JPH0626187B2 - Semiconductor crystal manufacturing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor crystal manufacturing apparatus, and more particularly to an apparatus for stacking and growing a plurality of epitaxial layers.

[Conventional technology]

In recent years, in order to obtain a multilayer epitaxial layer of semiconductor crystals,
MOCVD (Metal Organic Chemical Vapor D) by thermal decomposition growth of metal element hydride gas and organometallic gas
eposition) method is used extensively.

A conventional example of a semiconductor crystal manufacturing apparatus of this type is GaAs
A (gallium arsenide) -based and AlGaAs (aluminum gallium arsenide) -based MOCVD apparatus will be described as an example. FIG. 3 shows a schematic diagram of an example of the conventional MOCVD apparatus.

In FIG. 3, 1 is a GaAs substrate, 2 is a susceptor for supporting the GaAs substrate 1, 3 is a quartz reaction tube, and 4 is G.
It is a high frequency coil for heating the aAs substrate 1. 5
Is a P-type GaAs layer, N-type GaAs layer, P-type AlGaA
This is a common gas supply system for growing the s layer and the N-type AlGaAs layer, and this common gas supply system 5 is connected to the gas introduction port 7 of the quartz reaction tube 3 by a common gas introduction pipe 6.

Next, the conventional device will be described in more detail with reference to FIG.

In FIG. 4, 8 is A for supplying As (arsenic)
sH ₃ (arsine) cylinder, 9 is N-type dopant Se
H ₂ Se (hydrogen selenide) for supplying (selenium)
A cylinder, 10 is a trimethylgallium (TMG) source for supplying Ga (gallium), 11 is a trimethylaluminum (TMA) source for supplying Al, and 12 is Zn.
Diethyl zinc (DEZn) for supplying (zinc)
Is the source. Each material gas is sent out to a common gas introduction pipe 6 via an ON-OFF valve 13, a flow meter (MF) 14 and a switching valve 15. The switching valve 15 is for introducing or stopping each material gas into the quartz reaction tube 3 or the exhaust (VENT) system. On the other hand, at one end of the gas introduction pipe 6, H ₂ (hydrogen gas) as a carrier gas for pushing the raw material gas sent out into the quartz reaction tube 3 is supplied as a back flow carrier gas and an ON-OFF valve. It is supplied via 13.

[Problems to be solved by the invention]

However, in the conventional semiconductor crystal manufacturing apparatus described above, since the material gas for growing a plurality of epitaxial layers is supplied to the quartz reaction tube 3 by the common gas supply system 5, the multilayer epitaxial layer having a steep interface is formed. The problem is that it is difficult to grow the layers. This is because there is a so-called memory effect in which the previous material gas remains in the gas introducing pipe 6 and further in the switching valve portion and the pipe caecum even if the switching valve 15 is stopped to switch the material gas. Is.

Hereinafter, this problem will be specifically described with reference to FIGS. 5 and 6.

FIG. 5 shows the relationship between the length of the gas introduction pipe 6 and the material gas switching time when the epitaxial layer is grown by the above-mentioned conventional MOCVD apparatus, using the flow rate of the carrier gas as a parameter. Further, FIG. 6 shows the relationship between the flow rate of the carrier gas and the growth amount per second when the length of the gas introduction pipe 6 is 10 m.

As can be understood from these figures, when the length of the gas introduction pipe 6 is 10 m and the flow rate of the carrier gas for pushing is 10 / min, the material gas is changed to, for example, AlGa.
It theoretically takes about 1.7 seconds to switch from As to GaAs (or P-type to N-type GaAs). This switching time is actually longer when the adsorption of the material gas on the tube wall and turbulent flow are taken into consideration. When the flow rate of the carrier gas for boosting is 10 / min, the growth rate is 16.2Å /
Since it is sec, a transition layer of about 27 Å will grow before the material gas is completely switched.

When the thickness of the transition layer is increased in this way, there arises inconveniences such as variations in characteristics such as poor uniformity of the semiconductor laser and deterioration of its reliability.

