JPH0710677A - Production of compound semiconductor and unit therefor - Google Patents

Abstract

PURPOSE:To enable the growth of single crystal in high yield by allowing the right cylinder part to grow after the initial shoulder of the crystal is formed and the vessel support including the molten compound semiconductor is increased in its capacity and keeping the solid-liquid interface convex. CONSTITUTION:In the shoulder-growing stage from the seeding zone 19 to the right cylinder zone, the vessel 1 for the melt 4 is supported with the first supporter 12 of a small volume and the heat flows toward the center to make the solid-liquid interface convex toward the crystal melt and enable so-called 'convex growth'. After coming in the right cylinder growth stage, the first melt supporter 12 and the second supporter 13 are united and the vessel 1 is supported with the supporter having a larger capacity than that of the first one 12 and the heat mainly flows toward the center or downward to maintain the solid-liquid interface convex. Accordingly, during the crystal growth, the solid-liquid interface can be always kept convex, thus the yield of single crystal is largely increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a compound semiconductor, and more particularly to a method manufactured by the vertical Bridgman method.

[0002]

2. Description of the Related Art A typical Bridgman method (abbreviated as VB method) for growing compound semiconductors such as GaAs is
There are a horizontal Bridgman method, (abbreviated as HB method), and a liquid sealing pulling method (abbreviated as LEC method). The HB method has a low crystal defect density because it can be grown with a low temperature gradient, but the material loss is large because it is necessary to hollow out the crystal. LEC
In the method, the crystal defect density is high due to the high temperature gradient, and since the crystal is pulled while rotating, there is a variation in the outer shape, and the loss is large because a crystal thicker than the desired diameter must be produced.

On the other hand, the VB method is a vertical version of the HB method and can be solidified in a cylindrical container, and is the best method for obtaining a circular wafer having a low defect density. .

In the VB method, a GaAs melt is prepared in a cylindrical crucible having a conical shape at the bottom, and a seed crystal arranged in a seed crystal storage portion provided at the bottom of the bottom serves as a nucleus. This is a method of growing a single crystal by solidifying upward in one direction.

A feature of this method is that it is possible to produce a crystal with a low crystal defect density because it can be produced under a gentle temperature gradient (several ° C / cm) as described above. In general, in a device using a compound semiconductor such as GaAs, a crystal defect often deteriorates the characteristics of the device, for example, as a crystal defect part becomes a non-emission deteriorated part in a light emitting diode. Desired. This is also the reason why the VB method is receiving attention.

[0006]

By the way, the greatest drawback of the VB method is that the state of seeding cannot be observed in situ. In the HB method and the LEC method, since the part where the growth starts from the seed crystal can be observed, when there is an inhibition in the growth of the single crystal, the single crystal can be melted and re-grown, but in the VB method, until the final removal from the container. It is not possible to recognize whether it is a single crystal. Therefore, the most important point is to find a condition that makes it easy to form a single crystal and maintain its reproducibility. But V
In method B, it is difficult to control the solid-liquid interface during growth, and it is difficult to form a single crystal. That is, for single crystal growth, it is preferable that the solid-liquid interface has a slightly convex shape toward the melt, and it is maintained throughout the growth, but it grows slightly concave than the seeded portion. In addition, since the solid-liquid interface is curved in a wavy shape, twins and polycrystals are likely to occur. Therefore, the loss of raw materials and work is extremely large, and the single crystal yield is poor.

Specifically, as shown in FIG. 3, the whole container 1 containing the seed crystal 3 and the melt 4 is supported by a container support 2 made of graphite or quartz. Therefore, as shown by the arrow 6 in the figure, a heat flow occurs toward the outside of the container 1. The solid-liquid interface 5 is likely to be formed perpendicular to the heat flow, and as a result, the solid-liquid interface 5 has a concave shape toward the melt 4. Once it becomes concave, it does not easily turn into convex and, as a result, it tends to become polycrystalline. An object of the present invention is to provide a method for producing a compound semiconductor, in which a solid-liquid interface is maintained in a convex shape during crystal growth, the above-mentioned drawbacks of the prior art are solved, and a single crystal can be grown in high yield. Especially.

