JPS63222094A - Crucible for producing single crystal - Google Patents

Abstract

PURPOSE:To obtain a crucible for producing a single crystal, consisting of the upper large-diameter part for mainly, containing a liquid encapsulating agent, the lower small-diameter part for mainly containing a raw material melt and an intermediate horizontal stage connecting both and capable of readily washing a liquid encapsulating agent without limiting diameter of the single crystal in a hermetically sealed space. CONSTITUTION:The interior of a pressure-resistant vessel of a furnace is decompressed to a vacuum and an inert gas, such as N2, is introduced to provide a high-pressure inert gas atmosphere. A crucible 1 is then heated to melt an encapsulating agent and raw material solid and form a two-layered structure of the raw material melt 2 and the liquid encapsulating agent 3. A pulling up shaft 5 is then lowered to dip the lower end of the hermetically sealed vessel 4 in the encapsulating agent 3 and form a hermetically sealed space (S). The shaft 5 is further lowered to dip a seed crystal 6 in the melt 2 and carry out seeding. The shaft 5 is subsequently pulled up while being rotated to pull up the seed crystal 6 and then a single crystal. During the time, the single crystal in in the hermetically sealed space (S). Since the partial pressure of a groove V element is high, evaporation of the groove V element from the surface of the single crystal can be prevented without causing a phenomenon, such as roughening of the surface.

Description

[Detailed Description of the Invention] B) Technical Field This invention is applicable to GaAs, InP, GaP, InA.
The present invention relates to a crucible used for producing a single crystal of a compound semiconductor containing a volatile group V element such as s.

A single crystal of a ■-■ group compound semiconductor is often manufactured by the HB method or the LEC method.

Among these, the LEC method is a pulling method, and has the advantage that it produces a circular single crystal ingot, so there is little material waste, and that it is easy to obtain a semi-insulating non-doped single crystal.

(a) The conventional technology LEC method is Liquid Encapsulate.
d An abbreviation of the Czochralski method, which is also called the liquid capsule method.

Put the ■-■ compound raw material into the crucible, and add B2O on top of it.
Enter 3. When heated with a heater, the top of the raw material melt becomes B2.
The O3 liquid capsule becomes covering. Volatilization of the group V element can be prevented by applying pressure with an inert gas to press down the liquid capsule.

According to the liquid capsule method, the liquid in the crucible has a two-layer structure of the raw material melt and B2O3. The surface of B2O3 is under high pressure due to the inert gas. This inert gas spreads throughout the pressure vessel. Only in the vicinity of the crucible,
It's not a closed space.

For this reason, the pulled crystal is exposed to intense convection of the inert gas, causing thermal distortion. Furthermore, there is a possibility that group (I) elements are removed from the surface of the crystal, causing the surface to become rough.

In this way, in the LEC method, the space above B2O3 is an open space. Because it is an open space, there are the following drawbacks. However, on the other hand, it has the advantage of freely transmitting information such as inert gas pressure control and pressure changes.

The LEC method is a relatively new method.

Before the invention of the LEC method, GaAS was often manufactured by a method in which pulling was performed in a closed space.

This uses a vertically long quartz tube. The bottom is wide and made of GaAS
Add the raw materials.

A pulling shaft with a seed crystal attached to the lower end is suspended, and the middle part of the quartz tube is tapered to the extent that it comes into contact with the outer surface of the pulling shaft.

B2O3 is placed between the two shafts and the intermediate reduced diameter part of the quartz tube. The space between the pulling shaft and the reduced diameter portion is sealed by B2O3.

The lower half of the crucible becomes a closed space. Raw material melt is B2
Not covered by O3. The pressure in the space is the sum of the partial pressures of the component gases evaporated and volatilized from the free surface of the raw material melt.

For this reason, the partial pressure of the group ■ elements increases, and V from the melt increases.
It becomes balanced with the volatilization of group elements. Furthermore, since the single crystal is drawn into a closed space, there is almost no loss of group II elements.

In this way, a single crystal with good stoichiometry is pulled.

In this method, liquid is sealed between the reduced diameter part of the quartz tube and the pulling shaft using B2O3.
This is called the Hralski method.

