Coil, Magnet for Single Crystal Manufacturing Apparatus, Single Crystal Manufacturing Apparatus, and Single Crystal Manufacturing Method

Abstract

To provide a coil used for a magnet used for a single crystal manufacturing apparatus and capable of suppressing the reduction of oxygen concentration in the peripheral part of a wafer obtained from a manufactured single crystal while suppressing a variation in crystal drawing speed.SOLUTION: A coil 1 used for a magnet used in a single crystal manufacturing apparatus for pulling a single crystal while applying a horizontal magnetic field to a single crystal raw material melt stored in a crucible by the Czochralski method has a recessed part 1a in the upper part and is annular.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a coil, a magnet for a single crystal manufacturing apparatus, a single crystal manufacturing apparatus, and a single crystal manufacturing method.

Background Art

[0002] Generally, as a substrate for semiconductor devices, those made of a single crystal of a semiconductor such as silicon are used. As a typical method for manufacturing such a single crystal of a semiconductor, the Czochralski (CZ) method can be mentioned. The CZ method is a method of manufacturing a single crystal by growing a single crystal below a seed crystal by accommodating a semiconductor raw material in a crucible, melting it, dropping a seed crystal onto the molten single crystal raw material, and pulling it up.

[0003] As the crucible for accommodating the single crystal raw material, generally, those made of quartz are used. Therefore, when the convection of the single crystal raw material melt accommodated in the crucible is fast, the dissolved amount of oxygen contained in the quartz crucible increases, and the oxygen concentration of the single crystal becomes high. Therefore, in order to control the oxygen concentration of the single crystal, a horizontal magnetic field is applied to the raw material melt in the crucible to suppress the convection of the raw material melt while pulling up the single crystal (see, for example, Patent Document 1).

[0004] Figure 1 shows an example of an apparatus for manufacturing a single crystal by a horizontal magnetic field application method. The single crystal manufacturing apparatus 100 shown in this figure includes a crucible 12 that houses a raw material (e.g., polycrystalline silicon) of a single crystal (e.g., silicon) 16 in a chamber 11, a heater 14 that heats the raw material in the crucible 12 to form a raw material melt 13, a crucible rotation mechanism 15 provided at the lower part of the crucible 12 that rotates the crucible 12 in the circumferential direction, a seed crystal holder 18 that holds a seed crystal 17 for growing the single crystal 16, a wire rope 19 attached to the tip of the seed crystal holder 18, and a winding mechanism 20 that rotates the wire rope 19 while rotating and pulling up the single crystal 16, the seed crystal 17, and the seed crystal holder 18. Further, outside the lower part of the chamber 11, a magnet 21 having a plurality of coils 22 that apply a horizontal magnetic field (transverse magnetic field) to the silicon melt 13 in the crucible 12 is arranged.

[0005] Using such a single crystal manufacturing apparatus 10, a single crystal 16 can be manufactured as follows. That is, first, a predetermined amount of the raw material of the single crystal is accommodated in the crucible 12 and heated by the heater 14 to form a raw material melt 13, and a predetermined horizontal magnetic field is applied to the raw material melt 13 by the magnet 21.

[0006] Next, with a horizontal magnetic field applied to the raw material melt 13, the seed crystal 17 held by the seed crystal holder 18 is immersed in the raw material melt 13. Then, the crucible 12 is rotated at a predetermined rotation speed by the crucible rotation mechanism 15, and while rotating the seed crystal 17 (i.e., the single crystal 16) at a predetermined rotation speed, it is wound up by the winding mechanism 20 to pull up the seed crystal 17 and the single crystal 16 grown on the seed crystal 17. In this way, a single crystal having a predetermined diameter can be manufactured.

