Cu seed step coverage evolution with target lifetime for long-throw self ionized physical vapor deposition chambers

The major approach for the deposition of Cu seed layers in copper interconnects is physical vapor deposition (PVD), with a self-ionized plasma (SIP) approach. However, the cutting-edge technologies still lack a full characterization of their efficiency throughout the entire lifetime of a Cu target. Following a previous study on standard SIP technology, in this contribution the robustness of Cu processes obtained by more advanced SIP co-resputtering approaches are investigated as a function of the Cu target lifetime. The conformality and uniformity of the Cu seed layer were studied on nanostructured features adopted in 90-nm node technology, with an aspect ratio up to 8. Transmission electron microscopy was adopted to fully characterize the Cu growth on trench features, highlighting the optimal process windows to be adopted for different SIP technologies. Furthermore, the effect of the resputtering obtained by applying a substrate bias is analyzed as a function of the target lifetime, shedding a light on its contribution to the overall layer uniformity.