JPS6251179A - Lamp for infrared concentrated heating furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heating lamp used in a floating zone melting single crystal production apparatus using an infrared concentrated heating method, and more specifically,
The present invention relates to a lamp in which the temperature distribution on the surface of a sample can be adjusted by combining a main filament located at the focal point of a furnace and a sub-filament located away from the focal point.

[Prior Art] In an infrared concentrated heating furnace, a halogen lamp or the like serving as a light source is arranged at one focal point of a spheroidal mirror, and a transparent quartz tube is inserted through the other focal point. A rod-shaped sample is inserted inside the rod-shaped sample, and the infrared energy from the lamp is concentrated on a part of the rod-shaped sample to locally heat and melt it.
This is a device that grows crystals by moving a rod-shaped sample in its longitudinal direction. In the prior art, the lamps used as light sources only have a single filament, which is installed in such a way that it is located on one focus of the spheroidal mirror. Single crystals such as ferrite are produced using this type of apparatus.

Infrared concentrated heating furnaces have the advantage of being able to easily control the atmosphere that is essential for producing single crystals, being highly energy efficient, and being easy to handle as the heating is concentrated in the necessary areas. However, in order to keep the solid-liquid shape stable so that the molten sample does not drip inside the furnace, it is necessary to narrow the melting zone, and the infrared rays must be concentrated within a narrow region. In other words, the temperature gradient becomes very steep near the edge of the melting zone and on both sides thereof. As a result, especially due to the steep temperature gradient on the growing crystal side, thermal strain and cracks occur in the produced single crystal, and many growth stripes and lattice defects occur, which tends to cause a decrease in the quality of the crystal.

In order to produce high-quality crystals, a two-bath method is used, in which after crystal growth is performed, the sample is inserted into a heating furnace with a small temperature gradient for heat treatment, or in the case of one-bath method, a transparent quartz tube is used. An after-heater method is adopted in which an auxiliary heater is installed inside the crystal on the growing crystal side to gently control the temperature gradient.

[Problems to be Solved by the Invention] However, in the two-pass method as described above, since the single crystal must be passed through the heating furnace twice, the time required to produce the single crystal becomes extremely long and the cost increases.

In addition, in the one-bath method using an afterheater, an alumina cylinder wrapped with platinum wire must be inserted between the transparent quartz tube and the growing crystal, resulting in a complicated internal structure of the transparent tube and a reduction in its cross-sectional area. cannot be used effectively,
As a result, the transparent quartz tube becomes large and expensive, or it has the disadvantage that only small-diameter crystals can be produced. Furthermore, it is difficult to control the heater current to provide a predetermined temperature gradient in the growing crystal.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, and to eliminate the need for an auxiliary heater inside a transparent quartz tube or the like.
An object of the present invention is to provide a lamp for an infrared concentrated heating furnace that can easily control a temperature gradient to be gentle and produce high-quality crystals.

[Means for Solving the Problems] The configuration of the present invention capable of achieving the above-mentioned objects is such that, as a lamp that emits infrared rays in an infrared concentrated heating furnace, a main filament and a main filament located on one focal point of a spheroidal mirror are used. ,
It is equipped with a sub-filament located slightly away from the focal point, and by combining a plurality of these filaments, it is possible to adjust the temperature distribution on the sample surface.

The main filament, like the filament of a conventional lamp, has the ability to heat and melt a portion of a rod-shaped sample by itself, and the sub-filament has less radiant energy than the main filament.

Since the area where energy is concentrated differs depending on the position of the sub-filament, the position and the radiant energy are set to optimal conditions taking into consideration the temperature distribution desired to be formed on the sample surface. For example, when the sample is inserted into the spheroid mirror from above and the growing crystal is located below the melt zone, the growing crystal side can be heated by placing the sub-filament above the main filament.

[Action Infrared energy from the main filament is concentrated in a part of the rod-shaped sample, locally heated and melted, and crystal growth occurs. The infrared rays generated from the sub-filament provided at a position slightly deviated from the focal point irradiate an area that is also deviated from the other focal point by the amount that it is deviated from the focal point. If that area is set on the growing crystal side, it will be heated by the secondary filament, so the temperature of that area will rise and the temperature gradient on the growing crystal side will be gentle (
It is possible to form an asymmetric temperature distribution. As a result, good crystal growth can be achieved even in a one-pass method.

[Example] FIG. 1 is an explanatory diagram showing an example of the lamp IO for an infrared central heating furnace according to the present invention. The lamp 10 includes a main filament 12 and a sub-filament 14 therein,
It has a structure sealed inside a transparent tube 16. Here, the main filament I2 and the sub-filament 14 are connected in parallel. The resistance R of the main filament 12 is comparable to that of a conventional single filament, and is much smaller than the resistance R8 of the sub-filament 14. Furthermore, the structure is such that when installed in a heating furnace, the main filament 12 can be installed exactly on one focal point of the spheroidal mirror.

