Magnet for single crystal manufacturing device, single crystal manufacturing device, and single crystal manufacturing method

Abstract

To provide a magnet for a manufacturing apparatus of a single crystal capable of heightening flexibility of a design of a magnetic field distribution, even when arrangement of a coil constituting the magnet for the manufacturing apparatus of a single crystal is restricted.SOLUTION: In a manufacturing apparatus of a single crystal for pulling up a single crystal, while applying a horizontal magnetic field to a melt of a raw material of the single crystal stored in a crucible, a magnet 1 for the manufacturing apparatus of a single crystal for applying the horizontal magnetic field includes four or more coils 2, which are coils 2 in which the ratio of a height Hi to a width Wi of at least one coil 2 in the four or more coils 2 exceeds 1, and a control part capable of generating a magnetic field mutually independently to each of the four or more coils 2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Generally, semiconductor device substrates are made of single crystals of semiconductors such as silicon. A typical method for producing such semiconductor single crystals is the Czochralski (CZ) method. The CZ method involves placing semiconductor raw materials in a crucible and melting them, then immersing a seed crystal in the molten single crystal raw material and pulling it up, thereby growing a single crystal below the seed crystal.

[0003] The crucible used to contain the single crystal raw material is generally made of quartz. Therefore, if the single crystal raw material melt contained in the crucible convects rapidly, the amount of dissolved oxygen in the quartz crucible increases, resulting in a high oxygen concentration in the single crystal. Therefore, the oxygen concentration of the single crystal is controlled by applying a horizontal magnetic field to the raw material melt in the crucible to suppress convection in the raw material melt while pulling the single crystal.

[0004] Fig. 1 shows an example of a single crystal manufacturing apparatus using a horizontal magnetic field application method. The single crystal manufacturing apparatus 100 shown in this figure includes, within a chamber 11, a crucible 12 that contains a raw material (e.g., polycrystalline silicon) for a single crystal (e.g., silicon) 16, a heater 14 that heats the raw material in the crucible 12 to form a raw material melt 13, a crucible rotation mechanism 15 that is provided below the crucible 12 and 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 to which the seed crystal holder 18 is attached at its tip, and a winding mechanism 20 that rotates the wire rope 19 to rotate and pull up the single crystal 16, the seed crystal 17, and the seed crystal holder 18. Further, a magnet 21 having a plurality of coils 22 for applying a horizontal magnetic field (transverse magnetic field) to the silicon melt 13 in the crucible 12 is arranged on the outside of the lower part of the chamber 11 .

[0005] Such a single crystal manufacturing apparatus 10 0 Using the above, a single crystal 16 can be produced as follows: First, a predetermined amount of single crystal raw material is placed in a crucible 12 and heated by a heater 14 to form a raw material melt 13, and a predetermined horizontal magnetic field is applied to the raw material melt 13 by a 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 the seed crystal 17 (i.e., the single crystal 16) is wound up by the winding mechanism 20 while being rotated at the predetermined rotation speed, thereby pulling up the seed crystal 17 and the single crystal 16 grown below the seed crystal 17. In this way, a single crystal having a predetermined diameter can be produced.

[0007] An annular (bobbin-type) coil has been widely used as the coil 22 constituting the magnet 21. For example, Patent Document 1 describes a method for producing a high-quality semiconductor single crystal ingot by forming a magnetic field using a magnetic field application means having an even number of annular coils arranged in point symmetry such that a plane of maximum magnetic field concentration density (MGP) is located at a predetermined height from the surface of the semiconductor melt, and applying a magnetic field of predetermined strength to the semiconductor melt at a predetermined position in a crucible. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-173536 Summary of the Invention [Problem to be solved by the invention]

[0009] The distribution of the magnetic field applied to the raw material melt 13 can be designed by arranging the coil at an appropriate position, but the position at which the coil is arranged may be limited due to restrictions on the device configuration. In such cases, if the coil is annular as described in Patent Document 1, the width, i.e., the diameter, of the coil needs to be reduced in order to achieve the desired magnetic field distribution.

