JPS59107998A - Crystal growth method - Google Patents

Abstract

PURPOSE:To suppress the generation of fine reaction products which come flying and stick to a crystal substrate and form an ungrowing part by surrounding the circumference of the crystal substrate where a crystal is grown by MO-CVD method except a reaction gas flowing part with a crystal capable of growing the crystal. CONSTITUTION:A protecting tube 10 is mounted on a square pillar-shaped liner tube 9. A frame body 11 of the tube 10 is made of quartz, and into which a crystal substrate 12 consisting of e.g. MgO.Al2O3 is inserted and on which the crystal substrate 14 provided with a vent 13 is mounted. The circumference of a crystal substrate 1 which is placed on a carbon susceptor 3 and an epitaxial crystal growth is carried out is surrounded with substrates 12, 14 made of materials capable of performing similar crystal growth. The deposition which has been conventionally formed on the liner tube wall due to the heat of radiation from the susceptor 3, becomes to form a single crystal. The adhering force of the reaction product is so remarakably strong compared with that to the conventional quartz plate that the product is not stripped off and not scattered by a stream of carrier gas.

Description

[Detailed description of the invention] (a) Technical field of the invention The present invention relates to a crystal growth method that does not involve ungrown portions.

(b) Background of the technology The MO-CVD method was named because it uses an organometallic compound containing the component elements of this compound as a raw material in the vapor phase growth of compound crystals.
Vapor phase growth of crystals of group compounds and group II-V compounds is often carried out.

Now, to explain the case of groups IV, group Ⅰ element components include alkylated products such as methylated products or ethylated products of group Ⅰ metal elements such as gallium (Ga), aluminum (At), and indium (In). , Group V nonmetallic elements such as nitrogen (N), phosphorus (P
), arsenic (As), and other hydrides are used.

The characteristics of the MO-CVD method are that the constituent elements of the compound crystal to be grown can be introduced into the growth furnace in a gaseous state, and only the region of the substrate where crystal growth is to be performed needs to be heated to a constant temperature, so the configuration of the equipment can be simplified. It is simple, and since the crystal growth reaction is irreversible and proceeds thermally, epitaxial growth on a different type of substrate is possible, and the crystal growth rate can still be changed significantly.

What is required for epitaxial growth is that crystal growth be performed uniformly on the crystal substrate, and there must be no ungrown portions.

Therefore, during crystal growth, sufficient cleaning treatment is performed on the crystal substrate.

However, the component elements or compounds separated and separated on the reaction tube wall during crystal growth have a weak adhesion to the tube wall, so they are peeled off by the carrier gas flow, and they fly onto the crystal substrate and precipitate. This may result in ungrown areas. The present invention relates to a crystal growth method that eliminates such ungrown portions.

(c) Prior art and problems Figure 1 is a block diagram of a reaction tube for crystal growth using the MO-CVD method. Ga on a crystal substrate 1 such as
The case of epitaxial growth of As will be explained as follows.

A carbon susceptor 3 is placed in the center of the vertical reaction tube 2 made of quartz.
is provided on the rotating shaft 4 and is configured to be rotated at low speed by a motor. Carbon susceptor 3 is reaction tube 2
The carbon susceptor 3 is heated by induction by a high-frequency coil 5 provided outside the carbon susceptor 3, and a crystal substrate 1 on which crystal growth is to be performed is placed on four parts provided at the top of the carbon susceptor 3.

Here, the reaction gas consists of an alkylated Ga such as trimethylgallium (Ga (CH3)3) and a hydride of As such as arsine (AsHs), and a mixed gas of this and hydrogen gas (H2) used as a carrier gas is supplied. Air mouth 6
It is introduced into the reaction tube 2 while adjusting the composition ratio and flow rate, and after the thermal decomposition is completed, it is discharged from the discharge lower. Next, a liner tube 8 made of quartz is provided around the crystal substrate 1 where crystal growth is performed, but the purpose of providing this is to
The purpose is to prevent the inner walls of the pipe from being contaminated by thermal decomposition products.

GaAs, α・A40s 9Mg O・A40A
The growth of GaAs on the crystal substrate 1 consisting of
] by flowing a reactant gas while heating.

Ga (CH3)5 + A sH, -+ GaAs
The reaction of + 3 CH4-- (1) is allowed to proceed, and epitaxial growth or heteroepitaxial growth is performed.

