Discharge of m.n.o.s. structures

The discharge behaviour of m.n.o.s. structures with no applied voltage is investigated at temperatures from ¿¿155¿¿ C to 120¿¿ C for times from 10 to 104s. The decay rate is practically independent of the temperature up to 80¿¿ C but increases significantly at 120¿¿ C. The discharge curves are explained by direct tunnelling from traps, combined with the thermal excitation of these traps. The time dependence of the charge centroid is ascribed to a redistribution of the stored charge in the nitride. A correlation between the decay rate increase after write-erase cycling with the increased nitride conductivity is found.