JPH0364465A - Vapor growth method of organometallic compound - Google Patents

Abstract

PURPOSE:To accelerate the heating of a substrate and the thermal decomposition of a reaction product without sticking the product and to enhance the efficiency of utilizing gaseous raw materials by mixing a heated carrier gas with the gaseous raw material and heating the gaseous raw material just before introducing the carrier gas into a crystal growth chamber. CONSTITUTION:The gaseous raw material from a cylinder 11 flows through a piping 13 and arrives at a block valve 30. The carrier gas supplied from a cylinder 21 via a purifying device 22 flows through pipings 23, 24 and is heated to a prescribed temp. by a heater 50; thereafter, the gas arrives at the block valve 30. After the carrier gas and the gaseous raw material are mixed, the mixture advances immediately into a crystal growth device 40. The carrier gas heats the gaseous raw material in the block valve 30. The block valve 30 is disposed just before the crystal growth device 40. The gaseous mixture mixed and thermally decomposed in the block valve 30 is, therefore, admitted immediately into the crystal growth device (chamber) 40.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an organometallic vapor phase epitaxy method that improves the utilization efficiency of raw material gas, and is capable of thermal decomposition without raising the temperature of the substrate or causing attachment of reaction products. The purpose of the present invention is to provide an organometallic vapor phase growth method that accelerates the utilization efficiency of raw material gas, and includes the steps of introducing raw material gas into a crystal growth chamber with a carrier gas and thermally decomposing the raw material gas. In the organometallic vapor phase epitaxy method, the raw material gas is heated by mixing a heated carrier gas with the raw material gas immediately before introduction into the crystal growth chamber.

[Industrial application field]

The present invention relates to an organometallic vapor phase epitaxy method that improves the utilization efficiency of raw material gas.

[Conventional technology]

In the metal organic vapor phase epitaxy (MOVPE) method, a raw material gas is thermally decomposed to generate crystal constituent elements in atomic form, and the atoms are chemically bonded on a heated substrate to grow a crystal. Traditionally, this thermal decomposition was performed by heating the substrate.

In recent years, it has become possible to grow extremely high-quality crystals using organometallic vapor phase epitaxy, and in order to increase the steepness of heterointerfaces, more precise interface control is required. has been done. Low-temperature growth is attracting attention as one means for achieving this goal. In low-temperature growth, crystal growth is performed while maintaining the substrate temperature at a low temperature of, for example, (1) (2) about 400°C.

However, when the substrate temperature is lowered, the efficiency of thermal decomposition of the raw material gas also decreases rapidly. In particular, phosphine (PH3), arsine (Δ5Hs), which is a source of group
The decomposition efficiency of these gases significantly decreases when the substrate temperature becomes about 600° C. or lower, and the utilization efficiency of the raw material gas decreases extremely, which poses a serious problem in practice.

Conventionally, one method for dealing with this problem has been a method (photo-CVD method) in which the substrate is irradiated with laser light and the accompanying ultraviolet rays promote the decomposition reaction of the raw material gas. However, this method has problems such as low ultraviolet absorption efficiency of the raw material gas and the fact that the temperature of the substrate itself increases due to laser irradiation, making it impossible to obtain sufficient low-temperature growth effects. On the other hand, in order to avoid raising the temperature of the substrate, a method (Clara-Kink method) is used in which the raw material gas itself is thermally decomposed by heating it directly or by plasma in advance.

However, with this method as well, it is very difficult to efficiently decompose the raw material gas without disturbing the flow of the raw material gas. For example, in order to improve the thermal decomposition efficiency, it is important to determine where in the gas transport path from the raw material gas supply source (cylinder, bubbler, etc.) to the crystal growth chamber is heated.

FIG. 5 schematically shows a typical example of a source gas supply system in a conventional metal organic vapor phase epitaxy method. The raw material gas supplied from the cylinder 11 or the bubbler 12 passes through the pipe 13 or the pipe 4 and reaches the block valve 30. The carrier gas supplied from the cylinder 21 through the purification bag M22 is transferred to the pipe 23.
The block valve 30 is reached through the block valve 30. In this example, the same gas as the carrier gas (for example, H2) is supplied from the cylinder 21.
is supplied as bubbling gas and reaches the bubbler ↓2 via piping 15, where necessary raw material gas is generated. The high-pressure gas supplied from the cylinder is used in a reduced pressure state via a flow rate controller (mass flow controller) 35. The carrier gas and source gas that have reached the block valve 30 are mixed within the block valve 30 and then immediately enter the crystal growth chamber 40 . The used gas is removed from the crystal growth apparatus 40 (3) by the exhaust system 45.
) (4) is discharged to.

