JPH0573322B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an organometallic vapor phase growth apparatus for compound semiconductors. Relating to an organometallic vapor phase growth apparatus that improves the reproducibility of the characteristics of the grown layer and the steepness of composition changes and impurity concentration changes by having a structure in which there is no stagnation part of source gas in the valve after switching. .

[Conventional technology]

BACKGROUND ART Conventionally, a vapor phase growth apparatus (hereinafter referred to as an organometallic vapor phase growth apparatus) using organic metal compounds and hydrogen compounds of compound semiconductors as raw materials is well known.

Figure 3 is a diagram showing such a conventional metal-organic vapor phase epitaxy apparatus, and here the most common hydrogen
The conventional technology will be explained using an organic metal vapor phase growth apparatus for GaAs and AlGaAs using H ₂ as a carrier gas as an example. In the figure, 1 is a reactor, 2 is a high-frequency induction heating coil, and 3 is a high-frequency induction heating coil.
is a susceptor, 4 is a substrate, 5a is a constant temperature bath for saturated vaporization of trimethyl gallium (TMG), 5b
6 is a constant temperature bath for saturated vaporization of trimethylaluminum (hereinafter referred to as TMA), and 6 is arsine (hereinafter referred to as AsH ₃ ).
7a, 7b, 7c, 7d are mass flow meters,
8, 9, 10, 11 are valves, 12 is a line for TMG steam, 13 is a line for TMA steam, 14
is the line for AsH ₃ diluted with hydrogen (H ₂ ), 1
5 is a vent line, and 16a and 16b are retention areas.

In the figure, when epitaxially growing GaAs, valves 8 and 10 are first closed, valves 9 and 11 are left open, and the inside of container 6 is grown.
A predetermined flow rate of AsH ₃ obtained through the mass flow meter 7d is similarly diluted with H ₂ which is reduced in weight by the mass flow meter 7c, and is flowed into the reaction path 1 through the line 14, where it is heated by high frequency induction to a predetermined growth temperature. The temperature is raised by coil 2. After that, close the valve 9,
By opening the valve 8, TMG vapor, which is a raw material for Ga, flows into the reactor 1 through the line 12, and GaAs is epitaxially grown on the substrate 4 placed on the susceptor 3 by a thermal decomposition reaction.
Furthermore, when epitaxially growing AlGaAs continuously, valve 11 is closed and valve 1 is closed.
By opening 0, TMA steam flows into line 13.
It flows into the reactor 1 through the reactor 1, and epitaxial growth is performed by a thermal decomposition reaction.

Furthermore, when doping with P-type and n-type impurities, doping raw materials of organometallic compounds or hydrogen compounds have been introduced into the reactor in a similar manner.

[Problems to be solved by the invention]

However, in this conventional metal-organic vapor phase epitaxy apparatus, there is a finite region where a high concentration of raw material gas remains in the parts indicated by thick lines 16a and 16b in FIG. There were problems in that it was difficult to obtain a steep change in properties, composition change, and impurity concentration change. Furthermore, it is possible to reduce the volume of the raw material gas retention parts 16a and 16b by using a group of three-way valves for switching the raw material gas, but the pressure inside the reactor and the total volume decrease when the valves are switched. Changes occur in the gas flow rate, and the above problem has not been fundamentally solved.

The present invention is intended to solve the above problems,
By creating a structure in which there is no stagnation part of the source gas inside the valve when switching the source gas, it is possible to epitaxially grow a high-quality compound semiconductor layer with good reproducibility, and to form a steep compositional change and impurity distribution. The purpose of the present invention is to provide an organometallic vapor phase growth apparatus that achieves the following.

