Low-Frequency Noise After Channel Soft Oxide Breakdown in HfLaSiO Gate Dielectric

Low-frequency noise (LFN) after channel soft oxide breakdown (SBD) of n-MOSFETs with a HfLaSiO gate dielectric and TaN metal gate shows a Lorentzian-like spectrum, which is not observed in HfSiO gate dielectric devices after channel SBD. This is related to the spatial location of the SBD spot. Because La weakens atomic bonding in the interface layer, the SBD spot is generated close to the Si/SiO₂ interface. This is verified by using time domain analysis. To examine the property of this Lorentzian-like noise, LFNs after channel SBD are measured repeatedly after arbitrary times. After about 20 h, LFN finally shows an increase only at the low-frequency part of the noise spectrum (f < 1 kHz). These results suggest that the trap distribution after arbitrary times spreads instead of remaining localized. Therefore, the traps or the La-O defect clusters have severe unstable distribution and induce an increase of the localized field, which, in turn, causes the traps to percolate through the high-k dielectric.