Inspection for critical issue of floating body effects in SOI-MOSFET using nuclear particles

Floating body effects are problems induced by the excess carriers generated in an SOI body, which results in enhancement of the body potential in SOI-MOSFETs. Such excess carriers are induced by hot electrons generated by a strong field gradient at and nearby the source and drain. Suppression of the floating body effects is important for realization of SOI-MOSFETs. There are two types of SOI substrate: one is a fully depleted (FD) substrate, where the SOI layer is <50 nm, and the other is a partially depleted (PD) substrate where the SOI layer is >100 nm. PD substrate fabrication is simple, but an SOI-MOSFET on PD substrate has kinks and floating body effects (Colinge, 1998). A PD-SOI-MOSFET with body-tied structure is the simplest way to suppress the floating body effects, in which body contact electrodes are put on the side of the SOI body and tied to the source contact. In our recent studies, floating body effects in parallel connected PD-SOI-MOSFETs were induced by nuclear microprobe irradiation (Takai et al, 1999; Iwamatsu et al, 2000). The effectiveness of the body contact electrodes was clarified. In this study, instability of parallel and single PD and FD SOI-MOSFETs has been studied by experiments and two types of three dimensional computer simulations.