Influence of interfacial copper during the dealloying and nitridation of Cu-Ti films

Cu(Ti 27 at.%) alloy and Cu(90 nm) /Ti(20 nm) bilayer films were deposited on thermally grown silicon-dioxide and dealloyed under thermal treatment at temperatures 400-700°C for 30 min in an ammonia ambient. During annealing Ti segregated to both the free surface and the alloy/SiO₂ interface. At the interface the Ti dissociated the SiO₂ and reacted with the freed Si and O to form a TiO/Ti₅Si₃ structure. High-resolution energy dispersive X-ray technique revealed the presence of interfacial copper between the Ti-silicide and Ti-oxide layers. The interfacial copper did not reduce the reaction temperature. Nevertheless it was associated with the enhanced dissociation of SiO₂. The data suggested that in the presence of the interfacial copper, the rate of oxide consumption is increased by a factor of 3 to 4. The enhancement of the oxide consumption was observed at temperatures between 450 and 600°C. It is believed that the higher reaction rate is due to a catalytic effect exhibited by the interfacial Cu when it exists in the form of Cu₂O.