Abstract
Since Al was replaced by Cu for high-end IC products in 1997, the stability of the Cu–dielectric interface has become an increasingly important topic. In the dual damascene interconnect structure, Cu interconnects are surrounded by various barriers. The Cu lines are capped with a dielectric layer of materials, which is used as a diffusion barrier and an etch-stop layer. Cu migration through the capping layer is an increasingly serious concern because this layer is moving from a conventional dense material (Si3N4 ) to lower-k barrier materials such as SiC, SiCO, and SiCN. The sidewalls of the Cu lines are encapsulated by metallic diffusion barrier materials, which also present a problem. It is increasingly more challenging to contain Cu within the interconnect lines because the aggressive shrinking of via and trench size requires thinner barrier layers. The local depletion of barrier layers may eventually expose Cu directly to the low-k interlayer dielectrics. In addition, the stability of barrier metals themselves with low-k dielectrics could also be an issue under bias-temperature stress. In any event, the stability of Cu–dielectric interfaces has become a pressing issue.
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He, M., Lu, TM. (2012). Cu-Dielectric Interfaces. In: Metal-Dielectric Interfaces in Gigascale Electronics. Springer Series in Materials Science, vol 157. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-1812-2_5
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