A study of layer-structured conductors with 3 different widths revealed that the lifetime (defined as a 1% increase in resistance) depended upon 2 critical parameters. These were the grain-size/conductor-width ratio, and the grain orientation. These 2 parameters affected the results independently and monotonically. An investigation of the numbers and sizes of voids which were formed by electromigration showed that the lifetime was proportional to the square of the number of voids. This relationship was independent of the line-width and current density. The experimental relationship was that the 1% lifetime was proportional to the mth power of the grain size/conductor-width, multiplied by the nth power of the full-width at half-maximum; where m was equal to about 4, and n was equal to 2. The void size distribution was log-normal.

K.Hinode, S.Kondo, O.Deguchi: Journal of Vacuum Science and Technology B, 1996, 14[2], 687-90