Multiprincipal-Element AlCrTaTiZr-Nitride Nanocomposite Film of Extremely High Thermal Stability as Diffusion Barrier for Cu Metallization

To inhibit Cu diffusion in interconnects, an effective diffusion barrier of high thermal stability is strongly demanded. Thus in this study, a nitride nanocomposite film of equimolar five-element high-entropy alloy, (AlCrTaTiZr)N, was developed and deposited by reactive sputtering. Thermal stability of the (AlCrTaTiZr)N film and its barrier performance to the interdiffusion of Si and Cu were investigated under thermal annealing at 700 to 900°C. The (AlCrTaTiZr)N, constructed of mixed crystalline and amorphous nanocomposite structure, was found to remain thermally stable at an extremely high temperature of 900°C. Neither interdiffusion between Si and Cu through the (AlCrTaTiZr)N layer nor formation of any silicides occurred. Severe lattice distortions caused by the incorporation of multiprincipal elements and the nanocomposite structure of nanocrystallites surrounded by an amorphous matrix without the existence of grain boundaries were expected as the dominant factors for the high thermal stability and superior diffusion resistance of the (AlCrTaTiZr)N film