JP3158661B2 - Method and apparatus for producing high dissociation pressure single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates mainly to GaAs, Ga
III such as P, GaSb, InAs, InP, InSb
-V group compound semiconductor single crystal and CdTe, Hg _1-x Cd _x
The present invention relates to a method and an apparatus for producing a high dissociation pressure single crystal such as a II-VI compound semiconductor single crystal such as Te and ZnSe.

[0002]

2. Description of the Related Art A typical method for growing a high dissociation pressure single crystal is the LEC method. In a normal LEC method, crystal growth is performed in an inert gas such as nitrogen or argon. In these gases, if the temperature gradient in the direction of the growth axis is reduced to lower the dislocation density, decomposition will occur on the crystal surface and crystal defects will occur, making it impossible to grow crystals with a low dislocation density. Met.

In order to solve such a problem of the LEC method, a method for growing a crystal in an airtight container hermetically sealing a high dissociation pressure component gas as shown in FIG. 3 has been developed.
In this method, even if the temperature of the crystal becomes high, the decomposition reaction does not occur because of the high dissociation pressure component element gas atmosphere. Therefore, a crystal having a low dislocation density can be grown under a small temperature gradient. An example of this method is described in, for example, JP-A-60-3639.
7, and JP-A-63-215593.

[0004] This type of apparatus is generally constructed so that an airtight container can be divided into two parts so that grown crystals can be taken out. A method using a liquid sealant, a method using a solid gasket, a method for fitting, and the like have been devised to make the junction of the divided hermetic containers airtight. Among them, the easiest and airtight method is to use a liquid sealant.

[0005]

In a conventional apparatus of this type using a liquid sealant at a joint, after cooling the crystal to room temperature, the airtight container is divided and the crystal is taken out. However, at room temperature, the liquid sealant solidifies and fixes the joint of the airtight container, so the joint is damaged when the airtight container is split, or the shrinkage stress during cooling and solidification of the liquid sealant causes the container to break. And the life of the hermetic container was significantly shortened.

As the material of the airtight container, PBN (pyrolytic boron nitride), PG (pyrolytic graphite), vitrified carbon, SiC or a material obtained by coating them on a graphite base material is suitable. Since a strong strength is obtained and a container having a complicated shape can be easily manufactured, a material in which PBN (pyrolytic boron nitride), PG (pyrolytic graphite), vitrified carbon, SiC, etc. are coated on a graphite base material is used. Commonly used.

However, with such a material, the thin coating layer is damaged when the airtight container is divided, and the airtightness of the container is likely to be impaired. Further, there arises a problem that the graphite of the base material is exposed on the surface and contaminates the crystal material, and the life of the container is particularly short.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a high dissociation pressure element gas is sealed in an airtight container which is constructed so as to be dividable and has a structure in which a junction of the divided parts is sealed with a liquid sealant. A method for growing a single crystal in which a high dissociation pressure single crystal is grown in a container, wherein the junction of the hermetic container is divided at a temperature higher than the temperature at which the liquid sealing material solidifies, and the hermetic container is opened. This is a method for growing a high dissociation pressure single crystal. Suitably, the hermetic container is divided at a temperature not higher than 85% of the melting point of the crystal.

The high-dissociation pressure single crystal manufacturing apparatus of the present invention is configured such that a high-dissociation pressure component gas is sealed in an airtight container that is configured to be dividable and that has a structure in which the joint is sealed with a liquid sealant. In a single crystal growth apparatus for growing a high dissociation pressure single crystal in a container, a projection for supporting an upper airtight container is provided on a crystal pulling shaft. Further, the apparatus for producing a high dissociation pressure single crystal of the present invention is characterized in that an elevating operation rod is provided in an upper airtight container.

[0010]

According to the method and the apparatus of the present invention, the airtight container is divided before the liquid sealant is solidified and the joint of the airtight container is fixed. There is no breakage of the container due to shrinkage stress during cooling and solidification of the airtight container. In addition, the airtight container is coated with PBN (pyrolytic boron nitride), PG (pyrolytic graphite), vitrified carbon, SiC, etc. on a graphite base material. Since the coating is hard to be peeled off when made, the life of the airtight container is significantly prolonged.

Further, since coatings such as PBN (pyrolytic boron nitride), PG (pyrolytic graphite), vitrified carbon, and SiC are difficult to peel off, the graphite of the base material is exposed on the surface and contaminates the crystalline material. No problem such as
Since the raising and lowering operation of the upper airtight container is performed by using the projection or the raising and lowering operation rod provided on the crystal pulling shaft, it is possible to easily raise and lower the crystal growth without affecting the crystal growth.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus for producing a high dissociation pressure single crystal according to an embodiment of the present invention will be described with reference to FIG. In FIG. 1, a chamber 1 is provided with a pull-up shaft 2 that can be rotated up and down and a crucible rotation shaft 3. The airtight container provided in the chamber 1 is divided into an upper airtight container 4 and a lower airtight container 5. The lower airtight container 5 is attached to the upper end of the crucible rotation shaft 3, and can be rotated up and down together with the crucible by rotating the crucible rotation shaft 3 up and down.

