JPH06204145A - Organic metal vapor growth equipment of compound semiconductor - Google Patents

Abstract

PURPOSE:To obtain uniformly mixed gas of a plurality of material, gases, and enable forming a steep interface at the time of changeover to mixed crystal of different composition. CONSTITUTION:In an organic metal vapor growth equipment of compound semiconductor which forms thin film crystal on a substrate W, a plurality of branch lines 11, 12 are connected with a feeding line 2 linked with a reaction tube 1, and valves 3, 4 and pressure reducing valves 5, 6 are interposed in the branch lines. One or more organic metal compound sources 13, 14, 18, 19 are connected with the respective branch lines. Thereby gases different in composition are instantaneously supplied to the reaction tube by changing over the branch lines, and a sharp interface is formed. The material gas is subjected to adiabatic expansion by the pressure reducing valves, and uniformly mixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-organic vapor phase epitaxy apparatus for forming, for example, a III-V group compound semiconductor thin film.

[0002]

2. Description of the Related Art Generally, as one of the methods for producing a thin film crystal of a compound semiconductor, a metal methyl compound, an ethyl compound or the like is introduced onto a substrate heated to a high temperature to cause a predetermined chemical reaction. A metalorganic vapor phase epitaxy method for forming a thin film crystal is known. FIG. 2 shows a schematic configuration diagram of an apparatus for performing the above-mentioned growth method.

Bubblers 7 and 8 are connected to a supply line 2 connected to a reaction tube 1 via switching valves 3 and 4 and pressure reducing valves 5 and 6, respectively. One bubbler 7 contains, for example, trimethylaluminum (TMA), the other bubbler 8 contains, for example, drimethylgallium (TMG), and hydrogen gas is introduced as a carrier. Further, an arsine cylinder 1 is provided as a source of arsine in the supply line 2 via a switching valve 9, for example.
0 is connected.

Arsine, which is a hydride containing a group V element, such as As (arsenic), is supplied from the arsine cylinder 10 to the reaction tube 1, and hydrogen gas is generally used as a diluent gas. Organometallic materials TMA and TMG containing a group III element, such as Al and Ga, are supplied to the reaction tube 1 by transporting vapor pressure components at appropriate temperatures from the bubblers 7 and 8 using hydrogen gas as a carrier.
The supplied gases are switched to the reaction tube 1 or the vent side by the switching valves 3, 4, and 9, respectively, and the gas supplied to the reaction tube 1 is thermally decomposed by high-frequency induction heating or the like, and thin film crystals are formed on the substrate W. Will be formed.

When a mixed crystal is required when creating a device,
A predetermined mixed crystal is obtained by simultaneously supplying two or more kinds of organometallic compounds to the reaction tube side. For example, AlGa
When an As (aluminum gallium arsenide) / GaAs thin film crystal is formed, an organometallic compound containing Ga such as TMG and a gas containing As such as arsine are supplied to the reaction tube 1.
In addition to growing GaAs, an organometallic compound containing Al such as TMA is also supplied to grow AlGaAs.

[0006]

By the way, for example, Al
xGaAs (x = 0.3) / AlxGaAs (x = 0.
45), etc., when it is desired to stack AlGaAs crystals having different Al compositions, or when growth layers of different types are stacked, the growth rate is kept constant, or the total supply amount of group III elements and the total amount of group V elements are When it is desired to keep the supply ratio (V / III ratio) constant, it is necessary to change the supply amount of each organometallic compound. In this case, the flow rate of the carrier gas supplied to the group III material is switched and controlled, but this flow rate is generally a relatively small flow rate of several cc to several tens of cc, so the flow rate is stabilized. However, there is a problem in that the change in the crystal composition before and after the switching is not steep but gradual.

Further, the distance from the switching valve to the reaction tube is preferably short because a long time during which the III-V group compound is joined causes adverse effects such as decomposition. In that case, when forming a mixed crystal, the respective materials are supplied without being sufficiently mixed, and as a result, the in-plane uniformity of the crystal composition in the substrate is impaired and the group III element is rich. Part or V
There is a problem that a portion rich in group element is generated. The present invention focuses on the above problems and was devised to effectively solve them. The purpose is to produce a uniform mixed gas of a plurality of raw material gases, and to form a mixed crystal having different compositions. An object of the present invention is to provide a metal-organic vapor phase epitaxy apparatus capable of forming a steep interface even when switching between.

