JPH0669132A - Vapor phase epitaxial growth system - Google Patents

Abstract

PURPOSE:To realize MOCVD in which material gas is decomposed efficiently on a substrate and consumption of material gas is reduced. CONSTITUTION:In a vapor phase epitaxial growth system comprising a reaction tube 1 in which a substrate 3 is placed and a plurality of gas introduction pipes 4A, 4B, 4C, 4D for feeding material gases having different decomposition temperatures, each of the plurality of gas introduction pipes 4A, 4B, 4C, 4D is provided with a temperature control means 11 for heating or cooling thus controlling the temperature of material gas in each gas introduction pipe 4A, 4B, 4C, 4D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth apparatus, especially MO
The present invention relates to a CVD (Metal Organic Chemical Vapor Deposition) apparatus.

The metal-organic vapor phase epitaxy method using an organic metal compound such as dimethyl cadmium or diisopropyl tellurium as a source gas is performed on a heterogeneous substrate such as gallium arsenide or sapphire on which mercury, cadmium, tellurium () whose constituent elements are different from those of the substrate. Epitaxial growth of compound semiconductor crystals such as Hg _1-x Cd _x Te) is possible, and it is also possible to grow and supply large-area epitaxial crystals at low cost.

Further, crystals having different characteristics can be continuously formed, which is an extremely effective method for forming a semiconductor element.

[0004]

2. Description of the Related Art In such a MOCVD apparatus, p-type Hg is used.
A conventional MOCVD apparatus for growing a _1-x Cd _x Te crystal will be described.

As shown in FIG. 3, a reaction vessel 1 made of quartz is used.
A substrate mounting table 2 made of carbon is installed in the inside, and cadmium tellurium (CdT) for epitaxial growth is mounted thereon.
A substrate 3 such as e) or gallium arsenide (GaAs) is placed.

Dimethyl cadmium supported by hydrogen gas as a carrier gas is provided on the upper portion of the reaction container 1 in the reaction container 1.
4A for introducing gas into the reaction vessel, gas introduction tube for introducing diisopropyl tellurium supported by hydrogen gas into the reaction vessel 1
4B, a gas introducing pipe 4C for introducing mercury supported by hydrogen gas into the reaction vessel 1, and a gas introducing pipe 4D for introducing tertiary butylarsine as a doping gas into the reaction vessel 1 which is carried by hydrogen gas. Each of the gas introduction pipes 4A, 4B, 4C, 4D is provided and connected before reaching the reaction vessel 1.

A heater 6 for preventing the condensation of mercury is provided around the gas introducing pipe 4C for introducing the mercury carried by the hydrogen gas into the reaction vessel 1. Then, the respective raw material gases in the respective gas introduction pipes 4A, 4B, 4C, 4D are introduced into the reaction vessel 1 in a mixed state. Then, the mixed raw material gases are heated by heating the substrate installation table 2 by the high frequency induction coil 5 to heat the substrate 3, and the raw material gas reaching the substrate 3 to be mixed is thermally decomposed to generate p-type Hg _{1- x} Cd
_x Te crystals are grown epitaxially.

However, the above-mentioned mercury is a simple metal element,
The decomposition temperature at which an organometallic gas such as dimethylcadmium or diisopropyl tellurium decomposes into a metal atom and an organic gas is different, and in particular tertiary butylarsine used as a p-type dopant has a molecular formula of C ₄ H ₉ AsH ₂ , Dimethyl cadmium with a decomposition temperature of 360 ℃
The decomposition temperature is as high as 500 ° C as compared with organic metal gas such as diisopropyl tellurium at 400 ° C, and these four kinds of gases are mixed as raw material gas, and p-type Hg _{1-x is formed} on the substrate 3 such as CdTe.
When vapor-depositing a Cd _x Te crystal, there is a problem in setting the heating temperature of the substrate 3.

In other words, when the heating temperature of the CdTe substrate 3 is increased, the decomposition rate of dimethylcadmium and diisopropyltetel, which have a low decomposition temperature, is higher than that of tertiary-butylarsine, so that the carrier concentration is low and the resistance of the p-type Hg is high.
_It tends to be _1-x Cd _x Te crystals.

