Quantitative control of plasma-surface interactions for highly reliable interconnects

Plasma technologies for highly reliable Cu/low-k interconnects were developed. Although good dual damascene profiles were fabricated, insufficiently optimized plasma for etching (and/or ashing) degraded Cu and SiOCH surface, and corrupted the interface between Cu and barrier metal (BM) after all. Therefore, we clarified the effect of degradation in the interconnect reliabilities, and controlled the densities of reactive species (CFx and O) in the plasma to optimize the reactions between plasma and material surfaces. Consequently, we achieved high yield and high reliability for 90-nm-node Cu/low-k interconnects in over 40 lots.