JP3090232B2 - Compound semiconductor thin film formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the formation of III-V compound semiconductor thin films.

[0002]

SUMMARY OF THE DISCLOSURE The present invention relates to a method for forming a group III-V compound semiconductor thin film on a substrate heated by a hydrogen atom.
Group hydrides alternately flow over the substrate,

In the step of stopping the introduction of the organic metal while transporting the hydrogen carrier gas, the stop time is 3 minutes or more, or by irradiating the substrate surface with ultraviolet or visible light in the step of stopping.

[0004] A monoatomic layer of a group III element and a monoatomic layer of a group V element are alternately formed on a substrate, and a thin film of a III-V compound semiconductor is formed on the substrate. The present invention discloses a technology that has a self-limiting function for the growth rate of a semiconductor layer and enables the growth of a high-quality compound semiconductor thin film with few lattice defects and impurities and a hetero structure having an extremely steep characteristic.

[0005]

2. Description of the Related Art As a method of forming a compound semiconductor thin film on a substrate, an atomic layer epitaxy method (US Pat. No. 4,058,430) is used.
No. 1977) is known. In addition, laser light II
An example of irradiation at the time of supply of a group I raw material (TMG) or a group V raw material (AsH ₃ ) to promote decomposition is described in A. Doi, Y. Aoyagi and SN
A paper by amba, "Growth of GaAs by switched laser m
etalorganic vapor phase epitaxy ", Appl.Phys.Lett.4
8, (26), 30 June 1986.
Atomic layer epitaxy, proposed by T. Suntola et al., Alternately supplies each of the semiconductor elements on a pulse to deposit a monoatomic layer on the substrate alternately.
The atomic layer epitaxy will be described using GaAs as an example.
Trimethylgallium (CH) which is an organometallic compound of Ga introduced into a heated GaAs substrate placed in a reaction tube
_{3) 3} Ga forms the end surface on the substrate surface in a CH ₃ group. It transported over a single atomic layer in the termination substrate surface by CH ₃ groups (CH _{3) 3} Ga does not adhere to the surface by intermolecular repulsion of the end surface in the CH ₃ group. Next, for about 1 to 5 seconds (C
After the step of stopping the introduction of H ₃ ) ₃ Ga, hydride arsine AsH ₃ is transported to the substrate surface. AsH ₃
Reacts with Ga terminated with CH ₃ groups on the substrate surface and decomposes to form a GaAs monoatomic layer. By repeating this process, a GaAs crystal grows. In this growth method, AsH ₃ is supplied and reacts and grows on the Ga surface terminated with a CH ₃ group, so that carbon is taken in and the crystallinity is deteriorated. In addition, the reaction of the group V hydride is slow on the surface of the CH ₃ -terminated substrate, the formation of the group V monolayer is incomplete, and the self-limiting phenomenon of the growth rate of the monolayer per cycle cannot be obtained. Was.

[0006]

As described above, the prior art is characterized by deterioration of crystallinity due to incorporation of carbon, and slow reaction of group V hydride on a surface terminated with CH ₃ groups. There is a defect that the self-limiting phenomenon of the growth rate of the atomic layer cannot be obtained.

[0007] The present invention solves the above-mentioned drawbacks and provides a lattice defect,
It is an object of the present invention to grow a high-quality compound semiconductor thin film with few impurities by realizing a self-limiting phenomenon of a growth rate of a monoatomic layer per cycle.

[0008]

In the present invention, a group III organometallic compound and a group V hydride diluted with hydrogen are alternately placed on a heated substrate with a stopping step using a hydrogen carrier gas interposed therebetween. In the step of flowing and stopping the introduction of the group III organometallic compound, the introduction time of the group III organometallic compound is reduced by setting the suspension time to 3 minutes or more, or irradiating the substrate surface with ultraviolet or visible light in the stopping step. After the step of stopping, forming a monoatomic layer of a group III element on the substrate, supplying a group V hydride to the surface,
By repeating the step of forming a group V monoatomic layer,
A thin film of a III-V compound semiconductor is formed on a substrate.

