JPH09221377A - Single crystal growth method and apparatus - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a silica glass growth container used in the vertical Bridgman method in which a GaAs melt placed in a silica glass growth container is gradually solidified from a lower part to an upper part, even at a high temperature during growth. It should not be deformed and should not be damaged during cooling after growth. SOLUTION: The outer periphery of a cylindrical quartz glass growth container 1 for crystal growth is supported by a cylindrical ceramic supporter 5. The tubular ceramic support 5 is axially divided into at least three parts so that it can be assembled into a tubular shape. During the growth, in order to prevent thermal deformation of the quartz glass growth container 1, a heat-resistant metal wire 6 is wound around the outer periphery of the divided ceramic support tool 5, and the clamping force of the metal wire 6 causes the ceramic support tool 5 to grow. Is fixed to the outer circumference of the quartz glass growth container 1. The metal wire 6 is tightened by a radially outward external force applied to the ceramic support 5 due to a difference in thermal contraction rate between the ceramic support 5 and the quartz glass growth container 1 during cooling after crystal solidification. To be released.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a single crystal by a vertical Bridgman method and an apparatus therefor, and more particularly to a supporting method and a supporting tool for supporting a quartz glass growth container in order to prevent deformation of the quartz glass growth container. It relates to the improved one.

[0002]

2. Description of the Related Art In recent years, a vertical Bridgman method has been attracting attention as a method for obtaining a GaAs crystal having a large size exceeding φ3 inches and a low dislocation density, instead of the liquid sealing pulling method (LEC method). . In this method, a seed crystal is placed in the lower part of the growth vessel, a GaAs raw material is placed on it, and in a vertical electric furnace in which the temperature distribution is high in the upper part and low in the lower part, from the lower part to the upper part on the seed crystal side This is a method of solidifying the crystals.

The vertical Bridgman method itself is based on GaAs
Other than the above, it is a method that has been known for a long time for growing crystals of group II-IV. In the vertical Bridgman method, it was found that an undoped semi-insulating GaAs crystal was obtained by the LEC method by the development of pyrolytic boron nitride (pBN). Has been reviewed as a leading method, and is currently being studied in various fields.

However, the vertical Bridgman method, which is currently under study, was originally intended to obtain a semi-insulating crystal.
A BN growth container is used (see the following documents (1) to (3)).

(1) J. Cryst. Growth 74 , 491 (1986) (2) J. Mater. Res. Vol. 5, No. 7, 1468 (1990) (3) J. Cryst. Growth 94 , 643 ( 1989) However, pBN growth vessels are (1) very expensive,
(2) Impurities from pBN are mixed into the crystal unless it is covered with B ₂ O ₃ , (3) Similarly, bubbles are generated at the boundary with pBN on the crystal surface and the crystal surface becomes uneven, and crystals from this part defects are likely to occur, when covered with _{(4) B 2 O 3 B} 2 O
B (boron) reduced from ₃ has a fairly high concentration of GaAs
There were various drawbacks that it was mixed in the crystal.

[0006]

Recently, demand for not only semi-insulating crystals but also conductive crystals has been increasing. This is because conductive crystals such as Si-doped and Zn-doped have come to be used as substrates for semiconductor lasers and light-emitting diodes. In the vertical Bridgman method, a pBN container is not necessary to obtain a conductive crystal, and a quartz glass growth container is sufficient. The quartz glass growth vessel has already been used as a quartz boat by the horizontal Bridgman method (HB method).

However, when crystal growth is attempted using a quartz glass growth container as in the HB method, the quartz glass growth container is deformed in the GaAs growth temperature region (melting point 1238 ° C.). That is, if a large quartz glass growth container containing a GaAs melt is placed at a high temperature, it will be deformed by heat, so it is impossible to hold the quartz glass growth container in an upright position. Especially, the crystal length is 100
When the length is further increased from mm, the deformation of the quartz glass growth container becomes remarkable, and the crystal growth itself may become impossible.

Therefore, it is conceivable to enclose the outside of the quartz glass growth container with some kind of support member so as not to cause deformation of the quartz glass growth container, but this method involves heat shrinkage during the cooling process after solidification of the crystal. The difference in the rate (the thermal contraction rate of quartz glass is very small) damages the support member and the quartz glass growth container.

