JPS639941A - Vapor phase epitaxial crystal growth device - Google Patents

Abstract

PURPOSE:To stabilize the flow of a raw material gas, and to grow a thin-film consisting of a compound semiconductor crystal, etc., having a uniform crystalline composition on the surface of a substrate in an epitaxial manner by forming the shape of a susceptor in a wing body having a streamline cross section along the flow of the raw material gas and arranging the susceptor at the central position of a reaction pipe. CONSTITUTION:A susceptor 12 for arranging a substrate 14 to be crystal-grown is formed in a wing body having a streamline cross section along the direction of flow of a raw material gas in a reaction pipe 11 while a substrate fitting and disposing section 13 is formed to one part of the upper surface of the susceptor 12. The susceptor 12 is formed in structure in which it is disposed at the central position of the reaction pipe 11 so that upper and lower surfaces thereof are wrapped by the raw material gas flowing in the reaction pipe 11. According to the structure, the raw material gas flowing in the reaction pipe uniformly flows to a shape that it wraps the upper and lower surfaces of the susceptor. As a result, a back flow and disturbance resulting from the vortex of the raw material gas flowing along the surface of the susceptor 12 holding the substrate 14 to be crystal-grown are removed, and a stable flow is acquired. Consequently, a thin-film composed of a compound semiconductor crystal, etc. having equal crystalline composition can be grown on the surface of the substrate 14 in an epitaxial manner.

Description

[Detailed Description of the Invention] [1 Summary] The present invention uses HgCdTe (mercury, cadmium, tellurium).
In an apparatus for epitaxially growing thin film crystals of compound semiconductors such as GaAs (gallium arsenide) and GaAs (gallium arsenide), the shape of the susceptor for holding the substrate is a wing body with a streamlined cross-section along the flow of source gas, and the substrate is fitted onto the top surface of the susceptor. By providing a joint arrangement portion and arranging the susceptor at a central position of the reaction tube where the upper and lower surfaces are covered with the raw material reaction gas flowing inside the reaction tube, the raw material gas flow is formed on the outer peripheral surface of the susceptor. This stabilizes the flow of the raw material gas flowing along the susceptor surface that holds the substrate by eliminating the separation of the boundary layer formed by this and the generation of vortices caused by this, thereby creating compound semiconductor crystals with uniform crystal composition on the substrate surface. This thin film is epitaxially grown.

[Industrial application field]

The present invention relates to a vapor phase epitaxial crystal growth apparatus, and particularly to improvements in the shape of a susceptor that holds a substrate for crystal growth and its arrangement within a reaction tube.

For example, Hg
CdTe (mercury, cadmium, tellurium) and GaAs (
When epitaxially growing thin film crystals of compound semiconductors such as gallium arsenide, it is required that the composition of the grown film crystals be uniform.

In such vapor phase eviaxial crystal growth, for example, a susceptor holding a substrate for crystal growth is placed in a horizontal reaction tube, a raw material gas is introduced, and the raw material gas is thermally decomposed to form an il film on the substrate. This is used to epitaxially grow crystals, and the flow state of the raw material reaction gas introduced into the reaction tube varies greatly depending on the shape of the susceptor that holds the substrate. , the flow of the raw material gas is disturbed and the composition of the raw material gas near the substrate becomes non-uniform, which greatly affects the uniformity of the composition of the thin film crystal epitaxially grown on the substrate.

Therefore, in order to easily obtain an epitaxially grown thin film with a uniform crystal composition, a vapor phase epitaxial crystal growth apparatus is required in which the shape of the susceptor and its arrangement in the reaction tube are improved so that vortices are not generated in the flow of the raw material gas. ing.

[Conventional technology]

As shown in FIG. 3, a conventional vapor phase epitaxial crystal growth apparatus includes a horizontal reaction tube 1 and a predetermined area within the horizontal reaction tube 1 facing the flow direction of raw material gas introduced as shown by arrow A. Then, a susceptor 2 for holding the substrate has an inclined surface such that the distance between the inner wall of the reaction tube l and the surface of the substrate 3 becomes narrower from the front toward the rear.
A compound semiconductor substrate 3 made of (cadmium, tellurium) is held.

