Microprobe Reflection High-energy Electron Research Articles

Low-temperature SOI (Si-on-insulator) formation by lateral solid-phase epitaxy

Low-temperature (550–600 °C) formation of a Si-on-insulator structure by a solid-phase process is investigated. A microprobe (μ) reflection high-energy electron diffraction observation reveals that oriented crystal growth propagates from the seeding area in solid-phase epitaxy (SPE). The effects of random nucleation, epitaxial alignment, and local doping on lateral (L)-SPE are examined. As a result, a relatively large L-SPE area, 14 μm from the seeding area, is achieved on insulating regions. Crystal quality and electrical properties of L-SPE layers are examined using μ-Raman spectroscopy and field-effect transistor fabrication. A small stress field, 2.5×109 dyn/cm2, and high electron mobility, 720 cm2/V s, comparable to that of bulk Si are obtained.

マイクロプローブ反射電子回折法による表面研究

Si (111) surface topography changed during Si molecular beam epitaxial growth were observed by reflection electron microscope images using microprobe reflection high-energy electron diffraction (RHEED) . When RHEED intensity oscillations were observed at low substrate tempe-rature (350°C), it was found that the shape of atomic steps on the substrate was preserved during the growth and the surface topographies changed repeatedly with the period of the oscillations. When almost no oscillations were observed at higher substrate temperature (500°C), the shape of the atomic steps changed during the growth. These observations provide direct evidence that RHEED intensity oscillations occur as the result of layer-by-layer two-dimensional nucleation growth.

Observation of Si(111) surface topography changes during Si molecular beam epitaxial growth using microprobe reflection high-energy electron diffraction

Si(111) surface topography changes during Si molecular beam epitaxial growth were observed by reflection electron microscope images using microprobe reflection high-energy electron diffraction (RHEED). When RHEED intensity oscillations were observed at low substrate temperature (350 °C), it was found that the shape of atomic steps on the substrate was preserved during the growth and the surface topographies changed repeatedly with the period of the oscillations. When almost no oscillations were observed at higher substrate temperature (500 °C), the shape of the atomic steps changed during the growth. These observations provide direct evidence that RHEED intensity oscillations occur as the result of layer-by-layer two-dimensional nucleation growth.

Observation of Si(111) and gold-deposited Si(111) surfaces using micro-probe reflection high-energy electron diffraction

Observations of clean Si(111) and gold-deposited Si(111) surfaces have been performed using micro-probe reflection high-energy electron diffraction. It was found that many atomic steps on a Si(111) surface run in nearly the same direction, about 9° off the [1̄1̄2] direction. When gold was deposited on this surface at a substrate temperature of about 800°C, 5 × 1, diffuse √3 × √3 R30°, sharp √3 × √3 R30° structures and Au clusters appeared on the surface with continuation of the deposition. During the deposition process, it was found that one kind of Si(111) 5 × 1 Au domain grew selectively along these atomic steps and nearly covered the entire surface. A phenomenon of gold clusters moving during the deposition was also observed. These clusters all moved in nearly the same direction so as to climb the atomic steps.

Observation of Si(111) and gold-deposited Si(111) surfaces using micro-probe reflection high-energy electron diffraction

Observation of Si(111) and gold-deposited Si(111) surfaces using micro-probe reflection high-energy electron diffraction

Observation of Surface Micro-Structures by Micro-Probe Reflection High-Energy Electron Diffraction

A new micro-probe reflection high-energy electron diffraction technique has been developed for observing micro-structures on crystal surfaces. In this technique, an electron beam of diameter 20 nm at a beam current of 8 nA and a beam angular divergence of 2 mrad has been achieved by using a field emission gun, making it possible to obtain bright, sharp diffraction patterns from surface micro-areas. A diffraction spot on a fluorescent screen is focused on an apperture by an optical lens; and part of the intensity is used as a signal to produce a scanning electron microscope image. This image is very sensitive to changes in surface crystallographic orientation, and can show areas in which the orientation change is of the order of 0.1 mrad. When the technique was used to observe Si(111) surfaces and metal-deposited Si(111) surfaces, image contrasts caused by screw dislocations, atomic steps and domain structures on the surfaces were obtained.

Micro-Probe Reflection High-Energy Electron Diffraction Technique. III. Observation of Polycrystalline Silicon Film on Crystalline Silicon Substrate Irradiated by Continuous-Wave Ar+-Laser

A micro-probe reflection high-energy electron diffraction (micro-probe RHEED) technique has been used to observe polycrystalline Si film on crystalline Si substrate irradiated by continuous-wave Ar+-laser. Dependency of degree of crystallization on laser irradiation conditions has been examined in detail by making areas irradiated under various conditions on the same sample surface. Two kinds of crystalline states have been found on the irradiated areas. The degree of crystallization of one is nearly equal, and the other inferior, to that of crystalline Si substrate. As laser power decreases and laser scan speed increases, the latter kind of crystalline state becomes pre-dominant in the irradiated areas. These results show that the micro-probe RHEED technique is useful in studying crystal growth of materials whose surfaces can not be physically cleaned in order to maintain initial crystalline state.

Characterization of seeded-lateral epitaxial layer by microprobe reflection high-energy electron diffraction

The crystallinity and regrowth mechanism of a seeded-lateral epitaxial layer of Si on a SiO2 substrate is evaluated using a newly developed microprobe reflection high-energy electron diffraction method. Measurements with a spatial resolution of 0.1 μm reveal that the lateral seeding process actually occurs in the regrowth process and that the seeding area is indispensable to the process, though a seed length of less than 0.5 μm is required.

Micro-Probe Reflection High-Energy Electron Diffraction Technique. I. Determination of Crystallographic Orientations of Polycrystal-Silicon Surfaces

A micro-probe reflection high-energy electron diffraction (RHEED) apparatus including an electron gun with a probe size of 0.1 µm operated under ultrahigh vacuum, has been constructed. This makes it possible to obtain bright, sharp diffraction patterns from micro-areas of clean surfaces, and to take RHEED-microscope images of crystal surfaces. Using this apparatus, a technique for determining the crystallographic orientations of surface micro-areas within an accuracy of ±1° has been developed. This is done by analyzing Kikuchi patterns emitted at low angles, and spatial distributions having various crystallographic orientations are obtained by taking RHEED-microscope images. From the results of applying this technique to polycrystal-Silicon surfaces, it is found that it is very useful in determining the crystallographic orientations of surface micro-areas.

Micro-Probe Reflection High-Energy Electron Diffraction Technique. II. Observation of Aluminum Epitaxial Growth on a Polycrystal-Silicon Surface by Vacuum Evaporation

A micro-probe reflection high-energy electron diffraction (micro-probe RHEED) technique has been used to observe the epitaxial growth of Al at room temperature on a polycrystal-Si (poly-Si) surface. A new beam-scanning method has also been developed to remove the image-shortening effect caused by a small glancing angle of incidence. From the Auger electron intensities, diffraction patterns and RHEED microscope images of an Al-deposited poly-Si surface, it is found that an Al film several atomic layers thick with the Al lattice constant grows epitaxially on the poly-Si surface with almost uniform sticking probability. The results show that the micro-probe RHEED technique is useful in studying the crystal growth of materials deposited on crystal surfaces, especially on polycrystal surfaces.