Single crystal pulling device

Abstract

The present invention provides a single crystal pulling device, which is provided with: a chamber; a crucible disposed in the chamber and storing a silicon melt; a pulling unit that pulls the single crystal silicon and has a pulling shaft having a seed crystal attached to one end thereof and a pulling drive unit that lifts and rotates the pulling shaft; a heat shield provided above the crucible so as to surround the single crystal silicon; and a magnetic field applying unit for applying a horizontal magnetic field to the silicon melt in the crucible, in which a plurality of cutout parts are formed at the lower end of the heat shield, and the plurality of cutout parts are arranged so as to be double symmetrical about the pulling axis.

Description

Technical Field

[0001] The present invention relates to a single crystal pulling device for growing single crystal silicon. Background Art

[0002] As a method for producing single crystal silicon, the Czochralski method is known. In recent years, the so-called MCZ method is generally used, in which a single crystal silicon is grown while applying a horizontal magnetic field to a silicon melt.

[0003] However, in the growth of single crystal silicon based on the MCZ method, even if the same single crystal pulling apparatus is used and single crystal silicon is grown under the same process conditions, the quality of the grown single crystal silicon, especially the oxygen concentration in the single crystal silicon, may vary.

[0004] The following two factors are considered to be the main causes of the variation in oxygen concentration during the growth of single crystal silicon by the MCZ method.

[0005] The first major reason is the rotation direction of the convection generated in the silicon melt due to the application of the horizontal magnetic field (hereinafter referred to as the "convection mode"). The inventors have learned that in the process of applying a horizontal magnetic field and pulling the single crystal silicon after solid polycrystalline silicon raw materials are put into a crucible for melting, a convection rotating from the bottom of the crucible toward the surface of the silicon melt is generated.

[0006] FIG1 is a schematic diagram for explaining the convection mode, and is a diagram of the crucible 3 viewed from the direction of application of the horizontal magnetic field. The convection mode is the following two cases: a case where the right-handed convection C1 in the crucible 3 is dominant as shown in FIG1(a) (hereinafter referred to as the right-handed vortex mode); and a case where the left-handed convection C2 in the crucible 3 is dominant as shown in FIG1(b) (hereinafter referred to as the left-handed vortex mode). In FIG1 , reference symbol MD is the direction of application of the magnetic field center of the horizontal magnetic field.

[0007] The second main reason is the symmetry of the structure constituting the single crystal pulling device.

[0008] Generally, a single crystal pulling device is designed to have an axisymmetric structure with respect to the pulling axis. This is because in a system where the silicon single crystal and the crucible rotate, a system where the rotation axes are the same and the axisymmetric structure is more thermally stable.

[0009] However, in reality, the electrode portion of the heater for heating the crucible, the observation window, etc. are structures that cannot be made axisymmetric and cannot be completely axisymmetric.

[0010] When pulling a single crystal of silicon, oxygen will dissolve from the crucible, and the oxygen will be transported to the growing solid-liquid interface due to the above convection, and enter the crystal. Here, if the single crystal pulling device is a completely axisymmetric structure and the process conditions are the same, the amount of oxygen entering the crystal is equal regardless of the convection mode.

[0011] However, in reality, due to the thermal environment inhomogeneity caused by the single crystal pulling device not being a completely axisymmetric structure, the oxygen flow rates conveyed in the right-hand vortex mode and the left-hand vortex mode are different. As a result, single crystal silicon with different oxygen concentrations is grown in the convection mode.

[0012] Even if single crystal silicon is grown using the same single crystal pulling apparatus and under the same process conditions, crystals having different oxygen concentrations are grown due to differences in convection patterns, resulting in a decrease in the yield of the produced single crystal silicon.

[0013] Patent Document 1 discloses a method for eliminating the deviation of oxygen concentration caused by the convection mode by stably selecting one of two convection modes (right-hand vortex mode or left-hand vortex mode). Specifically, by actively biasing the heating capacity of the heater to one side, the convection mode is fixed to one side, and the deviation of oxygen concentration of each single crystal silicon is suppressed.

[0014] Furthermore, Patent Document 2 discloses a method of fixing the convection pattern in one direction by deflecting the flow of an inert gas flowing between a heat shield and the surface of a silicon melt.