A raw material gas consisting of, for example, hydrogen gas carrying dimethyl cadmium, diethyl tellurium, and mercury is introduced into the reaction tube 1, and heating means (not shown) provided on the outer periphery of the reaction tube 1, for example, high-frequency heating, is used. By heating the susceptor 2 with a device or the like, the held compound semiconductor substrate 3 is heated, and a thin film crystal layer made of HgCdTe is epitaxially grown on the surface of the substrate 3 by a thermal decomposition reaction of the flowing raw material gas.

[Problem that the invention seeks to solve]

By the way, in such a conventional vapor phase epitaxial crystal growth apparatus, as shown in FIG. Near the inner wall of the tube 1 and the outer peripheral surface of the susceptor 2, a pressure gradient is generated due to frictional stress on the wall surface, and a boundary layer 4 is formed.

In general, the velocity of the raw material gas tends to slow down as it goes downstream, so the boundary layer 4 becomes thicker as it goes downstream along the inner wall surface of the reaction tube l and the outer peripheral surface of the susceptor 2. When the layer 4 becomes thick, the raw material gas loses its kinetic energy due to its viscosity, and the velocity gradient at the wall surface becomes zero, causing a phenomenon called separation, which causes the problem of generation of vortices downstream.

In particular, if there are sharp corners at the front end 2a and rear end 2b of the inclined surface as in the susceptor 2, the boundary layer 4 formed on the inner wall surface of the reaction tube 1 becomes thick at the front end 2a, and the flow becomes difficult. Because it rapidly attenuates and the velocity gradient at that part becomes zero, separation occurs and vortices are likely to occur.

Further, the boundary layer 4 formed on the inclined surface of the susceptor 2 also becomes thick at the rear end portion 2b, and the flow is rapidly attenuated, and the velocity gradient at that portion becomes zero, causing separation and generation of vortices.

Therefore, a strong interference effect occurs between the uniform flow of the raw material gas flowing in the reaction tube 1 as shown by the arrow and the vortices formed near the tube wall surface and the inclined surface of the susceptor 2. The formation of the boundary layer 4 that should be formed along the slope of the substrate 3 becomes unstable, and the substrate 3 is disposed on the slope of the susceptor 2.
The raw material composition of the raw material gas flowing along the surface becomes non-uniform,
There is a drawback that it is difficult to obtain an epitaxially grown S film with a uniform crystal composition.

In view of the above-mentioned conventional circumstances, the present invention improves the structure of the susceptor that holds the substrate and the arrangement within the reaction tube.
A novel gas method that eliminates the separation of the boundary layer formed along the surface of the susceptor and the generation of vortices caused by the separation, thereby easily epitaxially growing a compound semiconductor crystal thin film with a uniform crystal composition on the substrate surface. The object of the present invention is to provide a phase epitaxial crystal growth apparatus.

[Means for solving problems]

In order to achieve the above object, the present invention uses a susceptor for arranging a substrate for crystal growth in a reaction tube as a wing body having a streamlined cross-section along the flow direction of raw material gas, and a part of the upper surface of the susceptor. The susceptor is arranged at the center of the reaction tube so that its upper and lower surfaces are covered by the raw material gas flowing inside the reaction tube.

[For production]

In the vapor phase epitaxial crystal growth apparatus of the present invention, the shape of the susceptor, which holds the substrate for crystal growth in the reaction tube and is placed at the center of the reaction tube, is shaped like a smooth streamlined blade along the flow direction of the raw material gas. Since there are no sharp corners or the like with respect to the gas flow as in conventional reactor tubes, the raw material gas flowing into the reaction tube flows uniformly to cover the upper and lower surfaces of the reaction tube.

At this time, a boundary layer is formed on the upper and lower surfaces of the susceptor of the wing body due to the raw material gas flowing along both surfaces, but these boundary layers merge continuously in the downstream direction from the trailing edge and flow uniformly. Therefore, there is no separation phenomenon at the trailing edge, and therefore no vortices are generated.

Therefore, the backflow and turbulence caused by the vortices of the source gas flowing along the susceptor surface holding the substrate for crystal growth are eliminated, resulting in a stable flow, and a thin film such as a compound semiconductor crystal with a uniform crystal composition is coated on the surface of the substrate. It becomes possible to grow epitaxially.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of the vapor phase epitaxial crystal growth apparatus according to the present invention, and FIG.
-■ is a cross-sectional view taken along the cutting line.

