Void formation in the Cu layer during thermal treatment of SiN x /Cu/Ta 73 Si 27 /SiO 2 /Si systems

The thermal stability of a SiN x passivation layer and its influence on the annealing behavior of an amorphous Ta 73 Si 27 diffusion barrier deposited between copper and SiO 2 were analyzed by X‐ray diffraction, glow discharge optical emission spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. During heat treatment at a temperature T an = 500 °C, diffusion of Cu atoms out of the Cu metallization into the SiN x passivation occurs. The Cu diffusion intensifies with increasing annealing temperature and annealing time and seems to be a necessary precondition for a defect formation process observed within the Cu metallization. Depending on the chemical composition of the SiN x /Cu interface, voids in the μm‐range can be formed within the Cu film. Compared to an unpassivated sample, heat treatment leads to a reduced diffusion of Ta atoms from the barrier through the copper into the SiN x /Cu interface. The barrier crystallization process into Ta 5 Si 3 occurring during annealing at T an = 600 °C is principally not affected by the presence of a SiN x passivation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)