Thermal and voltage instabilities of hafnium oxide films prepared by sputtering technique

Hafnium oxide (HfO2) films are not stable at a high-temperature thermal treatment and under high-field stressing. The thermally-induced instabilities might involve the formation of nanocrystalline phases, interface reactions, and out-diffusion of substrate silicon. Our results indicate that there exists an optimal thermal treatment temperature which compromises these effects and yields the best electrical properties of the HfO2 films. This observation has a high practical value in deciding the processing temperatures for MOS device fabrication using a high-k material as the gate dielectric film.