The effect of current density, stripe length, stripe width, and temperature on resistance saturation during electromigration testing

摘要

Resistance saturation as a function of current density, stripe length, stripe width, and temperature is investigated for a two-level structure with Ti/AlCu/Ti/TiN stripes and interlevel W stud vias. A simple model based on first principles is presented, which relates the maximum fractional resistance change to the current density and stripe length. Experimental results for stripe lengths of 30, 50, 70, and 100 μm are in good agreement with the model predictions. Estimated void sizes based on the resistance saturation data are consistent with the actual void sizes determined from scanning electron microscopy analysis. A weak temperature dependence is found for 0.33 μm-wide samples in the range 170-250℃, while a strong width dependence is observed between 0.33 and 1.50 μm-wide samples. The width dependence is qualitatively explained in terms of a relaxed bulk modulus that depends on the aspect ratio of the interconnect lines.