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 0W to 100W. 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 degrees C to 800 degrees C. Formation of TaSi2 starts at 750 degrees C in films formed with lower oxygen concentration (0.95 at.%), while Ta2O5 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. (C) 2011 Elsevier B.V. All rights reserved.