Variation of local chemical compositions of (Ti, Al)N films on inner wall of small hole deposited by high-power impulse magnetron sputtering

Highlights: • (Ti, Al)N was deposited on inner-wall of holes by HiPIMS at different substrate bias (85). • Chemical compositions of (Ti, Al)N were varied on inner-wall depending on the depth (83). • Higher content ratio of N was obtained at deeper position of the inner-wall (73). • Relative Ti content ratio to (Ti + Al) was decreased with increasing the hole depth (84). • Chemical composition of (Ti, Al)N was varied significantly at higher substrate bias (84). - Abstract: The local chemical composition of (Ti, Al)N thin films grown on the inner-walls of holes by high-power impulse magnetron sputtering (HiPIMS) was analyzed in detail to investigate the transport behavior of ionized and neutral species into small holes. HiPIMS deposition was performed at the floating substrate potential and at − 50 and − 150 V with a fixed pulse length of 100 μs and a frequency of 333 Hz. The deposition rate on the inner-walls decreased with increasing substrate bias at all hole depth. From the obtained local chemical compositions of (Ti, Al)N films on inner-walls, it was found that the content of the metal elements, Ti and Al, decreases with increasing depth. In addition, the rate of decrease of the Ti content with increasing depth on the inner-walls is greater than that of the Al content. This tendency becomes increasingly significant with increasing substrate bias voltage. These bias dependencies are discussed by considering the degree of thermalization for ionized species from the viewpoint of the difference in the mass number between Ti, Al, and the gas species.