JPH0613320A - Organic metal vapor phase epitaxy method - Google Patents

Abstract

PURPOSE:To minimize the variation of film thickness distribution in the rotational direction between wafers in a vapor phase epitaxy method using a barrel type susceptor by limiting the number of revolution of the susceptor below a specified value. CONSTITUTION:A barrel type susceptor 2 of a truncated pyramid shape is provided in a reactor 1, a sheet of wafer 3 is placed on each surface. The susceptor 2 and wafer 3 are heated to a specified temperature through the high frequency induction using an external RF filter 4. Then raw gas together with carrier gas is introduced through a gas introduction inlet 5 to cause thermochemical reaction near the heated wafer 3, so that a thin film crystal is grown on the wafer 3. At that time, the speed of revolution of the susceptor 2 during crystal growth is limited below 0.8rpm. Thus, the revolution speed of the susceptor can be lowered for smaller variation of gas flow speed distribution between wafers, resulting in the smaller variation of film thickness distribution between wafers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal organic chemical vapor deposition method for growing a single crystal thin film on a semiconductor substrate.

[0002]

2. Description of the Related Art Metalorganic vapor phase epitaxy (MOVPE method)
Is a type of vapor phase growth method in which a thin film crystal is grown on a semiconductor substrate by utilizing a chemical reaction due to thermal decomposition of an organic metal.
It is used for crystal growth of aAs and AlGaAs.

According to this method, a plurality of semiconductor substrates (hereinafter referred to as wafers) are formed on each surface of a so-called barrel type susceptor.
Place the raw material gas together with the carrier gas from the gas inlet, and heat the wafer and the raw material gas with an external high frequency induction heating coil (hereinafter referred to as RF coil) to cause a thermal decomposition reaction and keep the temperature at a high temperature. A single crystal layer is formed by depositing atoms on a tumbled wafer. During crystal growth, it is necessary to rotate the susceptor in order to make the carrier concentration and film thickness of each wafer uniform.

[0004]

Using the above-mentioned MOVPE method, trimethylgallium (Ga (CH ₃ ) ₃ ) and arsine (As H ₃ ) are used as source gases, and hydrogen (H ₂ ) is used as a carrier gas to grow GaAs. I went. As the growth conditions, the wafer temperature was 650 ° C., and the rotation speed of the susceptor was 3.0 rpm in the right direction. The shape of the susceptor was a hexagonal pyramid, and a total of 6 wafers were placed on each surface, and growth was performed simultaneously.

As a result, six wafers (surface numbers 1 to
When the film thickness distribution in the rotation direction of 6) is examined, as shown in FIG. 5, there is a difference in the film thickness distribution of each wafer, and the film thickness uniformity is ± 3 to 7% as shown in FIG. Made a difference.

Generally, for a wafer having a downwardly convex film thickness distribution (for example, a wafer having a surface number of 4), the film thickness at both ends can be reduced by reducing the gas introduction amount during growth. It is possible to improve the film thickness uniformity. However, when the gas introduction amount is reduced, in a wafer having a lowered film thickness distribution on one end (for example, a wafer having a surface number 1), the film thickness of the lowered portion becomes thinner,
There is an inconvenience that the uniformity is further deteriorated.

On the contrary, when the gas introduction amount is increased, the film thickness distribution of the wafer of surface number 1 is improved for the opposite reason, but the film thickness distribution of the wafer of surface number 4 is deteriorated. Occurs. As described above, according to the conventional method, a difference occurs in the film thickness distribution in the rotational direction between the wafers, so that it is not possible to mass-produce a wafer having high film thickness uniformity.

An object of the present invention is to provide a method for reducing the difference in film thickness distribution in the direction of rotation between wafers and for mass-producing wafers with high film thickness uniformity.

[0009]

The metal-organic vapor phase epitaxy method according to the present invention is characterized in that in the vapor phase epitaxy method using a barrel type susceptor, the rotation speed of the susceptor is 0.8 rpm or less.

[0010]

According to the present invention, the difference in the film thickness distribution in the rotational direction between wafers can be controlled within the in-plane uniformity by vapor-depositing a thin film on the wafer with the rotation speed of the susceptor being 0.8 rpm or less.
It can be reduced to 1% or less, and by optimizing the gas introduction amount during growth after reducing the difference in film thickness distribution between wafers, wafers with high film thickness uniformity can be grown in mass production. I can do it now.

[0011]

FIG. 1 is a schematic configuration diagram showing an example of a MOVPE apparatus for carrying out the metal organic chemical vapor deposition method according to the present invention. In this apparatus, a hexagonal pyramid-shaped barrel-shaped susceptor 2 made of carbon is installed in a reactor 1, and a total of 6 semiconductor substrates (wafers) 3 are placed on each surface. And an external high frequency induction heating coil (RF filter) 4
The susceptor 2 and the wafer 3 are heated to a predetermined temperature by high frequency induction by.

