Optimizing ion-assisted deposition: Passivation behavior of Y₂O₃ and YAG thin films in plasma environments

The semiconductor manufacturing equipment market is essentially driven by the need for high-quality corrosion-resistant coatings in order to deliver longer durability and better performance. This study explores the formation, growth, and stability of fluorine-enhanced passivation layers on Y₂O₃ and YAG thin films prepared via ion-assisted electron beam evaporation with various ion source voltages (120 V, 140 V, 160 V). This study advances the understanding of Y₂O₃ and YAG materials by examining their different passivation behaviors under CF₄/O₂ plasma etching, highlighting the critical role of ion energy in controlling fluorine incorporation, surface morphology evolution, and the formation of stable passivation layers that enhance plasma resistance. Results show that increasing the ion source voltage in the ion source system creates better fluorine retention in Y₂O₃ particles, generating the smoothest morphology and the thickest passivation layer at 160 V, resulting in better corrosion resistance. In contrast, YAG exhibits the most favorable passivation characteristics at 140 V, where it achieves the lowest roughness, highest fluorine incorporation, and the most uniform passivation layer. Moreover, YAG films exhibit better passivation characteristics, and the long-term stability test (up to 6 h) shows the dynamic protection mechanism, with a continuously growing passivation layer (44.51 nm to 54.70 nm) and a maintained smooth surface. On the other hand, although the Y₂O₃ films also form a passivation layer, the protective nature of this layer is essentially undermined by the crystalline nature of the films. This results in a less stable and effective barrier than the dense, uniform layer formed on the amorphous YAG, which leads to poor long-term plasma resistance. Moreover, XPS analysis confirmed the formation of a dense, fluorine-rich passivation layer on both materials, indicated by the significant suppression of the underlying Y and Al signals after plasma exposure.