JPH0479233A - Manufacture device of compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To make raw gas concentration formed on a substrate uniform and to realize uniformity of composition and thickness by dividing a cross section of an introduction tube of gas supplied to a reaction tube into a plurality of regions and by supplying raw gas of different concentrations to an inside of the regions. CONSTITUTION:A gas introduction tube 5 connected to a reaction tube 1 is divided into a plurality of regions so that the upper the gas introduction tube is, that is, the farther from a substrate surface the gas introduction tube is, the higher a concentration of raw gas is supplied, and the lower the gas introduction tube is, that is, the nearer the substrate surface the gas introduction tube is, the lower a concentration of raw gas is supplied. A layer of uniform gas concentration formed by a gas flow of a layer flow, that is a concentration boundary layer 14 can be cut off to take in gas flowing outside the concentration boundary layer into a concentration boundary layer and a gas control board 12 can be attached to an area near substrate 3 by a proper jig by a substrate installation stand2. Since raw gas concentration in a substrate surface can be thereby controlled constant, a compound semiconductor crystal having stable film thickness and composition can be acquired.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an apparatus for manufacturing compound semiconductor crystals, and aims to provide an apparatus in which the thickness and composition of the compound semiconductor crystal layer to be formed are stable. In a crystal manufacturing apparatus in which a substrate is placed on a substrate installation stand, a raw material gas introduced into the reaction tube is thermally decomposed, and raw material gas components are deposited on the substrate, a gas that supplies the raw material gas into the reaction tube. The cross section of the introduction pipe is divided into multiple regions,
The structure is such that raw material gases having different concentrations are supplied to each region.

[Industrial application field]

The present invention relates to an apparatus for manufacturing compound semiconductor crystals.

Compound semiconductor crystals such as mercury, cadmium, and tellurium, which have narrow energy band gaps, are used as materials for forming photodetecting elements.

As such a compound semiconductor crystal, a crystal with a large area and a thin layer is desired for convenient device formation.
CV D (Metal Organic Chell)
A vapor phase epitaxial growth method such as a vapor deposition method is used.

Then, hydrogen gas carrying mercury, diethyl tellurium, and dimethyl cadmium, and hydrogen gas as a carrier gas are supplied into the reaction tube 1 as raw material gases from the gas introduction tube 5 connected to the reaction tube 1, and this supplied raw material gas is thermally decomposed by heating the substrate installation stand 2, and mercury, cadmium, tellurium (Hg+
□CdXTe) compound semiconductor crystal is grown. The remaining raw material gas that did not contribute to growth is exhausted to the outside through the gas exhaust pipe 6.

[Prior Art] The production of a compound semiconductor crystal using a conventional vapor phase epitaxial growth method will be described with reference to FIG.

As shown in FIG. 6, a substrate 3 for epitaxial growth such as cadmium telluride (CdTe) is placed on a substrate mounting stand 2 made of carbon or the like in a horizontal reaction tube 1, and a high-frequency induction wave is placed around the reaction tube. A heating means 4 consisting of a coil is provided.

[Problem to be solved by the invention]

By the way, in the conventional method, on the substrate 3 for epitaxial growth, as shown in curve m7 in FIG. The concentration tends to gradually decrease.

This is because even if a source gas with a predetermined initial concentration of C0 is supplied onto the substrate, the source gas is consumed for epitaxial growth along the direction of gas movement during the epitaxial growth process.

Therefore, the concentration of the source gas on the substrate for epitaxial growth fluctuates, creating a concentration gradient as shown in curve 7, and a uniform concentration of the source gas is not supplied over the entire substrate. There is a problem that the composition and thickness of compound semiconductor crystals are not uniform.

This type of gas supply is necessary in order for the crystals to be formed to have a uniform composition and thickness, so that the gas flow is supplied in a laminar flow state.The conditions for this laminar flow are It is determined by the flow rate of the gas, the viscosity of the gas, the density of the gas, the diameter of the reaction tube, etc.

Conventionally, in order to obtain a uniform composition and thickness of the crystal to be formed, as shown in FIG. 8 is used to provide a rotating mechanism, which rotates the substrate to determine the composition of the crystal formed on the substrate,
I tried to keep the thickness uniform.

However, as shown by curve 7 in FIG. 7, the concentration of the source gas supplied onto the substrate does not vary linearly, so even if the substrate is rotated in this way, the concentration of the source gas on the substrate remains unchanged. There is a problem that it is not uniform.

The present invention solves the above-mentioned problems and provides an apparatus capable of manufacturing a compound semiconductor crystal having a uniform composition and thickness by making the concentration of the raw material gas formed on the substrate uniform over the entire region of the substrate. With the goal.

