JPH01119593A - Crystal growing device - Google Patents

Abstract

PURPOSE:To prevent the drop of a molten metal temp. arising from charging of raw materials by providing a stagnating part for stagnating the raw materials for a specified period of time to a supplying pipe for supplying the raw materials to the molten metal in a crucible. CONSTITUTION:Polycrystals are melted to form the molten metal Y in the 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 through the supplying pipe 10 according to the pulling up amt. of the crystal. The stagnating part 11 which is, for example, a T-pipe part is formed to the bottom end of the supplying pipe 10 and the horizontal length and bore of said part are so set that the raw materials coming down in the pipe 10 stagnate for the desired period of time in the stagnating part 11 and are then dropped successively to the molten metal Y without allowing only the part thereof to remain. The raw materials are thereby stagnated for the prescribed period of time in the stagnating part 11 and are dropped to the molten metal; therefore, the time when the raw materials receive radiant heat during this time is long and the raw materials are subjected to efficient heat transfer by the contact with the inside base of the stagnating part 11. The raw materials are therefore largely heated up before the raw materials fall to the molten metal Y.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a crystal growth apparatus used for producing 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 m decreases due to crystal pulling, the contact area between the molten metal and the quartz crucible changes, and the oxygen elution m from the crucible changes. However, recently, strict tolerance standards have been set for both oxygen concentration and dopant concentration for silicon single crystals used as semiconductor device substrates, and for this reason, only a portion of the pulled single crystal can be used as semiconductor devices. However, there was a problem that the yield of raw materials was poor.

Therefore, in order to improve this problem, granular silicon raw materials are sequentially supplied into the crucible through the supply pipe depending on the amount of crystals to be pulled. Various devices have been proposed in the past that maintain n rA constant and prevent changes in elution conditions (for example, Japanese Patent Publication No. 57-40119).

"Problems to be Solved by the Invention" However, in the above-mentioned apparatus, the low-temperature raw material is directly charged into the high-temperature molten metal (approximately 1400°C), which lowers the molten metal temperature and has a negative effect on crystal growth. was there. In particular, when the crucible is small or when the pulling speed is set higher than usual to speed up the growth of the single crystal, the temperature of the molten metal may drop significantly, and the raw materials introduced may not be completely melted or the periphery of the molten metal may The drawback is that the soluble material starts to solidify.

Therefore, a configuration has been proposed in which a heater is attached to the raw material supply mechanism to preheat the raw material before inputting the raw material, but this increases the cost of the device and inevitably increases the complexity and size of the device.

"Means for Solving the Problems" The present invention has been made to solve the above problems, and includes providing a retention section for retaining the raw materials for a certain period of time in the supply pipe for supplying the raw materials to the molten metal in the crucible. This is characterized by raising the temperature of the raw material in the furnace atmosphere and preventing the temperature of the molten metal from decreasing as the raw material is introduced.

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 (not 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 reference numeral 10.

This supply pipe IO is made of quartz and has a circular cross section connected to the raw material supply mechanism (not shown) at the base end, is fixed through the wall of the furnace body, is bent downward within the furnace body 1, and is The lower end is positioned near the inner peripheral surface of the crucible 6 and slightly above the molten metal Y. Then, the granular silicon raw material introduced from the raw material supply mechanism is dropped into the molten metal Y. A T-shaped pipe section (retention section) 11 is formed at the lower end of this supply pipe 10, and the horizontal length and diameter of this single-shaped pipe section 11 are such that the raw material coming down the supply pipe IO is It is set so that it stays in Part II for a desired time and then falls into the molten metal Y one after another without leaving any part of it behind.

In the crystal growth apparatus having the above configuration, the raw material supplied by the raw material supply mechanism is supplied to the single-shaped pipe portion 1 formed at the lower end of the supply pipe 10.
1 for a predetermined time and then fall into the molten metal, the time for receiving radiant heat during this time is long, and the heat is efficiently transferred through contact with the inner bottom surface of the single-shaped tube portion 11. Therefore, the temperature of the raw material can be significantly raised before it falls into the molten metal Y, reducing the temperature difference between the raw material and the molten metal Y, effectively reducing changes in the temperature of the molten metal due to raw material input. Can be done.

Therefore, there is no problem that the input raw material is not completely melted or the molten metal Y is solidified, and the occurrence of crystal defects due to temperature changes in the single crystal growth area can be prevented.

