JPH06140331A - Organic metallic molecular beam epitaxial growth method - Google Patents

Abstract

PURPOSE:To selectively grow high-purity GaAs, n-type GaAs, etc., at a substrate temperature lower than before, in the organic metallic molecular beam epitaxial growth method for a group III-V compound semiconductor. CONSTITUTION:A substrate is irradiated with a halogen gas such as Cl2, etc., or hydrogen halides gas such as HCL, etc., or those decomposed substances. Hereby, it becomes easy for group III material to be desorbed on an SiO2 film 2, by the existence of halogen elements, so polycrystalline GaAs does not accumulate on the SiO2 mask 2, and it becomes possible to selectively grow a high- purity GaAs layer or a high impurity concentration of n-type GaAs layer 3 at a substrate temperature lower than before.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for epitaxially growing a metal-organic molecular beam on a III-V compound semiconductor.

[0002]

2. Description of the Related Art In a method for growing a compound semiconductor, a metal-organic molecular beam epitaxial growth method (hereinafter referred to as "MOMBE"), which uses the same ultrahigh vacuum-compatible growth chamber as an ordinary molecular beam epitaxial growth apparatus and uses an organic metal gas as a raw material thereof, is used.
(Abbreviated as law) is known. Compared with the molecular beam epitaxial method, the MOMBE method has advantages such as less surface defects and better selective growth. Further, the organometallic vapor phase epitaxy method has advantages such as high controllability of film thickness and composition and good uniformity, and is very useful as a method for growing a compound semiconductor.

The MONBE method is used for crystal growth of many semiconductor devices. For example, gallium arsenide (Ga
When As is grown, trimethylgallium (TMGa) or triethylgallium (TEGa) is used as a gallium (Ga) raw material, and metal arsenic (As) is used as an arsenic (As) raw material.
₄ ) or arsine (AsH ₃ ) or the like is used. When growing aluminum arsenide (AlAs), trimethylaluminum (TMAl) or triethylaluminum (TEA) is used as an aluminum (Al) raw material.
l) and the like are used.

Actually, for example, in crystal growth of a heterojunction bipolar transistor (HBT), TEGa, TMGa, TEAl or the like is used as a group III raw material, and AsH ₃ or the like is used as a group V raw material.

When a methyl-based raw material such as TMGa is used as the group III raw material, carbon in the methyl group is likely to be incorporated into the growth layer during the growth to become p-type. Therefore, in the case of growing a high-purity group III-V compound semiconductor having a low dopant concentration, II having an alkyl group such as an ethyl group which is more easily desorbed from a group III atom than a methyl group is used.
A Group I raw material is used. This method is described in, for example, N.
N. Furuhata et al., Journal. of. crystal. Grouse (Journal.
of. Crystal. Growth) Volume 102, 8
Page 14 (1990) and Journal. of. crystal. Grouse (Journal.of.Crysta)
l. (Growth) 112, 1 (1991).

When TEGa and As ₄ are used, the carrier concentration is 1.5 × 10 ¹⁴ cm ^{− under} a substrate temperature of 500 ° C., a TEGa flow rate of 0.8 cc / min, and an As ₄ pressure of 1.5 × 10 ⁻⁴ Torr. It is possible to grow high-purity GaAs having a p-type of ³ and a carrier mobility of 400 cm ² / Vs at room temperature. Furthermore, by doping an n-type impurity such as silicon (Si) during the growth, it is possible to grow an excellent n-type group III-V compound semiconductor layer with a low degree of compensation.

[0007]

In such a conventional growth method, when a high-purity or n-type III-V group compound semiconductor is grown using an ethyl-based raw material such as TEGa, silicon dioxide on a substrate is used. There is a problem that the property of growing the III-V group compound semiconductor only on the substrate in the opening portion of the mask such as a (SiO ₂ ) film, that is, the selective growth property is poor.

For example, in the case of growing GaAs using TEGa, 500 ° C. is required to grow high-purity GaAs.
A low substrate temperature is suitable. At a substrate temperature higher than that, high impurity concentration p-type GaAs grows and high purity G
You cannot get aAs. Therefore, even if the n-type impurity is highly doped, only the n-type GaAs layer having a very high compensation ratio can be obtained. However, unless the growth temperature is higher than 600 ° C., the selective growth property cannot be obtained, and at the growth temperature of 600 ° C. or lower, polycrystalline GaAs is deposited on the SiO ₂ mask. I couldn't.

Due to the above problems, it has been difficult to produce a high-performance device having a low source resistance, which has a structure in which, for example, a high impurity concentration n-type GaAs layer is selectively grown only in the ohmic electrode formation portion. .

An object of the present invention is to provide a method for selectively growing a high-purity or n-type III-V group compound semiconductor by a MOMBE method at a substrate temperature lower than the conventional method.

