Step like degradation profile of electromigration of W-plug contact

The electromigration (EM) of a W-plug contact to silicon has been investigated by high resolution resistance measurement (HRRM). Step-like resistance degradation curves was observed in EM tests. Scanning electron microscope (SEM) observation shows that the number of voids observed in the Al stripe has a good correlation with that of steps in the degradation profile. A new model was developed to associate the microstructure change to the resistance variation. It was found that each step corresponds to one void completely severing the line. We also showed that the interfacial diffusion is a dominant mechanism of bamboo structures in EM measurements.