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

Zr Nx 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 Zr Nx films, before and after vacuum annealing at 500-900 °C, were investigated. At 2% N2, the resistivity of Zr Nx films decreases with increasing substrate bias due to reduction of incorporated oxygen and porosity. Additionally, the resistivity of -200 V biased Zr Nx films (% N2 =2%) are about the same before and after annealing, but the resistivities of zero and -100 V biased Zr Nx films increase with increasing annealing temperature. In addition, the Zr O2 phases (monoclinic and tetragonal) are found in Zr Nx films deposited with 2% N2 and no substrate bias after annealing at 900 °C; however, ZrN and tetragonal Zr O2 phases are revealed in Zr Nx films sputtered with a substrate bias at the same temperature. On the other hand, the resistivities of -200 V biased Zr Nx films at high nitrogen flow ratio (% N2 >2%) increase after annealing at 500 °C, and then decrease with increasing annealing temperature, up to 900 °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 Zr Nx films after annealing at high temperature. The connection between the resistivity and crystal structure of Zr Nx films and how they are influenced by the substrate bias, nitrogen flow ratio, and annealing temperature is discussed.