Analysis of failure mechanisms in erased state of sub 20-nm NAND Flash memory

Abstract

In this paper, we analyzed the characteristics of dominant failure mechanisms in the erased (ERS) state of sub 20-nm NAND Flash memory with an accurate compact model. As a result, it was observed that various charge loss and charge gain mechanisms are mixed together. While the detrapping and the interface trap recovery (Nit) mechanism contribute to the charge loss, the trap-assisted tunneling (TAT) is the charge gain mechanism in the ERS state due to the negative electric field across tunneling oxide layer. At the less cycled cells, the charge gain is dominant due to the TAT mechanism. However, as increasing the cycling times, the detrapping component becomes larger by trapped carriers and the TAT component gets reduced as the detrapped electrons raise the energy level of floating gate (FG) and energy barrier of tunneling oxide layer. Therefore, the charge loss becomes dominant at increased cycling times.