JP2717971B2 - Vapor phase growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] The present invention relates to the structure of a vertical vapor phase epitaxy apparatus, which aims to prevent the reaction products peeled off from the reaction tube wall from scattering and adhering to the substrate surface. In a vertical vapor phase growth apparatus having a structure for supplying gas and discharging waste gas from above, a funnel-shaped sub-exhaust port is provided around a raw material gas supply port to suck a dropped reaction product. I do.

This prevents the product from being blown up into the source gas supply airflow.

[Industrial applications]

The present invention relates to a vertical vapor phase growth apparatus typically used for epitaxial growth of a semiconductor layer, and more particularly to a vapor phase growth apparatus that supplies a source gas from below and discharges a waste gas from above. Things.

In the semiconductor industry, it has become possible to form devices with special structures with the progress of crystal growth technology,
On the other hand, a finer crystal growth technique is required to improve the characteristics of these devices.

Such devices include, for example, high electron mobility transistors (HEMTs), resonant tunneling hot electron transistors (RHETs), and devices with a superlattice structure. This is an epitaxial growth method capable of precisely controlling the thickness, that is, so-called atomic layer epitaxy.

In order to realize a superlattice-like structure by vapor phase epitaxial growth, it is essential to rapidly exchange and supply different source gases, for which the flow in the reaction tube is smooth and a part of the gas is The structure must be such that it does not stay in the pipe.

[Conventional technology]

In order to satisfy such a condition, a vapor phase growth apparatus having a structure in which a reaction tube is used in a vertical position, and a raw material gas is supplied from below and discharged upward. A schematic cross-sectional view of the apparatus is shown in FIG. 3, where 1 is a reaction tube made of quartz or the like, 2 is a susceptor, 3 is a holder for supporting and moving the susceptor, and 4 is a crystal growth. The substrate 5 is an RF coil for heating, 6 is an exhaust port, and 7 is an air supply port.

Since the epitaxial growth using this type of apparatus is a well-known technique, details thereof will not be described. However, in the case of epitaxially growing a superlattice structure, the first raw material gas is supplied for a predetermined time (typically, about several seconds to several tens of seconds). The gas is replaced with a carrier gas or the like, and the second source gas is supplied for a predetermined time. Thereafter, the first source gas and the second source gas are alternately supplied with the carrier gas interposed therebetween, and a predetermined number of layers are epitaxially grown.

As described above, in order to replace the different gases in the reaction tube as quickly as possible, the updraft generated by the heat of the susceptor is
A structure that does not cause gas to stay in the pipe is required, and in that sense, a lower supply / upper exhaust is employed.

[Problems to be solved by the invention]

In the actual operation of epitaxial growth, it is rare that the reaction tube is replaced or cleaned every time a new substrate is set, and the reaction tube is replaced or cleaned after performing several times of growth. This is because replacing or washing the reaction tube not only reduces the number of operations, but also decreases the operation rate of the apparatus, such as requiring a certain amount of time for the operation of the apparatus to stabilize.

As described above, when the growth process is repeatedly performed in one reaction tube, the reaction product adheres to the inner wall of the reaction tube and the surface of the susceptor. Become.

However, since the lower end of the reaction tube is usually funnel-shaped as shown in the apparatus of FIG. 3 in order to smooth the gas flow lines, the separated pieces falling in the tube collect at the gas supply port. Then, it is blown up by the flow of the raw material gas or the replacement gas and scattered in the reaction tube.

If the scattered fine pieces adhere to the substrate surface, the crystal growth is hindered and the surface state of the crystal becomes poor. Therefore, such fine foreign matter must be prevented from scattering as much as possible. This is a serious problem particularly when the gas supply speed is high, such as in atomic layer epitaxy.

An object of the present invention is to provide a vapor phase growth apparatus in which fine pieces dropped from the inner wall or the susceptor surface of a reaction tube are not returned into the reaction tube again, whereby the thickness was controlled in atomic layer units. The purpose is to obtain a good epitaxial growth layer.

[Means for solving the problem]

In order to achieve the above object, a vapor phase growth apparatus of the present invention has a structure in which a source gas is supplied from below a substrate and a waste gas is discharged from above a substrate, and a source provided at the bottom of a funnel type reaction tube. A sub exhaust port is provided so as to surround the gas supply port, and has a structure for sucking and removing falling micro exfoliated pieces.

[Action]

FIG. 1 schematically shows the basic structure of the vapor phase growth apparatus of the present invention.

The parts indicated by 1 to 7 are the same as those already described in FIG. 3, but in the apparatus shown in FIG. 3, since a secondary exhaust port 8 is provided surrounding the gas supply port 7, The reduced piece peeled off from the pipe wall is sucked into the secondary exhaust port before reaching the air supply port, and is not blown up by the airflow from the air supply port.

Therefore, the deterioration of the surface state of the epitaxial growth layer due to the adhesion of foreign matter is effectively suppressed, and good atomic layer epitaxy is realized.

〔Example〕

FIG. 2 schematically shows the structure of a vapor phase growth apparatus according to an embodiment of the present invention. Also in this figure, the parts indicated by numerals 1 to 8 are the same as those in FIG. 3 described above, and the point that the sub exhaust port 8 is provided also differs from the basic structure in FIG. Is the same as

Although the epitaxial growth operation using the apparatus is roughly the same as the well-known epitaxial growth operation, when using the apparatus, the valve 61 of the main exhaust port and the valve 81 of the sub-exhaust port are adjusted and fed into the reaction tube. About 10% of the source gas or the replacement gas is discharged from the sub exhaust port.

When the fine foreign matter pieces peeled off from the tube wall or the like fall into the auxiliary exhaust port, they are drawn into the auxiliary exhaust port by the exhaust gas flow, so that they are not blown up into the reaction tube again, and the surface of the epitaxial growth layer is good. Become.

Layers to be epitaxially grown are, for example, GaAs, AlGaA
Binary or ternary III- such as s, InGaAs, AlInAs
Although the present invention is a V compound semiconductor, the present invention can be applied to the growth of a single semiconductor material layer such as Si.

〔The invention's effect〕

As described above, in the vapor phase growth apparatus of the present invention, even if the flow rate of the gas to be supplied is increased, the fine foreign matter pieces are not blown up into the reaction tube, so that no foreign matter adheres to the growth layer surface, It is suitable for atomic layer epitaxy such as formation of a superlattice structure.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a basic structure of a vapor phase growth apparatus of the present invention, FIG. 2 is a schematic view showing a basic structure of a vapor phase growth apparatus of an embodiment, and FIG. It is a schematic diagram which shows the structure of a vapor phase growth apparatus, In the figure, 1 is a reaction tube, 2 is a susceptor, 3 is a susceptor holder, 4 is a substrate, 5 is an RF coil, 6 is an exhaust port, 7 is a supply port. 8 is a sub exhaust port, and 61 and 81 are valves.

Claims (1)

(57) [Claims] 1. A vapor-phase growth apparatus for supplying a vapor-phase raw material from below a heated crystal growth substrate and discharging vapor-phase waste from above the substrate, wherein a gas supply for supplying the vapor-phase raw material is provided. A vapor deposition apparatus comprising a secondary exhaust port surrounding an opening.