JPH04105315A - Vapor epitaxial growth method of compound semiconductor - Google Patents

Abstract

PURPOSE:To stabilize the impurity concentration level of an epitaxial growth level by a simple means, by always supplying oxygen by a growth cycle constituting one cycle of a growth process for forming an epitaxial growth layer and a baking process for eliminating unnecessary deposit formed in a reaction tube and cleaning it. CONSTITUTION:Metal Ga 8 contained in a quartz vessel 9 is arranged in a reaction tube 1 and heated while reaction gas is supplied in the reaction tube 1, thereby forming compound containing Ga. When compound semiconductor is grown on a substrate 5 set in the reaction tube 1, and an epitaxial growth layer 12 is grown, oxygen is always supplied by a growth cycle constituting one cycle of the following; a growth process for forming an epitaxial layer 12 on a substrate 5 set in the reaction tube 1, and a baking process for eliminating unnecessary deposit 13 formed in the reaction tube 1 and cleaning it. Thereby the melting amount of Si into the metal Ga in the vessel is made constant, and the impurity concentration level in the epitaxial growth layer can be stabilized.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for vapor phase epitaxial growth of compound semiconductors.
The present invention relates to a method of growing a compound semiconductor such as aAs on a substrate to form an epitaxial growth layer.

[Conventional technology]

In manufacturing semiconductor devices such as Gunn diodes, a vapor phase epitaxial growth apparatus shown in FIG. 4 is used to grow GaAs, which is a compound semiconductor, on a substrate to form an epitaxial growth layer.

This vapor phase epitaxial growth apparatus consists of a horizontally long reaction tube (1)
An air supply port (2) is provided at one end, a lid (3) is removably attached to the other open end, and an exhaust port (4) is provided near the end. . A support rod (7) for supporting a susceptor (6) for holding the GaAs substrate (5) in a predetermined posture within the reaction tube (1) is attached to the lid (3). Also, reaction tube (1)
A quartz container (9) containing metal gallium (8) is placed on the air supply port side. On the outer periphery of the reaction tube (1), a first heater (10) for heating the metal gallium (8) in the container (9) to a predetermined temperature and a Ga on the susceptor (6) are installed.
A second heater (1) heats the As substrate (5) to a predetermined temperature.
1) is installed.

Vapor phase epitaxial growth using this growth apparatus is performed as follows. That is, first, the metal gallium (8) in the container (9) is heated to 800 to 35
High frequency heating is performed to about 0°C, and in this state, H2 and AsCj! are supplied from the air supply port (2). A reaction gas mixed with 3 is supplied into the reaction tube (1). Then, ^sc1. in the reaction gas.
3 and metal gallium (8) react (12Ga±41scl
3-=12GaCf±As+) GaCl and As4, which are raw materials for epitaxial growth, are produced. On the other hand, the Ga on the susceptor (6) is heated by the second heater (IX).
The As substrate (5) is heated to about 700 to 750°C, and in this state, the above-mentioned GaCl! , ^s4, and H2 are G
It is supplied to the aAs substrate (5). This GaAs substrate (5
), AsCl3 and metallic gallium (8) in the reaction gas
GaCl2J''As4 and H2 react (4GaCl+As4 +2H2→4GaAs+4HC) because the temperature is set lower than the reaction temperature (800-850'C) with
f) GaAs is produced and grown on the GaAs substrate (5) to form an epitaxial growth layer (12).

By the way, the container (9) containing the metal gallium (8)
In consideration of high purity and heat resistance, quartz (SiOz
) products are generally used. for that,
The above metal gallium (8) and quartz react (SiOz+
2Ga→2GaO+Si) L, Si melts into metal gallium (8) as an impurity, thereby forming GaAs.
Epitaxial growth layer (12) formed on the substrate (5)
) It has become difficult to reduce the impurity concentration below about 101' to 10'3 (hereinafter this concentration level will be referred to as the bank ground [BG] level).

