JPH01286992A - Apparatus for growing single crystal - Google Patents

Abstract

PURPOSE:To prevent leak of a group V element gas and enable precise and proper vapor pressure control of an inner vessel, by forming a pBN film by vapor growth on the inner or outer surface of the inner vessel, provided in an outer vessel and splittable into the upper and lower parts. CONSTITUTION:An inner vessel, consisting of an almost cylindrical hermetically sealed vessel and splittable into the upper and lower parts is provided in an outer container 1 consisting of a cylindrical high pressure-resistant vessel having both closed ends. The inner vessel 2 is formed of graphite and a pBN film is formed on the inner and outer surfaces thereof by a CVD method. The upper part (2a) of the inner vessel and the lower part (2b) thereof are joined by grinding and heaters 3 and 4 are respectively provided on the outer peripheries of the lower part (2b) of the inner vessel and upper part (2a) thereof. A pulling up shaft 5 and crucible rotating shaft 6 are airtightly introduced from the outside of the outer vessel 1 into the inner vessel 2. The pulling up shaft 5 and crucible rotating shaft 6 are respectively liftably and rotatably provided on the same shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a single crystal growth apparatus, and particularly to a single crystal growth apparatus for growing a high dissociation pressure compound semiconductor single crystal.

[Prior Art] Generally, in the growth of high dissociation pressure compound semiconductor single crystals such as GaAs, GaP, InAs, and InP, group V elements with high vapor pressures such as As and P are used in the raw material melt and the crystal being grown. Liquid encapsulation Czochralski method (LEC method) is used as a method to prevent dissociation from the surface. This LEC method is a method in which the raw material melt in a crucible is sealed with a liquid sealant such as B201, and the crystals are pulled up while applying high pressure to the liquid sealant with an inert gas.
Evaporation of volatile elements from the raw material melt is effectively suppressed.

However, since the crystal is pulled under high pressure, the temperature inside the furnace becomes unstable due to gas convection, and temperature differences tend to occur in the crystal growth environment, resulting in a problem of high dislocations in the pulled crystal.

In addition, since the upper part of the liquid sealant is at a high temperature, the crystals being grown will undergo surface decomposition at the upper part of the liquid sealant.
The problem was the proliferation of dislocations inside the pulled crystal.

Therefore, in recent years, a crystal pulling method called a vapor pressure control method has been used to solve the above problems and grow a low dislocation crystal without surface decomposition. This vapor pressure control method is a method in which an inner container made of a small sealed container is provided inside an outer container made of a high pressure resistant container, and crystal growth is performed within this inner container to maintain a sufficient vapor pressure of group By applying this, it is possible to prevent the dissociation of group (I) elements from the raw material melt and the surface of the growing crystal.

What is important in the vapor pressure control method is to improve the airtightness of the inner container to effectively prevent leakage of group (I) elements applied inside the container to the outside of the container.

For this reason, methods have been used, such as forming the inner container as a single piece made of quartz, or making the inner container made of quartz separable, applying a sealant to the joint, and applying force in the joining direction to make them stick together. It is.

Further, the gap between the pulling shaft and the crucible rotating shaft introduced into the inner container and the inner container is usually hermetically sealed with a sealing agent. However, since the material of the inner container is quartz, the inner container has good wettability with the sealant, and if the sealant adheres to the surface of the inner container, the quartz on the surface of the inner container will peel off, damaging the inner container. This was done frequently.

In addition, the inner container made of quartz has low strength and is often damaged when assembling the furnace material.

Conventionally, single crystal growth apparatuses have been constructed using an inner container made of graphite that has sufficient strength, is easy to process and handle, and does not peel off due to sealant.

[Problems to be Solved by the Invention] However, in the conventional single crystal growth apparatus using an inner container made of graphite, since the porosity of graphite is high, the Group III element gas applied to the inside of the inner container is It was easy to leak from the wall to the outside, making precise control of vapor pressure difficult.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a single crystal growth apparatus that prevents leakage of group V element gas and enables precise and appropriate vapor pressure control within the inner container. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an inner container which can be divided into upper and lower parts inside the outer container, a heater is arranged outside the inner container, and a crucible is installed in the lower part of the inner container. In a single crystal growth apparatus that grows a high dissociation pressure compound semiconductor single crystal by a pulling method by placing raw materials and a sealant in the crucible, the inner container is formed of graphite, and the inner surface of the inner container is Alternatively, a pBN film is formed on at least one of the outer surfaces by vapor phase growth.