In both of these figures, 11 is a horizontal crystal growth reaction tube with a rectangular cross-sectional shape so that the pressure gradient of the raw material gas flowing along the surface of the substrate 14, which will be described later, is constant, and 12 is a horizontal reaction tube for crystal growth that faces, for example, the flow direction of the raw material gas. The front edge end 12a has a rounded shape,
The susceptor is made of graphite or the like and has a streamlined wing body in cross section with a trailing edge end 12b forming an acute angle, and a substrate fitting arrangement part 13 on a part of the surface of which a substrate 14 for crystal growth is arranged. is provided.

The susceptor 12 having the above structure, on which the compound semiconductor substrate 14 made of, for example, CdTe is disposed, has a convex portion provided in the reaction tube 11, for example, so as to be located at the center of the reaction tube 11, as shown in FIG. The portion 11a and the recess 12c provided on the side of the susceptor 12 can be used to fit and arrange the susceptor 12.

With this arrangement, the raw material gas consisting of hydrogen gas carrying dimethyl cadmium, diethyl tellurium, and mercury at a predetermined composition ratio flowing into the reaction tube 11 flows around the susceptor 12 as shown by the arrow. At this time, a thin boundary layer 15a, 1 of raw material gas is formed along the upper and lower surfaces of the susceptor I2 made of the blade body.
5b is formed, but since the front end 12a of the susceptor 12 is rounded, the velocity gradient of the gas flow on the wall surface always takes a positive value and becomes a uniform flow, so that the boundary layer 1 there is formed.
The separation of 5a and 15b is eliminated, and the generation of vortices is also eliminated.

Also, a boundary layer 15a formed on the upper and lower surfaces of the susceptor 12
, 15b smoothly merge downstream from the trailing edge 12b and flow away continuously and uniformly, so that the separation phenomenon of the boundary layers 15a, 15b at the trailing edge 12b is eliminated. This also eliminates the generation of vortices.

Therefore, the problem of backflow or turbulence of the raw material gas flowing along the surface of the susceptor 12 holding the substrate 14 due to vortices is eliminated, and the flow becomes stable, so that the crystal composition is A thin film such as a compound semiconductor crystal made of uniform l1gCdTe can be epitaxially grown.

In the above embodiments, an example was explained in which a horizontal reaction tube for crystal growth with a square cross-sectional shape was used, but the present invention is not limited to this. Alternatively, the susceptor may be a wing body having a streamlined cross-section with both the leading edge and the trailing edge forming an acute angle.

〔Effect of the invention〕

As is clear from the above description, according to the vapor phase epitaxial crystal growth apparatus according to the present invention, during epitaxial growth, separation of the boundary layer due to the source gas formed on the susceptor on which the substrate for crystal growth is disposed is prevented. In addition, there is no generation of vortices due to separation of the boundary layer, so the flow of the raw material gas around the susceptor on which the substrate is arranged can be a stable flow without backflow or turbulence. This has an excellent effect that it is possible to easily epitaxially grow a thin film of compound semiconductor crystal or the like having a uniform crystal composition on the surface of the substrate.

Therefore, it is extremely advantageous for the vapor phase epitaxial growth of various compound semiconductor crystals.

[Brief explanation of the drawing]

1 is a vertical cross-sectional view of essential parts showing an embodiment of a vapor phase epitaxial crystal growth apparatus according to the present invention; FIG. 2 is a cross-sectional view taken along the line nn' shown in FIG. 1; The figure is a longitudinal sectional view of a main part for explaining a conventional vapor phase epitaxial crystal growth apparatus. 1 and 2, 11 is a reaction tube, 12 is a susceptor, 12a is a front edge end, 1
2b is a rear edge end, 13 is a board fitting arrangement part, 14 is a board,
15a and 15b indicate boundary layers, respectively.

Claims (1)

[Claims] Susceptor (12) holding a substrate for crystal growth (14)
In this apparatus, the susceptor (12) is arranged in a reaction tube (11), a raw material gas is introduced, and the raw material gas is thermally decomposed to epitaxially grow a thin film crystal on the substrate (14). The wing body has a streamlined cross-section along the gas flow, and a board fitting arrangement part (
13), and the susceptor (12) is connected to the reaction tube (
11) A vapor phase epitaxial crystal growth apparatus characterized in that it is arranged at the center of the reaction tube (11) whose upper and lower surfaces are covered by the source gas flowing therethrough.