JPH0687459B2 - Vapor phase growth equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vapor phase growth apparatus suitable for vapor phase growth of III-V group compound semiconductors such as gallium arsenide (GaAs).

[Conventional technology]

In recent years, microwave devices using GaAs, especially GaAs FET
Demand is rapidly increasing. The GaAs FET is formed in an epitaxial layer grown on a semi-insulating GaAs substrate, and a vapor phase growth method using a Ga / AsCl ₃ / H ₂ system is generally used to grow this epitaxial layer.

Figure 4 shows the growth system used for Ga / AsCl ₃ / H ₂ system vapor phase growth. In the figure, 1 is a reaction tube, 2 is a growth furnace, 3 is a Ga source, 4 is a source boat, 5 is a substrate, 6 is a substrate boulder, 7
Is a source gas supply unit, and 8 is an etching gas supply unit.

Further, FIG. 5 shows the temperature distribution in the growth apparatus shown in FIG. 4, S4 is the temperature distribution in the Ga source region, and S5 is the temperature distribution in the growth region.

Epitaxial growth using this growth apparatus is not recommended for reaction tube 1
The Ga source 3 placed in the internal temperature region S4 is made to react with the gaseous raw material containing As supplied from the raw material gas supply unit 7, and the generated reaction product gas is made to react in the low temperature region S5, so that it is placed on the substrate 5. It is for epitaxial growth of GaAs.

By the way, in this type of epitaxial growth, Ga
Reproducible and stable reaction between the source and As is essential for improving the quality of the epitaxial growth layer. In addition, as an important factor for stabilizing the Ga source reaction, a thin solid-state film called GaAs crust, which is generated in the supersaturated state by dissolving As in the Ga source, is uniformly present on the entire source surface during growth. Need to be present.

Therefore, in the prior art, prior to the above-mentioned epitaxial growth, the Ga source 3 was placed in a high temperature region at a constant temperature of about 865 ° C., and a gaseous raw material containing As was flown into the Ga source to cause the GaAs crust generated in As supersaturation in Ga to occur on the source surface. It is formed uniformly over the whole.

Further, at this time, HCl generated by the decomposition of the gaseous raw material containing As reacts with Ga of the Ga source, and is moved onto the substrate 5 in the form of GaCl, where it reacts with As and GaAs is deposited on the substrate. It may grow epitaxially. For this reason,
It is necessary to form a GaAs crust uniformly over the entire surface of the source, then perform a task of etching this growth phase with an etching gas, and then use this Ga source to grow a desired epitaxial layer. .

[Problems to be solved by the invention]

However, when the Ga source is grown in a temperature range of about 865 ° C., the GaAs source cannot supply As to form the crust with respect to consumption of the Ga crust,
The crust disappeared part appears on the Ga source surface. For this reason, the source reaction becomes non-uniform over the entire Ga source, and this causes a problem that hillocks and pits frequently occur on the surface of the epitaxial layer grown on the substrate, resulting in deterioration of quality.

When FETs are manufactured using such defective epitaxial layers, the manufacturing yield decreases due to pattern blurring,
The defect of damaging the mask, and further, the concentration of the electric field on the defect during the operation of the device will cause the deterioration of the characteristics.

An object of the present invention is to provide a vapor phase growth apparatus capable of forming a good epitaxial layer with few crystal defects in the grown epitaxial layer and few hillocks or pits on the surface.

[Means for solving problems]

The vapor phase growth apparatus of the present invention uses Ga formed on the surface of a Ga source.
In a vapor phase epitaxy apparatus that performs epitaxial growth on a substrate using As crust, the Ga source is configured to be movable to different regions in the reaction tube during the epitaxial growth and before the growth is started, and the Ga source before the epitaxial growth is started. The temperature of the source region is set to be higher than the temperature of the Ga source region during epitaxial growth.

Here, the former region temperature is 10 ° C higher than the latter region temperature.
It is set high.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of an embodiment of the present invention, in which the same parts as those in the conventional structure are designated by the same reference numerals.

In the figure, the reaction tube 1 is arranged inside the growth furnace 2 so that the inside thereof is heated. In the reaction tube 1, a source board 4 containing a Ga source 3 is mounted so that its position can be moved. A substrate 5 for epitaxial growth is mounted on the reaction tube 1 by a substrate boulder 6. Further, a raw material gas supply unit 7 and an etching gas supply unit 8 are arranged in the reaction tube 1.

FIG. 2 shows the temperature distribution in the reaction tube 1 described above,
By controlling the temperature in the tube axis direction in the growth furnace 2, as shown in the figure, the source boat region S1 at the highest temperature (875 ° C.) before the start of growth length and the source board during growth at a temperature slightly lower than this (865 ° C.) Each region of the region S2 and the adjustment region S3 of lower temperature (750 ° C.) is configured.

