JPS63313826A - Vapor phase epitaxy method - Google Patents

Abstract

PURPOSE:To enable an epitaxial layer in high quality and stable composition to be formed by a method wherein multiple gas leading-in pipes are provided while the positions of outlet ends are differentiated along the shifting direction and then the concentration or flow rate of gas is varied. CONSTITUTION:Three each of mercury gas leading-in pipes 11A-11C are provided while the positions P1-P3 of outlet ends are respectively differentiated along the gas shifting direction as shown by arrow D. Then, the concentration or flow rate of a material gas is varied so that the concentration of gas reaching the surface of a substrate 13 from respective outlet ends of the gas leading-in pipes 11A-11C may be made even and then the gas is led in the gas leading-in pipes 11A-11C. Through these procedures, the mercury gas can be fed to all positions along the gas shifting direction on the substrate 13 in even concentration to form epitaxial crystal in even concentration to form epitaxial crystal in even composition on the substrate 13.

Description

[Detailed Description of the Invention] [Summary] A method for vapor phase epitaxial growth of a compound semiconductor, comprising:
Mercury gas and raw materials such as diethyl tellurium and dimethyl cadmium are each carried by a carrier gas and introduced onto a substrate placed on a susceptor, and by heating the susceptor, the raw material gases react with each other on the substrate and are transferred onto the substrate. A method for forming an epitaxial layer, in which a plurality of gas introduction tubes for raw material gas are provided, the positions of the outlet ends of the gas introduction tubes in the reaction tube are different, and the substrate is removed from each gas introduction tube. In order to maintain a constant concentration of the gases that reach different positions along the gas movement direction, gases with different concentrations or gases with a constant concentration and different flow rates are introduced from each gas introduction pipe onto the substrate. so that an epitaxial layer with a uniform composition is formed.

[Industrial application field]

The present invention relates to improvements in vapor phase epitaxial growth methods, and particularly to improvements in vapor phase epitaxial growth methods for compound semiconductor crystals using mercury as a source gas.

Mercury-cadmium-tellurium (Hg+-XCdXTe) crystals are used as materials for infrared sensing elements.
A vapor phase epitaxial growth method is used to form such crystals of mercury, cadmium, and tellurium in a thin layer and over a large area so as to be convenient for device formation.

When forming epitaxial crystals of mercury, cadmium, and tellurium, mercury gas and organic metal gas such as diethyl tellurium are used as raw material gases for forming the epitaxial layer. There is a need for a method that eliminates the phenomenon of reacting with other source gases in the gas phase before reacting.

[Conventional technology]

Using this vapor phase epitaxial growth method, mercury and
When forming cadmium tellurium crystals on a substrate, conventionally, as shown in FIG. After the substrate 2 is introduced into the reaction tube 3, the inside of the reaction tube is evacuated.

Next, hydrogen gas carrying dimethyl cadmium and hydrogen gas carrying diethyl tellurium are introduced into the reaction tube 3 through the gas introduction pipe 4 as raw material gases, and hydrogen gas is introduced into the reaction tube as a carrier gas. Further, hydrogen gas carrying mercury is introduced into the reaction tube 3 through a gas introduction tube 5 extending near the substrate 2 in the reaction tube 3 .

Next, a high frequency induction heating coil 6 installed around the reaction tube 3
By applying a high frequency voltage to the susceptor 1, the susceptor 1 is heated by high frequency induction, thereby increasing the temperature of the substrate 2 and the temperature inside the reaction tube around the substrate 2. A source gas consisting of mercury, dimethyl cadmium, and diethyl tellurium introduced into the substrate is decomposed, and the decomposed components are reacted with each other to epitaxially grow a crystalline layer of mercury, cadmium, and tellurium on the substrate.

[Problem that the invention seeks to solve]

Incidentally, in the conventional method, the position P of the outlet end of the mercury gas inlet tube 5 in the reaction tube is installed extending in the direction of the substrate 2, but it is still installed at a distance l from the surface of the substrate. has been done.

As shown in FIG. 4, when mercury gas is introduced into the reaction tube through the gas introduction tube 5, the gas flow is laminar in order to obtain an epitaxial layer of uniform thickness. Since the laminar flow gas flows out from the gas introduction tube 5, it diffuses and spreads in all directions within the reaction tube 3, so that the gas is introduced into the substrate in the same direction. The concentration gradient of the gas that reaches the unit area at each position ^, B, and C on the side is different, and there is a problem that an epitaxial crystal with a uniform composition cannot be obtained.

The present invention solves the above problems, and when a chemically active raw material gas reaches a substrate, the concentration of the gas that reaches the substrate has a concentration gradient at each position on the substrate along the direction of gas movement. The purpose of the present invention is to provide a vapor phase epitaxial growth method that allows uniform growth.

[Means for solving problems]

The vapor phase epitaxial growth method of the present invention for achieving the above object includes installing a susceptor provided with a substrate in a reaction tube, and carrying a plurality of raw material gases chemically active in the gas phase in the reaction tube as a carrier gas. In the method of forming an epitaxial layer containing components of the plurality of raw material gases by causing the raw material gases to react with each other on the substrate by heating the susceptor, In addition to arranging a plurality of gas inlet tubes, the positions of the outlet ends of the gas inlet tubes in the reaction tube are different from each other, so that the concentration of the gas reaching the substrate surface from each outlet end of the gas inlet tubes is constant. The raw material gas is introduced into each gas introduction pipe while changing its concentration or gas flow rate so that

[Effect]

In the vapor phase epitaxial growth method of the present invention, a plurality of gas introduction tubes for the raw material gas are provided, the positions of the outlet ends in the reaction tube are varied along the moving direction of the gas, and the source gas is introduced into the plurality of gas introduction tubes. By varying the concentration of the gas supplied or the flow rate of the gas, the concentration of the gas supplied at a plurality of positions along the direction of gas movement of the substrate is made uniform, so that there is no compositional variation on the substrate surface. A high-quality epitaxial layer with a stable composition is formed.

