The Dielectric Characteristics and Thermal Stability of Hf-Silicate Films with Different Si Contents

We investigated the dielectric characteristics of Hf-silicate films which were grown on Si(100) substrates by atomic layer deposition. The X-ray photoelectron spectroscopy results indicated that the atomic concentrations of HfO 2 and SiO 2 in the Hf-silicate films were similar to the cycle ratio between the number of HfO 2 deposition cycles and that of SiO 2 deposition cycles. The flatband voltage of Hf-silicate films increased as the compositional deviation from the stoichiometric compound HfSi0 4 increased. For Hf-rich silicate films, the flatband voltages were lowered due to the increase of the positive fixed charge in SiO 2 with the increase of SiO 2 content. In addition, the crystallization temperatures were below 900°C after postannealing for 1 min in N 2 ambient and accompanied the phase-separation process as the Si content increased. However, in the case of Si-rich Hf-silicate films, the increase of the effective metal work function dominated and increased the flatband voltages as the Si composition increased. The crystallization and phase separation of Hf-silicate films were not observed even after annealing at 900°C.