[0007] As the coil 22 constituting the magnet 21, for example, a horizontally long annular rectangular one as shown in Fig. 2(a) can be mentioned. And as shown in Fig. 2(b), the magnet 21 can be configured using two coils 22 arranged to face the periphery of the chamber 11. Note that as shown in Fig. 2(b), the coil 22 is curved on the outer surface 22a side, and its inner surface 22b is arranged facing the chamber 11 side.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] When manufacturing the single crystal 16, if the temperature of the raw material melt 13 supplied to the interface between the single crystal 16 and the raw material melt 13 (hereinafter also referred to as the "crystal / melt interface") changes due to fluctuations in the flow distribution of the raw material melt 13, the diameter of the single crystal 16 (hereinafter also referred to as the "crystal diameter") fluctuates. Therefore, the pulling speed of the single crystal 16 (hereinafter also referred to as the "crystal pulling speed") is adjusted according to the fluctuation of the crystal diameter to keep the crystal diameter constant. However, the crystal pulling speed is also used for controlling crystal defects that affect the quality of the single crystal 16, and fluctuations in the crystal pulling speed lead to fluctuations in the quality (crystal defects) of the manufactured single crystal 16. Therefore, it is preferable that the fluctuation of the crystal pulling speed with respect to the set value is small.

[0010] Also, a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the manufactured single crystal 16 reduces the mechanical strength of the outer peripheral portion of the wafer and becomes a factor causing deformation during heat treatment at the time of device manufacturing. Therefore, it is preferable that the amount of decrease in the oxygen concentration in the outer peripheral portion of the wafer is small.

[0011] The present invention has been made in view of the above problems, and an object thereof is to propose a coil used for a magnet for a single crystal manufacturing apparatus that can suppress a decrease in the oxygen concentration in the outer peripheral portion of a wafer obtained from the manufactured single crystal while suppressing fluctuations in the pulling speed of the single crystal.

Means for Solving the Problems

[0012] The present invention for solving the above problems is as follows. [1] A coil used for a magnet for a single crystal manufacturing apparatus that pulls up the single crystal while applying a horizontal magnetic field to a melt of a raw material of the single crystal accommodated in a crucible by the Czochralski method, The coil is characterized by having a concave portion in the upper part and being annular.

[0013] [2] A magnet for a single crystal manufacturing apparatus for applying a horizontal magnetic field in a single crystal manufacturing apparatus that pulls up the single crystal while applying a horizontal magnetic field to a melt of a raw material of the single crystal accommodated in a crucible by the Czochralski method, The magnet has two coils of the same shape and the same size, the two coils are symmetrically arranged with respect to a plane perpendicular to the application direction of the horizontal magnetic field, and both of the two coils are the annular coils described in [1].

[0014] [3] When the magnetic flux density at the origin O(0 mm, 0 mm, 0 mm) is M, the magnetic flux density at point A(0 mm, 0 mm, -400 mm) is 0.58×M or more, and the magnetic flux density at point B(400 mm, 0 mm, 0 mm) is 1.47×M or more. The magnet for a single crystal manufacturing apparatus according to [2] that can generate a magnetic field distribution.

[0015] [4] A single crystal manufacturing apparatus including the magnet described in [2] or [3], and pulling up the single crystal while applying a horizontal magnetic field to the melt by the magnet.

[0016] [5] A method for manufacturing a single crystal, which uses the single crystal manufacturing apparatus described in [4] above and pulls up the single crystal while applying the horizontal magnetic field.

[0017] [6] The method for manufacturing a single crystal according to [5] above, wherein the single crystal is a silicon single crystal.

Advantages of the Invention

[0018] It is possible to suppress a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the manufactured single crystal while suppressing fluctuations in the pulling speed of the single crystal.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiment for Carrying Out the Invention

[0020] (Coil) Hereinafter, embodiments of the present invention will be described with reference to the drawings. The coil according to the present invention is a coil used for a magnet of a single crystal manufacturing apparatus that pulls up a single crystal while applying a horizontal magnetic field to a melt of a single crystal raw material accommodated in a crucible by the Czochralski method. Here, it is characterized by having a concave portion at the upper part and being annular. Generally, the shape of a conventional coil used for a magnet of a single crystal manufacturing apparatus has a shape with no unevenness at the upper part (Figure 2) or a shape that draws an arc. However, the coil according to the present invention is different from the shape of the conventional coil in that the shape of its upper part is concave, and the shape of the coil opening is also characterized in that its upper part is concave.

