JPS6246990A - Method and apparatus for producing single crystal by light-high frequency induction heating - Google Patents

Abstract

PURPOSE:To grow a single crystal having a large diameter and high quality by further subjecting the part to be heated between a raw material bar and crystal bar melted by optical heating with IR lamps to high-frequency induction heating so that even a high melting insulating material such as oxide is melted by heating. CONSTITUTION:The IR rays irradiated from the IR lamps 15, 16 disposed at the 1st and 2nd focuses F1, F2 of rotating ellipsoidal mirrors 13, 14 are reflected by the mirrors 13, 14 and are condensed to the part 17 to be heated disposed at the focus F0, by which said part is optically heated. The bottom end of the raw material bar 19 and the top end of the crystal bar 21 are brought into smooth contact with each other while both ends are heated and melted by the radiation energy of such optical heating, by which a melt zone, i.e., the part 17 to be heated is formed between the raw material bar 19 and the crystal bar 21. The part 17 is further subjected to the high-frequency induction heating by a high-frequency coil 22 to form the melt zone of a large capacity. The bar 19 and the bar 21 are lowered in a vertical direction while the bars are kept rotated in this state, by which the large-diameter single crystal is grown.

Description

[Detailed Description of the Invention] The present invention relates to a method and apparatus for manufacturing a single crystal by optical/high-frequency induction heating, and more specifically, the present invention relates to a method and apparatus for producing a single crystal by optical/high-frequency induction heating, and more specifically, by complementary application of concentrated optical heating and high-frequency induction heating, the production of oxide magnetic materials. The present invention relates to a method and apparatus for growing single crystals of electrically insulating materials with high melting points, such as dielectric materials and oxide dielectric materials.

For example, in the production of single crystals of electrically insulating materials such as high-melting point oxides, floating zone type single crystal production equipment using concentrated light heating, which uses infrared lamps such as halogen lamps as the heating source, is used. ing.

The above-mentioned infrared beam heating single crystal production device uses
Times f and i: A birch external ray lamp such as a halogen lamp is placed as a heat source at one focal point of the ellipsoidal mirror, and an object to be heated such as a raw material rod or crystal rod is placed at the other focal point, and the object is irradiated by the infrared lamp. This is a device for concentrating heating by reflecting the red ellipsoid on a spheroidal mirror and concentrating it on the object to be heated.In this device, the spheroidal mirror is one small ellipse, or each half is A bielliptic type mirror is generally used, in which two substantially equal spheroidal mirrors are arranged facing each other so that the focal points of each mirror coincide with each other.

For example, a specific example of a bielliptic optically concentrated heating single crystal manufacturing apparatus will be described with reference to FIGS. 5 and 6. In the figure, (1) and (2) are two symmetrical spheroidal mirrors, which are arranged to face each other so that the focal points Fo and Fo of each mirror coincide. (3) and (4) are the respective first and second focal points F1 and F2 of the other spheroidal mirrors (1) and (2).
two heat sources, for example infrared lamps, such as halogen lamps, fixedly arranged on the lamp. (5) is each spheroidal mirror (1)
In the heated part placed at the coincident focal point Fo in (2), the part where the raw material rod (6) extending vertically downward from above and the crystal rod (7) extending vertically upward from below meet, that is, the single crystal (8) is a transparent quartz tube that surrounds the raw material rod (6) and the crystal rod (7), which is a molten zone (floating zone) where crystal growth takes place; It is filled with a suitable atmosphere gas.

In eye crystal growth by concentrated light heating using the above device, each of the first and second focal points F of each spheroidal mirror (1) and (2),
The infrared rays emitted from the infrared lamps (3) and (4) placed at ,F, , are reflected by the spheroidal mirrors (1) and (2), and the infrared rays are reflected at the focal point F.

The tip of the leaf is heated centrally in the heated part (5) located at the top of the leaf.

The heated part (5) is melted by the radiant energy of this infrared irradiation, and the raw material rod (6) and crystal rod (7) are rotated to perform sufficient stirring and soaking radiation while lowering in the vertical direction. Single crystal growth is performed by

By the way, in order to melt a crystal material, there is a method of heating with a high frequency coil using the principle of high frequency induction heating.

