Effect of aluminum content on plasma resistance and contamination particle generation in yttrium aluminum oxide coatings

Yttrium aluminum oxide (YAO) has garnered interest due to its ability to protect the interior parts of process chambers from the corrosive effects of fluorine-based plasma. This ability is attributed to its low melting point, which enhances the internal bonding capabilities of the atmospheric plasma spray (APS) method. We explored the resistance of YAO coatings, with varying yttrium-to-aluminum content ratios, to fluorine-based plasma. These coatings were applied using the APS method and subsequently subjected to NF3/O2 gas. Our results revealed that a higher Al content ratio resulted in a decreased number of defects within the coating, which also led to selective etching at the initial Al2O3-rich sites, primarily creating relatively weak Al-F bonds and smaller particles. In particular, selecting an appropriate yttrium-to-aluminum content ratio significantly reduced the coating defects and enhanced the etch rate compared to coatings with a higher yttrium content ratio. This improvement was attributed to the balanced presence of Al-F and Y-F bonds. Furthermore, for coatings rich with the yttrium aluminum garnet (YAG) phase, the resistance to fluorine-based plasma was primarily influenced by the thickness of the APS-Y2O3 layer. This layer, used to augment adhesion to parts, relies on the low-temperature crystallization features of YAG. The findings of this study offer valuable insights for optimizing YAG coating in dry-etching processes requiring high-density APS coatings.