NBCO thin films have been fabricated by magnetron sputtering technique on heated $SrTiO_3$ substrates. The oxidation and crystallization of the films were strongly dependent on the distance between the targets and the substrate, as well as on the oxygen partial pressure. The critical temperatures were above 80K for the films prepared under the condition of a small target to substrate gap, in spite of a very low oxygen pressure of 0.2Pa. The results suggest the importance of the activated oxygen uptake into the films during sputtering.