Single crystal production method

Abstract

To provide a single crystal production method capable of suppressing deterioration of controllability of a crystal pulling rate as a single crystal production process progresses.SOLUTION: A single crystal production method is a method of producing a single crystal by the Czochralski method in which a single crystal is pulled up while a horizontal magnetic field is applied to a raw material melt 13 accommodated in a crucible 12. The method is characterized in that, when, in a horizontal plane including the surface of the raw material melt 13, the direction of the component of a magnetic field line at an origin C that is parallel to the horizontal plane is defined as the x-axis and the direction perpendicular to the x-axis and passing through the origin C is defined as the y-axis, a magnetic flux density ratio Bp / Bc is lowered during the pulling of the single crystal, where Bp is a magnetic flux density at an intersection point P of the y-axis and the inner wall surface of the crucible 12, and Bc is a magnetic flux density at the origin C.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a single crystal.

Background Art

[0002] Generally, as a substrate for semiconductor devices, a semiconductor wafer made of a single crystal of a semiconductor such as silicon is 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 melted single crystal raw material, and pulling it up. A semiconductor wafer can be obtained by subjecting the grown single crystal ingot (hereinafter also referred to as "single crystal" or simply "crystal") to wafer processing.

[0003] In recent years, with the further miniaturization and high integration of semiconductor devices, the semiconductor wafer as a substrate is required to have no grown-in defects, that is, to be defect-free. Grown-in defects refer to void defects formed by aggregation of vacancies, interstitial-type dislocation clusters in which interstitial atoms precipitate, etc., and remain in the manufactured semiconductor wafer, which can cause deterioration of the gate oxide film and leakage current in semiconductor devices.

[0004] The above defect-free crystal is manufactured by suppressing the convection of the raw material melt in the crucible and controlling the pulling speed of the crystal within a speed range in which a defect-free crystal can be obtained (see, for example, Patent Document 1).

[0005] 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 10 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 1 having a plurality of coils 2 that apply a horizontal magnetic field (transverse magnetic field) to the raw material melt 13 in the crucible 12 is arranged.

[0006] 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, 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.

[0007] 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 rotational speed by the crucible rotation mechanism 15, and while rotating the seed crystal 17 (i.e., the single crystal 16) at a predetermined rotational speed, it is wound up by the winding mechanism 20 to pull up the seed crystal 17 and the single crystal 16 grown under the seed crystal 17. In this way, a single crystal having a predetermined diameter can be manufactured.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Non-Patent Documents

[0009] [Non-Patent Document 1] R. Suewaka and K. Nakamura, Jpn. J. Appl. Phys. 59, 015502 (2020). [Summary of the Invention] [Problems to be Solved by the Invention]

[0010] When manufacturing a defect-free silicon single crystal using the single crystal manufacturing apparatus 10 of the horizontal magnetic field method shown in FIG. 1, if the temperature of the silicon melt supplied to the region near the solid-liquid interface between the silicon single crystal and the silicon melt changes, the diameter of the crystal will fluctuate. Therefore, when manufacturing a defect-free silicon single crystal, the pulling speed of the crystal is controlled so that the diameter of the pulled crystal does not fluctuate.

[0011] However, when the present inventors manufacture a silicon single crystal using the single crystal manufacturing apparatus 10 shown in FIG. 1, as the crystal pulling progresses, the variation in the crystal pulling speed (that is, the fluctuation of the crystal pulling speed) becomes large, and it has been found that the controllability of the crystal pulling speed may deteriorate. As described above, when manufacturing a defect-free silicon single crystal, the pulling speed of the crystal is controlled within the speed range where a defect-free crystal can be obtained, but the above speed range is extremely narrow. Therefore, due to the variation in the pulling speed, it may deviate from the speed range where a defect-free crystal can be obtained, and a defect-free crystal cannot be obtained, which may reduce the yield of defect-free crystal manufacturing.

