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.