Single crystal pulling apparatus

Abstract

[Problem] To provide a single crystal pulling apparatus capable of preventing thermal liquid splashed and attached to a heat insulating member from falling onto a raw material melt surface in a simple manner. [Solution] A single crystal pulling apparatus using the Czochralski method, characterized by having a heat insulating member opposed to a raw material melt surface, the heat insulating member having a recess in a lower end surface thereof opposed to the raw material melt surface, the surface area of the lower end surface being 120% or more based on the surface area of a flat lower end surface not having the recess.

Description

Technical Field

[0001] This invention relates to a single crystal pulling device. Background Technology

[0002] In the growth of single crystals using the CZ method, the semiconductor raw material initially fed into the crucible (hereinafter referred to as raw material) is heated by a heater arranged in a manner that surrounds the crucible, and forms a raw material melt (initial charge).

[0003] In this initial loading, when the raw material in the lower part of the crucible melts, the raw material in the upper part deforms and falls into the molten liquid (first stage of falling). At this time, hot liquid splashes occur, and the molten raw material adheres to the lower end face of the heat insulation component.

[0004] In addition, the porosity of the raw material initially filled into the crucible is relatively large, and the filling rate of the raw material in the crucible is relatively small after the initial charge melts. Therefore, raw materials are usually added into the crucible after the initial charge melts.

[0005] During the addition of this raw material, when the raw material added into the crucible falls into the molten raw material, hot liquid splashes occur, and the molten raw material adheres to the lower end surface of the heat insulation component located above the surface of the molten raw material.

[0006] In cases of significant hydrothermal splashing, the splashes adhering to the lower surface of the insulation component aggregate and fall into the crucible due to their own weight. The insulation component is typically made of graphite. The graphite in the insulation component melts from the raw material adhering to it (hereinafter referred to as "hydrothermal splash"), resulting in a high carbon concentration in the hydrothermal splashes falling into the crucible. This creates a technical problem of carbon from the hydrothermal splashes being incorporated into the grown single crystal.

[0007] In addition, it is also believed that when growing single crystals using heat-insulating components with attached raw material molten liquid, if dopants such as boron and phosphorus, as well as impurities such as iron, are mixed in with the attached hot liquid splash in addition to carbon, the resistivity of the single crystal will change, resulting in crystallization defects.

[0008] Moreover, the following technical problems exist: the falling hydrothermal fluid splashes onto the surface of the raw material melt, causing the falling hydrothermal fluid to splash, solidify and suspend on the surface of the raw material melt along with the falling fluid, and attach to the growing single crystal, or the single crystal may become dislocated due to hydrothermal surface vibrations generated when falling onto the raw material melt.

[0009] Therefore, in order to prevent the molten material from scattering, when adding raw materials to the crucible, the surface of the molten material is solidified after the initial charging is completed. However, there are the following technical problems: depending on the progress of solidification, the quartz crucible may be damaged, causing the inner surface of the quartz crucible to peel off. The peeled quartz chips adhere to the growing single crystal, causing dislocation in the single crystal.

[0010] Furthermore, if over-curing occurs, the possibility of cracks appearing in the quartz crucible, leading to leakage of the molten material to the outside. Additionally, after reducing the heater power to allow the molten surface to solidify, raw materials are filled into the quartz crucible, and the heater power is increased again for melting. This results in time losses until solidification occurs and time losses until the solidified material after filling is melted.

[0011] To address the problem of increased carbon concentration caused by hot liquid splashing from the insulation component entering the crucible during operation, Patent Document 1 proposes a method to reduce carbon concentration in single crystals. This method involves a lower end of a shielding member made of graphite (used to prevent shielding against radiant heat) that becomes contaminated by contact with molten silicon. By using quartz as the material for the lower end of the shielding member, impurities generated from contact with the molten silicon are reduced. In this method, since the radiation shielding member is protected by the quartz-made lower end, even if silicon adhering to the lower end of the shielding member enters the crucible, an increase in carbon concentration during crystallization is prevented. However, in this method, since the radiation shielding member is in contact with the lower end of the shielding member, there is a problem of CO gas being generated due to the contact between the graphite component and the quartz. Specifically, in an embodiment of the method, a silicon single crystal with a diameter of 8 inches (200 mm) is grown. However, in a silicon single crystal manufacturing apparatus with a diameter of 12 inches (300 mm), due to the increased contact area between the radiation shield and the lower end of the shield, there is a problem that the generated CO gas mixes into the melt, causing the carbon concentration in the crystal to increase further.