The structure of the present invention is as described below. That is, the present invention transports a group III organometallic compound and a group V hydride onto a heated substrate, and thermally decomposes the group III-
In a compound semiconductor thin film forming method for growing a Group V compound semiconductor on a substrate, a first step of introducing a Group III organometallic compound diluted with hydrogen onto the substrate, and the step of transporting a hydrogen carrier gas to the organometallic compound. A second step of stopping the introduction of hydrogen, a third step of introducing a group V hydride diluted with hydrogen onto the substrate, and a fourth step of stopping the introduction of the hydride while transporting a hydrogen carrier gas. Repeating the steps, wherein the organometallic compound is a metallic compound having a methyl group, and the time for stopping the introduction of the organometallic compound while transporting the hydrogen carrier gas is 3 minutes or more. It has a configuration as a thin film forming method, or

The group III organometallic compound and the group V hydride are transported onto a heated substrate and subjected to thermal decomposition to obtain III-V
In a compound semiconductor thin film forming method for growing a group III compound semiconductor on a substrate, a first step of introducing a group III organometallic compound diluted with hydrogen onto the substrate, and a step of transporting a hydrogen carrier gas to the organic metal compound. A second step of stopping the introduction, a third step of introducing a group V hydride diluted with hydrogen onto the substrate, and a fourth step of stopping the introduction of the hydride while transporting a hydrogen carrier gas. Is repeated, and the substrate surface is irradiated with ultraviolet or visible light in a fourth step of stopping the introduction of the organometallic compound while transporting the hydrogen carrier gas, wherein the organometallic compound is a metal compound having a methyl group. And a method for forming a compound semiconductor thin film.

[0011]

The operation of the present invention will be described with reference to FIGS. 1 to 5, taking InP as a group III-V compound semiconductor as an example. III on a heated InP substrate with hydrogen carrier gas
Group organometallic trimethylindium (CH ₃ ) ₃ I
Flow n. (CH ₃ ) ₃ In is thermally decomposed and adsorbed on the surface to form an indium monoatomic layer terminated with CH ₃ groups. (CH ₃ ) ₃ In supplied to a monoatomic layer or more does not adhere to the substrate surface due to intermolecular repulsion with the CH ₃ group on the substrate surface (FIG. 1). Next, while flowing hydrogen carrier gas,
The supply of (CH ₃ ) ₃ In is stopped for 3 minutes or more. In the stopping step, the CH ₃ group covering the surface reacts with the hydrogen carrier gas, is reduced to methane, and is desorbed (FIG. 2) to form an indium metal surface (FIG. 3). CH
_{Since the three} groups are eliminated, carbon is not taken into the crystal. After the step of stopping (CH ₃ ) ₃ In, phosphine PH ₃ is supplied to the surface. Since the CH ₃ group is eliminated to form a metal indium surface, PH ₃ is easily decomposed by a catalytic action with the metal indium to form a phosphorus monoatomic layer (FIG. 4). This cycle is repeated for InP
Grows while generating the self-limiting phenomenon of the growth rate of the monoatomic layer per cycle.

As shown in FIG. 1, after the adsorption of (CH ₃ ) ₃ In on the growth surface is saturated, the supply of (CH ₃ ) ₃ In is stopped while transporting a hydrogen carrier gas. The surface is irradiated with ultraviolet or visible light (FIG. 5). Ultraviolet or visible light irradiated on the surface of the growth layer electronically excites indium terminated with CH ₃ groups on the surface to cause photodecomposition. That is, CH ₃ groups are eliminated from the surface of the growth layer, and are reduced to methane by hydrogen. Therefore, high quality crystals grow without carbon contamination. (CH ₃ )
After the step of stopping ₃ In, PH ₃ is supplied to the surface. C
Since the H ₃ group is eliminated to form a metal indium surface (FIG. 3), PH ₃ is easily decomposed by a catalytic action to form a phosphorus monoatomic layer (FIG. 4). By repeating this cycle, InP grows while generating a self-limiting phenomenon of the growth rate of the monoatomic layer per cycle.

[0013]

Embodiments of the present invention will be described below in detail.