[0010] However, when the diameter of the annular coil is reduced, the height of the coil is also reduced, which affects the magnetic field applied in the height direction to the raw material melt 13 contained in the crucible 12. Thus, when the coil 22 constituting the magnet 21 is annular, there is a problem in that the degree of freedom in designing the magnetic field distribution to be applied to the raw material melt 13 is low.

[0011] The present invention was made in consideration of the above-mentioned problems, and its purpose is to propose a magnet for single crystal manufacturing equipment that can increase the freedom of designing the magnetic field distribution even when the arrangement of the coils that make up the magnet of the single crystal manufacturing equipment is restricted. [Means for solving the problem]

[0012] The present invention, which solves the above problems, is as follows. [1] A magnet for a single crystal manufacturing apparatus for applying a horizontal magnetic field to a melt of a single crystal raw material contained in a crucible while pulling the single crystal, four or more coils, wherein at least one of the four or more coils has a height to width ratio greater than 1; a control unit that can generate magnetic fields for each of the four or more coils independently of one another; A magnet for a single crystal manufacturing apparatus, comprising:

[0013] [2] The magnet for use in a single crystal manufacturing apparatus according to [1] above, wherein the coil is rectangular and annular.

[0014] [3] The magnet for use in a single crystal manufacturing apparatus according to [1] or [2] above, wherein the height is 600 mm or more.

[0015] [4] A magnet for single crystal manufacturing equipment according to any one of [1] to [3] above, in which, when the magnetic flux density at the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane 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.

[0016] [5] A single crystal manufacturing apparatus comprising: a crucible for containing a melt of a raw material for a single crystal; and a magnet according to any one of [1] to [4] above, arranged around the crucible, wherein the magnet applies a horizontal magnetic field to the melt while pulling up the single crystal.

[0017] [6] A method for producing a single crystal by the Czochralski method using the single crystal production apparatus described in [5] above, A method for producing a single crystal, wherein the horizontal magnetic field is applied to the melt by the magnet so that, when the magnetic flux density at the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane 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.

[0018] [7] The method for producing a single crystal according to [6] above, wherein the single crystal is a silicon single crystal. [Effects of the Invention]

[0019] According to the present invention, even when the arrangement of the coils that constitute the magnets of the single crystal manufacturing apparatus is restricted, the degree of freedom in designing the magnetic field distribution can be increased. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing an example of a single crystal manufacturing apparatus using a horizontal magnetic field application method. [Figure 2]It is a diagram showing a preferred example of a coil constituting a magnet according to the present invention. (a) is an overall view, (b) is a front view, (c) is a side view, and (d) is a bottom view. [Figure 3] It is an example of the arrangement of a plurality of coils constituting a magnet. (a) relates to the case where there are 4 coils, and (b) relates to the case where there are 12 coils. [Figure 4] It is a diagram for explaining the relationship between the arrangement relationship of the coils shown in Fig. 3(a) and the magnetic flux density of the region surrounded by the coils. [Figure 5] It is a diagram showing the magnetic flux density of the region surrounded by the coils in the case of Da < Db. (b) is the magnetic flux density along the x-axis direction, and (c) is the magnetic flux density along the y-axis direction. [Figure 6] It is a diagram showing the magnetic flux density of the region surrounded by the coils in the case of Da > Db. (b) is the magnetic flux density along the x-axis direction, and (c) is the magnetic flux density along the y-axis direction. [Figure 7] It is a diagram for explaining the relationship between the output relationship of the coils shown in Fig. 3(b) and the magnetic flux density of the region surrounded by the coils. (b) is the magnetic flux density along the x-axis direction, and (c) is the magnetic flux density along the y-axis direction. [Figure 8] It is a diagram showing an example of an apparatus for manufacturing a single crystal according to the present invention. [Figure 9] It is a diagram for explaining the positions of the center O, point A, point B, and point C of the magnetic field neutral plane. (a) is a view of the crucible seen from above, and (b) is a view of the crucible seen from the side. [Figure 10] It is a diagram showing the variation of the oxygen concentration in the axial direction of a silicon single crystal. (a) is a comparative example, (b) is Invention Example 1, and (c) is Invention Example 2. [Figure 11] It is a diagram showing the time variation of the temperature of the solid-liquid interface by three-dimensional fluid simulation. (a) is a comparative example, (b) is Invention Example 1, and (c) is Invention Example 2.

