JPS6065793A - Vapor-phase growing method - Google Patents

Abstract

PURPOSE:To improve the quality of the grown layer of a compound semiconductor crystal, by baking the holding table of a substrate at a temperature higher than the growth temperature before the initiation of the crystal growth by vapor-phase growing process and before placing the substrate on the table. CONSTITUTION:Before the initiation of the crystal growth by vapor-phase growing process in the reaction furnace 2, and before placing the substrate 4 on the table 5, the table 5 is heated by the high-frequency coil 6 at a temperature higher than the crystal growth temperature while supplying hydrogen gas through the inlet pipe 1 and/or 3 to the reaction furnace 3 to effect the release and removal of the gas from the material attached to the table 5 and the inner wall of the reaction furnace 2. The effect can be promoted by reducing the pressure in the reaction furnace 2. Thereafter, the temperature of the table 5 is decreased to the crystal growth temperature, the substrate 4 is placed on the table 5, and the source material is introduced together with carrier gas through the inlet pipes 1, 3 to effect the growth of the crystal on the substrate 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vapor phase growth method using a thermal decomposition reaction, which makes it possible to obtain a high quality compound semiconductor crystal growth layer.

Conventional structure and its problems With the recent development of the optical industry, compound semiconductors tn #
The metal chemical vapor deposition method (MOCVD method) is attracting attention.

This MOCVD method uses an alkylated material (
This is a vapor phase growth method that uses thermal decomposition reactions of organic metals, mainly methylated and ethylated compounds.

For example, when growing Kawa-■ group compound semiconductor crystals, which are used to make semiconductor lasers, light-emitting devices, light-receiving devices, etc., using the MOCVD method, alkylated compounds of these elements (A°C.

Methylated products or ethylated products of Ga, In, etc.) are used.

Since these are mostly liquids with relatively high vapor pressure,
It is contained in a carrier gas (mainly hydrogen gas) and supplied to the reactor.On the other hand, as a source material for group Ⅰ elements, hydrides of group V elements (PH3, Asf (3°SbH3, etc.)
, or use an alkylated product.

FIG. 1 shows a schematic structural diagram of a reactor section of a general MOCVD apparatus. An alkylated compound, which is a source material for a group Ill element, is supplied to a reactor 2 from an inlet pipe 1 together with a carrier gas. On the other hand, the hydride, which is the source material for the group Ⅰ element, is also fed from the inlet pipe 3 to the reactor 2 along with the carrier gas. A thermal decomposition reaction of the source material gas supplied to the reactor 2 proceeds irreversibly on the substrate surface at the growth temperature, resulting in the formation of a ■-■ group compound semiconductor crystal (for example, In
P, GaAs, or a mixed crystal thereof) grows. Note 6
is a high frequency coil. The exhaust gas after the reaction exits from the exhaust pipe 7.

However, since it is the graphite substrate holder 5 that is heated by high-frequency heating, this holder 6 is also at the growth temperature. Further, the inner wall of the reactor near where the holding table 6 is located is also heated to near the growth temperature by the radiant heat of the holding table. Therefore, the source material supplied to the reactor undergoes a thermal decomposition reaction at this growth temperature or at a temperature φ close to this temperature, so the thermally decomposed material of the source material is deposited on the holding table 5 and the inner wall of the reactor 2. (Group ■ elements, Group ■ elements, or compounds thereof) are attached.

These deposits do not simply adhere, but when the temperature approaches the growth temperature, they become gas again and come out in the reactor. For this reason, during the next crystal growth, by the time the substrate 4 is heated to the growth temperature and each source material gas whose flow rate is controlled is supplied to start growth, the gas generated from these crystals may cause a Crystals different from the one you want to grow may precipitate on the substrate surface, and during growth, gases from deposits may cause the ratio of supply amounts of each source material gas that reaches the substrate surface to be disrupted, resulting in crystals with a composition that is different from the one you want to grow. It has been difficult to grow high-quality crystals because of the growth of crystals.

In order to improve the above points, conventionally, after crystal IJk length, HC
The method of flowing Jlt gas into the reactor, heating it, and cleaning it, and making the reactor tube a double structure as shown in Figure 2 and using a water-cooling system to prevent the temperature of the reactor inner wall from increasing, will reduce the amount of deposits. There are ways to suppress the generation of gas. However, since the former method uses H (4 gas), which has strong Ifd phagocytosis,
There are problems in that the gas piping system is easily damaged, and in the latter method, the situation with the holding table is exactly the same as before, and the structure of the reaction tube becomes complicated.