This method is currently rarely used. Since the single crystal is pulled in the closed space of a quartz tube, it is not possible to produce long crystals with large diameters. It would be difficult to make such a complicated shape without a quartz tube, but if a quartz crucible is used, Si contained in the quartz may mix into the raw material melt and the impurity concentration may fluctuate. Since Si is an n-type impurity in GaAs, it is difficult to obtain a semi-insulating substrate using this method.

Another drawback is that the pressure in the sealed space cannot be controlled because the raw material is enclosed.

Currently, PBN crucibles are frequently used as crucibles.

PBN does not contaminate the raw material melt and is an extremely excellent material. However, it has the disadvantage of being expensive. Furthermore, it is insufficient in terms of rigidity, and is usually held by a carbon susceptor.

PBN (pyrolitic BN) does not have the ability to be freely shaped like quartz, so it is not possible to use PBN as a material to make containers using the complicated LiquidSeal Czochralski method. Therefore, it is used as a crucible for the LEC method, but in this case, it is a simple cylindrical shape with a bottom.

Both the Liquid 5eal Czchralski method and the LEC method have their own advantages.

Therefore, a new method was proposed that combines the advantages of both methods. FIG. 3 shows a longitudinal cross-sectional view of the main parts. This is a combination of a crucible 7 and a downwardly open sealed container 4 supported by a pulling shaft 5.

The crucible 7 contains a raw material melt 2 and a liquid sealant 3.

The closed container 4 has a shaft hole 9 in the upper part. Above this is a tray 10. Pass the pulling shaft 5 through the shaft hole 9,
For the receiver, put liquid sealant (B203) 3 in the tray 10.

A seed crystal 6 is attached to the lower end of the pulling shaft 5.

Although not shown, there is a resistance heater around the crucible 7. Furthermore, the entire structure is surrounded by a pressure-resistant container.

Such a configuration can be referred to as a double container configuration.

The lower end of the closed container 4 is immersed in the liquid sealant 3.

In this way, a closed space S is created. Closed space S is closed container 4
This is a space surrounded by the liquid sealant 3 and the liquid sealant 3.

The pressure in the closed space S is the sum of the partial pressure of the inert gas and the partial pressure of the V group element gas.

At the outer edge of the crucible 7, the liquid sealant 3 is applied to the outer furnace space T.
is in contact with. The furnace space T is a space surrounded by a pressure vessel. This pressure can be freely controlled by adjusting the amount of inert gas to be introduced.

In order to balance the liquid level of the liquid sealant 3 in the crucible 7 inside and outside the closed container 4, the pressure in the furnace space T must be controlled.

From the raw material melt 2 in the crucible 7, a gas of group Ⅰ elements is generated. This dissociation pressure is determined by temperature. However, liquid sealant 3
, and because there is an inert gas (nitrogen, argon, etc.) in the closed space, the partial pressure of the group element element in the closed space does not always have to be the same as that of the group Ⅰ element in the closed space. As the crystal is pulled up, ■
The partial pressures of group elements are balanced, and the escape of group (Ⅰ) elements from the crystal surface is suppressed.

FIG. 4 shows another conventional example.

The point that the closed container 4, which is opened downward, is suspended by the upper shaft 5 remains unchanged. The crucible is not a simple cylinder with a bottom. A circumferential groove 11 for filling the liquid sealant 3 on the upper periphery is integrally formed with the crucible 8.

A liquid sealant 3 is contained in the circumferential groove 11.

The lower end of the airtight container 4 is submerged here.

In this way, a closed space S is created by the closed container 4 and the crucible 8. There is no liquid sealant on the raw material melt 2.

In this way, the diameter of the closed container 4 can be made comparable to that of the crucible.

Since the single crystal will be pulled up into the closed space S,
The partial pressure of the group (■) is balanced on the surface of the single crystal, and there is no possibility that the group V elements will volatilize from the surface of the single crystal. There is no possibility that the single crystal will be cooled by the vigorous thermal convection of the inert gas in the furnace space T, causing thermal distortion. A good single crystal can be pulled.

By adjusting the pressure of the inert gas in the furnace, the liquid sealant 3 is balanced between the inside and outside at the position of the circumferential groove 11.