[0008]

In order to solve the above problems, the present invention provides an organometallic compound containing a predetermined group element,
In the metal-organic chemical vapor deposition apparatus for a compound semiconductor, wherein a hydride or an organic compound containing another predetermined group element is supplied to a reaction tube through a supply line to grow a thin film crystal of the compound semiconductor on a substrate. A plurality of branch lines provided with a valve and a pressure reducing valve, and one or a plurality of organometallic compound sources for obtaining thin film crystals of different compositions are connected to the respective branch lines. .

[0009]

Since the present invention is configured as described above, for example, when growing a thin film crystal having a different composition or material, the branch line is switched by operating the valve, and the raw material supplied to the supply line side is changed. It changes the composition of the gas at once. This makes it possible to form a sharp interface in the crystal. Further, since the pressure reducing valve is provided in the branch line, the plurality of raw material gases flowing from the upstream side are uniformly mixed due to expansion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a compound semiconductor metal-organic vapor phase epitaxy apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a metal-organic vapor phase epitaxy apparatus for compound semiconductors of the present invention. The same parts as those of the conventional device shown in FIG. 2 are designated by the same reference numerals. Further, this embodiment will be described by taking an example of stacking AlGaAs thin film crystals having different compositions.

As shown in the figure, this device is, for example, an RF
It has a reaction tube 1 made of, for example, quartz that heats the substrate W and the like by (high frequency), and is connected to a supply line 2 for supplying a raw material gas necessary for the reaction. The supply line 2 includes a plurality of, for example, two branch lines 11,
12 is a valve, for example, a switching valve 3,
4, and pressure reducing valves 5 and 6 are provided on the upstream sides of the respective branch lines 11 and 12, respectively. For example, a gas pressure of normal pressure 760 Torr is a reaction pressure, for example, 10
The pressure is reduced to about Torr by adiabatic expansion.

A first trimethylgallium (TMG) bubbler 13 and a first trimethylaluminum (TMA) bubbler 14 are connected to one branch line 11 as a source of an organometallic compound, and each of them is a mass flow controller 15. , 16 to supply the organic metal by bubbling with a carrier gas whose flow rate is controlled, for example, hydrogen gas. Also, this branch line 11
A dilution gas line 18 having a mass flow controller 17 interposed in the middle is connected to this, and a gas of the same kind as the carrier gas, that is, hydrogen gas is supplied for dilution.

On the other hand, the same gas source as described above is also connected to the other branch line 12. That is, the branch line 12 has a second TMG as a source of the organometallic compound.
The bubbler 18 and the second TMA bubbler 19 are connected to each other, and an organic metal is supplied by bubbling with a carrier gas whose flow rate is controlled by the mass flow controllers 20 and 21, for example, hydrogen gas. Further, a gas line 23 for dilution having a mass flow controller 22 interposed therein is connected to the branch line 12 so as to supply a gas of the same type as the carrier gas, that is, hydrogen gas for dilution. There is.

Further, in the supply line 2, an arsine cylinder 10 filled with arsine containing As of Group V other than the above-mentioned organometallic compound, for example, a switching valve 2 is provided.
4 and the mass flow controller 25,
Further, hydrogen gas for purging is flown through the valve 24,
The gas line 27 is connected. Arsine gas is set to a predetermined concentration, and the secondary side mass flow controller 25
The supply amount is controlled by controlling the flow rate with. In addition, each of the switching valves is a reaction tube 1
Alternatively, it can be switched to the vent side.

Next, the metal organic chemical vapor deposition method which is carried out by using the above apparatus will be explained. In this embodiment, AlxGaAs (x = 0.3) / Al having different composition ratios
A case of stacking xGaAs (x = 0.45) will be described. First, in the branch line 11, by controlling the respective mass flow controllers, trimethylameminium (TMA) and trimethylgallium (TM) from the first TMA bubbler 14 and the first TMG bubbler 13 are controlled.
G) is a flow rate ratio that gives one composition (x = 0.3), and in the other branch line 12, by controlling each mass flow controller, the second TMA bubbler 18 and the second TMG bubbler 18 are controlled. TMA and T from Bubbler 19
MG is a flow rate ratio that gives the other composition (x = 0.45).