[0012] Thus, if there is a variation in the crystal pulling speed and the controllability of the crystal pulling speed deteriorates, there is a risk that a crystal with desired characteristics cannot be obtained. Therefore, it is desired to propose a single crystal manufacturing method that can suppress the deterioration of the controllability of the crystal pulling speed.

[0013] The present invention has been made in view of the above problems, and an object thereof is to propose a single crystal manufacturing method that can suppress the deterioration of the controllability of the crystal pulling speed as the single crystal manufacturing progresses.

Means for Solving the Problem

[0014] The present invention for solving the above problems is as follows.

[0015] [1] In a method for manufacturing a single crystal by the Czochralski method of pulling up a single crystal while applying a horizontal magnetic field to a raw material melt accommodated in a crucible, In a horizontal plane including the surface of the raw material melt, with the intersection point of the central axis of the crucible as the origin, the direction of the component of the magnetic field line parallel to the horizontal plane at the origin as the x-axis, and the direction perpendicular to the x-axis passing through the origin as the y-axis, the ratio of the magnetic flux density Bp at the intersection point of the y-axis and the inner wall surface of the crucible to the magnetic flux density Bc at the origin is defined as Bp / Bc. During the pulling up of the single crystal, a method for manufacturing a single crystal, characterized in that the magnetic flux density ratio Bp / Bc of the magnetic flux density Bp to the magnetic flux density Bc is decreased.

[0016] [2] The method for manufacturing a single crystal according to [1], wherein the single crystal is pulled up under a condition that the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.7 is smaller than the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.1.

[0017] [3] The method for manufacturing a single crystal according to [1] or [2], wherein the single crystal is pulled up under a condition that the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.7 is smaller than the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.2.

[0018] [4] The method for manufacturing a single crystal according to [3], wherein the single crystal is pulled up with the difference between the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.2 and the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.7 being 0.1 or more.

[0019] [5] The method for manufacturing a single crystal according to any one of [1] to [4], wherein the single crystal is pulled up under a condition that the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.2 is 1.0 or more.

[0020] [6] When the solidification rate of the single crystal is 0.2, the magnetic flux density ratio Bp / Bc is 1.3 and the magnetic flux density Bc is 3500 G. When the solidification rate of the single crystal is 0.7, the single crystal is pulled up under the condition that the magnetic flux density ratio Bp / Bc is 1.0 and the magnetic flux density Bc is 3500 G. The method for manufacturing a single crystal according to any one of [1] to [5] above.

[0021] [7] The single crystal is a silicon single crystal. The method for manufacturing a single crystal according to any one of [1] to [6] above.

Effect of the Invention

[0022] According to the present invention, it is possible to suppress the deterioration of the controllability of the crystal pulling speed accompanying the progress of the single crystal production.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 8C

Figure 8D

Figure 8E

Figure 8F

Figure 8G

Figure 9

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The method for manufacturing a single crystal according to the present invention is a method for manufacturing a single crystal by the CZ method in which a horizontal magnetic field is applied to a raw material melt accommodated in a crucible while pulling up the single crystal. Here, in a horizontal plane including the surface of the raw material melt, with the intersection point with the central axis of the crucible as the origin, the direction of the component of the magnetic field line parallel to the horizontal plane at the origin as the x-axis, and the direction perpendicular to the x-axis passing through the origin as the y-axis, the ratio of the magnetic flux density Bp at the intersection of the y-axis and the inner wall surface of the crucible to the magnetic flux density Bc at the origin is defined as Bp / Bc. During the pulling up of the single crystal, the magnetic flux density ratio Bp / Bc of the magnetic flux density Bp to the magnetic flux density Bc is decreased. Note that the direction of the component of the magnetic field line parallel to the horizontal plane at the origin means the direction of the component parallel to the horizontal plane when the magnetic field line at the origin is decomposed into a component perpendicular to the horizontal plane and a component parallel to the horizontal plane.

