Oxide trapped charge and time to breakdown of pulsed current measurements in the Fowler-Nordheim regime

In this research work, the trapped oxide charge (Q/sub ox/) and the time to breakdown (t/sub bd/) of a thin dielectric (SiO/sub 2/) layer were investigated using a constant current with low current characterisation pulses. The results imply that the stress method of DiMaria et al. (1976) is not suitable for a quantitative determination of Q/sub ox/, or at least must be used very carefully in order to avoid crucial mistakes. For stress interval t/sub high/<1 s t/sub bd/ decreases and V-t curves deviate, in contradiction to common understanding of a t/sub bd/ increase with pulsed measurements. The voltage transients at the beginning of the low current step are the reason for these observations. When the oxide does not reach a steady-state because of fast switching from high to low currents the measured data deviate significantly from expected results.