Next, an epitaxial growth method using this growth apparatus will be described.

First, before starting the growth, the source board 4 containing the Ga source 3 is placed in the source boat region S1 before starting the growth, the growth furnace 2 is heated, and the temperature distribution in the reaction tube 1 is shown in FIG. Stabilize to the temperature distribution shown in.

Then, after the temperature is stabilized, a gaseous raw material containing Aa is flown into the Ga source 3 from the raw material gas supply unit 7 to uniformly form GaAs crust generated in the supersaturated state of As in Ga over the entire surface of the GA source 3. .

Next, after the distribution of the GaAs crust on the surface of the Ga source 3 becomes uniform, the source boat 4 is moved to the source boat 4 and the region S2 during growth which is lower by about 10 ° C., and the etching gas from the etching gas supply unit 8 is reacted. It is supplied into the tube 1 and the epitaxial layer grown on the substrate 5 at the same time when the GaAs crust is formed in the previous step is removed by etching. At this time, the gaseous raw material containing As continues to flow.

After that, the supply of the etching gas is stopped, and the vapor phase reaction is performed in the same manner as before to grow a desired epitaxial layer on the substrate 5.

Therefore, according to this vapor phase growth apparatus,
Since the GaAs crust is formed by setting the Ga source 3 at a high temperature, the GaAs crust is a state in which a large amount of As is dissolved in Ga, that is, a thick GaAs crust is formed.
Therefore, during the epitaxial growth, the Ga surface does not have any GaAs crust disappeared, the source reaction is uniform over the entire source, and the number of crystal defects in the epitaxial layer is small, so that there are few hillocks or pits on the surface. Growth of various epitaxial layers can be realized.

FIG. 3 shows an example in which the temperature distribution between the source boat region S1 before the start of growth and the source boat region S2 during growth in the apparatus is changed in a slanted manner at a constant rate.

That is, in the above embodiment, the source boat region S1 before the start of growth
The temperature distribution of the source boat region S2 during growth is changed stepwise. However, even if the temperature distribution between the two is inclined in this way, the same epitaxial growth as in the above embodiment can be performed.

In addition, it is easier to actually set the temperature distribution than to set the temperature distribution in a stepwise manner as in the above-described embodiment by setting the temperature distribution that changes in a gradient at a constant rate. There is an effect that the temperature inside the reaction tube can be easily controlled.

〔The invention's effect〕

As described above, the present invention is configured such that the Ga source can be moved to different regions in the reaction tube during the epitaxial growth and before the growth is started, and the temperature of the Ga source region before the start of the epitaxial growth is set at the time of the epitaxial growth. Since the temperature is set higher than that of the Ga source region, it is always uniform and uniform during epitaxial growth.
GaAs crust can be formed, and Ga is formed on the Ga source surface.
No part where As crust disappears does not appear, and a good epitaxial layer with few crystal defects and few hillocks and pits can be grown.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing a temperature distribution in the growth apparatus shown in FIG. 3, FIG. 3 is a diagram showing different temperature distributions in the growth apparatus shown in FIG. 1, FIG. 4 is a schematic sectional view of a conventional growth apparatus, and FIG. It is a figure which shows the temperature distribution in the growth apparatus of the figure. DESCRIPTION OF SYMBOLS 1 ... Reaction tube, 2 ... Growth furnace, 3 ... Ga source, 4 ... Source boat, 5 ... Substrate, 6 ... Substrate holder, 7 ... Raw material gas supply section, 8 ... Etching gas supply section, S1 ... Source area before start of growth , S2… Growth Ga source region, S3… Growth region, S4… Ga
Source area, S5 ... Growth area.

Claims (2)

[Claims] 1. A Ga source and a substrate are placed in a reaction tube, a source gas containing As and an etching gas are supplied into the reaction tube, and a GaAs crust formed on the surface of the Ga source is used to form a substrate on the substrate. In the vapor phase growth apparatus for performing epitaxial growth, the Ga source is configured to be movable to different regions in the reaction tube during the epitaxial growth and before the growth is started, and the temperature of the Ga source region before the start of the epitaxial growth is set to the temperature during the epitaxial growth. The vapor phase growth apparatus is characterized in that the temperature is set higher than the temperature of the Ga source region in. 2. The region temperature before the start of epitaxial growth is
The vapor phase growth apparatus according to claim 1, wherein the temperature is set to be 10 ° C. higher than the region temperature at the time of epitaxial growth.