JPH0864531A - Atomic site epitaxially selecting method - Google Patents

Abstract

PURPOSE: To select atomic adsorption site on a substrate for controlling a two-dimensional array of atoms epitaxially growing on a substrate. CONSTITUTION: A vacuum vessel 1 is exhausted in ultra high vacuum state by a vacuum exhauster 2. A substrate as a specimen 3 is arranged on a specimen base 4 capable of maintaining the temperature at an arbitrary value from 150K to 2000K. The specimen base 4 can change the incoming angle of X ray and visible ray with the substrate. Next, the specimen 3 is irradiated with the X ray and the visible ray respectively through a beryllium-made window 5 and a quartz-made window 6. Next, hydrogen atoms and the other atoms deposited on the substrate surface are fed to a vacuum vessel 1. In such a constitution, the kinds and quality of desorbed atoms from the substrate surface are measured by a quardruple mass spectrometer 9 so that a monatomic layer of atoms on the substrate surface may be observed by a scanning tunneling microscope 10.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for controlling the atomic arrangement of a monoatomic layer thin film. Its fields of application are observation of segregation on the alloy surface, observation of the growth process of alloy crystals at the atomic level, observation of atomic diffusion at grain boundaries, underlayer for processing at the atomic level of the material surface, quantum wires, Examples include low-dimensional quantum systems such as quantum dots.

[0002]

2. Description of the Related Art The conventional atomic layer epitaxy method is suitable for depositing one atomic layer on a substrate, but is not suitable for controlling the arrangement of elements in the atomic layer plane. For atomic layer epitaxy, see, for example:
Extended Abstracts of the Sixty International International Conference on Solid State Devices and Materials p. 647 (1984) (T.Suntola: Extended A
bstracts of the 16th International Conf. on Solid S
tate Devices and Materials, p.647 (1984 ) ( Te _Lee -
Soundtrack: Summary of 16th International Conference on Solid State Materials, page 6
47, 1984)).

According to this, for example, zinc atoms are not attached to the atomic layer of zinc but tellurium atoms are attached thereto, and zinc atoms are attached to the atomic layer of tellurium but not tellurium atoms. By utilizing this property, an epitaxially grown film in which one atomic layer of zinc and one atomic layer of tellurium are alternately deposited can be obtained. This method has an advantage that an epitaxial film in which atomic layers are alternately stacked can be produced with good reproducibility.

However, in this method, the atoms are uniformly deposited on the surface, so that there is a limitation in that the deposition position of the atoms cannot be controlled.

[0005]

An object of the present invention is to select atomic adsorption sites on a substrate in order to control the two-dimensional arrangement of atoms epitaxially grown on the substrate.

[0006]

In order to solve the above-mentioned problems, blocking of adsorption sites by hydrogen atoms and desorption of adsorbed atoms by excitation of underlying atoms are utilized.

[0007]

Function: Hydrogen atoms are known to be adsorbed on the surface of clean crystals. The number of adsorbed hydrogen atoms per base atom may be one or plural. By adjusting the total number of adsorbed hydrogen atoms, it is possible to form a hydrogen two-dimensional structure of about one atomic layer on the surface of the underlying crystal. In the present invention, the hydrogen atoms adsorbed on a specific site are selectively removed, and the target atom is deposited on the empty site created by this. The hydrogen atoms adsorbed on the surface of the substrate serve to prevent the target atoms from directly binding to the atoms on the surface of the substrate, but ultimately these hydrogen atoms can be removed.

The selective removal of hydrogen atoms is possible by two methods: indirect removal by excitation of the underlying atom and direct removal by excitation of the hydrogen bond itself. Hydrogen desorption by surface heating is not suitable for the present invention because it has no site selectivity.

When the core level of an atom is excited, the atomic bond changes due to a change in the electronic state of the atom and the generation of secondary electrons, causing the desorption of adsorbed atoms. The excited level is at least one of K shell, L shell, and M shell. The hydrogen bond is also broken by the excitation of the hydrogen bond itself. Excitation of atomic core levels and excitation of hydrogen bonds are possible by irradiation with monochromatic X-rays with variable energy and visible light.
Although the energy of the core level takes discontinuous values, it varies depending on the element, so that selective excitation of a specific element is possible. On the other hand, the hydrogen bond energy also takes different values depending on the bond pair, so that selective excitation is possible. By utilizing the polarization characteristics of X-rays and visible light, that is, by adjusting the polarization vector in the direction of hydrogen bonds, the efficiency of hydrogen removal and site selectivity are increased.

By utilizing the above properties, site selective epitaxy of atoms becomes possible. Even when hydrogen atoms are not used, it is possible to obtain atomic site selectivity by continuously exciting the underlying atoms. Even in this case, it is possible to break the bond with the atom of the specific element.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the basic configuration of an apparatus used for implementing the present invention
Shown in The inside of the vacuum container 1 is 2 × 1 using the vacuum exhaust device 2.
Can exhaust up to / 10 ⁸ Pa. The substrate (sample) 3 is placed on the sample table 4. The temperature of the sample table 4 can be controlled and maintained at any value between 150K and 2000K. Furthermore, a rotation mechanism is attached so that the incident angles of X-ray and visible light can be changed. The X-rays pass through the window 5 made of beryllium and the visible light passes through the window 6 made of quartz to irradiate the sample. Hydrogen atoms are supplied from a pipe 7 communicating with a hydrogen cylinder (not shown). Atoms to be deposited on the surface of the substrate are supplied from a pipe 8 communicating with an atom source (not shown). A quadrupole mass spectrometer 9 is provided to measure the type and number of desorbed atoms from the substrate surface. In order to observe the atomic arrangement of one atomic layer on the surface of the substrate, a scanning tunneling microscope 10
Is equipped with.

