Effects of substrate bias and nitrogen flow ratio on the resistivity and crystal structure of reactively sputtered ZrNx films at elevated temperature

ZrNx films were sputtered in an Ar+N2 atmosphere, with different substrate biases (zero to -200 V) at a 2% nitrogen flow ratio and various nitrogen flow ratios (%N2=0.5%-24%) under -200 V of substrate bias. The resistivity, crystal structure, and compositional depth profiles of ZrNx films, before and after vacuum annealing at 500-900 deg. C, were investigated. At 2% N2, the resistivity of ZrNx films decreases with increasing substrate bias due to reduction of incorporated oxygen and porosity. Additionally, the resistivity of -200 V biased ZrNx films (%N2=2%) are about the same before and after annealing, but the resistivities of zero and -100 V biased ZrNx films increase with increasing annealing temperature. In addition, the ZrO2 phases (monoclinic and tetragonal) are found in ZrNx films deposited with 2% N2 and no substrate bias after annealing at 900 deg. C; however, ZrN and tetragonal ZrO2 phases are revealed in ZrNx films sputtered with a substrate bias at the same temperature. On the other hand, the resistivities of -200 V biased ZrNx films at high nitrogen flow ratio (%N2>2%) increase after annealing at 500 deg. C, and then decrease with increasing annealing temperature, up to 900 deg. C. Furthermore, the major phase in 0.5%-24% N2 flow films with -200 V substrate bias is ZrN before and after annealing. Nitrogen outdiffusion is observed for ZrNx films after annealing at high temperature. The connection between the resistivity and crystal structure of ZrNx films and how they are influenced by the substrate bias, nitrogen flow ratio, and annealing temperature is discussed