JPH1129390A - Single crystal growth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing a single crystal capable of eliminating evil practices in the seeding work such that more than necessary dissolution of a seed crystal is caused by the rapid flow of a molten liquid at the shoulder part into the set position of the seed crystal during the elevation of temperature before the seeding, or on the other hand the amount of the molten liquid becomes too little by the too slow elevation of the temperature. SOLUTION: This method for growing a single crystal is provided by preparing a quartz boat 7 made of a quartz and having 55 mm width and 600 mm length in the horizontal type Bridgeman method, charging 2,500 g Ga and 2,700 g As in the quartz boat 7, and placing a seed crystal having 2 cm width and 5 cm length at the one end of the quartz boat 7 and 20 g blocks of 10 mm cube collected from crushed GaAs crystals 9 at the shoulder part 9. The weight of the portion corresponding to the shoulder part is 100 g, thus the weight ratio is 20 %. The GaAs crystal is grown under the above conditions. The melting at the seeding is well controlled and the seeding is also smoothly performed. The melting property can be controlled in the above conditions better than the case of making the weight ratio of 40% and other conditions the same.

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, and can be applied, for example, to fabricating a compound semiconductor single crystal such as GaAs by the Bridgman method.

[0002]

2. Description of the Related Art The main industrial semiconductor crystal material that is currently industrialized is silicon, but GaAs, InP, GaP and the like.
III-V group compound semiconductor crystal materials such as, for example, have a characteristic that silicon does not have, such as a high electron transfer speed in the material and light emission at a pn junction.
It is one of the industrially important materials as a substitute for silicon or a material that complements silicon.

The Bridgman method is widely used as one of the manufacturing methods. This method is a crystal growth method in a container in which a crystal melt accommodated in a container is gradually increased in diameter or width from a seed crystal arranged at one end and solidified so as to have a substantially constant shape. Either a method of moving the container with respect to the furnace body or a method of moving the furnace body with respect to the container is used as a method of solidification.

[0004] A flat-bottomed boat-shaped container is often used,
Sometimes called the boat method. There are a horizontal Bridgman method (FIG. 3) and a vertical Bridgman method depending on the direction of solidification and the shape of the container, but the basics of the Bridgman method are the same. In addition, a slow cooling method (Gradie) in which a crystal is grown by changing the temperature distribution in the furnace without moving the furnace body.
nt Freezing Method), which is an improved method for eliminating a mechanical part for driving the furnace body and the vessel in the Bridgman method, and is treated here as being the same as the Bridgman method. A method combining the Bridgman method and the slow cooling method has also been developed.
This is also treated here as being the same as the Bridgman method.

[0005] Horizontal, vertical Bridgman method, horizontal, horizontal,
The characteristics of crystal growth in a container such as the vertical slow cooling method are that it can be manufactured in relatively small equipment and that the crystal growth is easy. This is a widely used crystal growth method.

For example, GaAs crystals made of the above-mentioned materials and used in industrially important products such as light-emitting diodes, laser diodes, field-effect transistors and integrated circuits have also been produced by this manufacturing method. The crystal growth method related to the Bridgman method for III-V compound semiconductor crystals is described in detail in the literature: "Bulk Crystal Growth Technology", Advanced Electronics Series, edited by Keigo Chikawa, and published by Baifukan.

[0007] In the Bridgman method, a so-called seeding step of starting the growth of a crystal from a seed crystal is one of the important steps. In this step, after one end of the seed crystal is slightly melted and blended with the melt, solidification is started by lowering the temperature of the melt. Whether a crystal becomes a single crystal or a crystal with excellent crystallinity grows
It can be said that it is almost determined in this seeding step.

Generally, a seed crystal having a diameter smaller than a target crystal size is used. After the seeding is completed, the crystal size is gradually increased to a desired size. this is,
This is to avoid a large change in the amount of heat and a large change in the thermal strain by rapidly increasing the crystal size. Such a portion where the size gradually increases is called a crystal shoulder. The container used in the Bridgman method for this purpose has a shape in which a seed crystal portion, a tapered shoulder portion, and a fixed portion (straight body portion) are connected in this order.

[0009] The seeding operation comprises a continuous operation of melting, holding and solidifying, and the melting step is a particularly important operation. In the Bridgman method, if an example of GaAs is used, G is a raw material of GaAs in a container.
GaAs is synthesized by charging and heating a and As, an additive dopant metal, and a GaAs seed crystal, and a melt is prepared. Then, a seeding operation is performed.

