JPS59121917A - Vapor growth device - Google Patents

Abstract

PURPOSE:To enable to attain epitaxial growth of high quality with high efficiency, and to reduce sharply supply of a harmful V group element hydrogen compound at a vapor growth device by a method wherein material gas generators are discriminated according to stability of gas, and exciting light projected from an ultraviolet exciting light source guided into a cracker. CONSTITUTION:III group element compound gas, dopant gas and carrier gas are generated from a first material gas generator 1. V group element compound gas such as FH3, AsH3, etc., and carrier gas are generated from a second material gas generator 4. Gases thereof are introduced into a gas supply tube 2 through a cracker 5, and the mixed gas thereof is introduced into a reaction tube 3. A substrate 7 is set on a substrate holder 6 in the reaction tube 3, a shaft 8 is rotated, and the substrate is heated up to the proper temperature according to a reaction tube heating coil 9. Moreover, a cracker heating coil 10 is provided, exciting light 12 projected from an ultraviolet exciting light source 11 is introduced into the cracker 5 through a reflecting mirror 13, a lens 14, and a window material 15, and gas is excited in the cracker 5 coaxially along the direction of the gas current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an open-tube type vapor phase growth apparatus that uses a carrier gas to transport a reactive gas, and is particularly capable of increasing the precipitation ratio of desired elements and obtaining high-quality epitaxial crystal growth. The present invention relates to a high-performance vapor phase growth apparatus.

Vapor-phase growth technology is suitable for mass-producing relatively high-purity crystal planes, and has therefore become an indispensable technology in the conductor industry. In general, the vapor phase growth technology for I-III group compounds uses halides such as GaCl and InCl as the I-group element gas.
There is an organometallic method that uses an alkyl compound of a group I element such as n (02H5n).

The transport method using Ga/AsCl3/H2 system is (3
This is the method used to manufacture the vast majority of aAs microwave devices. On the other hand, with the organometallic method, whereas the halog/transport method requires heating the entire reaction tube, this method does not require heating of the reaction tube other than the substrate installed inside the reaction tube. It has excellent features such as the ability to form extremely steep interfaces with only 0N10FF of source gas and doping gas. The organometallic method was found to be useful for the growth of quantum well lasers and the formation of superlattice dino In the case of the organometallic method, which is currently being actively researched and developed as an essential technology for manufacturing devices and ultra-high-speed semiconductor devices, an all-organometallic gas method that uses an organometallic gas for the vJ element is also possible. Due to problems with the purity of the raw material gas and process problems, currently the main methods are to use hydrides such as A s H3PH3 for the group V element gas and organic metals for the group I element gas and dopant gas. has been adopted.

Therefore, by taking as an example the vapor phase growth of a group IV compound using an organometallic method, the conventional vapor phase growth method will first be explained, and the drawbacks of the conventional method will also be described.

In the organometallic vapor phase epitaxy method for group ■-■ compounds, the main method is to use an organic metal gas as a group-■ element gas and some dopant gases, and to use a hydride such as PH3 or AsH3 as a group-■ element gas. has been adopted. As the carrier gas, a nitrogen gas, an inert gas such as nitrogen gas, or an alcohol gas, or a mixture thereof is used. For raw materials that are liquid at room temperature, these carrier gases are used to cause the raw materials to bubble and to be used by vaporizing them. Ga for ultra high speed devices
Compounds such as As-based and InP-based compounds are useful, but most of the reported examples have been limited to Ga-As-based compounds, and InP-? Growth of InP-based compounds such as InGaAsP has been difficult to achieve. One reason for this is PH3 (PH3), which is used as a group V raw material compound.
Because phosphine) is very stable, the rate of thermal decomposition on a heated substrate is small, and furthermore, In(C2H5)3 (triethyl indium), etc. Because of its instability, an increase in the gas temperature in the raw material transport region may generate reactants before the raw material gas reaches the substrate, inhibiting epitaxial growth on the substrate. In order to maintain low temperature and to grow high quality crystals with steep interfaces,
It is desirable that the crystal growth temperature be lower. Therefore, the crystal growth temperature (substrate temperature) is set as low as possible within a range that does not cause amorphous or polycrystalline formation. For example, InAsP
The growth temperature is 550 for
The temperature is set at ~600°C. However, PH3 is 37
Although it is said that decomposition begins at 5°C, the decomposition rate is not that fast, so even if the substrate is heated to 700°C or higher, a small amount of PH3 will still be exhausted without reacting. arise. Therefore, some kind of countermeasure is required to achieve the P partial pressure necessary for crystal growth even at a relatively low growth temperature.

