the material atoms changes in a complex manner, resulting in changes in the distribution of residual stress inside the quartz glass crucible after cooling, thereby affecting the crucible's strength.

[0007] Patent Document 1 discloses a method for manufacturing monocrystalline silicon using a quartz glass crucible that suppresses deformation even under prolonged high-temperature conditions. The quartz glass crucible used in this method comprises: a compressive stress layer having a transparent layer on its inner side and a bubble layer on its outer side, with compressive stress remaining on the inner surface 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, with residual tensile stress.

[0008] Patent Document 2 discloses a quartz glass crucible with high strength at high temperatures and easy removal at the end of the lifting process. The quartz glass crucible comprises an outer quartz glass layer disposed on the outer surface of the crucible, an inner quartz glass layer disposed on the inner surface of the crucible, and an intermediate quartz glass layer disposed between the outer quartz glass layer and the inner quartz glass layer.

[0009] Patent document 3 discloses a quartz glass crucible that suppresses the expansion of bubbles present in the quartz glass crucible and obtains a high single crystallization rate. In this quartz glass crucible, the transparent layer contains compressive stress that is half the breaking strength of the opaque layer.

[0010] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2017-001951 Patent Document 2: International Publication No. 2011 / 013695 Patent document 3: Japanese Patent Application Publication No. 11-278855. Summary of the Invention

[0011] The technical problem that the invention aims to solve The quality of the quartz glass crucible is closely related to the quality of the single-crystal silicon (silicon ingot) produced when single-crystal silicon is pulled using the quartz glass crucible (e.g., CZ method). For example, tiny debris (particles detached from the crucible, etc.) caused by defects on the inner surface of the quartz glass crucible and the rupture or fragmentation of bubbles can detach into the silicon molten metal. This debris can lead to dislocations in the silicon ingot.

[0012] Furthermore, when filling a quartz glass crucible with silicon material, the silicon material (polycrystalline silicon) sometimes collides violently with the inner surface of the crucible. If the strength of the inner surface of the crucible is insufficient, cracks or fractures may occur on the inner surface of the crucible during the filling of silicon material.

[0013] Furthermore, when handling quartz glass crucibles, there is a possibility that an object may collide with the outer surface of the crucible. If the strength of the outer surface of the crucible is insufficient, cracks or breaks may sometimes occur in the quartz glass crucible.

[0014] Furthermore, if the surface roughness of the outer surface of the crucible is below a specified value, the friction between the quartz glass crucible and the carbon substrate will decrease in the CZ pulling device, and the quartz glass crucible will deform during CZ pulling, which will cause a decrease in the quality of single crystal silicon (e.g., single crystallization rate).

[0015] The purpose of this invention is to provide a quartz glass crucible that can adequately ensure the strength of the inner and outer surfaces of the crucible.

[0016] Solutions for solving technical problems One aspect of the present invention comprises a quartz glass crucible having a cylindrical sidewall portion, a curved bottom portion, and a corner portion having a curvature higher than that of the bottom portion disposed between the sidewall portion and the bottom portion. The quartz glass crucible includes: a first region disposed from the inner surface of the crucible to the middle in the wall thickness direction; a second region disposed further outward in the wall thickness direction than the first region and having a different strain distribution than the first region; and a third region disposed further outward in the wall thickness direction than the second region and disposed to the outer surface of the crucible, and having a different strain distribution than the second region. The internal residual stress of the first region and the third region is compressive stress, and the internal residual stress of the second region includes tensile stress.

[0017] According to this structure, as the internal residual stress of the quartz glass crucible, the inner surface side (region 1) and the outer surface side (region 3) in the wall thickness direction become compressive stress, while the central part (region 2) becomes tensile stress. Therefore, the strength of the inner surface and the outer surface of the crucible can be sufficiently ensured respectively.

[0018] In the aforementioned quartz glass crucible, the internal residual stress in the second region may be configured such that it does not include compressive stress, and the second region is adjacent to both the first and third regions. This creates a three-layer structure with a stress distribution of compressive stress, tensile stress, and internal residual stress along the wall thickness direction of the quartz glass crucible.

[0019] In the aforementioned quartz glass crucible, the wall thickness in the first region can be 1 mm or more from the inner surface of the crucible, preferably 3 mm or more. Therefore, when polycrystalline silicon, the material used for pulling monocrystalline silicon, is filled into the quartz glass crucible, sufficient strength can be ensured even if the polycrystalline silicon impacts the inner surface of the crucible.

[0020] In the aforementioned quartz glass crucible, the wall thickness of the third region can be 1 mm or more from the outer surface of the crucible, preferably 5 mm or more. Therefore, even when applying pressure to the outer surface of the crucible during handling, sufficient strength can be ensured.

