JP2849537B2 - Single crystal pulling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a method in which single crystal silicon is subjected to an MCZ method (magnetic field application Czochralski method: Magne
tic field applied Czochra
lski crystal growth method
d) improving the single crystal pulling technique for production.

[0002]

2. Description of the Related Art The MCZ method has been devised for producing large-diameter silicon single crystals. The single crystal pulling apparatus by the MCZ method includes a magnetic field applying device that generates a magnetic field in a horizontal direction, a furnace body provided between both poles of the magnetic field applying device, and a silicon melt provided inside the furnace body. A quartz crucible to be held, a heater to heat the silicon melt,
A pulling mechanism for pulling up the silicon single crystal rod while rotating it.

In this apparatus, a seed crystal of a silicon single crystal is immersed in a silicon melt in a quartz crucible in a magnetic field, and the seed crystal is gradually pulled up while rotating, so that a silicon single crystal having a large diameter in the same direction as the seed crystal. Grow crystals. By applying a magnetic field, the thermal convection of the silicon melt in the quartz crucible is suppressed, thereby greatly reducing the contamination of impurities from the quartz crucible and keeping the silicon solid-liquid interface more static. .

[0004] As this kind of MCZ technology, a technology described in, for example, Japanese Patent Publication No. 2-44799 has been known. In this technique, a lateral magnetic field of 3500 gauss is applied, and the crucible rotation speed is set to 20 rpm. The crucible is rotated at high speed to pull up single crystal silicon having a high oxygen concentration (about 2 × 10 ¹⁸ cm ⁻³ ). Single crystal silicon having a high oxygen concentration is used for forming a device as having, for example, an IG function.

[0005]

SUMMARY OF THE INVENTION Such a conventional MC
In the Z technology, high-speed rotation of the crucible was required to obtain single-crystal silicon having a high oxygen concentration. However,
When such high-speed rotation is performed, the state of the solid-liquid interface becomes very unstable in the crucible, and for example, a problem has arisen that a part of the pulled crystal is easily polycrystallized. In addition, for pulling a large-diameter, heavy-weight single crystal, the rotation driving mechanism itself of the crucible itself is inadequate at present, and stable pulling was impossible.

Therefore, the present inventor measured the temperature distribution of the silicon melt by the MCZ method. In the MCZ method, the convection in the vertical direction in the vertical plane of the silicon melt was suppressed. It has been found that the oxygen concentration in the inside decreases. Therefore, since the supply amount of molten oxygen is proportional to the temperature of the wall of the quartz crucible, the temperature of the wall of the quartz crucible at a portion that does not affect the convection of the silicon melt and make the state of the solid-liquid interface unstable. It has been found that by increasing the value of, it is possible to increase the amount of dissolved oxygen from the quartz crucible and to pull up single-crystal silicon having a high oxygen concentration.

[0007]

According to the first aspect of the present invention, a single crystal rod is applied while applying a magnetic field to a silicon melt in a horizontal direction and rotating a quartz crucible holding the silicon melt. In a single crystal pulling method for pulling out from a silicon melt, 2.0 to 2.5 × 10 ¹⁸
In order to obtain a single crystal rod having a high oxygen concentration of atoms / cm ³ , the rotation speed of the quartz crucible is 1 to 10 rpm, the magnetic field strength is 500 to 5000 Gauss, and the pulling speed is 0.5 to 2. This is a single crystal pulling method in which the heating temperature of the bottom wall of the quartz crucible is controlled within the range of 1500 to 1800 ° C. at 0 mm / min.

