JPH01278490A - Growth of crystal and crucible therefor - Google Patents

Abstract

PURPOSE:To facilitate a device of seed crystal and to lessen deviation of direction of growth of crystal by preparing a crucible and a seed crystal holding part separated from the crucible, packing a crystal raw material to the crucible, fixing seed crystal on the crucible and growing crystal. CONSTITUTION:In vertical Bridgman method, a main body 15 of crucible is charged with a crystal raw material 10. Then a seed crystal holding part 16 previously supporting seed crystal 1 is engaged with the outside of a lower opening of the main body 15 of crystal and the seed crystal 1 is attached to a seed crystal fixing part 18. After the single crystal 1 is attached to the fixing part 18, the seed crystal holding part, a member different from the main body 15 of crucible is engaged with the outside of the seed crystal fixing part 18 formed at the lower side of the main body 15. Single crystal is grown from the seed crystal 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crystal growth method and a crystal growth crucible.

More specifically, it is known as the vertical Bridgman method (vertical temperature gradient solidification method) or the liquid-sealed vertical Bridgman method (liquid-sealed vertical temperature gradient solidification method). The present invention relates to a crystal growth method for growing single crystals of metals or semiconductors (including compound semiconductors) using seed crystals, and a crucible for crystal growth used in this method.

[Prior art] GaAsj
The conventional technique will be described in detail below, taking the case of growing an L crystal as an example.

Figure 6 shows GaAs produced by the liquid-sealed vertical Bridgman method.
FIG. 2 is a schematic cross-sectional view schematically showing the inside of a furnace used for crystal growth. In FIG. 6, 1 is a seed crystal, 2 is a grown GaAs crystal, 3 is a crystal raw material (e.g., GaAs) melt, 4 is a liquid sealant (e.g., B20.), and 5 is a crucible having a generally circular cross-sectional shape. , 6 crucible holder, 7
A crucible shaft, 8 a heating element made of a single heating element or a combination of a plurality of heating elements, and 9 an airtight container.

In such a furnace configuration, crystal growth is normally performed in a similar manner. The procedure will be explained based on the Saimo style diagrams of FIGS. 6 and 7.

First, the seed crystal 1 is inserted into the crucible 5 from above, and the seed crystal 1 is attached to the seed crystal attachment part 12 that is integrally formed at the lower part of the crucible 5. Next, the crucible 5 is filled with a solid crystal raw material (GaAs raw material) 10 and a liquid sealant 11 which is also solid. After filling these, the inside of the furnace is heated to a high temperature by the heating element 8 to soften the liquid sealant 11 and to soften the GaAs raw material 10.
After melting, single crystal growth begins by seeding,
Crystal growth is gradually progressed to achieve a crystal growth state as shown in FIG.

[Problems to be Solved by the Invention] In the conventional crystal growth crucible 5 as described above, pyrolytic nitride (p-BN) is used as the material in order to reduce the amount of impurities mixed into the crystal. ) are frequently used.

However, it is known that the p-BN crucible has a very high manufacturing cost and that the finished dimensional accuracy of the crucible shape is not necessarily good due to its manufacturing principle.

On the other hand, the dimensional accuracy of the seed crystal attachment part 12 formed at the lower part of the crucible 5 has an important influence on the difficulty of attaching and detaching the seed crystal 1 and the yield of single crystal growth. for example,
If the inner diameter of the seed crystal mounting portion 12 is smaller than the specified value, it is necessary to reduce the outer diameter of the seed crystal by etching or the like to match the inner diameter of the seed crystal mounting portion 12. Also,
Even if the crucibles are aligned, if it is a little tight, it will be difficult to attach it, or if you force it to attach it, it will be difficult to attach and detach it after crystal growth, which will destroy the grown crystal and expensive crucible. It also led to results.

On the other hand, if the inner diameter of the seed crystal attachment part 12 is larger than the specified value, as schematically shown in FIG. As schematically shown in FIG. 9, during seeding, contact sometimes occurs between the tip 13 of the seed crystal 1 and the inner wall of the crucible 5, and as a result, grain boundaries 14 occur in the grown crystal 2. The grown crystal 2 becomes polycrystalline.

As described above, the conventional crucibles have many problems in crystal growth, particularly due to poor structure and dimensional accuracy of the seed crystal mounting portion 12.