[0021] The present inventors have earnestly studied a method for suppressing a decrease in the oxygen concentration in the outer peripheral portion of a wafer obtained from a manufactured single crystal while suppressing fluctuations in the pulling speed of the single crystal. In the process, attention was paid to the coil used for the magnet of the single crystal manufacturing apparatus.

[0022] As described above, when the temperature of the raw material melt 13 supplied to the crystal / melt interface changes due to fluctuations in the flow distribution of the raw material melt 13, the crystal pulling speed is adjusted in accordance with fluctuations in the crystal diameter, and the crystal diameter is controlled to be constant, but this leads to fluctuations in the quality of the single crystal 16.

[0023] The fluctuations in the flow distribution of the raw material melt 13 can be suppressed by applying a magnetic field to the raw material melt 13 by the magnet 21 to generate a Lorentz force due to the current and magnetic field in the raw material melt 13. In order to suppress fluctuations in the flow distribution of the raw material melt 13, it is preferable to apply a magnetic field with a high magnetic flux density to the raw material melt 13.

[0024] On the other hand, the decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the manufactured single crystal reduces the mechanical strength of the outer peripheral portion of the wafer and becomes a factor causing deformation during the heat treatment in device manufacturing. Therefore, it is preferable that the amount of decrease in the oxygen concentration in the outer peripheral portion of the wafer is small.

[0025] Figure 3 shows the flow distribution of the raw material melt 13 on the surface of the raw material melt 13 obtained by simulation. As shown in Figure 3, at the crystal / melt interface during crystal pulling, convection occurs to take in the surface raw material melt 13 due to the induced current generated in the single crystal 16 rotating in the magnetic field and the Lorentz force due to the magnetic field. On the surface of the raw material melt 13, there is a raw material melt 13 with a reduced oxygen concentration due to evaporation, and it is considered that the oxygen concentration in the outer peripheral portion of the wafer decreases when the single crystal 16 takes in such a raw material melt 13 with a low oxygen concentration. Therefore, in order to suppress the decrease in the oxygen concentration in the outer peripheral portion of the wafer, it is preferable to apply a magnetic field with a low magnetic flux density to the raw material melt 13 near the single crystal 16.

[0026] Thus, while it is effective to apply a magnetic field with a high magnetic flux density to the raw material melt 13 in terms of suppressing fluctuations in the crystal pulling speed, it is effective to apply a magnetic field with a low magnetic flux density to the raw material melt 13 in terms of suppressing the decrease in the oxygen concentration in the outer peripheral portion of the wafer, and there is a trade-off relationship between suppressing fluctuations in the crystal pulling speed and suppressing the decrease in the oxygen concentration in the outer peripheral portion of the wafer.

[0027] The inventors of the present invention have intensively studied a method that can achieve both suppression of fluctuations in the crystal pulling speed and suppression of the decrease in the oxygen concentration in the outer peripheral portion of the wafer. As a result, they came up with an annular coil having a concave portion at the upper part. By constructing a magnet using such a coil, a magnetic field with a low magnetic flux density can be applied to the raw material melt 13 around the single crystal 16, while a magnetic field with a high magnetic flux density can be applied to the other raw material melt 13, and it is possible to achieve both suppression of fluctuations in the crystal pulling speed and suppression of the decrease in the oxygen concentration in the outer peripheral portion of the wafer. Thus, the present invention has been completed.

[0028] As is clear from the above description, the coil according to the present invention is characterized by its shape, and other configurations are not limited, and conventionally known ones can be appropriately used. Hereinafter, the coil according to the present invention will be specifically described, but the present invention is not limited thereto.

[0029] FIG. 4 shows a preferred example of a coil constituting a magnet for a single crystal manufacturing apparatus according to the present invention, where (a) is an overall view, (b) is a front view, and (c) is a top view. The coil 1 shown in FIG. 4 has a recess 1a at the upper part and is configured in an annular shape. More specifically, as shown in FIG. 4(b), the coil 1 has two first portions 2 extending in the vertical direction, two second portions 3 extending in the horizontal direction, and four connecting portions 4 connecting the first portion 2 and the second portion 3.

