Passivation and adhesion layers for Cu have been formed by nitridation of Cu(90 nm)/Ti(20 nm)/SiO 2 (90 nm) bilayers and 163 nm thick Cu(Ti 27 at.%) alloys at 400-700°C for 30 min in an ammonia ambient. In both systems Ti segregated during annealing to the free surface to react with the NH 3 and formed an oxygen-rich Ti nitride passivation layer. The thickness of these layers was ∼12 nm for the bilayers and ∼20 nm for the alloys. Evaluation of the Ti nitride surface layers as diffusion barriers for Al and Cu showed stability up to 500°C. The interfacial reaction between Ti and SiO 2 substrate resulted in the formation of a Ti 5 Si 3 /TiO w , structure. Adhesion results obtained from a scratch test showed that the bilayers exhibited good adhesion in the as-deposited state and were stable up to 400°C, but displayed only fair adhesion above that temperature. The alloys exhibited poor to fair adhesion in the as-deposited condition and at 400°C, but adhesion improved considerably after a 500°C anneal. The behavior of the adhesion properties of both the bilayer and alloy system were related to the interfacial reaction.