[Means for solving problems]

For this purpose, the organometallic vapor phase growth apparatus of the present invention has the following features:
an organometallic compound supply means for supplying an organometallic compound that has been diluted and whose flow rate has been adjusted; a hydrogen compound supply means that supplies a hydrogen compound that has been diluted and whose flow rate has been adjusted;
a four-way valve having two inlet ports and two outlet ports connected to the organometallic compound supplying means and the purge gas supplying means through piping, respectively; The two inlet ports of the four-way valve include a reactor connected through piping to one outlet port of the valve and a hydrogen compound supply means, and a discharge piping connected to the other outlet port of the four-way valve. , the same flow rate of the organometallic compound and the purge gas are supplied respectively through the adjusted flow rate, and by switching the four-way valve, the same flow rate of the organometallic compound or the purge gas is supplied to the reactor from the exit port of the one, and the same flow rate of the organometallic compound or the purge gas is supplied to the reactor from the exit port of the one and the other. It is characterized in that it flows out from the outlet port to the discharge piping.

[Effect]

The organometallic vapor phase growth apparatus of the present invention eliminates the presence of a stagnation part of the raw material gas in the switching valve when switching the raw material gas, and maintains the pressure in the reactor and the total gas flow constant at all times. , a high-quality compound semiconductor layer is epitaxially grown with good reproducibility, and furthermore, a steep compositional change and impurity distribution are formed.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing an embodiment of the metal-organic vapor phase growth apparatus according to the present invention, and FIGS. In the figure, the same numbers as those in FIG. 3 indicate the same contents.

In FIG. 1, 1 to 1 shown in the device of FIG.
6, 7c, 7d, 14, and 15 will not be described in detail here, but the newly added means will be explained.

In the figure, 7e, 7f, 7g, 7h, 7i, 7j are mass flow meters, 17 is a line that supplies TMG gas diluted with hydrogen, and 18 is a line that supplies TMG gas diluted with hydrogen.
A line for supplying TMA gas, 19 is a line for supplying purge hydrogen (H ₂ ) carrier gas, 20
2 is a line for supplying purge hydrogen (H ₂ ) carrier gas, and 21a and 21b are switching valves.

Before the start of epitaxial growth, TMG and TMA sealed in a stainless steel container are passed through H ₂ controlled by mass flow meters 7f and 7i in constant temperature layers 5a and 5b maintained at a predetermined temperature, respectively. As a result, TMG+H ₂ and TMA+H ₂ are extracted as saturated vapors. Immediately after extraction, ₅₀₀ c.c./
Raw material gas TMG + H ₂ and
TMA+H ₂ is line 17 and line 19 respectively
The air flows out into the vent line 15 via the switching valves 21a and 21b.

On the other hand, by mass flowmeters 7g and 7j, respectively.
Purging H ₂ carrier gas whose flow rate is controlled at 500 c.c./min flows into the reactor 1 via lines 18 and 20 and switching valves 21a and 21b. In addition, AsH ₃ in the container 6, which was similarly calculated by the mass flow meter 7d, was diluted with H ₂ gas measured by the mass flow meter 7c, and 300 c.c./
AsH ₃ +H ₂ gas with flow rate adjusted to min is line 1
4 into the reactor 1.

Epitaxial growth is started after the susceptor 3 is heated by the high-frequency induction heating coil and the substrate 4 reaches a predetermined growth temperature.

When performing epitaxial growth of GaAs,
The switching valve 21a allows the TMG+H ₂ gas that was prevented from flowing into the vent line 15 to flow into the reactor 1, and at the same time, the purge gas that was being flowed into the reactor 1
By venting the H ₂ carrier gas to vent line 15, epitaxial growth of GaAs is accomplished. Furthermore, when performing epitaxial growth of AlGaAs, the TMA+H ₂ that had been flowing out to the vent line 15 is caused to flow into the reactor 1 by the switching valve 21b, and at the same time, the purge H ₂ carrier gas that was flowing into the reactor 1 is By flowing out to the vent line 15, epitaxial growth of AlGaAs is achieved. The raw material gases thus supplied to the reactor 1 are thermally decomposed on or near the substrate 4 heated by the high-frequency induction heating coil 2, and an epitaxial layer is deposited. Similarly, in doping with impurities, diluted raw material gas flows into the reactor 1 and is taken into the epitaxial layer.