On the other hand, it is considered possible to use only crucibles with uniform dimensions through inspection after crucible manufacturing, but in reality, it is difficult to precisely measure the dimensions of the narrow part of the seed crystal attachment part 12 of the crucible 5. It is not an effective solution because it is difficult to do so, and treating substandard crucibles as defective products will further increase the manufacturing cost of expensive p-BN crucibles.

Furthermore, in the conventional crucible, the solid crystal raw material 10 is filled inside the crucible 5 after the seed crystal 1 is mounted on the seed crystal mounting part 12 formed at the lower part of the crucible 5. During filling, the crystal raw material 10 hits the tip of the seed crystal 1, and there is a slight gap between the seed crystal and the seed crystal device, so the seed crystal deviates from the initially measured position, causing the crystal orientation of the seed crystal to change. There is a problem in that the growth direction of the grown crystal is shifted due to this.

The present invention has been made to solve the problems of the prior art, and aims to provide a new crystal growth method and a crystal growth crucible.

That is, an object of the present invention is to provide a crucible for crystal growth in which the seed crystal can be easily attached and the orientation of the seed crystal can be set reliably.

Another object of the present invention is to provide a crucible for crystal growth that allows easy and efficient (in a short time) work to remove the grown crystal from the crucible after crystal growth.

Furthermore, the present invention allows seed crystals to be attached reliably and
It is an object of the present invention to provide a crucible for crystal growth which can be performed without contacting the crucible wall and which can greatly improve the yield of grown single crystals.

The present invention provides a crystal growth method that can avoid misalignment of the crystal raw material to the seed crystal that occurs when filling the crystal raw material, and furthermore, can grow a single crystal with less misalignment in the crystal growth direction. With the goal.

[Means to solve the problem] The above problem is solved by the present invention described below.

The present invention provides a crucible for crystal growth used in a crystal growth method for growing a single crystal from a seed crystal attached to the lower part of the crucible, in which the crucible has a seed crystal insertion part opening downward on the outside of the crucible body. A first aspect of the present invention relates to a crucible for crystal growth, which is separate from the crucible body and is fitted with a seed crystal holding part for holding a seed crystal.

The present invention also provides a crystal growth method for growing a single crystal from a seed crystal attached to a lower part of a crucible; filling a crystal raw material inside a crucible body having a seed crystal insertion part opening downward; Seed crystals can be attached to the seed crystal loading part by fitting and attaching a seed crystal holding part which is separate from the crucible and holds the seed crystals in advance to the outside of the crucible body, or After being attached to the seed crystal charging part, a seed crystal holding part that is separate from the crucible body is fitted and attached to the outside of the crucible body; and then, crystal growth is performed after melting the crystal raw material. There is a second gist in the crystal growth method.

After all, the first gist of the present invention is that, as a means to solve the problems of the prior art, a crucible body and a seed crystal holding part are prepared separately from the crucible body, and these two parts are fitted and attached to each other for crystal growth. The main idea is to create a melting pot.

A second gist of the present invention is to use the crucible according to the first gist, fill the crucible with a crystal raw material, attach a seed crystal, and then grow the crystal.

The concept of the present invention will be explained below along with its operation while showing some embodiments.

(First aspect) FIG. 1 is a schematic cross-sectional view showing a first embodiment of the present invention.

In this embodiment, a seed crystal holding component 16 that is separate from the crucible body 15 and that holds the seed crystal 1 is fitted onto the outside of the crucible body 15 that has the seed crystal insertion portion 18 that opens downward. The crucible is assembled by fitting.

In the state shown in FIG. 1, the crucible body 15 is first filled with a solid crystal raw material (for example, GaAs raw material) 10 and a solid 820311 as a liquid sealant, and then the seed crystal holding part 1
The seed crystal 1 is fitted into the seed crystal fitting part 17 of 6, and the seed crystal 1 is held in the seed crystal holding part 16. With the seed crystal 1 held, the seed crystal holding part 16 is attached to the crucible body 1.
This is achieved by fitting the outside of the seed crystal insertion part 18 formed at the lower part of the seed crystal inserting part 5.

In this embodiment, since the seed crystal holding component 16 is thus separate from the crucible body 15, the seed crystal 1 can be attached easily and reliably.

In addition, in order to fit and attach the seed crystal 1 to the crucible body 5 after filling the crystal raw material 10 into the crucible body 15, the crystal raw material 1
It is possible to avoid misalignment between the crystal raw material 10 and the seed crystal 1 that occurs when filling the seed crystal 1, and it is possible to grow a crystal without misalignment of crystal orientation.