In this method, when the material is an insulator, that is, has a high electrical resistance, a crucible is formed using metal, graphite, molybdenum silicide, etc., and the crucible is heated by high-frequency induction to melt the material inside. In this method, a susceptor made of a similar metal, graphite, or molybdenum silicide ring is prepared, the crucible containing the material is surrounded, and the susceptor is heated by high-frequency induction. Therefore, the concept will be explained with reference to FIG. 9. In a suitable atmospheric gas, a crystal rod (10) extending vertically downward from above and a high frequency heating coil (11' located below)
The raw material (
9''), by pulling up the crystal rod (10) in the vertical direction while rotating it,
This method grows single crystals and is called the Czochralski method.

Further, the crystal material is preferably a conductor, that is, one with low electrical resistance. If the electrical resistance is high, the composition is improved by preheating or adding metal to reduce the electrical resistance, and then directly high-frequency heating is performed.

On the other hand, as a method other than the above-mentioned Chickralski method, there is a floating zone method that does not use a crucible, and high-frequency induction heating is also used in this case. That is, an example of silicon single crystal growth will be explained with reference to FIG. 7 or FIG. 8. First, a raw material rod (9) extending vertically downward from above and a crystal rod (10) extending vertically upward from below are arranged facing each other in a suitable atmospheric gas, and the surrounding area between the raw material rod (9) and crystal rod (10) is A high frequency coil is placed in the By the way, since the silicon raw material rod (9) is an electrical insulator until it reaches a high temperature, it cannot be directly heated by high frequency induction. Therefore, an auxiliary heating a (12) made of a conductive material such as graphite is placed in advance near the bottom of the raw material rod (9),
Conductive auxiliary heating R (12) using the high frequency coil (11)
) is heated by high-frequency induction, and the heated auxiliary heating source (
The lower end of the raw material rod (9) is indirectly heated or melted by the radiant energy of 12). When exposed to high temperatures, silicon's electrical resistance decreases and it becomes electrically conductive.
The raw material rod (9) can be heated by high frequency induction. Therefore, when the lower end of the raw material rod (9) melts as described above, the auxiliary heating source (12) is removed, the raw material rod (9) and the crystal rod (10) are butted together, and the high frequency A melting zone (floating zone) is formed by high-frequency induction heating by a coil (11), and single crystal growth is performed by lowering the raw material rod (9) and crystal rod (10) in the vertical direction while rotating them.

At present, single crystal growth by optical heating using the above-mentioned infrared lamps (3) and (4) uses electrically insulating materials with a melting point of around 2000°C and a diameter of 0.5°C. The growth of small-diameter single crystals of about 5 inches is the limit, and it has been difficult to grow large-diameter single crystals, which have been increasingly requested in recent years.On the other hand, the Czochralski one-way 0s method using high-frequency induction heating using a high-frequency coil has been difficult.
In rr crystal growth, a large diameter single crystal of 6 to 8 inches is grown in the case of silicon, and a large diameter single crystal of 3 to 4 inches is grown in the case of oxide, which is an electrical insulator. has been done. However, in this case, since the crucible (26) is heated, there are drawbacks that impurities from the crucible (26) are mixed in, and raw materials of high melting point substances such as oxides cannot be melted at a temperature higher than the melting temperature of the crucible material.

Furthermore, in the case of silicon, large-diameter single crystals of 3 to 4 inches are grown by floating zone type single crystal growth using high frequency induction heating using a high frequency coil. However, since high-melting-point substances such as oxides with high electrical resistance are electrical insulators, it is difficult to perform high-frequency induction heating directly, and when the melting point is high, the auxiliary heating source (12) is It was limited by the physical properties of time.

The present invention has been proposed in view of the above problem, and the technical means in the first invention to solve this problem is to heat the heated part between the raw material rod and the crystal rod by infrared rays. This is a single crystal manufacturing method in which a lamp is used to optically heat the material to melt it, and a heated portion that has been melted by the optical heating is subjected to high frequency induction heating using a high frequency coil to grow a single crystal.