(b) Problems to be Solved by the Invention In the structure shown in FIG. 3, the outer diameter of the closed container 4 is smaller than the inner diameter of the crucible. The single crystal grows in a narrow closed space S. Therefore, the size of the single crystal is limited by the closed container 4.

Roughly speaking, the relationship between the size of the crucible and the single crystal is such that twice the outer diameter of the single crystal is equal to the inner diameter of the crucible.

However, in the apparatus shown in FIG. 3, the closed container 4 is narrow, so the single crystal becomes thinner.

It is strongly desired to grow a single crystal with a large diameter, and a structure that limits the diameter of the single crystal is not preferred.

The structure of FIG. 4 is free from such drawbacks. However, since the liquid sealant 3 is held in the circumferential groove, there is a drawback that processing after crystal growth is difficult.

B2O3 is a material with poor removability. After cooling and solidifying, it must be removed from the crucible 8, but the narrow circumferential groove 1
It is difficult to remove the B2O3 that has solidified inside 1. When the crucible and the circumferential groove 11 are repeatedly deformed manually, the B2O3 gradually peels off. This will be done manually. It does not always work, and there is a high possibility that the crucible will be damaged.

00 Purpose It is possible to pull compound semiconductor single crystals in a sealed space, and the diameter of the single crystal is limited.

It is an object of the present invention to provide a crucible for pulling a single crystal in which the liquid sealant can be easily cleaned without causing any damage.

(4) Structure The crucible of the present invention is an inverted convex crucible consisting of an upper large-diameter part that mainly contains a liquid sealant, a lower small-diameter part that mainly contains a raw material melt, and an intermediate horizontal stage that connects the two. It is in the form of a shape.

FIG. 1 is a sectional view of a crucible for producing a single crystal according to the present invention.

It is different from a normal cylindrical crucible with a bottom.

A wide cylindrical large diameter section 13 is located above. Following the large diameter portion 13 is a disk-shaped horizontal step 14 . A small diameter portion 15 is formed following the horizontal stage 14. The cylindrical small diameter part 15 has an inner bottom part 17, and the lower part is a closed container. The upper part is a wide opening 16.

Although it has rotational symmetry, it has a stepped opening-shaped form.

FIG. 2 shows a part of a single crystal growth apparatus using this crucible.

A raw material melt 2 and a liquid sealant 3 are housed in a cross-shaped crucible 1. The liquid sealant 3 mainly exists in the large diameter portion 13.

The raw material melt 2 mainly exists in the small diameter portion 15 .

Of course, as the raw material melt 2 decreases as the crystal growth progresses, the liquid sealant 3 also moves toward the small diameter portion 15.

The closed container 4 is a container with an opening at the bottom, and its lower end is inside the large diameter portion 13 of the crucible 1. It is immersed in the liquid sealant 3 in the large diameter portion 13.

A shaft through hole 9 is formed in the upper part of the closed container 4 with a reduced diameter and through which only the pulling shaft 5 passes. Above the shaft hole 9, the expanded receiver becomes a tray 10, in which the liquid sealant 3 is accommodated. The liquid sealant 3 is made of Liquid 5eal to prevent gas from flowing through the gap between the shaft through hole 9 and the two shafts 5.
I'm there.

If the inner diameter of the lower half of the sealed container 4 is r, the inner diameter of the large diameter part of the pot 1 is Σ, and the inner diameter of the small diameter part is A, then Σ> r > A
The inequality (1,) holds true.

This figure is a schematic diagram, and there is a resistance heater around the crucible 1. There is a lower shaft supporting the inner bottom 17 of the crucible 1. Furthermore, a pressure-tight container is provided surrounding the entirety of these mechanisms.

It has a double container structure. Same as Figure 3 < , Liquid
The structure is a compromise between the SealCZ method and the LEC method.

Balancing the pressure in the closed space S and the furnace space T)
This maintains the same liquid level height inside and outside the liquid sealant 3.

(2) Action: Pull up the lifting shaft 5 and press <. A solid raw material for a compound semiconductor and a solid B2O3 as a liquid sealant are placed in a crucible 1. After making such preparations, close the pressure vessel of the furnace.