Upper airtight container 4, lower airtight container 5, conduit 1
P and the material of the high-dissociation pressure component partial pressure control unit 11 are P
BN (Pyrolytic boron nitride), PG
(Pyrolytic graphite), vitrified carbon, SiC, and those obtained by coating them on a graphite substrate are suitable. In this case, a material obtained by coating PBN (pyrotic boron nitride) on a graphite substrate is used. did. Although the airtight container can be made of quartz, there are problems such as deformation of the container at high temperatures, contamination of the raw material with Si, and breakage of the liquid sealant reservoir when the liquid sealant solidifies.

A liquid sealant reservoir 6 is provided at the upper end of the lower hermetic container 5, and a liquid sealant 7 is stored therein. The lower end of the upper airtight container 4 is immersed in the liquid sealant 7, and the connection between the upper airtight container 4 and the lower airtight container 5 is kept airtight. A liquid sealant reservoir 8 is provided at a portion where the pulling shaft 2 penetrates the upper airtight container 4, and a liquid sealant 9 is provided.
Is stored, and the pulling shaft 2 is rotatably airtightly sealed. A protrusion 23 is provided at a tip portion of the pulling shaft 2, and the upper airtight container 4 can be lifted by pulling the pulling shaft 2 upward to be separated from the lower airtight container 5.

A high-dissociation pressure component partial pressure control unit 11 is attached to a part of the upper hermetic container 4 through a conduit 10, and a temperature is controlled by a heater 12 so that a desired high-dissociation pressure component Control to pressure. In the figure, reference numeral 13 denotes a solid raw material for supplying a necessary high dissociation pressure component element gas into the hermetic container. Quartz or P
A crucible 14 made of BN is held, and a raw material 15 and, if necessary, a liquid sealant 16 are charged. A seed crystal 17 is attached to the tip of the pulling shaft 2. 18 to 2 in the figure
1 is a heater.

FIG. 2 shows another embodiment of the apparatus for producing a high dissociation pressure single crystal of the present invention. In FIG. 2, an operation rod 24 is provided on the upper airtight container 4. Operation rod 2 during cooling after crystal growth
By pulling up the upper airtight container 4, the upper airtight container 4 can be lifted and divided from the lower airtight container 5. The operation rod 24 is not necessarily directly connected to the upper airtight container 4.
It is not necessary to fix to the upper airtight container 4 at the time of the dividing operation.

In the first embodiment shown in FIG. 1, the grown crystal 22 is lifted simultaneously with the upper hermetic container 4 in order to lift the upper hermetic container 4 using the pulling shaft 2.
Therefore, when dividing the airtight container, it is difficult to keep the grown crystal independently in a required temperature range. On the other hand, in the second embodiment shown in FIG. 2, since the grown crystal 22 and the upper airtight container 4 can be operated separately,
It is possible to lift the upper airtight container 4 while keeping the crystal 22 in the required temperature range. That is, the second embodiment has an advantage that the heat history of the grown crystal during cooling can be controlled more freely.

Next, one embodiment of the method for growing a high dissociation pressure single crystal of the present invention will be described. Ga using the apparatus shown in FIG.
An As single crystal was grown. The crucible 14 has a diameter of 200
mm PBN crucible and GaAs polycrystalline raw material 1
2 kg and 1 kg of B ₂ O ₃ were charged as the liquid sealant 16. B ₂ O ₃ was also used for the liquid sealants 7 and 9. 100 g of As was charged as a solid raw material 13 for supplying a necessary high dissociation pressure component element gas into the airtight container.

A gas mixture of As and nitrogen is placed in the airtight container.
Further, 5 kg / c of nitrogen gas was introduced into the chamber 1 respectively.
m ² each to balance the pressure inside and outside the airtight container. The crucible 14 is rotated by the crucible rotating shaft 3, and the seed crystal 17 attached to the tip of the pulling shaft 2 is immersed in the raw material melt 15 and pulled up while rotating, and has a diameter of 110 mm and a length of 27 mm.
A 0 mm GaAs single crystal was grown. During the crystal growth, the partial pressure of As gas in the hermetic container is controlled by the high dissociation pressure component partial pressure controller 11.
By controlling the temperature.