[0015] Prior art literature

[0016] Patent Literature

[0017] Patent Document 1: Japanese Patent Application Publication No. 2019-151502

[0018] Patent Document 2: Japanese Patent Application Publication No. 2019-151503 Summary of the invention

[0019] Technical problem to be solved by the invention

[0020] However, the method described in the above patent document has a problem that the thermal environment around the pulled silicon single crystal becomes non-uniform due to the forced fixing of the convection mode, making stable pulling difficult.

[0021] An object of the present invention is to provide a single crystal pulling apparatus capable of suppressing the variation in oxygen concentration of each silicon single crystal without fixing the convection mode.

[0022] Solutions for solving technical problems

[0023] The single crystal pulling device of the present invention is characterized by comprising: a chamber; a crucible, which is arranged in the chamber and stores molten silicon; a pulling part, which has a pulling shaft with a seed crystal installed at one end and a pulling drive part that lifts and rotates the pulling shaft, and pulls the single crystal silicon; a heat shielding body, which is arranged above the crucible in a manner surrounding the single crystal silicon; and a magnetic field applying part, which applies a horizontal magnetic field to the molten silicon in the crucible, and a plurality of notch parts are formed at the lower end of the heat shielding body, and the plurality of notch parts are arranged in a doubly symmetrical manner with the pulling shaft as the center.

[0024] In the above-mentioned single crystal pulling apparatus, it is preferable that the chamber is provided with a plurality of observation windows, and the plurality of observation windows are arranged to be doubly symmetrical with the pulling axis as a center.

[0025] The single crystal pulling device of the present invention is characterized in that it comprises: a chamber; a crucible, which is arranged in the chamber and stores molten silicon; a pulling part, which has a pulling shaft with a seed crystal installed at one end and a pulling drive part that lifts and lowers and rotates the pulling shaft, and pulls the single crystal silicon; a heat shielding body, which is arranged above the crucible in a manner surrounding the single crystal silicon; a magnetic field applying part, which applies a horizontal magnetic field to the molten silicon in the crucible; and a plurality of observation windows, which are formed in the chamber; the plurality of observation windows are arranged in a doubly symmetrical manner with the pulling shaft as the center.

[0026] In the above-mentioned single crystal pulling apparatus, it is preferable that a plurality of dopant supply devices are provided, a plurality of dopant inlets are provided in the chamber, and the plurality of dopant inlets are arranged to be doubly symmetrical with the pulling axis as the center.

[0027] In the above-mentioned single crystal pulling apparatus, it is preferable that a cylindrical heat insulating material is provided along the inner side surface of the chamber, and a plurality of holes are formed in the heat insulating material. The plurality of holes are arranged to be doubly symmetrical with the pulling axis as the center.

[0028] In the above-mentioned single crystal pulling apparatus, it is preferable that the pair of notch portions are arranged so as to be aligned along the direction in which the magnetic field center of the horizontal magnetic field is applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1A is a schematic diagram illustrating the convection pattern.

[0030] Figure 1B is a schematic diagram illustrating the convection pattern.

[0031] Figure 2 It is a schematic cross-sectional view of a single crystal pulling apparatus according to an embodiment of the present invention.

[0032] Figure 3It is a schematic plan view for explaining the arrangement of a magnetic field applying portion, an observation window, and a notch portion of a single crystal pulling apparatus according to an embodiment of the present invention.

[0033] Figure 4A It is a schematic diagram explaining the relationship between the flow of the inert gas and the flow of the convection.

[0034] Figure 4B It is a schematic diagram explaining the relationship between the flow of the inert gas and the flow of the convection.

[0035] Figure 5 It is a schematic cross-sectional view of a single crystal pulling apparatus according to a modified example of the present invention.

[0036] Figure 6 It is a schematic plan view for explaining the arrangement of a magnetic field applying unit, an observation window, and a notch portion of a single crystal pulling apparatus according to a modified example of the present invention.

