Plasma etching of Hf-based high-k thin films. Part III. Modeling the reaction mechanisms

Abstract

A generalized etch rate model was formulated to describe metal oxide etching in complex plasma chemistries, based on the understanding gained from detailed plasma characterization and experimental investigation into the metal oxide etching mechanisms. Using a surface site balance-based approach, the correct etch rate dependencies on neutral-to-ion flux ratio, ion energy, competing deposition and etching reaction pathways, and film properties were successfully incorporated into the model. The applicability of the model was assessed by fitting to experimental etch rate data in both Cl2 and BCl3 chemistries. Plasma gas phase analysis as well as etch and deposition rate measurements were used to calculate initial values and appropriate ranges for model parameter variation. Physically meaningful parameter values were extracted from the modeling fitting to the experimental data, thereby demonstrating the applicability of this model in assessing the plasma etching of other complex materials systems.