JPS6285422A - Vertical organic metal thermal decomposition vapor growth apparatus - Google Patents

Abstract

PURPOSE:To reduce the exchanging frequency of a filter by first accumulating fine powder in exhaust gas on a partition plate provided on the bottom of a growing furnace, and then removing only dusts having been forcibly accumulated on the side wall of a cooled lower chamber and not able to be processed by a filter provided at the rear. CONSTITUTION:Parts of thermally decomposed gas or undecomposed AsH3 gas thermally decomposed near a substrate but not grown are accumulated on the inner wall of a growing furnace of a partition plate 6. They are further guided through a hole 31 opened concentrically with the inner wall of the lower chamber 8 through the plate 6 to the chamber 8. Since the heated gas is water- cooled in the chamber 8, the gas is quickly cooled to be secured to the inner wall of the chamber. To protect an O-ring 21 formed at the lower end of the chamber, a collar 22 is provided on a shaft 4 so that the ring 21 is not damaged by fine powder in the exhaust gas. The thermally decomposed gas not able to be processed even in the chamber 8 is fed through a 3-way valve 14 into a filter housing to be filtered. Undecomposed AsH3 gas is purified by an exhaust gas processor, and then exhausted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an organometallic pyrolysis vapor phase growth apparatus, and particularly to an organometallic pyrolysis vapor phase growth apparatus suitable for compound semiconductors.

[Technical background of the invention and its problems]

Semiconductor lasers, such as gallium aluminum arsenide (Ga
A-eAs) Compound semiconductor thin film crystal growth method for semiconductor lasers uses trimethyl gallium (TMG), which is a type of organic metal, trimethyl gallium (TMG), which is a type of organic metal, flusine (IH), which is a hydrogen compound of arsenic, and The 5-organic metal pyrolysis vapor phase growth method (Meta
l Organic Chemical VaporD
eposltlorB MOCVD) is known.

The MOCVD method is expected to be a mass production technology for semiconductor lasers because it supplies all raw materials in gaseous form, making it easy to control the composition, and allowing uniform crystal growth on a large-area substrate.

When carrying out the MO (uD method), a vertical vapor phase growth furnace is often used from the viewpoint of saving raw material gas.In other words, in a vertical growth furnace, approximately Since the raw material gas is supplied vertically, the gas supply m
The direction of crystal growth coincides with that of the crystal, and therefore vapor phase growth can be performed with a small amount of gas supplied.

In vapor phase growth by thermal decomposition of organic metals, a method using high frequency heating is generally used as a heat source in order to avoid thermal decomposition outside the vicinity of the substrate. For this reason, the sample support stand serves as a heat source for high-frequency heating, and is made of carbon or the like, and the sample is placed on it to perform crystal growth. It is believed that crystal growth is carried out by introducing a raw material gas having a predetermined composition from the upper part of the growth furnace and thermally decomposing it near the upper part of the substrate on which crystal growth is to be performed. This process is expressed as follows.

ni sJ (V) → 4 A! 14 (V) + 2 Hz (
V) And at the gas-solid interface Ga(V) +4 A 5(v)4 Ga A 8
(S). (References, e.g. J. Cryst, Gr.
owth, 62225-229 (1983>) The thermally decomposed gas that did not contribute to crystal growth is completely detoxified and then discharged.By the way, the thermally decomposed gas contains unreacted As HB gas and several Contains fine powder of μm or less.

Normally, these fine powders in the waste gas are collected by a filter, and then unreacted AsH is oxidized with a treatment agent containing ferric chloride as a main component, and the above-mentioned AsH is oxidized in the state of 5O5 (arsenic oxide). The filter that traps these fine particles, which are fixed in the processing agent and removed (oxidation fixation method), becomes clogged as the number of times it is used increases, leading to an increase in the pressure inside the growth furnace. When crystal growth is carried out at normal pressure, this pressure increase significantly reduces the quality of the crystal. In other words, those grown under high pressure have a lower Ga −r value than those grown under normal pressure.
Ga-ric, which was found to generate Ieh abnormal layer
The h layer has a higher average 7' concentration than the normally grown G a k g A B layer, and in severe cases, the conductivity type changes, resulting in an abnormal φ-n junction. This phenomenon is fatal to the device, and in order to obtain GaAJAs crystals of good quality, it is extremely important to keep the pressure constant during growth. For this reason, it is necessary to optimize the pore diameter of the filter and to replace the filter frequently in order to prevent pressure rise.

