Effects of film thickness and annealing temperature on the properties of molybdenum carbide films prepared using pulsed direct-current magnetron sputtering

Abstract

Molybdenum carbide (Mo _2 C) films were prepared using pulsed direct-current (DC) magnetron sputtering. The effects of film thickness on the phase structure, surface morphology, and optical constants of the films were examined using X-ray diffraction (XRD), atomic force microscopy, and extreme ultraviolet reflectivity. XRD analysis showed that the as-sputtered films with thicknesses between 30 nm and 150 nm were almost amorphous. New phase α -MoC _1-x with the (111), (200), (220), (311), and (222) crystal planes appeared in films with thicknesses between 200 nm and 400 nm. The phase transition and chemical composition of the Mo _2 C films treated using vacuum heat treatment were analyzed in detail. For 150 nm-thick films, the as-deposited as well as the 600 °C-annealed films were amorphous. The phase structures of the 150 nm-thick film annealed at 700 °C, 750 °C, and 800 °C were orthogonal Mo _2 C ( α –Mo _2 C), multiphase structure ( β –Mo _2 C, monoclinic MoO _2 , and cubic Mo _2 N), and monoclinic MoO _2 , respectively. X-ray photoelectron spectrometry revealed that the Mo-Mo bonds of the films transformed into Mo-C, Mo-O, and Mo-N bonds under 750 ℃-annealing, further confirming the formation of a multiphase structure after annealing. Thus, film thickness and annealing temperature considerably influence the properties of Mo _2 C films.

Keywords

• molybdenum carbide film
• phase transition
• EUV optical constant
• vacuum annealing
• pulsed DC magnetron sputtering