Impact of strain and strain-relaxation on the low-frequency noise of SRB silicon n-MOSFETs

This paper describes the low-frequency noise behaviour of n-MOSFETs, fabricated in different types of strained-silicon (SSi) substrates. It is shown that compared with standard silicon devices, both a lower and a higher LF noise can be obtained for long-channel (L=1μm) transistors. The noise reduction is ascribed to the inherently better Si-SiO₂ interface quality on a tensile-strained silicon substrate. The higher noise has been found in components were it is believed that the strain is completely relaxed, giving rise to extended defects near the active device regions and an associated excess generation-recombination noise component. It will finally be shown that the better noise performance on SSi substrates may become lost for shorter channel lengths (L=0.15 μm), due to the dominance of random telegraph signal fluctuations.