[0014]

Example 1 An InP thin film was grown on an InP substrate.
The substrate is a single crystal and the growth surface is (001). Phosphine PH ₃ was used as a hydride of a group V element, and trimethylindium (CH ₃ ) ₃ In was used as a group III organometallic compound.

FIG. 6 shows an outline of an embodiment of the apparatus of the present invention.
1 is a reaction furnace, 2 is a susceptor that supports the substrate, 3 is an InP substrate, 4 is an RF coil for heating the substrate, 5 is hydrogen gas, 6 is a group III organic metal (CH ₃ ) ₃ In, and 7 is PH ₃ , 8, 9 which are group V hydrides are (CH ₃ ) ₃ I
n, starting the supply of PH _3, a valve for stopping.

FIG. 7 shows the supply program. First, the valve 8 is opened for 1 second, (CH ₃ ) ₃ In of 6 is supplied, the supply of (CH ₃ ) ₃ In is stopped for 3 minutes while the hydrogen gas 5 is flowing, and then the valve 9 is opened for 10 seconds, While supplying ₃ and supplying hydrogen gas 5, supply of PH ₃ is stopped for 1 second. By repeating this cycle, InP is grown.

First, the case where (CH ₃ ) ₃ In is supplied to the InP substrate surface will be described. The RF coil of No. 4 was heated, the temperature of the substrate 2 was set to 350 ° C., and while the hydrogen carrier gas of No. 5 was flowing at 5 SLM, the valve of No. 8 was opened for 1 second, and the (CH ₃ ) ₃ In No. FIG. 8 shows the change in reflectance of the surface light absorption method (SPA) when 0.6 μmol was supplied.
Shown in At a substrate temperature of 350 ° C., the SPA reflection intensity becomes smaller (reflection intensity 2.7 × 10 ⁻² ) than the value of the metal indium surface (reflection intensity 6.2 × 10 ⁻² ) as the supply amount of (CH ₃ ) ₃ In increases. ^-2 ) shows significant saturation. This saturation characteristic indicates that the adsorption of (CH ₃ ) ₃ In molecules on the growth surface is caused by saturation.

Next, while flowing hydrogen gas, (CH ₃ ) ₃ I
The step of stopping the supply of n will be described. FIG. 9 shows (C
The change in SPA reflection intensity in the stopping step after supplying 0.6 μmol of H ₃ ) ₃ In is shown. From the surface terminated with CH ₃ immediately after the supply of (CH ₃ ) ₃ In, the SPA reflection intensity increases as the stop time increases, and the surface is saturated with the metal indium surface. This indicates that the CH ₃ group covering the surface reacts with the hydrogen carrier gas, is reduced and becomes methane, and is desorbed, thereby forming a metal indium surface.

[0019] After the last (CH _{3) 3} In the step of stopping the supply of, when opening the valve 9, which supplies the PH ₃ S
FIG. 10 shows the change in PA reflection intensity. PH ₃ is 50scc
m. Since the metal indium surface has been formed by the supply stop process for 3 minutes, after starting the supply of PH ₃ ,
In about 10 seconds, the SPA reflection intensity reaches the phosphorus stabilized surface. This indicates that PH ₃ is easily decomposed by the catalytic effect with the metal indium surface to form a phosphorus monoatomic layer.

By repeating the supply program shown in FIG. 7, InP grows while generating the self-limiting phenomenon of the growth rate of the monoatomic layer per cycle.

[0021]

Example 2 An InP thin film was grown on an InP substrate.
The substrate is a single crystal and the growth surface is (001). Phosphine PH ₃ was used as a hydride of a group V element, and trimethylindium (CH ₃ ) ₃ In was used as a group III organometallic compound.

FIG. 6 shows an outline of an embodiment of the apparatus of the present invention.
1 is a reaction furnace, 2 is a susceptor that supports the substrate, 3 is an InP substrate, 4 is an RF coil for heating the substrate, 5 is hydrogen gas, 6 is a group III organic metal (CH ₃ ) ₃ In, and 7 is PH ₃ , 8, 9 which are group V hydrides are (CH ₃ ) ₃ I
n, starting the supply of PH _3, valves for stopping, 10
Is an ultraviolet or visible light source. In this case, an excimer laser having a wavelength of 193 nm was used as an ultraviolet light source. Also,
The substrate temperature during growth was set to 350 ° C.