In the following, the effect of the present invention will be clarified by calculating the temperature rise of silicon raw material particles due to radiant heat transfer. Particle size D
= 1 mm, and the emissivity ε of the silicon particle is 0.45, each parameter of the particle is as follows.

Surface area S=4πD”=3.142X 1O-8(R
') Volume V = 4/3π(D /2)3 = 5.24
X 10-” (m') Mass M=V-g=1.22X
10-' (kg) Heat capacity C= M-Cp= 8.3
x 10-' (J/°C) Particle temperature T 'C1If the Ar atmosphere temperature is 1000°C, then the radiation heat transfer received by the particles per second is 1kQ = 4.88S ε ((1273/100)'-((
T +273)/+00)')・103・4.187・
1/60”・t (J) Particle temperature rise ΔT=Q/C(
℃) When calculating the change in particle temperature over time due to radiant heat transfer using the above formula, the following result is obtained.

Initial temperature 25°C 1 second later... 276°C 2 seconds later...
510°C 3 seconds later...704604 seconds later...840°
C5 seconds later...920606 seconds later...962°C 7 seconds later...982°C8 seconds later...992°C9 seconds later...
・996°C 10 seconds later...998°C On the other hand, if a silicon particle is allowed to fall 50cm freely, it will fall into the molten metal in 0.32 seconds, and the temperature will only rise to about 100°C (calculated from the above formula) during this time. Therefore, by extending the falling time by a few seconds,
It is clear that the particles can be heated significantly. Moreover, the above calculation takes only radiant heat transfer into consideration; in reality, heat transfer due to contact with the high-temperature atmospheric gas inside the supply pipe IO and heat transfer due to contact with the inner surface of the supply pipe IO also occurs, so the residence time It is expected that the temperature increase effect due to extension will be even more pronounced.

Moreover, compared to a device in which a preheating heater is attached to the raw material supply mechanism, this device has the advantage that the implementation cost is low because it is only necessary to process the supply pipe IO, and the device is small and simple.

Furthermore, in this device, the falling speed of the particles decreases due to collision with the single-shaped tube part 11, so the vibration of the molten metal Y when the raw material is introduced is small, and the vibration causes defects such as dislocations in the crystal growth part of the single crystal. There is no fear. Therefore, from this point as well, it is possible to produce a high-quality single crystal.

It should be noted that the supply pipe of the present invention is not limited to the above-mentioned embodiment, but can also be implemented as shown in FIGS. 3 to 5.

FIG. 3 shows a configuration in which a gently sloped portion 12 of a constant length extending in the inner peripheral direction of the crucible 6 is formed at the lower end of the supply pipe 10, and the lower end opening is directed downward again, so that the raw material falling inside the pipe is ,
It is moved slowly along the gently sloped portion 12. According to this, the retention time can be easily adjusted by simply changing the angle and length of the gently sloped part 12, and since the gently sloped part 12 is close to the molten metal, the raw material in the supply pipe IO receives a large amount of radiant heat. There is.

In FIG. 4, the lower end of the supply pipe 10 is closed in a hemispherical shape, and a large number of holes 13 are formed therein.

In FIG. 5, the lower end of the supply pipe IO is swollen into a spherical shape to form a reservoir 14, and a small hole 15 is formed in the lower end surface of the supply pipe IO. By setting the neck method, the residence time of raw materials can be significantly extended.

Note that the present invention is not limited to the above-mentioned embodiments, and the above-mentioned embodiments can be combined or modified as appropriate.

"Effects of the Invention" As explained above, in the crystal growth apparatus of the present invention, the raw material descends in the supply pipe over time due to the action of the retention section, so that the amount of radiant heat received by the raw material and other heat transfer m are reduced. big. Therefore, it is possible to significantly raise the temperature of the raw material before it falls into the molten metal, and it is possible to effectively reduce changes in the temperature of the molten metal by adding the raw material, so that the raw material does not completely melt or the molten metal Y There is no problem of solidification,
Prevent crystal defects from occurring due to temperature changes in the single crystal growth area.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a silicon crystal growth apparatus according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a supply pipe used in the same apparatus, and FIGS. FIG. 1...furnace body, 6...crucible, 7...
Pulling wire, 10... Supply pipe, (hereinafter referred to as retention part) 11... T-shaped pipe part, 12... Gentle slope part, 13
...hole, 14...reservoir, 15...hole.

Claims (1)

[Scope of Claims] 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, characterized in that a retention section for retaining the raw material for a certain period of time is provided at the lower part of the supply pipe.