JPH042138A - Vapor phase epitaxial growth system - Google Patents

Abstract

PURPOSE:To obtain high-quality epitaxial crystals free from variation in composition and thickness through supply of a material gas in a laminar state onto an epitaxial growth substrate by fitting a gas introduction tube that is the reaction tube with a gas flow control plate having a paraboloid and by constituting them so that the cross section of a gas passage formed between this gas flow control plate and the inner wall of the reaction tube may become gradually larger. CONSTITUTION:A gas flow control plate 12 having such a paraboloid that a position corresponding to the tube axis 11 of a reaction tube 1 is maximum is so provided as to have a specified interval to the gas introduction side inner wall 1A of the reaction tube, so that the material gas introduced into the reaction tube may be introduced into the reaction tube on the gas outlet side while passing between the inner wall 1A of the reaction tube and the gas flow control plate 12. This design makes the cross section of the gas passage gradually larger and therefore allows gas to be supplied onto an epitaxial growth substrate 3 in a laminar state of its flow. As a result, high-quality Hg1-xCdxTe epitaxial crystals free from variations in composition and thickness can be obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding a vapor phase epitaxial growth apparatus, the purpose is an apparatus in which a source gas flows in a laminar flow state over a substrate for epitaxial growth. thermally decomposing the source gas by heating an epitaxial growth substrate placed on a susceptor;
In an apparatus for growing epitaxial crystals on a substrate,
A gas flow control plate having a substantially parabolic surface with a maximum position corresponding to the tube axis of the reaction tube is provided at a predetermined distance from the inner wall of the reaction tube on the gas introduction side. The cross-sectional area of the passage is gradually increased, and the raw material gas introduced into the reaction tube is guided to the gas outlet side of the reaction tube while passing between the inner wall of the reaction tube and the gas flow control plate. Configure.

[Industrial application field]

The present invention relates to a vapor phase epitaxial growth apparatus.

Mercury, cadmium, tellurium (HgI-x C
A compound semiconductor crystal such as dXTe) is used.

When such a HgI-x Cdx Te crystal is conveniently formed as a device forming material in a large area and in a thin layer, HgI-x Cdx Te crystal is formed on a cadmium telluride (CdTe) substrate.
The g1-XCdXTe crystal is formed using a vapor phase growth method or the like.

[Conventional technology]

Using such a vapor phase growth method, HgI-x CdXT
When an e-crystal is epitaxially grown on a CdTe substrate, hydrogen gas as a carrier gas is introduced into an evaporator containing a raw material liquid such as dimethyl cadmium, diethyl tellurium, or mercury, and hydrogen supporting the components of the raw material liquid is introduced. A gas is introduced into the reaction tube to remove CdT on the susceptor inside the reaction tube.
The e-substrate is heated and the source gas is thermally decomposed to grow HgI-x CdXTe crystals on the CdTe substrate by vapor phase epitaxial growth.

By the way, the carrier gas carrying the components of these raw material liquids needs to be supplied in a laminar flow state rather than in a turbulent swirling flow onto the substrate. It is said that an epitaxial crystal with a certain composition cannot be obtained.

Whether the flow of this raw material gas is laminar or turbulent is
If there is a point where the cross-sectional area of the reaction tube through which the raw material gas passes suddenly changes, the gas flow will create a vortex at that point.
It is necessary not to provide such a location.

From the above-mentioned viewpoint, conventionally, as shown in FIG. 4, as a device for supplying such raw material gas to a laminar flow state to a substrate for epitaxial growth, the cross-sectional area of the reaction tube 1 for epitaxial growth is changed to a gas introduction tube. 2, a structure is adopted in which the source gas is gradually expanded until it reaches the epitaxial growth substrate 3 placed on the susceptor 4, so that the raw material gas is supplied in a laminar flow state over the substrate.

