JPH0825834B2 - Single crystal pulling device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a single crystal pulling apparatus for producing a silicon single crystal, a germanium single crystal, or the like.

2. Description of the Related Art The double crucible method is a method for pulling a single crystal using a double crucible having an inner crucible and an outer crucible.
A dopant is added to the inner crucible, and the dopant that becomes thicker according to the deviation coefficient is diluted with the melt from the outer crucible to pull up the crystal. Since the dopant concentration in the inner crucible is kept constant, a crystal having a uniform resistivity can be obtained. However, if the double crucible method is applied to the ordinary CZ (pull-up) method,
Oxygen concentration is 20 × 10 ¹⁷ (same as ASTM F121-79 and below) / cm ³ or more, and oxygen concentration usually used (5-18 ×
It was a problem because it exceeded 10 ¹⁷ / cm ³ ). Third
See figure. However, in FIG. 3, the area A is the control range of the oxygen concentration when the double crucible method is applied to the CZ method, and the area B is the MCZ.
The control range of the oxygen concentration when the double crucible method is applied to the method is shown.

Moreover, in the double crucible method, the height of the upper edge of the inner crucible and the outer crucible is usually low in the inner crucible.

MCZ method is Magnetic Field Applied Czochralsky Me
Abbreviation for thod. In the MCZ method, a strong static magnetic field is applied to a melt (eg, silicon melt) when pulling a single crystal by the CZ (pull-up) method. This static magnetic field suppresses stirring of the silicon melt due to thermal convection, and crystal growth is performed in a thermally and chemically stable state. The MCZ method includes a method of applying a horizontal magnetic field and a method of applying a vertical magnetic field. According to the MCZ method, it is easy to control the oxygen concentration, and it is difficult to manufacture with the ordinary CZ method.
It is possible to grow crystals with a low oxygen concentration of ~ 10 × 10 ¹⁷ atoms / cm ³ .

By combining the double crucible method and the MCZ method, there has been proposed a method for producing a single crystal having a low oxygen concentration and a uniform resistivity, making the most of the advantages of the two methods.

Problems to be Solved by the Invention In the MCZ method (transverse magnetic field), for example, (vertical) convection of a silicon melt is suppressed. Therefore, the heat exchange of the silicon solution is mainly performed in the horizontal direction, and the temperature difference in the radial direction of the crucible is smaller than that in the usual CZ method.

When the MCZ method is combined with the double crucible, the problem of the temperature difference in the radial direction cannot be ignored.
That is, the heat is shielded by the inner crucible, and the temperature difference becomes smaller than that in the case of the MCZ method alone (the thermal response becomes worse). Therefore, when pulling up the crystal, a polycrystal is likely to precipitate from the inner crucible, and there is a problem in the quality of the obtained single crystal. Further, when the pulling rate is increased, the polycrystal is more likely to be precipitated, so that the pulling rate must be kept low and the production efficiency of the single crystal cannot be increased.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a single crystal pulling apparatus that can efficiently obtain a single crystal having a low oxygen concentration and a uniform resistivity.

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a single crystal pulling apparatus described in claims.

Means for Solving the Problems A single crystal pulling apparatus of the present invention is a single crystal pulling apparatus having a double crucible composed of an inner crucible and an outer crucible.
A magnet is provided outside the double crucible, and the single crystal is pulled in a static magnetic field formed by the magnet. Further, the upper edge of the inner crucible is higher than the upper edge of the outer crucible. .

A superconducting magnet may be used as the magnet for generating the static magnetic field. The static magnetic field may be either a horizontal magnetic field or a vertical magnetic field.

As an operation example, a case of manufacturing single crystal silicon will be described. The upper portion of the inner crucible 22 is heated by receiving heat from the heater 24, and this heat is transmitted to the lower portion of the inner crucible 22 to heat the molten silicon 23 near the inner crucible. Therefore, the molten silicon 23 in the crucible has an appropriate temperature difference in the inner diameter direction of the inner crucible. Therefore, even if the pulling rate is increased, it becomes difficult for polycrystals to precipitate.

Embodiments Embodiments of a single crystal pulling apparatus according to the present invention will be described below with reference to the drawings.

