Etch damage of Ge₂Sb₂Te₅ for different halogen gases

Etch damage of Ge₂Sb₂Te₅ (GST) has been investigated after etching in halogen inductively coupled plasmas (ICPs) such as CF₄, Cl₂, and HBr. X-ray photoelectron spectra of Ge, Sb, and Te on the etched surfaces showed different depths of etch damage depending on the halogen-based plasmas. The blank GST etched by CF₄ showed a lower total-halogen-percentage remaining on the etched surface than that etched by Cl₂ even though the depth of halogenations was the deepest for the GST etched by CF₄ owing to the highest reactivity. However, when a GST feature masked by SiO₂/Ti/TiN was etched, owing to the reaction of O from the SiO₂ mask and C from CF₄, a thinner/or no C-F polymer appeared to be formed on the etched sidewall; therefore, the highest halogenation was observed on the GST etched by CF₄. Among the halogen-gases investigated, HBr showed the lowest damage due to the lowest reactivity.