In this case, the total flow rates of TMA and TMG are different in the respective branch lines 11 and 12, but the flow rates of the diluting hydrogen gas from the diluting gas lines 18 and 23 in the respective lines are set to the mass flow controller 17, respectively. The total flow rate in each of the branch lines 11 and 12 is equalized by controlling by 22. Even if the branch line communicating with the reaction tube 1 is switched, the pressure fluctuation in the reaction tube 1 hardly occurs as described later. It is done like this. In addition, each branch line 11, 12
Each of the pressure reducing valves 5 and 6 is interposed between the pressure reducing valves 5 and 6, and the bubbler side is set to normal pressure, for example, 760 Torr, and the supply line 2 side is set to reaction pressure, for example, about 10 Torr. , Adiabatic expansion, for example.

First, Al having a composition of x = 0.3
In order to grow GaAs, the switching valve 3 on the branch line 11 side is switched to the reaction tube 1 side, at the same time, the switching valve 4 on the other branch line 12 side is switched to the vent side, and further, a predetermined flow rate from the arsine cylinder 10 is set. Arsine gas is caused to flow while the flow rate is controlled by the mass flow controller 25. As a result, the mixed gas having a predetermined composition and the arsine gas are supplied from the branch line 11 into the reaction tube 1, and AlxGaAs (x = 0.
The thin film crystal of 3) is created.

After performing this creating operation for a predetermined time, next,
At the same time that the switching valve 3 on the branch line 11 side is switched to the vent side, the switching valve 4 on the other branch line 12 side is switched to the reaction tube 1 side. As a result, the mixed gas on the side of the branch line 12 flows into the reaction tube 1 instantly, and A is formed on the AlxGaAs (x = 0.3) crystal.
A thin film crystal of lxGaAs (x = 0.45) is created. The number of branch lines corresponding to the number of mixed crystals to be formed in this way is formed, and a flow rate at which a predetermined composition is obtained is made to flow in each branch line, and they are switched as necessary to the reaction tube 1 to form the mixed gas. Since, for example, the interface of different composition becomes a steep interface, it is possible to obtain a compound semiconductor of good quality.

Since the branch lines 11 and 12 are provided with the pressure reducing valves 5 and 6, respectively, the mixed gas is rapidly expanded from normal pressure, that is, 760 Torr to crystal growth pressure, for example, several tens Torr. The gas is mixed uniformly in the process. Therefore, the composition distribution of the thin film crystal grown on the substrate becomes uniform, and the composition can be prevented from being biased. Further, since the mixed gas can be made uniform as described above, the switching valve 3
Even if the distance from to the reaction tube 1 is made as short as possible, it does not affect the uniformity of the supply gas at all.

In the above embodiments, the case of growing thin film crystals of the same material but having different compositions has been described, but the present invention is not limited to this. For example, when stacking growth layers of different materials or at this time the growth rate. Can be applied to a constant value, or a case where it is desired to keep the ratio (V / III ratio) of the total supply amount of the group III element and the total supply amount of the group V element constant. Further, it can be applied not only to the III-V group compound semiconductor, but also to the case of growing a II-VI group compound semiconductor, for example.

[0021]

As described above, according to the metal-organic vapor phase epitaxy apparatus of the present invention, the following excellent operational effects can be exhibited. Since branch lines are provided by the required number of mixed crystals and these are switched to perform crystal growth, it is possible to form interfaces having abruptly different compositions. Further, when a plurality of compound sources are provided in the branch line, these can be uniformly mixed when expanded by the pressure reducing valve.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a metal-organic vapor phase epitaxy apparatus for compound semiconductors of the present invention.

FIG. 2 is a configuration diagram showing a conventional metal-organic vapor phase epitaxy apparatus.

[Explanation of symbols]

1 ... Reaction tube, 2 ... Supply line, 3, 4 ... Switching valve (valve), 5, 6 ... Pressure reducing valve, 10 ... Arsine cylinder,
11, 12 ... Branch line, 13 ... First TMG bubbler (organic metal compound source), 14 ... First TMA bubbler (organic metal compound source), 18 ... Second TMG bubbler (organic metal compound source) ), 19 ... A second bubbler for TMA (organic metal compound source), W ... Substrate.

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[Procedure amendment]

[Submission date] February 22, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (1)

[Claims] 1. An organometallic compound containing a predetermined group element,
In the metal-organic chemical vapor deposition apparatus for a compound semiconductor, wherein a hydride or an organic compound containing another predetermined group element is supplied to a reaction tube through a supply line to grow a thin film crystal of the compound semiconductor on a substrate. A compound characterized in that a plurality of branch lines with a valve and a pressure reducing valve interposed therebetween are formed, and one or more organometallic compound sources for obtaining thin film crystals of different compositions are connected to each of the branch lines. Metal-organic vapor phase epitaxy system for semiconductors.