Melting of GaAs before seeding is mainly performed from the end opposite to the seed crystal. After melting the straight body, the shoulder is melted, and finally the end of the seed crystal comes into contact with the melt. To do. At this time, it is necessary to gradually raise the temperature of the melt.

[0011]

However, in general, a seed crystal having a square or column shape of 5 to 40 mm and a length of about 100 mm or less is used. The seeding operation is usually performed within a range where about 10 mm of the seed crystal is melted. The reason is that the oxidized portion of the seed crystal surface cannot be melted by melting of about 1 to 2 mm, so that polycrystallization is likely to occur at the surface portion as a nucleus. This is because single crystal growth starts in a long region, but it is difficult to set temperature conditions necessary for single crystallization in that region, and polycrystal is easily formed.

When the temperature is raised before seeding, there is a possibility that the melt at the melted shoulder portion rapidly flows into the installation portion of the seed crystal 2 (FIG. 3) and dissolves the seed crystal 2 more than necessary. On the other hand, if the temperature is raised too slowly, the melting portion will be too small. Since the seeding portion cannot be seen directly by the vertical growth method, it is performed depending on the temperature, and it is often difficult to observe the seeding portion even in the horizontal type. In the crystal growth of the GaAs crystal 3, it is generally difficult to observe because the crystal is grown in the ampoule 5 made of quartz glass. In addition, since the quartz boat 1 is used as a growth vessel, heat conduction to the melt is poor, and responsiveness to temperature change is poor, so that the seeding operation relying on temperature is a difficult operation requiring skill.

The single crystallization rate greatly depends on the success or failure of this seeding operation. In industrial production, reproducibility, maintenance of yield, and effective utilization of expensive rare raw materials such as Ga and As are considered in industrial production. There is an economic problem.

In view of the above, there is a need to provide a new crystal growth method by the Bridgman method that enables seeding work that does not require skill, and to solve industrial and economic problems. I have. That is, in the temperature increase before seeding, the melt at the melted shoulder rapidly flows into the seed crystal setting portion and dissolves the seed crystal more than necessary, or on the other hand, the temperature rises too slowly and the melting portion is small. By providing a method that can eliminate the harmful effects of seeding work such as being too long, it is necessary to make it easier to perform the seeding work that has to rely on temperature because it is impossible to directly look at the work state in the past. Have been.

[0015]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for growing a single crystal in which a melt is brought into contact with a single crystal seed crystal disposed at one end of a crystal growth vessel and then solidified from the single crystal. Solves the above-mentioned problem with the following characteristic configuration.

That is, according to the present invention, a portion between a seed crystal and a regular crystal in a crystal growth vessel used for growing a single crystal, which corresponds to a shoulder portion where the crystal outer diameter gradually increases, is added to the shoulder portion. When charging the corresponding crystal raw material, a crystal raw material whose size does not exceed a predetermined volume is
At the time of crystal growth, the above-mentioned charge is performed by including a predetermined ratio or more with respect to the weight existing in the above-mentioned portion.

As described above, a method of charging a crystal having a size not exceeding a predetermined volume in a portion corresponding to the shoulder portion by including a predetermined ratio or more of the weight existing in the shoulder portion during the crystal growth is employed. Of the raw material at the shoulder portion can be easily melted. In other words, by disposing a material having a small heat capacity on the shoulder, a state in which the material is easily melted is generated,
As a result, the melting can be performed depending on the slow rate of the temperature rising rate of the melt controlled by the furnace temperature, and the seeding can be easily performed.

Specifically, it is preferable that the predetermined volume of the crystal raw material has a size not exceeding about 1 cm ³ and the predetermined ratio of the above weight is about 20% or more. Further, the crystal raw material is preferably a block or a wafer-like flake obtained by crushing a GaAs crystal.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the drawings.

In the present embodiment, when a raw material in a crystal growth vessel used in the Bridgman method is charged, a crystal having a volume not exceeding 1 cm ³ is grown at a portion corresponding to a shoulder. In some cases, the method of charging by adding more than 20% of the weight present in the shoulder portion facilitates melting of the raw material of the shoulder portion during the seeding operation, thereby making the seeding operation simple and excellent in reproducibility. Improve.

