JPH10245300A - Production apparatus for compound semiconductor single crystal and production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LEC apparatus capable of growing a crystal in a high monocrystallization ratio. SOLUTION: A reflector 100 having an emissivity higher than 0.4 obtained by coating the underside of a refractor with a high-emissivity member 100 is liftably installed above a crystal pulling up space in a high pressure container 5. The reflector 100 is set at the optimum position according to the objective length of the crystal to be pulled up and then crystal is pulled up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing a compound semiconductor single crystal, and more particularly to an improvement of a manufacturing apparatus used for manufacturing a compound semiconductor single crystal by a liquid-sealed Czochralski (LEC) method and its improvement. The present invention relates to a manufacturing method using a manufacturing apparatus.

[0002]

2. Description of the Related Art As a method of manufacturing a single crystal of a III-V compound semiconductor such as GaAs or InP, a crucible containing a raw material and a sealant is heated by a heater, and a seed crystal is brought into contact with the surface of the raw material melt. There is known an LEC method for growing a single crystal by gradually pulling it while rotating it.
Since the LEC method is performed in a high-pressure atmosphere using an inert gas, a heater, a crucible, and the like are conventionally housed in a high-pressure container having a water-cooled jacket structure made of stainless steel in the manufacturing apparatus.

As one of such LEC apparatuses, the present applicant has disclosed that at least the inner surface of the ceiling portion of a high-pressure vessel is made of graphite (G), boron nitride (BN), boron nitride-coated graphite, pyrographite, silicon nitride (silicon nitride). A single crystal manufacturing apparatus which is coated with one or two or more substances selected from the group consisting of SiN) and silicon carbide (SiC) having an emissivity higher than 0.4 has been filed earlier (Japanese Patent Application Laid-Open No. H08-208,1992). -73295). According to the manufacturing apparatus according to this prior application, the emissivity of at least the inner surface of the ceiling portion of the high-pressure vessel is higher than 0.4, which is the emissivity of the ceiling portion of the high-pressure vessel in the manufacturing apparatus up to that time. The heat absorption capacity above the crystal is higher than that of the manufacturing equipment, and sufficient heat is radiated through the crystal even if the growth length of the crystal is longer, so that the shape of the solid-liquid interface is maintained in an ideal downward convex shape. Dripping. Therefore, the straight body of the pulled crystal can be polycrystallized in the middle, or twins can enter the shoulder and the straight body, and the problem of the single crystal rate can be reduced. The effect is obtained.

[0004]

However, according to our subsequent studies, it has been found that not only is it difficult to coat the inner surface of the ceiling of the high-pressure vessel with the above-listed substances, but also that it cannot be used repeatedly. Yes, the above prior art was found to be impractical.

The present invention has been made to solve the above problems, and an object thereof is to easily realize an LEC apparatus capable of growing a crystal with a high single crystallization ratio.

Another object of the present invention is to provide such an L
An object of the present invention is to provide a method for producing a crystal having a high single crystallization ratio by using an EC device.

[0007]

In order to achieve the above object, a single crystal manufacturing apparatus according to the present invention comprises a crucible containing a raw material and, if necessary, a sealant is placed in a high-pressure vessel. A manufacturing apparatus used for growing a single crystal by heating a heater provided in a vessel to melt the raw material and the sealing material, bringing a seed crystal into contact with the surface of the raw material melt, and gradually pulling the seed crystal. In the above, a reflector that can be raised and lowered is provided above the crystal pulling space in the high-pressure vessel, and the reflector is inclined so as to increase from near the inner peripheral surface of the high-pressure vessel toward the central axis of the high-pressure vessel. In addition, at least the lower surface of the reflector has an emissivity higher than 0.4. Therefore, as in the prior art of Japanese Patent Application Laid-Open No. H8-73295, the heat absorption capacity above the crystal is increased as compared with the conventional manufacturing apparatus, and even if the growth length of the crystal becomes long, a sufficient amount of heat passes through the crystal. Since the heat is dissipated, the shape of the solid-liquid interface is kept in an ideal downward convex shape, and a high single crystallization ratio can be obtained. In addition, if the distance between the crystal and the reflector is short, the solid angle between the crystal and the reflector (hereinafter referred to as a radiation solid angle) increases, so that the radiation by radiation increases. Therefore, by adjusting the distance between the crystal and the reflector according to the growth of the crystal,
An ideal downward convex solid-liquid interface shape is obtained. According to the present invention, a single crystal manufacturing apparatus capable of obtaining such a high single crystallization ratio can be realized more easily than the prior application.