After the crystal growth, the temperature of the heaters 12 and 18 to 21 was gradually lowered while controlling the inside of the airtight container to a desired temperature distribution, and the crystal was cooled at a rate of 3 to 5 ° C./min.
When the temperature reached 650 ° C., the upper airtight container 4 was raised by lifting the pulling shaft 2 upward, and the airtight container was opened. Immediately thereafter, the inside of the chamber 1 was depressurized to foam the liquid sealants 7, 9 and the liquid sealant 16, and then cooled to room temperature. B ₂ O _{3 for} liquid sealants 7 and 9
Therefore, it is necessary to open the airtight container at 400 ° C. or higher, which is the softening temperature of the sealing material. It is desirable to open the airtight container at 600 ° C. or higher from the viewpoint of the viscosity of the sealing material.

As a result of the above operation, there was no crack in the upper hermetic container 4 and the lower hermetic container 5, and the life of the upper hermetic container 4 and the lower hermetic container 5 was greatly extended. Further, since PBN (pyrolytic boron nitride) was not removed, crystals having a low carbon concentration could be grown stably.

The optimum temperature for opening the airtight container differs depending on the type of crystal and liquid sealant. If the temperature is lowered to a very low temperature before opening, the liquid sealant 7 solidifies, and it becomes difficult to divide the airtight container. Further, if the airtight container is divided at an excessively high temperature, the crystal is exposed to a high temperature, and the crystal is damaged. Suitably, the airtight container is opened at a temperature below 85% of the melting point of the crystal. If the pressure in the chamber 1 is reduced after the airtight container is divided as in the embodiment, the components dissolved in the liquid sealant are gasified and the liquid sealant is foamed and solidified. More preferred.

In the embodiment, the upper airtight container 4 is raised by pulling up the pulling shaft 2 to open the airtight container. However, the operation rod 24 is pulled upward by using the apparatus shown in FIG. 4 may be lifted, or the crucible rotating shaft 3 may be simply lowered to open the airtight container. Regarding the operation of opening the airtight container, the same effect can be obtained by using the pulling shaft 2, the crucible rotating shaft 3, or the operating rod 24.

[0024]

According to the method and the apparatus of the present invention, the hermetic container is divided before the liquid sealant solidifies and the joint of the hermetic container is fixed. There is no breakage of the container due to shrinkage stress at the time of cooling and solidification of the sealant, and the airtight container is made of PBN (pyrolytic boron nitride), PG (pyrolytic graphite), vitrified carbon, SiC, etc. In the case of a product made by coating, the life of the airtight container is significantly prolonged because the coating is difficult to peel off.

Therefore, it is not necessary to frequently replace the expensive airtight container, and the cost can be reduced. Also, PBN
(Pyrolytic boron nitride), PG (Pyrolytic graphite), vitrified carbon, Si
Since the coating such as C does not easily peel off, there is no problem that the graphite of the base material is exposed on the surface and contaminates the crystal material, so that a high-quality single crystal with stable electric characteristics can be stably obtained. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus for producing a high dissociation pressure single crystal showing one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of an apparatus for producing a high dissociation pressure single crystal showing another embodiment of the present invention.

FIG. 3 is a schematic sectional view of a conventional apparatus for producing a high dissociation pressure single crystal.

[Explanation of symbols]

 1: Chamber 2: Pull-up shaft 3: Crucible rotating shaft 4: Upper airtight container 5: Lower airtight container 6,8: Liquid sealant reservoir 7, 9: Liquid sealant 10: Conduit 11: High dissociation pressure component partial pressure control Part 12: Heater 13: Solid raw material 14: Crucible 15: Raw material 16: Liquid sealant 17: Seed crystal 18-21: Heater 22: Single crystal 23: Projection 24: Operation rod 25: Heat insulating material

Claims (4)

(57) [Claims] 1. A high-dissociation pressure component element gas is sealed in an airtight container which is configured to be separable and has a structure in which a joint portion is sealed with a liquid sealant, and a high-dissociation pressure single crystal is grown in the container. In the method for growing a single crystal to be performed, the junction of the hermetic container is divided at a temperature higher than the temperature at which the liquid sealing material solidifies during cooling after the single crystal is grown, and the hermetic container is opened. Method for producing crystals. 2. A high-dissociation pressure component element gas is sealed in an airtight container that is configured to be separable and has a structure in which a joint is sealed with a liquid sealant, and a high-dissociation pressure single crystal is grown in the container. An apparatus for producing a high dissociation pressure single crystal, wherein a projection for supporting an upper airtight container is provided on a crystal pulling shaft in a single crystal growth apparatus to be performed. 3. A high dissociation pressure component element gas is sealed in an airtight container that is configured to be separable and has a structure in which a joint portion is sealed with a liquid sealant, and a high dissociation pressure single crystal is grown in the container. An apparatus for producing a high dissociation pressure single crystal, comprising an operation rod for raising and lowering an upper airtight container in a single crystal growth apparatus to be performed. 4. The method for producing a high dissociation pressure single crystal according to claim 1, wherein the airtight container is divided at a temperature of 85% or less of the melting point of the crystal.