Interaction between electromigration and mechanical-stress-induced migration; New insights by a simple, wafer-level resistometric technique

A wafer-level resistometric technique was used as an indirect way to detect the combined effect of mechanical stress migration and electromigration (EM). A technique was developed to perform reliable high-resolution resistance measurements. In this technique, the compensation of small thermal instabilities is achieved by means of an additional measurement on a reference device. EM tests performed at constant temperature and current on Al-1%Si stripes exhibit an initial nonlinear resistance vs. time behavior, probably due to the simultaneous action of the accumulated mechanical stress and the high current density, followed by linear behavior. An activation energy is extracted by means of an original statistical analysis of the experimental data, and its meaning is discussed, taking into account the influence of temperature- and time-dependent mechanical stress. It is concluded that kinetics of stress relaxation should be known more deeply in order to perform reliable operating temperature extrapolations from the calculated activation energies