In the above supply system, it would be ideal if the heating could be performed efficiently at the position (A), that is, within the crystal growth chamber 40, after the gas is introduced until it reaches the substrate, but in reality, at this position, the heating range is sufficiently limited. This makes it difficult to heat the product sufficiently using a non-contact method.

On the other hand, if a heating element with a large surface area is inserted into this position in order to perform direct heating, decomposition products will adhere to the surface of the heating element and turn into fine powder, causing defects on the surface of the substrate 42.

Furthermore, if heating is performed at the position (B), that is, before the block valve 30 which is the final valve to the crystal growth chamber 40, a sufficient heating range can be obtained, but some of the decomposition products It adheres to the block valve 30 and impedes controllability of the valve.

Regarding the position (C), that is, between the raw material gas supply sources 11 and 12 and the mass flow controller 35, the situation is also as shown in (B).
The same is true for .

[Problem to be solved by the invention]

An object of the present invention is to provide an organometallic vapor phase epitaxy method that promotes thermal decomposition without raising the temperature of the substrate or causing attachment of reaction products, thereby increasing the utilization efficiency of raw material gas.

[Means to solve the problem]

According to the present invention, the above object is achieved by using a heated carrier gas to crystallize in an organometallic vapor phase growth method including a step of introducing a raw material gas as a carrier gas into a crystal growth chamber and a step of thermally decomposing the raw material gas. This is achieved by a metal organic vapor phase growth method characterized by heating the source gas by mixing it with the source gas immediately before introducing it into the growth chamber.

In the present invention, thermal decomposition of the raw material gas is performed not by direct heating of the raw material gas but by indirect heating via a heated carrier gas.

As the carrier gas, gases conventionally used as carrier gas in organometallic vapor phase epitaxy, such as H2, 4
A gas such as r, N2, etc. is used.

The raw material gas may be selected in the conventional manner depending on the type of crystal to be grown; for example, an InP crystal layer and a QaInA layer.
When growing a layer of s crystal, TM■ (trimethylindium), TMG (trimethylgallium),
PH3 (Hoffine) and ASH3 (Arsine) are used.

The raw material gas is normally used after being diluted with a required amount of diluent gas, as in the past. In other words, phosphine etc. are extremely toxic, so from the viewpoint of safety during work, usually 10%
It is stored in cylinders in a moderately diluted state. Furthermore, if it is necessary to stably flow a very small amount of raw material gas depending on the composition of the crystal to be grown, the absolute value of the gas flow rate is increased by diluting it with a diluent gas to ensure the accuracy of flow rate control. Usually, the same gas as the carrier gas is used as the diluent gas.

Embodiment FIG. 1 shows an example of the arrangement of equipment for carrying out the method of the present invention. The raw material gas supplied from the cylinder 11 or the bubbler 12 passes through the pipe 13 or 14 and reaches the block valve 30. The block valve 30 is a valve device in which a plurality of valves are arranged along a common flow path and integrated. The carrier gas supplied from the cylinder 21 via the purification device 22 passes through the pipes 23 and 24, is heated to a predetermined temperature by the heater 50, and then reaches the block valve 30. In this example, the same gas (for example, N2) as the carrier gas is supplied from the cylinder 21 as a bubbling gas, reaches the bubbler 12 via the pipe 15, and generates the necessary raw material gas there. The high-pressure gas supplied from the cylinder is used in a reduced pressure state via a flow rate controller (mass flow controller) 35. The carrier gas and source gas that have reached the block valve 30 are mixed within the block valve 30 and then immediately enter the crystal growth chamber 40 . The used gas is exhausted to the outside of the crystal growth apparatus 40 by an exhaust system 45.

The carrier gas is heated in advance by the heater 50 and then mixed with the source gas in the block valve 30 to heat the source gas. This block valve 30 is placed at the end of the gas transport path from the gas supply source to the crystal growth chamber, that is, immediately before the crystal growth chamber 40. Therefore, the mixed gas mixed and thermally decomposed in the block valve 30 immediately enters the crystal growth chamber 40. Therefore, the raw material gas can be heated with high efficiency without reducing the controllability of the block valve due to the decomposition products of the raw material gas.