[0008]

[0009]

According to the method of the present invention, a horizontal magnetic field is applied to the silicon melt. As a result, the generation of convection in the vertical direction inside the silicon melt is suppressed. Therefore, the interface between the silicon melt and the pulled single crystal rod is kept in a stable state. Further, since the rotation speed of the quartz crucible is also low, the solid-liquid interface is not disturbed. By heating the bottom wall of the quartz crucible, oxygen is dissolved into the silicon melt from the bottom wall of the quartz crucible. As a result of this molten oxygen being taken directly into the single crystal rod, a single crystal rod having a high oxygen concentration can be pulled up in a stable state. In this case, since the side wall of the quartz crucible does not rise above the predetermined temperature, the amount of molten oxygen due to convection from the side wall does not increase. Since the side wall does not reach a high temperature in this way, the solid-liquid interface of the silicon melt maintains a stable state by applying a magnetic field. That is, the single crystal rod can be pulled up in a stable state, and the oxygen concentration of the single crystal rod can be increased. Here, in the present invention, the lifting speed is set to 0.5 to 2.
The crucible rotation speed is controlled to an arbitrary value within the range of 0 mm / min, the crucible rotation speed of 1 to 10 rpm, the applied magnetic field strength of 500 to 5000 Gauss, and the heating temperature of the crucible bottom wall in the range of 1500 to 1800 ° C. This is 2.0-2.5 × 10 ¹⁸ ato
This is for obtaining a silicon single crystal rod having a high oxygen concentration of ms / cm ³ .

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a single crystal pulling apparatus according to one embodiment of the present invention.

As shown in FIG. 1, an N pole and an S pole of a magnetic field applying device 12 are disposed on both sides of the furnace body 11 of the single crystal pulling apparatus in the figure, in the vicinity of the furnace body 11. . In the magnetic field applying device 12, the left side in the drawing is the S pole and the right side is the N pole with respect to the furnace body 11, and a magnetic field is generated horizontally from the N pole toward the S pole (the N pole and the S pole are May be arranged in reverse). Inside the furnace body 11, a quartz crucible 13 into which silicon melt Si (Melt) is injected is provided. The quartz crucible 13 has a bowl shape or a bottomed cylindrical shape with an open upper side, is fitted to a graphite susceptor 14 having substantially the same shape, and is detachably supported. A motor driven rotary shaft 15 is attached to the center of the bottom wall of the graphite susceptor 14.

The graphite susceptor 14 is provided inside the furnace body 11.
Around the silicon melt Si
A heater 16 for heating (Melt) is provided. Further, the outside of the annularly arranged heater 16 is surrounded by a heat shield member 17 for keeping heat. Further, a pulling mechanism (not shown), an inlet for introducing argon gas into the furnace body 11, and the like are provided at an upper portion of the furnace body 11. The pulling wire 19, which is a part of the pulling mechanism, is configured to move up and down above the quartz crucible 13 while rotating in the opposite direction to the quartz crucible 13. A silicon single crystal seed crystal is attached to the tip of the pulling wire via a chuck. Further, an exhaust port is provided at a lower portion of the furnace body 11, and the exhaust port is connected to a vacuum device. This seed crystal is immersed in a silicon melt Si (Melt) and then raised, and a silicon single crystal rod Si (C
r) is pulled up in an argon atmosphere.

In this single crystal pulling apparatus,
An annular heater 18 is provided directly below the bottom surface of the graphite susceptor 14. The heater 18 directly heats only the bottom wall portion 13A of the quartz crucible 13. In order to increase the heating efficiency, the graphite susceptor 14
Forming an opening in a part of the bottom wall of the crucible directly to the crucible bottom wall portion 13
A may be configured to be heated by the heater 18. Further, the heater 18 may be arranged close to the crucible bottom wall portion corresponding to the shape of the crucible bottom wall portion, and may be configured to heat a corner portion of the bottom wall portion.

Next, a method of pulling a silicon single crystal using this single crystal pulling apparatus will be described. Prior to the lifting, high-purity polycrystalline silicon is charged into the quartz crucible 13. After the inside of the furnace body 11 was evacuated, argon gas was supplied from the inlet, and the inside of the furnace body 11 was
An argon atmosphere of 0 Torr is kept. Further, the heater 16 is energized to heat the quartz crucible 13 to melt the raw material silicon. After the silicon is melted, a magnetic field of 3500 gauss is applied using the magnetic field applying device 12. Convection occurs horizontally.

