JP2003095788A - Silicon single crystal pulling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which the production of an ingot by means of high speed pulling can be realized. SOLUTION: A quartz crucible 12 rotates at a predetermined rotation speed R1 , and a silicon single crystal ingot 13 being pulled from a silicon melt 11 is rotated at a predetermined rotation speed R2 . An upper coil 14 and a lower coil 16 are arranged at a predetermined interval in the vertical direction in such a manner that the center of each coil coincides with the rotation axis of the crucible 12. Then, cusp magnetic fields 17 passing through a neutral plane 17a between the coils from the center of each coil are generated by passing electric currents through those coils in such a manner that the directions of the currents flowing through the coils are reverse to each other. The ingot is pulled with a speed such that the ingot is formed, and the rotation speed R1 is controlled so as to satisfy following relation: |R1 |>=0.3 rpm, wherein |R1 | means an absolute figure of R1 and the rotation speed R2 of the ingot is controlled so as to satisfy the following relation: R1 =-(0.01 to 100)R2 so that the form of the solid-liquid interface 22 between the melt and the ingot becomes convex downward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pulling an ingot of a silicon single crystal from a silicon melt while applying a cusp (CUSP) magnetic field to the silicon melt. More specifically, it relates to a method for pulling an ingot used as a substrate for epitaxial growth at high speed.

[0002]

2. Description of the Related Art As a method for producing a silicon single crystal as a semiconductor substrate material, a method is known in which a silicon single crystal ingot is pulled by the Czochralski method (hereinafter referred to as the CZ method). As shown in FIG. 3, in this CZ method, a seed crystal 3 having a specific crystal plane is brought into contact with a silicon melt 2 stored in a quartz crucible 1, and the seed crystal 3 is rotated while rotating the quartz crucible 1 and the seed crystal 3. Is a method for producing a cylindrical silicon single crystal ingot 4 by gradually pulling up the silicon in accordance with the growth rate of the solidified crystal.
Reference numeral 5 in FIG. 3 indicates a solid-liquid interface between the silicon melt 2 and the ingot, and reference numeral 6 indicates a heater. Usually, a single crystal grown from the seed crystal 3 is first called a seed diaphragm, and an elongated neck portion 7 for forming a dislocation-free crystal is formed. Next, the shoulder portion 8 for increasing the diameter to the target single crystal diameter is grown, and the shoulder is changed to shift to the body portion 9 growing step in which the diameter is constant. After growing the body length to a predetermined length, in order to separate it from the melt in a dislocation-free state, a tail squeezing is performed to reduce the diameter. After the crystals are separated from the melt, they are taken out of the manufacturing apparatus and cooled under predetermined conditions. The silicon single crystal thus obtained is used as a wafer, which is a cut piece in a plane perpendicular to the growth direction, and is used as a substrate material for various devices. In such an ingot manufacturing method, it is known that the maximum crystal growth rate decreases as the diameter of the grown crystal increases. This is because the rate of crystal growth is determined by the heat balance of the growing crystal. That is, since the surface area of the grown crystal ingot increases linearly with the increase of the crystal diameter, the heat radiation amount is linearly proportional to the crystal diameter, but the heating amount is proportional to the crystallization volume proportional to the square of the diameter. Due to that.

On the other hand, in semiconductor device manufacturing, an epitaxial growth technique for growing a crystal having the same orientation as that of a single crystal substrate having a certain orientation is frequently used. Therefore, it is required to mass-produce the single crystal substrate used for this epitaxial growth technique faster and in large quantities. As one of the measures, when pulling a single crystal ingot, a method of growing the ingot at a higher pulling speed can be considered.

