Plasma sheath modelling to predict etch-induced overlay

Abstract

In this work a two-dimensional, axisymmetric plasma sheath model is presented that is used to predict ion trajectory deviations in the plasma-wafer interface for a given set of physical etch conditions and chamber geometries. The model successfully predicts the plasma sheath deformation and the associated ion tilt in the vicinity of the wafer edge due to electrical discontinuities. We couple the predictive power of the plasma sheath model with a feature-scale kinetic Monte Carlo etch model to determine the asymmetries in post-etched structures and hence on-product overlay. The feature-scale model serves as a tool to translate the ion tilt within plasma sheath to the sidewall angle asymmetries in the etched trenches and the resulting overlay errors in two adjacent layers of a semiconductor device that could ultimately affect the device yield.