SiO₂ etch characteristics and environmental impact of Ar/C₃F₆O chemistry

Perfluorocarbon gases are commonly used for nanoscale etching in semiconductor processing; however, they have the disadvantages of a long lifetime and inducing global warming effects when released into the atmosphere. In this study, the SiO₂ etch characteristics and global warming effects of C₃F₆O gas chemistry, which has a low global warming potential, were compared with those of C₄F₈ chemistry, which is commonly used in semiconductor processing. Using Ar/C₃F₆O, the SiO₂ etch rate was higher and the etch selectivity of SiO₂ over the amorphous carbon hardmask layer was lower than the etch rate and etch selectivity using Ar/C₄F₈/O₂, with all other etch conditions the same. Furthermore, using Ar/C₃F₆O exhibited more anisotropic SiO₂ etch profiles by suppressing the bowing, narrowing, and necking effects compared to the etch profiles using Ar/C₄F₈/O₂. The global warming effects were evaluated by calculating the million metric ton carbon equivalents (MMTCEs) from the volumetric concentrations of the emitted by-product species and process gases, and the results showed that, in the optimized conditions, Ar/C₃F₆O exhibited a lower environmental impact with an MMTCE of <24% than that of Ar/C₄F₈/O₂. Therefore, it is suggested that the Ar/C₃F₆O gas mixture is a potential replacement for Ar/C₄F₈/O₂ because of its lower MMTCE and acceptable SiO₂ etch characteristics.