An object of the present invention is to solve the above-mentioned problems of the prior art, a single crystal growth method in which a quartz glass growth container is not deformed even at a high temperature during growth, and is not damaged during cooling after growth, and a method thereof. To provide a device.

[0010]

A method for growing a single crystal according to the present invention is a method for growing a single crystal by the vertical Bridgman method, in which a cylindrical ceramic supporter divided in advance into at least three parts is prepared. Then, the divided ceramic support tool is installed so as to surround the cylindrical quartz glass growth vessel, and the ceramic support tool is fixed by the tightening force of the heat-resistant metal wire wound around the outer circumference thereof. Then, the raw material melt placed in the quartz glass growth container is gradually crystallized from the lower part to the upper part, and at the time of cooling after the crystal solidification, the thermal contraction rate of the ceramic support and the quartz glass growth container Due to the external force in the radial direction given to the ceramic support from the quartz glass growth container due to the difference, the clamping force of the metal wire that fixed the ceramic support. In which it was to be released.

The vertical Bridgman method includes a vertical gradient freezing method (VGF method) in which growth is performed only by a temperature drop, a vertical Bridgman method (VB method) in which a growth container is relatively lowered to grow, and an As pressure. Both the control method and the method of covering the surface of the melt with B ₂ O ₃ to prevent the volatilization of As are included.

Further, in the single crystal growth apparatus of the present invention, a cylindrical quartz glass growth container is arranged vertically, and the raw material melt placed in the quartz glass growth container is gradually crystallized from the lower part to the upper part. In a single crystal growth apparatus for solidifying, a cylindrical ceramic supporter that is divided into at least three in the axial direction and supports the outer periphery of the quartz glass growth container, and tightens from the outer periphery of the divided ceramic supporter. Give power,
And at the time of cooling after crystal solidification, the ceramic support is cut by the external force in the radial direction given to the ceramic support from the quartz glass growth container due to the difference in thermal shrinkage between the support and the quartz glass growth container, or And a heat-resistant metal wire that extends.

In this case, as the material of the ceramic support tool and the metal wire, there are combinations of graphite support tool and Mo wire, or SiC support tool and Kanthal wire.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the single crystal growth method and apparatus of the present invention will be described in detail below. FIG. 1 is a schematic vertical cross-sectional view of a single crystal growth apparatus of this embodiment, and FIG. 2 is a perspective view of a ceramic supporter that supports a quartz glass growth container.

In FIG. 1, a quartz glass growth container 1 is placed in a vertical electric furnace 10 and mounted on a drive stand 7.
It is designed to descend while rotating. Vertical electric furnace 1
The electric furnace heating elements 8 which are divided into three in the horizontal direction are provided in 0, and each electric furnace heating element 8 has a low temperature in the lower part, a solidification temperature of the single crystal 3 in the intermediate part, and a raw material melt 4 in the upper part. It is controlled to maintain a high temperature.

The quartz glass growth container 1 has a cylindrical shape, and has a shoulder portion and a small-diameter seed crystal mounting portion for mounting the seed crystal 2 on the lower portion, and the shoulder portion is provided on the drive frame 7. It is placed on the shoulder susceptor 9 and vertically arranged in the furnace. G on the seed crystal 2 mounted on the seed crystal mounting part in the quartz glass growth container 1
A crystal raw material such as aAs is added.

The entire circumference of the quartz glass growth container 1 including the shoulder susceptor 9 is cylindrical and has an inner diameter substantially equal to the outer diameter of the quartz glass growth container 1 and surrounds and supports the quartz glass growth container 1. The supporting tool 5 is installed. This cylindrical ceramic supporter 5 is divided in the axial direction, a metal wire 6 is wound around several points on its outer circumference, and it is fixed to the outer circumference of the quartz glass growth container 1 by its clamping force.
Even if the metal wire 6 is tied after being wound one or more times,
Alternatively, it may be left as it is without being tied while being wound twice or more. The metal wire 6 has heat resistance to withstand the high temperature during crystal growth, and during cooling after crystal solidification, due to the difference in thermal contraction rate between the ceramic support 5 and the quartz glass growth container 1, the quartz glass growth container 1 is made of ceramics. The support 5 has such strength that the tightening force is released by an external force in the radial direction applied to the support 5. As shown in FIG. 2, the ceramic support 5 is composed of an arc-shaped segment 5a that is divided into at least three parts in the axial direction, and the divided ends 12 of the segment 5a are provided with steps so that they are meshed with each other, and when assembled into a cylindrical shape. The cylindrical shape can be securely supported by surrounding the outer periphery of the quartz glass growth container 1 without being displaced. Further, the ceramic support 5 assembled in a cylindrical shape has a metal wire 6 bound to the outer periphery thereof.
A plurality of ring-shaped wire grooves 11 for accommodating the wires are formed at intervals in the axial direction (three upper, middle, and lower in the illustrated example) to facilitate binding of the metal wire 6 and prevent misalignment. doing.

