Significance of Gate Oxide Thinning below 1.5 nm on 1/ f Noise Behavior in n-Channel Metal–Oxide–Semiconductor Field-Effect Transistors under Electrical Stress

Abstract

The purpose of this study is to investigate the effects of electrical stress on the 1/ f noise behavior in n-channel metal–oxide–semiconductor transistors with ultrathin gate oxides. Even under a weak electrical stress, the drain current noise (Sid) of the device with a 1.4-nm-thick oxide was found to increase abruptly beyond a certain critical gate bias. This deteriorated noise property was proven to be from simultaneous increases in gate current noise (Sig) and the correlation between Sid and Sig, which were directly related to oxide trap generation and gate/drain current (Ig/Id) ratio, respectively. Meanwhile, the increase in Sid in the device with a 2.3-nm-thick oxide after stress, with a comparable transconductance degradation, was relatively insignificant because of the device's smaller Ig/Id ratio, even if the measured Sig was comparable to that of the thinner oxide device. Consequently, the 1/ f noise degradation could be much more significant than the accompanying DC characteristic degradations in the thin gate oxide below 1.5 nm.