Another object of the present invention is to provide a simple structure.
An object of the present invention is to provide a compound semiconductor manufacturing apparatus capable of maintaining a solid-liquid interface in a convex shape during crystal growth.

[0009]

A method for producing a compound semiconductor according to the present invention is a vertical Bridgman method in which a compound semiconductor melt contained in a container supported by a container support is solidified sequentially from below to grow a crystal. In the manufacturing method of the compound semiconductor used, the first shoulder portion growth step of the solidification step,
The volume of the container support that supports the container is increased in the subsequent stage of growing the straight body part.

Further, in the compound semiconductor manufacturing apparatus of the present invention, the container containing the compound semiconductor melt is lowered from the high temperature part to the low temperature part, and the melt is introduced from below with the seed crystal provided at the lower end of the container as the nucleus. In a manufacturing apparatus for a compound semiconductor that sequentially solidifies and grows a crystal consisting of a shoulder portion where the crystal diameter gradually expands and a straight body portion where the crystal diameter is constant, a container support that lowers the container while supporting the container. First, two bodies are provided in series in the descending direction of the container, and the two container supports support the container and descend integrally with the container during the shoulder part growing stage from the seeding part to the straight body part. Of the container support and the first container support are gradually combined at the time when the growth of the shoulder portion is completed, and the container and the first container support are integrally lowered during the straight body part growing stage. It is composed of a container support. The combined volume when the first container support and the second container support are combined is particularly preferably 1.5 times or more the volume of the first container support.

In this case, the compound semiconductor is GaA.
s, InP, or GaP, and the first and second container supports are preferably heat-resistant ceramics such as graphite, silicon carbide (SiC), or quartz. The container is preferably made of high-purity heat-resistant material such as quartz or pyrolytic BN (pBN).

[0012]

The disadvantage of the VB method is that the single crystal yield is poor because regrowth cannot be performed because seeding cannot be observed, and this drawback is compensated by thermally controlling the solid-liquid interface from the seeding stage. There is a need. Therefore, the crystal growth is 2
The heat flow is controlled in stages.

When the container containing the melt is supported by the first container support having a small volume in the step of growing the shoulder part from the seeding part to the body part, the heat flow is directed to the center, and the solid-liquid interface is formed. It becomes convex toward the melt and so-called convex growth is possible.

When the container is supported by the united container support having a larger volume than the first container support after entering the body part growing stage, a large heat flow occurs in the center or downward,
The direction of the convex surface of the solid-liquid interface can be maintained.

As described above, in the seeding section of the VB method, by using the container support capable of controlling the heat flow,
During crystal growth, the solid-liquid interface can be made to have an ideal convex shape toward the melt, so that the yield of single crystals can be greatly improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the present example, in the VB method, the shape of the solid-liquid interface is always convex toward the melt in the shoulder part growing stage from seeding to the straight body part and the straight body part growing stage after that. , The volume of the container support is switched.

FIG. 1 shows a first container support 12 (FIG. 1 (A)) used in the shoulder growing stage and a second container support 13 (FIG. 1 (B) additionally used in the body growing stage). )) Is shown.

The container supports 12 and 13 support the container (crucible) 1 for containing the GaAs melt 4 from below. The shape of the container 1 supported by this is vertically long, the lower part projects in a substantially conical shape, and the upper part has a cylindrical shape with a constant diameter. The lower part that protrudes in a substantially conical shape is composed of a small-diameter seed crystal accommodating portion into which a seed crystal is inserted at the tip and a conical conical portion.
Therefore, the shape of the GaAs crystal 11 solidified in the container 1 has a shoulder portion whose diameter gradually increases from the seeding portion,
It consists of a straight body with a constant diameter.