[0012] In Patent Document 2, CO gas generation is suppressed and carbon concentration is prevented by holding a quartz plate at a distance from the radiation shield. However, due to the dual structure of quartz and heat insulation, the structure is complex and expensive. Furthermore, since the quartz is located directly above the melt, it may soften, thus limiting the power operation of the heater.

[0013] As a method for preventing molten hot liquid splashing, as described in Patent Document 3, there is also a method for feeding raw materials using a structure with an inner container and an outer container that slides. However, since it is a dual structure, the precision required to ensure the gap between the various structures makes it complex and expensive.

[0014] Patent Document 4 provides a device for preventing contamination of molten silicon. This device processes a heat-insulating component and uses a heat-insulating body surrounding the lifting path of monocrystalline silicon to prevent dust from falling into the molten silicon. Regarding the heat-insulating component, the upper opening is larger than the lower opening, and between the upper and lower openings, there is a raised surface with a height difference of approximately 0.5 to 10.0 mm on the inclined surface facing the lifting path of the monocrystalline silicon. Therefore, when hot liquid splashes adhere to the inner surface of the heat-insulating component, the raised surface suppresses the movement of the adhered silicon. However, since no raised surface is formed on the outer surface of the heat-insulating component, when hot liquid splashes adhere to the outer surface facing the molten raw material, the raised surface causes the adhered hot liquid splashes to collect due to gravity and fall from the heat-insulating component, mixing into the molten raw material.

[0015] Patent Document 5 proposes a method in which a recess is formed on the lower end face of a heat insulation component facing the molten silicon surface, and a reference reflector is placed inside the recess. This reference reflector is used to measure the distance between the lower end face of the heat insulation component and the molten silicon surface. Additionally, Patent Document 6 proposes a method where a groove serving as a scale is provided on a portion of the bottom surface of the heat insulation component. The position of the scale image formed on the surface of the molten silicon by reflection is observed to determine the height of the molten silicon.

[0016] However, patent documents 5 and 6 do not address the problem of hot liquid splashing from the heat insulation component onto the raw material molten liquid, nor do they mention any solutions to this problem.

[0017] Existing technical documents

[0018] Patent documents

[0019] Patent Document 1: Japanese Patent Application Publication No. 2007-191353

[0020] Patent Document 2: Japanese Patent Application Publication No. 2018-95538

[0021] Patent Document 3: Japanese Patent Application Publication No. 2005-1977

[0022] Patent Document 4: Japanese Patent Application Publication No. 2009-184917

[0023] Patent Document 5: Description of Japanese Patent No. 5577873

[0024] Patent Document 6: Japanese Patent Publication No. 2016-530206 Summary of the Invention

[0025] (a) Technical problems to be solved

[0026] The present invention is intended to solve the above-mentioned technical problems, and its purpose is to provide a single crystal pulling device that can prevent hot liquid splashing and adhering to the heat insulation component from falling onto the surface of the raw material melt in a simple way.

[0027] (II) Technical Solution

[0028] To solve the above-mentioned technical problems, the present invention provides a single crystal pulling device using the Czeklaussky method, characterized in that it has a heat insulation component facing the surface of the raw material melt, the lower end face of the heat insulation component facing the surface of the raw material melt having a recess, and the surface area of ​​the lower end face without the recess being a reference is 120% or more.

[0029] In the case of the single-crystal pulling apparatus of the present invention, even if hydrothermal splashes adhere to the heat insulation component, the adhered hydrothermal splashes extend towards the lower end face of the heat insulation component with the recess and penetrate along the recess, thus preventing the hydrothermal splashes from falling to the surface of the raw material melt due to their own weight. Therefore, by using the single-crystal pulling apparatus of the present invention, it is possible to prevent the introduction of impurities such as carbon into the grown single crystal.

[0030] Furthermore, according to the single crystal pulling apparatus of the present invention, a simple method can be used to prevent hot liquid from splashing onto the surface of the raw material melt without using a complex structure.

[0031] The maximum depth of the recess is preferably between 0.5 mm and 30 mm.

[0032] If the maximum depth of the recess is within this range, it can prevent the thermal insulation component from becoming too heavy and can more reliably prevent hot liquid splashes from falling onto the surface of the raw material melt due to their own weight.