On the contrary, when the heating temperature of the CdTe substrate 3 is lowered, dimethylcadmium, which has a low decomposition temperature, and diisopropyl tether are decomposed by the radiant heat of the substrate before reaching the surface of the substrate, so that the HgCdTe crystal does not grow. is there.

Therefore, conventionally, the substrate 3 is heated to a temperature at which the organometallic gas such as dimethyl cadmium or diisopropyl tellurium and mercury are most efficiently decomposed, and tertiary butyl arsine having poor decomposition efficiency is introduced into the reaction vessel 1. The amount of gas was increased to compensate for the poor decomposition efficiency.

[0012]

However, the above-mentioned tertiary butyl arsine is expensive, and the production cost of the Hg _1-x Cd _x Te crystal formed when a large amount of such an organometallic gas is used increases. There's a problem.

Isopropyl iodine used as an n-type dopant for Hg _1-x Cd _x Te crystals has a molecular formula of (CH ₃ ) CHI and has a decomposition temperature as low as 40 ° C., but dimethylcadmium,
It functions as a catalyst for promoting decomposition when diisopropyl tellurium is mixed and decomposed, but it is necessary to cool the gas introduction pipe in order to prevent decomposition of isopropyl iodine itself.

Under the above circumstances, when gases having different decomposition temperatures are mixed before being introduced into the reaction vessel, these mixed gases react with each other before being introduced into the reaction vessel and are formed. There is a problem that the electrical characteristics such as the composition of Hg _1-x Cd _x Te crystal and the resistance value become unstable.

The present invention solves the above-mentioned problems and suppresses or accelerates the reaction between organometallic gases caused by using a plurality of organometallic gases having different decomposition temperatures, thereby improving the yield. Moreover, it is an object of the present invention to provide a vapor phase growth apparatus capable of surely performing impurity doping.

[0016]

According to the vapor phase growth apparatus of the present invention, as shown in claim 1, a reaction vessel having a substrate and a source gas connected to the reaction vessel and having different decomposition temperatures are introduced. In a vapor phase growth apparatus having a plurality of gas introduction pipes, each of the plurality of gas introduction pipes is provided with heating or cooling means, and the temperature of the raw material gas in each of the gas introduction pipes can be controlled. It is characterized by

Further, as described in claim 2, the plurality of gas introducing pipes are connected to each other at a position separated from the reaction container by a predetermined gas passage, or are connected immediately before the reaction container, and the combined gas is connected. It is characterized in that the introduction pipe is further provided with a temperature control means so as to accelerate or suppress the reaction between the raw material gases joined by the combined gas introduction pipe.

Further, as described in claim 3, in the plurality of gas introduction pipes and the joint portion of the gas introduction pipes, the raw material gas is flowed in the gas introduction pipe and the joint portion of the gas introduction pipe to the raw material gas. A means for forming a gas plasma of gas or an intermediate product of the raw material gas is provided.

Further, as described in claim 4, a light irradiating means for forming the plurality of gas introducing pipes and the connecting portion with a light transmitting material and capable of irradiating the raw material gas in the gas introducing pipe and the connecting portion with light. It is characterized by being provided.

Further, as described in claim 5, the source gas flowing into the gas introduction pipe is zinc, cadmium, selenium,
Tellurium, aluminum, indium, gallium, arsenic,
It is characterized in that it is either an organometallic compound gas of antimony, a hydrogen compound gas of sulfur, chlorine, iodine or phosphorus, or a gas of elemental element of mercury.

[0021]

In the vapor phase growth apparatus of the present invention, temperature control means such as a heater is provided in each of the gas introduction pipes for introducing a plurality of raw material gases having different decomposition temperatures, and the temperature of the raw material gas in each gas introduction pipe is increased. Can be controlled separately.

Further, by connecting the above-mentioned gas introducing pipe immediately before the reaction vessel, it is possible to prevent the mixed gases from reacting with each other after the raw material gases are mixed with each other. Further, the above-mentioned gas introduction pipe is connected at a position separated from the reaction vessel by a predetermined distance, and after the raw material gases are mixed,
Allow the mixed gases to promote reaction with each other.

