JPH0697071A - Method of forming quantum line and quantum box by the growth of atomic layer - Google Patents

Abstract

PURPOSE:To provide a method of forming a quantum box and quantum line by the growth of atomic layer being capable of forming good-shaped quantum lines and quantum box, capable of making a greater difference in growth speed due to plane azimuth without the occurrence of abnormal growth and capable of improving shape controllability compared to the conventional one. CONSTITUTION:A recessed portion is formed by etching on a substrate 3, this substrate 3 is placed on a susceptor 2 in a vacuum container 1, and this substrate 3 is heated to a predetermined temperature by a lamp 6. And valves 7 are opened and closed for alternately supplying raw materials, and the quantum fine line and quantum box are formed inside the recessed portion of the substrate 3 by the growth of the atomic layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming quantum wires and quantum boxes constituting a semiconductor device or the like by selectively performing atomic layer growth.

[0002]

2. Description of the Related Art It is known that quantum effects due to the electrons confined inside appear in a fine structure so-called quantum wire and quantum box having a size (about several tens nm) less than the wavelength of electrons in a semiconductor crystal. Therefore, development of semiconductor devices and the like utilizing such a phenomenon is under way.

As a method of forming such quantum wires and quantum boxes, there is known a method using MOVPE (Metal Organic Chemical Vapor Deposition) in which crystals are grown by using the plane orientation dependence of the growth rate. In this method, by forming a V-shaped concave portion on the substrate by substrate processing such as chemical etching, a plurality of plane orientations are created on the substrate surface before crystal growth, and then a desired surface is formed by MOVPE growth. A thin film is selectively formed. In the MOVPE growth, for example, G
When forming an aAs film, a source gas containing Ga and a source gas containing As are simultaneously supplied to cause a reaction in the gas phase.

[0004]

However, in the above-mentioned conventional MOVPE method, the difference in the growth rate with respect to the plane orientation cannot be increased so much that the ideal quantum wires and quantum boxes are formed. There is a problem that it is difficult to control. Also, MOVP
In the method according to E, since the unreacted source gas flows from the non-crystal growth site to the crystal growth site, there is a problem that abnormal growth is likely to occur especially at the boundary between these sites and its control is difficult.

The present invention has been made in response to such a conventional situation, and it is possible to increase the difference in the growth rate depending on the plane orientation and to prevent the occurrence of abnormal growth. An object of the present invention is to provide a method for forming a quantum wire and a quantum box by atomic layer growth that can be improved and can form a quantum wire and a quantum box having a good shape.

[0006]

That is, a method of forming a quantum wire and a quantum box by atomic layer growth according to the present invention is to form a thin film selectively on a crystal plane of a substrate having a plane orientation, and to form a quantum wire and a quantum box. In forming the film, at least two kinds of raw material gases each containing different raw material forming a thin film are alternately supplied at a predetermined time interval, and the growth temperature is selectively changed only on a desired crystal plane to form an atomic layer. It is characterized by setting a temperature at which the growth is performed and selectively forming a thin film by atomic layer growth only on a desired crystal plane.

[0007]

For example, when forming a GaAs film, the present inventors alternately supply a source gas containing Ga and a source gas containing As to form a thin film on an atomic layer basis (ALE). We have been conducting research on technology related to), and as a result, we have obtained the following findings.

That is, in atomic layer growth, there is a plane orientation dependence of atom adsorption (or desorption after adsorption) due to the difference in the number of chemical bonds depending on the plane orientation. The difference in the growth rate with respect to the orientation can be increased, and the plane orientation selective growth of the crystal becomes possible.

Here, the graph of FIG. 2 in which the vertical axis represents the crystal growth rate and the horizontal axis represents the growth temperature shows the plane orientation dependence of the growth rate with respect to the growth temperature in GaAs-ALE growth. As shown in the figure, temperature regions 530 to 570 in which atomic layer growth is realized on the GaAs (100) surface.
At a temperature of 560 ° C. or higher, the growth rates of the (111) A face and the (110) face become zero.

Therefore, in the method of the present invention, atomic layer growth is performed at a growth temperature at which atomic layer growth is selectively performed, for example, at 560 ° C. or higher in the case of a GaAs film, and a desired crystal plane, for example, (100). A thin film is selectively formed on the surface, thereby forming a quantum wire and a quantum box.

In the method of the present invention, if not only the growth temperature but also the time interval between the supply of the source gas and the supply of the source gas is lengthened, desorption after atom adsorption progresses during this time, and the growth rate with respect to the plane orientation is The difference can be large.

In atomic layer growth, for example, if a source gas containing Ga and a source gas containing As are alternately supplied, a thin film of only one atomic layer is formed per one source supply cycle, so that unreacted. Even if the above source gas is excessively supplied to the thin film formation site, abnormal growth does not occur. Therefore, MOV
With the method using PE, it is possible to form quantum wires and quantum boxes by forming a film in a shape whose shape is difficult to control due to abnormal growth, for example, in a rectangular recess.

[0013]

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

FIG. 1 shows the structure of the apparatus used in this embodiment. In FIG. 1, reference numeral 1 indicates a vacuum container having a double tube structure. A carbon susceptor 2 is provided in the vacuum container 1, and a substrate 3 is provided on the susceptor 2.
Is mounted and the substrate 3 can be heated to a predetermined temperature from the back surface side of the susceptor 2 by a lamp 4 provided outside the vacuum container 1.

