Study of the Structural Properties of Silicon-on-Sapphire Layers in Hydride-Chloride Vapor-Phase Epitaxy

Abstract

The surface of silicon-on-sapphire (SOS) epitaxial layers is studied by atomic-force microscopy and the UV (ultraviolet) scattering method. X-Ray diffraction analysis of the SOS layers is carried out. The silicon-sapphire transition region is studied by the photovoltage method. The problem of the accumulation of by-products formed during the synthesis of silicon from monosilane is considered and experimentally confirmed. It is found that the addition of chlorine-containing reagents to the epitaxial process makes it possible to exclude the influence exerted by these products on the growing layer and also to modify the surface microprofile. Analysis of the surface and structure of the SOS layers demonstrates that film growth occurs by the Stranski–Krastanov mechanism. It is shown that a combined method in which a 30–60-nm-thick SOS layer is preliminarily grown from pure SiH₄ and then a layer is additionally grown at a 2SiH₄:1SiC1₄ ratio of gas component flow rates is the most preferable method for the fabrication of SOS structures with layer thicknesses of 300 nm and more.