シリコン完全結晶のエピタキシャル成長(<特集>Growth and Characterization of Silicon Crystals)

抄録

Recently, perfect crystals are desired to fabricate semiconductor devices because of a good performance and a high yield rate. In this review, it is mentioned on growth mechanisms and defects in the epitaxial growth of silicon, which lead successfully to obtain perfect crystals. Growth mechanisms in the chemical vapor deposition methods are devided into the volume reaction dominatingly occuring in the pyrolysis of SiH_4 and the surface reaction in the hydrogen reduction of chlorosilane such as SiCl_4, SiHCl_3, etc.. The volume reaction has been suggested by the fact that silicon fine particles are nucleated above a critical SiH_4 concentration. The surface reaction mechanism has been investigated by the light-irradiated growth, the infrared-absorption spectroscopy of products and the observation of surface morphologies. Important products from a chlorosilane have been considered to be SiCl_2 and SiH_2Cl_2, which contribute both of the growth and the etching reaction. The observation of surfaces of grown layers has resulted in the conclusion that the surface migration of adsorbed clusters may limit the growth rate and cause the rapid layer growth combined with the Kossel's mechanism. The purity of epitaxial layers is interfered by the redistribution of back-etched impurities as well as the generation of defects. The significant defect is dislocations generated mainly by the lattice misfit. However, this is relieved by the lattice-strain compensation using another impurities additional to the usual doped impurity. We have pointed out the point defects and their influences in the last section of this review.