Investigation of Random Telegraph Noise Under Different Programmed Cell V_t Levels in Charge Trap Based 3D NAND Flash

Abstract

As an important constraint on the threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) distribution, the random telegraph noise (RTN) has attracted much attention due to the widely used multi-bit-per-cell technology in 3D NAND flash. This work investigated the physical mechanisms of RTN in charge- trap-based 3D NAND flash. According to statistical 3D TCAD simulation analysis, the fringing field from the control gate and the random discrete nitride trapped charges, two competitive mechanisms, are proposed to be responsible for the non-monotonic RTN behavior. As the programmed cell V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> level increases, the increasing fringing field from the control gate reduces the current-path percolation effect and the RTN amplitude. However, once the random discrete nitride trapped charges start to dominate the percolation current path, the RTN amplitude increases significantly. Instructively, the clarification of RTN competitive mechanisms contributes to compacting V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> distributions specifically in multi-level 3D NAND flash.