The Cu grain boundary diffusivity in electroless-deposited Co0.9W0.02P0.08 and Co0.9P0.1 at temperatures ranging from 300 to 450C was studied quantitatively and compared with physical vapor deposited pure Co films. The transport of Cu atoms through these films occurred mainly via the grain boundaries according to type-C diffusion kinetics. The diffusivity values were deduced from Cu depth profiles as measured by using secondary ion mass spectrometry. The Cu diffusion through the various Co films obeyed an Arrhenius relationship (figure 3). The Cu diffusivity in the electroless films was 2 to 3 orders of magnitude smaller than that in physical vapor deposited Co films. The diffusivity of Cu through electroless deposited Co0.9W0.02P0.08 was 5 to 10 times smaller than that in electroless deposited Co0.9P0.1. The reduced diffusivity in the electroless films was the result of a significantly lower value of the pre-exponential factor. A qualitative explanation for the reduction of this factor was suggested which was based upon a

previous study that had demonstrated that the Cu concentration in the grain boundaries of electroless deposited Co-based films was considerably smaller than that in pure Co.

Copper Grain Boundary Diffusion in Electroless Deposited Cobalt Based Films and its Influence on Diffusion Barrier Integrity for Copper Metallization. A.Kohn, M.Eizenberg, Y.Shacham-Diamand: Journal of Applied Physics, 2003, 94[5], 3015-24