JPH02248034A - Epitaxy method - Google Patents

Abstract

PURPOSE:To enable a hetero-structure to be formed in a fine local region by a method wherein, after irradiating a substrate surface with the first element molecules cut of III, V group elements, a specified region of the surface is irradiated with electron beam and then the second molecules. CONSTITUTION:A GaAs substrate 13 is fixed on a substrate holder 12 in a highly vacuumized deposition chamber 10. Later, the substrate 13 is heated and irradiated with TEG(triethylgallium) molecules from a TEG molecular beam source 16 to make monomolecular layer chemically adsorb on the surface of the substrate 13. Next, the surface of the substrate 13 is irradiated with electron beam focussed from an electron beam source 15 for scanning and exposure. At this time, the chemically adsorbed molecules in the region irradiated with the electron beam are released. Next, when the substrate 13 is irradiated with TEI(triethylindium) molecules from a TEI molecular beam source 17, the monomolecular layer selectively having In atoms is chemically absorbed on the region wherefrom the chemically adsorbed layer is vanished by the irradiation with electron beam. Finally, the substrate 13 is irradiated with As molecules from an arsenic molecular beam source 14. Through these procedures, an epitaxial layer of InAs molecular layer in quantum size can be formed in a GaAs monomolecular layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an epitaxial growth method, and more particularly to an atomic layer epitaxial growth method for growing a thin film of compound semiconductor crystal using a molecular beam containing a material element.

[Prior art] The atomic layer epitaxial growth method involves alternately irradiating molecules containing material elements onto a semiconductor substrate held and heated in a vacuum.
This epitaxial growth method has excellent features such as the formation of a steep Peter's growth interface at the atomic level and the local formation of a film by irradiation with a light beam or the like.

An example of epitaxial growth of gallium arsenide using this growth method is Proceedings of the 49th Japan Society of Applied Physics Academic Conference Volume 1
, 4a-W=1. I), 199 days have been reported. In this conventional example, triethyl gallium (abbreviated as TE) is used as a group material.
G, molecular formula: (C2H5)3Ga), arsine (molecular formula: ASH3) is used as the V group material, these gases are alternately irradiated onto a gallium arsenide substrate heated and maintained at the growth temperature in a high vacuum, and argon laser light is applied. is irradiated to cause local epitaxial growth. In this conventional example, a linear pattern with a width of 0.1 mm made of gallium arsenide is formed in the area irradiated with the laser beam.

[Problems to be solved by the invention] However, since the area that can be formed locally is limited by the spot size of the laser beam, it is difficult to reduce the area to 11JIn or less, and it is difficult to form a heterointerface in the in-plane direction at the same time. There are problems such as not being able to do it. Therefore, it was not possible to form a good heterostructure in a minute local region of 10 nm or less where the quantum size effect becomes noticeable.

The present invention has been made in view of the conventional circumstances as described above, and it is an object of the present invention to provide an atomic layer epitaxial growth method capable of forming a good heterostructure in a minute local region of 10 nm or less.

[Means for Solving the Problems] The present invention performs epitaxial growth by alternately irradiating molecules containing Group I elements and molecules containing Group V elements onto a semiconductor substrate held and heated in vacuum, which serves as a molecular flow region. In the atomic layer epitaxial growth method, at least one of the step of irradiating molecules containing a group I element and the step of irradiating molecules containing a group V element comprises a step of irradiating a substrate surface with molecules containing a first element; The substrate surface is characterized by comprising the steps of irradiating a predetermined region of the surface with an electron beam, and irradiating the substrate surface with molecules containing a second element that is in the same group as the first element and is different in type. This is an epitaxial growth method.

[Function] In the atomic layer epitaxial growth method according to the present invention, the step of irradiating molecules containing group (I) and/or group V elements consists of the following three steps.

That is, the first step is a step in which the semiconductor substrate is irradiated with molecules containing element A, which is a group I or group V element, and is chemically adsorbed on the entire surface. The second step is to locally irradiate an electron beam to locally desorb the chemically adsorbed molecules. In the third step, the entire surface of the substrate is irradiated with a molecule containing an element B, which is the same group as the element A contained in the molecule and is different from the element, and the molecule is selectively applied to the region locally desorbed by the electron beam. This is a step in which molecules containing element B are chemically adsorbed.

As a result of the above steps, a chemisorption layer is obtained in which molecules containing element B are chemically adsorbed in the area where the electron beam was irradiated on the surface of the semiconductor substrate, and molecules containing element A are chemically adsorbed in the area where the electron beam was not irradiated. I can do it. By repeating the formation of chemisorption layers by the process consisting of the above three steps alternately for Group II and/or Group V, one
A heterostructure can be formed with a microscopic size of 0 nm or less.

Here, the acceleration voltage of the electron beam used in the second step needs to be set so that energy greater than the difference between the adsorption energy of the chemically adsorbed molecules and the thermal energy of the substrate temperature can be given to the electrons. This is because, in this second stage, the chemisorbed molecules are desorbed by providing the chemisorbed molecules with the energy required to desorb them from the electrons. However, this does not apply if the electron current can be increased to such an extent that multiple electrons participate in the desorption process.

Furthermore, the reason why molecules containing element B are selectively chemisorbed in the region locally desorbed by the electron beam in the third step is as follows. That is, after the second step, on the surface of the semiconductor substrate, there are chemically adsorbed molecules in the area where the electron beam was not irradiated, and there is no layer of chemically adsorbed molecules in the irradiated area.