[0008] In the present invention, the emissivity of at least the lower surface of the reflector is preferably 0.7 or more,
More preferably, it is good to be 0.8 or more. If the emissivity of at least the lower surface is at least 0.7, a more stable high single crystallization rate can be obtained, and if the emissivity is at least 0.8, a more stable high single crystallization rate can be obtained. Is obtained.

[0009] At least the lower surface of the reflector may be coated with one or more substances selected from the group consisting of graphite, boron nitride, boron nitride-coated graphite, pyrographite, silicon nitride and silicon carbide. Good. Each of these substances has a higher emissivity than stainless steel conventionally used for reflectors, so that a high single crystallization rate can be obtained.

Further, the reflector may be cooled by cooling water passed through the inside of the reflector. Then, the heat absorption capacity above the pulled crystal is further increased, and a higher single crystallization ratio is obtained.

Further, the angle of inclination of the reflector with respect to the horizontal is preferably 10 ° or more and 35 ° or less. The reason is that if the inclination angle of the reflector is less than 10 °, the cooling capacity is reduced due to a decrease in the radiation solid angle, and a long single crystal cannot be obtained at a high yield. This is because the gas convection is disturbed, and the temperature fluctuation of the melt in the crucible becomes large, which is not preferable.

Further, in order to achieve the above object, a method for producing a single crystal according to the present invention uses the above-described apparatus for producing a single crystal, and places a crucible containing raw materials and a sealant as necessary in a high-pressure vessel. In order to grow a single crystal by installing and melting the raw material and the encapsulant by heating with a heater provided in the high-pressure vessel, and gradually pulling the seed crystal in contact with the surface of the raw material melt, The optimum height position of the reflector is determined in advance, and the reflector is moved up and down to match the optimum height position before pulling up the crystal. Therefore, since the height position of the reflector can be changed according to the length of the crystal to be pulled, the heat absorption capacity above the crystal can be optimally set according to the target crystal length, and the single crystallinity can be increased. Thus, crystal growth can be performed.

In the present invention, the reflector may be moved up and down while the crystal is being pulled. Then, the degree of heat radiation above the crystal through the pulled crystal can be kept optimal at any time.
Crystal growth can be performed with a higher single crystallization ratio.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a single crystal manufacturing apparatus according to the present invention will be described below with reference to FIG.

FIG. 1 shows a single crystal pulling furnace used for carrying out the present invention. A reflector 100 suspended from the ceiling so as to be able to move up and down is provided in the sealed high-pressure container 5. The emissivity of the lower surface of the reflector 100 is higher than 0.4.

A substantially cylindrical heater 1 is disposed in the high-pressure vessel 5, and a crucible 2 is disposed at the center of the heater 1. The raw material melt 3 is placed in the crucible 2, and the upper surface of the melt 3 is covered with a liquid sealant 4 made of, for example, B ₂ O ₃ . A heat insulating material 10 is provided outside the heater 1. The crucible 2 is supported by a crucible support shaft 7 via a susceptor 6 so as to be rotatable and vertically movable. From above the crucible 2, a crystal pulling shaft 8 is suspended in the high-pressure vessel 5 so as to be able to rotate and move up and down. A seed crystal 9 is held at the lower end of the crystal pulling shaft 8,
It can be brought into contact with the surface of the raw material melt 3 in the crucible 2. Then, the single crystal 11 is pulled up by gradually pulling the seed crystal 9 in contact with the surface of the raw material melt 3.

The reflector 100 is, for example, inclined from the circular periphery of the reflector 100 close to the inner peripheral surface of the high-pressure vessel 5 toward the center through which the crystal pulling shaft 8 penetrates so as to be umbrella-shaped. ing. The inclination angle θ is not less than 10 ° and not more than 35 ° with respect to the horizontal. The reason is,
If the inclination angle θ is less than the lower limit, the cooling capacity is reduced, and a sufficiently high single crystallization rate cannot be obtained.On the other hand, if the upper limit is exceeded, gas convection is disturbed, and the temperature in the crucible is increased. This is because the temperature fluctuation of the melt becomes large, which is not preferable.

The inclined lower surface of the reflector 100 is coated with a high emissivity member 110 having, for example, the above emissivity (higher than 0.4, preferably 0.7 or higher, more preferably 0.8 or higher). ing.

The reflector 100 can be moved up and down by a power unit (not shown).
It can be stopped at any height.

Although not particularly shown, the reflector 100 is cooled by cooling water passed therein. Therefore, as described above, since the high emissivity member 110 is in close contact with the lower surface of the low temperature reflector 100, the synergistic effect of the low temperature and high emissivity due to cooling increases the ability of radiant heat exchange above the crystal, and Heat radiation from crystal 11 occurs efficiently. Thereby, the shape of the solid-liquid interface between the grown crystal 11 and the raw material melt 3 is always kept in a downward convex shape, and it becomes possible to grow a long single crystal with a high single crystallization ratio.

