Instability of incorporated nitrogen in HfO₂ films grown on strained Si_0.7 Ge_0.3 layers

The interfacial characteristics and thermal stability of nitrided HfO ₂ films grown on strained Si_0.7 Ge_0.3 layers were investigated by medium energy ion scattering, high-resolution x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure. N incorporation of HfO₂ films grown on Si_0.7 Ge _0.3 layers was strongly related to the diffusion of Si and Ge from strained Si_0.7 Ge_0.3 layers in the interfacial region between HfO2 films and Si_0.7 Ge_0.3 layers by the annealing treatment in NH3 ambient. The chemical states of SiO_xN_y and GeO_x N_y were formed in the interfacial region by N incorporation, and SiOx Ny was dominant chemical states rather than that of GeO_x N_y. However, the incorporated N was not stable, which was mostly diffused out during the postnitridation annealing in a N₂ ambient. The instability of incorporated N through the additional annealing treatment extensively caused the change in the structure of HfO₂.