JPS59184520A - Suscepter for supporting substrate crystal - Google Patents

Abstract

PURPOSE:To enable formation of the epitaxial layer having highly uniform film thickness over all of the plural substrates of arbitrary forms by forming a polycrystalline thin film deposition layer consisting of the same compound as crystal of the substrate on the suscepter for supporting substrates used for vapor growth of a compound semiconductor. CONSTITUTION:A polycrystalline thin film deposition layer 20 consisting of the same compound as crystal of the substrate 16 is formed on a suscepter 17 for supporting substrate crystal used for vapor growth of a compound semiconductor. For example, when placing the GaAs substrate 16 on the suscepter 17 to perform vapor growth of GaAs crystal, a GaAs polycrystalline thin film layer 20 deposited to about 50mum of thickness on the suscepter 17. Consequently, as growing speed of GaAs crystal on the GaAs polycrystalline thin film deposition layer 20 is the same as that on the GaAs substrate 16, there is practically no gap when the substrate is placed on the suscepter. Accordingly, the epitaxial growth layer having a fixed film-thickness distribution constantly irrespective of a shape or an area of the substrate to be placed can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a susceptor in which a substrate crystal (hereinafter referred to as a substrate) used for vapor phase growth of a ■-■ group compound semiconductor is installed.

In recent years, with the rapid increase in demand for various electronic devices, mass production of ■-V group compound semiconductor epitaxial wafers, which are necessary for device formation, is desired. Phase growth is most suitable. In open tube vapor phase growth of gallium arsenide (GaAs), gallium chloride (GaAs) is used as a reactive gas.
CA') and arsenic (Al1), hydrogen (N2), nitrogen (
A carrier gas such as N2) is used to transport and react onto a substrate placed on a susceptor in a growth region in a reaction tube, thereby causing epitaxial growth. Conventionally, in order to increase the number of substrates, a method has been used in which a large number of substrates are installed parallel to the gas flow direction. At this time, in order to increase the product yield of semiconductor devices manufactured using epitaxial wafers, it is particularly required that the epitaxial growth layer has high film thickness uniformity. However, with conventional methods, it has been very difficult to achieve film thickness uniformity that is good enough to satisfy the requirements.

That is, in the GaAs vapor phase growth reaction, the reaction gas G
aCA! and As are transported from upstream to downstream while precipitating GaAs crystals on the substrates placed side by side on the susceptor, they are consumed and their concentration decreases. This decrease in the concentration of reactant gas results in a decrease in the growth rate.

Furthermore, the growth rate tends to be especially high in a range of several tens of millimeters from the gas upstream end of the substrate, and the film thickness in that region becomes considerably thick.

Incidentally, in order to rationalize the element manufacturing process, it is an absolute requirement that the shape of the substrate be circular. Therefore, when the substrates are placed side by side on the susceptor, there is always a gap, which complicates the phenomena of both a decrease in the growth rate due to a decrease in the concentration of the reactant gas from upstream to downstream, and a thick growth at the gas upstream end. Due to mutual influence, the film thickness uniformity of the epitaxially grown layer on each substrate was low, and the reproducibility of the film thickness distribution was also poor. Furthermore, conventionally, a method has been used in which a dummy substrate is installed on the gas upstream side to equalize the elongation thickness, but it is actually difficult to process the dummy substrate so that it adjoins the circular substrate without any gaps. Although the occurrence of gaps was inevitable, it was not possible to obtain a satisfactory film uniformity.

The purpose of the present invention is to eliminate the problems of the above-mentioned conventional methods and to provide a new susceptor for mounting substrates that can form an epitaxial layer with a highly uniform pattern on all of a large number of circular or arbitrarily shaped substrates. be.

According to the present invention, there is obtained a susceptor for installing a substrate crystal used in vapor phase growth of a compound semiconductor, characterized in that a polycrystalline thin film deposited layer made of the same compound as the substrate crystal is formed. .

The present invention will be explained in detail below based on the figures.

Figure 1 is a cross-sectional view of a commonly used open-tube horizontal GaAs vapor phase growth apparatus, in which 11 is a quartz reaction tube, 12 is an electric furnace, 13 is a mixture of H2 and doping gas, and 14 is trichloride. A mixed gas of arsenic (5C13) and H2, 15 a source gallium (Ga), 16 a GaAs substrate, 17 a susceptor, and 18 a holder. As4 generated by the decomposition of AsCl3 and GaC4 generated from the source Ga 1 s
is transported onto the Q a As substrate 16 placed on the susceptor 17 in the growth region of the reaction tube 11, and an epitaxial growth reaction is performed.