[0037] Figure 7 It is a schematic plan view for explaining the arrangement of observation windows and notches of single crystal pulling apparatuses according to the embodiment and the comparative example. DETAILED DESCRIPTION

[0038] [Background of the Invention]

[0039] As described above, if the single crystal pulling apparatus has a completely axisymmetric structure, the amount of oxygen entering the single crystal silicon is equal regardless of the convection mode. However, due to the existence of structures that cannot be axisymmetric, a completely axisymmetric structure cannot be achieved.

[0040] The present inventors have examined the effect of a static magnetic field on silicon melt while studying the structure of a single crystal pulling apparatus for suppressing the quality difference of single crystal silicon caused by a convection mode.

[0041] The effect of static magnetic field on silicon melt, namely Lorentz force, is the same regardless of the positive or negative direction of the magnetic field. If the magnetic field is set to B, the induced current is set to j, and the Lorentz force is set to F (B, j, and F are all vectors), then F = j × B (outer product).

[0042] Here, if magnetic field B'=-B is applied, induced current j' becomes j'=-j. Lorentz force F' becomes F'=j'×B'=-j×-B=j×B=F, and F and F' become the same. Therefore, the entire system including the magnetic field is doubly symmetric (180-degree rotational symmetry).

[0043] Based on the above, it can be seen that if the structure of the single crystal pulling device is set to be doubly symmetrical with the pulling axis as the center, the influence of the device and the magnetic field on the silicon melt is the same regardless of whether the convection mode is a right-hand vortex mode or a left-hand vortex mode. In other words, it is believed that by setting the structure of the single crystal pulling device to be doubly symmetrical, the deviation of the oxygen concentration can be suppressed.

[0044] [Structure of single crystal pulling device]

[0045] The structure of a single crystal pulling apparatus according to an embodiment of the present invention will be described below.

[0046] like Figure 2 As shown, the single crystal pulling device 1 is a device for pulling a single crystal silicon SM by the MCZ method, which comprises a chamber 2, a crucible 3 arranged in the chamber 2 and storing a silicon melt M, a heater 4, a pulling part 5 for pulling the single crystal silicon SM, a heat shielding body 6 arranged above the crucible 3 in a manner of surrounding the single crystal silicon SM, an insulating material 7 arranged along the inner side surface of the chamber 2, a crucible driving part 8 and a magnetic field applying part 9 for applying a horizontal magnetic field to the silicon melt M.

[0047] The crucible 3 has a double structure consisting of a quartz crucible 3A and a graphite crucible 3B that accommodates the quartz crucible 3A.

[0048] The crucible driving unit 8 includes a support shaft 11 that supports the crucible 3 from below, and rotates and elevates the crucible 3 at a predetermined speed.

[0049] The chamber 2 includes a main chamber 12 and a crystal pulling chamber 13 connected to an upper portion of the main chamber 12. The main chamber 12 and the crystal pulling chamber 13 are connected via a gate valve 14.

[0050] The main chamber 12 includes a main body 12A on which the crucible 3, the heater 4, the heat shield 6, etc. are arranged, and a cover 12B that closes the upper surface of the main body 12A. The cover 12B is provided with an opening 15 for introducing an inert gas such as argon into the main chamber 12 and a pair of quartz observation windows 16 for observing the interior of the chamber 2 using an optical observation member, etc. A support portion 17 extending to the inside is provided between the main body 12A and the cover 12B.

[0051] The crystal pulling chamber 13 is provided with a gas inlet 20 for introducing an inert gas into the main chamber 12. A gas exhaust port 21 is provided at the lower portion of the main body 12A of the main chamber 12. The gas in the main chamber 12 is sucked and discharged by driving a vacuum pump (not shown).

[0052] The inert gas introduced into the chamber 2 from the gas inlet 20 descends between the growing single crystal silicon SM and the heat shield 6. Then, after passing through the gap between the lower end of the heat shield 6 and the liquid surface of the silicon melt M, the inert gas flows toward the outside of the heat shield 6 and then toward the outside of the crucible 3. Thereafter, the inert gas descends outside the crucible 3 and is discharged from the gas exhaust port 21.

[0053] The heater 4 is of a resistance heating type and is disposed around the crucible 3 .

[0054] The heat insulating material 7 is formed into a cylindrical shape and is provided along the inner side surface of the chamber 2 outside the heater 4 .