[0004]

However, as shown in FIG. 4 (a), in the conventional pulling method described above, when pulling at a pulling speed as low as the conventional one, a single crystal ingot of good quality is obtained. 4B and FIG. 4 are obtained.
As shown in (c), when the ingot 4 is pulled at a pulling speed of medium speed or high speed, the inside of the grown crystal ingot is not sufficiently cooled, and the crystal growth rate inside the ingot becomes slow. As a result, the shape of the solid-liquid interface 5 becomes extremely convex upward, and the pulled single crystal ingot undergoes crystal deformation, which causes a problem that the straight body portion is not formed. Further, when the solid-liquid interface shape is extremely convex upward, the inside of the grown crystal ingot is solidified later than the outside, so that the inside of the ingot is solidified after the outside of the ingot is solidified. Since the density of silicon is lower than the density of liquid, the volume of silicon increases when it is solidified. Therefore, in the process of solidification of the melt inside, the silicon expands due to the difference in density between the liquid and the solid, and the outside of the previously solidified ingot may be damaged.

It is an object of the present invention to provide a method for pulling a silicon single crystal which enables the production of an ingot by high speed pulling.

[0006]

The invention according to claim 1 is
As shown in FIG. 1, quartz that stores the silicon melt 11 is used.
The crucible 12 is rotated at a predetermined rotation speed, and the silicon melt 1
Silicon single crystal ingot 13 pulled up from 1
Rotate at a predetermined rotation speed, and from the outer diameter of the quartz crucible 12
Upper coil 14 and lower, each having a large coil diameter
The coils 16 are respectively attached to the rotating shafts of the quartz crucible 12.
Place it at the center and at a predetermined interval in the vertical direction.
Currents flowing in opposite directions to the coil 14 and the lower coil 16
From the center of each coil of the upper coil and the lower coil
A cusp magnet passing through the neutral surface 17a between the upper coil and the lower coil.
Siri pulling up ingot 13 while generating field 17
This is an improvement in the pulling method for single crystal Cong. Its characteristic structure
The rotation speed of the quartz crucible 12 is R₁, Ingot 1
The rotation speed of 3 is R₂And the silicon melt 11 and a
The shape of the solid-liquid interface 22 with the ngot 13 is convex downward.
Sea urchin rotation speed R₁To | R₁Specified within the range of ≧ 0.3 rpm
And R₁=-(0.01-100) R₂To meet
Rotation speed R of ngot 13₂Is in control.
However, | R₁| Is R ₁Indicates the absolute value of.

In the method for pulling a silicon single crystal according to the first aspect, the quartz crucible 12 and the ingot 13 are used.
When the ingot is pulled up while controlling the rotation speed of each of them so as to satisfy any of the above-mentioned ranges, predetermined convections 11a and 11b are generated in the silicon melt 11, and these convections 11a and 11b cause a solid-liquid interface 22. The shape is significantly convex downward. As a result, when pulling is performed at a higher pulling speed than the conventional pulling speed, even if the solid-liquid interface is pushed up by the forced convection generated by pulling and the solid-liquid interface rises significantly, its shape is It does not project upward. Therefore, since the pulled silicon single crystal ingot does not cause crystal deformation, it is possible to manufacture the ingot by high-speed pulling.

Here, when the distance between the neutral surface 17a of the cusp magnetic field 17 and the surface of the silicon melt 11 is H, -3
Neutral surface 17 so as to satisfy 00 mm ≦ H ≦ 300 mm
It is preferable to control a above or below the surface of the silicon melt 11. In addition, the strength of the cusp magnetic field 17 increases as the diameter of the quartz crucible 12 increases.
The current flowing through the upper coil 14 and the lower coil 16 can be controlled.

