Effect of annealing ambient on structural and electrical properties of Ge metal-Oxide-Semiconductor capacitors with Pt gate Electrode and HfO₂ gate dielectric

We fabricated Ge metal-oxide-semiconductor (MOS) devices with Pt/HfO ₂ gate stacks and investigated the effect of thermal treatment on their structural and electrical properties in oxygen (O₂) and forming gas (FG) environments. The annealing ambient dependency of the structural and electrical properties of Ge MOS devices was directly compared to that of Si MOS devices. For both Ge and Si MOS devices, the thermal treatment process led to a decrease in accumulation capacitance regardless of the annealing ambient. The interfacial layer (IL) at the HfO₂/Ge stack was much thinner than the HfO₂/Si stack. O₂ annealing resulted in the improvement of the HfO2 interfacial quality of Ge and Si MOS devices, although the improvement of the Ge devices was greater than that of the Si devices. FG annealing was much more effective in the reduction of interface state density (D_it) in Si devices than in Ge devices. A negligible IL at a HfO ₂/Ge stack could be a main cause of deeraded electrical performance of a Ge device with FG annealing.