JPH11307453A - Formation of single crystalline thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a formation method of a single crystalline thin film which restrains problems of a conventional method such as lowering of purity of a single crystalline thin film to be formed and lowering of operation rate of a device due to washing of a reaction furnace. SOLUTION: In this formation method, a single crystalline thin film is formed on a coating substrate 2 installed on a susceptor 3, while organic metallic gas is made to flow inside a reaction furnace. When a radius of the susceptor 3 is (a) and a distance from an outer circumference of the susceptor 3 to an inner wall of the reaction furnace is (b), a relation of a>=n is set and the single crystalline thin film is formed while barrier gas such as hydrogen gas and nitrogen gas of 100 cc/cm<2> or more is supplied from an upper part of the reaction furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a method for forming a single crystal thin film by growing a single crystal thin film using an Organic Chemical Vapor Deposition apparatus.

[0002]

2. Description of the Related Art FIG. 4 shows an MOCVD apparatus used in a conventional method for forming a single crystal thin film. A susceptor 3 for mounting the substrate 2 and a heater 4 for heating the substrate 2 are provided in the reactor 1, and a source gas supply port 5 for supplying a source gas is provided above the reactor 1. At the same time, an exhaust port 6 is provided at the lower part of the reactor 1.

[0003] A carrier gas such as hydrogen gas or nitrogen gas is introduced into a reaction furnace 1 at a rate of 0.1 to 10 liters per minute, and trimethylgallium and arsine are flowed into the carrier gas, and the temperature of the substrate 2 on the susceptor 3 is increased by a heater. The temperature is raised to a desired temperature in 4 and, if necessary, the susceptor 3 is rotated,
The source gas 5 is introduced into the reaction furnace 1 to form a single-crystal thin film on the substrate 2.

In order to prevent the inside of the reaction furnace 1 from being opened to the atmosphere, a loading chamber 7 is provided via a gate valve 9 if necessary. The inside of the loading chamber 7 is evacuated from the exhaust port 8 and kept at a high vacuum.

[0005]

However, in the MOCVD apparatus used in the conventional method for forming a single-crystal thin film, the distance between the outer peripheral portion of the susceptor 3 and the inner wall of the reaction furnace 1 is short. As the film formation is repeated, an unnecessary residual film 11 is deposited on the inner wall of the reactor 1.

From the residual film 11, degassing occurs during the subsequent formation of the single-crystal thin film, and is mixed into the single-crystal thin film being formed and taken in as an impurity, thereby deteriorating the characteristics of the single-crystal thin film. There was a problem.

[0007] As the growth is repeated, the thickness of the residual film 11 attached to the inner wall of the reactor 1 becomes thicker, the purity of the single crystal thin film to be grown is reduced, and many particles are removed from the residual film 11 by the single crystal thin film. Therefore, it is necessary to periodically clean the reactor 1, which greatly reduces the operation rate of the apparatus.

[0008] The present invention has been made in view of such problems of the conventional method, and it is said that the purity of a single crystal thin film to be grown is reduced, and that the operation rate of an apparatus for cleaning a reactor is reduced. It is an object of the present invention to provide a method for forming a single crystal thin film which has solved the problems of the conventional method.

[0009]

In order to achieve the above object, a method for forming a single crystal thin film according to the present invention comprises a method of forming a single crystal thin film on a substrate to be mounted on a susceptor while flowing an organic metal gas into a reaction furnace. In the method for forming a single crystal thin film for growing a crystal thin film, when a radius of the susceptor is a and a distance from the outer periphery of the susceptor to the inner wall of the reactor is b, a
≤ b and a barrier gas such as hydrogen gas or nitrogen gas is supplied from the upper part of the reactor at a rate of 100 cc / c.
The single crystal thin film is grown while supplying m ² or more.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an MOCVD apparatus used in the method for forming a single crystal thin film according to the present invention.
Is a heater, 5 is a source gas supply port, 6 is an exhaust port, 7 is a loading chamber, 8 is an exhaust port, 9 is a gate valve, 1
0 is a barrier gas supply port.

A support rod 3a is inserted from the bottom into a reaction furnace 1 made of quartz or the like, and a susceptor 3 made of carbon or the like is supported on the support rod 3a. A single crystal semiconductor substrate or a single crystal insulating substrate 2 such as single crystal sapphire is mounted. The support rod 3a is rotated by a motor (not shown). Below the susceptor 3, a resistance heater 4 is arranged. The heater 4 is not limited to the resistance heating type, but may be an induction heating type.

A source gas supply port 5 is provided in the upper part of the reaction furnace 1. An exhaust port 6 for a source gas is provided at the bottom of the reaction furnace 1. A loading chamber 7 is provided at the inlet of the reaction furnace 1 via a gate valve 9.

The susceptor 3 is heated to 400 to 800 ° C. by the heater 4 of the MOCVD apparatus, and the reaction gas is supplied from the supply port 5 while the substrate 2 is heated to the same temperature. A compound semiconductor is grown by reaction.

In the method for forming a single-crystal thin film of the present invention, the radius of the susceptor 3 is a, and the reactor 1
When the distance to the inner wall is b, the relationship a ≦ b is satisfied, and a barrier gas such as hydrogen gas or nitrogen gas is supplied from the upper portion of the reactor 1 through the barrier gas supply port 10 to 100 cc / cm.
^A semiconductor thin film is formed while supplying ^two or more.