[0025] In earnest consideration of a way to solve the above problems, the present inventors focused on the convection of the raw material melt 13 in the crucible 12. Hereinafter, the case where the single crystal 16 is a silicon single crystal will be described as an example.

[0026] Conventionally, when manufacturing a silicon single crystal by the CZ method of the horizontal magnetic field method, it has been considered that the silicon melt in the crucible 12 convects while forming two roll-shaped vortices that convect in opposite directions around an axis parallel to the direction of the horizontal magnetic field. However, the latest three-dimensional flow analysis shows that, as shown in FIG. 2, convection occurs while forming one large flow (hereinafter referred to as the "main flow") along the inner wall of the crucible 12 and the free surface of the silicon melt. The three-dimensional flow analysis also shows that, as shown in FIG. 3, there is a small flow (hereinafter referred to as the "sub-flow") that convects inside the main flow.

[0027] According to the above three-dimensional flow analysis, there is no significant change in the behavior of the main flow during crystal pulling. On the other hand, for the secondary flow, the number and position thereof vary during crystal pulling. For example, the secondary flow is formed in the region near the free surface of the silicon melt (i.e., the relatively upper region), moves below the crucible 12, and then rises again and is absorbed into the main flow and disappears. In addition, multiple secondary flows may integrate to form one secondary flow. Thus, the secondary flow of the silicon melt exhibits complex behaviors of generation, movement, and disappearance during crystal pulling.

[0028] The behavior of the secondary flow of the silicon melt directly below the solid-liquid interface is considered to affect the temperature of the silicon melt supplied to the region near the solid-liquid interface, vary the diameter of the silicon single crystal, and ultimately lead to fluctuations in the crystal pulling speed. Therefore, in order to suppress the deterioration of the controllability of the crystal pulling speed as the production of the single crystal progresses, it is considered essential to control the behavior of the secondary flow of the above silicon melt. Therefore, the inventors of the present invention studied the horizontal magnetic field distribution applied to the silicon melt.

[0029] The influence of the magnetic field distribution on the silicon melt can be evaluated to some extent based on Bp / Bc, where in the horizontal plane including the surface of the raw material melt 13, the direction of the component of the magnetic field line parallel to the horizontal plane at the origin C is the x-axis, the direction perpendicular to the x-axis passing through the origin C is the y-axis, and Bp / Bc is the ratio of the magnetic flux density Bp at the intersection point P of the y-axis and the inner wall surface of the crucible 12 to the magnetic flux density Bc at the origin C.

[0030] FIG. 4 is a schematic diagram showing the relationship between the magnetic flux density ratio Bp / Bc and the magnetic field distribution in the silicon melt. Here, FIG. 4(a) corresponds to the case where the magnetic flux density ratio is 1.0, FIG. 4(b) corresponds to the case where the magnetic flux density ratio Bp / Bc is 1.3, and FIG. 4(c) corresponds to the case where the magnetic flux density ratio Bp / Bc is 1.5. Based on the case where Bp / Bc shown in FIG. 4(a) is 1.0, when the magnetic flux density ratio Bp / Bc is made larger than 1.0, as shown in FIG. 4(b), a region with a high magnetic flux density occurs on the outer peripheral side of the crucible. Further, when the magnetic flux density ratio Bp / Bc is made even larger, as shown in FIG. 4(c), the region with a high magnetic flux density becomes larger.

[0031] In the region with a high magnetic flux density, the braking property of the silicon melt becomes high, while in the region with a low magnetic flux density, the braking property of the silicon melt becomes low. According to three-dimensional flow analysis, the secondary flow exists in the region with a low magnetic flux density, and by increasing the magnetic flux density ratio Bp / Bc, the existence region of the secondary flow will be narrowed. Therefore, in order to stabilize the behavior of the secondary flow of the silicon melt, it is considered important the "size of the region below the magnetic flux density at the origin C" and the "balance of the braking forces between the region below the magnetic flux density at the origin C and the region with a magnetic flux density greater than the magnetic flux density at the origin C".

