Characterisation of CuAl alloy for future interconnect technologies

A copper-aluminium alloy (90:10wt%) has been investigated as a possible candidate for future interconnect applications. The tendency of the Al to segregate at the surface of the Cu following thermal anneal makes this alloy potentially suitable to function as a self-forming Cu diffusion barrier layer. X-ray photoelectron spectroscopy (XPS) and electrical characterisation measurements were used to study the segregation of Al from the alloy bulk during annealing treatments. Four point probe measurements were used to gain additional information as to the electrical resistance of the CuAl alloy when annealed at various temperatures in vacuum using pure Cu as a reference. Capacitance-voltage (CV), current-voltage (IV) and bias thermal stress (BTS) test measurements were made on metal-oxide-semiconductor (MOS) structures fabricated with the CuAl alloy and compared to identical structures with pure Cu and Al contacts.