JPH03276717A - Vapor growth apparatus - Google Patents

Abstract

PURPOSE:To prevent the defective vapor growth of a crystal substrate by making rougher the surface of the inner wall of a reacting tube located at least at the upstream side of the crystal substrate mounted on a susceptor than other parts, forming a minute irregular surface, and decreasing the fall of dust on the crystal substrate. CONSTITUTION:A part of an inner wall surface 1d of a reacting tube 1 higher than a crystal substrate 4 is etched with, e.g. hydrofluoric acid, and the surface of the inner wall is made rough. Thus, a minute irregular surface 8 is formed. The surface of area of this part is made sufficiently large. The temperature of the inner wall surface 1d which is located higher than a susceptor 3 in the reacting pipe 1 becomes high. Therefore, crystals are grown even on the inner surface wall 1d, and reaction products 7 are deposited. Since the minute irregular surface 8 is formed on the inner wall surface 1d, the reaction products 7 are deposited on the minute irregular surface 8. The surface area of the inner wall surface 1d becomes large owing to the minute irregular surface 8. Therefore, the reaction products 7 are rigidly attached to the minute irregular surface 8. Thus, the peeling of a part of the reaction products 7 and the falling of the dust on the crystal substrate 4 are decreased to a large extent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a vapor phase growth apparatus used for manufacturing, for example, petrostructure compound semiconductors.

(Prior Art) A conventional vapor phase growth apparatus for manufacturing a compound semiconductor by vapor phase growing a compound semiconductor film on a crystal substrate is configured as shown in FIG. 3, for example.

As shown in this figure, in the conventional vapor phase growth apparatus, a susceptor 3 fixed to a support rod 2 is disposed in a reaction tube 1 made of quartz, and a crystal substrate 4 is placed on the susceptor 3. ing. The reaction tubes 1 are removably connected to each other in an airtight manner via an O-ring 5 at the flange portion 1a.
Gas (growth gas,
An air supply port]b for supplying carrier gas, inert gas, etc.) is formed on the lower side of the reaction tube 1, which is divided by the flange 1a. An exhaust port 1c is formed for constant adjustment. Furthermore, a high frequency coil 6 for heating the susceptor 3 (crystal substrate 4) is disposed outside the reaction tube 1, and the inner wall surface 1d of the reaction tube 1 has good surface precision and is transparent.

The conventional vapor phase growth apparatus is constructed as described above, and after placing the crystal substrate 4 on the susceptor 3 and connecting the flange portion 1a of the reaction tube 1 in an airtight state, the high frequency coil 6 is energized. The susceptor 3 in the reaction tube 1 is heated to raise the temperature of the crystal substrate 4 to a predetermined temperature.

Then, a growth gas (for example, arsine (ASH3),) trimethyl gallium (TMG) is introduced into the reaction tube 1 from the air supply port 1b.
), trimethylaluminum), etc. together with carrier gas (
For example, (2) is introduced to grow a compound semiconductor film on the crystal substrate 4 in a vapor phase.

At this time, the inner wall surface 1d of the reaction tube 1 located above the crystal substrate 4 also becomes high temperature at the same time, so when the growth gas etc. is introduced from the air supply port 1b, crystals grow on the inner wall surface 1d of the reaction tube 1 as well. The reaction product 7 is deposited and becomes thicker each time the growth is repeated.

Then, the reaction product 7 deposited on the inner wall surface 1d of the reaction tube 1
Finally, a part of it peels off, turns into dust 7a, and falls onto the crystal substrate 4 during vapor phase growth.

That is, when the reaction tube 1 is heated by the high-frequency coil 6 and the heating is stopped after crystal growth, the coefficient of thermal expansion of the reaction tube] and the reaction product 7 are greatly different, so that the inner wall surface 1d of the reaction tube 1
A gap is created between the reaction product 7 and the reaction product 7, and a part of the reaction product 7 peels off and falls onto the crystal substrate 4 as dust 7a. When the dust 7a of the reaction product 7 adheres to the crystal substrate 4 from above, the crystal growth film becomes non-uniform or the composition changes, resulting in a defective product.

