Impact of gate tunneling floating-body charging on drain current transients of 0.10 μm-CMOS partially depleted SOI MOSFETs

Abstract

In this paper, the impact of majority carriers introduced into the film by gate-body Electron Valence Band (EVB) tunneling in ultrathin gate oxide (2.5 nm) PD SOI MOSFETs is studied by analyzing “switch-off” drain current ( I d) transients measured with different front gate voltage steps and drain bias ( V d) conditions. A change in the I d transients shape from undershoot to overshoot is appreciated at low V d for sufficiently high “on” gate voltages, which enable gate-body EVB tunneling to introduce majority carriers into the film. The shape and the transition time of these EVB-induced I d overshoots have been found to be in good agreement with conventional (EVB-free) “switch-on”-type transients, which enable the extraction of the majority carrier recombination lifetime. It has been found that the magnitude of the EVB-induced I d overshoot decreases with increasing V d, finally resulting in an undershoot for sufficiently high V d. In order to characterize the effect of the charges introduced into the film during the different “switch-off” conditions, an effective gate voltage overdrive (Δ V geff) has been defined and extracted for all I d transients. It has been found that the transition from overshoot to undershoot can be explained by means of a body potential increase associated with the high V d condition, which results in a lower gate-to-film voltage drop and a reduced EVB majority carriers injection into the film.