Mode for Carrying Out the Invention

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The magnet for a single crystal manufacturing apparatus according to the present invention is a magnet for a single crystal manufacturing apparatus for applying a horizontal magnetic field to a melt of single crystal raw material contained in a crucible while pulling a single crystal. Here, the magnet is characterized by comprising four or more coils, at least one of which has a height-to-width ratio greater than 1, and a control unit that can generate magnetic fields for each of the four or more coils independently of one another.

[0022] As mentioned above, when there are restrictions on the arrangement of the coils that make up the magnets of a single crystal manufacturing apparatus, if the coils are of a bobbin type, there is a problem in that the degree of freedom in designing the magnetic field distribution to be applied to the raw material melt in the crucible is low. After extensive research into ways to solve the above problem, the inventors came up with the idea of ​​configuring the coils that make up the magnets so that the ratio of their height to their width exceeds 1, that is, making them vertical.

[0023] In other words, by using a vertical coil, when the arrangement of the coil is limited due to the constraints of the device configuration, it becomes possible to deal with the problem by reducing only the width of the coil without changing the height of the coil. As a result, when adjusting the angle between the coils to achieve a desired magnetic field distribution, it is possible to suppress the influence of the magnetic field applied to the raw material melt in the height direction, and it is possible to increase the degree of freedom in designing the magnetic field distribution.

[0024] However, after further investigation, the inventors discovered that simply making the coils vertical is not sufficient to achieve the desired magnetic field distribution, and that it is essential that the magnet have four or more coils, at least one of which is vertical, and that each of the four or more coils is provided with a control unit that can generate a magnetic field independently of each other, thereby completing the present invention.

[0025] As is clear from the above description, the magnet for use in a single crystal manufacturing apparatus of the present invention is characterized by its shape and a control unit that can generate a magnetic field independently from the coil, and other configurations are not limited, and conventionally known magnets can be used as appropriate. The magnet of the present invention will be described in detail below, but the present invention is not limited thereto.

[0026] Figure 2 shows a preferred example of a coil constituting a magnet for a single crystal production apparatus according to the present invention, with (a) an overall view, (b) a front view, (c) a side view, and (d) a bottom view. The coil 2 shown in Figure 2 is configured so that the ratio of its height to its width exceeds 1, i.e., it is vertically oriented. More specifically, the coil 2 constituting the magnet 1 according to the present invention is rectangular and annular, and has two first portions 3 that are longitudinal members extending vertically, two second portions 4 that are short members extending horizontally, and four connecting portions 5 that connect the first portions 3 and second portions 4.

[0027] In the coil 2, the length Hi of the first portion 3 is configured to be greater than the length Wi of the second portion 4. As a result, the height of the coil 2 is also greater than the width, and the height-to-width ratio exceeds 1. In the present invention, the "height of the coil" refers to the length of the longest portion of the opening 2a of the annular coil in the up-down direction (vertical direction) (in FIG. 2, the length Hi of the first portion 3), and the "width of the coil" refers to the length of the longest portion of the opening 2a in the horizontal direction (in FIG. 2, the length Wi of the second portion 4). When the coil 2 is curved toward the outer surface 2b as shown in FIG. 2(d), the width of the coil 2 is the length along the inner surface 2c of the coil 2.

[0028] The coils 2 constituting the magnet 1 according to the present invention are preferably rectangular as shown in Figure 2, but are not limited to this and can also be elliptical, for example. It is also preferable that all of the coils 2 are vertical and have the same shape. This allows for the formation of a highly symmetrical magnetic field distribution.

[0029] With a coil 2 having such a configuration, even if the placement of the coil 2 is limited due to constraints on the device configuration, it is possible to reduce only the width of the coil 2 without reducing the height of the coil 2, thereby suppressing the impact on the magnetic field applied to the raw material melt 13 in the height direction and increasing the freedom in designing the magnetic field distribution.