As described above, since the ceramic support 5 is used to prevent the deformation of the quartz glass growth container 1 and supports the outer circumference of the quartz glass growth container 1, the quartz is supported by the ceramic support 5 during crystal growth. It is possible to effectively prevent the glass growth container 1 from being thermally deformed. Therefore, it is possible to grow even in a growth container having a length of more than 100 mm.

Further, when the ceramic support 5 is divided in the vertical direction, and the periphery thereof is bound by the metal wire 6 and fixed to the outer periphery of the quartz glass growth container 1, the quartz support grows more than the ceramic support 5. Since the thermal contraction rate of the container 1 is small, the quartz glass growth container 1 is not cooled during cooling after crystal solidification.
Although the outer diameter of the ceramic support 5 is slightly reduced, the ceramic support 5 is significantly reduced in diameter, so that the ceramic support 5 receives an external force pushed outward from the quartz glass growth container 1. At that time, the force cannot be resisted and the tightening force of the metal wire 6 fixing the ceramic support 5 is released. As a result, if the metal wire 6 is bound, it is cut and wound twice or more. In the case of being kept rotated, it loosens, so that the ceramic support 5 and the quartz glass growth container 1 are free from damage.

[0020]

[Table 1]

Here, a mechanism of cutting the metal wire 6 will be described. As shown in Table 1, both the ceramics and the metal wires have a coefficient of thermal expansion larger by one digit or more than the coefficient of thermal expansion of quartz glass (about 5 × 10 ⁻⁷ (K ⁻¹ )). That is, when the temperature is raised, both the ceramics and the metal wire are loosened with respect to the quartz glass. However, during the crystal growth, the quartz glass growth container 1 is thermally deformed (due to both the thermal deformation due to the weight of the quartz glass itself and the thermal deformation due to the weight of the crystal melt), and the metal wire 6 is passed through the ceramic support tool 5. Since the force in the pushing-out direction is applied, the metal wire 6 is not loosened. When cooled from this state to room temperature, the ceramic support 5 is vertically divided into three parts, so there is no stress-related problem, but only the metal wire 6 contracts greatly, and if it is tied, it will eventually be cut. . However, if the metal wire 6 has a high malleability, it will stretch without being cut.

When the metal wire 6 is cut, if the ceramic support 5 is divided into two parts, quartz glass growth is performed from both ends in the diameter direction of the quartz glass growth container 1 corresponding to the joint of the two parts. A stress toward the center is applied to the container 1, and there is a high possibility of breaking the quartz glass growth container 1. If it is divided into three or more, the contraction stress of the ceramic support tool 5 escapes to the outside and there is no possibility of breaking the quartz glass.

[0023]

【Example】

(Example 1) A GaAs single crystal growth will be described as an example with reference to FIG. After the seed crystal 2 and 3000 g of the GaAs raw material are placed in the quartz glass growth container 1, the quartz glass growth container 1 is sealed in vacuum. A graphite support, which is divided into three parts in the vertical direction, surrounds the quartz glass growth container 1 together with the shoulder susceptor 9, and is tied and fixed with a thin molybdenum wire of φ0.3 from the periphery and installed on the drive frame 7. After replacing the atmosphere in the furnace with Ar gas, the temperature of the vertical electric furnace 10 is raised. The seed crystal part is adjusted to about 1200 ° C, and the upper raw material part is adjusted to about 1245 ° C. After melting the raw materials to form a melt 4, the quartz glass growth vessel 1 is rotated and raised while seeding is performed while adjusting the temperature gradient at the solid-liquid interface to about 4 ° C./cm. Thereafter, while rotating, the quartz glass growth container 1 is lowered at a speed of 3 mm / h as shown by an arrow to solidify the crystal. After the whole is solidified, it is cooled to room temperature at about 100 ° C./h, and the quartz glass growth container 1 is taken out from the electric furnace together with the graphite support.