In addition, MQW (Multi Quantum) that alternately grows GaAs and AlGaAs by several atoms (several Å)
Well) formation of the structure was completely impossible.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a semiconductor crystal manufacturing apparatus capable of stack-growing a plurality of epitaxial layers having steep interfaces. .

[Means for solving problems]

In the semiconductor crystal manufacturing apparatus according to the present invention, the number of gas systems that generate a mixed gas by mixing a plurality of material gases selected in advance according to the composition of each epitaxial layer is equal to that of the composition of each epitaxial layer. Provided, each gas system and the reaction part, are individually connected by a gas introduction pipe for introducing the mixed gas generated in each of these gas systems into the reaction part, and in the middle of each gas introduction pipe, A valve for selecting the mixed gas was provided.

[Operation] In the present invention, a gas system for mixing a plurality of material gases selected in advance according to the composition of each epitaxial layer is
Since there are as many as the number corresponding to the composition of each epitaxial layer, simply select the mixed gas by the valve in the middle of the gas introduction pipe connected to each gas system, and the mixing ratio according to the composition of the epitaxial layer. A material gas sufficiently preliminarily prepared so as to be immediately introduced into the reaction section. For this reason, the gas switching is performed quickly, and a plurality of epitaxial layers having a steep interface can be grown.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a semiconductor crystal manufacturing apparatus according to an embodiment of the present invention.

In the figure, the same reference numerals as those in the conventional example shown in FIGS. 3 and 4 indicate the same parts, and therefore the description thereof will be omitted here.

In FIG. 1, reference numeral 21 is a P-type GaAs gas system for growing a P-type GaAs layer, and this gas system is TM
Source gas sources of G, AsH ₃ and DEZn are provided. 22 is an N-type GaAs gas system for growing an N-type GaAs layer, 23 is a P-type AlGaAs gas system for growing a P-type AlGaAs layer, and 24 is an N-type AlGaA.
It is an N-type AlGaAs gas system provided for growing the s layer. The material gas from each of the gas systems 21 to 24 has a plurality of gas introduction pipes 25 ₁ to 2 2 independently provided.
5 through ₄ and ON-VENT valve ₂₆ 1-26 ₄ (or ON-OFF valves), it is supplied individually to a quartz reaction tube 3. In order to reduce the amount of material gas remaining in the piping from the gas inlet of the quartz reaction tube 3 until ON-VENT valve ₂₆ 1-26 _4, the above-described O
N-VENT valve ₂₆ 1-26 ₄ is preferably provided as close as possible to quartz reaction tube 3.

Next, the operation of the above-described embodiment will be described.

For example, when a normal double hetero structure is grown, the required material gas from each of the gas systems 21 to 24 is VENT in advance.
Pour it to the side. Then, the P-type AlGaAs gas system 23
Open the only on-VENT valve 26 ₃ corresponding to,
By supplying the material gas into the quartz reaction tube 3,
A P-type AlGaAs layer is grown on the GaAs substrate 1 to a desired thickness. Then P-type GaAs from the P-type AlGaAs gas system 23 by opening only ON-VENT valve 26 ₁
The gas system 21 is switched to and a P-type GaAs layer is grown. Furthermore, from P-type GaAs gas system 21 to N-type AlGa
The cladding layer is grown by switching to the As gas system 24, and finally the GaAs contact layer is grown by switching from the N-type AlGaAs gas system 24 to the N-type GaAs gas system 22.

As described above, in the above-described embodiment, the material gas supply system necessary for each growth layer is independently provided, and the growth of the epitaxial layer is switched by turning on and off the introduction of each material gas into the quartz reaction tube 3. Therefore, the switching time of the material gas is short, and the residual or adsorption of the material gas in the pipe is extremely small, and it has become possible to grow an epitaxial layer at the atomic layer level of about several tens of liters.

Further, in the above-mentioned embodiment, since a single material gas supply system corresponding to each epitaxial layer is provided and the material gas required for growth can be constantly flowed, the flow fluctuation of the material gas is very small, and therefore each layer is The composition and the reproducibility of the impurity concentration can be made very excellent.

Next, another embodiment of the present invention will be described with reference to FIG.

