Corrosion behaviour of thin-film metallizations on CVD W and sputtered W-Ti barrier layers

The results of a study using DC polarization techniques are explained on the basis of the galvanic couple formed between the metallization and the barrier layer, as well as the difference between the surface topographies of CVD W and sputtered W-Ti (10%). A galvanic series developed for several couples was used to compare materials that exhibited a strong tendency to corrode, or were more anodic, to those which did not, or were more noble. Although the galvanic series revealed that the CVD W and sputtered W-Ti (10%) barrier metals were more noble than Al, polarization scans demonstrated that the Al and the W-Ti (10%) barrier layers exhibited passive behavior and were not as susceptible to corrosion because of the protection afforded by a protective oxide layer. In addition, the corrosion rate was enhanced by the increased cathodic surface area afforded by the CVD W, which acted as an efficient cathode. Immersion tests substantiated these results.<>