[0021] In the aforementioned quartz glass crucible, when a punch is struck against the inner surface of the crucible with a force of 300 Newtons (N), the diameter of the indentation on the inner surface of the crucible can be 5 mm or less, preferably 1 mm or less. Therefore, when polycrystalline silicon, the material used for pulling monocrystalline silicon, is filled into the quartz glass crucible, sufficient strength can be ensured even when the polycrystalline silicon impacts the inner surface of the crucible.

[0022] In the aforementioned quartz glass crucible, the surface roughness of the outer surface of the crucible can be 10 μm or more and 50 μm or less, measured in Ra (arithmetic mean roughness: JIS (Japanese Industrial Standard) B0601-2001). This suppresses the formation of cracks or fractures caused by unevenness on the outer surface of the crucible, and the appropriate unevenness optimizes the friction between the quartz glass crucible and the carbon substrate.

[0023] Invention Effects According to the present invention, a quartz glass crucible that can sufficiently ensure the strength of the inner and outer surfaces of the crucible can be provided. Attached Figure Description

[0024] Figure 1 (a) and (b) are schematic diagrams illustrating quartz glass crucibles.

[0025] Figure 2 (a) and (b) are diagrams illustrating the area of ​​the quartz glass crucible.

[0026] Figure 3 (a) to (c) are figures illustrating the measurement results of the internal residual stress of a quartz glass crucible.

[0027] Figure 4 This is a diagram illustrating the impact position based on automatic center punch.

[0028] Figure 5 (a) and (b) are illustrations of impact marks.

[0029] Figure 6This is a flowchart schematically illustrating the manufacturing process of a quartz glass crucible.

[0030] Figure 7 (a) and (b) are schematic diagrams illustrating the manufacturing method of a quartz glass crucible.

[0031] Figure 8 (a) and (b) are schematic diagrams illustrating the manufacturing method of a quartz glass crucible.

[0032] Figure 9 This is a schematic diagram showing the overall structure of a monocrystalline silicon manufacturing apparatus, namely a Czochralski device.

[0033] Figure 10 (a) to (c) are schematic diagrams illustrating the method for manufacturing monocrystalline silicon using the quartz glass crucible described in this embodiment.

[0034] Figure 11 This is a schematic diagram illustrating a single-crystal silicon ingot. Detailed Implementation

[0035] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the following description, the same reference numerals will be used to denote the same parts, and descriptions of parts that have already been described once will be omitted where appropriate.

[0036] <Quartz Glass Crucible> Figure 1 (a) and (b) are schematic diagrams illustrating quartz glass crucibles.

[0037] exist Figure 1 (a) shows a perspective view of the quartz glass crucible 11. Figure 1 (b) shows a cross-sectional view of the quartz glass crucible 11.

[0038] The quartz glass crucible 11 has a corner portion 11b with a relatively high curvature, a cylindrical sidewall portion 11a with an edge portion having an opening on the upper surface, and a bowl-shaped bottom 11c composed of straight lines or curves with a relatively low curvature.

[0039] In this embodiment, corner 11b is the portion connecting sidewall 11a and bottom 11c, and represents the portion from the point where the tangent of the curve of corner 11b overlaps with the sidewall 11a of the quartz glass crucible 11 to the point where it shares a common tangent with the bottom 11c. In other words, the point where the curvature of the sidewall 11a of the quartz glass crucible 11 begins is the boundary between the sidewall 11a and corner 11b. Furthermore, the portion of the bottom of the quartz glass crucible 11 where the curvature is substantially constant is the bottom 11c, and the point where the curvature begins to change as the distance from the center of the bottom of the quartz glass crucible 11 increases is the boundary between the bottom 11c and corner 11b.

[0040] In the wall thickness direction (also referred to as the thickness direction) of the quartz glass crucible 11, a transparent layer 13 is provided on the inner surface of the crucible (hereinafter also referred to as "inner surface IS") and a non-transparent layer 15 is provided on the outer surface of the crucible (hereinafter also referred to as "outer surface OS").

[0041] The transparent layer 13 is a layer that is substantially free of bubbles. Here, "substantially free of bubbles" means the bubble content and bubble size that do not reduce the monocrystalline silicon yield due to bubbles. For example, the bubble content of the transparent layer 13 is less than 0.1%, and the average diameter of the bubbles is less than 100 μm.

[0042] The transparent layer 13 preferably comprises synthetic quartz glass on its inner surface IS side. Synthetic quartz glass, for example, refers to quartz glass manufactured by melting raw materials synthesized through the hydrolysis of silanolates. Generally, synthetic quartz has the characteristic of lower concentrations of metallic impurities and higher concentrations of OH groups compared to natural quartz. For example, the content of each metallic impurity in synthetic quartz is less than 0.05 ppm, and the content of OH groups is 30 ppm or more. Since synthetic quartz containing metallic impurities such as Al is known, whether it is synthetic quartz should not be determined based on a single factor, but rather on a comprehensive assessment of multiple factors. Thus, synthetic quartz glass has fewer impurities than natural quartz glass, thereby preventing the increase of impurities molten into the silicon from the crucible, and thus improving the silicon single crystallization rate.

