CN116254596A - Coil, magnet for single crystal manufacturing apparatus, and single crystal manufacturing method - Google Patents

Abstract

The present invention relates to a coil, a magnet for a single crystal manufacturing apparatus, and a single crystal manufacturing method. Provided is a coil used for a magnet for a single crystal manufacturing apparatus, which can suppress variation in the pulling rate of a crystal and can suppress reduction in the oxygen concentration in the outer periphery of a wafer obtained from a manufactured single crystal. The coil (1) of the present invention is a coil used in a magnet for a single crystal manufacturing apparatus that pulls a single crystal by applying a horizontal magnetic field to a melt of a raw material of the single crystal stored in a crucible by the Czochralski method. The ring-shaped heat exchanger is characterized in that the ring-shaped heat exchanger has a concave part (1 a) at the upper part.

Description

Coil, magnet for single crystal manufacturing apparatus, and single crystal manufacturing method

Technical Field

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

Background

Generally, as a substrate of a semiconductor device, a substrate made of a single crystal of a semiconductor such as silicon is used. As a typical method for producing such a single crystal of a semiconductor, a Czochralski (CZ) method is given. The CZ method is as follows: the semiconductor material is stored in a crucible and melted, and a seed crystal is attached to the melted material of the single crystal and pulled, whereby the single crystal is grown under the seed crystal and manufactured.

As a crucible for storing the raw material of the single crystal, a crucible made of quartz is generally used. Therefore, when the raw material melt of the single crystal stored in the crucible is convected rapidly, the amount of oxygen contained in the quartz crucible increases, and the oxygen concentration of the single crystal increases. Thus, the following operations are performed: the single crystal is pulled up while a horizontal magnetic field is applied to the raw material melt in the crucible to suppress convection of the raw material melt, thereby controlling the oxygen concentration of the single crystal (for example, refer to patent document 1).

Fig. 1 shows an example of a horizontal magnetic field application type single crystal manufacturing apparatus. The single crystal manufacturing apparatus 100 shown in the figure includes, in a chamber 11, a crucible 12 for storing a raw material (e.g., polycrystalline silicon) of a single crystal (e.g., silicon) 16, a heater 14 for heating the raw material in the crucible 12 as a raw material melt 13, a crucible rotation mechanism 15 provided at a lower portion of the crucible 12 and rotating the crucible 12 in a circumferential direction, a seed crystal holder 18 for holding a seed crystal 17 for growing the single crystal 16, a wire rope 19 having the seed crystal holder 18 attached to a tip thereof, and a winding mechanism 20 for rotating and pulling the single crystal 16, the seed crystal 17, and the seed crystal holder 18 while rotating the wire rope 19. Further, a magnet 21 is disposed outside the lower portion of the chamber 11, and the magnet 21 has a plurality of coils 22 for applying a horizontal magnetic field (transverse magnetic field) to the silicon melt 13 in the crucible 12.

With this single crystal manufacturing apparatus 100, the single crystal 16 can be manufactured as follows. That is, first, a predetermined amount of single crystal raw material is stored in the crucible 12, heated by the heater 14 to obtain the raw material melt 13, and a predetermined horizontal magnetic field is applied to the raw material melt 13 by the magnet 21.

Next, the seed crystal 17 held by the seed crystal holder 18 is immersed in the raw material melt 13 in a state where a horizontal magnetic field is applied to 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 by the winding mechanism 20 while being rotated at the predetermined rotation speed, whereby the seed crystal 17 and the single crystal 16 grown on the seed crystal 17 are pulled. Thus, a single crystal having a predetermined diameter can be produced.

As the coil 22 constituting the magnet 21, for example, a coil having a horizontally long annular rectangular shape as shown in fig. 2 (a) can be given. As shown in fig. 2 (b), the magnet 21 may be configured using two coils 22 disposed so as to face the periphery of the chamber 11. As shown in fig. 2 (b), the coil 22 is bent toward the outer surface 22a, and the inner surface 22b is disposed toward the chamber 11.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2007-204312.