The high emissivity member 110 is, for example, graphite, boron nitride, boron nitride coated graphite, pyrographite, silicon nitride, silicon carbide, or the like. These materials are formed into a sheet shape according to the shape of the lower surface of the reflector 100, and are adhered to the lower surface so as to cover the lower surface. Or,
These materials may be coated on the lower surface of the reflector 100 by coating, plating, or the like.

Here, the emissivity of the high emissivity member 110 is
As described above, if it is higher than 0.4, a desired effect of improving the heat absorption capacity above the crystal can be obtained, but it is preferably 0.7 or more, and more preferably 0.8 or more. . The reason is that the heat absorption capacity above the crystal is much better. In addition, graphite,
The emissivity of each of boron nitride, boron nitride-coated graphite, pyrographite, silicon nitride, and silicon carbide is about 0.9.

When a crystal is grown using the manufacturing apparatus having the above-described structure, the reflector 1 is first set before starting the crystal pulling.
The reflector 100 is moved up and down to position the reflector 100 at an optimum height according to the target length of the crystal to be grown. Thereafter, the crystal is pulled by the LEC method as usual. The optimum height position of the reflector according to the crystal length to be grown is determined in advance by conducting experiments for growing crystals of various lengths.

According to the above embodiment, the reflector 100
Since the lower emissive member 110 is coated with the high emissivity member 110, the heat absorption capacity above the crystal is increased, and a sufficient amount of heat is radiated through the pulled crystal, so that the shape of the solid-liquid interface becomes an ideal downward convex shape. Thus, a high single crystallization ratio can be obtained.
Further, such a manufacturing apparatus is easily realized.

In the above embodiment, the lower surface of the reflector 100 is coated with the high emissivity member 110. However, the present invention is not limited to this. The lower surface of the reflector 100 itself may be surface-treated to increase the emissivity. .

In addition, the high emissivity member 110 may be a member in which the surface is treated with another metal material such as a copper plate to increase the emissivity in addition to those listed above. It may be attached to the lower surface of the reflector 100.

[0027]

EXAMPLES The features of the present invention will be clarified below with reference to examples and comparative examples. It is needless to say that the present invention is not limited by the following embodiments. Example 1 A crystal pulling furnace having the structure shown in FIG. 1 was used.
The lower surface of the stainless steel reflector was coated with isotropic graphite having a thickness of 3 mm to 10 mm as a high emissivity member. The tilt angle θ of the reflector with respect to the horizontal (see FIG. 1) was 23 °. Raise and lower this reflector,
It was positioned at an optimum height according to a target grown crystal length, which was obtained in advance through experiments or the like.

Then, Ga was directly synthesized in the crucible so that the charged amount of GaAs was 8.3 kg using Ga of 6N purity and As of 6N as GaAs raw materials.
In addition, 1.1 kg of B ₂ O ₃ was used as a sealant. The heating length of the heater was 145 mm. The crucible was made of pBN (pyrolytic boron nitride) with a diameter of 8 inches.
The relative rotation speed of the crucible was 20-30 rpm, and the crystal pulling speed was 7.5-9.0 mm / hr. When a GaAs single crystal having a diameter of 3 inches was repeatedly grown, the average length of the straight body length of the obtained GaAs single crystal was 180 mm.
± 10%. Example 2 A GaAs single crystal having a diameter of 3 inches was repeatedly grown under the same conditions as in Example 1 except that the angle of inclination θ of the reflector with respect to the horizontal (see FIG. 1) was set to 10 °. The average straight body length of the obtained GaAs single crystal was 173 mm ± 13%. Example 3 A GaAs single crystal having a diameter of 3 inches was repeatedly grown under the same conditions as in Example 1 except that the angle of inclination θ of the reflector with respect to the horizontal (see FIG. 1) was 35 °. The average straight body length of the obtained GaAs single crystal was 176 mm ± 15%. Comparative Example 1 A GaAs single crystal having a diameter of 3 inches was repeatedly grown under the same conditions as in Example 1 except that the angle of inclination θ of the reflector with respect to the horizontal (see FIG. 1) was set to 0 °. The average straight body length of the obtained GaAs single crystal was 155 mm ± 30%. Also, in the first embodiment,
The variation in the average length of the straight body length was larger than in Examples 2 and 3. Comparative Example 2 A GaAs single crystal having a diameter of 3 inches was repeatedly grown under the same conditions as in Example 1 except that the tilt angle θ of the reflector with respect to the horizontal (see FIG. 1) was 45 °. The average straight body length of the obtained GaAs single crystal was 150 mm ± 35%. Also, in the first embodiment,
The variation in the average length of the straight body length was larger than in Examples 2 and 3. (Comparative Example 3) A GaAs single crystal having a diameter of 3 inches was repeated under the same conditions as in Example 1 except that a water-cooled reflector made of stainless steel whose lower surface was not coated with a high emissivity member was used. Was trained. The average length of the straight body length of the obtained GaAs single crystal was 140 mm ± 40.
%Met.

