Effect of Microstructure on Electromigration-Induced Stress

Abstract

In this paper, a finite element based simulation approach for predicting the effect of microstructure on the stresses resulting from electromigration-induced diffusion is described. The electromigration and stress-driven diffusion equation is solved coupled to the mechanical equilibrium and elastic constitutive equation, where a diffusional inelastic strain is introduced. Here, the focus is on the steady state, infinite life case, when the current-driven diffusion is balanced by the resulting stress gradient. The effect of the crystal orientation in Sn-based solder joints on the limiting current density for an infinite life is investigated and compared to experimental observations in the literature. The effect of the grain structure for Al interconnect lines on the dominant diffusion path and estimates for the effective charge number for two different diffusion paths in Al interconnects determined by matching simulations to experimental measurements of elastic strain components in the literature are also presented.

Implementation of General Coupling Model of Electromigration in ANSYS

“…Except above mentioned works, there are many papers with detailed numerical analysis and results, but some of the coupling terms in those governing equations are missing in one way or another. [17][18][19][20][21][22][23][24]. Until recently, a general coupling theory for electromigration has been developed, in which all important physical fields and its effects on electromigration are considered and fully coupled.…”

The effects of grain structure on electromigration failure of the lead-free solder bump

“…Since solders usually form one or a few large grains, the microstructure of the solder plays an important role in the electromigration induced degradation. In particular, the effect of Sn grain orientation on electromigration induced failure is a very important issue in flip-chip solder joints [7][8]. Lu et al [9] proposed two EM degradation modes in high Sn-based Pb-free solder joints that are associated with different diffusion process.…”