Since the graphite support has a higher thermal shrinkage than the quartz glass growth container 1, the graphite support is pushed out by the quartz glass growth container 1 during cooling to room temperature. By cutting only the quartz glass growth container 1 and the graphite support, damage was avoided. By this method, a GaAs single crystal with a diameter of about 80 mm and a straight body length of about 100 mm was obtained.

(Example 2) A SiC support was used as a ceramic support, and a kathal wire having a diameter of 0.5 mm was used in place of the molybdenum wire, and the crystal growth in air was performed in the same procedure as in Example 1. Was done. Also in this case, the quartz glass growth container and the SIC supporting tool are not damaged,
The crystals could be taken out.

In the above-mentioned embodiment, the case where the quartz glass growth container itself was regarded as the growth crucible for the growth was explained. Even when covered, the quartz ampoule is supported around the same by a split-type ceramic support as in the example to prevent deformation during growth, and after crystal solidification, the quartz ampoule is not damaged from the furnace. You can take it out.

The metal wire may be tied in a lateral direction on the ceramic support as in the embodiment, or in a diagonal direction. Also, for metal wire,
It also includes a ribbon-shaped part, which is partially constricted and is cut at that part. In addition, although the GaAs single crystal growth is described in the present embodiment, the GaAs
Besides, it can be applied to the growth of single crystal such as InP and GAP.

[0028]

According to the present invention, when a single crystal is grown in a quartz glass growth container by the vertical Bridgman method, the quartz glass growth container is supported by a ceramic support tool. The deformation during the growth of the container can be effectively prevented. Further, the ceramic support is divided into at least three parts, which are fixed to the quartz glass growth container by the metal wire tightening force, and the metal wire tightening force is released by the external force applied to the ceramic support during cooling. Since this is done, it is possible to effectively prevent damage to the quartz glass growth container and the ceramic support.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a single crystal growth apparatus for carrying out a vertical Bridgman method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a split type ceramic support of the present embodiment.

[Explanation of symbols]

 1 Quartz Glass Growth Container 3 Single Crystal 4 Raw Material Melt 5 Ceramic Support 6 Metal Wire 10 Vertical Electric Furnace

Claims (4)

[Claims] 1. A method for growing a single crystal by the vertical Bridgman method, in which at least three cylindrical ceramic supports are prepared in advance in the axial direction, and the divided ceramic supports are cylindrical. The quartz glass growth container is placed so as to surround it, and the ceramic support is fixed by the tightening force of the heat-resistant metal wire wound around the outer circumference of the quartz support, and the raw material melted in the quartz glass growth container is fixed. The liquid is gradually crystallized and solidified from the lower part to the upper part, and during cooling after the solidification, it is given to the ceramic support from the quartz glass growth container due to the difference in thermal shrinkage between the ceramic support and the quartz glass growth container. A single crystal characterized in that the tightening force of the metal wire fixing the ceramic support tool is released by an external force in the radially outward direction. Long way. 2. A single crystal growth apparatus in which a cylindrical quartz glass growth container is vertically arranged, and a raw material melt placed in the quartz glass growth container is gradually crystallized and solidified from a lower part to an upper part. A cylindrical ceramic support that is divided into at least three parts in the direction and supports the outer periphery of the quartz glass growth container, and a clamping force is applied from the outer periphery of the divided ceramic support, and after crystal solidification At the time of cooling, due to the difference in the thermal contraction rate between the ceramic support and the quartz glass growth container, the heat resistance which is cut or extended by the external force in the radial direction given to the ceramic support from the quartz glass growth container A single crystal growth apparatus comprising: a metal wire. 3. The single crystal growth apparatus according to claim 2, wherein a graphite support is used as the ceramic support and a Mo wire is used as the metal wire. 4. The single crystal growth apparatus according to claim 2, wherein a silicon carbide (SiC) support is used as the ceramic support, and a Kanthal wire is used as the metal wire.