JPS6330393A - Crystal producing device - Google Patents

Abstract

PURPOSE:To effectively impress a magnetic field to a melting liquid and to miniaturize a magnetic field impressing device by using the axis supporting a melting crucible as a magnetic path in the Czochralski method. CONSTITUTION:A raw material charged in the crucible 10 is heated and melted by a heating means 14 while the axis 20 supporting the crucible 10 is rotated to rotate a melting body 12. A magnetic field is impressed to this melting body 12 through the supporting axis 20 formed with a magnetic material by a magnetic field impressing means 22, and radiating magnetic lines 24 are formed in the melting body 12. The melted liquid is prevented to flow near the interface of the crystal while the melted liquid is agitated near the peripheral part of the crucible 10, and a single crystal 16 is continuously pulled up from the molten body 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a crystal manufacturing apparatus, and particularly provides a new magnetic field application method in the pulling method or CZ method.

[Prior Art] In recent years, demand for semiconductor devices, especially integrated circuits, has been increasing rapidly, and with this, demand for silicon single crystals has also increased. Furthermore, in order to improve productivity, single crystal growth furnaces are becoming larger, and the diameter of the single crystals being pulled is also rapidly increasing.

On the other hand, as the degree of integration of integrated circuits increases, there is a growing demand for higher quality such that impurity concentrations and other organic properties are uniform within the crystal. For example, in silicon single crystals, it is said that the uniformity of impurities such as boron and phosphorus added to determine resistivity and oxygen impurities mixed in from the crucible material is particularly important.

The existence of thermal convection within the silicon melt has been pointed out as a cause of deteriorating the uniformity. As a means to suppress this heat convection, for example, Japanese Patent Laid-Open No. 57-17
There is a method using a magnetic field as disclosed in Japanese Patent Publication No. 0890, Japanese Patent Publication No. 58-50951, or Japanese Patent Application Laid-open No. 102893-1983. These methods utilize the phenomenon that applying a magnetic field to an electrically conductive melt increases the effective permeability of the melt, thereby making convection less likely to occur, and is an effective means for suppressing convection. It is.

[Problems to be Solved by the Invention] However, as mentioned above, when trying to increase the size of a single crystal, the method of applying a DC magnetic field in the vertical or transverse direction as disclosed in the above-mentioned publication is difficult to use. This results in the inconvenience of becoming extremely large and complex.

Furthermore, when processing is carried out in a batch method in a normal single crystal pulling apparatus, a problem arises of macroscopic segregation of doped impurities. For this reason, various methods of continuous lifting have been proposed. In this case, since the single crystal is pulled on one side while the raw material is supplied on the other side, the flow of the melt becomes even more important than in the batch method.

Therefore, it is necessary to control convection in some way.
A conceivable method for this is control using the above-mentioned magnetic field.

However, even if such control is performed, the apparatus will be extremely large due to the presence of the raw material supply means, and therefore the magnetic field application means will also have to be enlarged, and the power loss will also be extremely large.

Furthermore, according to the above-described magnetic field application method, since the heating means is placed in the magnetic field in any case, vibrations occur due to the interaction between the magnetic field and the current flowing through the heating means. In order to prevent this, it is essential to use high-grade direct current as a heating power source, which is disadvantageous in that an expensive power source device is required.

Furthermore, when applying a magnetic field, the disadvantages of using alternating current as the heater current of the heating means were disclosed in Japanese Patent Publication No. 58-5095.
This is pointed out in Publication No. 1. In other words, the special public official court Sho 58-5
According to Publication No. 0951, when applying a magnetic field to pull a single crystal using the Czochralski method, if alternating current is used as the heater current, the interaction between the heater current and the magnetic field causes unnecessary vibrations in the heater. It is said that this causes vibrations on the melt surface, significantly inhibiting healthy crystal growth, and furthermore, when the magnetic field is strong, the heater may be damaged.

In order to prevent such damage to the heater, it is essential to use high-quality direct current as a heating power source, which has the disadvantage of requiring an expensive power supply device.

The present invention has been made in view of these points, and it aims at miniaturizing the magnetic field applying means, increasing the efficiency of effective magnetic field application to the melt, and furthermore, making it possible to increase the efficiency of the heating means even when using an inexpensive power supply device. The object of the present invention is to provide a crystal manufacturing apparatus suitable for continuous pulling of a single crystal without causing damage.

[Means for Solving the Problems] The present invention provides a magnetic field applying means around a support shaft which is the center of rotation of the crucible, and the magnetic field applying means applies a magnetic field to the melt housed in the crucible via the support shaft. , to form a magnetic field.

[Function] According to the present invention, the magnetic flux generated by the magnetic field application means passes through the melt housed in the crucible via the support shaft, and the axially symmetrical and radial magnetic field penetrates the melt inside the melt. is formed.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a perspective view of an embodiment of the invention. FIG. 2 also shows a sectional view. - In these FIGS. 1 and 2, a melt 12 of, for example, silicon is accommodated in a crucible 10. A heating section 14 having a heater for heating is provided on the outside of the crucible 10.
is located. The single crystal 16 is pulled upward from the center of the liquid level of the crucible 10.

- The crucible 10 is supported by a support shaft 20 via a heat insulating material 18, and as the support shaft 20 rotates, the crucible 10
is set to rotate.

A treid magnet 22 is arranged around this support shaft 20 so that the support @20 is a pole piece of the magnet. The support shaft 20 is made of a material with good magnetic permeability.

