On the relationship between stress induced leakage currents and catastrophic breakdown in ultra-thin SiO₂ based dielectrics

Stress induced leakage currents have been measured on capacitor structures with gate dielectrics approximately 19 Å thick, grown in N2O. Both n+/p and p+/n (poly-silicon gate/ silicon substrate) structures were fabricated to allow electron injection using both positive and negative bias. We have measured the statistical distribution (64 devices for each condition) of the SILC as a function of the stress bias condition. Both charge to breakdown (QDB) and time to breakdown (TDB) are found to be strong functions of the applied bias. The change in the stress induced leakage (ΔJ/Jo) at breakdown is found to be relatively independent of the magnitude and polarity of the bias during stress. We suggest that (ΔJ/Jo) at breakdown is a measure of a critical defect density required to cause catastrophic breakdown in ultra-thin dielectrics and this critical density is not dependent upon the electron energy during stress.