It is needless to say that the present invention can be applied not only to the production of GaAs single crystals but also to the production of other compound semiconductor single crystals such as InP, InAs and GaSb.

[0030]

According to the present invention, a crucible containing a raw material and, if necessary, a sealant is placed in a high-pressure container, and the crucible is heated by a heater provided in the high-pressure container, and the raw material and the crucible are heated. In a manufacturing apparatus used for growing a single crystal by melting a sealing material and gradually bringing a seed crystal into contact with the surface of a raw material melt, the crystal can be raised and lowered above a crystal pulling space in the high-pressure vessel. Reflectors are provided,
The reflector is inclined so as to be higher from the vicinity of the inner peripheral surface of the high-pressure container toward the central axis of the high-pressure container, and at least the lower surface of the reflector has an emissivity of 0.1 mm.
Since it is higher than 4, it is possible to easily realize a single crystal manufacturing apparatus capable of growing a crystal at a high single crystallization rate.

According to the present invention, a crucible containing raw materials and, if necessary, a sealant is installed in a high-pressure vessel using the above-described single crystal manufacturing apparatus, and is provided in the high-pressure vessel. In order to grow a single crystal by heating with a heater to melt the raw material and the encapsulant and gradually pulling the seed crystal into contact with the surface of the raw material melt, an optimum height position of the reflector is determined in advance. Since the pulling of the crystal is started after the reflector is raised and lowered and adjusted to the optimum height position, the height position of the reflector is optimally adjusted according to the length of the crystal to be pulled up.
The endothermic capacity above the crystal can be optimally set according to the target crystal length, and single crystals of various lengths can be grown with a high single crystallization ratio.

[Brief description of the drawings]

FIG. 1 is a schematic view of a single crystal pulling furnace used in practicing the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heater 2 Crucible 3 Raw material melt 4 Liquid sealant 5 High-pressure container 6 Susceptor 7 Crucible support shaft 8 Crystal pulling shaft 9 Seed crystal 10 Heat insulator 11 Single crystal 100 Reflector 110 High emissivity member

Claims (7)

[Claims] 1. A crucible containing a raw material and, if necessary, a sealant is placed in a high-pressure container, and heated by a heater provided in the high-pressure container to melt the raw material and the sealing material. In a manufacturing apparatus used for growing a single crystal by bringing a seed crystal into contact with the surface of a raw material melt and gradually pulling the same, a reflector capable of ascending and descending is provided above a crystal pulling space in the high-pressure vessel. And the reflector is
While being inclined so as to become higher from the vicinity of the inner peripheral surface of the high-pressure container toward the central axis of the high-pressure container, at least the lower surface of the reflector has an emissivity higher than 0.4. For manufacturing compound semiconductor single crystals. 2. The compound semiconductor single crystal manufacturing apparatus according to claim 1, wherein the emissivity of at least the lower surface of the reflector is preferably 0.7 or more, more preferably 0.8 or more. . 3. At least a lower surface of the reflector is coated with one or more substances selected from the group consisting of graphite, boron nitride, boron nitride-coated graphite, pyrographite, silicon nitride, and silicon carbide. 3. The method according to claim 1, wherein
An apparatus for producing a compound semiconductor single crystal according to the above. 4. The apparatus for producing a compound semiconductor single crystal according to claim 1, wherein the reflector is cooled by cooling water passed through the inside of the reflector. 5. The compound semiconductor single crystal manufacturing apparatus according to claim 1, wherein an angle of inclination of the reflector with respect to the horizontal is 10 ° or more and 35 ° or less. 6. A crucible containing raw materials and a sealant as necessary is installed in a high-pressure vessel using the apparatus according to any one of claims 1 to 5, and is provided in the high-pressure vessel. In order to grow a single crystal by heating the raw material and the sealing material by heating with a heater and gradually pulling the seed crystal in contact with the surface of the raw material melt, the optimum height position of the reflector is determined in advance. A method of manufacturing a compound semiconductor single crystal, comprising: raising and lowering the reflector to adjust the height to the optimum height position; and starting pulling the crystal. 7. The method for producing a compound semiconductor single crystal according to claim 6, wherein the reflector is raised and lowered during crystal pulling.