3D TCAD Model for Poly-Si Channel Current and Variability in Vertical NAND Flash Memory

Abstract

The polycrystalline nature of state-of-the-art 3D NAND flash channels complicates on-current and variability modeling. We have therefore developed a 3D TCAD model that captures percolating current behavior and the resulting variability, and implemented it into the Global TCAD Solutions software package. In our simulation flow, we model the channel transport through the randomly generated grain structure with thermionic emission modulated by discrete traps at the grain boundaries, combined with a crystal orientation dependent mobility model inside the grains. We show that this approach can reproduce experimentally observed on-current temperature dependence and variability and use it to investigate the influence of defect density levels and average grain size.