Thermal Stability of a Thin HfO₂/Ultrathin SiO₂/Si Structure: Interfacial Si Oxidation and Silicidation

We examine the thermal stability of a 2.6-nm-HfO 2 /0.3-nm-SiO 2 /Si structure in O 2 pressure and in an ultrahigh vacuum. The temperature and O 2 -pressure dependence of Si oxidation at the HfO 2 /Si interface indicates that high-vacuum conditions are required to suppress interfacial oxidation (order of 10 -7 Torr at 800°C). The void nucleation of Hf silicide (<1000 cm -2 ) takes place at temperatures higher than 900°C, which raises the issue of failure when HfO 2 film is used in metal-insulator-semiconductor devices.