[0043] Multiple air bubbles are present within the opaque layer 15. The opaque layer 15 appears cloudy due to these air bubbles. The opaque layer 15 is preferably made of natural quartz glass. Natural quartz glass refers to quartz glass manufactured by melting natural raw materials such as natural crystal and silica. Generally, natural quartz has the characteristic of having a higher concentration of metallic impurities and a lower concentration of OH groups compared to synthetic quartz. For example, natural quartz contains more than 1 ppm of Al, more than 0.1 ppm of alkali metals (Na, K, and Li), and less than 60 ppm of OH groups.

[0044] Furthermore, determining whether something is natural quartz should not be based on a single factor, but rather on a comprehensive assessment of multiple factors. Natural quartz has higher viscosity at high temperatures compared to synthetic quartz, thus improving the overall heat resistance of the crucible. Moreover, natural raw materials are cheaper than synthetic quartz, offering a cost advantage.

[0045] Figure 2 (a) and (b) are diagrams illustrating the area of ​​the quartz glass crucible.

[0046] exist Figure 2 (a) shows the view from the top end face TP side. Figure 1 The enlarged cross-sectional view of the quartz glass crucible 11 shown is in... Figure 2 (b) shows the route along Figure 2 Example of internal residual stress in line SL in the wall thickness direction in (a).

[0047] like Figure 2 As shown in (a), the quartz glass crucible 11 of this embodiment includes a first region R1 that extends from the inner surface IS to the middle in the wall thickness direction, a second region R2 that is located further outward than the first region R1 in the wall thickness direction, and a third region R3 that is located further outward than the second region R2 in the wall thickness direction and is located on the outer surface OS.

[0048] like Figure 2 As shown in (b), in this embodiment, the internal residual stress in region 1 R1 is compressive stress, the internal residual stress in region 2 R2 is tensile stress, and the internal residual stress in region 3 R3 is compressive stress. Furthermore, in Figure 2 In (b), the horizontal axis represents the position on line SL in the wall thickness direction with the inner surface as the origin "0", and the vertical axis represents the magnitude of the internal residual stress with "+" representing the compression side and "-" representing the tension side. In addition, in this embodiment, unless otherwise specified, the compressive stress and tensile stress represent the internal residual stress.

[0049] exist Figure 2 In the example shown, region 2 R2 does not contain compressive stress, and region 2 R2 is adjacent to region 1 R1 and region 3 R3 respectively. Thus, in the wall thickness direction, a three-layer structure is formed that constitutes the stress of region 1 R1, region 2 R2 and region 3 R3.

[0050] In the quartz glass crucible 11, regions R1, R2, and R3 are continuous in the circumferential direction. That is, for each of regions R1, R2, and R3, there is no significant stress variation (the stress distribution is substantially the same) at least in the circumferential direction.

[0051] In the quartz glass crucible 11, the first region R1 becomes compressive stress, improving the strength of the inner surface IS. For example, when using the quartz glass crucible 11 for the pulling of single-crystal silicon, polycrystalline silicon is filled inside the quartz glass crucible 11. At this time, the inner surface IS of the quartz glass crucible 11 is susceptible to impact. By using the first region R1 as compressive stress, sufficient resistance to impacts during the filling of polycrystalline silicon can be obtained.

[0052] Furthermore, in the quartz glass crucible 11, the compressive stress in the third region R3 increases the strength of the outer surface OS. Therefore, even when applying pressure to the outer surface OS during handling of the quartz glass crucible 11, sufficient strength can be ensured.

[0053] Figure 3 (a) to (c) are figures illustrating the measurement results of the internal residual stress of a quartz glass crucible.

[0054] exist Figure 3 In (a) to (c), for samples SP1 to SP3 from which a portion of the quartz glass crucible was cut out, the results of measuring the internal residual stress by the sharp colorimetric method are shown.

[0055] Here, sharp colorimetry refers to a method that observes the presence and direction of internal stress (tensile stress / compressive stress) by placing two polarizers orthogonally between them and observing the change in the glass color when a component with strained glass, creating an optical path difference, is added between them. In sharp colorimetry, the background color becomes purplish-red. When there is no internal stress in the observed object, the same color as the background is observed. On the other hand, when internal stress exists in the observed object, a color change such as blue or orange is observed depending on the direction of the tensile / compressive stress.

