Electromigration in narrow and large damascene copper lines

This paper presents a study on electromigration performances of narrow and wide damascene copper lines with a view to always be aware of the limitations of circuit lifetime with respect to this failure mechanism. It appears that narrow and large lines do not present the same activation energy. Narrow lines are characterized by a rather high activation energy, around 0.90 eV, referring to copper migration at the copper/top barrier interface, whereas large lines present an activation energy around 0.74 eV, apparently referring to copper migration at the grain boundaries. These experimental results suggest a careful choice in interconnect design, depending on the circuit application (digital/analog), to always provide a robust circuit.