Note that a heat insulating material 18 is provided between the support shaft 20 and the crucible 10.
is interposed, so that the support shaft 20 is well thermally protected.

Next, the overall operation of the above embodiment will be explained. first,
The melt 12 in the crucible 10 is maintained at a high temperature by heating by the heating unit 14, and at this time, convection of the melt 12 occurs. On the other hand, the magnetic flux generated by the solenoid magnet 22 passes through the support shaft 20 and reaches the melt 12 because the support shaft 20 has high magnetic permeability. Then, the melt 1 is aimed at the center of rotation of the crucible 10 rotating in the direction of the arrow FA.
Expands within 2. That is, axially symmetrical and radial lines of magnetic force 24 are formed within the melt 12.

When a magnetic field is formed by the lines of magnetic force 24, convection within the melt 12 is uniformly suppressed, and an axially symmetrical temperature distribution is maintained. On the other hand, the single crystal 16 is rotated from the center of the axis as shown by the arrow FB and pulled up as shown by the arrow FC.

As described above, according to the present embodiment, the single crystal 16 has a uniform circular cross section, and the occurrence of defects is also favorably reduced.

Further, according to this embodiment, the magnetic field is strong near the center of the crucible support shaft 20 and becomes weaker as it moves away from the crucible 10, so the following effects are produced.

First of all, when performing continuous pulling to grow the single crystal 16 semi-continuously, the flow of the melt 12 should be prevented as much as possible near the crystal growth interface, and the flow of the melt 12 should be prevented as much as possible in the vicinity of the crucible where raw materials are added. Although a certain degree of stirring is required from the viewpoint of uniform dopant mixing, this embodiment satisfies such requirements.

Furthermore, in this embodiment, as described above, the strength of the magnetic field rapidly attenuates as it moves away from the support shaft 20, that is, as it approaches the heating section 14, so the interaction between the heating section 14 and the magnetic field increases. is extremely small. Therefore, it is also possible to use alternating current as the current applied to the heating section 14. Furthermore, when direct current is used, as pointed out in Japanese Patent Publication No. 58-50951, there is no need for the ripple content to be 4% or less, and low-grade direct current is sufficient.

As described above, according to this embodiment, since it is possible to use low-grade direct current or commercial frequency alternating current as the heating power source, extremely inexpensive equipment is required, and furthermore,
By placing a very compact magnet at the bottom of the crucible 10, it is possible to achieve this purpose. Therefore,
It is extremely useful industrially for single crystal pulling equipment, which is expected to become larger in size in the future, especially for equipment that continuously pulls single crystals by continuously charging raw materials.

Generally, the heater of the heating section 14 has a heating capacity of 100
A large current of 0 ampere or more is flowing, and if an external magnetic field is applied, there is a risk of damaging the heater due to the Lorentz force as described above.

However, in this embodiment, as described above, the magnetic field rapidly weakens as it moves away from the center of the crucible, that is, at the location where the heating section 14 is located, so the risk of heater damage is significantly reduced.

Note that the present invention is not limited to the above embodiments in any way. For example, in the melt 12, the influence of the magnetic field is reduced at a position away from the magnet 22.

In such a case, an air-core solenoid magnet may be placed near the meniscus surrounding the single crystal 16.

Alternatively, the heater of the heating section 14 may have a spiral structure, and by applying a direct current to this heater, the heater itself may be magnetized to prevent the attenuation of the magnetic field by the solenoid magnet 22 installed at the bottom.

In addition, in order to make the magnetic field effectively act on the crystal growth surface,
Processing the tip end of the support shaft 20 into an uneven shape as necessary does not impede the effects of the present invention.

[Effects of the Invention] As explained above, according to the crystal manufacturing apparatus according to the present invention, a magnetic field can be effectively applied to the melt, and the magnetic field applying apparatus can be downsized. Furthermore, it has the effect of being able to cope well with continuous pulling of single crystals.

In addition, according to the present invention, the strength of the magnetic field is strong at the center of the crucible and becomes weaker toward the periphery, so that the flow of the solution is effectively prevented near the crystal interface, and at the periphery of the crucible where raw materials are added, the magnetic field is Stirring is performed which is convenient for uniform mixing of the components, and furthermore, the risk of damage to the heating section is significantly reduced.

[Brief explanation of the drawing]

Figure S1 is a partially cutaway perspective view of the main parts of an embodiment of the crystal manufacturing apparatus according to the present invention, and Figure 2 is a sectional view of the apparatus shown in Figure 1. 10... Crucible, melt 12... Melt, 14... Heating section, 16... Single crystal, 18... Heat insulating material, 20...
- Support shaft, 22... Solenoid magnet, 24... Lines of magnetic force.

Claims (3)

[Claims] (1) In a crystal manufacturing apparatus that heats a crucible containing a molten material serving as a raw material by a heating means, and pulls and produces a single crystal while rotating the molten material by rotating a support shaft that supports the crucible, the support A crystal manufacturing apparatus characterized in that a magnetic field applying means for applying a magnetic field to the melt using the support shaft as a main magnetic path is arranged around the shaft. (2) The crystal manufacturing apparatus according to claim 1, wherein the support shaft is made of a magnetic material. (3) The crystal manufacturing apparatus according to claim 1 or 2, wherein either alternating current or low-grade direct current is applied to the heating means.