Multiscale simulation of lateral charge loss in Si3N4 3D NAND flash based on density functional theory

Abstract

Multiscale simulation combining density functional theory of defect physics and charge transport calculation is carried out to understand the intrinsic mechanism of the lateral charge loss in silicon nitride (Si3N4)-based 3D NAND flash memory. In this work, the defects’ structures, trapping centers, and trap levels are investigated by ab initio calculations. Wherein, the focus is put on the nitrogen vacancy (VN), puckered nitrogen vacancy (VNP) and H-/O- incorporation. It shows that the VNP and O atom will introduce extremely shallow electron traps which can be eliminated by the H passivation. The stability of several kinds of defects is also studied. To shed new light on the impact of trap levels on the charge de-trapping and the lateral charge loss, numerical simulations are performed with the drift-diffusion model and Poole–Frenkel model.