Influence of Common Source and Word Line Electrodes on Program Operation in SuperFlash Memory

Abstract

A theoretical study of the influence of word line and common source electrodes on the program operation in shrank SuperFlash memory is proposed. Numerical simulations demonstrate that the literature model defined for previous nodes is not always suitable, due to the continuous cell physical size reduction and to the consequent increment of capacitive coupling between the floating gate and adjacent electrodes. To get a deeper insight, an analytical model of the electric field in the region of source side injection is proposed. This model describes the impact of the cell physical and electrical parameters on the vertical and horizontal field components and highlights the strong dependence of the carrier injection on the technology node. Furthermore, the numerical and analytical models estimate the influence of the word line and common source electrodes on the time-to-program, the floating gate potential and the source side injection efficiency, taking into consideration, at the same time, their possible impact on the cell reliability.