That is, by arranging a material having a small heat capacity on the shoulder, which is the final melting portion, a state in which the material is easily melted is generated, and as a result, the temperature rise of the melt controlled by the temperature of the furnace is performed. Facilitating the seeding operation by allowing melting to occur depending on the slow speed.

Here, the reason why the crystal has a size not exceeding 1 cm ^{3 is} that if it is too large, it will not be easily melted. For the same reason, charging is performed by including at least 20% of the shoulder weight. Even if the size is appropriate, if the ratio is too small, it will be difficult to melt, and if it is too large, it will be easy to melt. Because it is too long.

The raw material of the crystal is suitable for obtaining a crystal having the above-mentioned size, such as a crushed GaAs crystal block or a wafer-like flake. Further, a combination of a block and a wafer-shaped flake may be used.

Regardless of the horizontal or vertical Bridgman method or the method used in combination with the slow cooling method, the same effect can be obtained by charging the raw material obtained by the above-described crystal growth method to the shoulder of a container used. .

The inclination of the shoulder portion of the container from the seed crystal accommodating portion to the straight body portion, which is called a so-called shoulder angle, depends on the manufacturing method.
Depends on conditions. However, in the present embodiment, it is clear from the principle of the effect that the same effect can be obtained regardless of the shape, if it is placed on the shoulder, regardless of the shape, it is clear from the experiment. Was also confirmed.

[0026]

Next, embodiments of the present invention will be described.

(Embodiment 1) FIG. 1 is a conceptual diagram of a crystal material charge by a horizontal Bridgman method for explaining Embodiment 1 of the present invention. Table 1 shows the outline and results of the raw material charges of Examples 1-1, 1-2, 1-3, and 1-4 with respect to Comparative Examples 1 and 2.

[0028]

[Table 1]

In a horizontal (horizontal) Bridgman method, a quartz boat-shaped vessel (quartz boat 7) having a width of about 55 mm and a length of about 600 mm is prepared, and 2500 g of Ga and 2700 As are prepared.
g, charged into the quartz boat 7. In Example 1-1, one end of the quartz boat 7 has a width of 2 cm and a length of 5 cm.
The seed crystal 8 was placed on the shoulder 15 and 20 g of a block of about 10 mm square collected from the crushed GaAs crystal was placed on the shoulder 15.

The weight of the portion corresponding to the shoulder 15 is about 100
g, and the weight ratio (charge amount ratio) is 20% (= 20
g / 100 g). Under these conditions, 5100 g of GaAs single crystal was grown. Melting during seeding,
The controllability was good and the seeding was smooth. In Example 1-2, the meltability could be controlled by setting the weight ratio to 40% under the same conditions.

On the other hand, in Comparative Example 1 in which no block was added, it was difficult to control the melting, and it was difficult to perform seeding. In addition, as shown in Comparative Example 2, the size of the raw material was 1 cm.
^{When the} size was changed from ³ to 1.5 cm ³ , a good effect was not exhibited with a large crystal material size, and the size of the crystal material was 1 cm.
If ^{the 3} not exceeding, 0.2 cm ³ of Example 1-3, when the 0.05 cm ³ of Example 1-4, a good control of the melt was easy seeding. Further, it was confirmed that the same effect can be obtained not only in a block shape but also in a wafer shape.

(Embodiment 2) Next, Embodiment 2 will be described. Table 2 shows Example 2- for Comparative Examples 3-1 and 3-2.
1 shows an outline and results of charge of crystal raw materials 1 and 2-2.

[0033]

[Table 2]

In the same manner as in the first embodiment, in the horizontal Bridgman method, a quartz boat-shaped vessel (quartz boat 7) having a width of about 55 mm and a length of about 600 mm was prepared.
5100 g of GaAs from 2700 g of raw material charge
An s single crystal was grown.

On the shoulder 15, 20 g of a block of about 6 mm square taken from the crushed GaAs crystal was placed. The weight of the portion corresponding to the shoulder is about 100 g, and the weight ratio is 20.
% (Example 2-1). At this time, the melting at the time of seeding was well controlled and the seeding was smooth.

In Example 2-2, when the weight ratio was 25% under the same conditions, the meltability could be more controlled. On the other hand, in Comparative Example 3-1, when the weight ratio was set to 15%, and in Comparative Example 3-2, the weight ratio was set to 5%, it was difficult to control the melting and difficult to perform seeding.