[0030] The height of the coil 2 is preferably 600 mm or more. This allows a horizontal magnetic field to be effectively applied to the molten raw material 13 contained in the crucible 12 when producing a single crystal having a diameter of 300 mm or more (for example, a diameter of 301 to 340 mm for a silicon single crystal for a φ300 mm wafer, or a diameter of 451 to 500 mm for a silicon single crystal for a φ450 mm wafer). The height of the coil 2 is more preferably 750 to 1000 mm when producing a silicon single crystal for a φ300 mm wafer, and 1125 to 1500 mm when producing a silicon single crystal for a φ450 mm wafer.

[0031] 2(d), it is preferable that the second portion 4 of the coil 2 be curved toward the outer surface 2b of the coil 2. This allows the coil 2 to be arranged along the outer wall of the chamber 11, saving the space required for arranging the coil 2 and making the entire magnet 1 compact, but the second portion 4 may also be configured linearly to form a flat coil 2.

[0032] The external width Wo of coil 2 (i.e., the length of second portion 4 plus the two connecting portions 5) is 1 / 4 or less of the circumference L of magnet 1, more preferably 1 / 6 or less, even more preferably 1 / 8 or less, and most preferably 1 / 12 or less of the circumference L of magnet 1. By making the external width Wo of coil 2 smaller relative to the circumference L of the magnet, more coils 2 can be arranged, increasing the freedom to space coils 2 more closely, and increasing the freedom to design the magnetic field distribution.

[0033] In addition, when the coil 2 is curved toward the outer surface 2b as shown in Figure 2(d), the outer width Wo of the coil 2 is the length along the inner surface 2c of the coil 2 as shown in Figure 2(d). By making the outer width Wo of the coil 2 smaller relative to the circumference L of the magnet, more coils 2 can be arranged, increasing the degree of freedom in the spacing between the coils 2 and increasing the degree of freedom in the design of the magnetic field distribution. In addition, when the coils 2 are curved toward the outer surface 2b and the inner surfaces 2c of four or more coils 2 form a circle, the "perimeter of the magnet" refers to the length of the circumference of the circle formed by the inner surfaces 2c of the coils 2 when the magnet 1 is viewed from above. In addition, when the coils 2 are flat or the inner surfaces 2c of the coils 2 do not form a circle, the "perimeter of the magnet" refers to the length of the circumference of the circle (four coils) formed by the centers of the inner surfaces 2c of the coils 2 (the midpoints of the line segments corresponding to the inner surfaces 2c) when the magnet 1 is viewed from above. End It refers to the length of the circumference of a circle (a circle passing through the midpoint of a circle).

[0034] In relation to the relationship between the width Wo of the coil 2 and the circumference L of the magnet 1, the number of coils 2 is set to four or more. By setting the number of coils 2 to four or more, sufficient freedom in designing the magnetic field distribution to be applied to the raw material melt 13 contained in the crucible 12 can be ensured. The number of coils 2 is preferably a multiple of two. By setting the number of coils 2 to a multiple of two, the coils 2 can be arranged with high symmetry. The number of coils 2 is more preferably six or more, even more preferably eight, and most preferably twelve. Furthermore, the number of coils 2 is preferably 40 or less. This allows for a high degree of freedom in magnetic field design while avoiding complexity in the magnetic field design, and also reduces the cost of the magnet 1.

[0035] The coil 2 can be constructed by preparing the annular support shown in Fig. 2, providing a recess in the outer peripheral surface 2d that defines the outer shape of the support when viewed from above as shown in Fig. 2(b), or in the inner peripheral surface 2e that defines the opening of the support, and winding the wire around the recess. Alternatively, the coil 2 can be constructed without a support, by winding the wire into the shape shown in Fig. 2 and solidifying it with resin.

[0036] Furthermore, when the winding is wound around the outer peripheral surface 2d or inner peripheral surface 2e of the support, it is preferable that the outer peripheral surface 2d or inner peripheral surface 2e of the connection portion 5 constituting the coil 2 has rounded corners to enable smooth winding of the winding that constitutes the coil 2. Furthermore, when the winding is not wound around the support, it is preferable that the portion corresponding to the connection portion 5 is rounded when winding.