[Problem to be solved by the invention]

However, in the conventional structure described above, if the taper angle θ at the point where the cross-sectional area of the reaction tube changes is not controlled to an appropriate value, the gas flow will swirl and become turbulent at the point where the cross-sectional area of the reaction tube changes. This gas is supplied onto the substrate, so
The epitaxial crystal formed on the substrate has a predetermined composition,
Alternatively, there is a problem that the film is not formed to a predetermined thickness.

Furthermore, in the above structure, if θ is made small to prevent sudden changes in the gas flow, the overall length of the reaction tube becomes longer, and therefore the composition of the HgI-x Cdy Te crystals is varied and stacked into a multilayer structure. When forming such a multilayer crystal, there is a problem that switching of the raw material gas in the reaction tube cannot be carried out quickly, and such a multilayer crystal structure is not formed.

It is an object of the present invention to provide an apparatus which eliminates the above-mentioned problems and allows source gas for epitaxial growth to be supplied onto a substrate in a laminar flow state without increasing the length of the reaction tube.

[Means to solve the problem]

The vapor phase epitaxial growth apparatus of the present invention which achieves the above object introduces a raw material gas into a reaction tube 1 and heats an epitaxial growth substrate 3 placed on a susceptor 4 in the reaction tube, as shown in FIG. In an apparatus for thermally decomposing the raw material gas and growing epitaxial crystals on a substrate, the gas flow control has a substantially parabolic surface such that the position corresponding to the tube axis 11 of the reaction tube 1 is the maximum. The plate 12 is provided at a predetermined distance from the inner wall 1A on the gas introduction side of the reaction tube, so that the cross-sectional area of the gas passage is gradually increased (and the raw material gas introduced into the reaction tube 1 is is introduced into the gas outlet side of the reaction tube while passing between the inner wall 1^ of the reaction tube and the gas flow control plate 12.

Further, the reaction tube described above may have either a horizontal or vertical structure.

[For production]

The apparatus of the present invention has a tube axis 1 of a reaction tube 1 as shown in FIG.
A gas flow control plate 12 having a parabolic surface such that the position corresponding to 1 is maximum is provided at a predetermined distance from the inner wall 18 on the gas introduction side of the reaction tube, and The raw material gas to be introduced is introduced into the gas outlet side of the reaction tube while passing between the inner wall 18 of the reaction tube and the gas flow control plate 12.

In this way, the raw material gas introduced into the reaction tube 1 from the gas introduction tube 13 is transferred to the inner wall 1A of the reaction tube and the gas flow control plate 1.
2, the cross-sectional area of the gas passage gradually increases, so that the gas flows in a laminar flow state and is supplied onto the substrate.

In addition, by doing this, the length from the gas introduction tube 13 of the reaction tube 1 to reach the epitaxial growth substrate can be shortened, and when forming the Hgt-x CdXTe crystal into a multilayer structure by changing the composition, it is possible to It is possible to reliably switch the raw material gas used.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side view of a first embodiment of the apparatus of the present invention, and FIG. 2 is a plan view of the main part of FIG. 1.

As shown in FIGS. 1 and 2, the apparatus of the present invention includes a gas flow control plate 12 made of quartz glass and having a parabolic surface such that the position corresponding to the tube axis 11 of the reaction tube 1 is the maximum. of,
It is provided at a predetermined distance from the inner wall 1A of the reaction tube 1 on the gas introduction side.

Then, after passing through the gas flow control plate 12, a gas introduction pipe 13 for introducing the raw material gas into the reaction tube 1 is bent so as to pass through it again. While supplying the raw material gas between the inner wall 1A of the reaction tube and the gas flow control plate 12,
lead to the gas outlet side.

The distance between the gas flow control plate 12 and the inner wall of the reaction tube 1 is minimum at a location corresponding to the tube axis 11, and increases toward the side of the reaction tube, so that the gas flow control plate has a curved surface. Because of this structure, the cross-sectional area of the passage of the raw material gas introduced from the gas introduction pipe does not expand rapidly, but gradually expands, so there are no places where flow vortices occur, and the raw material gas is layered. is supplied onto the substrate in a flowing state.

