Evidence for a “linear kink effect” in ultra- thin gate oxide SOI n-MOSFETs

Introduction An excess of the drain current ID, related to the floating body effect and hole generation by impact ionization, can appear in the saturation region of SOI MOSFETs [1]. This mechanism has been reported for drain voltages below the band-gap voltage (VD=0.7 V) by including additional energy gain mechanisms to overcome the thresholds of impact ionization processes [2,3]. In this paper we examine a new type of “kink effect” appearing in the linear regime (VD” P9 RI XOWUD-thin gate SOI n-MOSFETs: the Linear Kink Effect (LKE). As will be shown, the LKE gives rise to a second peak in the linear transconductance Gm and an overshoot in the low-frequency noise spectral density SI for front gate voltages exceeding 1 V. The effect occurs both in Partially (PD) and Fully Depleted (FD) devices. For the latter case, the back gate should preferably be biased in accumulation. Moreover, the LKE affects drastically the switch off behavior of the transistors, which has consequences both for circuit operation and lifetime extraction. Finally, a possible model will be proposed, explaining the observations in terms of electron valence band tunneling through the ultra-thin oxide.