Therefore, in order to reduce the impurity concentration of the epitaxial growth layer (12), conventionally, a reaction gas H2 is introduced into the reaction tube (1) from the air supply port (2) as shown by the broken line arrow in FIG.
and AsC1, , oxygen 0□ is supplied. This supply of oxygen 0□ causes the reverse reaction of the reaction between the quartz in the container (9) and the metal gallium (8) (2GaOMoSi→5
i02÷2Ga) to suppress the infiltration of Si as an impurity into the metal gallium (8), thereby reducing the impurity concentration of the epitaxial growth layer (12) from the BG level to 10" am. -' can be set.

[Problem to be solved by the invention]

By the way, after epitaxial growth, unnecessary GaAs deposits (13) generated during epitaxial growth remain attached to the inner wall of the reaction tube (1) and the susceptor (6), as shown in FIG. After the GaAs substrate (5) on which the layer (12) has been formed is taken out from the reaction tube (1), unnecessary GaAs deposits (13) are removed by heating the entire reaction tube (1). Clean it.

After this baking step, a new GaAs substrate (5) is set in the reaction tube (1), and an epitaxially grown layer (1) is formed on the GaAs substrate (5) using a reaction gas.
2) Form. After this growth step, the above-described baking step and growth step are repeated as one cycle to form a growth cycle.

Conventionally, during this growth cycle, oxygen O2 was supplied only during the growth process, so as shown in FIG. However, since there is no supply of oxygen 02 during the baking process (1),
The impurity concentration level L tends to recover toward the BG level. Therefore, the impurity concentration level L changes throughout the growth cycle (C), making it difficult to maintain a desired impurity concentration constant. In addition, since the amount of Si melted into the metal gallium (8) varies depending on the oxygen flow rate during the previous growth step (a), the amount of Si melted into the metal gallium (8) differs depending on the oxygen flow rate during the previous growth step (a). The oxygen flow rate had to be finely adjusted based on the impurity concentration level L in a), making it extremely difficult to control the impurity concentration level.

The present invention has been proposed in view of the above-mentioned problems, and its purpose is to provide a method for vapor-phase epitaxial growth of compound semiconductors that can stabilize the impurity concentration level of an epitaxially grown layer by a simple means. There is a particular thing.

[Means to solve the problem]

The technical means for achieving the above object of the present invention is to place metal gallium housed in a quartz container in a reaction tube, and heat it while supplying a reaction gas into the reaction tube, thereby producing a gallium-containing compound. a growth step of setting the substrate in the reaction tube and forming an epitaxial growth layer on the substrate; , Oxygen is constantly supplied during the growth cycle, which includes a baking process for removing and cleaning unnecessary deposits generated in the reaction tube.

[Effect]

In the method of the present invention, oxygen is constantly supplied during the growth cycle in which the growth step and the baking step are one cycle, so that the amount of Si dissolved into the metal gallium in the container can be maintained constant at all times. As a result, the impurity concentration level of the epitaxially grown layer can be easily controlled and stabilized.

〔Example〕

An embodiment of the method for vapor phase epitaxial growth of compound semiconductors according to the present invention will be described with reference to FIGS. 1 to 3. The embodiment described below is applied to the GaAs vapor phase epitaxial growth apparatus shown in FIGS. 4 and 5, and the same parts are given the same reference numerals and redundant explanation will be omitted.

The vapor phase epitaxial growth of the present invention is performed using this growth apparatus as follows.

First, as shown in Fig. 1, GaAs is placed on the susceptor (6).
With the substrate (5) set, turn on the first heater (
10), the metal gallium (8) in the container (9) is
Heat to about 0 to 850℃ and supply H2 and A from the air supply port (2).
The reaction gas of sCf3 (solid arrow in the figure) and oxygen 0□ (
(dashed arrow in the figure) is supplied into the reaction tube (1). Reaction tube (
In 1), AsCl3 and metallic gallium (8
) is the reaction (12Ga+4^SCI 3-+ 12GaC
ffi +AS4) to produce GaCl and As4, which are raw materials for epitaxial growth.