[0032] As described above, it has been found that as the crystal pulling progresses, variations in the crystal pulling speed may occur and the controllability of the pulling speed may deteriorate. As the crystal pulling progresses, the remaining amount of the silicon melt in the crucible 12 decreases, so it is considered that the region where the secondary flow of the silicon melt exists also narrows as the crystal pulling progresses.

[0033] For these reasons, the inventors considered that as the crystal pulling progresses, the region where the secondary flow of the silicon melt exists is narrowed, resulting in unstable behavior of the secondary flow, which may adversely affect the temperature of the silicon melt supplied to the region near the solid-liquid interface. As a result of intensive studies on the means to stabilize the behavior of the secondary flow of the silicon melt, the inventors came up with the idea of reducing Bp / Bc during crystal pulling.

[0034] FIG. 5 is a diagram for explaining the change in the magnetic field distribution when Bp / Bc is decreased during crystal pulling. Here, FIG. 5(a) shows the case where the remaining amount of the silicon melt is large and the magnetic flux density ratio is 1.3, and FIG. 5(b) shows the case where the remaining amount of the silicon melt is small and the magnetic flux density ratio Bp / Bc is 1.0. As shown in FIG. 5(a), when the remaining amount of the silicon melt is large and the magnetic flux density ratio Bp / Bc is large, the region where the secondary flow can exist is limited. On the contrary, as shown in FIG. 5(b), when the remaining amount of the silicon melt decreases and the magnetic flux density ratio Bp / Bc is reduced, the region where the secondary flow can exist is expanded, and it is considered that the secondary flow can exist stably. As shown in the examples described later, it has been found that by reducing Bp / Bc during crystal pulling, the variation in the crystal pulling speed can be reduced and the deterioration of the controllability of the crystal pulling speed can be suppressed. Thus, the present invention has been completed. Hereinafter, each step of the method for manufacturing a single crystal will be described.

[0035] First, the raw material of the single crystal 16 is filled in the crucible 12. When the single crystal 16 is a silicon single crystal, the raw material is, for example, polycrystalline silicon. At this time, the inside of the chamber 11 is depressurized and maintained in an inert gas atmosphere such as Ar gas.

[0036] Next, the raw material in the crucible 12 is heated and melted by the heater 14 to form a raw material melt 13 in the crucible 12.

[0037] Subsequently, the crucible 12 is raised to the pulling start position.

[0038] Thereafter, the wire rope 19 is lowered by the winding mechanism 20, and the seed crystal 17 held by the seed crystal holder 18 is dipped into the raw material melt 13, and the seed crystal 17 and then the single crystal 16 are pulled up from the raw material melt 13. Specifically, while rotating the crucible 12 and the wire rope 19 in a predetermined direction, the wire rope 19 is wound by the winding mechanism 20, and a single crystal 16 is grown below the seed crystal 17. Note that as the growth of the single crystal 16 progresses, the amount of the raw material melt 13 decreases, but the crucible 12 is raised to maintain the height position of the surface of the raw material melt 13.

[0039] In the pulling of the above-mentioned seed crystal 17 (single crystal 16), first, in order to make the single crystal 16 dislocation-free, seed necking (necking) is performed by the dash method to form a neck portion. Next, a shoulder portion is grown, and when the single crystal 16 reaches a desired diameter, the diameter is made constant and a body portion is grown. After growing the straight body portion to a predetermined length, tail necking is performed to separate the single crystal 16 from the raw material melt 13 in a dislocation-free state and form a tail portion.