Further, when the current values to be passed through the upper coil 14 and the lower coil 16 are I ₁ and I ₂ , and the magnitudes of the current values I ₁ and I ₂ are different from each other, I ₁ =-(0.5 to 2.0)
The current value I ₂ flowing through the lower coil 16 can be controlled so as to satisfy I ₂ . Further, by the above control, the pulling speed V of the ingot can be raised at a speed satisfying the range of 0.5 mm / min ≦ V ≦ 5.0 mm / min.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the method for pulling a silicon single crystal according to the present invention is a method for pulling a silicon single crystal from a silicon melt 11 by rotating a quartz crucible 12 storing a silicon melt 11 at a predetermined rotation speed R ₁ . A method of pulling up the ingot 13 from the silicon melt 11 while rotating the ingot 13 at a predetermined rotation speed R ₂ and applying a cusp magnetic field 17 to the silicon melt 11 using the upper coil 14 and the lower coil 16. Is. The upper coil 14 and the lower coil 16 have a coil diameter larger than the outer diameter of the quartz crucible 12, and are arranged with the rotation axis of the quartz crucible 12 as the coil center and at a predetermined interval in the vertical direction. Further, currents in opposite directions are applied to the upper coil 14 and the lower coil 16, whereby the upper coil 1
A cusp magnetic field 17 is generated from each coil center of the lower coil 4 and the lower coil 16 and passes through a neutral surface 17a between the upper coil and the lower coil. The quartz crucible 12 is surrounded and supported by the graphite susceptor 18 on the outer peripheral surface and the outer bottom surface. The susceptor 18 is fixed to the upper end of a support shaft 19, and the lower part of the support shaft 19 is connected to a crucible driving means (not shown). The neutral plane 17a is a horizontal plane between the upper coil 14 and the lower coil 16 in which the magnetic field strength in the vertical direction is zero. The diameters of the upper coil and the lower coil, the number of windings, and the like may be the same or different.
Reference numeral 21 in FIG. 1 is a heater that surrounds the outer peripheral surface of the quartz crucible 12.

A feature of the present invention is that the quartz crucible 12
Let R _{1 be} the rotation speed of the ingot 13 and R _{2 be} the rotation speed of the ingot 13, let the rotation speed R ₁ be | R so that the shape of the solid-liquid interface 22 between the silicon melt 11 and the ingot 13 is convex downward.
₁ | ≧ 0.3 rpm, R ₁ =-(0.01 ~
100) so as to satisfy R _2, controls the rotation speed R ₂ of the ingot 13. Here, when the rotation speed R ₁ or R ₂ is positive, the rotation direction is counterclockwise when viewed from above, and when the rotation speed R ₁ or R ₂ is negative, the rotation direction is clockwise when viewed from above. Indicates. Further, the rotation speeds R ₁ and R ₂ are limited to the above-mentioned ranges. When the numerical values outside these ranges are set, the convection generated in the silicon melt 11 below the ingot 13 becomes downward and the solid-liquid interface 22
This is because there is a problem that is convex to the upper side. The rotation speed R ₁ of the quartz crucible 12 is preferably | R ₁ | ≧ 0.1 rpm,
_{R 1 = - (0.01~100) R} 2, preferably R ₁ = -
It is preferable to control the rotation speed R ₂ of the ingot 13 so as to satisfy (0.1 to 10) R ₂ .

Specifically, the neutral surface 17 of the cusp magnetic field 17
When the distance between a and the surface of the silicon melt 11 is H,
−300 mm ≦ H ≦ 300 mm, preferably −100 m
The neutral surface 17a so as to satisfy m ≦ H ≦ 100 mm
Is controlled above or below the surface of the silicon melt 11.
Here, the distance H is limited to the above range because the ingot 1 is in the range where the distance H is less than the lower limit value or more than the upper limit value.
3 The convection generated in the lower silicon melt 11 is directed upward, and the solid-liquid interface 22 becomes convex upward, or the magnetic field strength is too weak so that the solid-liquid interface 22 becomes convex downward. This is because a problem occurs such that the convection currents 11a and 11b generated in the liquid 11 cannot be controlled.

