Threshold-Voltage statistics and conduction regimes in nanocrystal memories

Results of three-dimensional Monte Carlo simulations of nanocrystal (NC) memory cells are presented to investigate the statistical properties of the threshold-voltage shift (ΔV_T). It is shown that NC-number fluctuations dominate the ΔV_T spread in the ON-state cell conduction regime, while percolation effects add a significant contribution to the statistical spread in the subthreshold region. The dependence of the ΔV_T statistics on the cell geometry is also investigated, which shows that NC number and position fluctuations can strongly affect the memory performance and must be suitably modeled.