Current increase in thin gate-oxide (3.5–7.0 nm) metal–oxide–silicon structures with the boron-doped polycrystalline-silicon gates biased negatively

Abstract

We have investigated gate-current instability in boron-doped polycrystalline-silicon gate metal–oxide–silicon structures. Gate-current increase is observed only for oxide thicknesses of 3.5–7.0 nm and for negative gate voltage. The current-increase characteristics are reversible for positive and negative bias cycles. When the gate is negatively or positively biased, the flatband voltage remains constant, suggesting that there is no positive charge buildup at the Si–SiO2 interface. The experimental results suggest that a positive charge buildup or the formation of a conductive region at the gate–SiO2 interface is involved in the current increase. A model for this current instability is presented.