Disclosure of Invention

Problems to be solved by the invention

In the production of the single crystal 16, when 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 "crystal/melt interface") changes due to the fluctuation of the flow distribution of the raw material melt 13, the diameter of the single crystal 16 (hereinafter, also referred to as "crystal diameter") fluctuates. Therefore, the pulling rate of the single crystal 16 (hereinafter, also referred to as "crystal pulling rate") is adjusted in accordance with the variation in crystal diameter, so that the crystal diameter is constant. However, the crystal pulling rate is also used for controlling crystal defects that affect the quality of the single crystal 16, and variation in the crystal pulling rate causes variation in the quality (crystal defects) of the single crystal 16 to be produced. Therefore, it is preferable that the variation of the crystal pulling rate with respect to the set value is small.

Further, a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the produced single crystal 16 decreases the mechanical strength of the outer peripheral portion of the wafer, and causes deformation due to heat treatment during device production. Therefore, the amount of decrease in oxygen concentration at the outer peripheral portion of the wafer is preferably small.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a coil used in a magnet for a single crystal manufacturing apparatus, which can suppress a variation in the pulling rate of a single crystal and can suppress a decrease in the oxygen concentration in the outer periphery of a wafer obtained from the manufactured single crystal.

Means for solving the problems

The present invention to solve the above problems is as follows.

[1] A coil used for a magnet for a manufacturing apparatus for pulling up a single crystal of a single crystal contained in a crucible by applying a horizontal magnetic field to a melt of the raw material of the single crystal by a Czochralski method,

the coil has a recess in an upper portion and is annular.

[2] A magnet for a single crystal production apparatus for applying a horizontal magnetic field to a melt of a raw material of a single crystal contained in a crucible by a Czochralski method and pulling the single crystal, characterized in that,

the magnet for a single crystal manufacturing apparatus has 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 the two coils being the annular coil described in [1 ].

[3] The magnet for a single crystal production apparatus according to the above [2], wherein the magnet for a single crystal production apparatus is capable of generating the following magnetic field distribution: when the magnetic flux density at the origin O (0 mm ) is M, the magnetic flux density at the point A (0 mm, -400 mm) is 0.58 XM or more, and the magnetic flux density at the point B (400 mm,0 mm) is 1.47 XM or more.

[4] A single crystal production apparatus comprising the magnet according to [2] or [3], wherein the magnet is used to apply a horizontal magnetic field to the melt and pull the single crystal.

[5] A method for producing a single crystal, wherein in the method for producing a single crystal, the horizontal magnetic field is applied to pull the single crystal by using the apparatus for producing a single crystal described in [4 ].

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

Effects of the invention

The variation in the pulling rate of the single crystal can be suppressed, and the decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the produced single crystal can be suppressed.

Drawings

Fig. 1 is a diagram showing an example of a horizontal magnetic field applying type single crystal manufacturing apparatus.

Fig. 2 is a diagram showing an example of a coil constituting a conventional magnet, in which (a) is an overall diagram, and (b) is a diagram illustrating the arrangement of the coil.

Fig. 3 is a diagram showing a flow distribution of the raw material melt on the surface of the raw material melt obtained by simulation.

Fig. 4 is a diagram showing a preferred example of the coil of the present invention, in which (a) is an overall diagram, (b) is a front diagram, and (c) is a plan view.

Fig. 5 is a diagram illustrating the arrangement of coils in an example of the magnet of the present invention.

Fig. 6 is a diagram illustrating positions of an origin O, a point B, and a point C, (a) is a diagram of the crucible viewed from above, and (B) is a diagram of the crucible viewed from the side.

Fig. 7 is a diagram showing an example of an apparatus for producing a single crystal according to the present invention.

Fig. 8 is a diagram showing the magnetic flux density distribution of the coil of the conventional example and the coil of the invention example, (a) is the magnetic flux density in the x-axis direction, (b) is the magnetic flux density in the y-axis direction, and (c) is the magnetic flux density in the z-axis direction.

Fig. 9 is a graph showing time variation of the average temperature of the solid-liquid interface.

Fig. 10 is a graph showing a relationship between a distance from the center of a wafer and an oxygen concentration.

