Kinetic study of electromigration failure in Cr/Al-Cu thin film conductors covered with polyimide and the problem of the stress dependent activation energy

The electromigration lifetime of Cr/Al-Cu conductors covered with polyimide passivation was studied as a function of temperature and current density. The activation energy for failure was found to be substantially higher than that found in studies of similar metals without polyimide. A current exponent of 2 was determined in the absence of temperature gradient failure. An improved method for calculating the activation energy for temperature gradient failure is described. The problem of the apparent stress-dependent activation energies is discussed.<>