[0030] Also, the upper second portion 3 has two first sub-portions 31 extending in the horizontal direction, one second sub-portion 32 located below the first sub-portion 31 and extending in the horizontal direction, two third sub-portions 33 extending in the vertical direction, and four sub-connecting portions 34 connecting the first sub-portion 31 or the second sub-portion 32 and the third sub-portion 33. The recess 1a of the coil 1 is defined by the second sub-portion 32, the two third sub-portions 33, and the four sub-connecting portions 34. In the example shown in FIGS. 4(a) to 4(c), the recess 1a is provided at the center of the upper second portion 3.

[0031] The coil 1 having such a configuration is applied to a magnet for a single crystal manufacturing apparatus and arranged around the chamber 11, and a current is passed through the coil 1. As a result, a magnetic field with a low magnetic flux density can be applied to the raw material melt 13 near the single crystal 16, while a magnetic field with a high magnetic flux density can be applied to the raw material melt 13 away from the other single crystals 16. As a result, it is possible to suppress fluctuations in the pulling speed of the single crystal and suppress a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the manufactured single crystal.

[0032] The depth of the recess 1a of the coil 1 (i.e., the distance (height difference) between the upper surface 31a of the first sub - portion 31 and the upper surface 32a of the second sub - portion 32) and the width (i.e., the length of the second sub - portion 32) can be appropriately set according to the dimensions of the crucible 12 that houses the raw material melt 13. For example, the depth of the recess 1a is preferably set to a height of 40% - 60% of the coil height. Here, the "coil height" means the length of the longest part in the vertical direction at the opening of the coil 1. That is, for the coil 1 shown in FIG. 4, it is the distance between the lower surface 31b of the first sub - portion 31 of the upper second portion 3 and the upper surface 3a of the lower second portion 3. Also, in the examples shown in FIGS. 4(a) - (c), the upper surface 31a and the lower surface 31b of the first sub - portion 31, the upper surface 32a of the second sub - portion 32, and the upper surface 3a of the lower second portion 3 are all planes parallel to the horizontal plane.

[0033] Further, the width of the recess 1a is preferably set to a width of 90% - 110% with respect to the crystal diameter of the single crystal to be grown. When the second portion 3 is curved toward the outer surface 1d side as shown in FIG. 4, the "width of the recess" means the length at the inner surface 1d of the recess 1a when the coil 1 is viewed from the front. The crystal diameter can be 300 mm or more (for example, in the case of a silicon single crystal for a φ300 mm wafer, the diameter is 301 - 340 mm, and in the case of a silicon single crystal for a φ450 mm wafer, the diameter is 451 - 500 mm), and the present invention is suitable for the production of single crystals with a crystal diameter of 300 mm or more.

[0034] For the coil 1, a support with the shape shown in FIG. 4 can be prepared. As shown in FIG. 4(a), a recess (not shown) is provided on the outer peripheral surface 1b that defines the outer shape of the support or the inner peripheral surface 1c that defines the opening of the support, and the winding is accommodated in the recess and wound to form the coil. Also, the coil 1 can be formed by winding it into the shape shown in FIG. 4 without providing a support and then solidifying it with resin.

[0035] Also, when winding the winding around the outer peripheral surface 1b or the inner peripheral surface 1c of the support, the outer peripheral surface 1b or the inner peripheral surface 1c of the support preferably has a rounded (rounded) corner so that the winding constituting the coil 1 can be smoothly wound. Also, when the winding is not wound around the support, it is preferable to wind it with a rounded corner.

[0036] In addition, the coil 1 preferably curves toward the outer surface 1d side as shown in FIGS. 4(a) and (c), for example. Thereby, the inner surface 1e of the coil 1 can be directed toward the chamber 11 side and the coil 1 can be arranged along the outer wall of the chamber 11, saving the space required for arranging the coil 1 and enabling a compact configuration. However, the coil 1 does not necessarily have to be curved and may be a flat coil 1.