FIG. 1 shows a case where the gas introduction pipes 4A, 4B, 4C and 4D are connected to each other just before the reaction vessel 1. By mixing the raw material gases with each other just before the reaction vessel 1 as described above, the reaction between the organometallic gases is suppressed, and the decomposition of the organometallic gas induced as a result of the reaction is suppressed.

Further, in FIG. 2, the gas introducing pipes 4A, 4B, 4C and 4E are connected at a position separated from the reaction container 1 by a predetermined distance, and the pipes from the connected position to the inside of the reaction container 1 are connected. A heating means is provided to accelerate the reaction.

By doing so, the reaction between the organometallic gases is promoted, and the production of intermediate products is induced. The obtained intermediate product is kept at a predetermined temperature by the temperature controller 11 so that the intermediate product is efficiently decomposed.

The gas introduction pipe 4 shown in FIGS. 1 and 2 as described above.
By appropriately combining the arrangement states of A, 4B, 4C, 4D, and 4E with respect to the reaction container 1, it is possible to obtain a condition in which the source gas is most efficiently decomposed on the substrate.

[0027]

Embodiments of the present invention will be described in detail below with reference to the drawings. The case of vapor phase growth of p-type Hg _1-x Cd _x Te crystal is described.

Dimethyl cadmium carried by hydrogen gas from the gas introducing pipe 4A of FIG. 1, diisopropyl tellurium carried by hydrogen gas by the gas introducing pipe 4B, and metallic mercury carried by hydrogen gas by the gas introducing pipe 4C. The supplied tertiary butylarsine, which is a p-type impurity gas supported by hydrogen gas, is supplied into the reaction vessel 1 through the gas introduction pipe 4D.

The above-mentioned metal mercury gas introduction tube 4C is 300
The temperature of the dimethyl cadmium gas introducing pipe 4A and the diisopropyl tellurium gas introducing pipe 4B are heated to 400 ° C., and the temperature of the tertiary butyl arsine gas introducing pipe 4D is heated to 360 ° C. by the temperature controller 11.

The gas introduction pipes 4A, 4 for the respective gases thus formed
B, 4C, 4D are bonded at a position separated from the reaction vessel 1 by a gas passage 12 at a predetermined distance, and among the above-mentioned source gases, dimethylcadmium gas and tertiary butylarsine gas react with each other, An intermediate product is formed by the reaction of both gases.

In order to further promote the decomposition of such an intermediate product, a temperature controller 11 composed of a heater is provided between the reaction vessel 1 and the joint portion 13 of the gas introduction pipes 4A, 4B, 4C and 4D. Then, by heating, the source gases are supplied to the substrate 3 in the reaction container 1 in a state of being mixed with each other and reacted, so that the doping efficiency of impurities is also improved.

As another embodiment, the above-mentioned raw material gas is introduced through the gas introduction pipes 4A, 4B and 4C described above, and the gas introduction pipes are introduced.
N-type Hg _1-x Cd _x Te by introducing isopropyl iodine from 4E
When forming a crystal, the temperature of the gas introduction pipe 4E is kept at a low temperature of 40 ° C. by the temperature controller 11 so as not to promote the reaction, and the gas introduction pipes 4A, 4B, 4C and 4E are combined. Part 13
Although not shown, the reaction container 1 and the joint 13 are heated to prevent condensation of the mixed gases, while keeping the distance between the reaction container 1 and the reaction container 1 short.

As another embodiment, a microwave is applied to the coupling portion 13 of the gas introduction pipes 4A, 4B, 4C, 4D, 4E and the gas introduction pipe described above by using a microwave oscillator to irradiate the gas introduction pipes. A gas plasma is formed in the raw material gas in the joint portion of the gas introduction pipe to form an intermediate product of these mixed gases, and the reaction of the mixed gas introduced into the reaction vessel 1 is promoted.

Alternatively, as another embodiment, the gas introducing pipe
4A, 4B, 4C, 4D, 4E and the coupling portion 13 of the gas introduction pipe with a predetermined interval, electrodes are installed, high voltage is applied between the electrodes gas introduction pipe 4A, 4B, 4C, A method of applying an electric field to the raw material gas in 4D and 4E and the joint portion 13 to decompose the raw material gas to form a decomposition product to accelerate the decomposition reaction may be adopted.