Here, the gas switching operation of the device of the present invention is performed in a second manner.
This will be explained in detail with reference to Figures A and B.

FIG. 2A shows the operation of the switching valves 21a and 21b when the raw material gas 22 flows into the reactor 1 and epitaxial growth is performed.The arrows indicate the flow direction of the gas, and the diagonal lines indicate the The flow path of the raw material gas 22 is shown. At this time, raw material gas 2
H 2 carrier gas 23 having the same flow rate as H ₂ carrier gas 2 is discharged to vent line 15 .

FIG. 2B shows the case where the gas flow path is changed by the switching valves 21a and 21b, and the raw material gas 22 is flowed out to the vent line 15 at the same time as the flow path changes from the reaction path 1 to the vent line 15.
H ₂ carrier gas 23 is flowed into the reactor 1 and the raw material gas 22 remaining in the switching valve is completely purged.

In this way, when switching the raw material gas, there is no stagnant portion of the raw material gas in the switching valves 21a and 21b, and it is possible to switch the raw material gas without changing the pressure in the reactor 1 or the total gas flow rate.

When undoped GaAs was grown using the organometallic vapor phase growth apparatus shown in the above example, an n-type epitaxial layer with a residual carrier concentration of 10 ¹⁴ to 10 ¹⁵ cm ^-3 was obtained with good reproducibility, and Even in an undoped GaAs epitaxial layer immediately after P-type impurity doping with dimethyl zinc (DMZ), it shows n-type with a residual carrier concentration of 10 ¹⁴ to 10 ¹⁵ cm ^-3 and a high-quality epitaxial layer can be obtained with good reproducibility. This was confirmed.

In addition, as a result of epitaxially growing a heterostructure of GaAs and Al _0.5 Ga _0.5 As and measuring the steepness of the structural change, the transition region of both was found to be 1 to 2 atomic layers (<5
Å), and it was confirmed that a very steep interface was formed.

Although the above embodiments have been explained using metal organic vapor phase growth equipment for GaAs and AlGaAs as an example, the present invention
It goes without saying that the present invention is not limited to GaAs or AlGaAs, and is not limited to the shape or pressure of the reactor at all, and can be applied to all types of compound semiconductor organometallic vapor phase epitaxy equipment.

〔Effect of the invention〕

As described above, according to the present invention, in an organometallic vapor phase growth apparatus, when switching the source gas, the source gas and the residual portion in the valve are removed, and the source gas and the remaining portion are removed so that the pressure in the reactor and the total gas flow rate do not change. By switching the gas, it becomes possible to epitaxially grow a high-quality compound semiconductor layer with good reproducibility and to form a more abrupt change in composition and impurity concentration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a metal-organic vapor phase growth apparatus according to the present invention, FIGS. It is a figure showing a growth apparatus. 1...Reaction furnace, 2...High frequency induction heating coil,
3...Susceptor, 4...Substrate, 5a, 5b...Thermostatic chamber, 6...Arsine container, 7a-7j...Mass flow meter, 8-11...Valve, 12, 13, 1
4, 17, 18... Raw material gas supply line, 15...
...Vent line, 16a, 16b...Gas retention area, 19,20...Carrier gas line, 21
a, 21b...Switching valve.

Claims (1)

[Claims] 1. An organometallic compound supply means for supplying a diluted organometallic compound whose flow rate has been adjusted; a hydrogen compound supply means that supplies a diluted hydrogen compound whose flow rate has been adjusted; and a purge gas supply that supplies a purge gas whose flow rate has been adjusted. a four-way valve having two inlet ports and two outlet ports connected to the organometallic compound supply means and the purge gas supply means through piping, respectively; and one outlet port of the four-way valve and piping to the hydrogen compound supply means. and a discharge pipe connected to the other outlet port of the four-way valve. Gas is supplied to each reactor, and by switching the four-way valve, the same flow rate of the organometallic compound or purge gas flows out from one of the exit ports to the reactor and from the other exit port to the discharge piping. An organometallic vapor phase growth apparatus featuring: