JPH1087306A - Pyrolytic boron nitride vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the control of the internal temp. distribution of a pyrolytic boron nitride vessel used in the production of a compd. semiconductor signal crystal as well as to easily form a temp. gradient of molten starting material in the vessel by exposing a laminated cross section of pyrolytic boron nitride in a part of the inner surface of the vessel. SOLUTION: A laminated cross section of pyrolytic boron nitride is exposed in part of the inner surface of a pyrolytic boron nitride vessel for holding molten starting material used in the production of a compd. semiconductor single crystal. In the case where the compd. semiconductor single crystal is produced by LEC method, the central protruding part of the inner bottom of the vessel is removed by a prescribed thickness by mechanical polishing to exposed a laminated cross section in the part. The angle between the inner surface of the vessel and a laminated face in the laminated cross section exposed part (e.g. the angle θ25 at 25mm radius from the central axis of the vessel and the angle θ50 at 50mm radius) is preferably regulated to 0.5-90 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a pyrolytic boron nitride container, and more particularly, to a III-V method by LEC or boat method.
The present invention relates to a pyrolytic boron nitride container suitable for holding a raw material melt used for growing a group III compound semiconductor single crystal.

[0002]

2. Description of the Related Art Methods for producing a group III-V compound semiconductor single crystal, for example, a GaAs single crystal, a GaP single crystal, an InP single crystal, and the like are generally roughly divided into a liquid-sealed Czochralski method (LEC method) and a boat. There is a law.

In the LEC method, for example, as shown in FIG.
A carbon susceptor 3 and a raw material holding container 4 held by a support shaft 2 that can rotate and move up and down are disposed substantially at the center of the chamber 1. Fill a sealant to prevent element volatilization. This is heated by, for example, a two-zone heater 7 made of carbon, which is arranged so as to surround the raw material holding container, to melt the polycrystalline raw material and the sealant, and melt the polycrystalline raw material 5 and the sealant melt 6. And Next, a seed crystal 9 suspended from a shaft 8 that can rotate and move vertically is immersed in the raw material melt 5 from above, and the target rod-shaped single crystal 10 is slowly pulled up while rotating the shaft 8. Can be nurtured.

The boat method further includes a horizontal Bridgman method (HB method), a vertical Bridgman method (VB method), a horizontal temperature gradient solidification method (HGF method), and a vertical temperature gradient solidification method (V
GF method). In these boat methods, generally, the raw material melt is held in a fixed container, and the raw material is melted by moving the heat source while heating it from an external heat source, or by applying a heating distribution by the heat source itself. A single crystal is grown by applying a temperature gradient to the liquid and solidifying it from the seed crystal side.

In the LEC method or the boat method, a quartz container has conventionally been used as a container for holding a raw material melt. When quartz is used as the container material in this way, there is a problem that Si, which is a constituent component of quartz, is mixed as an impurity into the grown crystal, and Si acts as an amphoteric dopant for the III-V compound semiconductor. . Therefore, using a quartz container, III-V
When growing a group III compound semiconductor single crystal by the LEC method or the boat method, a method is usually employed in which a crystal is grown by doping with Cr. However, like this,
Doping decreases the insulating properties of the crystal, and these are not suitable as IC substrates. Also,
A chemical reaction occurs between the quartz container and the raw material melt, a so-called wetting phenomenon occurs, and there is a problem that crystal defects such as twins are likely to occur (electronic materials, Vol32, No1, p3).
2-37).

Accordingly, recently, high-purity, non-doped I
In order to obtain a group II-V compound semiconductor single crystal, a pyrolytic boron nitride (PBN) container has begun to be adopted as a container for producing the same. If this PBN is used as a container material, even if impurities of B and N, which are constituent components of the container, are mixed into a single crystal, the impurity level does not form enough to act as a dopant. There is an advantage that the electrical characteristics of the semiconductor single crystal do not deteriorate.

[0007]

However, this PBN
Has a large thermal conductivity in the lamination surface direction, that is, in the plane direction,
It exhibits anisotropy of 30 to 70 times in the thickness direction, which works to equalize the temperature in the container, it is difficult to control the temperature distribution in the container by the LEC method, and it is difficult to control the temperature distribution in the container by the boat method. It becomes a hindrance in forming a temperature gradient, has a property that is not suitable for a container for producing a single crystal by the LEC method or the boat method, and causes a decrease in the single crystallization rate of the crystal actually grown. Has become.

Accordingly, the present invention has been made in view of the above problems, and has been made in the art of manufacturing a compound semiconductor single crystal.
In particular, by making it possible to conduct heat efficiently and intensively to the portion of the inner surface of the pyrolytic boron nitride container used in the LEC method and the boat method where a higher temperature is desired, the raw material melt in the container is To provide a PBN container capable of easily forming a temperature gradient and facilitating control of the temperature distribution in the container.
It is an object of the present invention to improve the single crystallization rate of a group V compound semiconductor single crystal.

[0009]

Means for Solving the Problems In order to solve such a problem, the invention described in claim 1 of the present invention is directed to a method for producing a compound semiconductor single crystal, which comprises a thermal decomposition for holding a raw material melt. A pyrolytic boron nitride container, wherein a laminated cross section of pyrolytic boron nitride is exposed on a part of the inner surface of the container. In this way, by exposing the laminated cross section of the pyrolytic boron nitride at a portion where the inner surface of the container is desired to be heated, heat is efficiently and intensively transmitted to that portion, and the raw material in the container is exposed. The temperature gradient can be easily formed in the melt, and the temperature distribution in the container can be easily controlled.

[0010] The invention described in claim 2 of the present invention is a pyrolytic boron nitride container for holding a raw material melt, which is used in the production of a compound semiconductor single crystal by the LEC method. A pyrolytic boron nitride container characterized in that a laminated cross section of pyrolytic boron nitride is exposed on the inner surface of the bottom. As described above, by exposing the laminated cross section of the pyrolytic boron nitride to the inner surface of the bottom of the pyrolytic boron nitride container used in the production of the compound semiconductor single crystal by the LEC method, heat can be efficiently applied to the bottom of the container. To facilitate the control of the temperature distribution of the melt in the container and to suppress the convection of the melt.

A third aspect of the present invention is directed to a pyrolytic boron nitride container for holding a raw material melt, which is used in the production of a compound semiconductor single crystal by a boat method. On the inner surface opposite the seed crystal,
A pyrolytic boron nitride container characterized in that a laminated cross section of pyrolytic boron nitride is exposed. Thus, by exposing the laminated cross section of the pyrolytic boron nitride on the inner surface opposite to the seed crystal of the pyrolytic boron nitride container used in the production of the compound semiconductor single crystal by the boat method, the seed crystal of the container is exposed. The temperature on the crystal growth side, which is the opposite side, can be increased, and the crystal can be grown in an ideal temperature environment.

According to a fourth aspect of the present invention, there is provided the pyrolytic boron nitride container according to any one of the first to third aspects, wherein the inner surface of the container at the exposed portion of the lamination cross-section is removed. The angle between the layer and the stacking surface is 0.5 degrees or more and 90
Degrees or less. Thus, the angle between the inner surface of the container and the lamination surface at the exposed portion of the lamination cross section is equal to 0.
By setting the temperature to 5 degrees or more and 90 degrees or less, heat can be efficiently and intensively conducted to the exposed portion.

Hereinafter, the present invention will be described in more detail, but the present invention is not limited thereto. First, in the LEC method, since the heater is disposed so as to surround the pyrolytic boron nitride container as described above, the raw material melt is heated from the side of the container. Therefore, as shown in the conceptual diagram of FIG. 8, the raw material melt generates heat convection from the bottom to the top at the periphery of the container and from top to bottom at the center. In this case, if the temperature difference between the bottom part and the side part of the container becomes too large, the convection becomes violent, crystal growth becomes unstable, and the single crystal is liable to be dislocated. In other words, in the LEC method, the heating source is usually on the side, the side of the container is at a high temperature, and heat is not easily transmitted to the bottom, so that the bottom is at a relatively low temperature. Although PBN has good thermal conductivity in the plane direction, it cannot transmit a sufficient amount of heat for heating the bottom portion due to the relatively small thickness of the container and a small heat propagation area. Therefore, in the LEC method, it is necessary to prevent the dislocation of the single crystal by keeping the temperature at the bottom of the container not so much lower than the side and suppressing the heat convection of the raw material melt as much as possible.

Further, in the boat method, it is necessary to provide a temperature gradient in the direction of crystal growth, that is, a temperature gradient in which the temperature on the seed crystal side is low and the temperature on the crystal growth side opposite thereto is high. Due to the anisotropy of the pyrolytic boron nitride, the inside of the container is soaked, and it is difficult to form a temperature gradient of the raw material melt and control the temperature distribution of the raw material melt.

