ELECTROMIGRATION PROPERTIES OF COPPER-ZIRCONIUM ALLOY INTERCONNECTS

Highly reliable interconnects for reducing electromigration failure we re demonstrated using a Cu-Zr alloy. The Cu-Zr alloy separates into Cu and precipitates containing Cu-Zr compounds after annealing at 500 de grees C. The precipitates were observed at grain boundaries and interf aces between the Cu-Zr alloy and surrounding materials. Consequently, because the precipitates prevent the diffusion of Cu, the electromigra tion lifetimes of the Cu-Zr interconnects are 10 to 100 times longer t han those of Cu interconnects. Moreover, the resistivity of the CuZr a lloy after precipitation annealing is about 2 mu Omega cm because the Zr concentration in the grain interior is below the detection limit of energy-dispersive x-ray spectrometry. Therefore, the Cu-Zr interconne cts are suitable for future use in logic devices that will be operated at current densities higher than 1 MA/cm(2) and at temperatures highe r than 100 degrees C. (C) 1998 American Vacuum Society. [S0734-211X(98 )02605-5].