Low-frequency noise measurement of copper damascene interconnects

This paper presents results of using low-frequency noise measurement to characterize the quality and reliability of state-of-the-art copper damascene interconnects. Wafer-level low-frequency noise measurement was performed under high current density on a conventional NIST test structure with various copper line-widths. The Cu test structures were capped with a bi-layer of silicon nitride and silicon oxide to prevent formation of copper oxide on its surface. Low-frequency noise measurement was found to be a more sensitive monitor than solely resistance measurement for assessing the quality and reliability of long copper signal lines. The magnitude of the flicker (or l/f) noise was found to be related to the physical void formation along the line.