One of the countermeasures is to significantly increase the supply of PH3. However, the permissible concentration of PH3 is 0.3pp.
In addition to being extremely toxic, it is also dangerous to ignite in the presence of air even with the slightest stimulation, so supplying large amounts of PI3 would pose problems in the exhaust gas, and the aim was to mass produce it. P4 is generated during crystal growth,
This is supplied to the reaction tube (P2 and P4 are easily decomposed into P and precipitated on the substrate). A vapor phase growth apparatus equipped with a PH3 decomposition furnace for this purpose has recently been developed, and it can be used in combination with the reduced pressure growth method.
Prototypes such as heterojunction lasers have begun to be produced.

However, this conventional vapor phase growth apparatus still had the following drawbacks, so it was not possible to use it as Tenkawa. That is, since the PH3 decomposition furnace used in the conventional vapor phase growth apparatus has a still low decomposition ratio of PH3, the above-mentioned problems have only been slightly alleviated. Conventional PH3 decomposition furnaces were used with the temperature of the decomposition furnace raised to about 800°C, but even this was still insufficient to thermally decompose PH3. In addition, since the flow rate of the carrier gas containing PH3 is as high as 1 to 5 m/s, a long heating furnace is required to perform sufficient heat exchange with the gas, which is disadvantageous.

Furthermore, the decomposition ratio of PH3 can be increased by increasing the temperature of the decomposition furnace or increasing the surface area inside the decomposition furnace.
Or, as a result of a rapid increase in the generation of impurities from pipe materials such as stainless steel piping, or as a result of higher temperature gas being introduced into the gas supply pipe 2, etc., the raw material gas may come into contact with the Group III raw material compound before it reaches the substrate. As a result, epitaxial growth on the substrate is inhibited, making it impossible to obtain high-quality and uniform crystal growth.

An object of the present invention is to provide an economical and high-performance vapor phase growth apparatus that can eliminate the above-mentioned conventional drawbacks and perform high-quality epitaxial growth with high efficiency.

According to this invention, since the precipitation ratio of thermally stable elements (especially P) is increased, the supply amount of harmful Group V element hydrogen compounds such as PH3 can be significantly reduced, and this is an industrially essential exhaust gas treatment measure. It also has the advantage of being easier.

Next, this invention will be explained in detail using the drawings.

The figure is a schematic diagram of an embodiment of the vapor phase growth apparatus of the present invention.

In(02H5)3,G from the first raw material gas generator 1
Group I element compound gases such as a(C2H5)3 and H
A dopant gas such as 2S, zn(C2Hs)z and an inert gas (carrier gas) containing hydrogen gas are generated, and the gases are introduced into the gas supply pipe 2. is P H3, A s H3, etc.■
A group element compound gas and an inert gas (carrier gas) containing hydrogen gas are generated and passed through the decomposition F5 to the gas supply pipe 2.
In the gas supply pipe 2, the mixed gas is thoroughly mixed with the gas generated from the first raw material gas generator 1, and this mixed gas is introduced into the reaction tube 3.

Inside the reaction tube 3, a substrate 7 is installed on a substrate holding A (?segment) 6], and this substrate 7 is rotated at a constant speed inside the reaction tube 3 by rotating a shaft 8. It is now possible to do so.

9 is a reaction tube heating coil, which heats the substrate to an appropriate temperature.

10 is a cracking furnace heating coil. Reference numeral 11 denotes an ultraviolet excitation light source. Excitation light 12 emitted from the light source 11 is introduced into the decomposition furnace 5 via a reflecting mirror 13, a lens 14, and a window material 15. , excitation coaxially along the direction of gas flow. As an ultraviolet excitation light source, it is desirable that the main emission wavelength coincides with the absorption peak of the desired group Ⅰ element compound gas to be decomposed. If the excitation is carried out coaxially, the length effective for excitation can be increased, so that even a light source having an emission wavelength slightly shifted from the absorption peak wavelength of the gas can be used without any problem.

