JPS62188217A - Vertical type organic metal thermal decomposition vapor growth equipment - Google Patents

Abstract

PURPOSE:To enable reducing the maintenance operation of an equipment by exhausting a gas through a filter filled with a fiber like insulating material in a container which is provided at the bottom of a growth furnace. CONSTITUTION:A thermally decomposed gas which did not contribute to growth near a substrate 2 and part of undecomposed AsH3 gas are deposited on the inner wall, etc. of a growth furnace 1 and most of the remaining exhaust gas passes a hole 19 provided on the top of the container 8 of a prefilter provided at the bottom of the growth furnace. Minute powder contained in the exhaust gas is trapped by a fiber like insulating material 9 made of glass wool, then passes through a hole 20 provided on the outer wall of the container and most of the minute powder is caught by the prefilter. Since the prefilter is made of the fiber like insulating material, almost no pressure loss exists. The holes provided in the container 8 are also isotropic against the central axis of the growth furnace and cause no unequal film thickness due to a drift.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a metal-organic pyrolytic vapor phase growth apparatus, and more particularly to a vertical metal-organic pyrolytic vapor-phase growth apparatus suitable for crystal growth of compound semiconductors.

[Technical background of the invention and its problems]

Semiconductor lasers, such as gallium aluminum arsenide (Ga
As a method for growing compound semiconductor thin film crystals for semiconductor lasers (AIAs), trimethylgallium (
TMG), metal-organic pyrolysis vapor phase epitaxy (Meta
l Organic Chemical Vapor
Deposition (MOCVD) is known. The MOCVD method is expected to be a mass production technology for semiconductor lasers because all raw materials are supplied in gaseous form, making it easy to control the composition and allowing uniform crystal growth on a large-area substrate.

When implementing the MOCVD method, a vertical vapor phase growth furnace that can uniformly grow on a plurality of wafers is often used.

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 crystal growth 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 a crystal growth substrate (sample) is placed on this stand for crystal growth. Crystal growth is performed by introducing a raw material gas having a predetermined composition from the upper part of the growth furnace and thermally decomposing it above the substrate on which crystal growth is to be performed. This process is expressed as follows.

(2 people below) (C) 13 ) 3 ・Ga (V) + T117 (V) →
Ga (V)+ 3CL (V)ASI+3 (v)→
As4(■)+2 Then, at the interface between the gas phase and the solid phase, Ga(v)±As(V)→GaAs(S). (
References: e.g. J. Cryst, Growth 62
225-229 (1983)) Pyrolysis gas that did not contribute to crystal growth is completely detoxified and then exhausted.

Incidentally, the thermally decomposed gas contains unreacted AsH, gas, and several fine powders. Normally, these fine powders in the exhaust gas are collected by a filter, while unreacted arsine gas is oxidized with a processing agent whose main component is ferric chloride, and fixed in the processing agent in the form of AsO2 (arsenic oxide). and remove it (oxidation fixing method). Filters that trap fine powder become clogged as they are used more frequently, leading to an increase in pressure inside the growth furnace. When crystal growth is performed at normal pressure, this pressure increase significantly reduces the quality of the crystal.

In other words, when a GaAlAs crystal is grown under high pressure inside the growth reactor, the Ga-r
It was found that an ich abnormal layer was formed. Gari
The ch layer has a higher carrier concentration than a normally grown GaAlAs layer, and in significant cases, the conductivity type changes.
An abnormal pn junction will result. This phenomenon is fatal to devices such as semiconductor lasers, and in order to obtain GaAlAs crystals of good quality, it is extremely important to keep the pressure constant during growth. In order to prevent a pressure increase in the growth reactor, it was necessary to optimize the pore size of the filter and to replace the filter frequently.

Further, the fine powder contained in the exhaust gas was deposited at the bottom of the growth furnace and in the pipes leading to the filter, causing the inconvenience that the valves provided in the middle of the pipes were 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. This reduces the amount of sulfur deposited on the growth furnace, suppresses filter clogging, and suppresses pressure rise in the growth furnace to homogenize the sulfur crystal composition.In addition, by using a removable and washable pre-filter, the equipment can be easily cleaned. A vertical metal organic pyrolysis vapor phase growth apparatus that can reduce maintenance work is provided.

[Summary of the invention]

In the present invention, a pre-filter consisting of a container and a fibrous insulator filled in the container is disposed at the lower part of the growth furnace, and fine powder in the exhaust gas is efficiently collected directly below the growth furnace.

[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 metal organic pyrolysis vapor phase growth apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the exhaust gas treatment system. A sample 2 and a sample support 3 on which the sample is placed are arranged in the growth furnace 1 . The sample support stand 3 is heated by high-frequency induction using a carbon ring, and serves as a heat source for pyrolysis growth. The sample support stand 3 can be rotated via a shaft 4 by a rotating mechanism 5. At the bottom of the growth reactor, a quartz container 8 is arranged, as shown in FIGS. 3(a) and 3(b), with concentric holes perforated in a surface 6 perpendicular to the central axis of the growth reactor and in an outer wall 7. . The container 8 consists of a double cylindrical bottomed container 24 and an upper lid 6. This container 8 is filled with a fibrous insulator 9 made of glass wool, for example, to constitute a pre-filter. Container 8
The top lid 6 is removable, and if the glass wool 9 becomes dirty with dust, it can be taken out and disposed of, and the container 8 can be washed with aqua regia and reused. An exhaust gas outlet duct 11 is connected to the lower chamber 10 housing this pre-filter.

