A novel analysis method of threshold voltage shift due to detrap in a multi-level flash memory

With the aim of improving flash-memory retention characteristics, we investigated threshold voltage shift (/spl Delta/V/sub th/) due to charge detrapping from the tunnel oxide. Accordingly, we propose a new parameter that can reveal the main origin of detrapping (hole/electron) and the detrap centroid. We found that the main origin of detrapping changes from holes to electrons depending on the degree of tunnel-oxide degradation. Since the hole detrapping increases V/sub th/ of a programmed memory cell, this V/sub th/ increase must be considered, especially when designing a multi-level flash memory.