Detailed Description

(coil)

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The coil of the present invention is a coil used in a magnet for a single crystal manufacturing apparatus that pulls up a single crystal by applying a horizontal magnetic field to a melt of a raw material of the single crystal stored in a crucible by the Czochralski method. Here, a feature is that the upper part has a concave portion and is annular. In general, a conventional coil shape used for a magnet for a single crystal manufacturing apparatus is a shape having no irregularities on an upper portion thereof (fig. 2) or a shape describing an arc. However, the coil of the present invention is characterized in that the shape of the upper part is different from the shape of the conventional coil, the upper part of the coil is concave, and the upper part of the shape of the coil opening is also concave.

The present inventors have conducted intensive studies on a method capable of suppressing a variation in the pulling rate of a single crystal and suppressing a decrease in the oxygen concentration in the outer peripheral portion of a wafer obtained from a produced single crystal. In this process, attention is paid to a coil used for a magnet for a single crystal manufacturing apparatus.

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

By applying a magnetic field to the raw material melt 13 by the magnet 21 to generate a lorentz force due to a current and a magnetic field in the raw material melt 13, the fluctuation of the flow distribution of the raw material melt 13 can be suppressed. In order to suppress the fluctuation of the flow distribution of the raw material melt 13, it is preferable to apply a magnetic field having a high magnetic flux density to the raw material melt 13.

In contrast, a decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the single crystal produced decreases the mechanical strength of the outer peripheral portion of the wafer, and causes deformation due to heat treatment during device production. Therefore, the amount of decrease in oxygen concentration at the outer peripheral portion of the wafer is preferably small.

Fig. 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 fig. 3, at the crystal/melt interface at the time of crystal pulling, a lorentz force due to an induced current generated in the single crystal 16 rotated in a magnetic field and the magnetic field generates convection that guides the raw material melt 13 on the surface. It is considered that the source material melt 13 whose oxygen concentration is reduced by evaporation is present on the surface of the source material melt 13, and that the single crystal 16 is introduced into the source material melt 13 having such a low oxygen concentration, whereby the oxygen concentration at the outer peripheral portion of the wafer is reduced. Therefore, in order to suppress the decrease in the oxygen concentration at the outer peripheral portion of the wafer, it is preferable to apply a magnetic field having a low magnetic flux density to the raw material melt 13 in the vicinity of the single crystal 16.

In this way, it is effective to apply a magnetic field of high magnetic flux density to the raw material melt 13 in order to suppress the fluctuation of the crystal pulling rate, while it is effective to apply a magnetic field of low magnetic flux density to the raw material melt 13 in order to suppress the decrease in the oxygen concentration in the wafer outer periphery, and the suppression of the fluctuation of the crystal pulling rate and the suppression of the decrease in the oxygen concentration in the wafer outer periphery are in a trade-off relationship.

The present inventors have conducted intensive studies on a method capable of simultaneously suppressing the variation in the crystal pulling rate and suppressing the decrease in the oxygen concentration at the outer peripheral portion of the wafer. As a result, a ring-shaped coil having a concave portion in the upper portion is conceivable. By using such a coil to construct a magnet, a magnetic field having a low magnetic flux density can be applied to the raw material melt 13 around the single crystal 16, and a magnetic field having a high magnetic flux density can be applied to the raw material melt 13 other than the raw material melt, so that both of suppression of fluctuation in crystal pulling rate and suppression of reduction in oxygen concentration in the outer peripheral portion of the wafer can be achieved. Thus, the present invention has been completed.

As is clear from the above description, the coil of the present invention has characteristics in terms of its shape, and other configurations are not limited, and conventionally known configurations can be appropriately used. The coil of the present invention will be specifically described below, but the present invention is not limited thereto.

Fig. 4 shows a preferred example of a coil constituting a magnet for a single crystal manufacturing apparatus according to the present invention, (a) shows an overall view, (b) shows a front view, and (c) shows a plan view. The coil 1 shown in fig. 4 has a concave portion 1a at an upper portion and is configured in a ring 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 portions 2 and the second portions 3.

Furthermore, 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-connection portions 34 connecting the first sub-portion 31 or the second sub-portion 32 and the third sub-portions 33. Further, the recess 1a of the coil 1 is delimited by a second sub-portion 32, two third sub-portions 33 and four sub-connection portions 34. In the examples shown in fig. 4 (a) to (c), a concave portion 1a is provided in the center of the upper second portion 3.