[0033] The width of the recess is preferably 2 mm or more and less than 30 mm.

[0034] If the width of the recess is within this range, the processing of the heat insulation component becomes easier, and it can reliably prevent hot liquid splashes from accumulating and falling within the inner plane of the recess.

[0035] For example, the single crystal is a silicon single crystal.

[0036] This invention is not limited to the manufacture of silicon single crystals, but can also be applied to the manufacture of compound semiconductors. However, by applying it to the manufacture of silicon single crystals, it is possible to manufacture silicon single crystals with low carbon concentration in a simpler way.

[0037] (III) Beneficial Effects

[0038] As described above, the single-crystal pulling apparatus according to the present invention can easily prevent hot liquid adhering to the heat insulation component from splashing onto the surface of the raw material melt. Therefore, with the single-crystal pulling apparatus of the present invention, it is possible to prevent the introduction of impurities such as carbon into the grown single crystal. Attached Figure Description

[0039] Figure 1 This is a schematic cross-sectional view illustrating an example of the single-crystal pulling apparatus of the present invention.

[0040] Figure 2 This is a schematic perspective view showing an example of a heat-insulating component that the single-crystal pulling device of the present invention can have.

[0041] Figure 3 yes Figure 2 A schematic cross-sectional view of a portion of the thermal insulation component shown.

[0042] Figure 4 This is a schematic diagram showing some examples of the recessed pattern on the lower end face of the heat insulation component of the single crystal pulling device of the present invention.

[0043] Figure 5 This is a graph showing the relationship between the surface area of ​​the lower end face of the heat insulation component in the embodiments and comparative examples and the carbon concentration in the obtained silicon single crystal.

[0044] Figure 6 This is a schematic perspective view showing an example of a heat insulation component where no recess is formed on the lower end face.

[0045] Explanation of reference numerals in the attached figures

[0046] 1-Cavity; 1a-Main chamber; 1b-Pulling chamber; 2-Seed holder; 3-Seed; 4-Single crystal (silicon single crystal); 5-Cylinder; 6-Heater; 7-Insulation component; 8 and 8'-Insulation components; 8a and 8a'-Lower end face; 8b-Recess; 8c-Through hole; 9-Quartz crucible; 10-Graphite crucible; 11-Holding shaft; 12-Gas inlet; 13-Gas outlet; 14-Material melt (silicon melt); 15-Metal wire; 100-Single crystal pulling device. Detailed Implementation

[0047] As mentioned above, there is a need to develop a single-crystal pulling device that does not generate reaction gases between the insulation component and the quartz material, and can suppress contamination of the raw material melt in the crucible by impurities such as carbon due to hot liquid splashing from the insulation component onto the surface of the raw material melt.

[0048] The inventors conducted numerous thorough studies on the aforementioned technical problems and discovered that by processing the surface of the heat insulation component opposite to the molten raw material with a geometrically patterned concave portion, the surface area can be increased by more than 20%. This allows for a simple method to prevent hot liquid that has splashed onto the heat insulation component from landing on the surface of the molten raw material, thus completing the present invention.

[0049] That is, the present invention is a single crystal pulling device using the Czeklauski method, characterized in that it has a heat insulation component facing the surface of the raw material melt, the lower end face of the heat insulation component facing the surface of the raw material melt has a recess, and the surface area of ​​the lower end face without the recess is 120% or more based on the surface area of ​​the flat lower end face.

[0050] The present invention will now be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

[0051] Figure 1 This is a schematic cross-sectional view illustrating an example of the single-crystal pulling apparatus of the present invention.

[0052] Figure 1 The single crystal pulling apparatus 100 shown is used in the Czochralski method for growing single crystals. In the single crystal pulling apparatus 100, generally, a quartz crucible 9 and a graphite crucible 10, a heater 6, a heat insulation component 7, and a heat insulation element 8 are arranged in the main chamber 1a for growing the single crystal 4. The quartz crucible 9 contains the raw material melt (e.g., molten silicon) 14. The graphite crucible 10 supports the quartz crucible 9. The heater 6 is arranged to surround the crucibles 9 and 10. The heat insulation component 7 is arranged to surround the heater 6. The heat insulation element 8 has a lower end face 8a opposite the surface of the raw material melt 14. A pulling chamber 1b is connected to the single crystal pulling apparatus 100. The pulling chamber 1b is used to receive and remove the single crystal 4 grown in the upper part of the main chamber 1a. The main chamber 1a and the pulling chamber 1b constitute chamber 1. The quartz crucible 9 and the graphite crucible 10 are held on the retaining shaft 11 in a way that allows them to be raised and lowered.