Further, the technical means in the second invention includes a spheroidal mirror, an infrared lamp disposed at one focal point of the spheroidal mirror, a raw material rod and a raw material rod disposed at the other focal point of the spheroidal mirror. This single crystal manufacturing apparatus includes a high-frequency coil placed near the other focal point of the spheroidal mirror so as to surround the heated portion between the crystal rods.

According to this invention, even if the material is a high melting point oxide with great electrical insulation, the heated portion between the raw material rod and the crystal rod is first brought into contact with each other while being heated with light to melt and form a molten zone. can be done.

Furthermore, the volume of the melting zone can be increased by subjecting the melting zone to high-frequency induction heating in that state. Moreover, in this invention, optical heating and high-frequency induction heating can be performed without a crucible or an auxiliary heating source, and a large-diameter, high-quality single crystal can be produced without worrying about contamination of the melting zone.

An embodiment in which the present invention is applied to a biellipsoidal light reflection concentration type single crystal manufacturing apparatus will be described with reference to FIGS. 1 to 4. FIG. 1 is a cross-sectional view showing an example of an apparatus for implementing the present invention;
FIG. 2 is a sectional view taken along line A--A in FIG. 1. In the figure, (13) and (14) are two symmetrical spheroidal mirrors, which are coupled to face each other so that the focal points Fo, Fo of each mirror coincide, to form a heating furnace. The inner surfaces of the spheroidal mirrors (13) and (14), that is, the reflective surfaces, are gold-plated to reflect infrared rays with a high reflectance. (15) (16) are the other first and second focal points F of each spheroidal mirror (13) (14),
This is an infrared lamp, such as a halogen lamp or a xenon lamp, which is fixedly arranged at F2. (17) is a heated part placed at the coincident focal point FO of each spheroidal surface It (13) and (14), and the upper principal axis (
This is the part where the raw material rod (19) fixed to the lower end of 18) and the crystal rod (21) fixed to the upper end of the lower main shaft (20) extending vertically upward from below are butted together.

(22) is a high frequency coil placed near the focal point FO of the spheroidal surface &1llll (13) (14) so as to surround the heated portion (17). (23) is the raw material rod (
19) and the crystal rod (21), and a space (m2) where the infrared lamps (15) (i6) are arranged, forming a sample chamber (24). A quartz plate is used to fill the sample chamber (24) with an atmospheric gas suitable for crystals, and to safely light the infrared lamps (15) and (16) using the quartz plate (23). The infrared lamps (15) (16) are air cooled.

In the rod crystal growth according to the present invention, the spheroidal mirror (13)
(14) The first and second focal points F1. The infrared rays emitted from the infrared lamp (15) (1G) placed at F2 are reflected by the spheroidal mirror (13) (14), and the leaves are directed to the heated part (17) placed at the focal point FO. Lightly heat it first. The lower end of the raw material rod (19) and the upper end of the crystal rod (21) are heated and melted by the radiant energy from this infrared irradiation, and are brought into contact with Nissin, thereby forming a bond between the raw material rod (19) and the crystal rod (21). A melting zone (floating zone), that is, a heated portion (17) is formed. Once this heated part (17) undergoes f4vIAi,
It is known that even electrically insulating materials, especially raw material rods such as oxide ceramics, have low specific resistance and are electrically conductive. Therefore, high frequency induction heating becomes possible. Therefore, the heated part (17) is further subjected to high-frequency induction heating by a high-frequency coil (22), and the high-frequency energy absorbed by the heated part (17) forms a larger-volume melting zone, and the raw material rod (19) Large-diameter single crystal growth is performed by lowering the crystal rod (21) in the vertical direction while rotating the crystal rod (21).

