JPH0574724A - Method for growing atomic layer of aluminum compound - Google Patents

Abstract

(57) [Summary] [Structure] In an atomic layer growth method for growing a thin film of a compound containing aluminum in atomic layer units, a gas containing alkylaluminum hydride, which is an aluminum source, and a partner are provided on a substrate heated to a predetermined temperature. An atomic layer growth method for an aluminum compound, characterized in that a source gas is supplied alternately. [Effect] According to the present invention, since aluminum aluminum hydride is used as a source gas of aluminum, a self-stop function can be realized in the atomic layer growth of aluminum. Therefore,
By alternately supplying the source gas to the substrate, a thin film of an aluminum compound can be formed in atomic layer units.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic layer growth method, and more specifically, aluminum for forming a thin film in atomic layer units by alternately supplying raw materials of respective elements constituting a compound crystal to a substrate. A method for growing a compound atomic layer.

[0002]

2. Description of the Related Art A method of forming a thin film in atomic layer units by alternately supplying raw materials of respective elements constituting a compound crystal to a substrate is called an atomic layer growth method. At that time, it is necessary that only one layer or n layer of each element is adsorbed on the surface during the raw material supply pulse, and the extra raw material does not contribute to the growth. This is called growth self-termination.

In atomic layer growth, the film thickness can be accurately controlled by the number of raw material supply cycles as long as it has a self-stopping effect on growth, and does not depend on the growth temperature, the raw material flow rate, and the raw material supply time. Therefore, a film having excellent film thickness controllability and in-plane uniformity can be formed. In addition, lateral growth on a substrate having a complicated structure is possible. Furthermore, since it is a growth method utilizing surface reaction, it is suitable for selective growth. Due to these characteristics, the atomic layer growth method is very effective in forming ultra-thin films and ultra-fine structures.

For example, by forming a quantum wire structure or a quantum box structure, it can be expected that mobility will be increased as an electrical characteristic and efficiency of a semiconductor laser will be improved and threshold value will be reduced as an optical characteristic.

Before the atomic layer growth of a compound containing aluminum, first, the atomic layer growth of another compound will be sequentially described. First, in the atomic layer growth of a II-VI group compound such as ZnS, since the vapor pressures of both Zn and S are high, extra atoms other than one atomic layer chemically adsorbed on the substrate surface do not adhere. Therefore, atomic layer growth can be realized relatively easily.

Next, in the atomic layer growth of GaAs,
Since As has a high vapor pressure, it has a self-terminating function as an atomic property like ZnS. However, since Ga has a low vapor pressure, excess atoms physically adsorbed beyond one atomic layer can no longer be desorbed and contribute to growth. Therefore, the property of the compound raw material containing Ga is used instead of the property of Ga atom. That is, when trimethylgallium (hereinafter, referred to as TMGa) is used as a Ga raw material, TMG is formed on the As atomic layer under appropriate conditions.
While a is decomposed, it is not decomposed on the Ga atomic layer, and Ga is self-stopped on the atomic layer.

However, in the case of atomic layer growth of AlAs, which is a compound containing aluminum, when trimethylaluminum (hereinafter referred to as TMAl) is used as an Al raw material, the conditions under which Al self stops in one atomic layer or two atomic layers are , Extremely narrow.

[0008]

[Problems to be Solved by the Invention] By the atomic layer growth method,
In order to control the film thickness by the number of supply cycles of raw material gas,
It is important that the growth self-stops within a relatively wide range with respect to the growth conditions (growth temperature, raw material flow rate, raw material supply time). When the conditions for obtaining atomic layer growth are narrow,
Although the growth conditions must be strictly controlled in terms of time and space, this is almost the same as strictly controlling the film thickness by a general growth method (eg, metalorganic vapor phase epitaxy). The growth method has few advantages.

Therefore, also in the atomic layer growth of a compound containing aluminum, it is required to broaden the conditions under which the growth is self-stopped. The object of the present invention is that Al is 1
An object of the present invention is to provide an atomic layer growth method that can take a wide range of conditions for self-stopping in an atomic layer or two atomic layers.

[0010]

That is, the present invention relates to an atomic layer growth method for growing a thin film of a compound containing aluminum in atomic layer units, and alkyl hydride aluminum such as dimethyl hydrido aluminum AlR.
_m H _n (R is an alkyl group, m and n are 1 or 2 and the sum thereof is 3) is used as an aluminum raw material, and is alternately supplied to a substrate heated to a predetermined temperature with a counterpart raw material gas. Atomic layer growth method of aluminum compound.

The aluminum compound referred to here is AlA.
Examples include s, AlP, AlN, Al ₂ O _{3 and the} like. Al
In the case of As, the partner material gas is AsH ₃ , in the case of AlP, the partner material gas is PH ₃ , and in the case of AlN, the partner material gas is NH ₃ . In the case of Al ₂ O ₃ , H ₂ O
CH ₃ OH and CH ₃ OH are selected as the source gas.

FIG. 1 is an explanatory view showing an example of an apparatus for carrying out the atomic layer growth method of the present invention. In the figure, a support 2 is placed in a reaction container 1, and a substrate 3 is placed thereon.
In the illustrated example, a heating device 4 is provided on the outer periphery of the reaction container 1 to heat the substrate 3 to a predetermined temperature. From the left side of the reaction vessel 1, three types of carrier gas, alkylaluminum hydride and a partner material gas are introduced. The three kinds of gas are introduced into the reaction vessel 1 intermittently, that is, in a pulsed manner, by the valves 6 attached to the respective introduction pipes 5.