The coil 1 having such a structure is applied to a magnet for a single crystal manufacturing apparatus, and is disposed around the chamber 11 so that a current flows through the coil 1. Thus, a magnetic field having a low magnetic flux density can be applied to the raw material melt 13 in the vicinity of the single crystal 16, and a magnetic field having a high magnetic flux density can be applied to the raw material melt 13 apart from the single crystal 16 in addition thereto. As a result, the variation in the pulling rate of the single crystal can be suppressed, and the decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the produced single crystal can be suppressed.

The depth (i.e., the difference in height) and width (i.e., the length of the second sub-portion 32) of the recess 1a of the coil 1 can be appropriately set according to the size of the crucible 12 containing the raw material melt 13, for example, the depth of the recess 1a is preferably 40% to 60% of the coil height, and the "coil height" is the length of the longest portion in the up-down direction of the opening of the coil 1, that 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 with respect to the coil 1 shown in fig. 4, and in the examples shown in fig. 4 (a) to (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 parallel to the horizontal plane.

Further, it is preferable that the width of the concave portion 1a is 90% to 110% of the width of the crystal diameter of the grown single crystal. In the case where the second portion 3 is curved toward the outer surface 1d as shown in fig. 4, the "width of the recess" refers to the length of the inner surface 1e of the recess 1a when the coil 1 is viewed from the front. The crystal diameter can be 300mm or more (for example, 301 to 340mm in the case of a silicon single crystal for a phi 300mm wafer and 451 to 500mm in the case of a phi 450mm wafer), and the present invention is suitable for the production of a single crystal having a crystal diameter of 300mm or more.

As for the coil 1, a support having a shape shown in fig. 4 is prepared, and as shown in fig. 4 a, a recess (not shown) may be provided in an outer peripheral surface 1b defining the outer shape of the support or an inner peripheral surface 1c defining the opening of the support, and the coil may be wound while being accommodated in the recess. The coil 1 may be formed by winding the coil into the shape shown in fig. 4 without providing a support and fixing the coil with a resin.

In the case of winding the winding around the outer peripheral surface 1b or the inner peripheral surface 1c of the support, it is preferable that the corners of the outer peripheral surface 1b or the inner peripheral surface 1c of the support have R (roundness) so that the winding constituting the coil 1 is smoothly wound. In the case where the winding is not wound around the support, R is preferably applied to the corner portion to perform winding.

Further, for example, as shown in fig. 4 (a) and (c), the coil 1 is preferably bent toward the outer surface 1d thereof. Thus, the coil 1 can be disposed along the outer wall of the chamber 11 so that the inner surface 1e of the coil 1 faces the chamber 11, and the space required for disposing the coil 1 can be saved and the structure can be made compact. However, the coil 1 does not necessarily need to be bent, and may be a flat coil 1.

The recess 1a of the coil 1 shown in fig. 4 is rectangular, but is not limited thereto, and may have any shape such as a semicircle, a semi-ellipse, or a polygon other than a rectangle.

(magnet for Single Crystal manufacturing apparatus)

The single crystal production apparatus of the present invention is a magnet for a single crystal production apparatus for applying a horizontal magnetic field to a melt of a raw material of a single crystal stored in a crucible by a Czochralski method and pulling the single crystal. The magnet is characterized by having a plurality of coils, and a part or all of the plurality of coils are the coils of the present invention described above.

Fig. 5 is a diagram illustrating the arrangement of coils in an example of the magnet of the present invention. Note that 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 of the present invention shown in fig. 4, and these two coils 1 having the same shape and the same size are disposed so as to face the periphery of the chamber 11 symmetrically (that is, symmetrically with respect to the xz plane (plane perpendicular to the application direction of the horizontal magnetic field)). As described above, since the coil 1 has the concave portion 1a in the upper portion, it is possible to apply a magnetic field having a low magnetic flux density to the raw material melt 13 in the vicinity of the single crystal 16 and to apply a magnetic field having a high magnetic flux density to the raw material melt 13 apart from the single crystal 16 in addition thereto. Thus, when applied to a single crystal manufacturing apparatus, it is possible to suppress variation in the pulling rate of a single crystal and to suppress reduction in the oxygen concentration in the outer periphery of a wafer obtained from the manufactured single crystal.