Note that when filling the crystal raw material 10, small blocks of the crystal raw material 10 come out from the opening of the seed crystal charging section 18, but large blocks of the crystal raw material 10 cause a so-called bridging phenomenon, and It forms a space nearby and stays within the crucible body. Therefore, when filling the solid crystal raw material 10, it is preferable to fill the large blocks first.

Figure 2 shows a schematic diagram of the state shown in Figure 1, which is heated by heating elements placed around it, softens the B20311, melts the GaAs raw material 10, and then adjusts the temperature of one part of the seed crystal to achieve the optimal seeding state. FIG.

In addition, in FIGS. 1 and 2, the diameter d of the seed crystal 1
In contrast, the inner diameter d° of the seed crystal insertion part 18 formed at the lower part of the crucible body 15 is within a certain tolerance range (however, the tolerance range is determined by the surface tension of the melt and d, d'). If you choose a larger size, the area around the seed crystal 1 will be B2.
034, and a meniscus 19 is formed at the upper end of the seed crystal, so that stable seeding can be achieved.

(Second Embodiment) FIG. 3 is a schematic sectional view showing an example of a crucible structure according to another embodiment that satisfies the gist of the present invention. Note that in this figure, illustration of the crystal raw material is omitted.

In this embodiment, the inner diameter of the seed crystal holding component 16 is narrow throughout its entire length. Therefore, processing is easy and higher dimensional accuracy can be obtained. Even in such a case, by making the diameter of the seed holding part 20 of the seed crystal 1 smaller than the diameter of the seed crystal holding part 21 of the seed crystal 1, the same effect as that shown in FIG. Stable seeding (due to meniscus formation) can be obtained.

(Third Embodiment) FIG. 4 is a schematic sectional view showing an example of a crucible structure according to another embodiment that satisfies the gist of the present invention.

In this embodiment, the seed crystal holding part 16 is made of a material different from that of the crucible body 15 which is made of p-BN, such as graphite or quartz, which is thermochemically stable even at high temperatures and has excellent workability. This is the case when it is configured as follows.

In this case, by selecting the difference between the diameter d of the seed crystal and the inner diameter d° of the seed crystal insertion part 18 to be smaller than a certain value, the softened liquid sealant (B20s) 4 can enter the seed crystal insertion part 18 and the seed crystal can be inserted into the seed crystal insertion part 18. It is also possible to prevent contact with the holding part 16. Thereby, there is no problem of contamination of impurities from the seed crystal holding part 16 made of a material different from that of the crucible body 15.

On the other hand, when the seed crystal holding part 16 is made of a material different from that of the crucible body 15 as in the above example, there is an advantage that the machining accuracy of the seed crystal holding part 16 can be improved. There are advantages such as an increase in the degree of freedom in thermal design of the seed crystal portion by selecting a material that is suitable for the seed crystal.

(Fourth aspect) FIG. 5 is a schematic sectional view showing another embodiment of the present invention.

In this embodiment, the crucible holder 22 also serves as a seed crystal holding component. That is, in this embodiment, the crucible holder 6 shown in FIG. 6 is characterized in that it has both the original function of holding the crucible and the function of the seed crystal holding component according to the present invention.

In this embodiment, after filling the crucible main body 15 with the crystal raw material 10, the seed crystal 1 is inserted into the seed crystal insertion part 18 at the lower end of the crucible main body 15, and then the entire crucible main body 15 is
It is fitted and mounted inside the crucible holder 22 which becomes the seed crystal holding part 22. As a result, the crucible holder (seed crystal holding part) 22 holds the seed crystal 1 with the seed crystal support part 23 at the lower part thereof, and also holds the crucible body 15, so that the state shown in FIG. 5 is realized.

The present invention as described above not only makes it easier to attach and detach seed crystals to and from crucibles, which has been a problem in the past when it comes to crystal growth operations, but also makes it possible to use expensive crucibles effectively. The improvement in yield will be explained by the following examples. Note that, as a matter of course, the scope of the present invention is not limited to the following examples.

[Example] (First Example) In this example, the crucible shown in FIG. 1 was used, and crystals were grown according to the following procedure.

Approximately 2000 g of GaAs raw material 10 and approximately 2008
820311 was filled. Next, a p-BN seed crystal holding component 16 with a diameter d of 7 mm and a growth direction of <
After fitting the seed crystal 1 of 100>, the seed crystal holding part 16 was fitted and attached to the seed crystal insertion part 18 formed at the lower part of the crucible body 15.

