JPH0699222B2 - Crucible for single crystal production - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crucible for producing a single crystal used in a method for producing a silicon single crystal by the Czochralski method.

"Prior art" Generally, in this type of crucible, the inner surface of the crucible reacts with the molten silicon to be deteriorated during the production of a single crystal, and high heat causes thermal fatigue inside the crucible to cause deterioration such as strength reduction. Occurs. In addition, after the production of the single crystal, the molten silicon remaining in the crucible is solidified, and the volume change occurring at that time may destroy the crucible. For this reason, such a crucible cannot be reused and must be discarded and replaced with a new one each time a single crystal is manufactured. In this case, there is no problem if the crucible is inexpensive.

"Problems to be solved by the invention" However, the crucible used in this manufacturing method should be able to directly hold a high temperature silicon melt (1400 ° C or higher) and have heat resistance, and the material should be a silicon melt. Even if it melts, it does not affect the purity of the melt,
It is integrally molded using expensive high-purity quartz. Also,
Since the raw material to be melted is usually silicon in the form of granules, powder, lumps, rods, etc., the crucible's internal volume should be able to hold a volume of the raw material that is 2 to 3 times the volume of molten metal required to produce a single crystal. Since it is set to, the crucible is relatively large. Therefore, discarding such an expensive crucible each time a single crystal is manufactured is wasteful and costly.

"Means for Solving Problems" A crucible for producing a single crystal according to the present invention comprises a bottomed cylindrical crucible lower body and a cylindrical crucible upper body separably disposed on the crucible lower body. It is characterized by

In addition, the crucible upper body and the crucible lower body may be formed of materials different from each other.

Further, the inner diameter of the crucible upper body may be formed to be slightly larger than the inner diameter of the crucible lower body.

[Operation] In the crucible for producing a single crystal of the present invention, the crucible upper body does not come into contact with the melt at high temperature and therefore does not deteriorate even after being used for producing the single crystal. Therefore, the crucible upper body can be detached, washed, and combined with a new crucible lower body so as to be used again and again.

Further, by forming the crucible upper body and the crucible lower body from materials having different thermal conductivities, the temperature gradient in the vertical direction in the crucible during heating can be appropriately changed, thereby adjusting the growth rate of the single crystal and the like. It is possible.

In addition, by making the inner diameter of the crucible upper body slightly larger than the inner diameter of the crucible lower body, even when a slight deviation occurs between the upper body and the lower body, impurities such as silicon monoxide are added to the lower end of the crucible upper body. Can be prevented from adhering.

[Example] Hereinafter, a crucible for producing a single crystal according to an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side sectional view of a single crystal manufacturing apparatus using a crucible for manufacturing a silicon single crystal according to an embodiment. In the figure, reference numeral 1 is a furnace body, and a shaft 2 which is rotated by a motor (not shown) is provided at the center of the furnace body 1. A cylindrical graphite susceptor 3 having a bottom is attached to the upper end of the shaft 2, and a crucible 4 is housed inside the graphite susceptor 3.

The crucible 4 includes a crucible lower body 4a having a bottomed cylindrical shape, and a cylindrical crucible upper body 4b that is separably mounted thereon. Both the crucible lower body 4a and the crucible upper body 4b are molded from high-purity quartz, and both are detachably held by the graphite susceptor 3. The crucible lower body 4a has an internal capacity capable of holding an amount of molten silicon required for producing a single crystal. On the other hand, the crucible upper body 4b, in a state of being combined with the crucible lower body 4a, in a granular form (or powder form, sufficient to generate the required amount of molten metal).
The internal volume is such that it can hold silicon raw materials in the form of lumps, rods, etc.

Further, a heater 5 for heating the crucible and a heat insulating material 6 are arranged on the outer periphery of the graphite susceptor 3. Further, a pulling mechanism (not shown) is provided above the furnace body 1, and a pulling wire 8 having a seed 7 attached to its tip is moved up and down. Then, this seed 7 is melted 9
After being dipped in, the single crystal ingots 9A successively grown from the seed 7 as a starting point can be pulled up.

