Low-Frequency Noise Measurements to Characterize Cu-Electromigration Down to 44nm Metal Pitch

This paper demonstrates the deteriorating electromigration (EM) reliability of Cu interconnects when scaling the metal pitch from 54 to 44nm. The study is carried out using a new EM test method based on low-frequency noise. Both EM lifetime and activation energy are found to decrease when scaling the line-width from 32 to 22nm. The decreasing activation energy is attributed to an increased number of grain boundaries and therefore enhanced grain boundary diffusion in narrow lines. The paper also shows that EM lifetimes can be qualitatively predicted based on the data obtained from LFN measurements.

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