Effects of stress and temperature gradients on the evolution of void in metal interconnects driven by electric current and mechanical stress

Abstract

The effects of the electromigration-induced stress gradient and temperature gradient on the void evolution in interconnect are examined by numerical simulation. It is found that the void in a stress gradient field will move to higher stress zone, regardless of tensile stress or compressive stress. The void motion driven by electromigration will be retarded by compressive stress gradient and accelerated by tensile stress gradient. The stress gradient has the effect of elongating the void along the interconnect line, shorting its size in line width. Hence, it may delay the open failure of the interconnect line. The temperature gradients due to current crowding cause local changes in resistivity and diffusivity in the vicinity of the evolving void, leading to void motion more rapidly along the interconnect line and void growth in the line width. Thus, the temperature gradient around the void tends to accelerate the open failure process of the interconnect.