JPS6061000A - Formation of gallium arsenide layer - Google Patents

Abstract

PURPOSE:To form efficiently GaAs layers having high uniformity under mild reaction conditions in a high yield using inexpensive starting materials by bringing vaporized GaCl2 and vaporized As (compound) into contact with substrates kept in a high energy state. CONSTITUTION:Ge wafers 9 are placed on a jig 8 as substrates, and GaCl2 is charged into an evaporator 18. A reaction tube 4 is evacuated with a vacuum pump 16 while introducing gaseous Ar 19. Gaseous Ar 2 contg. AsH3 is introduced, the introduction of gaseous Ar 19 is reduced, and the substrates are heated with an oven 3. At the same time, the GaCl2 in the evaporator 18 is heated with a heater 10. The substrates 9 are kept at 500 deg.C, and when the GaCl2 is heated to 190 deg.C, gaseous Ar is introduced from a pipe 1 for 0.5hr. After stopping the introduction, the heating with the oven 3 and the evacuation with the pump 16 are stopped, and the tube 4 is filled with a gaseous mixture of Ar with AsH3 under ordinary pressure. The tube 4 is then allowed to cool, and GaAs layers deposited on the substrates 9 are taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for depositing a layer of gallium arsenide on a solid surface from a gas phase, and particularly to a method for depositing a layer of gallium arsenide on a substrate surface from a gas phase in which vaporized gallium chloride (U) and vaporized arsenic or an arsenic compound coexist. The present invention relates to a method for depositing a gallium arsenide semiconductor layer.

Conventionally, as a method for depositing a gallium arsenide layer on the surface of a substrate, it has been known to bring vaporized gallium (III) chloride and vaporized arsenic compound into contact with the surface of the substrate heated in a reducing atmosphere containing hydrogen. ing. However, since this conventional method requires a chemical process to reduce gallium (III) chloride, the temperature of the substrate must be raised to approximately 700°C or higher, and even then, the reduction efficiency is low.
In order to obtain a gallium arsenide layer of the desired thickness, the operating efficiency of the apparatus was also low, which was unsatisfactory.

In addition, in the method of thermally decomposing a mixed gas of metal compounds as described above, a method has been proposed (Japanese Patent Publication No. 51-13554) in which a substance containing two types of metals in one molecule is used as a raw material. Although this method is effective in improving the stoichiometric ratio of semiconductor crystals, it was not intended to improve the drawbacks of the conventional method as described above.

Furthermore, methods using organic compounds such as trimethyl gallium have been proposed, but although these improved methods are highly efficient in forming gallium arsenide layers at lower temperatures, the synthesis and purification of the raw materials are not necessarily easy. Therefore, there was a problem in that the cost was inevitably high.

As a result of conducting various studies on methods for vapor phase growth of gallium arsenide layers, the present inventor found that gallium (II) chloride is easily decomposed by energy such as heat to produce gallium and gallium chloride (I[[). The present invention was achieved as a result of paying attention to this phenomenon and proceeding with further research using this as a hint.

According to the present invention, vaporized gallium chloride (■) is
In this method, a gallium arsenide layer is formed by mixing vaporized arsenic or an arsenic compound in a carrier gas and bringing the mixture into contact with a substrate in a high energy state.

In the present invention, gallium (II) chloride, which can be easily purified to a high purity and is a relatively inexpensive raw material, is used, and under mild reaction conditions that are easy to control, high efficiency and high performance can be achieved. Since a gallium arsenide layer with high yield and high uniformity can be formed on a substrate, it is much more economical than conventional methods to produce products with uniform performance when used in the manufacture of semiconductor devices. This opened the door for me to be able to obtain good results.

The formation of a gallium arsenide layer according to the conventional technology utilizes the reaction according to the following equation (1) as an elementary reaction 2 Ga Cl 3 + 3 H2 → 2 Ga +
6 In order to produce HCII-(1), three types of raw materials are required: gallium chloride (Ill), hydrogen, and an arsenic source such as arsenic or an arsenic compound, and the reaction will not proceed at all unless the hydrogen partial pressure is increased. Otherwise, if the hydrogen partial pressure is too high, the gas phase reaction becomes the main reaction, resulting in a problem that the uniformity of the gallium arsenide layer deteriorates.

On the other hand, in the present invention, 3GaCI according to the formula (2)
Since the 12-Ga+2GaCA3-(2) reaction is used as an elementary reaction, two types of raw materials, gallium chloride (n) and an arsenic source, are sufficient, and the above-mentioned problems do not occur.

Also, while the reaction (1) requires 700°C,
The reaction (2) proceeds even at 2°OoC, and proceeds very rapidly and quantitatively at 500°C or higher. Since an arsenic source coexists, a layer of gallium arsenide is immediately formed at the same time as single gallium is precipitated at temperatures above 400°C.

3GaCj22 +As-4GaAs+2GaCff3
...(3) The arsenic raw material in the present invention may be simple arsenic,
It may also be an arsenic compound such as arsine (ASH3). In addition, when the arsenic compound is arsenic chloride (AsCβ3), the following reaction occurs with the precipitated gallium and arsenic is reduced and produced, so the yield of gallium arsenide decreases. There is no particular problem in forming the gallium arsenide layer.

AsCj23+Ga-As4-G a C7!3- (
4) In this way, when a halide such as arsenic chloride is used as the arsenic compound, the reduction of arsenic can be promoted by containing hydrogen in the carrier gas, so a decrease in the yield of gallium arsenide can be prevented. It is possible to prevent this. However, in the present invention, the presence of hydrogen has no essential significance not only for the reduction of gallium (III) chloride but also for the isolation and precipitation of gallium from gallium (II) chloride, but under the higher temperature reaction conditions. When selecting , reduction of gallium (III) chloride can occur, so even higher yields can be expected due to the advantages of the prior art.

