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.

Can amorphization take place in nanoscale interconnects?

“…The amorphization process does not have such requirements. In principle, none of the motive forces for electromigration (mechanical stress gradient [20,21], chemical potential gradient and temperature gradient [22]) is needed for amorphization to occur. We therefore argue that amorphization is a favorable degradation process that could be concurrent with electromigration.…”

Electromigration-induced stress in a confined bamboo interconnect with randomly distributed grain sizes

“…High tensile stress induced by EM facilitates void nucleation and growth, which can eventually cause failure of devices. The stress-induced void dynamics has been extensively studied [7,10,14,18,26]. Therefore, understanding the stress field in bamboo interconnects prior to void initiation is essential for the failure analysis.…”