In the above-described embodiment, TM is used for each gas system 21-24.
Although each material gas source such as G, AsH ₃ and DEZn was provided, in this embodiment, the material gas source may not be provided for each gas system by providing these material gas sources in common for each gas system. I am trying.

That is, the P-type GaAs gas system 31 is used as the AsH ₃ gas source 3
5, TMG gas source 36 and the material gas delivered from DEZn gas source 37, are collected in the gas introduction pipe 25 ₁ through each individual flow system (MF) 14, ON-VENT
It is supplied to a quartz reaction tube 3 through the valve 26 _1.

The P-type AlGaAs gas system 32 includes an AsH ₃ gas source 35,
TMG gas source 36, DEZn gas source 37 and first TM
Each material gas delivered from the A gas source 38, are collected in the gas introduction pipe 25 ₂ through each individual flow system (MF) 14, a quartz reaction tube 3 through the ON-VENT valve 26 ₂
It will be supplied inside.

The N-type AlGaAs gas system 33 includes an AsH ₃ gas source 35,
TMG gas source 36, H ₂ Se gas source 39 and second TM
Each material gas delivered from the A gas source 40, are collected in the gas introduction pipe 25 ₃ through each individual flow system (MF) 14, a quartz reaction tube 3 through the ON-VENT valve 26 ₃
It will be supplied inside.

The N-type GaAs gas system 34 is an AsH ₃ gas source 35, TM
Each material gas delivered from the G gas source 36 and _H 2 Se gas source 39, are collected in the gas introduction pipe 25 ₄ through each individual flow system (MF) 14, ON-VENT valve 2
6 ₄ via a are supplied to a quartz reaction tube 3.

In the above two embodiments, GaAs, AlGaA
Although the s-based MOCVD apparatus has been described, the present invention can be applied to other III-V group compound semiconductors, II-VI group compound semiconductors, or vapor phase epitaxial method (VPE).

Further, in the above-mentioned embodiment, all the material gas supply systems provided in the MOCVD apparatus are independently provided, but it is not always necessary to provide all the material gas supply systems independently, and a particularly steep interface is required. The material gas system for growing the epitaxial layer may be independent, and the other material gas supply systems may be common.

〔The invention's effect〕

As described above, according to the present invention, the gas system that mixes a plurality of material gases selected in advance according to the composition of each epitaxial layer is provided in the number corresponding to the composition of each epitaxial layer, By simply selecting the mixed gas with a valve in the middle of the gas introduction pipe that is individually connected to each gas system, the material gas that has been sufficiently prepared in advance so that the mixing ratio according to the composition of the epitaxial layer reacts immediately. Introduced in the department. For this reason, gas switching is performed quickly, and a sharp interface at the atomic layer level can be provided in the predetermined epitaxial layer.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the outline of the constitution of a semiconductor crystal manufacturing apparatus according to an embodiment of the present invention, FIG. 2 is a constitutional view of another embodiment of the present invention, and FIG. 3 is a constitution of a conventional apparatus. FIG. 4 is a detailed view of the conventional apparatus shown in FIG. 3, FIG. 5 is a relationship diagram between the gas switching time and the length of the gas introduction pipe in the conventional apparatus, and FIG. FIG. 6 is a relationship diagram between the growth amount of an epitaxial layer and a carrier gas flow rate in the conventional device. In the figure, 1 is a GaAs substrate, 3 is a quartz reaction tube, 21
Is P-type GaAs gas system, 22 is N-type GaAs gas system, 2
3 is P-type AlGaAs gas system, 24 is N-type AlGaAs
Gas _system, 25 to 253 ₄ gas introducing _pipe, 26 1-26
Reference numeral ₄ is an ON-VENT valve. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A semiconductor crystal manufacturing apparatus for laminating and growing a plurality of epitaxial layers having different compositions by reacting a plurality of material gases in a reaction part, and a plurality of preselected ones depending on the composition of each epitaxial layer. The number of gas systems that mix the material gases of to produce a mixed gas are provided in a number corresponding to the composition of each epitaxial layer. An apparatus for manufacturing a semiconductor crystal, which is individually connected by a gas introduction pipe introduced into a reaction part, and a valve for selecting the mixed gas is provided in the middle of each gas introduction pipe.