Experimental results are presented on the diffusion of Cu in silicon and Black Diamond¶ (BD). Cu coated silicon samples, with and without the BD layer, are annealed at various temperatures and times. It is concluded that Cu diffusion in silicon is inhibited in the presence of a copper silicide formed during annealing and/or low solubility at temperatures less than 400°C. On the other hand, the incorporation of Cu in the BD film is observed to be strongly dependant on the method of deposition of the Cu layer. It is further concluded, based on device reliability data, that intentional backside Cu contamination does not pose serious device reliability problems even when subjected to annealing at temperatures typically used for backend processing.