Behavior of oxide regrowth during the selective Si3N4 etching process on 3D NAND structures using finite element computational simulations.

[Display omitted] • Oxide regrowth on 3D NAND was implemented by finite element modeling simulation. • Concentrations of etching byproduct, H 2 SiO 3 , under various Si 3 N 4 etching conditions were investigated. • 85 wt% H 3 PO 4 cannot avoid oxide regrowth on ultra-high-number 3D NAND structure. • Increase in the diffusivity of H 2 SiO 3 significantly suppresses oxide regrowth. Oxide regrowth should be suppressed during the etching of silicon nitride, which is used to fabricate three-dimensional Not AND (3D NAND) devices. This requires a detailed understanding on the mass-transfer characteristics of Si 3 N 4 etching byproducts that cause oxide regrowth. Finite element method (FEM) simulations are performed to investigate the mass transfer of Si 3 N 4 etching byproducts (EB Si3N4) and oxide regrowth during Si 3 N 4 etching on a 3D Si 3 N 4 /SiO 2 multistack. In particular, the concentration profiles of the byproducts under various etching conditions, such as different numbers of Si 3 N 4 /SiO 2 multistacks, diffusion coefficients of the byproducts, etching rates of Si 3 N 4 , and initial concentrations of Si-based additives, are monitored. Furthermore, the in-situ generation of oxide regrowth under various etching conditions is evaluated. Consequently, an increase in the diffusion coefficient of the byproducts is proposed as the most promising method for suppressing oxide regrowth during Si 3 N 4 etching on high-numbered 3D NAND stacks. The FEM simulation results are strongly supported by data from Si 3 N 4 etching experiments on Si 3 N 4 /SiO 2 multistacks. [ABSTRACT FROM AUTHOR]