JPS60145606A - Vapor growth method and device thereof - Google Patents

Abstract

PURPOSE:To obtain a multilayer structure which has almost no crystalline composition transition layer in a boundary of epitaxial layers by providing the step of breaking a substrate form a stock gas in the meantime immediately before the composition of the gas is altered until the alteration is completed. CONSTITUTION:Stock gas is thermally decomposed on the surface of a high temperature GaAs substrate 5, and precipitated on the substrate 5 as a crystal. At this time, the gas is not introduced from a gas inlet tube 6, and hydrogen 9 is flowed at the flow rate of the degree which does not affect the large influence to the flow 8 of the gas. In order to grow an A GaAs layers of the following different compositions, hydrogen diluted with a large amount of arsine from the tube 6 is flowed and sprayed to the substrate 6. This gas flow 11 coats the substrate 5 to intertupt from the flow 10 of the gas. The gas of the composition at the previous epitaxial growth time remaining in the gas tube and a reaction chamber 3 is passed through the substrate 5 at the gas composition altering time, and this state remains until the composition of the gas becomes the normal state to perform the next epitaxial growth.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vapor phase growth method and a vapor phase growth apparatus that can reduce drooping of the crystal composition at the interface of an epitaxial layer.

In epitaxial growth of crystals of semiconductor devices such as semiconductor lasers using 1-V group compound semiconductors, vapor phase growth methods have recently been in the spotlight. Compared to the conventionally used liquid phase growth method, the vapor phase growth method has superior uniformity in the thickness of the epitaxial layer and can slow down the crystal growth rate. It is also possible to form ultra-thin films. Furthermore, since the crystal can be grown on a large-area substrate, mass productivity is also excellent.

The thickness of the composition transition region at the interface of the epitaxial layer is less than a few tens of amps, which is superior to the several hundred amps of liquid phase growth, but it is necessary to change the composition of one source gas to change the composition of the epitaxial layer. When changing the epitaxial layer, it is unavoidable that a compositional transition region is formed at the epitaxial layer interface due to crystal precipitation due to gas remaining in the gas piping or reaction chamber. Normally, the gas piping is shortened and the flow rate of the raw material gas is increased to minimize the amount of residual gas and the residence time. However, residual gas in the volume of the reaction chamber upstream of the substrate cannot be avoided.
K, which increases the flow velocity, also has a limit.

The present invention provides a vapor phase growth method that eliminates the above-mentioned drawbacks of conventional vapor phase growth methods and can almost completely eliminate the crystal composition transition region at the interface of an epitaxial layer, and a vapor phase growth apparatus that realizes the method. It is something.

The present invention provides a vapor phase growth method for growing crystals on a substrate by chemical reaction or thermal decomposition of a source gas, in which the composition of the substrate is grown from immediately before changing the composition of the source gas until the end of the change. The method is characterized by comprising a step of blowing a gas containing a gas that prevents thermal decomposition and having a composition that does not cause crystal growth on the substrate at a sufficient flow rate to cut off the substrate from the source gas. .

The vapor phase growth apparatus of the present invention includes a reaction tube equipped with a raw material gas introduction tube, a susceptor installed in the reaction tube, a heating means for heating at least a substrate, and a gas that prevents thermal decomposition of the substrate. and at least a gas inlet pipe capable of spraying a gas having a composition that does not cause crystal growth on the substrate at a sufficient flow rate to isolate the substrate from the source gas. There is.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the vapor phase growth method and vapor phase growth apparatus of the present invention will be described in detail below with reference to the drawings. The following detailed explanation will be given by taking as an example the growth of AlGaAs using a metal organic chemical paper deposition method (abbreviated as MO-OVD method) among vapor phase growth methods.

