Effect of ash process on leakage mechanism of Cu/ELK (k=2.5) interconnect for 65/45 nm generation

This work investigates the leakage and breakdown mechanisms in a Cu damascene structure with carbon-doped CVD extra low-k material (ELK, k=2.5) as intermetal dielectric. The effects of ash processing by inductively coupled plasma (ICP) and reactive ion etching (RIE) modes were extensively characterized. Due to the dominance of Frenkel-Poole (FP) emission in the leakage mechanism between Cu lines, we extracted for the first time the effective k through leakage measurements under various ash conditions. We demonstrate that RIE ash is promising to reduce leakage current, to improve dielectric breakdown, and to retain effective k for Cu/ELK applications. Finally, the mechanisms of ELK damages by ICP and RIE ash are explained.