Yttrium fluoride (YF₃) films were grown on sapphire substrate by a radio frequency magnetron using a commercial ceramic target in a vacuum chamber. The structure, composition, and plasma etching behavior of the films were systematically investigated. The YF₃ film was deposited at a working pressure of 5 mTorr and an RF power of 150 W. The substrate-heating temperature was increased from 400 to 700 °C in increments of 100 °C. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction results confirmed an orthorhombic YF₃ structure was obtained at a substrate temperature of 700 °C for 2 h. X-ray photoelectron spectroscopy revealed a strongly fluorinated bond (Y⁻F bond) on the etched surface of the YF₃ films. HRTEM analysis also revealed that the YF₃ films became yttrium-oxyfluorinated after exposure to fluorocarbon plasma. The etching depth was three times lower on YF₃ film than on Al₂O₃ plate. These results showed that the YF₃ films have excellent erosion resistance properties compared to Al₂O₃ plates.
Keywords: films; plasma processing equipment; yttrium fluoride.