Further, the fine powder contained in the exhaust gas accumulates at the bottom of the reactor and in the piping before reaching the filter, causing the inconvenience that a valve provided in the middle of the piping is clogged.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to efficiently collect fine powder in exhaust gas during crystal growth of a compound semiconductor thin film. The metal-organic pyrolysis method reduces the amount deposited on the growth furnace, suppresses filter clogging, stabilizes the pressure in the growth reactor, and homogenizes the crystal composition to obtain good crystals. An object of the present invention is to provide a vapor phase growth apparatus.

[Summary of the invention]

In the present invention, a raw material gas is introduced into a growth furnace having a raw material gas inlet in the upper part and a raw material gas discharge part in the lower part, thermal decomposition is performed, and a single crystal is grown on a crystal substrate placed in the growth furnace. In a vertical metal organic pyrolysis vapor phase growth apparatus, a lower chamber having a cooling means is provided at the lower part of the growth furnace, and a partition plate having an opening is provided between the growth furnace and the lower chamber,
This vertical organometallic pyrolysis vapor phase growth apparatus is particularly noteworthy in that the raw material gas that does not contribute to crystal growth is discharged through the lower chamber, and the fine powder in the exhaust gas is efficiently collected. I can do it.

[Effects of the Invention] According to the present invention, the fine powder in the exhaust gas is first deposited on the partition plate installed at the bottom of the growth furnace, and then forcibly deposited on the side wall of the cooled lower chamber, Since only the unprocessed dust is removed by the filter provided at the rear, the filter is less likely to be clogged, the frequency of replacement can be reduced, and growth efficiency can be improved. Furthermore, since the increase in pressure is extremely small, the composition can be homogenized.

For example, when a semiconductor laser is manufactured using a substrate subjected to crystal growth according to the present invention, the yield can be improved.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a diagram showing a schematic configuration of a growth furnace of a vertical vapor phase growth apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the exhaust gas treatment system.

In FIG. 1, a sample IJ and a sample support stand 3 on which the sample is placed are arranged in a growth furnace l.

The sample support stand 3 is made of carbon and is heated by high frequency induction and serves as a heat source for pyrolysis growth. The sample support stand 3 is connected to the shaft 4
It can be rotated by the rotation mechanism 5 via. It is in airtight contact with the bottom of the growth reactor via a jacket having concentric openings 31 as shown in FIG.

The lower chamber 8 is cooled, for example, by water, and has exhaust gas outlet holes 10.
It consists of 1 cooling water inlet and 12 outlets. In addition, the first
In the figure, reference numeral 19 is an RF coil for high frequency heating.

A raw material gas introduction duct 13 is connected to the upper part of the growth furnace I. The gas introduced from the raw material gas introduction duct 13 is thermally decomposed in the growth furnace 1, grows crystals on the sample (substrate) 2, and passes through the gas outlet hole 1.

is discharged from the filter through the three-way valve 14
5. A filter 16 is installed inside the filter housing 15 to filter out fine powders in the exhaust gas, and after detoxification by an exhaust gas treatment device, the exhaust gas is exhausted outdoors.

A vacuum pump 18 is connected to the three-way valve 14 so that the gas in the growth furnace can be exhausted prior to the growth of the Ni crystal.

Gas introduction duct) 13 includes a raw material gas source and a flow rate control valve (
(both not shown) are attached. In this example, arsine (&@H1) diluted with hydrogen as the gas source
Trimethyl gallium (TMG) is vaporized by this hydrogen gas and supplied to the nu doping gas (I(,Se)), which becomes the nu doping gas. ),) remethylrlumi=
C A (TMA) and diethyl zinc (DBZ), which serves as a p-temperature doping gas, are connected. the r lucin,
Trimethylgallium and trimethylaluminum are thermally decomposed in a growth furnace to achieve vapor phase growth of gallium, aluminum, and arsenic, and the hydrogen gas serves as a carrier gas.

