Ni-Co-P alloy films were deposited on silicon substrate by electroless technique for diffusion barrier application in copper interconnects technology. The composition of films was varied by varying the concentration of contents in electroless deposition baths. The thermal stability of the films was evaluated by the annealing of samples at elevated temperature and the samples were characterised by using X-ray diffractometer (XRD), four probe method and field-emission scanning electron microscope (FE-SEM). Results indicated that barrier properties degraded with increasing the concentration of Co i.e. decreasing the P. The lower Co and higher P contents alloy film act as a good diffusion barrier up to the 500 degrees C. (c) 2012 Elsevier B.V. All rights reserved.