Structural and Fluorine Plasma Etching Behavior of Sputter-Deposition Yttrium Fluoride Film

Yttrium fluoride (YF(3)) 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 YF(3) 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 YF(3) 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 YF(3) films. HRTEM analysis also revealed that the YF(3) films became yttrium-oxyfluorinated after exposure to fluorocarbon plasma. The etching depth was three times lower on YF(3) film than on Al(2)O(3) plate. These results showed that the YF(3) films have excellent erosion resistance properties compared to Al(2)O(3) plates.