[0011]

In order to achieve the above object, the metal organic molecular beam epitaxial growth method according to the present invention is a metal organic molecular beam epitaxial growth method for growing a selective growth layer on a III-V compound semiconductor substrate. Then, either one of the halogen gas and the hydrogen halide gas is applied to the substrate during the growth of the selective growth layer.

Further, it is a metalorganic molecular beam epitaxial growth method for growing a selective growth layer on a III-V compound semiconductor substrate, wherein either halogen gas or hydrogen halide gas is supplied during the growth of the selective growth layer. It decomposes and irradiates the substrate.

[0013]

[Function] Here, chlorine (Cl ₂ ) is used as the halogen gas.
The selective growth of GaAs when using is described. II
TEGa is used as the group I raw material, and As ₄ or AsH ₃ is used as the group V raw material.

TEGa decomposes on the substrate or on SiO _{2 into} monoethylgallium (MEGa) or diethylgallium (DEGa). These decompositions are 500
It easily occurs even at low growth temperatures below ℃. On GaAs, MEGa or DEGa binds to As,
GaAs grows.

[0015] Here, in the growth method using only conventional TEGa, MEGA and DEGa also on SiO ₂ is As
Since polycrystalline GaAs is deposited in combination with the above, selective growth was not obtained.

However, in the method of the present invention, SiO ₂
Above, MEGa and DEGa react with Cl ₂ before binding with As and are eliminated as GaCl. for that reason,
Nuclei for GaAs growth are not formed on the SiO ₂ mask, and polycrystalline GaAs does not grow. Therefore, the method of the present invention enables selective growth even at a growth temperature of 500 ° C. or lower, which is lower than the conventional growth temperature.

Also, on the GaAs substrate, some MEG
a or DEGa is released by reacting with Cl ₂ , but G
Since the aAs growth rate is higher, the influence on the growth rate is small. Furthermore, Cl atoms are not taken into the film, and high-purity GaAs can be grown in the same manner as the conventional growth method using only TEGa. Low good n-type Ga
As is obtained.

Furthermore, when the halogen gas is decomposed by a thermal decomposition cell or the like and irradiated on the substrate, an atomic halogen element having high reactivity is generated, so that the group III element is easily desorbed. . Therefore, even if the flow rate of the halogen gas is reduced, good selective growth can be obtained. The influence on the growth rate is small, and high-purity GaAs can be grown. Further, since the flow rate of the halogen gas, which is a corrosive gas, can be reduced, the maintenance of the device becomes easy.

Although the crystal growth of GaAs has been described here, the same effect can be obtained with other III-V group compound semiconductors or mixed crystals thereof.

In addition to Cl ₂ , fluorine (F ₂ ) is used as a halogen gas, and hydrogen chloride (HC is used as a hydrogen halide).
The same effect can be obtained by using l), hydrogen fluoride (HF), or the like. That is, since the group III raw material is desorbed as a halide on SiO ₂ , good selective growth can be obtained.

[0021]

EXAMPLE 1 Next, Example 1 of the present invention will be described with reference to FIGS. FIG. 2 is a schematic sectional view showing an organic metal molecular beam epitaxial growth apparatus used in an example of the method of the present invention. In FIG. 2, the apparatus of the present invention comprises a supply line 5 for an organometallic raw material, a supply line 6 for a halogen gas or a hydrogen halide gas, mass flow controllers 7 and 8 for controlling respective gas flow rates, an organometallic raw material and a halogen. Gas cells 9 and 10 for introducing gas or hydrogen halide gas into the growth chamber, and the growth chamber 11
And an exhaust device 12 and a substrate heating mechanism 13. In addition, 14 is a group V raw material cell, 15 is a dopant cell, and 16 is a nude ion gauge for measuring the degree of vacuum.

First, as Example 1 of the present invention, Cl ₂ was used as a halogen gas, and TEGa was used as a group III raw material.
A case where a high impurity concentration n-type GaAs selective growth layer is grown on an n-type GaAs substrate by using As ₄ as a V-group material and Si as an n-type dopant will be described.

FIG. 1 is a schematic sectional view of a growth layer formed by the growth method of the present invention. The SiO ₂ mask 2 formed on the n-type GaAs substrate 1 is formed by chemical vapor deposition (CV) of SiO _2.
It is formed by a photolithography method using a resist and an etching method using a hydrofluoric acid solution.

High impurity concentration n-type GaAs selective growth layer 3
Are grown under the following growth conditions. That is, TE
Ga flow rate is 1 cc / min, Cl ₂ gas pressure is 1 × 10
^-6 Torr, As ₄ pressure is 1 × 10 ^-4 Torr, and substrate temperature is 500 ° C. TEGa supply line is about 70 ℃
By heating to 1, the above flow rate can be stably obtained. The Cl ₂ cell is at room temperature. The temperature of the Si cell is 105
Set to 0 ° C. Under this condition, high impurity concentration n-type Ga
The growth rate of the As selective growth layer 3 is about 1 μm / hr,
The n-type impurity concentration is 3 × 10 ¹⁸ cm ⁻³ .