-4. The GaAs substrate (5) on the susceptor (6) is heated to about 700 to 750°C by the second heater (11), and the above-mentioned GaCl, 8S4 and H2 are heated to the GaAs substrate (5).
5). In this GaAs substrate (5), GaCQ, As4 and H2 react (4GaC1+As4
+2H2→4GaAs+4HC1) GaAs is produced and grown on the GaAs substrate (5) to form an epitaxial growth layer (12). In this growth step, the metal gallium (8) and the quartz in the container (9) react (SiO, +2Ga-"2GaO+Si) and form Si
tries to dissolve into metal gallium (8) as an impurity, but the reverse reaction of the above reaction (2Ga
O+Si→SiO□+2Ga) is promoted to suppress Si from entering the metal gallium (8) as an impurity, thereby reducing the impurity concentration of the epitaxial growth layer (12) to the BG level (10'' to 10''C11).・After the above growth process, unnecessary GaAs deposits generated during epitaxial growth are deposited on the inner wall of the reaction tube (1) and the susceptor (6) as shown in Figure 2. (13) remains attached. Therefore, after completing the formation of the epitaxial growth layer (12),
After taking out the aAs substrate (5) from the reaction tube (1), unnecessary Ga is removed by heating the entire reaction tube (1).
The As deposit (13) is removed and cleaned. In this baking process, following the growth process, the air supply port (2)
Continue to supply oxygen o2 into the reaction tube (1). After the above baking process, a new GaAs substrate (5) is applied.
is set in the reaction tube (1), and the growth process is started again to form an epitaxially grown layer (12) on the GaAs substrate (5) while supplying reactive gases of H2 and AsCl3 and oxygen 02. In this way, the growth process and the baking process are considered as one cycle, and a growth cycle is constructed by repeating this cycle. In the method of the present invention, oxygen 02 is constantly supplied during this growth cycle, so that the dissolution of Si into the metal gallium (8) in the container (tough) can always be maintained constant. As shown in the figure, the impurity concentration level L of the epitaxial growth layer (12) decreases from the BG level, and becomes saturated and stabilized while the growth step (a) and baking step (b) are repeated in the growth cycle (c). This stabilization level is determined by the reaction tube (1
) is set by the flow rate of oxygen 02 supplied to the

In the above embodiments, the vapor phase epitaxial growth of GaAs has been described, but the present invention is not limited thereto, and is of course applicable to the epitaxial growth of other compound semiconductors containing gallium.

[Effect of the invention] According to the method of the present invention, the growth step and the baking step are performed in one step.
Since oxygen is constantly supplied during the growth cycle, the dissolution of Si into the metal gallium in the container can be maintained at a constant level, reducing the concentration of undesirable substances in the epitaxially grown layer. It is easy to control and stabilize the process, which greatly improves workability and yield, and provides high-quality semiconductor nil.

[Brief explanation of drawings]

1 to 3 are for explaining an embodiment of the method of the present invention, and FIG. 1 is a cross-sectional view showing a reaction tube in the growth process;
Figure 2 is a sectional view showing the reaction tube in the baking process, Figure 3
The figure is a waveform diagram showing changes in impurity concentration level during the growth cycle. Figures 4 to 6 are for explaining a conventional example of the vapor phase epitaxial growth method for compound semiconductors. Figure 4 is a cross-sectional view showing a reaction tube in the growth process, and Figure 5 is a reaction diagram in the baking process. FIG. 6 is a cross-sectional view of the tube and a waveform diagram showing changes in impurity concentration level during the growth cycle. (1) −m=reaction tube, (5) one substrate, (8
) -Metallic gallium, (9)...~container, (121-epitaxial growth layer, (a)-one growth step, (b)--baking step, (C)-growth cycle.

Claims (1)

[Claims] (1) Metallic gallium contained in a quartz container is placed in a reaction tube, and a compound containing gallium is generated by heating while supplying a reaction gas into the reaction tube, and is placed on a substrate set in the reaction tube. When growing a compound semiconductor to form an epitaxial growth layer, there is a growth process in which a substrate is set in the reaction tube and an epitaxial growth layer is formed on the substrate, and unnecessary deposits generated in the reaction tube are removed. 1. A method for vapor phase epitaxial growth of a compound semiconductor, characterized in that oxygen is constantly supplied during a growth cycle including a baking step for cleaning.