Investigation of Oxide Regrowth in the Selective Si<sub>3</sub>N<sub>4</sub> Etching Process for 3D NAND Fabrication by Using Finite Element Modeling Simulation

Abstract

In the process of manufacturing three-dimensional Not AND (3D NAND) flash memory devices, oxide regrowth occurs during the selective Si3N4 etching process on the Si3N4/SiO2 multi-stack structures. The oxide regrowth issue must be suppressed. Thus, effects of two factors, the mass transfer ability of etching byproduct and the stack number of 3D NAND structure, on oxide regrowth were investigated in this study using finite element method (FEM) simulation. Using FEM simulation, we predicted that increase in the stack number of the 3D NAND structure and decrease in the diffusivity of Si3N4 etching byproducts highly aggravated the oxide regrowth. Therefore, it was suggested that an etchant capable of promoting H2SiO3 diffusion behavior would inhibit the oxide regrowth during the selective Si3N4 etching process of the 3D NAND structure.