Molecular-dynamics calculations have been performed to examine behavior of carbon (C) atoms during crystal silicon (Si) growth from melted Si based on the ordinary Langevin equation employing the Tersoff empirical potential. From the analysis of the radial distribution functions, local coordination, and bond angle distributions, it was found that C atoms are four-fold coordinated in liquid Si and occupy the substitutional sites in crystalline Si grown from the melt. It has been also shown that aggregation of these substitutional C atoms induces defects such as five-and seven-member rings in crystalline Si.
In this year, we lost our leader in ultrafine particle science which was born in 1963 in Japan. This field is again attracting interest as the mesoscopic physics, nano-structure, quantum dot and chemistry and physics of small many body system. The ultrafine particl escience may develop not only in material science but also in the fields of planetary science and echo-technology. In this report, brief summary on books of Uyeda is given. It is then shown that the essence in considering the growth of ultrafine particles is on temperature of the particle, convection and growth in smoke. An example of the controlled growth and characteristic nature of ultrafine particle is shown by using Te crystal. By the use of oxidation of metallic particles, the possibility toward the production of functional particles may be opened. Some fundamental experimental results are summarized. Size effect on the reaction between ultrafine particle and thin film have been indicated. This result shows a new nature in nano particle.
The morphology of thermally induced oxygen precipitates in Czochralski Silicon Crystals and its dependence upon oxygen supersaturation in Czochralski Silicon Crystals were investigated using transmission electron microscopy. The morphology of oxygen precipitates depend upon not only annealing temperatures but also the oxygen supersaturation. The oxygen precipitates near the surface denuded zone are octahedral, independent of annealing temperatures, This result demonstrates the oxygen concentration plays an important role in the morphology change. In this paper, we discuss the morphology of oxygen precipitates depending upon the oxygen supersaturation, based on the diagram of the morphology in snow crystals.
The grown-in defects induced in CZ-Si during crystal growth was investigated. we used the non-destructive measurement method, Bright Field infrared laser Interferometer (known as Oxygen Precipitate Profiler; OPP), for the analysis of the number density, size and morphology of grown-in defects. TEM observation of grown-in defects was also performed using OPP and focused-ion-beam (FIB) for the TEM sample fabrication. It is revealed that the grown-in defects are octahedral void-like defects of 0.1-0.2μm. They degrade the GOI yield and therefore the GOI improvement is achieved by the reduction of the grown-in defects. The formation of the grown-in defects is supposed to occur in the temperature range between 1070℃ and 1100℃. The total volume of the grown-in defects per unit silicon volume is estimated to be constant value of 10^<12>-10^<13> nm^3/cm^3. The growth and decrease of density of grown-in defects are occurred in the same temperature range because the foormation mechanism could be the Ostwald ripening. Assuming the Ostwald ripening mechanism, the time dependence of size is indicated to be a reaction-limited phenomena.
Behavior of COP pits on the substrate surface during Si epitaxial growth is studied. COPs easily disappear by atmospheric pressure epitaxy using SiHCl_3 and SiH_2Cl_2. However, in the case of the reduced pressure epitaxy, many COPs remain as pits on the surface of epitaxial layer up to 5μm thickness. Such behaviors depend on the growth conditions.
The development of Czhochralski silicon crystal 400 mm in diameter is progressing in Japan. The influence of a cusp magnetic field on thermal environment of huge silica crucible has been investigated by computer simulation. We expect that suppression of melt convection by Lorentz force can elongate the life time of silica crucible. Magnetic field slows down the melt flow and hence reduce the oxygen transport and the dissolution speed. We found the optimum magnetic strength with 36 and 48 inch silica crucible was about 2000 0e. In this region, crucible temperature was lower than in the absence of a magnetic field and temperature fluctuation in the molten silicon was very small. On the other hand, the oscillation of melt temperature was observed with the magnetic strength of 300 0e. the 2000 Oe, magnetic field leads to a rise in teh crucible wall temperature and softenit.