After this, in the third step, when molecules containing element B are irradiated,
Certain regions of the molecular layer that have already been chemisorbed are inert to adsorption and thus prevent new adsorption. On the other hand, adsorption occurs in areas where there is no adsorption layer. As a result, molecules containing element B can be selectively chemically adsorbed only in the region where the surface of the semiconductor substrate is irradiated with the electron beam. However, it is necessary to select the temperature of the semiconductor substrate at a temperature at which single molecules of irradiated molecules are adsorbed.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of an atomic layer epitaxial growth chamber for explaining one embodiment of the present invention. In this example, the group III material is triethyl gallium (molecular formula: (02H5)3G
a) and triethylindium (abbreviated as TEI, molecular formula: (C2Hs)3I n ), arsine is used as the V group material, and these gases are heated and maintained at the growth temperature in a high vacuum on a potassium arsenide substrate as follows. It was irradiated during the process to grow epitaxially.

The growth chamber 10 holds a GaAs substrate 13, and also includes a substrate holder 12 that heats the substrate to the growth temperature, and an arsenic molecular beam source 14.
, an electron beam source 15, a TEG molecular beam source 16, and a TE molecular beam source 17, which are evacuated to a high vacuum by a vacuum pump 11. The arsenic molecular beam source 14 is equipped with a heater (not shown) for thermally decomposing arsine gas, and the arsine gas is heated to 950'C and thermally decomposed by this heater to form arsenic molecules (molecular formula: AS2). Become. Further, the electron beam source 15 includes an electron gun, an accelerating electrode, and a focusing lens therein, and focuses the electron beam to a required spatial resolution or less.

When growing a heteroepitaxial layer having a medium-sized InAs quantum box in a medium-thin GaAS single crystal, the following procedure was performed. First, a GaAs substrate 13 whose surface has been cleaned by chemical etching and degassing treatment is placed on the substrate holder 1.
2 and evacuated to high vacuum using the vacuum pump 11. Next, heating of the GaAs substrate 13 is started, and the substrate temperature reaches 40°C.
When the temperature exceeds 0°C, turn the arsine gas into an arsenic molecular beam source 14.
The oxide layer on the substrate surface was removed by introducing an arsenic beam into the substrate and irradiating it with an arsenic beam.

After the substrate temperature reached the growth temperature of 450'C, TEG gas was introduced into the TEG molecular beam source 16 to grow a buffer layer of about 100 nm.

Subsequently, the substrate temperature was maintained at 350'G, and a heteroepitaxial layer was grown in the following manner. That is, first, the introduction of arsine gas to the arsenic molecular beam source 14 is stopped, and TEG molecules are irradiated from the TEG molecular beam source 16 to chemically adsorb one molecular layer on the surface of the GaAs substrate 13. At this time, excessive TE
Since G molecules are not adsorbed on the surface of the chemisorption layer, chemical adsorption of one molecular layer is automatically achieved. Second, a focused electron beam from the electron beam source 15 was irradiated onto the surface of the GaAs substrate 13 to scan and draw a 5 nm square shape. At this time, molecules chemically adsorbed in the region irradiated with the electron beam are desorbed. Third, when TEI molecules are irradiated from the TEI molecular beam source 17, one molecular layer containing In atoms is selectively chemisorbed in the region where the chemisorption layer has disappeared due to the electron beam irradiation. At this time, the TEI molecule is formed by the initially formed Ga
Since it does not adsorb to the surface of the chemisorption layer containing atoms, selectivity is automatically achieved. Fourth, arsenic molecules were irradiated from the arsenic molecular beam source 14.

Through the above first to fourth steps, a heteroepitaxial layer having one quantum-sized InAS molecular layer in a three-layer GaA molecular layer was formed. By repeating this process, I
We were able to grow a heteroepitaxial layer with nAs quantum boxes.

In the above embodiments, the growth method of the present invention was used to form the group Ⅰ atomic layer, but the growth method of the present invention can also be used to form a pattern in the formation of the group V atomic layer.

In the above examples, triethyl gallium and triethylindium were used as material compounds, but organometallic compounds having other organic groups such as trimethyl gallium may also be used, and diethyl, which is a material having a chloride group and forming a molecular layer, may also be used. Gallium chloride (molecular formula: (C2H5
)2 GaCff1 ), diethyl indium chloride (molecular formula; % formula % toride, or gallium chloride (molecular formula; GaC1
, indium chloride (molecular formula: InCf>, etc.) may be used.

In the above examples, alkyl compounds of gallium and indium were used as material compounds, or aluminum, phosphorus,
Other constituent elements of compound semiconductors, such as arsenic, antimony, zinc, and beryllium, and organic compounds of impurities may also be used.

[Effects of the Invention] As explained above, according to the epitaxial growth method of the present invention, a petrostructure can be formed in a minute local region having a size about the diameter of an electron beam in the in-plane direction and one atomic layer in the layer thickness direction. It is possible to form a heteroepitaxial layer having the following properties.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an example of an atomic layer epitaxial growth chamber used in the method of the present invention.

Claims (1)

[Claims] (1) In an atomic layer epitaxial growth method in which molecules containing group III elements and molecules containing group V elements are epitaxially grown by alternately irradiating molecules containing group III elements and molecules containing group V elements onto a semiconductor substrate held and heated in vacuum, which serves as a molecular flow region, group III elements are used. At least one of the step of irradiating molecules containing a group V element and the step of irradiating molecules containing a group V element includes a step of irradiating a substrate surface with molecules containing a first element, and irradiating a predetermined region of the substrate surface with an electron beam. An epitaxial growth method comprising the steps of: irradiating a substrate surface with a molecule containing a second element that is in the same group as the first element and of a different type.