As shown in FIG. 1A, the first container support 12 is designed to support only a substantially conical lower part of the container 1 and has an upper outer diameter for supporting the lower part of the container 1. Container 1
The outer diameter is almost the same. Specifically, in order to support the container 1 from below, a substantially conical recessed engaging hole 14 that engages with a lower part of the container 1 protruding in a substantially conical shape is provided in the upper part, and the first container support is provided in the lower part. It has a rod 15 which is connected to an elevating rod (not shown) for elevating the body 12. Therefore,
By integrally supporting the container 1 with this first container support 12, the heat flow is directed to the center of the seed crystal 3 as shown by an arrow 6 in the figure, and the shape of the solid-liquid interface 5 is projected toward the melt 4 side. become.

As shown in FIG. 1B, the second container support 13 supports the entire container 1, and the outer diameter of the upper portion supporting the container 1 is larger than the outer diameter of the container 1. It is getting bigger. Specifically, the container 1 and the first container support 12 integrated together are supported so that the first container support 12 supporting the container 1 is supported together, that is, the first container support 12 is nested. It has an engaging hole 16 which is recessed in a cylindrical shape to fit, and a rod 17 which is connected to an elevating rod (not shown) for elevating the second container support 13 in the lower part in the lower part. This rod 17 includes the lower rod 1 of the first container support 12.
A through hole 18 for inserting 5 is provided. Therefore,
With this second container support 13, the container 1 and the first container support 1
By supporting 2 in a nested manner, a large heat flow occurs in the center or in the downward direction as shown by an arrow 6 in the figure, so that the convex direction of the solid-liquid interface 5 can be maintained.

As will be described later, the volume of the entire container support when the first container support 12 is nested in the second container support 13 and combined is 1.
5 times or more. The first container support 12 does not necessarily have to cover only the lower portion of the container 1, but may cover the entire container 1 completely. In this case, it is desirable to reduce the thickness of the portion that covers the upper cylindrical portion of the container 1 in terms of heat flow. As described above, the container 1 is pBN.
Etc., the container supports 12 and 13 are preferably made of graphite or the like.

In this way, when the container 1 containing the melt 4 is supported by the first container support 12 having a small volume in the stage of growing the shoulder part from the seeding part 19 to the straight body part, heat of the container 1 is reduced. The flow is directed to the center, the solid-liquid interface 5 is convex toward the melt,
So-called convex growth is possible. After the straight body part is grown, the first container support 12 and the second container support 13 are united to form a container 1 with a combined container support having a larger volume than the first container support 12. When it is supported, a large heat flow occurs in the center or downward, so that the direction of the convex surface of the solid-liquid interface 5 can be maintained. Therefore, since the solid-liquid interface 5 can be always convex toward the melt 4 during the crystal growth, the yield of the single crystal can be significantly improved.

Next, a specific example of the above-mentioned GaAs manufacturing method will be described with reference to FIG.

(Concrete example) Outer diameter 78 mm, wall thickness 1 mm, length of conical portion corresponding to shoulder portion is 50 mm, length of cylindrical portion corresponding to straight body portion is 500 mm, bottom is 7 mm, diameter and length 4
Crucible 21 made of pBN with a seed crystal storage 20 of 0 mm
Prepared.

7,000 g of GaAs polycrystal 22 produced in advance was crushed and put in this crucible 21, and As23 was added to 5
After the addition of g, the whole was placed in a graphite container that is almost airtight. This graphite container 27 is a growth furnace (not shown) in which a heater is placed in a stainless chamber.
, And the crucible 21 was moved downward to grow from the seeding portion 24.

At the first shoulder portion growing stage, the first container support 25 shown in the upper portion of FIG. 2 was used as the container support. As shown in the figure, the first container support 25 used has a shape that covers the entire crucible 21.

At the next stage of growing the straight body part, the one in which the first container support 25 was united with the second container support 26 shown in the lower part of FIG. 2 was used. That is, the crucible 21 and the first container support 25 that have moved downward are gradually brought into contact with and integrated with the second container support 26 at the time when the growth of the shoulder portion is completed. After that, until the solidification of all the GaAs melts was completed, the first and second container supports 25 and 26 were made integral and moved downward to grow.