Further, the currents flowing through the upper coil 14 and the lower coil 16 are controlled so that the strength of the cusp magnetic field 17 becomes stronger as the diameter of the quartz crucible 12 becomes larger. In this way, the currents of the upper coil and the lower coil are controlled by increasing the Lorentz force for generating convection in the silicon melt 11 so that the solid-liquid interface 22 is convex downward, and increasing the diameter of the quartz crucible 12. It is necessary to increase the size according to. For example, when the quartz crucible 12 having an inner diameter of 550 to 650 mm is used to pull up the ingot 13 having a diameter of 200 mm at a high speed, the strength of the cusp magnetic field 17 is set to 1
When the quartz crucible 12 having the inner diameter of 650 to 800 mm is used to pull up the ingot 13 having the diameter of 300 mm, the strength of the cusp magnetic field 17 is controlled to 300 to 300. Control to a constant value within the range of 5000 Gauss.

When the current values I ₁ and I ₂ flowing through the upper coil 14 and the lower coil 16 are different, I ₁ =-(0.5 to
2.0) Current value I flowing through the lower coil 16 so as to satisfy I ₂
Control ₂ When the current value I ₁ is below the lower limit and above the upper limit, the distance H between the neutral surface 17a and the surface of the silicon melt 11 is out of the range, and the solid-liquid interface shape 2
2 does not have a magnetic field distribution that can control convection so that it is convex downward. Preferably, the current value I ₂ flowing through the lower coil 16 is controlled so as to satisfy I ₁ = − (0.7 to 1.5) I ₂ .

Further, by the above control, the pulling speed V of the ingot can be raised at a speed satisfying the range of 0.5 mm / min.ltoreq.V.ltoreq.5.0 mm / min. The pulling speed V is
For example, the diameter of the pulled silicon single crystal ingot is 20
In case of 0 mm, 1.0 mm / min ≦ V ≦ 5.0 mm /
Min, diameter is 300 mm, 0.5 mm / min ≤ V
≦ 3.0 mm / min is preferable.

As described above, by pulling up the ingot while controlling the rotational speeds of the quartz crucible 12 and the ingot 13 so as to satisfy any of the above ranges, the predetermined convection currents 11a and 11b flow into the silicon melt 11. 2 are generated by these convections 11a and 11b.
As shown in (a), the shape of the solid-liquid interface 22 is largely convex downward. As a result, as shown in FIGS. 2 (b) and 2 (c), even if the pulling speed of the single crystal ingot is raised at a medium or high pulling speed as compared with the conventional pulling speed, solid-liquid Since the interface shape is controlled so as to be largely convex downward, even if the solid-liquid interface rises due to insufficient cooling of the inside of the crystal, it does not become convex upward. Similarly, it is not extremely convex upward. Therefore, crystal deformation does not occur, the grown crystal does not break,
It is possible to enable ingot production by high-speed pulling.

[0017]

As described above, according to the present invention, by pulling the ingot while controlling the rotational speeds of the quartz crucible 12 and the ingot 13 so as to satisfy any of the above ranges, the silicon melting point is increased. Predetermined convection is generated in the liquid 11, and the shape of the solid-liquid interface 22 is largely projected downward due to these convections. As a result, the pulling speed of the single crystal ingot is higher than that of the conventional pulling speed of 0.
Even if the ingot is pulled at a pulling speed in the range of 5 mm / min ≤ V ≤ 5.0 mm / min, the solid-liquid interface shape is controlled so as to be significantly convex downward, so the force generated by pulling The solid-liquid interface is pushed up by convection, and even if the solid-liquid interface rises significantly, it does not project upward. Therefore, it is possible to manufacture an ingot by pulling at high speed without causing crystal deformation.

[Brief description of drawings]

FIG. 1 is a sectional configuration view showing a state where a silicon single crystal ingot according to an embodiment of the present invention is pulled up.

FIG. 2 (a) is a cross-sectional configuration diagram showing a solid-liquid interface shape when pulling at a low pulling speed in FIG. (b) FIG. 1 is a cross-sectional configuration diagram showing a solid-liquid interface shape when pulling at a medium pulling speed. (c) FIG. 1 is a cross-sectional configuration diagram showing a solid-liquid interface shape when pulling at a high pulling speed in FIG. 1.