[0053] A cylindrical section 5 is disposed at the top of the main chamber 1a. The cylindrical section 5 extends from the top of the main chamber 1a toward the raw material melt 14, and a heat insulation component 8 is installed at its end.

[0054] Details of the heat insulation component 8 will be described later.

[0055] The single crystal pulling device 100 also includes a gas inlet 12 and a gas outlet 13.

[0056] When manufacturing a single crystal 4 using such a single crystal pulling device 100, the seed crystal 3 installed in the seed holder 2 is immersed in the raw material melt 14. The metal wire 15 is gently wound while rotating the seed crystal 3 in the desired direction using a pulling mechanism (not shown). While the single crystal 4 grows at the front end of the seed crystal 3 and the rod-shaped single crystal 4 is pulled up, the crucibles 9 and 10 are raised according to the growth of the single crystal 4, so that the height of the melt surface used to obtain the desired diameter and crystal quality is always kept constant.

[0057] Furthermore, when growing single crystal 4, after immersing the seed crystal 3 installed in the seed crystal holder 2 into the raw material melt 14, the metal wire 15 is gently wound around the seed crystal 3 while rotating it in the desired direction using a lifting mechanism (not shown), so that the single crystal 4 grows at the front end of the seed crystal 3.

[0058] A magnetic field application device (not shown) for applying a magnetic field to the raw material melt 14 during single crystal pulling can also be provided on the outer periphery of the main chamber 1a of the single crystal pulling device 100 of the present invention.

[0059] In the single crystal pulling device 100 of the present invention, the lower end face 8a of the heat insulation member 8, which faces the surface of the raw material melt 14, has a recess.

[0060] Figure 2 This is a schematic perspective view showing an example of a heat-insulating component that can be included in the single-crystal pulling apparatus of the present invention. Additionally, Figure 3 express Figure 2 A schematic cross-sectional view of a portion of the thermal insulation component shown.

[0061] exist Figure 2 and Figure 3 In the example shown, the lower end face 8a of the heat insulation component 8 has a plurality of concentric circular recesses 8b. Furthermore, a through hole 8c is provided in the center of the heat insulation component 8, but this through hole 8c is not a recess as described in this invention. The through hole 8c is, for example... Figure 1 The single crystal 4 shown is through a through-hole that it passes through during its pulling process.

[0062] like Figure 3 As shown, in this example, a plurality of recesses 8b are provided at intervals P on the lower end face 8a of the heat insulation component 8. Each recess 8b has a rectangular cross-sectional shape with a depth D and a width W.

[0063] In addition, for comparison, in Figure 6 The diagram shows a schematic perspective view of an existing thermal insulation component, which has a flat lower end face without a recess. Figure 6 The heat insulation component 8' shown is flat on its lower end face 8a' instead of having a recess, and is similar to... Figure 2 The heat insulation component 8 shown is the same.

[0064] In the heat insulation component 8 of the single crystal pulling device 100 of the present invention, by providing a heat insulation component on the lower end face 8a, Figure 2 and Figure 3 The recess 8b shown, thereby... Figure 6 The surface area of ​​the flat lower end face 8a' without the concave portion shown is taken as a reference (100%), and the surface area of ​​the lower end face 8a is more than 120%.

[0065] That is, by forming the recess 8b, the surface area of ​​the lower end surface 8a of the heat insulation component 8 is increased by more than 20% compared with the surface area of ​​the flat lower end surface 8a' without the recess.

[0066] The single crystal pulling device 100 of the present invention, by having such a heat insulation member 8, is able to prevent hot liquid that has been scattered and attached to the heat insulation member 8 from splashing down onto the surface of the raw material melt 14.

[0067] The reasons are explained below.

[0068] For example, the graphite insulating component 8 has good wettability with the raw material (e.g., silicon; the following description assumes silicon as the raw material, but the same applies to other raw materials) attached by the hot liquid splash. The force acting on the attached hot liquid splash extends inward toward the lower end face 8a of the insulating component 8, which can suppress the hot liquid splash attached to the insulating component 8 from falling into the molten raw material 14 in the quartz crucible 9 due to its own weight. However, this alone is not enough to sufficiently suppress the hot liquid splash from falling into the molten raw material 14.

