This extensive simulation study results in certain analytical connections concerning thermal grooving, and electromigration induced cathode voiding and cathode drifting, which are in corresponce with the
experimental studies in literature.
üA technologically vital relationship is obtained which describes the current density dependence of mean time to failure (MTTF):
The first term in this equationis describesthe electromigration dominating stage, and the second term is noting but capillary prevailing regime over the external applied electric field.
The second regime is very important for the device operations, hence they are exposed to lower current densities and temperatures compared to accelarated electromigration testing.
This situation becomes more trouble some if one considers the effect of the miniaturization on MTTF. Since the second capillary dominating regime has very strong dependence on the size such as line width or thickness h^-3rather h^-1 in the EM dominating regime.
The change over current density between these two regimes is given as:
This threshold current density should be as small as possible for the benefit of MTTF.
Hence, one should try to select those materials for the underlayers that they can be able to modify the properties of the interfacial layers to obtain low specific surface Gibbs energies, high specificresistivity and diffusion coefficients.