[Function] In the single crystal growth apparatus having such a configuration, at least one of the inner and outer surfaces of the graphite inner container is pB.
Since it is coated with the N film, the pores of the inner container are closed and leakage of group V element gas is prevented.

[Example 1] For example, as shown in the figure, the single crystal growth apparatus of the present invention includes a substantially cylindrical sealed container that can be divided into upper and lower parts, and an outer container 1 that is a cylindrical high pressure resistant container that is closed at both ends. An inner container 2 is provided.

The inner container 2 is made of graphite, and its inner and outer surfaces are coated with a film thickness of 100 to 20 mm by CVD.
A pBN film of about 0 μm is formed. Further, the inner container upper part 2a and the inner container lower part 2b are joined by sliding, and heaters 3 and 4 are arranged on the outer peripheries of the inner container lower part 2b and the inner container upper part 2a, respectively.

Further, a pulling shaft 5 and a crucible rotation shaft 6 are introduced into the inner container 2 from outside the outer container 1 in an airtight manner. The pulling shaft 5 and the crucible rotation shaft 6 are provided coaxially, and are provided so as to be movable up and down and rotatable, respectively. The inner end of the pulling shaft 5 is capable of supporting a seed crystal 7, and the inner end of the crucible rotation shaft 6 has a susceptor 8 fixed thereto. This susceptor 8 is formed to be able to support a roof 11 containing a raw material melt (semiconductor material) 9 and a liquid sealant 10.

The pulling shaft 5 and the inner container upper part 2a are hermetically sealed by a seal adapter 12 into which the pulling shaft 5 is inserted in a sliding structure. The crucible rotation shaft 6 and the inner container lower part 2b are connected to a cylindrical tubular adapter 15, which houses a sealant 14 in a seal container 13 that is fitted and fixed to the outer periphery of the crucible rotation shaft 6, and is attached to the inner container lower part 2b. The lower end is immersed in a sealant 14 to be airtightly sealed. Here, the seal container 13 and the adapter 15 are each made of a material that has heat resistance and has poor wettability with the sealant 14, such as metal. Further, the sealing agent 14 is melted by the temperature inside the outer container 1 rising when the inner container lower part 2b is heated by the heater 3 and the raw material melt 9 and the liquid sealant 1o are heated and melted.

Furthermore, the bottom of the inner container lower part 2b has a vapor pressure that communicates with the inside of the inner container 2! A li-conditioning container 16 is installed,
A volatile material 17 made of a volatile group Ⅰ element is housed in the vapor pressure regulating container 16 . Also, the vapor pressure of the volatile material 17 contained! l On the outer periphery of the conditioning container 16,
A heater 18 is provided.

In the single crystal growth apparatus having the above configuration, when the temperature in the outer container 1 becomes sufficiently high due to heating by the heater 3 and the sealing agent 14 in the sealing container 13 is melted, the crucible rotating shaft 6 is raised. The lower end of the adapter 15 is immersed in the sealant 14 to seal the crucible rotating shaft 6. At the same time, the pulling shaft 5 is also inserted into the seal adapter 12 to seal the pulling shaft 5, thereby bringing the inside of the inner container 2 into a sealed state. Thereafter, the volatile material 17 in the vapor pressure adjustment container 16 is evaporated by heating with the heater 18, and the inner container 2 is filled with the vapor of the volatile material 17. At the same time, an inert gas is introduced into the outer container 1 so that the external pressure of the inner container 2 is equal to or higher than the internal pressure.

Using the single crystal growth apparatus of this example, G
An aAs single crystal was grown.

First, there is high purity (7N) Ga inside Rupo 11.

A raw material 9 made of As and a liquid sealant 10 made of BoO1 were placed. Then, this Ruppo 11 was placed on a susceptor 8 provided at the inner end of the crucible rotating shaft 6. In addition, about 15% of high purity (7N) As is contained in the vapor pressure adjustment vessel 16.
In addition to storing 0g, B, 0g are stored in the sealed container 13.
A sealing agent 14 consisting of 3 was stored.

Next, after placing the inner container upper part 2a on the inner container lower part 2b and joining them, the outer container 1 is sealed and the inside is evacuated, and then the inside is pressurized with Ar gas, and the heater 3
Heating was started. First, the liquid sealant 10 in the crucible 11 melts and seals the Ga and As of the raw material 9, and then the G
A and As reacted to form GaAs, and when the temperature was further increased, GaAs melted and became a liquid. At this point, the sealant 14 in the seal container 13 has melted due to the temperature rise in the outer container 1, so the crucible rotation shaft 6 is raised, the lower end of the adapter 15 is immersed in the sealant 14, and the crucible rotation shaft At the same time, the pulling shaft 5 was lowered and inserted into the seal adapter 12 to seal the pulling shaft 5 and the inner container upper part 2a.