The inventors of the present invention have made various studies and found that the problem can be solved by actively utilizing the anisotropy of the pyrolytic boron nitride, and completed the present invention. In other words, by exposing the laminated cross section of the pyrolytic boron nitride in a portion of the inner surface of the pyrolytic boron nitride container where a higher temperature is desired, heat energy supplied from the outside is conducted in the direction of the laminating surface, and the laminated cross sectional exposed portion So that heat transfer occurs efficiently and intensively. Thus, a desired temperature gradient can be formed in the raw material melt in the container, and the temperature distribution in the container can be easily controlled.

Therefore, in the LEC method, as described above, since it is desired to raise the temperature of the bottom, the laminated section of the pyrolytic boron nitride may be exposed on the inner surface of the bottom of the pyrolytic boron nitride container. In such a pyrolytic boron nitride container used in the production of a compound semiconductor single crystal by the LEC method, the heat supplied from the side surface is efficiently conducted in the direction of the lamination surface and concentrated on the inner surface at the bottom. . As a result, the temperature distribution of the melt in the container can be easily controlled, and the convection of the melt can be suppressed.

In the boat method, as described above,
Since it is desired to raise the temperature on the side opposite to the seed crystal, the laminated section of the pyrolytic boron nitride may be exposed on the inner surface of the pyrolytic boron nitride container on the side opposite to the seed crystal. like this,
In a pyrolytic boron nitride container used in the production of a compound semiconductor single crystal by the boat method, heat supplied from the outside is efficiently conducted in the direction of the lamination plane and concentrated on the inner surface opposite to the seed crystal. . As a result, the temperature on the seed crystal side of the container can be lowered and the temperature on the crystal growth side opposite to the seed crystal side can be raised, and crystals can be grown in an ideal temperature environment.

In this case, the angle between the inner surface of the container and the lamination surface (the angle between the surface of the substrate on which the pyrolytic boron nitride is vapor-phase grown and the surface of the container actually used) at the exposed portion of the lamination cross section is zero. It is preferable that it is not less than 0.5 degrees and not more than 90 degrees. This is because the angle between the inner surface of the container and the lamination surface is 0.5
This is because if it is not more than the degree, it is hardly different from the actual lamination surface, so that heat cannot be efficiently concentrated at the exposed portion of the lamination cross section. Therefore, it is desirable that this angle is as large as possible from the point of heat concentration,
The maximum is 90 degrees.

As a method of exposing the laminated cross section of the pyrolytic boron nitride, the inner surface of a desired portion of the pyrolytic boron nitride molded body obtained by vapor phase growth is formed by shaving off by mechanical means, for example, polishing. be able to. Therefore, the portion where the laminated cross section is exposed is deposited on the final container shape in advance by depositing pyrolytic boron nitride in a protruding shape or reducing the inner diameter or increasing the wall thickness, and then polishing this portion by polishing. By shaving, a laminated cross section is exposed and a pyrolytic boron nitride container having a desired final shape can be obtained.

[0020]

Next, embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these.

[0021]

EXAMPLES Examples and comparative examples of the present invention will be described below. (Examples and Comparative Examples) A cylindrical graphite mandrel having an outer diameter of 200 mm and a height of 200 mm was protruded in the center of the bottom of the container as shown in FIG. 1 in a cylindrical CVD reactor made of graphite. In the comparative example, as shown in FIG. 5, the container was arranged so that the bottom of the container had a normal round bottom. 1 L / min of boron trichloride and 4 L / min of ammonia were supplied thereto, and reacted under the conditions of an average pressure of 2 Torr and 1900 ° C. in the center of the furnace, a thickness of 1.5 to 2.5 mm, a diameter of 8 inches and a height of 8 inches. A 180-mm-thick thermally decomposed boron nitride compact used for the LEC method was deposited. After the completion of the reaction, the PBN molded body and the mandrel were separated to obtain a pyrolytic boron nitride container having a sectional shape as shown in FIGS. 2 and 6, respectively. Then, in the example, the convex part at the center of the inner bottom part of the molded body of FIG. (See FIG. 3). At this time, a radius of 25 mm and a radius of 50 m from the central axis of the pyrolytic boron nitride container as shown in FIG.
The angles θ ₂₅ and θ ₅₀ formed between the inner surface of the container and the lamination surface at the exposed portion of the lamination cross section m were measured. On the other hand, the pyrolytic boron nitride container of the comparative example was obtained as it was in the shape of FIG. 6, and was not polished.

