Thickness-dependent power-law of dielectric breakdown in ultrathin NMOS gate oxides

We experimentally investigated the breakdown lifetime of NMOS under inversion condition as a function of gate voltage by long-time-span tests and new power-law criteria. The lifetime followed the 1/E-rule above ∼4 V, but the power-law below ∼4 V. The power index decreased when the oxide became thinner. We observed no trace of the E-rule. We propose to adopt the powerlaw and the 1/E-rule in the reliability projection of core and I/O oxides, respectively. We need to appropriately consider the direct tunneling to model the breakdown below ∼4 V. The hole injection still seems to be playing an important role.