Figure 1 shows a schematic diagram of the vicinity of the reaction chamber and gas flow of the MO-OVD apparatus during epitaxial growth, and Figure 2 shows a schematic diagram of the vicinity of the reaction chamber and gas flow of the vapor phase growth apparatus when switching the source gas composition. . During epitaxial growth, (Fig. 1)
The raw material gas is diluted with hydrogen, which is a carrier gas, and is introduced into the reaction chamber 3 inside the reaction tube 2 through the raw material gas introduction pipe 1, and flows as shown by an arrow 8. The GaAs substrate 5 is placed on the carbon susceptor 4 and heated by the high-frequency coil 7, and the raw material gas is thermally decomposed on the surface of the high-temperature GaAs substrate 5, and is deposited on the GaAs substrate 5 as crystals.

At this time, the raw material gas is introduced from the gas introduction pipe 6
Hydrogen or hydrogen diluted with arsine is allowed to flow at a flow rate that does not flow into Flow 8JC and does not significantly affect the flow 8JC of raw material gas (Flow 9). Immediately before switching the source gas composition to grow the next AlGaAs layer with a different composition, a large flow of hydrogen diluted with arsine is flowed through the gas introduction pipe 6 and sprayed onto the GaAs substrate 5. (
Figure 2). The gas flowing in from the gas introduction pipe 6 flows into the flow IIK.
As shown, the KGaAs substrate 5 is covered, and the source gas flow 10 is
Be more insulated. Then, when the gas composition is switched, the raw material gas with the composition used in the previous epitaxial growth remaining in the gas pipe and the reaction chamber 3 passes through the substrate 5-, and the composition of the raw material gas is brought to a steady state for the next epitaxial growth. The state shown in FIG. 2 is maintained until the state shown in FIG. Thereafter, the flow rate of the gas flowing in from the gas introduction pipe 6 is returned to the state shown in FIG. 1, and the next epitaxial growth is performed.

According to the above method, at the epitaxial layer interface,
11 can completely eliminate the crystal composition transition layer caused by thermal decomposition and precipitation of residual gas when switching the raw material gas composition. Further, since arsine, which prevents thermal decomposition of the GaAs substrate, flows in from the gas introduction pipe 6, thermal deterioration of the GaAs substrate in the state shown in FIG. 2 can be suppressed.

As described in detail above, by using the vapor phase growth method and vapor phase growth apparatus of the present invention, it is possible to obtain a multilayer structure crystal with almost no crystal composition transition layer at the epitaxial layer interface. Such a vapor phase growth method and vapor phase growth apparatus are:
It is extremely useful for producing ultra-thin films of several tens of amperes or less, and even of several atomic layers.

In the above detailed explanation, the MO-OVD method was used to take AI GaA+s growth on a nine Ga As substrate as an example, but the present invention can also be applied to other substrates using other vapor phase epitaxy methods. Needless to say, this method can be applied to crystal growth of materials such as

1 and 2 are diagrams showing an example of a vapor phase growth apparatus used in the vapor phase growth method using the MO-OVD method according to the present invention. This shows the time of composition switching.

l... Raw material gas introduction pipe, 2... Reaction tube, 3...
Reaction chamber, 4... carbon susceptor, 5... Ga
A s substrate, 6... Gas introduction pipe, 7... High frequency coil, 8.10... Flow of raw material gas, 9.11...
The flow of gas flowing through the gas introduction pipe.

Figure 1 Figure 2

Claims (2)

[Claims] (1) In a vapor phase growth method in which a desired crystal is grown on a substrate by chemical reaction or thermal decomposition of a raw material gas, the substrate is thermally decomposed from immediately before changing the composition of the raw material gas until the change is completed. A vapor phase growth method comprising the step of: spraying a gas at a sufficient flow rate onto the substrate, including a gas that prevents the growth of crystals on the substrate, and cutting off the substrate from the source gas. (2) A vapor phase growth apparatus comprising at least a reaction tube equipped with a raw material gas introduction tube, a susceptor installed in the reaction tube, and a heating means for heating at least a substrate installed on the susceptor, A gas inlet pipe is provided that is capable of discharging the substrate from the source gas by spraying a gas containing a gas that prevents thermal decomposition of the substrate and having a composition that does not cause crystal growth on the substrate to the substrate at a sufficient flow rate. A vapor phase growth apparatus characterized in that a pipe port is installed close to the substrate.