[0055] The pulling unit 5 includes a pulling shaft A having a seed crystal SC attached to one end thereof and a pulling driving unit 23 for lifting and rotating the pulling shaft A.

[0056] The heat shield 6 shields the growing single crystal silicon SM from the high-temperature radiant heat from the silicon melt M in the crucible 3, the heater 4, or the side wall of the crucible 3. In addition, the heat shield 6 suppresses the diffusion of heat to the outside near the solid-liquid interface as the crystal growth interface, and controls the temperature gradient in the vertical direction of the center and the periphery of the single crystal silicon SM.

[0057] Furthermore, the heat shield 6 functions as a rectifying tube that exhausts evaporated products from the silicon melt M to the outside of the furnace by the inert gas introduced from above the furnace.

[0058] The upper end of the heat shielding body 6 is supported by the support portion 17 of the chamber 2. The heat shielding body 6 is formed in a truncated cone cylindrical shape whose diameter decreases toward the lower end.

[0059] A pair of notches 6A are formed at the lower end of the heat shield 6. By forming the notches 6A, the flow of the inert gas flowing on the silicon melt M can be intentionally distributed. In other words, by forming the notches 6A, the flow rate and flow velocity of the inert gas flowing between the single crystal silicon SM and the heat shield 6 can be made different in the circumferential direction. The position of the notches 6A will be described later.

[0060] The shape of the heat shield 6 is not limited to the above-mentioned shape, and may be formed into a truncated cone shape, for example, having a cylindrical main body and a protrusion protruding inwardly from the entire circumference of the lower end of the main body, and the protrusion is truncated cone-shaped with a diameter decreasing as it goes downward.

[0061] Figure 3 1 is a schematic top view for explaining the arrangement of the magnetic field applying unit 9, a pair of observation windows 16, and a pair of notch portions 6A. Figure 3 Simplifications have been made, for example, only the outer shape of the chamber 2 is shown.

[0062] like Figure 3 As shown in FIG. 1 , the magnetic field applying unit 9 includes a first magnetic body 9A and a second magnetic body 9B formed of electromagnetic coils. The magnetic bodies 9A and 9B sandwich the crucible 3 (see FIG. 1 ) on the outside of the chamber 2. Figure 2 By configuring the magnetic field applying unit 9 in this way, the application direction MD of the magnetic field center of the magnetic field is configured in a horizontal direction passing through the central axis C of the crucible 3. That is, the magnetic field center is in the horizontal direction passing through the central axis C of the crucible 3.

[0063] A pair of notches 6A are formed at positions that are doubly symmetrical about the pulling axis A. The pair of notches 6A are arranged so that the two notches 6A are arranged along the direction MD of application of the magnetic field. In other words, one notch 6A is on the upstream side of the direction MD of application of the magnetic field, and the other notch 6A is on the downstream side of the direction MD of application of the magnetic field, and is arranged at the most distant positions from each other.

[0064] Similar to the notch portion 6A, the pair of observation windows 16 are formed at positions that are doubly symmetrical about the pulling axis A. The pair of observation windows 16 are arranged so that the two observation windows 16 are aligned along the magnetic field application direction MD.

[0065] In addition, the double symmetry does not need to be exactly 180° rotational symmetry, and the rotational symmetry of 180±2° is sufficient.

[0066] In addition, the central axis C of the heat shield 6 (see Figure 2 ) does not need to be completely aligned with the central axis of the pulling axis A, and can be offset by a maximum of 2.5 mm in any horizontal direction. The heater 4, the insulating material 7, and the main body 12A of the chamber 2 can also be offset by a maximum of 2.5 mm in any horizontal direction.

[0067] When manufacturing single crystal silicon SM using such single crystal pulling apparatus 1, all silicon raw materials are melted in the absence of a magnetic field, and after all silicon raw materials are melted, a horizontal magnetic field is applied to restrict the flow of convection and pull up the single crystal silicon SM.

[0068] In addition, from the gas inlet 20 (refer to Figure 2 ) is supplied to the surface of the silicon melt M and flows toward the outside of the crucible 3 along the surface of the silicon melt M. At this time, the flow rate of the inert gas flowing through the notch portion 6A is accelerated as the gap increases due to the notch portion 6A.