A raw material gas supply pipe 5 for supplying a raw material gas from a predetermined raw material gas supply source (not shown) is connected to one end of the vacuum container 1, and an exhaust pipe 6 is connected near the other end of the vacuum container 1. And these raw material gas supply pipes 5
Further, the exhaust pipe 6 is configured to allow a desired raw material gas to flow in the vacuum container 1. A valve 7 is inserted in each source gas supply pipe 5 so that the source gas can be switched at a desired timing.

In this embodiment, as shown in FIG. 3, a cross section V is formed on the substrate (GaAs substrate) 3 by chemical etching in advance.
A letter-shaped concave portion is formed, a (111) A surface (inclined surface in the figure) is exposed on the substrate surface, the substrate 3 is placed on the susceptor 2 in the vacuum container 1, and the substrate 6 is moved to 560 by the lamp 6. The valve 7 is opened and closed while heating to ℃, and the AlGaAs film and the GaAs are formed in the recess of the substrate 3 by atomic layer growth as follows.
The films were alternately formed to form a quantum wire structure.

The source gas of Al is DMAH.
(Dimethyl aluminum hydride), Ga source gas is T
The source gas of MG (trimethylgallium) and As is AsH.
₃ , and H ₂ gas was used as a carrier gas. As shown in FIG. 4, each source gas is supplied by DMAH and T
The valve 7 was opened and closed so that the MG supply time was 2 seconds, the AsH ₃ supply time was 1 second, and the interval between the gas supply was 1 second. The gas supply rate at this time is 10 ^-7 mol / cycle in the case of DMAH and TMG,
In the case of AsH ₃ , it is 10 ⁻⁵ mol / cycle.

Substrate 3 thus obtained by atomic layer growth
When observed with an electron microscope, as shown in FIG.
The (100) plane could be deposited with high selectivity, and a quantum wire structure could be obtained.

In the above embodiment, for example, if the time interval between the source gas supply is increased,
During this period, desorption after atom adsorption progresses, and the difference in growth rate with respect to the plane orientation can be further increased.

Further, in the above embodiment, the quantum wire structure was formed in the recess having a V-shaped cross section, but as shown in FIG. 6, the quantum wire structure may be formed in the recess having a rectangular cross section. In this case, only a groove having a width of about 50 nm can be formed by, for example, electron beam lithography, so first, a rectangular groove 21 having a width of about 50 nm is formed on the substrate 20 by electron beam lithography or the like (a).

Next, at a relatively low temperature (about 530 ° C.), Al is mainly grown on the lateral (110) plane by atomic layer growth.
A GaAs film 22 or the like is formed to narrow the width of the groove 21 to about 10 nm which is a quantum wire (b).

Thereafter, similarly to the above-mentioned embodiment, the quantum wire structure can be formed by selectively forming the GaAs film 23, the AlGaAs film 22 and the like on the (100) plane at a high temperature (about 560 ° C.). (C).

In this way, the quantum box structure can be formed in the well-shaped recess having a rectangular cross section. When forming a quantum wire or the like in such a rectangular groove,
In the conventional method using MOVPE, abnormal growth occurs, and it is difficult to control the shape.

[0024]

As described above, according to the method of forming a quantum wire and a quantum box by atomic layer growth of the present invention, it is possible to increase the difference in growth rate depending on the plane orientation and to prevent abnormal growth. In addition, the shape controllability can be improved as compared with the related art, and a quantum wire and a quantum box having a good shape can be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram showing the plane orientation dependence of the growth rate with respect to the growth temperature.

FIG. 3 is an enlarged view showing a state of a substrate surface.

FIG. 4 is a diagram for explaining a timing of supplying a raw material gas.

FIG. 5 is a diagram schematically showing the result of atomic layer growth in Examples.

FIG. 6 is a diagram for explaining a procedure for forming a quantum wire in a recess having a rectangular cross section.

[Explanation of symbols]

 1 vacuum container 2 susceptor 3 substrate 4 lamp 5 raw material gas supply pipe 6 exhaust pipe 7 valve

Claims (3)

[Claims] 1. When selectively forming a thin film on a crystal plane of a substrate having a plane orientation to form a quantum wire and a quantum box, at least two kinds of raw material gases containing different raw materials constituting each thin film are used. While alternately supplying at a predetermined time interval, the growth temperature is set to a temperature at which atomic layer growth is selectively performed only on a desired crystal plane, and the atomic layer growth is selectively performed on only the desired crystal plane. A method for forming a quantum wire and a quantum box by atomic layer growth, which comprises forming a thin film. 2. The method of forming a quantum wire and a quantum box by atomic layer growth according to claim 1, wherein a recess having a substantially rectangular cross section is bored in the substrate to form a plane orientation, and thereafter, atoms are deposited in the recess. A method for forming a quantum wire and a quantum box by atomic layer growth, which comprises forming a thin film having a desired thickness by layer growth and setting an inner diameter of the recess to a desired size. 3. The method for forming a quantum wire and a quantum box by atomic layer growth according to claim 1, wherein the thin film is a GaAs film and an AlGaAs film. Forming method.