Germanium diffusion from buried SiO$_2$ layer and SiGe phase formation

The Ge diffusivity from the buried SiO$_2$ layer of silicon-on-insulator structure as a function of annealing temperature was studied. It was shown that at an annealing temperature below 900$^\circ$C, almost all Ge is localized in the implantation region in the SiO$_2$ layer. As annealing temperature reached 1100$^\circ$C, the migration of ion-implanted Ge is accompanied by several processes: diffusion in SiO$_2$, accumulation at the Si/SiO$_2$ interface, diffusion into Si as well as evaporation from silicon. The Ge diffuses from SiO$_2$ to the bonding interface of the silicon-on-insulator structure with the diffusion coefficient of $\sim$2$\cdot$10–15 cm$^2$/s that is two orders of magnitude higher than its equilibrium value. Depending on the thickness of the silicon layer, the formation of the Ge or SiGe phase after annealing at a temperature of 1100$^\circ$C was detected.