After that, heating of the heater 18 is started, and the vapor pressure adjustment container 1 is heated.
The volatile material 17 in the inner container 2 is vaporized, and As is added to the inner container 2.
While filling the container with steam, Ar gas was introduced into the container 1. The introduction of this Ar gas is carried out while monitoring the temperature of the vapor pressure adjustment container 16.
The test was carried out so that the external pressure of the inner container 2 was always higher than the internal pressure in accordance with the pressure increase due to the application of the s pressure. Further, at the same time as heating the vapor pressure adjustment container 16, the inner container upper part 2a was also heated by the heater 4. This is the inner container 2a
This is to prevent As from becoming a low-temperature part and evaporating As from precipitating.

After filling the inner container 2 with As vapor in this way, the pulling shaft 5 and the crucible rotating shaft 6 are driven, and the seed crystal 7 provided at the inner end of the pulling shaft 5 is poured into the raw material melt 9. The crystal was pulled while the pulling shaft 5 and the crucible rotating shaft 6 were immersed in the immersion, and a 3-inch GaAs single crystal was grown. It was found that sufficient As vapor pressure was applied within the inner container 2 during crystal growth.

In addition, when we investigated the dislocation density inside the crystal of the above-mentioned grown crystal, it was found to be 5,000 cm-''.On the other hand, the dislocation density of the crystal grown using the conventional apparatus was 30,000 to 500 cm-''.
00aa-'', and it was found that the crystal grown by the apparatus of the above example had significantly lower dislocations.

Furthermore, when the grown crystal was taken out from the single crystal growth apparatus and the apparatus was inspected, it was confirmed that all of the inner container 2 and the like were not damaged and could be used repeatedly.

In addition, in the above example, the prepared volatile material (As
) When the initial amount of 17 was 160 g, the amount of As leaked after 1 hour from the start of crystal growth was 5 g, and the amount of As leaked after 10 hours was 40 g. On the other hand, in the conventional example where the inner container is made of graphite and no pBN film is formed, the amount of As leaked after 1 hour is 100 g, and the amount of As leaked after 10 hours is 140 g, which is a large amount. A part has leaked. In addition, in the case where the inner container was made of graphite and a film of BN paint was formed, the amount of As leaked after 1 hour was Log, and the amount of As leaked after 10 hours was 75 g.

On the other hand, when the inner container is made of ceramics or a heat-resistant metal material, there are problems such as generation of impurities and difficulty in precision machining. In addition, if the inner container is made of gas-impermeable carbon,
There were problems such as the inner container becoming expensive and having poor thermal durability.

In the above example, the pBN coating was formed on both the inner and outer surfaces of the inner container 2. However, the present invention is not limited to such an example. Almost the same effect can also be obtained by forming a pBN film on the surface. Further, in the above embodiment, when sealing the inner container 2 and the crucible rotating shaft 6,
Although the adapter 15 is provided, the inner container 2 may be directly immersed in the sealant 14.

[Effects of the Invention] As described above, according to the single crystal growth apparatus of the present invention, the inner container is formed of graphite, and a pBN film is formed by vapor phase growth on at least one of the inner surface or outer surface of the inner container. Therefore, it is possible to prevent the Group 1 element gas from leaking to the outside of the inner container, and it is possible to precisely and appropriately control the vapor pressure within the inner container.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view showing an embodiment of a single crystal growth apparatus according to the present invention. 1... Outer container, 2... Inner container, 2a...
・Inner container upper part, 2b... Inner container lower part, 3, 4.
... Heater, 5 ... Pulling shaft, 6 ... Crucible rotation shaft, 7 ... Seed crystal, 9 ... Raw material melt, 10
・・・Liquid sealant, 11... Crucible, 17...
・Volatile material. 4 +2

Claims (1)

[Claims] (1) An inner container that can be divided into upper and lower parts is provided within the outer container,
A heater is installed on the outside of this inner container, and a crucible is installed in the lower part of the inner container, and raw materials and sealant are placed in the crucible, heated and melted, and a high dissociation pressure compound semiconductor single crystal is produced by a pulling method. 1. A single crystal growth apparatus for growing a single crystal, characterized in that an inner container is formed of graphite, and a pBN film is formed by vapor phase growth on at least one of the inner or outer surface of the inner container.