JPS6051690A - Manufacturing apparatus of single crystal - Google Patents

Abstract

PURPOSE:To manufacture a good-quality single crystal with a convenient and inexpensive equipment by constituting a titled apparatus wherein a single crystal is pulled up after a DC magnetic field is impressed to a molten body surrounded circumferentially by a Helmholtz coil wherein two circular coils are arranged oppositely. CONSTITUTION:A Helmholtz coil, obtained by arranging oppositely two circular solenoid coils 15 and 16 contained respectively in crystals 17 and 18 surrounding circumferentially a molten body 3, is provided to the outside of a heater 2 in a single crystal manufacturing apparatus of the Czochralski method wherein after a seed crystal 4 is dipped in and then pulled up from the molten body 3 obtained by heating a starting material in a crucible 1 with a heater 2 surrounding concentrically the crucible 1, a single crystal 5 is grown in company with the seed crystal 4. A magnetic field is generated by using the Helmholtz coil as a superconducting magnet, and a DC magnetic field 14, which is symmetrical to a crystal-growth axis 7 and has a uniform distribution of magnetic field along the crystal-growth surface, is impressed to the molten body 3. The heat convection in the molten body 3 is restrained in this way, and the high-quality single crystal 5 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an apparatus for producing a single crystal using the Czochralski method, and more particularly to an apparatus for producing a grown crystal from a conductive melt.

[Prior art and its problems]

Single crystals such as 8i and GaAS used in the semiconductor industry are mainly manufactured by the Czochralski method. This method uses a circular crucible (1
) is charged with raw material, and heated by a heater (2) coaxially surrounding the crucible to form a molten material (3).

After that, a seed crystal (4) is placed in the center of the surface of this melt (3).
), and by gradually pulling up the seed crystal (4), a desired single crystal (5) is grown continuously from the first seed crystal (4).

By the way, the heating to the melt (3) is done in the crucible (1).
), inside the melt (3) there is a temperature gradient that is high in the outer part (lower in the center). Therefore, inside the melt (3) there is a temperature gradient mainly from the outer part to the center. Direct heat convection (6) occurs.Such heat convection (6) is caused by crystal (5)
As a result of varying the temperature at the growth interface of the growing crystal (5
) may cause inconveniences such as non-uniform properties and crystal defects.

In an attempt to improve these drawbacks, a method of applying a magnetic field to the melt from the outside when growing a single crystal from a conductive melt has been studied in the Jλ limit, and is disclosed in Japanese Patent Laid-Open No. 57-14984. etc. are disclosed. In other words, by applying a magnetic field, a fluid with conductivity crosses the lines of magnetic field, and as a result, the electric plate flows in a direction perpendicular to the direction of fluid motion and the magnetic field, and a force is generated in the direction perpendicular to the current and magnetic field. occurs. This force is in the opposite direction to thermal convection and suppresses thermal convection. This method uses the above principle, and as shown in Figure 2, the magnetic field is applied using two magnets (
81 and +91 and apply a transverse magnetic field (1,0) generated by these magnets to the bath melt (3). ) is provided with a cylindrical solenoid (1υ) concentrically surrounding it, and a vertical magnetic field (12) is applied to the melt (3) by passing a current through it. Applying a transverse magnetic field had the disadvantage that a magnetic field distribution symmetrical to the crystal growth axis (71) could not be obtained.Also, in the latter application of a longitudinal magnetic field, although it was possible to obtain a magnetic field distribution symmetrical to the crystal growth axis (71),
As shown in FIG. 4, it is difficult to obtain a uniform magnetic field distribution in the molten body (314M direction, that is, along the crystal growth interface).

t1. K Wachi, Solenoid coil (1υ Tortuho f1) (7) Is it possible to obtain a uniform magnetic field distribution along the crystal growth interface by making the diameter ratio sufficiently thick?Is it possible to obtain a uniform magnetic field distribution along the crystal growth interface? However, there is a problem that it is easy to use, and there is a drawback that it lacks simplicity.

In addition, in any of the above methods, there is a limit to the ability to custom improve the in-plane uniformity of the grown crystal (5) and reduce crystal defects.

[Purpose of the invention]

This invention was made to solve the above-mentioned problems, and its purpose is to form a crystal M, which is symmetrical to the crystal growth axis and
The object of the present invention is to provide a simple and inexpensive magnetic field stamp 7JiQ crystal manufacturing apparatus that can obtain a uniform magnetic field distribution along the long plane.