Next, a seed crystal of silicon single crystal is attached to the chuck, and the seed crystal is silicon melt Si (Mel).
Touch to t). Thereafter, the rotating shaft 15 is rotated by the motor at a rotation speed of 5 rotations / minute. At the same time, the seed crystal is slowly raised by the pulling mechanism while rotating at a crystal rotation speed of 10 to 15 rotations / minute in a direction opposite to the rotation of the crucible 13. As a result, a silicon single crystal rod Si (Cr) grows from the seed crystal and is pulled up. And
The diameter of the silicon single crystal rod Si (Cr) is monitored by a diameter control optical sensor provided obliquely above the quartz crucible 13 and the pulling speed of the pulling mechanism is changed (average 1.0 to 1.5).
mm / min) so that the diameter is always constant.

At the time of lifting, the heater 1
8 is used to heat the bottom wall portion 13A of the quartz crucible 13 to a predetermined temperature. The heating temperature is 1500-1800 ° C.
As a result, oxygen is eluted from the bottom wall portion 13A of the quartz crucible 13 into the silicon melt, and the silicon melt S having a high oxygen concentration is dissolved.
i (Melt) is obtained. When the oxygen concentration in the silicon single crystal rod Si (Cr) thus grown was examined, it was found that:
^{4 × 10 18 atoms / cm 3} ~2.5 × 10 18 ato
A high oxygen concentration of ms / cm ³ was obtained.
Table 1 shows the lifting conditions.

[0017]

[Table 1]

Table 2 shows these magnetic field strengths, crucible rotation speeds,
It is an example showing an upper limit value and a lower limit value for the crystal pulling speed and the bottom heating temperature. That is, 1.4 × 10 ¹⁸ at
It shows the upper and lower limits of each pulling condition for obtaining a silicon single crystal rod having a high oxygen concentration of oms / cm ^{3 to} 2.5 × 10 ¹⁸ atoms / cm ³ .

[0019]

[Table 2]

[0020]

According to the present invention, the convection of the silicon melt can be controlled and the solid-liquid interface can be stably maintained. At the same time, the amount of molten oxygen from the bottom wall of the quartz crucible can be increased, and the oxygen concentration in the silicon melt can be increased. Therefore, a silicon single crystal rod having a high oxygen concentration can be stably pulled up.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a single crystal pulling apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 12 magnetic field applying device (magnetic field applying means) 13 quartz crucible 13A bottom wall portion of quartz crucible 15 rotation axis 16 heater (heating means) 18 heater (bottom wall heating means) 19 pulling wire (pulling means) Si (Melt) silicon Melt Si (Cr) Silicon single crystal rod

Continuing from the front page (72) Inventor Yoshiaki Arai 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Mitsui Materials Co., Ltd. (72) Inventor Hisashi Furiya 1-297 Kitabukuro-cho, Omiya City, Saitama Prefecture Mitsubishi Materials Corporation Central Research Laboratory (56) References JP-A-2-229786 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) C30B 15/00-15/36 C30B 28/00-35/00

Claims (1)

(57) [Claims] 1. A method for pulling a single crystal from a silicon melt while applying a magnetic field in a horizontal direction to the silicon melt and rotating a quartz crucible holding the silicon melt. The rotation speed of the quartz crucible is 1 to 10 rpm, the magnetic field strength is 500 to 5000 Gauss, and the pulling speed is so as to obtain a single crystal rod having a high oxygen concentration of 0.0 to 2.5 × 10 ¹⁸ atoms / cm ^3. A single crystal pulling method in which the heating temperature of the bottom wall of the quartz crucible is controlled within a range of 1500 to 1800 ° C., with an average value of 0.5 to 2.0 mm / min.