Next, a method of using the crucible 4 for producing a single crystal described above will be described.

First, as shown in FIG. 2 (a), a necessary amount of granular silicon raw material 10 is put in the crucible 4 and heated by the heater 5. Then, the silicon raw material 10 is sequentially melted from the bottom to become the molten silicon 9 as shown in FIG. 2 (b), and its liquid level rises to a position slightly lower than the upper edge of the crucible lower body 4a.

In this state, as shown in FIG. 1, the single crystal ingot 9A is pulled up. In the process, the inner surface of the crucible lower body 4a reacts with the molten silicon 9 and is exposed to high temperature. Fatigue occurs and deteriorates. On the other hand, crucible upper body 4b
Does not directly contact the molten metal 9, so that such deterioration does not occur.

After each part is cooled after pulling the single crystal, the upper body 4b and the lower body 4a of the crucible are taken out from the susceptor 3, and the upper body 4b is washed successively with a hydrofluoric acid / nitric acid mixed solution and an organic solvent, and the surface thereof. The impurities adhering to the are removed.
By doing so, the crucible upper body 4b can be reused, and single crystal production can be performed again by combining with the new crucible lower body 4a. Further, by repeating this operation, the crucible upper body 4b can be used repeatedly as many times as desired.

According to the crucible 4 for producing a single crystal having such a structure, even if the crucible lower body 4a becomes unusable, the crucible upper body 4b is obtained.
Since it can be reused by washing, it is not necessary to discard the entire crucible every time a single crystal is manufactured unlike the conventional crucible, and the expensive high-purity quartz that is the material of the crucible is not wasted, The manufacturing cost can be reduced accordingly.

Although the crucible upper body 4b and the lower body 4a are both made of quartz in the above-mentioned embodiment, they may be made of different materials. For example, if the crucible lower body is made of quartz and the crucible upper body is made of a material such as metal having a higher thermal conductivity than quartz, the heat dissipation effect from the crucible upper body is enhanced and the growth of the silicon single crystal rod is increased. It is possible to increase the temperature gradient in the part and accelerate the growth of the single crystal ingot. On the contrary, if the crucible upper body is made of a material such as carbon, which is made of quartz and has low thermal conductivity, the heat dissipation effect from the crucible upper body is reduced, and the thermal gradient of the single crystal growth portion is reduced. Can be reduced and the frequency of dislocation generation in the crystal can be reduced.

In addition, the material of the crucible upper body is not required to have a higher quality than that of the crucible lower body, because there is no possibility of melting into the silicon melt. Therefore, the crucible upper body can be molded from an inexpensive material, and in that case, the cost of the crucible itself can be reduced. Furthermore, by configuring the crucible upper body from a plurality of members made of various materials,
It is also possible to finely adjust the temperature gradient in the crucible.

By the way, in the above-mentioned embodiment, the inner diameter of the crucible upper body 4b and the inner diameter of the crucible lower body 4a were made equal.
If the joint between the upper body 4b and the lower body 4a is misaligned as shown in the figure, silicon monoxide will adhere to the part where the lower edge of the crucible upper body 4b protrudes inward of the crucible (the part indicated by the arrow a in the figure). Then
This may later fall into the molten metal 9 and disturb the crystal structure.

FIG. 4 shows another embodiment of the present invention which solves this problem. In this embodiment, the crucible upper body 11b has the same outer shape as the crucible lower body 11a and is formed to be slightly thinner. It is characterized by As a result, the crucible upper body 11b
The inner diameter of is slightly larger than the inner diameter of the crucible lower body 11a, and even if there is some deviation between the upper body 11b and the lower body 11a, the lower end edge of the upper body 11b does not protrude inward of the crucible. Therefore, according to such a crucible, not only can the silicon monoxide be prevented from adhering to the lower end edge of the crucible upper body 11b, but the crucible upper body 11b was made thinner than the above-mentioned embodiment, so that the manufacturing amount was increased. The cost can be reduced.