Melt formed in the heated portion (17) -! 418: The castle is equipped with infrared lamps (15) (16) as shown in Figure 3.
), and is also subjected to high-frequency induction heating by a high-frequency coil (22). Specifically, in the central part (A1) of the melting zone, the high-frequency induction heating is mainly performed by the high-frequency coil (22). In addition, since the upper part of the melting zone (A2) is at a temperature just below the melting point due to heat conduction from the central part (A1), the energy difference until melting is heated by the infrared lamps (15) and (16). This is the part that is being replenished and melting. Furthermore, in the lower part of the melting zone (A3), in addition to the energy from high-frequency induction heating, energy from optical heating is given, and the melting zone expands by the increase in energy due to this optical heating, allowing for the growth of large-diameter single crystals. It becomes realizable. In this large-diameter single crystal growth, the high-frequency coil (22) is arranged around the molten zone of the heated part <17), so the Lorentz force generated from the high-frequency coil (22) causes the molten zone to become Since it is pressed to the center as shown by the broken line arrow in Figure 3, it is held in the shape shown without sagging by the own vehicle, making it easy to grow a large-diameter single crystal.

At the start of the above-mentioned crystal growth, a molten zone is formed by butting the raw material rod (19) whose tip has been melted by light heating with the crystal rod (21), but at this time, the crystal rod (2
If the temperature in i) is relatively low, when the molten tip of the raw material rod (19) and the crystal rod (21) are combined, the molten tip will solidify), so as a step to prevent this, As shown in FIG. 4, a melt material (25) of the same quality as the sword-shaped raw material rod may be placed on the crystal rod (21). That is, if the melt material (25) is provided,
At the start of single crystal growth, the tip of the raw material rod (19) is melted by optical heating, and the melt material (2) on the crystal rod (21) is melted.
5) is also melted to form the raw material rod (19) and crystal rod (21).
It becomes easy to form a molten zone by butting the two.

Moreover, the high frequency coil (22) has a spheroidal surface tA(1
3) The high-frequency coil (22) is placed near the focal point Fo in (14), but in practice, the high-frequency coil (22) is placed slightly below the focal point Fo in order to sequentially melt the raw material rods by infrared irradiation focused on the focal point Fo. It is considered desirable to place Furthermore, the high-frequency coil (22) may be arranged so that it can move up and down by a small amount.

In the above embodiment, two spheroidal mirrors (13)
(14) has been described, but the present invention is not limited to this, and the present invention can also be applied to a single ellipse or a furnace with three or more spheroidal mirrors assembled. Of course, it is applicable.

If the present invention is carried out, light heating by the first light heat source,
Even high-melting-point insulating materials such as oxides, which was previously impossible with high-frequency induction heating, can now be heated and melted, and can be melted without a crucible. Furthermore, since high-frequency induction heating is performed as a second heat source, it is possible to grow large-diameter single crystals that cannot be obtained by optical heating alone. In this way, the advantages and disadvantages of optical heating and high-frequency induction heating can be complemented, making it possible to manufacture high-quality single crystals, which was previously difficult to achieve.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of an apparatus for implementing the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIG. FIG. 4 is an enlarged front view of the main part for explaining single crystal growth using a melt material. FIG. 5 is a vertical cross-sectional view showing a conventional single crystal manufacturing apparatus using optical heating with an infrared lamp;
Figure 6 is a cross-sectional view taken along the line B-B in Figure 5, and Figures 7 and 8 are enlarged views of the main parts to explain floating zone method single crystal growth using high-frequency induction heating using a high-frequency coil. The front view and FIG. 9 are enlarged front views of main parts for explaining Czochralski one-type single crystal growth using high-frequency induction heating using a high-frequency coil. (13) (14) - - Rotary ellipse boundary, (15)
(16) - Infrared lamp, (17) - Heated part, (
19) -Abrasion rod, (21) -Crystal rod, (22)-・
-High frequency coil, Fo, F,, F2. - Image point.

Claims (2)

[Claims] (1) The heated portion between the raw material rod and the crystal rod is optically heated and melted using an infrared lamp, and the heated portion that has been melted by the optical heating is subjected to high-frequency induction heating using a high-frequency coil to grow a single crystal. A method for producing a single crystal by optical/high frequency induction heating, characterized by: (2) A heated portion between a spheroidal mirror, an infrared lamp placed at one focal point of the spheroidal mirror, and a raw material rod and a crystal rod placed at the other focal point of the spheroidal mirror. 1. An optical-high-frequency induction heating single crystal production apparatus comprising: a high-frequency coil placed near the other focal point of the spheroidal mirror so as to surround the ellipsoidal mirror.