[0069] In the single-crystal pulling apparatus 100 of the present invention, as described above, the lower end surface 8a of the heat insulation member 8 to which the hot liquid splash is attached has a recess 8b, which is a concave-convex shape. Therefore, the contact area between the heat insulation member 8 and the hot liquid splash attached to it increases, and the force by which the hot liquid splash extends toward the lower end surface 8a of the heat insulation member 8 also increases, thus... Figure 6 Compared to the heat insulation component 8 with a flat lower end face 8a' shown, the amount of molten material containing impurities such as carbon splashing into the raw material molten material 14 in the crucible can be reduced, and the carbon concentration in the manufactured single crystal 4 can be expected to be reduced.

[0070] Furthermore, since the attached hot liquid splashes penetrate along the recesses 8b, the direction of expansion and the size of the collected hot liquid splashes can be controlled by the number and shape of the recesses 8b. Therefore, it is possible to prevent the hot liquid splashes attached to the heat insulation component 8 from collecting into droplets and falling due to their own weight.

[0071] In this invention, by setting the surface area of ​​the lower end surface 8a to 120% or more based on the flat lower end surface 8a' as described above, it is possible to reliably suppress the splashing of hot liquid onto the surface of the raw material molten liquid 14.

[0072] On the other hand, even if a recess 8b is formed, if the increase rate of the surface area of ​​the lower end face 8a is small, that is, if the surface area of ​​the lower end face 8a is less than 120% based on the flat lower end face 8a', the ability of the recess 8b to suppress the splashing of hot liquid decreases, and it can only exert the same level of suppression force as the existing structure with a flat lower end face.

[0073] Thus, according to the present invention, without the need for a complex structure, the splashing of hot liquid onto the surface of the raw material molten liquid 14 can be reliably suppressed by a simple and inexpensive method of machining the lower end face 8a of the heat insulation component 8. Moreover, in the present invention, there is no problem of the reaction gas between the graphite component and the quartz as in Patent Document 1.

[0074] Furthermore, if the surface area of ​​the lower end face 8a can be 120% or more of the area of ​​the flat lower end face 8a', then the shape of the recess 8b is not limited to a concentric circle, and the same effect can be achieved regardless of the shape. For example Figure 4 As shown, the recess 8b can also be set as a spiral ( Figure 4 (a) of, polygon ( Figure 4 (b) ), grid ( Figure 4 (c)), water droplet pattern ( Figure 4 (d) ), striped pattern ( Figure 4 (e)), checkered pattern ( Figure 4 Arbitrary geometric patterns such as (f)).

[0075] On the other hand, since the surface area of ​​the lower end surface 8a is increased by forming multiple protrusions instead of recesses 8b on the lower end surface 8a of the heat insulation member 8, the attached hot liquid splashes are more likely to fall along the protrusions. Therefore, in this invention, recesses 8b are formed instead of protrusions.

[0076] Furthermore, if the recess 8b is a narrower recess shape, more hydrothermal splash can be stored in the recess 8b. In this way, by making the recess 8b a narrower recess shape, the surface area can be increased, and by storing hydrothermal splash in the recess 8b, the effect of further preventing the accumulation of hydrothermal splash can be expected.

[0077] The depth D of the recess 8b is preferably between 0.5 mm and 30 mm.

[0078] The deeper the recess 8b, the greater the surface area of ​​the lower end face 8a of the heat insulation member 8. However, since the temperature decreases further away from the hydrothermal surface (the surface of the raw material molten liquid 14), the hydrothermal splash entering the recess 8b of the heat insulation member 8 can only penetrate to a certain extent. In addition, by setting the maximum depth of the recess 8b to 30 mm or less, it is not necessary to increase the wall thickness of the material constituting the heat insulation member 8 (e.g., isotropic graphite) to deepen the recess 8b, thus preventing excessive weight. On the other hand, by setting the maximum depth of the recess 8b to 0.5 mm or more, it is possible to more reliably prevent the hydrothermal splash entering the recess 8b from overflowing from the recess 8b, or even the hydrothermal splash falling.

[0079] In addition, the width W of the recess 8b is preferably 2 mm or more and less than 30 mm.

