JPS61115324A - Vapor growth method - Google Patents

Abstract

PURPOSE:To remove unstableness of growth conditions at the starting of the growth and to improve remarkably quality of the growth layer, by eliminating pressure variation when switching gases. CONSTITUTION:Non-raw-material gas is supplied into an exhausting line 4 or an introducing line 5 through a gas flow rate controller 3 from a supplying line 2, the same as raw material gas is supplied. At the beginning, the pressure of the introducing line 5 is regulated at the atmospheric pressure through a carrier gas supplying line 6 by a flow rate regulator 7, for the purpose of eliminating large variation of the pressure in the vessel when it is switched from the exhausting line 4 with the atmospheric pressure into the introducing line 5 with a reduced pressure F (0.1 barometric pressure) through the flow rate regulator 7 by switching cocks 8 (81 or 82). At the initial state, the gas switching cock 81 is connected to the exhausting line 4 while the switching cock 82 is connected to the introducing line 5, so that raw material gas resulted from TEI bubbling and non-raw-material H2 gas being controlled at the same flow rate as the raw material gas can be simultaneously switched and supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for supplying raw material gas during the vapor phase growth process of semiconductors.

Conventional technology The vapor phase growth method for semiconductors is the most effective method for forming semiconductor thin films because it can form a much thinner growth layer with uniform thickness and precision compared to the liquid phase epitaxial growth method. . Recently, quantum well lasers, high-performance field effect transistors, and the like have been realized by vapor phase growth technology in which thin film layers of different compositions are grown alternately.

Problems to be Solved by the Invention In the conventional vapor phase growth method as described above, in order to increase the uniformity of the grown layer and obtain a thin film layer with higher precision, it is necessary to lower the pressure inside the apparatus and perform growth under reduced pressure. People are starting to do it. In such a case, when the raw material gas for vapor phase growth is introduced into the growth apparatus from an empty flow state, the raw material gas and the pressure inside the growth apparatus fluctuate, making it impossible to control the flow rate of the raw material gas transiently. As a result, instability occurs, such as the composition and properties of the grown layer becoming uncontrollable at the start of growth.

Means to Solve the Problem The present invention focuses on the fact that the above problem is caused by a change in the total amount of introduced gas before and after introducing the raw material gas, and in order to solve this problem, pressure is adjusted in parallel with the raw material gas. A line for supplying a non-source gas with hydrogen gas or an inert gas is provided, and the source gas and the pressure-adjusted non-source gas are connected oppositely to an exhaust line and an inlet line to the growth apparatus. This is a supply method that can be switched to, and the equipment is equipped with a switching cock.

According to the present invention, based on the above structure, the flow rate of the pressure-adjusted non-source gas is made equal to that of the source gas, and the total amount of gas flowing into the growth apparatus is kept constant before and after introducing the source gas. By maintaining this, pressure fluctuations in the growth apparatus and in the raw material gas supply line can be suppressed, and the flow rate at the start of growth can be easily controlled.

Embodiment FIG. 1 is a schematic diagram of an apparatus used in an embodiment of the present invention, and FIG. 2 is an example of its application. An example in which the method of the present invention is applied to an organic metal pyrolysis growth method of indium phosphide (InP) will be described. As the raw material gas, a mixture of phosphine (PH3) and triethyl indium (TRI) is supplied from the supply line 1.

Since TRI is a liquid at room temperature, to form this mixture, hydrogen gas (H2) is poured into the TRI container 1 as shown in Figure 2.
The TRI is supplied by bubbling in the TRI and evaporating it to the saturated vapor pressure. Therefore, the amount of TRI supplied changes depending on the H2 flow rate, temperature, and pressure within the container, and these must be accurately controlled. The non-source gas is supplied to the exhaust line 4 or the inlet line 5 via the gas flow rate controller 3 in the same way as the supply line 2 and the source gas. First, the pressure in the introduction line 6 is adjusted to atmospheric pressure by the flow regulator 7 through the carrier gas supply line 6. This is due to the large pressure inside the container when switching from the atmospheric pressure exhaust line 4 through the switching cock 8 (81 or 82) to the reduced pressure F (0.1 atm) introduction line 5 via the flow regulator 7. This is to eliminate fluctuations. In the initial state, the gas switching cock 81 is connected to the exhaust line 4, while the switching cock 82 is connected to the introduction line 6, and the non-raw material gas H2 gas is controlled to the same flow rate as the material gas by TRI bubbling. It is configured to switch and supply at the same time. In addition, in FIG. 2, phosphine is supplied from a switching cock 83 through another supply line 12.

From this state, when the changeover cocks 81 and 82 were switched simultaneously in opposite directions to examine the amount of variation in pressure and flow rate when TRI was introduced, almost no variation was observed.

On the other hand, as an example of the method of the present invention in which the non-raw material gas supply line 2 is not used, the carrier gas flow rate is H2: 500.
cc/min, TRI/bubbling gas flow rate H2:2
00 Cc for 7 minutes, and the pressure fluctuation was similarly investigated.

After switching the cock, the pressure increased to 1.4 atm, which corresponds to a reduction in the amount of TRI evaporation by about 2/3. Further, the time required for the pressure fluctuation is about 15 seconds, and when converted into a growth layer thickness, it means that a transition region layer of about 60 people is formed.

Figure 3 summarizes the above results, and shows that the pressure fluctuations during gas switching in the conventional method show large fluctuations as in characteristic B, whereas in the method of the present invention, as in characteristic B, It was confirmed that the problems associated with pressure fluctuations were significantly improved.

As described in detail, the method of the present invention eliminates pressure fluctuations during gas switching, thereby eliminating instability in growth conditions at the start of growth and significantly improving the quality of the grown layer. Furthermore, since there is no transient layer caused by pressure fluctuations, it is possible to provide a high-quality thin film layer with good reproducibility, and its industrial value can be said to be great.

[Brief Description of the Drawings] Figure 1 is a diagram showing the configuration of the method of the present invention, Figure 2 is a diagram showing the configuration of an embodiment of the present invention, and Figure 3 is a diagram showing pressure fluctuations in the introduction line compared to the conventional method. Bamboo and azusa surface ζ compared with the embodiment of the present invention
"A3゜1... Raw material gas supply line, 2... Non-raw material gas supply line, 3... Gas flow rate controller,
4...Exhaust line, 6...Introduction line, 8 (81, 82, 83)...Gas switching cock. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 31! I Ki-ma [Excerpt]

Claims (1)

[Claims] The first step in supplying raw material gas for vapor phase growth with controlled pressure and flow rate.
When switching from the second system to the second system for supplying non-raw material gas controlled at a different pressure and flow rate, the non-raw material gas controlled to be equal in amount to the raw material gas is transferred from the second system to the second system for supplying non-raw material gas, which is controlled at a different pressure and flow rate. A vapor phase growth method characterized by switching to system 1.