Deposition of NbN thin films by DC magnetron sputtering process

Thin films of niobium nitride (NbN) were deposited on SKD11 tool steel substrate by a DC magnetron sputtering system. The influence of the N2/Ar gas ratio of the inlet gases, the deposition temperature, the substrate bias potential on the mechanical and the structural properties of the films were investigated. X-ray diffraction data showed that cubic NbN was formed at a low N2/Ar gas ratio. With the increase in the N2/Ar gas ratio, hexagonal NbN was formed, resulting in a mixture of cubic NbN and hexagonal NbN. The hardness of the films also increased with an increase in the deposition temperature up to 300 °C. Adhesion of the films decreased, however, with an increase in the deposition temperature. The hardness of the films reached maximum level at the bias potential of −200 V and decreased with a further increase of the bias potential. The films deposited at the substrate bias potential range from −50 to −150 V exhibited relatively high adhesion.