Deep Trap States in Si3N4 Layer on Si Substrate

Abstract

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.