[0037] Also, although the recess 1a of the coil 1 shown in FIG. 4 is rectangular, it is not limited thereto and can have any shape such as a semi-circular shape, a semi-elliptical shape, or a polygon other than a rectangle.

[0038] (Magnet for single crystal manufacturing apparatus) The single crystal manufacturing apparatus according to the present invention is a magnet for a single crystal manufacturing apparatus for applying a horizontal magnetic field while pulling up a single crystal by the Czochralski method while applying a horizontal magnetic field to a melt of a single crystal raw material accommodated in a crucible. Here, the magnet has a plurality of coils, and some or all of the plurality of coils are the coils according to the present invention described above.

[0039] FIG. 5 is a diagram for explaining the arrangement of coils in an example of a magnet according to the present invention. The same components as those of the single crystal manufacturing apparatus 100 shown in FIG. 1 are denoted by the same reference numerals. The magnet 50 for a single crystal manufacturing apparatus shown in FIG. 5 includes two coils 1 according to the present invention shown in FIG. 4, and these two coils 1 having the same shape and the same size are arranged symmetrically (that is, symmetrically with respect to the xz plane (a plane perpendicular to the direction in which the horizontal magnetic field is applied)) around the chamber 11. As described above, since the coil 1 has the concave portion 1a at the upper part, a magnetic field with a low magnetic flux density is applied to the raw material melt 13 near the single crystal 16, while a magnetic field with a high magnetic flux density can be applied to the raw material melt 13 away from the other single crystals 16. Thereby, when applied to a single crystal manufacturing apparatus, it is possible to suppress fluctuations in the pulling speed of the single crystal and suppress a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the manufactured single crystal.

[0040] Further, it is preferable that the magnet 50 can generate a magnetic field distribution such that when the magnetic flux density at the origin O (0 mm, 0 mm, 0 mm) described later is M, the magnetic flux density at the point A (0 mm, 0 mm, -400 mm) is 0.58 × M or more, and the magnetic flux density at the point B (400 mm, 0 mm, 0 mm) is 1.47 × M or more.

[0041] The inventors of the present invention have found that in a coordinate system with the magnetic field center, which is the intersection of the plane including the point at the lowest height position of the lower surface 32b of the second sub - portion 32 of the coil 1 and the crystal pulling axis, as the origin O, the magnetic flux density at a specific position (point) is closely related to the fluctuations in the oxygen concentration in the crystal pulling direction and the fluctuations in the pulling speed of the crystal.

[0042] In general, since the central axis of the magnet 50 for a single crystal manufacturing apparatus (see the dashed - dotted line in FIG. 4) coincides with the crystal pulling axis, when the magnet 50 is removed from the single crystal manufacturing apparatus, that is, in the case of the magnet alone, the origin O can be defined as the intersection of the plane including the point at the lowest height position of the lower surface 32b of the second sub - portion 32 in FIG. 4 and the central axis of the magnet 50.

[0043] When there are only two coils 1 arranged facing each other on the magnet 50, the origin O is defined as the intersection of the line connecting two points at the lowest height position on the lower surface 32b of the second sub-part 32 and the central axis of the magnet 50. When the line connecting the two points does not intersect the central axis of the magnet 50, it is defined as the intersection of the line connecting the two points when the line connecting the two points is horizontally moved so as to intersect the central axis of the magnet 50 and the central axis of the magnet 50. As shown in FIG. 4, when the lower surface 32b of the second sub-part 32 is a horizontal plane, the origin O is the intersection of the horizontal plane including the lower surface 32b and the central axis of the magnet 50.

