XPS Study of the Thermal Instability of HfO[sub 2] Prepared by Hf Sputtering in Oxygen with RTA

Hafnium oxide gate dielectric film was prepared by Hf sputtering in oxygen, and the thermal instability of was investigated by rapid thermal annealing (RTA) in nitrogen. X-ray photoelectron spectroscopy study reveals that the film is thermally unstable at postmetallization annealing temperatures The film decomposes and some oxygen atoms are released upon the RTA in nitrogen. In addition, the current-voltage characteristics of the capacitor are also highly unstable at temperatures higher than 300 K. These observations suggest that although has a much higher dielectric constant, it may not be suitable for the gate dielectric application because the postdeposition thermal treatment deteriorates both the physical and the electrical properties of the film.