Furthermore, it is preferable that the magnet 50 is capable of generating the following magnetic field distribution: when the magnetic flux density at the origin O (0 mm ) described later is set to M, the magnetic flux density at the point a (0 mm, -400 mm) is set to 0.58×m or more, and the magnetic flux density at the point B (400 mm,0 mm) is set to 1.47×m or more.

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

Further, since the center axis of the magnet 50 (see the chain line in fig. 4) for the single crystal manufacturing apparatus generally coincides with the crystal pulling axis, when the magnet 50 is removed from the single crystal manufacturing apparatus, that is, when the magnet is alone, the origin O can be defined as the intersection point of the center axis of the magnet 50 and the plane including the point of the lowest height position of the lower surface 32b of the second sub-portion 32 in fig. 4.

When the coils 1 disposed on the magnet 50 are disposed in two opposing directions, the origin O is defined as the intersection point of the central axis of the magnet 50 and the line connecting the 2 points at the lowest height position of the lower surface 32b of the second sub-portion 32. When the line connecting the 2 points does not intersect with the central axis of the magnet 50, the line connecting the 2 points is defined as an intersection point between the line connecting the 2 points and the central axis of the magnet 50 when the line connecting the 2 points is horizontally moved so as to intersect with the central axis of the magnet 50. As shown in fig. 4, when the lower surface 32b of the second sub-portion 32 is a horizontal surface, the origin O is an intersection point of the horizontal surface including the lower surface 32b and the central axis of the magnet 50.

Here, a positional relationship between the origin O and the liquid surface of the raw material melt 13 (the surface of the raw material melt 13) in the crucible 12 will be described. When the magnet 50 of the present invention is provided in a single crystal manufacturing apparatus and a horizontal magnetic field is applied to manufacture a single crystal, the height position of the liquid surface of the raw material melt 13 in the crucible 12 is generally near the middle position in the height direction of the coil 1. Therefore, when the magnet 50 is provided in the apparatus for producing a single crystal and a horizontal magnetic field is applied to produce a single crystal, it is 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, is substantially equal to the height position of the liquid surface of the raw material melt 13 in the crucible 12. Therefore, when the magnet 50 of the present invention is installed in a single crystal manufacturing apparatus and a horizontal magnetic field is applied to manufacture a single crystal, the origin O can be regarded as the intersection point of the liquid surface of the raw material melt 13 in the crucible 12 and the central axis of the crystal.

That is, in a state where the magnetic field is applied to the crucible 12 by the magnet 50 and the origin O is disposed at the same height position as the surface of the raw material melt 13, as shown in fig. 6 (a) and (b), the axis passing through the origin O and parallel to the direction of the magnetic field projected on the horizontal plane is set to the y-axis, the axis perpendicular to the direction of the magnetic field projected on the horizontal plane is set to the x-axis, and the axis passing through the origin O and perpendicular to the horizontal plane is set to the z-axis. At this time, the inventors found that, when the point inside (inner wall) the crucible 12 on the z-axis is set to 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 considered to be because, when the magnetic flux density at the bottom of the crucible 12 is low, the intensity of the lorentz force controlling the convection of the raw material melt 13 is small, the influence of the shearing force caused by the rotation of the crucible 12 is large, and the fluctuation of the flow distribution of the raw material melt 13 is large, which affects the fluctuation of the oxygen concentration.

Further, the present inventors found that, when the point inside (inner wall) the crucible 12 on the x-axis is set to point B, the magnetic flux density at point B is closely related to the variation in crystal pulling speed when a defect-free single crystal is pulled. This is considered because, when a horizontal magnetic field is applied to the raw material melt 13 of a conductor such as silicon, a coil-like convection current rotating in the direction of the horizontal magnetic field is generated, but when the magnetic flux density at the point B is high, the damping properties of the upward flow and the downward flow are improved, the fluctuation in the temperature of the solid-liquid interface is suppressed, and the fluctuation in the crystal pulling rate v is suppressed.