FIG. 2 shows how to make the substrate used in the embodiment of the present invention. From silicon single crystal Si of appropriate thickness (1
A thin plate (shown by Si (100) in the figure) having the surface 00 as the surface is cut out. On this surface, n layers of germanium Ge layers and silicon Si layers having a thickness of 100 Å are alternately laminated. Then, this laminated portion is formed at an angle of 30 ° with respect to the surface, that is, from the <100> direction to the <001> direction by
Polishing was performed in a tilted direction to prepare a substrate in which germanium Ge layers and silicon Si layers are alternately arranged. The surface was treated with hydrofluoric acid and then placed in the vacuum container 1. 1/10
^The substrate was heated to 1100 K under a vacuum of ⁸ Pascal to remove oxides, impurities and the like on the substrate surface to prepare a clean surface.

FIG. 3A shows a sectional view of the substrate thus obtained. That is, the layer of germanium Ge and the layer of silicon Si are arranged at 115.5Å intervals with an inclination of 60 ° with respect to the surface.

3 (b) to 3 (e) show the basic procedure for carrying out the atomic site selective epitaxy of the embodiment of the present invention using this substrate.

As shown in FIG. 3B, after returning the substrate temperature to the ambient temperature, hydrogen atoms were introduced to form an adsorption layer of about one atomic layer.

Then, as shown in FIG. 3C, this substrate was irradiated with a 2.3 keV monochromatic X-ray capable of exciting only elemental Si. The X-rays are linearly polarized in a direction substantially perpendicular to the substrate. The dose of X-rays was 10 ³⁰ photons / cm ² / sec. Therefore, hydrogen that was uniformly on the substrate was left only in the element Ge portion.

Next, as shown in FIG. 3D, germanium atoms corresponding to one atomic layer were generated by an atomic source, introduced through a pipe 8 and deposited on the substrate.

Next, as shown in FIG. 3 (e), 1/1
By heating the substrate up to 800K under vacuum at 0 ⁸ Pascals, to remove the hydrogen atoms adsorbed on the germanium atoms. At this time, the germanium atoms deposited on the hydrogen atoms are also removed together with the hydrogen atoms,
Confirmed by quadrupole mass spectrometer 9. On the other hand, desorption of silicon atoms was not observed.

When the atomic arrangement on the surface of the substrate thus obtained was observed using the scanning tunneling microscope 10, the film thickness was about one atomic layer and the width was about 115.5Å.
The atomic arrangement of was formed at intervals of about 115.5Å.

Next, another embodiment will be described with reference to FIG. The substrate used is made by the same method.

As shown in FIG. 4A, the substrate has 2.3 ke
Germanium atom Ge was deposited at a rate of 0.02Å / s while irradiating a monochromatic X-ray of V. At this time, the X-ray was linearly polarized in a direction substantially perpendicular to the substrate. The dose of X-rays was 10 ³² photons / cm ² / sec. 60
The deposition was stopped after 2 seconds. The atomic arrangement on the surface of the substrate was observed using a scanning tunneling microscope. as a result,
As shown in FIG. 4B, it was confirmed that an atomic arrangement having a film thickness of about 1 atomic layer and a width of about 115.5Å was formed at intervals of about 115.5Å.

In this embodiment, it was possible to deposit germanium atoms only on the silicon atoms of the substrate in which the silicon and germanium atoms are periodically arranged.

[0023]

According to the present invention, selective epitaxy corresponding to a plurality of elements is possible.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the configuration of an atomic site selective epitaxy fabrication apparatus for carrying out the method of the present invention.

FIG. 2 is a diagram illustrating a method for manufacturing a substrate according to an example of the present invention.

FIG. 3 is a view for explaining the procedure of one embodiment of the present invention.

FIG. 4 is a diagram illustrating a procedure of another embodiment of the present invention.

[Explanation of symbols]

1: Vacuum container 1, 2: Vacuum exhaust device, 3: Sample substrate, 4: Sample stand, 5: Beryllium window 5, 6: Quartz window 6, 7: Pipe connecting to hydrogen cylinder, 8: Atom Pipe communicating with the source, 9: quadrupole mass spectrometer, 10: scanning tunneling microscope.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Wada 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Stock Company Hitachi Research Laboratory (72) Inventor Yoshihiko Yamamoto 2520 Amanuma, Hanuma-cho, Hiki-gun Saitama Prefecture Stock Association Hitachi Research Laboratory

Claims (2)

[Claims] 1. A surface defined by an arbitrary Miller index of a single crystal material composed of a plurality of elements, a clean surface deviated by an arbitrary angle from the surface, or a composition modulated at an arbitrary cycle. After uniformly adsorbing about one atomic layer of hydrogen on the existing crystal surface, it is possible to excite at least one of the K, L, and M levels of the element contained in the underlying crystal. By irradiating either or both of X-rays of energy or light having a binding energy of the underlying atom and the hydrogen atom or more, the hydrogen atom bonded to or adsorbed to the atom of a specific element is selectively selected. After the removal, the target atom is deposited on the empty site generated by the removal of the hydrogen atom by about one atomic layer, and the atomic site selective epitaxy method. 2. The composition is modulated at a surface defined by an arbitrary Miller index of a single crystal material composed of a plurality of elements, a surface deviated by an arbitrary angle from the surface, or at an arbitrary cycle. When forming an atomic arrangement of atoms of a target element on the crystal surface with a thickness of about one atomic layer, at least one of K, L, and M levels of the element contained in the underlying crystal is formed. Irradiates the surface with X-rays having an energy capable of exciting X-rays, and prevents new atoms from being newly deposited on the atoms of the specific element exposed on the outermost surface of the X-ray absorbing single crystal material. Atomic site selective epitaxy method characterized by the above.