Analysis of the Effect of Residual Holes on Lateral Migration During the Retention Operation in 3-D NAND Flash Memory

Abstract

In this article, we analyze the effect of residual holes on lateral migration (LM) mechanism at low program voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\mathrm {PGM}}$ </tex-math></inline-formula> ) during the retention operation in 3-D NAND flash memories. In the previous study, we suggested that the failure mechanism by the residual holes is a major charge loss component as the program verify (PV) level lowered. Through TCAD simulation, we analyzed the impact of residual holes on LM in detail, and this influence was redefined with the focus of electron movement during the retention operation. In addition, we separated the LM affected by adjacent cells into another failure mechanism and analyze the effect of residual holes and adjacent cells on retention characteristics at various <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\mathrm {PGM}}$ </tex-math></inline-formula> using the three failure mechanisms associated with LM. For low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\mathrm {PGM}}$ </tex-math></inline-formula> and the specific pattern, the retention characteristics are also affected by the number of holes stored in adjacent cells. In this case, it was founded that the Z-interference component is considered in the stretched exponential function through the analysis of the erase time and spacer length.