Molecular model for intrinsic time-dependent dielectric breakdown in SiO2 dielectrics and the reliability implications for hyper-thin gate oxide

SiO2 films, at constant electric field, show a significant reduction in time-dependent dielectric breakdown (TDDB) performance when the thickness t(ox) is scaled below 4.0 nm. This reduction in TDDB performance is coincident with and scales with the increase in direct tunnelling (DT) leakage through these hyper-thin oxide films. Assuming that the increase in DT leakage leads to more hole injection and trapping in the SiO2, the enhanced dielectric degradation rate with t(ox) reduction can be explained on the basis of an intrinsic molecular model where hole capture serves to catalyze Si-O bond breakage.