JPH03236221A - Vapor growth apparatus - Google Patents

Abstract

PURPOSE:To achieve high uniformity in a growing film from the upstream side to the downstream side by providing a cooling-gas introducing mechanism for cooling a liner tube part at the upper part from a substrate which is mounted on a susceptor from the outside of the liner tube. CONSTITUTION:At the time of growing, a susceptor 6 on which a substrate 5 is mounted is heated with a high-frequency coil 7. Raw material gas is introduced into a liner tube 2 from a raw-material-gas introducing pipe 3. The gas is discharged through an exhaust port 9 with purging gas. The gas around the susceptor and the liner tube 2 are heated by the thermal conduction and heat radiation from the susceptor 6 to high temperature. Cooling gas is blown to a liner tube part 11 at the upper part from the susceptor 6 from the tip of a liner-tube-cooling-gas introducing pipe 10. Thus, the rise of the temperature at the liner tube part 11 at the upper part from the substrate is considerably suppressed. The cooling gas is blown to the outside of the liner tube, and the flow of the raw material gas in the liner tube is not disturbed.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a vapor phase growth apparatus that deposits a thin film on a substrate by vapor phase growth, and is capable of producing a film with excellent uniformity even when the decomposition temperature of the source gas is close to the temperature of the susceptor. The purpose of the present invention is to provide a vapor phase growth apparatus that can perform growth, and is a horizontal reaction tube type vapor growth apparatus that includes a reaction tube and a liner tube disposed inside the reaction tube and through which source gas flows. The structure includes a cooling gas introduction mechanism for cooling the liner tube portion above the mounted substrate from the outside of the liner tube.

[Industrial Application Field] The present invention relates to a vapor phase growth apparatus for depositing a thin film on a substrate by vapor phase growth.

[Conventional technology] FIG. 3 is a schematic side sectional view of a conventional vapor phase growth apparatus.

In Fig. 3, 1 is a reaction tube, 2 is a liner tube, 3 is a raw material gas introduction tube, 4 is a purge gas introduction tube, 5 is a substrate, 6 is a carbon susceptor, 7 is a high frequency coil for heating the susceptor, and 8 is a growth coil. Deposits deposited on the inner wall of the liner pipe during the period, 9 is the exhaust port.

During growth, the susceptor 6 on which the substrate 5 is placed serves as a high-frequency coil 7.
is heated by.

The raw material gas introduced from the raw material gas introduction pipe 3 deposits a thin film on the substrate 5, and is then discharged to the outside of the reaction tube 1 from the exhaust port 9 by the purge gas.

During the vapor phase growth, the gas around the susceptor 6 and the liner tube 2 are also heated by heat conduction and radiation from the susceptor 6 and reach a high temperature. Therefore, during growth, part of the raw material gas is heated and heated in the gas phase or on the inner wall surface of the liner tube 2.
It is decomposed and deposits 8 gradually accumulate on the inner wall of the liner tube 2.

The deposits 8 are mainly deposited above the liner pipe 2 from the tip of the susceptor 6 to the downstream side of the flow of raw material gas. On the upstream side as seen from the tip of the susceptor 6 in the flow direction of the raw material gas, the raw material gas has not yet been heated much, so there is little deposit of deposits.

[Problems to be Solved by the Invention] According to the above-mentioned conventional method, the liner tube 2 is gradually removed during growth.
Deposits accumulate on the inner walls of the The accumulation of deposits means that the raw material gas is consumed accordingly, and therefore the concentration of the raw material in the raw material gas gradually decreases from upstream to downstream of the flow of the raw material gas. Since the growth rate of the film grown on the substrate 5 is diffusion-limited by the concentration gradient, a problem arises in that the film becomes thicker upstream of the flow of source gas and thinner downstream of the flow of source gas, resulting in a non-uniform film.

Generally, the higher the temperature of the susceptor 6, the better the crystallinity of the grown film, but the easier it is for impurities to be incorporated into the grown film. Therefore, the temperature of the susceptor 6 is determined depending on the type of crystal to be grown so as to obtain a crystal with desired characteristics.

If the decomposition temperature of the raw material gas is sufficiently higher than the temperature of the susceptor 6 determined as described above, the deposition of deposits will be small (the uniformity of the grown film is still good, but if the decomposition temperature of the raw material gas is sufficiently higher than the temperature of the susceptor 6 determined as described above) The closer the temperature is, the more deposits will be deposited and the uniformity of the grown film will be poor.

In order to prevent such a decrease in the uniformity of the film, growth was conventionally performed with the inside of the liner tube 2 under reduced pressure. In the case of reduced pressure vapor phase growth, the gas flow rate is high, so the raw material gas concentration gradient near the susceptor is reduced, and the uniformity of the film is improved. However, the reduced pressure vapor phase growth apparatus has a problem in that the structure of the apparatus itself becomes complicated.

Therefore, an object of the present invention is to provide a vapor phase growth apparatus that can grow a film with excellent uniformity even when the decomposition temperature of the source gas is close to the temperature of the susceptor 6.

[Means for Solving the Problems] The above problem can be solved by supplying a cooling gas to the outside of the liner tube in order to cool the liner tube portion above the substrate 5 placed on the susceptor 6 shown in FIG. This is achieved by growing the film in a vapor phase growth apparatus equipped with a cooling gas introduction mechanism for spraying.

[Function] That is, the present invention sprays cooling gas onto the liner tube portion above the substrate 5 placed on the susceptor 6 during growth, so that the temperature of the susceptor 6 is not lowered, and the liner is removed from the portion where deposits are likely to adhere. By cooling the tube, deposits of deposits on the inner wall of the growing liner tube 2 are suppressed. by this,
This method reduces the change in the concentration of the raw material in the raw material gas from upstream to downstream in the flow of the raw material gas, and improves the uniformity of the grown film from upstream to downstream.