[0056] Figure 3 (a) The sample SP1 and Figure 3 (b) The sample SP2 shown is a portion cut from the quartz glass crucible 11 involved in this embodiment. Figure 3 (c) The sample SP3 shown is a portion cut from the quartz glass crucible involved in the reference example.

[0057] Each sample SP1 to SP3 was cut from the same part of the quartz glass crucible (150 mm in height from the top surface TP).

[0058] In each figure, areas where compressive stress was measured are marked with "+", and areas where tensile stress was measured are marked with "-".

[0059] exist Figure 3 In samples SP1 and SP2 shown in (a) and (b), the residual stress from the inner surface IS to the outer surface OS along the wall thickness direction changes in the order of compressive stress "+", tensile stress "-", and compressive stress "+". The region of compressive stress on the inner surface IS side is region 1 R1, the region of tensile stress is region 2 R2, and the region of compressive stress on the outer surface OS side is region 3 R3.

[0060] exist Figure 3 In sample SP3 shown in (c), the inner surface IS extends from the wall thickness direction to the outer surface OS, while the internal residual stress changes in the order of compressive stress "+", tensile stress "-", compressive stress "+" and tensile stress "-".

[0061] A strength (breakage) test was performed on the quartz glass crucibles before these samples SP1 to SP3 were cut. The quartz glass crucibles were 32 inches in outer diameter (approximately 81.2 cm in outer diameter).

[0062] Strength tests are conducted by applying an impact based on an automatic center punch to determine whether fracture occurs.

[0063] Here, the test based on the automatic center punch uses, for example, the method disclosed in International Publication No. 2016 / 047694. That is, the automatic center punch comprises a shaft consisting of a rod-shaped metal part with a sharp front end, a hammer located at the rear end of the shaft, a coil spring that applies force to the shaft in the direction of its rear end, a coil spring located at the rear end of the hammer, and a generally cylindrical housing housing them. The automatic center punch is capable of instantaneously applying a large load to an object in contact with the front end of the shaft.

[0064] Figure 4 This is a diagram illustrating the location of the impact. That is, as shown... Figure 4 As shown, the impact locations are the radii ra, rb, and rc, measured from the center (BC) of the bottom B on the inner surface of the quartz glass crucible when viewed from the top surface TP. The load applied by the automatic centering punch is 300 Newtons (N).

[0065] The experimental method is as follows.

[0066] (1) Impacts were applied sequentially to 16 points at a radius of ra = 200 mm.

[0067] (2) In (1) above, if no crack occurs, impact is applied sequentially to 16 points at a position with a radius of rb=150mm.

[0068] (3) In (2) above, if no crack occurs, impact is applied sequentially to 16 points at a position with a radius of rc = 250 mm.

[0069] The test results showed that no breakage occurred in the quartz glass crucibles based on samples SP1 and SP2. On the other hand, in the quartz glass crucible based on sample SP3, breakage occurred when an impact was applied at a position 200 mm from the center BC of the bottom B.

[0070] The experimental results show that sufficient strength can be ensured by having compressive stress in the regions on the inner surface (IS side) and outer surface (OS side) of the quartz glass crucible. Therefore, as in samples SP1 and SP2, the regions with compressive stress on the inner surface (IS side) and outer surface (OS side) are very important in obtaining sufficient strength for the quartz glass crucible.

[0071] The distribution of internal residual stress in the wall thickness direction varies depending on the thermal history, which is based on factors such as arc melting, cooling rate, and heating mode during the manufacture of the quartz glass crucible. By controlling the thermal history, regions of compressive stress can be created on both the inner surface (IS side) and the outer surface (OS side).

[0072] Figure 5 (a) and (b) are illustrations of impact marks based on automatic center punches.

[0073] exist Figure 5 (a) shows an example of an impact mark observed in a direction orthogonal to the inner surface. Figure 5 (b) shows an example of an impact mark observed in a direction orthogonal to the wall thickness direction.

[0074] like Figure 5 As shown in (a), the size of the impact mark is approximately 5 mm. Here, the size of the indentation produced when filling the quartz glass crucible with polycrystalline silicon is approximately 1 mm. Furthermore, as... Figure 5 As shown in (b), the depth of the impact mark is approximately 3 to 4 mm. Here, the depth of the indentation produced when polycrystalline silicon is filled into the quartz glass crucible is approximately 2 mm.

[0075] Thus, the impact of 300N from the automatic center punch is much greater than the indentation experienced when filling polycrystalline silicon. Therefore, in the quartz glass crucible (in this embodiment) based on samples SP1 and SP2, which did not crack according to the above test results, it can be said that the strength when filling polycrystalline silicon can be sufficiently ensured.

