Effect of oxygen concentration on the thermal stability of magnetron sputtered amorphous Ta–Ni thin films

Abstract

The effect of oxygen concentration on the thermal stability of amorphous Ta–Ni thin film alloy is studied in this work. The films were deposited on Si substrates by co-sputtering of Ta and Ni targets. The oxygen concentration in the Ta–Ni films was controlled by applying radio frequency (RF) substrate bias ranging from 0 W to 100 W. Ta–Ni Films with oxygen concentration from 0.95 to 5.25 at.% were obtained, with lower oxygen concentration obtained at higher RF bias. At the as-deposited state, all the Ta–Ni films are amorphous. Increase of oxygen concentration leads to increased electrical resistivity. The as-deposited amorphous films possess different thermal stability after annealing in vacuum for 30 min at temperatures ranging from 700 °C to 800 °C. Formation of TaSi 2 starts at 750 °C in films formed with lower oxygen concentration (0.95 at.%), while Ta 2O 5 and Ta-based phases are observed in films formed with higher oxygen concentration (4.89 at.% and 5.25 at.%). Our work shows that change of oxygen concentration affects the electrical conductivity and thermal stability of the Ta–Ni films. The presence of varying amount of oxygen also changes the Ta–Ni crystallization behavior as well as the interface stability of the Ta–Ni/Si film on silicon substrate.