JPH01119594A - Crystal growing device - Google Patents

Abstract

PURPOSE:To prevent the waving and oscillating of a molten metal surface during falling of raw materials by providing a decelerating part which lowers the falling speed of the raw materials to the molten metal to a supplying pipe for supplying polycrystal raw materials to the molten metal. CONSTITUTION:The polycrystals are melted to form the molten metal Y in a crucible 6 and a pulling up wire 7 is raised to pull up an Si single crystal, etc., from the molten metal Y. The raw materials are supplied to the molten metal Y through the supplying pipe 10 according to the pulling up amt. of the crystal. Baffle plates 11 (decelerating part) made of quartz are alternately fixed at every specified interval respectively in the downward inclined state to, for example, the inside of the inclined part of the supplying pipe 10. The baffle plates 11 form spacings between the bottom end edges thereof and the inside surface of the pipe. The min. width T of these spacings is set at the size at which the raw material grains can easily pass the spacing and at the value which is so considered as to provide an adequate decelerating effect. The angle of inclination of the baffle plates 11 is so set that the raw materials do not stop during the course of falling and the speed at the time of falling to the molten metal Y attains a prescribed value or below.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a crystal growth apparatus used for manufacturing high-purity silicon single crystals and the like.

"Prior Art" In the production of silicon single crystals by the CZ method, as the molten metal type decreases due to crystal pulling, the contact area between the molten metal and a quartz crucible changes, and the amount of oxygen eluted from the crucible changes. However, recently, strict tolerance standards have been set for silicon single crystals used as semiconductor device substrates for both the oxygen interlayer and dopan 1-6 degrees, and for this reason, only a few of the pulled single crystals can be used as semiconductor devices. There was a problem that the yield of raw materials was poor because it was only a part of the process.

Therefore, in order to improve this problem, a device was developed in which the granular Noricon raw material was sequentially supplied into the crucible through the supply pipe according to the amount of crystals pulled to keep the melt 78 rJi constant and prevent changes in the elution conditions. Various proposals have been made so far (for example, Japanese Patent Publication No. 57-40119).

``Problems that no invention can solve'' However, in this type of equipment, the melting surface becomes undulating when the raw material falls, and the vibrations are transmitted to the growing single crystal 113, causing crystal defects such as dislocations. was there. As a countermeasure, attempts have been made to place a cylindrical partition between the single crystal rod and the raw material falling part (U
No. S-2892739, JP-A-57-183392
(No. 61-36197, etc.), in these as well, vibrations were transmitted to the single crystal growth area through the communicating holes connecting the inside and outside of the partitioning material, and the effect was not perfect. In addition, if such a partition is provided, a crucible with a larger diameter than usual is required because it is necessary to leave a gap between the single crystal bar and the partition, and a gap between the partition and the crucible, which makes it difficult to increase the depth of molten metal required for pulling. A large amount of silicon raw material is required in order to secure it, and the yield of the raw material is inevitably lower than in the case without partitions, which has the drawback of high manufacturing cost. In addition, silicon crystals tend to precipitate on the surfaces of the partitions, resulting in changes in crystal growth conditions and, in some cases, inhibiting single crystal growth.

"Means for Solving the Problems" The present invention has been made to solve the above problems, and includes forming a deceleration part in the supply pipe that supplies the polycrystalline raw material to the molten metal to reduce the rate at which the raw material falls into the molten metal. It is characterized by
This prevents ripples and vibrations on the molten metal surface when the raw material falls.

Embodiment FIG. 1 is a longitudinal sectional view showing an embodiment of a crystal growth apparatus according to the present invention.

In the figure, reference numeral 1 denotes a furnace body, 2 a heat insulator, 3 a heater, 4 a graphite susceptor fixed to the upper end of the rotating shaft 5, and 6 a quartz crucible fitted in the graphite susceptor 4. Above is a pulling wire 7 with a seed S fixed to its lower end.
A lifting mechanism (path shown) is provided to raise and lower the

The above configuration is similar to the conventional one, and the feature of the present invention lies in the raw material supply pipe indicated by the symbol 1O.

This supply pipe IO is made of quartz and has a circular cross section, and its base end is connected to the raw material supply mechanism (path shown in the figure). is positioned near the inner peripheral surface of the crucible 6 and slightly above the melt 7HY. The structure is such that the granular silicon raw material introduced from the raw material supply mechanism is dropped into the molten 4kY.

