Mechanisms of dynamic pass leakage current in partially depleted SOI MOSFETs

Abstract

The floating body effect is one of the most serious problems for applications of partially depleted (PD) SOI MOSFETs. In particular, the dynamic pass leakage caused by the floating body effect (Assaderaghi et al., 1996) degrades retention time in SOI DRAMs (Kim et al., 1996) and produces timing errors in dynamic circuits (Canada et al., 1999). Two mechanisms have been considered so far as the origin of dynamic pass leakage: (1) parasitic bipolar current (Assaderaghi et al., 1997; Wei and Antoniadis, 1996) and (2) subthreshold current (Kim et al., 1996; Morishita et al., 1995), as shown here, taking SOI DRAM cells as an example. However, no experimental data have been reported that distinguish between these two currents, and the mechanism of the dynamic pass leakage has not been reported. In this paper, the parasitic bipolar current and subthreshold current have been successfully separated in the transient measurements and the origin of the dynamic pass leakage has been clarified, to our knowledge, for the first time.