Phase transformation of Ni–B, Ni–P diffusion barrier deposited electrolessly on Cu interconnect

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 8C and the Ni3P crystallized was decomposed to Ni and P2O5 above 600 8C respectively in Ar atmosphere. Also, the Ni3B was decomposed to Ni and free B above 400 8C and the Ni3P was decomposed to Ni and free P above 600 8C respectively in H2 atmosphere. The decomposed Ni formed a solid solution with Cu. The Cu diffusion occurred above 400 8C for Ni–B layer and above 600 8C for Ni–P layer, respectively. Because the decomposition temperature of Ni–P layer is about 200 8C higher than that of Ni–B layer, the Ni–P layer is a more effective barrier for Cu than the Ni–B layer