Low frequency noise in thin gate oxide MOSFETs

Low frequency, 1/f, noise of the drain current, I-D, fluctuations was measu red on a series of Si MOSFETs with the gate oxide thickness, t(ox), varied from 25 to 40 Angstrom by steps of 5 Angstrom. The salient point of this wo rk is a demonstration that, at sufficiently low I-D, intensities, a mean lo w noise level in the MOSFETs is reduced as the gate oxide becomes thinner. This is explained assuming that the noise originates from the electron capt ure/release on Si/SiO2 interface/border traps. The flat band voltage fluctu ations, observable as noise, are linked then to the oxide charge fluctuatio ns by a factor, that is inversely proportional to the gate capacitance, C-o x, and thus proportional to t(ox). At higher I-D, the results are more comp licated, as the access resistance noise is also involved. We provide an int erpretation of the ensemble of the data and show that the noise analysis ca n furnish quantitative estimates of several device characteristics. Device degradation and its consequences for the low frequency noise at higher curr ent levels are also discussed. (C) 2001 Elsevier Science Ltd. All rights re served.