Transgranular slit failure in aluminum interconnects under thermal stress and electromigration
- Univ. of California, Santa Barbara, CA (United States)
- China Textile Univ., Shanghai (Canada)
Continuing miniaturization of integrated circuits demands finer aluminum interconnect lines. Voiding due to electromigration and thermal stress has been a persistent reliability problem. Evidence has recently accumulated that a narrow interconnect under intense electric current can fail by a transgranular slit. A rounded void first forms, enlarges, changes its shape and drifts. When the void becomes sufficiently large, a narrow slit emerges at the expense of the void, running through the grain and across the linewidth. We describe a physical mechanism that explains this void shape change. The void changes its shape as atoms diffuse along the surface driven by the electric current, stress and surface energy. When surface energy dominates, the void keeps its rounded shape. When the stress or electric field is high, the rounded void becomes unstable and the slit emerges. Surface energy anisotropy plays an important role on the void instability. It provides a diffusion bias throughout the void shape evolution. A slight surface energy anisotropy could reduce the critical electric field by several times. Numerical simulation of the void evolution has been carried out based on a variational principle developed by us for this problem. The critical stress and current level of various situations are found. The sequence picture of the slit formation from a rounded void is presented. Our results are consistent on the order of magnitude with existing experimental data.
- OSTI ID:
- 175281
- Report Number(s):
- CONF-950686-; TRN: 95:006111-0238
- Resource Relation:
- Conference: Joint applied mechanics and materials summer meeting, Los Angeles, CA (United States), 28-30 Jun 1995; Other Information: PBD: 1995; Related Information: Is Part Of AMD - MD `95: Summer conference; PB: 520 p.
- Country of Publication:
- United States
- Language:
- English
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