[0069] When the pulling of the silicon single crystal SM reaches the end, the application of the horizontal magnetic field is stopped and the pulling is terminated.

[0070] In addition, the horizontal magnetic field may be applied before the silicon raw material is melted. That is, the application of the horizontal magnetic field may be started before or after the silicon raw material is melted.

[0071] According to the above embodiment, the structure of the single crystal pulling device 1 is made into a doubly symmetrical structure by arranging a pair of observation windows 16 and a pair of notch portions 6A at positions that are doubly symmetrical about the pulling axis A. As described above, if the structure of the single crystal pulling device 1 is made doubly symmetrical about the pulling axis A, the influences on the silicon melt M from the device and the magnetic field are the same regardless of the convection mode, so that the deviation of the oxygen concentration can be suppressed.

[0072] Furthermore, even when a plurality of single crystal pulling apparatuses are manufactured and single crystal silicon is pulled using each of the apparatuses, it is possible to suppress variations in oxygen concentration between the apparatuses.

[0073] In addition, as described above, since the flow rate of the inert gas flowing through the notch portion 6A increases, Figure 4A As shown, when a pair of notch portions 6A are arranged in a manner arranged along a horizontal direction D1 orthogonal to the application direction MD of the magnetic field center of the horizontal magnetic field, the inert gas GD with an increased flow rate conflicts with the flow of the convection C1 flowing through the liquid surface of the silicon melt M, affecting the flow of the convection C1.

[0074] Regarding the notch portion 6A of the present invention, a pair of notches 6 are arranged in a manner to be aligned along the direction MD of application of the magnetic field center of the horizontal magnetic field, such as Figure 4B As shown, the convection flow C1 does not conflict with the inert gas GD having a high flow rate. Therefore, the influence on the flow of the surface of the silicon melt M can be reduced by forming the notch 6A.

[0075] In addition, in the above-mentioned embodiment, although the notch 6A is arranged in a manner along the direction MD of application of the magnetic field center of the horizontal magnetic field, the present invention is not limited thereto. As long as the flow of the surface of the silicon melt M is not affected, for example, the notch 6A may be arranged in a manner along a direction orthogonal to the direction MD of application of the magnetic field center of the horizontal magnetic field. Similarly, the observation window 16 does not need to be arranged in a manner along the direction MD of application of the horizontal magnetic field.

[0076] In addition, in the single crystal pulling device 1 of the above-mentioned embodiment, a pair of observation windows 16 and a pair of notches 6A are provided to make the device a doubly symmetrical structure, but it is also possible to have only a pair of observation windows 16 and a doubly symmetrical structure without providing notches 6A. For such a device, when notches 6A are provided, it is preferable to arrange them in a doubly symmetrical configuration.

[0077] Likewise, the observation window 16 need not be provided, and only a pair of notches 6A may be provided to provide the device with a double symmetrical structure.

[0078] In the above embodiment, a pair of notch portions 6A and a pair of observation windows 16 are provided. However, the notch portions 6A and the observation windows 16 are not limited to one pair as long as the structure is doubly symmetrical. Four or more notch portions 6A and observation windows 16 may be provided.

[0079] [Variation]

[0080] Next, a modification of the single crystal pulling apparatus will be described.

[0081] like Figure 5 and Figure 6As shown, the single crystal pulling device 1B of the modified example can add dopants using a dopant supply device 25. The dopant supply device 25 is a device that has a dopant holding container 25A and a dopant drop tube 25B and can also fill and drop dopants during operation. The dopant drop tube 25B is inserted into the chamber 2 through a dopant drop port 26.

[0082] In the single crystal pulling apparatus 1B of the present modified example, a pair of dopant inlets 26 are arranged at positions that are doubly symmetrical about the pulling axis A as the center.

[0083] In the present modification, although two dopant supply devices 25 are provided, it is not necessary to use these two dopant supply devices 25 to supply the dopant, and only one dopant supply device 25 may be used to supply the dopant.

[0084] Furthermore, in the single crystal pulling apparatus 1B of the modified example, a temperature measuring device 27 is provided. The temperature measuring device 27 measures the temperature inside the chamber 2 via a hole 28 formed in the chamber 2 and the heat insulating material 7 .