FIG. 11 shows the supply program. First bal
And open the channel 8 for 1 second._Three) _ThreeSupply In and water
While flowing the raw gas 5, (CH_Three)_ThreeStop supplying In
And simultaneously irradiate the growth surface with excimer laser for 10 seconds
Then, open the valve 9 for 10 seconds,_ThreeSupply,
PH while supplying hydrogen gas 5_ThreeSupply for 1 second
I do. By repeating this sile, InP is grown.
Let me go.

The case where (CH ₃ ) ₃ In is supplied to the InP substrate surface is the same as in the first embodiment. That is, FIG.
As shown in the figure, as the (CH ₃ ) ₃ In supply amount increases, the SPA reflection intensity becomes smaller (reflection intensity 2.7 × 1 ⁻² ) than the value of the metal indium surface (reflection intensity 6.2 × 10 ⁻² ).
0 ^-2 ) shows significant saturation. This forms a surface terminated with CH ₃ , and due to intermolecular repulsion with the surface (C
This indicates that the adsorption of H ₃ ) ₃ In molecules on the growth surface is saturated.

Next, while flowing hydrogen gas, (CH ₃ ) ₃ I
The step of stopping the supply of n and irradiating an excimer laser will be described. FIG. 12 shows that (CH ₃ ) ₃ In
6 shows a change in the SPA reflection intensity at the time of excimer laser irradiation in the stop step after the supply of the ol. From the surface terminated with CH ₃ immediately after the supply of (CH ₃ ) ₃ In, the SPA reflection intensity increases with an increase in the excimer laser irradiation time, and becomes saturated on the metal indium surface. This is because the excimer laser irradiated on the surface of the growth layer electronically excites indium terminated with CH ₃ groups on the surface, causing photodecomposition, and the CH ₃ groups are desorbed from the surface of the growth layer, and metal indium is removed. This shows that a surface is formed.

Finally, the supply of (CH ₃ ) ₃ In is stopped,
After the step of excimer laser irradiation, the valve 9 is opened,
When PH ₃ was supplied, as described with reference to FIG. 10 of the first embodiment, since the metal indium surface was formed by the excimer laser irradiation process, approximately 10 seconds after the start of PH ₃ supply. SPA reflection intensity reaches the phosphorus stabilization surface. This indicates that PH ₃ is easily decomposed by the catalytic effect with the metal indium surface to form a phosphorus monoatomic layer.

By repeating the supply program shown in FIG. 11, InP grows while generating the self-limiting phenomenon of the growth rate of the monoatomic layer per cycle.

In the above embodiment, the substrate temperature is set to 350
The temperature was set to ° C., but it is determined by the material system, the geometrical shape of the growth apparatus, and the like.
It is in the range of 0 ° C or less. The following is a supplementary explanation. That is, the upper limit of the substrate temperature is determined by the self-limiting method.
It is 0 ° C. or less. The lower limit of the substrate temperature is determined from the epitaxial growth (single crystal growth) conditions, but cannot be uniquely determined because it depends on the material system and the device system.

In the description of the first and second embodiments, the example of trimethylindium In (CH ₃ ) ₃ is used.
However, it is not limited to this. It is clear from the operation principle shown in FIGS. 1 to 5 that a metal compound having a methyl group may be used.