In this way, the present inventors found that by pulling up a single crystal by applying a horizontal magnetic field to the melt so that the magnetic flux density at the points a and B falls within a predetermined range, specifically, so that the magnetic flux density at the point of origin O (0 mm ) is at least 0.58×m at the point of origin a (0 mm, -400 mm) and the magnetic flux density at the point of origin B (400 mm,0 mm) is at least 1.47×m, variation in oxygen concentration in the crystal pulling direction can be suppressed, and a defect-free single crystal can be produced.

When the magnetic flux density at the origin O is set to M, the magnetic flux density at the point a is set to 0.58M or more, whereby the variation in oxygen concentration in the crystal pulling direction in the single crystal can be suppressed. Preferably, the magnetic flux density at the point a is set to 0.64M or more. This can further suppress the variation in oxygen concentration in the crystal pulling direction in the single crystal.

Further, by setting the magnetic flux density at the point B to 1.47M or more, variation in crystal pulling rate of the defect-free single crystal can be suppressed. Preferably, the magnetic flux density at the point B is set to 2.23M or more. This can further suppress the variation in the crystal pulling rate of the defect-free single crystal.

Further, it is preferable to make the magnetic flux density at the point C (0 mm,400mm,0 mm) smaller than the magnetic flux density at the point B. This can further suppress the convection fluctuation of the raw material melt 13.

The control of the magnetic flux density at the points a and B is dependent on the configuration of the magnet 50, but can be performed 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, in the case of using the coil 1 shown in fig. 4, the height H1 of the coil at the position where the concave portion 1a is not present is formed at 750mm, the height H2 at the position where the concave portion 1a is present is formed at 375mm, the radius of curvature of the curved coil is formed at 900mm, and the first sub-portion 31 of the second portion 3 is formed at 45 ° (i.e., the portion of the concave portion 1a is 90 °), whereby the current and the direction flowing through the coil 1 can be controlled, whereby the magnetic flux densities at the points a and B can be controlled as described above.

(apparatus for producing Single Crystal)

The single crystal production apparatus of the present invention is an apparatus for producing a single crystal comprising: the crucible is provided with a crucible for containing a melt of a raw material of a single crystal, and the magnet of the present invention disposed around the crucible, and the single crystal is pulled by applying a horizontal magnetic field to the melt by the magnet.

Fig. 7 shows an example of an apparatus for producing a single crystal according to the present invention. Note that the same components as those of the single crystal manufacturing apparatus 100 shown in fig. 1 are denoted by the same reference numerals. The single crystal manufacturing apparatus 70 shown in fig. 7 includes the magnet 50 of the present invention described above in place of the magnet 21 in the single crystal manufacturing apparatus 100 shown in fig. 1. As described above, the magnet 50 has two coils of the same shape and the same size, which are symmetrically arranged with respect to a plane perpendicular to the application direction of the horizontal magnetic field, and both of the coils are constituted by the coil 1 of the present invention having the concave portion 1a in the upper portion and being annular. Thus, when the single crystal 16 is pulled, the fluctuation of the pulling rate of the single crystal can be suppressed, and the decrease of the oxygen concentration in the outer periphery of the wafer obtained from the produced single crystal can be suppressed. As a result, a defect-free single crystal in which the decrease in oxygen concentration at the outer peripheral portion of the wafer is suppressed can be produced.

(method for producing Single Crystal)

The method for producing a single crystal according to the present invention is characterized in that the single crystal is pulled up by applying a horizontal magnetic field to a melt of a raw material using the magnet using the apparatus for producing a single crystal according to the present invention.

As described above, by using the apparatus 70 for producing a single crystal according to the present invention, it is possible to suppress a variation in the pulling rate of the single crystal and suppress a decrease in the oxygen concentration in the outer periphery of the wafer obtained from the produced single crystal when the single crystal 16 is pulled. As a result, a defect-free single crystal in which the decrease in oxygen concentration at the outer peripheral portion of the wafer is suppressed can be produced.

The single crystal 16 is not particularly limited as long as it can be produced by the CZ method, but a single crystal of silicon having a small variation in oxygen concentration can be preferably produced.