[0037] As described above, the magnet 1 according to the present invention includes four or more coils 2. Each of the four or more coils 2 is connected to a control unit (not shown), which allows the current value of each coil 2 to be independently controlled. This allows each coil 2 to generate a magnetic field of different strength and direction.

[0038] When the magnet 1 is viewed from above, the multiple coils 2 are preferably arranged symmetrically with respect to an axis perpendicular to an axis that passes through the center of the magnet 1 and extends vertically. This allows a symmetrical magnetic field distribution to be formed.

[0039] 3 shows examples of the arrangement of multiple coils 2 that make up the magnet 1 according to the present invention, with (a) showing an example with four coils 2 and (b) showing an example with twelve coils 2. The arrows in the figures indicate the direction of the horizontal magnetic field.

[0040] For example, as shown in FIG. 3(a), when the magnet 1 has four coils 2, the distance D between two coils 2 is as shown in FIG. a (i.e., the distance between two coils 2 that do not sandwich the xz plane) and D b By adjusting the distance D (the distance between the two coils 2 on either side of the xz plane) as a parameter, it is possible to set an arbitrary magnetic field distribution. a When D is shortened, the magnetic flux density in region A shown in FIG. 4 increases, while the magnetic flux density in region B decreases. Specifically, as shown in FIG. 5(a), a <D b In this case, the magnetic flux density decreases along the x-axis direction from the magnetic field center O (Fig. 5(b)), while it increases along the y-axis direction (Fig. 5(c)).

[0041] Conversely, distance D b When D is shortened, the magnetic flux density in region B shown in FIG. 4 increases, while the magnetic flux density in region A decreases. Specifically, as shown in FIG. 6(a), a >D b In this case, the magnetic flux density increases along the x-axis direction from the magnetic field center O (Fig. 6(b)), while it decreases along the y-axis direction (Fig. 6(c)). a and D b Any magnetic field distribution can be set using these parameters.

[0042] Furthermore, as shown in Figure 3(b), if the magnet 1 has 12 coils 2, any magnetic field distribution can be set by changing the shape of the coils 2, the value of the current flowing through the coils 2, and the number of turns of the wire that makes up the coils 2.

[0043] Specifically, as shown in FIG. 7(a), of the 12 coils 2, coil 2 A , 2 C , 2 D , 2 F , 2 G , 2 I , 2 J , 2 L The output of coil 2 is relatively increased. B , 2 E , 2 H , 2 K By making the output of relatively small, the magnetic flux density along the x-axis direction (Fig. 7(b)) and the magnetic flux density along the y-axis direction (Fig. 7(c)) can be adjusted to set an arbitrary magnetic field distribution.

[0044] For the twelve coils 2 shown in FIG. 7(a), the control unit controls the six adjacent coils 2 (coils 2 J , 2 K , 2 L , 2 A , 2 B , 2 C ) and the remaining six adjacent coils 2 (coil 2I , 2 H , 2 G , 2 F , 2 E , 2 D 7A shows a case where the number of coils is 12, but in the case of other numbers of coils, it is also preferable that the direction of the current flowing through the coils 2 is opposite between the first coil group (the coil group arranged in the first and second quadrants) and the second coil group (the coil group arranged in the third and fourth quadrants).

[0045] In addition, for the 12 coils 2 shown in FIG. 7(a), the control unit C , 2 D , 2 I and 2 J Group of 2 B , 2 E , 2 H and 2 K Group of 2 A , 2 F , 2 G and 2 L It is preferable that the current values ​​of the three groups are configured to decrease in the above order. This makes it possible to suppress convection fluctuations in the raw material melt 13. Note that although Fig. 7(a) shows the case where the number of coils is 12, it is also preferable that the current value of the coil 2 adjacent to each other across the xz plane is configured to be larger than that of the other coils 2 in the other cases where the number of coils is six or more.