[0076] Based on the above test results, when the inner surface IS is impacted by an automatic center punch with a force of 300N, the diameter of the indentation on the inner surface IS is 5mm or less, preferably 1mm or less. Furthermore, in the quartz glass crucible 11 of this embodiment, the compressive stress, i.e., the thickness in the wall thickness direction of the first region R1, exists from the inner surface IS for 1mm or more, preferably 3mm or more, and more preferably the thickness of the transparent layer covers the entire region.

[0077] Therefore, when polycrystalline silicon is filled into the quartz glass crucible 11, even if the polycrystalline silicon collides with the inner surface of the crucible, its indentation is limited to the first region R1, thereby suppressing the generation of cracks based on the indentation and ensuring sufficient strength.

[0078] Furthermore, in the quartz glass crucible 11 of this embodiment, the wall thickness of the third region R3 is at least 1 mm from the outer surface OS, preferably at least 5 mm. Therefore, when handling the quartz glass crucible, even if pressure or impact is applied to the outer surface of the crucible, the indentation is confined within the third region R3, thereby suppressing the formation of cracks based on the indentation and ensuring sufficient strength.

[0079] In large crucibles (32 inches or more in outer diameter) or ultra-large crucibles (40 inches or more in outer diameter) of the quartz glass crucible 11, the distribution of internal residual stress in the thickness direction of the quartz glass crucible 11 has a significant impact on cracking, fracture, and peeling. Especially when the outer diameter of the crucible is increased, the rate of increase in wall thickness is higher than the rate of increase in outer diameter. That is, the wall thickness tends to increase relatively with the increase in the outer diameter of the crucible. Therefore, the larger the outer diameter of the crucible, the more complex the stress distribution in the wall thickness direction becomes, which easily leads to insufficient strength. In this embodiment, compressive stress is set in the first region R1 on the inner surface IS side and the third region R3 on the outer surface OS side in the wall thickness direction of the quartz glass crucible 11, which is particularly effective in improving the strength of large and ultra-large crucibles.

[0080] Furthermore, in the quartz glass crucible 11 according to this embodiment, the surface roughness of the outer surface OS, measured in terms of Ra (arithmetic mean roughness), is 10 μm or more and 50 μm or less. The surface roughness of the outer surface OS, measured in terms of Rz (maximum height), is 80 μm or more and 200 μm or less. In this embodiment, Ra (arithmetic mean roughness) and Rz (maximum height) are values ​​measured according to JIS (Japanese Industrial Standard) B0601-2001. If the unevenness (surface roughness) of the outer surface OS exceeds the above-mentioned upper limits, the unevenness of the outer surface OS becomes prominent, and the difference in height between these unevennesses makes it easy for cracks or breaks to occur at the recesses. The outer surface OS of the quartz glass crucible 11 is easily subjected to external forces during handling. Therefore, by specifying the surface roughness of the outer surface OS in the above manner, the generation of cracks or breaks caused by the difference in height between the unevenness of the outer surface OS can be suppressed.

[0081] On the other hand, if the surface roughness of the outer surface OS is less than the aforementioned lower limit, the quartz glass crucible 11 is prone to deviate within the carbon substrate during CZ lifting, and deformations such as sinking of the sidewall portion 11a are likely to occur when used at high temperatures. That is, if the surface roughness of the outer surface OS is too small, the friction between the outer surface OS and the carbon substrate decreases, making it easier for the quartz glass crucible 11 to deform during CZ lifting. Therefore, by setting the Rz (maximum height) of the outer surface OS to 80 μm or more, the friction between the quartz glass crucible 11 and the carbon substrate is increased to a certain extent through appropriate unevenness of the outer surface OS. This makes it easier to suppress deformation of the quartz glass crucible 11 during CZ lifting.

[0082] Furthermore, in the quartz glass crucible 11 according to this embodiment, an example of a stress-triple-layer structure is shown where the second region R2 is adjacent to both the first region R1 and the third region R3, but this is not a limitation. That is, the first region R1, which serves as compressive stress, is provided on the inner surface IS side, and the third region R3, which also serves as compressive stress, is provided on the outer surface OS side of the quartz glass crucible 11, with the second region R2, which serves as tensile stress, included between the first region R1 and the third region R3. For example, the region of tensile stress and the region of compressive stress may alternate between the first region R1 and the third region R3. In this case, both tensile and compressive stresses coexist in the second region R2.

[0083] <Method for Manufacturing Quartz Glass Crucibles> Figure 6 This is a flowchart schematically illustrating the manufacturing process of a quartz glass crucible.

[0084] and, Figure 7 (a) ~ Figure 8 (b) is a schematic diagram illustrating the manufacturing method of a quartz glass crucible.

[0085] The quartz glass crucible 11 is manufactured using a rotary molding process. For example... Figure 6 As shown, in the rotary molding process, the quartz glass crucible 11 is manufactured by forming a quartz powder layer on a carbon mold (step S101), arc melting and depressurization (step S102), cooling (step S103), polishing (step S104), and edge cutting and edge treatment (step S105).

