Dynamics of the Charge Centroid in Metal–Oxide–Nitride–Oxide–Silicon Memory Cells during Avalanche Injection and Fowler–Nordheim Injection Based on Incremental-Step-Pulse Programming

Abstract

In this study we have carried out a precise analysis on transient charge centroid dynamics during the programming of metal–oxide–nitride–oxide–silicon (MONOS) memory cells. Using the incremental-step-pulse programming (ISPP) scheme, the charge centroid is exactly extracted during the programming. Furthermore, avalanche injection enables low-field carrier injection, making it easy to identify the accessible trap sites in the charge trap layer. Avalanche injection is also used to study the field dependence of available traps. From this analysis, the charge centroid of MONOS memory is found to move from the tunnel layer/charge layer interface to the charge layer/block layer interface during low-field programming. In contrast, the location of the charge centroid is limited to the charge layer/block layer interface when the Fowler–Nordheim (FN) injection is used for programming at a high electric field. Furthermore, the low-electric-field programming achieves a high capture efficiency owing to a larger flatband shift in this programming than in high-electric-field programming. Therefore, low-electric-field programming is desired to increase the trap site availability and carrier capture efficiency.