Electrical analysis of energy depth of electron trap states in silicon nitride films for charge-trap flash memory application

The conduction current flowing through silicon nitride-silicon dioxide stacked films under negative gate bias at high temperatures has been analyzed and the electron transport mechanism in the stacked films has been studied. The trap depth for electrons in the silicon nitride film used in this work was estimated to be 1.3 eV, which was deeper as compared to that for holes (~1.0 eV). Next, the trap depths for electrons and holes in silicon nitride films with two different N/Si composition ratios were compared. Both trap states for electrons and holes were deeper in the silicon nitride film with the higher N/Si composition ratio. The analysis of the conduction current through silicon nitride-silicon dioxide stacked films is useful to evaluate the energy depth of trap states for electrons existing in silicon nitride films.