Electromigration Reliability of 60 nm Dual Damascene Cu Interconnects

Electromigration (EM) reliability was investigated for 60 nm wide lines fabricated using a SiON (siliconoxynitride) trench-filling process. EM was observed to be dominated by intrinsic failures due to void formation in the line trench. The lifetime was longer than that of a standard damascene structure, which can be attributed to a distinct via/metal-1 configuration in reducing process-induced defects at the via interface. The line scaling effect on EM reliability was investigated using three different line widths: 60 nm, 110 nm, and 185 nm. EM lifetimes were found to be similar for the different line widths, which is consistent with intrinsic failures due to void formation in the line trench. With a dense and stable SiON filling layer, the processing and thickness effects of the Ta barrier on EM reliability were found to be less significant than for Cu/low-k structures. Multi-linked EM test structures revealed no early failure in the 60 nm samples with a SiON filling layer, although process control of line dimension and geometry remained an issue