On the other hand, in the upper part of the growth furnace 1 there is a raw material gas introduction duct 1-12.
is connected. The gas introduced from the raw material gas introduction duct 12 is thermally decomposed in the growth furnace 1 to grow crystals on the sample (substrate) 2, and is discharged from the gas outlet duct 11 and sent to the filter housing 13 via the three-way valve 12. be guided. A filter 14 with a pore diameter of about 100 μm is installed inside the filter housing 13 to filter fine powders in the exhaust gas, and then the exhaust gas is detoxified by an exhaust gas treatment device 15 and then discharged outdoors. A vacuum pump 16 is connected to the three-way valve 12 so that the gas in the growth furnace can be evacuated and replaced with gas prior to crystal growth.

A source gas source and a flow control valve (both not shown) are attached to the gas introduction duct 12.

In this example, the gas sources are arsine gas diluted with hydrogen, hydrogenated selenium (H2Se) diluted with hydrogen and used as an n-type doping gas, and connected to a hydrogen gas supply source. Trimethylgallium (TMG) and trimethylaluminum (TMA), which are vaporized and supplied, become p-type doping gas.
Diethyl zinc (DEZ) is connected. Arsine, trimethyl potassium lz.

Trimethylaluminum is thermally decomposed in a growth furnace to achieve vapor phase growth of gallium, aluminum, and arsenic, and hydrogen gas serves as a carrier gas. In FIG. 1, reference numeral 17 is an RF coil for heating the specimen to the growth temperature via the sample support 3.

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, a GaAs substrate 2 with a (100) plane orientation is organically cleaned, then chemically etched with a sulfuric acid etchant, ion-exchanged water, and dried with a spinner.

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 750° C. by the RF coil 17.

Then, raw material gas mixed to a desired composition is introduced through the gas introduction duct 12. The introduced raw material gas is diffused by a diffusion plate 18 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 2 and crystallizes and grows on the substrate 2. The thickness of the growth layer is determined by the flow rate of the raw gases, namely trimethylgallium and 1-limethylaluminum, so the relationship between growth time and film thickness should be investigated in advance, and the film thickness can be controlled by controlling the growth time. do.

The pyrolysis gas that was thermally decomposed near the substrate 2 and did not participate in the growth, undecomposed As11, and a portion of the gas are deposited on the inner wall of the growth furnace 1, etc. Most of the remaining exhaust gas passes through a hole 19 bored in the upper surface of a pre-filter container 8 disposed at the bottom of the growth furnace. The fine powder contained in the exhaust gas is trapped by a fibrous insulator 9 made of glass wool, and then passes through a hole 20 bored in the outer wall of the container. Most of the fine powder is collected by the pre-filter. Since this pre-filter is made of fibrous insulator, there is almost no pressure loss. Further, since the holes bored in the container 8 are provided isotropically with respect to the central axis of the growth furnace, non-uniformity in film thickness due to drifted flow does not occur. In addition, ○ ring 2 provided at the lower end of the lower chamber
1, a collar 22 is provided on the shaft 4 to prevent the O-ring 21 from being damaged by fine powder in the exhaust gas. Exhaust gas that cannot be treated by the pre-filter is
After passing through the three-way pulp 12, it is introduced into the filter housing 13 and filtered. On the other hand, undecomposed AsH and gas are released after being detoxified by an exhaust gas treatment device.

When crystal growth is performed using the apparatus according to the present invention, the fine powder in the exhaust gas is collected immediately after the growth furnace, so there is less deposit in the exhaust gas piping.

The frequency of filter replacement can be reduced.

Furthermore, since clogging of the filter and exhaust gas piping was less likely to occur, no pressure increase in the growth furnace was observed and no abnormal layer was observed in the growth layer. Further, if the pre-filter is of a cartridge type as shown in FIG. 4, the dust containing arsenic can be easily disposed of.

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 GaAQAs using an organic metal and a hydrogen compound of arsenic, but it may also be applied to the vapor phase growth of GaAlAs using other substances or to the vapor phase growth of compound semiconductors other than GaAlAs. It is possible. In addition, various modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, fine powder in the exhaust gas is efficiently collected by the pre-filter provided at the bottom of the growth furnace.

Only the dust that cannot be processed is removed by the filter installed at the rear, which reduces filter clogging and the amount of deposits in the exhaust gas piping, suppressing the pressure rise in the reactor. , it is possible to obtain high quality thin film crystals with a small film thickness distribution.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view 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 top view showing the configuration of a pre-filter. FIG. 4 is a cross-sectional view of a prefilter of another embodiment. 1... Growth furnace 2... Sample 3... Sample support stand 4... Shaft 8... Container 9... Fibrous insulator 10... Lower chamber 11... Gas outlet duct 12. ...Gas introduction duct 17...RF coil agent Patent attorney Noriyuki Chika Yudo Norio Ogo Figure 1

Claims (5)

[Claims] (1) Introducing the raw material gas into a growth furnace that has a raw material gas introduction duct at the top and a gas exhaust section at the bottom to perform 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 filter consisting of a container and a fibrous insulator filled in the container is provided at the bottom of the growth furnace. A vertical metal organic pyrolysis vapor phase growth apparatus, characterized in that the gas is discharged through the filter. (2) The container has an outer circumferential surface and an upper surface in contact with the inside of the growth furnace, and an opening is formed in each of the outer circumferential surface and the upper surface. Vertical metal organic pyrolysis vapor phase growth apparatus. (3) The vertical organometallic pyrolysis gas phase according to claim 2, wherein the openings of the container are arranged isotropically with respect to the central axis of the growth furnace. growth equipment. (4) The vertical metal organic pyrolysis vapor phase growth apparatus according to claim 2, wherein the container comprises a double cylindrical bottomed container and an upper lid. (5) The vertical metal organic pyrolysis vapor phase growth apparatus according to claim 1, wherein the container is made of a material that is not corroded by aqua regia.