Third Embodiment Next, a third embodiment will be described. FIG. 2 is a vertical (vertical) view for explaining the third embodiment.
It is a conceptual diagram of the crystal raw material charge by a Bridgman method. In the vertical Bridgman method, a diameter of 75 mm and a length of about 3
A 100 mm pBN container was prepared, and Ga was synthesized in advance.
About 5000 g of As raw material was charged. A seed crystal 12 having a diameter of 10 mm and a length of 60 mm is placed at the lower end of the container.
A block collected from the crushed GaAs crystal 13 was placed on the slab. As a result, a single crystal having a diameter of 75 mm and a weight of 5000 g was obtained.

In this case, as in the case of the first and second embodiments, the size of the raw material at the portion corresponding to the shoulder is not effective for a large shape, and is melted when the size of the raw material does not exceed 1 cm ^3. The controllability was good, and the seeding was smooth and effective. The effect was effective at a weight ratio of 20% or more. The same effect was confirmed for the charge of the crystal raw material not only in the block shape but also in the wafer shape.

According to the first and second embodiments of the present invention, in the horizontal (horizontal) Bridgman method, a crystal having a volume not exceeding 1 cm ³ is placed at a portion corresponding to a shoulder portion by 20% or more by weight. By adding and charging, the controllability of melting is improved and the seeding can be easily performed. In Example 3, the same effect was obtained by the vertical (vertical) Bridgman method. That is, it was confirmed that the adoption of either the horizontal or vertical Bridgman method was effective.

In the above-described charge of the crystal raw material, an example has been described in which an undoped crystal is used without using a dopant. However, a similar effect can be obtained by using an n-type crystal doped with silicon or a p-type crystal doped with zinc. Confirmed that it can be done.

Regarding the charge of the crystal raw material, the same effect as described above can be obtained by starting from Ga and As in any of the manufacturing methods, starting from GaAs synthesized in advance, or mixing both. I was able to confirm.

From the above effects, it was confirmed that the seeding operation, which had conventionally relied on the operation of a skilled worker, can be sufficiently performed even at the reproducibility of an industrial level. Further, the single crystallization rate of the GaAs single crystal by the Bridgman method could be greatly improved. Therefore, the reproducibility and the yield can be maintained and improved in industrial production, and the expensive rare materials such as Ga and As can be effectively used.
It is also effective in terms of industrial production and economy.

[0043]

As described above, the present invention is applicable to a portion corresponding to a shoulder portion where a crystal outer diameter gradually increases from a seed crystal to a regular crystal in a crystal growth vessel used for single crystal growth. When charging the crystal raw material corresponding to the shoulder portion, the crystal raw material having a volume not exceeding a predetermined volume should be contained in the crystal raw material at a predetermined ratio or more with respect to the weight existing in the above-described region during crystal growth. By performing charging, it was possible to perform seeding that does not require skilled work.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a crystal material charge for a horizontal Bridgman method according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a crystal material charge for a vertical Bridgman method according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram of a furnace for performing crystal growth by a conventional horizontal (horizontal) Bridgman method.

[Explanation of symbols]

 1, 7, 11 Quartz boat 2, 14 GaAs crystal 3 GaAs crystal 4 As5 Quartz ampoule 6 Heater 8, 12 seed crystal 9, 13 Crushed GaAs 10 Ga 15, 16 Shoulder

Claims (4)

[Claims] 1. A single crystal growth method in which a melt is brought into contact with a single crystal seed crystal arranged at one end in a crystal growth vessel and then solidified from the single crystal. When charging the crystal raw material corresponding to the shoulder to a portion corresponding to the shoulder where the crystal outer diameter gradually increases from the seed crystal to the regular crystal in the crystal growth container, the volume of the crystal raw material is increased. A crystal raw material having a size not exceeding a predetermined volume is contained in a predetermined ratio or more with respect to the weight existing at the site during the crystal growth, and the charge is performed. 2. A predetermined volume of the crystal raw material is about 1 cm.
^{3. The} method for growing a single crystal according to claim 1, wherein 3. The single crystal growth method according to claim 1, wherein the predetermined ratio is approximately 20%. 4. The method for growing a single crystal according to claim 1, wherein said crystal raw material is a block and / or wafer-like flake obtained by crushing a GaAs crystal.