In the growth method of this embodiment, Cl ₂
Due to the presence of SiO ₂ , even if the substrate temperature is 500 ° C.
The decomposition product of TEGa on the mask 2 is desorbed, and polycrystalline GaA
s does not deposit. Also, since the Cl ₂ gas pressure is small, G
There is almost no effect on the growth rate on the aAs substrate. Further, Cl atoms are not taken into the film, and the high impurity concentration n-type GaAs selective growth layer 3 is obtained.

In such a high impurity concentration n-type GaAs selective growth layer 3, an electrode is formed on the selective growth layer 3 with, for example, an alloy layer of gold (Au) / germanium (Ge) / nickel (Ni). As a result, for example, it can be used as an ohmic electrode of a heterojunction field effect transistor, and thereby a high-performance semiconductor device with low source resistance can be obtained. For comparison, when the conventional TEGa alone is grown at a substrate temperature of 500 ° C., G
A high impurity concentration n-type GaAs selective growth layer 3'is grown on aAs, but at the same time, a thick polycrystalline Ga is formed on SiO _2.
The As deposit 4 is present and the resulting grown layer is not applicable to semiconductor devices.

Next, a second embodiment of the present invention will be described. In this example, as in Example 1, as raw materials, TEGa and As were used.
₄ , using Si, and further decomposing Cl ₂ and introducing it into the growth chamber, a high impurity concentration n-type GaAs selective growth layer is formed into n-type Ga.
A case of growing on an As substrate will be described. The organometallic molecular beam epitaxial growth apparatus used for growth is the same as that shown in FIG. Cl ₂ introduction gas cell is about 100
By heating to 0 ° C., Cl ₂ is thermally decomposed and reaches the substrate as atomic Cl.

Atomic Cl as well as Cl ₂ can be used in DEGa.
And GaGa to generate GaCl, which is desorbed. Atomic Cl has a very high reactivity, so that good selective growth can be obtained even when the gas pressure is significantly reduced as compared with the case of not thermally decomposing.

Here, microwaves or the like may be used for decomposing Cl ₂ . In that case, Cl radicals having higher reactivity than thermal decomposition can be generated to obtain better selective growth.

In this embodiment, the growth using Cl ₂ as the halogen gas has been described, but F ₂ may be used as another halogen gas and HCl, HF or the like may be used as hydrogen halide.

In addition, the growth method of the present invention can be applied to another III-V method.
The same effect can be obtained when applied to a group compound semiconductor or a mixed crystal thereof. For example, triethylindium (TEI
n) may be applied to the growth of indium arsenide.

Furthermore, the growth method of the present invention is applied to TMGa.
Even when it is applied to the selective growth of p-type GaAs using, for example, the low-temperature selective growth better than the conventional one can be obtained.

Although the case where the SiO ₂ mask is used has been described here, the same effect can be expected even when the mask made of another material such as silicon nitride is used.

[0034]

As described above, according to the present invention, due to the presence of the halogen gas, the hydrogen halide gas, or their decomposition products, it is possible to obtain good selective growth at a substrate temperature lower than the conventional one. . In the growth on the GaAs substrate, the decrease in the growth rate is small, and high-purity GaAs can be obtained. When n-type impurities are doped, good n-type GaAs with low compensation can be obtained. Therefore, for example, the high impurity concentration n
The type GaAs layer can be selectively grown only on the ohmic electrode formation portion, and when used in a heterojunction field effect transistor or the like, a high-performance device with low source resistance can be realized.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a growth layer by a growth method according to an example of the present invention.

FIG. 2 is a schematic cross-sectional view showing a growth apparatus used in the growth method of the example of the present invention.

FIG. 3 is a schematic cross-sectional view showing a growth layer formed by a conventional growth method.

[Explanation of symbols]

1 n-type GaAs substrate 2 SiO ₂ mask 3, 3'high impurity concentration n-type GaAs selective growth layer 4 polycrystalline GaAs deposit 5 supply line for organometallic raw material 6 supply line for halogen gas or hydrogen halide gas 7, 8 mass flow Controller 9, 10 Gas cell 11 Growth chamber 12 Exhaust device 13 Substrate heating mechanism 14 Group V source cell 15 Dopant cell 16 Nude ion gauge

Claims (2)

[Claims] 1. A metal-organic molecular beam epitaxial growth method for growing a selective growth layer on a III-V compound semiconductor substrate, wherein either a halogen gas or a hydrogen halide gas is added during the growth of the selective growth layer. An organometallic molecular beam epitaxial growth method, which comprises irradiating a substrate. 2. A metal-organic molecular beam epitaxial growth method for growing a selective growth layer on a III-V compound semiconductor substrate, wherein either a halogen gas or a hydrogen halide gas is added during the growth of the selective growth layer. A method for epitaxially growing a metalorganic molecular beam, which comprises decomposing and irradiating a substrate.