Conversion of Si(100) to Si1-x-yGexCy Alloy by Hydrogen Plasma Containing Ge and C Species

Abstract

The conversion of a crystal Si(100) surface to a Si1-x-yGexCy alloy layer by reaction with hydrogen plasma containing Ge and C species is studied at temperatures from 600°C to 900°C. At temperatures below 685°C, the Ge1-xCx layers are deposited and phase separation growth between Ge and C is observed. The phase separation results in the growth of crystalline Ge particles and amorphous C whiskers. At temperatures above 700°C, carbon layers are formed on the surface of Si(100) crystal. In a narrow temperature range of 685–700°C, the surface of the Si(100) crystal is converted into a smooth Si0.12Ge0.08C0.80 alloy layer in which no phase separation occurs. There are interdiffusions of atoms between the alloy layer and the Si crystal. The diffusion of Si atoms into the alloy layer leads to the formation of an amorphous SiC phase, which stops the phase separation growth and results in a SiC-stabilized Si1-x-yGexCy alloy layer with smooth morphology. The formation of the SiC phase results in a driving force for diffusion of Si atoms. On the other hand, the Ge and C atoms diffuse into the Si crystal during the conversion, and incorporate into substitutional sites. The atom interdiffusions may lattice match the Si1-x-yGexCy layer to the Si(100) crystal.