[0086] First, in the formation of the quartz powder layer of the carbon mold as shown in step S101, such as Figure 7 As shown in (a), a carbon mold 20 with a cavity matching the shape of the quartz glass crucible 11 is prepared. While rotating the carbon mold 20, first quartz powder 201 is supplied and scraped using a scraper until it reaches a predetermined thickness. This forms a layer of quartz powder along the inner surface of the mold. Because the carbon mold 20 rotates at a constant speed, the supplied first quartz powder 201, adhered to the inner surface of the mold due to centrifugal force, remains in a constant position, and its shape is maintained. The first quartz powder 201 is an opaque layer, therefore natural quartz powder is preferred.

[0087] Next, as Figure 7 As shown in (b), a second quartz powder 202 is supplied to the carbon mold 20 on which the first quartz powder 201 layer is formed, further thickening the quartz powder layer. The second quartz powder 202 is supplied to the first quartz powder 201 on the inner surface of the mold at a predetermined thickness. The second quartz powder 202 is preferably synthetic quartz powder, but it can also be natural quartz powder.

[0088] Next, in the arc melting and depressurization shown in step S102, as... Figure 8 As shown in (a), an arc potential 30 is set inside the cavity of the carbon mold 20. While rotating the carbon mold 20, an arc discharge is performed from the inside of the carbon mold 20, heating the entire quartz powder layer to above 1720°C and melting it. At this time, a thin quartz glass sealing layer is formed throughout the circumference. Moreover, at the same time as this heating, the pressure is reduced from the carbon mold 20 side, and the gas inside the quartz is drawn to the outer layer through the vent 21 provided in the carbon mold 20, and the voids in the heated quartz powder layer are degassed, thereby removing air bubbles from the inner surface of the crucible. As a result, a transparent layer 13 that does not contain air bubbles is formed.

[0089] A cooling mechanism (not shown) is provided in the carbon mold 20. This prevents the quartz that forms the outer surface of the quartz glass crucible 11 from vitrifying. The cooling temperature of the cooling mechanism is such that the quartz will not vitrify and will remain as a sintered body and powder residue.

[0090] Then, while continuing to heat, the pressure reduction used for degassing is reduced or stopped, leaving the bubbles behind, thereby forming an opaque layer 15 containing multiple tiny bubbles.

[0091] Next, in the cooling process shown in step S103, the power supply to the arc potential 30 is stopped to cool the molten quartz glass, thus forming the shape of the quartz glass crucible 11. During cooling, cooling gas is blown onto the quartz glass that forms the inner surface of the quartz glass crucible 11. The distribution of residual stress inside the quartz glass crucible 11 is determined based on cooling conditions such as the cooling rate and the method of blowing the cooling gas. Therefore, by adjusting the cooling conditions, a quartz glass crucible 11 with a desired strain distribution can be manufactured.

[0092] Furthermore, the internal residual stress of the quartz glass crucible 11 also changes according to the thermal history during the manufacture of the crucible. For example, the temperature gradient from the inner surface to the outer surface of the crucible, the stress distribution at the boundary between the softened and unsoftened parts, and the stress balance when the softened part is cooled and solidified, all change according to the thermal history until the quartz glass crucible 11 is completed.

[0093] Thus, based on the thermal history, the heating states differ from the inner surface to the outer surface of the crucible. Therefore, it is presumed that there are differences in the distribution of forces that are intended to suppress deformation in the heated area, and also in the state of the compressive / tensile stress layers distributed in layers from the inner surface to the outer surface of the crucible. Therefore, by controlling the thermal history, the desired strain distribution of the quartz glass crucible 11 can be obtained.

[0094] Next, as a polishing process shown in step S104, the outer surface OS of the quartz glass crucible 11 is sandblasted to achieve a specified surface roughness. In this embodiment, the surface roughness of the outer surface OS is set to be 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) through this polishing process.

[0095] Furthermore, in the edge cutting and edge processing shown in step S105, such as Figure 8 As shown in (b), the height of the quartz glass crucible 11 is adjusted by cutting a portion of the upper end of the side wall 11a of the quartz glass crucible 11 removed from the carbon mold 20. Then, the edges of the upper end face TP, namely the inner and outer peripheries, are chamfered to form a chamfered portion C. After cutting the edges, the crucible 11 is cleaned to complete the quartz glass crucible 11.

[0096] <Lifting Device> Figure 9 This is a schematic diagram showing the overall structure of a monocrystalline silicon manufacturing apparatus, namely a Czochralski device.

