Transient behavior of the kink effect in partially-depleted SOI MOSFET's

Abstract

The behavior of transients in the drain current of partially-depleted (PD) SOI MOSFET's down to L/sub eff/=0.2 μm is examined as a function of drain bias, gate pulses of varying magnitude (V/sub GS/), pulse duration, and pulse frequency. At fixed V/sub DS/, the gate is pulsed to values ranging from 0.1 V above V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> to V/sub GS/=V/sub DS/. A slow transient is seen when the drain is biased at a V/sub DS/ where the current kink is observable. This slow transient can be on the order of microseconds depending on the relative magnitude of the impact ionization rate. For short times after the pulse edge or for very short pulses at low frequencies, it is shown that the subthreshold drain current value can be very different from the corresponding DC, and that the kink characteristic of PD MOSFET's disappears. However, the kink values can be approached when the pulse frequency and/or duration applied to the gate is increased, due to the latent charge maintained in the floating body at higher frequencies. No transient current effects were observed in fully-depleted SOI MOSFET's.