2 and 3 are diagrams for explaining the variations in film thickness of an epitaxial layer formed on a GaAs substrate by a conventional method.
6 and a dummy substrate 19 are installed, and FIG. 3 is a film thickness distribution diagram of the epitaxially grown layer along lines AA, B-Bi, and C-C in FIG. 2 along the gas flow direction. Here, the GaAs substrate 16 has a diameter of 50 mm, the dummy machine 19 has a size of 50 x 20 dragons, and the growth conditions are the source Ga1s.
temperature of 850°C, growth region temperature of 750°C, AsC/3 mole fraction of 3×10. ) - Tal H2 flow rate is 41/min and growth time is 30 minutes. As shown in FIG. 2, there are gaps between the substrates arranged side by side. As can be seen from Fig. 3, the film thickness gradually decreases from upstream to downstream on the line B-B along the center of the substrate, with relatively little variation;
In line A and line C-C, the film thickness is thick overall, and is particularly thick at the upstream end of the substrate. Therefore, the variation in film thickness within the plane of one substrate is as large as approximately ±7 inches. This is caused by two phenomena: a decrease in the growth rate due to a decrease in the concentration of the reactant gas from upstream to downstream, and an increase in the growth rate at the gas upstream end of the substrate in contact with the K gap.

5- Figures 4 and 5 show Ga
FIG. 2 is a diagram for explaining variations in film thickness of an epitaxial layer formed on an As substrate. FIG. 4 is a plan view of the GaAs substrate 16 placed on the susceptor 17, in which 20 is a GaAs polycrystalline thin film layer deposited to a thickness of about 50 μm, and FIG. Figure 4 A/ A/
FIG. 3 is a film thickness distribution diagram of an epitaxially grown layer along lines B'-B' and C'C/. Substrate size, growth conditions,
The growth time etc. are the same as in the conventional method. As shown in FIG. 4, on the susceptor 17 is a GaAs polycrystal thin film deposited layer 2.
0 is formed, and a GaAs substrate 16 is formed thereon.
It is installed. G to GaAs polycrystalline thin film deposited layer 20
Since the growth rate of the aAs crystal is the same as that for the GaAs substrate 16, it is equivalent to having virtually no gaps when the substrate is placed on the susceptor according to the present invention, and therefore the shape and area of the substrate to be placed are An epitaxially grown layer having a constant film thickness distribution can be obtained regardless of the film thickness. In other words, as can be seen from Fig. 5, the thickness of the film 6- for line A'-A', line B'-B', and line C/C/ decreases gradually from upstream to downstream, and the level of film thickness also changes. Almost the same. Therefore, the variation in film thickness within the plane of one substrate is very small, about ±2 factors, and an epitaxially grown layer with a uniform film thickness can be obtained.

Note that the thickness of the GaAs polycrystal thin side deposit layer only needs to be about 50 μm, and it can be easily formed by ordinary CVD, evaporation, or other methods, and it can also be formed by vapor phase growth of impurity-doped GaAs crystals. It can be regenerated by removing it by means such as , vapor phase etching, etc., and can be used any number of times.

As described above, according to the present invention, it is possible to grow an epitaxial layer having a -j uniform thickness on a large number of substrates having arbitrary shapes and areas, and the effect can be said to be extremely large.

Although the susceptor of the present invention has been described above using gallium arsenide vapor phase growth as an example, the same effects can be obtained with other III-V group compound semiconductors, such as indium phosphide, gallium phosphide, and indium arsenide.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a horizontal GaAs vapor phase growth apparatus, 11 is a quartz reaction tube, 12 is an electric furnace, 13 is a mixed gas of H2 and doping gas, 14 is a mixed gas of AsCJ3 and H2, 15 is a source Ga, 16 is a GaAs substrate, 17
is a susceptor, and 18 is a holder. FIG. 2 is a plan view of a GaAs substrate installed on a susceptor according to the conventional method, and 19 is a dummy substrate.
FIG. 3 is a film thickness distribution diagram of an epitaxially grown layer along the line CC. FIG. 4 is a plan view of a GaAs substrate placed on a susceptor according to the present invention, 20 is a QaAs polycrystalline thin film deposited layer, and FIG. It is a film thickness distribution diagram of the epitaxially grown layer in the A/A/ line, the BtBt line, and the C/C/ line. 1□- 93- Jin V/) 8 Shin (Go d) House axis

Claims (1)

[Claims] A susceptor for installing a substrate crystal used in vapor phase growth of a compound semiconductor, characterized in that a polycrystalline thin film deposited layer made of the same compound as the substrate crystal is formed.