An example of an infrared concentrated heating furnace incorporating such a lamp 10 is shown in FIG. The basic configuration of the heating furnace is the same as that of the prior art except for the difference in the structure of the lamp 10. That is, the lamp 10 is placed at one focal point of the spheroidal mirror 20, and the transparent quartz tube 22 is inserted through the other focal point. A rod-shaped sample 24 is inserted into the transparent tube 22, and its upper and lower ends are each held by an elevating and rotating support device 26.

As mentioned above, the lamp 10 according to the present invention is mounted so that its main filament 12 is located exactly on the focal point of the spheroidal mirror 20, and the secondary filament 14 is located slightly above the focal point.

Infrared rays from one corner of the main filament 12 of the lamp 10 are transmitted directly or reflected by the spheroidal mirror 20 to the transparent tube 22.
The rod-shaped sample 24 located near the other focal point is locally heated to form a melt zone 28. Crystal growth begins by first placing a seed crystal near the melting zone. By gradually moving downward while rotating the upper and lower parts in opposite directions using the vertically rotating support device 18, the melt zone 28 in the rod-shaped sample 24 gradually moves, and accordingly, the region after melting continues crystal growth. .

Now, in the present invention, the infrared rays emitted from the secondary filament 14 above the main filament 12 are transmitted to the spheroidal mirror 20.
It is reflected by the other focal point and irradiates it over a somewhat wide range at a position slightly below the other focal point. This gives thermal energy to the growing crystal side, increases the temperature of the bottom part, and makes it possible to gently control the temperature gradient.

This situation is shown in FIG. 3. In the figure, the curve with a steep peak indicated by the broken line E is the temperature distribution obtained by the main filament alone. To put it bluntly, this is a temperature distribution that corresponds to the conventional technology. As a result, a steep temperature gradient having a peak between section A and B is provided, and a melt zone 28 is formed in a part of the rod-shaped sample 24. The curve below that indicated by the broken line F represents the temperature distribution given to the sample by the sub-filament 14, and the sample is heated gently and over a wide range in the section CD. In reality, these are superimposed on the rod-shaped sample, resulting in a temperature distribution as represented by the solid line G. For this reason, the growing crystal side 28 has a gentle temperature gradient, unlike the case of only the main filament (in the conventional case) as represented by curve E, thereby preventing the occurrence of thermal strain and cracks, and preventing growth streaks and various lattice defects. It is possible to grow high-quality crystals with a small amount of carbon in one bath.

Although a preferred embodiment of the present invention has been described above in detail, the present invention is not limited to this structure. In the above embodiment, there is only one sub-filament, but it is also possible to arrange two or more sub-filaments in parallel depending on the temperature distribution to be provided. The ratio of electrical resistance of the secondary filament to the main filament and its positional relationship can be changed as appropriate depending on the temperature gradient to be applied.9For example, if the position of the secondary filament is moved higher relative to the main filament in The filament allows the area to be irradiated to move further downward and to widen the irradiation range.

Furthermore, the main filament and the sub-filament do not necessarily need to be connected in parallel; the current may be controlled independently to form a desired temperature distribution.

[Effects of the Invention] As described above, in the present invention, the temperature distribution can be adjusted by providing the sub-filament at a position shifted from the main filament located on the focal point, so there is no sharp temperature gradient in the fusion zone. The temperature gradient on the growing crystal side can be gently controlled while stably maintaining a certain amount of melt zone by imparting a The pass method has the excellent effect of being able to grow high-quality crystals without growth stripes or lattice defects.

In addition, since it is only necessary to attach a lamp containing a sub-filament, conventional crystal manufacturing equipment can be used as is, so there is no equipment cost, and the equipment is much simpler than an after-heater or the like.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of an infrared central heating furnace lamp according to the present invention, Fig. 2 is an explanatory diagram showing an example of an infrared central heating furnace incorporating the lamp, and Fig. 3 is an explanatory diagram showing an example of an infrared central heating furnace incorporating the lamp. It is an explanatory view showing an example of temperature distribution in the case of. 10...Lamp, 12...Main filament, 14.
・・Secondary filament, 20・・Spheroidal mirror, 22・・
- Transparent tube, 24... Rod-shaped sample, 2G... Elevating and rotating support device, 28... Melting zone. Patent applicant Fuji Electrochemical Co., Ltd. Agent Shigeru Estimate Figure 1 Figure 2

Claims (1)

[Claims] 1. An infrared concentrated heating furnace lamp comprising a main filament located on one focal point of a spheroidal mirror and a sub-filament located slightly away from the focal point.