This state is shown in FIG. 2, which is a timing chart for one cycle. According to FIG. 2, the carrier gas is hydrogen gas, which prevents the two raw materials from being mixed,
It is introduced into the gap where both are introduced. In this way, by operating the valve 6, the raw material gas is introduced in a pulsed manner.

The alkylaluminum hydride used as the aluminum raw material is a substance in which 1 or 2 hydrogen and 2 or 1 alkyl group are bonded to aluminum, such as dimethyl hydride aluminum hydride.

When the vapor pressure is low and the atoms do not have a self-terminating action like gallium and aluminum, the self-terminating action of the compound raw material is utilized. For that purpose, it is necessary that the raw material is difficult to decompose in the gas phase.

As a gallium raw material, TMGa (trimethylgallium) satisfies these conditions. on the other hand,
Regarding the aluminum raw material, it is satisfied that TMAl is difficult to decompose in the gas phase, but since it is difficult to react even on the surface, an atomic layer of aluminum is not deposited as shown in FIG. It is considered that this can be realized only under the condition that the atomic layer growth is narrow. However, in order to increase the reactivity, triethyl aluminum (hereinafter referred to as TEAl)
When used, the decomposition takes place in the gas phase, and as shown in FIG.

Therefore, when alkylaluminum hydride is used, the conditions that it is difficult to decompose in the gas phase and that it is easy to react on the surface are satisfied, so that self-termination of growth can be realized under a wide range of growth conditions (see FIG. 5). Therefore, atomic layer growth of various Al compounds can be realized in combination with a partner element (As, P, N, O) having a high vapor pressure.

[0018]

In the present invention, since aluminum aluminum hydride is used as the source gas of aluminum, a self-stop function can be realized in the atomic layer growth of aluminum. Therefore, by alternately supplying the source gas to the substrate, it becomes possible to form a thin film of an aluminum compound in atomic layer units.

[0019]

EXAMPLE An example of the present invention was carried out using the growth apparatus shown in FIG. Atomic layer growth of AlAs was performed on a heated GaAs substrate by alternately supplying dimethylhydridoaluminum (hereinafter referred to as DMAlH) and AsH ₃ as raw materials. The substrate used is GaAs (100)
And H ₂ was used as a carrier gas. The growth pressure is 10 Torr, the total gas flow rate is 5 slm, and the gas flow rate on the substrate is 88 m / s. DMAlH is supplied by DMA
It was carried out by bubbling H ₂ in a mixture of 1H and TMAl, and AsH ₃ was introduced from a cylinder. As a typical growth condition, the raw material supply sequence is <H ₂
Only, DMAlH, H ₂ only, AsH ₃ > in order of <3 seconds, 4 seconds or 10 seconds, 3 seconds, 30 seconds>, respectively, and D
MAlH flow rate is 0.03 SCCM, AsH ₃ flow rate is 40 SCC
The growth temperature was 325 ° C. and the growth temperature was 425 ° C.

As described above, the atomic layer growth appears as a flat region in which the growth rate does not depend on the growth temperature, the raw material flow rate, and the raw material supply time. FIG. 6 shows the temperature dependence of the growth rate per raw material supply cycle. The figure shows stable flat regions at one and two molecular layers. The DMAlH supply time dependency also shows the existence of a self-stop function of growth in one molecular layer / cycle and two molecular layers / cycle, as shown in FIG. Furthermore, according to FIG. 8, DMAlH when bubbling in DMAlH
Also in the flow rate dependence, one molecular layer / period and two
It is recognized that the molecule layer / cycle has a self-stop function.

[0021]

[Effect] According to the present invention, since aluminum aluminum hydride is used as a source gas of aluminum, a self-stop function can be realized in the atomic layer growth of aluminum. Therefore,
By alternately supplying the source gas to the substrate, a thin film of an aluminum compound can be formed in atomic layer units. The aluminum compound produced by the present invention is capable of forming a quantum wire structure or a quantum box structure. As a result, mobility can be expected to increase as an electrical characteristic, and semiconductor laser efficiency can be improved and a threshold value can be reduced as an optical characteristic.

[0022]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus for performing an atomic layer growth method of the present invention.

FIG. 2 is an explanatory diagram showing an example of a gas introduction timing in the aluminum compound atomic layer growth method of the present invention.

FIG. 3 is an explanatory diagram showing a situation in which atomic layer growth is not achieved when trimethylaluminum is used.

FIG. 4 is an explanatory diagram showing a situation in which atomic layer growth is not achieved when triethylaluminum is used.

FIG. 5 is an explanatory view showing a state of atomic layer growth of the present invention using dimethyl hydride aluminum.

FIG. 6 is a graph showing the growth temperature dependence of atomic layer growth of the aluminum compound of the present invention.

FIG. 7 is a graph showing the dependence of atomic layer growth of the aluminum compound of the present invention on the aluminum source supply time.

FIG. 8 is a graph showing the dependence of atomic layer growth of the aluminum compound of the present invention on the flow rate of an aluminum raw material.

[Explanation of symbols]

 1 Reaction Container 2 Support 3 Substrate 4 Heating Device 5 Introducing Pipe 6 Valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Kano 5-7-11 Chuorinkan, Yamato-shi, Kanagawa

Claims (1)

[Claims] 1. An atomic layer growth method for growing a thin film of a compound containing aluminum in atomic layer units, wherein an alkyl aluminum hydride such as dimethyl hydride aluminum AlR _m H _n (R is an alkyl group and m and n are 1). Alternatively, the sum of 2) and 3) is used as an aluminum raw material, and the aluminum raw material is supplied alternately onto the substrate heated to a predetermined temperature, and the atomic layer growth method of the aluminum compound.