Electromigration properties of copper-zirconium alloy interconnects

Highly reliable interconnects for reducing electromigration failure were demonstrated using a Cu-Zr alloy. The Cu-Zr alloy separates into Cu and precipitates containing Cu-Zr compounds after annealing at 500 °C. The precipitates were observed at grain boundaries and interfaces between the Cu-Zr alloy and surrounding materials. Consequently, because the precipitates prevent the diffusion of Cu, the electromigration lifetimes of the Cu-Zr interconnects are 10 to 100 times longer than those of Cu interconnects. Moreover, the resistivity of the CuZr alloy after precipitation annealing is about 2 μΩ cm because the Zr concentration in the grain interior is below the detection limit of energy-dispersive x-ray spectrometry. Therefore, the Cu-Zr interconnects are suitable for future use in logic devices that will be operated at current densities higher than 1 MA/cm2 and at temperatures higher than 100 °C.