M. Depas et al., WEAR-OUT OF ULTRA-THIN GATE OXIDES DURING HIGH-FIELD ELECTRON-TUNNELING, Semiconductor science and technology, 10(6), 1995, pp. 753-758
Ultra-thin (<6 nm) SiO2 wear-out is characterized by time-dependent di
electric breakdown and stress-induced leakage current (SILC) measureme
nts on n(+) poly-Si/SiO2/n-Si capacitors, stressed by high-field tunne
l injection of electrons from the Si substrate. A drastic increase of
the charge to breakdown (Q(BD)) and a strong decrease of the SILC are
observed for thinner oxide layers and lower tunnel current densities.
This is explained by the corresponding reduction of the hot-electron e
nergy during stressing. With the decrease in gate oxide thickness from
6 nm to 3 nm, a transition from Fowler-Nordheim to direct electron tu
nnelling is observed in the current-voltage characteristics of the cap
acitors. It is demonstrated that no significant wear-out occurs in a 3
.5 nm oxide layer for direct tunnelling of electrons from the Si subst
rate.