Inside the inclined portion of the supply pipe IO, as shown in FIGS. 2 and 3, quartz baffle plates 11 (reduction parts) are fixed at fixed intervals in a downwardly inclined state. has been done. These baffle plates 11 form gaps between their lower edges and the inner surface of the tube, and the minimum width T of these gaps is:
The size is such that the raw material granules can easily pass through, and the value has been taken into consideration so that an appropriate deceleration effect can be obtained. Further, the inclination angle of the baffle plate It is set in consideration of the inclination angle of the supply pipe 10 so that the raw material does not stop mid-fall and the speed at which it falls into the molten metal is below a predetermined value. There is.

According to the crystal growth apparatus having the above configuration, the raw material falling through the supply pipe IO collides with each baffle plate 11 and is deprived of interlocking energy, and is also refracted in a complicated path, so that it falls into the molten metal Y. It is possible to reduce the rippling of the molten metal Y. Therefore, it is possible to reduce the possibility of causing dislocations by applying vibrations to the crystal growth part of the single crystal, and to produce high-quality single crystals with few defects. It is possible to improve the yield of raw materials.In addition, compared to equipment with partitions inside the crucible, a smaller crucible can be used, so the cost of the crucible is lower and there is less leftover raw material. The yield is good and there are no problems such as crystals adhering to the partitions.

Furthermore, in the above device, since the residence time of the raw material in the supply pipe IO is extended, the raw material is preheated by the surrounding air inside the furnace body l,
It is possible to reduce the temperature change of the molten metal due to raw material input and prevent unnecessary recrystallization of the molten metal.

Note that FIG. 4 shows a modification of the above embodiment, in which the supply pipe 10
It is characterized in that a bifurcated tube portion 12 is formed at the lower end of the tube. In this way, the raw material is further decelerated due to collision with the bifurcated pipe section 12, and the falling points of the raw material are dispersed to reduce the melt iQ.
The effect of preventing Y ripples can be obtained. However, in this case, it is necessary to arrange the bifurcated tube portion 12 toward the circumferential direction of the crucible 6.

Further, FIG. 5 shows a modification in which the supply pipe IO is flattened and the baffle plate 11 is lengthened. In this case, the deceleration effect is improved, and the residence time of the raw material is further extended to enhance the heating effect.

In each of the above-described embodiments, the speed reduction section was configured by the baffle plate 11, but as shown in FIG. As shown in the figure, it is also possible to use the supply pipe IO by bending the entire pipe into a waveform, spiral shape, etc. to use it as a deceleration part, and with these, the manufacturing cost of the supply pipe can be reduced.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and the above-mentioned embodiments can be combined and modified, and it is also possible to obtain a more complete effect by combining with the method of providing partitions in the crucible described above. It is.

"Effects of the Invention" As explained above, in the crystal growth apparatus of the present invention, the speed of the raw material falling into the molten metal is reduced by the deceleration part formed in the supply pipe, so it is possible to reduce ripples in the molten metal. This makes it possible to reduce the possibility of causing dislocations by applying vibration to the crystal growth part of the single crystal. Therefore, it is possible to manufacture a high-quality single crystal with few defects, and the yield of raw materials can be improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a silicon crystal growth apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 are a cross-sectional view and a vertical cross-sectional view of a supply pipe. Moreover, FIGS. 4 to 7 are cross-sectional views showing supply pipes according to other embodiments of the present invention. l... Furnace body, 6... Crucible, 7...
Pulling wire, IO... supply pipe, (hereinafter referred to as deceleration part) 11... baffle plate, 12... bifurcated pipe part, 13
...Protrusion.

Claims (3)

[Claims] (1) A crystal growth device equipped with a crucible for melting polycrystals into a molten metal, a supply pipe for supplying a polycrystalline raw material to the molten metal, and a pulling mechanism for pulling up a single crystal from the molten metal in the crucible. A crystal growth apparatus according to the present invention, wherein the supply pipe is provided with at least one deceleration portion that reduces the rate at which the raw material falls into the molten metal. (2) The first aspect of the present invention is characterized in that the speed reducer is constituted by a baffle plate provided within the supply pipe.
Crystal growth apparatus described in Section 1. (3) The crystal growth apparatus according to claim 1, wherein the speed reduction section is constructed by bending a part of the supply pipe.