Tunnel Oxide Nitridation Effect on the Evolution of $V_{t}$ Instabilities (RTS/QED) and Defect Characterization for Sub-40-nm Flash Memory

We report the impact of tunnel oxide nitridation (TON) on the evolution of random telegraph signal (RTS) and quick electron detrapping (QED) and investigate their microscopic origin. Applying nitridation at the SiO₂/Si interface increases both Fermi level (RTS) and general midgap (QED) defects in fresh devices. However, it slows down additional defect generation and demonstrates improvement after severe program/erase cycling. Results from low-frequency 1/f noise indicate that TON aggravates RTS for high energy defects but hardens low energy defects, resulting in improved postcycled RTS. The suggestive defect chemistry is that strong Si-N bonding replaces relatively stable (but distorted) Si-O bonding, rather than passivating high energy dangling bonds. The Si-N bonding also causes more interface bonds to break, reducing strain and improving immunity against Fowler-Nordheim stress.