[0080] The narrower the width W of the recess 8b, the greater the increase in surface area, and the more difficult it is for the hot liquid splashes of the attached molten material to collect within the plane inside the recess 8b. Conversely, the larger the width W of the recess 8b, the easier it is to manufacture the heat insulation component 8. If the width W of the recess 8b is in the range of 2 mm or more and less than 30 mm, the manufacturing of the heat insulation component 8 becomes easier, and it can reliably prevent hot liquid splashes from collecting within the plane inside the recess 8b and falling down.

[0081] The spacing P of the recess 8b is not particularly limited.

[0082] Furthermore, since the purpose is to store the material adhering due to hot liquid splashing in the recess 8b of the heat insulation component 8, the cross-sectional shape of the recess 8b is not limited to... Figure 3 The shape of the quadrilateral shown can also be curved like an arc.

[0083] Furthermore, the single crystal pulling device of the present invention is not limited to use in the manufacture of silicon single crystals, but can also be applied to the manufacture of compound semiconductors. By applying it to the manufacture of silicon single crystals, it is possible to manufacture silicon single crystals with low impurity concentrations such as low carbon concentration in a simpler way.

[0084] 【Example】

[0085] The present invention will now be described in detail with reference to examples and comparative examples, but the present invention is not limited thereto.

[0086] (Examples 1-5, Comparative Example 2)

[0087] Used in Figure 1 The schematic diagram shows a single crystal pulling device 100, equipped with a quartz crucible with a diameter of 800 mm (32 inches), using 400 kg of polycrystalline silicon, and growing and pulling 12-inch (300 mm) silicon single crystals using the Czechlauski method (MCZ method) with magnetic field applied.

[0088] Generally, the CZ process includes a crucible filled with molten raw material and a heater arranged to surround the crucible. After immersing a seed crystal in the crucible, a rod-shaped single crystal is pulled from the molten raw material. The crucible can be raised and lowered along the crystal growth axis to replenish the portion of the molten raw material that has decreased in level during crystal growth.

[0089] A single silicon crystal 4 was grown using the single crystal pulling apparatus 100. At this time, the lower end face 8a of the heat insulation component 8, which faces the molten raw material 14, has... Figure 2 The diagram schematically shows a plurality of concentric recesses 8b. Regarding the recesses 8b, Figure 3 In a portion of the cross-section, the spacing P of the recesses 8b is 5 mm, the depth D of the recesses 8b is 2.5 mm, and the cross-section is rectangular. Furthermore, in Examples 1-5 and Comparative Example 2, the width W of the recesses 8b is set to 0.5 mm (Example 1), 2 mm (Example 2), 5 mm (Example 3), 10 mm (Example 4), 16 mm (Example 5), and 30 mm (Comparative Example 2), respectively, which are different from each other.

[0090] (Comparative Example 1)

[0091] In Comparative Example 1, in addition to replacing the heat insulation component 8, it used... Figure 6 Except for the heat insulation component 8' shown, which does not have a recess on its lower end face 8a', silicon single crystals were grown and pulled in the same manner as in Example 1. That is, in the heat insulation component 8' used in Comparative Example 1, the width of the recess was set to 0 mm.

[0092] Regarding the surface area of ​​the lower end face 8a of the heat insulation member 8 used in Examples 1 to 5 and Comparative Example 2, based on the surface area of ​​the lower end face 8a' of the heat insulation member 8' in Comparative Example 1 (100%), the percentages are 192% (Example 1), 170% (Example 2), 148% (Example 3), 132% (Example 4), 121% (Example 5), and 113% (Comparative Example 2).

[0093] As an evaluation of the single crystals pulled in the various embodiments and comparative examples, a sample with a thickness of about 1.5 mm was cut from the rear end of the main body of the grown single crystal, and the carbon concentration was confirmed using FT-IR.

[0094] exist Figure 5 The diagram shows the relative values ​​of carbon concentration for single crystals grown using the heat insulation component 8 with recesses 8b in Examples 1-5, where the carbon concentration of the single crystal grown in Comparative Example 1 (where the width and spacing of the recesses are 0 mm, i.e., the lower end face 8a' does not have a recess) is set to 1; and the relative values ​​of carbon concentration for single crystals grown using the heat insulation component 8 with recesses 8b of the present invention; and the relative values ​​of carbon concentration for single crystals grown in Comparative Example 2 (where the surface area of ​​the lower end face 8a is 113% based on the lower end face 8a' of Comparative Example 1). Figure 5 The illustrations shown are, from left to right, those of Comparative Example 1, Comparative Example 2, Example 5, Example 4, Example 3, Example 2, and Example 1.