Next, a case will be described in which a thin film crystal of gallium aluminum arsenide is grown using the vapor phase growth apparatus configured as described above. First, sJl was applied to mirror-polished Ga having an area of approximately 10 crIt and having a plane orientation of (100).

Plate 2 is organically cleaned and then chemically etched with a sulfuric acid based etchant. Next, the substrate is placed on the sample support stand 3. Next, the inside of the growth furnace 1 is evacuated, and then the inside of the growth furnace 1 is replaced with hydrogen gas. After the gas in the growth furnace 1 has been sufficiently replaced, it is heated to about 750C by the RF coil 19. Then, raw material gas mixed to a desired composition is introduced from the gas introduction duct 18.

The introduced raw material gas is diffused by a diffusion plate 20 provided at the upper part of the growth furnace and flows from the top to the bottom of the growth furnace. The mixed gas is thermally decomposed near the substrate and grows as crystals on the substrate. The thickness of the grown layer is determined by the flow rate of Group 1 gases, ie, trimethylgallium and trimethylaluminum, so the relationship between growth time and film thickness is investigated in advance, and the film thickness is controlled by controlling the growth time.

A portion of the pyrolysis gas and undecomposed A s Hs gas that is thermally decomposed near the substrate and does not participate in the growth is deposited on the inner wall of the growth furnace and the upper surface of the partition plate 6 . Furthermore, it passes through an opening 31 formed in the partition plate 6 concentrically with the inner wall of the lower chamber 8 and is guided to the lower chamber 8 . Since the lower chamber 8 is water-cooled, the heated gas is rapidly cooled with a collar 22 to prevent the Y-ring 21 from being damaged by fine powder in the exhaust gas. The pyrolysis gas that cannot be treated even in the lower chamber 8 passes through the three-way pulp 14 and is then introduced into the filter housing and filtered. On the other hand, undecomposed AsH1 gas is detoxified by an exhaust gas treatment device and then released. 'The deposits accumulated on the upper surface of the partition plate 6 can be easily removed with aqua regia or the like, and can be reused. Furthermore, deposits accumulated on the lower chamber wall can be easily removed with a vacuum cleaner or the like. As a result, clogging of the filter can be significantly reduced, and the frequency of filter replacement can be reduced.

In the crystals grown using the apparatus according to the present invention, no abnormal layer due to pressure increase is observed, and the yield of semiconductor lasers made using these substrates is high, and their industrial value is extremely large. .

Note that the present invention is not limited to the embodiments described above. In the above embodiment, the method was applied to the vapor phase growth of Ga-containing 1NS using an organic metal and a hydrogen compound of arsenic.
It is also possible to apply to the vapor phase growth of compound semiconductors other than a. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross section of a growth furnace of a vapor phase growth apparatus according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing an exhaust gas treatment system, and FIG. 3 is a diagram showing a plane of a partition plate. It is. l... Growth furnace 2... Sample (substrate) 3...
Sample support stand 6... Partition plate 8... Water-cooled lower chamber
13... Raw material gas inlet hole 15... Filter housing 17... Exhaust gas treatment device 18... Vacuum pump agent Patent attorney Noriyuki Chika Shinshin Bureau Norio Ogo Figure 1 Figure 2

Claims (3)

[Claims] (1) Introducing the raw material gas into a growth furnace that has a raw material gas introduction part in the upper part and a raw material gas discharge part in the lower part, and performing thermal decomposition,
In a vertical metal-organic pyrolysis vapor phase growth apparatus for growing a single crystal on a crystal substrate placed in a growth furnace, a lower chamber having a cooling means is provided at a lower part of the growth furnace, and a lower chamber including a cooling means is connected to the growth furnace and the lower chamber. 1. A vertical metal-organic pyrolysis vapor phase growth apparatus, characterized in that a partition plate having an opening is provided between the metal organic pyrolysis vapor phase growth apparatus and the material gas which does not contribute to crystal growth is discharged through the lower chamber. (2) The vertical metal organic pyrolysis vapor phase growth apparatus according to claim 1, wherein the partition plate is removable. (3) The vertical metal-organic pyrolysis vapor phase growth apparatus according to claim 1, wherein the opening of the partition plate is formed concentrically with respect to the lower chamber.