Physical modeling of single-trap RTS statistical distribution in flash memories

In this paper we present an accurate physical modeling for the statistical distribution of Random Telegraph Signal threshold voltage fluctuations in Flash memories by means of 3D device simulations accounting for realistic cell morphology, random discrete doping and random trap location. The model quantitatively describes the statistical behavior of the fluctuation amplitude, pointing out an exponential distribution which is in quite good agreement to what experimentally observed. The large distribution spread is explained on the basis of inhomogeneous substrate conduction, i.e. percolation effects induced by fixed charge, random discrete doping and current crowding due to local field enhancement. In addition, we investigate also the statistical spread dependence on technological parameters such as substrate doping, deriving design guidelines for technology optimization against Random Telegraph Signal instabilities.