Fabrication of SiGe-on-insulator through thermal diffusion of Ge on Si-on-insulator substrate

We report on the fabrication of a homogeneous SiGe-on-insulator as a substrate for strained Si-on-insulator (SOI) metaloxide-semiconductor field-effect-transistors. The fabrication process includes the growth of a thin Ge film on a commercially available SOI substrate at 100°C using a molecular beam epitaxy system, the formation of a SiO₂ cap layer by radio-frequency sputtering, and rapid thermal annealing (RTA) in an Ar atmosphere. After RTA at an appropriate temperature, the SiGe-on-insulator with a laterally homogeneous Si fraction was successfully obtained by the formation of epitaxial SiGe on a thin SOI as a seed and interdiffusion of Ge and Si atoms. However, inhomogeneous SiGe films were obtained when the annealing temperature was very high. The conditions for the realization of SiGe with a homogeneous Si fraction were found to be closely related to the phase diagram of the Si-Ge binary alloy.