Yttrium oxyfluoride ceramics, YOF and Y 5 O 4 F 7 , are promising materials with plasma durability and they are expected to be suitable for plasma etching equipment. In this study, high energy fluorocarbon and oxygen plasma exposure behavior of YOF and Y 5 O 4 F 7 was evaluated. Due to simultaneous sputtering and chemical reaction, etching rates depended not on materials but on plasma conditions. Surfaces of Y 2 O 3 , YOF and Y 5 O 4 F 7 showed crater-like patterns after exposure to high-energy plasmas. Morphological observation and line roughness evaluation showed good durability of Y 5 O 4 F 7 because it had a flatter surface than YOF and Y 2 O 3 after plasma irradiation. TEM cross-sectional observation confirmed a disordered lattice pattern on Y 2 O 3 and YOF after fluorocarbon plasma and oxygen plasma exposure.

Dense bulk of Y2O3, YOF, Y5O4F7 and Y5O4F7 + YF3 ceramics samples were immersed in HCl, HNO3, and HF solutions at room temperature. Scanning electron microscopy revealed that HCl and HNO3 severely damaged Y2O3 while these acid solutions attacked grain boundaries of YOF, Y5O4F7 and Y5O4F7 + YF3 ceramics. Energy-dispersive X-ray spectroscopy analysis resulted that Y5O4F7 + YF3 ceramics immersed in HCl and HNO3 were partially corroded in its YF3 region. Y5O4F7 showed better durability than YOF and Y5O4F7 + YF3 in viewpoint of weight losses and microstructure change. Weight change after dilute HF immersion was negligible and almost the same among the samples. Slight reaction at grain boundaries were observed in Y2O3, YOF, Y5O4F7 and Y5O4F7 + YF3 after dilute HF immersion. Y–O–F ceramics samples are as durable as conventional Y2O3 against HF.