Reversible leakage current switching in thin gate oxides - soft breakdown or noise? [MOSFETs]

In this study, p-MOSFETs with 3.5 nm gate oxide thickness are stressed electrically in inversion mode. Next to the better known random leakage current fluctuations such as bursts, pronounced reversible switching or RTS behaviour has been observed in these devices. The cause of reversible switching must be qualitatively different from irreversible breakdown phenomena such as soft or hard breakdown. Positively charged traps within the oxide layer, which can switch from neutral to positive by trapping or de-trapping of an electron into or out of a deep state, are proposed as the cause for reversible, pre-breakdown leakage current switching.