JPS6259592A - Production of compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To efficiently produce a compound semiconductor, by placing crucible on an intermediate stepped part in the from of curved surface of a cylindrical sealed tube having the lower part constricted by the above-mentioned stepped part and heating the crucible to generate a large temperature gradient in a melt in the crucible. CONSTITUTION:A vertical furnace having a high-temperature furnace 1 in the upper part separated from a low-temperature furnace 2 in the lower part is used and a cylindrical sealed tube 3 is inserted thereinto. The sealed tube 3 is has the lower part constricted from the upper part by an intermediate stepped part 10 in the form of a curved surface. A more volatile material (B) is contained in the bottom of the sealed tube 3 and a crucible 4 containing a more slightly volatile material (A) is placed on the stepped part 10. The vapor of the more volatile material (B) fills the interior of the sealed tube 3 to react with the more slightly volatile material (A) and form a compound semiconductor. Since there is a temperature difference between the upper and lower parts in the melt, the semiconductor diffues and moves downward and deposits as crystals 5 in the bottom. Since the shapes of the crucible bottom and the stepped part 10 are almost the same, the heat of the crucible bottom is transmitted to the sealed tube wall by conduction between solids and efficiently released to the outside air. Thereby, the aimed compound semiconductor is efficiently produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for growing compound semiconductor crystals in a solution using a temperature gradient.

The method for manufacturing compound semiconductor crystals is to insert a sealed tube with a constant diameter into a vertical tubular heating furnace with a high-temperature section at the top and a low-temperature section at the bottom. , the vapor from the more easily vaporized material at the bottom of the sealed tube reacts with the melt of the more difficult to vaporize material placed in the crucible at the top of the sealed tube.

Conventionally, a method has been used in which crystals are precipitated by a temperature gradient in the melt. For example, as shown in Figure 3,
When a sealed tube is inserted into the high-temperature furnace 1 and low-temperature furnace 2 provided above and below, the B component (component that vaporizes more easily) at the bottom of the sealed tube vaporizes.
The A component (component that is more difficult to vaporize) in the upper crucible 4 is melted, and the compound semiconductor AB produced on the surface of the melt is precipitated as a single crystal 5 at the bottom of the crucible (Japanese Patent Publication No. 1973).
-Refer to Publication No. 20106).

However, in this case, heat dissipation from the bottom is poor due to the space existing between the bottom of the crucible and the wall of the sealed tube, and the radiated heat is hardly dissipated outside the sealed tube and only warms the bottom of the sealed tube. However, there is a disadvantage that the temperature drop at the bottom of the crucible is small and a temperature gradient of only about 20/1 can be obtained.

In addition, as shown in FIG. 4, in order to improve heat dissipation from the bottom of the crucible, a bottom forming member 6 made of carbon or the like having high thermal conductivity and a heat dissipating body 7 made of silicon, which also has high thermal conductivity, are attached to the crucible 4. A method is used to improve heat dissipation and increase the temperature gradient by placing it on the bottom (Utility Model Publication No. 59-3171).
(See Publication No. 1).

However, in this case, carbon and silicon may enter the compound semiconductor as impurities, lowering the purity of the crystal and deteriorating the electrical characteristics.

In addition, as shown in Fig. 5, a heater 8 dedicated to temperature gradient setting is provided.
A method of obtaining a temperature gradient of as much as 7 cm was also carried out (see Japanese Patent Publication No. 59-38199), but this method resulted in a complicated and expensive apparatus and was problematic in practice.

Furthermore, as shown in FIG. 6, a high temperature furnace 1 and a low temperature furnace 2 are placed in contact with each other, and a stainless steel tube 9 is inserted into the low temperature furnace from the lower part of the crucible 4 placed inside the inserted sealed tube. There are examples of attempts to increase the temperature gradient of the Jour
al of Crystal Growth, 52 (1
981), 679-683), the temperature gradient is 10-1
Since it is only about 5 K/, a sufficient effect on increasing the efficiency of crystal production cannot be expected.

As a result of repeated research in order to solve the problems of the above-mentioned conventional technology, the inventor of the present invention has developed a method for efficiently manufacturing compound semiconductor crystals by generating a large temperature gradient in the melt in the crucible. This was successful and led to the present invention. That is, the present invention
A cylindrical sealed tube with a lower part reduced by a curved step in the middle is inserted into a vertical tubular heating furnace with a high temperature at the top and a low temperature section at the bottom. This is a method for manufacturing a compound semiconductor crystal, which is characterized in that a crucible containing a raw material that is easy to vaporize is placed therein, and a crucible containing a raw material that is difficult to vaporize is placed on the stepped portion.

The method of the invention will be explained in more detail below with reference to the apparatus shown in the drawings.

FIG. 1 shows an example of an apparatus for implementing the present invention.