[0040] Also, the pulling of the above-mentioned seed crystal 17 (single crystal 16) is performed while applying a horizontal magnetic field to the raw material melt 13 by the magnet 1 composed of the coil 2. The distribution of the horizontal magnetic field can be adjusted by the magnitude and direction of the current flowing through the coil 2 constituting the magnet 1. Specifically, the magnet 1 is composed of a plurality of coils 2, a part of which is a main coil set and the rest is a sub-coil set. By changing the magnitude and direction of the current flowing through the coil 2 between the main coil set and the sub-coil set, various magnetic field distributions can be formed. Also, by configuring the magnitude and direction of the current flowing through each of the coils 2 constituting the magnet 1 to be controllable and setting the magnitude and direction of the current flowing through each coil 2, various magnetic field distributions can also be formed.

[0041] As described above, the horizontal magnetic field distribution can be evaluated based on Bp / Bc, where Bp / Bc is the ratio of the magnetic flux density Bp at the intersection point P between the y-axis and the inner wall surface of the crucible 12 to the magnetic flux density Bc at the origin C, with the magnetic flux density Bc at the origin C, the direction of the magnetic field line at the origin C as the x-axis, and the direction perpendicular to the x-axis passing through the origin C as the y-axis.

[0042] In the present invention, the value of the magnetic flux density ratio Bp / Bc at the start of pulling the crystal 16 is set to be 0.5 or more and 2.3 or less. The value of the magnetic flux density ratio Bp / Bc is preferably 1.0 or more and 1.5 or less, more preferably 1.1 or more and 1.3 or less. Note that the adjustment of the value of Bp / Bc may be performed by changing both Bp and Bc, or by keeping one of Bp and Bc constant and changing the other. For example, Bp can be changed while keeping Bc constant.

[0043] As described above, in the present invention, during the pulling of the seed crystal 17 (crystal 16), the magnetic flux density ratio Bp / Bc of the magnetic flux density Bp to the magnetic flux density Bc is decreased. Thereby, the variation in the pulling speed of the crystal 16 can be suppressed, and the deterioration of the controllability of the crystal pulling speed can be suppressed.

[0044] The method of decreasing the magnetic flux density ratio Bp / Bc is not particularly limited. As shown in FIG. 9, it can also be decreased at a constant rate from the start to the end of the pulling. Further, after making it constant until the solidification rate of the crystal 16 reaches a predetermined value, it can be decreased at a constant rate until the end of the pulling. Furthermore, after decreasing at a constant rate from the start of the crystal pulling until the solidification rate of the crystal reaches a predetermined value, it can be made constant until the end of the pulling. In this specification, the "solidification rate" indicates the ratio of the raw material melt 13 that has solidified, with the case where all of the raw material melt 13 has solidified being 1. For example, a state where 1 / 10 of the entire raw material melt 13 has solidified is represented as a solidification rate of 0.1, and a state where 1 / 5 has solidified is represented as a solidification rate of 0.2.

[0045] The pulling of the seed crystal 17 (single crystal 16) is preferably performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.7 is smaller than the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.1. Thereby, the deterioration of the variation in the crystal pulling speed can be suppressed.

[0046] The pulling of the seed crystal 17 (single crystal 16) is preferably performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.7 is smaller than the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.2. Thereby, the deterioration of the variation in the crystal pulling speed can be suppressed. The positions in the single crystal 16 corresponding to the times when the solidification rates of the single crystal are 0.2 and 0.7 are as shown in FIG. 7.

[0047] Also, the pulling of the seed crystal 17 (single crystal 16) is preferably performed with the difference between the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.2 and the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.7 being 0.1 or more. Thereby, variations in the crystal pulling rate over the entire crystal length can be suppressed.

[0048] The magnetic flux density Bc at the origin C is set to be 1000 G or more and 4000 G or less. The magnetic flux density Bc at the origin C is preferably 2000 G or more and 4000 G or less, more preferably 2500 G or more and 3500 G or less.

[0049] The pulling of the seed crystal 17 (single crystal 16) is preferably performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.2 is 1.0 or more. Thereby, deterioration of variations in the crystal pulling rate can be suppressed.

