Cell endurance prediction from a large-area SONOS capacitor

Endurance considerations induced by the degradation of top and bottom oxides are proposed for a SONOS memory. First, a correlation is found between the widespread C-V curves induced by interface generation and cycling numbers (cyc. #). Unlike V_FB (accumulation region), V_T (inversion region) shows a much severe shift. Interface state (N_it) is identified as a key factor even when a 2 nm bottom oxide is used. Moreover, charge to breakdown (Q_BD) for an ONO capacitor under positive and negative constant current stress (CCS) is investigated. Our study reveals that Q_BD of such stacks strongly depends on the top oxide thickness. A field enhancement induced by charges in a trapping nitride layer is the root cause. Based on Weibull statistics, the risk of dielectric breakdown for both blocking layers is then evaluated.