Remove the air from the pressure container to create a vacuum. After this, nitrogen,
Inject an inert gas such as argon to create a high-pressure inert gas atmosphere.

The heater is energized to heat the crucible 1. The liquid sealant melts first. When the heater power is further increased, the raw material solid melts. Then, the fluid has a two-layer structure of the raw material melt 2 and the liquid sealant 3.

The raw material melt 2 has a melting point or higher, and group V elements tend to dissociate from the melt. However, since the liquid sealant 3 is held down by the high pressure of the inert gas, the group Ⅰ elements do not dissociate.

Lower the pulling shaft 5. The lower end of the sealed container 4 is immersed in the liquid sealant 3. A closed space S is formed. Further, the pulling shaft 5 is lowered, and the seed crystal 6 is immersed in the raw material melt 2 for seeding. Thereafter, the pulling shaft 5 is pulled up while being rotated.

Following the seed crystal 6, a single crystal is pulled. The single crystal is inside the closed space S. Since the partial pressure of the group V element is high, volatilization of the group V element from the surface of the single crystal can be prevented.

No surface roughening occurs.

Also, the single crystal is in a closed space and is not exposed to thermal convection of an inert gas. Therefore, it is possible to avoid the drawback of conventional LECs, such as the generation of crystal defects due to rapid cooling.

(→ Effect The closed container 4 has an inner diameter wider than the inner diameter of the small diameter portion 15 of the crucible 1. Therefore, it is possible to pull a single crystal with a large diameter. teeth,
This is effective for lowering the cost per unit element in the subsequent wafer processing.

Furthermore, it is easy to clean the crucible after pulling the crystal. The liquid sealant 3 solidifies and remains in the large diameter portion of the crucible. The raw material solids easily peel off from the crucible, but B2O3
is sticky and does not peel off easily. When the upper part expands like this, B2O3 can be easily removed.

PBN is often used as a crucible, but if you pour a suitable solvent into a PBH crucible and deform it by hand, B
2O3 gradually peels off.

In this respect, it differs from the crucible 8 shown in FIG. B2O3 solidified in the narrow circumferential groove 11 cannot be easily removed.

Thus, with the present invention, there is less chance of damaging the crucible due to the removal of B2O3. This is desirable since crucibles are extremely expensive. Expensive crucibles can be used over and over again.

In other words, the present invention makes it possible to manufacture high-quality compound semiconductor single crystals at low cost.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a crucible for producing a single crystal according to the present invention. FIG. 2 is a longitudinal sectional view of a single crystal growth apparatus using the crucible of the present invention. FIG. 3 is a longitudinal sectional view of a conventional single crystal growth apparatus. FIG. 4 is a longitudinal sectional view of a conventional single crystal growth apparatus. 1...... Crucible 2...
......Raw material melt 3...Liquid sealant 4...-
・・・・・・Airtight container 5・・・・・・・・・Pull up shaft 6・・・・・・
... Seed Crystal 7 ... Crucible 8 ... Crucible 9 ...
.........Shaft through hole 10......Socket plate 11...
...... Circumferential groove 13 ......
...Large diameter part 14...Horizontal
Step 15...Small diameter section S...
・・・・・・・・・Closed space T・・・・・・・・・Furnace space Inventor Masahiro Nakayo 1) Masami Hiro Niryumi

Claims (1)

[Claims] (1) A crucible 1 containing a raw material melt 2 of a compound semiconductor and a liquid sealant 3 is covered with a closed container 4 having an opening at the bottom, a closed space S is formed, and a liquid is drawn through the closed container 4. Axis 5
A seed crystal 6 is attached to the lower end of the raw material melt 2.
This crucible is used in a compound semiconductor single crystal growth device in which the single crystal is pulled up in a closed space S by dipping it in water and pulling it up while rotating, and it is mainly filled with a liquid sealant 3. A crucible for producing a single crystal, characterized by comprising an upper large diameter part 13, a lower small diameter part 15 into which the raw material melt 2 is mainly placed, an intermediate horizontal stage 14, and a lower circular bottom part 17.