Examples (example)

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

Fig. 8 shows the magnetic flux density distribution of the conventional coil (conventional example) shown in fig. 2 and the coil (inventive example) shown in fig. 4, (a) is the magnetic flux density in the x-axis direction, (b) is the magnetic flux density in the y-axis direction, and (c) is the magnetic flux density in the z-axis direction. In fig. 8, each of the drawings has the origin O as the origin.

As shown in fig. 8 (a), it is clear that the coil 1 of the invention example does not change the magnetic flux density of the melt region in the magnetic field distribution in the x-axis direction and reduces the magnetic flux density at the crystal/melt interface with respect to the magnetic flux density distribution of the coil 22 of the conventional example. As shown in fig. 8 (b), it is clear that the coil 1 of the present invention can form a magnetic field having a smaller magnetic flux density than the coil 22 of the conventional example in the magnetic field distribution in the y-axis direction. Further, as shown in fig. 8 (c), it is clear that in the magnetic field distribution in the z-axis direction of the coil 1 of the present invention, the peak value of the magnetic flux density can be moved to the melt side and the maximum value can be increased, and a magnetic field having a high magnetic flux density in the melt region and a low magnetic flux density in the crystal region can be formed.

Fig. 9 shows the time variation of the average temperature of the solid-liquid interface. As is clear from fig. 9, the higher the magnetic flux density applied to the raw material melt 13 stored in the crucible 12, the smaller the time variation in the average temperature of the solid-liquid interface. This can suppress the variation in the crystal pulling rate and, in turn, the variation in the quality of the single crystal to be produced.

Fig. 10 shows the distance from the center of the wafer as a function of oxygen concentration. As shown in the figure, it is understood that when the coil 1 of the invention example is used, a decrease in oxygen concentration at the outer peripheral portion of the wafer can be suppressed as compared with the coil 22 of the conventional example.

Industrial applicability

According to the present invention, the variation in the pulling rate of the crystal can be suppressed, and the decrease in the oxygen concentration in the outer peripheral portion of the wafer obtained from the single crystal to be produced can be suppressed, and therefore, the present invention is useful in the semiconductor wafer manufacturing industry.

Description of the reference numerals

1. 22: coil

1a: concave part

1b: an outer peripheral surface

1c: an inner peripheral surface

1d: outer surface

1e: inner surface

2: first part

3: second part

3a: upper surface of

4: connection part

11: chamber chamber

12: crucible pot

13: raw material melt

14: heater

15: crucible rotating mechanism

16: single crystal

17: seed crystal

18: seed crystal holder

19: wire rope

20: winding mechanism

21. 50: magnet

22a: outer surface

22b: inner surface

31: first subsection

31a: upper surface of

31b: lower surface of

32: a second sub-part

32a: upper surface of

32b: lower surface of

33: third subsection

34: sub-connection portion

70. 100: apparatus for producing single crystals.

Claims (6)

1. A coil used for a magnet for a manufacturing apparatus for pulling up a single crystal of a single crystal contained in a crucible by applying a horizontal magnetic field to a melt of the raw material of the single crystal by a Czochralski method,

the coil has a recess in an upper portion and is annular.

2. A magnet for a single crystal production apparatus for applying a horizontal magnetic field to a melt of a raw material of a single crystal contained in a crucible by a Czochralski method and pulling the single crystal, characterized in that,

the magnet for a single crystal manufacturing apparatus has 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 the two coils being the annular coil according to claim 1.

3. The magnet for a single crystal production apparatus according to claim 2, wherein,

the magnet for a single crystal manufacturing apparatus can generate the following magnetic field distribution: when the magnetic flux density at the origin O (0 mm ) is M, the magnetic flux density at the point A (0 mm, -400 mm) is 0.58 XM or more, and the magnetic flux density at the point B (400 mm,0 mm) is 1.47 XM or more.

4. A single crystal production apparatus, wherein,

the apparatus for producing a single crystal according to claim 2 or 3, wherein the single crystal is pulled by applying a horizontal magnetic field to the melt using the magnet.

5. A method for producing a single crystal, wherein,

in the method for producing a single crystal, the single crystal is pulled by applying the horizontal magnetic field using the apparatus for producing a single crystal according to claim 4.

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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