[0085] In the single crystal pulling apparatus 1B of the present modified example, a pair of holes 28 are formed at positions that are doubly symmetrical about the pulling axis A as the center.

[0086] As described above, considering the influence of the uniformity of the thermal environment, the structure should be set to a double symmetrical structure.

[0087] [Examples and Comparative Examples]

[0088] Next, the examples and comparative examples of the present invention are described. Figure 2 Specifically, after 400 kg of polysilicon raw material was put into a crucible with a diameter of 32 inches and melted, a single crystal silicon with a diameter of 300 mm was pulled under the same process conditions. At this time, the temperature measuring unit 30 (refer to Figure 2 ) determined the convection pattern.

[0089] The temperature measuring unit 30 includes a pair of reflecting units 30A and a pair of radiation thermometers 30B, and measures the surface temperature of the silicon melt M. As shown in FIG.

[0090] [Comparative Example 1]

[0091] Figure 7 It is a schematic plan view for explaining the arrangement of observation windows and notches of single crystal pulling apparatuses according to the embodiment and the comparative example.

[0092] like Figure 7As shown, in the single crystal pulling device of Comparative Example 1, one observation window 16 is provided, and one notch 6A is formed in the heat shield 6. That is, the observation window 16 and the notch 6A of Comparative Example 1 are not doubly symmetrical structures.

[0093] Specifically, the observation window 16 of Comparative Example 1 is arranged only on the upstream side of the magnetic field application direction MD when viewed from above, passing through the lifting axis A. The notch portion 6A of Comparative Example 1 is arranged only on the downstream side of the magnetic field application direction MD.

[0094] [Example 1]

[0095] like Figure 7 As shown, in the single crystal pulling device of Example 1, one observation window 16 is provided. In addition, in the heat shield 6 of the single crystal pulling device of Example 1, two notches 6A are arranged at positions that are doubly symmetrical about the pulling axis A as the center.

[0096] Specifically, the observation window 16 of Example 1 is arranged only on the upstream side in the direction of application MD of the magnetic field. The notch portion 6A of Example 1 is arranged on the upstream side and the downstream side in the direction of application MD of the magnetic field.

[0097] [Example 2]

[0098] like Figure 7 As shown, in the single crystal pulling apparatus of the second embodiment, two observation windows 16 are arranged at positions that are doubly symmetrical about the pulling axis A. In addition, in the heat shielding body 6 of the single crystal pulling apparatus of the second embodiment, one notch portion 6A is formed.

[0099] Specifically, the observation window 16 of Example 2 is arranged on the upstream side and the downstream side in the direction of application MD of the magnetic field. The notch portion 6A of Example 2 is arranged only on the downstream side in the direction of application MD of the magnetic field.

[0100] [Example 3]

[0101] like Figure 7 As shown, in the single crystal pulling device of Example 3, two observation windows 16 are arranged at positions that are doubly symmetrical about the pulling axis A. In addition, in the heat shielding body 6 of the single crystal pulling device of Example 2, two notches 6A are arranged at positions that are doubly symmetrical about the pulling axis A.

[0102] Specifically, the observation window 16 of Example 3 is arranged on the upstream side and the downstream side in the direction of application MD of the magnetic field. The notch portion 6A of Example 3 is arranged on the upstream side and the downstream side in the direction of application MD of the magnetic field.

[0103] 〔evaluate〕

[0104] In the comparative example and the working example described above, the difference in oxygen concentration between the wafers cut from the silicon single crystal pulled in the state where the convection mode is the clockwise vortex mode and the wafers cut from the silicon single crystal pulled in the state where the convection mode is the counterclockwise vortex mode was evaluated.

[0105] Five silicon single crystals were pulled up in the clockwise vortex mode and five in the counterclockwise vortex mode, and the wafer at a position 500 mm below the top of the silicon single crystal was cut out, and the oxygen concentration was measured.

[0106] Specifically, the difference between the average oxygen concentration of 5 wafers in the clockwise vortex mode and the average oxygen concentration of 5 wafers in the counterclockwise vortex mode accounted for a percentage of the average oxygen concentration of all (10) wafers. That is, the evaluation index α can be expressed by the following mathematical formula (1).

