A drain leakage phenomenon in poly silicon channel 3D NAND flash caused by conductive paths along grain boundaries

In this paper, a new drain leakage current phenomenon in the polycrystalline silicon channel three-dimensional (3D) NAND flash cell is discovered, which we have modeled as leakage paths along the grain boundaries. This drain leakage current increases sharply with the growth of channel diameter, and a current increasing phenomenon under voltage stress appears in the device with large drain leakage current. This leakage current can adversely affect memory operation, and reduces device-to-device uniformity. Based on our model, we can alleviate the effect of this phenomenon by optimizing polysilicon formation process and channel polysilicon thickness. (C) 2018 Elsevier B.V. All rights reserved.