[0030]

As described above, in the present invention,
By alternately supplying a group III organic metal and a group V hydride while interposing a purge step with a hydrogen carrier gas
In the method of forming a group III-V compound semiconductor thin film, the purging time with a hydrogen carrier gas after supply of a group III organic metal is set to 3 minutes or more, or the purging step with a hydrogen carrier gas after supply of a group III organic metal causes an ultraviolet ray on the surface of the growth layer. Alternatively, it emits visible light. By setting the hydrogen purge time to 3 minutes or longer, CH covering the growth layer surface is removed.
_{The three} groups are reduced by hydrogen to methane and desorb. By irradiating ultraviolet or visible light, the CH ₃ group covering the surface of the growth layer is electronically excited, photo-decomposed, and desorbed. As a result, a group III metal surface is formed after the end of the hydrogen purge or after the irradiation of ultraviolet or visible light. Thereafter, a Group V hydride is supplied and catalytically decomposed on the Group III metal surface to form a Group V monoatomic layer. Since the group III metal plane and the group V plane grow while being alternately formed after the purge step, the incorporation of carbon is small and the crystallinity is improved.
In addition, it becomes possible to realize the self-limiting phenomenon of the growth rate of the monoatomic layer per cycle.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the operation principle of the present invention, in which (CH ₃ ) ₃ In supplied to a monoatomic layer or more does not adhere to a substrate surface due to intermolecular repulsion with a CH ₃ group on the substrate surface. It is a figure showing a situation.

FIG. 2 is a view for explaining the operation principle of the present invention, and shows a state in which a CH ₃ group covering the surface reacts with a hydrogen carrier gas in a stopping step, and is reduced to methane and desorbed. It is.

FIG. 3 is a diagram for explaining the operation principle of the present invention and is a diagram showing a state of forming an indium metal surface.

FIG. 4 is a view for explaining the principle of operation of the present invention, showing how phosphine PH ₃ is separated by catalytic action with indium metal to form a phosphorus monoatomic layer.

FIG. 5 is a view for explaining the operation principle of the present invention, showing a state in which the surface of a growth layer is irradiated with ultraviolet or visible light.

FIG. 6 is a diagram showing an outline of an embodiment of the apparatus of the present invention.

FIG. 7 is a diagram showing a supply program according to the embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the supply amount of trimethylindium and the SPA reflection intensity.

FIG. 9 is a diagram showing the effect of the supply stop time of trimethylindium.

FIG. 10 is a view showing decomposition of phosphine on a metal indium surface.

FIG. 11 is a diagram showing a supply program according to the embodiment of the present invention.

FIG. 12 is a diagram showing an effect of laser irradiation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tube 2 Susceptor 3 Substrate 4 RF coil 5 Hydrogen gas 6 Group III organometallic 7 Group V hydride 8, 9 Bulb 10 Ultraviolet or visible light source

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-38823 (JP, A) JP-A-1-316925 (JP, A) JP-A-5-62902 (JP, A) JP-A-5-62902 175145 (JP, A) JP-A-4-226018 (JP, A) JP-A-63-253619 (JP, A) JP-A-59-3099 (JP, A) JP-A-61-275195 (JP, A) JP-A-4-368120 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 H01L 21/31 H01S 5/00 C30B 25/00 C23C 16/00

Claims (2)

(57) [Claims] 1. A group III organometallic compound and a group V hydride are transported onto a heated substrate, and the III-
A compound semiconductor thin film forming method for growing a group V compound semiconductor on a substrate, wherein a first step of introducing a group III organometallic compound diluted with hydrogen onto the substrate; and A second step of stopping the introduction of hydrogen, and a third step of introducing a group V hydride diluted with hydrogen onto the substrate.
And a fourth step of stopping the introduction of the hydride while transporting the hydrogen carrier gas, wherein the organometallic compound is a metal compound having a methyl group, and A method for forming a compound semiconductor thin film, wherein the time for stopping the introduction of the organometallic compound is 3 minutes or more. 2. A group III organometallic compound and a group V hydride are transported onto a heated substrate, and the group III-
A compound semiconductor thin film forming method for growing a group V compound semiconductor on a substrate, wherein a first step of introducing a group III organometallic compound diluted with hydrogen onto the substrate; and A second step of stopping the introduction of hydrogen, and a third step of introducing a group V hydride diluted with hydrogen onto the substrate.
And a fourth step of stopping the introduction of the hydride while transporting the hydrogen carrier gas, wherein the organometallic compound is a metal compound having a methyl group, and A method of forming a compound semiconductor thin film, comprising irradiating a substrate surface with ultraviolet or visible light in a fourth step of stopping introduction of an organometallic compound.