OBJECTS OF THE INVENTION The present invention aims to improve the quality of epitaxially grown layers of compound semiconductors by heating a reactor to a temperature higher than the growth temperature before crystal growth in vapor phase growth.

Structure of the Invention In the present invention, in vapor phase growth, before starting crystal growth,
A dust burning procedure is performed in which the holder is heated to a temperature higher than the growth temperature without the substrate placed on the holder, and this removes gases generated from substances adhering to the holder and the inner walls of the reactor. This is a vapor phase growth method that makes it possible to suppress the generation of gas from deposits during the next crystal growth by removing the deposits in advance, thereby making it possible to obtain a high-quality growth layer.

DESCRIPTION OF THE EMBODIMENTS A description will be given based on a case in which semi-active InP crystals of the ■-■ group are epitaxially grown by the 1M0 cVD method. Before starting crystal growth, as shown in FIG. 3, the same conditions as when growing InP crystals are created without placing the substrate on the holding table 5.

Next, hydrogen gas is supplied from the introduction pipe 1 or 3 or both, and the holding table 5 is heated by high frequency heating.
Heat to a temperature higher than the nP growth chamber (usually 600-70oC), for example 800'C, and keep for 1 hour or more. Therefore, the inner wall of the reactor 2 near where the holding table 6 is located is
It is heated by the radiant heat of the holding table 5. Therefore, gas (I
In the case of nP growth, I n Jp P vapor, etc.)
This causes a sufficient amount of

Here, the pressure inside the reactor 2 is pumped to 100T using a depressurizing pump.
This effect will further increase if the pressure is reduced to below orr.

After that, while lowering the temperature of the holding table to the crystal growth temperature IW or lower, the holding table 5 is held with a quartz rod 10 as shown in FIG. The substrate 4 is placed on the holding table 5. Next, the holding table 6 is returned to the reactor 2 again, and the procedure moves on to InP crystal growth. The holding table 5 is placed on a table 13 made of stone pods, and since the airtight door 11 only moves, almost no heat from the holding table is transferred to the airtight door. Therefore, the airtight door may be a commonly used gate knob.

As described above, according to the vapor phase growth method in which dry firing is performed at a temperature higher than the growth temperature before InP growth, during InP growth,
Gas generation from the holding table and the inner wall of the reactor was suppressed, and high quality InP crystals were obtained.

-Also, although we have explained the case of InP crystals, in the case of m-■ group ternary or quaternary mixed crystals, the generation of gas from these deposits has a large effect on the mixed crystal ratio. . Therefore, by performing this procedure before crystal growth, a crystal having a desired mixed crystal ratio can be obtained.

As described above, according to this example, a high quality epitaxial growth layer can be obtained.

The above explanation is based on MOCVD of ■-■ group compound semiconductors.
Although the present invention has been described based on the method, the present invention may be any vapor phase growth method that utilizes the thermal decomposition reaction of a nonce material, for example, ■-■
It can also be applied to the growth method of group compound semiconductors.

Effects of the Invention As described above, the present invention uses a vapor phase growth method that includes a step of heating the inside of the reactor to a temperature higher than the growth temperature before crystal growth.
High quality epitaxial growth layer? l) It has certain effects. Therefore, if the growth layer (2) is used, a device with better characteristics can be obtained and the yield can be improved.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of the reactor of a general fJMOCvD device, and Figure 2 is a conventional MOOCvD reactor with an improved reaction tube.
3 is a schematic cross-sectional view of the reactor of the MOCVD apparatus in the dry firing procedure used in the present invention; FIG. 4 is a schematic cross-sectional view of the reactor of the MOCVD apparatus; FIG. FIG. 2...Reactor, 4...Substrate, 6... Graphite substrate holding stand.

Claims (2)

[Claims] (1) Before starting crystal growth using the vapor phase growth method, dry baking is performed by heating the holder to a temperature higher than the growth temperature without placing the substrate on the holder, and then crystal growth is performed. A vapor phase growth method characterized by performing. (2) The vapor phase growth method according to claim 1, characterized in that the holding table is heated to a temperature higher than the growth temperature and the pressure inside the reactor is reduced.