[0095] The result is, such as Figure 5 As shown, Examples 1-5 of the present invention yielded silicon single crystals with lower carbon concentrations compared to Comparative Example 1, which used a conventional heat-insulating member 8' with a flat lower end face 8a'. Furthermore, it is observed that as the surface area of ​​the lower end face 8a with the recess 8b of the heat-insulating member 8 increases, the carbon concentration in the silicon single crystal decreases. This is because a larger surface area of ​​the lower end face 8a with the recess 8b of the heat-insulating member 8 allows for greater storage of hydrothermal splashes, thus reducing the carbon concentration. Based on this result, increasing the surface area is desirable.

[0096] Furthermore, when the surface area of ​​the lower end surface 8a of the heat insulation member 8 exceeds 170% based on the surface area of ​​the flat lower end surface 8a' of Comparative Example 1, almost no change in carbon concentration is observed. Therefore, considering the processing effort, it is desirable that the upper limit of the surface area of ​​the lower end surface 8a of the heat insulation member 8 is about 170% based on the surface area of ​​the flat lower end surface 8a' of Comparative Example 1 (for example, the interval P is about 5 mm relative to the width W being 2 mm).

[0097] Furthermore, as in Comparative Example 2, when the surface area of ​​the lower end surface 8a of the heat insulation member 8 increases at a relatively small rate (13%) even when a recess 8b is provided on the lower end surface 8a, the spacing without the recess 8b is larger than the diameter of the hot liquid splash with a weight relative to the surface tension. The ability of the recess 8b to suppress the hot liquid splashing is reduced, and it can only exert the same level of suppression force as the existing structure, i.e., Comparative Example 1. Therefore, it is believed that the carbon concentration increases.

[0098] (Example 6)

[0099] Furthermore, as in Example 6, similarly to Comparative Example 2, the width W of the recess 8b of the lower end surface 8a of the heat insulation member 8 was set to 30 mm, and the interval P and depth D were adjusted. Silicon single crystals were grown and pulled using the heat insulation member 8 with a surface area of ​​120% of the surface area of ​​the lower end surface 8a' of Comparative Example 1 as a reference.

[0100] The carbon concentration in the pulled silicon single crystal was measured. It was found that the carbon concentration in the silicon single crystal obtained in Example 6 was higher than that in Examples 1 to 5, but lower than that in Comparative Examples 1 and 2.

[0101] (Example 7)

[0102] In addition, besides using the shape of the recess 8b on the lower end face 8a from Figure 2 The concentric concave portions shown are respectively changed to Figure 4 The recesses of polygonal, grid, water droplet, striped, or checkered patterns shown in (a) to (f), and except for the heat insulation component 8 whose lower end surface 8a is 120% or more of the surface area of ​​the flat lower end surface 8a' of Comparative Example 1, were grown and pulled in the same manner as in Example 1. As a result, all the above-mentioned geometric patterns, as in Examples 1 to 5, resulted in single-crystal silicon with a lower carbon concentration than Comparative Examples 1 and 2.

[0103] Furthermore, the main purpose of this invention is to reduce the splashing of hot liquid adhering to the heat insulation component into the raw material melt when the raw material melts by providing a recess on the lower end surface of the heat insulation component facing the raw material melt such as silicon melt. As a result, the concentration of impurities such as carbon mixed in during crystallization is reduced.

[0104] Furthermore, the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any solution having a structure that is substantially the same as the technical concept described in the claims of the present invention and achieving the same effect is included within the technical scope of the present invention.

Claims

1. A single-crystal Czochralski device, which utilizes the Czeklaussky method, characterized in that, The heat insulation component has a heat insulation member facing the surface of the raw material melt, and the lower end face of the heat insulation component facing the surface of the raw material melt has a recess, and the surface area of ​​the lower end face is 120% or more based on the surface area of ​​the flat lower end face without the recess.

2. The single crystal pulling device according to claim 1, characterized in that, The maximum depth of the recess is between 0.5 mm and 30 mm.

3. The single crystal pulling device according to claim 1, characterized in that, The width of the recess is greater than 2 mm and less than 30 mm.

4. The single-crystal pulling device according to claim 2, characterized in that, The width of the recess is greater than 2 mm and less than 30 mm.

5. The single-crystal pulling apparatus according to any one of claims 1 to 4, characterized in that, The single crystal is a silicon single crystal.

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