[0044] Here, the positional relationship between the origin O and the liquid level of the raw material melt 13 in the crucible 12 (the surface of the raw material melt 13) will be described. When the magnet 50 according to the present invention is installed in a single crystal manufacturing apparatus and a single crystal is manufactured while applying a horizontal magnetic field, generally, the height position of the liquid level of the raw material melt 13 in the crucible 12 is near the intermediate position in the height direction of the coil 1. Therefore, when the magnet 50 according to the present invention is installed in a single crystal manufacturing apparatus and a single crystal is manufactured while applying a horizontal magnetic field, it may be considered that the lowest height position of the lower surface 32b of the concave portion 1a of the coil 1, which is a feature of the present invention, substantially coincides with the height position of the liquid level of the raw material melt 13 in the crucible 12. Therefore, when the magnet 50 according to the present invention is installed in a single crystal manufacturing apparatus and a single crystal is manufactured while applying a horizontal magnetic field, the origin O may be regarded as the intersection of the liquid level of the raw material melt 13 in the crucible 12 and the crystal central axis.

[0045] That is, a magnetic field is applied to the crucible 12 by the magnet 50. With the origin O being located at the same height as the surface of the raw material melt 13, as shown in FIGS. 6(a) and (b), an axis passing through the origin O and parallel to the direction of the magnetic field projected onto the horizontal plane is defined as the y-axis, an axis perpendicular to the direction of the magnetic field projected onto the horizontal plane is defined as the x-axis, and an axis passing through the origin O and perpendicular to the horizontal plane is defined as the z-axis. At this time, the inventor found that when a point on the inner side (inner wall) of the crucible 12 on the z-axis is designated as point A at the start of crystal pulling, the magnetic flux density at point A is closely related to the variation in the oxygen concentration of the single crystal in the crystal pulling direction. This is presumably because when the magnetic flux density at the bottom of the crucible 12 is low, the intensity of the Lorentz force that controls the convection of the raw material melt 13 decreases, the influence of the shearing force due to the rotation of the crucible 12 becomes large, and the variation in the flow distribution of the raw material melt 13 increases, which affects the variation in the oxygen concentration.

[0046] Further, the inventors found that when a point on the inner side (inner wall) of the crucible 12 on the x-axis is designated as point B, the magnetic flux density at point B is closely related to the variation in the crystal pulling speed when pulling a defect-free single crystal. This is because when a horizontal magnetic field is applied to the raw material melt 13 of a conductor such as silicon, roll-shaped convection occurs around the direction of the horizontal magnetic field. However, when the magnetic flux density at point B is high, the braking performance of the upward flow and the downward flow is enhanced, the variation in the temperature of the solid-liquid interface is suppressed, and the variation in the crystal pulling speed v is suppressed.

[0047] Thus, the inventors found that by applying a horizontal magnetic field to the above-mentioned melt and pulling a single crystal so that the magnetic flux densities at the above-mentioned points A and B are within a predetermined range. Specifically, when the magnetic flux density at the origin O (0 mm, 0 mm, 0 mm) is M, the magnetic flux density at point A (0 mm, 0 mm, -400 mm) is 0.58×M or more, and the magnetic flux density at point B (400 mm, 0 mm, 0 mm) is 1.47×M or more, it is possible to manufacture a defect-free single crystal while suppressing the variation in the oxygen concentration in the crystal pulling direction.

[0048] When the magnetic flux density at the origin O is M, by setting the magnetic flux density at point A to 0.58M or more, it is possible to suppress fluctuations in the oxygen concentration in the crystal pulling direction in a single crystal. Preferably, the magnetic flux density at point A is 0.64M or more. Thereby, fluctuations in the oxygen concentration in the crystal pulling direction in the single crystal can be further suppressed.

[0049] Also, by setting the magnetic flux density at point B to 1.47M or more, it is possible to suppress fluctuations in the crystal pulling speed of a defect-free single crystal. Preferably, the magnetic flux density at point B is 2.23M or more. Thereby, fluctuations in the crystal pulling speed of a defect-free single crystal can be further suppressed.

[0050] Also, it is preferable that the magnetic flux density at point C(0 mm, 400 mm, 0 mm) is smaller than the magnetic flux density at point B. Thereby, convective fluctuations in the raw material melt 13 can be further suppressed.