As carrier gas, inert gases such as argon,
Helium or the like can be used, and hydrogen or the like can also be contained therein as a gas for keeping the reaction atmosphere reducing, as described above.

The substrate for forming the gallium arsenide layer needs to be in a high energy state, and this energy may be anything that can cause the reaction to proceed, such as heat, light, or electron beams. It is most preferable that this energy be concentrated and applied only to the substrate surface, but in consideration of economic efficiency and other considerations, it is convenient to maintain the substrate surface at a high temperature by infrared rays or thermal conduction. In this case, the temperature of the substrate is preferably 400°C or higher, and 450°C or higher.
'C or higher is more preferable.

The substrate for forming the gallium arsenide layer may be any substrate as long as it can be used as a semiconductor substrate, but in order to obtain a single crystal layer of gallium arsenide, for example, single crystal gallium arsenide, single crystal germanium, sapphire, etc. It is preferable to use a single crystal substrate having a frame constant equal to or close to that of gallium arsenide. A gallium arsenide layer formed on such a single crystal substrate becomes a single crystal having the same crystal axis as that of the substrate, and is particularly suitable for manufacturing semiconductor devices.

Hereinafter, the present invention will be described in detail based on drawings and examples.

The drawing is a cross-sectional configuration diagram of an example of an apparatus according to the present invention. Reference numeral 4 denotes a quartz glass reaction tube with a diameter of 30 and a fin length of 6001, and one end 12 has an inlet tube opening formed by fusion-connecting tubes 14 and 15 for introducing raw material gas and a tube 19 for introducing inert gas. The other side is fused and sealed, and the open type on the opposite side is connected to a vacuum pump 16. 6 is a pressure gauge. Reference numeral 9 denotes a base body placed sequentially from a position approximately 50t11 from the raw material introduction end in the reaction tube, 8 a jig made of quartz that supports the base body, and 5 a temperature measurement end. 3. A heating length 300 mya furnace for heating the substrate. 1
8 is a quartz evaporator for storing and evaporating gallium chloride (n), which is connected to the reaction tube through an introduction tube 15;
) is connected to an argon gas supply system that is introduced to promote vaporization. 17 is gallium chloride (■) placed in 18, 10 is evaporator 18 and introduction pipe 1
11 is a heater for heating 5 to a constant temperature, and 11 is a heater for heating 5 to a constant temperature.
This is a thermometer for measuring the temperature of the heater 10. Reference numeral 2 denotes an inlet tube for arsine diluted with alcone, one end of which is connected to the reaction tube 4 and the other end connected to an arsine and argon mixed gas supply system. Reference numeral 19 denotes an inert gas supply pipe, which can supply inert gas into the reaction tube as required.

Examples of the present invention using the above-described apparatus will be described below.

As an example gas, six germanium wafers were placed on the jig 8, and 50 g of agglomerated gallium (II) was placed on the evaporator 18.
I put it inside.

First, from 19, argon gas is converted to 15 per minute at room temperature and normal pressure.
0m7! The reactor was introduced at a rate of 100 mHg while being evacuated using the vacuum pump 16, and the internal pressure of the reaction tube was maintained at 10' mHg. After 0.5 hours, argon gas containing 5% by volume of arsine was introduced from 2 at a rate of 120 mβ per minute at room temperature and normal pressure, and then argon gas was introduced from 19 at a rate of 30 m1 per minute at room temperature and normal pressure. The substrate was heated in the furnace 3. At the same time, the heater 10 heated gallium chloride (n) in the evaporator 18 .

After measuring the temperature of the substrate with the temperature measuring end 5 and keeping it at 500"C, when the temperature of gallium (II) chloride reaches 190"C as measured with the thermometer 11, Introduction of argon gas was started at a rate of 30 mβ per minute (converted to room temperature and normal pressure), and the introduction of argon gas from 19 was stopped.The temperature of the heater 10 was maintained at 190°C, and the introduction of argon gas from 1 was stopped. After continuing for 0.5 hours, it was stopped, and then the heating by the furnace 3 and the exhaust by the vacuum pump were stopped.
The reaction tube was left to cool while being filled with a mixed substrate of argon and arsine under tight pressure.

After cooling, the inside of the reaction tube was alternately introduced with argon from 19 and evacuated using vacuum pump 16 to create an argon atmosphere, and then the sample was taken out and examined.

The surface of the sample was a shiny mirror surface, and the formation of gallium arsenide was confirmed by X-ray diffraction. Furthermore, it was confirmed by audio spectroscopy that the molar ratio of arsenic to gallium on the surface was 1:1.

Furthermore, the average thickness of the produced gallium arsenide film is approximately 0.9
It was a micron.

[Brief explanation of drawings]

The figure is a cross-sectional configuration diagram of an example of an apparatus for carrying out the present invention. 1... Argon gas introduction tube, 2... Arsine mixed argon gas introduction tube, 3... Heating furnace, 4... Reaction tube,
5...Temperature measurement end, 6...Pressure gauge, 8...Jig,
9... Base body, 10... Heater, 11... Thermometer,
16...Vacuum pump, 17...Gallium chloride (If
), 18...evaporator, 19... argon gas introduction pipe.

Claims (1)

[Scope of Claims] 1. A method for forming a gallium arsenide layer characterized by bringing vaporized gallium chloride (or chloride) into contact with a substrate in a high energy state together with vaporized arsenic or an arsenic compound. 2. When the arsenic compound is arsine 3. The method according to claim 1 or 2, wherein the high energy state is achieved by heating.