In another embodiment, the gas introducing pipes 4A, 4B, 4C, 4D, 4E and the connecting portion 13 of the gas introducing pipes are formed of a transparent light transmitting material such as quartz glass, and the gas introducing pipes are formed. A method of irradiating the joint between the pipe and the gas introduction pipe with ultraviolet rays to decompose the raw material gas by a photochemical reaction to form an intermediate product of the raw material gas to accelerate the decomposition reaction may be adopted.

The source gases usable in the apparatus of the present invention are dimethylcadmium, diisopropyl tellurium, mercury, tert-butylarsine, isopropyl iodine, zinc, cadmium, mercury, sulfur and selenium as described in this embodiment. , Tellurium, aluminum, indium, gallium,
Either a simple substance gas of each element of chlorine, iodine, phosphorus, arsenic, or antimony, an organometallic compound gas of each of the above elements, or a hydrogen compound gas of each of the above elements may be used.

In this embodiment, the method of introducing the source gas from the upper part of the reaction vessel is adopted. However, the substrate is installed horizontally by using a horizontal reaction vessel, and the source gas is introduced into the substrate from the horizontal direction. The present invention can also be applied to a horizontal vapor phase growth apparatus that performs the above.

[0038]

As described above, according to the vapor phase growth apparatus of the present invention, it becomes possible to most efficiently decompose the raw material gases having different decomposition temperatures in the reaction vessel, and the expensive raw material gas is used. The effect of reducing the consumption amount of the compound semiconductor and the manufacturing cost of the compound semiconductor crystal is reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of a vapor phase growth apparatus of the present invention.

FIG. 2 is an explanatory view of a second embodiment of the vapor phase growth apparatus of the present invention.

FIG. 3 is an explanatory diagram of a conventional vapor phase growth apparatus.

[Explanation of symbols]

 1 Reaction vessel 2 Substrate installation table 3 Substrate 4A, 4B, 4C, 4D, 4E Gas introduction tube 5 High frequency induction coil 11 Temperature controller 12 Gas passage

Claims (5)

[Claims] 1. A reaction vessel (1) having a substrate (3) installed, and a plurality of gas introduction pipes (4A, 4B, 4C) connected to the reaction vessel (1) for introducing raw material gases having different decomposition temperatures. , 4D, 4E) in a vapor phase growth apparatus, the plurality of gas introduction pipes (4A, 4B, 4C, 4D, 4E) each heated,
Alternatively, a vapor phase growth characterized in that the temperature control means (11) capable of cooling is provided, and the temperature of the raw material gas in each of the gas introduction pipes (4A, 4B, 4C, 4D, 4E) can be controlled apparatus. 2. A plurality of gas introduction pipes (4A, 4) according to claim 1.
B, 4C, 4D, 4E) the joint (13) is located at a predetermined distance from the reaction vessel (1), or the joint (13) is close to the reaction vessel (1) And the joint (1
A temperature control means (11) is further provided in the gas introduction pipe from 3) to the reaction vessel (1) so as to promote or suppress the reaction between the raw material gases joined at the coupling part (13). A vapor phase growth apparatus characterized by: 3. A gas plasma of the raw material gas as a raw material gas flowing through the plurality of gas introduction pipes (4A, 4B, 4C, 4D, 4E) and the joint portion (13) according to claim 1 or 2. Alternatively, the vapor phase growth apparatus is provided with a means capable of forming a raw material gas intermediate product. 4. The plurality of gas introducing pipes (4A, 4B, 4C, 4D, 4E) and the connecting portion (13) according to claim 1 or 2 are formed of a light transmitting material, and the gas introducing pipes (4A , 4B, 4C, 4D, 4E) and light irradiation means for irradiating the raw material gas of the joint portion (13) with light. 5. The raw material gas flowing into the gas introduction pipe (4A, 4B, 4C, 4D, 4E) according to any one of claims 1 to 4, is zinc, cadmium, selenium, tellurium, aluminum, indium,
Organometallic compound gas of gallium, arsenic, antimony,
A vapor phase growth apparatus characterized in that it is either a hydrogen compound gas of sulfur, chlorine, iodine or phosphorus or a gas of a single element of mercury.