The effect of powder particle size on the corrosion behavior of atmospheric plasma spray-Y2O3 coating: Unraveling the corrosion mechanism by fluorine-based plasma

The atmospheric plasma spray (APS) -Y2O3 coatings are widely used to minimize damage to internal parts of the chamber caused by the strong corrosive effect of fluorine-based plasma used in dry etching; however, the poor density of APS-Y2O3 coatings results in low plasma corrosion resistance. This is a major cause of the generation of contamination particles during CF4/O2 plasma etching. Hence, defects inside the coating must be eliminated to improve the plasma corrosion resistance of APS-Y2O3 coatings. The correlation between the decrease in the number of defects inside the APS-Y2O3 coatings according to the powder particle size and the surface corrosion process by CF4/O2 plasma etching was confirmed. We verified that the internal defects in APS-Y2O3 coatings can be controlled with small powder particles because the powder particles in the APS layer melt efficiently under the APS coating conditions; in addition, the fluorine content rate inside the coating is improved. After the focused ion beam (FIB) process, by examining YOxFy layer with a field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS); we observed the formation of a thick YOxFy layer with decreasing number of defects inside the APS-Y2O3 coatings; thereby, the bonding strength among the Y2O3 powder particles was increased, and corrosion of YOxFy layer due to physical and chemical reactions decreased; as a result, the etch amount was significantly reduced. Therefore, it can be seen that the generation of contamination particles in the CF4/O2 plasma etching can be reduced by controlling the occurrence of defects inside the APS-Y2O3 coatings. The results of this study demonstrate the possibility of minimizing the effect of contamination particles generated in the dry etching process to remove YOxFy layer using chamber self-cleaning such as waferless step. This paper presents a new direction for controlling contamination particles in the inner coating parts of the plasma etching chamber.