[0051] Although the control of the magnetic flux density at points A and B depends on the configuration of the magnet 50, it can be achieved by arranging the coil 1 at an appropriate position and adjusting the magnitude and direction of the current applied to the coil 1. For example, when using the coil 1 shown in FIG. 4, the height H1 of the coil at the position without the recess 1a is 750 mm, the height H2 at the portion with the recess 1a is 375 mm, the radius of curvature of the curved coil is 900 mm, the first sub-portion 31 of the second portion 3 is configured at 45° (i.e., the portion of the recess 1a is 90°), and by controlling the magnitude and direction of the current flowing through the coil 1, the magnetic flux density at points A and B can be controlled as described above.

[0052] (Single crystal manufacturing apparatus) The single crystal manufacturing apparatus according to the present invention includes a crucible that houses a melt of a single crystal raw material and a magnet according to the present invention described above that is disposed around the crucible, and is a single crystal manufacturing apparatus that pulls up a single crystal while applying a horizontal magnetic field to the melt by the magnet.

[0053] FIG. 7 shows an example of an apparatus for manufacturing a single crystal according to the present invention. The same components as those of the single crystal manufacturing apparatus 100 shown in FIG. 1 are denoted by the same reference numerals. In the single crystal manufacturing apparatus 70 shown in FIG. 7, instead of the magnet 21 in the single crystal manufacturing apparatus 100 shown in FIG. 1, the magnet 50 according to the present invention described above is provided. As described above, the magnet 50 has two coils having the same shape and the same size, and these two coils are symmetrically arranged with respect to a plane perpendicular to the application direction of the horizontal magnetic field. Further, both of the two coils are constituted by the coil 1 according to the present invention having a concave portion 1a at the upper part and being annular. Thereby, when pulling up the single crystal 16, it is possible to suppress a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the manufactured single crystal while suppressing fluctuations in the pulling speed of the single crystal. As a result, it is possible to manufacture a defect-free single crystal in which a decrease in the oxygen concentration in the outer peripheral portion of the wafer is suppressed.

[0054] (Method for manufacturing a single crystal) The method for manufacturing a single crystal according to the present invention is characterized in that a horizontal magnetic field is applied to a melt of a raw material by the above-described magnet using the apparatus for manufacturing a single crystal according to the present invention, and the single crystal is pulled up.

[0055] As described above, by using the single crystal manufacturing apparatus 70 according to the present invention, when pulling up the single crystal 16, it is possible to suppress a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the manufactured single crystal while suppressing fluctuations in the pulling speed of the single crystal. As a result, it is possible to manufacture a defect-free single crystal in which a decrease in the oxygen concentration in the outer peripheral portion of the wafer is suppressed.

[0056] The single crystal 16 is not particularly limited as long as it can be manufactured by the CZ method, but a silicon single crystal with small fluctuations in oxygen concentration can be preferably manufactured.

Example

[0057] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the examples.

[0058] Figure 8 shows the magnetic flux density distributions of the conventional coil (conventional example) shown in Figure 2 and the coil according to the present invention (invention example) shown in Figure 4. (a) is the magnetic flux density along the x-axis direction, (b) is the magnetic flux density along the y-axis direction, and (c) is the magnetic flux density along the z-axis direction. In Figure 8, all the figures have the origin O as the origin.

[0059] As shown in Figure 8(a), it can be seen that for the coil 1 of the invention example, with respect to the magnetic flux density distribution of the coil 22 of the conventional example, in the magnetic field distribution in the x-axis direction, the magnetic flux density at the crystal / melt interface can be decreased without changing the magnetic flux density in the melt region. Also, as shown in Figure 8(b), it can be seen that for the coil 1 of the invention example, in the magnetic field distribution in the y-axis direction, a magnetic field smaller than that of the coil 22 of the conventional example can be formed. Further, as shown in Figure 8(c), it can be seen that for the coil 1 of the invention example, in the magnetic field distribution in the z-axis direction, the peak of the magnetic flux density can be shifted to the melt side and the maximum value can be increased, and a magnetic field with a high magnetic flux density in the melt region and a low magnetic flux density in the crystal region can be formed.

