Study on the failure analysis of graphite-based SiC coatings in harsh etching environments

A B S T R A C T This study investigates the multiscale degradation of a graphite-supported CVD-SiC upper electrode protection ring after 1000 h of service in an 8-inch production plasma etcher. XRD and Raman results indicate that the residual β-SiC coating retains its main crystallographic structure, whereas the surface exhibits a pronounced radial degradation gradient consistent with coupled physical sputtering and fluorine-assisted chemical erosion. In the mildly eroded regions, shallow craters and an increase in the mean Sa to 11.16 ± 1.15 μm suggest that physical ion sputtering is the main contributor. With increasing damage severity, these surface defects may act as preferential sites for fluorine-containing reactive species. EDS analyses reveal localized Si depletion, C enrichment, and F accumulation within deep pits. The Si content decreases to 11.9 at.%, which is consistent with preferential Si removal and the possible formation of volatile SiF 4 species. These observations support a positive-feedback degradation mechanism that may promote pit growth and transform the coating into a highly porous structure with a mean Sa value of 208.2 ± 11.6 μm, approximately 460 times that of the pristine surface. The resulting fragile surface features may perturb the local plasma environment and increase the risk of particle release. These findings provide guidance for optimizing component geometry and developing erosion-resistant coatings.