On the other hand, in this example, the inner diameter d° of the seed crystal insertion part 18 is d'
= 8.5 mm, so the crucible body 15 of the seed crystal 1
The installation work was extremely easy.

Thereafter, in a normal vertical Bridgman furnace as shown in FIG. 6, the crystal raw material 10 was melted, seeded, and grown to form crystals.

As a result, a single crystal in which all of the GaAs melt 3 was solidified as shown in FIG. 2 was obtained. In this example, the crystals are taken out from the crucible using the seed crystal holding part 1 shown in FIG.
After cutting 6 and the seed crystal 1 along the two-dot chain line AA', the entire crucible body 15 having the grown crystal inside is immersed in hot water to dissolve and remove the solidified B2O5, thereby removing the seeds in a short time. This could be easily done without destroying the grown crystal containing the part.

In addition, as a result of inspecting the crystal growth direction using X-ray diffraction, it was within ±0.5 degrees including measurement error, which met the practical requirements (
±1 degree or less).

Furthermore, as a result of growing a large number of crystals by the method described above, single crystals with a predetermined orientation were obtained with a high yield of 80% or more, compared to the conventional 30%.

Furthermore, no damage occurred to the crucible body 15 during the extraction of the crystals. In addition, the crucible body 15 is 2
It was also confirmed that it can be reused more than 0 times.

In this embodiment, in order to efficiently take out the grown crystal, a method of cutting the seed crystal holding part 16 and the seed crystal 1 was adopted. However, this method is not always necessary, and the seed crystal holding part 16 can be removed. It is also possible to take out the crystal without destroying it, in which case the seed crystal holding part 16
Like the crucible body 15, it can be reused many times. However, the seed crystal holding part 16 is a small part compared to the crucible body 15, and the material does not have to be the same as that of the crucible body 15, so it can be manufactured at a low cost, so there is no problem even if it is used destructively every time. This is also a big advantage.

(Second Example) In this example, a crystal holding part 16 shown in FIG. 3 was used as the crystal holding part.

That is, the crystal holding component in this example had an inner diameter of 0.15 mm over its entire length. The inner diameter d° of the seed crystal charging portion 18 was set to 8.5 mm as in the first embodiment.

On the other hand, the outer diameter d of the seeded portion 20 of the seed crystal 1 was made smaller than the outer diameter of the seed crystal holding portion 21, which was 7 mm.

Crystal growth was otherwise performed in the same manner as in the first example.

In this example, a meniscus was formed similarly to the first example, and stable seeding was possible.

Furthermore, the deviation in the growth direction of the grown crystals obtained was extremely small as in the first example, and the yield was also high as in the first example.

In this example, the dimensional accuracy of the seed crystal holder 16 was particularly good, and the seed crystal 1 could be attached extremely easily and reliably.

(Third Example) In this example, the pot shown in FIG. 4 was used. The crucible body 15 was made of p-BN, while the seed crystal holding part 16 was made of graphite. That is, in this example, the crucible body 15 and the seed crystal holding component 16 are made of different materials.

In addition, in this example, the inner diameter d° of the seed crystal charging section 18 is 8 m.
m, and the seed crystal 1 used had an outer diameter of 7.5 mm. That is, in this example, the seed crystal charging section 1
8 and fm child crystal 1 was made smaller than in other examples.

Crystal growth was otherwise performed in the same manner as in the first example.

The quality of the grown crystal obtained in this example was investigated. first,
When the impurity concentration was measured, there was no difference from the first example. Furthermore, the quality with respect to deviations in crystal orientation, etc., was also good as in the first example.

Note that when the inner wall of the seed crystal charging section 18 was observed after crystal growth, no BxO3 was found to be attached thereto.

(Fourth Example) In this example, a crystal holding component shown in FIG. 5 was used. In other words, the crucible holder also has the function of a crystal holding component.

In this example, after filling the crystal raw material 10 into the crucible body 15,
The seed crystal 1 was inserted into the seed crystal insertion part 18, and then the crystal holding part 22 was fitted and attached to the entire crucible body 15.

Crystal growth was otherwise performed in the same manner as in the first example.

When the quality of the obtained grown crystal was examined, it was found to have the same quality as in the first example.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

(Effects of Claim 1) The work of attaching the seed crystal to the crucible, which has been a problem in the crystal growth work in the past, becomes easier, and the orientation of the seed crystal can be set reliably.

