Investigation of thermal stress effects during annealing of hafnia-made thin film using molecular dynamics simulations

Abstract

Hafnia or hafnium oxide is a high-kappa dielectric material with paramount importance in the realm of semiconductor devices. Recent advancements in 3D device structures require a few nanometer-thick conformal films on nonplanar substrates. During the fabrication stage, the annealing process of thin films has been discovered to mitigate delamination issues at the film-substrate interface. However, it has been observed that the residual stress, which emerges as the film cools to room temperature, may lead to delamination. In this study, we propose an idealized atomistic model to mimic the critical region of a 3D-NAND structure, to get insights into the effect of thermal stress and delamination during the annealing of hafnia-made thin film. We employ molecular dynamics simulation using charge-optimized many-body potential (COMB) to perform heating and cooling simulations for different thicknesses of the hafnia layer. Our results suggest that, during heating, as the annealing temperature increases, the severity of delamination decreases. At extremely low thickness of the hafnia layer, delamination does not occur. However, significant delamination is observed during the cooling process, especially when the high temperature gradient is high.