〔Example〕

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

FIG. 1 is a schematic diagram of the apparatus used in the method of the invention.

As shown in FIG. 1, the method of the present invention has the greatest influence on the compositional variation of the epitaxial layer formed. Set the position to PlI P2. As shown in P3, they are made to vary along the gas movement direction shown by the arrows.

Here, the positions of the CdTe substrate 13 placed on the susceptor 12 along the gas movement direction are designated as A, B, and C.

The total pressure, which is the sum of the partial pressures of raw material gases such as mercury gas, dimethyl cadmium gas and diethyl telluride gas, and carrier gas consisting of hydrogen gas, introduced into the reaction tube 14 is 1 atmosphere, and the gas is introduced from the gas introduction tube 11A. The partial pressure of the mercury gas introduced is set to 200 torr.

As shown in FIGS. 1 and 2(a), the concentration of mercury gas led out from the gas introduction tube 11A when it reaches position A on the substrate 13 is set to When the mercury gas reaches position B of the substrate 13, the gas concentration is 2 torr, which is 1/100 of the initial concentration.
When the mercury gas reaches the position C of the substrate 13, the concentration of the gas is 1 of the initial concentration of 17200.
torr. This state is shown in Figure 2(a).
as shown by straight line 21.

In the figure, the vertical axis shows the concentration of mercury gas, and the horizontal axis shows the position of the substrate.

Furthermore, as shown in FIGS. 1 and 2 (B), when the mercury gas led out from the gas introduction pipe 11B reaches the position of the substrate 13, the concentration of the gas is zero, and the concentration of the gas is zero at the position of the substrate 13 i&B. When the mercury gas reaches position C on the substrate, the gas concentration is set to 18 torr, which is 1/10 of the initial concentration, and the gas concentration is set to 17 torr, which is 1/10 of the initial concentration.
The concentration should be 9 torr, which is 20 torr. This state is shown by curve 22 in FIG. 2(b).

Further, as shown in FIGS. 1 and 2(C), the concentration of the mercury gas led out from the gas introduction pipe 11C is zero at positions A and B on the substrate 13, and the mercury gas is brought out at position C on the substrate. When the gas concentration reaches 1/1 of the initial concentration
The concentration is set to 10 torr, which is 0. This state is shown by curve 23 in FIG. 2(d).

And as shown in FIG. 2(d), the gas introduction pipe 11A.

A curve 24 shows the gas concentration curve at all positions A, B, and C of the substrate when gas is led into the reaction tube from all the gas introduction pipes 11B and 11C. If the number of gas introduction pipes is further increased in this way, the substrate 13
The gas concentrations at positions ^, B, and C are uniform.

This state is summarized in Table 1.

Table 1 Each value in Table 1 corresponds to position A and B on the board.

At C, the concentration of the gas led out from the gas introduction pipes 11A, 11B, and 11G is expressed in partial pressure (torr). Since the gas concentration is all 20 torr and mercury gas with a uniform concentration is supplied onto the substrate, an epitaxial layer with a uniform composition can be obtained.

As described above, according to the method of the present invention, mercury gas is supplied at a uniform concentration over all positions on the substrate, so that an epitaxial layer with a uniform composition is formed on the substrate.

Note that if a larger number of gas introduction tubes are provided along the gas introduction direction or in a direction perpendicular to the gas introduction direction, with different gas introduction ends, the gas can be supplied to the substrate with a more uniform concentration. be done.

〔Effect of the invention〕

As mentioned above, mercury gas is supplied at a uniform concentration to all positions along the gas transport direction on the substrate, which has the effect of forming epitaxial crystals with a uniform composition on the substrate. .

[Brief explanation of drawings]

Figure 1 is a detailed explanatory diagram of the present invention, Figure 2 (a), Figure 2 (b), Figure 2 (C), Figure 2 (
d) is a concentration distribution diagram of mercury gas in the method of the present invention, FIG. 3 is an explanatory diagram of the conventional method, and FIG. 4 is an explanatory diagram of disadvantageous conditions in the conventional method. In the figure, 11A, 11B, 11C are gas introduction tubes, 12 is a susceptor, 13 is a substrate, 14 is a reaction tube, 21, 22, 23.
24 is the mercury gas concentration distribution curve in the reaction tube, A, B
, C indicates the position of the substrate, and PI, Pg, and P3 indicate the output end of the gas introduction pipe. The method of the present invention is shown in Figure 1.
Figure Conventional-1 ``Tayo 5-U Medical Examination Tomoe Moe-on I Figure 3 Conventional-Fugunban 7 Company ゛n Cane Meiji Figure 4

Claims (1)

[Claims] A susceptor (with a substrate (13) provided inside a reaction tube (14)
12) is installed, a plurality of raw material gases that are chemically active in the gas phase are introduced into the reaction tube (14), supported by a carrier gas, and the raw material gases are heated by heating the susceptor (12). In the method of forming an epitaxial layer containing components of the plurality of raw material gases by reacting them on the substrate (13), gas introduction pipes (11A, 11B, 11C) for the raw material gases;
A plurality of are arranged, and the reaction tube (
The position of the outlet end in the gas introduction pipe (11) is varied along the moving direction of the introduced gas.
A, 11B, 11C) from the respective outlet ends of the substrate (
13) A vapor phase epitaxial growth method characterized in that the concentration of the raw material gas or the gas flow rate is varied and introduced into each gas introduction pipe so that the gas concentration gradient reaching the surface is constant.