[0046] In addition, for the 12 coils 2 shown in FIG. 7(a), J and coil 2 I Between and coil 2 C and coil 2 DIt is preferable that the distance between adjacent coils 2 is shorter than the distance between other adjacent coils 2. This increases the magnetic flux density gradient near the coil 2, improving the effect of suppressing convection fluctuations. Note that although FIG. 7(a) shows the case where the number of coils is 12, it is also preferable that the distance between adjacent coils 2 across the xz plane is shorter than the distance between other adjacent coils 2, even in the case of other numbers of coils.

[0047] Magnet 1 can be an electromagnet (normally conducting) or a superconducting electromagnet, but a superconducting electromagnet is preferable because it can generate a stronger magnetic field. When magnet 1 is configured as a superconducting electromagnet, the windings that make up coil 2 are made of a superconducting material such as a niobium-based alloy. Four or more coils 2 are then housed in a cylindrical vacuum vessel (not shown), and arranged so that, for example, two coils 2 face each other. Then, for example, the coils 2 are filled with a cooling solvent, and configured so that the coils 2 can be cooled to the transition temperature using a cooling device.

[0048] (Single crystal manufacturing equipment) The single crystal manufacturing apparatus according to the present invention comprises a crucible containing a melt of raw material for the single crystal, and the magnet according to the present invention described above, arranged around the crucible, the magnet having four or more coils, and pulling up the single crystal while applying a horizontal magnetic field to the melt using the magnet.

[0049] FIG. 8 shows an example of a single crystal manufacturing apparatus according to the present invention. Components identical to those in the single crystal manufacturing apparatus 100 shown in FIG. 1 are designated by the same reference numerals. The single crystal manufacturing apparatus 10 shown in FIG. 8 includes the magnet 1 according to the present invention, as described above, instead of the magnet 21 in the single crystal manufacturing apparatus 100 shown in FIG. 1. As described above, the magnet 1 includes four or more coils 2 with a height-to-width ratio greater than 1, and each of the four or more coils 2 is configured to generate a magnetic field independently of one another via a control unit. This allows for greater freedom in designing the magnetic field distribution, even when the arrangement of the coils constituting the magnet of the single crystal manufacturing apparatus is limited. The single crystal manufacturing apparatus 10 including such a magnet 1 applies a magnetic field with a desired magnetic field distribution to the raw material melt 13, thereby producing a single crystal with desired properties, such as a defect-free single crystal.

[0050] Furthermore, as shown in Figure 9, magnet 1 according to the present invention is preferably a magnet in which, when the magnetic flux density at the center O of the magnetic field neutral plane (0mm, 0mm, 0mm) is M, the magnetic flux density at point A (0mm, 0mm, -400mm) is 0.58 x M or more, and the magnetic flux density at point B (400mm, 0mm, 0mm) is 1.47 x M or more. This makes it possible to suppress fluctuations in the oxygen concentration in the pulling direction of the single crystal, as well as fluctuations in the pulling speed of the single crystal, thereby producing a defect-free single crystal. Details of points A, B, and the magnetic field neutral plane will be described later.

[0051] (Method of manufacturing single crystals) The method for producing a single crystal according to the present invention is a method for producing a single crystal by the Czochralski method using the single crystal production apparatus according to the present invention described above, and is characterized in that when the magnetic flux density at the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane 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, by applying a horizontal magnetic field to the melt of the raw material using the magnet to pull up the single crystal.

[0052] As described above, by using the single crystal manufacturing apparatus 10 according to the present invention, it is possible to manufacture a single crystal having desired properties by applying a magnetic field with a desired magnetic field distribution to the raw material melt 13. The inventors have found that by using the manufacturing apparatus 10 to apply an appropriate magnetic field distribution to the raw material melt 13, it is possible to manufacture a single crystal with little variation in oxygen concentration.

[0053] That is, the inventors discovered that, as shown in FIG. 9, when the magnetic flux density at the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane is M, by applying a horizontal magnetic field to the raw material melt using magnet 1 to pull up the single crystal so that 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 suppress fluctuations in the oxygen concentration in the pulling direction of the single crystal and also suppress fluctuations in the pulling speed of the single crystal, thereby producing a defect-free single crystal.