[0050] The pulling of the seed crystal 17 (single crystal 16) is preferably performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.2 is 1.3, the magnetic flux density Bc is 3500 G, the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal 16 is 0.7 is 1.0, and the magnetic flux density Bc is 3500 G. Thereby, variations in the crystal pulling rate over the entire crystal length can be suppressed.

[0051] The single crystal 16 is not particularly limited as long as it can be manufactured by the CZ method, but a single crystal of silicon for semiconductors with small fluctuations in oxygen concentration or a defect-free silicon single crystal can be preferably manufactured.

Example

[0052] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the examples.

[0053] (Inventive Example 1) Using a single-crystal manufacturing apparatus equipped with a magnet having six coils, a silicon single crystal with a diameter of 310 mm was manufactured by the CZ method. First, 400 kg of polycrystalline silicon, which is a silicon raw material accommodated in a crucible, was melted to form molten silicon. Next, a seed crystal was dipped into the molten silicon and rotated at 10 rpm, and while rotating the crucible at 0.5 rpm, it was pulled up, and a silicon single crystal was manufactured below the seed crystal. At that time, the magnitude and direction of the current flowing through the coil were adjusted so that the magnetic flux density at the origin C was 3500 G. Then, during the production of the silicon single crystal, by adjusting Bp, the magnetic flux density ratio Bp / Bc at a solidification rate of 0.2 was adjusted to 1.5, and Bp / Bc was decreased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.0. The relationship between the solidification rate of the silicon single crystal and the variation in the pulling-up speed is shown in Fig. 8A.

[0054] (Inventive Example 2) Similar to Inventive Example 1, a silicon single crystal was manufactured. However, during the production of the silicon single crystal, the magnetic flux density ratio Bp / Bc was decreased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.1. All other conditions were exactly the same as those in Inventive Example 1. The relationship between the solidification rate of the silicon single crystal and the variation in the pulling-up speed is shown in Fig. 8A.

[0055] (Inventive Example 3) Similar to Inventive Example 1, a silicon single crystal was manufactured. However, during the production of the silicon single crystal, the magnetic flux density ratio Bp / Bc was decreased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.3. All other conditions were exactly the same as those in Inventive Example 1. The relationship between the solidification rate of the silicon single crystal and the variation in the pulling-up speed is shown in Fig. 8A.

[0056] (Conventional Example 1) Similar to Inventive Example 1, a silicon single crystal was manufactured. However, during the production of the silicon single crystal, the magnetic flux density ratio Bp / Bc was not decreased, and the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 was kept at 1.5. All other conditions were exactly the same as those in Inventive Example 1. The relationship between the solidification rate of the silicon single crystal and the variation in the pulling-up speed is shown in Fig. 8A.

[0057] (Inventive Example 4) In the same manner as in Invention Example 1, a single crystal silicon was produced. However, the magnetic flux density ratio Bp / Bc at a solidification rate of 0.2 was adjusted to be 1.3. Other conditions were exactly the same as those in Invention Example 1. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in FIG. 8B.

[0058] (Invention Example 5) In the same manner as in Invention Example 4, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was decreased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.1. Other conditions were exactly the same as those in Invention Example 4. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in FIG. 8B.

[0059] (Conventional Example 2) In the same manner as in Invention Example 4, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was not decreased, and the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 was kept at 1.3. Other conditions were exactly the same as those in Invention Example 4. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in FIG. 8B.

[0060] (Comparative Example 1) In the same manner as in Invention Example 4, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was increased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.5. Other conditions were exactly the same as those in Invention Example 4. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in FIG. 8B.

[0061] (Invention Example 6) In the same manner as in Invention Example 1, a single crystal silicon was produced. However, the magnetic flux density ratio Bp / Bc at a solidification rate of 0.2 was adjusted to be 1.1. Other conditions were exactly the same as those in Invention Example 1. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in FIG. 8C.

[0062] (Conventional Example 3) In the same manner as in Invention Example 6, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was not decreased, and the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 was kept at 1.1. All other conditions were the same as those in Invention Example 6. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8C.