FIG. 2 shows the relationship between b / a and D when the maximum value of the residual GaAs film adhering to the inner wall of the reactor 1 is D. FIG. 2 shows a case where the susceptor has a radius of 60 mm, hydrogen gas is introduced at a rate of 2 liters per minute as a carrier gas, and 0.8 cc of trimethylgallium per minute and 35 c
By supplying arsine gas of c, 5 μm GaAs
Is grown 50 times and the total film thickness is 250 μm GaAs.
This is the value after growing s. At this time, the flow rate F of hydrogen gas per unit area from the barrier gas supply port 10 in FIG. 1 is 100 cc / cm ² . As is clear from FIG. 2, when b / a is 0.5, the maximum value D of the residual GaAs film was about 4000 μm, but b / a was 0.7.
When the value is 5, the maximum value D of the residual GaAs film is about 2000 μm, and when b / a is 1, the maximum value D of the residual GaAs film is approximately 50 μm.

When b / a = 1, the flow rate F (cc / cm ² ) of hydrogen gas per unit area from the barrier gas supply port 10 in FIG. 1 and the maximum value D of the residual GaAs film are determined.
Is shown in FIG. As is apparent from FIG. 3, when the flow rate F of hydrogen gas per unit area is 50 cc / cm ² , the maximum value D of the residual GaAs film is 1000 μm, and the flow rate F of hydrogen gas per unit area is 75 cc / cm ^2. In this case, the maximum value D of the residual GaAs film is 400 μm, and the flow rate F of hydrogen gas per unit area is 100 cc / cm ^2.
In this case, the maximum value D of the residual GaAs film is 50 μm, and the flow rate F of hydrogen gas per unit area is 150 cc / cm.
^{In the case of 2} , the maximum value D of the residual GaAs film is 40 μm.

Therefore, b / a is set to 1 or less, and the flow rate F of hydrogen gas per unit area is set to 100c.
When it is set to c / cm ² or less, it is possible to reduce as much as possible residual gas adhering to the inner wall of the reactor 1 and depositing a residual film.

When the conventional MOCVD apparatus shown in FIG. 4 is used and a 5 μm GaAs film is grown by one film formation, the residual film 11 adhered to the inner wall in the reactor 1 shown in FIG.
Assuming that the maximum value of the film thickness of D is D, the D after the GaAs film is repeatedly grown 50 times becomes 2000 μm or more. As a result, the impurity concentration in the GaAs film increases and a large amount of particles are introduced. Therefore, it is necessary to disassemble and clean the reaction furnace 1 to remove the residual film 11 on the inner wall.

On the other hand, in the method for forming a single crystal thin film according to the present invention, the maximum thickness of the residual film 11 on the inner wall of the reactor 1 after growing 5 μm GaAs 50 times is 100 μm or less. Therefore, the frequency of disassembling and cleaning the reactor 1 is reduced by half.
0 or less, and the operation rate of the apparatus can be greatly improved. Furthermore, high-purity Ga with few particles
It has the characteristic that an As film can be grown.

It should be noted that the present invention is not limited to the growth of GaAs alone, and the same effects can be obtained even when applied to the growth of other compound semiconductors.

[0021]

As described above, according to the method for forming a single crystal thin film according to the present invention, when the radius of the susceptor is a and the distance from the outer periphery of the susceptor to the inner wall of the reactor is b,
Since a is set to satisfy a ≦ b and a barrier gas such as hydrogen gas or nitrogen gas is supplied from the upper part of the reactor at 100 cc / cm ² or more, a film of a residual film deposited on the inner wall of the reactor as the growth is repeated. Since the thickness can be greatly reduced, the frequency of disassembling and cleaning the reaction furnace of the MOCVD apparatus can be reduced, and the operation rate of the apparatus can be greatly improved.

Further, the concentration of impurities and particles taken into the single crystal thin film during its growth can be greatly reduced, and a high-purity single crystal thin film can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a MOCVD apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between a radius a of a susceptor, a distance b between an inner wall of a reactor and a susceptor, and a residual film thickness D adhered to an inner wall of the reactor.

FIG. 3 is a diagram showing a relationship between a flow rate F of hydrogen gas per unit area and a residual film thickness D.

FIG. 4 is a sectional view showing a conventional MOCVD apparatus.

[Explanation of symbols]

1 ‥‥‥ growth furnace, 2 ‥‥‥ substrate, 3 ‥‥‥ susceptor, 4
{Heater, 5} Raw material gas, 6} Exhaust port, 7
‥‥‥ Loading chamber, 8 ‥‥‥ Exhaust port, 9 ‥
{Gate valve, 10} Barrier gas, 11}
Residual film

Claims (1)

[Claims] 1. A method for forming a single crystal thin film on a substrate to be deposited on a susceptor while flowing an organic metal gas in a reactor, wherein the susceptor has a radius of a, When the distance from the reaction furnace to the inner wall of the reactor is b, the relationship is set as a ≦ b, and the single crystal is supplied while supplying a barrier gas such as hydrogen gas or nitrogen gas at 100 cc / cm ² or more from the upper part of the reactor. A method for forming a single crystal thin film, comprising growing a thin film.