The heater 50 can be easily installed using an indirect heating method in which a heating element, such as an electric resistance type, is placed outside the piping over a required length. Alternatively, a direct heating method in which a heating element is installed in the carrier gas flow path can also be used. Even if the carrier gas is used directly, there will be no problem caused by reaction with the heating element.

Note that the carrier gas branched from the pipe 23 to the pipe 25 is set at a plurality of flow rates by a block valve, and is used as a dummy gas for balance corresponding to switching of a plurality of types of raw material gas.

FIG. 2 shows another example of the arrangement of the apparatus for carrying out the method of the invention. In the figure, the Maslow controller is omitted.

FIG. 3 shows details of the block valve and the vicinity of the crystal growth chamber of the apparatus shown in FIG. 2.

In FIG. 2, for example, at a substrate temperature of 400°C, InP,
When growing Ga InAs, the carrier gas (for example, N2, N2, etc.) separated at the position (2) is heated to about 400° C. to 600° C. by the heater 50 at the position (2). The heated carrier gas reaches the block valve 30 at position (3).

On the other hand, In and Ga source gases TMI (trimethylindium) and TMG (trimethylgallium) are generated in bubblers 12a and 12b, respectively, using the same gas as the carrier gas as bubbling gas, and P
and As source gas PH3 (hofin) and Δs■
-■3 (Arsine) is a cylinder lla llb
Supplied from.

These raw material gases reach the block valve 30 at the position (3), where they are mixed with the carrier gas and heated, and are carried as they are by the carrier gas and introduced into the crystal growth chamber 40.

In FIG. 3, the positions from ■ to ■ in FIG. 2 are shown in an enlarged scale. Carrier gas flows in from the left end in the figure. In the figure, A1 and A2 are block valve inlets of TMI and PH3, respectively, whose flow rates were adjusted for InP growth, and B1. , B2. and B3 are TM I A s H, respectively, with flow rates adjusted for GaInAs growth.
3, and the TMG block valve inlet. Also, C is a dummy gas (carrier gas and dummy gas)
This is the inlet of the block valve. Raw material gas of a type and flow rate depending on the type of crystal to be grown is caused to flow into the block valve, but the flow of the negative raw material gas is stopped. In this way, the source gas is switched each time the growth layer is changed, so in order to keep the pressure inside the crystal growth chamber constant, a dummy gas of an inflow amount equal to the stopped source gas is introduced in synchronization with the switching of the source gas.

FIG. 4 shows another example of the arrangement from the block valve to the vicinity of the crystal growth chamber. Each symbol in the figure has the same meaning as in FIG. 3. Group V elements (P, A
The raw material gas (P H3ASH3) of
In particular, thermal decomposition of the group Ⅰ element material gases is preferentially promoted by flowing in the material gases (A2, B3) upstream of the material gases (TMI, TMG) of group (n, Ga).

〔Effect of the invention〕

As described above, according to the present invention, it is possible to promote thermal decomposition without raising the temperature of the substrate or causing attachment of reaction products, thereby increasing the utilization efficiency of raw material gas.

[Brief explanation of drawings]

FIG. 1 is a layout diagram showing an example of an apparatus for carrying out the method of the present invention, FIG. 2 is a layout diagram showing another example of an apparatus for carrying out the method of the invention, and FIG. 2 is a layout diagram showing an example of the arrangement near the block valve of the device, FIG. 4 is a layout diagram showing another example of the arrangement near the block valve of the device of FIG. FIG. 2 is a layout diagram showing a gas supply system in a vapor phase growth method. (11) (12) 1.1, 21: cylinder, 12; bubbler, 1.3. 14
．． 15. 23. 24. 25: Piping, 30: Block valve, 40: Crystal growth chamber, 50: Heater

Claims (1)

[Claims] 1. In the organometallic vapor phase growth method, which includes a step of introducing a raw material gas into a crystal growth chamber using a carrier gas and a step of thermally decomposing the raw material gas, the heated carrier gas is mixed with the raw material gas immediately before introduction into the crystal growth chamber. An organometallic vapor phase epitaxy method characterized in that the above-mentioned raw material gas is heated by.