Effects of substrate bias and nitrogen flow ratio on the surface morphology and binding state of reactively sputtered ZrNx films before and after annealing

ZrNx films were sputtered in an Ar + N2 atmosphere, with different substrate biases (0 to −200 V) at various nitrogen flow ratios (%N2 = 0.5-24%). The surface morphology, resistivity, crystllinity, and bonding configuration of ZrNx films, before and after vacuum annealing, were investigated. As compared with ZrNx films grown without substrate bias, before and after annealing, the resistivity of 1% and 2% N2 films decreases with increasing substrate biases. Simultaneously, if the applied bias is too high, the crystallinity of ZrNx film will decrease. The surfaces of 1% and 2% N2 flow films deposited without bias have small nodules, whereas the surface morphology of films deposited at −100 V of substrate bias exhibits large nodules and rugged surface. Once a −200 V of substrate bias is applied to the substrate, the surface morphology of ZrNx films, grown at 1% and 2% nitrogen flow ratios, is smooth. Furthermore, there are two deconvoluted peaks in XPS spectra (i.e., Zr-O and Zr-N) of ZrNx films deposited at −200 V of substrate bias before and after annealing. On the other hand, the surface morphology changes dramatically from rugged surfaces for film deposited at lower nitrogen flow ratio (%N2 < 1%) to smoother and denser surfaces for film grown at higher nitrogen flow ratio (%N2 ≥ 1%). The Zr-N bonding in 2% N2 films still exist after annealing at 700 °C, while the Zr-N bonding in 0.5% and 16% N2 flow film vanish at the same temperature. The connection between the resistivity, crystallinity, surface morphology, and bonding configuration of ZrNx films and how they are influenced by the substrate bias and nitrogen flow ratio are discussed in this paper.