The single crystal pulling apparatus 10 has a magnet 11. The magnet 11 forms a static magnetic field, and pulls a single crystal of a semiconductor such as silicon in the static magnetic field. A superconducting magnet may be used as the magnet 11. The direction of the magnetic field may be either a horizontal magnetic field or a vertical magnetic field, but the pulling is usually performed in the horizontal magnetic field.

A decompression container 27 is provided inside the magnet 11. Decompression container
A pump system for setting the inside of the container chamber 28 to a predetermined atmosphere is connected to 27, but is omitted in the drawing.

A double crucible consisting of an inner crucible 22 and an outer crucible 21 is provided at the center of the decompression container 27.

Around the crucible is a semiconductor material (eg silicon 23)
A heater 24 is provided for heating the.

 A heat insulating material 29 is installed outside the heater 24.

The upper edge of the inner crucible 22 is formed higher (for example, about 30 to 70 mm) than the upper edge of the outer crucible 21. Therefore, the upper part of the inner crucible directly receives heat from the heater 24. This heat is transferred from the upper part to the lower part of the inner crucible and heats the molten silicon 23 near the inner crucible. Therefore, the molten silicon in the crucible 23
Has an appropriate temperature difference in the inner diameter direction of the inner crucible. However, when pulling up, the tip of the crucible must not exceed the height of the heater until just before the end of the straight body part.

The inner crucible 22 and the outer crucible 21 can be made of a material such as quartz glass or carbon. A tube with a diameter of 6 mm and a length of 150 mm is installed below the inner crucible to connect the inner crucible and the outer crucible. However, it is not shown in the drawings for simplicity.

By adjusting the height of the upper edge of the inner crucible 22 and the height of the upper edge of the outer crucible 21, the temperature distribution of the molten silicon 23 can be set to a desired distribution. Also, cover the upper part of the inner crucible with something with good thermal conductivity (such as carbon),
You may make it easy to absorb the radiation from a heater.

A single crystal lifting device 25 is provided above the double crucible. Further, a crucible rotation support device is provided below the double crucible.
26 are installed.

As an example, FIG. 1 schematically shows a state in which a single crystal silicon 23 'is lifted by a single crystal lifting device 25.

Next, an experimental example of producing single crystal silicon using the single crystal pulling apparatus of the present invention will be described.

The inner crucible and the outer crucible of the single crystal pulling apparatus shown in FIG. 1 were charged with 20 kg poly silicon, and phosphorus (P) was added as a dopant. A static magnetic field of 0.3 T (tesla) was applied as a transverse magnetic field to pull up a 5-inch crystal in the orientation (111).

The average pulling speed of silicon single crystal is 1.08mm / m.
I went in. This is a speed 35% higher than the pulling speed of the double crucible of about 0.8 mm / min by the usual MCZ method.

The resistivity distribution of the pulled crystal was as shown in FIG. 2 and was almost constant, which was good.

The invention is not limited to the embodiments described above. For example, the structure of the double crucible of the present invention can be applied to a single crystal pulling apparatus by a normal double crucible method (CZ method).

EFFECTS OF THE INVENTION According to the single crystal pulling apparatus of the present invention, a single crystal having a low oxygen concentration and a uniform resistivity can be efficiently obtained. In addition, the pulling speed can be greatly improved.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of a single crystal pulling apparatus according to the present invention, and FIG. 2 shows the resistivity of single crystal silicon produced by the single crystal pulling apparatus shown in FIG. 1 and a normal single crystal pulling apparatus. The graph shown in Fig. 3 is the oxygen concentration control range (area A) and MCZ when the double crucible method is applied to the CZ method.
6 is a graph showing a control range (region B) of oxygen concentration when a double crucible method is applied to the method. 10 …… Single crystal pulling device 29 …… Insulation material 21 …… Outer crucible 22 …… Inner crucible 23 …… Molten silicon 23 ………… Single crystal silicon 24 …… Heater 25 …… Single crystal lifting device 26 …… Crucible rotation Supporting device 27 ... decompression container 28 ... container chamber

Claims (1)

[Claims] 1. A single crystal pulling apparatus for MCZ method having a double crucible consisting of an inner crucible and an outer crucible, wherein the upper edge of the inner crucible is higher than the upper edge of the outer crucible. Lifting device.