Fluorination behavior of Y2O3-MgO nanocomposite films irradiated by CF4/O2 plasma

In this study, the Y2O3-MgO (YM) nanocomposite film was prepared using radio frequency magnetron sputtering. The microstructures, chemical compositions, and fluorination behavior of YM films were systematically investigated and compared to those of Y2O3 and MgO films. After exposure to CF4/O2 etching plasma, the surface morphology of the YM nanocomposite film exhibited uniform etching behavior and preserved its original smooth surface. Energy dispersive X-ray spectroscopy mapping and transmission electron microscopy revealed that fluorine atoms present near surface region of the YM nanocomposite film and formed a thin homogeneous fluorinated layer having an average thickness of approximately 20 nm. Furthermore, the fluorinated layer of the YM nanocomposite film did not expand with prolonged plasma exposure. These results demonstrate that the chemical stability of the fine-grained YM nanocomposite film against damage due to the suppression of surface fluorination during CF4/O2 plasma etching.