[0097] Inside the chamber 510 that forms the exterior of the lifting device 500, a quartz glass crucible 11 containing molten silicon 23 is disposed, and a carbon base 520 is disposed to cover the outer side of the quartz glass crucible 11. The carbon base 520 is fixed to the upper end of a support shaft 530 parallel to the vertical direction. The quartz glass crucible 11, fitted into the carbon base 520, rotates together with the carbon base 520 in a predetermined direction via the support shaft 530, and can move vertically to control the liquid level of the molten silicon relative to the heater 540 in the furnace to a constant height (making the temperature gradient constant).

[0098] The outer periphery of the quartz glass crucible 11 and the carbon substrate 520 is surrounded by a heater 540. Furthermore, the heater 540 is surrounded by an insulation cylinder 550. During the raw material melting process in the growth of monocrystalline silicon, the high-purity polycrystalline silicon raw material filled in the quartz glass crucible 11 is heated and melted by the heater 540 to become molten silicon 23.

[0099] A lifting mechanism 560 is provided at the upper end of the chamber 510 of the lifting device 500. A steel wire rope 561, hanging downwards towards the rotation center of the quartz glass crucible 11, is installed in this lifting mechanism 560, and a lifting motor (not shown) is provided for winding or feeding the steel wire rope 561. A seed crystal 24 is installed at the lower end of the steel wire rope 561. During lifting, the seed crystal 24 rotates, and the monocrystalline silicon 25 (ingot) also rotates simultaneously with growth.

[0100] A cylindrical heat shield 570 is disposed between the growing monocrystalline silicon 25 and the insulation cylinder 550, surrounding the growing monocrystalline silicon 25. The heat shield 570 has a tapered portion 571 and a flange portion 572. By mounting the flange portion 572 to the insulation cylinder 550, the heat shield 570 is positioned at a predetermined location (hot zone). The monocrystalline silicon 25 can be manufactured using this lifting device 500.

[0101] <Methods for Manufacturing Monocrystalline Silicon> Figure 10 (a) to (c) are schematic diagrams illustrating the method for manufacturing monocrystalline silicon using the quartz glass crucible described in this embodiment.

[0102] Monocrystalline silicon 25 is manufactured by placing the quartz glass crucible 11 involved in this embodiment on the pulling device 500 described above and pulling it.

[0103] First, such as Figure 10 As shown in (a), polycrystalline silicon is filled into a quartz glass crucible 11. In this state, the polycrystalline silicon is melted by heating with a heater disposed around the quartz glass crucible 11. This yields molten silicon 23. At this time, by using the quartz glass crucible 11 according to this embodiment, breakage of the crucible during filling can be prevented.

[0104] Next, the seed crystal 24, mounted on the steel wire rope 561, is lowered into contact with the molten silicon 23. Then, while rotating the steel wire rope 561, it is slowly pulled up. Thus, as Figure 10 As shown in (b), monocrystalline silicon 25 is grown below the seed crystal 24. The pulling process is continued while controlling the pulling speed, as... Figure 10 As shown in (c), monocrystalline silicon 25 is grown into an ingot.

[0105] In the quartz glass crucible 11 of this embodiment, since cracks or defects on the inner surface IS or the outer surface OS are suppressed, foreign matter contamination during CZ pulling can be suppressed. Furthermore, due to the appropriate surface roughness of the outer surface OS, the frictional force between the quartz glass crucible 11 and the carbon substrate is increased in the CZ pulling apparatus, thereby suppressing the deformation of the quartz glass crucible 11 during CZ pulling, and thus enabling the production of single-crystal silicon with excellent quality (e.g., single crystallization rate).

[0106] <Single Crystal Silicon Ingot> Figure 11 This is a schematic diagram illustrating a single-crystal silicon ingot.

[0107] The monocrystalline silicon ingot 600 is manufactured by placing the quartz glass crucible 11 involved in this embodiment in the pulling device 500 and pulling it using the monocrystalline silicon manufacturing method described above.

[0108] Ingot 600 has a shoulder 610 on the side of the seed crystal 24, a straight body 620 continuing from the shoulder 610, and a tail 630 continuing from the straight body 620. Sometimes the seed crystal 24 is removed from ingot 600. The diameter of the shoulder 610 increases from the side of the seed crystal 24 throughout the straight body 620. The diameter of the straight body 620 is approximately constant. The diameter of the tail 630 decreases with distance from the straight body 620.

[0109] The quality of ingot 600 is closely related to the quality of the quartz glass crucible 11 used for pulling. For example, the incorporation of impurities (e.g., impurity metal elements in the glass) or foreign matter into the quartz glass crucible 11 can lead to dislocation of the single-crystal silicon in ingot 600. Furthermore, depending on the smoothness (visible unevenness) of the inner surface of the quartz glass crucible 11, the amount and size of bubbles near the surface, if tiny debris (particles peeled off from the inner surface of the crucible, etc.) caused by defects on the crucible surface, bubble rupture, and fragmentation falls into the molten silicon, it will be incorporated into the ingot and lead to dislocation of the single crystal.

