Dielectric breakdown characteristics and interface trapping of hafnium oxide films

The reliability and integrity of HfO2 prepared by direct sputtering of hafnium were studied. By monitoring the current-voltage and current-stressing duration characteristics, we found a significant charge trapping effect in thin film with very short stressing time (<30 s) but the stress-induced trap generation is insignificant. The breakdown characteristics of hafnium gate oxide were also investigated in detail. We found that several soft breakdowns take place before a hard breakdown. Area and stress-voltage effects of the time-dependent dielectric breakdown were observed. Results suggest that the soft and hard breakdowns should have different precursor defects. A two-layer breakdown model of is proposed to explain these observations.