In this paper, we report that the phase transformation of Ni-B, Ni-P diffusion barriers deposited electrolessly on Cu, for the reason that the Ni-P layer is a more effective diffusion barrier than the Ni-B layer. The Ni3B crystallized was decomposed to Ni and B2O3 above 400 degrees C and the Ni3P crystallized was decomposed to Ni and P2O5 above 600 degrees C respectively in H-2 atmosphere. Also, the Ni3B was decomposed to Ni and free B above 400 degrees C and the Ni3P was decomposed to Ni and free P above 600 degrees C respectively in H-2 atmosphere. The decomposed Ni formed a solid solution with Cu. The Cu diffusion occurred above 400 degrees C for Ni-B layer and above 600 degrees C for Ni-P layer, respectively. Because the decomposition temperature of Ni-P layer is about 200 degrees C higher than that of Ni-B layer, the Ni-P layer is a more effective barrier for Cu than the Ni-B layer. (c) 2006 Elsevier B.V. All rights reserved.