[0054] The "magnetic field neutral plane" refers to the plane that includes the center of gravity of all of the coils 2 that make up the magnet 1, and the "center of the magnetic field neutral plane" refers to the point where the magnetic field neutral plane intersects with the crystal rotation axis. The coils 2 are preferably arranged so that the height of the centers of gravity of all of the coils 2 is the same and the magnetic field neutral plane is a horizontal plane.

[0055] When magnet 1 is installed in single crystal manufacturing equipment 10 and a horizontal magnetic field is applied to manufacture a single crystal, the central axis of magnet 1 generally coincides with the crystal rotation axis. In other words, the axis extending vertically through the center of magnet 1 according to the present invention can be considered to be the same as the crystal rotation axis. Therefore, the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane can generally be rephrased as the point where the magnetic field neutral plane intersects with the axis extending vertically through the center of magnet 1. In particular, when magnet 1 is removed from the single crystal manufacturing equipment, i.e., when magnet 1 is used alone, the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane is the point where the magnetic field neutral plane intersects with the axis extending vertically through the center of magnet 1, i.e., the central axis of magnet 1.

[0056] Furthermore, points A and B are defined on the magnetic field neutral plane, with the origin O being the center of the magnetic field, the y-axis being the axis that passes through the origin O and is parallel to the direction of the magnetic field, the x-axis being the axis that is perpendicular to the direction of the magnetic field, and the z-axis being the axis that passes through the origin O and is perpendicular to the magnetic field neutral plane. At the start of pulling the crystal, point A is a point on the z-axis inside (inner surface) of crucible 12, and point B is a point on the x-axis inside (inner surface) of crucible 12. When the magnetic field neutral plane is a horizontal plane, the z-axis and the crystal rotation axis coincide.

[0057] The magnetic flux density requirements at points A and B can be achieved by making the height of the magnetic field neutral plane and the surface of the raw material melt 13 the same and making the angle between the coils 2 90° or more.

[0058] Furthermore, it is preferable that the magnetic flux density at point C (0 mm, 400 mm, 0 mm) on the inside (inner surface) of crucible 12 on the y-axis, which is at the same height as point B, is smaller than the magnetic flux density at point B. This makes it possible to further suppress convection fluctuations in raw material melt 13.

[0059] The single crystal 16 is not particularly limited as long as it can be produced by the CZ method, but it is possible to suitably produce a single crystal of semiconductor silicon with small fluctuations in oxygen concentration. [Example]

[0060] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0061] (Example 1) Silicon single crystals with a diameter of 310 mm were produced using a single crystal production apparatus equipped with a magnet having a vertical rectangular annular coil as shown in Figure 2. The rectangular annular coils were configured so that the height of the magnetic field neutral plane was the same as point A in Figure 9(b), and four coils were arranged with a coil angle of 60°. Each coil was vertical and had the same shape, and the magnetic field neutral plane was configured to be a horizontal plane. The magnitude and direction of the current flowing through the coils were then adjusted to obtain a magnetic flux density of 0.58 M at point A and a magnetic flux density of 1.4 M at point B. 7A magnetic field distribution was generated such that M. Under these conditions, polycrystalline silicon, the silicon raw material contained in the crucible, was melted, and a seed crystal was immersed in the molten silicon and pulled up, and a silicon single crystal was grown below the seed crystal.

[0062] (Example 2) Silicon single crystals were produced in the same manner as in Example 1. However, the height of the magnetic field neutral plane relative to point A was changed so that the magnetic flux density at point A was 0.64 times the magnetic flux density M at the magnetic field center O, and the magnetic flux density at point B was 2.23 times. All other conditions were the same as in Example 1.

[0063] (Comparative Example) Silicon single crystals were produced in the same manner as in Example 1. However, the height of the magnetic field neutral plane relative to point A was changed so that the magnetic flux density at point A was 0.53 times the magnetic flux density M at the magnetic field center O, and the magnetic flux density at point B was 1.03 times. All other conditions were the same as in Example 1.

