Oxidation of tungsten surface with reactive oxygen plasma

We report on the oxidation of tungsten at different temperatures with an oxygen plasma studied with photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass-spectrometry (ToF-SIMS). The oxidation of the tungsten surface has been performed in a low-temperature oxygen plasma for different time intervals and various substrate temperatures. The stoichiometry of the formed oxide films was evaluated from O 1s and W 4f XPS peak ratio and was found to be independent of the plasma exposure time and the substrate temperature in the investigated range. The ToF-SIMS results show an increased thickness of the surface oxide layer upon increased substrate temperature during oxidation. The raise the substrate temperature in the process of oxide formation also causes the total amount of hydrogen and water bonded in the film structure to be reduced.