Using the three kinds of pyrolytic boron nitride containers thus manufactured, using an apparatus as shown in FIG.
Actually, a 3-inch GaAs single crystal was grown by the LEC method. The GaAs polycrystalline raw material was 10 kg, ₃ kg of B ₂ O ₃ was added as a sealant, and Ar gas / 40 was used.
The crystal was pulled under atmospheric pressure. The crystal pulling speed is
It was about 10 mm / hr. Such a crystal pulling test by the LEC method was performed eight times for each of the above three types of pyrolytic boron nitride containers, and the single crystallization ratio (the number of dislocation-free / the total number of pulled) was compared. The results are shown in Table 1.

[0023]

[Table 1]

As can be seen from Table 1, in the container of the embodiment in which the laminated cross section is exposed at the bottom of the pyrolytic boron nitride container,
It can be seen that the single crystallization ratio is improved as compared with a conventional container in which such treatment is not performed. In particular, when a container having an angle of 0.5 or more between the inner surface of the container and the lamination surface in the exposed portion of the laminated cross section is used, single crystallization is achieved with a high probability, and heat is applied to the exposed portion of the laminated cross section. Since the convection of the raw material melt was ideally conducted and the convection of the raw material melt was ideal, the single crystal could be grown extremely stably.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

For example, in the above description, the case where the raw material melt is heated from the outside of the container, as in the case where resistance heating is used as a heat source, has been described. However, the present invention is not limited to this. As a matter of course, the present invention can be naturally applied to the case where the material is heated from the side of the raw material melt in the container, and the effect can be obtained.

The portion where the laminated cross section is exposed is not limited to the bottom portion in the LEC method or the side opposite to the seed crystal in the boat method. The lamination cross section can be exposed at a portion to be concentrated.

[0028]

According to the present invention, the laminated cross section is exposed on a part of the inner surface of the pyrolytic boron nitride container used in the LEC method or the boat method, so that the exposed portion can be efficiently and intensively concentrated. Since heat energy can be conducted, temperature control of the raw material melt in the container becomes easy, convection in the raw material melt can be suppressed, and the temperature gradient of the raw material melt is ideal for growing crystals. Things. Therefore, if a III-V compound semiconductor single crystal is manufactured by the LEC method or the boat method using this, a high-purity crystal can be manufactured by remarkably improving the single crystallization ratio. Its utility in industry is extremely high.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a graphite mandrel in an example. (A shape that can be convex at the bottom center of the container)

FIG. 2 is a schematic cross-sectional view of a pyrolytic boron nitride molded body in an example.

FIG. 3 is a schematic sectional view of a pyrolytic boron nitride container according to the present invention.

FIG. 4 is an explanatory view of an angle formed between the inner surface of the pyrolytic boron nitride container and the laminating surface at an exposed portion of the laminar cross-section having a radius of 25 mm and a radius of 50 mm from the central axis of the container.

FIG. 5 is a schematic sectional view of a graphite mandrel in a comparative example. (Usual round bottom shape)

FIG. 6 is a schematic cross-sectional view of a pyrolytic boron nitride molded body in a comparative example.

FIG. 7 is a schematic sectional view of an apparatus of the LEC method.

FIG. 8 is a conceptual diagram showing a state of convection of a raw material melt in the LEC method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Chamber, 2 ... Support shaft, 3 ... Carbon susceptor, 4 ... Material holding container, 5 ... Polycrystalline material melt, 6 ... Sealant melt, 7 ... 2-zone heater, 8 ... Shaft, 9 ... Seed crystal ,
10 Single crystal.

Claims (4)

[Claims] 1. A pyrolytic boron nitride container for holding a raw material melt used in the production of a compound semiconductor single crystal, wherein a laminated cross section of the pyrolytic boron nitride is formed on a part of the inner surface of the container. A pyrolytic boron nitride container, which is exposed. 2. A pyrolytic boron nitride container for holding a raw material melt, which is used in the production of a compound semiconductor single crystal by the LEC method, wherein a bottom inner surface of the container is provided with:
A pyrolytic boron nitride container, wherein a laminated cross section of the pyrolytic boron nitride is exposed. 3. A thermally decomposed boron nitride container for holding a raw material melt, which is used in the production of a compound semiconductor single crystal by a boat method, wherein an inner surface of the container opposite to a seed crystal is thermally decomposed. A pyrolytic boron nitride container, wherein a laminated cross section of boron nitride is exposed. 4. The container according to claim 1, wherein an angle formed between the inner surface of the container and the laminating surface at the exposed portion of the laminating cross section is not less than 0.5 degrees and not more than 90 degrees. The pyrolytic boron nitride container as described.