Further, the single crystal production crucible of the present invention is not limited to the silicon single crystal crucible using the Czochralski method, but by appropriately changing the materials of the crucible upper and lower bodies, other compound single crystals, etc. It can be used for manufacturing, and in that case, the same effect can be obtained.

"Experimental Example" Next, an experimental example will be given to further clarify the effect of the present invention.

(Experimental Example 1) Crucible (crucible diameter 250 mm, overall crucible height 190 mm, crucible lower body height 100 mm, crucible upper body height 90)
mm, both made of high-purity quartz), 8 kg of raw material silicon was put and melted to obtain a molten metal having a depth of 80 mm. Then, a single crystal rod was pulled out from this molten metal as usual.

After the production of the single crystal was completed, the crucible upper body and the crucible lower body were extracted from the susceptor, and the crucible lower body was discarded, while the crucible upper body was washed with a hydrofluoric acid / nitric acid mixture solution and an organic solvent such as acetone. As a result, it was confirmed that the upper crucible body can be used again for producing a silicon single crystal, and that the same operation can be repeated to reuse the crucible body 5 times or more.

(Experimental Example 2) A crucible upper body was formed from molybdenum molybdenum having a higher thermal conductivity than that of quartz, and a single crystal was produced under the same conditions as in Experimental Example 1. The pulling rate was 1.6 m.
m / min. was achieved. This is faster than the pulling rate of 1.3 mm / min. When the conventional quartz crucible is used.

"Effects of the Invention" According to the crucible for producing a single crystal of the present invention, the following effects can be obtained.

By reaction with the melt in the crucible or thermal fatigue,
Even when the lower crucible becomes unusable, the upper crucible does not come into contact with the melt and therefore does not deteriorate. Therefore, the crucible upper body can be repeatedly reused, and the cost can be reduced accordingly.

By molding the crucible upper body and the crucible lower body from materials having different thermal conductivities, the vertical temperature gradient in the crucible can be appropriately changed. For example, when a crucible obtained by molding a crucible upper body with a material having high thermal conductivity (high heat dissipation effect) is used for manufacturing a single crystal, the temperature gradient in the single crystal growth portion is increased to increase the temperature of the single crystal. It is possible to increase the growth rate. Conversely, by molding the crucible upper body from a material having low thermal conductivity (high heat retention), the thermal gradient in the single crystal growth portion can be reduced and the frequency of dislocation generation in the single crystal can be reduced. Further, since the upper body of the crucible is not required to have higher purity than the lower body, it can be molded from an inexpensive material and the cost of the crucible itself can be reduced.

[Brief description of drawings]

FIG. 1 is a side sectional view of a manufacturing apparatus using a crucible for manufacturing a single crystal according to an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are side sectional views for explaining the operation of the crucible. is there. Further, FIG. 3 is a side sectional view showing a problem of the above embodiment, and FIG. 4 is a side sectional view of a crucible for producing a single crystal of another embodiment of the present invention which solves the problem. 4 ... crucible for single crystal production 4a ... crucible lower body 4b ... crucible upper body 11a ... crucible lower body 11b ... crucible upper body

Claims (3)

[Claims] 1. A crucible for producing a single crystal, comprising: a crucible lower body having a bottomed cylindrical shape, and a cylindrical crucible upper body that is separably disposed on the crucible lower body. 2. The crucible for producing a single crystal according to claim 1, wherein the crucible upper body and the crucible lower body are formed of materials different from each other. 3. The crucible for producing a single crystal according to claim 1 or 2, wherein the inner diameter of the crucible upper body is slightly larger than the inner diameter of the crucible lower body.