Oxidation and wet etching behavior of sputtered Mo-Ti-Al films

Exposure of Mo thin films above 300 °C in ambient atmosphere results in surface oxidation, leading to the formation of colored oxide films deteriorating their performance in thin film transistor liquid crystal displays. In this study, the influence of the alloying elements Ti and Al on microstructure, electrical properties, oxidation and wet etching behavior of Mo thin films was investigated. Mo_1−x−yTi_xAl_y films (with x ≈ 0.08 and 0 ≤ y ≤ 0.24) were deposited by direct current magnetron sputtering and annealed in ambient air at 330 °C for 1 h. The oxidation resistance of Mo-Ti-Al films was enhanced with increasing Al content. A minimum Al content of y = 0.16 was necessary to form a thin protective Al₂O₃ surface layer and to prevent the formation of colored molybdenum oxides. The wet etching rate of the Mo-Ti-Al films in a commonly used mixture of phosphoric-, acetic-, and nitric acid decreased with increasing Al content, but was still acceptable for thin film transistor liquid crystal displays applications.