As the ultraviolet excitation light source 1, an incoherent light source such as a high-pressure mercury lamp, or a 193 nm A r F -r-
A high-power ultraviolet laser light source such as an eximer laser or a 249 nm KrF excimer laser is used. When using a high-pressure mercury lamp, the directivity of the light source is not good, so it is necessary to use a lamp with a high output of at least IKW.゛-1゛When using an excimer laser, an average output of several + W is sufficient, but since the laser oscillation operation can only be performed in pulses, it is difficult to optically excite the gas while it is flowing through the cracking furnace. It is necessary to repeat the gas at a high speed of about 100 pulses per second or higher.In the decomposition furnace 5, the gas is heated to about 600'C, so the gas is not only vibrated from the ground state but also excited. The absorption of ultraviolet light also occurs due to the state, and this causes efficient photodissociation, resulting in a high decomposition rate that would have been impossible with thermal decomposition alone in a conventional decomposition furnace.
It is possible to decompose group (2) element compound gases. However, among group V element gases, A s H3 is relatively easy to thermally decompose compared to PH3, etc., so it may be supplied from the first raw material generator 1 without passing through the decomposition furnace 5. .

As explained above, according to the present invention, it is possible to efficiently decompose a group (I) element compound gas at a lower decomposition humidity than before, so that the amount of supply of harmful group V element hydrides such as PH3 can be reduced. Even if the amount is reduced, group (I) elements can be precipitated at a high precipitation ratio. Furthermore, since the decomposition can be performed at a lower temperature than in the past, the generation of impurities in the decomposition furnace and intermediate piping can be suppressed as much as possible, making it possible to obtain high-quality epitaxial growth.

In the above embodiment, the raw material gas discharged from the cracking furnace 5 was introduced into the gas supply pipe 2, but if a sufficient mixing effect can be obtained upstream of the reaction tube 3, a 2 openings may be provided to directly introduce the raw material gas into the reaction tube 3 independently of the raw material gas supplied from the first raw material gas generator 1. However, since the temperature inside the reaction tube is extremely high, it is never desirable for reactive gases to remain there for a long time, so it is better to keep the distance from the upstream side of the reaction tube to the substrate as short as possible. Good. For this reason, it is better to avoid mixing the Group I element gas and the Group V element gas in the reaction tube if possible. When mixing Group I element gas and Group V element gas in the gas supply pipe 2,
It is preferable to keep the gas supply pipe 2 cooled so that unnecessary reactions do not proceed, and it is preferable to keep the gas flowing in the pipe so low that it does not become droplets.

In the InP crystal formed by vapor phase growth and release of M-V group compounds according to the present invention, the carrier concentration in the buffer 7 layer is sufficiently reduced without any practical problems, and the 40,000 G1! /V-S or higher was obtained.

Moreover, this invention is applicable not only to InP (, InGaAs
It can be widely applied to the epitaxial growth of multilayer structures of multi-element 1-■ compounds with P.

In the embodiment of the present invention, the excitation light 12 is coaxially incident into the decomposition furnace 5 along the gas flow.
If the wall surface of the decomposition P5 is made into a mirror surface, it is also possible to make the entire excitation light travel in a zigzag manner within the decomposition furnace 5 by, for example, making it obliquely incident, thereby increasing the effective excitation length.

[Brief explanation of drawings]

The figure is a schematic configuration diagram showing the configuration of an embodiment of the present invention. In the figure, l is a first raw material gas generator, 2 is a gas supply pipe, 3 is a reaction tube, 4 is a second raw material gas generator, 5 is a decomposition furnace, 6 is a substrate holder, 7 is a substrate, 8 is shaft, 9
10 is a reaction tube heating coil, 10 is a decomposition furnace heating coil, 11 is an ultraviolet excitation light source, 12 is a #l light emitter, 13 is a reflecting mirror, 14 is a lens, and 15 is a window material.

Claims (1)

[Claims] A reaction tube through which gas flows from the upstream side to the downstream side, a gas supply tube opening on the upstream side within the reaction tube, and a first gas supply tube containing a thermally unstable compound gas connected to the gas supply tube. comprising a raw material gas generation device and a second raw material gas generation device containing a thermally stable compound gas connected to the gas supply pipe via a decomposition furnace, and on a substrate installed in the reaction tube. A vapor phase growth apparatus for guiding gas and performing epitaxial growth, further comprising an ultraviolet excitation light source and a light guiding means for guiding excitation light emitted from the light source into the decomposition furnace.