Transient drain current and propagation delay in SOI CMOS

The transient overshoot in drain current that occurs in thin-film SOI (Si-on-SiO
2
) MOSFET's because of the floating body in analyzed, and the benefit it can provide to propagation delay (speed) in SOI CMOS digital circuits is assessed. The analysis accounts for the charge coupling between the front and back gates, and hence describes the dependence of the transient drain (saturation) current and propagation delay on the back-gate bias as well as on the switching frequency. Measurements of the transient current in recrystallized SOI MOSFET's and of propagation delay in SOI CMOS inverters and ring oscillators are described and shown to support the theoretical analysis. The current overshoot is especially beneficial in low-voltage circuits, although at high frequencies other floating-body effects can degrade the speed.