Three-dimensional simulation of the dependence of the programming window of SOI nanocrystal memories on the channel width

In this paper, we present an approach based on three-dimensional simulations for the investigation of the dependence of the programming window of silicon-on-insulator (SOI) nanocrystal memories on the width of the silicon channel. Recent experiments show that the threshold voltage shift after programming increases with decreasing channel width. By evaluating the consequences of possible assumptions on the charge stored in the nanocrystals, we show that such behavior can be consistently explained by the preferential injection of electrons, during the program operation, through the oxide near the edges of the channel. As a consequence, charge is mostly stored in the dots close to the edges and, therefore, is more and more effective as the channel width is decreased. Experiments and simulations on SOI nanocrystal memories show support of our interpretation with respect to different proposed mechanisms.