[Ammonium sulfate of invention]

In order to achieve this object, the present invention uses a Helmholtz coil type magnet for generating a superconducting magnetic field, in which two circular coils surrounding the melt are placed facing each other outside the melt. As a result, as shown in Fig. 5, a longitudinal magnetic field (4) symmetrical to the crystal growth axis (7) is obtained, and due to the convergence of the magnetic fields generated from the upper and lower coils (15) and (16), As shown in FIG. 6, a uniform magnetic field distribution (17) is realized horizontally within the i55 lines, that is, along the crystal growth plane.

〔Effect of the invention〕

As explained above, the single crystal production apparatus of the present invention allows the crystal growth to be symmetrical in the production of a fleshy single crystal in which the melt has conductive properties using the Czochralski method. In addition, it is possible to obtain a uniform magnetic field distribution along the crystal growth surface, so thermal convection within the 1-F melt is effectively suppressed. ”
L. As a result, crystal heterogeneity based on thermal convection,
High-quality single crystals without crystal defects can be molded. Furthermore, the device has a single-H configuration in which two circular coils are placed opposite each other, and is of a superconducting type, so it is small and available in large quantities.

[Embodiments of the invention]

Embodiment 1 of the present invention will be described below based on the drawings. Fifth
As shown in the figure, there are two upper and lower coils (
15) and (16) were placed opposite each other. The number of turns of each of the upper and lower two coils (15) and (16) is 1800%.The coil cross section is a square of 30 x 30 m+r+,
100 for the Chosha guide break of Kazu-nii ii' CuN i/NbTi
The filtering, resulting in a coil current density of A/mm2, produced a primarily longitudinal focused magnetic field of 1500 Gauss, sufficient to reduce thermal convection within the M melt. Upper and lower coils (13J.

(14) are each separate cryostat (17)
, (1B) and these two cryostats (
17) and (18) into two flexible pipes (1
9), combined with C2(1).

One of them is the upper and lower coil (15), (1,6)
The other pipe is for injecting liquid helium. Figure 61 shows that in this device, 1,500 gauss of dust [1,? This is the horizontal magnetic field strength distribution (17) obtained when the field was applied, and an almost uniform horizontal distribution was obtained in the central 150 mm region.

Using the apparatus of the present invention, an 81 single crystal with a diameter of 76 mm was grown from a crucible with an inner diameter of 1'50 mm, and the result was a uniform in-plane distribution of oxygen concentration without striations, which could not be obtained with conventional methods. A high quality single crystal was obtained.

As explained above, in the single crystal M manufacturing apparatus of the present invention, undesirable thermal convection occurs during crystal growth within the linear body.
Since the magnetic field for this purpose can be applied uniformly to the bath melt, it is possible to search for and create high-quality crystals with good uniformity and fewer monomer defects by applying a relatively small magnetic field. In addition, since it can be realized in the II4-type ζ type, in which two circular coils with a super L-sensing type are placed opposite each other, it can be realized as a small 4W, light 1
It is possible to change the method, and the advantages over the previous method are extremely large.

A: The present invention is not limited to the production of Si monocrystals as described in the above embodiments, but is also applicable to other types of GaAs, Gap 7; J, etc.

[Brief explanation of the drawing]

Figure 41 shows the production of single crystals using the Czochralski method:
Kyori, Keimei! J, W, Figure 112 and Figure 3 are diagrams showing the conventional crystal tone @ boundary A, Ka41 bacteria is an explanatory diagram of the prior art series, and Figure 5 shows a method for producing crystals; 1 that is different from the present invention. G4
, FIG. 6 is an explanatory diagram of an example of the technique of the present invention. 1... Crucible, 2... Heater, 3... Molten body, 4...
... Seed crystal, 5... Single crystal, 6... Heat convection, 7...
・Crystal growth axis. 8.9...Permanent magnet, 10,12.14...Magnetic field,
11... Solenoid coil, 13.17... Magnetic field strength distribution. 15.16... Solenoid coil, 17.18...
Talaiostanoto% 19.20...Flexible pipe. Representative Patent Attorney Kensuke Chika (and 1 other person) Figure 4 Figure 5 Figure 6 0 RO o 0 0 0 o.

Claims (2)

[Claims] (1) In an apparatus for manufacturing a single crystal by the Czochralski method by applying a direct current magnetic field to a melt, the magnetic field applying device is a Helmholtz coil in which two circular coils circumferentially surrounding the bath melt are arranged opposite each other. A single crystal manufacturing device characterized by being equipped with a coil. (2) The apparatus for manufacturing a single crystal according to claim 1, wherein the Helmholtz coil in which two one-circular coils are arranged opposite each other in the magnetic field applying device is a superconducting magnet.