At this time, the first container support 25 shown in FIG.
In each of the examples, the ratio of the volume V ₁ of the united support to the volume V ₀ of the same was changed to approximately 2 times (Example 1), 1.5 times (Example 2), and 1.0 times (Example 3). I made 5 crystals each.

As a result, φ75 mm, straight body is about 250 mm
GaAs single crystal was obtained.

(Comparative Example) First container support 25 shown in FIG.
While keeping the second container support 26 integrated from the beginning, five crystals were grown under the same conditions as in the other examples.

(Results) The results of Examples 1 to 3 and Comparative Example are summarized in Table 1.

[0032]

[Table 1]

Table 1 shows the comparison of the single crystal yields by obtaining the ratio of the length of the single crystal to the length of the straight body part from each of the five crystals obtained under each condition. from this result,
When V ₁ / V ₀ ≧ 1.5, the single crystal yield is extremely high,
It was found to be very useful.

[0034]

【The invention's effect】

(1) According to the invention described in claim 1, since the solid-liquid interface can be ideally made convex, the single crystal yield can be dramatically improved, and the original feature of the VB method is obtained. It is possible to provide a high-quality crystal having a low defect density, which is

(2) According to the present invention as set forth in claims 2 to 4, the first container support body which has supported the container at the shoulder portion growing stage is combined with the second container support body at the straight body portion growing stage. By increasing the volume of the container support in the shoulder part growing stage and the straight body part growing stage, or by increasing the volume to a predetermined ratio, the solid-liquid interface is kept convex during crystal growth. It is easy to control heat.

[Brief description of drawings]

FIG. 1 is a main part diagram of a vertical Bridgman apparatus for controlling heat flow in two stages according to an embodiment of a method for manufacturing a compound semiconductor of the present invention.

FIG. 2 is a main part view of a vertical Bridgman device according to a specific example of a compound semiconductor manufacturing device of the present invention.

FIG. 3 is a main part diagram of a vertical Bridgman device for explaining a conventional heat flow.

[Explanation of symbols]

 1 Container 3 Seed Crystal 4 GaAs Melt 5 Solid-Liquid Interface 6 Heat Flow 11 GaAs Crystal 12 First Container Support 13 Second Container Support 19 Seeding Section

Claims (4)

[Claims] 1. A method for producing a compound semiconductor using a vertical Bridgman method in which a compound semiconductor melt contained in a container supported by a container support is solidified sequentially from below to grow crystals. The step of growing the shoulder part of, and the step of growing the straight body part after that, grow the straight body part by increasing the volume of the container support that supports the container after growing the shoulder part. A method of manufacturing a compound semiconductor, comprising: 2. A container containing a compound semiconductor melt is lowered from a high temperature part to a low temperature part, and the melt is sequentially solidified from below with a seed crystal provided at the lower end of the container as a nucleus to gradually expand the crystal diameter. In a compound semiconductor manufacturing apparatus for growing a crystal comprising a shoulder portion having a diameter and a straight body portion having a constant crystal diameter, a container support for lowering the container while supporting the container is connected in series in the descending direction of the container. A first container support that supports the above-mentioned container and descends integrally with the container during the shoulder section growing stage from the seeding section to the straight body section,
From the container and the second container support descending integrally with the above-mentioned container and the first container support during the straight body part growing stage by gradually combining with the first container support at the time when the shoulder part growth is completed. An apparatus for manufacturing a compound semiconductor, which is configured. 3. The combined volume of the first container support and the second container support when combined together is 1.5 times or more the volume of the first container support. Manufacturing equipment for compound semiconductors. 4. The production of a compound semiconductor according to claim 2, wherein the compound semiconductor is GaAs, InP, or GaP, and the first and second container supports are graphite, silicon carbide, or quartz. apparatus.