Analysis of channel-width effects in 0.3 mu m ultra-thin SOI NMOSFETs

Experiment-based new phenomena, such as LIF energy and channel width effects in ultra-thin (T-Si = 700 Angstrom) 0.3 um SOI NMOSFETs, are analysed using TCAD tools. The relatively higher doping profile along with the width direction silicon edge can improve the breakdown characteristics (i.e., BV congruent to 0 V at W/L = 0.4 um/0.3 um). This effect, which does not coincide with typical BV characteristics in very-small SOIs, is caused by the reduction or the impact ionisation rats due to the doping and geometric effects of the silicon edge as the channel-width becomes narrower. It implies that very small SOI NMOSFETs can be well adopted for the ultra-high density DRAM cells when an optimised doping profile is provided.