Enhancing Cu interconnect reflow in back-end-of-line metal wiring with ultrathin Co liners

This research investigates the gap-fill characteristics of Cu in back-end-of-line (BEOL) interconnects, focusing on Co liner deposition using chemical vapor deposition (CVD) and cyclic-CVD (C-CVD). Providing superior gap-fill characteristics for BEOL interconnect applications is important. Three methods—CVD, C-CVD, and a combination of the two—were compared in terms of their effects on Cu reflow and electrical performance. CVD exhibited the lowest resistivity (44 μΩ cm at 10 nm thickness) and the fewest carbon impurities, confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Atomic force microscopy (AFM) revealed that CVD produced the smoothest surface (Rq ∼0.5 nm), enabling better adhesion and uniform Cu reflow. At 300 °C, Co liners deposited by CVD achieved void-free Cu-Mn filling in 20 nm trenches, which showed CVD to outperform other methods. These findings highlight CVD as the most effective technique for precise Co liner deposition, ensuring reliable Cu interconnects in advanced semiconductor nodes.