[0063] (Comparative Example 2) In the same manner as in Invention Example 6, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was increased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.3. All other conditions were the same as those in Invention Example 6. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8C.

[0064] (Comparative Example 3) In the same manner as in Invention Example 6, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was increased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.5. All other conditions were the same as those in Invention Example 6. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8C.

[0065] (Conventional Example 4) In the same manner as in Invention Example 1, a single crystal silicon was produced. However, the value of the magnetic flux density ratio Bp / Bc before the start of pulling up the single crystal silicon was set to 1.0, and during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was not decreased, and the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 was kept at 1.0. All other conditions were the same as those in Invention Example 1. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8D.

[0066] (Comparative Example 4) In the same manner as in Conventional Example 4, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was increased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.1. All other conditions were the same as those in Conventional Example 4. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8D.

[0067] (Comparative Example 5) In the same manner as in Conventional Example 4, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was increased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.3. All other conditions were the same as those in Conventional Example 4. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling rate is shown in Fig. 8D.

[0068] (Comparative Example 6) In the same manner as in Conventional Example 4, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was increased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.5. All other conditions were the same as those in Conventional Example 4. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling rate is shown in Fig. 8D.

[0069] (Inventive Example 7) In the same manner as in Inventive Example 1, a single crystal silicon was produced. However, the magnetic flux density at the origin C was set to 3000 G. Also, during the production of the single crystal silicon, by adjusting Bp, the magnetic flux density ratio Bp / Bc at a solidification rate of 0.2 was adjusted to 1.2, and Bp / Bc was decreased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 became 1.0. All other conditions were the same as those in Inventive Example 1. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling rate is shown in Fig. 8E.

[0070] (Conventional Example 5) In the same manner as in Inventive Example 7, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was not decreased, and the magnetic flux density Bp / Bc at a solidification rate of 0.7 was kept at 1.2. All other conditions were the same as those in Inventive Example 7. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling rate is shown in Fig. 8E.

[0071] (Comparative Example 7) In the same manner as in Inventive Example 7, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density Bp / Bc was increased so that the magnetic flux density Bp / Bc at a solidification rate of 0.7 became 1.3. All other conditions were the same as those in Inventive Example 7. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling rate is shown in Fig. 8E.

[0072] (Example 8 of the Invention) In the same manner as in Invention Example 1, a single crystal silicon was produced. However, the magnetic flux density at the origin C was set to 2500 G. Also, during the production of the single crystal silicon, by adjusting Bp, the magnetic flux density ratio Bp / Bc at a solidification rate of 0.2 was adjusted to 1.3, and Bp / Bc was decreased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 would be 1.2. All other conditions were exactly the same as those in Invention Example 1. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8F.

[0073] (Conventional Example 6) In the same manner as in Invention Example 8, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was not decreased, and the magnetic flux density Bp / Bc at a solidification rate of 0.7 was kept at 1.3. All other conditions were exactly the same as those in Invention Example 8. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8F.

[0074] (Example 9 of the Invention) In the same manner as in Invention Example 1, a single crystal silicon was produced. However, the magnetic flux density at the origin C was set to 2000 G. Also, during the production of the single crystal silicon, by adjusting Bp, the magnetic flux density ratio Bp / Bc at a solidification rate of 0.2 was adjusted to 2.3, and Bp / Bc was decreased so that the magnetic flux density ratio Bp / Bc at a solidification rate of 0.7 would be 1.5. All other conditions were exactly the same as those in Invention Example 1. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8G.

[0075] (Conventional Example 7) In the same manner as in Invention Example 9, a single crystal silicon was produced. However, during the production of the single crystal silicon, the magnetic flux density ratio Bp / Bc was not decreased, and the magnetic flux density Bp / Bc at a solidification rate of 0.7 was kept at 2.3. All other conditions were exactly the same as those in Invention Example 9. The relationship between the solidification rate of the single crystal silicon and the variation in the pulling-up speed is shown in Fig. 8G.