Using such a device of the present invention, Hg is deposited on a CdTe substrate.
A case in which a t-x CdXTe crystal is grown by vapor phase epitaxial growth will be described.

As shown in FIG. 1, a CdTe epitaxial growth substrate 3 is placed on a susceptor 4, and an exhaust pipe 14
After evacuating to a vacuum level of about 10-' torr using an exhaust pump connected to the tank, hydrogen gas carrying dimethyl cadmium was introduced from the gas introduction pipe 13 at a partial pressure of 5.0 Xl0-' atm, and diethyl tellurium was carried therein. 2.4 hydrogen gas
Assuming that the partial pressure of Xl0-'atmosphere and the partial pressure of hydrogen gas supporting mercury are 6.0 Xl0-'atmosphere, the total flow rate of hydrogen gas is 54! It is introduced into the reaction tube 1 at a flow rate of /min.

Then, the raw material gas introduced into the reaction tube 1 from this gas introduction tube 13 collides with the inner wall 1^ of the reaction tube, is mixed uniformly, and passes between the gas flow control plate 12 and the inner wall 1A of the reaction tube. do. Since the distance between the gas flow control plate 12 and the inner wall 18 of the reaction tube gradually increases, the gas flow from the reaction tube 1 becomes laminar because there is no sudden change in the cross-sectional area of the gas passage. guided to the tube side.

In this state, the high frequency induction coil 15 is energized and the susceptor 4
is heated to thermally decompose the source gas to epitaxially grow Hg1-x Cdx Te crystals on the epitaxial growth substrate.

Then, the raw material gas is stably supplied in a laminar flow onto the epitaxial growth substrate, so that a high-quality Hgt -X Cdx Te epitaxial crystal with no fluctuation in composition and thickness can be obtained.

Furthermore, according to this example, since the raw material gas in a laminar flow state can be supplied onto the epitaxial growth substrate without increasing the length of the reaction tube, when Hgt-XCdXTe crystals are stacked in a multilayer structure with varying compositions, Even in this case, since the raw material gas in the reaction tube can be quickly switched, a high quality IIg+-x Cdx Te crystal with a multilayer structure can be obtained.

As another example of this embodiment, as shown in FIG. 3, the reaction tube 1 has a vertical structure, and the gas flow control plate 12 has a parabolic curved surface such that the portion corresponding to the tube axis 11 is maximum. Even if it is provided, the same effect as in the first embodiment can be obtained.

control board, 13 is a gas introduction pipe; A wave induction coil is shown.

14 is an exhaust pipe, and 15 is Takaoka. [Effects of the Invention] As is clear from the above description, according to the present invention, the raw material gas is supplied onto the epitaxial growth substrate in a laminar flow state, so that the composition and thickness can be adjusted. This has the effect of obtaining high quality epitaxial crystals that do not fluctuate.

[Brief explanation of the drawing]

FIG. 1 is a side view of the first embodiment of the apparatus of the present invention, FIG. 2 is a plan view showing the main parts of FIG. 1, FIG. 3 is an explanatory diagram of the second embodiment of the present invention, and FIG. 4 is an explanatory diagram of a conventional device. In the figure,

Claims (1)

[Scope of Claims] A raw material gas is introduced into the reaction tube (1), and the reaction tube (1) is
) in which the epitaxial growth substrate (3) placed on the susceptor (4) is heated to thermally decompose the source gas and grow an epitaxial crystal on the epitaxial growth substrate, the reaction tube A gas flow control plate (12) having a substantially parabolic surface such that the position corresponding to the tube axis (11) of (1) is the maximum,
The gas passage is provided at a predetermined distance from the inner wall (1A) on the gas introduction side of the reaction tube, and the cross-sectional area of the gas passage is gradually increased, so that the raw material gas introduced into the reaction tube (1) is A vapor phase epitaxial growth apparatus characterized in that the gas is guided to the gas outlet side of the reaction tube while passing between the inner wall (1A) of the reaction tube and the gas flow control plate (12).