Transient conductive path induced in floating gate memories by single ions

Floating gate (FG) memory arrays were irradiated with heavy ions. After being hit by a single ion, a FG cell exhibit large threshold voltage shift due to charge loss. In particular, FGs hit by ions experience a charge loss linearly dependent on ion LET and on the electric field across the tunnel oxide. Since charge loss is by far larger than that expected from a simple generation-recombination model, we are proposing a semi-empirical model based on the idea that a conductive path assimilable to a resistance connects the FG to the substrate during the time (10^-14s) needed for electrons to escape the tunnel oxide. The model is fully consistent with a broad range of theoretical and experimental results, and has excellent fitting capabilities.