Analysis of Blech product threshold in passivated AlCu interconnections

The Blech product threshold (Blech, J. Appl. Phys. vol. 47, pp. 1203-1208, 1976) of encapsulated AlCu metallization was investigated in two level structures where W studs are located at both ends of the metal stripes. A high value of 10/sup 4/ A/cm was experimentally measured either for multigrain and for quasi-bamboo microstructures. This value, about 5 times higher than previous values reported for unpassivated structure is explained on the basis of stresses in the structure.