FIG. 3 is a cross-sectional configuration diagram showing a state in which a silicon single crystal ingot is pulled up without applying a conventional magnetic field.

4 (a) is a cross-sectional configuration diagram showing a solid-liquid interface shape when pulling at a low pulling speed in FIG. (b) FIG. 3 is a cross-sectional configuration diagram showing a solid-liquid interface shape when pulling at a medium pulling speed. (c) A cross-sectional configuration diagram showing the solid-liquid interface shape when pulling at a high pulling speed in FIG. 3.

[Explanation of symbols]

11 Silicon melt 12 Quartz crucible 13 Silicon single crystal ingot 14 Upper coil 16 Lower coil 17 Cusp magnetic field 17a Neutral plane of cusp magnetic field 22 Solid-liquid interface

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiro Harada             3-5-1 Otemachi, Chiyoda-ku, Tokyo             Ryo Material Silicon Co., Ltd. (72) Inventor Hisashi Furuya             3-5-1 Otemachi, Chiyoda-ku, Tokyo             Ryo Material Silicon Co., Ltd. (72) Inventor Akira Higuchi             3-5-1 Otemachi, Chiyoda-ku, Tokyo             Ryo Material Silicon Co., Ltd. F-term (reference) 4G077 AA02 BA04 CF10 EH08 EJ02                       HA12 PG01 PG03

Claims (5)

[Claims] 1. A quartz crucible for storing a silicon melt (11).
(12) is rotated at a predetermined rotation speed, the silicon melt (1
A silicon single crystal ingot (13) pulled up from 1) is rotated at a predetermined rotation speed to form an upper coil (14) and a lower coil (16) each having a coil diameter larger than the outer diameter of the quartz crucible (12). By arranging the quartz crucible (12) with the rotation axis of each as the center of the coil and at predetermined intervals in the vertical direction, by applying currents in opposite directions to the upper coil (14) and the lower coil (16). A neutral plane between the upper coil and the lower coil from the center of each coil of the upper coil and the lower coil
In the method of pulling a silicon single crystal that pulls up the ingot (13) while generating a cusp magnetic field (17) passing through (17a), the rotational speed of the quartz crucible (12) is R ₁ , and the ingot is
When the rotation speed of (13) is R ₂ , the rotation speed R _{1 is set} so that the shape of the solid-liquid interface (22) between the silicon melt (11) and the ingot (13) is convex downward.
Is defined as a range of | R ₁ | ≧ 0.3 rpm, and R ₁ = − (0.
01 to 100) R ₂ to satisfy the above ingot (13)
A method for pulling a silicon single crystal, which comprises controlling the rotation speed of a silicon single crystal. However, | R ₁ | indicates the absolute value of R ₁ . 2. When the distance between the neutral surface (17a) of the cusp magnetic field (17) and the surface of the silicon melt (11) is H, it is -300 m.
The neutral surface (17a) so as to satisfy m ≦ H ≦ 300 mm
The method for pulling a silicon single crystal according to claim 1, wherein the temperature is controlled above or below the surface of the silicon melt (11). 3. The upper coil for increasing the strength of the cusp magnetic field (17) as the diameter of the quartz crucible (12) increases.
The method for pulling a silicon single crystal according to claim 1 or 2, wherein the current flowing through (14) and the lower coil (16) is controlled. 4. The current values to be passed through the upper coil (14) and the lower coil (16) are I ₁ and I ₂ , and when the current values I ₁ and I ₂ have different magnitudes,
I ₁ = - (0.5~2.0) lower coil so as to satisfy I ₂ (1
The method for pulling a silicon single crystal according to any one of claims 1 to 3, wherein the current value I ₂ flowing in 6) is controlled. 5. The method for pulling a silicon single crystal according to claim 1, wherein when the pulling speed of the ingot is V, the pulling speed is such that 0.5 mm / min ≦ V ≦ 5.0 mm / min.