For this reason, it was necessary to separate the reaction tube 1 from the flange portion 1a every predetermined vapor phase growth time and clean the inner wall surface 1d of the reaction tube 1 to remove the accumulated reaction product 7, which was inefficient.

In addition, the growth gas generally contains many hazardous gases, and hazardous chemicals are also used when cleaning the inner wall surface 1d of the reaction tube 1. It was necessary to pay sufficient attention to cleaning the inner wall surface 1d.

(Problems to be Solved by the Invention) As described above, in the conventional vapor phase growth apparatus, the dust 7a of the reaction product 7 deposited on the inner wall surface 1d of the reaction tube 1 falls onto the crystal substrate 4 during crystal growth. As a result, the crystal substrate 4 becomes a defective product. Therefore, it is necessary to frequently clean the inner wall surface 1d of the reaction tube 1 to remove the deposited reaction product 7, which is inefficient.

The present invention was made for the purpose of solving the above-mentioned problems, and is intended to reduce the fall of reaction product dust deposited on the inner wall surface of a reaction tube onto a crystal substrate, thereby preventing defects in vapor phase growth of the crystal substrate. The purpose is to provide a vapor phase growth apparatus that can achieve this.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes a method in which a crystal substrate is placed on a susceptor provided in a reaction tube, and a crystal substrate is placed on a susceptor of the reaction tube from the upstream side of the susceptor. In a vapor phase growth apparatus that introduces a growth gas to perform vapor phase growth on the crystal substrate, at least the surface of the inner wall surface of the reaction tube located upstream of the crystal substrate placed on the susceptor is removed from other parts. It is characterized in that it is made rougher to form a finely uneven surface.

(Function) According to the present invention, the surface of the inner wall of the reaction tube is roughened to form a finely uneven surface to increase the surface area of the inner wall, so that reaction products can be spread onto the finely uneven surface formed on the inner wall. Since it adheres firmly, it is possible to significantly reduce the fall of reaction product dust onto the crystal substrate.

(Example) Hereinafter, the present invention will be described in detail based on an illustrated example. In addition, the same reference numerals are attached to the same members as in the conventional case for explanation.

FIG. 1 is a sectional view showing a vapor phase growth apparatus according to the present invention. As shown in this figure, a disk-shaped susceptor 3 on which a crystal substrate 4 is placed, and a support rod 2 that detachably supports the susceptor 3 are arranged in a reaction tube 1 made of quartz.

The reaction tube 1 has an air supply port 1b formed in the upper part for supplying gas (growth gas, carrier gas, inert gas, etc.) into the reaction tube 1, and a lower part for exhausting unreacted gas in the reaction tube 1. An exhaust port]C is formed to adjust the internal pressure to a constant level,
The upper and lower parts of the reaction tube 1 are removably connected in an airtight manner through a flange portion 1a with an O-ring 5 interposed therebetween. Further, on the outside of the reaction tube 1, a high frequency coil 6 for heating the susceptor 3 (crystal substrate 4) is arranged along the periphery of the susceptor 3. These structures are similar to the conventional vapor phase growth apparatus shown in FIG.

In the vapor phase growth apparatus according to the present invention, the inner wall surface 1d of the reaction tube above the crystal substrate 4 is etched with, for example, hydrofluoric acid to roughen the surface of the inner wall surface 1d to create a fine uneven surface. 8 (shaded area), the surface area of this area is increased.

Then, the susceptor 3 on which the crystal substrate 4 is placed is heated by energizing the high frequency coil 6 to raise the crystal substrate 4 to a predetermined temperature, and the growth gas (for example, A carrier gas (for example, H2, etc.) is introduced together with arsine (As H3), trimethylgallium (TMG), trimethylaluminum), etc., and the crystal substrate 4 is
A compound semiconductor film is grown in vapor phase on top.

At this time, the inner wall surface 1d of the reaction tube 1 located above the susceptor 3 also becomes high temperature, so crystals grow on this inner wall surface 1d and reaction products 7 are deposited. 8 is formed, the reaction product 7 is deposited on the finely uneven surface 8.