[0060] Figure 9 shows the time variation of the average temperature of the solid-liquid interface. As is clear from Figure 9, it can be seen that the higher the magnetic flux density applied to the raw material melt 13 accommodated in the crucible 12, the smaller the time variation of the average temperature of the solid-liquid interface. Thereby, fluctuations in the crystal pulling speed and, consequently, fluctuations in the quality of the produced single crystal can be suppressed.

[0061] Figure 10 shows the relationship between the distance from the wafer center and the oxygen concentration. As shown in this figure, it can be seen that when the coil 1 of the invention example is used, the decrease in the oxygen concentration at the outer peripheral portion of the wafer can be suppressed compared to the coil 22 of the conventional example.

Industrial Applicability

[0062] According to the present invention, since it is possible to suppress fluctuations in the crystal pulling speed and suppress a decrease in the oxygen concentration at the outer peripheral portion of the wafer obtained from the produced single crystal, it is useful in the semiconductor wafer manufacturing industry.

Explanation of Reference Numerals

[0063] 1,22 coil 1a recess 1b outer peripheral surface 1c inner peripheral surface 1d outer surface 1e inner surface 2 first part 3 second part 3a upper surface 4 connecting part 11 chamber 12 crucible 13 raw material melt 14 heater 15 crucible rotation mechanism 16 single crystal 17 seed crystal 18 seed crystal holder 19 wire rope 20 take-up mechanism 21,50 magnet 22a outer surface 22b inner surface 31 first sub-part 31a upper surface 31b lower surface 32 second sub-part 32a upper surface 32b lower surface 33 third sub-part 34 sub-connecting part 70,100 single crystal manufacturing apparatus

Claims

1. A coil used for a magnet of a single crystal manufacturing apparatus that pulls up a single crystal while applying a horizontal magnetic field to a melt of a raw material of the single crystal accommodated in a crucible by the Czochralski method, having a concave portion recessed toward the center side of the coil at the upper part, and the shape of the upper part of the opening of the coil being concave and annular.

2. A magnet for a single crystal manufacturing apparatus for applying a horizontal magnetic field in a single crystal manufacturing apparatus that pulls up a single crystal while applying a horizontal magnetic field to a melt of a raw material of the single crystal accommodated in a crucible by the Czochralski method, having two coils of the same shape and the same size, the two coils being symmetrically arranged with respect to a plane perpendicular to the application direction of the horizontal magnetic field, and both of the two coils being the coil according to Claim 1.

3. Taking the intersection point of the liquid surface of the melt of the raw material of the single crystal in the crucible and the central axis of the single crystal as the origin, a axis passing through the origin and parallel to the direction of the horizontal magnetic field projected on the horizontal plane as the y-axis, a axis passing through the origin and perpendicular to the direction of the horizontal magnetic field projected on the horizontal plane as the x-axis, a axis passing through the origin and perpendicular to the horizontal plane as the z-axis, the intersection point of the z-axis and the inner surface of the crucible as point A, the intersection point of the x-axis and the inner surface of the crucible as point B, when the magnetic flux density at the origin O(0 mm, 0 mm, 0 mm) is M, the magnetic flux density at point A(0 mm, 0 mm, -400 mm) is 0.58×M or more, and the magnetic flux density at point B(400 mm, 0 mm, 0 mm) is 1.47×M or more, the magnet for a single crystal manufacturing apparatus according to Claim 2 that can generate a magnetic field distribution.

4. A single crystal manufacturing apparatus comprising the magnet for a single crystal manufacturing apparatus according to Claim 2 or 3, and pulling up the single crystal while applying a horizontal magnetic field to the melt by the magnet.

5. A single crystal manufacturing method using the single crystal manufacturing apparatus according to Claim 4 and pulling up a single crystal by applying the horizontal magnetic field.

6. The method for manufacturing a single crystal according to claim 5, wherein the single crystal is a silicon single crystal.

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