Deep Trap States in Si3N4 Layer on Si Substrate

Charge transfer processes in metal-nitride-semiconductor (MNS) diodes are investigated. The spatial and energetic distributions of the trap state density in Si3N4 layers on Si substrates are determined by measuring the amount of transferred charge in MNS diodes. We apply to MNS diodes relatively wide and low-pulsed voltages so that trap states spatially distributed deep in the Si3N4 layer can be examined, and we analyze the electronic properties of the trap states without any pre-assumptions as made in past analyses. The results show that (i) charging and discharging processes are mainly due to direct tunneling of electrons, (ii) donor-like trap states lie near the mid-gap of the Si3N4 layer on an Si substrate, (iii) they are distributed uniformly in the region of 26–44 Å from the Si/Si3N4 interface, and (iv) their density is 3×1019 cm-3.