Thick AlCu-metal reliability characterization

The layout and design of the on-chip metallization can influence the reliability of products. Thick wide metal tracks are sensitive for failure mechanisms like electromigration (EM), cracking and delamination. The thermal expansion and the volume increase due to mass transport can also influence neighbor interconnects or devices. Process, stack and geometry changes are realized to improve the quality of thick metals. But for some of these changes interactions of different effects can occur. Simulation investigations reveal a side effect of a thick metal stack change. The use of multiple liner layers in a wide thick metal track changes the mechanical properties and the EM performance decreases. The so called highly robust (HiRo) metallization shows typically a significant better EM performance and favorable mechanical properties. The paper presents simulation investigations on HiRo thick metal tracks with multiple liners. The sandwich stack shows also an increase in the EM mass flux. The mechanical properties are also affected but the influence on the mechanical performance will be not significant.