[Means for Solving the Problems] The above-mentioned object is to divide the cross section of the gas introduction pipe for supplying the raw material gas into the reaction tube of the present invention into a plurality of regions, and to supply the raw material gas with different concentrations into each region. Achieved with advanced manufacturing equipment.

Further, a gas flow control plate is provided close to the substrate to cut off the flow of the raw material gas introduced into the reaction tube and vary the flow of the raw material gas.

Further, an auxiliary gas introduction pipe is provided separately from the gas introduction pipe so that the raw material gas is supplied to the substrate surface, and the raw material gas is supplied into the reaction tube from the gas introduction pipe and the auxiliary gas introduction pipe.

[For production]

FIG. 4 shows a schematic diagram of the gas flow of the source gas supplied onto the substrate. As shown in the figure, from point a on the gas inflow side of the substrate,
A laminar gas concentration boundary layer 14 is formed on the substrate toward point d on the gas outflow side of the substrate, and the gas concentration remains constant within this concentration boundary layer.

Further, FIG. 5(a) shows the concentration of the raw material gas on the substrate at point a on the substrate on the gas inflow side of the substrate shown in FIG. 4, and FIG. b of the board shown in Figure 4
FIG. 5C shows the concentration of the source gas on the substrate near points c and d of the substrate shown in FIG. 4. Figure 5(a), 5th
In FIGS. 5(b) and 5(c), the vertical axis indicates the concentration of the source gas, and the horizontal axis indicates the height h from the substrate surface.

As shown in FIG. 5(a), at point a of the substrate, the concentration of the source gas shows a uniform concentration C0 along the height direction above the substrate surface, but as shown in FIG. 5(b), At point b of the substrate, the source gas is consumed on the substrate during the epitaxial growth process, so the concentration of the source gas becomes uniform at a height of 61 above the substrate surface, as shown in Figure 5 (C). At points c and d of the substrate, the concentration of the raw material gas becomes uniform at a position where the height above the substrate surface is δ.

The gas concentration at points c and d on the substrate is the concentration at which the epitaxial growth reaches a steady state, so the gas concentration on the substrate reaches the state shown in FIG. 5(C) over the entire area of the substrate. It is hoped that this will be achieved across the board.

In FIG. 5(C), the gas concentration is lower at the surface of the substrate, and the gas concentration increases as you move upwards from the surface of the substrate, so in order to achieve this state, It is preferable to supply the raw material gas so that it has a concentration gradient between this state and the inside of the reaction tube.

For this purpose, as shown in FIG. 1(a) and FIG. 1(b), the gas introduction tube 5 connected to the reaction tube 1 is divided into a plurality of regions, and the upper part of the gas introduction tube, that is, the upper part from the substrate surface. A source gas with a high concentration is supplied toward the bottom of the gas introduction pipe, and a source gas with a low concentration is supplied toward the bottom of the gas introduction pipe, that is, toward the surface of the substrate.

In addition, as shown in FIG. 2, a layer with a uniform gas concentration formed by the laminar gas flow near the substrate 3, that is, a concentration boundary layer 14, is cut, and the gas flowing outside the concentration boundary layer is cut. A gas flow control plate 12 that is taken into the concentration boundary layer to make the gas concentration uniform may be attached near the substrate from the substrate installation stand 2 using a suitable jig.

In addition, as shown in FIG. 3, an auxiliary gas introduction pipe 15 is installed near the substrate surface so that the source gas can be directly supplied to the surface of the substrate 3, so that the concentration gradient of the source gas shown in FIG. The state may be realized. A plurality of these auxiliary gas introduction pipes may be provided, and the raw material gases introduced into this auxiliary gas introduction pipe may be mixed or may be supplied alone without being mixed.

〔Example〕

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

FIG. 1(a) and FIG. 1(b) are schematic diagrams of the apparatus of the present invention, and FIG. 1(b) is the lI of the gas introduction pipe of FIG. 1(a).
FIG.

As shown in FIG. 1(a) and FIG. 1(b), the gas introduction pipe 5 connected to the reaction tube is enlarged to form a plurality of regions 5A.
, 5B, 5C, and 5D.

In the uppermost region 58 of the gas introduction pipe of the present invention, hydrogen gas is supplied as a carrier gas at a rate of 642/min, and diethyl tellurium gas is supplied at a partial pressure of 2.4XIO as a raw material gas.
-' Atmospheric pressure, the partial pressure of dimethyl cadmium gas is 5.0XI
The pressure of mercury gas is 0-5 atm and the partial pressure of mercury gas is 6.0 Xl0-' atm.

Further, hydrogen gas as a carrier gas is added to the region 5B.
127mln, the partial pressure of diethyl tellurium gas at 40% of the gas concentration supplied to area 5A as raw material gas is 0.4X2
．． 4 Xl0-' atmospheric pressure, the partial pressure of dimethyl cadmium gas is 0.4 X5. OxlO-5 atmospheres, partial pressure of mercury gas is 0.4X6. The mixture is introduced so that the pressure is OXl0-'atmospheric pressure.