[0107] [Formula 1]

[0108]

[0109] The evaluation index α represents the difference in oxygen concentration between the right-hand vortex mode and the left-hand vortex mode. The larger α is, the greater the difference in oxygen concentration is, which means that the oxygen concentration deviation between batches is large.

[0110] [Table 1]

[0111]

[0112] As shown in Table 1, by setting the observation window 16 or the notch 6A to a double symmetric structure, the difference in oxygen concentration between the right-hand vortex mode and the left-hand vortex mode can be reduced. In particular, it can be seen that by setting the observation window 16 and the notch 6A to a double symmetric structure in Example 3, there is no difference in oxygen concentration between the right-hand vortex mode and the left-hand vortex mode, and single crystal silicon of the same quality can be obtained.

[0113] Furthermore, even in the case where only the notch portion is formed into a doubly symmetrical structure in Example 1, the difference in oxygen concentration between the right-hand vortex mode and the left-hand vortex mode can be reduced compared to Comparative Example 1 having a conventional structure.

[0114] Furthermore, it can be seen that when only the observation window is set as a double symmetric structure in Example 2, the difference in oxygen concentration between the right-hand vortex mode and the left-hand vortex mode is smaller than that in Example 1. That is, it can be seen that setting the observation window as a double symmetric structure is more effective than setting the notch portion as a double symmetric structure.

[0115] The above shows that by making the observation window or the notch of the single crystal pulling apparatus into a doubly symmetrical structure, it is possible to reduce the variation in oxygen concentration between batches.

[0116] Description of Reference Numerals

[0117] 1-single crystal pulling device, 2-chamber, 3-crucible, 5-pulling part, 6-heat shielding body, 6A-notch part, 7-insulating material, 9-magnetic field applying part, 16-observation window, 23-pulling driving part, 25-dopant supplying device, 26-dopant inlet, 28-hole, A-pulling axis, M-silicon melt, SC-seed crystal, SM-single crystal silicon.

Claims

1. A single crystal pulling device, comprising: Chamber; A crucible, disposed in the chamber and storing silicon melt; A pulling part, comprising a pulling shaft with a seed crystal mounted on one end and a pulling driving part for lifting and rotating the pulling shaft, and pulling the single crystal silicon; A heat shield is disposed above the crucible in a manner of surrounding the single crystal silicon; and a magnetic field applying unit for applying a horizontal magnetic field to the silicon melt in the crucible, A plurality of notches are formed at the lower end of the heat shield, and the plurality of notches are arranged to be doubly symmetrical with the pulling axis as the center.

2. The single crystal pulling device according to claim 1, wherein: The chamber is provided with a plurality of observation windows, and the plurality of observation windows are arranged to be doubly symmetrical with the pulling axis as a center.

3. A single crystal pulling device, comprising: Chamber; A crucible, disposed in the chamber and storing silicon melt; A pulling part, comprising a pulling shaft with a seed crystal mounted on one end and a pulling driving part for lifting and rotating the pulling shaft, and pulling the single crystal silicon; A heat shield is disposed above the crucible in a manner of surrounding the single crystal silicon; A magnetic field applying unit applies a horizontal magnetic field to the silicon melt in the crucible; and a plurality of observation windows formed in the chamber; The plurality of observation windows are arranged to be doubly symmetrical with the pulling axis as the center.

4. The single crystal pulling device according to any one of claims 1 to 3, wherein: A plurality of dopant supply devices are provided, The chamber is provided with a plurality of dopant inlets, and the plurality of dopant inlets are arranged to be doubly symmetrical with the pulling axis as the center.

5. The single crystal pulling device according to any one of claims 1 to 3, wherein: A cylindrical heat insulating material is provided along the inner side surface of the chamber, The heat insulating material has a plurality of holes formed therein, and the plurality of holes are arranged to be doubly symmetrical with the pulling axis as the center.

6. The single crystal pulling device according to claim 2, wherein: The plurality of notches are arranged so as to be aligned along the direction in which the magnetic field center of the horizontal magnetic field is applied.

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