Since the inner wall surface 1d has a large surface area due to the minute unevenness surface 8, the reaction product 7 is firmly attached to the minute unevenness surface 8, so that a part of the reaction product 7 is peeled off. Dust falling onto the crystal substrate 4 is significantly reduced.

At this time, a fine uneven surface 8 formed on the inner wall surface 1d of the reaction tube 1
The surface roughness of is formed to be in the range of about 10 to 5008. In other words, as is clear from the experimental results shown in FIG. When the surface roughness of the uneven surface 8 is about IO3, the effect that the reaction product 7 is firmly attached can be obtained. In this figure, the horizontal axis represents the surface roughness of the minutely uneven surface 8 formed on the inner wall surface 1d of the reaction tube 1, and the vertical axis represents the amount of reaction product 8 depending on the surface roughness of the minutely uneven surface 8. It represents the time (arbitrary unit) until falling. Note that when the surface roughness of the micro-asperity surface 8 is 100S or more, the time required for the reaction product 8 to fall is approximately constant, but when the surface roughness is about 500S or more, the reaction product 8 falls from the air supply port 1b to the reaction tube 1. Since the flow of gas introduced into the substrate is greatly disturbed, crystal growth on the crystal substrate 4 is adversely affected. Therefore, when the surface roughness of the finely uneven surface 8 is about 10 to 5,003, it is possible to obtain the effect that the reaction product 7 is firmly attached.

In this way, by forming the minute unevenness surface 8 on the inner wall surface 1d of the reaction tube 1, the falling of the dust of the reaction product 7 onto the crystal substrate 4 is greatly reduced, so that the crystal substrate during vapor phase growth is This prevents the film thickness of No. 4 from becoming non-uniform and the composition from changing.

Further, since the dust of the reaction product 7 deposited on the micro-asperity surface 8 is significantly reduced from falling onto the crystal substrate 4, and the time required for the dust to fall is also significantly lengthened, the reaction tube 1 is connected to the flange portion 1a. By significantly reducing the number of times the reaction product 7 separated from the inner wall surface 1d and deposited on the finely uneven surface 8 of the inner wall surface 1d is washed, the chances of contact with harmful raw material gases and hazardous chemicals can be reduced.

Furthermore, although the previous embodiments used a reaction tube made of quartz, the present invention is not limited thereto, and the present invention can be similarly applied to cases where the reaction tube is made of metal or other materials.

[Effects of the Invention] As described above in detail based on the examples, according to the present invention, the reaction product is firmly attached to the microscopic uneven surface formed on the inner wall surface of the reaction tube, so that crystals are Since the fall of reaction product dust onto the substrate is greatly reduced, a crystal substrate on which crystal growth with uniform film thickness and composition can be obtained can be obtained.

In addition, the amount of dust from the reaction product falling onto the crystal substrate is greatly reduced, and the time it takes for the dust to fall is also significantly extended, making it possible to significantly reduce the number of times the inner wall of the reaction tube needs to be cleaned. Therefore, safety is improved and vapor phase growth can be performed efficiently.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a vapor phase growth apparatus according to the present invention, and FIG. 2 is a graph showing the relationship between the surface roughness of the inner wall of the reaction tube and the time required for dust from the reaction products attached to the inner wall to fall. A diagram showing the relationship, FIG. 3, is a cross-sectional view showing a conventional vapor phase growth apparatus. 1... Reaction tube 1a... Flange part 1b...
・Air supply port IC...Exhaust port 1d...Inner wall surface
3... Susceptor 4... Crystal substrate 6... High frequency coil 7... Reaction product 7a... Dust 8...
・Minute uneven surface

Claims (2)

[Claims] (1) A vapor phase growth apparatus in which a crystal substrate is placed on a susceptor provided in a reaction tube, and a growth gas is introduced from the upstream side of the susceptor of the reaction tube to perform vapor phase growth on the crystal substrate. A vapor phase growth apparatus characterized in that an inner wall surface of the reaction tube located upstream of a crystal substrate placed on a susceptor is made rougher than other parts to form a finely uneven surface. (2) The vapor phase growth apparatus according to claim (1), wherein the surface roughness of the finely uneven surface is set in a range of 10 to 500S.