In addition, hydrogen gas as a carrier gas is added to the region 5C.
42/min, the partial pressure of diethyl tellurium gas at 20% of the gas concentration supplied to region 5A as a raw material gas is 0.2X2
．． 4 Xl0-' atmospheric pressure, the partial pressure of dimethyl cadmium gas is 0.2 x5. OxlO-5 atmospheres, partial pressure of mercury gas is 0.2X6. The mixture is introduced so that the pressure is OXl0-'atmospheric pressure.

Further, in the region 5D at the bottom of the gas introduction pipe, hydrogen gas was supplied as a carrier gas at 61/min, and a partial pressure of diethyl tellurium gas at a concentration of 15% of the gas supplied to the region 5A as a raw material gas was 0.15×2.4. Xl0-' atmospheric pressure, the partial pressure of dimethyl cadmium gas is 0.15X5. OXl0-'
The atmospheric pressure and partial pressure of mercury gas are 0.15X6. The mixture is introduced so that the pressure is OXl0-'atmospheric pressure.

In this way, the concentration distribution of the raw material gas on the substrate as shown in FIG. 5(C) described above can be obtained, and a compound semiconductor crystal having a uniform composition and thickness can be obtained.

Further, as shown in FIG. 2, a gas flow control plate 12 made of quartz or carbon is attached close to the substrate 3 using a jig 13 or the like extending from the side of the substrate installation stand 2. Then, by supplying the raw material gas onto the substrate in a laminar flow state, a region with a uniform gas concentration is formed on the substrate, that is, a concentration boundary layer 14 of the raw material gas is cut by the gas flow rate control plate 12.
The gas flow may be introduced from outside the concentration boundary layer 14 so that the gas concentration is constant over the entire area on the substrate, or the gas concentration may vary linearly on the substrate. Also good. The number of gas flow control plates may be one or more.

As another example, as shown in FIG. 3, an auxiliary gas introduction pipe 15 is provided so that the raw material gas is directly supplied onto the substrate 3 for epitaxial growth.
At the same time, a single raw material gas or a mixture of raw material gases is supplied from this auxiliary gas introduction pipe 15, and the concentration of the raw material gas introduced into the reaction tube from the auxiliary gas introduction pipe is adjusted to the concentration of the gas on the substrate surface. The raw material gas may be supplied from the gas introduction pipe and the auxiliary gas introduction pipe so that the concentration remains constant or decreases linearly.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the concentration of the source gas on the substrate surface can be controlled to a constant level, so that a compound semiconductor crystal having a stable film thickness and composition can be obtained.

In the figure, 1 is a reaction tube, 2 is a substrate installation stand, 3 is a substrate, 5 is a gas introduction tube, 12 is a gas flow control plate, 13 is a jig, 14 is a concentration boundary layer, and 15 is an auxiliary gas introduction tube. .

[Brief explanation of drawings]

Figures 1(a) and 1(b) are schematic diagrams of the device of the present invention; Figure 2 is an explanatory diagram of the gas flow control plate used in the device of the present invention; and Figure 3 is an illustration of the auxiliary gas used in the device of the present invention. An explanatory diagram of the introduction pipe, Figure 4 is a schematic diagram of the raw material gas flow on the substrate, Figure 5 (a),
Figures 5(b) and 5(C) are gas concentration distribution diagrams at various positions on the substrate, Figure 6 is a schematic diagram of the apparatus used in the conventional method, and Figure 7 is the diagram of the gas concentration distribution at each position on the substrate. FIG. 3 is a gas concentration distribution diagram on a substrate.

Claims (3)

[Claims] (1) A substrate (3) for epitaxial growth is installed on the substrate installation stand (2) in the reaction tube (1), and the raw material gas introduced into the reaction tube (1) is thermally decomposed to form the raw material on the substrate. In the crystal device for depositing gas components, the cross section of the gas introduction pipe (5) for supplying the raw material gas into the reaction tube is partitioned into a plurality of regions, and raw material gas with different concentrations is supplied to each region. A compound semiconductor crystal manufacturing device characterized by: (2) Cut off the flow of the raw material gas introduced into the reaction tube (1), vary the flow of the raw material gas, and direct the gas flow to the gas concentration boundary layer (14) formed on the substrate. 2. The compound semiconductor crystal manufacturing apparatus according to claim 1, wherein a gas flow control plate (12) to be taken in is provided close to the substrate. (3) Separately from the gas introduction pipe (5), an auxiliary gas introduction pipe (15
), and the raw material gas is supplied into the reaction tube from the gas introduction pipe (5) and the auxiliary gas introduction pipe (15).