[0076] As shown in Fig. 8B, in the case of Conventional Example 2 where the magnetic flux density ratio Bp / Bc before crystal pulling is 1.3 and this value is maintained, it can be seen that as the solidification rate increases, that is, as the crystal pulling progresses, the variation in the pulling rate becomes larger. However, as shown in Fig. 8B, it can be seen that by decreasing the magnetic flux density ratio Bp / Bc during crystal pulling, as in Invention Examples 4 and 5, the variation in the pulling rate can be reduced compared to the case where the magnetic flux density ratio Bp / Bc is kept constant at 1.3.

[0077] As shown in Fig. 8C, a similar tendency is also observed when the magnetic flux density ratio Bp / Bc before the start of crystal pulling is 1.1, and it can be seen that by decreasing the magnetic flux density ratio Bp / Bc during crystal pulling, the variation in the pulling rate can be reduced compared to the case where the magnetic flux density ratio Bp / Bc is kept constant at 1.1. Also, as shown in Fig. 8F, a similar tendency is observed when the magnetic flux density at the origin C at the start of crystal pulling is 2500 G, and it can be seen that by decreasing the magnetic flux density ratio Bp / Bc during crystal pulling, the variation in the pulling rate can be reduced.

[0078] On the other hand, as shown in Fig. 8A, when the magnetic flux density ratio Bp / Bc before the start of pulling is maintained at 1.5, even as the solidification rate increases, that is, as the crystal pulling progresses, the variation in the pulling rate hardly changes and the variation in the pulling rate is large. However, it can be seen that by decreasing the magnetic flux density ratio Bp / Bc during crystal pulling, the variation in the crystal pulling rate can be reduced.

Industrial Applicability

[0079] According to the present invention, it is possible to suppress the deterioration of the controllability of the crystal pulling rate as the production of the single crystal progresses.

Explanation of Signs

[0080] 1 Magnet 2 Coil 10 Single crystal production apparatus 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

Claims

1. A method for manufacturing a single crystal by the Czochralski method of pulling up a single crystal while applying a horizontal magnetic field to a raw material melt accommodated in a crucible, wherein in a horizontal plane including the surface of the raw material melt, with the intersection point with the central axis of the crucible as the origin, the direction of the component of the magnetic field line parallel to the horizontal plane at the origin as the x-axis, and the direction perpendicular to the x-axis passing through the origin as the y-axis, the ratio of the magnetic flux density Bp at the intersection point of the y-axis and the inner wall surface of the crucible to the magnetic flux density Bc at the origin is defined as Bp / Bc, and during the pulling up of the single crystal, the magnetic flux density ratio Bp / Bc of the magnetic flux density Bp to the magnetic flux density Bc is decreased. A method for manufacturing a single crystal, characterized by this.

2. The method for manufacturing a single crystal according to claim 1, wherein the pulling up of the single crystal is performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.7 is smaller than the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.

1.

3. The method for manufacturing a single crystal according to claim 1 or 2, wherein the pulling up of the single crystal is performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.7 is smaller than the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.

2.

4. The method for manufacturing a single crystal according to claim 3, wherein the pulling up of the single crystal is performed with the difference between the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.2 and the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.7 being 0.1 or more.

5. The method for manufacturing a single crystal according to claim 1 or 2, wherein the pulling up of the single crystal is performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.2 is 1.0 or more.

6. The method for manufacturing a single crystal according to claim 1 or 2, wherein the pulling up of the single crystal is performed in a state where the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.2 is 1.3, the magnetic flux density Bc is 3500 G, and the magnetic flux density ratio Bp / Bc at the time when the solidification rate of the single crystal is 0.7 is 1.0 and the magnetic flux density Bc is 3500 G.

7. The method for manufacturing a single crystal according to claim 1 or 2, wherein the single crystal is a silicon single crystal.

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