W/TiN double layers as barrier system for use in Cu metallization

The properties of Cu/W/TiN film stacks were studied. Adding at thin W layer to a known stable TiN diffusion barrier significantly affects the whole metallization system. The introduction of a thin W interlayer causes a significant change of the Cu texture, while the film stress remains stable. The adhesion of Cu on W is excellent, if deposited without vacuum break. The poor adhesion of Cu on air exposed W/TiN is improved by a subsequent annealing step in H2. The performed analytical and electrical barrier tests demonstrate the tandem barrier to be stable up to 650 °C.