Interfacial characteristics of HfO2 grown on nitrided Ge (100) substrates by atomic-layer deposition

The microstructural and electrical properties of Ge-based metal–oxide–semiconductor capacitors containing high-$k$ gate dielectric layers were investigated with and without the presence of a $\mathrm{Ge}{\mathrm{O}}_x{\mathrm{N}}_y$ interface layer. The effect of this nitrided layer on thermal stability of the metal oxide/Ge structures was probed by medium energy ion energy spectroscopy (MEIS). Atomic-layer deposited $\mathrm{Hf}{\mathrm{O}}_2$ on a chemical oxide-terminated Ge (100) surface exhibited poor capacitance–voltage behavior; however, direct substrate surface nitridation at $600°\mathrm{C}$ in $\mathrm{N}{\mathrm{H}}_3$ ambient before $\mathrm{Hf}{\mathrm{O}}_2$ deposition improved the carrier trapping characteristics. Diffusion of metal impurities (including Hf) into the interfacial oxide/Ge-substrate may be an important source of the measured degradation of electrical properties. MEIS results suggested that the $\mathrm{Ge}{\mathrm{O}}_x{\mathrm{N}}_y$ interface layer may inhibit Hf diffusion into the underlying semiconductor at the temperatures investigated.