[Example] Hereinafter, the present invention will be specifically explained with reference to an illustrated example.

FIG. 1 is a schematic side sectional view of a vapor phase growth apparatus in one embodiment of the present invention.

In Fig. 2, 1 is a reaction tube, 2 is a liner tube, 3 is a raw material gas introduction tube, 4 is a purge gas introduction tube, 5 is a substrate, and 6
7 is a carbon susceptor; 7 is a high-frequency coil for heating the susceptor; 8 is deposits deposited on the inner wall of the liner tube during growth; 9
10 is an exhaust port, 10 is a gas inlet pipe for cooling the liner tube, 11 is a liner tube portion above the substrate, 12 is a tube that securely fixes each tube in 3.4.10 and stands out, and seals the reaction tube 1. The lid 13 is a lid that seals the reaction tube 1 on the opposite side from the lid 12.

During growth, the susceptor 6 on which the substrate 5 is placed is heated by the high-frequency coil 7, introduced into the source gas liner tube 2 from the source gas introduction tube 3, and exhausted from the exhaust port 9 with a purge gas. Gas and liner pipes around the susceptor 2
However, the cooling gas blowing out from the tip of the liner tube cooling gas introduction tube 10 toward the liner tube section 11 above the susceptor 6 causes the temperature to rise above the substrate. The rise in temperature of the liner tube section 11 is considerably suppressed. Note that since this cooling gas is blown to the outside of the liner tube, it does not disturb the flow of the raw material gas inside the liner tube.

It is preferable that the cooling gas introduction pipe 11 of the liner pipe protrudes from the lid 12. The structure of the reaction tube l becomes complicated,
Although not preferred, a hole may be made in the side wall of the reaction tube 1 to cool the liner tube portion 11 for removing the substrate.

As a result of suppressing the temperature rise of the liner tube above the substrate by the cooling gas, the liner tube portion 11 above the substrate 5 is
The adhesion of deposits 8 to the inner walls of the is reduced. This reduces the change in the concentration of the raw material in the raw material gas from upstream to downstream in the flow of the raw material gas, and improves the uniformity of the growing film from upstream to downstream.

As an example of the conventional method, the susceptor temperature is 630° C., the hydrogen gas flow rate from the source gas introduction pipe 3 is E5j2/min, and the hydrogen gas flow rate from the purge gas introduction pipe 4 is 10j2/m.
In, the hydrogen gas flow rate from the liner tube cooling gas introduction pipe 10 was set to 0.5β/win, and TMG (
trimethyl gallium) at 2.6 cc/min,
TM I ('t-limethylindium) at 0.63c
c/l! lin, AsHm (arsine) 18
When an InGaAs film was grown at normal pressure on a 3-inch GaAs substrate by flowing cc/min raw material gas from the inlet pipe 3, as shown by the dotted line in Fig. 3, the upstream of the flow of raw material gas on the 3-inch substrate In the downstream direction, the In composition of the InGaAs film decreased from 0.15 to O. This is TM
This is because TMI, which is more thermally decomposable than G (decomposition temperature: 300° C.), reacted with As Ha on the upstream side of the substrate, and TMI was depleted on the downstream side of the substrate.

Next, as an example of the present invention, an InGaAs film was grown with the hydrogen gas flow rate from the liner tube cooling gas introduction pipe 10 set to 1012/win and other growth conditions being the same, as shown by the solid line in FIG. In addition, the I nGaAs film is
The n composition decreased only slightly from 0.15 to 0.13. In this way, the liner pipe cooling gas introduction pipe 1
The uniformity of the In composition of the InGaAs film was greatly improved by flowing the cooling gas from 0 to 10β/+++in.

[Effects of the Invention] As described above, according to the present invention, during growth at normal pressure, cooling gas is sprayed onto the liner tube portion 11 above the substrate to cool this portion, thereby cooling the substrate during growth. Since it is possible to suppress the accumulation of deposits inside the upper liner pipe section 11 and to reduce the change in the concentration of the raw material in the raw material gas from upstream to downstream of the flow of the raw material gas,
This is effective in making the grown film highly uniform from upstream to downstream.

Although the device of the present invention is effective depending on the degree of pressure reduction even when used at reduced pressure, the effect is greater when the pressure is closer to normal pressure.

[Brief explanation of drawings]

Fig. 1 is a schematic side sectional view of a vapor phase growth apparatus in an embodiment of the present invention, and Fig. 2 shows an example of the raw material concentration in the raw material gas and the film thickness of the grown film from upstream to downstream of the flow of the raw material gas. The graph shown in FIG. 3 is a schematic side sectional view of a conventional vapor phase growth apparatus. 1- is a reaction tube, 2- is a liner tube, 3- is a raw material gas introduction tube,
4-Purge gas introduction pipe, 5-Substrate, 6-Carbon susceptor, 7-High frequency coil for heating the susceptor, 8-Deposits deposited on the inner wall of the liner tube during growth, 9-Exhaust port, 10
- Liner tube cooling gas introduction tube, liner tube portion above the substrate 11 Patent applicant Fujitsu Limited

Claims (1)

[Claims] 1. In a horizontal reaction tube type vapor phase growth apparatus comprising a reaction tube and a liner tube placed inside the reaction tube through which source gas flows, the liner tube portion above the substrate placed on the susceptor is connected to the liner tube. A vapor phase growth apparatus characterized by being equipped with a cooling gas introduction mechanism for cooling from the outside.