[0110] Furthermore, when there is a crack or defect on the outer surface of the crucible, tiny cracks remain in that area. If silicon material is filled inside the crucible and a force is applied, there is a concern that these cracks may propagate. If these cracks develop into a fracture of the crucible, there is a possibility that the molten silicon material may leak out.

[0111] In the quartz glass crucible 11 of this embodiment, since the cracking or defects of the inner surface IS or the outer surface OS are suppressed, the crystal defects of the pulled ingot 600 can be suppressed by the quartz glass crucible 11.

[0112] As described above, according to the embodiments, a quartz glass crucible 11 that sufficiently ensures the strength of the inner surface IS and the outer surface OS of the quartz glass crucible 11, and a method for manufacturing high-quality single-crystal silicon, can be provided. In particular, a preferred quartz glass crucible 11 suitable for manufacturing single-crystal silicon for semiconductors by the CZ method is provided.

[0113] Furthermore, while the embodiments described above are specific to this invention, the invention is not limited to these examples. For instance, any additions, deletions, design changes, or appropriate combinations of features of the embodiments made by those skilled in the art to the foregoing embodiments, provided they capture the essence of the invention, are included within the scope of this invention.

[0114] Explanation of reference numerals in the attached figures 11-Quartz glass crucible, 11a-Sidewall, 11b-Corner, 11c-Bottom, 13-Transparent layer, 15-Opaque layer, 20-Carbon mold, 21-Ventilation hole, 23-Molten silicon, 23a-Liquid surface, 24-Seed crystal, 25-Single crystal silicon, 30-Arc potential, 201-First quartz powder, 202-Second quartz powder, 500-Pulling device, 510-Cavity, 520-Carbon base, 530-Support shaft, 540-Heater, 550-Insulation cylinder, 5 60 - Lifting mechanism, 561 - Steel wire rope, 570 - Heat shielding component, 571 - Conical part, 572 - Flange part, 600 - Spindle, 610 - Shoulder part, 620 - Straight body part, 630 - Tail part, B - Bottom, C - Chamfered part, IS - Inner surface, OS - Outer surface, R1 - Region 1, R2 - Region 2, R3 - Region 3, SP1 - Sample, SP2 - Sample, SP3 - Sample, TP - Upper end face, ra - Radius, rb - Radius, rc - Radius.

Claims

1. A quartz glass crucible comprising a cylindrical sidewall, a curved bottom, and a corner portion disposed between the sidewall and the bottom and having a curvature greater than that of the bottom, the quartz glass crucible comprising: The first region extends from the inner surface of the crucible to the middle in the wall thickness direction; The second region, located further outward in the wall thickness direction than the first region, has a different strain distribution than the first region; and The third region, located further outward in the wall thickness direction than the second region and extending to the outer surface of the crucible, has a different strain distribution than the second region. The residual stress inside the first region and the third region is compressive stress. The internal residual stress in the second region includes tensile stress. The aforementioned first region, second region, and third region are continuous in the circumferential direction. The surface roughness of the outer surface of the crucible is greater than or equal to 10 μm and less than 50 μm in terms of Ra, and greater than or equal to 80 μm and less than 200 μm in terms of Rz. Ra is the arithmetic mean roughness, measured according to Japanese Industrial Standard JIS B0601-2001; Rz is the maximum height, measured according to Japanese Industrial Standard JIS B0601-2001. The thickness of the third region is greater than or equal to the thickness of the first region. No fracture occurred when 16 points with a radius of ra = 200 mm were impacted sequentially.

2. The quartz glass crucible according to claim 1, wherein, The internal residual stress in the second region does not include compressive stress. The second region is adjacent to both the first region and the third region.

3. The quartz glass crucible according to claim 1 or 2, wherein, The thickness of the first region in the wall thickness direction is 1 mm or more from the inner surface of the crucible, preferably 3 mm or more.

4. The quartz glass crucible according to any one of claims 1 to 3, wherein, The thickness of the third region in the wall thickness direction is 1 mm or more from the outer surface of the crucible, preferably 5 mm or more.

5. The quartz glass crucible according to any one of claims 1 to 4, wherein, When the punch strikes the inner surface of the crucible with a force of 300N, the diameter of the indentation on the inner surface of the crucible is less than 5mm, preferably less than 1mm.

6. The quartz glass crucible according to any one of claims 1 to 5, wherein, A transparent layer is provided on the inner surface of the crucible, and a non-transparent layer is provided on the outer surface of the crucible. The first region is located over the entire thickness of the transparent layer.

7. The quartz glass crucible according to any one of claims 1 to 6, wherein, The quartz glass crucible has an outer diameter of 32 inches or more.

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