-However, the reaction products do not grow only on the crystal substrate 1, but also precipitate on the liner tube 8 and carbon susceptor 3.
In this case, since epitaxial growth is not performed, the adhesion is weak, and the gas flow of the carrier gas may cause the film to peel off and become fine powder for complementation.

In addition, the decomposition products are limited to GaAs.Ga(CHs)s
GalA s, which is produced by the independent decomposition of Ash and Ash. Therefore, if such fine powder adheres to the crystal substrate before or during crystal growth, crystal growth will not occur in that area and a pit-like ungrown area will occur.
Become. In order to avoid this, the liner tube 8 provided around the crystal substrate 1 must be removed from the reaction tube 2 every time crystal growth is performed, and a cleaning process must be performed to dissolve and remove deposits. This hindered the efficiency of the crystal growth process.

(d) Purpose of the Invention The object of the present invention is to suppress the generation of minute reaction products that fly and adhere to a crystal substrate during epitaxial growth to form ungrown portions.

(e) Structure of the Invention The object of the present invention is achieved by performing crystal growth in a state in which the crystal substrate on which crystal growth is performed is surrounded by crystals capable of bitaxial growth, excluding the reaction gas flow area. be able to.

(f) Embodiments of the Invention The present invention improves the adhesion of the reaction product by covering the periphery of the crystal substrate on which epitaxial growth is performed with a crystal substrate on which epitaxial growth or heteroepitaxial growth can be varied, thereby improving the adhesion of the reaction product. This prevents the comple- ment from occurring.

Fig. 2 is a block diagram of a reaction tube in which the present invention is implemented, Fig. 3 is a perspective view of a protection tube according to the invention provided on the upper part of the liner tube, and Fig. 4 shows the frame of the protection tube and crystallization. FIG. 3 is a plan view showing the relationship with the substrate.

The present invention modifies a conventional liner tube and replaces its upper part with a protective tube lined with a crystal substrate.

That is, in the embodiment shown in FIGS. 2 to 4, the quartz liner tube 9 has a prismatic shape, and the protection tube 10 is placed on top of the quartz liner tube 9. Here, the frame 11 of the protective tube 10 is made of quartz, and the crystal substrate 12 made of, for example, MgO''A403 is inserted therein, and the crystal substrate 14 on which the ventilation window 13 is provided is made of quartz. It is placed on a frame 11.

If the crystal substrate 1 placed on the carbon susceptor 3 and subjected to crystal growth is surrounded by a crystal substrate 12, 14 made of a material capable of epitaxial growth in the same manner as above, the crystal substrate 1 placed on the carbon susceptor 3 can be In the present invention, the precipitates generated on the liner tube wall due to heating by radiation are precipitated as single crystals on the crystal substrate 12.14, so the adhesion force of the reaction products is lower than that of conventional quartz plates. Since it is extremely strong, it will not be separated and complemented by the flow of carrier gas.

In the case of arsine and trimethyl gallium, a reaction occurs from about 400°C, but the carrier gas flow toward the susceptor remains at a high temperature and reaches the relatively low temperature part of the crystal substrate 12.14, where it decomposes. Since there is a crystal substrate, in that case it will be deposited as a single crystal, and in particular it will not be complemented later with a carrier gas.

Therefore, in the past, it was necessary to remove the liner tube every time crystal growth was performed and perform a cleaning process to dissolve and remove the deposits, but when using the protection tube according to the present invention, it is necessary to perform a cleaning process periodically. good.

(g) Effects of the invention In the present invention, a part of the liner tube is improved so that the single crystal is placed in the place where the reaction gas decomposes and precipitates. By suppressing the generation of fine reaction products that form .

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional reaction tube, Fig. 2 is a block diagram of a reaction tube according to the present invention, Fig. 3 is a perspective view of a protection tube, and Fig. 4 is a diagram of the relationship between the frame and the crystal substrate. be. In the figure, 1.12.14 is a crystal substrate, 2 is a reaction tube,
3 is a carbon susceptor, 8 and 9 are liner tubes, 10 is a protection tube, and 11 is a frame body.

Claims (1)

[Claims] When epitaxial growth is performed on a crystal substrate by the MO-CVD method using an alkylated metal element and a hydride of a non-metal element as raw materials, epitaxial growth is possible around the substrate where the crystal is grown, excluding the reaction gas flow area. A crystal growth method characterized by surrounding the crystal with