Crystal removal work after crystal growth can be performed easily and efficiently (in a short time).

Since the seed crystal can be attached reliably and contact with the crucible wall can be reliably prevented, the yield of single crystal growth can be greatly improved.

Separating the crucible into the crucible body and the seed crystal holding part not only increases the number of reuses of the expensive crucible body, but also allows freedom in selecting the material of the seed crystal holding part, which is important for single crystal growth. This increases the degree of freedom in thermal design of the seed crystal part.

(Effect of Claim 2) Since the seed crystal is attached after the crystal raw material is filled, it is possible to avoid the positional shift of the crystal raw material to the seed crystal that occurs in the conventional technology, and to obtain a grown crystal without any shift in crystal orientation. be able to.

In the above explanation, the case where a GaAs crystal is grown by the liquid-sealed vertical Bridgman method was explained as an example, but the gist of the present invention can be applied to other crystals and other growth methods, and similar effects can be expected. There's no need to explain what you can do.

Furthermore, although p-BN has been mainly described as the material for the crucible body, it goes without saying that this is not the only material, and other materials can also be used.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views schematically showing the structure of a crucible and the inside of the crucible according to the first aspect of the present invention. FIG. 3 is a sectional view schematically showing the structure of a crucible and the inside of the crucible according to the second aspect of the present invention. FIG. 4 is a sectional view schematically showing the structure of a crucible and the inside of the crucible according to the third aspect of the present invention. FIG. 5 is a sectional view schematically showing the structure of a crucible and the inside of the crucible according to the fourth aspect of the present invention. FIG. 6 is a schematic cross-sectional view of the inside of a furnace showing the growth of GaAs crystals by the conventional liquid-sealed vertical Bridgman method. 7 to 9 are schematic sectional views showing changes in the internal state of the pot shown in FIG. 1. FIG. (Explanation of symbols) 1... Seed crystal 2... Grown GaAs crystal 3... Crystal raw material melt (GaAs raw material melt) 4... Liquid sealant (B203) 5... Crucible 6 ... Crucible holder 7 ... Crucible shaft 8 ... Heating element 9 ... Airtight container 10 ... Solid crystal raw material (Ga As raw material) 11
... Solid liquid sealant (B2 o3) 12 ... Seed crystal attachment part 13 ... Seed crystal tip part 14 ... Grain boundary in growing crystal 15 ... Crucible body 16 ... Seed crystal holding part 17... Seed crystal fitting part 18... Seed crystal insertion part 19... Meniscus 20... Seed part 21... Seed crystal holding part 22... Crucible holder (seed crystal holding parts) 23.
... Seed crystal support part Fig. 2 1 ... Seed crystal 10 ... Solid crystal raw material (GaAs raw material) 11 ...
Solid liquid sealant (B2 o3) 15... Crucible body 1B... Seed crystal holding part 17... Seed crystal fitting part 18... Seed crystal insertion part Figure 1 μl 2 Figure 3 4 Figure 11... Solid liquid sealant (E203) 15...
Crucible main body 23... Seed crystal support part Fig. 5 Fig. 7 Fig. 8 l... Seed crystal 2... Grown crystal (GaAs condensation 3... Crystal raw material melt (G aA sf4 cage 4) ...
Liquid sealant (B2 o3) 5... Crucible 14... Crystal boundary in growing crystal Figure 9

Claims (2)

[Claims] (1) In a crucible for crystal growth used in a crystal growth method of growing a single crystal from a seed crystal attached to the lower part of the crucible, the crucible has a seed crystal insertion part opening downward, on the outside of the crucible body. 1. A crucible for crystal growth, characterized in that the crucible is formed separately from the crucible body and is fitted with a seed crystal holding part for holding a seed crystal. (2) In a crystal growth method of growing a single crystal from a seed crystal attached to the lower part of a crucible; filling a crystal raw material inside a crucible body having a seed crystal insertion part opening downward; separate from the crucible body; Either the seed crystal is attached to the seed crystal loading part by fitting and attaching the seed crystal holding part which has a solid body and holds the seed crystal in advance to the outside of the crucible body, or the seed crystal is attached to the seed crystal loading part. After being attached to the crucible, a seed crystal holding component that is separate from the crucible body is fitted and attached to the outside of the crucible body; and then crystal growth is performed after melting the crystal raw material. Method.