[0064] <Oxygen concentration in the axial direction of a single crystal> FIG. 10 shows the variation in oxygen concentration in the axial direction of a silicon single crystal, with (a) for a comparative example, (b) for example 1, and (c) for example 2. In FIG. 10, the axial position and oxygen concentration of the single crystal are normalized by predetermined values. For the comparative example shown in FIG. 10(a), the variation in oxygen concentration in the axial direction of the single crystal was large and did not fall within the specified oxygen concentration range. On the other hand, for examples 1 and 2 shown in FIGS. 10(b) and 10(c), the variation in oxygen concentration was reduced compared to the comparative example. In particular, for example 2, the variation in oxygen concentration was reduced to about one-fifth of that of the comparative example.

[0065] <Temperature fluctuation at the solid-liquid interface> Figure 11 shows the time variation of the solid-liquid interface temperature obtained by a three-dimensional fluid simulation, with (a) for the comparative example, (b) for example 1, and (c) for example 2. In Figure 11, the time and the solid-liquid interface temperature are normalized by predetermined values. For the comparative example shown in Figure 11(a), the time variation of the solid-liquid interface temperature was large, which in turn led to large fluctuations in the crystal pulling speed, making it impossible to obtain defect-free silicon single crystals. On the other hand, for examples 1 and 2 shown in Figures 11(b) and 11(c), the time variation of the solid-liquid interface temperature was reduced compared to the comparative example, and the fluctuations in the crystal pulling speed were small, making it possible to obtain defect-free silicon single crystals. In particular, for example 2, the time variation of the solid-liquid interface temperature was reduced to about 1 / 50 of that of the comparative example. [Industrial Applicability]

[0066] According to the present invention, even when the arrangement of the coils that make up the magnets of the single crystal manufacturing equipment is restricted, the degree of freedom in designing the magnetic field distribution can be increased, and therefore the present invention is useful in the semiconductor wafer manufacturing industry. [Explanation of symbols]

[0067] 1,21 Magnet 2,22 Coil 2a opening 2b External surface 2c Inner surface 2d outer surface 2e Inner surface 3. First Part 4. Second Part 5 Connection part 10,100 Single crystal manufacturing equipment 11 Chambers 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 Winding mechanism

Claims

1. A magnet for a single crystal manufacturing apparatus for applying a horizontal magnetic field to a melt of a single crystal raw material contained in a crucible while pulling the single crystal, the magnet comprising: four or more coils, wherein at least one of the four or more coils has a height to width ratio greater than 1; a control unit that can generate magnetic fields for each of the four or more coils independently of one another; Equipped with The plane including all of the centers of gravity of the four or more coils is defined as the magnetic field neutral plane, the point where the magnetic field neutral plane intersects with the rotation axis of the single crystal is defined as the center O, the axis passing through the center O and parallel to the direction of the magnetic field is defined as the y axis, the axis perpendicular to the direction of the magnetic field is defined as the x axis, and the axis passing through the center O and perpendicular to the magnetic field neutral plane is defined as the z axis. A magnet for single crystal manufacturing equipment, characterized in that, when the magnetic flux density at the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane is M, the magnetic flux density at point A (0 mm, 0 mm, -400 mm) on the z axis is 0.58 × M or more, and the magnetic flux density at point B (400 mm, 0 mm, 0 mm) on the x axis is 1.47 × M or more.

2. 2. The magnet for a single crystal manufacturing apparatus according to claim 1, wherein said coil is rectangular and annular.

3. 3. The magnet for use in a single crystal manufacturing apparatus according to claim 1, wherein the height is 600 mm or more.

4. A single crystal manufacturing apparatus comprising: a crucible for containing a melt of a single crystal raw material; and the magnet according to any one of claims 1 to 3, arranged around the crucible, wherein the magnet applies a horizontal magnetic field to the melt while pulling up the single crystal.

5. A method for producing a single crystal by the Czochralski method using the single crystal production apparatus according to claim 4, a method for producing a single crystal, wherein the horizontal magnetic field is applied to the melt by the magnet so that, when the magnetic flux density at the center O (0 mm, 0 mm, 0 mm) of the magnetic field neutral plane is M, the magnetic flux density at the point A (0 mm, 0 mm, -400 mm) on the z axis is 0.58 × M or more, and the magnetic flux density at the point B (400 mm, 0 mm, 0 mm) on the x axis is 1.47 × M or more.

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

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