The source gas and the carrier gas together with the reactor 1
The gas is introduced through the gas introduction port 5 to cause a thermochemical reaction in the vicinity of the heated wafer 3 to grow a thin film crystal on the wafer 3, and the gas is exhausted from the gas exhaust port 6. During crystal growth, the susceptor 2 is rotated by the shaft 7 for the purpose of averaging the differences among the plurality of wafers 3.

On the outside of the reactor 1, a cooling jocket 8 is formed at a portion which contacts the inside of the RF coil 4.
The cooling water supplied from the cooling water inlet 9 circulates in the jacket 8 and is discharged from the cooling water outlet 10. In addition to this, the reactor 1 includes a gate valve 11, a prechamber 12,
A gas introduction path 13 and a wafer outlet 14 are provided respectively.

The present invention uses this apparatus under the same conditions as described above, that is, using trimethylgallium (Ga (CH ₃ ) ₃ ) and arsine (As H ₃ ) as source gases.
Hydrogen (H ₂ ) was used as a carrier gas, and GaAs was grown at a wafer temperature of 650 ° C. However, the rotation speed of the susceptor 2 was 0.8 rpm, and the amount of gas introduced during growth was 5
It was set to 0 liter / min.

As a result, the film thickness distribution of the six wafers is
As shown in FIG. 2, although there was a difference in thickness at both ends, the distribution shape was convex downward. Further, as shown in FIG. 3, the in-plane film thickness uniformity is ± 4 to 5 for all six wafers.
% And within ± 1%, and the difference in the film thickness distribution between wafers decreased.

Next, the reason why the rotation speed of the susceptor 2 is set to 0.8 rpm will be described. As a result of detailed investigations and experiments, the present inventor has found that the difference in the film thickness distribution in the rotational direction between the wafers 3 is due to the difference in the gas flow rate in the reactor due to the asymmetry of the susceptor 2 and the reactor 1. What happens, the second
It was found that there is a difference in the gas flow velocity distribution between the wafers 3 due to gas compression / diffusion caused by the rotation of the susceptor 2. After further experimentation, the above 2
It was clarified that the difference in the film thickness distribution in the rotation direction between the wafers 3 becomes smaller by improving one of the factors.

Therefore, an attempt was first made to improve the symmetry of the susceptor 2 and the reactor 1. However, in the method of heating from the outside by the RF coil 4, the susceptor 2 and the reactor 1 are heated.
It is very difficult to maintain good symmetry at all times because the material is a material such as carbon or quartz that is difficult to achieve dimensional accuracy.

Then, when the rotational speed of the susceptor 2 is reduced next, the difference in the film thickness distribution in the rotational direction between the wafers 3 is reduced, and especially when the rotational speed of the susceptor 2 is 0.8 rpm or less, the film thickness uniformity is reduced. It was found that the difference was ± 1% or less.

By the way, when the film thickness distribution in the rotational direction between the wafers 3 is downwardly convex, it is effective to reduce the gas introduction amount during the growth as described above in order to improve the uniformity. is there. Therefore, in order to optimize the gas introduction amount during the growth, the gas introduction amount was reduced from 50 liters / min to 40 liters / min, and the film thickness distribution was investigated. As a result, as shown in FIG. 4, the film thickness uniformity of all six wafers was ± 2 to 3%, and the in-plane film thickness uniformity of each wafer was greatly improved.

[0020]

According to the present invention, the difference in gas flow velocity distribution between wafers can be reduced by reducing the rotational speed of the susceptor, and thereby the difference in film thickness distribution between wafers can be reduced. It was Further, thereafter, by optimizing the gas introduction amount, it becomes possible to mass-produce a wafer having a highly uniform film thickness distribution.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a MOVPE device for carrying out the present invention.

FIG. 2 is a graph showing a film thickness distribution of six wafers obtained according to the present invention.

FIG. 3 is a graph showing the film thickness uniformity of six wafers obtained according to the present invention.

FIG. 4 is a graph showing the film thickness uniformity of six wafers obtained according to the present invention.

FIG. 5 is a graph showing a film thickness distribution of six wafers obtained by a conventional method.

FIG. 6 is a graph showing the film thickness uniformity of six wafers obtained by a conventional method.

[Brief description of reference numerals] 1 reactor 2 susceptor 3 semiconductor substrate (wafer) 4 RF coil 5 gas inlet 6 exhaust port 7 shaft 8 cooling jacket 9 cooling water inlet 10 cooling water outlet

Claims (1)

[Claims] 1. A vapor phase epitaxy method using a barrel type susceptor, wherein the number of revolutions of the susceptor is 0.8 rpm or less.