This apparatus uses a vertical tubular heating furnace in which a high temperature furnace 1 is placed above and a low temperature furnace 2 is placed below, separated from each other, and a cylindrical sealed tube 3 is inserted into the furnace. The upper part of the sealed tube has a larger diameter than the lower part, and the intermediate step part 10 has a curved shape. A material that is easily vaporized is stored in the bottom of the sealed tube, and a crucible 4 containing a material that is more difficult to vaporize is placed on the stepped portion. The vapor of the easily vaporized material fills the sealed tube and reacts with the molten material that is difficult to vaporize, producing a compound semiconductor. Because there is a temperature difference between the top and bottom in the melt, the semiconductor diffuses, moves downward, and precipitates as crystals 5 at the bottom, since the shapes of the crucible bottom and the step are almost the same. Through conduction between solids, the heat at the bottom of the crucible is transferred to the wall of the sealed tube, where it is efficiently dissipated into the outside air. If the diameter of the upper part of the sealed tube is twice that of the lower part, 75% of the bottom of the crucible will contact the stepped portion and radiate heat. Also, 75% of the heat radiation from the bottom of the crucible is radiated outside through the sealed tube wall because the diameter of the bottom is small. Moreover, since the high-temperature furnace 1 and the low-temperature furnace 2 are separated and communicated with the outside air 11, the step part and the lower part of the sealed tube that follows it can be easily cooled by the outside air.In this case, if a blower or the like is used, the area around the step part can be more effectively cooled. Can be cooled. As a result, a large temperature gradient is generated in the melt in the crucible, and compound semiconductor crystals can be efficiently produced, and the crucible is stable against the sealed tube, giving the advantage of ease of operation.

In this case, in order for the compound semiconductor to precipitate at the bottom of the crucible, it goes without saying that the vapor pressure of the easily vaporized material must be selected to be higher than the decomposition pressure of the compound semiconductor.

If quartz glass is used as the material for the sealed tube, the material can be easily sealed by welding, but boron nitride, stainless steel, alumina, or ceramics thereof can also be used as the material for the sealed tube.

As described above, the present invention has the effect of increasing the temperature gradient in the melt, so it can be used not only for compound semiconductor solution growth methods but also for melt growth methods such as vertical Bridgman method, horizontal Bridgman method, etc. It can also be used for vapor phase growth and in-phase growth.

11. Using the device shown in Figure 1, injects In into the step part of the quartz glass sealed tube.
Place the crucible containing P on the bottom bottom of the small diameter sealed tube.
was housed and inserted into a vertical tubular heating furnace to melt In and vaporize P. P vapor reacted with In on the surface of the In melt to generate InP, which moved to the bottom of the crucible due to the temperature difference within the melt and precipitated as crystals. The conditions and results at this time are shown in the table below.

In this case, since the latent heat generated during crystal growth was efficiently removed, unnecessary nucleation was suppressed and the crystal growth surface was stabilized, making it possible to obtain a collection of long and large crystals as shown in FIG. The table above shows I by the conventional method using the same materials.
The results of a comparative example in which nP was produced are also shown, and it is clear that the present invention is superior.

This method is applicable to the production of compound semiconductor crystals such as GaP, GaAs, and InAs in addition to InP.

m days [1] By placing the crucible on the stepped portion of the sealed tube, the present invention transmits heat from the bottom of the melt to the outside through the bottom of the crucible and the stepped portion of the sealed tube. Because they are spaced apart, this heat can be efficiently discharged to the outside air. In addition, the heat radiated downward from the bottom of the crucible is dissipated to the outside through the sealed tube wall, and the temperature at the bottom of the sealed tube is less likely to rise.
This creates a sufficient temperature gradient for the melt inside the crucible.
A highly pure compound semiconductor crystal can be efficiently produced. Moreover, the structure of the furnace remains unchanged.

This is an industrially useful invention that is extremely easy to implement just by devising the shape of the sealed tube.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the apparatus for carrying out the present invention, FIG. 2 is the appearance of the crystal obtained by the present invention, FIGS. 3, 4,
FIGS. 5 and 6 show explanatory diagrams of an apparatus for carrying out the conventional method. 1. High-temperature furnace, 2. Low-temperature furnace, 3. Sealed tube. 4... Crucible, 5... Crystal, 6... Bottom forming member, 7... Heat sink, 8... Heater for temperature gradient setting, 9... Stainless steel tube, 10... Step Part 11: Outside air, A: Raw material that is more difficult to vaporize, B: Raw material that is easier to vaporize. December 4, 1985 1. Display of the incident 1985 Patent Application No. 200234 2. Name of the invention Method for manufacturing compound semiconductor crystals 3. Relationship with the case of the person making the amendment Patent applicant name: Shin-Etsu Semiconductor Co., Ltd. 4. Agent address: 4-9 Nihonbashi Honmachi, Chuo-ku, Tokyo 103 Date of dispatch: November 26, 1985 6. Subject of amendment Drawing 7, contents of correction

Claims (1)

[Scope of Claims] 1) A cylindrical sealed tube with a lower part reduced by a curved stepped portion in the middle is inserted into a vertical tubular heating furnace in which the upper part is a hotter part and the lower part is a colder part, which are separated from each other. 1. A method for manufacturing a compound semiconductor crystal, comprising storing a compound semiconductor raw material that is more easily vaporized at the bottom, and placing a crucible containing a less easily vaporized raw material at the stepped portion. 2) The method according to claim 1, wherein the curved surface of the stepped portion and the bottom surface of the crucible have substantially the same shape. 3) The method of claim 1, wherein the spaced apart portions are in communication with outside air.